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Sample records for above-ground biomass agb

  1. A cost effective and operational methodology for wall to wall Above Ground Biomass (AGB) and carbon stocks estimation and mapping: Nepal REDD+

    NASA Astrophysics Data System (ADS)

    Gilani, H., Sr.; Ganguly, S.; Zhang, G.; Koju, U. A.; Murthy, M. S. R.; Nemani, R. R.; Manandhar, U.; Thapa, G. J.

    2015-12-01

    Nepal is a landlocked country with 39% forest cover of the total land area (147,181 km2). Under the Forest Carbon Partnership Facility (FCPF) and implemented by the World Bank (WB), Nepal chosen as one of four countries best suitable for results-based payment system for Reducing Emissions from Deforestation and Forest Degradation (REDD and REDD+) scheme. At the national level Landsat based, from 1990 to 2000 the forest area has declined by 2%, i.e. by 1467 km2, whereas from 2000 to 2010 it has declined only by 0.12% i.e. 176 km2. A cost effective monitoring and evaluation system for REDD+ requires a balanced approach of remote sensing and ground measurements. This paper provides, for Nepal a cost effective and operational 30 m Above Ground Biomass (AGB) estimation and mapping methodology using freely available satellite data integrated with field inventory. Leaf Area Index (LAI) generated based on propose methodology by Ganguly et al. (2012) using Landsat-8 the OLI cloud free images. To generate tree canopy height map, a density scatter graph between the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud, and Land Elevation Satellite (ICESat) estimated maximum height and Landsat LAI nearest to the center coordinates of the GLAS shots show a moderate but significant exponential correlation (31.211*LAI0.4593, R2= 0.33, RMSE=13.25 m). From the field well distributed circular (750m2 and 500m2), 1124 field plots (0.001% representation of forest cover) measured which were used for estimation AGB (ton/ha) using Sharma et al. (1990) proposed equations for all tree species of Nepal. A satisfactory linear relationship (AGB = 8.7018*Hmax-101.24, R2=0.67, RMSE=7.2 ton/ha) achieved between maximum canopy height (Hmax) and AGB (ton/ha). This cost effective and operational methodology is replicable, over 5-10 years with minimum ground samples through integration of satellite images. Developed AGB used to produce optimum fuel wood scenarios using population and road

  2. Forest Above Ground Biomass Estimation in China

    NASA Astrophysics Data System (ADS)

    Zhao, D.; Zeng, Y.; Wu, B.; Li, X.

    2013-12-01

    In order to study the carbon cycling in China deeply, a forest above ground biomass (AGB) estimation research is carried out under the support of 'Strategic Priority Research Program - Climate Change: Carbone Budget and Related Issues' of the Chinese Academy of Sciences (Carbon Project). The research aims to estimate the forest AGB in 2000, 2005 and 2010 in China, and analyzes its dynamic changes. The overall thinking of the research is using field works and airborne LiDAR data as basis to estimate the AGB in GLAS footprints, and then extrapolating discrete AGB to continuous results with optical and auxiliary data. Due to the large area of China, totally 8 sub-areas are marked out based on the different forest ecosystems and some other factors (Table 1 and Fig. 1). Here, a latest China's land cover product (the background of Fig 1), named 'ChinaCover', and also supported by the 'Carbon Project', is imported to classify the forest types. There are around 5000 sample plots (Table 1) surveyed by the 'Carbon Project'. It can provide a large number of training and validation data. At the same time, the research sets 6 other typical sample areas, which have areas of 60 to 200 km2, and airborne LiDAR flights are carried out to obtain high accuracy AGB in these areas. With the sample plots and 6 typical sample areas, the AGB in GLAS footprint is estimated. Since the sample plots and LiDAR flights were carried out in 2012, the height and area parameters extracted from GLAS footprint are corrected by tree growth model of different forest types. In a further step, extrapolation models are built together with time-series MODIS and auxiliary data. These models fully consider the time-series features and propose several long time-series indices to minimize the influence of spectral saturation. Results are validated by samples and compared to the result of some other researches. At last, the models are applied to the data of 2000, 2005 and 2010 to get the corresponding AGB maps

  3. Single Baseline Tomography SAR for Forest Above Ground Biomass Estimation

    NASA Astrophysics Data System (ADS)

    Li, Wenmei; Chen, Erxue; Li, Zengyuan; Wang, Xinshuang; Feng, Qi

    2013-01-01

    Single baseline tomography SAR is used for forest height estimation as its little restriction on the number of baselines and configurations of tracks in recent years. There existed two kinds of single baseline tomography SAR techniques, the polarimetric coherence tomography (PCT) and the sum of Kronecker product (SKP), algebraic synthesis (AS) and Capon spectral estimator approach (SKP-AS-Capon). Few researches on forest above ground biomass (AGB) estimation are there using single baseline tomography SAR. In this paper, PCT and SKP-AS-Capon approaches are proposed for forest AGB estimation. L-band data set acquired by E-SAR airborne system in 2003 for the forest test site in Traunstein, is used for this experiment. The result shows that single baseline polarimetric tomography SAR can obtain forest AGB in forest stand scale, and SKP-AS-Capon method has better detailed vertical structure information, while the Freeman 3-component combined PCT approach gets a homogenous vertical structure in forest stand.

  4. Comparative study of above ground biomass estimates for conterminous US

    NASA Astrophysics Data System (ADS)

    Neeti, N.; Kennedy, R. E.

    2013-12-01

    Accurate estimates of forest biomass are important for carbon accounting at both regional and national scale. There are four above ground biomass (AGB) maps available for conterminous US, one from the National Aeronautics and Space Administration (NASA), two from the United States Forest Service (USFS) (Blackard and Wilson) and one from the Woods Hole Research Center (WHRC). Although all four maps are meant to represent similar quantities, spatial patterns of AGB vary considerably from map to map. To use any of these AGB maps for carbon accounting, it is important to understand sources of uncertainty in individual maps and agreement and disagreement among them. Therefore, we compared the four AGB maps at ecoregion and state level to gain understanding of map consistency, leveraging discrepancies among maps to gain insight into the method and data sources. We also developed statewide summaries to compare with FIA forest AGB estimates, which are typically reported at the state level. We examined both absolute differences among these aggregated maps, and relative differences among regions within each map. The result shows that NASA biomass estimates are highest and Blackard estimates are lowest compared to other maps at both ecoregion and state level. The AGB for WHRC and Wilson are very similar at both ecoregion and state level specifically in the lower biomass regions compared to higher biomass regions. This could be associated with the differences in the spatial resolution of the data sources uses to generate these maps. At state level, WHRC map is found to be most similar and NASA biomass estimates least similar to FIA plot data. We discuss these differences in light of the different methods and data sources used to generate the maps.

  5. Above-ground biomass and structure of 260 African tropical forests

    PubMed Central

    Lewis, Simon L.; Sonké, Bonaventure; Sunderland, Terry; Begne, Serge K.; Lopez-Gonzalez, Gabriela; van der Heijden, Geertje M. F.; Phillips, Oliver L.; Affum-Baffoe, Kofi; Baker, Timothy R.; Banin, Lindsay; Bastin, Jean-François; Beeckman, Hans; Boeckx, Pascal; Bogaert, Jan; De Cannière, Charles; Chezeaux, Eric; Clark, Connie J.; Collins, Murray; Djagbletey, Gloria; Djuikouo, Marie Noël K.; Droissart, Vincent; Doucet, Jean-Louis; Ewango, Cornielle E. N.; Fauset, Sophie; Feldpausch, Ted R.; Foli, Ernest G.; Gillet, Jean-François; Hamilton, Alan C.; Harris, David J.; Hart, Terese B.; de Haulleville, Thales; Hladik, Annette; Hufkens, Koen; Huygens, Dries; Jeanmart, Philippe; Jeffery, Kathryn J.; Kearsley, Elizabeth; Leal, Miguel E.; Lloyd, Jon; Lovett, Jon C.; Makana, Jean-Remy; Malhi, Yadvinder; Marshall, Andrew R.; Ojo, Lucas; Peh, Kelvin S.-H.; Pickavance, Georgia; Poulsen, John R.; Reitsma, Jan M.; Sheil, Douglas; Simo, Murielle; Steppe, Kathy; Taedoumg, Hermann E.; Talbot, Joey; Taplin, James R. D.; Taylor, David; Thomas, Sean C.; Toirambe, Benjamin; Verbeeck, Hans; Vleminckx, Jason; White, Lee J. T.; Willcock, Simon; Woell, Hannsjorg; Zemagho, Lise

    2013-01-01

    We report above-ground biomass (AGB), basal area, stem density and wood mass density estimates from 260 sample plots (mean size: 1.2 ha) in intact closed-canopy tropical forests across 12 African countries. Mean AGB is 395.7 Mg dry mass ha−1 (95% CI: 14.3), substantially higher than Amazonian values, with the Congo Basin and contiguous forest region attaining AGB values (429 Mg ha−1) similar to those of Bornean forests, and significantly greater than East or West African forests. AGB therefore appears generally higher in palaeo- compared with neotropical forests. However, mean stem density is low (426 ± 11 stems ha−1 greater than or equal to 100 mm diameter) compared with both Amazonian and Bornean forests (cf. approx. 600) and is the signature structural feature of African tropical forests. While spatial autocorrelation complicates analyses, AGB shows a positive relationship with rainfall in the driest nine months of the year, and an opposite association with the wettest three months of the year; a negative relationship with temperature; positive relationship with clay-rich soils; and negative relationships with C : N ratio (suggesting a positive soil phosphorus–AGB relationship), and soil fertility computed as the sum of base cations. The results indicate that AGB is mediated by both climate and soils, and suggest that the AGB of African closed-canopy tropical forests may be particularly sensitive to future precipitation and temperature changes. PMID:23878327

  6. Estimating above-ground biomass on mountain meadows and pastures through remote sensing

    NASA Astrophysics Data System (ADS)

    Barrachina, M.; Cristóbal, J.; Tulla, A. F.

    2015-06-01

    Extensive stock-breeding systems developed in mountain areas like the Pyrenees are crucial for local farming economies and depend largely on above-ground biomass (AGB) in the form of grass produced on meadows and pastureland. In this study, a multiple linear regression analysis technique based on in-situ biomass collection and vegetation and wetness indices derived from Landsat-5 TM data is successfully applied in a mountainous Pyrenees area to model AGB. Temporal thoroughness of the data is ensured by using a large series of images. Results of on-site AGB collection show the importance for AGB models to capture the high interannual and intraseasonal variability that results from both meteorological conditions and farming practices. AGB models yield best results at midsummer and end of summer before mowing operations by farmers, with a mean R2, RMSE and PE for 2008 and 2009 midsummer of 0.76, 95 g m-2 and 27%, respectively; and with a mean R2, RMSE and PE for 2008 and 2009 end of summer of 0.74, 128 g m-2 and 36%, respectively. Although vegetation indices are a priori more related with biomass production, wetness indices play an important role in modeling AGB, being statistically selected more frequently (more than 50%) than other traditional vegetation indexes (around 27%) such as NDVI. This suggests that middle infrared bands are crucial descriptors of AGB. The methodology applied in this work compares favorably with other works in the literature, yielding better results than those works in mountain areas, owing to the ability of the proposed methodology to capture natural and anthropogenic variations in AGB which are the key to increasing AGB modeling accuracy.

  7. Comment on 'A first map of tropical Africa's above-ground biomass derived from satellite imagery'

    NASA Astrophysics Data System (ADS)

    Mitchard, E. T. A.; Saatchi, S. S.; Lewis, S. L.; Feldpausch, T. R.; Gerard, F. F.; Woodhouse, I. H.; Meir, P.

    2011-10-01

    We present a critical evaluation of the above-ground biomass (AGB) map of Africa published in this journal by Baccini et al (2008 Environ. Res. Lett. 3 045011). We first test their map against an independent dataset of 1154 scientific inventory plots from 16 African countries, and find only weak correspondence between our field plots and the AGB value given for the surrounding 1 km pixel by Baccini et al. Separating our field data using a continental landcover classification suggests that the Baccini et al map underestimates the AGB of forests and woodlands, while overestimating the AGB of savannas and grasslands. Secondly, we compare their map to 216 000 × 0.25 ha spaceborne LiDAR footprints. A comparison between Lorey's height (basal-area-weighted average height) derived from the LiDAR data for 1 km pixels containing at least five LiDAR footprints again does not support the hypothesis that the Baccini et al map is accurate, and suggests that it significantly underestimates the AGB of higher AGB areas. We conclude that this is due to the unsuitability of some of the field data used by Baccini et al to create their map, and overfitting in their model, resulting in low accuracies outside the small areas from which their field data are drawn.

  8. Investigating Appropriate Sampling Design for Estimating Above-Ground Biomass in Bruneian Lowland Mixed Dipterocarp Forest

    NASA Astrophysics Data System (ADS)

    Lee, S.; Lee, D.; Abu Salim, K.; Yun, H. M.; Han, S.; Lee, W. K.; Davies, S. J.; Son, Y.

    2014-12-01

    Mixed tropical forest structure is highly heterogeneous unlike plantation or mixed temperate forest structure, and therefore, different sampling approaches are required. However, the appropriate sampling design for estimating the above-ground biomass (AGB) in Bruneian lowland mixed dipterocarp forest (MDF) has not yet been fully clarified. The aim of this study was to provide supportive information in sampling design for Bruneian forest carbon inventory. The study site was located at Kuala Belalong lowland MDF, which is part of the Ulu Tembulong National Park, Brunei Darussalam. Six 60 m × 60 m quadrats were established, separated by a distance of approximately 100 m and each was subdivided into quadrats of 10 m × 10 m, at an elevation between 200 and 300 m above sea level. At each plot all free-standing trees with diameter at breast height (dbh) ≥ 1 cm were measured. The AGB for all trees with dbh ≥ 10 cm was estimated by allometric models. In order to analyze changes in the diameter-dependent parameters used for estimating the AGB, different quadrat areas, ranging from 10 m × 10 m to 60 m × 60 m, were used across the study area, starting at the South-West end and moving towards the North-East end. The derived result was as follows: (a) Big trees (dbh ≥ 70 cm) with sparse distribution have remarkable contribution to the total AGB in Bruneian lowland MDF, and therefore, special consideration is required when estimating the AGB of big trees. Stem number of trees with dbh ≥ 70 cm comprised only 2.7% of all trees with dbh ≥ 10 cm, but 38.5% of the total AGB. (b) For estimating the AGB of big trees at the given acceptable limit of precision (p), it is more efficient to use large quadrats than to use small quadrats, because the total sampling area decreases with the former. Our result showed that 239 20 m × 20 m quadrats (9.6 ha in total) were required, while 15 60 m × 60 m quadrats (5.4 ha in total) were required when estimating the AGB of the trees

  9. Above-ground biomass estimation of tuberous bulrush ( Bolboschoenus planiculmis) in mudflats using remotely sensed multispectral image

    NASA Astrophysics Data System (ADS)

    Kim, Ji Yoon; Im, Ran-Young; Do, Yuno; Kim, Gu-Yeon; Joo, Gea-Jae

    2016-03-01

    We present a multivariate regression approach for mapping the spatial distribution of above-ground biomass (AGB) of B. planiculmis using field data and coincident moderate spatial resolution satellite imagery. A total of 232 ground sample plots were used to estimate the biomass distribution in the Nakdong River estuary. Field data were overlain and correlated with digital values from an atmospherically corrected multispectral image (Landsat 8). The AGB distribution was derived using empirical models trained with field-measured AGB data. The final regression model for AGB estimation was composed using the OLI3, OLI4, and OLI7 spectral bands. The Pearson correlation between the observed and predicted biomass was significant (R = 0.84, p < 0.0001). OLI3 made the largest contribution to the final model (relative coefficient value: 53.4%) and revealed a negative relationship with the AGB biomass. The total distribution area of B. planiculmis was 1,922,979 m2. Based on the model estimation, the total AGB had a dry weight (DW) of approximately 298.2 tons. The distribution of high biomass stands (> 200 kg DW/900 m2) constituted approximately 23.91% of the total vegetated area. Our findings suggest the expandability of remotely sensed products to understand the distribution pattern of estuarine plant productivity at the landscape level.

  10. A terrestrial biosphere model optimized to atmospheric CO2 concentration and above ground woody biomass

    NASA Astrophysics Data System (ADS)

    Saito, M.; Ito, A.; Maksyutov, S. S.

    2013-12-01

    This study documents an optimization of a prognostic biosphere model (VISIT; Vegetation Integrative Similator for Trace gases) to observations of atmospheric CO2 concentration and above ground woody biomass by using a Bayesian inversion method combined with an atmospheric tracer transport model (NIES-TM; National Institute for Environmental Studies / Frontier Research Center for Global Change (NIES/FRCGC) off-line global atmospheric tracer transport model). The assimilated observations include 74 station records of surface atmospheric CO2 concentration and aggregated grid data sets of above ground woody biomass (AGB) and net primary productivity (NPP) over the globe. Both the biosphere model and the atmospheric transport model are used at a horizontal resolution of 2.5 deg x 2.5 deg grid with temporal resolutions of a day and an hour, respectively. The atmospheric transport model simulates atmospheric CO2 concentration with nine vertical levels using daily net ecosystem CO2 exchange rate (NEE) from the biosphere model, oceanic CO2 flux, and fossil fuel emission inventory. The models are driven by meteorological data from JRA-25 (Japanese 25-year ReAnalysis) and JCDAS (JMA Climate Data Assimilation System). Statistically optimum physiological parameters in the biosphere model are found by iterative minimization of the corresponding Bayesian cost function. We select thirteen physiological parameter with high sensitivity to NEE, NPP, and AGB for the minimization. Given the optimized physiological parameters, the model shows error reductions in seasonal variation of the CO2 concentrations especially in the northern hemisphere due to abundant observation stations, while errors remain at a few stations that are located in coastal coastal area and stations in the southern hemisphere. The model also produces moderate estimates of the mean magnitudes and probability distributions in AGB and NPP for each biome. However, the model fails in the simulation of the terrestrial

  11. Using satellite radar backscatter to predict above-ground woody biomass: A consistent relationship across four different African landscapes

    NASA Astrophysics Data System (ADS)

    Mitchard, E. T. A.; Saatchi, S. S.; Woodhouse, I. H.; Nangendo, G.; Ribeiro, N. S.; Williams, M.; Ryan, C. M.; Lewis, S. L.; Feldpausch, T. R.; Meir, P.

    2009-12-01

    Regional-scale above-ground biomass (AGB) estimates of tropical savannas and woodlands are highly uncertain, despite their global importance for ecosystems services and as carbon stores. In response, we collated field inventory data from 253 plots at four study sites in Cameroon, Uganda and Mozambique, and examined the relationships between field-measured AGB and cross-polarized radar backscatter values derived from ALOS PALSAR, an L-band satellite sensor. The relationships were highly significant, similar among sites, and displayed high prediction accuracies up to 150 Mg ha-1 (±˜20%). AGB predictions for any given site obtained using equations derived from data from only the other three sites generated only small increases in error. The results suggest that a widely applicable general relationship exists between AGB and L-band backscatter for lower-biomass tropical woody vegetation. This relationship allows regional-scale AGB estimation, required for example by planned REDD (Reducing Emissions from Deforestation and Degradation) schemes.

  12. Optimal Atmospheric Correction for Above-Ground Forest Biomass Estimation with the ETM+ Remote Sensor.

    PubMed

    Nguyen, Hieu Cong; Jung, Jaehoon; Lee, Jungbin; Choi, Sung-Uk; Hong, Suk-Young; Heo, Joon

    2015-01-01

    The reflectance of the Earth's surface is significantly influenced by atmospheric conditions such as water vapor content and aerosols. Particularly, the absorption and scattering effects become stronger when the target features are non-bright objects, such as in aqueous or vegetated areas. For any remote-sensing approach, atmospheric correction is thus required to minimize those effects and to convert digital number (DN) values to surface reflectance. The main aim of this study was to test the three most popular atmospheric correction models, namely (1) Dark Object Subtraction (DOS); (2) Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) and (3) the Second Simulation of Satellite Signal in the Solar Spectrum (6S) and compare them with Top of Atmospheric (TOA) reflectance. By using the k-Nearest Neighbor (kNN) algorithm, a series of experiments were conducted for above-ground forest biomass (AGB) estimations of the Gongju and Sejong region of South Korea, in order to check the effectiveness of atmospheric correction methods for Landsat ETM+. Overall, in the forest biomass estimation, the 6S model showed the bestRMSE's, followed by FLAASH, DOS and TOA. In addition, a significant improvement of RMSE by 6S was found with images when the study site had higher total water vapor and temperature levels. Moreover, we also tested the sensitivity of the atmospheric correction methods to each of the Landsat ETM+ bands. The results confirmed that 6S dominates the other methods, especially in the infrared wavelengths covering the pivotal bands for forest applications. Finally, we suggest that the 6S model, integrating water vapor and aerosol optical depth derived from MODIS products, is better suited for AGB estimation based on optical remote-sensing data, especially when using satellite images acquired in the summer during full canopy development. PMID:26263996

  13. Optimal Atmospheric Correction for Above-Ground Forest Biomass Estimation with the ETM+ Remote Sensor

    PubMed Central

    Nguyen, Hieu Cong; Jung, Jaehoon; Lee, Jungbin; Choi, Sung-Uk; Hong, Suk-Young; Heo, Joon

    2015-01-01

    The reflectance of the Earth’s surface is significantly influenced by atmospheric conditions such as water vapor content and aerosols. Particularly, the absorption and scattering effects become stronger when the target features are non-bright objects, such as in aqueous or vegetated areas. For any remote-sensing approach, atmospheric correction is thus required to minimize those effects and to convert digital number (DN) values to surface reflectance. The main aim of this study was to test the three most popular atmospheric correction models, namely (1) Dark Object Subtraction (DOS); (2) Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) and (3) the Second Simulation of Satellite Signal in the Solar Spectrum (6S) and compare them with Top of Atmospheric (TOA) reflectance. By using the k-Nearest Neighbor (kNN) algorithm, a series of experiments were conducted for above-ground forest biomass (AGB) estimations of the Gongju and Sejong region of South Korea, in order to check the effectiveness of atmospheric correction methods for Landsat ETM+. Overall, in the forest biomass estimation, the 6S model showed the bestRMSE’s, followed by FLAASH, DOS and TOA. In addition, a significant improvement of RMSE by 6S was found with images when the study site had higher total water vapor and temperature levels. Moreover, we also tested the sensitivity of the atmospheric correction methods to each of the Landsat ETM+ bands. The results confirmed that 6S dominates the other methods, especially in the infrared wavelengths covering the pivotal bands for forest applications. Finally, we suggest that the 6S model, integrating water vapor and aerosol optical depth derived from MODIS products, is better suited for AGB estimation based on optical remote-sensing data, especially when using satellite images acquired in the summer during full canopy development. PMID:26263996

  14. Sensitivity of Above-Ground Biomass Estimates to Height-Diameter Modelling in Mixed-Species West African Woodlands

    PubMed Central

    Aynekulu, Ermias; Pitkänen, Sari; Packalen, Petteri

    2016-01-01

    It has been suggested that above-ground biomass (AGB) inventories should include tree height (H), in addition to diameter (D). As H is a difficult variable to measure, H-D models are commonly used to predict H. We tested a number of approaches for H-D modelling, including additive terms which increased the complexity of the model, and observed how differences in tree-level predictions of H propagated to plot-level AGB estimations. We were especially interested in detecting whether the choice of method can lead to bias. The compared approaches listed in the order of increasing complexity were: (B0) AGB estimations from D-only; (B1) involving also H obtained from a fixed-effects H-D model; (B2) involving also species; (B3) including also between-plot variability as random effects; and (B4) involving multilevel nested random effects for grouping plots in clusters. In light of the results, the modelling approach affected the AGB estimation significantly in some cases, although differences were negligible for some of the alternatives. The most important differences were found between including H or not in the AGB estimation. We observed that AGB predictions without H information were very sensitive to the environmental stress parameter (E), which can induce a critical bias. Regarding the H-D modelling, the most relevant effect was found when species was included as an additive term. We presented a two-step methodology, which succeeded in identifying the species for which the general H-D relation was relevant to modify. Based on the results, our final choice was the single-level mixed-effects model (B3), which accounts for the species but also for the plot random effects reflecting site-specific factors such as soil properties and degree of disturbance. PMID:27367857

  15. Sensitivity of Above-Ground Biomass Estimates to Height-Diameter Modelling in Mixed-Species West African Woodlands.

    PubMed

    Valbuena, Rubén; Heiskanen, Janne; Aynekulu, Ermias; Pitkänen, Sari; Packalen, Petteri

    2016-01-01

    It has been suggested that above-ground biomass (AGB) inventories should include tree height (H), in addition to diameter (D). As H is a difficult variable to measure, H-D models are commonly used to predict H. We tested a number of approaches for H-D modelling, including additive terms which increased the complexity of the model, and observed how differences in tree-level predictions of H propagated to plot-level AGB estimations. We were especially interested in detecting whether the choice of method can lead to bias. The compared approaches listed in the order of increasing complexity were: (B0) AGB estimations from D-only; (B1) involving also H obtained from a fixed-effects H-D model; (B2) involving also species; (B3) including also between-plot variability as random effects; and (B4) involving multilevel nested random effects for grouping plots in clusters. In light of the results, the modelling approach affected the AGB estimation significantly in some cases, although differences were negligible for some of the alternatives. The most important differences were found between including H or not in the AGB estimation. We observed that AGB predictions without H information were very sensitive to the environmental stress parameter (E), which can induce a critical bias. Regarding the H-D modelling, the most relevant effect was found when species was included as an additive term. We presented a two-step methodology, which succeeded in identifying the species for which the general H-D relation was relevant to modify. Based on the results, our final choice was the single-level mixed-effects model (B3), which accounts for the species but also for the plot random effects reflecting site-specific factors such as soil properties and degree of disturbance. PMID:27367857

  16. Above-ground biomass of mangrove species. I. Analysis of models

    NASA Astrophysics Data System (ADS)

    Soares, Mário Luiz Gomes; Schaeffer-Novelli, Yara

    2005-10-01

    This study analyzes the above-ground biomass of Rhizophora mangle and Laguncularia racemosa located in the mangroves of Bertioga (SP) and Guaratiba (RJ), Southeast Brazil. Its purpose is to determine the best regression model to estimate the total above-ground biomass and compartment (leaves, reproductive parts, twigs, branches, trunk and prop roots) biomass, indirectly. To do this, we used structural measurements such as height, diameter at breast-height (DBH), and crown area. A combination of regression types with several compositions of independent variables generated 2.272 models that were later tested. Subsequent analysis of the models indicated that the biomass of reproductive parts, branches, and prop roots yielded great variability, probably because of environmental factors and seasonality (in the case of reproductive parts). It also indicated the superiority of multiple regression to estimate above-ground biomass as it allows researchers to consider several aspects that affect above-ground biomass, specially the influence of environmental factors. This fact has been attested to the models that estimated the biomass of crown compartments.

  17. Range vegetation type mapping and above-ground green biomass estimations using multispectral imagery. [Wyoming

    NASA Technical Reports Server (NTRS)

    Houston, R. S. (Principal Investigator); Gordon, R. C.

    1974-01-01

    The author has identified the following significant results. Range vegetation types have been successfully mapped on a portion of the 68,000 acre study site located west of Baggs, Wyoming, using ERTS-1 imagery. These types have been ascertained from field transects over a five year period. Comparable studies will be made with EREP imagery. Above-ground biomass estimation studies are being conducted utilizing double sampling techniques on two similar study sites. Information obtained will be correlated with percent relative reflectance measurements obtained on the ground which will be related to image brightness levels. This will provide an estimate of above-ground green biomass with multispectral imagery.

  18. Final Harvest of Above-Ground Biomass and Allometric Analysis of the Aspen FACE Experiment

    SciTech Connect

    Mark E. Kubiske

    2013-04-15

    The Aspen FACE experiment, located at the US Forest Service Harshaw Research Facility in Oneida County, Wisconsin, exposes the intact canopies of model trembling aspen forests to increased concentrations of atmospheric CO2 and O3. The first full year of treatments was 1998 and final year of elevated CO2 and O3 treatments is scheduled for 2009. This proposal is to conduct an intensive, analytical harvest of the above-ground parts of 24 trees from each of the 12, 30 m diameter treatment plots (total of 288 trees) during June, July & August 2009. This above-ground harvest will be carefully coordinated with the below-ground harvest proposed by D.F. Karnosky et al. (2008 proposal to DOE). We propose to dissect harvested trees according to annual height growth increment and organ (main stem, branch orders, and leaves) for calculation of above-ground biomass production and allometric comparisons among aspen clones, species, and treatments. Additionally, we will collect fine root samples for DNA fingerprinting to quantify biomass production of individual aspen clones. This work will produce a thorough characterization of above-ground tree and stand growth and allocation above ground, and, in conjunction with the below ground harvest, total tree and stand biomass production, allocation, and allometry.

  19. Estimating above-ground carbon biomass in a newly restored coastal plain wetland using remote sensing.

    PubMed

    Riegel, Joseph B; Bernhardt, Emily; Swenson, Jennifer

    2013-01-01

    Developing accurate but inexpensive methods for estimating above-ground carbon biomass is an important technical challenge that must be overcome before a carbon offset market can be successfully implemented in the United States. Previous studies have shown that LiDAR (light detection and ranging) is well-suited for modeling above-ground biomass in mature forests; however, there has been little previous research on the ability of LiDAR to model above-ground biomass in areas with young, aggrading vegetation. This study compared the abilities of discrete-return LiDAR and high resolution optical imagery to model above-ground carbon biomass at a young restored forested wetland site in eastern North Carolina. We found that the optical imagery model explained more of the observed variation in carbon biomass than the LiDAR model (adj-R(2) values of 0.34 and 0.18 respectively; root mean squared errors of 0.14 Mg C/ha and 0.17 Mg C/ha respectively). Optical imagery was also better able to predict high and low biomass extremes than the LiDAR model. Combining both the optical and LiDAR improved upon the optical model but only marginally (adj-R(2) of 0.37). These results suggest that the ability of discrete-return LiDAR to model above-ground biomass may be rather limited in areas with young, small trees and that high spatial resolution optical imagery may be the better tool in such areas. PMID:23840837

  20. Estimating Above-Ground Carbon Biomass in a Newly Restored Coastal Plain Wetland Using Remote Sensing

    PubMed Central

    Riegel, Joseph B.; Bernhardt, Emily; Swenson, Jennifer

    2013-01-01

    Developing accurate but inexpensive methods for estimating above-ground carbon biomass is an important technical challenge that must be overcome before a carbon offset market can be successfully implemented in the United States. Previous studies have shown that LiDAR (light detection and ranging) is well-suited for modeling above-ground biomass in mature forests; however, there has been little previous research on the ability of LiDAR to model above-ground biomass in areas with young, aggrading vegetation. This study compared the abilities of discrete-return LiDAR and high resolution optical imagery to model above-ground carbon biomass at a young restored forested wetland site in eastern North Carolina. We found that the optical imagery model explained more of the observed variation in carbon biomass than the LiDAR model (adj-R2 values of 0.34 and 0.18 respectively; root mean squared errors of 0.14 Mg C/ha and 0.17 Mg C/ha respectively). Optical imagery was also better able to predict high and low biomass extremes than the LiDAR model. Combining both the optical and LiDAR improved upon the optical model but only marginally (adj-R2 of 0.37). These results suggest that the ability of discrete-return LiDAR to model above-ground biomass may be rather limited in areas with young, small trees and that high spatial resolution optical imagery may be the better tool in such areas. PMID:23840837

  1. Use of Radar to Estimate Above-Ground Biomass in Disturbed Tropical Landscapes

    NASA Technical Reports Server (NTRS)

    Houghton, R. A.

    1998-01-01

    The overall purpose of this work was to evaluate the use of satellite radar in distinguishing, first, different cover classes in tropical landscapes and, second, cover classes with different amounts of above-ground biomass. The work focused on Ama7onian forests around Paragominas, Para, Brazil where extensive ground data had been obtained through previous field work.

  2. Study on forest above-ground biomass synergy inversion from GLAS and HJ-1 data

    NASA Astrophysics Data System (ADS)

    Fang, Zhou; Cao, Chunxiang; Ji, Wei; Xu, Min; Chen, Wei

    2012-10-01

    The need exists to develop a systematic approach to inventory and monitor global forests, both for carbon stock evaluation and for land use change analysis. The use of freely available satellite-based data for carbon stock estimation mitigates both the cost and the spatial limitations of field-based techniques. Spaceborne lidar data have been demonstrated as useful for forest aboveground biomass (AGB) estimation over a wide range of biomass values and forest types. However, the application of these data is limited because of their spatially discrete nature. Spaceborne multispectral sensors have been used extensively to estimate AGB, but these methods have been demonstrated as inappropriate for forest structure characterization in high-biomass mature forests. This study uses an integration of ICESat Geospatial Laser Altimeter System (GLAS) lidar and HJ-1 satellites data to develop methods to estimate AGB in an area of Qilian Mountains, Northwest China. Considering the study area belongs to mountainous terrain, the difficulties of this article are how to extract canopy height from GLAS waveform metrics. Combining with HJ-1 data and ground survey data of the study area, we establish forest biomass estimation model for the GLAS data based on BP neural network model. In order to estimate AGB, the training sample data includes the canopy height extracted from GLAS, LAI, vegetation coverage and several kinds of vegetation indices from HJ-1 data. The results of forest aboveground biomass are very close to the fields measured results, and are consistent with land cover data in the spatial distribution.

  3. Above ground biomass estimation from lidar and hyperspectral airbone data in West African moist forests.

    NASA Astrophysics Data System (ADS)

    Vaglio Laurin, Gaia; Chen, Qi; Lindsell, Jeremy; Coomes, David; Cazzolla-Gatti, Roberto; Grieco, Elisa; Valentini, Riccardo

    2013-04-01

    The development of sound methods for the estimation of forest parameters such as Above Ground Biomass (AGB) and the need of data for different world regions and ecosystems, are widely recognized issues due to their relevance for both carbon cycle modeling and conservation and policy initiatives, such as the UN REDD+ program (Gibbs et al., 2007). The moist forests of the Upper Guinean Belt are poorly studied ecosystems (Vaglio Laurin et al. 2013) but their role is important due to the drier condition expected along the West African coasts according to future climate change scenarios (Gonzales, 2001). Remote sensing has proven to be an effective tool for AGB retrieval when coupled with field data. Lidar, with its ability to penetrate the canopy provides 3D information and best results. Nevertheless very limited research has been conducted in Africa tropical forests with lidar and none to our knowledge in West Africa. Hyperspectral sensors also offer promising data, being able to evidence very fine radiometric differences in vegetation reflectance. Their usefulness in estimating forest parameters is still under evaluation with contrasting findings (Andersen et al. 2008, Latifi et al. 2012), and additional studies are especially relevant in view of forthcoming satellite hyperspectral missions. In the framework of the EU ERC Africa GHG grant #247349, an airborne campaign collecting lidar and hyperspectral data has been conducted in March 2012 over forests reserves in Sierra Leone and Ghana, characterized by different logging histories and rainfall patterns, and including Gola Rainforest National Park, Ankasa National Park, Bia and Boin Forest Reserves. An Optech Gemini sensor collected the lidar dataset, while an AISA Eagle sensor collected hyperspectral data over 244 VIS-NIR bands. The lidar dataset, with a point density >10 ppm was processed using the TIFFS software (Toolbox for LiDAR Data Filtering and Forest Studies)(Chen 2007). The hyperspectral dataset, geo

  4. Are Inventory Based and Remotely Sensed Above-Ground Biomass Estimates Consistent?

    PubMed Central

    Hill, Timothy C.; Williams, Mathew; Bloom, A. Anthony; Mitchard, Edward T. A.; Ryan, Casey M.

    2013-01-01

    Carbon emissions resulting from deforestation and forest degradation are poorly known at local, national and global scales. In part, this lack of knowledge results from uncertain above-ground biomass estimates. It is generally assumed that using more sophisticated methods of estimating above-ground biomass, which make use of remote sensing, will improve accuracy. We examine this assumption by calculating, and then comparing, above-ground biomass area density (AGBD) estimates from studies with differing levels of methodological sophistication. We consider estimates based on information from nine different studies at the scale of Africa, Mozambique and a 1160 km2 study area within Mozambique. The true AGBD is not known for these scales and so accuracy cannot be determined. Instead we consider the overall precision of estimates by grouping different studies. Since an the accuracy of an estimate cannot exceed its precision, this approach provides an upper limit on the overall accuracy of the group. This reveals poor precision at all scales, even between studies that are based on conceptually similar approaches. Mean AGBD estimates for Africa vary from 19.9 to 44.3 Mg ha−1, for Mozambique from 12.7 to 68.3 Mg ha−1, and for the 1160 km2 study area estimates range from 35.6 to 102.4 Mg ha−1. The original uncertainty estimates for each study, when available, are generally small in comparison with the differences between mean biomass estimates of different studies. We find that increasing methodological sophistication does not appear to result in improved precision of AGBD estimates, and moreover, inadequate estimates of uncertainty obscure any improvements in accuracy. Therefore, despite the clear advantages of remote sensing, there is a need to improve remotely sensed AGBD estimates if they are to provide accurate information on above-ground biomass. In particular, more robust and comprehensive uncertainty estimates are needed. PMID:24069275

  5. Latitudinal Characteristics of Below- and Above-ground Biomass of Typha: a Modelling Approach

    PubMed Central

    ASAEDA, TAKASHI; HAI, DINH NGOC; MANATUNGE, JAGATH; WILLIAMS, DAVID; ROBERTS, JANE

    2005-01-01

    • Background and Aims The latitudinal differences in the growth characteristics of Typha are largely unknown, although a number of studies have pointed out the effects of climate on the growth and productivity of Typha. Therefore, a dynamic growth model was developed for Typha to examine the effects of latitudinal changes in temperature and radiation on partitioning of the total biomass during the growing season into rhizomes, roots, flowering and vegetative shoots, and inflorescences. • Methods After validating the model with data from growth studies of Typha found in past literature, it was used to investigate the dynamics of above- and below-ground biomasses at three latitudes: 30°, 40° and 50°. • Key Results Regardless of the initial rhizome biomass, both above- and below-ground biomass values converged to a latitude-specific equilibrium produced by the balance between the total production and respiration and mortality losses. Above-ground biomass was high from 10° to 35° latitude with sufficient radiation, despite high metabolic losses; however, it decreased markedly at higher latitudes due to a low photosynthetic rate. Below-ground biomass, on the other hand, increased with latitude up to 40° due to decreasing metabolic losses, and then markedly decreased at higher latitudes. Above-ground biomass was enhanced with an increasing number of cohorts regardless of latitude. However, although more cohorts resulted in a larger below-ground biomass at low latitudes, the largest below-ground biomass was provided by a smaller number of cohorts at high latitudes. This difference is due to low production rates of late-season cohorts in high latitudes, compared with consumption for shooting and establishing foliage. • Conclusions The model could be used to predict the potential growth of Typha in given conditions over a wide range of latitudes and is useful for practical applications such as wetland management or wastewater treatment systems using Typha

  6. Phosphorus Concentrations in Above Ground Plant Biomass under Changing Climate Conditions

    NASA Astrophysics Data System (ADS)

    Selvin, C.; Paytan, A.; Roberts, K.

    2013-12-01

    The Jasper Ridge Global Change Experiment explores the effects of climate change on annual grasslands with different combinations of elevated or ambient levels of carbon dioxide, heat, precipitation, and nitrate deposition. The nested split-plot design allows for analysis of each variable, combinations of variables, and secondary effects. In this study, plant nutrient levels in homogenized above ground biomass are analyzed to assess the utility of this parameter as a tool to describe the response of an ecosystem to environmental changes. Total phosphorus concentrations showed considerable variability within treatment (n=8) and therefore no significant differences between treatments (n=16) is found. Carbon and nitrogen concentrations in bulk above ground biomass are being analyzed to determine nitrogen and carbon ratios and further elucidate the environmental response of phosphorus levels in plants to the modified parameters. P concentrations and elemental ratios will also be related to other parameters such as soil humidity, microbial biomass, enzyme activity, and plant diversity to determine the parameters influencing P content in the biomass.

  7. Spatial Structure of Above-Ground Biomass Limits Accuracy of Carbon Mapping in Rainforest but Large Scale Forest Inventories Can Help to Overcome

    PubMed Central

    Guitet, Stéphane; Hérault, Bruno; Molto, Quentin; Brunaux, Olivier; Couteron, Pierre

    2015-01-01

    Precise mapping of above-ground biomass (AGB) is a major challenge for the success of REDD+ processes in tropical rainforest. The usual mapping methods are based on two hypotheses: a large and long-ranged spatial autocorrelation and a strong environment influence at the regional scale. However, there are no studies of the spatial structure of AGB at the landscapes scale to support these assumptions. We studied spatial variation in AGB at various scales using two large forest inventories conducted in French Guiana. The dataset comprised 2507 plots (0.4 to 0.5 ha) of undisturbed rainforest distributed over the whole region. After checking the uncertainties of estimates obtained from these data, we used half of the dataset to develop explicit predictive models including spatial and environmental effects and tested the accuracy of the resulting maps according to their resolution using the rest of the data. Forest inventories provided accurate AGB estimates at the plot scale, for a mean of 325 Mg.ha-1. They revealed high local variability combined with a weak autocorrelation up to distances of no more than10 km. Environmental variables accounted for a minor part of spatial variation. Accuracy of the best model including spatial effects was 90 Mg.ha-1 at plot scale but coarse graining up to 2-km resolution allowed mapping AGB with accuracy lower than 50 Mg.ha-1. Whatever the resolution, no agreement was found with available pan-tropical reference maps at all resolutions. We concluded that the combined weak autocorrelation and weak environmental effect limit AGB maps accuracy in rainforest, and that a trade-off has to be found between spatial resolution and effective accuracy until adequate “wall-to-wall” remote sensing signals provide reliable AGB predictions. Waiting for this, using large forest inventories with low sampling rate (<0.5%) may be an efficient way to increase the global coverage of AGB maps with acceptable accuracy at kilometric resolution. PMID

  8. Spatial Structure of Above-Ground Biomass Limits Accuracy of Carbon Mapping in Rainforest but Large Scale Forest Inventories Can Help to Overcome.

    PubMed

    Guitet, Stéphane; Hérault, Bruno; Molto, Quentin; Brunaux, Olivier; Couteron, Pierre

    2015-01-01

    Precise mapping of above-ground biomass (AGB) is a major challenge for the success of REDD+ processes in tropical rainforest. The usual mapping methods are based on two hypotheses: a large and long-ranged spatial autocorrelation and a strong environment influence at the regional scale. However, there are no studies of the spatial structure of AGB at the landscapes scale to support these assumptions. We studied spatial variation in AGB at various scales using two large forest inventories conducted in French Guiana. The dataset comprised 2507 plots (0.4 to 0.5 ha) of undisturbed rainforest distributed over the whole region. After checking the uncertainties of estimates obtained from these data, we used half of the dataset to develop explicit predictive models including spatial and environmental effects and tested the accuracy of the resulting maps according to their resolution using the rest of the data. Forest inventories provided accurate AGB estimates at the plot scale, for a mean of 325 Mg.ha-1. They revealed high local variability combined with a weak autocorrelation up to distances of no more than10 km. Environmental variables accounted for a minor part of spatial variation. Accuracy of the best model including spatial effects was 90 Mg.ha-1 at plot scale but coarse graining up to 2-km resolution allowed mapping AGB with accuracy lower than 50 Mg.ha-1. Whatever the resolution, no agreement was found with available pan-tropical reference maps at all resolutions. We concluded that the combined weak autocorrelation and weak environmental effect limit AGB maps accuracy in rainforest, and that a trade-off has to be found between spatial resolution and effective accuracy until adequate "wall-to-wall" remote sensing signals provide reliable AGB predictions. Waiting for this, using large forest inventories with low sampling rate (<0.5%) may be an efficient way to increase the global coverage of AGB maps with acceptable accuracy at kilometric resolution. PMID:26402522

  9. Optimizing the number of training areas for modeling above-ground biomass with ALS and multispectral remote sensing in subtropical Nepal

    NASA Astrophysics Data System (ADS)

    Rana, Parvez; Gautam, Basanta; Tokola, Timo

    2016-07-01

    Remote sensing-based inventories of above-ground forest biomass (AGB) require a set of training plots representative of the area to be studied, the collection of which is the most expensive part of the analysis. These are time-consuming and costly because the large variety in forest conditions requires more plots to adequately capture this variability. A field campaign in general is challenging and is hampered by the complex topographic conditions, limited accessibility, steep mountainous terrains which increase labor efforts and costs. In addition it is also depend on the ratio between size of study area and number of training plots. In this study, we evaluate the number of training areas (sample size) required to estimate AGB for an area in the southern part of Nepal using airborne laser scanning (ALS), RapidEye and Landsat data. Three experiments were conducted: (i) AGB model performance, based on all the field training plots; (ii) reduction of the sample size, based on the ALS metrics and the AGB distribution; and (iii) prediction of the optimal number of training plots, based on the correlation between the remote sensing and field data. The AGB model was fitted using the sparse Bayesian method. AGB model performance was validated using an independent validation dataset. The effect of the strategies for reducing the sample size was readily apparent for the ALS-based AGB prediction, but the RapidEye and Landsat sensor data failed to capture any such effect. The results indicate that adequate coverage of the variability in tree height and density was an important condition for selecting the training plots. In addition, the ALS-based AGB prediction required the smallest number of training plots and was also quite stable with a small number of field plots.

  10. Assessing General Relationships Between Above-Ground Biomass and Vegetation Structure Parameters for Improved Carbon Estimate from Lidar Remote Sensing

    NASA Astrophysics Data System (ADS)

    Ni-Meister, W.; Lee, S.; Strahler, A. H.; Woodcock, C. E.; Schaaf, C.; Yao, T.; Ranson, J.; Sun, G.; Blair, J. B.

    2009-12-01

    Lidar remote sensing uses vegetation height to estimate large-scale above-ground biomass. However, lidar height and biomass relationships are empirical and thus often lead to large uncertainties in above-ground biomass estimates. This study uses vegetation structure measurements from field: an airborne lidar (Laser Vegetation Imaging Sensor, LVIS)) and a full wave form ground-based lidar (Echidna® validation instrument, EVI) collected in the New England region in 2003 and 2007, to investigate using additional vegetation structure parameters besides height for improved above-ground biomass estimation from lidar. Our field data analysis shows that using woody volume (approximated by the product of basal area and top 10% tree height) and vegetation type (conifer/softwood or deciduous/hardwood forests, providing wood density) has the potential to improve above-ground biomass estimates at large scale. This result is comparable to previous work by Chave et al. (2005), which focused on individual trees. However this study uses a slightly different approach, and our woody volume is estimated differently from Chave et al. (2005). Previous studies found that RH50 is a good predictor of above-ground biomass (Drake et al., 2002; 2003). Our LVIS data analysis shows that structure parameters that combine height and gap fraction, such as RH100*cover and RH50*cover, perform similarly or even better than RH50. We also found that the close relationship of RH100*cover and RH50*cover with woody volume explains why they are good predictors of above-ground biomass. RH50 is highly related to RH100*cover, and this explains why RH50 is a better predictor of biomass than RH100. This study shows that using structure parameters combining height and gap fraction improve above-ground biomass estimate compared to height alone, and fusion of lidar and optical remote sensing (to provide vegetation type) will provide better above-ground biomass estimates than lidar alone. Ground lidar analysis

  11. Sensitivity of Backscatter Intensity of ALOS/PALSAR to Above-ground Biomass and Other Biophysical Parameters of Boreal Forests in Alaska and Japan

    NASA Astrophysics Data System (ADS)

    Suzuki, R.; Hayashi, M.; Kim, Y.; Ishii, R.; Kobayashi, H.; Shoyama, K.; Adachi, M.; Takahashi, A.; Saigusa, N.; Ito, A.

    2012-12-01

    For the better understanding of the carbon cycle in the global environment, investigations on the spatio-temporal variation of the carbon stock which is stored as vegetation biomass is important. The backscatter intensity of "Phased Array type L-band Synthetic Aperture Radar (PALSAR)" onboard the satellite "Advanced Land Observing Satellite (ALOS)" provides us the information which is applicable to estimate the forest above-ground biomass (AGB). This study examines the sensitivity of the backscatter intensity of ALOS/PALSAR to the forest AGB and other biophysical parameters (tree height, tree diameter at breast height (DBH), and tree stand density) for boreal forests in two geographical regions of Alaska and Kushiro, northern Japan, and compares the sensitivities in two regions. In Alaska, a forest survey was executed in the south-north transect (about 300 km long) along a trans-Alaska pipeline which profiles the ecotone from the boreal forest to tundra in 2007. Forest AGBs and other biophysical parameters at 29 forests along the transect were measured by Bitterlich method. In Kushiro, a forest survey was carried out at 42 forests in 2011 and those parameters were similarly obtained by Bitterlich method. 20 and 2 scenes of ALOS/PALSAR FBD Level 1.5 data that cover the regions in Alaska and Kushiro, respectively, were collected and mosaicked. Backscatter intensities of ALOS/PALSAR in HH (horizontally polarized transmitted and horizontally polarized received) and HV (horizontally polarized transmitted and vertically polarized received) modes were compared with the forest AGB and other biophysical parameters. The intensity generally increased with the increase of those biophysical parameters in both HV and HH modes, but the intensity in HV mode generally had a stronger correlation to those parameters than in HH mode in both Alaska and Kushiro. The HV intensity had strong correlation to the forest AGB and DBH, while weak correlation to the tree stand density in Alaska

  12. [Vegetation above-ground biomass and its affecting factors in water/wind erosion crisscross region on Loess Plateau].

    PubMed

    Wang, Jian-guo; Fan, Jun; Wang, Quan-jiu; Wang, Li

    2011-03-01

    Field investigations were conducted in Liudaogou small watershed in late September 2009 to study the differences of vegetation above-ground biomass, soil moisture content, and soil nutrient contents under different land use patterns, aimed to approach the vegetation above-ground biomass level and related affecting factors in typical small watershed in water/wind erosion crisscross region on Loess Plateau. The above-ground dry biomass of the main vegetations in Liudaogou was 177-2207 g x m(-2), and that in corn field, millet field, abandoned farmland, artificial grassland, natural grassland, and shrub land was 2097-2207, 518-775, 248-578, 280-545, 177-396, and 372-680 g x m(-2), respectively. The mean soil moisture content in 0-100 layer was the highest (14.2%) in farmlands and the lowest (10.9%) in shrub land. The coefficient of variation of soil moisture content was the greatest (26. 7% ) in abandoned farmland, indicating the strong spatial heterogeneity of soil moisture in this kind of farmland. The mean soil water storage was in the order of farmland > artificial grassland > natural grassland > shrub land. Soil dry layer was observed in alfalfa and caragana lands. There was a significant positive correlation (r = 0.639, P < 0.05) between above-ground dry biomass and 0-100 cm soil water storage, and also, a very significant positive correlation between above-ground fresh biomass and vegetation height. The above-ground biomass of the higher vegetations could potentially better control the wind and water erosion in the water/wind erosion crisscross region. Vegetation above-ground biomass was highly correlated with soil moisture and nutrient contents, but had no significant correlations with elevation, slope gradient, slope aspect, and soil bulk density. PMID:21657007

  13. Above-ground biomass and carbon estimates of Shorea robusta and Tectona grandis forests using QuadPOL ALOS PALSAR data

    NASA Astrophysics Data System (ADS)

    Behera, M. D.; Tripathi, P.; Mishra, B.; Kumar, Shashi; Chitale, V. S.; Behera, Soumit K.

    2016-01-01

    Mechanisms to mitigate climate change in tropical countries such as India require information on forest structural components i.e., biomass and carbon for conservation steps to be implemented successfully. The present study focuses on investigating the potential use of a one time, QuadPOL ALOS PALSAR L-band 25 m data to estimate above-ground biomass (AGB) using a water cloud model (WCM) in a wildlife sanctuary in India. A significant correlation was obtained between the SAR-derived backscatter coefficient (σ°) and the field measured AGB, with the maximum coefficient of determination for cross-polarized (HV) σ° for Shorea robusta, and the weakest correlation was observed with co-polarized (HH) σ° for Tectona grandis forests. The biomass of S. robusta and that of T. grandis were estimated on the basis of field-measured data at 444.7 ± 170.4 Mg/ha and 451 ± 179.4 Mg/ha respectively. The mean biomass values estimated using the WCM varied between 562 and 660 Mg/ha for S. robusta; between 590 and 710 Mg/ha for T. grandis using various polarized data. Our results highlighted the efficacy of one time, fully polarized PALSAR data for biomass and carbon estimate in a dense forest.

  14. Modelling Growth and Partitioning of Annual Above-Ground Vegetative and Reproductive Biomass of Grapevine

    NASA Astrophysics Data System (ADS)

    Meggio, Franco; Vendrame, Nadia; Maniero, Giovanni; Pitacco, Andrea

    2014-05-01

    In the current climate change scenarios, both agriculture and forestry inherently may act as carbon sinks and consequently can play a key role in limiting global warming. An urgent need exists to understand which land uses and land resource types have the greatest potential to mitigate greenhouse gas (GHG) emissions contributing to global change. A common believe is that agricultural fields cannot be net carbon sinks due to many technical inputs and repeated disturbances of upper soil layers that all contribute to a substantial loss both of the old and newly-synthesized organic matter. Perennial tree crops (vineyards and orchards), however, can behave differently: they grow a permanent woody structure, stand undisturbed in the same field for decades, originate a woody pruning debris, and are often grass-covered. In this context, reliable methods for quantifying and modelling emissions and carbon sequestration are required. Carbon stock changes are calculated by multiplying the difference in oven dry weight of biomass increments and losses with the appropriate carbon fraction. These data are relatively scant, and more information is needed on vineyard management practices and how they impact vineyard C sequestration and GHG emissions in order to generate an accurate vineyard GHG footprint. During the last decades, research efforts have been made for estimating the vineyard carbon budget and its allocation pattern since it is crucial to better understand how grapevines control the distribution of acquired resources in response to variation in environmental growth conditions and agronomic practices. The objective of the present study was to model and compare the dynamics of current year's above-ground biomass among four grapevine varieties. Trials were carried out over three growing seasons in field conditions. The non-linear extra-sums-of-squares method demonstrated to be a feasible way of growth models comparison to statistically assess significant differences among

  15. Examining the potential of Sentinel-2 MSI spectral resolution in quantifying above ground biomass across different fertilizer treatments

    NASA Astrophysics Data System (ADS)

    Sibanda, Mbulisi; Mutanga, Onisimo; Rouget, Mathieu

    2015-12-01

    The major constraint in understanding grass above ground biomass variations using remotely sensed data are the expenses associated with the data, as well as the limited number of techniques that can be applied to different management practices with minimal errors. New generation multispectral sensors such as Sentinel 2 Multispectral Imager (MSI) are promising for effective rangeland management due to their unique spectral bands and higher signal to noise ratio. This study resampled hyperspectral data to spectral resolutions of the newly launched Sentinel 2 MSI and the recently launched Landsat 8 OLI for comparison purposes. Using Sparse partial least squares regression, the resampled data was applied in estimating above ground biomass of grasses treated with different fertilizer combinations of ammonium sulfate, ammonium nitrate, phosphorus and lime as well as unfertilized experimental plots. Sentinel 2 MSI derived models satisfactorily performed (R2 = 0.81, RMSEP = 1.07 kg/m2, RMSEP_rel = 14.97) in estimating grass above ground biomass across different fertilizer treatments relative to Landsat 8 OLI (Landsat 8 OLI: R2 = 0.76, RMSEP = 1.15 kg/m2, RMSEP_rel = 16.04). In comparison, hyperspectral data derived models exhibited better grass above ground biomass estimation across complex fertilizer combinations (R2 = 0.92, RMSEP = 0.69 kg/m2, RMSEP_rel = 9.61). Although Sentinel 2 MSI bands and indices better predicted above ground biomass compared with Landsat 8 OLI bands and indices, there were no significant differences (α = 0.05) in the errors of prediction between the two new generational sensors across all fertilizer treatments. The findings of this study portrays Sentinel 2 MSI and Landsat 8 OLI as promising remotely sensed datasets for regional scale biomass estimation, particularly in resource scarce areas.

  16. Development of a data driven process-based model for remote sensing of terrestrial ecosystem productivity, evapotranspiration, and above-ground biomass

    NASA Astrophysics Data System (ADS)

    El Masri, Bassil

    2011-12-01

    Modeling terrestrial ecosystem functions and structure has been a subject of increasing interest because of the importance of the terrestrial carbon cycle in global carbon budget and climate change. In this study, satellite data were used to estimate gross primary production (GPP), evapotranspiration (ET) for two deciduous forests: Morgan Monroe State forest (MMSF) in Indiana and Harvard forest in Massachusetts. Also, above-ground biomass (AGB) was estimated for the MMSF and the Howland forest (mixed forest) in Maine. Surface reflectance and temperature, vegetation indices, soil moisture, tree height and canopy area derived from the Moderate Resolution Imagining Spectroradiometer (MODIS), the Advanced Microwave Scanning Radiometer (AMRS-E), LIDAR, and aerial imagery respectively, were used for this purpose. These variables along with others derived from remotely sensed data were used as inputs variables to process-based models which estimated GPP and ET and to a regression model which estimated AGB. The process-based models were BIOME-BGC and the Penman-Monteith equation. Measured values for the carbon and water fluxes obtained from the Eddy covariance flux tower were compared to the modeled GPP and ET. The data driven methods produced good estimation of GPP and ET with an average root mean square error (RMSE) of 0.17 molC/m2 and 0.40 mm/day, respectively for the MMSF and the Harvard forest. In addition, allometric data for the MMSF were used to develop the regression model relating AGB with stem volume. The performance of the AGB regression model was compared to site measurements using remotely sensed data for the MMSF and the Howland forest where the model AGB RMSE ranged between 2.92--3.30 Kg C/m2. Sensitivity analysis revealed that improvement in maintenance respiration estimation and remotely sensed maximum photosynthetic activity as well as accurate estimate of canopy resistance will result in improved GPP and ET predictions. Moreover, AGB estimates were

  17. Estimating Mangrove Canopy Height and Above-Ground Biomass in Everglades National Park with Airbone LiDAR and TanDEM-X Data.

    NASA Astrophysics Data System (ADS)

    Feliciano, E. A.; Wdowinski, S.; Potts, M. D.; Fatoyinbo, T. E.; Lee, S. K.

    2014-12-01

    The coastal mangroves forests of Everglades National Park (ENP) are well protected from development. Nevertheless, climate change, hurricanes and other anthropogenic disturbances have affected these intertidal ecosystems. Understanding and monitoring forest structural parameters such as canopy height and above-ground biomass (AGB) are important for the establishment of an historical database for past, present and future ecosystem comparison. Forest canopy height has a well understood and directly proportional correlation with AGB. It is possible to derive it using (1) airborne LiDAR/Laser Scanning (ALS) or (2) space-borne radar systems such as Shuttle Radar Topography Mission (SRTM) and TanDEM-X (TDX). A previous study of the mangrove canopy height and AGB in the ENP was conducted a decade ago based on ALS data acquired in 2004 in conjunction with SRTM data, which were acquired in 2000 (Simard et al. 2006). In this study we estimated canopy height and AGB using an ALS dataset acquired in 2012 and TDX data acquired during the years 2012-2014. The ALS dataset was acquired along a 16.5 x 1.5 km swath of mangrove forest with variable canopy height. The sampled areas were representative of mangrove stature and structure in the whole ENP. Analysis of the ALS dataset showed that mangrove canopy height can reach up to ~25 meters close to the coastal ENP waters. Additionally, by comparing our ALS results with those of a previous study by Simard et al. (2006) we identified areas where mangrove height changes greater than ± 3 meters occurred. To expand the study area to the full ENP mangrove ecosystem we processed single-polarization TDX data to obtain a Digital Canopy Model (DCM) that represents the mangrove canopy height. In order to obtain the true canopy height we calibrated the TDX phase center height with ALS true canopy height. Preliminary results of a corrected single-polarized (HH) TDX scene show that mangrove canopy height can reach up to ~25 meters in the western

  18. Rapid assessment of above-ground biomass of Giant Reed using visibility estimates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method for the rapid estimation of biomass and density of giant reed (Arundo donax L.) was developed using estimates of visibility as a predictive tool. Visibility estimates were derived by capturing digital images of a 0.25 m2 polystyrene whiteboard placed a set distance (1m) from the edge of gia...

  19. Predictive modeling of hazardous waste landfill total above-ground biomass using passive optical and LIDAR remotely sensed data

    NASA Astrophysics Data System (ADS)

    Hadley, Brian Christopher

    This dissertation assessed remotely sensed data and geospatial modeling technique(s) to map the spatial distribution of total above-ground biomass present on the surface of the Savannah River National Laboratory's (SRNL) Mixed Waste Management Facility (MWMF) hazardous waste landfill. Ordinary least squares (OLS) regression, regression kriging, and tree-structured regression were employed to model the empirical relationship between in-situ measured Bahia (Paspalum notatum Flugge) and Centipede [Eremochloa ophiuroides (Munro) Hack.] grass biomass against an assortment of explanatory variables extracted from fine spatial resolution passive optical and LIDAR remotely sensed data. Explanatory variables included: (1) discrete channels of visible, near-infrared (NIR), and short-wave infrared (SWIR) reflectance, (2) spectral vegetation indices (SVI), (3) spectral mixture analysis (SMA) modeled fractions, (4) narrow-band derivative-based vegetation indices, and (5) LIDAR derived topographic variables (i.e. elevation, slope, and aspect). Results showed that a linear combination of the first- (1DZ_DGVI), second- (2DZ_DGVI), and third-derivative of green vegetation indices (3DZ_DGVI) calculated from hyperspectral data recorded over the 400--960 nm wavelengths of the electromagnetic spectrum explained the largest percentage of statistical variation (R2 = 0.5184) in the total above-ground biomass measurements. In general, the topographic variables did not correlate well with the MWMF biomass data, accounting for less than five percent of the statistical variation. It was concluded that tree-structured regression represented the optimum geospatial modeling technique due to a combination of model performance and efficiency/flexibility factors.

  20. A hyperspectral imaging system for an accurate prediction of the above-ground biomass of individual rice plants.

    PubMed

    Feng, Hui; Jiang, Ni; Huang, Chenglong; Fang, Wei; Yang, Wanneng; Chen, Guoxing; Xiong, Lizhong; Liu, Qian

    2013-09-01

    Biomass is an important component of the plant phenomics, and the existing methods for biomass estimation for individual plants are either destructive or lack accuracy. In this study, a hyperspectral imaging system was developed for the accurate prediction of the above-ground biomass of individual rice plants in the visible and near-infrared spectral region. First, the structure of the system and the influence of various parameters on the camera acquisition speed were established. Then the system was used to image 152 rice plants, which selected from the rice mini-core collection, in two stages, the tillering to elongation (T-E) stage and the booting to heading (B-H) stage. Several variables were extracted from the images. Following, linear stepwise regression analysis and 5-fold cross-validation were used to select effective variables for model construction and test the stability of the model, respectively. For the T-E stage, the R(2) value was 0.940 for the fresh weight (FW) and 0.935 for the dry weight (DW). For the B-H stage, the R(2) value was 0.891 for the FW and 0.783 for the DW. Moreover, estimations of the biomass using visible light images were also calculated. These comparisons showed that hyperspectral imaging performed better than the visible light imaging. Therefore, this study provides not only a stable hyperspectral imaging platform but also an accurate and nondestructive method for the prediction of biomass for individual rice plants. PMID:24089866

  1. Wildfires in bamboo-dominated Amazonian forest: impacts on above-ground biomass and biodiversity.

    PubMed

    Barlow, Jos; Silveira, Juliana M; Mestre, Luiz A M; Andrade, Rafael B; Camacho D'Andrea, Gabriela; Louzada, Julio; Vaz-de-Mello, Fernando Z; Numata, Izaya; Lacau, Sébastien; Cochrane, Mark A

    2012-01-01

    Fire has become an increasingly important disturbance event in south-western Amazonia. We conducted the first assessment of the ecological impacts of these wildfires in 2008, sampling forest structure and biodiversity along twelve 500 m transects in the Chico Mendes Extractive Reserve, Acre, Brazil. Six transects were placed in unburned forests and six were in forests that burned during a series of forest fires that occurred from August to October 2005. Normalized Burn Ratio (NBR) calculations, based on Landsat reflectance data, indicate that all transects were similar prior to the fires. We sampled understorey and canopy vegetation, birds using both mist nets and point counts, coprophagous dung beetles and the leaf-litter ant fauna. Fire had limited influence upon either faunal or floral species richness or community structure responses, and stems <10 cm DBH were the only group to show highly significant (p = 0.001) community turnover in burned forests. Mean aboveground live biomass was statistically indistinguishable in the unburned and burned plots, although there was a significant increase in the total abundance of dead stems in burned plots. Comparisons with previous studies suggest that wildfires had much less effect upon forest structure and biodiversity in these south-western Amazonian forests than in central and eastern Amazonia, where most fire research has been undertaken to date. We discuss potential reasons for the apparent greater resilience of our study plots to wildfire, examining the role of fire intensity, bamboo dominance, background rates of disturbance, landscape and soil conditions. PMID:22428035

  2. Wildfires in Bamboo-Dominated Amazonian Forest: Impacts on Above-Ground Biomass and Biodiversity

    PubMed Central

    Barlow, Jos; Silveira, Juliana M.; Mestre, Luiz A. M.; Andrade, Rafael B.; Camacho D'Andrea, Gabriela; Louzada, Julio; Vaz-de-Mello, Fernando Z.; Numata, Izaya; Lacau, Sébastien; Cochrane, Mark A.

    2012-01-01

    Fire has become an increasingly important disturbance event in south-western Amazonia. We conducted the first assessment of the ecological impacts of these wildfires in 2008, sampling forest structure and biodiversity along twelve 500 m transects in the Chico Mendes Extractive Reserve, Acre, Brazil. Six transects were placed in unburned forests and six were in forests that burned during a series of forest fires that occurred from August to October 2005. Normalized Burn Ratio (NBR) calculations, based on Landsat reflectance data, indicate that all transects were similar prior to the fires. We sampled understorey and canopy vegetation, birds using both mist nets and point counts, coprophagous dung beetles and the leaf-litter ant fauna. Fire had limited influence upon either faunal or floral species richness or community structure responses, and stems <10 cm DBH were the only group to show highly significant (p = 0.001) community turnover in burned forests. Mean aboveground live biomass was statistically indistinguishable in the unburned and burned plots, although there was a significant increase in the total abundance of dead stems in burned plots. Comparisons with previous studies suggest that wildfires had much less effect upon forest structure and biodiversity in these south-western Amazonian forests than in central and eastern Amazonia, where most fire research has been undertaken to date. We discuss potential reasons for the apparent greater resilience of our study plots to wildfire, examining the role of fire intensity, bamboo dominance, background rates of disturbance, landscape and soil conditions. PMID:22428035

  3. Testing the generality of above-ground biomass allometry across plant functional types at the continent scale.

    PubMed

    Paul, Keryn I; Roxburgh, Stephen H; Chave, Jerome; England, Jacqueline R; Zerihun, Ayalsew; Specht, Alison; Lewis, Tom; Bennett, Lauren T; Baker, Thomas G; Adams, Mark A; Huxtable, Dan; Montagu, Kelvin D; Falster, Daniel S; Feller, Mike; Sochacki, Stan; Ritson, Peter; Bastin, Gary; Bartle, John; Wildy, Dan; Hobbs, Trevor; Larmour, John; Waterworth, Rob; Stewart, Hugh T L; Jonson, Justin; Forrester, David I; Applegate, Grahame; Mendham, Daniel; Bradford, Matt; O'Grady, Anthony; Green, Daryl; Sudmeyer, Rob; Rance, Stan J; Turner, John; Barton, Craig; Wenk, Elizabeth H; Grove, Tim; Attiwill, Peter M; Pinkard, Elizabeth; Butler, Don; Brooksbank, Kim; Spencer, Beren; Snowdon, Peter; O'Brien, Nick; Battaglia, Michael; Cameron, David M; Hamilton, Steve; McAuthur, Geoff; Sinclair, Jenny

    2016-06-01

    Accurate ground-based estimation of the carbon stored in terrestrial ecosystems is critical to quantifying the global carbon budget. Allometric models provide cost-effective methods for biomass prediction. But do such models vary with ecoregion or plant functional type? We compiled 15 054 measurements of individual tree or shrub biomass from across Australia to examine the generality of allometric models for above-ground biomass prediction. This provided a robust case study because Australia includes ecoregions ranging from arid shrublands to tropical rainforests, and has a rich history of biomass research, particularly in planted forests. Regardless of ecoregion, for five broad categories of plant functional type (shrubs; multistemmed trees; trees of the genus Eucalyptus and closely related genera; other trees of high wood density; and other trees of low wood density), relationships between biomass and stem diameter were generic. Simple power-law models explained 84-95% of the variation in biomass, with little improvement in model performance when other plant variables (height, bole wood density), or site characteristics (climate, age, management) were included. Predictions of stand-based biomass from allometric models of varying levels of generalization (species-specific, plant functional type) were validated using whole-plot harvest data from 17 contrasting stands (range: 9-356 Mg ha(-1) ). Losses in efficiency of prediction were <1% if generalized models were used in place of species-specific models. Furthermore, application of generalized multispecies models did not introduce significant bias in biomass prediction in 92% of the 53 species tested. Further, overall efficiency of stand-level biomass prediction was 99%, with a mean absolute prediction error of only 13%. Hence, for cost-effective prediction of biomass across a wide range of stands, we recommend use of generic allometric models based on plant functional types. Development of new species

  4. Using multi-frequency radar and discrete-return LiDAR measurements to estimate above-ground biomass and biomass components in a coastal temperate forest

    NASA Astrophysics Data System (ADS)

    Tsui, Olivier W.; Coops, Nicholas C.; Wulder, Michael A.; Marshall, Peter L.; McCardle, Adrian

    2012-04-01

    Height measurements from small-footprint discrete-return LiDAR and backscatter coefficients from C- and L-band radar were used independently and in combination to estimate above-ground component and total biomass for a coniferous temperate forest, located on Vancouver Island, British Columbia, Canada. Reference biomass data were obtained from plot-level data and used for comparison against the LiDAR and radar-based biomass models. For the LiDAR-only model, height metrics such as mean first return height and percentiles (e.g., 10th and 90th) of first returns correlated best to total above-ground and stem biomass. While percent of first returns above 2 m and percentiles (75th and 90th) of first returns height metrics correlated best to crown biomass. A comparison between above-ground components and total biomass indicate that stem biomass displayed the highest relationship with the LiDAR measurements while crown biomass showed the lowest relationship with relative root mean squared error ranging from 16% to 22%, respectively. Alternatively, the radar-only models indicated that for C-band radar, a combination of HH and VV backscatter demonstrated the most significant correlation with forest biomass compared to coherence based models with a relative root mean squared error of 53%. For L-band radar, a combination of HH and HV backscatter showed the most significant correlation compared to coherence based models with a relative root mean squared error of 44%. Exploring a mixture of C- and L-band backscatter and coherence based models revealed that a combination of C-HV and L-HV coherence magnitudes provided the best radar relationship with forest biomass with a relative root mean squared error of 35%. Also for all radar-based models, L- and C-band backscatter and coherence magnitudes were poorly correlated with individual biomass components when compared to total above-ground biomass. The addition of C- and L-band backscatter and coherence variables to the Li

  5. Interactive effects of frequent burning and timber harvesting on above ground carbon biomass in temperate eucalypt forests

    NASA Astrophysics Data System (ADS)

    Collins, Luke; Penman, Trent; Ximenes, Fabiano; Bradstock, Ross

    2015-04-01

    The sequestration of carbon has been identified as an important strategy to mitigate the effects of climate change. Fuel reduction burning and timber harvesting are two common co-occurring management practices within forests. Frequent burning and timber harvesting may alter forest carbon pools through the removal and redistribution of biomass and demographic and structural changes to tree communities. Synergistic and antagonistic interactions between frequent burning and harvesting are likely to occur, adding further complexity to the management of forest carbon stocks. Research aimed at understanding the interactive effects of frequent fire and timber harvesting on carbon biomass is lacking. This study utilised data from two long term (25 - 30 years) manipulative burning experiments conducted in southern Australia in temperate eucalypt forests dominated by resprouting canopy species. Specifically we examined the effect of fire frequency and harvesting on (i) total biomass of above ground carbon pools and (ii) demographic and structural characteristics of live trees. We also investigated some of the mechanisms driving these changes. Frequent burning reduced carbon biomass by up to 20% in the live tree carbon pool. Significant interactions occurred between fire and harvesting, whereby the reduction in biomass of trees >20 cm diameter breast height (DBH) was amplified by increased fire frequency. The biomass of trees <20 cm DBH increased with harvesting intensity in frequently burnt areas, but was unaffected by harvesting intensity in areas experiencing low fire frequency. Biomass of standing and fallen coarse woody debris was relatively unaffected by logging and fire frequency. Fire and harvesting significantly altered stand structure over the study period. Comparison of pre-treatment conditions to current conditions revealed that logged sites had a significantly greater increase in the number of small trees (<40 cm DBH) than unlogged sites. Logged sites showed a

  6. Lasting effects of climate disturbance on perennial grassland above-ground biomass production under two cutting frequencies.

    PubMed

    Zwicke, Marine; Alessio, Giorgio A; Thiery, Lionel; Falcimagne, Robert; Baumont, René; Rossignol, Nicolas; Soussana, Jean-François; Picon-Cochard, Catherine

    2013-11-01

    Climate extremes can ultimately reshape grassland services such as forage production and change plant functional type composition. This 3-year field research studied resistance to dehydration and recovery after rehydration of plant community and plant functional types in an upland perennial grassland subjected to climate and cutting frequency (Cut+, Cut-) disturbances by measuring green tissue percentage and above-ground biomass production (ANPP). In year 1, a climate disturbance gradient was applied by co-manipulating temperature and precipitation. Four treatments were considered: control and warming-drought climatic treatment, with or without extreme summer event. In year 2, control and warming-drought treatments were maintained without extreme. In year 3, all treatments received ambient climatic conditions. We found that the grassland community was very sensitive to dehydration during the summer extreme: aerial senescence reached 80% when cumulated climatic water balance fell to -156 mm and biomass declined by 78% at the end of summer. In autumn, canopy greenness and biomass totally recovered in control but not in the warming-drought treatment. However ANPP decreased under both climatic treatments, but the effect was stronger on Cut+ (-24%) than Cut- (-15%). This decline was not compensated by the presence of three functional types because they were negatively affected by the climatic treatments, suggesting an absence of buffering effect on grassland production. In the following 2 years, lasting effects of climate disturbance on ANPP were observable. The unexpected stressful conditions of year 3 induced a decline in grassland production in the Cut+ control treatment. The fact that this treatment cumulated higher (45%) N export over the 3 years suggests that N plays a key role in ANPP stability. As ANPP in this mesic perennial grassland did not show engineering resilience, long-term experimental manipulation is needed. Infrequent mowing appears more

  7. Influence of landscape heterogeneity on spatial patterns of wood productivity, wood specific density and above ground biomass in Amazonia

    NASA Astrophysics Data System (ADS)

    Anderson, L. O.; Malhi, Y.; Ladle, R. J.; Aragão, L. E. O. C.; Shimabukuro, Y.; Phillips, O. L.; Baker, T.; Costa, A. C. L.; Espejo, J. S.; Higuchi, N.; Laurance, W. F.; López-González, G.; Monteagudo, A.; Núñez-Vargas, P.; Peacock, J.; Quesada, C. A.; Almeida, S.

    2009-09-01

    Long-term studies using the RAINFOR network of forest plots have generated significant insights into the spatial and temporal dynamics of forest carbon cycling in Amazonia. In this work, we map and explore the landscape context of several major RAINFOR plot clusters using Landsat ETM+ satellite data. In particular, we explore how representative the plots are of their landscape context, and test whether bias in plot location within landscapes may be influencing the regional mean values obtained for important forest biophysical parameters. Specifically, we evaluate whether the regional variations in wood productivity, wood specific density and above ground biomass derived from the RAINFOR network could be driven by systematic and unintentional biases in plot location. Remote sensing data covering 45 field plots were aggregated to generate landscape maps to identify the specific physiognomy of the plots. In the Landsat ETM+ data, it was possible to spectrally differentiate three types of terra firme forest, three types of forests over Paleovarzea geomorphologycal formation, two types of bamboo-dominated forest, palm forest, Heliconia monodominant vegetation, swamp forest, disturbed forests and land use areas. Overall, the plots were generally representative of the forest physiognomies in the landscape in which they are located. Furthermore, the analysis supports the observed regional trends in those important forest parameters. This study demonstrates the utility of landscape scale analysis of forest physiognomies for validating and supporting the finds of plot based studies. Moreover, the more precise geolocation of many key RAINFOR plot clusters achieved during this research provides important contextual information for studies employing the RAINFOR database.

  8. Influence of landscape heterogeneity on spatial patterns of wood productivity, wood specific density and above ground biomass in Amazonia

    NASA Astrophysics Data System (ADS)

    Anderson, L. O.; Malhi, Y.; Ladle, R. J.; Aragão, L. E. O. C.; Shimabukuro, Y.; Phillips, O. L.; Baker, T.; Costa, A. C. L.; Espejo, J. S.; Higuchi, N.; Laurance, W. F.; López-González, G.; Monteagudo, A.; Núñez-Vargas, P.; Peacock, J.; Quesada, C. A.; Almeida, S.; Vásquez, R.

    2009-02-01

    Long-term studies using the RAINFOR network of forest plots have generated significant insights into the spatial and temporal dynamics of forest carbon cycling in Amazonia. In this work, we map and explore the landscape context of several major RAINFOR plot clusters using Landsat ETM+ satellite data. In particular, we explore how representative the plots are of their landscape context, and test whether bias in plot location within landscapes may be influencing the regional mean values obtained for important forest biophysical parameters. Specifically, we evaluate whether the regional variations in wood productivity, wood specific density and above ground biomass derived from the RAINFOR network could be driven by systematic and unintentional biases in plot location. Remote sensing data covering 45 field plots were aggregated to generate landscape maps to identify the specific physiognomy of the plots. In the Landsat ETM+ data, it was possible to spectrally differentiate three types of terra firme forest, three types of alluvial terrain forest, two types of bamboo-dominated forest, palm forest, Heliconia monodominant vegetation, swamp forest, disturbed forests and land use areas. Overall, the plots were generally representative of the forest physiognomies in the landscape in which they are located. Furthermore, the analysis supports the observed regional trends in those important forest parameters. This study demonstrates the utility of landscape scale analysis of forest physiognomies for validating and supporting the finds of plot based studies. Moreover, the more precise geolocation of many key RAINFOR plot clusters achieved during this research provides important contextual information for studies employing the RAINFOR database.

  9. A Comparison of Two Above-Ground Biomass Estimation Techniques Integrating Satellite-Based Remotely Sensed Data and Ground Data for Tropical and Semiarid Forests in Puerto Rico

    EPA Science Inventory

    Two above-ground forest biomass estimation techniques were evaluated for the United States Territory of Puerto Rico using predictor variables acquired from satellite based remotely sensed data and ground data from the U.S. Department of Agriculture Forest Inventory Analysis (FIA)...

  10. Diversity and Above-Ground Biomass Patterns of Vascular Flora Induced by Flooding in the Drawdown Area of China's Three Gorges Reservoir

    PubMed Central

    Wang, Qiang; Yuan, Xingzhong; Willison, J.H.Martin; Zhang, Yuewei; Liu, Hong

    2014-01-01

    Hydrological alternation can dramatically influence riparian environments and shape riparian vegetation zonation. However, it was difficult to predict the status in the drawdown area of the Three Gorges Reservoir (TGR), because the hydrological regime created by the dam involves both short periods of summer flooding and long-term winter impoundment for half a year. In order to examine the effects of hydrological alternation on plant diversity and biomass in the drawdown area of TGR, twelve sites distributed along the length of the drawdown area of TGR were chosen to explore the lateral pattern of plant diversity and above-ground biomass at the ends of growing seasons in 2009 and 2010. We recorded 175 vascular plant species in 2009 and 127 in 2010, indicating that a significant loss of vascular flora in the drawdown area of TGR resulted from the new hydrological regimes. Cynodon dactylon and Cyperus rotundus had high tolerance to short periods of summer flooding and long-term winter flooding. Almost half of the remnant species were annuals. Species richness, Shannon-Wiener Index and above-ground biomass of vegetation exhibited an increasing pattern along the elevation gradient, being greater at higher elevations subjected to lower submergence stress. Plant diversity, above-ground biomass and species distribution were significantly influenced by the duration of submergence relative to elevation in both summer and previous winter. Several million tonnes of vegetation would be accumulated on the drawdown area of TGR in every summer and some adverse environmental problems may be introduced when it was submerged in winter. We conclude that vascular flora biodiversity in the drawdown area of TGR has dramatically declined after the impoundment to full capacity. The new hydrological condition, characterized by long-term winter flooding and short periods of summer flooding, determined vegetation biodiversity and above-ground biomass patterns along the elevation gradient in

  11. A comparison of two above-ground biomass estimation techniques integrating satellite-based remotely sensed data and ground data for tropical and semiarid forests in Puerto Rico

    NASA Astrophysics Data System (ADS)

    Iiames, J. S.; Riegel, J.; Lunetta, R.

    2013-12-01

    Two above-ground forest biomass estimation techniques were evaluated for the United States Territory of Puerto Rico using predictor variables acquired from satellite based remotely sensed data and ground data from the U.S. Department of Agriculture Forest Inventory Analysis (FIA) program. The U.S. Environmental Protection Agency (EPA) estimated above-ground forest biomass implementing methodology first posited by the Woods Hole Research Center developed for conterminous United States (National Biomass and Carbon Dataset [NBCD2000]). For EPA's effort, spatial predictor layers for above-ground biomass estimation included derived products from the U.S. Geologic Survey (USGS) National Land Cover Dataset 2001 (NLCD) (landcover and canopy density), the USGS Gap Analysis Program (forest type classification), the USGS National Elevation Dataset, and the NASA Shuttle Radar Topography Mission (tree heights). In contrast, the U.S. Forest Service (USFS) biomass product integrated FIA ground-based data with a suite of geospatial predictor variables including: (1) the Moderate Resolution Imaging Spectrometer (MODIS)-derived image composites and percent tree cover; (2) NLCD land cover proportions; (3) topographic variables; (4) monthly and annual climate parameters; and (5) other ancillary variables. Correlations between both data sets were made at variable watershed scales to test level of agreement. Notice: This work is done in support of EPA's Sustainable Healthy Communities Research Program. The U.S EPA funded and conducted the research described in this paper. Although this work was reviewed by the EPA and has been approved for publication, it may not necessarily reflect official Agency policy. Mention of any trade names or commercial products does not constitute endorsement or recommendation for use.

  12. Forest above ground biomass estimation and forest/non-forest classification for Odisha, India, using L-band Synthetic Aperture Radar (SAR) data

    NASA Astrophysics Data System (ADS)

    Suresh, M.; Kiran Chand, T. R.; Fararoda, R.; Jha, C. S.; Dadhwal, V. K.

    2014-11-01

    Tropical forests contribute to approximately 40 % of the total carbon found in terrestrial biomass. In this context, forest/non-forest classification and estimation of forest above ground biomass over tropical regions are very important and relevant in understanding the contribution of tropical forests in global biogeochemical cycles, especially in terms of carbon pools and fluxes. Information on the spatio-temporal biomass distribution acts as a key input to Reducing Emissions from Deforestation and forest Degradation Plus (REDD+) action plans. This necessitates precise and reliable methods to estimate forest biomass and to reduce uncertainties in existing biomass quantification scenarios. The use of backscatter information from a host of allweather capable Synthetic Aperture Radar (SAR) systems during the recent past has demonstrated the potential of SAR data in forest above ground biomass estimation and forest / nonforest classification. In the present study, Advanced Land Observing Satellite (ALOS) / Phased Array L-band Synthetic Aperture Radar (PALSAR) data along with field inventory data have been used in forest above ground biomass estimation and forest / non-forest classification over Odisha state, India. The ALOSPALSAR 50 m spatial resolution orthorectified and radiometrically corrected HH/HV dual polarization data (digital numbers) for the year 2010 were converted to backscattering coefficient images (Schimada et al., 2009). The tree level measurements collected during field inventory (2009-'10) on Girth at Breast Height (GBH at 1.3 m above ground) and height of all individual trees at plot (plot size 0.1 ha) level were converted to biomass density using species specific allometric equations and wood densities. The field inventory based biomass estimations were empirically integrated with ALOS-PALSAR backscatter coefficients to derive spatial forest above ground biomass estimates for the study area. Further, The Support Vector Machines (SVM) based Radial

  13. The response of tundra plant biomass, above-ground production, nitrogen, and CO{sub 2} flux to experimental warming

    SciTech Connect

    Hobbie, S.E.; Chapin, F.S. III

    1998-07-01

    The authors manipulated air temperature in tussock tundra near Toolik Lake, Alaska, and determined the consequences for total plant biomass, aboveground net primary production (ANPP), ecosystem nitrogen (N) pools and N uptake, and ecosystem CO{sub 2} flux. After 3.5 growing seasons, in situ plastic greenhouses that raised air temperature during the growing season had little effect on total biomass, N content, or growing-season N uptake of the major plant and soil pools. Similarly, vascular ANPP and net ecosystem CO{sub 2} exchange did not change with warming, although net primary production of mosses decreased with warming. Such general lack of response supports the hypothesis that productivity in tundra is constrained by the indirect effects of cold temperatures rather than by cold growing-season temperatures per se. Despite no effect on net ecosystem CO{sub 2} flux, air warming stimulated early-season gross photosynthesis (GP) and ecosystem respiration (ER) throughout the growing season. This increased carbon turnover was probably associated with species-level responses to increased air temperature. Warming increased the aboveground biomass of the overstory shrub, dwarf birch (Betula nana), and caused a significant net redistribution of N from the understory evergreen shrub, Vaccinium vitis-idaea, to B. nana, despite no effects on soil temperature, total plant N, or N availability.

  14. Soil water content and patterns of allocation to below- and above-ground biomass in the sexes of the subdioecious plant Honckenya peploides

    PubMed Central

    Sánchez-Vilas, Julia; Bermúdez, Raimundo; Retuerto, Rubén

    2012-01-01

    Background and aims Dioecious plants often show sex-specific differences in growth and biomass allocation. These differences have been explained as a consequence of the different reproductive functions performed by the sexes. Empirical evidence strongly supports a greater reproductive investment in females. Sex differences in allocation may determine the performance of each sex in different habitats and therefore might explain the spatial segregation of the sexes described in many dimorphic plants. Here, an investigation was made of the sexual dimorphism in seasonal patterns of biomass allocation in the subdioecious perennial herb Honckenya peploides, a species that grows in embryo dunes (i.e. the youngest coastal dune formation) and displays spatial segregation of the sexes at the studied site. The water content in the soil of the male- and female-plant habitats at different times throughout the season was also examined. Methods The seasonal patterns of soil-water availability and biomass allocation were compared in two consecutive years in male and female H. peploides plants by collecting soil and plant samples in natural populations. Vertical profiles of below-ground biomass and water content were studied by sampling soil in male- and female-plant habitats at different soil depths. Key Results The sexes of H. peploides differed in their seasonal patterns of biomass allocation to reproduction. Males invested twice as much in reproduction than females early in the season, but sexual differences became reversed as the season progressed. No differences were found in above-ground biomass between the sexes, but the allocation of biomass to below-ground structures varied differently in depth for males and females, with females usually having greater below-ground biomass than males. In addition, male and female plants of H. peploides had different water-content profiles in the soil where they were growing and, when differences existed (usually in the upper layers of the

  15. Top-down and bottom-up inventory approach for above ground forest biomass and carbon monitoring in REDD framework using multi-resolution satellite data.

    PubMed

    Sharma, Laxmi Kant; Nathawat, Mahendra Singh; Sinha, Suman

    2013-10-01

    This study deals with the future scope of REDD (Reduced Emissions from Deforestation and forest Degradation) and REDD+ regimes for measuring and monitoring the current state and dynamics of carbon stocks over time with integrated geospatial and field-based biomass inventory approach. Multi-temporal and multi-resolution geospatial synergic approach incorporating satellite sensors from moderate to high resolution with stratified random sampling design is used. The inventory process involves a continuous forest inventory to facilitate the quantification of possible CO2 reductions over time using statistical up-scaling procedures on various levels. The combined approach was applied on a regional scale taking Himachal Pradesh (India), as a case study, with a hierarchy of forest strata representing the forest structure found in India. Biophysical modeling implemented revealed power regression model as the best fit (R (2) = 0.82) to model the relationship between Normalized Difference Vegetation Index and biomass which was further implemented to calculate multi-temporal above ground biomass and carbon sequestration. The calculated value of net carbon sequestered by the forests totaled to 11.52 million tons (Mt) over the period of 20 years at the rate of 0.58 Mt per year since 1990 while CO2 equivalent reduced from the environment by the forests under study during 20 years comes to 42.26 Mt in the study area. PMID:23604728

  16. Storage tanks: Going above ground

    SciTech Connect

    Wilson, T.C. )

    1994-03-01

    This article examines the trend toward above ground storage tanks for petroleum products and certain hazardous substances. The topics of the article include the advantages and disadvantages of above ground storage tanks, regulations for use of above ground storage tanks, design options, safety issues, and a description of typical users of above ground storage tanks.

  17. Structural, physiognomic and above-ground biomass variation in savanna-forest transition zones on three continents - how different are co-occurring savanna and forest formations?

    NASA Astrophysics Data System (ADS)

    Veenendaal, E. M.; Torello-Raventos, M.; Feldpausch, T. R.; Domingues, T. F.; Gerard, F.; Schrodt, F.; Saiz, G.; Quesada, C. A.; Djagbletey, G.; Ford, A.; Kemp, J.; Marimon, B. S.; Marimon-Junior, B. H.; Lenza, E.; Ratter, J. A.; Maracahipes, L.; Sasaki, D.; Sonke, B.; Zapfack, L.; Villarroel, D.; Schwarz, M.; Yoko Ishida, F.; Gilpin, M.; Nardoto, G. B.; Affum-Baffoe, K.; Arroyo, L.; Bloomfield, K.; Ceca, G.; Compaore, H.; Davies, K.; Diallo, A.; Fyllas, N. M.; Gignoux, J.; Hien, F.; Johnson, M.; Mougin, E.; Hiernaux, P.; Killeen, T.; Metcalfe, D.; Miranda, H. S.; Steininger, M.; Sykora, K.; Bird, M. I.; Grace, J.; Lewis, S.; Phillips, O. L.; Lloyd, J.

    2015-05-01

    Through interpretations of remote-sensing data and/or theoretical propositions, the idea that forest and savanna represent "alternative stable states" is gaining increasing acceptance. Filling an observational gap, we present detailed stratified floristic and structural analyses for forest and savanna stands located mostly within zones of transition (where both vegetation types occur in close proximity) in Africa, South America and Australia. Woody plant leaf area index variation was related to tree canopy cover in a similar way for both savanna and forest with substantial overlap between the two vegetation types. As total woody plant canopy cover increased, so did the relative contribution of middle and lower strata of woody vegetation. Herbaceous layer cover declined as woody cover increased. This pattern of understorey grasses and herbs progressively replaced by shrubs as the canopy closes over was found for both savanna and forests and on all continents. Thus, once subordinate woody canopy layers are taken into account, a less marked transition in woody plant cover across the savanna-forest-species discontinuum is observed compared to that inferred when trees of a basal diameter > 0.1 m are considered in isolation. This is especially the case for shrub-dominated savannas and in taller savannas approaching canopy closure. An increased contribution of forest species to the total subordinate cover is also observed as savanna stand canopy closure occurs. Despite similarities in canopy-cover characteristics, woody vegetation in Africa and Australia attained greater heights and stored a greater amount of above-ground biomass than in South America. Up to three times as much above-ground biomass is stored in forests compared to savannas under equivalent climatic conditions. Savanna-forest transition zones were also found to typically occur at higher precipitation regimes for South America than for Africa. Nevertheless, consistent across all three continents coexistence

  18. Impacts of cattle grazing on spatio-temporal variability of soil moisture and above-ground live plant biomass in mixed grasslands

    NASA Astrophysics Data System (ADS)

    Virk, Ravinder

    Areas with relatively high spatial heterogeneity generally have more biodiversity than spatially homogeneous areas due to increased potential habitat. Management practices such as controlled grazing also affect the biodiversity in grasslands, but the nature of this impact is not well understood. Therefore this thesis studies the impacts of variation in grazing on soil moisture and biomass heterogeneity. These are not only important in terms of management of protected grasslands, but also for designing an effective grazing system from a livestock management point of view. This research is a part of the cattle grazing experiment underway in Grasslands National Park (GNP) of Canada since 2006, as part of the adaptive management process for restoring ecological integrity of the northern mixed-grass prairie region. An experimental approach using field measurements and remote sensing (Landsat) was combined with modelling (CENTURY) to examine and predict the impacts of grazing intensity on the spatial heterogeneity and patterns of above-ground live plant biomass (ALB) in experimental pastures in a mixed grassland ecosystem. The field-based research quantified the temporal patterns and spatial variability in both soil moisture (SM) and ALB, and the influence of local intra-seasonal weather variability and slope location on the spatio-temporal variability of SM and ALB at field plot scales. Significant impacts of intra-seasonal weather variability, slope position and grazing pressure on SM and ALB across a range of scales (plot and local (within pasture)) were found. Grazing intensity significantly affected the ALB even after controlling for the effect of slope position. Satellite-based analysis extended the scale of interest to full pastures and the surrounding region to assess the effects of grazing intensity on the spatio-temporal pattern of ALB in mixed grasslands. Overall, low to moderate grazing intensity showed increase in ALB heterogeneity whereas no change in ALB

  19. Estimating Above-Ground Biomass Within the Footprint of an Eddy-Covariance Flux Tower: Continuous LiDAR Based Estimates Compared With Discrete Inventory and Disturbance History Based Stratification Boundaries

    NASA Astrophysics Data System (ADS)

    Ferster, C. J.; Trofymow, J. A.; Coops, N. C.; Chen, B.; Black, T. A.

    2008-12-01

    Eddy-covariance (EC) flux towers provide data about carbon (C) exchange between land and the atmosphere at an ecosystem scale. However, important research questions need to be addressed when placing EC flux towers in complex heterogeneous forest landscapes, such as the coastal forests of Western Canada. Recently available footprint analysis, which describes the contribution function and catchment area where EC flux is being measured, can be used to relate EC flux tower measurements with the biological structure and carbon stock distributions of complex forest landscapes. In this study, above ground biomass is estimated near an EC flux tower using two approaches. In the first approach, a remote sensing based surface representing above ground biomass was estimated using small footprint, discrete return, light detection and ranging (LiDAR) data. Plot level LiDAR metrics were supplemented with metrics calculated using individual tree detection. A multiple regression model was developed to estimate above ground biomass using ground plot and LiDAR data, and then the model was applied across the EC flux footprint area to estimate the spatial distribution of above ground biomass. In the second approach, line boundaries from forest inventory, disturbance history, and site series were used to delineate discrete stratification units and the measured groundplot data assigned to the various strata. Within the heterogeneous tower footprint area, footprint weighting allows us to compare and contrast above ground biomass estimates from these two approaches. Using this methodology we then plan to compare, for the same period, ground-based measurements of ecosystem C stock changes with accumulative EC measured net ecosystem C flux.

  20. LINE-ABOVE-GROUND ATTENUATOR

    DOEpatents

    Wilds, R.B.; Ames, J.R.

    1957-09-24

    The line-above-ground attenuator provides a continuously variable microwave attenuator for a coaxial line that is capable of high attenuation and low insertion loss. The device consists of a short section of the line-above- ground plane type transmission lime, a pair of identical rectangular slabs of lossy material like polytron, whose longitudinal axes are parallel to and indentically spaced away from either side of the line, and a geared mechanism to adjust amd maintain this spaced relationship. This device permits optimum fineness and accuracy of attenuator control which heretofore has been difficult to achieve.

  1. Comparing the above-ground component biomass estimates of western junipers using airborne and full-waveform terrestrial laser scanning data

    NASA Astrophysics Data System (ADS)

    Shrestha, R.; Glenn, N. F.; Spaete, L.; Hardegree, S. P.

    2012-12-01

    With the rapid expansion into shrub steppe and grassland ecosystems over the last century, western juniper (Juniperus occidentalis var. occidentalis Hook) is becoming a major component of the regional carbon pool in the Intermountain West. Understanding how biomass is allocated across individual tree components is necessary to understand the uncertainties in biomass estimates and more accurately quantify biomass and carbon dynamics in these ecosystems. Estimates of component biomass are also important for canopy fuel load assessment and predicting rangeland fire behavior. Airborne LiDAR can capture vegetation structure over larger scales, but the high crown penetration and sampling density of terrestrial laser scanner (TLS) instruments can better capture tree components. In this study, we assessed the ability of airborne LiDAR to estimate biomass of tree components of western juniper with validation data from field measured tees and a full-waveform TLS. Sixteen juniper trees (height range 1.5-10 m) were randomly selected using a double sampling strategy from different height classes in the Reynolds Creek Experimental Watershed in the Owyhee Mountains, southwestern Idaho, USA. Each tree was scanned with a full-waveform TLS, and the dry biomass of each component (foliage, branches and main stem) were measured by destructive harvesting of the trees. We compare the allometric relationships of biomass estimates of the tree components obtained from field-measured trees and TLS-based estimates with the estimates from discrete-return airborne-LiDAR based estimates.

  2. Evaluating Post-fire Ecosystem Effects in Tussock Tundra of the Seward Peninsula: Characterizing Above-ground Biomass Accumulation, Soil Nutrient Pools, and Foliar Nitrogen.

    NASA Astrophysics Data System (ADS)

    Hollingsworth, T. N.; Mack, M. C.; Breen, A. L.

    2014-12-01

    Over the last century in the circumpolar north, changes in vegetation include shrub cover expansion and shifts in tree line. Invasion of tundra by trees and shrubs may be further facilitated by wildfire disturbance, which creates opportunities for establishment where recruitment is otherwise rare. Even moderate increases in warm-season temperatures are predicted to increase the likelihood of tundra fires. Understanding the consequences of a change in fire regime are complicated by the fact that there are relatively few large recent fires to study. However, the Seward Peninsula is a region that currently experiences more frequent and large fires than other tundra regions in Arctic Alaska. In this tundra region, there are areas of overlapping burns dating back to the 1970s. Using a chronosequence approach, we looked at post-fire biomass accumulation as well as foliar and soil C and N. Our experimental design incorporated sites that showed no evidence of recent burning, sites that burned in 1971, 1997, 2002, and 2011 as well as sites that burned multiple times over the last 30 years. We found that fire had a significant effect on total biomass and shrub basal area in tussock tundra. Our site that burned in 2011 had the lowest total biomass, about half of the biomass of our unburned site. However, our results indicated the site that burned in 1971 had over double the aboveground biomass and more soil N than the unburned site. We found that sites that repeatedly burned since 1971 were very similar in biomass to unburned tundra. This suggests that repeat fires keep a post-fire site at unburned levels of biomass. However, in these repeat fire sites, foliar C/N was ~25% greater and soil C and N was ~50% less than in unburned tundra. These results indicate that repeat fires are potentially causing nitrogen loss that not likely to be replenished into the system. As tundra fires become more frequent prediction of post-fire ecosystem effects is critical due to impacts on

  3. [Accuracy comparison of BJ-1, HJ and Landsat data in the retrieval of grassland vegetation coverage, leaf area index and above ground biomass].

    PubMed

    Wang, Hong-Yan; Li, Xiao-Song; Zhang, Jin; Gao, Zhi-Hai

    2013-10-01

    Domestic satellites BJ-1, HJ and the most widely used satellite Landsat were selected to systematically compare their abilities and differences on the estimation of the biophysical parameters of grassland in sandstorm source region in Beijing and Tianjin, with the combination of field-measured fractional coverage, leaf area index and aboveground biomass data. The result shows: (1) In terms of the surface reflectance, HJ-1B and Landsat have a higher correlation with biophysical parameters in red band, compared with BJ-1, while BJ-1's near infra-red band was obviously superior to HJ-1B and Landsat, (2) with respect to the vegetation indices, Landsat performed best, HJ-1B was the second, and BJ-1 was the worst, (3) compared with vegetation indices, multiple regression model can raise the estimation accuracy, BJ-1 based model improved significantly, while Landsat and HJ-1B based models were less obvious. Among them, the highest accuracy was acquired for leaf area index estimation through the BJ-1 based model (R2 = 0.61, RMSEP = 0.15). In general, domestic satellites have their own unique features, which remain a huge potential to be further tapped. PMID:24409740

  4. The effect of wildfire and clear-cutting on above-ground biomass, foliar C to N ratios and fiber content throughout succession: Implications for forage quality in woodland caribou (Rangifer tarandus caribou)

    NASA Astrophysics Data System (ADS)

    Mallon, E. E.; Turetsky, M.; Thompson, I.; Noland, T. L.; Wiebe, P.

    2013-12-01

    Disturbance is known to play an important role in maintaining the productivity and biodiversity of boreal forest ecosystems. Moderate to low frequency disturbance is responsible for regeneration opportunities creating a mosaic of habitats and successional trajectories. However, large-scale deforestation and increasing wildfire frequencies exacerbate habitat loss and influence biogeochemical cycles. This has raised concern about the quality of the under-story vegetation post-disturbance and whether this may impact herbivores, especially those vulnerable to change. Forest-dwelling caribou (Rangifer tarandus caribou) are declining in several regions of Canada and are currently listed as a species at risk by COSEWIC. Predation and landscape alteration are viewed as the two main threats to woodland caribou. This has resulted in caribou utilizing low productivity peatlands as refuge and the impact of this habitat selection on their diet quality is not well understood. Therefore there are two themes in the study, 1) Forage quantity: above-ground biomass and productivity and 2) Forage quality: foliar N and C to N ratios and % fiber. The themes are addressed in three questions: 1) How does forage quantity and quality vary between upland forests and peatlands? 2) How does wildfire affect the availability and nutritional quality of forage items? 3) How does forage quality vary between sites recovering from wildfire versus timber harvest? Research sites were located in the Auden region north of Geraldton, ON. This landscape was chosen because it is known woodland caribou habitat and has thorough wildfire and silviculture data from the past 7 decades. Plant diversity, above-ground biomass, vascular green area and seasonal foliar fiber and C to N ratios were collected across a matrix of sites representing a chronosequence of time since disturbance in upland forests and peatlands. Preliminary findings revealed productivity peaked in early age stands (0-30 yrs) and biomass peaked

  5. Modelling above-ground carbon dynamics using multi-temporal airborne lidar: insights from a Mediterranean woodland

    NASA Astrophysics Data System (ADS)

    Simonson, W.; Ruiz-Benito, P.; Valladares, F.; Coomes, D.

    2016-02-01

    Woodlands represent highly significant carbon sinks globally, though could lose this function under future climatic change. Effective large-scale monitoring of these woodlands has a critical role to play in mitigating for, and adapting to, climate change. Mediterranean woodlands have low carbon densities, but represent important global carbon stocks due to their extensiveness and are particularly vulnerable because the region is predicted to become much hotter and drier over the coming century. Airborne lidar is already recognized as an excellent approach for high-fidelity carbon mapping, but few studies have used multi-temporal lidar surveys to measure carbon fluxes in forests and none have worked with Mediterranean woodlands. We use a multi-temporal (5-year interval) airborne lidar data set for a region of central Spain to estimate above-ground biomass (AGB) and carbon dynamics in typical mixed broadleaved and/or coniferous Mediterranean woodlands. Field calibration of the lidar data enabled the generation of grid-based maps of AGB for 2006 and 2011, and the resulting AGB change was estimated. There was a close agreement between the lidar-based AGB growth estimate (1.22 Mg ha-1 yr-1) and those derived from two independent sources: the Spanish National Forest Inventory, and a tree-ring based analysis (1.19 and 1.13 Mg ha-1 yr-1, respectively). We parameterised a simple simulator of forest dynamics using the lidar carbon flux measurements, and used it to explore four scenarios of fire occurrence. Under undisturbed conditions (no fire) an accelerating accumulation of biomass and carbon is evident over the next 100 years with an average carbon sequestration rate of 1.95 Mg C ha-1 yr-1. This rate reduces by almost a third when fire probability is increased to 0.01 (fire return rate of 100 years), as has been predicted under climate change. Our work shows the power of multi-temporal lidar surveying to map woodland carbon fluxes and provide parameters for carbon

  6. Modelling above-ground carbon dynamics using multi-temporal airborne lidar: insights from a Mediterranean woodland

    NASA Astrophysics Data System (ADS)

    Simonson, W.; Ruiz-Benito, P.; Valladares, F.; Coomes, D.

    2015-09-01

    Woodlands represent highly significant carbon sinks globally, though could lose this function under future climatic change. Effective large-scale monitoring of these woodlands has a critical role to play in mitigating for, and adapting to, climate change. Mediterranean woodlands have low carbon densities, but represent important global carbon stocks due to their extensiveness and are particularly vulnerable because the region is predicted to become much hotter and drier over the coming century. Airborne lidar is already recognized as an excellent approach for high-fidelity carbon mapping, but few studies have used multi-temporal lidar surveys to measure carbon fluxes in forests and none have worked with Mediterranean woodlands. We use a multi-temporal (five year interval) airborne lidar dataset for a region of central Spain to estimate above-ground biomass (AGB) and carbon dynamics in typical mixed broadleaved/coniferous Mediterranean woodlands. Field calibration of the lidar data enabled the generation of grid-based maps of AGB for 2006 and 2011, and the resulting AGB change were estimated. There was a close agreement between the lidar-based AGB growth estimate (1.22 Mg ha-1 year-1) and those derived from two independent sources: the Spanish National Forest Inventory, and a~tree-ring based analysis (1.19 and 1.13 Mg ha-1 year-1, respectively). We parameterised a simple simulator of forest dynamics using the lidar carbon flux measurements, and used it to explore four scenarios of fire occurrence. Under undisturbed conditions (no fire occurrence) an accelerating accumulation of biomass and carbon is evident over the next 100 years with an average carbon sequestration rate of 1.95 Mg C ha-1 year-1. This rate reduces by almost a third when fire probability is increased to 0.01, as has been predicted under climate change. Our work shows the power of multi-temporal lidar surveying to map woodland carbon fluxes and provide parameters for carbon dynamics models. Space

  7. 49 CFR 195.254 - Above ground components.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Above ground components. 195.254 Section 195.254 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.254 Above ground components. (a) Any component may be installed above ground...

  8. 49 CFR 195.254 - Above ground components.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Above ground components. 195.254 Section 195.254 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.254 Above ground components. (a) Any component may be installed above ground...

  9. 49 CFR 195.254 - Above ground components.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Above ground components. 195.254 Section 195.254 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.254 Above ground components. (a) Any component may be installed above ground...

  10. 49 CFR 195.254 - Above ground components.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Above ground components. 195.254 Section 195.254 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.254 Above ground components. (a) Any component may be installed above ground...

  11. 49 CFR 195.254 - Above ground components.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Above ground components. 195.254 Section 195.254 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.254 Above ground components. (a) Any component may be installed above ground...

  12. Characterizing uncertainties of the national-scale forest gross aboveground biomass (AGB) loss estimate: a case study of the Democratic Republic of the Congo

    NASA Astrophysics Data System (ADS)

    Tyukavina, A.; Stehman, S.; Potapov, P.; Turubanova, S.; Baccini, A.; Goetz, S. J.; Laporte, N. T.; Houghton, R. A.; Hansen, M.

    2013-12-01

    Modern remote sensing techniques enable the mapping and monitoring of aboveground biomass (AGB) carbon stocks without relying on extensive in situ measurements. The Democratic Republic of the Congo (DRC) is among the countries where a national forest inventory (NFI) has yet to be established due to a lack of infrastructure and political instability. We demonstrate a method for producing national-scale gross AGB loss estimates and quantifying uncertainty of the estimates using remotely sensed-derived forest cover loss and biomass carbon density data. Forest cover type and loss were characterized using published Landsat-based data sets and related to LIDAR-derived biomass data from the Geoscience Laser Altimeter System (GLAS). We produced two gross AGB loss estimates for the DRC for the last decade (2000-2010): a conservative estimate accounting for classification errors in the 60-m resolution FACET forest cover change product, and a maximal estimate that also took into consideration omitted change at the 30m spatial resolution. Omitted disturbances were largely related to smallholder agriculture, the detection of which is scale-dependent. The use of LIDAR data as a substitute for NFI data to estimate AGB loss based on Landsat-derived activity data was demonstrated. Comparisons of our forest cover loss and AGB estimates with published studies raise the issue of scale in forest cover change mapping and its impact on carbon stock change estimation using remotely sensed data.

  13. DETAIL OF ORNAMENTAL TERRA COTTA FRIEZE ABOVE GROUND FLOOR AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF ORNAMENTAL TERRA COTTA FRIEZE ABOVE GROUND FLOOR AND TYPICAL TERRA COTTA WINDOW SILL. CORNER OF CLAY AND 15TH STREETS - John Breuner & Company Building, 1515 Clay Street, Oakland, Alameda County, CA

  14. Above- and Belowground Biomass Allocation in Shrub Biomes across the Northeast Tibetan Plateau

    PubMed Central

    Yang, Yuanhe; Yang, Lucun; Zhou, Guoying

    2016-01-01

    Biomass partitioning has been explored across various biomes. However, the strategies of allocation in plants still remain contentious. This study investigated allocation patterns of above- and belowground biomass at the community level, using biomass survey from the Tibetan Plateau. We explored above- and belowground biomass by conducting three consecutive sampling campaigns across shrub biomes on the northeast Tibetan Plateau during 2011–2013. We then documented the above-ground biomass (AGB), below-ground biomass (BGB) and root: shoot ratio (R/S) and the relationships between R/S and environment factors using data from 201 plots surveyed from 67 sites. We further examined relationships between above-ground and below-ground biomass across various shrub types. Our results indicated that the median values of AGB, BGB, and R/S in Tibetan shrub were 1102.55, 874.91 g m-2, and 0.85, respectively. R/S showed significant trend with mean annual precipitation (MAP), while decreased with mean annual temperature (MAT). Reduced major axis analysis indicated that the slope of the log-log relationship between above- and belowground biomass revealed a significant difference from 1.0 over space, supporting the optimal hypothesis. Interestingly, the slopes of the allometric relationship between log AGB and log BGB differed significantly between alpine and desert shrub. Our findings supported the optimal theory of above- and belowground biomass partitioning in Tibetan shrub, while the isometric hypothesis for alpine shrub at the community level. PMID:27119379

  15. Regional analysis of ground and above-ground climate

    NASA Astrophysics Data System (ADS)

    1981-12-01

    The regional suitability of underground construction as a climate control technique is discussed with reference to (1) a bioclimatic analysis of long term weather data for 29 locations in the United States to determine appropriate above ground climate control techniques, (2) a data base of synthesized ground temperatures for the coterminous United States, and (3) monthly dew point ground temperature comparisons for identifying the relative likelihood of condensation from one region to another. It is concluded that the suitability of Earth tempering as a practice and of specific Earth sheltered design stereotypes varies geographically; while the subsurface almost always provides a thermal advantage on its own terms when compared to above ground climatic data, it can, nonetheless, compromise the effectiveness of other, regionally more important climate control techniques. Reviews of above and below ground climate mapping schemes related to human comfort and architectural design, and detailed description of a theoretical model of ground temperature, heat flow, and heat storage in the ground are included. Strategies of passive climate control are presented in a discussion of the building bioclimatic analysis procedure which has been applied in a computer analysis of 30 years of weather data for each of 20 locations in the United States.

  16. Regional analysis of ground and above-ground climate

    SciTech Connect

    Not Available

    1981-12-01

    The regional suitability of underground construction as a climate control technique is discussed with reference to (1) a bioclimatic analysis of long-term weather data for 29 locations in the United States to determine appropriate above ground climate control techniques, (2) a data base of synthesized ground temperatures for the coterminous United States, and (3) monthly dew point ground temperature comparisons for identifying the relative likelihood of condensation from one region to another. It is concluded that the suitability of earth tempering as a practice and of specific earth-sheltered design stereotypes varies geographically; while the subsurface almost always provides a thermal advantage on its own terms when compared to above ground climatic data, it can, nonetheless, compromise the effectiveness of other, regionally more important climate control techniques. Also contained in the report are reviews of above and below ground climate mapping schemes related to human comfort and architectural design, and detailed description of a theoretical model of ground temperature, heat flow, and heat storage in the ground. Strategies of passive climate control are presented in a discussion of the building bioclimatic analysis procedure which has been applied in a computer analysis of 30 years of weather data for each of 29 locations in the United States.

  17. Incorporating Canopy Cover for Airborne-Derived Assessments of Forest Biomass in the Tropical Forests of Cambodia

    PubMed Central

    Singh, Minerva; Evans, Damian; Coomes, David A.; Friess, Daniel A.; Suy Tan, Boun; Samean Nin, Chan

    2016-01-01

    This research examines the role of canopy cover in influencing above ground biomass (AGB) dynamics of an open canopied forest and evaluates the efficacy of individual-based and plot-scale height metrics in predicting AGB variation in the tropical forests of Angkor Thom, Cambodia. The AGB was modeled by including canopy cover from aerial imagery alongside with the two different canopy vertical height metrics derived from LiDAR; the plot average of maximum tree height (Max_CH) of individual trees, and the top of the canopy height (TCH). Two different statistical approaches, log-log ordinary least squares (OLS) and support vector regression (SVR), were used to model AGB variation in the study area. Ten different AGB models were developed using different combinations of airborne predictor variables. It was discovered that the inclusion of canopy cover estimates considerably improved the performance of AGB models for our study area. The most robust model was log-log OLS model comprising of canopy cover only (r = 0.87; RMSE = 42.8 Mg/ha). Other models that approximated field AGB closely included both Max_CH and canopy cover (r = 0.86, RMSE = 44.2 Mg/ha for SVR; and, r = 0.84, RMSE = 47.7 Mg/ha for log-log OLS). Hence, canopy cover should be included when modeling the AGB of open-canopied tropical forests. PMID:27176218

  18. Incorporating Canopy Cover for Airborne-Derived Assessments of Forest Biomass in the Tropical Forests of Cambodia.

    PubMed

    Singh, Minerva; Evans, Damian; Coomes, David A; Friess, Daniel A; Suy Tan, Boun; Samean Nin, Chan

    2016-01-01

    This research examines the role of canopy cover in influencing above ground biomass (AGB) dynamics of an open canopied forest and evaluates the efficacy of individual-based and plot-scale height metrics in predicting AGB variation in the tropical forests of Angkor Thom, Cambodia. The AGB was modeled by including canopy cover from aerial imagery alongside with the two different canopy vertical height metrics derived from LiDAR; the plot average of maximum tree height (Max_CH) of individual trees, and the top of the canopy height (TCH). Two different statistical approaches, log-log ordinary least squares (OLS) and support vector regression (SVR), were used to model AGB variation in the study area. Ten different AGB models were developed using different combinations of airborne predictor variables. It was discovered that the inclusion of canopy cover estimates considerably improved the performance of AGB models for our study area. The most robust model was log-log OLS model comprising of canopy cover only (r = 0.87; RMSE = 42.8 Mg/ha). Other models that approximated field AGB closely included both Max_CH and canopy cover (r = 0.86, RMSE = 44.2 Mg/ha for SVR; and, r = 0.84, RMSE = 47.7 Mg/ha for log-log OLS). Hence, canopy cover should be included when modeling the AGB of open-canopied tropical forests. PMID:27176218

  19. Above-ground Antineutrino Detection for Nuclear Reactor Monitoring

    SciTech Connect

    Sweany, Melinda; Brennan, James S.; Cabrera-Palmer, Belkis; Kiff, Scott D.; Reyna, David; Throckmorton, Daniel J.

    2014-08-01

    Antineutrino monitoring of nuclear reactors has been demonstrated many times, however the technique has not as of yet been developed into a useful capability for treaty verification purposes. The most notable drawback is the current requirement that detectors be deployed underground, with at least several meters-water-equivalent of shielding from cosmic radiation. In addition, the deployment of liquid-based detector media presents a challenge in reactor facilities. We are currently developing a detector system that has the potential to operate above ground and circumvent deployment problems associated with a liquid detection media: the system is composed of segments of plastic scintillator surrounded by 6LiF/ZnS:Ag. ZnS:Ag is a radio-luminescent phosphor used to detect the neutron capture products of lithium-6. Because of its long decay time compared to standard plastic scintillators, pulse-shape discrimination can be used to distinguish positron and neutron interactions resulting from the inverse beta decay (IBD) of antineutrinos within the detector volume, reducing both accidental and correlated backgrounds. Segmentation further reduces backgrounds by identifying the positron’s annihilation gammas, which are absent for most correlated and uncorrelated backgrounds. This work explores different configurations in order to maximize the size of the detector segments without reducing the intrinsic neutron detection efficiency. We believe this technology will ultimately be applicable to potential safeguards scenarios such as those recently described.

  20. Above-ground Antineutrino Detection for Nuclear Reactor Monitoring

    DOE PAGESBeta

    Sweany, Melinda; Brennan, James S.; Cabrera-Palmer, Belkis; Kiff, Scott D.; Reyna, David; Throckmorton, Daniel J.

    2014-08-01

    Antineutrino monitoring of nuclear reactors has been demonstrated many times, however the technique has not as of yet been developed into a useful capability for treaty verification purposes. The most notable drawback is the current requirement that detectors be deployed underground, with at least several meters-water-equivalent of shielding from cosmic radiation. In addition, the deployment of liquid-based detector media presents a challenge in reactor facilities. We are currently developing a detector system that has the potential to operate above ground and circumvent deployment problems associated with a liquid detection media: the system is composed of segments of plastic scintillator surroundedmore » by 6LiF/ZnS:Ag. ZnS:Ag is a radio-luminescent phosphor used to detect the neutron capture products of lithium-6. Because of its long decay time compared to standard plastic scintillators, pulse-shape discrimination can be used to distinguish positron and neutron interactions resulting from the inverse beta decay (IBD) of antineutrinos within the detector volume, reducing both accidental and correlated backgrounds. Segmentation further reduces backgrounds by identifying the positron’s annihilation gammas, which are absent for most correlated and uncorrelated backgrounds. This work explores different configurations in order to maximize the size of the detector segments without reducing the intrinsic neutron detection efficiency. We believe this technology will ultimately be applicable to potential safeguards scenarios such as those recently described.« less

  1. Above-ground antineutrino detection for nuclear reactor monitoring

    NASA Astrophysics Data System (ADS)

    Sweany, M.; Brennan, J.; Cabrera-Palmer, B.; Kiff, S.; Reyna, D.; Throckmorton, D.

    2015-01-01

    Antineutrino monitoring of nuclear reactors has been demonstrated many times (Klimov et al., 1994 [1]; Bowden et al., 2009 [2]; Oguri et al., 2014 [3]), however the technique has not as of yet been developed into a useful capability for treaty verification purposes. The most notable drawback is the current requirement that detectors be deployed underground, with at least several meters-water-equivalent of shielding from cosmic radiation. In addition, the deployment of liquid-based detection media presents a challenge in reactor facilities. We are currently developing a detector system that has the potential to operate above ground and circumvent deployment problems associated with a liquid detection media: the system is composed of segments of plastic scintillator surrounded by 6LiF/ZnS:Ag. ZnS:Ag is a radio-luminescent phosphor used to detect the neutron capture products of 6Li. Because of its long decay time compared to standard plastic scintillators, pulse-shape discrimination can be used to distinguish positron and neutron interactions resulting from the inverse beta decay (IBD) of antineutrinos within the detector volume, reducing both accidental and correlated backgrounds. Segmentation further reduces backgrounds by identifying the positron's annihilation gammas, a signature that is absent for most correlated and uncorrelated backgrounds. This work explores different configurations in order to maximize the size of the detector segments without reducing the intrinsic neutron detection efficiency. We believe that this technology will ultimately be applicable to potential safeguards scenarios such as those recently described by Huber et al. (2014) [4,5].

  2. Lidar with multi-temporal MODIS provide a means to upscale predictions of forest biomass

    NASA Astrophysics Data System (ADS)

    Li, Le; Guo, Qinghua; Tao, Shengli; Kelly, Maggi; Xu, Guangcai

    2015-04-01

    Forests play a key role in the global carbon cycle, and forest above ground biomass (AGB) is an important indictor to the carbon storage capacity and the potential carbon pool size of a forest ecosystem. Accurate estimation of forest AGB has become increasingly important for a wide range of end-users. Although satellite remote sensing provides abundant observations to monitor forest coverage, validation of coarse-resolution AGB derived from satellite observations is difficult because of the scale mismatch between the footprints of satellite observations and field measurements. In this study, we use airborne Lidar to bridge the scale gaps between satellite-based and field-based studies, and evaluate satellite-derived indices to estimate regional forest AGB. We found that: (1) Lidar data can be used to accurately estimate forest AGB using tree height and tree quadratic height, (2) linear regression, among four tested models, achieve the best performance (R2 = 0.74; RMSE = 183.57 Mg/ha); (3) for MODIS-derived vegetation indices at varied spatial resolution (250-1000 m), accumulated NDVI, accumulated LAI, and accumulated FPAR could explain 53-74% variances of forest AGB, whereas accumulated NDVI derived from 1 km MODIS products gives higher R2 (74%) and lower RMSE (13.4 Mg/ha) than others. We conclude that Lidar data can be used to bridge the scale gap between satellite and field studies. Our results indicate that combining MODIS and Lidar data has the potential to estimate regional forest AGB.

  3. Lidar Estimation of Aboveground Biomass in a Tropical Coastal Forest of Gabon

    NASA Astrophysics Data System (ADS)

    Meyer, V.; Saatchi, S. S.; Poulsen, J.; Clark, C.; Lewis, S.; White, L.

    2012-12-01

    Estimation of tropical forest carbon stocks is a critical yet challenging problem from both ground surveys and remote sensing measurements. However, with its increasing importance in global climate mitigation and carbon cycle assessment, there is a need to develop new techniques to measure forest carbon stocks at landscape scales. Progresses have been made in terms of above ground biomass (AGB) monitoring techniques using ground measurements, with the development of tree allometry techniques. Besides, studies have shown that new remote sensing technologies such as Lidar can give accurate information on tree height and forest structure at a landscape level and can be very useful to estimate AGB. This study examines the ability of small footprint Lidar to estimate above ground biomass in Mondah forest, Gabon. Mondah forest is a coastal tropical forest that is partially flooded and includes areas of mangrove. Its mean annual temperature is 18.8C and mean annual precipitation is 2631mm/yr. Its proximity to the capital of Gabon, Libreville, makes it particularly subject to environmental pressure. The analysis is based on small footprint Lidar waveform information and relative height (RH) metrics that correspond to the percentiles of energy of the signal (25%, 50%, 75% and 100%). AGB estimation is calibrated with ground measurements. Ground-estimated AGB is calculated using allometric equations based on tree diameter, wood density and tree height. Lidar-derived AGB is calculated using a linear regression model between the four Lidar RH metrics and ground-estimated AGB and using available models developed in other tropical regions that use one height metric, average wood density, and tree stocking number. We present uncertainty of different approaches and discuss the universality of lidar biomass estimation models in tropical forests.

  4. Error propagation and scaling for tropical forest biomass estimates.

    PubMed Central

    Chave, Jerome; Condit, Richard; Aguilar, Salomon; Hernandez, Andres; Lao, Suzanne; Perez, Rolando

    2004-01-01

    The above-ground biomass (AGB) of tropical forests is a crucial variable for ecologists, biogeochemists, foresters and policymakers. Tree inventories are an efficient way of assessing forest carbon stocks and emissions to the atmosphere during deforestation. To make correct inferences about long-term changes in biomass stocks, it is essential to know the uncertainty associated with AGB estimates, yet this uncertainty is rarely evaluated carefully. Here, we quantify four types of uncertainty that could lead to statistical error in AGB estimates: (i) error due to tree measurement; (ii) error due to the choice of an allometric model relating AGB to other tree dimensions; (iii) sampling uncertainty, related to the size of the study plot; (iv) representativeness of a network of small plots across a vast forest landscape. In previous studies, these sources of error were reported but rarely integrated into a consistent framework. We estimate all four terms in a 50 hectare (ha, where 1 ha = 10(4) m2) plot on Barro Colorado Island, Panama, and in a network of 1 ha plots scattered across central Panama. We find that the most important source of error is currently related to the choice of the allometric model. More work should be devoted to improving the predictive power of allometric models for biomass. PMID:15212093

  5. Spatio-Temporal Variation in Vegetation Biomass and Its Relationships with Climate Factors in the Xilingol Grasslands, Northern China

    PubMed Central

    Gao, Tian; Yang, Xiuchun; Jin, Yunxiang; Ma, Hailong; Li, Jinya; Yu, Haida; Yu, Qiangyi; Zheng, Xiao; Xu, Bin

    2013-01-01

    Knowledge about grassland biomass and its dynamics is critical for studying regional carbon cycles and for the sustainable use of grassland resources. In this study, we investigated the spatio-temporal variation of biomass in the Xilingol grasslands of northern China. Field-based biomass samples and MODIS time series data sets were used to establish two empirical models based on the relationship of the normalized difference vegetation index (NDVI) with above-ground biomass (AGB) as well as that of AGB with below-ground biomass (BGB). We further explored the climatic controls of these variations. Our results showed that the biomass averaged 99.01 Tg (1 Tg=1012 g) over a total area of 19.6×104 km2 and fluctuated with no significant trend from 2001 to 2012. The mean biomass density was 505.4 g/m2, with 62.6 g/m2 in AGB and 442.8 g/m2 in BGB, which generally decreased from northeast to southwest and exhibited a large spatial heterogeneity. The year-to-year AGB pattern was generally consistent with the inter-annual variation in the growing season precipitation (GSP), showing a robust positive correlation (R2=0.82, P<0.001), but an opposite coupled pattern was observed with the growing season temperature (GST) (R2=0.61, P=0.003). Climatic factors also affected the spatial distribution of AGB, which increased progressively with the GSP gradient (R2=0.76, P<0.0001) but decreased with an increasing GST (R2=0.70, P<0.0001). An improved moisture index that combined the effects of GST and GSP explained more variation in AGB than did precipitation alone (R2=0.81, P<0.0001). The relationship between AGB and GSP could be fit by a power function. This increasing slope of the GSP–AGB relationships along the GSP gradient may be partly explained by the GST–GSP spatial pattern in Xilingol. Our findings suggest that the relationships between climatic factors and AGB may be scale-dependent and that multi-scale studies and sufficient long-term field data are needed to examine the

  6. PALSAR 50 m mosaic data based national level biomass estimation in Cambodia for implementation of REDD+ mechanism.

    PubMed

    Avtar, Ram; Suzuki, Rikie; Takeuchi, Wataru; Sawada, Haruo

    2013-01-01

    Tropical countries like Cambodia require information about forest biomass for successful implementation of climate change mitigation mechanism related to Reducing Emissions from Deforestation and forest Degradation (REDD+). This study investigated the potential of Phased Array-type L-band Synthetic Aperture Radar Fine Beam Dual (PALSAR FBD) 50 m mosaic data to estimate Above Ground Biomass (AGB) in Cambodia. AGB was estimated using a bottom-up approach based on field measured biomass and backscattering (σ(o)) properties of PALSAR data. The relationship between the PALSAR σ(o) HV and HH/HV with field measured biomass was strong with R(2) = 0.67 and 0.56, respectively. PALSAR estimated AGB show good results in deciduous forests because of less saturation as compared to dense evergreen forests. The validation results showed a high coefficient of determination R(2) = 0.61 with RMSE  = 21 Mg/ha using values up to 200 Mg/ha biomass. There were some uncertainties because of the uncertainty in the field based measurement and saturation of PALSAR data. AGB map of Cambodian forests could be useful for the implementation of forest management practices for REDD+ assessment and policies implementation at the national level. PMID:24116012

  7. PALSAR 50 m Mosaic Data Based National Level Biomass Estimation in Cambodia for Implementation of REDD+ Mechanism

    PubMed Central

    Avtar, Ram; Suzuki, Rikie; Takeuchi, Wataru; Sawada, Haruo

    2013-01-01

    Tropical countries like Cambodia require information about forest biomass for successful implementation of climate change mitigation mechanism related to Reducing Emissions from Deforestation and forest Degradation (REDD+). This study investigated the potential of Phased Array-type L-band Synthetic Aperture Radar Fine Beam Dual (PALSAR FBD) 50 m mosaic data to estimate Above Ground Biomass (AGB) in Cambodia. AGB was estimated using a bottom-up approach based on field measured biomass and backscattering (σo) properties of PALSAR data. The relationship between the PALSAR σo HV and HH/HV with field measured biomass was strong with R2 = 0.67 and 0.56, respectively. PALSAR estimated AGB show good results in deciduous forests because of less saturation as compared to dense evergreen forests. The validation results showed a high coefficient of determination R2 = 0.61 with RMSE  = 21 Mg/ha using values up to 200 Mg/ha biomass. There were some uncertainties because of the uncertainty in the field based measurement and saturation of PALSAR data. AGB map of Cambodian forests could be useful for the implementation of forest management practices for REDD+ assessment and policies implementation at the national level. PMID:24116012

  8. Modeling the spatial distribution of above-ground carbon in Mexican coniferous forests using remote sensing and a geostatistical approach

    NASA Astrophysics Data System (ADS)

    Galeana-Pizaña, J. Mauricio; López-Caloca, Alejandra; López-Quiroz, Penélope; Silván-Cárdenas, José Luis; Couturier, Stéphane

    2014-08-01

    Forest conservation is considered an option for mitigating the effect of greenhouse gases on global climate, hence monitoring forest carbon pools at global and local levels is important. The present study explores the capability of remote-sensing variables (vegetation indices and textures derived from SPOT-5; backscattering coefficient and interferometric coherence of ALOS PALSAR images) for modeling the spatial distribution of above-ground biomass in the Environmental Conservation Zone of Mexico City. Correlation and spatial autocorrelation coefficients were used to select significant explanatory variables in fir and pine forests. The correlation for interferometric coherence in HV polarization was negative, with correlations coefficients r = -0.83 for the fir and r = -0.75 for the pine forests. Regression-kriging showed the least root mean square error among the spatial interpolation methods used, with 37.75 tC/ha for fir forests and 29.15 tC/ha for pine forests. The results showed that a hybrid geospatial method, based on interferometric coherence data and a regression-kriging interpolator, has good potential for estimating above-ground biomass carbon.

  9. Biomass Estimation of Dry Tropical Woody Species at Juvenile Stage

    PubMed Central

    Chaturvedi, R. K.; Raghubanshi, A. S.; Singh, J. S.

    2012-01-01

    Accurate characterization of biomass in different forest components is important to estimate their contribution to total carbon stock. Due to lack of allometric equations for biomass estimation of woody species at juvenile stage, the carbon stored in this forest component is ignored. We harvested 47 woody species at juvenile stage in a dry tropical forest and developed regression models for the estimation of above-ground biomass (AGB). The models including wood-specific gravity (ρ) exhibited higher R2 than those without ρ. The model consisting of ρ, stem diameter (D), and height (H) not only exhibited the highest R2 value but also had the lowest standard error of estimate. We suggest that ρ-based regression model is a viable option for nondestructive estimation of biomass of forest trees at juvenile stage. PMID:22448139

  10. 30 CFR 77.807-1 - High-voltage powerlines; clearances above ground.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... OF UNDERGROUND COAL MINES Surface High-Voltage Distribution § 77.807-1 High-voltage powerlines; clearances above ground. High-voltage powerlines located above driveways, haulageways, and railroad...

  11. 30 CFR 77.807-1 - High-voltage powerlines; clearances above ground.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... OF UNDERGROUND COAL MINES Surface High-Voltage Distribution § 77.807-1 High-voltage powerlines; clearances above ground. High-voltage powerlines located above driveways, haulageways, and railroad...

  12. 30 CFR 77.807-1 - High-voltage powerlines; clearances above ground.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... OF UNDERGROUND COAL MINES Surface High-Voltage Distribution § 77.807-1 High-voltage powerlines; clearances above ground. High-voltage powerlines located above driveways, haulageways, and railroad...

  13. 30 CFR 77.807-1 - High-voltage powerlines; clearances above ground.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... OF UNDERGROUND COAL MINES Surface High-Voltage Distribution § 77.807-1 High-voltage powerlines; clearances above ground. High-voltage powerlines located above driveways, haulageways, and railroad...

  14. 30 CFR 77.807-1 - High-voltage powerlines; clearances above ground.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... OF UNDERGROUND COAL MINES Surface High-Voltage Distribution § 77.807-1 High-voltage powerlines; clearances above ground. High-voltage powerlines located above driveways, haulageways, and railroad...

  15. Uncertainty estimation in integrated LiDAR- and radar-derived biomass maps at key national-level map scales

    NASA Astrophysics Data System (ADS)

    Joshi, N.; Fensholt, R.; Saatchi, S. S.; Mitchard, E. T.

    2013-12-01

    The international Reducing Emissions from Deforestation and Degradation (REDD) program requires accurate and cost-effective techniques of national-level mapping of above-ground biomass (AGB) and ground-sampling strategies. This paper explores a multi-sensor (radar and low-density airborne LiDAR) integration approach for country-wide AGB estimation and mapping in Denmark, selected as a test-country due to the unique availability of country-wide remote sensing and forest inventory data. We assess the potential use of ALOS PALSAR L-band radar and ENVISAT ASAR C-band radar in prediction and mapping of AGB with accuracies similar to LiDAR-derived AGB estimates at different map scales. We start by creating a LiDAR-based ';ground truth' map, using LiDAR-derived 95th Percentile of heights >1 m weighted by the Canopy Density ratio, together with 113 AGB plots to map AGB at a 0.25 ha resolution across the country. A leave-20%-out cross-validation indicates that the AGB estimates have a mean absolute error of 41 Mg ha-1 and a negative mean bias error of 1.7 Mg ha-1. Though the LiDAR model appears to have an overall species-specific bias for conifers and broadleaf (-5.2 Mg ha-1 and +12.3 Mg ha-1 respectively), these are found to be insignificant (p>0.05) when accounting for species sampling bias and the under-prediction of plots containing high-biomass (> 350 Mg ha-1). Using the LiDAR-derived biomass map as a ';truth-map', biomass-backscatter relations will be quantified at three map scales (0.25 ha, 1 ha and 100 ha) and using three spatial sampling frameworks (full-dataset, stratified random sampling equally representing low and high biomass pixels, clustered sampling). The approach aims to derive a minimal-sampling and mapping strategy for L- and C-band radar that achieves at least 20% accuracy in AGB estimation, along with quantified sources of error from ground-AGB estimates, scaling and sampling. It is expected that mapping techniques, uncertainty quantification and

  16. Below-ground herbivory limits induction of extrafloral nectar by above-ground herbivores

    PubMed Central

    Huang, Wei; Siemann, Evan; Carrillo, Juli; Ding, Jianqing

    2015-01-01

    Background and Aims Many plants produce extrafloral nectar (EFN), and increase production following above-ground herbivory, presumably to attract natural enemies of the herbivores. Below-ground herbivores, alone or in combination with those above ground, may also alter EFN production depending on the specificity of this defence response and the interactions among herbivores mediated through plant defences. To date, however, a lack of manipulative experiments investigating EFN production induced by above- and below-ground herbivory has limited our understanding of how below-ground herbivory mediates indirect plant defences to affect above-ground herbivores and their natural enemies. Methods In a greenhouse experiment, seedlings of tallow tree (Triadica sebifera) were subjected to herbivory by a specialist flea beetle (Bikasha collaris) that naturally co-occurs as foliage-feeding adults and root-feeding larvae. Seedlings were subjected to above-ground adults and/or below-ground larvae herbivory, and EFN production was monitored. Key Results Above- and/or below-ground herbivory significantly increased the percentage of leaves with active nectaries, the volume of EFN and the mass of soluble solids within the nectar. Simultaneous above- and below-ground herbivory induced a higher volume of EFN and mass of soluble solids than below-ground herbivory alone, but highest EFN production was induced by above-ground herbivory when below-ground herbivores were absent. Conclusions The induction of EFN production by below-ground damage suggests that systemic induction underlies some of the EFN response. The strong induction by above-ground herbivory in the absence of below-ground herbivory points to specific induction based on above- and below-ground signals that may be adaptive for this above-ground indirect defence. PMID:25681822

  17. Recovery of above-ground woody biomass using operational modifications of conventional harvesting systems

    SciTech Connect

    Herschelman, J. W.; Domenech, D. W.

    1980-06-01

    Two harvesting systems were assembled during each of two summers to compare the operational efficiency of a whole tree harvesting system with a conventional harvesting system. Skidding of whole trees proved to be 27% more efficient than the skidding of primary stems because of operators habits of underutilizing skidder capacity. Although 5% more gals/hour were used by the whole tree system, there was a net gain of 21% more tons/gal. produced by this same system. A whole tree chipper was analyzed for its potential to process large hardwood trees for energy products. A comparison of five harvesting systems revealed that whole tree systems producing sawtimber, round pulpwood and energy chips proved most energy efficient and economically viable. A variety of machine/system factors were measured. It was determined that with certain modifications, whole tree chippers offer the best potential for processing logging residue for fuel. Forty-eight equations were developed predicting green and ovendry weights in summer and winter for whole tree weight, primary product weight, and the weight of limbs and tops for hardwood trees associated with the oak-hickory forest type in the Southern Appalachian Region based on diameter at breast height and whole tree length. Eight sawlog prediction equations were also developed based on log length, diameter small end outside bark and diameter large end outside bark. The energy efficiency of harvesting systems was studied by analyzing the equipment involved in manual and mechanized shortwood, longwood, and whole tree systems.

  18. Spatially Explicit Large Area Biomass Estimation: Three Approaches Using Forest Inventory and Remotely Sensed Imagery in a GIS

    PubMed Central

    Wulder, Michael A.; White, Joanne C.; Fournier, Richard A.; Luther, Joan E.; Magnussen, Steen

    2008-01-01

    Forest inventory data often provide the required base data to enable the large area mapping of biomass over a range of scales. However, spatially explicit estimates of above-ground biomass (AGB) over large areas may be limited by the spatial extent of the forest inventory relative to the area of interest (i.e., inventories not spatially exhaustive), or by the omission of inventory attributes required for biomass estimation. These spatial and attributional gaps in the forest inventory may result in an underestimation of large area AGB. The continuous nature and synoptic coverage of remotely sensed data have led to their increased application for AGB estimation over large areas, although the use of these data remains challenging in complex forest environments. In this paper, we present an approach to generating spatially explicit estimates of large area AGB by integrating AGB estimates from multiple data sources; 1. using a lookup table of conversion factors applied to a non-spatially exhaustive forest inventory dataset (R2 = 0.64; RMSE = 16.95 t/ha), 2. applying a lookup table to unique combinations of land cover and vegetation density outputs derived from remotely sensed data (R2 = 0.52; RMSE = 19.97 t/ha), and 3. hybrid mapping by augmenting forest inventory AGB estimates with remotely sensed AGB estimates where there are spatial or attributional gaps in the forest inventory data. Over our 714,852 ha study area in central Saskatchewan, Canada, the AGB estimate generated from the forest inventory was approximately 40 Mega tonnes (Mt); however, the inventory estimate represents only 51% of the total study area. The AGB estimate generated from the remotely sensed outputs that overlap those made from the forest inventory based approach differ by only 2 %; however in total, the remotely sensed estimate is 30 % greater (58 Mt) than the estimate generated from the forest inventory when the entire study area is accounted for. Finally, using the hybrid approach, whereby

  19. Contrasting patterns of diameter and biomass increment across tree functional groups in Amazonian forests.

    PubMed

    Keeling, Helen C; Baker, Timothy R; Martinez, Rodolfo Vasquez; Monteagudo, Abel; Phillips, Oliver L

    2008-12-01

    Species' functional traits may help determine rates of carbon gain, with physiological and morphological trade-offs relating to shade tolerance affecting photosynthetic capacity and carbon allocation strategies. However, few studies have examined these trade-offs from the perspective of whole-plant biomass gain of adult trees. We compared tree-level annual diameter increments and annual above-ground biomass (AGB) increments in eight long-term plots in hyper-diverse northwest Amazonia to wood density (rho; a proxy for shade tolerance), whilst also controlling for resource supply (light and soil fertility). rho and annual diameter increment were negatively related, confirming expected differences in allocation associated with shade tolerance, such that light-demanding species allocate a greater proportion of carbon to diameter gain at the expense of woody tissue density. However, contrary to expectations, we found a positive relationship between rho and annual AGB increment in more fertile sites, although AGB gain did not differ significantly with rho class on low-fertility sites. Whole-plant carbon gain may be greater in shade-tolerant species due to higher total leaf area, despite lower leaf-level carbon assimilation rates. Alternatively, rates of carbon loss may be higher in more light-demanding species: higher rates of litterfall, respiration or allocation to roots, are all plausible mechanisms. However, the relationships between rho and AGB and diameter increments were weak; resource availability always exerted a stronger influence on tree growth rates. PMID:18853192

  20. Achieving Accuracy Requirements for Forest Biomass Mapping: A Data Fusion Method for Estimating Forest Biomass and LiDAR Sampling Error with Spaceborne Data

    NASA Technical Reports Server (NTRS)

    Montesano, P. M.; Cook, B. D.; Sun, G.; Simard, M.; Zhang, Z.; Nelson, R. F.; Ranson, K. J.; Lutchke, S.; Blair, J. B.

    2012-01-01

    The synergistic use of active and passive remote sensing (i.e., data fusion) demonstrates the ability of spaceborne light detection and ranging (LiDAR), synthetic aperture radar (SAR) and multispectral imagery for achieving the accuracy requirements of a global forest biomass mapping mission. This data fusion approach also provides a means to extend 3D information from discrete spaceborne LiDAR measurements of forest structure across scales much larger than that of the LiDAR footprint. For estimating biomass, these measurements mix a number of errors including those associated with LiDAR footprint sampling over regional - global extents. A general framework for mapping above ground live forest biomass (AGB) with a data fusion approach is presented and verified using data from NASA field campaigns near Howland, ME, USA, to assess AGB and LiDAR sampling errors across a regionally representative landscape. We combined SAR and Landsat-derived optical (passive optical) image data to identify forest patches, and used image and simulated spaceborne LiDAR data to compute AGB and estimate LiDAR sampling error for forest patches and 100m, 250m, 500m, and 1km grid cells. Forest patches were delineated with Landsat-derived data and airborne SAR imagery, and simulated spaceborne LiDAR (SSL) data were derived from orbit and cloud cover simulations and airborne data from NASA's Laser Vegetation Imaging Sensor (L VIS). At both the patch and grid scales, we evaluated differences in AGB estimation and sampling error from the combined use of LiDAR with both SAR and passive optical and with either SAR or passive optical alone. This data fusion approach demonstrates that incorporating forest patches into the AGB mapping framework can provide sub-grid forest information for coarser grid-level AGB reporting, and that combining simulated spaceborne LiDAR with SAR and passive optical data are most useful for estimating AGB when measurements from LiDAR are limited because they minimized

  1. Comparison of buried soil sensors, surface chambers and above ground measurements of carbon dioxide fluxes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil carbon dioxide (CO2) flux is an important component of the terrestrial carbon cycle. Accurate measurements of soil CO2 flux aids determinations of carbon budgets. In this study, we investigated soil CO2 fluxes with time and depth and above ground CO2 fluxes in a bare field. CO2 concentrations w...

  2. ETR, TRA642. CAMERA IS ON SCAFFOLD OR CATWALK ABOVE GROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    ETR, TRA-642. CAMERA IS ON SCAFFOLD OR CATWALK ABOVE GROUND FLOOR FOR A CONTEXTUAL VIEW OF REACTOR PIT AND CANAL. CAMERA FACING WESTERLY. INL NEGATIVE NO. 56-3717. R.G. Larsen, Photographer, 11/13/1956 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  3. Characteristics of train noise in above-ground and underground stations with side and island platforms

    NASA Astrophysics Data System (ADS)

    Shimokura, Ryota; Soeta, Yoshiharu

    2011-04-01

    Railway stations can be principally classified by their locations, i.e., above-ground or underground stations, and by their platform styles, i.e., side or island platforms. However, the effect of the architectural elements on the train noise in stations is not well understood. The aim of the present study is to determine the different acoustical characteristics of the train noise for each station style. The train noise was evaluated by (1) the A-weighted equivalent continuous sound pressure level ( LAeq), (2) the amplitude of the maximum peak of the interaural cross-correlation function (IACC), (3) the delay time ( τ1) and amplitude ( ϕ1) of the first maximum peak of the autocorrelation function. The IACC, τ1 and ϕ1 are related to the subjective diffuseness, pitch and pitch strength, respectively. Regarding the locations, the LAeq in the underground stations was 6.4 dB higher than that in the above-ground stations, and the pitch in the underground stations was higher and stronger. Regarding the platform styles, the LAeq on the side platforms was 3.3 dB higher than on the island platforms of the above-ground stations. For the underground stations, the LAeq on the island platforms was 3.3 dB higher than that on the side platforms when a train entered the station. The IACC on the island platforms of the above-ground stations was higher than that in the other stations.

  4. Cadmium uptake in above-ground parts of lettuce (Lactuca sativa L.).

    PubMed

    Tang, Xiwang; Pang, Yan; Ji, Puhui; Gao, Pengcheng; Nguyen, Thanh Hung; Tong, Yan'an

    2016-03-01

    Because of its high Cd uptake and translocation, lettuce is often used in Cd contamination studies. However, there is a lack of information on Cd accumulation in the above-ground parts of lettuce during the entire growing season. In this study, a field experiment was carried out in a Cd-contaminated area. Above-ground lettuce parts were sampled, and the Cd content was measured using a flame atomic absorption spectrophotometer (AAS). The results showed that the Cd concentration in the above-ground parts of lettuce increased from 2.70 to 3.62mgkg(-1) during the seedling stage, but decreased from 3.62 to 2.40mgkg(-1) during organogenesis and from 2.40 to 1.64mgkg(-1) during bolting. The mean Cd concentration during the seedling stage was significantly higher than that during organogenesis (a=0.05) and bolting (a=0.01). The Cd accumulation in the above-ground parts of an individual lettuce plant could be described by a sigmoidal curve. Cadmium uptake during organogenesis was highest (80% of the total), whereas that during bolting was only 4.34%. This research further reveals that for Rome lettuce: (1) the highest Cd content of above-ground parts occurred at the end of the seedling phase; (2) the best harvest time with respect to Cd phytoaccumulation is at the end of the organogenesis stage; and (3) the organogenesis stage is the most suitable time to enhance phytoaccumulation efficiency by adjusting the root:shoot ratio. PMID:26685781

  5. Increasing biomass in Amazonian forest plots.

    PubMed Central

    Baker, Timothy R; Phillips, Oliver L; Malhi, Yadvinder; Almeida, Samuel; Arroyo, Luzmila; Di Fiore, Anthony; Erwin, Terry; Higuchi, Niro; Killeen, Timothy J; Laurance, Susan G; Laurance, William F; Lewis, Simon L; Monteagudo, Abel; Neill, David A; Vargas, Percy Núñez; Pitman, Nigel C A; Silva, J Natalino M; Martínez, Rodolfo Vásquez

    2004-01-01

    A previous study by Phillips et al. of changes in the biomass of permanent sample plots in Amazonian forests was used to infer the presence of a regional carbon sink. However, these results generated a vigorous debate about sampling and methodological issues. Therefore we present a new analysis of biomass change in old-growth Amazonian forest plots using updated inventory data. We find that across 59 sites, the above-ground dry biomass in trees that are more than 10 cm in diameter (AGB) has increased since plot establishment by 1.22 +/- 0.43 Mg per hectare per year (ha(-1) yr(-1), where 1 ha = 10(4) m2), or 0.98 +/- 0.38 Mg ha(-1) yr(-1) if individual plot values are weighted by the number of hectare years of monitoring. This significant increase is neither confounded by spatial or temporal variation in wood specific gravity, nor dependent on the allometric equation used to estimate AGB. The conclusion is also robust to uncertainty about diameter measurements for problematic trees: for 34 plots in western Amazon forests a significant increase in AGB is found even with a conservative assumption of zero growth for all trees where diameter measurements were made using optical methods and/or growth rates needed to be estimated following fieldwork. Overall, our results suggest a slightly greater rate of net stand-level change than was reported by Phillips et al. Considering the spatial and temporal scale of sampling and associated studies showing increases in forest growth and stem turnover, the results presented here suggest that the total biomass of these plots has on average increased and that there has been a regional-scale carbon sink in old-growth Amazonian forests during the previous two decades. PMID:15212090

  6. The Biomass mission: a step forward in quantifying forest biomass and structure

    NASA Astrophysics Data System (ADS)

    LE Toan, T.

    2015-12-01

    The primary aim of the ESA BIOMASS mission is to determine, for the first time and in a consistent manner, the global distribution of above-ground forest biomass (AGB) in order to provide greatly improved quantification of the size and distribution of the terrestrial carbon pool, and improved estimates of terrestrial carbon fluxes. Specifically, BIOMASS will measure forest carbon stock, as well as forest height, from data provided by a single satellite giving a biomass map covering tropical, temperate and boreal forests at a resolution of around 200 m every 6 months throughout the five years of the mission. BIOMASS will use a long wavelength SAR (P-band) providing three mutually supporting measurement techniques, namely polarimetric SAR (PolSAR), polarimetric interferometric SAR (PolInSAR) and tomographic SAR (TomoSAR). The combination of these techniques will significantly reduce the uncertainties in biomass retrievals by yielding complementary information on biomass properties. Horizontal mapping: For a forest canopy, the P-band radar waves penetrate deep into the canopy, and their interaction with the structure of the forest will be exploited to map above ground biomass (AGB), as demonstrated from airborne data for temperate, boreal forests and tropical forest. Height mapping: By repeat revisits to the same location, the PolInSAR measurements will be used to estimate the height of scattering in the forest canopy. The long wavelength used by BIOMASS is crucial for the temporal coherence to be preserved over much longer timescales than at L-band, for example. 3D mapping: The P-band frequency used by BIOMASS is low enough to ensure penetration through the entire canopy, even in dense tropical forests. As a consequence, resolution of the vertical structure of the forest will be possible using tomographic methods from the multi-baseline acquisitions. This is the concept of SAR tomography, which will be implemented in the BIOMASS mission. The improvement in the

  7. Mapping afforestation and forest biomass using time-series Landsat stacks

    NASA Astrophysics Data System (ADS)

    Liu, Liangyun; Peng, Dailiang; Wang, Zhihui; Hu, Yong

    2014-11-01

    Satellite data can adequately capture forest dynamics over larger areas. Firstly, the Landsat ground surface reflectance (GSR) images from 1974 to 2013 were collected and processed based on 6S atmospheric transfer code and a relative reflectance normalization algorithm. Subsequently, we developed a vegetation change tracking method to reconstruct the forest change history (afforestation and deforestation) from the dense time-series Landsat GSR images, and the afforestation age was successfully retrieved from the Landsat time-series stacks in the last forty years and shown to be consistent with the surveyed tree ages. Then, the above ground biomass (AGB) regression models were greatly improved by integrating the simple ratio vegetation index (SR) and tree age. Finally, the forest AGB images were mapped at eight epochs from 1985 to 2013 using SR and afforestation age. The total forest AGB in six counties of Yulin District increased by 20.8 G kg, from 5.8 G kg in 1986 to 26.6 G kg in 2013, a total increase of 360%. For the forest area, the forest AGB density increased from 15.72 t/ha in 1986 to 44.53 t/ha in 2013, with an annual rate of about 1 t/ha. The results present a noticeable carbon increment for the planted artificial forest in Yulin District over the last four decades.

  8. Estimation of Biomass Carbon Stocks over Peat Swamp Forests using Multi-Temporal and Multi-Polratizations SAR Data

    NASA Astrophysics Data System (ADS)

    Wijaya, A.; Liesenberg, V.; Susanti, A.; Karyanto, O.; Verchot, L. V.

    2015-04-01

    The capability of L-band radar backscatter to penetrate through the forest canopy is useful for mapping the forest structure, including above ground biomass (AGB) estimation. Recent studies confirmed that the empirical AGB models generated from the L-band radar backscatter can provide favourable estimation results, especially if the data has dual-polarization configuration. Using dual polarimetry SAR data the backscatter signal is more sensitive to forest biomass and forest structure because of tree trunk scattering, thus showing better discriminations of different forest successional stages. These SAR approaches, however, need to be further studied for the application in tropical peatlands ecosystem We aims at estimating forest carbon stocks and stand biophysical properties using combination of multi-temporal and multi-polarizations (quad-polarimetric) L-band SAR data and focuses on tropical peat swamp forest over Kampar Peninsula at Riau Province, Sumatra, Indonesia which is one of the most peat abundant region in the country. Applying radar backscattering (Sigma nought) to model the biomass we found that co-polarizations (HH and VV) band are more sensitive than cross-polarization channels (HV and VH). Individual HH polarization channel from April 2010 explained > 86% of AGB. Whereas VV polarization showed strong correlation coefficients with LAI, tree height, tree diameter and basal area. Surprisingly, polarimetric anisotropy feature from April 2007 SAR data show relatively high correlations with almost all forest biophysical parameters. Polarimetric anisotropy, which explains the ratio between the second and the first dominant scattering mechanism from a target has reduced at some extent the randomness of scattering mechanism, thus improve the predictability of this particular feature in estimating the forest properties. These results may be influenced by local seasonal variations of the forest as well as moisture, but available quad-pol SAR data were unable to

  9. Calculations of lightning return stroke electric and magnetic fields above ground

    NASA Technical Reports Server (NTRS)

    Master, M. J.; Uman, M. A.; Ling, Y. T.; Standler, R. B.

    1981-01-01

    Lin et al., (1980) presented a lightning return stroke model with which return stroke electric and magnetic fields measured at ground level could be reproduced. This model and a modified version of it, in which the initial current peak decays with height above ground, are used to compute waveforms for altitudes from 0-10 km and at ranges of 20 m to 10 km. Both the original and modified models gave accurate predictions of measured ground-based fields. The use of the calculated fields in calibrating airborne field measurements from simultaneous ground and airborne data is discussed.

  10. Forest soil respiration rate and delta13C is regulated by recent above ground weather conditions.

    PubMed

    Ekblad, Alf; Boström, Björn; Holm, Anders; Comstedt, Daniel

    2005-03-01

    Soil respiration, a key component of the global carbon cycle, is a major source of uncertainty when estimating terrestrial carbon budgets at ecosystem and higher levels. Rates of soil and root respiration are assumed to be dependent on soil temperature and soil moisture yet these factors often barely explain half the seasonal variation in soil respiration. We here found that soil moisture (range 16.5-27.6% of dry weight) and soil temperature (range 8-17.5 degrees C) together explained 55% of the variance (cross-validated explained variance; Q2) in soil respiration rate (range 1.0-3.4 micromol C m(-2) s(-1)) in a Norway spruce (Picea abies) forest. We hypothesised that this was due to that the two components of soil respiration, root respiration and decomposition, are governed by different factors. We therefore applied PLS (partial least squares regression) multivariate modelling in which we, together with below ground temperature and soil moisture, used the recent above ground air temperature and air humidity (vapour pressure deficit, VPD) conditions as x-variables. We found that air temperature and VPD data collected 1-4 days before respiration measurements explained 86% of the seasonal variation in the rate of soil respiration. The addition of soil moisture and soil temperature to the PLS-models increased the Q2 to 93%. delta13C analysis of soil respiration supported the hypotheses that there was a fast flux of photosynthates to root respiration and a dependence on recent above ground weather conditions. Taken together, our results suggest that shoot activities the preceding 1-6 days influence, to a large degree, the rate of root and soil respiration. We propose this above ground influence on soil respiration to be proportionally largest in the middle of the growing season and in situations when there is large day-to-day shifts in the above ground weather conditions. During such conditions soil temperature may not exert the major control on root respiration. PMID

  11. Deep Neural Networks for Above-Ground Detection in Very High Spatial Resolution Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Marmanis, D.; Adam, F.; Datcu, M.; Esch, T.; Stilla, U.

    2015-03-01

    Deep Learning techniques have lately received increased attention for achieving state-of-the-art results in many classification problems, including various vision tasks. In this work, we implement a Deep Learning technique for classifying above-ground objects within urban environments by using a Multilayer Perceptron model and VHSR DEM data. In this context, we propose a novel method called M-ramp which significantly improves the classifier's estimations by neglecting artefacts, minimizing convergence time and improving overall accuracy. We support the importance of using the M-ramp model in DEM classification by conducting a set of experiments with both quantitative and qualitative results. Precisely, we initially train our algorithm with random DEM tiles and their respective point-labels, considering less than 0.1% over the test area, depicting the city center of Munich (25 km2). Furthermore with no additional training, we classify two much larger unseen extents of the greater Munich area (424 km2) and Dongying city, China (257 km2) and evaluate their respective results for proving knowledge-transferability. Through the use of M-ramp, we were able to accelerate the convergence by a magnitude of 8 and achieve a decrease in above-ground relative error by 24.8% and 5.5% over the different datasets.

  12. Above-ground woody carbon sequestration measured from tree rings is coherent with net ecosystem productivity at five eddy-covariance sites.

    PubMed

    Babst, Flurin; Bouriaud, Olivier; Papale, Dario; Gielen, Bert; Janssens, Ivan A; Nikinmaa, Eero; Ibrom, Andreas; Wu, Jian; Bernhofer, Christian; Köstner, Barbara; Grünwald, Thomas; Seufert, Günther; Ciais, Philippe; Frank, David

    2014-03-01

    • Attempts to combine biometric and eddy-covariance (EC) quantifications of carbon allocation to different storage pools in forests have been inconsistent and variably successful in the past. • We assessed above-ground biomass changes at five long-term EC forest stations based on tree-ring width and wood density measurements, together with multiple allometric models. Measurements were validated with site-specific biomass estimates and compared with the sum of monthly CO₂ fluxes between 1997 and 2009. • Biometric measurements and seasonal net ecosystem productivity (NEP) proved largely compatible and suggested that carbon sequestered between January and July is mainly used for volume increase, whereas that taken up between August and September supports a combination of cell wall thickening and storage. The inter-annual variability in above-ground woody carbon uptake was significantly linked with wood production at the sites, ranging between 110 and 370 g C m(-2) yr(-1) , thereby accounting for 10-25% of gross primary productivity (GPP), 15-32% of terrestrial ecosystem respiration (TER) and 25-80% of NEP. • The observed seasonal partitioning of carbon used to support different wood formation processes refines our knowledge on the dynamics and magnitude of carbon allocation in forests across the major European climatic zones. It may thus contribute, for example, to improved vegetation model parameterization and provides an enhanced framework to link tree-ring parameters with EC measurements. PMID:24206564

  13. Mapping vegetation cover and biomass on the Qinghai-Tibet-Plateau using hyperspectral measurements and multispectral satellite images

    NASA Astrophysics Data System (ADS)

    Meyer, Hanna; Lehnert, Lukas W.; Wang, Yun; Reudenbach, Christoph; Nauss, Thomas; Bendix, Jörg

    2016-04-01

    Pastoralism is the dominant land-use on the Qinghai-Tibet-Plateau (QTP) providing the major economic resource for the local population. However, the pastures are highly supposed to be affected by ongoing degradation whose extent is still disputed. This study uses hyperspectral in situ measurements and multispectral satellite images to assess vegetation cover and above ground biomass (AGB) as proxies of pasture degradation on a regional scale. Using Random Forests in conjunction with recursive feature selection as modeling tool, it is tested whether the full hyperspectral information is needed or if multispectral information is sufficient to accurately estimate vegetation cover and AGB. To regionalize pasture degradation proxies, the transferability of the locally derived models to high resolution multispectral satellite data is assessed. For this purpose, 1183 hyperspectral measurements and vegetation records were sampled at 18 locations on the QTP. AGB was determined on 25 0.5x0.5m plots. Proxies for pasture degradation were derived from the spectra by calculating narrow-band indices (NBI). Using the NBI as predictor variables vegetation cover and AGB were modeled. Models were calculated using the hyperspectral data as well as the same data resampled to WorldView-2, QuickBird and RapidEye channels. The hyperspectral results were compared to the multispectral results. Finally, the models were applied to satellite data to map vegetation cover and AGB on a regional scale. Vegetation cover was accurately predicted by Random Forest if hyperspectral measurements were used. In contrast, errors in AGB estimations were considerably higher. Only small differences in accuracy were observed between the models based on hyper- compared to multispectral data. The application of the models to satellite images generally resulted in an increase of the estimation error. Though this reflects the challenge of applying in situ measurements to satellite data, the results still show a

  14. Predicting biomass of hyperdiverse and structurally complex Central Amazon forests - a virtual approach using extensive field data

    NASA Astrophysics Data System (ADS)

    Magnabosco Marra, D.; Higuchi, N.; Trumbore, S. E.; Ribeiro, G. H. P. M.; dos Santos, J.; Carneiro, V. M. C.; Lima, A. J. N.; Chambers, J. Q.; Negrón-Juárez, R. I.; Holzwarth, F.; Reu, B.; Wirth, C.

    2015-09-01

    Old-growth forests are subject to substantial changes in structure and species composition due to the intensification of human activities, gradual climate change and extreme weather events. Trees store ca. 90 % of the total AGB above-ground biomass in tropical forests and AGB estimation models are crucial for forest management and conservation. In the Central Amazon, predicting AGB at large spatial-scales is a challenging task due to the heterogeneity of successional stages, high tree species diversity and inherent variations in allometry and architecture. We parameterized generic AGB estimation models applicable across species and a wide range of structural and compositional variation related to species sorting into height layers as well as frequent natural disturbances. We used 727 trees from 101 genera and at least 135 species harvested in a contiguous forest near Manaus, Brazil. Sampling from this dataset we assembled six scenarios designed to span existing gradients in floristic composition and size distribution in order to select models that best predict AGB at the landscape-level across successional gradients. We found that good individual tree model fits do not necessarily translate into good predictions of AGB at the landscape level. When predicting AGB (dry mass) over scenarios using our different models and an available pantropical model, we observed systematic biases ranging from -31 % (pantropical) to +39 %, with RMSE root-mean-square error values of up to 130 Mg ha-1 (pantropical). Our first and second best models had both low mean biases (0.8 and 3.9 %, respectively) and RMSE (9.4 and 18.6 Mg ha-1) when applied over scenarios. Predicting biomass correctly at the landscape-level in complex tropical forests, especially allowing good performance at the margins of data availability for model parametrization, requires the inclusion of predictors related to species architecture. The model of interest should comprise the floristic composition and size

  15. Variability of above-ground litter inputs alters soil physicochemical and biological processes: a meta-analysis of litterfall-manipulation experiments

    NASA Astrophysics Data System (ADS)

    Xu, S.; Liu, L. L.; Sayer, E. J.

    2013-11-01

    Global change has been shown to alter the amount of above-ground litter inputs to soil greatly, which could cause substantial cascading effects on below-ground biogeochemical cycling. Despite extensive study, there is uncertainty about how changes in above-ground litter inputs affect soil carbon and nutrient turnover and transformation. Here, we conducted a meta-analysis on 70 litter-manipulation experiments in order to assess how changes in above-ground litter inputs alter soil physicochemical properties, carbon dynamics and nutrient cycles. Our results demonstrated that litter removal decreased soil respiration by 34%, microbial biomass carbon in the mineral soil by 39% and total carbon in the mineral soil by 10%, whereas litter addition increased them by 31, 26 and 10%, respectively. This suggests that greater litter inputs increase the soil carbon sink despite higher rates of carbon release and transformation. Total nitrogen and extractable inorganic nitrogen in the mineral soil decreased by 17 and 30%, respectively, under litter removal, but were not altered by litter addition. Overall, litter manipulation had a significant impact upon soil temperature and moisture, but not soil pH; litter inputs were more crucial in buffering soil temperature and moisture fluctuations in grassland than in forest. Compared to other ecosystems, tropical and subtropical forests were more sensitive to variation in litter inputs, as altered litter inputs affected the turnover and accumulation of soil carbon and nutrients more substantially over a shorter time period. Our study demonstrates that although the magnitude of responses differed greatly among ecosystems, the direction of the responses was very similar across different ecosystems. Interactions between plant productivity and below-ground biogeochemical cycling need to be taken into account to predict ecosystem responses to environmental change.

  16. Advanced Coupled Simulation of Borehole Thermal Energy Storage Systems and Above Ground Installations

    NASA Astrophysics Data System (ADS)

    Welsch, Bastian; Rühaak, Wolfram; Schulte, Daniel O.; Bär, Kristian; Sass, Ingo

    2016-04-01

    Seasonal thermal energy storage in borehole heat exchanger arrays is a promising technology to reduce primary energy consumption and carbon dioxide emissions. These systems usually consist of several subsystems like the heat source (e.g. solarthermics or a combined heat and power plant), the heat consumer (e.g. a heating system), diurnal storages (i.e. water tanks), the borehole thermal energy storage, additional heat sources for peak load coverage (e.g. a heat pump or a gas boiler) and the distribution network. For the design of an integrated system, numerical simulations of all subsystems are imperative. A separate simulation of the borehole energy storage is well-established but represents a simplification. In reality, the subsystems interact with each other. The fluid temperatures of the heat generation system, the heating system and the underground storage are interdependent and affect the performance of each subsystem. To take into account these interdependencies, we coupled a software for the simulation of the above ground facilities with a finite element software for the modeling of the heat flow in the subsurface and the borehole heat exchangers. This allows for a more realistic view on the entire system. Consequently, a finer adjustment of the system components and a more precise prognosis of the system's performance can be ensured.

  17. Net Changes in Above Ground Woody Carbon Stock in Western Juniper Woodlands using Wavelet Techniques and Multi-temporal Aerial Photography

    NASA Astrophysics Data System (ADS)

    Strand, E. K.; Bunting, S. C.; Smith, A. M.

    2006-12-01

    Expansion of woody plant cover in semi-arid ecosystems previously occupied primarily by grasses and forbs has been identified as an important land cover change process affecting the global carbon budget. Although woody encroachment occurs worldwide, quantifying changes in carbon pools and fluxes related to this phenomenon via remote sensing is challenging because large areas are affected at a fine spatial resolution (1- 10 m) and, in many cases, at slow temporal rates. Two-dimensional spatial wavelet analysis (SWA) represents a novel image processing technique that has been successful in automatically and objectively quantifying ecologically relevant features at multiple scales. We apply SWA to current and historic 1-m resolution black and white aerial photography to quantify changes in above ground woody biomass and carbon stock of western juniper (Juniperus occidentalis subsp. occidentalis) expanding into sagebrush (Artemisia spp.) steppe on the Owyhee Plateau in southwestern Idaho. Due to the large land area (330,000 ha) and variable availability of historical photography, we sampled forty-eight 100-ha blocks situated across the area, stratified using topographic, soil, and land stewardship variables. The average juniper plant cover increased one-fold (from 5.3% to 10.4% total cover) at the site during the time period of 1939-1946 to 1998-2004. Juniper plant density has increased by 128% with a higher percentage of the plant population in the smaller size classes compared to the size distribution 60 years ago. After image-based SWA delineation of tree crown sizes, we computed the change in above ground woody plant biomass and carbon stock between the two time periods using allometry. Areas where the shrub steppe is dominated by low sagebrush (Artemisia arbuscula) has experienced little to no expansion of western juniper. However, on deeper, more well drained soils capable of supporting mountain big sagebrush (Artemisia tridentata subsp. vaseyana), the above

  18. The Uncertainty of Biomass Estimates from Modeled ICESat-2 Returns Across a Boreal Forest Gradient

    NASA Technical Reports Server (NTRS)

    Montesano, P. M.; Rosette, J.; Sun, G.; North, P.; Nelson, R. F.; Dubayah, R. O.; Ranson, K. J.; Kharuk, V.

    2014-01-01

    The Forest Light (FLIGHT) radiative transfer model was used to examine the uncertainty of vegetation structure measurements from NASA's planned ICESat-2 photon counting light detection and ranging (LiDAR) instrument across a synthetic Larix forest gradient in the taiga-tundra ecotone. The simulations demonstrate how measurements from the planned spaceborne mission, which differ from those of previous LiDAR systems, may perform across a boreal forest to non-forest structure gradient in globally important ecological region of northern Siberia. We used a modified version of FLIGHT to simulate the acquisition parameters of ICESat-2. Modeled returns were analyzed from collections of sequential footprints along LiDAR tracks (link-scales) of lengths ranging from 20 m-90 m. These link-scales traversed synthetic forest stands that were initialized with parameters drawn from field surveys in Siberian Larix forests. LiDAR returns from vegetation were compiled for 100 simulated LiDAR collections for each 10 Mg · ha(exp -1) interval in the 0-100 Mg · ha(exp -1) above-ground biomass density (AGB) forest gradient. Canopy height metrics were computed and AGB was inferred from empirical models. The root mean square error (RMSE) and RMSE uncertainty associated with the distribution of inferred AGB within each AGB interval across the gradient was examined. Simulation results of the bright daylight and low vegetation reflectivity conditions for collecting photon counting LiDAR with no topographic relief show that 1-2 photons are returned for 79%-88% of LiDAR shots. Signal photons account for approximately 67% of all LiDAR returns, while approximately 50% of shots result in 1 signal photon returned. The proportion of these signal photon returns do not differ significantly (p greater than 0.05) for AGB intervals greater than 20 Mg · ha(exp -1). The 50m link-scale approximates the finest horizontal resolution (length) at which photon counting LiDAR collection provides strong model

  19. Root growth dynamics linked to above-ground growth in walnut (Juglans regia)

    PubMed Central

    Contador, Maria Loreto; Comas, Louise H.; Metcalf, Samuel G.; Stewart, William L.; Porris Gomez, Ignacio; Negron, Claudia; Lampinen, Bruce D.

    2015-01-01

    Background and Aims Examination of plant growth below ground is relatively scant compared with that above ground, and is needed to understand whole-plant responses to the environment. This study examines whether the seasonal timing of fine root growth and the spatial distribution of this growth through the soil profile varies in response to canopy manipulation and soil temperature. Methods Plasticity in the seasonal timing and vertical distribution of root production in response to canopy and soil water manipulation was analysed in field-grown walnut (Juglans regia ‘Chandler’) using minirhizotron techniques. Key Results Root production in walnuts followed a unimodal curve, with one marked flush of root growth starting in mid-May, with a peak in mid-June. Root production declined later in the season, corresponding to increased soil temperature, as well as to the period of major carbohydrate allocation to reproduction. Canopy and soil moisture manipulation did not influence the timing of root production, but did influence the vertical distribution of roots through the soil profile. Water deficit appeared to promote root production in deeper soil layers for mining soil water. Canopy removal appeared to promote shallow root production. Conclusions The findings of this study add to growing evidence that root growth in many ecosystems follows a unimodal curve with one marked flush of root growth in coordination with the initial leaf flush of the season. Root vertical distribution appeared to have greater plasticity than timing of root production in this system, with temperature and/or carbohydrate competition constraining the timing of root growth. Effects on root distribution can have serious impacts on trees, with shallow rooting having negative impacts in years with limited soil water or positive impacts in years with wet springs, and deep rooting having positive impacts on soil water mining from deeper soil layers but negative impacts in years with wet springs

  20. Imaging the Socorro Magma Body Using Free Above-Ground Sources

    NASA Astrophysics Data System (ADS)

    Hyde, E.; Saldana, S.; Snelson, C. M.; Greschke, B.

    2008-12-01

    The Socorro Magma Body (SMB) is located within the Rio Grande Rift and is intersected by the Precambrian Socorro Fracture Zone near Socorro, NM. The SMB seems to be the source of a 5,000 km2 area of elevated seismic region known as the Socorro Seismic Anomaly. The first evidence of a subsurface reflector was from microearthquake studies. A COCORP seismic reflection profile provided further evidence for an essentially flat magmatic sill-like intrusion approximately 19 km below the surface, with less than a 1° slope and a lateral area of about 3400 km2 with an estimated thickness of about 100 m. A fundamental question regarding the SMB is related to the nature of its activity. The uplift associated with the SMB coupled with the presence of shallow earthquake swarms in the area is typically associated with the movement of magma, which may be indicative of active magmatic emplacement. As a pilot test to obtain P-wave velocity data, we used free explosive sources from the Energetic Materials Research and Testing Center (EMRTC) at New Mexico Tech in Socorro, NM. Our goals were to determine how much seismic energy is necessary to receive a decent signal back on the recorders and also to develop a preliminary refraction velocity model over the SMB. For this refraction experiment, 59 single-channel recorders (Texans - RT125a) were deployed over a distance of 125 km for a 1-week period centered at the EMRTC blast site. Over that time period, EMRTC set off six ~9,000 lb (4,082 kg) ANFO shots above ground. Although much of this energy went into the air, we were able to recover a small amount of this energy to build preliminary velocity models. The energy created by the blasts propagated about halfway through the array. These data have been used to produce a couple of 1-D models and a preliminary 2-D model of apparent velocity. We plan to use these results to develop a proposal to conduct a full controlled and passive-source experiment over the SMB in the near future.

  1. Below-ground plant-fungus network topology is not congruent with above-ground plant-animal network topology.

    PubMed

    Toju, Hirokazu; Guimarães, Paulo R; Olesen, Jens M; Thompson, John N

    2015-10-01

    In nature, plants and their pollinating and/or seed-dispersing animals form complex interaction networks. The commonly observed pattern of links between specialists and generalists in these networks has been predicted to promote species coexistence. Plants also build highly species-rich mutualistic networks below ground with root-associated fungi, and the structure of these plant-fungus networks may also affect terrestrial community processes. By compiling high-throughput DNA sequencing data sets of the symbiosis of plants and their root-associated fungi from three localities along a latitudinal gradient, we uncovered the entire network architecture of these interactions under contrasting environmental conditions. Each network included more than 30 plant species and hundreds of mycorrhizal and endophytic fungi belonging to diverse phylogenetic groups. The results were consistent with the notion that processes shaping host-plant specialization of fungal species generate a unique linkage pattern that strongly contrasts with the pattern of above-ground plant-partner networks. Specifically, plant-fungus networks lacked a "nested" architecture, which has been considered to promote species coexistence in plant-partner networks. Rather, the below-ground networks had a conspicuous "antinested" topology. Our findings lead to the working hypothesis that terrestrial plant community dynamics are likely determined by the balance between above-ground and below-ground webs of interspecific interactions. PMID:26601279

  2. Below-ground plant–fungus network topology is not congruent with above-ground plant–animal network topology

    PubMed Central

    Toju, Hirokazu; Guimarães, Paulo R.; Olesen, Jens M.; Thompson, John N.

    2015-01-01

    In nature, plants and their pollinating and/or seed-dispersing animals form complex interaction networks. The commonly observed pattern of links between specialists and generalists in these networks has been predicted to promote species coexistence. Plants also build highly species-rich mutualistic networks below ground with root-associated fungi, and the structure of these plant–fungus networks may also affect terrestrial community processes. By compiling high-throughput DNA sequencing data sets of the symbiosis of plants and their root-associated fungi from three localities along a latitudinal gradient, we uncovered the entire network architecture of these interactions under contrasting environmental conditions. Each network included more than 30 plant species and hundreds of mycorrhizal and endophytic fungi belonging to diverse phylogenetic groups. The results were consistent with the notion that processes shaping host-plant specialization of fungal species generate a unique linkage pattern that strongly contrasts with the pattern of above-ground plant–partner networks. Specifically, plant–fungus networks lacked a “nested” architecture, which has been considered to promote species coexistence in plant–partner networks. Rather, the below-ground networks had a conspicuous “antinested” topology. Our findings lead to the working hypothesis that terrestrial plant community dynamics are likely determined by the balance between above-ground and below-ground webs of interspecific interactions. PMID:26601279

  3. Impact of Ground-Applied Termiticides on the Above-Ground Foraging Behavior of the Formosan Subterranean Termite.

    PubMed

    Henderson, Gregg; Gautam, Bal K; Wang, Cai

    2016-01-01

    We conducted a laboratory study to determine the impact of ground-applied termiticides on the above-ground foraging behavior of Coptotermes formosanus. Two concentrations (1 and 10 ppm) each of three termiticides, viz. fipronil, imidacloprid and chlorantraniliprole, were tested. After one month post-treatment (fipronil 10 ppm was run for 12 days only and all other treatments were run for one month), fipronil had the lowest percentage of survival (3%-4%) at both concentrations. Termite survival ranged from 31% to 40% in the case of imidacloprid treatments and 10 ppm chlorantraniliprole. However, 1 ppm chlorantraniliprole did not cause significant mortality compared to the controls. Foraging on the bottom substrate was evident in all replicates for all chemicals initially. However, a portion of the foraging population avoided the ground treatment toxicants after several days of bottom foraging. Only the slower-acting non-repellents created this repellent barrier, causing avoidance behavior that was most likely due to dead termites and fungus buildup on the treated bottom substrate. Fipronil appeared more toxic and faster acting at the concentrations tested, thus limiting this repellent effect. Suggestions by the pest control industry in Louisiana that some non-repellents can create a repellent barrier stranding live termites above ground are supported by this laboratory study. PMID:27571108

  4. Estimating tropical forest biomass with a combination of SAR image texture and Landsat TM data: An assessment of predictions between regions

    NASA Astrophysics Data System (ADS)

    Cutler, M. E. J.; Boyd, D. S.; Foody, G. M.; Vetrivel, A.

    2012-06-01

    Quantifying the above ground biomass of tropical forests is critical for understanding the dynamics of carbon fluxes between terrestrial ecosystems and the atmosphere, as well as monitoring ecosystem responses to environmental change. Remote sensing remains an attractive tool for estimating tropical forest biomass but relationships and methods used at one site have not always proved applicable to other locations. This lack of a widely applicable general relationship limits the operational use of remote sensing as a method for biomass estimation, particularly in high biomass ecosystems. Here, multispectral Landsat TM and JERS-1 SAR data were used together to estimate tropical forest biomass at three separate geographical locations: Brazil, Malaysia and Thailand. Texture measures were derived from the JERS-1 SAR data using both wavelet analysis and Grey Level Co-occurrence Matrix methods, and coupled with multispectral data to provide inputs to artificial neural networks that were trained under four different training scenarios and validated using biomass measured from 144 field plots. When trained and tested with data collected from the same location, the addition of SAR texture to multispectral data showed strong correlations with above ground biomass (r = 0.79, 0.79 and 0.84 for Thailand, Malaysia and Brazil respectively). Also, when networks were trained and tested with data from all three sites, the strength of correlation (r = 0.55) was stronger than previously reported results from the same sites that used multispectral data only. Uncertainty in estimating AGB from different allometric equations was also tested but found to have little effect on the strength of the relationships observed. The results suggest that the inclusion of SAR texture with multispectral data can go someway towards providing relationships that are transferable across time and space, but that further work is required if satellite remote sensing is to provide robust and reliable

  5. Integrating disparate lidar data at the national scale to assess the relationships between height above ground, land cover and ecoregions

    USGS Publications Warehouse

    Stoker, Jason M.; Cochrane, Mark A.; Roy, David P.

    2013-01-01

    With the acquisition of lidar data for over 30 percent of the US, it is now possible to assess the three-dimensional distribution of features at the national scale. This paper integrates over 350 billion lidar points from 28 disparate datasets into a national-scale database and evaluates if height above ground is an important variable in the context of other nationalscale layers, such as the US Geological Survey National Land Cover Database and the US Environmental Protection Agency ecoregions maps. While the results were not homoscedastic and the available data did not allow for a complete height census in any of the classes, it does appear that where lidar data were used, there were detectable differences in heights among many of these national classification schemes. This study supports the hypothesis that there were real, detectable differences in heights in certain national-scale classification schemes, despite height not being a variable used in any of the classification routines.

  6. Facilitation and inhibition: changes in plant nitrogen and secondary metabolites mediate interactions between above-ground and below-ground herbivores.

    PubMed

    Huang, Wei; Siemann, Evan; Yang, Xuefang; Wheeler, Gregory S; Ding, Jianqing

    2013-09-22

    To date, it remains unclear how herbivore-induced changes in plant primary and secondary metabolites impact above-ground and below-ground herbivore interactions. Here, we report effects of above-ground (adult) and below-ground (larval) feeding by Bikasha collaris on nitrogen and secondary chemicals in shoots and roots of Triadica sebifera to explain reciprocal above-ground and below-ground insect interactions. Plants increased root tannins with below-ground herbivory, but above-ground herbivory prevented this increase and larval survival doubled. Above-ground herbivory elevated root nitrogen, probably contributing to increased larval survival. However, plants increased foliar tannins with above-ground herbivory and below-ground herbivory amplified this increase, and adult survival decreased. As either foliar or root tannins increased, foliar flavonoids decreased, suggesting a trade-off between these chemicals. Together, these results show that plant chemicals mediate contrasting effects of conspecific larval and adult insects, whereas insects may take advantage of plant responses to facilitate their offspring performance, which may influence population dynamics. PMID:23902902

  7. Tropical-Forest Biomass Dynamics from X-Band, TanDEM-X DATA

    NASA Astrophysics Data System (ADS)

    Treuhaft, R. N.; Neumann, M.; Keller, M. M.; Goncalves, F. G.; Santos, J. R.

    2015-12-01

    The measurement of the change in above ground biomass (AGB) is key for understanding the carbon sink/source nature of tropical forests. Interferometric X-band radar from the only orbiting interferometer, TanDEM-X, shows sensitivity to standing biomass up to at least 300 Mg/ha. This sensitivity may be due in part to the propagation of the shorter X-band wavelength (0.031 m) through holes in the canopy. This talk focuses on estimating the change in AGB over time. Interferometric baselines from TanDEM-X have been obtained in Tapajós National Forest in the Brazilian Amazon over a 4-year period, from 2011 to 2015. Lidar measurements were also acquired during this period. Field measurements of height, height-to-base-of-crown, species, diameter, and position were acquired in 2010, 2013, and 2015. We show interferometric phase height changes, and suggest how these phase height changes are related to biomass change. First we show height changes between baselines separated by one month, over which we expect no change in AGB, to evaluate precision. We find an RMS of <2 m for ~85 stands in the phase height over one month, corresponding to about a 10% measurement of change, which suggests we can detect about a 17 Mg/ha change in AGB at Tapajos. In contrast, interferometric height changes over the period 2011 to 2014 have larger RMS scatters of > 3 m, due to actual change. Most stands show changes in interferometric phase height consistent with regrowth (~10 Mg/ha/yr), and several stands show abrupt, large changes in phase height (>10 m) due to logging and natural disturbance. At the end of 2015, we will acquire more TanDEM-X data over Tapajos, including an area subjected to selective logging. We are doing "before" (March 2015) and "after" (October 2015) fieldwork to be able to understand the signature of change due to selective logging in TanDEM-X interferometric data.

  8. The effect of freezing and drying on leaching of DOM from above ground vascular plant material from the Alaskan Arctic

    NASA Astrophysics Data System (ADS)

    Khosh, M. S.; McClelland, J. W.

    2014-12-01

    Our understanding of the seasonal dynamics of fluvial dissolved organic matter (DOM) concentrations and fluxes in Arctic catchments has increased substantially during recent years, especially during the spring, which historically has been an under-sampled time period. While a number of studies have observed peaks in both DOM concentrations and fluxes during the spring snowmelt, our knowledge of the mechanisms that control these observations are still lacking. During the initial snowmelt period, frozen ground and the snow matrix act to constrain melt-water to the soil surface. We hypothesize that restriction of flow during this time facilitates leaching of DOM from senescent above ground vegetation and detritus contributing to the high DOM concentrations observed during the spring melt. This study focuses on the effect of freezing and drying on the leaching of dissolved organic carbon and nitrogen (DOC and DON) from above ground vascular plant material. Specifically, we examined the treatment effects of freezing, drying, and freeze-drying on three genera of common Alaskan Arctic vascular plants; Eriophorum (spp.), Carex (spp.), and Salix (spp.). Frozen and freeze-dried plant material released more DOC over the experimental 96 hour leaching period compared to plant material that was only dried. Qualitatively, these patterns were similar among the different plant types, while quantitatively Salix leached more DOC than either Eriophorum or Carex in all treatments. Similar patterns were also seen for DON between the different treatments and among the different plant types. Compositionally, DOM that was leached from frozen and freeze-dried material had higher C:N ratios than material that was only dried. Comparatively, DOM leached from Salix had much higher C:N ratios than either Eriophorum or Carex. During the first 24 hours of leaching, C:N ratios tended to increase followed by a subsequent leveling or decrease, suggesting that the composition of leached DOM varied

  9. AGB stars and presolar grains

    SciTech Connect

    Busso, M.; Trippella, O.; Maiorca, E.; Palmerini, S.

    2014-05-09

    Among presolar materials recovered in meteorites, abundant SiC and Al{sub 2}O{sub 3} grains of AGB origins were found. They showed records of C, N, O, {sup 26}Al and s-element isotopic ratios that proved invaluable in constraining the nucleosynthesis models for AGB stars [1, 2]. In particular, when these ratios are measured in SiC grains, they clearly reveal their prevalent origin in cool AGB circumstellar envelopes and provide information on both the local physics and the conditions at the nucleosynthesis site (the H- and He-burning layers deep inside the structure). Among the properties ascertained for the main part of the SiC data (the so-called mainstream ones), we mention a large range of {sup 14}N/{sup 15}N ratios, extending below the solar value [3], and {sup 12}C/{sup 13}C ratios ≳ 30. Other classes of grains, instead, display low carbon isotopic ratios (≳ 10) and a huge dispersion for N isotopes, with cases of large {sup 15}N excess. In the same grains, isotopes currently feeded by slow neutron captures reveal the characteristic pattern expected from this process at an efficiency slightly lower than necessary to explain the solar main s-process component. Complementary constraints can be found in oxide grains, especially Al{sub 2}O{sub 3} crystals. Here, the oxygen isotopes and the content in {sup 26}Al are of a special importance for clarifying the partial mixing processes that are known to affect evolved low-mass stars. Successes in modeling the data, as well as problems in explaining some of the mentioned isotopic ratios through current nucleosynthesis models are briefly outlined.

  10. Galactic Sodium from AGB Stars

    NASA Astrophysics Data System (ADS)

    Izzard, R. G.; Gibson, B. K.; Stancliffe, R. J.

    2007-11-01

    Galactic chemical evolution (GCE) models which include sodium from type II supernovae (SNe) alone underestimate the abundance of sodium in the interstellar medium by a factor of 2 to 3 over about 3 ridex in metallicity and predict a flat behavior in the evolution of riNafe at super-solar metallicities. Conversely, recent observations of stars with rifeh ˜ +0.4 suggest that riNafe increases at high metallicity. We have combined stellar evolution models of asymptotic giant branch (AGB) and Wolf-Rayet (WR) stars with the latest SN yields in an attempt to resolve these problems dots and have created many more.

  11. Disease ecology across soil boundaries: effects of below-ground fungi on above-ground host-parasite interactions.

    PubMed

    Tao, Leiling; Gowler, Camden D; Ahmad, Aamina; Hunter, Mark D; de Roode, Jacobus C

    2015-10-22

    Host-parasite interactions are subject to strong trait-mediated indirect effects from other species. However, it remains unexplored whether such indirect effects may occur across soil boundaries and connect spatially isolated organisms. Here, we demonstrate that, by changing plant (milkweed Asclepias sp.) traits, arbuscular mycorrhizal fungi (AMF) significantly affect interactions between a herbivore (the monarch butterfly Danaus plexippus) and its protozoan parasite (Ophryocystis elektroscirrha), which represents an interaction across four biological kingdoms. In our experiment, AMF affected parasite virulence, host resistance and host tolerance to the parasite. These effects were dependent on both the density of AMF and the identity of milkweed species: AMF indirectly increased disease in monarchs reared on some species, while alleviating disease in monarchs reared on other species. The species-specificity was driven largely by the effects of AMF on both plant primary (phosphorus) and secondary (cardenolides; toxins in milkweeds) traits. Our study demonstrates that trait-mediated indirect effects in disease ecology are extensive, such that below-ground interactions between AMF and plant roots can alter host-parasite interactions above ground. In general, soil biota may play an underappreciated role in the ecology of many terrestrial host-parasite systems. PMID:26468247

  12. Above-Ground Dimensions and Acclimation Explain Variation in Drought Mortality of Scots Pine Seedlings from Various Provenances.

    PubMed

    Seidel, Hannes; Menzel, Annette

    2016-01-01

    Seedling establishment is a critical part of the life cycle, thus seedling survival might be even more important for forest persistence under recent and future climate change. Scots pine forests have been disproportionally more affected by climate change triggered forest-dieback. Nevertheless, some Scots pine provenances might prove resilient to future drought events because of the species' large distributional range, genetic diversity, and adaptation potential. However, there is a lack of knowledge on provenance-specific survival under severe drought events and on how acclimation alters survival rates in Scots pine seedlings. We therefore conducted two drought-induced mortality experiments with potted Scots pine seedlings in a greenhouse. In the first experiment, 760 three-year-old seedlings from 12 different provenances of the south-western distribution range were subjected to the same treatment followed by the mortality experiment in 2014. In the second experiment, we addressed the question of whether acclimation to re-occurring drought stress events and to elevated temperature might decrease mortality rates. Thus, 139 four-year-old seedlings from France, Germany, and Poland were subjected to different temperature regimes (2012-2014) and drought treatments (2013-2014) before the mortality experiment in 2015. Provenances clearly differed in their hazard of drought-induced mortality, which was only partly related to the climate of their origin. Drought acclimation decreased the hazard of drought-induced mortality. Above-ground dry weight and height were the main determinants for the hazard of mortality, i.e., heavier and taller seedlings were more prone to mortality. Consequently, Scots pine seedlings exhibit a considerable provenance-specific acclimation potential against drought mortality and the selection of suitable provenances might thus facilitate seedling establishment and the persistence of Scots pine forest. PMID:27458477

  13. Risk Assessment of Genetically Engineered Maize Resistant to Diabrotica spp.: Influence on Above-Ground Arthropods in the Czech Republic

    PubMed Central

    Svobodová, Zdeňka; Skoková Habuštová, Oxana; Hutchison, William D.; Hussein, Hany M.; Sehnal, František

    2015-01-01

    Transgenic maize MON88017, expressing the Cry3Bb1 toxin from Bacillus thuringiensis (Bt maize), confers resistance to corn rootworms (Diabrotica spp.) and provides tolerance to the herbicide glyphosate. However, prior to commercialization, substantial assessment of potential effects on non-target organisms within agroecosystems is required. The MON88017 event was therefore evaluated under field conditions in Southern Bohemia in 2009–2011, to detect possible impacts on the above-ground arthropod species. The study compared MON88017, its near-isogenic non-Bt hybrid DK315 (treated or not treated with the soil insecticide Dursban 10G) and two non-Bt reference hybrids (KIPOUS and PR38N86). Each hybrid was grown on five 0.5 ha plots distributed in a 14-ha field with a Latin square design. Semiquantitative ELISA was used to verify Cry3Bb1 toxin levels in the Bt maize. The species spectrum of non-target invertebrates changed during seasons and was affected by weather conditions. The thrips Frankliniella occidentalis was the most abundant species in all three successive years. The next most common species were aphids Rhopalosiphum padi and Metopolophium dirhodum. Frequently observed predators included Orius spp. and several species within the Coccinellidae. Throughout the three-year study, analysis of variance indicated some significant differences (P<0.05). Multivariate analysis showed that the abundance and diversity of plant dwelling insects was similar in maize with the same genetic background, for both Bt (MON88017) and non-Bt (DK315) untreated or insecticide treated. KIPOUS and PR38N86 showed some differences in species abundance relative to the Bt maize and its near-isogenic hybrid. However, the effect of management regime on arthropod community was insignificant and accounted only for a negligible portion of the variability. PMID:26083254

  14. Risk Assessment of Genetically Engineered Maize Resistant to Diabrotica spp.: Influence on Above-Ground Arthropods in the Czech Republic.

    PubMed

    Svobodová, Zdeňka; Skoková Habuštová, Oxana; Hutchison, William D; Hussein, Hany M; Sehnal, František

    2015-01-01

    Transgenic maize MON88017, expressing the Cry3Bb1 toxin from Bacillus thuringiensis (Bt maize), confers resistance to corn rootworms (Diabrotica spp.) and provides tolerance to the herbicide glyphosate. However, prior to commercialization, substantial assessment of potential effects on non-target organisms within agroecosystems is required. The MON88017 event was therefore evaluated under field conditions in Southern Bohemia in 2009-2011, to detect possible impacts on the above-ground arthropod species. The study compared MON88017, its near-isogenic non-Bt hybrid DK315 (treated or not treated with the soil insecticide Dursban 10G) and two non-Bt reference hybrids (KIPOUS and PR38N86). Each hybrid was grown on five 0.5 ha plots distributed in a 14-ha field with a Latin square design. Semiquantitative ELISA was used to verify Cry3Bb1 toxin levels in the Bt maize. The species spectrum of non-target invertebrates changed during seasons and was affected by weather conditions. The thrips Frankliniella occidentalis was the most abundant species in all three successive years. The next most common species were aphids Rhopalosiphum padi and Metopolophium dirhodum. Frequently observed predators included Orius spp. and several species within the Coccinellidae. Throughout the three-year study, analysis of variance indicated some significant differences (P<0.05). Multivariate analysis showed that the abundance and diversity of plant dwelling insects was similar in maize with the same genetic background, for both Bt (MON88017) and non-Bt (DK315) untreated or insecticide treated. KIPOUS and PR38N86 showed some differences in species abundance relative to the Bt maize and its near-isogenic hybrid. However, the effect of management regime on arthropod community was insignificant and accounted only for a negligible portion of the variability. PMID:26083254

  15. Above-Ground Dimensions and Acclimation Explain Variation in Drought Mortality of Scots Pine Seedlings from Various Provenances

    PubMed Central

    Seidel, Hannes; Menzel, Annette

    2016-01-01

    Seedling establishment is a critical part of the life cycle, thus seedling survival might be even more important for forest persistence under recent and future climate change. Scots pine forests have been disproportionally more affected by climate change triggered forest-dieback. Nevertheless, some Scots pine provenances might prove resilient to future drought events because of the species’ large distributional range, genetic diversity, and adaptation potential. However, there is a lack of knowledge on provenance-specific survival under severe drought events and on how acclimation alters survival rates in Scots pine seedlings. We therefore conducted two drought-induced mortality experiments with potted Scots pine seedlings in a greenhouse. In the first experiment, 760 three-year-old seedlings from 12 different provenances of the south-western distribution range were subjected to the same treatment followed by the mortality experiment in 2014. In the second experiment, we addressed the question of whether acclimation to re-occurring drought stress events and to elevated temperature might decrease mortality rates. Thus, 139 four-year-old seedlings from France, Germany, and Poland were subjected to different temperature regimes (2012–2014) and drought treatments (2013–2014) before the mortality experiment in 2015. Provenances clearly differed in their hazard of drought-induced mortality, which was only partly related to the climate of their origin. Drought acclimation decreased the hazard of drought-induced mortality. Above-ground dry weight and height were the main determinants for the hazard of mortality, i.e., heavier and taller seedlings were more prone to mortality. Consequently, Scots pine seedlings exhibit a considerable provenance-specific acclimation potential against drought mortality and the selection of suitable provenances might thus facilitate seedling establishment and the persistence of Scots pine forest. PMID:27458477

  16. Fungal endophytes in above-ground tissues of desert plants: infrequent in culture, but highly diverse and distinctive symbionts

    PubMed Central

    Massimo, Nicholas C.; Nandi Devan, MM; Arendt, Kayla R.; Wilch, Margaret H.; Riddle, Jakob M.; Furr, Susan H.; Steen, Cole; U'Ren, Jana M.; Sandberg, Dustin C.; Arnold, A. Elizabeth

    2015-01-01

    In hot deserts, plants cope with aridity, high temperatures, and nutrient-poor soils with morphological and biochemical adaptations that encompass intimate microbial symbioses. Whereas the root microbiomes of arid-land plants have received increasing attention, factors influencing assemblages of symbionts in above-ground tissues have not been evaluated for many woody plants that flourish in desert environments. We evaluated the diversity, host affiliations, and distributions of endophytic fungi associated with photosynthetic tissues of desert trees and shrubs, focusing on non-succulent woody plants in the species-rich Sonoran Desert. To inform our strength of inference, we evaluated the effects of two different nutrient media, incubation temperatures, and collection seasons on the apparent structure of endophyte assemblages. Analysis of >22,000 tissue segments revealed that endophytes were isolated four times more frequently from photosynthetic stems than leaves. Isolation frequency was lower than expected given the latitude of the study region, and varied among species a function of sampling site and abiotic factors. However, endophytes were very species-rich and phylogenetically diverse, consistent with less-arid sites of a similar latitudinal position. Community composition differed among host species, but not as a function of tissue type, sampling site, sampling month, or exposure. Estimates of abundance, diversity and composition were not influenced by isolation medium or incubation temperature. Phylogenetic analyses of the most commonly isolated genus (Preussia) revealed multiple evolutionary origins of desert-plant endophytism and little phylogenetic structure with regard to seasonality, tissue preference, or optimal temperatures and nutrients for growth in vitro. Together, these results provide insight into endophytic symbioses in desert plant communities, and can be used to optimize strategies for capturing endophyte biodiversity at regional scales. PMID

  17. Vegetation Structure, Tree Volume and Biomass Estimation using Terrestrial Laser Scanning Remote Sensing: A Case Study of the Mangrove Forests in the Everglades National Park

    NASA Astrophysics Data System (ADS)

    Feliciano, E. A.; Wdowinski, S.; Potts, M. D.

    2012-12-01

    Mangrove forests are being threatened by accelerated climate change, sea level rise and coastal projects. Carbon/above ground biomass (AGB) losses due to natural or human intervention can affect global warming. Thus, it is important to monitor AGB fluctuations in mangrove forests similar to those inhabiting the Everglades National Park (ENP). Tree volume and tree wood specific density are two important measurements for the estimation of AGB (mass = volume * density). Wood specific density is acquired in the laboratory by analyzing stem cores acquired in the field. However, tree volume is a challenging task because trees resemble tapered surfaces. The majority of published studies estimate tree volume and biomass using allometric equations, which describe the size, shape, volume or AGB of a given population of trees. However, these equations can be extremely general and might not give a representative value of volume or AGB for a specific tree species. In order to have precise biomass estimations, other methodologies for tree volume estimation are needed. To overcome this problem, we use a state-of-the-art remote sensing tool known as ground-based LiDAR a.k.a Terrestrial Laser Scanner (TLS), which can be used to precisely measure vegetation structure and tree volume from its 3-D point cloud. We surveyed three mangrove communities: (Rhizophora mangle, Laguncuria racemosa and Avicennia germinans) in three different sites along Shark River Slough (SRS), which is the primary source of water to the ENP. Our sites included: small-, intermediate- and tall- size mangroves. Our ground measurements included both: traditional forestry surveys and TLS surveys for tree attributes (tree height and diameter at breast height (DBH)) comparison. These attributes are used as input to allometric equations for the estimation of tree volume and AGB. A total of 25 scans were collected in 2011 with a Leica ScanStation C10 TLS. The 3-D point cloud acquired from the TLS data revealed that

  18. Chemical pollution from AGB Stars

    NASA Astrophysics Data System (ADS)

    Cristallo, S.; Straniero, O.; Gallino, R.; Piersanti, L.; Dominguez, I.

    Low mass AGB Stars are the main contributors to the Galactic s-process enrichment. We present new theoretical results obtained by adopting a full network from H to Bi coupled with the physical evolution of the stellar structure. We describe the formation of a 13C pocket as a consequence of H diffusion from the envelope into the He-rich intershell. Such 13C is burnt during the interpulse phase and provides the main neutron source in these stars. We computed two models with the same total mass (that is 2 M⊙) but two different initial chemical composition, namely (Y=0.269 - Z=0.015) and (Y=0.245 - Z=0.0001), representative of disk and halo stars respectively. We evaluate the differences in the final s-process surface composition and compare the results with the available observational data.

  19. ENVIROMETAL TECHNOLOGIES, INC. - METAL-ENHANCED DECHLORINATION OF VOLATILE ORGANIC COMPOUNDS USING AN ABOVE-GROUND REACTOR, INNOVATIVE TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    EnviroMetal Technology's metal-enhanced dechlorination technology employs an electrochemical process that involves oxidation of iron and reductive dehalogenation of halogenated VOCs in aqueous media. The process can be operated as an above ground reactor or can alternatively perf...

  20. Height and Biomass of Mangroves in Africa from ICEsat/GLAS and SRTM

    NASA Technical Reports Server (NTRS)

    Fatoyinbo, Temilola E.; Simard, Marc

    2012-01-01

    The accurate quantification of forest 3-D structure is of great importance for studies of the global carbon cycle and biodiversity. These studies are especially relevant in Africa, where deforestation rates are high and the lack of background data is great. Mangrove forests are ecologically significant and it is important to measure mangrove canopy heights and biomass. The objectives of this study are to estimate: 1. The total area, 2. Canopy height distributions and 3. Aboveground biomass of mangrove forests in Africa. To derive mangrove 3-D structure and biomass maps, we used a combination of mangrove maps derived from Landsat ETM+, LiDAR canopy height estimates from ICEsat/GLAS (Ice, Cloud, and land Elevation Satellite/Geoscience Laser Altimeter System) and elevation data from SRTM (Shuttle Radar Topography Mission) for the African continent. More specifically, we extracted mangrove forest areas on the SRTM DEM using Landsat based landcover maps. The LiDAR (Light Detection and Ranging) measurements from the large footprint GLAS sensor were used to derive local estimates of canopy height and calibrate the Interferometric Synthetic Aperture Radar (InSAR) data from SRTM. We then applied allometric equations relating canopy height to biomass in order to estimate above ground biomass (AGB) from the canopy height product. The total mangrove area of Africa was estimated to be 25 960 square kilometers with 83% accuracy. The largest mangrove areas and greatest total biomass was 29 found in Nigeria covering 8 573 km2 with 132 x10(exp 6) Mg AGB. Canopy height across Africa was estimated with an overall root mean square error of 3.55 m. This error also includes the impact of using sensors with different resolutions and geolocation error which make comparison between measurements sensitive to canopy heterogeneities. This study provides the first systematic estimates of mangrove area, height and biomass in Africa. Our results showed that the combination of ICEsat/GLAS and

  1. [Estimation of Winter Wheat Biomass Using Visible Spectral and BP Based Artificial Neural Networks].

    PubMed

    Cui, Ri-xian; Liu, Ya-dong; Fu, Jin-dong

    2015-09-01

    The objective of this study was to evaluate the feasibility of using color digital image analysis and back propagation (BP) based artificial neural networks (ANN) method to estimate above ground biomass at the canopy level of winter wheat field. Digital color images of winter wheat canopies grown under six levels of nitrogen treatments were taken with a digital camera for four times during the elongation stage and at the same time wheat plants were sampled to measure above ground biomass. Canopy cover (CC) and 10 color indices were calculated from winter wheat canopy images by using image analysis program (developed in Microsoft Visual Basic). Correlation analysis was carried out to identify the relationship between CC, 10 color indices and winter wheat above ground biomass. Stepwise multiple linear regression and BP based ANN methods were used to establish the models to estimate winter wheat above ground biomass. The results showed that CC, and two color indices had a significant cor- relation with above ground biomass. CC revealed the highest correlation with winter wheat above ground biomass. Stepwise multiple linear regression model constituting CC and color indices of NDI and b, and BP based ANN model with four variables (CC, g, b and NDI) for input was constructed to estimate winter wheat above ground biomass. The validation results indicate that the model using BP based ANN method has a better performance with higher R2 (0.903) and lower RMSE (61.706) and RRMSE (18.876) in comparation with the stepwise regression model. PMID:26669174

  2. Nucleosynthesis in Super-AGB Stars

    NASA Astrophysics Data System (ADS)

    Doherty, C. L.; Gil-Pons, P.; Lugaro, M.; Lau, H. H. B.; Lattanzio, J. C.; Siess, L.; Campbell, S. W.; Petermann, I.

    2015-08-01

    Super-AGB stars reside in the mass range ˜ 6.5-10 M⊙ and are characterised by off-center carbon ignition prior to a thermally pulsing super-AGB phase. These stars can undergo from many tens to even thousands of thermal pulses and experience extreme nucleosynthetic conditions, with temperatures both at the base of the convective envelope and within the helium-burning intershell regions far higher than in their lower-mass counterparts. This can result in interesting nucleosynthesis from extreme hot bottom burning and also different heavy-element distributions caused by the high neutron density generated within the thermal pulse, with this material later mixed to the surface during third dredge-up events. We discuss recent nucleosynthetic yield results for super-AGB stars over the range of metallicity Z = 0.02 × 10-5 ([Fe/H] ˜ 0 to -3.3), and present a small suite of heavy element super-AGB star yield predictions. We also apply our nucleosynthetic results to examine the possible role of super-AGB stars as polluters of the anomalous stars within globular clusters.

  3. Certified and Uncertified Logging Concessions Compared in Gabon: Changes in Stand Structure, Tree Species, and Biomass

    NASA Astrophysics Data System (ADS)

    Medjibe, V. P.; Putz, Francis E.; Romero, Claudia

    2013-03-01

    Forest management certification is assumed to promote sustainable forest management, but there is little field-based evidence to support this claim. To help fill this gap, we compared a Forest Stewardship Council (FSC)-certified with an adjacent uncertified, conventionally logged concession (CL) in Gabon on the basis of logging damage, above-ground biomass (AGB), and tree species diversity and composition. Before logging, we marked, mapped, and measured all trees >10 cm dbh in 20 and twelve 1-ha permanent plots in the FSC and CL areas, respectively. Soil and tree damage due to felling, skidding, and road-related activities was then assessed 2-3 months after the 508 ha FSC study area and the 200 ha CL study area were selectively logged at respective intensities of 5.7 m3/ha (0.39 trees/ha) and 11.4 m3/ha (0.76 trees/ha). For each tree felled, averages of 9.1 and 20.9 other trees were damaged in the FSC and CL plots, respectively; when expressed as the impacts per timber volume extracted, the values did not differ between the two treatments. Skid trails covered 2.9 % more of the CL surface, but skid trail length per unit timber volume extracted was not greater. Logging roads were wider in the CL than FSC site and disturbed 4.7 % more of the surface. Overall, logging caused declines in AGB of 7.1 and 13.4 % at the FSC and CL sites, respectively. Changes in tree species composition were small but greater for the CL site. Based on these findings and in light of the pseudoreplicated study design with less-than perfect counterfactual, we cautiously conclude that certification yields environmental benefits even after accounting for differences in logging intensities.

  4. Certified and uncertified logging concessions compared in Gabon: changes in stand structure, tree species, and biomass.

    PubMed

    Medjibe, V P; Putz, Francis E; Romero, Claudia

    2013-03-01

    Forest management certification is assumed to promote sustainable forest management, but there is little field-based evidence to support this claim. To help fill this gap, we compared a Forest Stewardship Council (FSC)-certified with an adjacent uncertified, conventionally logged concession (CL) in Gabon on the basis of logging damage, above-ground biomass (AGB), and tree species diversity and composition. Before logging, we marked, mapped, and measured all trees >10 cm dbh in 20 and twelve 1-ha permanent plots in the FSC and CL areas, respectively. Soil and tree damage due to felling, skidding, and road-related activities was then assessed 2-3 months after the 508 ha FSC study area and the 200 ha CL study area were selectively logged at respective intensities of 5.7 m(3)/ha (0.39 trees/ha) and 11.4 m(3)/ha (0.76 trees/ha). For each tree felled, averages of 9.1 and 20.9 other trees were damaged in the FSC and CL plots, respectively; when expressed as the impacts per timber volume extracted, the values did not differ between the two treatments. Skid trails covered 2.9 % more of the CL surface, but skid trail length per unit timber volume extracted was not greater. Logging roads were wider in the CL than FSC site and disturbed 4.7 % more of the surface. Overall, logging caused declines in AGB of 7.1 and 13.4 % at the FSC and CL sites, respectively. Changes in tree species composition were small but greater for the CL site. Based on these findings and in light of the pseudoreplicated study design with less-than perfect counterfactual, we cautiously conclude that certification yields environmental benefits even after accounting for differences in logging intensities. PMID:23277438

  5. The creation of AGB fallback shells

    NASA Astrophysics Data System (ADS)

    Chen, Zhuo; Frank, Adam; Blackman, Eric G.; Nordhaus, Jason

    2016-04-01

    The possibility that mass ejected during Asymptotic Giant Branch (AGB) stellar evolution phases falls back towards the star has been suggested in applications ranging from the formation of accretion discs to the powering of late-thermal pulses. In this paper, we seek to explicate the properties of fallback flow trajectories from mass-loss events. We focus on a transient phase of mass ejection with sub-escape speeds, followed by a phase of a typical AGB wind. We solve the problem using both hydrodynamic simulations and a simplified one-dimensional analytic model that matches the simulations. For a given set of initial wind characteristics, we find a critical shell velocity that distinguishes between `shell fallback' and `shell escape'. We discuss the relevance of our results for both single and binary AGB stars. In particular, we discuss how our results help to frame further studies of fallback as a mechanism for forming the substantial population of observed post-AGB stars with dusty discs.

  6. The Compensation Committee. AGB Effective Committee Series

    ERIC Educational Resources Information Center

    Hyatt, Thomas K.

    2013-01-01

    This publication is part of an Association of Governing Boards of Universities and Colleges (AGB) series devoted to strengthening the role of key standing committees of governing boards. While there is no optimum committee system for institutions of higher education, certain principles, practices, and procedures prevail. The best practices…

  7. The Facilities Committee. AGB Effective Committee Series

    ERIC Educational Resources Information Center

    Kaiser, Harvey H.

    2012-01-01

    This publication is part of an Association of Governing Boards of Universities and Colleges (AGB) series devoted to strengthening the role of key standing committees of governing boards. While there is no optimum committee system for institutions of higher education, certain principles, practices, and procedures prevail. The best practices…

  8. 2011 AGB Survey of Higher Education Governance

    ERIC Educational Resources Information Center

    Association of Governing Boards of Universities and Colleges, 2011

    2011-01-01

    This report, the second of AGB's studies of higher education governance, documents the extent to which college and university boards are following good-governance practices. In addition, it takes a focused look at board engagement to determine the degree to which governing boards are actively, intellectually, and strategically involved with their…

  9. The Executive Committee. AGB Effective Committee Series

    ERIC Educational Resources Information Center

    Legon, Richard D.

    2012-01-01

    This publication is part of an Association of Governing Boards of Universities and Colleges (AGB) series devoted to strengthening the role of key standing committees of governing boards. While there is no optimum committee system for institutions of higher education, certain principles, practices, and procedures prevail. The best practices…

  10. The Audit Committee. AGB Effective Committee Series

    ERIC Educational Resources Information Center

    Staisloff, Richard L.

    2011-01-01

    This publication is part of an Association of Governing Boards of Universities and Colleges (AGB) series devoted to strengthening the role of key standing committees of governing boards. While there is no optimum committee system for institutions of higher education, certain principles, practices, and procedures prevail. The best practices…

  11. The Investment Committee. AGB Effective Committee Series

    ERIC Educational Resources Information Center

    Yoder, Jay A.

    2011-01-01

    This publication is part of an AGB series devoted to strengthening the role of key standing committees of governing boards. While there is no optimum committee system for institutions of higher education, certain principles, practices, and procedures prevail. The best practices included in this text support the objectives of board committees:…

  12. Estimating aboveground biomass in interior Alaska with Landsat data and field measurements

    USGS Publications Warehouse

    Ji, Lei; Wylie, Bruce K.; Nossov, Dana R.; Peterson, Birgit; Waldrop, Mark P.; McFarland, Jack W.; Rover, Jennifer R.; Hollingsworth, Teresa N.

    2012-01-01

    Terrestrial plant biomass is a key biophysical parameter required for understanding ecological systems in Alaska. An accurate estimation of biomass at a regional scale provides an important data input for ecological modeling in this region. In this study, we created an aboveground biomass (AGB) map at 30-m resolution for the Yukon Flats ecoregion of interior Alaska using Landsat data and field measurements. Tree, shrub, and herbaceous AGB data in both live and dead forms were collected in summers and autumns of 2009 and 2010. Using the Landsat-derived spectral variables and the field AGB data, we generated a regression model and applied this model to map AGB for the ecoregion. A 3-fold cross-validation indicated that the AGB estimates had a mean absolute error of 21.8 Mg/ha and a mean bias error of 5.2 Mg/ha. Additionally, we validated the mapping results using an airborne lidar dataset acquired for a portion of the ecoregion. We found a significant relationship between the lidar-derived canopy height and the Landsat-derived AGB (R2 = 0.40). The AGB map showed that 90% of the ecoregion had AGB values ranging from 10 Mg/ha to 134 Mg/ha. Vegetation types and fires were the primary factors controlling the spatial AGB patterns in this ecoregion.

  13. Residential radon mitigations at Kitigan Zibi Anishinabeg: comparison of above ground level (RIM JOIST) and above roof line discharge of radon mitigation SUB-SLAB depressurization systems.

    PubMed

    Brossard, Mathieu; Brascoupé, Marcel; Ottawa, Celine Brazeau; Falcomer, Renato; Ottawa, William; Scott, Arthur; Whyte, Jeff

    2012-05-01

    Radon mitigations in nine houses were conducted by installing sub-slab depressurization systems (SSDS) with two types of discharge and fan locations: Ground level discharge with the fan located in the basement or roof-discharge with the fan located in the attic. This paper presents a detailed comparative analysis of the radon reduction efficiency, condensation problems, and the cost-effectiveness of both SSDS installation scenarios in nine houses. The mitigations from both SSDS scenarios were successful in reducing radon. The results of rim-joist installations discharging above ground level with the fans located in the basement show that a sealed radon fan with proper fittings and sealed piping were able to reduce the radon to acceptable levels in a cost-effective manner. PMID:22469999

  14. Asymmetries in AGB Stars: New Results from Aperture Masking Techniques

    NASA Astrophysics Data System (ADS)

    Lykou, F.; Hron, J.; Paladini, C.; Zijlstra, A. A.; Tuthill, P. G.; Norris, B.; Lagadec, E.

    2015-08-01

    Recent studies have shown that the extended circumstellar envelopes of AGB stars are not always spherical in shape. Moreover, the majority of post-AGB stars exhibit highly aspherical shapes, such as bipolar nebulae and equatorial waists in the form of dusty and gaseous disks and/or tori. As such, one should expect that the origin of the morphological changes seen in later evolutionary stages can be traced during the AGB phase. We now present a study of AGB stars using aperture masking interferometry to resolve such aspherical structures.

  15. Optically bright Post-AGB stars in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Kamath, D.; Wood, P. R.; Van Winckel, H.

    2014-04-01

    Post-AGB stars are low- to intermediate-mass stars in a rapid transition from the AGB phase to the Planetary Nebula (PN) phase. Post-AGB stars bear signatures of the structural and chemical composition changes that occur during the AGB phase of evolution and therefore can be used to constrain AGB models and also provide insight to the formation of PNes. In the Galaxy, the luminosities (and hence initial masses) of the diverse group of post-AGB candidates are badly affected by their unknown distances, making it difficult to use the observational characteristics of these interesting objects to throw light on the poorly-understood late stages of stellar evolution. In this talk, I will present the new results of a systematic search for post-AGB candidates in the Magellanic Clouds which became possible after the release of deep infrared surveys such as mid-infrared LMC and SMC Spitzer surveys. The catalog of post-AGB candidates in the Magellanic Clouds has been created firstly by selecting candidates based on the existence of a mid-infrared excess and secondly by obtaining low-resolution optical spectra. The optical spectra and broadband photometry were used to derive luminosities, effective temperatures and masses for the post-AGB candidates. Using a combination of colour criteria and SED analysis, we were able to classify between single and binary post-AGB objects. Binary post-AGB stars are likely to produce asymmetric PN (or bipolar PN). We also find that variability is displayed by several of the post-AGB candidates with the most common variability types being the Population II Cepheids (including RV-Tauri stars) and semi-regular variables. From the numbers of post-AGB candidates in the SMC and LMC, we were able to estimate evolutionary rates for the transient post-AGB phase. These catalogs of spectroscopically verified post-AGB candidates are a valuable resource for the study of late stages of single and binary star evolution as a function of initial mass and

  16. Post-AGB stars in the Magellanic Clouds and neutron-capture processes in AGB stars

    NASA Astrophysics Data System (ADS)

    Lugaro, M.; Campbell, S. W.; Van Winckel, H.; De Smedt, K.; Karakas, A. I.; Käppeler, F.

    2015-11-01

    Aims: We explore modifications to the current scenario for the slow neutron-capture process (the s-process) in asymptotic giant branch (AGB) stars to account for the Pb deficiency observed in post-AGB stars of low metallicity ([Fe/H] ≃-1.2) and low initial mass (≃ 1-1.5 M⊙) in the Large and Small Magellanic Clouds. Methods: We calculated the stellar evolution and nucleosynthesis for a 1.3 M⊙ star with [Fe/H] = -1.3 and tested different amounts and distributions of protons leading to the production of the main neutron source within the 13C-pocket and proton ingestion scenarios. Results: No s-process models can fully reproduce the abundance patterns observed in the post-AGB stars. When the Pb production is lowered, the abundances of the elements between Eu and Pb, such as Er, Yb, W, and Hf, are also lowered to below those observed. Conclusions: Neutron-capture processes with neutron densities intermediate between the s and the rapid neutron-capture processes may provide a solution to this problem and be a common occurrence in low-mass, low-metallicity AGB stars.

  17. Using pan-tropical biomass maps to improve IPCC Tier 1 default level emission factors - a case study for the Democratic Republic of the Congo (DRC)

    NASA Astrophysics Data System (ADS)

    Langner, Andreas; Achard, Frédéric; Grassi, Giacomo

    2014-05-01

    The IPCC proposes three Tier levels for greenhouse gas emission monitoring with a hierarchical order in terms of accuracy as well as data requirements/complexity. While Tier 1 provides default above-ground biomass (AGB) values per ecological zone and continent, Tier 2 and 3 are either based on country-specific remote sensing or permanent sample-plot data. Due to missing capacities most developing countries have to rely on Tier 1 default values, which show highest uncertainties. Furthermore, IPCC Tier 1 values lack transparency as they are based on a variety of studies that have been repeatedly updated and combined with expert opinions, thus blurring the original data sources. A possible way to increase credibility is a conservative monitoring approach, following the principle of conservativeness, thus reducing the likelihood of unjustified payments for emission reductions not reflecting reality. For the implementation of that principle knowledge about the distribution of the biomass within each ecological zone is essential. However, such information is not available for the IPCC Tier 1 values, which only provide mean values and/or AGB ranges that are not based on a common statistical analysis. Using the pan-tropical datasets of Saatchi et al (Proc Natl Acad Sci USA, 108, 9899-9904, 2011; 1km spatial resolution) and Baccini et al (Nat Climate Change, 2:182-185, 2012; 500m spatial resolution) we calculated the mean AGB values as well as their 50% confidence intervals for each ecological zone within the DRC using Globcover2009 as forest/non-forest mask and the FAO ecological zones dataset. Such analysis is more transparent while at the same time leading to "statistically improved" Tier 1 values, potentially allowing a conservative monitoring approach by selecting the lower bound of the confidence interval for emission estimation during the reference period and the higher bound for the assessment period. Within the DRC Baccini generally delivers higher AGB estimates

  18. The 2014 AGB Survey of Higher Education Governance

    ERIC Educational Resources Information Center

    Hodge-Clark, Kristen

    2014-01-01

    "The 2014 AGB Survey of Higher Education Governance" is the fourth in AGB's studies of college and university governance. This report, based on survey responses from 592 public and independent boards, addresses a range of important governance topics that are receiving attention from boards and the news media, including presidential…

  19. Approaching a Physical Calibration of the AGB Phase

    NASA Astrophysics Data System (ADS)

    Marigo, Paola

    2015-08-01

    The widespread impact of Asymptotic Giant Branch (AGB) stars on the observed properties of galaxies is universally accepted. Despite their importance, severe uncertainties plague AGB models and propagate through to current population synthesis studies of galaxies, undermining the interpretation of a galaxy's basic properties (mass, age, chemical evolution, dust budget). The only reliable path forward is to apply a physically-sound calibration of AGB stellar models in which all main physical processes and their interplay are taken into account (e.g., mixing, mass loss, nucleosynthesis, pulsation, molecular chemistry, dust formation). In this context, I will review recent and ongoing efforts to calibrate the evolution of AGB stars, which combine an all-round theoretical approach anchored by stellar physics with exceptionally high quality data of resolved AGB stars in the Milky Way and nearby galaxies.

  20. New input data for synthetic AGB evolution

    NASA Astrophysics Data System (ADS)

    Wagenhuber, J.; Groenewegen, M. A. T.

    1998-12-01

    Analytic formulae are presented to construct detailed secular lightcurves of both early asymptotic giant branch (AGB) and thermally pulsing AGB stars. They are based on an extensive grid of evolutionary calculations, performed with an updated stellar evolution code. Basic input parameters are the initial mass MI i, 0.8 <= MI i/Msun <= 7, metallicity ZI i =0.0001, 0.008, 0.02, and the mixing length theory (MLT) parameter. The formulae allow for two important effects, namely that the first pulses do not reach the full amplitude, and hot bottom burning (HBB) in massive stars, which are both not accounted for by core mass - luminosity relations of the usual type. Furthermore, the dependence of the effective temperature and a few other quantities characterizing the conditions at the base of the convective envelope, which are relevant for HBB, are investigated as functions of luminosity, total and core mass for different formulations of the convection theory applied, MLT or Canuto & Mazzitelli's (\\cite{can:maz}) theory.

  1. Allometric Equations for Aboveground and Belowground Biomass Estimations in an Evergreen Forest in Vietnam

    PubMed Central

    Nam, Vu Thanh; van Kuijk, Marijke; Anten, Niels P. R.

    2016-01-01

    Allometric regression models are widely used to estimate tropical forest biomass, but balancing model accuracy with efficiency of implementation remains a major challenge. In addition, while numerous models exist for aboveground mass, very few exist for roots. We developed allometric equations for aboveground biomass (AGB) and root biomass (RB) based on 300 (of 45 species) and 40 (of 25 species) sample trees respectively, in an evergreen forest in Vietnam. The biomass estimations from these local models were compared to regional and pan-tropical models. For AGB we also compared local models that distinguish functional types to an aggregated model, to assess the degree of specificity needed in local models. Besides diameter at breast height (DBH) and tree height (H), wood density (WD) was found to be an important parameter in AGB models. Existing pan-tropical models resulted in up to 27% higher estimates of AGB, and overestimated RB by nearly 150%, indicating the greater accuracy of local models at the plot level. Our functional group aggregated local model which combined data for all species, was as accurate in estimating AGB as functional type specific models, indicating that a local aggregated model is the best choice for predicting plot level AGB in tropical forests. Finally our study presents the first allometric biomass models for aboveground and root biomass in forests in Vietnam. PMID:27309718

  2. Allometric Equations for Aboveground and Belowground Biomass Estimations in an Evergreen Forest in Vietnam.

    PubMed

    Nam, Vu Thanh; van Kuijk, Marijke; Anten, Niels P R

    2016-01-01

    Allometric regression models are widely used to estimate tropical forest biomass, but balancing model accuracy with efficiency of implementation remains a major challenge. In addition, while numerous models exist for aboveground mass, very few exist for roots. We developed allometric equations for aboveground biomass (AGB) and root biomass (RB) based on 300 (of 45 species) and 40 (of 25 species) sample trees respectively, in an evergreen forest in Vietnam. The biomass estimations from these local models were compared to regional and pan-tropical models. For AGB we also compared local models that distinguish functional types to an aggregated model, to assess the degree of specificity needed in local models. Besides diameter at breast height (DBH) and tree height (H), wood density (WD) was found to be an important parameter in AGB models. Existing pan-tropical models resulted in up to 27% higher estimates of AGB, and overestimated RB by nearly 150%, indicating the greater accuracy of local models at the plot level. Our functional group aggregated local model which combined data for all species, was as accurate in estimating AGB as functional type specific models, indicating that a local aggregated model is the best choice for predicting plot level AGB in tropical forests. Finally our study presents the first allometric biomass models for aboveground and root biomass in forests in Vietnam. PMID:27309718

  3. Modeling Water and Nutrient Transport through the Soil-Root-Canopy Continuum: Explicitly Linking the Below- and Above-Ground Processes

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Quijano, J. C.; Drewry, D.

    2010-12-01

    Vegetation roots provide a fundamental link between the below ground water and nutrient dynamics and above ground canopy processes such as photosynthesis, evapotranspiration and energy balance. The “hydraulic architecture” of roots, consisting of the structural organization of the root system and the flow properties of the conduits (xylem) as well as interfaces with the soil and the above ground canopy, affect stomatal conductance thereby directly linking them to the transpiration. Roots serve as preferential pathways for the movement of moisture from wet to dry soil layers during the night, both from upper soil layer to deeper layers during the wet season (‘hydraulic descent’) and vice-versa (‘hydraulic lift’) as determined by the moisture gradients. The conductivities of transport through the root system are significantly, often orders of magnitude, larger than that of the surrounding soil resulting in movement of soil-moisture at rates that are substantially larger than that through the soil. This phenomenon is called hydraulic redistribution (HR). The ability of the deep-rooted vegetation to “bank” the water through hydraulic descent during wet periods for utilization during dry periods provides them with a competitive advantage. However, during periods of hydraulic lift these deep-rooted trees may facilitate the growth of understory vegetation where the understory scavenges the hydraulically lifted soil water. In other words, understory vegetation with relatively shallow root systems have access to the banked deep-water reservoir. These inter-dependent root systems have a significant influence on water cycle and ecosystem productivity. HR induced available moisture may support rhizosphere microbial and mycorrhizal fungi activities and enable utilization of heterogeneously distributed water and nutrient resources To capture this complex inter-dependent nutrient and water transport through the soil-root-canopy continuum we present modeling

  4. Above-ground sulfur cycling in adjacent coniferous and deciduous forest and watershed sulfur retention in the Georgia Piedmont, U.S.A.

    USGS Publications Warehouse

    Cappellato, R.; Peters, N.E.; Meyers, T.P.

    1998-01-01

    Atmospheric deposition and above-ground cycling of sulfur (S) were evaluated in adjacent deciduous and coniferous forests at the Panola Mountain Research Watershed (PMRW), Georgia U.S.A. Total atmospheric S deposition (wet plus dry) was 12.9 and 12.7 kg ha-1 yr-1 for the deciduous and coniferous forests, respectively, from October 1987 through November 1989. Dry deposition contributes more than 40% to the total atmospheric S deposition, and SO2 is the major source (~55%) of total dry S deposition. Dry deposition to these canopies is similar to regional estimates suggesting that 60-km proximity to emission sources does not noticeably impact dry deposition at PMRW. Below-canopy S fluxes (throughfall plus stemflow) in each forest are 37% higher annually in the deciduous forest than in the coniferous forest. An excess in below-canopy S flux in the deciduous forest is attributed to leaching and higher dry deposition than in the coniferous forest. Total S deposition to the forest floor by throughfall, stemflow and litterfall was 2.4 and 2.8 times higher in the deciduous and coniferous forests, respectively, than annual S growth requirement for foliage and wood. Although A deposition exceeds growth requirement, more than 95% of the total atmospheric S deposition was retained by the watershed in 1988 and 1989. The S retention at PMRW is primarily due to SO2+4 adsorption by iron oxides and hydroxides in watershed soils. The S content in while oak and loblolly pine boles have increased more than 200% in the last 20 yr, possibly reflecting increases in emissions.

  5. Potential use of Pseudomonas koreensis AGB-1 in association with Miscanthus sinensis to remediate heavy metal(loid)-contaminated mining site soil.

    PubMed

    Babu, A Giridhar; Shea, Patrick J; Sudhakar, D; Jung, Ik-Boo; Oh, Byung-Taek

    2015-03-15

    Endophytic bacteria have the potential to promote plant growth and heavy metal(loid) (HM) removal from contaminated soil. Pseudomonas koreensis AGB-1, isolated from roots of Miscanthus sinensis growing in mine-tailing soil, exhibited high tolerance to HMs and plant growth promoting traits. Transmission electron microscope (TEM) analysis revealed that AGB-1 sequestered HMs extracellularly and their accumulation was visible as dark metal complexes on bacterial surfaces and outside of the cells. DNA sequencing of HM resistance marker genes indicated high homology to the appropriate regions of the arsB, ACR3(1), aoxB, and bmtA determinants. Inoculating mining site soil with AGB-1 increased M. sinensis biomass by 54%, chlorophyll by 27%, and protein content by 28%. High superoxide dismutase and catalase activities, and the lower malondialdehyde content of plants growing in AGB-1-inoculated soil indicate reduced oxidative stress. Metal(loid) concentrations in roots and shoots of plants grown in inoculated soil were higher than those of the controls in pot trials with mine tailing soil. Results suggest that AGB-1 can be used in association with M. sinensis to promote phytostabilization and remediation of HM-contaminated sites. PMID:25575343

  6. Evolution and mixing on the AGB

    SciTech Connect

    Lattanzio, J.C.

    1988-07-27

    It is now well known that Nature can make Carbon stars at lower luminosities than can (human) theorists. A number of workers, stimulated by this challenge, have been attracted to the problem. In this paper I review recent evolutionary models of relatively low mass AGB stars, with emphasis placed on the mixing of carbon to the stellar surface. In particular I discuss some recent improvements in the physics used to construct stellar models. These topics include: breathing pulses of the convective core found during exhaustion of the core helium supply; the effects of carbon recombination; the occurrence of semiconvection in the region between the two nuclear burning shells, and the importance of mass loss. It appears that different effects may operate at different stellar masses and abundances. Recent calculations have successfully produced models of low luminosity Carbon stars. The strengths and weaknesses of these models will be contrasted. 60 refs., 5 figs.

  7. Comparison of Precision of Biomass Estimates in Regional Field Sample Surveys and Airborne LiDAR-Assisted Surveys in Hedmark County, Norway

    NASA Technical Reports Server (NTRS)

    Naesset, Erik; Gobakken, Terje; Bollandsas, Ole Martin; Gregoire, Timothy G.; Nelson, Ross; Stahl, Goeran

    2013-01-01

    Airborne scanning LiDAR (Light Detection and Ranging) has emerged as a promising tool to provide auxiliary data for sample surveys aiming at estimation of above-ground tree biomass (AGB), with potential applications in REDD forest monitoring. For larger geographical regions such as counties, states or nations, it is not feasible to collect airborne LiDAR data continuously ("wall-to-wall") over the entire area of interest. Two-stage cluster survey designs have therefore been demonstrated by which LiDAR data are collected along selected individual flight-lines treated as clusters and with ground plots sampled along these LiDAR swaths. Recently, analytical AGB estimators and associated variance estimators that quantify the sampling variability have been proposed. Empirical studies employing these estimators have shown a seemingly equal or even larger uncertainty of the AGB estimates obtained with extensive use of LiDAR data to support the estimation as compared to pure field-based estimates employing estimators appropriate under simple random sampling (SRS). However, comparison of uncertainty estimates under SRS and sophisticated two-stage designs is complicated by large differences in the designs and assumptions. In this study, probability-based principles to estimation and inference were followed. We assumed designs of a field sample and a LiDAR-assisted survey of Hedmark County (HC) (27,390 km2), Norway, considered to be more comparable than those assumed in previous studies. The field sample consisted of 659 systematically distributed National Forest Inventory (NFI) plots and the airborne scanning LiDAR data were collected along 53 parallel flight-lines flown over the NFI plots. We compared AGB estimates based on the field survey only assuming SRS against corresponding estimates assuming two-phase (double) sampling with LiDAR and employing model-assisted estimators. We also compared AGB estimates based on the field survey only assuming two-stage sampling (the NFI

  8. A new tool for post-AGB SED classification

    NASA Astrophysics Data System (ADS)

    Bendjoya, P.; Suarez, O.; Galluccio, L.; Michel, O.

    We present the results of an unsupervised classification method applied on a set of 344 spectral energy distributions (SED) of post-AGB stars extracted from the Torun catalogue of Galactic post-AGB stars. This method aims to find a new unbiased method for post-AGB star classification based on the information contained in the IR region of the SED (fluxes, IR excess, colours). We used the data from IRAS and MSX satellites, and from the 2MASS survey. We applied a classification method based on the construction of the dataset of a minimal spanning tree (MST) with the Prim's algorithm. In order to build this tree, different metrics have been tested on both flux and color indices. Our method is able to classify the set of 344 post-AGB stars in 9 distinct groups according to their SEDs.

  9. Rb and Zr abundances in massive Galactic AGB stars revisited

    NASA Astrophysics Data System (ADS)

    Pérez-Mesa, V.; Zamora, O.; García-Hernández, D. A.; Plez, B.; Manchado, A.; Karakas, A. I.; Lugaro, M.

    2016-07-01

    We report new abundances of Rb and Zr in a sample of massive Galactic asymptotic giant branch (AGB) stars that were previously studied with hydrostatic models by using more realistic dynamical model atmospheres. We use a modified version of the spectral synthesis code Turbospectrum, and consider the presence of a circumstellar envelope and a radial wind in the modelling of these Galactic AGB stars. The Rb and Zr are determined from the 7800 Å Rb I resonant line and the 6474 Å ZrO bandhead, respectively, and they are compared with the AGB nucleosynthesis theoretical predictions. The derived Rb abundances are much lower (∼⃒1-2 dex) with the new dynamical models, while the Zr abundances, however, are closer to the hydrostatic values. The new model atmospheres can help to resolve the problem of the mismatch between the observations and the nucleosynthesis theoretical predictions of massive AGB stars.

  10. Spectroscopic survey of post-AGB star candidates

    NASA Astrophysics Data System (ADS)

    Pereira, C. B.; Miranda, L. F.

    2007-01-01

    Aims:Our goal is to establish the true nature of post-AGB star candidates and to identify new post-AGB stars. Methods: We used low resolution optical spectroscopy and we compared the spectra of the candidate post-AGB stars with those of stars in the library specta available in the literature and with spectra of "standard" post-AGB stars, and direct imaging in narrow-band filters. Results: Spectra were obtained for 16 objects: 14 objects have not been observed previously and 2 objects are already known post-AGB stars used as "standards" for identification. From the spectra we identify: six new post-AGB stars with spectral types between G5 and F5, two H ii regions the morphology of which is revealed in the direct images for the first time, a G giant with infrared emission, a young stellar object, a probable post-AGB star with emission lines and three objects for which the classification is still unclear. As a whole, our results provide new, reliable identifications for 10 objects among listed post-AGB star candidates. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC), and at the Observatorio de Sierra Nevada, which is operated by the Consejo Superior de Investigaciones Científicas through the Instituto de Astrofísica de Andalucía (Granada, Spain). Appendices A-D are only available in electronic form at http://www.aanda.org

  11. Post-AGB Stars in the AKARI Survey

    NASA Astrophysics Data System (ADS)

    Siódmiak, N.; Cox, N.; Szczerba, R.; García-Lario, P.

    2009-12-01

    Obscured by their circumstellar dusty envelopes post-AGB stars emit a large fraction of their energy in the infrared and thus, infrared sky surveys like IRAS were essential for discoveries of post-AGBs in the past. Now, with the AKARI infrared sky survey we can extend our knowledge about the late stages of stellar evolution. The long-term goal of our work is to define new photometric criteria to distinguish new post-AGB candidates from the AKARI data. We have cross-correlated the Toruń catalogue of Galactic post-AGB and related objects with the AKARI/FIS All-Sky Survey Bright Source Catalogue (for simplicity, hereafter AKARI). The scientific and technical aspects of our work are presented here as well as our plans for the future. In particular, we found that only 9 post-AGB sources were detected in all four AKARI bands. The most famous objects like: Red Rectangle, Egg Nebula, Minkowski’s Footprint belong to this group. From the technical point of view we discuss positional accuracy by comparing (mostly) 2MASS coordinates of post-AGB objects with those given by AKARI; flux reliability by comparing IRAS 60 and 100 μm fluxes with those from AKARI -N65 and AKARI -90 bands, respectively; as well as completeness of the sample as a function of the IRAS fluxes.

  12. AGB Stars in the Large and Small Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Portman, Matthew; Sargent, Benjamin A.; Held, Leander; Kastner, Joel; SAGE Team

    2016-01-01

    Asymptotic giant branch (AGB) stars are evolved, pulsating variable stars that generate massive outflows of gas and dust, thereby enriching the interstellar medium (ISM) in the products of stellar nucleosynthesis. Recent studies find the dustiest, most extreme AGB stars contribute a disproportionately large amount of matter to their host galaxies; these extreme AGB stars are also the most variable, and they emit most of their energy at mid-infrared wavelengths. Therefore, using the Spitzer Space Telescope, we have imaged several target AGB stars identified in previous surveys of the Large and Small Magellanic Clouds (LMC and SMC, respectively). Our aim is to obtain light curves at 3.6 and 4.5 microns wavelength for these extreme AGB stars. Using multiple epochs of data taken within the last 3 years by our survey and then further comparing this data to past surveys of the SMC and LMC with Spitzer, we were able to generate preliminary light curves for a sample of 30 extreme AGB stars, as well as for other stars found within the image fields. This research project was made possible by the Rochester Institute of Technology Center for Imaging Science Research Experience for Undergraduates program, funded by National Science Foundation grant PHY-1359361 to RIT.

  13. Topo-edaphic controls over woody plant biomass in South African savannas

    NASA Astrophysics Data System (ADS)

    Colgan, M. S.; Asner, G. P.; Levick, S. R.; Martin, R. E.; Chadwick, O. A.

    2012-05-01

    The distribution of woody biomass in savannas reflects spatial patterns fundamental to ecosystem processes, such as water flow, competition, and herbivory, and is a key contributor to savanna ecosystem services, such as fuelwood supply. While total precipitation sets an upper bound on savanna woody biomass, the extent to which substrate and terrain constrain trees and shrubs below this maximum remains poorly understood, often occluded by local-scale disturbances such as fire and trampling. Here we investigate the role of hillslope topography and soil properties in controlling woody plant aboveground biomass (AGB) in Kruger National Park, South Africa. Large-area sampling with airborne Light Detection and Ranging (LiDAR) provided a means to average across local-scale disturbances, revealing an unexpectedly linear relationship between AGB and hillslope-position on basalts, where biomass levels were lowest on crests, and linearly increased toward streams (R2 = 0.91). The observed pattern was different on granite substrates, where AGB exhibited a strongly non-linear relationship with hillslope position: AGB was high on crests, decreased midslope, and then increased near stream channels (R2 = 0.87). Overall, we observed 5-to-8-fold lower AGB on clayey, basalt-derived soil than on granites, and we suggest this is due to herbivore-fire interactions rather than lower hydraulic conductivity or clay shrinkage/swelling, as previously hypothesized. By mapping AGB within and outside fire and herbivore exclosures, we found that basalt-derived soils support tenfold higher AGB in the absence of fire and herbivory, suggesting high clay content alone is not a proximal limitation on AGB. Understanding how fire and herbivory contribute to AGB heterogeneity is critical to predicting future savanna carbon storage under a changing climate.

  14. Topo-edaphic controls over woody plant biomass in South African savannas

    NASA Astrophysics Data System (ADS)

    Colgan, M. S.; Asner, G. P.; Levick, S. R.; Martin, R. E.; Chadwick, O. A.

    2012-01-01

    The distribution of woody biomass in savannas reflects spatial patterns fundamental to ecosystem processes, such as water flow, competition, and herbivory, and is a key contributor to savanna ecosystem services, such as fuelwood supply. While total precipitation sets an upper bound on savanna woody biomass, the extent to which substrate and terrain constrain trees and shrubs below this maximum remains poorly understood, often occluded by local-scale disturbances such as fire and trampling. Here we investigate the role of hillslope topography and soil properties in controlling woody plant aboveground biomass (AGB) in Kruger National Park, South Africa. Large-area sampling with airborne Light Detection and Ranging (LiDAR) provided a means to average across local-scale disturbances, revealing an unexpectedly linear relationship between AGB and hillslope-position on basalts, where biomass levels were lowest on crests, and linearly increased toward streams (R2 = 0.91). The observed pattern was different on granite substrates, where AGB exhibited a strongly non-linear relationship with hillslope position: AGB was high on crests, decreased midslope, and then increased near stream channels (R2 = 0.87). Overall, we observed 5-to-8-fold lower AGB on clayey, basalt-derived soil than on granites, and we suggest this is due to herbivore-fire interactions rather than lower hydraulic conductivity or clay shrinkage/swelling, as previously hypothesized. By mapping AGB within and outside fire and herbivore exclosures, we found that basalt-derived soils support tenfold higher AGB in the absence of fire and herbivory, suggesting high clay content alone is not a~proximal limitation on AGB. Understanding how fire and herbivory contribute to AGB heterogeneity is critical to predicting future savanna carbon storage under a changing climate.

  15. SUPER-AGB-AGB EVOLUTION AND THE CHEMICAL INVENTORY IN NGC 2419

    SciTech Connect

    Ventura, Paolo; D'Antona, Francesca; Carini, Roberta; Di Criscienzo, Marcella; D'Ercole, Annibale; Vesperini, Enrico

    2012-12-20

    We follow the scenario of formation of second-generation stars in globular clusters by matter processed by hot bottom burning (HBB) in massive asymptotic giant branch (AGB) stars and super-AGB stars (SAGB). In the cluster NGC 2419 we assume the presence of an extreme population directly formed from the AGB and SAGB ejecta, so we can directly compare the yields for a metallicity Z = 0.0003 with the chemical inventory of the cluster NGC 2419. At such a low metallicity, the HBB temperatures (well above 10{sup 8} K) allow a very advanced nucleosynthesis. Masses {approx}6 M{sub Sun} deplete Mg and synthesize Si, going beyond Al, so this latter element is only moderately enhanced; sodium cannot be enhanced. The models are consistent with the observations, although the predicted Mg depletion is not as strong as in the observed stars. We predict that the oxygen abundance must be depleted by a huge factor (>50) in the Mg-poor stars. The HBB temperatures are close to the region where other p-capture reactions on heavier nuclei become possible. We show that high potassium abundance found in Mg-poor stars can be achieved during HBB by p-captures on the argon nuclei, if the relevant cross section(s) are larger than listed in the literature or if the HBB temperature is higher. Finally, we speculate that some calcium production is occurring owing to proton capture on potassium. We emphasize the importance of a strong effort to measure a larger sample of abundances in this cluster.

  16. Ultraviolet emission from main-sequence companions of AGB stars

    NASA Astrophysics Data System (ADS)

    Ortiz, Roberto; Guerrero, Martín A.

    2016-09-01

    Although the majority of known binary asymptotic giant branch (AGB) stars are symbiotic systems (i.e. with a white dwarf as a secondary star), main-sequence companions of AGB stars can be more numerous, even though they are more difficult to find because the primary high luminosity hampers the detection of the companion at visual wavelengths. However, in the ultraviolet the flux emitted by a secondary with Teff > 5500 ˜ 6000 K may prevail over that of the primary, and then it can be used to search for candidates to binary AGB stars. In this work, theoretical atmosphere models are used to calculate the UV excess in the GALEX near- and far-UV bands due to a main-sequence companion. After analysing a sample of confirmed binary AGB stars, we propose as a criterium for binarity: (1) the detection of the AGB star in the GALEX far-UV band and/or (2) a GALEX near-UV observed-to-predicted flux ratio >20. These criteria have been applied to a volume-limited sample of AGB stars within 500 pc of the Sun; 34 out of the sample of 58 AGB stars (˜60 per cent) fulfill them, implying to have a main-sequence companion of spectral type earlier than K0. The excess in the GALEX near- and far-UV bands cannot be attributed to a single temperature companion star, thus suggesting that the UV emission of the secondary might be absorbed by the extended atmosphere and circumstellar envelope of the primary or that UV emission is produced in accretion flows.

  17. Modeling aboveground tree woody biomass using national-scale allometric methods and airborne lidar

    NASA Astrophysics Data System (ADS)

    Chen, Qi

    2015-08-01

    Estimating tree aboveground biomass (AGB) and carbon (C) stocks using remote sensing is a critical component for understanding the global C cycle and mitigating climate change. However, the importance of allometry for remote sensing of AGB has not been recognized until recently. The overarching goals of this study are to understand the differences and relationships among three national-scale allometric methods (CRM, Jenkins, and the regional models) of the Forest Inventory and Analysis (FIA) program in the U.S. and to examine the impacts of using alternative allometry on the fitting statistics of remote sensing-based woody AGB models. Airborne lidar data from three study sites in the Pacific Northwest, USA were used to predict woody AGB estimated from the different allometric methods. It was found that the CRM and Jenkins estimates of woody AGB are related via the CRM adjustment factor. In terms of lidar-biomass modeling, CRM had the smallest model errors, while the Jenkins method had the largest ones and the regional method was between. The best model fitting from CRM is attributed to its inclusion of tree height in calculating merchantable stem volume and the strong dependence of non-merchantable stem biomass on merchantable stem biomass. This study also argues that it is important to characterize the allometric model errors for gaining a complete understanding of the remotely-sensed AGB prediction errors.

  18. Impacts of Tree Height-Dbh Allometry on Lidar-Based Tree Aboveground Biomass Modeling

    NASA Astrophysics Data System (ADS)

    Fang, R.

    2016-06-01

    Lidar has been widely used in tree aboveground biomass (AGB) estimation at plot or stand levels. Lidar-based AGB models are usually constructed with the ground AGB reference as the response variable and lidar canopy indices as predictor variables. Tree diameter at breast height (dbh) is the major variable of most allometric models for estimating reference AGB. However, lidar measurements are mainly related to tree vertical structure. Therefore, tree height-dbh allometric model residuals are expected to have a large impact on lidar-based AGB model performance. This study attempts to investigate sensitivity of lidar-based AGB model to the decreasing strength of height-dbh relationship using a Monte Carlo simulation approach. Striking decrease in R2 and increase in relative RMSE were found in lidar-based AGB model, as the variance of height-dbh model residuals grew. I, therefore, concluded that individual tree height-dbh model residuals fundamentally introduce errors to lidar-AGB models.

  19. Assessing Performance of P-Band Backscattering Coefficients and TSAR in Hemi-Boreal Forest AGB Estimation

    NASA Astrophysics Data System (ADS)

    Li, Wenmei; Chen, Erxue; Li, Zengyuan; Feng, Qi

    2014-11-01

    To assess performance of P-band backscattering coefficients and TSAR for hemi-boreal forest AGB estimation, airborne P-band repeat-path Pol-InSAR data collected by ESAR in Ramingstorp test site during March and May 2007 are applied. The correlation coefficient (R) between P-band backscattering coefficients and in-situ biomass reaches 0.87 for HH polarization. Meanwhile, the R between P-band backscattering power at specific height and in-situ biomass are higher in VV polarization than that in HH and HV polarization. And R between P-band backscattering power and in-situ biomass reaches 0.70 at 5m and 10m height in VV polarization.

  20. Statewide Mapping of Aboveground Biomass by Integrating Airborne Lidar Data and National Forestry Inventory Plots

    NASA Astrophysics Data System (ADS)

    Chen, Q.; McRoberts, R. E.

    2015-12-01

    The freely available airborne lidar data at the sub-national level in the United States provide unprecedented opportunities for mapping large-area yet accurate information about vegetation structure, biomass, and carbon. However, the challenge of processing massive lidar data and extracting useful information is huge. This study is to conduct a statewide mapping study of aboveground biomass (AGB) by integrating airborne lidar data and FIA (Forest Inventory and Analysis) plot data for the whole state of Minnesota. We will share our experience and lessons in issues including 1) automatic generation of Digital Terrain Model from point cloud, 2) classification of vegetation returns, 3) calculation of AGB from FIA plots using different allometric models, 4) statistical modeling of AGB by integrating with FIA plots, and 5) assessing the uncertainty of mapped AGB.

  1. Historical forest biomass dynamics modelled with Landsat spectral trajectories

    NASA Astrophysics Data System (ADS)

    Gómez, Cristina; White, Joanne C.; Wulder, Michael A.; Alejandro, Pablo

    2014-07-01

    Estimation of forest aboveground biomass (AGB) is informative of the role of forest ecosystems in local and global carbon budgets. There is a need to retrospectively estimate biomass in order to establish a historical baseline and enable reporting of change. In this research, we used temporal spectral trajectories to inform on forest successional development status in support of modelling and mapping of historic AGB for Mediterranean pines in central Spain. AGB generated with ground plot data from the Spanish National Forest Inventory (NFI), representing two collection periods (1990 and 2000), are linked with static and dynamic spectral data as captured by Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) sensors over a 25 year period (1984-2009). The importance of forest structural complexity on the relationship between AGB and spectral vegetation indices is revealed by the analysis of wavelet transforms. Two-dimensional (2D) wavelet transforms support the identification of spectral trajectory patterns of forest stands that in turn, are associated with traits of individual NFI plots, using a flexible algorithm sensitive to capturing time series similarity. Single-date spectral indices, temporal trajectories, and temporal derivatives associated with succession are used as input variables to non-parametric decision trees for modelling, estimation, and mapping of AGB and carbon sinks over the entire study area. Results indicate that patterns of change found in Normalized Difference Vegetation Index (NDVI) values are associated and relate well to classes of forest AGB. The Tasseled Cap Angle (TCA) index was found to be strongly related with forest density, although the related patterns of change had little relation with variability in historic AGB. By scaling biomass models through small (∼2.5 ha) spatial objects defined by spectral homogeneity, the AGB dynamics in the period 1990-2000 are mapped (70% accuracy when validated with plot values of

  2. Biomass and energy productivity of Leucaena under humid subtropical conditions

    SciTech Connect

    Othman, A.B.; Prine, G.M.

    1984-01-01

    A table shows the amount and energy content of above-ground biomass produced in 1982 and 1983 by the 12 most productive of 62 accessions of Leucanena spp. established in 1979 at the University of Florida. Mean annual biomass production of the 12 accessions was 29.3 and 24.7 Mg/ha, with energy contents of 19,690 and 19,820 J/g, in 1982 and 1983 respectively.

  3. Why Galaxies Care about AGB Stars: Setting the Stage

    NASA Astrophysics Data System (ADS)

    Renzini, A.

    2015-08-01

    In this introduction to the Third Congress of Vienna on asymptotic giant branch (AGB) stars, I first try to highlight why it is so hard to cope with the AGB evolutionary phase. This phase is indeed dominated by three main physical processes concerning bulk motions of matter inside/around stars, namely envelope convection, mixing, and mass loss. They are inextricably interlaced with each other in a circular sequence of reactions and counter-reactions which has so far undermined our attempts at calibrating such processes independent of one another. The second part of this introduction is focused on globular clusters, illustrating how they came to be a new frontier for AGB evolution and a new opportunity to understand it.

  4. AGB yields and Galactic Chemical Evolution: last updated

    NASA Astrophysics Data System (ADS)

    Bisterzo, S.; Travaglio, C.; Wiescher, M.; Gallino, R.; Köppeler, F.; Straniero, O.; Cristallo, S.; Imbriani, G.; Görres, J.; deBoer, R. J.

    2016-01-01

    We study the s-process abundances at the epoch of the Solar-system formation as the outcome of nucleosynthesis occurring in AGB stars of various masses and metallicities. The calculations have been performed with the Galactic chemical evolution (GCE) model presented by [1, 2]. With respect to previous works, we used updated solar meteoritic abundances, a neutron capture cross section network that includes the most recent measurements, and we implemented the s-process yields with an extended range of AGB initial masses. The new set of AGB yields includes a new evaluation of the 22Ne(α, n)25Mg rate, which takes into account the most recent experimental information.

  5. Current hot questions on the s process in AGB stars

    NASA Astrophysics Data System (ADS)

    Lugaro, M.; Campbell, S. W.; D'Orazi, V.; Karakas, A. I.; Garcia-Hernandez, D. A.; Stancliffe, R. J.; Tagliente, G.; Iliadis, C.; Rauscher, T.

    2016-01-01

    Asymptotic giant branch (AGB) stars are a main site of production of nuclei heavier than iron via the s process. In massive (>4 M⊙) AGB stars the operation of the 22Ne neutron source appears to be confirmed by observations of high Rb enhancements, while the lack of Tc in these stars rules out 13C as a main source of neutrons. The problem is that the Rb enhancements are not accompanied by Zr enhancements, as expected by s-process models. This discrepancy may be solved via a better understanding of the complex atmospheres of AGB stars. Second- generation stars in globular clusters (GCs), on the other hand, do not show enhancements in any s-process elements, not even Rb. If massive AGB stars are responsible for the composition of these GC stars, they may have evolved differently in GCs than in the field. In AGB stars of lower masses, 13C is the main source of neutrons and we can potentially constrain the effects of rotation and proton-ingestion episodes using the observed composition of post-AGB stars and of stardust SiC grains. Furthermore, independent asteroseismology observations of the rotational velocities of the cores of red giants and of white dwarves will play a fundamental role in helping us to better constrain the effect of rotation. Observations of carbon-enhanced metal-poor stars enriched in both Ba and Eu may require a neutron flux in-between the s and the r process, while the puzzling increase of Ba as function of the age in open clusters, not accompanied by increase in any other element heavier than iron, require further observational efforts. Finally, stardust SiC provides us high-precision constraints to test nuclear inputs such as neutron-capture cross sections of stable and unstable isotopes and the impact of excited nuclear states in stellar environments.

  6. Sensitivity study for s process nucleosynthesis in AGB stars

    NASA Astrophysics Data System (ADS)

    Koloczek, A.; Thomas, B.; Glorius, J.; Plag, R.; Pignatari, M.; Reifarth, R.; Ritter, C.; Schmidt, S.; Sonnabend, K.

    2016-03-01

    In this paper we present a large-scale sensitivity study of reaction rates in the main component of the s process. The aim of this study is to identify all rates, which have a global effect on the s process abundance distribution and the three most important rates for the production of each isotope. We have performed a sensitivity study on the radiative 13C-pocket and on the convective thermal pulse, sites of the s process in AGB stars. We identified 22 rates, which have the highest impact on the s-process abundances in AGB stars.

  7. Do Globular Clusters Care about AGB Stars? Metallicity Distribution of AGB and RGB Stars in NGC 2808

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Primas, F.; Charbonnel, C.

    2015-08-01

    Galactic globular clusters are known to have multiple stellar populations with different scenarios being debated for their origin. In this context, the core of our project is to disentangle the first and second generation stars based on their chemical properties, in order to test different model predictions. Here we present a preliminary chemical analysis of a new sample of AGB stars in NGC 2808 observed at the VLT with FLAMES, in order to further investigate the recent finding that no Na-rich stars are found on the AGB.

  8. Mapping Africa Biomass with MODIS Imagery

    NASA Astrophysics Data System (ADS)

    Laporte, N.; Baccini, A.; Houghton, R.

    2006-12-01

    Central Africa contains the second largest block of tropical forest remaining in the world, and is one of the largest carbon reservoirs on Earth. The carbon dynamics of the region differ substantially from other tropical forests because most deforestation and land use is associated with selective logging and small-scale landholders practicing traditional "slash-and-burn" agriculture. Despite estimates of 1-2 PgC/yr released to the atmosphere from tropical deforestation, the amount released from Central Africa is highly uncertain relative to the amounts released from other tropical forest areas. The uncertainty in carbon fluxes results from inadequate estimates of both rates of deforestation and standing stocks of carbon (forest biomass). Here we present new results mapping above-ground forest biomass for tropical Africa using machine learning techniques to integrate MODIS 1km spectral reflectance with forest inventory measurements to calibrate an empirical relationship. The derived forest biomass at each MODIS pixel shows the spatial distribution of forest biomass over the entire tropical forest region. The model has been tested in Uganda, Mali and part of Republic of Congo where field data were available. The regression tree model based on MODIS NBAR surface reflectance for Uganda, Mali and Republic of Congo explains 94 percent of the variance in above-ground biomass with a root mean square error (RMSE) of 27 Tons/ha. The approach shows promise for use of optical remote sensing data in mapping the spatial distribution of forest biomass across the region.

  9. Estimating grassland aboveground biomass using multitemporal MODIS data in the West Songnen Plain, China

    NASA Astrophysics Data System (ADS)

    Li, Fei; Jiang, Lei; Wang, Xufeng; Zhang, Xiaoqiang; Zheng, Jiajia; Zhao, Qianjun

    2013-01-01

    The West Songnen Plain is an ecologically fragile area. The grasslands on the plain have been seriously degraded over the past five decades and this process is continuing. The reliable estimation of grassland aboveground biomass (AGB) provides scientific data for determining the livestock stocking rate on rangeland. AGB is also of considerable significance for biodiversity and environmental protection in this region. Remote sensing is the most effective way to estimate grassland AGB on a regional scale. Multitemporal, remotely sensed data were used for grassland AGB estimation with statistical models and an artificial neural network (ANN), and the accuracy of estimation for these methods was compared. The results demonstrate that the use of multi-temporal remotely sensed data has advantages for grassland AGB estimation, whether with statistical models or ANN methods, compared with single-temporal remotely sensed data, although the ANN had a higher accuracy of estimation for grassland AGB. Finally, the grassland AGB on the Songnen Plain was estimated with the ANN using multitemporal MODIS data. The spatial distribution pattern of grassland AGB showed large variations, and grassland productivity was generally low. The maximum green weight of the grassland AGB was 927.22 g/m2 and was mainly distributed on the northeast of the West Songnen Plain. The minimum green weight of the grassland AGB was 194.82 g/m2 and was mainly distributed on the central and southwestern West Songnen Plain. Most of the areas had medium- and low-yielding grasses. The significant increases of population and livestock number were the primary and direct reasons for the decrease in grassland quality. This study will contribute to policy making for the control of grazing and for biodiversity and environmental protection.

  10. Spectroscopic and photometric monitoring of southern post-AGB stars

    NASA Astrophysics Data System (ADS)

    Pooley, D. J.; Cottrell, P. L.; Pollard, K. R.; Albrow, M. D.

    2004-05-01

    We present the results of contemporaneous photometric and spectroscopic monitoring of 20 post-AGB stars from Mt John University Observatory. Photometric measures were carried our suing Johnson BV and Cousins RI filters, and the radial velocity measurements were acquired using spectra from an echelle spectrograph. Our program spanned five years and the stars covered a range of spectral types from B to K in order to investigate the behavior of post-AGB stars as they evolve away from the AGB. A number of stars proved to be variable inways incompatible with post-AGB models and are reclassified. Periodicities are presented for a number of stars. Photometrically, HD 70379 was found to be pulsating in two modes with periods of 85 and 97 d. The radial velocities also varied, with the peak amplitude occurring when the photometry was also changing most. AI CMi presented three different types of spectra associated with photometric brightness, with varying strengths of narrow emission lines and molecular bandheads. The Hα profiles in almost all of the stars show evidence of emission which varies on time scales of days to months. The Na D line profiles are generally complex showing between 4 and 7 components due to both circumstellar and interstellar material.

  11. Winds of Binary AGB Stars as Observed by Herschel

    NASA Astrophysics Data System (ADS)

    Mayer, A.; Jorissen, A.; Kerschbaum, F.; Ottensamer, R.; Mečina, M.; Paladini, C.; Cox, N. L. J.; Nowotny, W.; Aringer, B.; Pourbaix, D.; Mohamed, S.; Siopis, C.; Groenewegen, M. A. T.

    2015-08-01

    We present Herschel/PACS observations of the large-scale environments of binary AGB stars as part of the Mass-loss of Evolved StarS (MESS) sample. From the literature we found 18 of the objects to be members of physically bound multiple systems. Several show a large-scale far-IR emission which differs significantly from spherical symmetry. A probable cause is the gravitational force of the companion on the stellar AGB wind and the mass-losing star itself. A spiral pattern is thereby imprinted in the dusty stellar wind. The most remarkable structures are found around o Ceti, W Aquilæ, R Aquarii, and π1 Gruis. The environments of o Cet and W Aql show a spiral pattern while the symbiotic nature of R Aqr is revealed as two opposing arms which reflect a nova outburst. The emission around π1 Gru is dominated by two structures, a disk and an arc, which are presumably not caused by the same companion. We found evidence that π1 Gru is a hierarchical triple system in which a close companion attracts the AGB wind onto the orbital plane and the outer companion forms a spiral arm. These far-IR observations underline the role of a companion as a major external influence in creating asymmetric winds in the AGB phase, even before the star becomes a planetary nebula (PN).

  12. The Governance Committee: Independent Institutions. AGB Effective Committee Series

    ERIC Educational Resources Information Center

    Wilson, E. B.; Lanier, James L.

    2013-01-01

    This publication is part of an AGB series devoted to strengthening the role of key standing committees of governing boards. While there is no optimal committee system for institutions of higher education, certain principles, practices, and procedures prevail. The best practices outlined in this publication support the objectives of board…

  13. From Nuclei to Dust Grains: How the AGB Machinery Works

    NASA Astrophysics Data System (ADS)

    Gobrecht, D.; Cristallo, S.; Piersanti, L.

    2015-12-01

    With their circumstellar envelopes AGB stars are marvelous laboratories to test our knowledge of microphysics (opacities, equation of state), macrophysics (convection, rotation, stellar pulsations, magnetic fields) and nucleosynthesis (nuclear burnings, slow neutron capture processes, molecules and dust formation). Due to the completely different environments those processes occur, the interplay between stellar interiors (dominated by mixing events like convection and dredge-up episodes) and stellar winds (characterized by dust formation and wind acceleration) is often ignored. We intend to develop a new approach involving a transition region, taking into consideration hydrodynamic processes which may drive AGB mass-loss. Our aim is to describe the process triggering the mass-loss in AGB stars with different masses, metallicities and chemical enrichments, possibly deriving a velocity field of the outflowing matter. Moreover, we intend to construct an homogeneous theoretical database containing detailed abundances of atomic and molecular species produced by these objects. As a long term goal, we will derive dust production rates for silicates, alumina and silicon carbides, in order to explain laboratory measurements of isotopic ratios in AGB dust grains.

  14. The origin of fluorine: abundances in AGB carbon stars revisited

    NASA Astrophysics Data System (ADS)

    Abia, C.; Cunha, K.; Cristallo, S.; de Laverny, P.

    2015-09-01

    Context. Revised spectroscopic parameters for the HF molecule and a new CN line list in the 2.3 μm region have recently become available, facilitating a revision of the F content in asymptotic giant branch (AGB) stars. Aims: AGB carbon stars are the only observationally confirmed sources of fluorine. Currently, there is no consensus on the relevance of AGB stars in its Galactic chemical evolution. The aim of this article is to better constrain the contribution of these stars with a more accurate estimate of their fluorine abundances. Methods: Using new spectroscopic tools and local thermodynamical equilibrium spectral synthesis, we redetermine fluorine abundances from several HF lines in the K-band in a sample of Galactic and extragalactic AGB carbon stars of spectral types N, J, and SC, spanning a wide range of metallicities. Results: On average, the new derived fluorine abundances are systematically lower by 0.33 dex with respect to previous determinations. This may derive from a combination of the lower excitation energies of the HF lines and the larger macroturbulence parameters used here as well as from the new adopted CN line list. Yet, theoretical nucleosynthesis models in AGB stars agree with the new fluorine determinations at solar metallicities. At low metallicities, an agreement between theory and observations can be found by handling the radiative/convective interface at the base of the convective envelope in a different way. Conclusions: New fluorine spectroscopic measurements agree with theoretical models at low and at solar metallicity. Despite this, complementary sources are needed to explain its observed abundance in the solar neighbourhood.

  15. Impacts of Sample Design on Estimation of Aboveground Biomass: Implications for the Assimilation of Lidar and Forest Inventory Data

    NASA Astrophysics Data System (ADS)

    Duffy, P.; Keller, M. M.; Morton, D. C.; Schimel, D.

    2015-12-01

    The availability of lidar data that can be used to characterize forest structure and estimate aboveground biomass (AGB) is rapidly increasing. When lidar data are considered in conjunction with forest inventory data to estimate AGB, the order of acquisition for these data products may impact the quality of the resulting estimates. In this work, we address this question in the context of uncertainty reduction with respect to estimation of AGB in a degraded forest in Paragominas, Brazil. We have developed a simulation framework that quantitatively assesses the uncertainty associated with estimation of AGB for different sampling strategies that combine forest inventory and lidar data. We utilize a Bayesian hierarchical modeling (BHM) data assimilation framework to combine information from the forest inventory and lidar data products into a higher order data product of AGB. Spatially explicit realizations of AGB are generated under different sampling strategies. Sampling strategies are assessed using the distributional properties of the assimilated higher order data product in the context of uncertainty reduction. We consider both spatially explicit maps of uncertainty as well as the standard deviation of the posterior predictive distributions of AGB as endpoints for the quantification of uncertainty. This framework allows for the explicit characterization of important sources of uncertainty. Our results show that a significant reduction in the uncertainty associated with estimation of AGB can be realized when design optimization is utilized in this context.

  16. Forest biomass variation in Southernmost Brazil: the impact of Araucaria trees.

    PubMed

    Rosenfield, Milena Fermina; Souza, Alexandre F

    2014-03-01

    A variety of environmental and biotic factors determine vegetation growth and affect plant biomass accumulation. From temperature to species composition, aboveground biomass storage in forest ecosystems is influenced by a number of variables and usually presents a high spatial variability. With this focus, the aim of the study was to evaluate the variables affecting live aboveground forest biomass (AGB) in Subtropical Moist Forests of Southern Brazil, and to analyze the spatial distribution of biomass estimates. Data from a forest inventory performed in the State of Rio Grande do Sul, Southern Brazil, was used in the present study. Thirty-eight 1-ha plots were sampled and all trees with DBH > or = 9.5cm were included for biomass estimation. Values for aboveground biomass were obtained using published allometric equations. Environmental and biotic variables (elevation, rainfall, temperature, soils, stem density and species diversity) were obtained from the literature or calculated from the dataset. For the total dataset, mean AGB was 195.2 Mg/ha. Estimates differed between Broadleaf and Mixed Coniferous-Broadleaf forests: mean AGB was lower in Broadleaf Forests (AGB(BF)=118.9 Mg/ha) when compared to Mixed Forests (AGB(MF)=250.3 Mg/ha). There was a high spatial and local variability in our dataset, even within forest types. This condition is normal in tropical forests and is usually attributed to the presence of large trees. The explanatory multiple regressions were influenced mainly by elevation and explained 50.7% of the variation in AGB. Stem density, diversity and organic matter also influenced biomass variation. The results from our study showed a positive relationship between aboveground biomass and elevation. Therefore, higher values of AGB are located at higher elevations and subjected to cooler temperatures and wetter climate. There seems to be an important contribution of the coniferous species Araucaria angustifolia in Mixed Forest plots, as it presented

  17. Nucleosynthesis in AGB Stars Traced by Oxygen Isotopic Ratios

    NASA Astrophysics Data System (ADS)

    De Nutte, R.; Decin, L.; Olofsson, H.; de Koter, A.; Lombaert, R.; Milam, S.; Ramstedt, S.

    2015-08-01

    Isotopic ratios are by far the best diagnostic tracers of the stellar origin of elements, as they are very sensitive to the precise conditions in the nuclear burning regions. They allow us to give direct constraints on stellar evolution models and on the progenitor mass. However, up to now different isotopic ratios have been well constrained for only a handful of Asymptotic Giant Branch (AGB) stars. We present new data on isotopologue lines of a well-selected sample of AGB stars, covering the three spectral classes of C-, S- and M-type stars. We report on the first efforts made in determining accurate isotopologue fractions, focusing on oxygen isotopes which are a crucial tracer of the poorly constrained extra mixing processes in stellar atmospheres.

  18. Optical Spectroscopy of the Post-AGB Star HD 89353

    NASA Astrophysics Data System (ADS)

    Mohamad-Yob, S.-J.; Gopir, G. K.; Malasan, H. L.; Anwar, R.

    2009-08-01

    Using the compact spectrograph at 600 lines/mm, and the 50.8 cm telescope at the Langkawi National Observatory, we obtained moderate resolution spectra of the post-AGB star HD 89353. The objective is to measure carbon and nitrogen abundances as a test of nucleosynthesis in AGB stars. The wavelength covered is between 4800-5600, 6467-7276, and 7035-7840 Å. A preliminary analysis showed the presence of the CI lines: 4932.00, 5039.05, 6586.269, 7108.934, 7111.480, 7113.178, 7115.182, 7116.991 and 7119.656 Å, and the NI lines: 7442.28 and 7423.63 Å. There was also emission line of H-alpha. We measured the equivalent widths of the C and N lines for future abundance calculation.

  19. Starlight and Sandstorms: Mass Loss Mechanisms on the AGB

    NASA Astrophysics Data System (ADS)

    Höfner, S.

    2011-09-01

    There are strong observational indications that the dense slow winds of cool luminous AGB stars are driven by radiative pressure on dust grains which form in the extended atmospheres resulting from pulsation-induced shocks. For carbon stars, detailed models of outflows driven by amorphous carbon grains show good agreement with observations. Some still existing discrepancies may be due to a simplified treatment of cooling in shocks, drift of the grains relative to the gas, or effects of giant convection cells or dust-induced pattern formation. For stars with C/O < 1, recent models indicate that absorption by silicate dust is probably insufficient to drive their winds. A possible alternative is scattering by Fe-free silicate grains with radii of a few tenths of a micron. In this scenario one should expect less circumstellar reddening for M- and S-type AGB stars than for C-stars with comparable stellar parameters and mass loss rates.

  20. Nucleosynthesis in Low Mass Very Metal Poor AGB Stars

    NASA Astrophysics Data System (ADS)

    Serenelli, A.

    The evolution of a 1.5 M⊙, Z= 10-5 stellar model has been followed starting at the ZAMS up to the thermally pulsating asymptotic giant branch (TP-AGB) phase. Calculations were done using the LPCODE [1], to which some changes were done. The most important and relevant to this work is the incorporation of a full nuclear network from H to Po, comprising about 525 isotopes and 910 nuclear reactions, appropriate for the computation of the s-process occurring in AGB stars. Convection is treated according to the mixing length theory (λMLT = 1.7) and convective mixing as a diffusive process. Diffusive overshooting is also included according to [2] and the free parameter f adopted is 0.015. Mass loss is given by the Reimers formula, with the parameter η = 1.

  1. Wind Acceleration in AGB Stars: Solid Ground and Loose Ends

    NASA Astrophysics Data System (ADS)

    Höfner, S.

    2015-08-01

    The winds of cool luminous AGB stars are commonly assumed to be driven by radiative acceleration of dust grains which form in the extended atmospheres produced by pulsation-induced shock waves. The dust particles gain momentum by absorption or scattering of stellar photons, and they drag along the surrounding gas particles through collisions, triggering an outflow. This scenario, here referred to as Pulsation-Enhanced Dust-DRiven Outflow (PEDDRO), has passed a range of critical observational tests as models have developed from empirical and qualitative to increasingly self-consistent and quantitative. A reliable theory of mass loss is an essential piece in the bigger picture of stellar and galactic chemical evolution, and central for determining the contribution of AGB stars to the dust budget of galaxies. In this review, I discuss the current understanding of wind acceleration and indicate areas where further efforts by theorists and observers are needed.

  2. Probing the Mass Loss History of AGB Stars with Herschelfootnotemark

    NASA Astrophysics Data System (ADS)

    Kerschbaum, F.; Mecina, M.; Ottensamer, R.; Luntzer, A.; Groenewegen, M. A. T.; Blommaert, J. A. D. L.; Decin, L.; Royer, P.; Vandenbussche, B.; Waelkens, C.; Barlow, M.; Lim, T.

    2011-09-01

    An overview is given of AGB stars imaged with the PACS and SPIRE instruments on-board the Herschel Space Observatory in the framework of the MESS Guaranteed Time Key Programme. The objects AQ And, U Ant, W Aql, U Cam, RT Cap, Y CVn, TT Cyg, UX Dra, W Ori, AQ Sgr, and X TrA all show detached or extended circumstellar emission.

  3. Magnetic fields around AGB stars and Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Vlemmings, W. H. T.

    2014-08-01

    Stars with a mass up to a few solar masses are one of the main contributors to the enrichment of the interstellar medium in dust and heavy elements. However, while significant progress has been made, the process of the mass-loss responsible for this enrichment is still not exactly known and forces beyond radiation pressure might be required. Often, the mass lost in the last phases of the stars life will become a spectacular planetary nebula. The shaping process of often strongly a-spherical PNe is equally elusive. Both binaries and magnetic fields have been suggested to be possible agents although a combination of both might also be a natural explanation. Here I review the current evidence for magnetic fields around AGB and post-AGB stars pre-Planetary Nebulae and PNe themselves. Magnetic fields appear to be ubiquitous in the envelopes of apparently single stars, challenging current ideas on its origin, although we have found that binary companions could easily be hidden from view. There are also strong indications of magnetically collimated outflows from post-AGB/pre-PNe objects supporting a significant role in shaping the circumstellar envelope.

  4. The Case of the Missing Cyanogen-rich AGB Stars in Galactic Globular Clusters

    NASA Astrophysics Data System (ADS)

    Campbell, S. W.; Yong, D.; Wylie-de Boer, E. C.; Stancliffe, R. J.; Lattanzio, J. C.; Angelou, G. C.; Grundahl, F.; Sneden, C.

    2012-08-01

    The handful of available observations of AGB stars in Galactic Globular Clusters suggest that the GC AGB populations are dominated by cyanogen-weak stars (eg. Norris et al. 1981; Sneden et al. 2000). This contrasts strongly with the distributions on the RGB (and other) populations, which generally show a 50:50 bimodality in CN band strength. If this is a real difference then it presents a serious problem for low metallicity stellar evolution theory - since such a surface abundance change going from the RGB to AGB is not predicted by stellar models. However this is only a tentative conclusion, since it is based on very small AGB sample sizes. To test whether this problem really exists we have carried out an observational campaign targeting AGB stars in GCs. Our preliminary results indicate there is indeed a lack of CN-strong AGB stars.

  5. Testing the sensitivity of terrestrial carbon models using remotely sensed biomass estimates

    NASA Astrophysics Data System (ADS)

    Hashimoto, H.; Saatchi, S. S.; Meyer, V.; Milesi, C.; Wang, W.; Ganguly, S.; Zhang, G.; Nemani, R. R.

    2010-12-01

    There is a large uncertainty in carbon allocation and biomass accumulation in forest ecosystems. With the recent availability of remotely sensed biomass estimates, we now can test some of the hypotheses commonly implemented in various ecosystem models. We used biomass estimates derived by integrating MODIS, GLAS and PALSAR data to verify above-ground biomass estimates simulated by a number of ecosystem models (CASA, BIOME-BGC, BEAMS, LPJ). This study extends the hierarchical framework (Wang et al., 2010) for diagnosing ecosystem models by incorporating independent estimates of biomass for testing and calibrating respiration, carbon allocation, turn-over algorithms or parameters.

  6. S-process nucleosynthesis in AGB stars with the full spectrum of turbulence scheme for convection.

    NASA Astrophysics Data System (ADS)

    Yagüe, A.; García-Hernández, D. A.; Ventura, P.; Lugaro, M.

    2016-07-01

    The chemical evolution of asymptotic giant branch (AGB) stars models depends greatly on the input physics (e.g. convective model, mass loss recipe). Variations of hot bottom burning (HBB) strength, or third dredge-up (TDU) efficiency are among the main consequences of adopting different input physics in the AGB models. The ATON evolutionary code stands apart from others in that it uses the Full Spectrum of Turbulence convective model. Here we present the first results of a newly developed s-process nucleosynthesis module for ATON AGB models. Our results are compared also with observations and theoretical predictions of present AGB nucleosynthesis models using different input physics.

  7. An integrated pan-tropical biomass map using multiple reference datasets.

    PubMed

    Avitabile, Valerio; Herold, Martin; Heuvelink, Gerard B M; Lewis, Simon L; Phillips, Oliver L; Asner, Gregory P; Armston, John; Ashton, Peter S; Banin, Lindsay; Bayol, Nicolas; Berry, Nicholas J; Boeckx, Pascal; de Jong, Bernardus H J; DeVries, Ben; Girardin, Cecile A J; Kearsley, Elizabeth; Lindsell, Jeremy A; Lopez-Gonzalez, Gabriela; Lucas, Richard; Malhi, Yadvinder; Morel, Alexandra; Mitchard, Edward T A; Nagy, Laszlo; Qie, Lan; Quinones, Marcela J; Ryan, Casey M; Ferry, Slik J W; Sunderland, Terry; Laurin, Gaia Vaglio; Gatti, Roberto Cazzolla; Valentini, Riccardo; Verbeeck, Hans; Wijaya, Arief; Willcock, Simon

    2016-04-01

    We combined two existing datasets of vegetation aboveground biomass (AGB) (Proceedings of the National Academy of Sciences of the United States of America, 108, 2011, 9899; Nature Climate Change, 2, 2012, 182) into a pan-tropical AGB map at 1-km resolution using an independent reference dataset of field observations and locally calibrated high-resolution biomass maps, harmonized and upscaled to 14 477 1-km AGB estimates. Our data fusion approach uses bias removal and weighted linear averaging that incorporates and spatializes the biomass patterns indicated by the reference data. The method was applied independently in areas (strata) with homogeneous error patterns of the input (Saatchi and Baccini) maps, which were estimated from the reference data and additional covariates. Based on the fused map, we estimated AGB stock for the tropics (23.4 N-23.4 S) of 375 Pg dry mass, 9-18% lower than the Saatchi and Baccini estimates. The fused map also showed differing spatial patterns of AGB over large areas, with higher AGB density in the dense forest areas in the Congo basin, Eastern Amazon and South-East Asia, and lower values in Central America and in most dry vegetation areas of Africa than either of the input maps. The validation exercise, based on 2118 estimates from the reference dataset not used in the fusion process, showed that the fused map had a RMSE 15-21% lower than that of the input maps and, most importantly, nearly unbiased estimates (mean bias 5 Mg dry mass ha(-1) vs. 21 and 28 Mg ha(-1) for the input maps). The fusion method can be applied at any scale including the policy-relevant national level, where it can provide improved biomass estimates by integrating existing regional biomass maps as input maps and additional, country-specific reference datasets. PMID:26499288

  8. Mapping aboveground forest biomass combining dendrometric data and spectral signature of forest species

    NASA Astrophysics Data System (ADS)

    Avocat, H.; Tourneux, F.

    2013-12-01

    Accurate measures and explicit spatial representations of forest biomass compose an important aspect to model the forest productivity and crops, and to implement sustainable forest management. Several methods have been developed to estimate and to map forest biomass, combining point-sources measurements of biophysical variables such as diameter-at-breast height (DBH), tree height, crown size, crown length, crown volume and remote sensing data (spectral vegetation index values). In this study, we propose a new method for aboveground biomass (AGB) mapping of forests and isolated trees. This method is tested on a 1100 km2 area located in the eastern France. In contrast to most of studies, our model is not calibrated using field plot measurements or point-source inventory data. The primary goal of this model is to propose an accessible and reproducible method for AGB mapping of temperate forests, by combining standard biomass values coming from bibliography and remotely sensed data. This method relies on three steps. (1) The first step consists of produce a map of wooded areas including small woods and isolated trees, and to identify the major forest stands. To do this, we use an unsupervised classification of a Landsat 7 ETM+ image. Results are compared and improved with various land cover data. (2) The second step consists of extract the normalized difference vegetation index (NDVI) values of main forest stands. (3) Finally, these values are combined with standard AGB values provided by bibliography, to calibrate four AGB estimation models of different forest types (broadleaves, coniferous, coppices, and mixed stands). This method provides a map of aboveground biomass for forests and isolated trees with a 30 meters spatial resolution. Results demonstrate that 71 % of AGB values for hardwoods vary between 143 and 363 t.ha-1, i.e. × 1 standard deviation around the average. For coniferous stands, most of values of AGB range from 167 to 256 t.ha-1.

  9. The evaluation of different forest structural indices to predict the stand aboveground biomass of even-aged Scotch pine (Pinus sylvestris L.) forests in Kunduz, Northern Turkey.

    PubMed

    Ercanli, İlker; Kahriman, Aydın

    2015-03-01

    We assessed the effect of stand structural diversity, including the Shannon, improved Shannon, Simpson, McIntosh, Margelef, and Berger-Parker indices, on stand aboveground biomass (AGB) and developed statistical prediction models for the stand AGB values, including stand structural diversity indices and some stand attributes. The AGB prediction model, including only stand attributes, accounted for 85 % of the total variance in AGB (R (2)) with an Akaike's information criterion (AIC) of 807.2407, Bayesian information criterion (BIC) of 809.5397, Schwarz Bayesian criterion (SBC) of 818.0426, and root mean square error (RMSE) of 38.529 Mg. After inclusion of the stand structural diversity into the model structure, considerable improvement was observed in statistical accuracy, including 97.5 % of the total variance in AGB, with an AIC of 614.1819, BIC of 617.1242, SBC of 633.0853, and RMSE of 15.8153 Mg. The predictive fitting results indicate that some indices describing the stand structural diversity can be employed as significant independent variables to predict the AGB production of the Scotch pine stand. Further, including the stand diversity indices in the AGB prediction model with the stand attributes provided important predictive contributions in estimating the total variance in AGB. PMID:25663395

  10. Have ozone effects on carbon sequestration been overestimated? A new biomass response function for wheat

    NASA Astrophysics Data System (ADS)

    Pleijel, H.; Danielsson, H.; Simpson, D.; Mills, G.

    2014-08-01

    Elevated levels of tropospheric ozone can significantly impair the growth of crops. The reduced removal of CO2 by plants leads to higher atmospheric concentrations of CO2, enhancing radiative forcing. Ozone effects on economic yield, e.g. the grain yield of wheat (Triticum aestivum L.), are currently used to model effects on radiative forcing. However, changes in grain yield do not necessarily reflect changes in total biomass. Based on an analysis of 22 ozone exposure experiments with field-grown wheat, we investigated whether the use of effects on grain yield as a proxy for effects on biomass under- or overestimates effects on biomass. First, we confirmed that effects on partitioning and biomass loss are both of significant importance for wheat yield loss. Then we derived ozone dose response functions for biomass loss and for harvest index (the proportion of above-ground biomass converted to grain) based on 12 experiments and recently developed ozone uptake modelling for wheat. Finally, we used a European-scale chemical transport model (EMEP MSC-West) to assess the effect of ozone on biomass (-9%) and grain yield (-14%) loss over Europe. Based on yield data per grid square, we estimated above-ground biomass losses due to ozone in 2000 in Europe, totalling 22.2 million tonnes. Incorrectly applying the grain yield response function to model effects on biomass instead of the biomass response function of this paper would have indicated total above-ground biomass losses totalling 38.1 million (i.e. overestimating effects by 15.9 million tonnes). A key conclusion from our study is that future assessments of ozone-induced loss of agroecosystem carbon storage should use response functions for biomass, such as that provided in this paper, not grain yield, to avoid overestimation of the indirect radiative forcing from ozone effects on crop biomass accumulation.

  11. Biomass, productivity and density of the seagrass Thalassia testudinum at three sites in Cahuita National Park, Costa Rica.

    PubMed

    Paynter, C K; Cortés, J; Engels, M

    2001-12-01

    The basic ecology of seagrass beds was investigated by comparing biomass, productivity and density of Thalassia testudinum (turtle grass) at three sites: Puerto Vargas, Punta Cahuita and Rio Perezoso, in Cahuita National Park, Limón, Costa Rica, over a two month period (March-April 1999). Above ground biomass, density, and productivity were highest in the Puerto Vargas site while Punta Cahuita had the least non-green above ground biomass was significantly lower in total biomass than Puerto Vargas. Punta Cahuita was distinguished by the largest grain size, a very hard substrate, and shallower water. Rio Perezoso, on the other hand, had extremely fine sediment and lower salinity, while Puerto Vargas was intermediate both in sediment size and environmental conditions. It appears, therefore, that higher biomass and productivity result from a combination of moderate environmental characteristics and an intermediate sediment size. PMID:15264540

  12. Quantification of seasonal biomass effects on cosmic-ray soil water content determination

    NASA Astrophysics Data System (ADS)

    Baatz, Roland; Bogena, Heye; Hendriks-Franssen, Harrie-Jan; Huisman, Johan Alexander; Montzka, Carsten; Vereecken, Harry

    2014-05-01

    Cosmic-ray soil moisture probes (CRS) utilize the fact that high-energy cosmic-ray neutrons are moderated (slowed to lower energies) as they most effective collide with terrestrial hydrogen atoms contained in water molecules. Low-energy cosmic-ray neutron intensity near the ground is therefore a measure of the water content of nearby soils and any water on the ground. In this study we present calibration results of a cosmic-ray soil moisture network in the Rur catchment, Germany. We propose a method to correct for above ground biomass vegetation effects on neutron flux density to improve soil water content estimates from cosmic-ray measurements. The correction for above ground water equivalents aims to remove biases in soil water content measurements on sites with high seasonal vegetation dynamics such as agricultural fields. Above ground biomass is estimated as function of the normalized difference vegetation index using regression equations. The regression equations were obtained from literature information, ground-based control measurements, a crop growth model and globally available data from the Moderate Resolution Imaging Spectrometer (MODIS). The results show that above ground biomass could be well estimated during the first half of the year. Seasonal changes in vegetation water content yielded biases in soil water content of ~0.05 cm³/cm³ that could be corrected for with the vegetation correction. The vegetation correction has particularly high potential when applied at long term cosmic-ray monitoring sites and the cosmic-ray rover.

  13. Nonradial instability strips for post-AGB stars

    SciTech Connect

    Stanghellini, L. ); Cox, A.N. ); Starrfield, S.G. . Dept. of Physics and Astronomy Los Alamos National Lab., NM )

    1990-01-01

    We test several pre-degenerate (PNN and DO) and degenerate (DB) models for stability against nonradial oscillations. These models lie on the 0.6 M{sub {circle dot}} evolutionary track calculated by Iben. The post-AGB stars have a residual CO core with only a little surface hydrogen and helium. In order to match all the observed pulsators. We use three different surface compositions for the DO stars, and a pure helium surface for the DB white dwarfs. We find 3 DO and 1 DB instability strips that we compare to the available observations. 16 refs., 1 fig.

  14. HIRAS images of fossil dust shells around AGB stars

    NASA Technical Reports Server (NTRS)

    Waters, L. B. F. M.; Kester, Do J. M.; Bontekoe, Tj. Romke; Loup, C.

    1994-01-01

    We present high resolution HIRAS 60 and 100 micron images of AGB stars surrounded by fossil dust shells. Resolving the extended emission of the circumstellar dust allows a determination of the mass loss history of the star. We show that the geometry of the 60 micron emission surrounding HR 3126 agrees well with that of the optical reflection nebula. The emission around the carbon star U Hya is resolved into a central point source and a ring of dust, and the mass loss rate in the detached shell is 70 times higher than the current mass loss rate.

  15. Estimation of Regional Forest Aboveground Biomass Combining Icesat-Glas Waveforms and HJ-1A/HSI Hyperspectral Imageries

    NASA Astrophysics Data System (ADS)

    Xing, Yanqiu; Qiu, Sai; Ding, Jianhua; Tian, Jing

    2016-06-01

    Estimation of forest aboveground biomass (AGB) is a critical challenge for understanding the global carbon cycle because it dominates the dynamics of the terrestrial carbon cycle. Light Detection and Ranging (LiDAR) system has a unique capability for estimating accurately forest canopy height, which has a direct relationship and can provide better understanding to the forest AGB. The Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud, and land Elevation Satellite (ICESat) is the first polarorbiting LiDAR instrument for global observations of Earth, and it has been widely used for extracting forest AGB with footprints of nominally 70 m in diameter on the earth's surface. However, the GLAS footprints are discrete geographically, and thus it has been restricted to produce the regional full coverage of forest AGB. To overcome the limit of discontinuity, the Hyper Spectral Imager (HSI) of HJ-1A with 115 bands was combined with GLAS waveforms to predict the regional forest AGB in the study. Corresponding with the field investigation in Wangqing of Changbai Mountain, China, the GLAS waveform metrics were derived and employed to establish the AGB model, which was used further for estimating the AGB within GLAS footprints. For HSI imagery, the Minimum Noise Fraction (MNF) method was used to decrease noise and reduce the dimensionality of spectral bands, and consequently the first three of MNF were able to offer almost 98% spectral information and qualified to regress with the GLAS estimated AGB. Afterwards, the support vector regression (SVR) method was employed in the study to establish the relationship between GLAS estimated AGB and three of HSI MNF (i.e. MNF1, MNF2 and MNF3), and accordingly the full covered regional forest AGB map was produced. The results showed that the adj.R2 and RMSE of SVR-AGB models were 0.75 and 4.68 t hm-2 for broadleaf forests, 0.73 and 5.39 t hm-2 for coniferous forests and 0.71 and 6.15 t hm-2 for mixed forests respectively. The

  16. What Is, Or Should Be, The AGB? A Report from the Membership.

    ERIC Educational Resources Information Center

    Davis, Junius A.; And Others

    This document presents the results of a survey of member presidents and trustees of the Association of Governing Boards (AGB). The questionnaire employed several strategies for determining member needs and interests, and their perception of the role that the AGB should play in serving those needs and interests. First, a number of frequent concerns…

  17. Spitzer Light Curves of Dusty AGB Stars in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin; Meixner, Margaret; Riebel, David; Vijh, Uma; Hora, Joe; Boyer, Martha; Cook, Kem; Groenewegen, Martin; Whitelock, Patricia; Ita, Yoshifusa; Feast, Michael; Kemper, Ciska; Marengo, Massimo; Otsuka, Masaaki; Srinivasan, Sundar

    2014-12-01

    Asymptotic giant branch (AGB) variable stars are, together with supernovae, the main sources of enrichment of the interstellar medium (ISM) in processed material, particularly carbon, nitrogen and heavy s-process elements. The dustiest, extreme AGB stars contribute the largest enrichment per star. We propose to measure the first light curves for 32 of the dustiest AGB variable stars in the Small Magellanic Cloud (SMC) using the warm Spitzer mission's IRAC 3.6 and 4.5 micron imaging for monthly imaging measurements. We know most are variable based on dual-epoch observations from the Spitzer Surveying the Agents of Galaxy Evolution (SAGE) surveys of the SMC and ground-based near-infrared observations, but we have not observed these dusty SMC stars at the mid-infrared wavelengths available to Spitzer. Only Spitzer will be able to measure the light curve of this key phase of the AGB: the dustiest and indeed final stage of the AGB. Without this information, our developing picture of AGB evolution is decidedly incomplete. The observations we propose will test the validity of AGB evolution models, and, thus, their predictions of the return of mass and nucleosynthetic products to the ISM. A value-added component to this study is that we will obtain variability information on other AGB stars that lie within the fields of view of our observations. This proposal continues the studies we have begun with our Cycle 9 program (pid 90219) and our Cycle 10 program (pid 10154).

  18. Fresh Biomass Estimation in Heterogeneous Grassland Using Hyperspectral Measurements and Multivariate Statistical Analysis

    NASA Astrophysics Data System (ADS)

    Darvishzadeh, R.; Skidmore, A. K.; Mirzaie, M.; Atzberger, C.; Schlerf, M.

    2014-12-01

    Accurate estimation of grassland biomass at their peak productivity can provide crucial information regarding the functioning and productivity of the rangelands. Hyperspectral remote sensing has proved to be valuable for estimation of vegetation biophysical parameters such as biomass using different statistical techniques. However, in statistical analysis of hyperspectral data, multicollinearity is a common problem due to large amount of correlated hyper-spectral reflectance measurements. The aim of this study was to examine the prospect of above ground biomass estimation in a heterogeneous Mediterranean rangeland employing multivariate calibration methods. Canopy spectral measurements were made in the field using a GER 3700 spectroradiometer, along with concomitant in situ measurements of above ground biomass for 170 sample plots. Multivariate calibrations including partial least squares regression (PLSR), principal component regression (PCR), and Least-Squared Support Vector Machine (LS-SVM) were used to estimate the above ground biomass. The prediction accuracy of the multivariate calibration methods were assessed using cross validated R2 and RMSE. The best model performance was obtained using LS_SVM and then PLSR both calibrated with first derivative reflectance dataset with R2cv = 0.88 & 0.86 and RMSEcv= 1.15 & 1.07 respectively. The weakest prediction accuracy was appeared when PCR were used (R2cv = 0.31 and RMSEcv= 2.48). The obtained results highlight the importance of multivariate calibration methods for biomass estimation when hyperspectral data are used.

  19. Characterizing AGB stars in Wide-field Infrared Survey Explorer (WISE) bands

    NASA Astrophysics Data System (ADS)

    Lian, Jianhui; Zhu, Qingfeng; Kong, Xu; He, Jinhua

    2014-04-01

    Aims: Since asymptotic giant branch (AGB) stars are bright and extended infrared objects, most Galactic AGB stars saturate the Wide-field Infrared Survey Explorer (WISE) detectors and therefore the WISE magnitudes that are restored by applying point-spread-function fitting need to be verified. Statistical properties of circumstellar envelopes around AGB stars are discussed on the basis of a WISE AGB catalog verified in this way. Methods: We cross-matched an AGB star sample with the WISE All-Sky Source Catalog and the Two Mircon All Sky Survey catalog. Infrared Space Observatory (ISO) spectra of a subsample of WISE AGB stars were also exploited. The dust radiation transfer code DUSTY was used to help predict the magnitudes in the W1 and W2 bands, the two WISE bands most affected by saturation, for calibration purpose, and to provide physical parameters of the AGB sample stars for analysis. Results: DUSTY is verified against the ISO spectra to be a good tool to reproduce the spectral energy distributions of these AGB stars. Systematic magnitude-dependent offsets have been identified in WISE W1 and W2 magnitudes of the saturated AGB stars, and empirical calibration formulas are obtained for them on the basis of 1877 (W1) and 1558 (W2) AGB stars that are successfully fit with DUSTY. According to the calibration formulas, the corrections for W1 at 5 mag and W2 at 4 mag are -0.383 and 0.217 mag, respectively. In total, we calibrated the W1/W2 magnitudes of 2390/2021 AGB stars. The model parameters from the DUSTY and the calibrated WISE W1 and W2 magnitudes are used to discuss the behavior of the WISE color-color diagrams of AGB stars. The model parameters also reveal that O-rich AGB stars with opaque circumstellar envelopes are much rarer than opaque C-rich AGB stars toward the anti-Galactic center direction, which we attribute to the metallicity gradient of our Galaxy. The synthetic photometry and input parameters for the model grid are only available at the CDS via

  20. Out on a Limb: Updates on the Search for X-ray Emission from AGB Stars

    NASA Astrophysics Data System (ADS)

    Montez, Rodolfo; Ramstedt, Sofia; Santiago-Boyd, Andrea; Kastner, Joel; Vlemmings, Wouter

    2016-01-01

    X-rays from asymptotic giant branch (AGB) stars are rarely detected, however, few modern X-ray observatories have targeted AGB stars. In 2012, we searched a list of 480 galactic AGB stars and found a total of 13 targeted or serendipitous observations with few detections (Ramstedt et al. 2012). Since this initial search new programs have successfully targeted and detected X-ray emission from a handful of AGB stars. The X-ray emission, when detected, reveals high temperature plasma (>= 10 MK). This plasma might be heated by a large-scale magnetic field or indicate the presence of accretion onto a compact companion. In this poster, we update our search for X-ray emission from AGB stars with a review of their characteristics, potential origins, and impact of X-ray emission in this late stage of stellar evolution.

  1. Biomass Estimates for Five Western States.

    SciTech Connect

    Howard, James O.

    1990-10-01

    The purpose of this report is to describe the woody biomass resource within US Department of Energy's Pacific Northwest and Alaska Regional Biomass Program, comprised of southeast Alaska, Idaho, Montana, Oregon, and Washington. In addition to the regional forest biomass assessment, information will be presented for logging residue, which represents current energy conversion opportunities. The information presented in the report is based on data and relationships already published. Regionally applicable biomass equations are generally not available for species occurring in the west. Because of this, a number of assumptions were made to develop whole-tree biomass tables. These assumptions are required to link algorithms from biomass studies to regional timber inventory data published by the Forest Inventory and Analysis Research Units (FIA), of the Pacific Northwest and Intermountain Research Stations, US Forest Service. These sources and assumptions will be identified later in this report. Tabular biomass data will be presented for 11 resource areas, identified in the FS inventory publications. This report does not include information for the vast area encompassing interior Alaska. Total tress biomass as defined in the report refers to the above ground weight of a tree above a 1.0 foot stump, and exclusive of foliage. A glossary is included that defines specific terms as used in the report. Inventory terminology is derived from forest inventory reports from Forest Inventory and Analysis units at the Intermountain and Pacific Northwest Research Stations. 39 refs., 15 figs., 23 tabs.

  2. Estimation of aboveground biomass in Mediterranean forests by statistical modelling of ASTER fraction images

    NASA Astrophysics Data System (ADS)

    Fernández-Manso, O.; Fernández-Manso, A.; Quintano, C.

    2014-09-01

    Aboveground biomass (AGB) estimation from optical satellite data is usually based on regression models of original or synthetic bands. To overcome the poor relation between AGB and spectral bands due to mixed-pixels when a medium spatial resolution sensor is considered, we propose to base the AGB estimation on fraction images from Linear Spectral Mixture Analysis (LSMA). Our study area is a managed Mediterranean pine woodland (Pinus pinaster Ait.) in central Spain. A total of 1033 circular field plots were used to estimate AGB from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) optical data. We applied Pearson correlation statistics and stepwise multiple regression to identify suitable predictors from the set of variables of original bands, fraction imagery, Normalized Difference Vegetation Index and Tasselled Cap components. Four linear models and one nonlinear model were tested. A linear combination of ASTER band 2 (red, 0.630-0.690 μm), band 8 (short wave infrared 5, 2.295-2.365 μm) and green vegetation fraction (from LSMA) was the best AGB predictor (Radj2=0.632, the root-mean-squared error of estimated AGB was 13.3 Mg ha-1 (or 37.7%), resulting from cross-validation), rather than other combinations of the above cited independent variables. Results indicated that using ASTER fraction images in regression models improves the AGB estimation in Mediterranean pine forests. The spatial distribution of the estimated AGB, based on a multiple linear regression model, may be used as baseline information for forest managers in future studies, such as quantifying the regional carbon budget, fuel accumulation or monitoring of management practices.

  3. Spatial distribution of forest aboveground biomass in China: estimation through combination of spaceborne lidar, optical imagery, and forest inventory data

    NASA Astrophysics Data System (ADS)

    Xue, B. L.; Su, Y.; Guo, Q.; Hu, T.; Alvarez, O.; Tao, S.; Fang, J.

    2015-12-01

    The global forest ecosystem, which acts as a large carbon sink, plays an important role in modeling the global carbon balance. An accurate estimation of the total forest carbon stock in the aboveground biomass (AGB) is therefore necessary to improve our understanding of carbon dynamics, especially against the background of global climate change. The forest area of China is among the top five globally. However, because of limitations in forest AGB mapping methods and the availability of ground inventory data, there is still a lack in nationwide wall-to-wall forest AGB estimation map for China. In this study, we collected over 8000 ground inventory data from the literature, and developed an AGB mapping method using a combination of these ground inventory data, Geoscience Laser Altimeter System (GLAS)/Ice, Cloud, and Land Elevation Satellite (ICESat) data, optical imagery, climate surfaces, and topographic data. An uncertainty field model was introduced into the forest AGB mapping model to minimize the influence of plot locality uncertainty. Our nationwide wall-to-wall forest AGB mapping results show that the forest AGB density in China is 120 Mg/ha on average, with a standard deviation of 61 Mg/ha. Evaluation with an independent ground inventory dataset showed that our proposed method can accurately map wall-to-wall forest AGB across a large landscape. The coefficient of determination (R2) and root-mean-square error between our predicted results and the validation dataset were 0.75 and 42.39 Mg/ha, respectively. This new method and the resulting nationwide wall-to-wall AGB map will help to improve the accuracy of carbon dynamic predictions in China.

  4. Quantification of aboveground forest biomass using Quickbird imagery, topographic variables, and field data

    NASA Astrophysics Data System (ADS)

    Zhou, Jing-Jing; Zhao, Zhong; Zhao, Qingxia; Zhao, Jun; Wang, Haize

    2013-01-01

    Optical remote sensing is the most widely used method for obtaining forest biomass information. This research investigated the potential of using topographical and high-resolution optical data from Quickbird for measurement of black locust plantation aboveground biomass (AGB) grown in the hill-gully region of the Loess Plateau. Three different processing techniques, including spectral vegetation indices (SVIs), texture, and topography were evaluated, both individually and combined. Simple linear regression and stepwise multiple-linear regression models were developed to describe the relationship between image parameters obtained using these approaches and field measurements. SVI and topography-based approaches did not yield reliable AGB estimates, accounting for at best 23 and 19% of the observed variation in AGB. Texture-based methods were better, explaining up to 70% of the observed variation. A combination of SVIs, texture, and topography yielded an even better R value of 0.74 with the lowest root mean square error (17.21 t/ha) and bias (-1.85 t/ha). The results suggest that texture information from high-resolution optical data was more effective than SVIs and topography to estimate AGB. The performance of AGB estimation can be improved by adding SVIs and topography results to texture data; the best results can be obtained using a combination of these three data types.

  5. Non-Parametric Responses of Aboveground Biomass and NDVI to Land Surface Parameters in Arctic-Alpine Environments

    NASA Astrophysics Data System (ADS)

    Riihimäki, H. K.; Heiskanen, J.; Luoto, M.

    2015-12-01

    Aboveground biomass (AGB) is an important carbon pool and it affects various phenomena in Arctic and alpine areas, e.g. biodiversity, surface albedo and soil conditions. The growing availability of high-resolution digital elevation models (DEM) makes it possible to utilize topographical information for modeling local ground surface conditions globally. We investigated the effect of topography on field measured AGB (n = 359) and its commonly used proxy, the Normalized Difference Vegetation Index (NDVI) calculated from SPOT 5 imagery. The study area located in an Arctic-alpine treeline environment (69 °N, 21 °E). We performed the analyses with boosted regression trees method by using elevation and four land surface parameters (LSPs), derived from 10 m DEM, as predictors. The LSPs were namely Potential Incoming Solar Radiation (PISR, MJ m-2 a-1), Topographic Position Index (TPI, r = 300 m), Slope (angle in degrees) and Topographic Wetness Index (TWI). AGB varied from 0 to 5647 g m-2, while median AGB of the data was 449 g m-2. The explained deviance of the AGB and NDVI models were 53 % and 65 %, respectively. Elevation and PISR were the most important predictors. Their interaction was also significant in both cases as the highest AGB were at low-elevation, high-radiation sites, which implicates that PISR significantly improves the modelling of temperature related growing conditions. TWI had no clear effect to AGB nor to NDVI. TPI and Slope had a minor effect on AGB, but no effect to NDVI. Areas lower than their surroundings (negative TPI) had relatively high AGB. Furthermore, steeper slopes had higher AGB compared to flat sites. This is probably caused by the presence of mountain birch (Betula pubescens ssp. czerepanovii), which favors protected and steeper topography. Local topography is an important driver of the fine scale AGB patterns. Thus, DEM derived LSPs should be taken into account when modelling current and future biomass distributions in Arctic and alpine

  6. AGB stars in Leo P and their use as metallicity probes

    NASA Astrophysics Data System (ADS)

    Lee ( ), Chien-Hsiu

    2016-09-01

    Leo P is the most metal-poor yet star-forming galaxy in the local volume, and has the potential to serve as a local counterpart to interpret the properties of distant galaxies in the early universe. We present a comprehensive search of asymptotic giant branch (AGB) stars in Leo P using deep infrared imaging. AGB stars are the major dust contributors; the metal poor nature of Leo P can help to shed light on the dust formation process in very low-metallicity environments, similar to the early Universe. We select and classify oxygen-rich and carbon-rich candidate AGB stars using J - K versus K colour-magnitude diagram. To filter out contaminations from background galaxies, we exploit the high-resolution Hubble Space Telescope imaging and identify 9 oxygen-rich AGBs and 13 carbon-rich AGB stars in Leo P. We then use the ratio of carbon-rich and oxygen-rich AGB stars (C/M ratio) as an indicator of on-site metallicity and derive the global metallicity [Fe/H] = -1.8 dex for Leo P, in good agreement with previous studies using isochrone fitting. Follow-up observations of these Leo P AGB stars in the mid-infrared [e.g. Spitzer, James Webb Space Telescope (JWST)] will be invaluable to measure the dust formation rates using Spectral energy distribution (SED) fitting.

  7. Have ozone effects on carbon sequestration been over-estimated? A new biomass response function for wheat

    NASA Astrophysics Data System (ADS)

    Pleijel, H.; Danielsson, H.; Simpson, D.; Mills, G.

    2014-04-01

    Elevated levels of tropospheric ozone can significantly impair the growth of crops. The reduced removal of CO2 by plants leads to higher atmospheric concentrations of CO2, enhancing radiative forcing. Ozone effects on economic yield, e.g. the grain yield of wheat (Triticum aestivum L.) are currently used to model effects on radiative forcing. However, changes in grain yield do not necessarily reflect changes in total biomass. Based on analysis of 21 ozone exposure experiments with field-grown wheat, we investigated whether use of effects on grain yield as a~proxy for effects on biomass under- or over-estimates effects on biomass. First, we confirmed that effects on partitioning and biomass loss are both of significant importance for wheat yield loss. Then we derived ozone dose response functions for biomass loss and for harvest index (the proportion of above-ground biomass converted to grain) based on twelve experiments and recently developed ozone uptake modelling for wheat. Finally, we used a European scale chemical transport model (EMEP MSC-West) to assess the effect of ozone on biomass (-9%) and grain yield (-14%) loss over Europe. Based on yield data per grid square, we estimated above ground biomass losses due to ozone in 2000 in Europe totalling 22.2 million tonnes. Incorrectly applying the grain yield response function to model effects on biomass instead of the biomass response function of this paper would have indicated total above ground biomass losses totalling 38.1 million (i.e. overestimating effects by 15.9 million tonnes). A key conclusion from our study is that future assessments of ozone induced loss of agroecosystem carbon storage should use response functions for biomass, such as that provided in this paper, not grain yield, to avoid overestimation of the indirect radiative forcing from ozone effects on crop biomass accumulation.

  8. AGB sodium abundances in the globular cluster 47 Tucanae (NGC 104)

    SciTech Connect

    Johnson, Christian I.; McDonald, Iain; Zijlstra, Albert A. E-mail: iain.mcdonald-2@manchester.ac.uk; and others

    2015-02-01

    A recent analysis comparing the [Na/Fe] distributions of red giant branch (RGB) and asymptotic giant branch (AGB) stars in the Galactic globular cluster NGC 6752 found that the ratio of Na-poor to Na-rich stars changes from 30:70 on the RGB to 100:0 on the AGB. The surprising paucity of Na-rich stars on the AGB in NGC 6752 warrants additional investigations to determine if the failure of a significant fraction of stars to ascend the AGB is an attribute common to all globular clusters. Therefore, we present radial velocities, [Fe/H], and [Na/Fe] abundances for 35 AGB stars in the Galactic globular cluster 47 Tucanae (47 Tuc; NGC 104), and compare the AGB [Na/Fe] distribution with a similar RGB sample published previously. The abundances and velocities were derived from high-resolution spectra obtained with the Michigan/Magellan Fiber System and MSpec spectrograph on the Magellan–Clay 6.5 m telescope. We find the average heliocentric radial velocity and [Fe/H] values to be 〈RV{sub helio.}〉 = −18.56 km s{sup −1} (σ = 10.21 km s{sup −1}) and 〈[Fe/H]〉 = −0.68 (σ = 0.08), respectively, in agreement with previous literature estimates. The average [Na/Fe] abundance is 0.12 dex lower in the 47 Tuc AGB sample compared to the RGB sample, and the ratio of Na-poor to Na-rich stars is 63:37 on the AGB and 45:55 on the RGB. However, in contrast to NGC 6752, the two 47 Tuc populations have nearly identical [Na/Fe] dispersion and interquartile range values. The data presented here suggest that only a small fraction (≲20%) of Na-rich stars in 47 Tuc may fail to ascend the AGB, which is a similar result to that observed in M13. Regardless of the cause for the lower average [Na/Fe] abundance in AGB stars, we find that Na-poor stars and at least some Na-rich stars in 47 Tuc evolve through the early AGB phase. The contrasting behavior of Na-rich stars in 47 Tuc and NGC 6752 suggests that the RGB [Na/Fe] abundance alone is insufficient for predicting if a star will

  9. Impact of deforestation on biomass burning in the tropics

    SciTech Connect

    Hao, W.M.; Liu, M.H.; Ward, D.E.

    1994-12-31

    Fires are widely used for various land use practices in tropical countries. Large amounts of trace gases and aerosol particles are produced during the fires. It is important to assess the potential impact of these gases and particulate matter on the chemistry of the atmosphere and global climate. One of the largest uncertainties in quantifying the effects is the lack of information on the source strengths. The authors quantify the amount of biomass burned due to deforestation in each tropical country on basis of the deforestation rate, the above ground density, and the fraction of above ground biomass burned. Approximately 725 Tg of biomass were burned in 1980 and 984 Tg were burned in 1990. The 36% increase took place mostly in Latin America and tropical Asia. The largest source was Brazil, contributing about 29% of the total biomass burned in the tropics. The second largest source was Indonesia accounting for 10%, followed by Zaire accounting for about 8%. The burning of biomass due to increased deforestation has resulted in an additional 33 Tg CO and 2.5 Tg CH{sub 4} emitted annually to the atmosphere from 1980 to 1990.

  10. Biomass Burning

    Atmospheric Science Data Center

    2015-07-27

    Projects:  Biomass Burning Definition/Description:  Biomass Burning: This data set represents the geographical and temporal distribution of total amount of biomass burned. These data may be used in general circulation models (GCMs) and ...

  11. Phase-lag Distances of OH Masing AGB Stars

    NASA Astrophysics Data System (ADS)

    Engels, D.; Etoka, S.; Gérard, E.; Richards, A.

    2015-08-01

    Distances to AGB stars with optically thick circumstellar shells cannot be determined using optical parallaxes. However, for stars with OH 1612 MHz maser emission emanating from their circumstellar shells, distances can be determined by the phase-lag method. This method combines a linear diameter obtained from a phase-lag measurement with an angular diameter obtained from interferometry. The phase-lag of the variable emission from the back and front sides of the shells has been determined for 20 OH/IR stars in the galactic disk. These measurements are based on a monitoring program with the Nançay radio telescope ongoing for more than 6 years. The interferometric observations are continuing. We estimate that the uncertainties of the distance determination will be ˜20%.

  12. Herschel and ALMA observations of AGB star envelopes

    NASA Astrophysics Data System (ADS)

    Katrien Els Decin, Leen

    2015-08-01

    The stellar winds of evolved (super)giant stars are known to be the prime birthplaces for the interstellar material in our galaxy. Fusion in the stellar interiors creates carbon, nitrogen, oxygen, and for more massive stars elements such as magnesium, sulphur etc. are synthesized. Thanks to dredge-ups in the stellar atmosphere and subsequent extensive mass loss through a stellar wind this material is injected into the interstellar medium (ISM).These stellar winds are really unique chemical laboratories in which various gas-phase and gas-dust processes create and destroy gas and dust species and hence manufacture the pristine building blocks of the ISM. The efficiency and working of these various chemical processes is ultimately linked to the dynamical processes which establish the morpho-kinematical structure of the wind. Unraveling the intriguing coupling between these macro-scale dynamical and micro-scale chemical processes is a real challenge to which recent advances in instrumentation, theoretical modeling, and laboratory experiments have contributed a lot. Thanks to their unprecedented sensitivity, spatial resolution and wavelength coverage, Herschel and ALMA have proven to be two key instruments in solving some enigmas related to AGB stellar winds. In this talk, I will give a review of some of the most recent results in the field of AGB stellar winds based on Herschel and ALMA data and I will discuss some open questions that I hope will be answered in the next decade thanks to a combined effort between instrumentation and laboratory specialists and theoretical astrophysicists.

  13. Post-AGB Stars in the Halos of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Bond, Howard E.

    1999-02-01

    The visually brightest members of Population II are post-AGB (PAGB) stars evolving through spectral types F and A. The aim of this proposal is to find such PAGB stars in the halos of three galaxies that lie just outside the Local Group: Sextans A, NGC 3109, and NGC 5237. The importance of PAGB stars is: (1) they can probe the structure of galactic halos, in the form of test particles much more numerous than planetary nebulae or globular clusters, with which we can look for features such as clumps or tidal streams; (2) the number counts will tell us the theoretically poorly known transition time from AGB to planetary nebula; and (3) we believe that PAGB stars will prove to be a superb new PRIMARY distance indicator, comparable to or better than Cepheids. PAGB stars of types F and A are easily recognized because of their large Balmer jumps. Our uBVI photometric system is optimal for revealing them in galactic halos, due to their unique u-B colors, and the method is extremely efficient in its telescope time requirements. Sextans A and NGC 3109 have Cepheid and TRGB distances, so they are excellent test beds for a confrontation with our proposed Pop II primary standard candles. NGC 5237 has an uncertain distance, which PAGB stars should considerably improve. The 0.9-m telescope will be used (1) to obtain uBVI calibrations of our fields, thus saving the 4-m BTC mosaic for the deep observations; and (2) to complete our survey of Milky Way globular clusters for PAGB stars to used as Galactic calibrators of their luminosities and metallicity dependence.

  14. Post-AGB Stars in the Halos of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Bond, Howard E.

    1999-02-01

    The visually brightest members of Population II are post-AGB (PAGB) stars evolving through spectral types F and A. The aim of this proposal is to find such PAGB stars in the halos of Sextans A and B (two galaxies just outside the Local Group) and of NGC 4236 (a nearly edge-on spiral in the M81 Group). The importance of these stars is: (1) they will serve as probes of the structure of galactic halos, in the form of test particles much more numerous than planetary nebulae or globular clusters, with which we can look for features such as clumps or tidal streams; (2) the number counts will tell us the theoretically poorly known transition time from AGB to planetary nebula; and (3) we believe that PAGB stars will prove to be a superb new PRIMARY distance indicator, comparable to or better than Cepheids. PAGB stars of types F and A are easily recognized because of their large Balmer jumps. Our uBVI photometric system is optimal for revealing them in galactic halos, due to their unique u-B colors, and the method is extremely efficient in its telescope time requirements. In Sextans A and B PAGB stars will appear at V~eq22.3, and in NGC 4236 at V~eq24. Sextans A and B have Cepheid and TRGB distances, and NGC 4236 is a Tully-Fisher calibrator, so they are excellent test beds for a confrontation with our proposed Pop II primary standard candles. We will use the 0.9-m telescope for uBVI calibrations of our fields, saving the 4-m for the deep observations.

  15. Developing a generalized allometric equation for aboveground biomass estimation

    NASA Astrophysics Data System (ADS)

    Xu, Q.; Balamuta, J. J.; Greenberg, J. A.; Li, B.; Man, A.; Xu, Z.

    2015-12-01

    A key potential uncertainty in estimating carbon stocks across multiple scales stems from the use of empirically calibrated allometric equations, which estimate aboveground biomass (AGB) from plant characteristics such as diameter at breast height (DBH) and/or height (H). The equations themselves contain significant and, at times, poorly characterized errors. Species-specific equations may be missing. Plant responses to their local biophysical environment may lead to spatially varying allometric relationships. The structural predictor may be difficult or impossible to measure accurately, particularly when derived from remote sensing data. All of these issues may lead to significant and spatially varying uncertainties in the estimation of AGB that are unexplored in the literature. We sought to quantify the errors in predicting AGB at the tree and plot level for vegetation plots in California. To accomplish this, we derived a generalized allometric equation (GAE) which we used to model the AGB on a full set of tree information such as DBH, H, taxonomy, and biophysical environment. The GAE was derived using published allometric equations in the GlobAllomeTree database. The equations were sparse in details about the error since authors provide the coefficient of determination (R2) and the sample size. A more realistic simulation of tree AGB should also contain the noise that was not captured by the allometric equation. We derived an empirically corrected variance estimate for the amount of noise to represent the errors in the real biomass. Also, we accounted for the hierarchical relationship between different species by treating each taxonomic level as a covariate nested within a higher taxonomic level (e.g. species < genus). This approach provides estimation under incomplete tree information (e.g. missing species) or blurred information (e.g. conjecture of species), plus the biophysical environment. The GAE allowed us to quantify contribution of each different

  16. Constraining Mass Loss and Lifetimes of Low Mass, Low Metallicity AGB Stars

    NASA Astrophysics Data System (ADS)

    Rosenfield, P.; Marigo, P.; Girardi, L.; Dalcanton, J. J.; Bressan, A.; Gullieuszik, M.; Weisz, D. R.; Williams, B. F.; Dolphin, A.; Aringer, B.

    2015-08-01

    The evolution and lifetimes of thermally pulsing asymptotic giant branch (TP-AGB) stars suffer from significant uncertainties. We present a detailed framework for constraining model luminosity functions of TP-AGB stars using resolved stellar populations. We show an example of this method that compares various TP-AGB mass-loss prescriptions that differ in their treatments of mass loss before the onset of dust-driven winds (pre-dust). We find that models with more efficient pre-dust driven mass loss produce results consistent with observations, as opposed to more canonical mass-loss models. Efficient pre-dust driven mass-loss predicts, for [Fe/H] ≲ -1.2, that lower mass TP-AGB stars (M≲ 1 M⊙) must have lifetimes less than about 1.2 Myr.

  17. A Complete Sample of Hot Post-AGB Stars in Globular Clusters

    NASA Technical Reports Server (NTRS)

    Landsman, W.; Moehler, S.; Napiwotzki, R.; Heber, U.; Sweigart, A.; Catelan, M.; Stecher, T.

    1999-01-01

    Ultraviolet images of globular clusters are often dominated by one or two "UV-bright" stars. The most luminous of these are believed to be post-AGB stars, which go through a luminous UV-bright phase as they leave the AGB and move rapidly across the HR diagram toward their final white dwarf state. During the two flights of the ASTRO observatory in 1990 and 1995, the Ultraviolet Imaging Telescope (UIT, Stecher 1997, PASP, 109, 584) was used to obtained ultraviolet (1600 A) images of 14 globular clusters. These images provide a complete census of hot (> 8000 K) post-AGB stars in the observed globular clusters, because the 40' field of view of UIT is large enough to image the entire population of most Galactic globulars, and because the dominant cool star population is suppressed in ultraviolet images, allowing UV-bright stars to be detected into the cluster core. We have begun a program of optical and STIS ultraviolet spectroscopy to determine the fundamental stellar parameters (\\log L, T_eff, \\log g) of all the hot post-AGB candidates discovered on the UIT images. Among the goals of our program are to test theoretical post-AGB lifetimes across the HR diagram, and to estimate the mass of the currently forming white dwarfs in globular clusters. Two trends are already apparent in our survey. First, the UV-selected sample has removed a bias against the detection of the hottest post-AGB stars, and resulted in the discovery of five cluster post-AGB stars with Teff > 50,000 K. Second, most of the new discoveries have been lower luminosity (2.5 $<$\\log L $<$ 3.0) than expected for stars which leave the AGB during the thermally pulsating phase.

  18. Reducing Uncertainties in Satellite-derived Forest Aboveground Biomass Estimates using a High Resolution Forest Cover Map

    NASA Astrophysics Data System (ADS)

    Zhang, G.; Ganguly, S.; Nemani, R. R.; Milesi, C.; Basu, S.; Kumar, U.

    2014-12-01

    Several studies to date have provided an extensive knowledge base for estimating forest aboveground biomass (AGB) and recent advances in space-based modeling of the 3-D canopy structure, combined with canopy reflectance measured by passive optical sensors and radar backscatter, are providing improved satellite-derived AGB density mapping for large scale carbon monitoring applications. A key limitation in forest AGB estimation from remote sensing, however, is the large uncertainty in forest cover estimates from the coarse-to-medium resolution satellite-derived land cover maps (present resolution is limited to 30-m of the USGS NLCD Program). The uncertainties in forest cover estimates at the Landsat scale result in high uncertainties for AGB estimation, predominantly in heterogeneous forest and urban landscapes. We have successfully developed an approach using a machine learning algorithm and High-Performance-Computing with NAIP air-borne imagery data for mapping tree cover at 1-m over California and Maryland. In a comparison with high resolution LiDAR data available over selected regions in the two states, we found our results to be promising both in terms of accuracy as well as our ability to scale nationally. The generated 1-m forest cover map will be aggregated to the Landsat spatial grid to demonstrate differences in AGB estimates (pixel-level AGB density, total AGB at aggregated scales like ecoregions and counties) when using a native 30-m forest cover map versus a 30-m map derived from a higher resolution dataset. The process will also be complemented with a LiDAR derived AGB estimate at the 30-m scale to aid in true validation.

  19. Mid-Term Status of the Forest Dragon III: Data Collection and Regional Aboveground Biomass Estimation

    NASA Astrophysics Data System (ADS)

    Pang, Yong; Li, Zengyuan; Liu, Luxia; Lu, Hao; Jia, Wen; Liu, Qingwang; Tian, Xin; Zhang, Ruiying; Shmullius, Christiana

    2014-11-01

    In the 1st two years of Forest Dragon 3 project, Chinese groups engaged in following activities: 1) field measurements and airborne campaigns for forest map validation, 2) regional forest aboveground biomass (AGB) estimation algorithm development and map generation. The AGB estimation by fusion multisensor fusion was investigated. Two campaigns consist of in-situ observation, airborne flight and spaceborne measurements were designed and implemented in the Heilongjiang Province and Yunnan Province of China. The Heilongjiang Province is located in Northeast China and has typical temperate forest. The Yunnan Province is located in Southwest China and contains multiple forest types including tropical forest. By using these observation data from different scales, multi-source satellite data were used to estimate spatial explicit AGB for Da Xinganling study area.

  20. An extreme paucity of second population AGB stars in the `normal' globular cluster M4

    NASA Astrophysics Data System (ADS)

    MacLean, B. T.; Campbell, S. W.; De Silva, G. M.; Lattanzio, J.; D'Orazi, V.; Simpson, J. D.; Momany, Y.

    2016-07-01

    Galactic globular clusters (GCs) are now known to harbour multiple stellar populations, which are chemically distinct in many light element abundances. It is becoming increasingly clear that asymptotic giant branch (AGB) stars in GCs show different abundance distributions in light elements compared to those in the red giant branch (RGB) and other phases, skewing towards more primordial, field-star-like abundances, which we refer to as subpopulation one (SP1). As part of a larger programme targeting giants in GCs, we obtained high-resolution spectra for a sample of 106 RGB and 15 AGB stars in Messier 4 (NGC 6121) using the 2dF+HERMES facility on the Anglo-Australian Telescope. In this Letter, we report an extreme paucity of AGB stars with [Na/O] >-0.17 in M4, which contrasts with the RGB that has abundances up to [Na/O] =0.55. The AGB abundance distribution is consistent with all AGB stars being from SP1. This result appears to imply that all subpopulation two stars (SP2; Na-rich, O-poor) avoid the AGB phase. This is an unexpected result given M4's horizontal branch morphology - it does not have an extended blue horizontal branch. This is the first abundance study to be performed utilizing the HERMES spectrograph.

  1. An extreme paucity of second population AGB stars in the `normal' globular cluster M4

    NASA Astrophysics Data System (ADS)

    MacLean, B. T.; Campbell, S. W.; De Silva, G. M.; Lattanzio, J.; D'Orazi, V.; Simpson, J. D.; Momany, Y.

    2016-04-01

    Galactic Globular clusters (GCs) are now known to harbour multiple stellar populations, which are chemically distinct in many light element abundances. It is becoming increasingly clear that asymptotic giant branch (AGB) stars in GCs show different abundance distributions in light elements compared to those in the red giant branch (RGB) and other phases, skewing toward more primordial, field-star-like abundances, which we refer to as subpopulation one (SP1). As part of a larger program targeting giants in GCs, we obtained high-resolution spectra for a sample of 106 RGB and 15 AGB stars in Messier 4 (NGC 6121) using the 2dF+HERMES facility on the Anglo-Australian Telescope. In this Letter we report an extreme paucity of AGB stars with [Na/O] >-0.17 in M4, which contrasts with the RGB that has abundances up to [Na/O] =0.55. The AGB abundance distribution is consistent with all AGB stars being from SP1. This result appears to imply that all subpopulation two stars (SP2; Na-rich, O-poor) avoid the AGB phase. This is an unexpected result given M4's horizontal branch morphology - it does not have an extended blue horizontal branch. This is the first abundance study to be performed utilising the HERMES spectrograph.

  2. Hand-held spectral radiometer to estimate gramineous biomass. [with interfaced pocket calculator solution

    NASA Technical Reports Server (NTRS)

    Pearson, R. L.; Miller, L. D.; Tucker, C. J.

    1976-01-01

    A simple hand-held instrument has been designed and constructed to nondestructively estimate above-ground gramineous biomass using radiometric measurements. The prototype unit consists of a modified two-channel digital radiometer interfaced to a pocket calculator. A digital interface was constructed to join electronically and control the radiometer and calculator to enable the radiometer-calculator system to solve a linear conversion solution from radiometric units to estimated biomass. This instrument has been used to estimate radiometrically gramineous biomass in a more efficient fashion with a high degree of accuracy.

  3. High yielding biomass genotypes of willow (Salix spp.) show differences in below ground biomass allocation

    PubMed Central

    Cunniff, Jennifer; Purdy, Sarah J.; Barraclough, Tim J.P.; Castle, March; Maddison, Anne L.; Jones, Laurence E.; Shield, Ian F.; Gregory, Andrew S.; Karp, Angela

    2015-01-01

    Willows (Salix spp.) grown as short rotation coppice (SRC) are viewed as a sustainable source of biomass with a positive greenhouse gas (GHG) balance due to their potential to fix and accumulate carbon (C) below ground. However, exploiting this potential has been limited by the paucity of data available on below ground biomass allocation and the extent to which it varies between genotypes. Furthermore, it is likely that allocation can be altered considerably by environment. To investigate the role of genotype and environment on allocation, four willow genotypes were grown at two replicated field sites in southeast England and west Wales, UK. Above and below ground biomass was intensively measured over two two-year rotations. Significant genotypic differences in biomass allocation were identified, with below ground allocation differing by up to 10% between genotypes. Importantly, the genotype with the highest below ground biomass also had the highest above ground yield. Furthermore, leaf area was found to be a good predictor of below ground biomass. Growth environment significantly impacted allocation; the willow genotypes grown in west Wales had up to 94% more biomass below ground by the end of the second rotation. A single investigation into fine roots showed the same pattern with double the volume of fine roots present. This greater below ground allocation may be attributed primarily to higher wind speeds, plus differences in humidity and soil characteristics. These results demonstrate that the capacity exists to breed plants with both high yields and high potential for C accumulation. PMID:26339128

  4. AKARI All Sky Survey: contribution from AGB stars to the far infrared flux from the Milky Way related to point sources outside the Galactic plane

    NASA Astrophysics Data System (ADS)

    Pollo, A.; Takeuchi, T. T.; Rybka, P.

    2011-10-01

    Using data from the FIS AKARI All-Sky Survey, we make a first step towards the estimation of the contribution from Asymptotic Giant Branch (AGB) stars to the far-infrared (FIR) flux from the Milky Way. We estimate the contribution from the AGB, and post-AGB, stars to the total flux generated by point sources outside the Galactic plane. Additionally, we present the positions of different types of AGB, and post-AGB, stars in the FIR color-color diagrams. Our main conclusion is that there is a high contribution from AGB stars, and particularly post-AGB stars, to the FIR flux coming from point sources in the outer parts of the Milky Way and possibly other Milky Way-type galaxies. FIR colors of different types of AGB stars remain similar but post-AGB stars are redder in the FIR and, as a result, contribute more to the total Galaxy flux density at longer FIR wavelengths.

  5. Spatially explicit estimation of aboveground boreal forest biomass in the Yukon River Basin, Alaska

    USGS Publications Warehouse

    Ji, Lei; Wylie, Bruce K.; Brown, Dana R. N.; Peterson, Birgit; Alexander, Heather D.; Mack, Michelle C.; Rover, Jennifer R.; Waldrop, Mark P.; McFarland, Jack W.; Chen, Xuexia; Pastick, Neal J.

    2015-01-01

    Quantification of aboveground biomass (AGB) in Alaska’s boreal forest is essential to the accurate evaluation of terrestrial carbon stocks and dynamics in northern high-latitude ecosystems. Our goal was to map AGB at 30 m resolution for the boreal forest in the Yukon River Basin of Alaska using Landsat data and ground measurements. We acquired Landsat images to generate a 3-year (2008–2010) composite of top-of-atmosphere reflectance for six bands as well as the brightness temperature (BT). We constructed a multiple regression model using field-observed AGB and Landsat-derived reflectance, BT, and vegetation indices. A basin-wide boreal forest AGB map at 30 m resolution was generated by applying the regression model to the Landsat composite. The fivefold cross-validation with field measurements had a mean absolute error (MAE) of 25.7 Mg ha−1 (relative MAE 47.5%) and a mean bias error (MBE) of 4.3 Mg ha−1(relative MBE 7.9%). The boreal forest AGB product was compared with lidar-based vegetation height data; the comparison indicated that there was a significant correlation between the two data sets.

  6. Integrated Properties of AGB Stars in Resolved and Unresolved Stellar Populations: Simple Stellar Populations and Star Clusters

    NASA Astrophysics Data System (ADS)

    Lançon, A.

    2011-09-01

    The evolution of AGB stars is notoriously complex. The confrontation of AGB population models with observed stellar populations is a useful alternative to the detailed study of individual stars in efforts to converge towards a reliable evolution theory. I review here the impact of studies of star clusters on AGB models and AGB population synthesis, deliberately leaving out any more complex stellar populations. Over the last 10 years, despite much effort, the absolute uncertainties in the predictions of the light emitted by intermediate-age populations have not been reduced to a satisfactory level. Observational sample definitions, as well as the combination of the natural variance in AGB properties with small number statistics, are largely responsible for this situation. There is hope that the constraints may soon become strong enough, thanks to large unbiased surveys of star clusters, resolved colour-magnitude diagrams, and new analysis methods that can account for the stochastic nature of AGB populations in clusters.

  7. AKARI All-Sky Survey: Contribution from AGB Stars to the Far Infrared Flux of the Milky Way

    NASA Astrophysics Data System (ADS)

    Pollo, A.; Rybka, P.; Takeuchi, T. T.

    2011-09-01

    Using the data from the AKARI FIS All-Sky Survey, we estimate the contribution from AGB stars to the far-infrared (FIR) flux from the Milky Way. We check the positions of different types of AGB stars in FIR color-color diagrams. Our conclusion is a large contribution from AGB stars, and particularly post-AGB stars, to the FIR flux in the outer regions of the Milky Way, and possibly other similar galaxies. FIR colors of different types of AGB stars are similar, with a large scatter, but post-AGB stars seem to be significantly redder and, as a result, contribute more to the total Galaxy flux at longer FIR wavelengths.

  8. Lithium formation in massive AGB stars: new models

    NASA Astrophysics Data System (ADS)

    Mazzitelli, I.; D'Antona, F.; Ventura, P.

    We present new AGB models including full coupling of nuclear evolution and turbulent transport in a diffusive scheme (Ventura et al. 1998). The novelty of these computations resides in the use of a Full Spectrum of Turbulence (FST) convective model, which allows to compute not only the appropriate convective flux distribution of billions of eddy scales (opposed to the one-eddy Mixing Length approximation), but also the self consistent average turbulent velocity and convective scale length which enter in the computation of the diffusion coefficient. Thus this new model contains a smaller number of free parameters with respect to previous MLT based computations. The coupled diffusion scheme treats independently 14 elements from ^1H to 18O, and in particular treats the production and destruction of ^7Li in the Hot Bottom Burning phase, which the FST convective models naturally achieve for masses approximately greater than 4.5M_odot (D'Antona and Mazzitelli 1996). The dependence of Lithium production on the evolving stellar mass, on the mass loss rate and on the chemical composition is presented. Predictions are given on the role of this lithium production for the galactic chemical evolution (e.g. D'Antona and Matteucci 1991), and the complete project for the computations is outlined.

  9. Molecular processes from the AGB to the PN stage

    NASA Astrophysics Data System (ADS)

    García-Hernández, D. Anibal

    2012-08-01

    Many complex organic molecules and inorganic solid-state compounds have been observed in the circumstellar shell of stars (both C-rich and O-rich) in the transition phase between Asymptotic Giant Branch (AGB) stars and Planetary Nebulae (PNe). This short (~102-104 years) phase of stellar evolution represents a wonderful laboratory for astrochemistry and provides severe constraints on any model of gas-phase and solid-state chemistry. One of the major challenges of present day astrophysics and astrochemistry is to understand the formation pathways of these complex organic molecules and inorganic solid-state compounds (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene in the case of a C-rich chemistry and oxides and crystalline silicates in O-rich environments) in space. In this review, I present an observational review of the molecular processes in the late stages of stellar evolution with a special emphasis on the first detections of fullerenes and graphene in PNe.

  10. High rotational CO lines in post-AGB stars and PNe

    NASA Technical Reports Server (NTRS)

    Justtanont, K.; Tielens, Alexander G. G. M.; Skinner, C. J.; Haas, Michael R.

    1995-01-01

    A significant fraction of a star's initial mass is lost while it is on the Asymptotic Giant Branch (AGB). Mass loss rates range from 10(exp -7) solar mass/yr for early AGB stars to a few 10(exp -4) solar mass/yr for stars at the tip of the AGB. Dust grains condense from the outflow as the gas expands and form a dust shell around the central star. A superwind (approximately 10(exp -4) to 10(exp -3) solar mass/yr) is thought to terminate the AGB phase. In the post-AGB phase, the star evolves to a higher effective temperature, the mass loss decreases (approximately 10(exp -8) solar mass/yr), but the wind velocity increases (approximately 1000 km/s). During this evolution, dust and gas are exposed to an increasingly harsher radiation field and when T(sub eff) reaches about 30,000 K, the nebula is ionized and becomes a planetary nebula (PN). Photons from the central star can create a photodissociation region (PDR) in the expanding superwind. Gas can be heated through the photoelectric effect working on small grains and polycyclic aromatic hydrocarbons (PAH's). This gas can cool via the atomic fine structure lines of O I (63 microns and 145 microns) and C II (158 microns), as well as the rotational lines of CO. In the post-AGB phase, the fast wind from the central star will interact with the material ejected during the AGB phase. The shock caused by this interaction will dissociate and heat the gas. This warm gas will cool through atomic fine structure lines of O I and the rotational lines of (newly formed) CO.

  11. Estimating spatial variation in Alberta forest biomass from a combination of forest inventory and remote sensing data

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Huang, S.; Hogg, E. H.; Lieffers, V.; Qin, Y.; He, F.

    2014-05-01

    Uncertainties in the estimation of tree biomass carbon storage across large areas pose challenges for the study of forest carbon cycling at regional and global scales. In this study, we attempted to estimate the present aboveground biomass (AGB) in Alberta, Canada, by taking advantage of a spatially explicit data set derived from a combination of forest inventory data from 1968 plots and spaceborne light detection and ranging (lidar) canopy height data. Ten climatic variables, together with elevation, were used for model development and assessment. Four approaches, including spatial interpolation, non-spatial and spatial regression models, and decision-tree-based modeling with random forests algorithm (a machine-learning technique), were compared to find the "best" estimates. We found that the random forests approach provided the best accuracy for biomass estimates. Non-spatial and spatial regression models gave estimates similar to random forests, while spatial interpolation greatly overestimated the biomass storage. Using random forests, the total AGB stock in Alberta forests was estimated to be 2.26 × 109 Mg (megagram), with an average AGB density of 56.30 ± 35.94 Mg ha-1. At the species level, three major tree species, lodgepole pine, trembling aspen and white spruce, stocked about 1.39 × 109 Mg biomass, accounting for nearly 62% of total estimated AGB. Spatial distribution of biomass varied with natural regions, land cover types, and species. Furthermore, the relative importance of predictor variables on determining biomass distribution varied with species. This study showed that the combination of ground-based inventory data, spaceborne lidar data, land cover classification, and climatic and environmental variables was an efficient way to estimate the quantity, distribution and variation of forest biomass carbon stocks across large regions.

  12. BOREAS RSS-15 SIR-C and Landsat TM Biomass and Landcover Maps of the NSA

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); Ranson, K. Jon

    2000-01-01

    As part of BOREAS, the RSS-15 team conducted an investigation using SIR-C, X-SAR, and Landsat TM data for estimating total above-ground dry biomass for the SSA and NSA modeling grids and component biomass for the SSA. Relationships of backscatter to total biomass and total biomass to foliage, branch, and bole biomass were used to estimate biomass density across the landscape. The procedure involved image classification with SAR and Landsat TM data and development of simple mapping techniques using combinations of SAR channels. For the SSA, the SIR-C data used were acquired on 06-Oct-1994, and the Landsat TM data used were acquired on 02-Sep-1995. The maps of the NSA were developed from SIR-C data acquired on 13-Apr-1994. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  13. Local spatial structure of forest biomass and its consequences for remote sensing of carbon stocks

    NASA Astrophysics Data System (ADS)

    Réjou-Méchain, M.; Muller-Landau, H. C.; Detto, M.; Thomas, S. C.; Le Toan, T.; Saatchi, S. S.; Barreto-Silva, J. S.; Bourg, N. A.; Bunyavejchewin, S.; Butt, N.; Brockelman, W. Y.; Cao, M.; Cárdenas, D.; Chiang, J.-M.; Chuyong, G. B.; Clay, K.; Condit, R.; Dattaraja, H. S.; Davies, S. J.; Duque, A.; Esufali, S.; Ewango, C.; Fernando, R. H. S.; Fletcher, C. D.; Gunatilleke, I. A. U. N.; Hao, Z.; Harms, K. E.; Hart, T. B.; Hérault, B.; Howe, R. W.; Hubbell, S. P.; Johnson, D. J.; Kenfack, D.; Larson, A. J.; Lin, L.; Lin, Y.; Lutz, J. A.; Makana, J.-R.; Malhi, Y.; Marthews, T. R.; McEwan, R. W.; McMahon, S. M.; McShea, W. J.; Muscarella, R.; Nathalang, A.; Noor, N. S. M.; Nytch, C. J.; Oliveira, A. A.; Phillips, R. P.; Pongpattananurak, N.; Punchi-Manage, R.; Salim, R.; Schurman, J.; Sukumar, R.; Suresh, H. S.; Suwanvecho, U.; Thomas, D. W.; Thompson, J.; Uríarte, M.; Valencia, R.; Vicentini, A.; Wolf, A. T.; Yap, S.; Yuan, Z.; Zartman, C. E.; Zimmerman, J. K.; Chave, J.

    2014-04-01

    Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDD+. Though broad scale mapping is based primarily on remote sensing data, the accuracy of resulting forest carbon stock estimates depends critically on the quality of field measurements and calibration procedures. The mismatch in spatial scales between field inventory plots and larger pixels of current and planned remote sensing products for forest biomass mapping is of particular concern, as it has the potential to introduce errors, especially if forest biomass shows strong local spatial variation. Here, we used 30 large (8-50 ha) globally distributed permanent forest plots to quantify the spatial variability in aboveground biomass (AGB) at spatial grains ranging from 5 to 250 m (0.025-6.25 ha), and we evaluate the implications of this variability for calibrating remote sensing products using simulated remote sensing footprints. We found that the spatial sampling error in AGB is large for standard plot sizes, averaging 46.3% for 0.1 ha subplots and 16.6% for 1 ha subplots. Topographically heterogeneous sites showed positive spatial autocorrelation in AGB at scales of 100 m and above; at smaller scales, most study sites showed negative or nonexistent spatial autocorrelation in AGB. We further show that when field calibration plots are smaller than the remote sensing pixels, the high local spatial variability in AGB leads to a substantial "dilution" bias in calibration parameters, a bias that cannot be removed with current statistical methods. Overall, our results suggest that topography should be explicitly accounted for in future sampling strategies and that much care must be taken in designing calibration schemes if remote sensing of forest carbon is to achieve its promise.

  14. BIOMASS UTILIZATION

    EPA Science Inventory

    The biomass utilization task consists of the evaluation of a biomass conversion technology including research and development initiatives. The project is expected to provide information on co-control of pollutants, as well as, to prove the feasibility of biomass conversion techn...

  15. Biomass pretreatment

    SciTech Connect

    Hennessey, Susan Marie; Friend, Julie; Elander, Richard T; Tucker, III, Melvin P

    2013-05-21

    A method is provided for producing an improved pretreated biomass product for use in saccharification followed by fermentation to produce a target chemical that includes removal of saccharification and or fermentation inhibitors from the pretreated biomass product. Specifically, the pretreated biomass product derived from using the present method has fewer inhibitors of saccharification and/or fermentation without a loss in sugar content.

  16. FUV Emission from AGB Stars: Modeling Accretion Activity Associated with a Binary Companion

    NASA Technical Reports Server (NTRS)

    Stevens, Alyx Catherine; Sahai, Raghvendra

    2012-01-01

    It is widely believed that the late stages of evolution for Asymptotic Giant Branch (AGB) stars are influenced by the presence of binary companions. Unfortunately, there is a lack of direct observational evidence of binarity. However, more recently, strong indirect evidence comes from the discovery of UV emission in a subsample of these objects (fuvAGB stars). AGB stars are comparatively cool objects (< or =3000 K), thus their fluxes falls off drastically for wavelengths 3000 Angstroms and shorter. Therefore, ultraviolet observations offer an important, new technique for detecting the binary companions and/or associated accretion activity. We develop new models of UV emission from fuvAGB stars constrained by GALEX photometry and spectroscopy of these objects. We compare the GALEX UV grism spectra of the AGB M7 star EY Hya to predictions using the spectral synthesis code Cloudy, specifically investigating the ultraviolet wavelength range (1344-2831 Angstroms). We investigate models composed of contributions from a photoionized "hot spot" due to accretion activity around the companion, and "chromospheric" emission from collisionally ionized plasma, to fit the UV observations.

  17. The composition of freshly-formed dust in recent (post-)AGB thermal pulses

    NASA Astrophysics Data System (ADS)

    Gandhi, Poshak

    2013-01-01

    We recently discovered a candidate Asymptotic Giant Branch (AGB) star undergoing a thermal pulse (TP). WISE J1810--3305 is one of only two sources in the WISE sky survey which show very red WISE colors but a very blue 2MASS [K] vs. WISE [W1 (3.4 mu m)] color, and drastic brightening at 12 mu m since IRAS observation. This favours a scenario in which we have caught a massive dust ejection event during a TP that began only ~15 years ago. The other source is Sakurai's object, which also underwent a massive dust expulsion around the same time, but is in a later evolutionary (post-AGB) phase. Few firm constraints exist on the TP stage because of its brevity. These objects provide a unique opportunity for understanding TP evolution and dust production in real-time. Here we propose COMICS spectroscopy of WISE J1810--3305 in order to study the composition of the circumstellar dust. We will search for molecular bands, and identify whether the central object is an Oxygen or Carbon rich AGB star. We also propose identical spectroscopy of Sakurai's object in order to compare AGB with post-AGB evolution. These objects are presently brightest in the mid-IR, and COMICS is the only ground-based mid-IR camera with the requisite capability for observation.

  18. Estimating aboveground biomass in the boreal forests of the Yukon River Basin, Alaska

    NASA Astrophysics Data System (ADS)

    Ji, L.; Wylie, B. K.; Nossov, D.; Peterson, B.; Waldrop, M. P.; McFarland, J.; Alexander, H. D.; Mack, M. C.; Rover, J. A.; Chen, X.

    2011-12-01

    Quantification of aboveground biomass (AGB) in Alaska's boreal forests is essential to accurately evaluate terrestrial carbon stocks and dynamics in northern high-latitude ecosystems. However, regional AGB datasets with spatially detailed information (<500 m) are not available for this extensive and remote area. Our goal was to map AGB at 30-m resolution for the boreal forests in the Yukon River Basin of Alaska using recent Landsat data and ground measurements. We collected field data in the Yukon River Basin from 2008 to 2010. Ground measurements included diameter at breast height (DBH) or basal diameter (BD) for live and dead trees and shrubs (>1 m tall), which were converted to plot-level AGB using allometric equations. We acquired Landsat Enhanced Thematic Mapper Plus (ETM+) images from the Web Enabled Landsat Data (WELD) that provides multi-date composites of top-of-atmosphere reflectance and brightness temperature for Alaska. From the WELD images, we generated a three-year (2008 - 2010) image composite for the Yukon River Basin using a series of compositing criteria including non-saturation, non-cloudiness, maximal normalize difference vegetation index (NDVI), and maximal brightness temperature. Airborne lidar datasets were acquired for two sub-regions in the central basin in 2009, which were converted to vegetation height datasets using the bare-earth digital surface model (DSM) and the first-return DSM. We created a multiple regression model in which the response variable was the field-observed AGB and the predictor variables were Landsat-derived reflectance, brightness temperature, and spectral vegetation indices including NDVI, soil adjusted vegetation index (SAVI), enhanced vegetation index (EVI), normalized difference infrared index (NDII), and normalized difference water index (NDWI). Principal component analysis was incorporated in the regression model to remedy the multicollinearity problems caused by high correlations between predictor variables

  19. Improving artificial forest biomass estimates using afforestation age information from time series Landsat stacks.

    PubMed

    Liu, Liangyun; Peng, Dailiang; Wang, Zhihui; Hu, Yong

    2014-11-01

    China maintains the largest artificial forest area in the world. Studying the dynamic variation of forest biomass and carbon stock is important to the sustainable use of forest resources and understanding of the artificial forest carbon budget in China. In this study, we investigated the potential of Landsat time series stacks for aboveground biomass (AGB) estimation in Yulin District, a key region of the Three-North Shelter region of China. Firstly, the afforestation age was successfully retrieved from the Landsat time series stacks in the last 40 years (from 1974 to 2013) and shown to be consistent with the surveyed tree ages, with a root-mean-square error (RMSE) value of 4.32 years and a determination coefficient (R (2)) of 0.824. Then, the AGB regression models were successfully developed by integrating vegetation indices and tree age. The simple ratio vegetation index (SR) is the best candidate of the commonly used vegetation indices for estimating forest AGB, and the forest AGB model was significantly improved using the combination of SR and tree age, with R (2) values from 0.50 to 0.727. Finally, the forest AGB images were mapped at eight epochs from 1985 to 2013 using SR and afforestation age. The total forest AGB in seven counties of Yulin District increased by 20.8 G kg, from 5.8 G kg in 1986 to 26.6 G kg in 2013, a total increase of 360 %. For the persistent forest area since 1974, the forest AGB density increased from 15.72 t/ha in 1986 to 44.53 t/ha in 2013, with an annual rate of about 0.98 t/ha. For the artificial forest planted after 1974, the AGB density increased about 1.03 t/ha a year from 1974 to 2013. The results present a noticeable carbon increment for the planted artificial forest in Yulin District over the last four decades. PMID:25034235

  20. The nebula around the post-AGB star 89 Herculis

    NASA Astrophysics Data System (ADS)

    Bujarrabal, V.; van Winckel, H.; Neri, R.; Alcolea, J.; Castro-Carrizo, A.; Deroo, P.

    2007-06-01

    Aims:We aim to study the structure of the nebula around the post-AGB, binary star 89 Her. The presence of a rotating disk around this star had been proposed but not been yet confirmed by observations. Methods: We present high-resolution PdBI maps of CO J=2-1 and 1-0. Properties of the nebula are directly derived from the data and model fitting. We also present N-band interferometric data on the extent of the hot dust emission, obtained with the VLTI. Results: Two nebular components are found: (a) an extended hour-glass-like structure, with expansion velocities of 7 km s-1 and a total mass 3× 10-3 M{⊙}, and (b) an unresolved very compact component, smaller than 0.4 arcsec and with a low total velocity dispersion of 5 km s-1. We cannot determine the velocity field in the compact component, but we argue that it can hardly be in expansion, since this would require too recent and too sudden an ejection of mass. On the other hand, assuming that this component is a Keplerian disk, we derive disk properties that are compatible with expectations for such a structure; in particular, the size of the rotating gas disk should be very similar to the extent of the hot dust component from our VLTI data. Assuming that the equator of the extended nebula coincides with the binary orbital plane, we provide new results on the companion star mass and orbit. Based on observations carried out with the IRAM Plateau de Bure Interferometer, as well as on observations of the Belgian Guaranteed time on VISA (ESO). IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  1. Silicate features in Galactic and extragalactic post-AGB discs

    NASA Astrophysics Data System (ADS)

    Gielen, C.; Bouwman, J.; van Winckel, H.; Lloyd Evans, T.; Woods, P. M.; Kemper, F.; Marengo, M.; Meixner, M.; Sloan, G. C.; Tielens, A. G. G. M.

    2011-09-01

    Aims: In this paper we study the Spitzer and TIMMI2 infrared spectra of post-AGB disc sources, both in the Galaxy and the LMC. Using the observed infrared spectra we determine the mineralogy and dust parameters of the discs, and look for possible differences between the Galactic and extragalactic sources. Methods: Modelling the full spectral range observed allows us to determine the dust species present in the disc and different physical parameters such as grain sizes, dust abundance ratios, and the dust and continuum temperatures. Results: We find that all the discs are dominated by emission features of crystalline and amorphous silicate dust. Only a few sample sources show features due to CO2 gas or carbonaceous molecules such as PAHs and C60 fullerenes. Our analysis shows that dust grain processing in these discs is strong, resulting in large average grain sizes and a very high crystallinity fraction. However, we do not find any correlations between the derived dust parameters and properties of the central source. There also does not seem to be a noticeable difference between the mineralogy of the Galactic and LMC sources. Even though the observed spectra are very similar to those of protoplanetary discs around young stars, showing similar mineralogy and strong grain processing, we do find evidence for differences in the physical and chemical processes of the dust processing. Based on observations obtained at the European Southern Observatory (ESO), La Silla, observing program 072.D-0263 and 077.D-0555, and on observations made with the Spitzer Space Telescope (program id 3274 and 50092), which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.Appendix A is available in electronic form at http://www.aanda.org

  2. Biomass yielding potential of naturally regenerated Prosopis juliflora tree stands at three varied ecosystems in southern districts of Tamil Nadu, India.

    PubMed

    Saraswathi, K; Chandrasekaran, S

    2016-05-01

    Fuel energy demand is of great concern in recent times due to the depletion of fossil fuel resources. Biomass serves as widely available primary renewable energy source. Hence, a study was performed to assess the above-ground biomass yielding capability of fuel wood tree Prosopis juliflora in three varied ecosystems viz., coastal, fallow land and riparian ecosystems in southern districts of Tamil Nadu. The results showed that the biomass production potential and above-ground net primary productivity of P. juliflora depend on the age of the tree stands and the nature of ecosystem. A higher biomass yield was observed for P. juliflora trees with 5 to 10 years old when compared to less than 5 years of their age. Among the three ecosystems, the maximum biomass production was recorded in riparian ecosystem. The stands with less than 5-year-old P. juliflora trees gave 1.40 t/ha, and 5- to 10-year-old tree stands produced 27.69 t/ha in riparian ecosystem. Above-ground net primary productivity of both the age groups was high in fallow land ecosystem. In riparian ecosystem, the wood showed high density and low sulphur content than the other two ecosystems. Hence, P. juliflora biomass can serve as an environmentally and economically feasible fuel as well as their utilization proffers an effective means to control its invasiveness. PMID:26797948

  3. Accumulation and partitioning of biomass, nutrients, and trace elements in switchgrass for phytoremediation of municipal biosolids.

    PubMed

    Jeke, Nicholson N; Zvomuya, Francis; Ross, Lisette

    2016-09-01

    In situ phytoremediation of municipal biosolids is a promising alternative to the land spreading and landfilling of biosolids from end-of-life municipal lagoons. Accumulation and partitioning of dry matter, nitrogen (N), phosphorus (P), and trace elements were determined in aboveground biomass (AGB) and belowground biomass (BGB) of switchgrass (Panicum virgatum L.) to determine the harvest stage that maximizes phytoextraction of contaminants from municipal biosolids. Seedlings were transplanted into 15-L plastic pails containing 3.9 kg (dry wt.) biosolids. Biomass yield components and contaminant concentrations were assessed every 14 days for up to 161 days. Logistic model fits to biomass yield data indicated no significant differences in asymptotic yield between AGB and BGB. Switchgrass partitioned significantly more N and P to AGB than to BGB. Maximum uptake occurred 86 days after transplanting (DAT) for N and 102 DAT for P. Harvesting at peak aboveground element accumulation removed 5% of N, 1.6% of P, 0.2% of Zn, 0.05% of Cd, and 0.1% of Cr initially present in the biosolids. These results will contribute toward identification of the harvest stage that will optimize contaminant uptake and enhance in situ phytoremediation of biosolids using switchgrass. PMID:26940512

  4. Biomass Logistics

    SciTech Connect

    J. Richard Hess; Kevin L. Kenney; William A. Smith; Ian Bonner; David J. Muth

    2015-04-01

    Equipment manufacturers have made rapid improvements in biomass harvesting and handling equipment. These improvements have increased transportation and handling efficiencies due to higher biomass densities and reduced losses. Improvements in grinder efficiencies and capacity have reduced biomass grinding costs. Biomass collection efficiencies (the ratio of biomass collected to the amount available in the field) as high as 75% for crop residues and greater than 90% for perennial energy crops have also been demonstrated. However, as collection rates increase, the fraction of entrained soil in the biomass increases, and high biomass residue removal rates can violate agronomic sustainability limits. Advancements in quantifying multi-factor sustainability limits to increase removal rate as guided by sustainable residue removal plans, and mitigating soil contamination through targeted removal rates based on soil type and residue type/fraction is allowing the use of new high efficiency harvesting equipment and methods. As another consideration, single pass harvesting and other technologies that improve harvesting costs cause biomass storage moisture management challenges, which challenges are further perturbed by annual variability in biomass moisture content. Monitoring, sampling, simulation, and analysis provide basis for moisture, time, and quality relationships in storage, which has allowed the development of moisture tolerant storage systems and best management processes that combine moisture content and time to accommodate baled storage of wet material based upon “shelf-life.” The key to improving biomass supply logistics costs has been developing the associated agronomic sustainability and biomass quality technologies and processes that allow the implementation of equipment engineering solutions.

  5. Dust in the Early Universe and the Contribution of AGB Stars

    NASA Astrophysics Data System (ADS)

    Schneider, R.; Valiante, R.; Ventura, P.; dell'Agli, F.; di Criscienzo, M.

    2015-08-01

    We review the role of AGB stars in early dust enrichment in light of new theoretical dust yields for stars with mass 1-8 M⊙ and metallicity 3×10-4≥ Z ≥0.008, obtained with models that follow stellar evolution from the pre-main sequence phase until the almost complete ejection of the stellar mantle. The models have been shown to reproduce the measured dust production rates by carbon-rich and oxygen-rich AGB stars in the Small and Large Magellanic Clouds, as well as the observed colors of the so-called extreme stars in the LMC. We discuss the relative role of AGB stars and SNe in early dust enrichment and the impact of these two classes of stellar sources on the nature and composition of the first dust.

  6. Optical Properties of Amorphous Alumina Dust in the Envelopes around O-Rich AGB Stars

    NASA Astrophysics Data System (ADS)

    Suh, Kyung-Won

    2016-08-01

    We investigate optical properties of amorphous alumina (Al_2O_3) dust grains in the envelopes around O-rich asymptotic giant branch (AGB) stars using laboratory measured optical data. We derive the optical constants of amorphous alumina over a wide wavelength range that satisfy the Kramers-Kronig relation and reproduce the laboratory data. Using the amorphous alumina and silicate dust, we compare the radiative transfer model results with the observed spectral energy distributions. Comparing the theoretical models with observations on various IR two-color diagrams for a large sample of O-rich AGB stars, we find that the amorphous alumina dust (about 10-40%) mixed with amorphous silicate better models the observed points for the O-rich AGB stars with thin dust envelopes.

  7. VizieR Online Data Catalog: Torun catalog of post-AGB and related objects (Szczerba+, 2007)

    NASA Astrophysics Data System (ADS)

    Szczerba, R.; Siodmiak, N.; Stasinska, G.; Borkowski, J.

    2007-09-01

    With the ongoing AKARI infrared sky survey, of much greater sensitivity than IRAS, a wealth of post-AGB objects may be discovered. It is thus time to organize our present knowledge of known post-AGB stars in the galaxy with a view to using it to search for new post-AGB objects among AKARI sources. We searched the literature available on the NASA Astrophysics Data System up to 1 October 2006, and defined criteria for classifying sources into three categories: very likely, possible and disqualified post-AGB objects. The category of very likely post-AGB objects is made up of several classes. We have created an evolutionary, on-line catalogue of Galactic post-AGB objects, to be referred to as the Torun catalogue of Galactic post-AGB and related objects. The present version of the catalogue contains 326 very likely, 107 possible and 64 disqualified objects. For the very likely post-AGB objects, the catalogue gives the available optical and infrared photometry, infrared spectroscopy and spectral types, and links to finding charts and bibliography. (3 data files).

  8. Spatial distributions of forest aboveground biomass and landscape dynamics associated with conservation status and ownership in New England, USA

    NASA Astrophysics Data System (ADS)

    Zheng, D.; Heath, L. S.; Ducey, M. J.

    2009-05-01

    We combined remote sensing derived forest aboveground biomass (AGB) estimation and the Conservation Biology Institute/World Wildlife Fund Protected Area Database using GIS techniques and spatial pattern analysis to illustrate how different conservation status and ownership could affect the landscape dynamics and spatial distributions of AGB in New England states, USA. The AGB means between all pairs of protection status and ownership categories were significantly different (P < 0.05). The highest mean AGB was observed in the protected public lands (156 Mg/ha), 44% higher than the lowest AGB mean (108 Mg/ha) observed in private regulated lands (privately owned but under the regulatory control by a state agency), or 30% higher than that in privately owned lands on average (120 Mg/ha). Seventy-seven percent of the regional forests with AGB > 200 Mg/ha, totaling about 9,300 km2, were located outside protected areas and were concentrated in western MA, southern VT, southwestern NH, and northwestern CT. The fragmentation rate in protected public lands between 1992 and 2001 was the least with greater rates were observed in privately regulated and non-regulated lands. Changing rates for the 4 representative fragmentation indices (patch density (PD), edge density (ED), landscape shape index (LSI), and mean patch size (MPS)) ranged from 1% in MPS to 6% in PD in protected public lands during the 9-year period whereas the mean changing rates ranged from 21% in LSI to 32% in PD in private lands. Thus, ownership and conservation status appears to have a strong impact on the dynamic changes of landscape structures in the region. These results indicate that if maintenance and enhancement of relatively unfragmented, high-AGB forest is a goal, expansion of protected areas appears to be an important management strategy.

  9. Winds of M- and S-type AGB stars: an unorthodox suggestion for the driving mechanism

    NASA Astrophysics Data System (ADS)

    Höfner, S.; Andersen, A. C.

    2007-04-01

    Context: Current knowledge suggests that the dust-driven wind scenario provides a realistic framework for understanding mass loss from C-rich AGB stars. For M-type objects, however, recent detailed models demonstrate that radiation pressure on silicate grains is not sufficient to drive the observed winds, contrary to previous expectations. Aims: In this paper, we suggest an alternative mechanism for the mass loss of M-type AGB stars, involving the formation of both carbon and silicate grains due to non-equilibrium effects, and we study the viability of this scenario. Methods: We model the dynamical atmospheres and winds of AGB stars by solving the coupled system of frequency-dependent radiation hydrodynamics and time-dependent dust formation, using a parameterized description of non-equilibrium effects in the gas phase. This approach allows us to assess under which circumstances it is possible to drive winds with small amounts of carbon dust and to get silicate grains forming in these outflows at the same time. Results: The properties of the resulting wind models, such as mass-loss rates and outflow velocities, are well within the observed limits for M-type AGB stars. Furthermore, according to our results, it is quite unlikely that significant amounts of silicate grains will condense in a wind driven by a force totally unrelated to dust formation, as the conditions in the upper atmosphere and wind acceleration region put strong constraints on grain growth. Conclusions: .The proposed scenario provides a natural explanation for the observed similarities in wind properties of M-type and C-type AGB stars and implies a smooth transition for stars with increasing carbon abundance, from solar-composition to C-rich AGB stars, possibly solving the longstanding problem of the driving mechanism for stars with a C/O close to one.

  10. Variable X-Ray and UV emission from AGB stars: Accretion activity associated with binarity

    NASA Astrophysics Data System (ADS)

    Sahai, Raghvendra; Sanz-Forcada, Jorge; Sánchez Contreras, Carmen

    2016-07-01

    Almost all of our current understanding of the late evolutionary stages of (1 — 8) Mʘ stars is based on single-star models. However, binarity can drastically affect late stellar evolution, producing dramatic changes in the history and geometry of mass loss that occurs in stars as they evolve off the AGB to become planetary nebulae (PNe). A variety of binary models have been proposed, which can lead to the generation of accretion disks and magnetic fields, which in turn produce the highly collimated jets that have been proposed as the primary agents for the formation of bipolar and multipolar PNe. However, observational evidence of binarity in AGB stars is sorely lacking simply these stars are very luminous and variable, invalidating standard techniques for binary detection. Using an innovative technique of searching for UV emission from AGB stars with GALEX, we have identified a class of AGB stars with far- ultraviolet excesses (fuvAGB stars), that are likely candidates for active accretion associated with a binary companion. We have carried out a pilot survey for X-ray emission from fuvAGB stars. The X-ray fluxes are found to vary in a stochastic or quasi-periodic manner on roughly hour-long times-scales, and simultaneous UV observations show similar variations in the UV fluxes. We discuss several models for the X-ray emission and its variability and find that the most likely scenario for the origin of the X-ray (and FUV) emission involves accretion activity around a main-sequence companion star, with confinement by strong magnetic fields associated with the companion and/or an accretion disk around it.

  11. Quantification of seasonal biomass effects on cosmic-ray soil water content determination

    NASA Astrophysics Data System (ADS)

    Baatz, R.; Bogena, H. R.; Hendricks Franssen, H.; Huisman, J. A.; Qu, W.; Montzka, C.; Korres, W.; Vereecken, H.

    2013-12-01

    The novel cosmic-ray soil moisture probes (CRPs) measure neutron flux density close to the earth surface. High energy cosmic-rays penetrate the Earth's atmosphere from the cosmos and become moderated by terrestrial nuclei. Hydrogen is the most effective neutron moderator out of all chemical elements. Therefore, neutron flux density measured with a CRP at the earth surface correlates inversely with the hydrogen content in the CRP's footprint. A major contributor to the amount of hydrogen in the sensor's footprint is soil water content. The ability to measure changes in soil water content within the CRP footprint at a larger-than-point scale (~30 ha) and at high temporal resolution (hourly) make these sensors an appealing measurement instrument for hydrologic modeling purposes. Recent developments focus on the identification and quantification of major uncertainties inherent in CRP soil moisture measurements. In this study, a cosmic-ray soil moisture network for the Rur catchment in Western Germany is presented. It is proposed to correct the measured neutron flux density for above ground biomass yielding vegetation corrected soil water content from cosmic-ray measurements. The correction for above ground water equivalents aims to remove biases in soil water content measurements on sites with high seasonal vegetation dynamics such as agricultural fields. Above ground biomass is estimated as function of indices like NDVI and NDWI using regression equations. The regression equations were obtained with help of literature information, ground-based control measurements, a crop growth model and globally available data from the Moderate Resolution Imaging Spectrometer (MODIS). The results show that above ground biomass could be well estimated during the first half of the year. Seasonal changes in vegetation water content yielded biases in soil water content of ~0.05 cm3/cm3 that could be corrected for with the vegetation correction. The vegetation correction has particularly

  12. VizieR Online Data Catalog: Obscured AGB in Magellanic Clouds. I. (Loup+ 1997)

    NASA Astrophysics Data System (ADS)

    Loup, C.; Zijlstra, A. A.; Waters, L. B. F. M.; Groenewegen, M. A. T.

    1997-02-01

    We have selected 198 IRAS sources in the Large Magellanic Cloud, and 11 in the Small Magellanic Cloud, which are the best candidates to be mass-loosing AGB stars (or possibly post-AGB stars). We used the catalogues of Schwering & Israel (1990, Cat. ) and Reid et al. (1990, Cat. ). They are based on the IRAS pointed observations and have lower detection limits than the Point Source Catalogue. We also made cross-identifications between IRAS sources and optical catalogues. (8 data files).

  13. OT2_jalcolea_2: Additional Hpoint observations of large post-AGB sources from HIFIStars

    NASA Astrophysics Data System (ADS)

    Alcolea, J.

    2011-09-01

    One of the most spectacular phases in the evolution of intermediate mass stars takes place at the end of their lives. At the end of the AGB, the central star dashes across the HR diagram from the red giant to the blue dwarf region. At the same time, the spherically symmetric and slowly expanding circumstellar envelopes around AGB stars become planetary nebulae (PNe), displaying a large variety of shapes and structures far more complex. This transformation takes place at the very end of the AGB, and it is due to the interaction of fast and bipolar molecular winds with the fossil AGB circumstellar envelope. The origin of these post-AGB winds is still unclear, but we know that the resulting two-wind interactions are only active during a very short period of time, ~ 100 yr, but still they are able to strongly modify the kinematics of the nebulae and re-shape them. To better understand these processes we must study the warm molecular gas component of early post-AGB sources, both pre-planetary nebulae (pPNe) and young PNe. Herschel/HIFI is very well suited at this, because its spectral coverage, high velocity resolution, and superb sensitivity. For these reasons, 10 pPNe and young PNe were included in the KPGT HIFISTARS, were a large number of spectral lines are observed in a moderate number of frequency setups, but just at the central point. In many cases this is simply enough, since most post-AGB sources in HIFIStars are compact. However there are three cases in which the non spherically symmetric structures seen in the warm gas are larger than the telescope beam: OH231.8+4.2, NGC7027 and NGC6302. Therefore we propose to perform some additional points in these three sources in a selected sample of HIFISTARS frequency setups, were we have detected strong lines of CO, H2O, NH3 and OH. These observations are crucial to understand the kinematics and interactions traced by these warm gas probes, and gain insight in the intricate problem of the post-AGB dynamics.

  14. Forest biomass estimation with hemispherical photography for multiple forest types and various atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Clark, Joshua Andrew

    The importance of accurately identifying inventories of domestic energy, including forest biomass, has increasingly become a priority of the US government and its citizens as the cost of fossil fuels has risen. It is useful to identify which of these resources can be processed and transported at the lowest cost for both private and public landowners. Accurate spatial inventories of forest biomass can help landowners allocate resources to maximize forest biomass utilization and provide information regarding current forest health (e.g., forest fire potential, insect susceptibility, wildlife habitat range). This research has indicated that hemispherical photography (HP) may be an accurate and low cost sensing technique for forest biomass measurements. In this dissertation: (1) It is shown that HP gap fraction measurements and both above ground biomass and crown biomass have a linear relationship. (2) It is demonstrated that careful manipulation of images improves gap fraction estimates, even under unfavorable atmospheric conditions. (3) It is shown that estimates of Leaf Area Index (LAI), based on transformations of gap fraction measurements, are the best estimator for both above ground forest biomass and crown biomass. (4) It is shown that many factors negatively influence the utility of HP for biomass estimation. (5) It is shown that biomass of forests stands with regular spacing is not modeled well using HP. As researchers continue to explore different methods for forest biomass estimation, HP is likely to remain as a viable technique, especially if LAI can be accurately estimated. However, other methods should be compared with HP, particularly for stands where LAI is poorly estimated by HP.

  15. Estimation of Aboveground Biomass Change for Tropical Deciduous Forest in Bago Yoma, Myanmar between year 2000 and 2014 using Landsat Images and Ground Measurements

    NASA Astrophysics Data System (ADS)

    Kim, H. S.; Wynn, K. Z.; Ryu, Y.

    2015-12-01

    Even with recently increased awareness of the environmental conservation, the degradation of tropical forests are still one of the major sources of global carbon emission. Especially in Myanmar, the pressure to develop natural forest is growing rapidly after the change from socialism to capitalism in 2010. As the initial step of the forest conservation, the aboveground biomass(AGB) of South Zarmani Reserved Forest in Bago Yoma region were estimated using Landsat 8 OLI after the evaluation with 100 sample plot measurements. Multiple linear regression (MLR) model of band values and their principal component analysis (PCA) model were developed to estimate the AGB using the spectral reflectance from Landsat images and elevation as the input variables. The MLR model had r2 = 0.43, RMSE = 60.2 tons/ha, relative RMSE = 70.1%, Bias = -9.1 tons/ha, Bias (%) = -10.6%, and p < 0.0001, while the PCA model showed r2 = 0.45, RMSE = 55.1 tons/ha, relative RMSE = 64.1%, Bias = -8.3 tons/ha, Bias (%) = -9.7%, and p < 0.0001. The AGB maps of the study area were generated based on both MLR and PCA models. The estimated mean AGB values were 74.74±22.3 tons/ha and 73.04±17.6 tons/ha and the total AGB of the study area are about 5.7 and 5.6 million tons from MLR and PCA, respectively. Then, Landsat 7 ETM+ image acquired on 2000 was also used to compare the changing of AGB between year 2000 and 2014. The estimated mean AGB value generated from the Landsat 7 ETM+ image was 78.9±16.9 tons/ha, which is substantially decreased about 7.5% compared to year 2014. The reduction of AGB increased with closeness to village, however AGB in distant areas showed steady increases. In conclusion, we were able to generate solid regression models from Landsat 8 OLI image after ground truth and two regression models gave us very similar AGB estimation (less than 2%) of the study area. We were also able to estimate the changing of AGB from year 2000 to 2014 of South Zarmani Reserved Forest, Bago Yoma

  16. Aboveground Biomass Monitoring over Siberian Boreal Forest Using Radar Remote Sensing Data

    NASA Astrophysics Data System (ADS)

    Stelmaszczuk-Gorska, M. A.; Thiel, C. J.; Schmullius, C.

    2014-12-01

    Aboveground biomass (AGB) plays an essential role in ecosystem research, global cycles, and is of vital importance in climate studies. AGB accumulated in the forests is of special monitoring interest as it contains the most of biomass comparing with other land biomes. The largest of the land biomes is boreal forest, which has a substantial carbon accumulation capability; carbon stock estimated to be 272 +/-23 Pg C (32%) [1]. Russian's forests are of particular concern, due to the largest source of uncertainty in global carbon stock calculations [1], and old inventory data that have not been updated in the last 25 years [2]. In this research new empirical models for AGB estimation are proposed. Using radar L-band data for AGB retrieval and optical data for an update of in situ data the processing scheme was developed. The approach was trained and validated in the Asian part of the boreal forest, in southern Russian Central Siberia; two Siberian Federal Districts: Krasnoyarsk Kray and Irkutsk Oblast. Together the training and testing forest territories cover an area of approximately 3,500 km2. ALOS PALSAR L-band single (HH - horizontal transmitted and received) and dual (HH and HV - horizontal transmitted, horizontal and vertical received) polarizations in Single Look Complex format (SLC) were used to calculate backscattering coefficient in gamma nought and coherence. In total more than 150 images acquired between 2006 and 2011 were available. The data were obtained through the ALOS Kyoto and Carbon Initiative Project (K&C). The data were used to calibrate a randomForest algorithm. Additionally, a simple linear and multiple-regression approach was used. The uncertainty of the AGB estimation at pixel and stand level were calculated approximately as 35% by validation against an independent dataset. The previous studies employing ALOS PALSAR data over boreal forests reported uncertainty of 39.4% using randomForest approach [2] or 42.8% using semi-empirical approach [3].

  17. Sodium abundances of AGB and RGB stars in Galactic globular clusters. I. Analysis and results of NGC 2808

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Primas, F.; Charbonnel, C.; Van der Swaelmen, M.; Bono, G.; Chantereau, W.; Zhao, G.

    2016-07-01

    Context. Galactic globular clusters (GC) are known to have multiple stellar populations and be characterised by similar chemical features, e.g. O-Na anti-correlation. While second-population stars, identified by their Na overabundance, have been found from the main sequence turn-off up to the tip of the red giant branch (RGB) in various Galactic GCs, asymptotic giant branch (AGB) stars have rarely been targeted. The recent finding that NGC 6752 lacks an Na-rich AGB star has thus triggered new studies on AGB stars in GCs, since this result questions our basic understanding of GC formation and stellar evolution theory. Aims: We aim to compare the Na abundance distributions of AGB and RGB stars in Galactic GCs and investigate whether the presence of Na-rich stars on the AGB is metallicity-dependent. Methods: With high-resolution spectra obtained with the multi-object high-resolution spectrograph FLAMES on ESO/VLT, we derived accurate Na abundances for 31 AGB and 40 RGB stars in the Galactic GC NGC 2808. Results: We find that NGC 2808 has a mean metallicity of -1.11 ± 0.08 dex, in good agreement with earlier analyses. Comparable Na abundance dispersions are derived for our AGB and RGB samples, with the AGB stars being slightly more concentrated than the RGB stars. The ratios of Na-poor first-population to Na-rich second-population stars are 45:55 in the AGB sample and 48:52 in the RGB sample. Conclusions: NGC 2808 has Na-rich second-population AGB stars, which turn out to be even more numerous - in relative terms - than their Na-poor AGB counterparts and the Na-rich stars on the RGB. Our findings are well reproduced by the fast rotating massive stars scenario and they do not contradict the recent results that there is not an Na-rich AGB star in NGC 6752. NGC 2808 thus joins the larger group of Galactic GCs for which Na-rich second-population stars on the AGB have recently been found. Based on observations made with ESO telescopes at the La Silla Paranal Observatory

  18. Pattern and dynamics of biomass stock in old growth forests: The role of habitat and tree size

    NASA Astrophysics Data System (ADS)

    Yuan, Zuoqiang; Gazol, Antonio; Wang, Xugao; Lin, Fei; Ye, Ji; Zhang, Zhaochen; Suo, YanYan; Kuang, Xu; Wang, Yunyun; Jia, Shihong; Hao, Zhanqing

    2016-08-01

    Forest ecosystems play a fundamental role in the global carbon cycle. However, how stand-level changes in tree age and structure influence biomass stock and dynamics in old-growth forests is a question that remains unclear. In this study, we quantified the aboveground biomass (AGB) standing stock, the coarse woody productivity (CWP), and the change in biomass over ten years (2004-2014) in a 25 ha unmanaged broad-leaved Korean pine mixed forest in northeastern China. In addition, we quantified how AGB stock and change (tree growth, recruitment and mortality) estimations are influenced by the variation in habitat heterogeneity, tree size structure and subplot size. Our analysis indicated that Changbai forest had AGB of 265.4 Mg ha-1 in 2004, and gained1.36 Mg ha-1 y-1 between 2004 and 2014. Despite recruitment having better performance in nutrient rich habitat, we found that there is a directional tree growth trend independent of habitat heterogeneity for available nutrients in this old growth forest. The observed increases in AGB stock (∼70%) are mainly attributed to the growth of intermediate size trees (30-70 cm DBH), indicating that this forest is still reaching its mature stage. Meanwhile, we indicated that biomass loss due to mortality reduces living biomass, not increment, may be the primary factor to affect forest biomass dynamics in this area. Also, spatial variation in forest dynamics is large for small sizes (i.e. coefficient of variation in 20 × 20 m subplots is 53.2%), and more than 90 percent of the inherent variability of these coefficients was predicted by a simple model including plot size. Our result provides a mean by which to estimate within-plot variability at a local scale before inferring any directional change in forest dynamics at a regional scale, and information about the variability of forest structure and dynamics are fundamental to design effective sampling strategies in future study.

  19. Biomass energy: the scale of the potential resource.

    PubMed

    Field, Christopher B; Campbell, J Elliott; Lobell, David B

    2008-02-01

    Increased production of biomass for energy has the potential to offset substantial use of fossil fuels, but it also has the potential to threaten conservation areas, pollute water resources and decrease food security. The net effect of biomass energy agriculture on climate could be either cooling or warming, depending on the crop, the technology for converting biomass into useable energy, and the difference in carbon stocks and reflectance of solar radiation between the biomass crop and the pre-existing vegetation. The area with the greatest potential for yielding biomass energy that reduces net warming and avoids competition with food production is land that was previously used for agriculture or pasture but that has been abandoned and not converted to forest or urban areas. At the global scale, potential above-ground plant growth on these abandoned lands has an energy content representing approximately 5% of world primary energy consumption in 2006. The global potential for biomass energy production is large in absolute terms, but it is not enough to replace more than a few percent of current fossil fuel usage. Increasing biomass energy production beyond this level would probably reduce food security and exacerbate forcing of climate change. PMID:18215439

  20. Measuring Forest Biomass and Height from Space - Results from the assessment of ESA's BIOMASS satellite concept

    NASA Astrophysics Data System (ADS)

    Scipal, Klaus

    2010-05-01

    Knowledge about forest above-ground biomass is of fundamental importance in quantifying the terrestrial carbon cycle, but is also crucial in assessing forest resources and the ecosystem services provided by forests, and is an essential element in assessing carbon fluxes under the United Nations Framework Convention on Climate Change. For most parts of the world, in particular the tropical forests, information on biomass is currently very limited, at very coarse scales, and subject to large and unquantified errors. In response to the urgent need for greatly improved mapping of global biomass and the lack of any current space systems capable of addressing this need, the BIOMASS mission was proposed to the European Space Agency for the third cycle of Earth Explorer Core missions and was selected for Feasibility Study (Phase A) in March 2009. Over the five-year mission lifetime, it shall map the full range of the world's above-ground biomass with accuracy and spatial resolution compatible with the needs of national scale inventory and carbon flux calculations, and will map changes in forest biomass. The mission will carry a polarimetric P-Band SAR, capable of providing both direct measurements of biomass derived from inverting intensity data, and measurements of forest height derived from polarimetric interferometry. The BIOMASS payload consists of a fully polarimetric system operated at a centre frequency of 435 MHz (P-band) with a bandwidth of 6 MHz. To enable measurements at a scale comparable to that of deforestation and forest disturbance (i.e. around 1 ha), it is envisaged that BIOMASS will provide level-1 products with around 50 m x 50 m resolution at 4 looks, so around 16 looks at a scale of 1 ha. The satellite shall fly in a sun-synchronous dawn-dusk orbit to minimise ionospheric disturbances with a controlled drift to meet the revisit requirement for forest height recovery using Pol-InSAR techniques. The revisit time will be between 25-45 days to maintain

  1. FUV and Optical Spectroscopy of Hot Post-AGB Stars in Globular Clusters

    NASA Technical Reports Server (NTRS)

    Dixon, William V.

    2004-01-01

    The goal of this program was to determine the atmospheric parameters (effective temperature and surface gravity) and abundances of the hot, post-AGB (PAGB) stars in globular clusters observed with the Hopkins Ultraviolet Telescope (HUT) on the Astro-l and 2 missions.

  2. AKARI All-Sky Far-Infrared Survey: Where to Look for AGB Stars?

    NASA Astrophysics Data System (ADS)

    Rybka, P.; Pollo, A.; Takeuchi, T. T.

    2011-09-01

    We selected a sample of 5,176 far-infrared sources from the FIS AKARI All-Sky Survey. Searching public databases, we identified their counterparts observed at other wavelengths and derived a method to separate stars from galaxies. The sample of stars is dominated by AGB-related objects.

  3. AGB Statement on Board Responsibility for the Oversight of Educational Quality

    ERIC Educational Resources Information Center

    Association of Governing Boards of Universities and Colleges, 2011

    2011-01-01

    This "Statement on Board Responsibility for the Oversight of Educational Quality," approved by the Board of Directors of the Association of Governing Boards (AGB) in March 2011, urges institutional administrators and governing boards to engage fully in this area of board responsibility. The seven principles in this statement offer suggestions to…

  4. The LF of TP-AGB stars in the LMC/SMC

    NASA Technical Reports Server (NTRS)

    Bruzual, Gustavo; Charlot, Stephane; GonzalezLopezlira, Rosa; Srinivasan, Sundar; Boyer, Martha L.

    2013-01-01

    We show that Monte Carlo simulations of the TP-AGB stellar population in the LMC and SMC galaxies using the CB. models produce LF and color distributions that are in closer agreement with observations than those obtained with the BC03 and CB07 models. This is a progress report of work that will be published elsewhere.

  5. AGB stars as a source of short-lived radioactive nuclei in the solar nebula

    NASA Technical Reports Server (NTRS)

    Wasserburg, G. J.; Gallino, R.; Busso, M.; Raiteri, C. M.

    1993-01-01

    The purpose is to estimate the possible contribution of some short-lived nuclei to the early solar nebula from asymptotic giant branch (AGB) sources. Low mass (1 to 3 solar mass) AGB stars appear to provide a site for synthesis of the main s process component for solar system material with an exponential distribution of neutron irradiations varies as exp(-tau/tau(sub 0)) (where tau is the time integrated neutron flux with a mean neutron exposure tau(sub 0)) for solar abundances with tau(sub 0) = 0.28 mb(sup -1). Previous workers estimated the synthesis of key short-lived nuclei which might be produced in AGB stars. While these calculations exhibit the basic characteristics of nuclei production by neutron exposure, there is need for a self-consistent calculation that follows AGB evolution and takes into account the net production from a star and dilution with the cloud medium. Many of the general approaches and the conclusions arrived at were presented earlier by Cameron. The production of nuclei for a star of 1.5 solar mass during the thermal pulsing of the AGB phase was evaluated. Calculations were done for a series of thermal pulses with tau(sub 0) = 0.12 and 0.28 mb(sup -1). These pulses involve s nucleosynthesis in the burning shell at the base of the He zone followed by the ignition of the H burning shell at the top of the He zone. After about 10-15 cycles the abundances of the various nuclei in the He zone become constant. Computations of the abundances of all nuclei in the He zone were made following Gallino. The mass of the solar nebula was considered to consist of some initial material of approximately solar composition plus some contributions from AGB stars. The ratios of the masses required from the AGB He burning zone to the ISM necessary to produce the observed value of Pd-107/Pd-108 in the early solar system were calculated and this dilution factor was applied to all other relevant nuclei.

  6. Relics of Ancient Post-AGB Stars in a Primitive Meteorite

    NASA Astrophysics Data System (ADS)

    Jadhav, M.; Pignatari, M.; Herwig, F.; Zinner, E.; Gallino, R.; Huss, G. R.

    2013-11-01

    Graphite is one of the many presolar circumstellar condensate species found in primitive meteorites. While the isotopic compositions of low-density graphite grains indicate an origin in core-collapse supernovae, some high-density grains have extreme isotopic anomalies in C, Ca, and Ti, which cannot be explained by envelope predictions of asymptotic giant branch (AGB) stars or theoretical supernova models. The Ca and Ti isotopic anomalies, however, match the predictions of He-shell abundances in AGB stars. In this study, we show that the C, Ca, and Ti isotopic anomalies are consistent with nucleosynthesis predictions of the H-ingestion phase during a very late thermal pulse (VLTP) event in post-AGB stars. The low 12C/13C isotopic ratios in these grains are a result of abundant 12C efficiently capturing the protons that are being ingested during the VLTP. Very high neutron densities of ~1015 cm-3, typical of the i-process, are achieved during this phase in post-AGB stars. The large 42, 43, 44Ca excesses in some graphite grains are indicative of neutron capture nucleosynthesis during VLTP. The comparison of VLTP nucleosynthesis calculations to the graphite data also indicate that apparent anomalies in the Ti isotopic ratios are due to large contributions from 46, 48Ca, which cannot be resolved from the isobars 46, 48Ti during the measurements. We conclude that presolar graphite grains with moderate to extreme Ca and Ti isotopic anomalies originate in post-AGB stars that suffer a VLTP.

  7. X-ray Observations of AGB Stars with XMM-Newton

    NASA Astrophysics Data System (ADS)

    Kastner, J. H.; Soker, N.

    2003-12-01

    We report the preliminary results of an XMM-Newton observing program to determine the X-ray emission properties of a sample of well-studied AGB stars. Our goal is to set constraints on magnetic (dynamo) activity during mass-losing AGB evolutionary stages, and thereby test models wherein AGB star magnetic fields influence mass loss geometry and shape planetary nebulae. We detected X-ray emission from the Mira system, with a total EPIC count rate of ˜0.11 s-1. This emission may be due to accretion or magnetic activity associated with Mira B, a companion of uncertain nature located only 0.6" from the mass-losing AGB star. The X-ray spectrum of the Mira system displays emission from highly ionized Ne, and initial (single-component) spectral fits suggest a characteristic emission region temperature ˜10 MK, intervening absorbing column ˜3×1021 cm-2, and an intrinsic X-ray luminosity of ˜2×1029 ergs s-1. The (apparently single) star T Cas is undetected in X-rays. At the meeting, we will also report on results from observations of TX Cam, an AGB star for which the presence of relatively strong (5-10 G at ˜3 R⋆ ) magnetic fields has been inferred from maser polarization measurements in the radio. This research is partly supported via NASA/GSFC grant NAG5--13158 (XMM-Newton Guest Observer program) to the Center for Imaging Science at Rochester Institute of Technology.

  8. RELICS OF ANCIENT POST-AGB STARS IN A PRIMITIVE METEORITE

    SciTech Connect

    Jadhav, M.; Huss, G. R.; Pignatari, M.; Herwig, F.; Zinner, E.; Gallino, R.

    2013-11-10

    Graphite is one of the many presolar circumstellar condensate species found in primitive meteorites. While the isotopic compositions of low-density graphite grains indicate an origin in core-collapse supernovae, some high-density grains have extreme isotopic anomalies in C, Ca, and Ti, which cannot be explained by envelope predictions of asymptotic giant branch (AGB) stars or theoretical supernova models. The Ca and Ti isotopic anomalies, however, match the predictions of He-shell abundances in AGB stars. In this study, we show that the C, Ca, and Ti isotopic anomalies are consistent with nucleosynthesis predictions of the H-ingestion phase during a very late thermal pulse (VLTP) event in post-AGB stars. The low {sup 12}C/{sup 13}C isotopic ratios in these grains are a result of abundant {sup 12}C efficiently capturing the protons that are being ingested during the VLTP. Very high neutron densities of ∼10{sup 15} cm{sup –3}, typical of the i-process, are achieved during this phase in post-AGB stars. The large {sup 42,43,44}Ca excesses in some graphite grains are indicative of neutron capture nucleosynthesis during VLTP. The comparison of VLTP nucleosynthesis calculations to the graphite data also indicate that apparent anomalies in the Ti isotopic ratios are due to large contributions from {sup 46,48}Ca, which cannot be resolved from the isobars {sup 46,48}Ti during the measurements. We conclude that presolar graphite grains with moderate to extreme Ca and Ti isotopic anomalies originate in post-AGB stars that suffer a VLTP.

  9. Photodissociation and chemistry of N2 in the circumstellar envelope of carbon-rich AGB stars

    NASA Astrophysics Data System (ADS)

    Li, Xiaohu; Millar, Tom J.; Walsh, Catherine; Heays, Alan N.; van Dishoeck, Ewine F.

    2014-08-01

    Context. The envelopes of asymptotic giant branch (AGB) stars are irradiated externally by ultraviolet photons; hence, the chemistry is sensitive to the photodissociation of N2 and CO, which are major reservoirs of nitrogen and carbon, respectively. The photodissociation of N2 has recently been quantified by laboratory and theoretical studies. Improvements have also been made for CO photodissociation. Aims: For the first time, we use accurate N2 and CO photodissociation rates and shielding functions in a model of the circumstellar envelope of the carbon-rich AGB star, IRC +10216. Methods: We use a state-of-the-art chemical model of an AGB envelope, the latest CO and N2 photodissociation data, and a new method for implementing molecular shielding functions in full spherical geometry with isotropic incident radiation. We compare computed column densities and radial distributions of molecules with observations. Results: The transition of N2→ N (also, CO → C → C+) is shifted towards the outer envelope relative to previous models. This leads to different column densities and radial distributions of N-bearing species, especially those species whose formation/destruction processes largely depend on the availability of atomic or molecular nitrogen, for example, CnN (n = 1, 3, 5), CnN- (n = 1, 3, 5), HCnN (n = 1, 3, 5, 7, 9), H2CN and CH2CN. Conclusions: The chemistry of many species is directly or indirectly affected by the photodissociation of N2 and CO, especially in the outer shell of AGB stars where photodissociation is important. Thus, it is important to include N2 and CO shielding in astrochemical models of AGB envelopes and other irradiated environments. In general, while differences remain between our model of IRC +10216 and the observed molecular column densities, better agreement is found between the calculated and observed radii of peak abundance.

  10. Spectroscopic Determination of Aboveground Biomass in Grasslands Using Spectral Transformations, Support Vector Machine and Partial Least Squares Regression

    PubMed Central

    Marabel, Miguel; Alvarez-Taboada, Flor

    2013-01-01

    Aboveground biomass (AGB) is one of the strategic biophysical variables of interest in vegetation studies. The main objective of this study was to evaluate the Support Vector Machine (SVM) and Partial Least Squares Regression (PLSR) for estimating the AGB of grasslands from field spectrometer data and to find out which data pre-processing approach was the most suitable. The most accurate model to predict the total AGB involved PLSR and the Maximum Band Depth index derived from the continuum removed reflectance in the absorption features between 916–1,120 nm and 1,079–1,297 nm (R2 = 0.939, RMSE = 7.120 g/m2). Regarding the green fraction of the AGB, the Area Over the Minimum index derived from the continuum removed spectra provided the most accurate model overall (R2 = 0.939, RMSE = 3.172 g/m2). Identifying the appropriate absorption features was proved to be crucial to improve the performance of PLSR to estimate the total and green aboveground biomass, by using the indices derived from those spectral regions. Ordinary Least Square Regression could be used as a surrogate for the PLSR approach with the Area Over the Minimum index as the independent variable, although the resulting model would not be as accurate. PMID:23925082

  11. Allometric scaling relationship between above- and below-ground biomass within and across five woody seedlings

    PubMed Central

    Cheng, Dongliang; Ma, Yuzhu; Zhong, Quanling; Xu, Weifeng

    2014-01-01

    Allometric biomass allocation theory predicts that leaf biomass (ML) scaled isometrically with stem (MS) and root (MR) biomass, and thus above-ground biomass (leaf and stem) (MA) and root (MR) scaled nearly isometrically with below-ground biomass (root) for tree seedlings across a wide diversity of taxa. Furthermore, prior studies also imply that scaling constant should vary with species. However, litter is known about whether such invariant isometric scaling exponents hold for intraspecific biomass allocation, and how variation in scaling constants influences the interspecific scaling relationship between above- and below-ground biomass. Biomass data of seedlings from five evergreen species were examined to test scaling relationships among biomass components across and within species. Model Type II regression was used to compare the numerical values of scaling exponents and constants among leaf, stem, root, and above- to below-ground biomass. The results indicated that ML and MS scaled in an isometric or a nearly isometric manner with MR, as well as MA to MR for five woody species. Significant variation was observed in the Y-intercepts of the biomass scaling curves, resulting in the divergence for intraspecific scaling and interspecific scaling relationships for ML versus MS and ML versus MR, but not for MS versus MR and MA versus MR. We conclude, therefore, that a nearly isometric scaling relationship of MA versus MR holds true within each of the studied woody species and across them irrespective the negative scaling relationship between leaf and stem. PMID:25505524

  12. Aboveground biomass and carbon stocks modelling using non-linear regression model

    NASA Astrophysics Data System (ADS)

    Ain Mohd Zaki, Nurul; Abd Latif, Zulkiflee; Nazip Suratman, Mohd; Zainee Zainal, Mohd

    2016-06-01

    Aboveground biomass (AGB) is an important source of uncertainty in the carbon estimation for the tropical forest due to the variation biodiversity of species and the complex structure of tropical rain forest. Nevertheless, the tropical rainforest holds the most extensive forest in the world with the vast diversity of tree with layered canopies. With the usage of optical sensor integrate with empirical models is a common way to assess the AGB. Using the regression, the linkage between remote sensing and a biophysical parameter of the forest may be made. Therefore, this paper exemplifies the accuracy of non-linear regression equation of quadratic function to estimate the AGB and carbon stocks for the tropical lowland Dipterocarp forest of Ayer Hitam forest reserve, Selangor. The main aim of this investigation is to obtain the relationship between biophysical parameter field plots with the remotely-sensed data using nonlinear regression model. The result showed that there is a good relationship between crown projection area (CPA) and carbon stocks (CS) with Pearson Correlation (p < 0.01), the coefficient of correlation (r) is 0.671. The study concluded that the integration of Worldview-3 imagery with the canopy height model (CHM) raster based LiDAR were useful in order to quantify the AGB and carbon stocks for a larger sample area of the lowland Dipterocarp forest.

  13. Induction and characterization of suppressor T cells and soluble factors with modified timothy grass pollen AgB.

    PubMed

    Malley, A; Deppe, L B; Brandt, C J

    1981-01-01

    Previous studies demonstrated that antigen B (AgB), a major antigen of timothy grass pollen, modified by photooxidation (Ox-AgB) does not react with rabbit, human, or mouse antibodies directed against AgB and does not induce antibodies reactive with either native or modified AgB. However, immunization of mice with Ox-AgB in alum induces significant T helper cell activity. In this review, we describe the conditions and kinetics for Ox-AgB induction of T suppressor cells, the secretion of AgB-specific T suppressor factor (TSF), and the partial purification of AgB-specific TSF. PMID:6453098

  14. Abundances of presolar graphite and SiC from supernovae and AGB stars in the Murchison meteorite

    SciTech Connect

    Amari, Sachiko; Zinner, Ernst; Gallino, Roberto

    2014-05-02

    Pesolar graphite grains exhibit a range of densities (1.65 – 2.20 g/cm{sup 3}). We investigated abundances of presolar graphite grains formed in supernovae and in asymptotic giant branch (AGB) stars in the four density fractions KE3, KFA1, KFB1 and KFC1 extracted from the Murchison meteorite to probe dust productions in these stellar sources. Seventy-six and 50% of the grains in the low-density fractions KE3 and KFA1, respectively, are supernova grains, while only 7.2% and 0.9% of the grains in the high-density fractions KFB1 and KFC1 have a supernova origin. Grains of AGB star origin are concentrated in the high-density fractions KFB1 and KFC1. From the C isotopic distributions of these fractions and the presence of s-process Kr with {sup 86}Kr/{sup 82}Kr = 4.43±0.46 in KFC1, we estimate that 76% and 80% of the grains in KFB1 and KFC1, respectively, formed in AGB stars. From the abundance of graphite grains in the Murchison meteorite, 0.88 ppm, the abundances of graphite from supernovae and AGB stars are 0.24 ppm and 0.44 ppm, respectively: the abundances of graphite in supernovae and AGB stars are comparable. In contrast, it has been known that 1% of SiC grains formed in supernovae and 95% formed in AGB stars in meteorites. Since the abundance of SiC grains is 5.85 ppm in the Murchison meteorite, the abundances of SiC from supernovae and AGB stars are 0.063 ppm and 5.6 ppm, respectively: the dominant source of SiC grains is AGB stars. Since SiC grains are harder and likely to survive better in space than graphite grains, the abundance of supernova graphite grains, which is higher than that of supernova SiC grains, indicates that supernovae proficiently produce graphite grains. Graphite grains from AGB stars are, in contrast, less abundant that SiC grains from AGB stars (0.44 ppm vs. 5.6 ppm). It is difficult to derive firm conclusions for graphite and SiC formation in AGB stars due to the difference in susceptibility to grain destruction. Metallicity of

  15. Abundances of presolar graphite and SiC from supernovae and AGB stars in the Murchison meteorite

    NASA Astrophysics Data System (ADS)

    Amari, Sachiko; Zinner, Ernst; Gallino, Roberto

    2014-05-01

    Pesolar graphite grains exhibit a range of densities (1.65 - 2.20 g/cm3). We investigated abundances of presolar graphite grains formed in supernovae and in asymptotic giant branch (AGB) stars in the four density fractions KE3, KFA1, KFB1 and KFC1 extracted from the Murchison meteorite to probe dust productions in these stellar sources. Seventy-six and 50% of the grains in the low-density fractions KE3 and KFA1, respectively, are supernova grains, while only 7.2% and 0.9% of the grains in the high-density fractions KFB1 and KFC1 have a supernova origin. Grains of AGB star origin are concentrated in the high-density fractions KFB1 and KFC1. From the C isotopic distributions of these fractions and the presence of s-process Kr with 86Kr/82Kr = 4.43±0.46 in KFC1, we estimate that 76% and 80% of the grains in KFB1 and KFC1, respectively, formed in AGB stars. From the abundance of graphite grains in the Murchison meteorite, 0.88 ppm, the abundances of graphite from supernovae and AGB stars are 0.24 ppm and 0.44 ppm, respectively: the abundances of graphite in supernovae and AGB stars are comparable. In contrast, it has been known that 1% of SiC grains formed in supernovae and 95% formed in AGB stars in meteorites. Since the abundance of SiC grains is 5.85 ppm in the Murchison meteorite, the abundances of SiC from supernovae and AGB stars are 0.063 ppm and 5.6 ppm, respectively: the dominant source of SiC grains is AGB stars. Since SiC grains are harder and likely to survive better in space than graphite grains, the abundance of supernova graphite grains, which is higher than that of supernova SiC grains, indicates that supernovae proficiently produce graphite grains. Graphite grains from AGB stars are, in contrast, less abundant that SiC grains from AGB stars (0.44 ppm vs. 5.6 ppm). It is difficult to derive firm conclusions for graphite and SiC formation in AGB stars due to the difference in susceptibility to grain destruction. Metallicity of the parent AGB stars of

  16. VizieR Online Data Catalog: Galactic and MC O-AGBs and RSGs stars (Jones+, 2012)

    NASA Astrophysics Data System (ADS)

    Jones, O. C.; Kemper, F.; Sargent, B. A.; McDonald, I.; Gielen, C.; Woods, P. M.; Sloan, G. C.; Boyer, M. L.; Zijlstra, A. A.; Clayton, G. C.; Kraemer, K. E.; Srinivasan, S.; Ruffle, P. M. E.

    2015-11-01

    Our sample contains 69 oxygen-rich AGB stars (O-AGB) and 76 RSG stars in the Magellanic Clouds which were observed spectroscopically with Spitzer, and 131 Galactic field O-AGBs and RSGs observed with either Spitzer or ISO. The Spitzer spectra cover a wavelength range of 5.2-37.2um, while ISO spectra cover the 2.38-45.2um part of the spectrum. We combine this sample with 39 spectra from 14 GGCs to extend the low end of the metallicity range. (5 data files).

  17. Biomass Burning

    NASA Technical Reports Server (NTRS)

    Levine, Joel S.; Cofer, Wesley R., III; Pinto, Joseph P.

    1993-01-01

    Biomass burning may be the overwhelming regional or continental-scale source of methane (CH4) as in tropical Africa and a significant global source of CH4. Our best estimate of present methane emissions from biomass burning is about 51.9 Tg/yr, or 10% of the annual methane emissions to the atmosphere. Increased frequency of fires that may result as the Earth warms up may result in increases in this source of atmospheric methane.

  18. Detecting tropical forest biomass dynamics from repeated airborne lidar measurements

    NASA Astrophysics Data System (ADS)

    Meyer, V.; Saatchi, S. S.; Chave, J.; Dalling, J. W.; Bohlman, S.; Fricker, G. A.; Robinson, C.; Neumann, M.; Hubbell, S.

    2013-08-01

    Reducing uncertainty of terrestrial carbon cycle depends strongly on the accurate estimation of changes of global forest carbon stock. However, this is a challenging problem from either ground surveys or remote sensing techniques in tropical forests. Here, we examine the feasibility of estimating changes of tropical forest biomass from two airborne lidar measurements of forest height acquired about 10 yr apart over Barro Colorado Island (BCI), Panama. We used the forest inventory data from the 50 ha Center for Tropical Forest Science (CTFS) plot collected every 5 yr during the study period to calibrate the estimation. We compared two approaches for detecting changes in forest aboveground biomass (AGB): (1) relating changes in lidar height metrics from two sensors directly to changes in ground-estimated biomass; and (2) estimating biomass from each lidar sensor and then computing changes in biomass from the difference of two biomass estimates, using two models, namely one model based on five relative height metrics and the other based only on mean canopy height (MCH). We performed the analysis at different spatial scales from 0.04 ha to 10 ha. Method (1) had large uncertainty in directly detecting biomass changes at scales smaller than 10 ha, but provided detailed information about changes of forest structure. The magnitude of error associated with both the mean biomass stock and mean biomass change declined with increasing spatial scales. Method (2) was accurate at the 1 ha scale to estimate AGB stocks (R2 = 0.7 and RMSEmean = 27.6 Mg ha-1). However, to predict biomass changes, errors became comparable to ground estimates only at a spatial scale of about 10 ha or more. Biomass changes were in the same direction at the spatial scale of 1 ha in 60 to 64% of the subplots, corresponding to p values of respectively 0.1 and 0.033. Large errors in estimating biomass changes from lidar data resulted from the uncertainty in detecting changes at 1 ha from ground census data

  19. Remote Characterization of Biomass Measurements: Case Study of Mangrove Forests

    NASA Technical Reports Server (NTRS)

    Fatoyinbo, Temilola E.

    2010-01-01

    Accurately quantifying forest biomass is of crucial importance for climate change studies. By quantifying the amount of above and below ground biomass and consequently carbon stored in forest ecosystems, we are able to derive estimates of carbon sequestration, emission and storage and help close the carbon budget. Mangrove forests, in addition to providing habitat and nursery grounds for over 1300 animal species, are also an important sink of biomass. Although they only constitute about 3% of the total forested area globally, their carbon storage capacity -- in forested biomass and soil carbon -- is greater than that of tropical forests (Lucas et al, 2007). In addition, the amount of mangrove carbon -- in the form of litter and leaves exported into offshore areas is immense, resulting in over 10% of the ocean's dissolved organic carbon originating from mangroves (Dittmar et al, 2006) The measurement of forest above ground biomass is carried out on two major scales: on the plot scale, biomass can be measured using field measurements through allometric equation derivation and measurements of forest plots. On the larger scale, the field data are used to calibrate remotely sensed data to obtain stand-wide or even regional estimates of biomass. Currently, biomass can be calculated using average stand biomass values and optical data, such as aerial photography or satellite images (Landsat, Modis, Ikonos, SPOT, etc.). More recent studies have concentrated on deriving forest biomass values using radar (JERS, SIR-C, SRTM, Airsar) and/or lidar (ICEsat/GLAS, LVIS) active remote sensing to retrieve more accurate and detailed measurements of forest biomass. The implementation of a generation of new active sensors (UAVSar, DesdynI, Alos/Palsar, TerraX) has prompted the development of new tecm'liques of biomass estimation that use the combination of multiple sensors and datasets, to quantify past, current and future biomass stocks. Focusing on mangrove forest biomass estimation

  20. Predicting biomass of hyperdiverse and structurally complex central Amazonian forests - a virtual approach using extensive field data

    NASA Astrophysics Data System (ADS)

    Magnabosco Marra, Daniel; Higuchi, Niro; Trumbore, Susan E.; Ribeiro, Gabriel H. P. M.; dos Santos, Joaquim; Carneiro, Vilany M. C.; Lima, Adriano J. N.; Chambers, Jeffrey Q.; Negrón-Juárez, Robinson I.; Holzwarth, Frederic; Reu, Björn; Wirth, Christian

    2016-03-01

    Old-growth forests are subject to substantial changes in structure and species composition due to the intensification of human activities, gradual climate change and extreme weather events. Trees store ca. 90 % of the total aboveground biomass (AGB) in tropical forests and precise tree biomass estimation models are crucial for management and conservation. In the central Amazon, predicting AGB at large spatial scales is a challenging task due to the heterogeneity of successional stages, high tree species diversity and inherent variations in tree allometry and architecture. We parameterized generic AGB estimation models applicable across species and a wide range of structural and compositional variation related to species sorting into height layers as well as frequent natural disturbances. We used 727 trees (diameter at breast height ≥ 5 cm) from 101 genera and at least 135 species harvested in a contiguous forest near Manaus, Brazil. Sampling from this data set we assembled six scenarios designed to span existing gradients in floristic composition and size distribution in order to select models that best predict AGB at the landscape level across successional gradients. We found that good individual tree model fits do not necessarily translate into reliable predictions of AGB at the landscape level. When predicting AGB (dry mass) over scenarios using our different models and an available pantropical model, we observed systematic biases ranging from -31 % (pantropical) to +39 %, with root-mean-square error (RMSE) values of up to 130 Mg ha-1 (pantropical). Our first and second best models had both low mean biases (0.8 and 3.9 %, respectively) and RMSE (9.4 and 18.6 Mg ha-1) when applied over scenarios. Predicting biomass correctly at the landscape level in hyperdiverse and structurally complex tropical forests, especially allowing good performance at the margins of data availability for model construction/calibration, requires the inclusion of predictors that express

  1. On the formation of molecules and solid-state compounds from the AGB to the PN phases

    NASA Astrophysics Data System (ADS)

    García-Hernández, D. A.; Manchado, A.

    2016-07-01

    During the asymptoyic giant branch (AGB) phase, different elements are dredge- up to the stellar surface depending on progenitor mass and metallicity. When the mass loss increases at the end of the AGB, a circumstellar dust shell is formed, where different (C-rich or O-rich) molecules and solid-state compounds are formed. These are further processed in the transition phase between AGB stars and planetary nebulae (PNe) to create more complex organic molecules and inorganic solid-state compounds (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene precursors in C-rich environments and oxides and crystalline silicates in O-rich ones). We present an observational review of the different molecules and solid-state materials that are formed from the AGB to the PN phases. We focus on the formation routes of complex fullerene (and fullerene-based) molecules as well as on the level of dust processing depending on metallicity.

  2. Statistical models related to accumulated biomass of Hopea odorata in three soil series of ultisols

    NASA Astrophysics Data System (ADS)

    Maarof, Fauziah; Fauzi, Mohd Adi Faiz Ahmad; Mohamed, Shamsiah

    2014-07-01

    This paper presents results on statistical distribution fitting and polynomial regression on accumulated biomass of seven year-old tree species Hopea odorata, which were planted in three different soil series of ultisols, namely Rengggam, Baling and Kuala Berang. Data were collected from a study conducted in a Hopea odorata plantation at FRIM Research Station, Segamat, Johor. Thirty tree stands in each soil series were randomly sampled to measure their growth performance and accumulated biomass. The Kolmogorov-Smirnov and Anderson-Darling tests indicated that for all tree stands, diameter, height, above ground (stem, branch, leaves) and below ground (root) biomass were found to be best fitted with the four parameters Johnson's System Bounded (SB) distributions. Then, for each soil series, a polynomial regression model was estimated to describe the relationship between total accumulated biomass and functions of tree diameter and height.

  3. Remote sensing of biomass and annual net aerial primary productivity of a salt marsh

    NASA Technical Reports Server (NTRS)

    Hardisky, M. A.; Klemas, V.; Daiber, F. C.; Roman, C. T.

    1984-01-01

    Net aerial primary productivity is the rate of storage of organic matter in above-ground plant issues exceeding the respiratory use by the plants during the period of measurement. It is pointed out that this plant tissue represents the fixed carbon available for transfer to and consumption by the heterotrophic organisms in a salt marsh or the estuary. One method of estimating annual net aerial primary productivity (NAPP) required multiple harvesting of the marsh vegetation. A rapid nondestructive remote sensing technique for estimating biomass and NAPP would, therefore, be a significant asset. The present investigation was designed to employ simple regression models, equating spectral radiance indices with Spartina alterniflora biomass to nondestructively estimate salt marsh biomass. The results of the study showed that the considered approach can be successfully used to estimate salt marsh biomass.

  4. AGB Stars in Galactic Globular Clusters: Are They Really Chemically Distinct from Their Fellow RGB and HB Stars?

    NASA Astrophysics Data System (ADS)

    Campbell, S. W.; Yong, D.; Wylie-de Boer, E. C.; Stancliffe, R. J.; Lattanzio, J. C.; Angelou, G. C.; Grundahl, F.; Sneden, C.

    2011-09-01

    The handful of available observations of asymptotic giant branch (AGB) stars in Galactic globular clusters (GCs) suggest that the globular cluster AGB populations are dominated by cyanogen-weak (CN-weak) stars. This contrasts strongly with the distributions on the red giant branch (RGB) and other populations, which often show a 50:50 bimodality in CN band strength. If this is true then it presents a serious problem for low metallicity stellar evolution theory, since such a surface abundance change going from the RGB to AGB is not predicted by stellar models. However this is only a tentative conclusion, since it is based on very small AGB sample sizes. To test whether this problem really exists we have carried out an observational campaign targeting AGB stars in globular clusters. We have obtained medium resolution spectra for about 250 AGB stars across 9 Galactic globular clusters (NGC 1851, NGC 288, NGC 362, NGC 6752, M2, M4, M5, M10, and 47 Tuc) using the multi-object spectrograph on the Anglo-Australian Telescope (2df/AAOmega). In this contribution we present some preliminary findings of the study, in particular for the second-parameter pair NGC 288 and NGC 362.

  5. The Contribution of TP-AGB Stars to the Mid-infrared Colors of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Chisari, Nora E.; Kelson, Daniel D.

    2012-07-01

    We study the mid-infrared color space of 30 galaxies from the Spitzer Infrared Nearby Galaxies Survey (SINGS) survey for which Sloan Digital Sky Survey data are also available. We construct two-color maps for each galaxy and compare them to results obtained from combining Maraston evolutionary synthesis models, galactic thermally pulsating asymptotic giant branch (TP-AGB) colors, and smooth star formation histories. For most of the SINGS sample, the spatially extended mid-IR emission seen by Spitzer in normal galaxies is consistent with our simple model in which circumstellar dust from TP-AGB stars dominates at 8 and 24 μm. There is a handful of exceptions that we identify as galaxies that have high star formation rates presumably with star formation histories that cannot be assumed to be smooth, or anemic galaxies, which were depleted of their H I at some point during their evolution and have very low ongoing star formation rates.

  6. A chemically peculiar post-AGB star in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Kamath, D.; Van Winckel, H.; De Smedt, K.; Wood, P. R.

    2016-07-01

    Post-Asymptotic Giant Branch (post-AGB) stars bear signatures of the entire chemical and morphological changes that occur prior to and during the AGB phase of evolution. These objects also provide vital clues on the ultimate fate of the star. Detailed chemical abundance studies of some of these objects have shown that they are chemically much more diverse than anticipated. As expected, some are the most s-process enriched objects known to date while others are not s-process enriched. Our recent study has revealed a star in the Small Magellanic Cloud, J005252.87-722842.9, which displays a peculiar chemical signature that does not correspond to the expected chemical diversity observed in these objects. This unique object reveals the possibility of a new stellar evolutionary channel where the star evolves without any third dredge-up episodes or during its evolution becomes devoid of its nucleosynthetic history.

  7. An ALMA View of the Complex Circumstellar Environment of the Post-AGB Object HD 101584

    NASA Astrophysics Data System (ADS)

    Olofsson, H.; Vlemmings, W.; Maercker, M.; Humphreys, E.; Lindqvist, M.; Nyman, L.; Ramstedt, S.

    2015-12-01

    We use 12CO, 13CO, and C18O J = 2-1 lines and 1.3 mm continuum ALMA observations to study the circumstellar evolution of the binary HD 101584, a post-AGB star and a low-mass companion, which is most likely a post-common-envelope-evolution system. It is inferred that the circumstellar medium has a bipolar hour-glass structure, seen almost pole-on, formed by an energetic, ≍ 150 km s-1, jet. Significant amount of material resides in an unresolved central region. It is proposed that the circumstellar morphology is related to an event which took place ≍ 500 yr ago, possibly a capture event where the companion spiraled in towards the AGB star. However, the kinetic energy of the accelerated gas exceeds the released orbital energy. Hence, the observed phenomenon does not match current common-envelope scenarios, and another process must augment, or even dominate, the ejection process.

  8. THE CONTRIBUTION OF TP-AGB STARS TO THE MID-INFRARED COLORS OF NEARBY GALAXIES

    SciTech Connect

    Chisari, Nora E.; Kelson, Daniel D.

    2012-07-10

    We study the mid-infrared color space of 30 galaxies from the Spitzer Infrared Nearby Galaxies Survey (SINGS) survey for which Sloan Digital Sky Survey data are also available. We construct two-color maps for each galaxy and compare them to results obtained from combining Maraston evolutionary synthesis models, galactic thermally pulsating asymptotic giant branch (TP-AGB) colors, and smooth star formation histories. For most of the SINGS sample, the spatially extended mid-IR emission seen by Spitzer in normal galaxies is consistent with our simple model in which circumstellar dust from TP-AGB stars dominates at 8 and 24 {mu}m. There is a handful of exceptions that we identify as galaxies that have high star formation rates presumably with star formation histories that cannot be assumed to be smooth, or anemic galaxies, which were depleted of their H I at some point during their evolution and have very low ongoing star formation rates.

  9. The Impact of FUSE on our Understanding of Stellar Post-AGB Evolution

    SciTech Connect

    Rauch, T.; Werner, K.; Ziegler, M.; Koesterke, L.; Kruk, J. W.; Oliveira, C. M.

    2009-05-24

    State-of-the-art non-LTE spectral analysis requires high-resolution and high-S/N observations of strategic metal lines in order to achieve reliable photospheric parameters like, e.g., effective temperature, surface gravity, and element abundances.Hot stars with effective temperatures higher than about 40 000 K exhibit their metal-line spectrum arising from highly ionized species predominantly in the (far) ultraviolet wavelength range.FUSE observations of hot, compact stars provided the necessary data. With these, it has been, e.g., possible to identify fluorine for the first time in observations of post-AGB stars. The evaluation of ionization equilibria of highly ionized neon, phosphorus, sulfur, and argon provides a new sensitive tool to determine effective temperatures of the hottest stars precisely. Moreover, abundance determinations have put constraints on stellar evolutionary models which, in turn, have improved greatly our picture of post-AGB evolution.

  10. An ALMA view of the post-AGB object HD 101584

    NASA Astrophysics Data System (ADS)

    Olofsson, H.; Vlemmings, W.; Maercker, M.; Humphreys, E.; Lindqvist, M.; Nyman, L.; Ramstedt, S.

    2016-07-01

    ALMA cycles 1 and 3 observations of CO isotopologues and 1.3mm continuum are used in a study of the circumstellar environment of the binary HD 101584, a post-AGB star and a low-mass companion that is most likely a post-common-envelope-evolution system. These data are supplemented with new information from OH maser emission. It is inferred that the large- scale circumstellar medium has a bipolar hour-glass structure, seen almost pole-on, formed by an energetic, ≥⃒ 150 km s-1, jet. Significant amount of material still resides in the central region. It is proposed that the circumstellar morphology is related to an event which took place ≤⃒ 500 yr ago, possibly a capture event where the companion spiralled in towards the AGB star. Several observed features remain to be explained, and may hint to a more complicated scenario.

  11. Forest Biomass Mapping From Lidar and Radar Synergies

    NASA Technical Reports Server (NTRS)

    Sun, Guoqing; Ranson, K. Jon; Guo, Z.; Zhang, Z.; Montesano, P.; Kimes, D.

    2011-01-01

    The use of lidar and radar instruments to measure forest structure attributes such as height and biomass at global scales is being considered for a future Earth Observation satellite mission, DESDynI (Deformation, Ecosystem Structure, and Dynamics of Ice). Large footprint lidar makes a direct measurement of the heights of scatterers in the illuminated footprint and can yield accurate information about the vertical profile of the canopy within lidar footprint samples. Synthetic Aperture Radar (SAR) is known to sense the canopy volume, especially at longer wavelengths and provides image data. Methods for biomass mapping by a combination of lidar sampling and radar mapping need to be developed. In this study, several issues in this respect were investigated using aircraft borne lidar and SAR data in Howland, Maine, USA. The stepwise regression selected the height indices rh50 and rh75 of the Laser Vegetation Imaging Sensor (LVIS) data for predicting field measured biomass with a R(exp 2) of 0.71 and RMSE of 31.33 Mg/ha. The above-ground biomass map generated from this regression model was considered to represent the true biomass of the area and used as a reference map since no better biomass map exists for the area. Random samples were taken from the biomass map and the correlation between the sampled biomass and co-located SAR signature was studied. The best models were used to extend the biomass from lidar samples into all forested areas in the study area, which mimics a procedure that could be used for the future DESDYnI Mission. It was found that depending on the data types used (quad-pol or dual-pol) the SAR data can predict the lidar biomass samples with R2 of 0.63-0.71, RMSE of 32.0-28.2 Mg/ha up to biomass levels of 200-250 Mg/ha. The mean biomass of the study area calculated from the biomass maps generated by lidar- SAR synergy 63 was within 10% of the reference biomass map derived from LVIS data. The results from this study are preliminary, but do show the

  12. Monitoring grass nutrients and biomass as indicators of rangeland quality and quantity using random forest modelling and WorldView-2 data

    NASA Astrophysics Data System (ADS)

    Ramoelo, Abel; Cho, M. A.; Mathieu, R.; Madonsela, S.; van de Kerchove, R.; Kaszta, Z.; Wolff, E.

    2015-12-01

    Land use and climate change could have huge impacts on food security and the health of various ecosystems. Leaf nitrogen (N) and above-ground biomass are some of the key factors limiting agricultural production and ecosystem functioning. Leaf N and biomass can be used as indicators of rangeland quality and quantity. Conventional methods for assessing these vegetation parameters at landscape scale level are time consuming and tedious. Remote sensing provides a bird-eye view of the landscape, which creates an opportunity to assess these vegetation parameters over wider rangeland areas. Estimation of leaf N has been successful during peak productivity or high biomass and limited studies estimated leaf N in dry season. The estimation of above-ground biomass has been hindered by the signal saturation problems using conventional vegetation indices. The objective of this study is to monitor leaf N and above-ground biomass as an indicator of rangeland quality and quantity using WorldView-2 satellite images and random forest technique in the north-eastern part of South Africa. Series of field work to collect samples for leaf N and biomass were undertaken in March 2013, April or May 2012 (end of wet season) and July 2012 (dry season). Several conventional and red edge based vegetation indices were computed. Overall results indicate that random forest and vegetation indices explained over 89% of leaf N concentrations for grass and trees, and less than 89% for all the years of assessment. The red edge based vegetation indices were among the important variables for predicting leaf N. For the biomass, random forest model explained over 84% of biomass variation in all years, and visible bands including red edge based vegetation indices were found to be important. The study demonstrated that leaf N could be monitored using high spatial resolution with the red edge band capability, and is important for rangeland assessment and monitoring.

  13. Recent Progress in Measuring and Modeling Patterns of Biomass and Soil Carbon Pools Across the Amazon Basin

    NASA Technical Reports Server (NTRS)

    Potter, Christopher; Malhi, Yadvinder

    2004-01-01

    Ever more detailed representations of above-ground biomass and soil carbon pools have been developed during the LBA project. Environmental controls such as regional climate, land cover history, secondary forest regrowth, and soil fertility are now being taken into account in regional inventory studies. This paper will review the evolution of measurement-extrapolation approaches, remote sensing, and simulation modeling techniques for biomass and soil carbon pools, which together help constrain regional carbon budgets and enhance in our understanding of uncertainty at the regional level.

  14. Evolution models from the AGB to the PNe and the rapid evolution of SAO 244567

    NASA Astrophysics Data System (ADS)

    Lawlor, Timothy M.; Sebzda, Steven; Peterson, Zach

    2015-08-01

    We present evolution calculations from the Asymptotic Giant Branch (AGB) to the Planetary Nebula (PNe) phase for models of mass 1 M⊙ over a range of metallicities from primordial, Z = 10-14, through near solar, Z = 0.02. Using our grid of models, we determine a central star mass dependence on initial metallicity. We also present a range of low masses for our low to very low metal models. The understanding of these objects is an important part of galactic evolution and the evolution of the composition of the universe over a broad range of red shits. For our low Z models, we find key differences in how they cross the HR diagram to the PNe phase, compared with models with higher initial Z. Some of our models experience the so called AGB Final Thermal Pulse (AFTP), which is a helium pulse that occurs while leaving the AGB and causes a rapid looping evolution while evolving between the AGB and PN phase. We use these models to make comparisons to the central star of the Stingray Nebula, SAO 244567. This object has been observed to be rapidly evolving (heating) over more than the last 50 years and is the central star of the youngest known planetary nebula. These two characteristics are similar to what is expected for AFTP models. It is a short lived phase that is related to, but different than, very late thermal pulse objects such as Sakurai’s Object, FG Sge, and V605 Aql. These objects experienced a similar thermal pulse, but later on the white dwarf cooling track.

  15. A Pilot Deep Survey for X-Ray Emission from fuvAGB Stars

    NASA Astrophysics Data System (ADS)

    Sahai, R.; Sanz-Forcada, J.; Sánchez Contreras, C.; Stute, M.

    2015-09-01

    We report the results of a pilot survey for X-ray emission from a newly discovered class of AGB stars with far-ultraviolet excesses (fuvAGB stars) using XMM-Newton and Chandra. We detected X-ray emission in three of six fuvAGB stars observed—the X-ray fluxes are found to vary in a stochastic or quasi-periodic manner on roughly hour-long timescales, and simultaneous UV observations using the Optical Monitor on XMM for these sources show similar variations in the UV flux. These data, together with previous studies, show that X-ray emission is found only in fuvAGB stars. From modeling the spectra, we find that the observed X-ray luminosities are ˜(0.002-0.2) L⊙ and the X-ray-emitting plasma temperatures are ˜(35-160) × 106 K. The high X-ray temperatures argue against the emission arising in stellar coronae, or directly in an accretion shock, unless it occurs on a WD companion. However, none of the detected objects is a known WD-symbiotic star, suggesting that if WD companions are present, they are relatively cool (<20,000 K). In addition, the high X-ray luminosities specifically argue against emission originating in the coronae of main-sequence companions. We discuss several models for the X-ray emission and its variability and find that the most likely scenario for the origin of the X-ray (and FUV) emission involves accretion activity around a companion star, with confinement by strong magnetic fields associated with the companion and/or an accretion disk around it.

  16. Evolved stars in the Local Group galaxies. I. AGB evolution and dust production in IC 1613

    NASA Astrophysics Data System (ADS)

    Dell'Agli, F.; Di Criscienzo, M.; Boyer, M. L.; García-Hernández, D. A.

    2016-05-01

    We used models of thermally-pulsing asymptotic giant branch (AGB) stars, that also describe the dust-formation process in the wind, to interpret the combination of near- and mid-infrared photometric data of the dwarf galaxy IC 1613. This is the first time that this approach is extended to an environment different from the Milky Way and the Magellanic Clouds (MCs). Our analysis, based on synthetic population techniques, shows a nice agreement between the observations and the expected distribution of stars in the colour-magnitude diagrams obtained with JHK and Spitzer bands. This allows a characterization of the individual stars in the AGB sample in terms of mass, chemical composition, and formation epoch of the progenitors. We identify the stars exhibiting the largest degree of obscuration as carbon stars evolving through the final AGB phases, descending from 1 - 1.25M⊙ objects of metallicity Z = 10-3 and from 1.5 - 2.5M⊙ stars with Z = 2 × 10-3. Oxygen-rich stars constitute the majority of the sample (˜65%), mainly low mass stars (<2M⊙) that produce a negligible amount of dust (≤10-7M⊙/yr). We predict the overall dust-production rate from IC 1613, mostly determined by carbon stars, to be ˜6 × 10-7M⊙/yr with an uncertainty of 30%. The capability of the current generation of models to interpret the AGB population in an environment different from the MCs opens the possibility to extend this kind of analysis to other Local Group galaxies.

  17. On the nature of the most obscured C-rich AGB stars in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Ventura, P.; Karakas, A. I.; Dell'Agli, F.; García-Hernández, D. A.; Boyer, M. L.; Di Criscienzo, M.

    2016-04-01

    The stars in the Magellanic Clouds with the largest degree of obscuration are used to probe the highly uncertain physics of stars in the asymptotic giant branch (AGB) phase of evolution. Carbon stars in particular provide key information on the amount of third dredge-up and mass-loss. We use two independent stellar evolution codes to test how a different treatment of the physics affects the evolution on the AGB. The output from the two codes is used to determine the rates of dust formation in the circumstellar envelope, where the method used to determine the dust is the same for each case. The stars with the largest degree of obscuration in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are identified as the progeny of objects of initial mass 2.5-3 M⊙ and ˜1.5 M⊙, respectively. This difference in mass is motivated by the difference in the star formation histories of the two galaxies, and offers a simple explanation of the redder infrared colours of C-stars in the LMC compared to their counterparts in the SMC. The comparison with the Spitzer colours of C-rich AGB stars in the SMC shows that a minimum surface carbon mass fraction X(C) ˜ 5 × 10-3 must have been reached by stars of initial mass around 1.5 M⊙. Our results confirm the necessity of adopting low-temperature opacities in stellar evolutionary models of AGB stars. These opacities allow the stars to obtain mass-loss rates high enough (≳10-4 M⊙ yr-1) to produce the amount of dust needed to reproduce the Spitzer colours.

  18. Lithium and zirconium abundances in massive Galactic O-rich AGB stars

    NASA Astrophysics Data System (ADS)

    García-Hernández, D. A.; García-Lario, P.; Plez, B.; Manchado, A.; D'Antona, F.; Lub, J.; Habing, H.

    2007-02-01

    Lithium and zirconium abundances (the latter taken as representative of s-process enrichment) are determined for a large sample of massive Galactic O-rich AGB stars, for which high-resolution optical spectroscopy has been obtained (R˜ 40 000{-}50 000). This was done by computing synthetic spectra based on classical hydrostatic model atmospheres for cool stars and using extensive line lists. The results are discussed in the framework of "hot bottom burning" (HBB) and nucleosynthesis models. The complete sample is studied for various observational properties such as the position of the stars in the IRAS two-colour diagram ([ 12] - [25] vs. [ 25] - [60] ), Galactic distribution, expansion velocity (derived from the OH maser emission), and period of variability (when available). We conclude that a considerable fraction of these sources are actually massive AGB stars (M>3{-}4 M⊙) experiencing HBB, as deduced from the strong Li overabundances we found. A comparison of our results with similar studies carried out in the past for the Magellanic Clouds (MCs) reveals that, in contrast to MC AGB stars, our Galactic sample does not show any indication of s-process element enrichment. The differences observed are explained as a consequence of metallicity effects. Finally, we discuss the results obtained in the framework of stellar evolution by comparing our results with the data available in the literature for Galactic post-AGB stars and PNe. Based on observations at the 4.2 m William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofisica de Canarias. Also based on observations with the ESO 3.6 m telescope at La Silla Observatory (Chile). Tables [see full text]-[see full text] are only available in electronic form at http://www.aanda.org

  19. Evolved stars in the Local Group galaxies - I. AGB evolution and dust production in IC 1613

    NASA Astrophysics Data System (ADS)

    Dell'Agli, F.; Di Criscienzo, M.; Boyer, M. L.; García-Hernández, D. A.

    2016-08-01

    We used models of thermally pulsing asymptotic giant branch (AGB) stars, which also describe the dust-formation process in the wind, to interpret the combination of near- and mid-infrared photometric data of the dwarf galaxy IC 1613. This is the first time that this approach is extended to an environment different from the Milky Way and the Magellanic Clouds (MCs). Our analysis, based on synthetic population techniques, shows nice agreement between the observations and the expected distribution of stars in the colour-magnitude diagrams obtained with JHK and Spitzer bands. This allows a characterization of the individual stars in the AGB sample in terms of mass, chemical composition and formation epoch of the progenitors. We identify the stars exhibiting the largest degree of obscuration as carbon stars evolving through the final AGB phases, descending from 1-1.25 M⊙ objects of metallicity Z = 10-3 and from 1.5-2.5 M⊙ stars with Z = 2 × 10-3. Oxygen-rich stars constitute the majority of the sample (˜65 per cent), mainly low-mass stars (<2 M⊙) that produce a negligible amount of dust (≤10-7 M⊙ yr-1). We predict the overall dust-production rate from IC 1613, mostly determined by carbon stars, to be ˜6 × 10-7 M⊙ yr-1 with an uncertainty of 30 per cent. The capability of the current generation of models to interpret the AGB population in an environment different from the MCs opens the possibility to extend this kind of analysis to other Local Group galaxies.

  20. Evolved stars in the Local Group galaxies - I. AGB evolution and dust production in IC 1613

    NASA Astrophysics Data System (ADS)

    Dell'Agli, F.; Di Criscienzo, M.; Boyer, M. L.; García-Hernández, D. A.

    2016-08-01

    We used models of thermally-pulsing asymptotic giant branch (AGB) stars, that also describe the dust-formation process in the wind, to interpret the combination of near- and mid-infrared photometric data of the dwarf galaxy IC 1613. This is the first time that this approach is extended to an environment different from the Milky Way and the Magellanic Clouds (MCs). Our analysis, based on synthetic population techniques, shows a nice agreement between the observations and the expected distribution of stars in the colour-magnitude diagrams obtained with JHK and Spitzer bands. This allows a characterization of the individual stars in the AGB sample in terms of mass, chemical composition, and formation epoch of the progenitors. We identify the stars exhibiting the largest degree of obscuration as carbon stars evolving through the final AGB phases, descending from 1-1.25Msun objects of metallicity Z=0.001 and from 1.5-2.5Msun stars with Z=0.002. Oxygen-rich stars constitute the majority of the sample (65%), mainly low mass stars (<2Msun) that produce a negligible amount of dust (<10^{-7}Msun/yr). We predict the overall dust-production rate from IC 1613, mostly determined by carbon stars, to be 6x10^{-7}Msun/yr with an uncertainty of 30%. The capability of the current generation of models to interpret the AGB population in an environment different from the MCs opens the possibility to extend this kind of analysis to other Local Group galaxies.

  1. Surprising detection of an equatorial dust lane on the AGB star IRC+10216

    NASA Astrophysics Data System (ADS)

    Jeffers, S. V.; Min, M.; Waters, L. B. F. M.; Canovas, H.; Pols, O. R.; Rodenhuis, M.; de Juan Ovelar, M.; Keller, C. U.; Decin, L.

    2014-12-01

    Aims: Understanding the formation of planetary nebulae remains elusive because in the preceding asymptotic giant branch (AGB) phase these stars are heavily enshrouded in an optically thick dusty envelope. Methods: To further understand the morphology of the circumstellar environments of AGB stars we observe the closest carbon-rich AGB star IRC+10216 in scattered light. Results: When imaged in scattered light at optical wavelengths, IRC+10216 surprisingly shows a narrow equatorial density enhancement, in contrast to the large-scale spherical rings that have been imaged much further out. We use radiative transfer models to interpret this structure in terms of two models: firstly, an equatorial density enhancement, commonly observed in the more evolved post-AGB stars, and secondly, in terms of a dust rings model, where a local enhancement of mass-loss creates a spiral ring as the star rotates. Conclusions: We conclude that both models can be used to reproduce the dark lane in the scattered light images, which is caused by an equatorially density enhancement formed by dense dust rather than a bipolar outflow as previously thought. We are unable to place constraints on the formation of the equatorial density enhancement by a binary system. Final reduced images (FITS) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A3Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  2. Detailed Modelling of the Circumstellar Envelope of the S-type AGB Star W Aquilae

    NASA Astrophysics Data System (ADS)

    Danilovich, T.; Bergman, P.; Justtanont, K.; Lombaert, R.; Maercker, M.; Olofsson, H.; Ramstedt, S.; Royer, P.

    2015-08-01

    We present new Herschel HIFI (de Graauw et al. 2010) and PACS (Poglitsch et al. 2010) sub-millimeter and far-infrared line observations of several molecular species towards the S-type AGB star W Aql. We use these observations, which probe a wide range of gas temperatures, to constrain the circumstellar properties of W Aql, including mass-loss rate and molecular abundances.

  3. The Transformation of an AGB Star to a Planetary Nebula: How the Journey Begins

    NASA Astrophysics Data System (ADS)

    Sahai, Raghvendra; Blumenfeld, C.; Morris, M.; S'anchez Contreras, C.; Claussen, M.

    2010-01-01

    We report the results from an HST imaging survey of a sample of late AGB stars with a detected history of extensive past mass-loss, i.e., those in which this process has now come to an end. The goal of this survey is to identify and characterise the earliest stages of the process that transforms these objects, first into bipolar or multipolar pre-planetary nebulae (PPNe), and then into similarly-shaped planetary nebulae. Since the cessation of mass-loss leads to the lack of hot dust close to the star, their thermal emission at short ( 25 micron) wavelengths, is expected to be lower than that for typical AGB stars. We have therefore used the IRAS 25 to 12 micron flux ratio, F25/F12 > 0.33 (but < 0.67 in order to exclude PPNe), to select a list of 60 such ``nascent pre-planetary nebulae" (or nPPNe); 48 were imaged in our SNAPshot imaging program. We found compact, but non-stellar, morphologies in about a quarter of our observed sample. The remaining objects are either unresolved, or only marginally resolved. Aspherical structure is seen in the resolved objects. The aspherical structure in nPPNe is different from that observed in PPNe, which generally show limb-brightened, roughly equal-sized lobes on both sides of the center. In contrast, only one-sided structures are seen in our survey nPPNe. In some objects, a diffuse, round, halo is also seen, representing the undisturbed AGB mass-loss envelope. A few sources show discrete circular (partial) arc-like features. The discovery of the one-side collimated features, together with detailed earlier studies of a few nPPNe (e.g. V Hya, IRC+10216), supports the hypothesis that the mechanism for creating the large-scale density inhomogeneties are high velocity outflows carving the AGB mass-loss envelope from the inside out.

  4. Transitory O-rich chemistry in heavily obscured C-rich post-AGB stars

    NASA Astrophysics Data System (ADS)

    García-Hernández, D. A.; García-Lario, P.; Cernicharo, J.; Engels, D.; Perea-Calderón, J. V.

    2016-07-01

    Spitzer/IRS spectra of eleven heavily obscured C-rich sources rapidly evolving from asymptotic giant branch (AGB) stars to Planetary Nebulae are presented. IRAM 30m observations for three of these post-AGBs are also reported. A few (3) of these sources are known to exhibit strongly variable maser emission of O-bearing molecules such as OH and H2 O, suggesting a transitory O-rich chemistry because of the quickly changing physical and chemical conditions in this short evolutionary phase. Interestingly, the Spitzer/IRS spectra show a rich circumstellar carbon chemistry, as revealed by the detection of small hydrocarbon molecules such as C2H2, C4H2, C6H2, C6H6, and HCN. Benzene is detected towards two sources, bringing up to three the total number of Galactic post-AGBs where this molecule has been detected. In addition, we report evidence for the possible detection of other hydrocarbon molecules like HC3N, CH3C2H, and CH3 in several of these sources. The available IRAM 30m data confirm that the central stars are C-rich - in despite of the presence of O-rich masers - and the presence of high velocity molecular outflows together with extreme AGB mass-loss rates (∼⃒10-4 Mʘ /yr). Our observations confirm the polymerization model of Cernicharo [1] that predicts a rich photochemistry in the neutral regions of these objects on timescales shorter than the dynamical evolution of the central HII region, leading to the formation of small C-rich molecules and a transitory O-rich chemistry.

  5. Shell and explosive hydrogen burning. Nuclear reaction rates for hydrogen burning in RGB, AGB and Novae

    NASA Astrophysics Data System (ADS)

    Boeltzig, A.; Bruno, C. G.; Cavanna, F.; Cristallo, S.; Davinson, T.; Depalo, R.; deBoer, R. J.; Di Leva, A.; Ferraro, F.; Imbriani, G.; Marigo, P.; Terrasi, F.; Wiescher, M.

    2016-04-01

    The nucleosynthesis of light elements, from helium up to silicon, mainly occurs in Red Giant and Asymptotic Giant Branch stars and Novae. The relative abundances of the synthesized nuclides critically depend on the rates of the nuclear processes involved, often through non-trivial reaction chains, combined with complex mixing mechanisms. In this paper, we summarize the contributions made by LUNA experiments in furthering our understanding of nuclear reaction rates necessary for modeling nucleosynthesis in AGB stars and Novae explosions.

  6. Secondary Forest Age and Tropical Forest Biomass Estimation Using TM

    NASA Technical Reports Server (NTRS)

    Nelson, R. F.; Kimes, D. S.; Salas, W. A.; Routhier, M.

    1999-01-01

    The age of secondary forests in the Amazon will become more critical with respect to the estimation of biomass and carbon budgets as tropical forest conversion continues. Multitemporal Thematic Mapper data were used to develop land cover histories for a 33,000 Square kM area near Ariquemes, Rondonia over a 7 year period from 1989-1995. The age of the secondary forest, a surrogate for the amount of biomass (or carbon) stored above-ground, was found to be unimportant in terms of biomass budget error rates in a forested TM scene which had undergone a 20% conversion to nonforest/agricultural cover types. In such a situation, the 80% of the scene still covered by primary forest accounted for over 98% of the scene biomass. The difference between secondary forest biomass estimates developed with and without age information were inconsequential relative to the estimate of biomass for the entire scene. However, in futuristic scenarios where all of the primary forest has been converted to agriculture and secondary forest (55% and 42% respectively), the ability to age secondary forest becomes critical. Depending on biomass accumulation rate assumptions, scene biomass budget errors on the order of -10% to +30% are likely if the age of the secondary forests are not taken into account. Single-date TM imagery cannot be used to accurately age secondary forests into single-year classes. A neural network utilizing TM band 2 and three TM spectral-texture measures (bands 3 and 5) predicted secondary forest age over a range of 0-7 years with an RMSE of 1.59 years and an R(Squared) (sub actual vs predicted) = 0.37. A proposal is made, based on a literature review, to use satellite imagery to identify general secondary forest age groups which, within group, exhibit relatively constant biomass accumulation rates.

  7. Variability Studies in Two Hypergiants and a Post-AGB Object

    NASA Astrophysics Data System (ADS)

    Freund, Stephen; Hrivnak, Bruce J.; Lu, Wenxian

    2016-01-01

    In the course of long-term photometric monitoring of post-AGB stars at the Valparaiso University campus observatory, we have also observed some objects of uncertain evolutionary state. This includes two objects that have some of the characteristics of post-AGB stars, such as large IR excesses and F-G spectral types. The weight of recent evidence suggests that two of these, IRAS 19114+0002 (AFGL 2343) and IRAS 19244+1115 (IRC+10 420), are instead hypergiants, objects of very high luminosity arising from evolved high-mass progenitors. A third object, IRAS 20004+2955 (V1027 Cyg), appears to be a cool post-AGB star evolving from a low or intermediate-mass progenitor. We have light and color curves from 1994-2007, along with some radial velocity data from 1991-1995. These three objects display complex light and color curves with evidence of periodicity in the range of 100 to 300 days. We will present the results of these studies. This research is supported by grants from the National Science Foundation (most recently AST 1413660), the Indiana Space Grant Consortium, and Valparaiso University.

  8. Improving the distances of post-AGB objects in the Milky Way

    NASA Astrophysics Data System (ADS)

    Vickers, Shane B.; Frew, David J.; Owers, Matt S.; Parker, Quentin A.; Bojičič, Ivan S.

    2016-07-01

    Post-AGB (PAGB) stars are short-lived, low-intermediate mass objects transitioning from the asymptotic giant branch (AGB) to the white dwarf (WD) phase. These objects are characterised by a constant, core-mass dependent luminosity and a large infrared excess from the dusty envelope ejected at the top of the AGB. PAGB stars provide insights into the evolution of their direct descendants, planetary nebulae (PNe). Calculation of physical characteristics of PAGB are dependent on accurately determined distances scarcely available in the literature. Using the Torun catalogue for PAGB objects, supplemented with archival data, we have determined distances to the known population of Galactic PAGB stars. This is by modelling their spectral energy distributions (SED) with black bodies and numerically integrating over the entire wavelength range to determine the total integrated object flux. For most PAGB stars we assumed their luminosities are based on their positional characteristics and stellar evolution models. RV Tauri stars however are known to follow a period-luminosity relation (PLR) reminiscent of type-2 Cepheids. For these variable PAGB stars we determined their luminosities via the PLR and hence their distances. This allows us to overcome the biggest obstacle to characterising these poorly understood objects that play a vital part in Galactic chemical enrichment.

  9. ALMA reveals sunburn: CO dissociation around AGB stars in the globular cluster 47 Tucanae

    NASA Astrophysics Data System (ADS)

    McDonald, I.; Zijlstra, A. A.; Lagadec, E.; Sloan, G. C.; Boyer, M. L.; Matsuura, M.; Smith, R. J.; Smith, C. L.; Yates, J. A.; van Loon, J. Th.; Jones, O. C.; Ramstedt, S.; Avison, A.; Justtanont, K.; Olofsson, H.; Blommaert, J. A. D. L.; Goldman, S. R.; Groenewegen, M. A. T.

    2015-11-01

    Atacama Large Millimetre Array observations show a non-detection of carbon monoxide around the four most luminous asymptotic giant branch (AGB) stars in the globular cluster 47 Tucanae. Stellar evolution models and star counts show that the mass-loss rates from these stars should be ˜1.2-3.5 × 10-7 M⊙ yr-1. We would naïvely expect such stars to be detectable at this distance (4.5 kpc). By modelling the ultraviolet radiation field from post-AGB stars and white dwarfs in 47 Tuc, we conclude that CO should be dissociated abnormally close to the stars. We estimate that the CO envelopes will be truncated at a few hundred stellar radii from their host stars and that the line intensities are about two orders of magnitude below our current detection limits. The truncation of CO envelopes should be important for AGB stars in dense clusters. Observing the CO (3-2) and higher transitions and targeting stars far from the centres of clusters should result in the detections needed to measure the outflow velocities from these stars.

  10. Winds, Bubbles, ...but Magnetized: Solutions for High Speed Post-AGB Winds and Their Extreme Collimation

    NASA Astrophysics Data System (ADS)

    García-Segura, G.; López, J. A.; Franco, J.

    2003-01-01

    This paper provides solutions for the origin of post-AGB winds, their acceleration up to high speed, and the subsequent formation of extremely collimated proto-planetary nebulae. Several wind models with terminal velocities from a few tens of km/s up to 10^3km/s are calculated, which produce proto-planetary nebulae with linear momenta in the range 10^36 to 10^40gcm/s and with kinetic energies in the range 10^42 to 10^47 erg. These results match available observations of proto-planetary nebulae. In the present simplistic scheme, the driver of the wind is just the magnetic pressure at the stellar surface. Other forces are not taken into account in this study, except gravity. We conclude that mass-loss rates of post-AGB stars and transition times from late AGB up to planetary nebula central stars could be directly linked with the production of magnetic field at the stellar core. As an example, mass-loss rates as large as 8×10^-5 M[ sun ]/yr and transition times as short as 5000 years are predicted.

  11. VLT/NACO Imaging of the Nearest AGB Star, L2 Puppis

    NASA Astrophysics Data System (ADS)

    Montargès, M.; Kervella, P.; Ridgway, S. T.; Perrin, G.; Chesneau, O.

    2015-08-01

    AGB stars are the most important contributors to the chemical enrichment of the Galaxy. During their later evolutionary stages they experience intense pulsations and eject most of their layers as they become planetary nebulae (PNe). The process leading to the formation of bipolar PNe remains poorly understood. It is assumed that the circumstellar disk of an AGB star could collimate the stellar wind to form a bipolar PN, yet very few of these disks have been observed. Using the adaptive-optics system of the VLT/NACO instrument at the Paranal Observatory and a "lucky imaging" technique, our team obtained near-infrared diffraction-limited images of the nearest AGB star, L2 Puppis. The deconvolved images reveal a dark structure in front of the star whose morphology and photometry match a dusty edge-on disk of olivine and pyroxene modeled with a Monte-Carlo radiative transfer code. The L band images also show a loop structure, possibly the signature of an interacting hidden companion.

  12. Biomass energy

    SciTech Connect

    Smil, V.

    1983-01-01

    This book offers a broad, interdisciplinary approach to assessing the factors that are key determinants to the use of biomass energies, stressing their limitations, complexities, uncertainties, links, and consequences. Considers photosynthesis, energy costs of nutrients, problems with monoculture, and the energy analysis of intensive tree plantations. Subjects are examined in terms of environmental and economic impact. Emphasizes the use and abuse of biomass energies in China, India, and Brazil. Topics include forests, trees for energy, crop residues, fuel crops, aquatic plants, and animal and human wastes. Recommended for environmental engineers and planners, and those involved in ecology, systematics, and forestry.

  13. Stellar Dust Production in Chemically Primitive Environments: Infrared Lightcurves and Mass Loss in Extremely Metal-poor AGB Stars

    NASA Astrophysics Data System (ADS)

    Sonneborn, George

    In their final stage of evolution, asymptotic giant branch (AGB) stars inject a substantial amount of dust into the surrounding interstellar medium, potentially dominating the total stellar dust budgets of their host galaxies. However, stellar models conflict over whether metal-poor AGB stars can condense enough dust to drive a strong stellar wind, so it is unclear what role AGB stars play in the early Universe compared to other dust sources, e.g., in high-redshift quasars that show evidence for massive dust reservoirs. Empirically, AGB stars that are massive enough to contribute in the early Universe are only well studied in the Milky Way and the nearby Magellanic Clouds; all three environments are relatively metal-rich and thus unlikely to be representative of high-redshift AGB stars. This lack of observations of metal-poor AGB stars motivated the survey of DUST in Nearby Galaxies with Spitzer (DUSTiNGS), which imaged 50 nearby dwarf galaxies in the infrared and identified 526 dusty "extreme" AGB stars. The DUSTiNGS stars confirm that dust can form at metallicities as low as 0.008 solar, more than an order of magnitude lower than had been previously observed. However, very little is known about the DUSTiNGS stars; among the unknowns are the photospheric chemistries, stellar masses, temperatures, luminosities, pulsation periods and amplitudes, dust-production rates, and even their statuses as bona fide AGB stars. To eliminate these unknowns, we were awarded 56 hours of Priority 1 observing time in Spitzer's cycle 11 to obtain 6 new epochs of imaging for a subset of the DUSTiNGS variables over an 18 month baseline. These will be the first infrared light curves of metal-poor, dust-producing AGB stars, allowing us to study the influence of metallicity on pulsation and dust production. Combined with additional archival data, our cycle-11 Spitzer program will allow estimates of all of the parameters listed above, enabling the first direct comparisons to models of AGB

  14. Estimation of Boreal Forest Biomass Using Spaceborne SAR Systems

    NASA Technical Reports Server (NTRS)

    Saatchi, Sassan; Moghaddam, Mahta

    1995-01-01

    In this paper, we report on the use of a semiempirical algorithm derived from a two layer radar backscatter model for forest canopies. The model stratifies the forest canopy into crown and stem layers, separates the structural and biometric attributes of the canopy. The structural parameters are estimated by training the model with polarimetric SAR (synthetic aperture radar) data acquired over homogeneous stands with known above ground biomass. Given the structural parameters, the semi-empirical algorithm has four remaining parameters, crown biomass, stem biomass, surface soil moisture, and surface rms height that can be estimated by at least four independent SAR measurements. The algorithm has been used to generate biomass maps over the entire images acquired by JPL AIRSAR and SIR-C SAR systems. The semi-empirical algorithms are then modified to be used by single frequency radar systems such as ERS-1, JERS-1, and Radarsat. The accuracy. of biomass estimation from single channel radars is compared with the case when the channels are used together in synergism or in a polarimetric system.

  15. VizieR Online Data Catalog: Optical spectra of post-AGB stars (Bakker+ 1997)

    NASA Astrophysics Data System (ADS)

    Bakker, E. J.; van Dishoeck, E. F.; Waters, L. B. F. M.; Schoenmaker, T.

    1996-10-01

    We present optical high-resolution spectra of a sample of sixteen post-AGB stars and IRC +10216. Of the post-AGB stars, ten show C2 Phillips (A1{PI}u- X1{SIGMA}+g) and Swan (d3{PI}g-a3{PI}u) and CN Red System (A2{PI}-X2{SIGMA}+) absorption, one CH+ (A1{PI}-X1{SIGMA}+) emission, one CH+ absorption, and four without any molecules. We find typically Trot ~43-399, 155-202, and 18-50K, logN~14.90-15.57, 14.35, and 15.03-16.47cm-2 for C2, CH+, and CN respectively, and 0.6<=N(CN)/N(C2)<=11.2. We did not detect isotopic lines, which places a lower limit on the isotope ratio of 12C/13C>20. The presence of C2 and CN absorption is correlated with cold dust (Tdust<=300K) and the presence of CH+ with hot dust (Tdust>=300K). All objects with the unidentified 21μm emission feature exhibit C2 and CN absorption, but not all objects with C2 and CN detections exhibit a 21μm feature. The derived expansion velocity, ranging from 5 to 44km/s, is the same as that derived from CO millimeter line emission. This unambiguously proves that these lines are of circumstellar origin and are formed in the AGB ejecta (circumstellar shell expelled during the preceding AGB phase). Furthermore there seems to be a relation between the C2 molecular column density and the expansion velocity, which is attributed to the fact that a higher carbon abundance of the dust leads to a more efficient acceleration of the AGB wind. Using simple assumptions for the location of the molecular lines and molecular abundances, mass-loss rates have been derived from the molecular absorption lines and are comparable to those obtained from CO emission lines and the infrared excess. (6 data files).

  16. Evaluating land use and aboveground biomass dynamics in an oil palm-dominated landscape in Borneo using optical remote sensing

    NASA Astrophysics Data System (ADS)

    Singh, Minerva; Malhi, Yadvinder; Bhagwat, Shonil

    2014-01-01

    The focus of this study is to assess the efficacy of using optical remote sensing (RS) in evaluating disparities in forest composition and aboveground biomass (AGB). The research was carried out in the East Sabah region, Malaysia, which constitutes a disturbance gradient ranging from pristine old growth forests to forests that have experienced varying levels of disturbances. Additionally, a significant proportion of the area consists of oil palm plantations. In accordance with local laws, riparian forest (RF) zones have been retained within oil palm plantations and other forest types. The RS imagery was used to assess forest stand structure and AGB. Band reflectance, vegetation indicators, and gray-level co-occurrence matrix (GLCM) consistency features were used as predictor variables in regression analysis. Results indicate that the spectral variables were limited in their effectiveness in differentiating between forest types and in calculating biomass. However, GLCM based variables illustrated strong correlations with the forest stand structures as well as with the biomass of the various forest types in the study area. The present study provides new insights into the efficacy of texture examination methods in differentiating between various land-use types (including small, isolated forest zones such as RFs) as well as their AGB stocks.

  17. Multi- and hyperspectral remote-sensing retrieval of floodplain-forest aboveground biomass using machine learning

    NASA Astrophysics Data System (ADS)

    Filippi, A. M.; Guneralp, I.; Randall, J.

    2014-12-01

    Forests within dynamic floodplain landscapes, such as meandering-river landscapes, are composed of uneven-aged trees and entail high spatial variability, which results from intersecting hydrological, fluvial, and ecological processes. Floodplain forests are an important carbon sink relative to other terrestrial ecosystems and thus serve a critical role in the global carbon cycle. Accurate, quantitative aboveground biomass (AGB) retrieval within floodplain forests is urgently needed for improved carbon-pool estimates in such areas and enhanced process understanding of river-floodplain biomorphodynamics. We perform remote AGB retrieval for a meander-bend bottomland hardwood forest, based on utilization of stochastic gradient boosting (SGB), multivariate adaptive regression splines (MARS), and Cubist algorithms and multi- and hyperspectral image-based data sets. For multispectral experiments, we use 30-m and 10-m image bands (Landsat 7 ETM+ and SPOT 5, respectively) and ancillary input vectors; for hyperspectral-based experiments, we use 30-m Hyperion bands and other input variables. Results indicate that for both the multispectral and hyperspectral experimental trials, SGB- and MARS-derived AGB are significantly more accurate than Cubist estimates. (Cubist is used for U.S. national-scale forest biomass mapping.) For the multispectral results, across all data-experiments and algorithms, at 10-m spatial resolution, SGB gives the most accurate estimates (RMSE = 22.49 tonnes/ha; coefficient of determination (R2) = 0.96) when geomorphometric data are also included. For 30-m multispectral data trials, MARS performs the best (RMSE = 29.2 tonnes/ha; R2 = 0.94) when image-derived data are also incorporated. For the hyperspectral experiments, the most accurate MARS- and SGB-based retrievals have R2 of 0.97 and 0.95, respectively; the most accurate Cubist AGB retrieval has R2 of 0.85. MARS and SGB AGB are not significantly different though for the hyperspectral experiments. The

  18. The abundance of HCN in circumstellar envelopes of AGB stars of different chemical type

    NASA Astrophysics Data System (ADS)

    Schöier, F. L.; Ramstedt, S.; Olofsson, H.; Lindqvist, M.; Bieging, J. H.; Marvel, K. B.

    2013-02-01

    Aims: A multi-transition survey of HCN (sub-) millimeter line emission from a large sample of asymptotic giant branch (AGB) stars of different chemical type is presented. The data are analysed and circumstellar HCN abundances are estimated. The sample stars span a large range of properties such as mass-loss rate and photospheric C/O-ratio. The analysis of the new data allows for more accurate estimates of the circumstellar HCN abundances and puts new constraints on chemical models. Methods: In order to constrain the circumstellar HCN abundance distribution a detailed non-local thermodynamic equilibrium (LTE) excitation analysis, based on the Monte Carlo method, is performed. Effects of line overlaps and radiative excitation from dust grains are included. Results: The median values for the derived abundances of HCN (with respect to H2) are 3 × 10-5, 7 × 10-7 and 10-7 for carbon stars (25 stars), S-type AGB stars (19 stars) and M-type AGB stars (25 stars), respectively. The estimated sizes of the HCN envelopes are similar to those obtained in the case of SiO for the same sample of sources and agree well with previous results from interferometric observations, when these are available. Conclusions: We find that there is a clear dependence of the derived circumstellar HCN abundance on the C/O-ratio of the star, in that carbon stars have about two orders of magnitude higher abundances than M-type AGB stars, on average. The derived HCN abundances of the S-type AGB stars have a larger spread and typically fall in between those of the two other types, however, slightly closer to the values for the M-type AGB stars. For the M-type stars, the estimated abundances are much higher than what would be expected if HCN is formed in thermal equilibrium. However, the results are also in contrast to predictions from recent non-LTE chemical models, where very little difference is expected in the HCN abundances between the various types of AGB stars. This publication is based on data

  19. The influences of CO2 fertilization and land use change on the total aboveground biomass in Amazonian tropical forest

    NASA Astrophysics Data System (ADS)

    Castanho, A. D.; Zhang, K.; Coe, M. T.; Costa, M. H.; Moorcroft, P. R.

    2012-12-01

    Field observations from undisturbed old-growth Amazonian forest plots have recently reported on the temporal variation of many of the physical and chemical characteristics such as: physiological properties of leaves, above ground live biomass, above ground productivity, mortality and turnover rates. However, although this variation has been measured, it is still not well understood what mechanisms control the observed temporal variability. The observed changes in time are believed to be a result of a combination of increasing atmospheric CO2 concentration, climate variability, recovery from natural disturbance (drought, wind blow, flood), and increase of nutrient availability. The time and spatial variability of the fertilization effect of CO2 on above ground biomass will be explored in more detail in this work. A precise understanding of the CO2 effect on the vegetation is essential for an accurate prediction of the future response of the forest to climate change. To address this issue we simultaneously explore the effects of climate variability, historical CO2 and land-use change on total biomass and productivity using two different Dynamic Global Vegetation Models (DGVM). We use the Integrated Biosphere Simulator (IBIS) and the Ecosystem Demography Model 2.1 (ED2.1). Using land use changes database from 1700 - 2008 we reconstruct the total carbon balance in the Amazonian forest in space and time and present how the models predict the forest as carbon sink or source and explore why the model and field data diverge from each other. From 1970 to 2005 the Amazonian forest has been exposed to an increase of approximately 50 ppm in the atmospheric CO2 concentration. Preliminary analyses with the IBIS and ED2.1 dynamic vegetation model shows the CO2 fertilization effect could account for an increase in above ground biomass of 0.03 and 0.04 kg-C/m2/yr on average for the Amazon basin, respectively. The annual biomass change varies temporally and spatially from about 0

  20. Influence of the simulated microgravity on biomass and contents of carbohydrates at virus-infected wheat plants

    NASA Astrophysics Data System (ADS)

    Mishchenko, L.; Silayeva, A.; Mishchenko, I.; Boyko, A.

    The effects of clinostating has been studied on the contents of biomass, soluble carbohydrates and starches in Wheat streak mosaic virus (WSMV) infected plants of wheat Donska semidwarf, Albatross Odessky, Kollectivna-3 (summer), and Apogee (early-ripe, superdwarf). Plants in conditions of horizontal and vertical rotation with a frequency 2 min-1 were grown in containers during 35 days. WSMV was accumulated on barley i dicator plants of Ros' variety for then subsequent infestation by this virus of a part of clinostating and motionless wheat plants in a stage of 3 leaves. Researches have shown, that the most suitable for ground experiments with clinostating were Kollectivna-3 and Apogee varieties. At vertical and horizontal rotation of wheat plants of Kollectivna - 3 variety the weight of roots increased and that of above-ground part (leaves and stalks) decreased in comparison with motionless control plants, that resulted in decrease of the ratio of a biomass of an above-ground part to a root system. In Apogee variety the weight of the above-ground part of healthy plants at vertical clinostating decreased by 23 % in comparison with motionless variant, and the biomass of virus-infected plants was reduced on the average by 14 % in comparison with infected motionless control. The weight of above-ground part of infected and healthy motionless plants practically did not differ. Vertical clinorotation of plants caused the reduction of ear weight while in horizontally rotated plants and in the motionless control there were no difference. The number of ears in Apogee variety practically did not change in all variants of the experiment, and plant weight at clinostating decreased in both healthy, and virus infected plants. For the period of cultivation in Kollectivna-3 variety ears were not formed at all. The contents of soluble carbohydrates (reducing and saccharose) in leaves and stalks of healthy and virus infected at clinostating was increased in Apogee in 1,6-2,2 times

  1. Estimation of Aboveground Biomass in Alpine Forests: A Semi-Empirical Approach Considering Canopy Transparency Derived from Airborne LiDAR Data

    PubMed Central

    Jochem, Andreas; Hollaus, Markus; Rutzinger, Martin; Höfle, Bernhard

    2011-01-01

    In this study, a semi-empirical model that was originally developed for stem volume estimation is used for aboveground biomass (AGB) estimation of a spruce dominated alpine forest. The reference AGB of the available sample plots is calculated from forest inventory data by means of biomass expansion factors. Furthermore, the semi-empirical model is extended by three different canopy transparency parameters derived from airborne LiDAR data. These parameters have not been considered for stem volume estimation until now and are introduced in order to investigate the behavior of the model concerning AGB estimation. The developed additional input parameters are based on the assumption that transparency of vegetation can bemeasured by determining the penetration of the laser beams through the canopy. These parameters are calculated for every single point within the 3D point cloud in order to consider the varying properties of the vegetation in an appropriate way. Exploratory Data Analysis (EDA) is performed to evaluate the influence of the additional LiDAR derived canopy transparency parameters for AGB estimation. The study is carried out in a 560 km2 alpine area in Austria, where reference forest inventory data and LiDAR data are available. The investigations show that the introduction of the canopy transparency parameters does not change the results significantly according to R2 (R2 = 0.70 to R2 = 0.71) in comparison to the results derived from, the semi-empirical model, which was originally developed for stem volume estimation. PMID:22346577

  2. Numerical simulation of shock interaction with above-ground structures

    NASA Astrophysics Data System (ADS)

    Baum, Joseph D.; Lohner, Rainald

    1994-05-01

    This final report for DNA contract DNA 001-89-C-0098 for the time period May 15, 1989 to Dec 31, 1992 describes the results of several of the computations conducted under this research effort. The numerical simulations conducted simulated shock wave diffraction phenomenon about complex-geometry two-dimensional and three-dimensional structures. Since a significant part of this effort was composed of parametric studies that have been delivered to the sponsors, the Defense Nuclear Agency and the Air Force Ballistic Missile Organization (BMO), and conducted under the now defunct Rail Garrison project, we included in this report a detailed description of the results of the major computations, and a brief summary of all the repetitive computations. The final report is divided into three sections. Chapter 1 describes in detail the two-dimensional numerical methodology and typical two-dimensional computation, i.e., the application of the numerical methodology to the simulation of shock interaction with a typical 2-D train (a 2-D cut at the center of a 3-D train). Chapter 2 describes the numerical development of a passive shock reflector, a major effort undertaken in this project. The objective of this effort was to design a passive device that, while allowing the ventilation of the enclosure under steady conditions, will prevent blast waves impinging on the wall from entering the enclosure when the structure is impacted by a shock.

  3. Evaluating lidar point densities for effective estimation of aboveground biomass

    USGS Publications Warehouse

    Wu, Zhuoting; Dye, Dennis G.; Stoker, Jason; Vogel, John M.; Velasco, Miguel G.; Middleton, Barry R.

    2016-01-01

    The U.S. Geological Survey (USGS) 3D Elevation Program (3DEP) was recently established to provide airborne lidar data coverage on a national scale. As part of a broader research effort of the USGS to develop an effective remote sensing-based methodology for the creation of an operational biomass Essential Climate Variable (Biomass ECV) data product, we evaluated the performance of airborne lidar data at various pulse densities against Landsat 8 satellite imagery in estimating above ground biomass for forests and woodlands in a study area in east-central Arizona, U.S. High point density airborne lidar data, were randomly sampled to produce five lidar datasets with reduced densities ranging from 0.5 to 8 point(s)/m2, corresponding to the point density range of 3DEP to provide national lidar coverage over time. Lidar-derived aboveground biomass estimate errors showed an overall decreasing trend as lidar point density increased from 0.5 to 8 points/m2. Landsat 8-based aboveground biomass estimates produced errors larger than the lowest lidar point density of 0.5 point/m2, and therefore Landsat 8 observations alone were ineffective relative to airborne lidar for generating a Biomass ECV product, at least for the forest and woodland vegetation types of the Southwestern U.S. While a national Biomass ECV product with optimal accuracy could potentially be achieved with 3DEP data at 8 points/m2, our results indicate that even lower density lidar data could be sufficient to provide a national Biomass ECV product with accuracies significantly higher than that from Landsat observations alone.

  4. Biotechnology of biomass conversion

    SciTech Connect

    Wayman, M.; Parekh, S.R.

    1990-01-01

    This book covers: An introduction to biomass crops; The microbiology of fermentation processes; The production of ethanol from biomass crops, such as sugar cane and rubbers; The energy of biomass conversion; and The economics of biomass conversion.

  5. Biomass shock pretreatment

    DOEpatents

    Holtzapple, Mark T.; Madison, Maxine Jones; Ramirez, Rocio Sierra; Deimund, Mark A.; Falls, Matthew; Dunkelman, John J.

    2014-07-01

    Methods and apparatus for treating biomass that may include introducing a biomass to a chamber; exposing the biomass in the chamber to a shock event to produce a shocked biomass; and transferring the shocked biomass from the chamber. In some aspects, the method may include pretreating the biomass with a chemical before introducing the biomass to the chamber and/or after transferring shocked biomass from the chamber.

  6. EFFECT OF HIGH-ENERGY RESONANCES ON THE {sup 18}O(p, {alpha}){sup 15}N REACTION RATE AT AGB AND POST-AGB RELEVANT TEMPERATURES

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Mukhamedzhanov, A. M.

    2010-11-10

    The {sup 18}O(p, {alpha}){sup 15}N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as {sup 19}F, {sup 18}O, and {sup 15}N. Fluorine is synthesized in the intershell region of asymptotic giant branch (AGB) stars, together with s-elements, by {alpha} radiative capture on {sup 15}N, which in turn is produced in the {sup 18}O proton-induced destruction. Peculiar {sup 18}O abundances are observed in R-Coronae Borealis stars, having {sup 16}O/{sup 18}O {approx}< 1, hundreds of times smaller than the galactic value. Finally, there is no definite explanation of the {sup 14}N/{sup 15}N ratio in pre-solar grains formed in the outer layers of AGB stars. Again, such an isotopic ratio is influenced by the {sup 18}O(p, {alpha}){sup 15}N reaction. In this work, a high accuracy {sup 18}O(p, {alpha}){sup 15}N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. Indeed, current determinations are uncertain because of the poor knowledge of the resonance parameters of key levels of {sup 19}F. In particular, we have focused on the study of the broad 660 keV 1/2{sup +} resonance corresponding to the 8.65 MeV level of {sup 19}F. Since {Gamma} {approx} 100-300 keV, it determines the low-energy tail of the resonant contribution to the cross section and dominates the cross section at higher energies. Here, we provide a reaction rate that is a factor of two larger above T {approx} 0.5 10{sup 9} K based on our new improved determination of its resonance parameters, which could strongly influence present-day astrophysical model predictions.

  7. Effects of soil chemistry on tropical forest biomass and productivity at different elevations in the equatorial Andes.

    PubMed

    Unger, Malte; Homeier, Jürgen; Leuschner, Christoph

    2012-09-01

    The dependence of aboveground biomass and productivity of tropical forests on soil fertility is not fully understood, since previous studies yielded contrasting results. Here, we quantify aboveground biomass (AGB) and stem wood production, and examine the impact of soil chemistry on these parameters in mature tropical forest stands of the equatorial Andes in Ecuador. In 80 plots of 0.04 ha at four elevation levels (500, 1,000, 1,500 and 2,000 m a.s.l., total sample area = 3.2 ha), we measured ten important soil chemical parameters, inventoried all trees ≥10 cm dbh and monitored stem diameter growth with dendrometer tapes in 32 plots. Top canopy height and stem density significantly decreased from 500 to 2,000 m, while tree basal area increased and AGB remained invariant (344 ± 17 Mg DM ha(-1), mean ± SE) with elevation. Wood specific gravity (WSG) showed a significant, but small, decrease. Stem wood production decreased from 4.5 to 3.2 Mg DM ha(-1) year(-1) along the transect, indicating a higher biomass turnover at lower elevations. The only soil variable that covaried with AGB was exchangeable K in the topsoil. WSG increased with decreases in N mineralisation rate, soil pH and extractable Ca and P concentrations. Structural equation modelling (SEM) revealed that nitrogen availability acts on stem wood production only indirectly through a negative relation between N mineralisation rate and WSG, and a positive effect of a lowered WSG on stem growth. The SEM analysis showed neither direct nor indirect effects of resin-extractable P on wood production, but a negative P influence on AGB. We conclude that nitrogen availability significantly influences productivity in these Andean forests, but both N and P are affecting wood production mainly indirectly through alterations in WSG and stem density; the growth-promoting effect of N is apparently larger than that of P. PMID:22410639

  8. A search for water maser emission toward obscured post-AGB star and planetary nebula candidates

    NASA Astrophysics Data System (ADS)

    Gómez, J. F.; Rizzo, J. R.; Suárez, O.; Palau, A.; Miranda, L. F.; Guerrero, M. A.; Ramos-Larios, G.; Torrelles, J. M.

    2015-06-01

    Context. Water maser emission at 22 GHz is a useful probe for studying the transition between the nearly spherical mass loss in the asymptotic giant branch (AGB) to a collimated one in the post-AGB phase. In their turn, collimated jets in the post-AGB phase could determine the shape of planetary nebulae once photoionization starts. Aims: We intend to find new cases of post-AGB stars and planetary nebulae (PNe) with water maser emission, including some especially interesting and rare types: water fountains (evolved objects with high velocity collimated jets traced by water masers) or water-maser-emitting PNe. Since previous studies have shown a higher detection rate of water maser emission in evolved objects that are optically obscured, we selected a sample that contains a significant fraction of post-AGB and young PN candidate sources showing signs of strong obscuration. Methods: We searched for water maser emission in 133 evolved objects using the radio telescopes in Robledo de Chavela, Parkes, and Green Bank. Results: We detected water maser emission in 15 sources of our sample, of which seven are reported here for the first time (IRAS 13483-5905, IRAS 14249-5310, IRAS 15408-5413, IRAS 17021-3109, IRAS 17348-2906, IRAS 17393-2727, and IRAS 18361-1203). We identified three water fountain candidates: IRAS 17291-2147, with a total velocity spread of ≃96 km s-1 in its water maser components and two sources (IRAS 17021-3109 and IRAS 17348-2906) that show water maser emission whose velocity lies outside the velocity range covered by OH masers. We have also identified IRAS 17393-2727 as a possible new water-maser-emitting PN. Conclusions: The detection rate is higher in obscured objects (14%) than in those with optical counterparts (7%), which is consistent with previous results. Water maser emission seems to be common in objects that are bipolar in the near-IR (43% detection rate in such sources). The water maser spectra of water fountain candidates like IRAS 17291

  9. Near-infrared and Brγ observations of post-AGB stars

    NASA Astrophysics Data System (ADS)

    Van de Steene, G. C.; van Hoof, P. A. M.; Wood, P. R.

    2000-10-01

    In this article we report further investigations of the IRAS selected sample of Planetary Nebula (PN) candidates that was presented in Van de Steene & Pottasch (\\cite{VdSteene93}). About 20% of the candidates in that sample have been detected in the radio and/or Hα and later confirmed as PNe. Here we investigate the infrared properties of the IRAS sources not confirmed as PNe. We observed 28 objects in the N-band of which 20 were detected and 5 were resolved, despite adverse weather conditions. We obtained medium resolution Brgamma spectra and we took high resolution J H K L images of these 20 objects. We critically assessed the identification of the IRAS counterpart in the images and compared our identification with others in the literature. High spatial resolution and a telescope with very accurate pointing are crucial for correct identification of the IRAS counterparts in these crowded fields. Of sixteen positively identified objects, seven show Brgamma in absorption. The absorption lines are very narrow in six objects, indicating a low surface gravity. Another six objects show Brgamma in emission. Two of these also show photospheric absorption lines. All emission line sources have a strong underlying continuum, unlike normal PNe. In another three objects, no clear Brgamma absorption or emission was visible. The fact that our objects were mostly selected from the region in the IRAS color-color diagram where typically PNe are found, may explain our higher detection rate of emission line objects compared to previous studies, which selected their candidates from a region between AGB and PNe. The objects showing Brgamma in emission were re-observed in the radio continuum with the Australia Telescope Compact Array. None of them were detected above a detection limit of 0.55 mJy/beam at 6 cm and 0.7 mJy/beam at 3 cm, while they should have been easily detected if the radio flux was optically thin and Case B recombination was applicable. It is suggested that the

  10. Soil warming and CO2 enrichment induce biomass shifts in alpine tree line vegetation.

    PubMed

    Dawes, Melissa A; Philipson, Christopher D; Fonti, Patrick; Bebi, Peter; Hättenschwiler, Stephan; Hagedorn, Frank; Rixen, Christian

    2015-05-01

    Responses of alpine tree line ecosystems to increasing atmospheric CO2 concentrations and global warming are poorly understood. We used an experiment at the Swiss tree line to investigate changes in vegetation biomass after 9 years of free air CO2 enrichment (+200 ppm; 2001-2009) and 6 years of soil warming (+4 °C; 2007-2012). The study contained two key tree line species, Larix decidua and Pinus uncinata, both approximately 40 years old, growing in heath vegetation dominated by dwarf shrubs. In 2012, we harvested and measured biomass of all trees (including root systems), above-ground understorey vegetation and fine roots. Overall, soil warming had clearer effects on plant biomass than CO2 enrichment, and there were no interactive effects between treatments. Total plant biomass increased in warmed plots containing Pinus but not in those with Larix. This response was driven by changes in tree mass (+50%), which contributed an average of 84% (5.7 kg m(-2) ) of total plant mass. Pinus coarse root mass was especially enhanced by warming (+100%), yielding an increased root mass fraction. Elevated CO2 led to an increased relative growth rate of Larix stem basal area but no change in the final biomass of either tree species. Total understorey above-ground mass was not altered by soil warming or elevated CO2 . However, Vaccinium myrtillus mass increased with both treatments, graminoid mass declined with warming, and forb and nonvascular plant (moss and lichen) mass decreased with both treatments. Fine roots showed a substantial reduction under soil warming (-40% for all roots <2 mm in diameter at 0-20 cm soil depth) but no change with CO2 enrichment. Our findings suggest that enhanced overall productivity and shifts in biomass allocation will occur at the tree line, particularly with global warming. However, individual species and functional groups will respond differently to these environmental changes, with consequences for ecosystem structure and functioning. PMID

  11. Compact reflection nebulae, a transit phase of evolution from post-AGB to planetary nebulae

    NASA Technical Reports Server (NTRS)

    Hu, J. Y.; Slijkhuis, S.

    1989-01-01

    In a search of the optical counter-part of candidates of protoplanetary nebulae on the plates of UK Schmidt, ESO Schmidt, and POSS, five compact reflection nebulae associated with post-AGB stars were found. A simplified model (dust shell is spherical symmetric, expansion velocity of dust shell is constant, Q(sub sca)(lambda) is isotropic, and the dust grain properties are uniform) is used to estimate the visible condition of the dust shell due to the scattering of the core star's light. Under certain conditions the compact reflection nebulae can be seen of the POSS or ESO/SRC survey plates.

  12. Chemistry and distribution of daughter species in the circumstellar envelopes of O-rich AGB stars

    NASA Astrophysics Data System (ADS)

    Li, Xiaohu; Millar, Tom J.; Heays, Alan N.; Walsh, Catherine; van Dishoeck, Ewine F.; Cherchneff, Isabelle

    2016-03-01

    Context. Thanks to the advent of Herschel and ALMA, new high-quality observations of molecules present in the circumstellar envelopes of asymptotic giant branch (AGB) stars are being reported that reveal large differences from the existing chemical models. New molecular data and more comprehensive models of the chemistry in circumstellar envelopes are now available. Aims: The aims are to determine and study the important formation and destruction pathways in the envelopes of O-rich AGB stars and to provide more reliable predictions of abundances, column densities, and radial distributions for potentially detectable species with physical conditions applicable to the envelope surrounding IK Tau. Methods: We use a large gas-phase chemical model of an AGB envelope including the effects of CO and N2 self-shielding in a spherical geometry and a newly compiled list of inner-circumstellar envelope parent species derived from detailed modeling and observations. We trace the dominant chemistry in the expanding envelope and investigate the chemistry as a probe for the physics of the AGB phase by studying variations of abundances with mass-loss rates and expansion velocities. Results: We find a pattern of daughter molecules forming from the photodissociation products of parent species with contributions from ion-neutral abstraction and dissociative recombination. The chemistry in the outer zones differs from that in traditional PDRs in that photoionization of daughter species plays a significant role. With the proper treatment of self-shielding, the N → N2 and C+→ CO transitions are shifted outward by factors of 7 and 2, respectively, compared with earlier models. An upper limit on the abundance of CH4 as a parent species of (≲2.5 × 10-6 with respect to H2) is found for IK Tau, and several potentially observable molecules with relatively simple chemical links to other parent species are determined. The assumed stellar mass-loss rate, in particular, has an impact on the

  13. Carbon dust particle size distributions around mass-losing AGB stars

    NASA Astrophysics Data System (ADS)

    Jura, M.

    1997-03-01

    Solids of presolar SiC and interstellar carbon have qualitatively similar relative size distribution for particles with radii, a, in the range 0.35 μmAGB stars such as the well studied IRC+10216 seem to be smaller than the interstellar or presolar particles. The close binary system, the Red Rectangle, appears to produce much larger grains than does IRC+10216, and we suggest that many of the interstellar and presolar particles with radii >0.35 μm are produced by interacting binary systems rather than single mass-losing stars.

  14. The mass-loss evolution of oxygen-rich AGB stars and its consequences for stellar evolution

    NASA Astrophysics Data System (ADS)

    van der Veen, W. E. C. J.

    1989-02-01

    A semiempirical mass loss equation (MLE) for Asymptotic Giant Branch (AGB) stars with oxygen-rich circumstellar shells is presented. The MLE is a function of stellar luminosity, expansion velocity of the circumstellar shell, and the ratio between the IRAS 25 and 12 micron flux densities. The results are compared with previously derived MLEs. The IRAS Point Source Catalog is used to find the mass loss as a function of time. The MLE is tested by estimating the total mass lost on the AGB. A simple expression is found relating the initial main sequence mass and the maximum AGB luminosity. The time-dependent properties of the MLE are tested using a sample of Miras and OH/IR stars. A relation between period, luminosity, and stellar envelope mass is found and compared with the observed period-luminosity relations for globular cluster Miras and Miras in the LMC. Good agreement is found.

  15. Plant community composition and biomass in Gulf Coast Chenier Plain marshes: Responses to winter burning and structural marsh management

    USGS Publications Warehouse

    Gabrey, S.W.; Afton, A.D.

    2001-01-01

    Many marshes in the Gulf Coast Chenier Plain, USA, are managed through a combination of fall or winter burning and structural marsh management (i.e., levees and water control structures; hereafter SMM). The goals of winter burning and SMM include improvement of waterfowl and furbearer habitat, maintenance of historic isohaline lines, and creation and maintenance of emergent wetlands. Although management practices are intended to influence the plant community, effects of these practices on primary productivity have not been investigated. Marsh processes, such as vertical accretion and nutrient cycles, which depend on primary productivity may be affected directly or indirectly by winter burning or SMM. We compared Chenier Plain plant community characteristics (species composition and above- and belowground biomass) in experimentally burned and unburned control plots within impounded and unimpounded marshes at 7 months (1996), 19 months (1997), and 31 months (1998) after burning. Burning and SMM did not affect number of plant species or species composition in our experiment. For all three years combined, burned plots had higher live above-ground biomass than did unburned plots. Total above-ground and dead above-ground biomasses were reduced in burned plots for two and three years, respectively, compared to those in unburned control plots. During all three years, belowground biomass was lower in impounded than in unimpounded marshes but did not differ between burn treatments. Our results clearly indicate that current marsh management practices influence marsh primary productivity and may impact other marsh processes, such as vertical accretion, that are dependent on organic matter accumulation and decay.

  16. Optically visible post-AGB stars, post-RGB stars and young stellar objects in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Kamath, D.; Wood, P. R.; Van Winckel, H.

    2015-12-01

    We have carried out a search for optically visible post-asymptotic giant branch (post-AGB) stars in the Large Magellanic Cloud (LMC). First, we selected candidates with a mid-IR excess and then obtained their optical spectra. We disentangled contaminants with unique spectra such as M stars, C stars, planetary nebulae, quasi-stellar objects and background galaxies. Subsequently, we performed a detailed spectroscopic analysis of the remaining candidates to estimate their stellar parameters such as effective temperature, surface gravity (log g), metallicity ([Fe/H]), reddening and their luminosities. This resulted in a sample of 35 likely post-AGB candidates with late-G to late-A spectral types, low log g, and [Fe/H] < -0.5. Furthermore, our study confirmed the existence of the dusty post-red giant branch (post-RGB) stars, discovered previously in our Small Magellanic Cloud survey, by revealing 119 such objects in the LMC. These objects have mid-IR excesses and stellar parameters (Teff, log g, [Fe/H]) similar to those of post-AGB stars except that their luminosities (< 2500 L⊙), and hence masses and radii, are lower. These post-RGB stars are likely to be products of binary interaction on the RGB. The post-AGB and post-RGB objects show spectral energy distribution properties similar to the Galactic post-AGB stars, where some have a surrounding circumstellar shell, while some others have a surrounding stable disc similar to the Galactic post-AGB binaries. This study also resulted in a new sample of 162 young stellar objects, identified based on a robust log g criterion. Other interesting outcomes include objects with an UV continuum and an emission line spectrum; luminous supergiants; hot main-sequence stars; and 15 B[e] star candidates, 12 of which are newly discovered in this study.

  17. Aggravated phosphorus limitation on biomass production under increasing nitrogen loading: a meta-analysis.

    PubMed

    Li, Yong; Niu, Shuli; Yu, Guirui

    2016-02-01

    Nitrogen (N) and phosphorus (P), either individually or in combination, have been demonstrated to limit biomass production in terrestrial ecosystems. Field studies have been extensively synthesized to assess global patterns of N impacts on terrestrial ecosystem processes. However, to our knowledge, no synthesis has been done so far to reveal global patterns of P impacts on terrestrial ecosystems, especially under different nitrogen (N) levels. Here, we conducted a meta-analysis of impacts of P addition, either alone or with N addition, on aboveground (AGB) and belowground biomass production (BGB), plant and soil P concentrations, and N : P ratio in terrestrial ecosystems. Overall, our meta-analysis quantitatively confirmed existing notions: (i) colimitation of N and P on biomass production and (ii) more P limitation in tropical forest than other ecosystems. More importantly, our analysis revealed new findings: (i) P limitation on biomass production was aggravated by N enrichment and (ii) plant P concentration was a better indicator of P limitation than soil P availability. Specifically, P addition increased AGB and BGB by 34% and 13%, respectively. The effect size of P addition on biomass production was larger in tropical forest than grassland, wetland, and tundra and varied with P fertilizer forms, P addition rates, or experimental durations. The P-induced increase in biomass production and plant P concentration was larger under elevated than ambient N. Our findings suggest that the global limitation of P on biomass production will become severer under increasing N fertilizer and deposition in the future. PMID:26463578

  18. On the introduction of 17O+p reaction rates evaluated through the THM in AGB nucleosynthesis calculations

    NASA Astrophysics Data System (ADS)

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Spitaleri, C.

    2014-05-01

    The rates for the 17O(p,αα14N, 17O(p,α)18F and 18O(p,α)15N reactions deduced trough the Trojan Horse Method (THM) have been introduced into a state-of-the-art asymptotic giant branch (AGB) models for proton-capture nucleosynthesis and cool bottom process. The predicted abundances have been compared with isotopic compositions provided by geochemical analysis of presolar grains. As a result, an improved agreement is found between the models and the isotopic mix of oxide grains of AGB origins, whose composition is the signature of low-temperature proton-capture nucleosynthesis.

  19. Evolution of thermally pulsing asymptotic giant branch stars. IV. Constraining mass loss and lifetimes of low mass, low metallicity AGB stars

    SciTech Connect

    Rosenfield, Philip; Dalcanton, Julianne J.; Weisz, Daniel; Williams, Benjamin F.; Marigo, Paola; Girardi, Léo; Gullieuszik, Marco; Bressan, Alessandro; Dolphin, Andrew; Aringer, Bernhard

    2014-07-20

    The evolution and lifetimes of thermally pulsating asymptotic giant branch (TP-AGB) stars suffer from significant uncertainties. In this work, we analyze the numbers and luminosity functions of TP-AGB stars in six quiescent, low metallicity ([Fe/H] ≲ –0.86) galaxies taken from the ACS Nearby Galaxy Survey Treasury sample, using Hubble Space Telescope (HST) photometry in both optical and near-infrared filters. The galaxies contain over 1000 TP-AGB stars (at least 60 per field). We compare the observed TP-AGB luminosity functions and relative numbers of TP-AGB and red giant branch (RGB) stars, N{sub TP-AGB}/N{sub RGB}, to models generated from different suites of TP-AGB evolutionary tracks after adopting star formation histories derived from the HST deep optical observations. We test various mass-loss prescriptions that differ in their treatments of mass loss before the onset of dust-driven winds (pre-dust). These comparisons confirm that pre-dust mass loss is important, since models that neglect pre-dust mass loss fail to explain the observed N{sub TP-AGB}/N{sub RGB} ratio or the luminosity functions. In contrast, models with more efficient pre-dust mass loss produce results consistent with observations. We find that for [Fe/H] ≲ –0.86, lower mass TP-AGB stars (M ≲ 1 M{sub ☉}) must have lifetimes of ∼0.5 Myr and higher masses (M ≲ 3 M{sub ☉}) must have lifetimes ≲ 1.2 Myr. In addition, assuming our best-fitting mass-loss prescription, we show that the third dredge-up has no significant effect on TP-AGB lifetimes in this mass and metallicity range.

  20. The effects of rotation on the surface composition and yields of low mass AGB stars.

    NASA Astrophysics Data System (ADS)

    Cristallo, S.; Piersanti, L.; Straniero, O.

    Over the past 20 years, stellar evolutionary models have been strongly improved in order to reproduce with reasonable accuracy both photometric and spectroscopic observations. Notwithstanding, the majority of these models do not take into account macroscopic phenomena, like rotation and/or magnetic fields. Their explicit treatment could modify stellar physical and chemical properties. One of the most interesting problems related to stellar nucleosynthesis is the behavior of the s-process spectroscopic indexes ([hs/ls] and [Pb/hs]) in Asymptotic Giant Branch (AGB) stars. In this contribution we show that, for a fixed metallicity, rotation can lead to a spread in the [hs/ls] and [Pb/hs] in low-mass AGB stars. In particular, we demonstrate that the Eddington-Sweet and the Goldreich-Schubert-Fricke instabilities may have enough time to smear the 13C-pocket (the major neutron source) and the 14N-pocket (the major neutron poison). In fact, a different overlap between these pockets leads to a different neutrons-to-seeds ratio, with important consequences on the corresponding s-process distributions. Possible consequences on the chemical evolution of Galactic globular clusters are discussed.

  1. Calibration of Post-AGB Supergiants as Standard Extragalactic Candles for HST

    NASA Technical Reports Server (NTRS)

    Bond, Howard E.

    1998-01-01

    This report summarizes activities carried out with support from the NASA Ultraviolet, Visible, and Gravitational Astrophysics Research and Analysis Program. The aim of the program is to calibrate the absolute magnitudes of post-asymptotic-giant-branch (post-AGB or PAGB) stars, which we believe will be an excellent new "standard candle" for measuring extragalactic distances. The reason for this belief is that in old populations, the stars that are evolving through the PAGB region of the HR (Hertzsprung-Russell) diagram arise from only a single main-sequence turnoff mass. In addition, the theoretical PAGB evolutionary tracks show that they evolve through this region at constant luminosity; hence the PAGB stars should have an extremely narrow luminosity function. Moreover, as the PAGB stars evolve through spectral types F and A (en route from the AGB to hot stellar remnants and white dwarfs), they have the highest luminosities attained by old stars (both bolometrically and in the visual band). Finally, the PAGB stars of these spectral types are very easily identified, due to their large Balmer jumps, which are due to their very low surface gravities.

  2. Age Dating Merger Events in Early Type Galaxies via the Detection of AGB Light

    NASA Technical Reports Server (NTRS)

    Bothun, G.

    2005-01-01

    A thorough statistical analysis of the J-H vs. H-K color plane of all detected early type galaxies in the 2MASS catalog with velocities less than 5000 km/s has been performed. This all sky survey is not sensitive to one particular galactic environment and therefore a representative range of early type galaxy environments have been sampled. Virtually all N-body simulation so major mergers produces a central starburst due to rapid collection of gas. This central starburst is of sufficient amplitude to change the stellar population in the central regions of the galaxy. Intermediate age populations are given away by the presence of AGB stars which will drive the central colors redder in H-K relative to the J- H baseline. This color anomaly has a lifetime of 2-5 billion years depending on the amplitude of the initial starburst Employing this technique on the entire 2MASS sample (several hundred galaxies) reveals that the AGB signature occurs less than 1% of the time. This is a straightforward indication that virtually all nearby early type galaxies have not had a major merger occur within the last few billion years.

  3. An Analysis and Classification of Dying AGB Stars Transitioning to Pre-Planetary Nebulae

    NASA Technical Reports Server (NTRS)

    Blake, Adam C.

    2011-01-01

    The principal objective of the project is to understand part of the life and death process of a star. During the end of a star's life, it expels its mass at a very rapid rate. We want to understand how these Asymptotic Giant Branch (AGB) stars begin forming asymmetric structures as they start evolving towards the planetary nebula phase and why planetary nebulae show a very large variety of non-round geometrical shapes. To do this, we analyzed images of just-forming pre-planetary nebula from Hubble surveys. These images were run through various image correction processes like saturation correction and cosmic ray removal using in-house software to bring out the circumstellar structure. We classified the visible structure based on qualitative data such as lobe, waist, halo, and other structures. Radial and azimuthal intensity cuts were extracted from the images to quantitatively examine the circumstellar structure and measure departures from the smooth spherical outflow expected during most of the AGB mass-loss phase. By understanding the asymmetrical structure, we hope to understand the mechanisms that drive this stellar evolution.

  4. Pulsational variability in proto-planetary nebulae and other post-AGB objects

    NASA Astrophysics Data System (ADS)

    Hrivnak, Bruce J.

    2016-07-01

    Light and velocity curves of several classes of pulsating stars have been successfully modeled to determine physical properties of the stars. In this observational study, we review briefly the pulsational variability of the main classes of post-AGB stars. Our attention is focused in particular on proto-planetary nebulae (PPNe), those in the short-lived phase from AGB stars to the planetary nebulae. New light curves and period analyses have been used to determine the following general properties of the PPNe variability: (a) periods range from 35 to 160 days for those of F—G spectral types, with much shorter periods (< 1 day) found for those of early-B spectral type; (b) there is a correlation between the pulsation period, maximum amplitude, and temperature of the star, with cooler stars pulsating with longer periods and larger amplitudes; (c) similar correlations are found for carbon-rich, oxygen-rich, and lower-metalicity PPNe; and (d) multiple periods are found for all of them, with P2/P1 = 1.0±0.1. New models are needed to exploit these results.

  5. Detecting tropical forest biomass dynamics from repeated airborne Lidar measurements

    NASA Astrophysics Data System (ADS)

    Meyer, V.; Saatchi, S. S.; Chave, J.; Dalling, J.; Bohlman, S.; Fricker, G. A.; Robinson, C.; Neumann, M.

    2013-02-01

    Reducing uncertainty of terrestrial carbon cycle depends strongly on the accurate estimation of changes of global forest carbon stock. However, this is a challenging problem from either ground surveys or remote sensing techniques in tropical forests. Here, we examine the feasibility of estimating changes of tropical forest biomass from two airborne Lidar measurements acquired about 10 yr apart over Barro Colorado Island (BCI), Panama from high and medium resolution airborne sensors. The estimation is calibrated with the forest inventory data over 50 ha that was surveyed every 5 yr during the study period. We estimated the aboveground forest biomass and its uncertainty for each time period at different spatial scales (0.04, 0.25, 1.0 ha) and developed a linear regression model between four Lidar height metrics and the aboveground biomass. The uncertainty associated with estimating biomass changes from both ground and Lidar data was quantified by propagating measurement and prediction errors across spatial scales. Errors associated with both the mean biomass stock and mean biomass change declined with increasing spatial scales. Biomass changes derived from Lidar and ground estimates were largely (36 out 50 plots) in the same direction at the spatial scale of 1 ha. Lidar estimation of biomass was accurate at the 1 ha scale (R2 = 0.7 and RMSEmean = 28.6 Mg ha-1). However, to predict biomass changes, errors became comparable to ground estimates only at about 10-ha or more. Our results indicate that the 50-ha BCI plot lost a~significant amount of biomass (-0.8 ± 2.2 Mg ha-1 yr-1) over the past decade (2000-2010). Over the entire island and during the same period, mean AGB change is -0.4 ± 3.7 Mg ha-1 yr-1. Old growth forests lost biomass (-0.7 ± 3.5 Mg ha-1 yr-1), whereas the secondary forests gained biomass (+0.4 ± 3.4 Mg ha-1 yr-1). Our analysis demonstrates that repeated Lidar surveys, even with two different sensors, is able to estimate biomass changes in old

  6. Analysis of results of biomass forest inventory in northeastern Amazon for development of REDD+ carbon project.

    PubMed

    Mello, Leonel N C; Sales, Marcio H R; Rosa, Luiz P

    2016-03-01

    In Brazil, a significant reduction in deforestation rates occurred during the last decade. In spite of that fact, the average annual rates are still too high, approximately 400.000 ha/year (INPE/Prodes). The projects of emissions reduction through avoided deforestation (REED+) are an important tool to reduce deforestation rates in Brazil. Understanding the amazon forest structure, in terms of biomass stock is key to design avoided deforestation strategies. In this work, we analyze data results from aboveground biomass of 1,019.346,27 hectares in the state of Pará. It was collected data from 16,722 trees in 83 random independent plots. It was tested 4 allometric equations, for DBH > 10cm: Brown et al. (1989), Brown and Lugo (1999), Chambers et al. (2000), Higuchi et al. (1998). It revealed that the biggest carbon stock of above ground biomass is stocked on the interval at DBH between 30cm and 80cm. This biomass compartment stocks 75.70% of total biomass in Higuchi et al. (1998) equation, 75.56% of total biomass in Brown et al. (1989) equation, 78.83% of total biomass in Chambers et al. (2000) equation, and 73.22% in Brown and Lugo (1999) equation. PMID:26959317

  7. Simulations of Forest Structure and Biomass across Russia for Biomass Estimation under a Changing Climate.

    NASA Astrophysics Data System (ADS)

    Shugart, H. H., Jr.; Shuman, J. K.

    2014-12-01

    An important innovation in understanding the interactions among physical of forests and measurement of forest state is the potential deployment of active (RADAR and LiDAR) satellite reconnaissance systems. We investigate the potential gain in predictive capability of structural measures determined by these instruments. Observations and model results have identified climate change as a driver of structural and compositional change in forest of Russia, which may affect climate patterns beyond the region. Using an individual-tree-based model (UVAFME) for forests at 31,000+ grid points of a 22 km×22 km grid across Russia, we inspected the relationships between above-ground biomass and structural measures including maximum tree height and Lorey's height (average height for each tree weighted by basal area). At each of the grid points 200 independent 0.1hectare plots were simulated for 100 years using two climate change scenarios following a 500-year spin-up to produce a mature forest. Other simulations project the change of a forest-landscape mosaic with equal proportions of 0, 25, 50, 75 and 100 year-old stands to mimic a heterogeneous landscape mosaic typical of reoccurring wildfires. Qualitatively, maximum height and Lorey's height seem particularly useful in detecting forest change in the vicinity of forest transitions with other ecosystems. Quantitatively, maximum height and Lorey's height account for a large component of the variability in forest biomass. Results of exponential regression between height measurements and biomass show that r2 values can exceed 0.75. Lorey's height is more capable in this regard. The relationship between these measures of height and biomass can be improved with classification of forests into types. For example, Russian forest dominated by the tall, large diameter pines (Pinus koraiensis, P. sibirica, P. sylvestris) can have exceptional biomass compared to other forests across Russia, and produced biomass and height values higher

  8. Biomass torrefaction mill

    DOEpatents

    Sprouse, Kenneth M.

    2016-05-17

    A biomass torrefaction system includes a mill which receives a raw biomass feedstock and operates at temperatures above 400 F (204 C) to generate a dusty flue gas which contains a milled biomass product.

  9. Biomass Energy Research

    SciTech Connect

    Traylor, T.D.; Pitsenbarger, J.

    1996-03-01

    Biomass Energy Research announces on a bimonthly basis the current worldwide research and development (R&D) information available on biomass power systems, alternate feedstocks from biomass, and biofuels supply options.

  10. Quantification of uncertainty in aboveground biomass estimates derived from small-footprint LiDAR data

    NASA Astrophysics Data System (ADS)

    Xu, Q.; Greenberg, J. A.; Li, B.; Ramirez, C.; Balamuta, J. J.; Evans, K.; Man, A.; Xu, Z.

    2015-12-01

    A promising approach to determining aboveground biomass (AGB) in forests comes through the use of individual tree crown delineation (ITCD) techniques applied to small-footprint LiDAR data. These techniques, when combined with allometric equations, can produce per-tree estimates of AGB. At this scale, AGB estimates can be quantified in a manner similar to how ground-based forest inventories are produced. However, these approaches have significant uncertainties that are rarely described in full. Allometric equations are often based on species-specific diameter-at-breast height (DBH) relationships, but neither DBH nor species can be reliably determined using remote sensing analysis. Furthermore, many approaches to ITCD only delineate trees appearing in the upper canopy so subcanopy trees are often missing from the inventories. In this research, we performed a propagation-of-error analysis to determine the spatially varying uncertainties in AGB estimates at the individual plant and stand level for a large collection of LiDAR acquisitions covering a large portion of California. Furthermore, we determined the relative contribution of various aspects of the analysis towards the uncertainty, including errors in the ITCD results, the allometric equations, the taxonomic designation, and the local biophysical environment. Watershed segmentation was used to obtain the preliminary crown segments. Lidar points within the preliminary segments were extracted to form profiling data of the segments, and then mode detection algorithms were applied to identify the tree number and tree heights within each segment. As part of this analysis, we derived novel "remote sensing aware" allometric equations and their uncertainties based on three-dimensional morphological metrics that can be accurately derived from LiDAR data.

  11. Massive Open Online Courses (MOOCs): A Primer for University and College Board Members. An AGB White Paper

    ERIC Educational Resources Information Center

    Voss, Brian D.

    2013-01-01

    The environment in which MOOCs and other forms of online education operate is changing virtually every day. Based upon a presentation given to the board of directors of AGB, this white paper is an effort to give board chairs, presidents, and others some context to help guide discussions on their own campuses. It provides a primer on MOOCs,…

  12. SMA Spectral Line Imaging Survey at 279 - 355 GHz of the Oxygen-rich AGB Star IK Tau

    NASA Astrophysics Data System (ADS)

    De Beck, E.; Kamiński, T.; Menten, K. M.; Patel, N. A.; Young, K. H.; Gottlieb, C. A.

    2015-08-01

    Dedicated, unbiased spectral scans of asymptotic giant branch stars have so far been published only for a few carbon-rich stars, with a strong focus on the nearby and bright IRC +10216. We present results from a spectral survey of the circumstellar envelope of the oxygen-rich AGB star IK Tau obtained with the Submillimeter Array (SMA) at ~ 0'.9 angular resolution in the frequency range 279-355 GHz, expanding the molecular inventory for M-type evolved stars and filling an observational gap. The survey shows over 140 emission lines, belonging to more than 30 species. The emission of AlO and of several vibrationally excited species traces the acceleration of the wind. Isotopic ratios for carbon, silicon, and sulfur will be derived from the observed emission of isotopologues of CO, SiO, SiS, HCN, SO, and SO2. This will allow us to constrain the AGB nucleosynthesis of IK Tau. We highlight the first detection of PO and PN around an oxygen-rich AGB star, detected at unexpectedly high abundances, and emphasise the importance of unbiased spectral surveys of AGB stars and the need for updated chemical models.

  13. AGB nucleosynthesis at low metallicity: What can we learn from Carbon- and s-elements-enhanced metal-poor stars

    NASA Astrophysics Data System (ADS)

    Abate, C.; Pols, O. R.; Izzard, R. G.; Karakas, A. I.

    2013-02-01

    CEMP-s stars are very metal-poor stars with enhanced abundances of carbon and s-process elements. They form a significant proportion of the very metal-poor stars in the Galactic halo and are mostly observed in binary systems. This suggests that the observed chemical anomalies are due to mass accretion in the past from an asymptotic giant branch (AGB) star. Because CEMP-s stars have hardly evolved since their formation, the study of their observed abundances provides a way to probe our models of AGB nucleosynthesis at low metallicity. To this end we included in our binary evolution model the results of the latest models of AGB nucleosynthesis and we simulated a grid of 100 000 binary stars at metallicity Z = 0.0001 in a wide range of initial masses and separations. We compared our modelled stars with a sample of 60 CEMP-s stars from the SAGA database of metal-poor stars. For each observed CEMP-s star of the sample we found the modelled star that reproduces best the observed abundances. The result of this comparison is that we are able to reproduce simultaneously the observed abundance of the elements affected by AGB nucleosynthesis (e.g. C, Mg, s-elements) for about 60% of the stars in the sample.

  14. Testing the effect of continuum elimination methods on studies of infrared dust features from AGB star spectra

    NASA Astrophysics Data System (ADS)

    Delisle, Colby; Speck, A.

    2014-01-01

    Asymptotic Giant Branch (AGB) stars are major contributors of cosmic dust to the interstellar medium. Understanding the cosmic dust ejected from these stars is essential to understanding the broader topics of evolution and composition of stellar and interstellar objects in our universe. AGB stars produce either carbon- or oxygen (O)-rich dust. O-rich AGB stars have been classified into groups according to the shapes of their spectral features in the mid-infrared (IR). Because their spectral features are similar, stars within each group are expected to have similar dust shell parameters, especially with respect to the composition of the dust. We have selected a sample of 26 O-rich AGB stars, in a single group in order to investigate an apparently homogenous group of stars. In particular, we chose stars in group SE1. Using spectral data from the Infrared Space Observatory (ISO), and the Infrared Astronomical Satellite (IRAS) we investigated variations in the spectral parameters of these stars: i.e. continuum temperature, feature strength, peak position(s), FWHM. In this preliminary work we present a study of the effect of the methods by which we eliminate the continuum prior to measuring the feature parameters.

  15. A Forest Biomass Survey by Bitterlich Method With an Electronic Relascope for Satellite Data Validation

    NASA Astrophysics Data System (ADS)

    Suzuki, R.; Ishii, R.; Takao, G.; Nakano, T.; Yasuda, T.

    2006-12-01

    For the better understanding of the carbon cycle in the global ecosystem, an investigation on the spatio- temporal variation of the carbon stock which is stored as vegetation biomass should be important. "PALSAR (Phased Array type L-band Synthetic Aperture Radar)", an onboard sensor of the polar orbiting satellite "ALOS (Advanced Land Observing Satellite)" launched in January 2006, provides the information which can be used for the above-ground biomass estimation. It is expected that ALOS/PALSAR provides us a great opportunity to analyze the biomass dynamics over extensive regions. To derive the biomass from the ALOS/PALSAR measurement, it is inevitable to acquire in situ biomass measurement by ground-based forest surveys. Moreover, it is required to obtain such ground-based information at as possible many sites, because the region targeted by satellite remote sensing is extensive and the forest structure in that region is various. Therefore, a quick forest survey will be required to measure the biomass at as possible many sites. For the quick measurement of the forest above-ground biomass, we propose a way that is a combination of Bitterlich angle count sampling method and sampled-tree measuring method. First, a tree which has wider trunk than the basal area factor (BAF) angle is identified by the relascope from a representative point in the target forest. Next, the tree height and the breast height diameter (DBH) of the sampled tree are measured. The biomass of the tree is estimate by the allometric equation with the tree height and DBH measurements. Through these processes, the biomass density of the sampled tree per the forest area defined by the BAF is estimated. By sampling and measuring all trees (usually around 20 trees), the biomass of the forest can be estimate. A brand-new electronic relascope (Criterion RD 1000, Laser Technology Inc.) and laser range finder (TruPulse 200, Laser Technology Inc.) are used for the tree height and DBH measurements to

  16. ESTIMATION OF TROPICAL FOREST STRUCTURE AND BIOMASS FROM FUSION OF RADAR AND LIDAR MEASUREMENTS (Invited)

    NASA Astrophysics Data System (ADS)

    Saatchi, S. S.; Dubayah, R.; Clark, D. B.; Chazdon, R.

    2009-12-01

    Radar and Lidar instruments are active remote sensing sensors with the potential of measuring forest vertical and horizontal structure and the aboveground biomass (AGB). In this paper, we present the analysis of radar and lidar data acquired over the La Selva Biological Station in Costa Rica. Radar polarimetry at L-band (25 cm wavelength), P-band (70 cm wavelength) and interferometry at C-band (6 cm wavelength) and VV polarization were acquired by the NASA/JPL airborne synthetic aperture radar (AIRSAR) system. Lidar images were provided by a large footprint airborne scanning Lidar known as the Laser Vegetation Imaging Sensor (LVIS). By including field measurements of structure and biomass over a variety of forest types, we examined: 1) sensitivity of radar and lidar measurements to forest structure and biomass, 2) accuracy of individual sensors for AGB estimation, and 3) synergism of radar imaging measurements with lidar imaging and sampling measurements for improving the estimation of 3-dimensional forest structure and AGB. The results showed that P-band radar combined with any interformteric measurement of forest height can capture approximately 85% of the variation of biomass in La Selva at spatial scales larger than 1 hectare. Similar analysis at L-band frequency captured only 70% of the variation. However, combination of lidar and radar measurements improved estimates of forest three-dimensional structure and biomass to above 90% for all forest types. We present a novel data fusion approach based on a Baysian estimation model with the capability of incorporating lidar samples and radar imagery. The model was used to simulate the potential of data fusion in future satellite mission scenarios as in BIOMASS (planned by ESA) at P-band and DESDynl (planned by NASA) at L-band. The estimation model was also able to quantify errors and uncertainties associated with the scale of measurements, spatial variability of forest structure, and differences in radar and lidar

  17. Response of aboveground biomass and diversity to nitrogen addition – a five-year experiment in semi-arid grassland of Inner Mongolia, China

    PubMed Central

    He, Kejian; Qi, Yu; Huang, Yongmei; Chen, Huiying; Sheng, Zhilu; Xu, Xia; Duan, Lei

    2016-01-01

    Understanding the response of the plant community to increasing nitrogen (N) deposition is helpful for improving pasture management in semi-arid areas. We implemented a 5-year N addition experiment in a Stipa krylovii steppe of Inner Mongolia, northern China. The aboveground biomass (AGB) and species richness were measured annually. Along with the N addition levels, the species richness declined significantly, and the species composition changed noticeably. However, the total AGB did not exhibit a noticeable increase. We found that compensatory effects of the AGB occurred not only between the grasses and the forbs but also among Gramineae species. The plant responses to N addition, from the community to species level, lessened in dry years compared to wet or normal years. The N addition intensified the reduction of community productivity in dry years. Our study indicated that the compensatory effects of the AGB among the species sustained the stability of grassland productivity. However, biodiversity loss resulting from increasing N deposition might lead the semi-arid grassland ecosystem to be unsustainable, especially in dry years. PMID:27573360

  18. Response of aboveground biomass and diversity to nitrogen addition - a five-year experiment in semi-arid grassland of Inner Mongolia, China.

    PubMed

    He, Kejian; Qi, Yu; Huang, Yongmei; Chen, Huiying; Sheng, Zhilu; Xu, Xia; Duan, Lei

    2016-01-01

    Understanding the response of the plant community to increasing nitrogen (N) deposition is helpful for improving pasture management in semi-arid areas. We implemented a 5-year N addition experiment in a Stipa krylovii steppe of Inner Mongolia, northern China. The aboveground biomass (AGB) and species richness were measured annually. Along with the N addition levels, the species richness declined significantly, and the species composition changed noticeably. However, the total AGB did not exhibit a noticeable increase. We found that compensatory effects of the AGB occurred not only between the grasses and the forbs but also among Gramineae species. The plant responses to N addition, from the community to species level, lessened in dry years compared to wet or normal years. The N addition intensified the reduction of community productivity in dry years. Our study indicated that the compensatory effects of the AGB among the species sustained the stability of grassland productivity. However, biodiversity loss resulting from increasing N deposition might lead the semi-arid grassland ecosystem to be unsustainable, especially in dry years. PMID:27573360

  19. A G-Protein β Subunit, AGB1, Negatively Regulates the ABA Response and Drought Tolerance by Down-Regulating AtMPK6-Related Pathway in Arabidopsis

    PubMed Central

    Xu, Dong-bei; Chen, Ming; Ma, Ya-nan; Xu, Zhao-shi; Li, Lian-cheng; Chen, Yao-feng; Ma, You-zhi

    2015-01-01

    Heterotrimeric G-proteins are versatile regulators involved in diverse cellular processes in eukaryotes. In plants, the function of G-proteins is primarily associated with ABA signaling. However, the downstream effectors and the molecular mechanisms in the ABA pathway remain largely unknown. In this study, an AGB1 mutant (agb1-2) was found to show enhanced drought tolerance, indicating that AGB1 might negatively regulate drought tolerance in Arabidopsis. Data showed that AGB1 interacted with protein kinase AtMPK6 that was previously shown to phosphorylate AtVIP1, a transcription factor responding to ABA signaling. Our study found that transcript levels of three ABA responsive genes, AtMPK6, AtVIP1 and AtMYB44 (downstream gene of AtVIP1), were significantly up-regulated in agb1-2 lines after ABA or drought treatments. Other ABA-responsive and drought-inducible genes, such as RD29A (downstream gene of AtMYB44), were also up-regulated in agb1-2 lines. Furthermore, overexpression of AtVIP1 resulted in hypersensitivity to ABA at seed germination and seedling stages, and significantly enhanced drought tolerance in transgenic plants. These results suggest that AGB1 was involved in the ABA signaling pathway and drought tolerance in Arabidopsis through down-regulating the AtMPK6, AtVIP1 and AtMYB44 cascade. PMID:25635681

  20. My Biomass, Your Biomass, Our Solution

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The US is pursuing an array of renewable energy sources to reduce reliance on imported fossil fuels and reduce greenhouse gas emissions. Biomass energy and biomass ethanol are key components in the pursuit. The need for biomass feedstock to produce sufficient ethanol to meet any of the numerous stat...

  1. Detection of CI line emission from the detached CO shell of the AGB star R Sculptoris

    NASA Astrophysics Data System (ADS)

    Olofsson, H.; Bergman, P.; Lindqvist, M.

    2015-10-01

    Context. Stars on the asymptotic giant branch (AGB) lose substantial amounts of matter, to the extent that they are important for the chemical evolution of, and dust production in, the Universe. The mass loss is believed to increase gradually with age on the AGB, but it may also occur in the form of bursts, possibly related to the thermal pulsing phenomenon. Detached, geometrically thin, CO shells around carbon stars are good signposts of brief and intense mass ejection. Aims: We aim to put further constraints on the physical properties of detached CO shells around AGB stars. Methods: The photodissociation of CO and other carbon-bearing species in the shells leads to the possibility of detecting lines from neutral carbon. We have therefore searched for the CI(3P1-3P0) line at 492 GHz towards two carbon stars, S Sct and R Scl, with detached CO shells of different ages, ≈8000 and 2300 years, respectively. Results: The CI(3P1-3P0) line was detected towards R Scl. The line intensity is dominated by emission from the detached shell. The detection is at a level consistent with the neutral carbon coming from the full photodissociation of all species except CO, and with only limited photoionisation of carbon. The best fit to the observed 12CO and 13CO line intensities, assuming a homogeneous shell, is obtained for a shell mass of ≈0.002 M⊙, a temperature of ≈100 K, and a CO abundance with respect to H2 of 10-3. The estimated CI/CO abundance ratio is ≈0.3 for the best-fit model. However, a number of arguments point in the direction of a clumpy medium, and a viable interpretation of the data within such a context is provided. Based on observations with the Atacama Pathfinder EXperiment (APEX) telescope. APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.

  2. A Photometric and Spectroscopic Survey of AGB Stars in M31

    NASA Astrophysics Data System (ADS)

    Brewer, James P.

    1996-04-01

    Asymptotic giant-branch (AGB) stars are identified and classified in five 7' X 7' fields spaced along M31's SW semi-major axis using a four band photometric system. An investigation of the AGB luminosity functions and red giant-branch widths reveals significant differences between the star forming histories of the five fields. The distance modulus of M31 is derived using carbon stars (C-stars) and found to be consistent with both a value obtained from Cepheids and with values in the literature. The ratio of AGB C- to M-stars (C/M ratio) in the five fields is found to increase with galactocentric distance and it is shown that photometric incompleteness is not responsible for this effect. This is the first clear demonstration of a varying C/M ratio in an external galaxy. The C/M ratios appear to be insensitive to star-forming history differences but sensitive to metallicity differences between the fields. Previous observations are used to define a relationship between the C/M ratio and metallicity, and this is used to obtain estimates of the field metallicities. These estimates are found to be consistent with a previous measurement of M31's metallicity gradient. The C/M ratios measured in M31 indicate that the composition of M31's interstellar medium may be position dependent, and evidence is cited in favour of this. Follow up spectroscopy was obtained in two of the five fields, and is used to show that the photometric system did an excellent job of discriminating between M-, S- and C-stars. Of the 48 C-stars for which spectra were obtained, 7 have strongly enhanced 13C bands (J-stars), 2 have strong H-alpha emission, while 3 are found to exhibit enhanced Li absorption (Li-stars). Both the J- and Li-stars are fainter than predicted by current theoretical models, while the colours of the H-alpha stars suggest they may be in the terminal phases of their evolution. The C_2 and CN bandstrengths of the C-stars are measured, and no correlation between these bandstrengths

  3. A Photometric and Spectroscopic Survey of AGB Stars in M31

    NASA Astrophysics Data System (ADS)

    Brewer, James Philip

    1996-01-01

    Asymptotic giant-branch (AGB) stars are identified and classified in five 7^'times7 ^' fields spaced along M31's SW semi-major axis using a four band photometric system. An investigation of the AGB luminosity functions and red giant -branch widths reveals significant differences between the star forming histories of the five fields. The distance modulus of M31 is derived using carbon stars (C-stars) and found to be consistent with both a value obtained from Cepheids and with values in the literature. The ratio of AGB C- to M-stars (C/M ratio) in the five fields is found to increase with galactocentric distance and it is shown that photometric incompleteness is not responsible for this effect. This is the first clear demonstration of a varying C/M ratio in an external galaxy. The C/M ratios appear to be insensitive to star -forming history differences but sensitive to metallicity differences between the fields. Previous observations are used to define a relationship between the C/M ratio and metallicity, and this is used to obtain estimates of the field metallicities. These estimates are found to be consistent with a previous measurement of M31's metallicity gradient. The C/M ratios measured in M31 indicate that the composition of M31's interstellar medium may be position dependent, and evidence is cited in favour of this. Follow up spectroscopy was obtained in two of the five fields, and is used to show that the photometric system did an excellent job of discriminating between M -, S- and C-stars. Of the 48 C-stars for which spectra were obtained, 7 have strongly enhanced ^ {13}C bands (J-stars), 2 have strong H alpha emission, while 3 are found to exhibit enhanced Li absorption (Li-stars). Both the J- and Li-stars are fainter than predicted by current theoretical models, while the colours of the Hα stars suggest they may be in the terminal phase of their evolution. The C_2 and CN bandstrengths of the C-stars are measured, and no correlation between these

  4. Presolar Graphite from AGB Stars: Microstructure and s-Process Enrichment

    NASA Astrophysics Data System (ADS)

    Croat, Thomas K.; Stadermann, Frank J.; Bernatowicz, Thomas J.

    2005-10-01

    Correlated transmission electron microscopy and secondary ion mass spectrometry with submicron spatial resolution (NanoSIMS) investigations of the same presolar graphites spherules from the Murchison meteorite were conducted, to link the isotopic anomalies with the mineralogy and chemical composition of the graphite and its internal grains. Refractory carbide grains (especially titanium carbide) are commonly found within the graphite spherules, and most have significant concentrations of Zr, Mo, and Ru in solid solution, elements primarily produced by s-process nucleosynthesis. The effect of chemical fractionation on the Mo/Ti ratio in these carbides is limited, and therefore from this ratio one can infer the degree of s-process enrichment in the gas from which the graphite condensed. The resulting s-process enrichments within carbides are large (~200 times solar on average), showing that most of the carbide-containing graphites formed in the mass outflows of asymptotic giant branch (AGB) stars. NanoSIMS measurements of these graphites also show isotopically light carbon (mostly in the 100<12C/13C<400 range). The enrichment of these presolar graphites in both s-process elements and 12C considerably exceeds that astronomically observed around carbon stars. However, a natural correlation exists between 12C and s-process elements, as both form in the He intershell region of thermally pulsing AGB stars and are dredged up together to the surface. Their observation together suggests that these graphites may have formed in chemically and isotopically inhomogeneous regions around AGB stars, such as high-density knots or jets. As shown in the companion paper, a gas density exceeding that expected for smooth mass outflows is required for graphite of the observed size to condense at all in circumstellar environments, and the spatially inhomogeneous, high-density regions from which they condense may also be incompletely mixed with the surrounding gas. We have greatly expanded

  5. Pattern and dynamics of biomass stock in old growth forests: The role of habitat and tree size

    NASA Astrophysics Data System (ADS)

    Yuan, Zuoqiang; Gazol, Antonio; Wang, Xugao; Lin, Fei; Ye, Ji; Zhang, Zhaochen; Suo, YanYan; Kuang, Xu; Wang, Yunyun; Jia, Shihong; Hao, Zhanqing

    2016-08-01

    Forest ecosystems play a fundamental role in the global carbon cycle. However, how stand-level changes in tree age and structure influence biomass stock and dynamics in old-growth forests is a question that remains unclear. In this study, we quantified the aboveground biomass (AGB) standing stock, the coarse woody productivity (CWP), and the change in biomass over ten years (2004-2014) in a 25 ha unmanaged broad-leaved Korean pine mixed forest in northeastern China. In addition, we quantified how AGB stock and change (tree growth, recruitment and mortality) estimations are influenced by the variation in habitat heterogeneity, tree size structure and subplot size. Our analysis indicated that Changbai forest had AGB of 265.4 Mg ha-1 in 2004, and gained1.36 Mg ha-1 y-1 between 2004 and 2014. Despite recruitment having better performance in nutrient rich habitat, we found that there is a directional tree growth trend independent of habitat heterogeneity for available nutrients in this old growth forest. The observed increases in AGB stock (∼70%) are mainly attributed to the growth of intermediate size trees (30-70 cm DBH), indicating that this forest is still reaching its mature stage. Meanwhile, we indicated that biomass loss due to mortality reduces living biomass, not increment, may be the primary factor to affect forest biomass dynamics in this area. Also, spatial variation in forest dynamics is large for small sizes (i.e. coefficient of variation in 20 × 20 m subplots is 53.2%), and more than 90 percent of the inherent variability of these coefficients was predicted by a simple model including plot size. Our result provides a mean by which to estimate within-plot variability at a local scale before inferring any directional change in forest dynamics at a regional scale, and information about the variability of forest structure and dynamics are fundamental to design effective sampling strategies in future study.

  6. Evolution of Thermally Pulsing Asymptotic Giant Branch Stars. V. Constraining the Mass Loss and Lifetimes of Intermediate-mass, Low-metallicity AGB Stars

    NASA Astrophysics Data System (ADS)

    Rosenfield, Philip; Marigo, Paola; Girardi, Léo; Dalcanton, Julianne J.; Bressan, Alessandro; Williams, Benjamin F.; Dolphin, Andrew

    2016-05-01

    Thermally pulsing asymptotic giant branch (TP-AGB) stars are relatively short lived (less than a few Myr), yet their cool effective temperatures, high luminosities, efficient mass loss, and dust production can dramatically affect the chemical enrichment histories and the spectral energy distributions of their host galaxies. The ability to accurately model TP-AGB stars is critical to the interpretation of the integrated light of distant galaxies, especially in redder wavelengths. We continue previous efforts to constrain the evolution and lifetimes of TP-AGB stars by modeling their underlying stellar populations. Using Hubble Space Telescope (HST) optical and near-infrared photometry taken of 12 fields of 10 nearby galaxies imaged via the Advanced Camera for Surveys Nearby Galaxy Survey Treasury and the near-infrared HST/SNAP follow-up campaign, we compare the model and observed TP-AGB luminosity functions as well as the ratio of TP-AGB to red giant branch stars. We confirm the best-fitting mass-loss prescription, introduced by Rosenfield et al., in which two different wind regimes are active during the TP-AGB, significantly improves models of many galaxies that show evidence of recent star formation. This study extends previous efforts to constrain TP-AGB lifetimes to metallicities ranging ‑1.59 ≲ {{[Fe/H]}} ≲ ‑0.56 and initial TP-AGB masses up to ˜4 M ⊙, which include TP-AGB stars that undergo hot-bottom burning. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  7. Evolution of Thermally Pulsing Asymptotic Giant Branch Stars. V. Constraining the Mass Loss and Lifetimes of Intermediate-mass, Low-metallicity AGB Stars

    NASA Astrophysics Data System (ADS)

    Rosenfield, Philip; Marigo, Paola; Girardi, Léo; Dalcanton, Julianne J.; Bressan, Alessandro; Williams, Benjamin F.; Dolphin, Andrew

    2016-05-01

    Thermally pulsing asymptotic giant branch (TP-AGB) stars are relatively short lived (less than a few Myr), yet their cool effective temperatures, high luminosities, efficient mass loss, and dust production can dramatically affect the chemical enrichment histories and the spectral energy distributions of their host galaxies. The ability to accurately model TP-AGB stars is critical to the interpretation of the integrated light of distant galaxies, especially in redder wavelengths. We continue previous efforts to constrain the evolution and lifetimes of TP-AGB stars by modeling their underlying stellar populations. Using Hubble Space Telescope (HST) optical and near-infrared photometry taken of 12 fields of 10 nearby galaxies imaged via the Advanced Camera for Surveys Nearby Galaxy Survey Treasury and the near-infrared HST/SNAP follow-up campaign, we compare the model and observed TP-AGB luminosity functions as well as the ratio of TP-AGB to red giant branch stars. We confirm the best-fitting mass-loss prescription, introduced by Rosenfield et al., in which two different wind regimes are active during the TP-AGB, significantly improves models of many galaxies that show evidence of recent star formation. This study extends previous efforts to constrain TP-AGB lifetimes to metallicities ranging ‑1.59 ≲ {{[Fe/H]}} ≲ ‑0.56 and initial TP-AGB masses up to ∼4 M ⊙, which include TP-AGB stars that undergo hot-bottom burning. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  8. Infrared photometry and evolution of mass-losing AGB stars. III. Mass loss rates of MS and S stars

    NASA Astrophysics Data System (ADS)

    Guandalini, R.

    2010-04-01

    Context. The asymptotic giant branch (AGB) phase marks the end of the evolution for low- and intermediate-mass stars, which are fundamental contributors to the mass return to the interstellar medium and to the chemical evolution of galaxies. The detailed understanding of mass loss processes is hampered by the poor knowledge of the luminosities and distances of AGB stars. Aims: In a series of papers we are trying to establish criteria permitting a more quantitative determination of luminosities for the various types of AGB stars, using the infrared (IR) fluxes as a basis. An updated compilation of the mass loss rates is also required, as it is crucial in our studies of the evolutionary properties of these stars. In this paper we concentrate our analysis on the study of the mass loss rates for a sample of galactic S stars. Methods: We reanalyze the properties of the stellar winds for a sample of galactic MS, S, SC stars with reliable estimates of the distance on the basis of criteria previously determined. We then compare the resulting mass loss rates with those previously obtained for a sample of C-rich AGB stars. Results: Stellar winds in S stars are on average less efficient than those of C-rich AGB stars of the same luminosity. Near-to-mid infrared colors appear to be crucial in our analysis. They show a good correlation with mass loss rates in particular for the Mira stars. We suggest that the relations between the rates of the stellar winds and both the near-to-mid infrared colors and the periods of variability improve the understanding of the late evolutionary stages of low mass stars and could be the origin of the relation between the rates of the stellar winds and the bolometric magnitudes.

  9. VizieR Online Data Catalog: NGC 2808 AGB and RGB stars Na abundance (Wang+, 2016)

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Primas, F.; Charbonnel, C.; van der Swaelmen, M.; Bono, G.; Chantereau, W.; Zhao, G.

    2016-05-01

    The high-resolution spectra of our sample of AGB and RGB stars in the Galactic globular cluster NGC 2808 were obtained with the high-resolution multi-object spectrograph FLAMES, mounted on ESO/VLT-UT2. A combined mode was used where the brightest five objects was observed with UVES-fibre and the remaining targets with GIRAFFE/Medusa. The basic information of our sample stars are listed in Table 2, including the evolutionary phase, instrument used for observation, coordinates, photometry and barycentric radial velocity. Our Fe abundances were derived from the equivalent widths of Fe lines, while the Na abundances were determined with spectra synthesis. Both FeI and Na abundances have been corrected for the non-LTE effect. In Table 4 we show the derived stellar parameters of our sample stars, and the Na abundances are shown in Table 6. (3 data files).

  10. The detection of heavy metals in the circumstellar envelopes of post-AGB stars

    NASA Astrophysics Data System (ADS)

    Klochkova, V. G.; Panchuk, V. E.

    2016-03-01

    A new kind of peculiarity is discussed: splitting or asymmetry of strong absorption lines in the optical spectra of selected post-AGB stars with carbon envelopes and atmospheres enriched in carbon and s-process heavy metals. This effect is strongest for BaII ions, whose lines can be split into two or three components. Infrared and radio spectroscopy data are used to demonstrate that the individual components of split absorption lines are formed in structured circumstellar envelopes. Thus, this effect reveals efficient enrichment of the envelope in heavy metals synthesized during the star's earlier evolution. The nature of the strong absorption profile (split or asymmetric, number of components) could be related to the morphology and kinematical and chemical properties of the enenvelope.

  11. Optically Visible Post-AGB and Post-RGB Stars in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Kamath, D.; Wood, P. R.; Van Winckel, H.

    2015-08-01

    We have performed an extensive low-resolution (R ≍ 1300) optical spectral survey with the AAOmega multi-fiber spectrograph mounted on the 3.9-m Anglo Australian telescope, resulting in a clean and complete census of well-characterised post-AGB objects with spectroscopically determined stellar parameters - Teff, log g, [Fe/H] and E(B-V) - spanning a wide range in luminosity in the Small Magellanic Cloud (SMC) and Large Magellanic Cloud (LMC). The known distances to the Magellanic clouds enabled luminosity estimations for all the objects and led to one of the most important results of this survey: the serendipitous discovery of a group of new, low-luminosity, evolved, dusty post-RGB objects in both Clouds. In this paper, we present an overview of this survey and a few important results.

  12. Luminosities and mass-loss rates of SMC and LMC AGB stars and red supergiants

    NASA Astrophysics Data System (ADS)

    Groenewegen, M. A. T.; Sloan, G. C.; Soszyński, I.; Petersen, E. A.

    2009-11-01

    Context: Mass loss is one of the fundamental properties of Asymptotic Giant Branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking, particularly its dependence on metallicity. Aims: To investigate the relation between mass loss, luminosity and pulsation period for a large sample of evolved stars in the Small and Large Magellanic Cloud. Methods: Dust radiative transfer models are presented for 101 carbon stars and 86 oxygen-rich evolved stars in the Magellanic Clouds for which 5-35 μm Spitzer IRS spectra are available. The spectra are complemented with available optical and infrared photometry to construct the spectral energy distribution. A minimisation procedure is used to fit luminosity, mass-loss rate and dust temperature at the inner radius. Different effective temperatures and dust content are also considered. Periods from the literature and from new OGLE-III data are compiled and derived. Results: We derive (dust) mass-loss rates and luminosities for the entire sample. Based on luminosities, periods and amplitudes and colours, the O-rich stars are classified as foreground objects, AGB stars and Red Super Giants. For the O-rich stars silicates based on laboratory optical constants are compared to “astronomical silicates”. Overall, the grain type by Volk & Kwok (1988, ApJ, 331, 435) fits the data best. However, the fit based on laboratory optical constants for the grains can be improved by abandoning the small-particle limit. The influence of grain size, core-mantle grains and porosity are explored. A computationally convenient method that seems to describe the observed properties in the 10 μm window are a distribution of hollow spheres with a large vacuum fraction (typically 70%), and grain size of about 1 μm. Relations between mass-loss rates and luminosity and pulsation

  13. Artificial defoliation effect on Populus growth, biomass production, and total nonstructural carbohydrate concentration

    SciTech Connect

    Reichenbacker, R.R.; Hart, E.R.; Schultz, R.C.

    1996-06-01

    The impact of artificial defoliation on Populus growth, biomass production, and total nonstructural carbohydrate concentration was examined. Four Populus clones were field planted and artificially defoliated. Assigned defoliation levels (0, 25, 50, or 75%) were applied to leaves of leaf plastochron index 0 through 8 during a 6-d period in a 3-step incremental manner to simulate cottonwood leaf beetle, Chrysomela scripta F., larval feeding patterns. Artificial defoliations were timed to coincide with the outbreaks of natural beetle populations in adjacent areas. After 2 growing seasons, trees were measured for height, diameter, and biomass accumulation. Root samples were collected from 0 and 75% defoliation treatments for each clone. Biomass was reduced an average of 33% as defoliation level increased from 0 to 75%. As defoliation level increased from 0 to 75%, a consistent allocation ratio of biomass to 2/3 above and 1/3 below ground components continued in all clones. An overcompensation response occurred in above ground biomass when a defoliation level of 25% was applied. Between 25 and 75% a strong linear trend of decreasing biomass as defoliation increased was indicated. Vitality of the tree, as indicated by total nonstructural carbohydrate content, was affected only slightly by increasing defoliation. 26 refs., 1 fig., 6 tabs.

  14. Understanding AGB evolution in Galactic bulge stars from high-resolution infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Uttenthaler, S.; Blommaert, J. A. D. L.; Wood, P. R.; Lebzelter, T.; Aringer, B.; Schultheis, M.; Ryde, N.

    2015-08-01

    An analysis of high-resolution near-infrared spectra of a sample of 45 asymptotic giant branch (AGB) stars towards the Galactic bulge is presented. The sample consists of two subsamples, a larger one in the inner and intermediate bulge, and a smaller one in the outer bulge. The data are analysed with the help of hydrostatic model atmospheres and spectral synthesis. We derive the radial velocity of all stars, and the atmospheric chemical mix ([Fe/H], C/O, 12C/13C, Al, Si, Ti, and Y) where possible. Our ability to model the spectra is mainly limited by the (in)completeness of atomic and molecular line lists, at least for temperatures down to Teff ≈ 3100 K. We find that the subsample in the inner and intermediate bulge is quite homogeneous, with a slightly subsolar mean metallicity and only few stars with supersolar metallicity, in agreement with previous studies of non-variable M-type giants in the bulge. All sample stars are oxygen-rich, C/O < 1.0. The C/O and carbon isotopic ratios suggest that third dredge-up (3DUP) is absent among the sample stars, except for two stars in the outer bulge that are known to contain technetium. These stars are also more metal-poor than the stars in the intermediate or inner bulge. Current stellar masses are determined from linear pulsation models. The masses, metallicities and 3DUP behaviour are compared to AGB evolutionary models. We conclude that these models are partly in conflict with our observations. Furthermore, we conclude that the stars in the inner and intermediate bulge belong to a more metal-rich population that follows bar-like kinematics, whereas the stars in the outer bulge belong to the metal-poor, spheroidal bulge population.

  15. Nucleosynthesis Predictions for Intermediate-Mass AGB Stars: Comparison to Observations of Type I Planetary Nebulae

    NASA Technical Reports Server (NTRS)

    Karakas, Amanda I.; vanRaai, Mark A.; Lugaro, Maria; Sterling, Nicholas C.; Dinerstein, Harriet L.

    2008-01-01

    Type I planetary nebulae (PNe) have high He/H and N/O ratios and are thought to be descendants of stars with initial masses of approx. 3-8 Stellar Mass. These characteristics indicate that the progenitor stars experienced proton-capture nucleosynthesis at the base of the convective envelope, in addition to the slow neutron capture process operating in the He-shell (the s-process). We compare the predicted abundances of elements up to Sr from models of intermediate-mass asymptotic giant branch (AGB) stars to measured abundances in Type I PNe. In particular, we compare predictions and observations for the light trans-iron elements Se and Kr, in order to constrain convective mixing and the s-process in these stars. A partial mixing zone is included in selected models to explore the effect of a C-13 pocket on the s-process yields. The solar-metallicity models produce enrichments of [(Se, Kr)/Fe] less than or approx. 0.6, consistent with Galactic Type I PNe where the observed enhancements are typically less than or approx. 0.3 dex, while lower metallicity models predict larger enrichments of C, N, Se, and Kr. O destruction occurs in the most massive models but it is not efficient enough to account for the greater than or approx. 0.3 dex O depletions observed in some Type I PNe. It is not possible to reach firm conclusions regarding the neutron source operating in massive AGB stars from Se and Kr abundances in Type I PNe; abundances for more s-process elements may help to distinguish between the two neutron sources. We predict that only the most massive (M grester than or approx.5 Stellar Mass) models would evolve into Type I PNe, indicating that extra-mixing processes are active in lower-mass stars (3-4 Stellar Mass), if these stars are to evolve into Type I PNe.

  16. ALMA observations of the not-so detached shell around the carbon AGB star R Sculptoris

    NASA Astrophysics Data System (ADS)

    Maercker, Matthias

    2016-07-01

    I present our ALMA observations of the CO emission around the carbon AGB star R Sculptoris. The data reveal the known detached shell and a previously unknown, binary induced, spiral shape. The observations confirm a formation of the shell during a thermal pulse about 2300 years ago. The full analysis of the ALMA data shows that the shell around R Scl in fact is entirely filled with molecular gas, and hence not as detached as previously thought. This has implications for the mass-loss rate evolution immediately after the pulse, indicating a much higher mass-loss rate than previously assumed. Comparing the ALMA images to our optical observations of polarised, dust scattered light, we further show that the distributions of the dust and gas coincide almost perfectly, implying a common evolution of the dust and gas, and constraining the wind-driving mechanism. The mass-loss process and amount of mass lost during the thermal pulse cycle affect the chemical evolution of the star, its lifetime on the AGB, and the return of heavy elements to the ISM. New high-resolution ALMA observations constrain the parameters of the binary system and the inner spiral, and will allow for a detailed hydrodynamical modelling of the gas and dust during and after the last thermal pulse. Our results present the only direct measurements of the thermal pulse evolution currently available. They greatly increase our understanding of this fundamental period of stellar evolution, and the implications it has for the chemical evolution of evolved stars, the ISM, and galaxie

  17. IS THE POST-AGB STAR SAO 40039 MILDLY HYDROGEN-DEFICIENT?

    SciTech Connect

    Rao, S. Sumangala; Pandey, Gajendra; Giridhar, Sunetra; Lambert, David L. E-mail: pandey@iiap.res.in E-mail: dll@astro.as.utexas.edu

    2011-08-10

    We have conducted an LTE abundance analysis for SAO 40039, a warm post-AGB star whose spectrum is known to show surprisingly strong He I lines for its effective temperature and has been suspected of being H-deficient and He-rich. High-resolution optical spectra are analyzed using a family of model atmospheres with different He/H ratios. Atmospheric parameters are estimated from the ionization equilibrium set by neutral and singly ionized species of Fe and Mg, the excitation of Fe I and Fe II lines, and the wings of the Paschen lines. On the assumption that the He I lines are of photospheric and not chromospheric origin, a He/H ratio of approximately unity is found by imposing the condition that the adopted He/H ratio of the model atmosphere must equal the ratio derived from the observed He I triplet lines at 5876, 4471, and 4713 A, and singlet lines at 4922 and 5015 A. Using the model with the best-fitting atmospheric parameters for this He/H ratio, SAO 40039 is confirmed to exhibit mild dust-gas depletion, i.e., the star has an atmosphere deficient in elements of high condensation temperature. The star appears to be moderately metal-deficient with [Fe/H] = -0.4 dex. But the star's intrinsic metallicity as estimated from Na, S, and Zn, elements of a low condensation temperature, is [Fe/H]{sub o} {approx_equal} -0.2 ([Fe/H]{sub o} refers to the star's intrinsic metallicity). The star is enriched in N and perhaps O as well, changes reflecting the star's AGB past and the event that led to He enrichment.

  18. The carbon star adventure: modelling atmospheres of a set of C-rich AGB stars

    NASA Astrophysics Data System (ADS)

    Rau, Gioia; Paladini, Claudia; Hron, Josef; Aringer, Bernard; Erikssonn, Kjell; Groenewegen, Martin

    2015-08-01

    We study the atmospheres of a set of carbon rich AGB stars to improve our understanding of the dynamic processes happening in there.For the first time we compare in a systematic way spectrometric, photometric and mid-infrared (VLTI/MIDI) interferometric measurements with different type of model atmospheres: (1) hydrostatic models + MOD-dusty models (Groenewegen, 2012) added a posteriori; (2) self-consistent dynamic model atmospheres (Eriksson et al. 2014). These allow to interpret in a coherent way the dynamic behavior of gas and dust. In addition, the geometric model fitting tool for interferometric data GEM-FIND is applied to carry out a first interpretation of the structural environment of the stars.The results underline that the joint use of different kind of observations, as photometry, spectroscopy and interferometry, is essential for understanding and modeling the atmosphere of pulsating C-rich AGB stars. For our first target, the carbon-rich Mira star RU Vir, the dynamic model atmospheres fit well the ISO/SWS spectra in the wavelength range λ = [2.9, 13.0] μm. However, the object turned out to be “peculiar”: we notice a discrepancy in the visible part of the SED, and in the visibilities. Possible causes are intra/inter-cycle variations in the dynamic model atmospheres, and an eventual presence of a companion star and/or disk or clumps in the atmosphere of RU Vir (Rau et al. subm.). Results on further targets will also be presented.The increased sample of C-rich stars of this work provides crucial constraints for the atmospheric structure and the formation of SiC. Moreover the second generation VLTI instrument MATISSE will be a perfect tool to detect and study asymmetries, as it will allow interferometric imaging in the L, M, and N bands.

  19. The relationship between species richness and community biomass: the importance of environmental variables

    USGS Publications Warehouse

    Gough, L.; Grace, J.B.; Taylor, K.L.

    1994-01-01

    Several studies have used plant community biomass to predict species richness with varying success. In this study we examined the relationship between species richness and biomass for 36 marsh communities from two different watersheds. In addition, we measured several environmental variables and estimated the potential richness (the total number of species known to be able to occur in a community type) for each community. Above ground living and dead biomass combined was found to be weakly correlated with species richness (R2=0.02). Instead, a multiple regression model based on elevation (R2=0.47), salinity (R2=0.30), soil organic matter (R2=0.18), and biomass was able to explain 82% of the variance in species richness. It was found that environmental conditions could explain 89% of the variation in potential richness. Biomass had no relation to potential richness. When used as a predictor variable, potential richness was found to explain 72% of the variation in realized (observed) richness and biomass explained an addition 9% of the variance in realized richness. This finding suggests that realized richness in our system was controlled primarily by environmental regulation of potential richness and secondarily by biomass (as an indicator of competition). Further examination of the data revealed that when sites exposed to extreme environmental conditons were eliminated from the analysis, biomass became the primary predictor of realized richness and potential richness was of secondary importance. We conclude that community biomass has a limited capacity to predict species richness across a broad range of habitat conditions. Of particular importance is the inability of biomass to indicate the effect of environmental factors and evolutionary history on the potential species richness at a site.

  20. Changes in composition, structure and aboveground biomass over seventy-six years (1930-2006) in the Black Rock Forest, Hudson Highlands, southeastern New York State.

    PubMed

    Schuster, W S F; Griffin, K L; Roth, H; Turnbull, M H; Whitehead, D; Tissue, D T

    2008-04-01

    We sought to quantify changes in tree species composition, forest structure and aboveground forest biomass (AGB) over 76 years (1930-2006) in the deciduous Black Rock Forest in southeastern New York, USA. We used data from periodic forest inventories, published floras and a set of eight long-term plots, along with species-specific allometric equations to estimate AGB and carbon content. Between the early 1930s and 2000, three species were extirpated from the forest (American elm (Ulmus americana L.), paper birch (Betula papyrifera Marsh.) and black spruce (Picea mariana (nigra) (Mill.) BSP)) and seven species invaded the forest (non-natives tree-of-heaven (Ailanthus altissima (Mill.) Swingle) and white poplar (Populus alba L.) and native, generally southerly distributed, southern catalpa (Catalpa bignonioides Walt.), cockspur hawthorn (Crataegus crus-galli L.), red mulberry (Morus rubra L.), eastern cottonwood (Populus deltoides Bartr.) and slippery elm (Ulmus rubra Muhl.)). Forest canopy was dominated by red oak and chestnut oak, but the understory tree community changed substantially from mixed oak-maple to red maple-black birch. Density decreased from an average of 1500 to 735 trees ha(-1), whereas basal area doubled from less than 15 m(2) ha(-1) to almost 30 m(2) ha(-1) by 2000. Forest-wide mean AGB from inventory data increased from about 71 Mg ha(-1) in 1930 to about 145 Mg ha(-1) in 1985, and mean AGB on the long-term plots increased from 75 Mg ha(-1) in 1936 to 218 Mg ha(-1) in 1998. Over 76 years, red oak (Quercus rubra L.) canopy trees stored carbon at about twice the rate of similar-sized canopy trees of other species. However, there has been a significant loss of live tree biomass as a result of canopy tree mortality since 1999. Important constraints on long-term biomass increment have included insect outbreaks and droughts. PMID:18244941

  1. Biomass treatment method

    DOEpatents

    Friend, Julie; Elander, Richard T.; Tucker, III; Melvin P.; Lyons, Robert C.

    2010-10-26

    A method for treating biomass was developed that uses an apparatus which moves a biomass and dilute aqueous ammonia mixture through reaction chambers without compaction. The apparatus moves the biomass using a non-compressing piston. The resulting treated biomass is saccharified to produce fermentable sugars.

  2. Ecological Importance of Small-Diameter Trees to the Structure, Diversity and Biomass of a Tropical Evergreen Forest at Rabi, Gabon.

    PubMed

    Memiaghe, Hervé R; Lutz, James A; Korte, Lisa; Alonso, Alfonso; Kenfack, David

    2016-01-01

    Tropical forests have long been recognized for their biodiversity and ecosystem services. Despite their importance, tropical forests, and particularly those of central Africa, remain understudied. Until recently, most forest inventories in Central Africa have focused on trees ≥10 cm in diameter, even though several studies have shown that small-diameter tree population may be important to demographic rates and nutrient cycling. To determine the ecological importance of small-diameter trees in central African forests, we used data from a 25-ha permanent plot that we established in the rainforest of Gabon to study the diversity and dynamics of these forests. Within the plot, we censused 175,830 trees ≥1 cm dbh from 54 families, 192 genera, and 345 species. Average tree density was 7,026 trees/ha, basal area 31.64 m2/ha, and above-ground biomass 369.40 Mg/ha. Fabaceae, Ebenaceae and Euphorbiaceae were the most important families by basal area, density and above-ground biomass. Small-diameter trees (1 cm ≥ dbh <10 cm) comprised 93.7% of the total tree population, 16.5% of basal area, and 4.8% of the above-ground biomass. They also had diversity 18% higher at family level, 34% higher at genus level, and 42% higher at species level than trees ≥10 cm dbh. Although the relative contribution of small-diameter trees to biomass was comparable to other forests globally, their contribution to forest density, and diversity was disproportionately higher. The high levels of diversity within small-diameter classes may give these forests high levels of structural resilience to anthropogenic/natural disturbance and a changing climate. PMID:27186658

  3. Ecological Importance of Small-Diameter Trees to the Structure, Diversity and Biomass of a Tropical Evergreen Forest at Rabi, Gabon

    PubMed Central

    Memiaghe, Hervé R.; Lutz, James A.; Korte, Lisa; Alonso, Alfonso; Kenfack, David

    2016-01-01

    Tropical forests have long been recognized for their biodiversity and ecosystem services. Despite their importance, tropical forests, and particularly those of central Africa, remain understudied. Until recently, most forest inventories in Central Africa have focused on trees ≥10 cm in diameter, even though several studies have shown that small-diameter tree population may be important to demographic rates and nutrient cycling. To determine the ecological importance of small-diameter trees in central African forests, we used data from a 25-ha permanent plot that we established in the rainforest of Gabon to study the diversity and dynamics of these forests. Within the plot, we censused 175,830 trees ≥1 cm dbh from 54 families, 192 genera, and 345 species. Average tree density was 7,026 trees/ha, basal area 31.64 m2/ha, and above-ground biomass 369.40 Mg/ha. Fabaceae, Ebenaceae and Euphorbiaceae were the most important families by basal area, density and above-ground biomass. Small-diameter trees (1 cm ≥ dbh <10 cm) comprised 93.7% of the total tree population, 16.5% of basal area, and 4.8% of the above-ground biomass. They also had diversity 18% higher at family level, 34% higher at genus level, and 42% higher at species level than trees ≥10 cm dbh. Although the relative contribution of small-diameter trees to biomass was comparable to other forests globally, their contribution to forest density, and diversity was disproportionately higher. The high levels of diversity within small-diameter classes may give these forests high levels of structural resilience to anthropogenic/natural disturbance and a changing climate. PMID:27186658

  4. High resolution spectroscopy of the high latitude rapidly evolving post-AGB star SAO 85766 (= IRAS 18062+2410)

    NASA Astrophysics Data System (ADS)

    Parthasarathy, M.; García-Lario, P.; Sivarani, T.; Manchado, A.; Sanz Fernández de Córdoba, L.

    2000-05-01

    SAO 85766 (b = +20o) is an IRAS source with far-infrared colours similar to planetary nebulae. According to the HDE catalogue, its spectrum in 1940 was that of an A5 star. The UV fluxes and colours derived from data obtained by the TD1 satellite in 1972 also indicate that SAO 85766 was an A-type supergiant at that epoch. However, high resolution spectra of SAO 85766 obtained in 1993 in the wavelength interval 4350Ä to 8820Ä shows that now it is similar to that of an early B type post-AGB supergiant. In addition to the absorptions lines typical of a B1I type star, the spectrum of SAO 85766 is found to show numerous permitted and forbidden emission lines of several elements, typically observed in the spectra of young high density low excitation planetary nebulae. From an analysis of the absorption lines we have estimated Teff=22000+/-500 K, log g=3.0+/-0.5, xi t=15+/-2km s-1 and [M/H]=-0.6. Carbon is found to be strongly underabundant ([C/Fe] = -1.0), similarly to what has been observed in other high galactic latitude hot post-AGB stars. The underabundance of carbon and metals, high galactic latitude, high radial velocity (46 km s-1), the presence of planetary nebula type detached cold circumstellar dust shell and also the presence of low excitation nebular emission lines in the spectrum indicate that SAO 85766 is a low mass star in the post-AGB stage of evolution. The above mentioned characteristics and the variations observed in the spectrum of SAO 85766 suggest that it has rapidly evolved during the past 50 years and it is now in the early stages of the planetary nebula phase. The central star may just have become hot enough to photoionize the circumstellar envelope ejected during the previous AGB phase. >From an analysis of the nebular emission lines we find Te=10000+/- 500K and Ne=2.5 104 cm-3. The nebula also shows an abundance pattern similar to that of the central star. The rapid post-AGB evolution of SAO 85766 appears to be similar to that observed in the

  5. The effect of NaCl on stomatal opening in Arabidopsis wild type and agb1 heterotrimeric G-protein mutant plants.

    PubMed

    Yu, Yunqing; Assmann, Sarah M

    2016-01-01

    Salinity is a major agricultural problem that affects crop yield. Na(+) is transported to the shoot through the transpiration stream. The mutant of the sole Arabidopsis heterotrimeric G protein β subunit, agb1, is hypersensitive to salinity in part due to a higher transpiration rate. Here, we investigated the direct effect of Na(+) on stomatal opening using detached epidermal peels of wild type and agb1 plants. In both genotypes, NaCl is equally as effective as KCl in mediating stomatal opening at the concentrations tested. In both genotypes, ABA is less effective in inhibiting Na(+) mediated stomatal opening than K(+) mediated stomatal opening. The agb1 mutant is hyposensitive to ABA inhibition of K(+)-mediated but not Na(+)-mediated stomatal opening. These results suggest that the greater transpiration observed in agb1 plants grown in saline conditions is likely not mediated by differential genotypic direct effects of Na(+) on stomatal apertures. PMID:26431457

  6. The effect of NaCl on stomatal opening in Arabidopsis wild type and agb1 heterotrimeric G-protein mutant plants

    PubMed Central

    Yu, Yunqing; Assmann, Sarah M.

    2016-01-01

    Salinity is a major agricultural problem that affects crop yield. Na+ is transported to the shoot through the transpiration stream. The mutant of the sole Arabidopsis heterotrimeric G protein β subunit, agb1, is hypersensitive to salinity in part due to a higher transpiration rate. Here, we investigated the direct effect of Na+ on stomatal opening using detached epidermal peels of wild type and agb1 plants. In both genotypes, NaCl is equally as effective as KCl in mediating stomatal opening at the concentrations tested. In both genotypes, ABA is less effective in inhibiting Na+ mediated stomatal opening than K+ mediated stomatal opening. The agb1 mutant is hyposensitive to ABA inhibition of K+-mediated but not Na+-mediated stomatal opening. These results suggest that the greater transpiration observed in agb1 plants grown in saline conditions is likely not mediated by differential genotypic direct effects of Na+ on stomatal apertures. PMID:26431457

  7. Deadwood biomass: an underestimated carbon stock in degraded tropical forests?

    NASA Astrophysics Data System (ADS)

    Pfeifer, Marion; Lefebvre, Veronique; Turner, Edgar; Cusack, Jeremy; Khoo, MinSheng; Chey, Vun K.; Peni, Maria; Ewers, Robert M.

    2015-04-01

    Despite a large increase in the area of selectively logged tropical forest worldwide, the carbon stored in deadwood across a tropical forest degradation gradient at the landscape scale remains poorly documented. Many carbon stock studies have either focused exclusively on live standing biomass or have been carried out in primary forests that are unaffected by logging, despite the fact that coarse woody debris (deadwood with ≥10 cm diameter) can contain significant portions of a forest’s carbon stock. We used a field-based assessment to quantify how the relative contribution of deadwood to total above-ground carbon stock changes across a disturbance gradient, from unlogged old-growth forest to severely degraded twice-logged forest, to oil palm plantation. We measured in 193 vegetation plots (25 × 25 m), equating to a survey area of >12 ha of tropical humid forest located within the Stability of Altered Forest Ecosystems Project area, in Sabah, Malaysia. Our results indicate that significant amounts of carbon are stored in deadwood across forest stands. Live tree carbon storage decreased exponentially with increasing forest degradation 7-10 years after logging while deadwood accounted for >50% of above-ground carbon stocks in salvage-logged forest stands, more than twice the proportion commonly assumed in the literature. This carbon will be released as decomposition proceeds. Given the high rates of deforestation and degradation presently occurring in Southeast Asia, our findings have important implications for the calculation of current carbon stocks and sources as a result of human-modification of tropical forests. Assuming similar patterns are prevalent throughout the tropics, our data may indicate a significant global challenge to calculating global carbon fluxes, as selectively-logged forests now represent more than one third of all standing tropical humid forests worldwide.

  8. Community structure and biomass distribution of seagrasses and macrofauna in the flores sea, Indonesia

    NASA Astrophysics Data System (ADS)

    Nienhuis, P. H.; Coosen, J.; Kiswara, W.

    In several locations in the Flores Sea region the community structure and the biomass distribution of seagrasses were studied along transects perpendicular to the shoreline. The share of each species within a sample plot was estimated, divided in above- and below-ground biomass. Statistics regarding substrate coverage, shoot density and leaf-area index were sampled. A standard relation was calculated between seagrass dry weight, ash-free dry weight and organic carbon content. The biotic data were related to environmental factors: DOC and nutrients in the water, salinity, tidal amplitude, sediment composition. A relation was estimated between bottom coverage of seagrasses and standing stock. Further calculations of biomass-production ratios allow a quick and rough estimate of seagrass productivity. Maximum above-ground biomass values (500-700 g AFDW·m -2) together with qualitative data indicate resource (= space) partitioning among the component seagrasses within a community, and suggest a carrying capacity of the reefflat habitat for seagrass density and biomass. A tentative model was constructed, starting from a constant, non-distributed multispecies vegetation in the lower intertidal and subtidal zone on sand and coral rubble, and moving into several suboptimal situations. The upper shore carries an impoverished, constrained vegetation (irregular tides, desiccation, harvesting). Sediment reworking by animals and physical displacement of sand disturbs the vegetation and favours pioneer species. Muddy habitats bordering mangroves carry monospecific stands showing extremely high biomass ( e.g. below-ground Enhalus acoroides 3500 g AFDW·m -2). Thalassia hemprichii and Enhalus acoroides are the most constant species in all habitats mentioned. Macrofauna biomass within the seagrass beds fluctuated widely (maximum values 50-70 g AFDW·m -2 in mixed seagrass vegetations) and only a weak relation between benthic macrofauna biomass and seagrass community structure and

  9. On the introduction of {sup 17}O+p reaction rates evaluated through the THM in AGB nucleosynthesis calculations

    SciTech Connect

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Pizzone, R. G.; Lamia, L.; Spitaleri, C.

    2014-05-09

    The rates for the {sup 17}O(p,αα{sup 14}N, {sup 17}O(p,α){sup 18}F and {sup 18}O(p,α){sup 15}N reactions deduced trough the Trojan Horse Method (THM) have been introduced into a state-of-the-art asymptotic giant branch (AGB) models for proton-capture nucleosynthesis and cool bottom process. The predicted abundances have been compared with isotopic compositions provided by geochemical analysis of presolar grains. As a result, an improved agreement is found between the models and the isotopic mix of oxide grains of AGB origins, whose composition is the signature of low-temperature proton-capture nucleosynthesis.

  10. Detailed modelling of the circumstellar molecular line emission of the S-type AGB star W Aquilae

    NASA Astrophysics Data System (ADS)

    Danilovich, T.; Bergman, P.; Justtanont, K.; Lombaert, R.; Maercker, M.; Olofsson, H.; Ramstedt, S.; Royer, P.

    2014-09-01

    Context. S-type AGB stars have a C/O ratio which suggests that they are transition objects between oxygen-rich M-type stars and carbon-rich C-type stars. As such, their circumstellar compositions of gas and dust are thought to be sensitive to their precise C/O ratio, and it is therefore of particular interest to examine their circumstellar properties. Aims: We present new Herschel HIFI and PACS sub-millimetre and far-infrared line observations of several molecular species towards the S-type AGB star W Aql. We use these observations, which probe a wide range of gas temperatures, to constrain the circumstellar properties of W Aql, including mass-loss rate and molecular abundances. Methods: We used radiative transfer codes to model the circumstellar dust and molecular line emission to determine circumstellar properties and molecular abundances. We assumed a spherically symmetric envelope formed by a constant mass-loss rate driven by an accelerating wind. Our model includes fully integrated H2O line cooling as part of the solution of the energy balance. Results: We detect circumstellar molecular lines from CO, H2O, SiO, HCN, and, for the first time in an S-type AGB star, NH3. The radiative transfer calculations result in an estimated mass-loss rate for W Aql of 4.0 × 10-6 M⊙ yr-1 based on the 12CO lines. The estimated 12CO/13CO ratio is 29, which is in line with ratios previously derived for S-type AGB stars. We find an H2O abundance of 1.5 × 10-5, which is intermediate to the abundances expected for M and C stars, and an ortho/para ratio for H2O that is consistent with formation at warm temperatures. We find an HCN abundance of 3 × 10-6, and, although no CN lines are detected using HIFI, we are able to put some constraints on the abundance, 6 × 10-6, and distribution of CN in W Aql's circumstellar envelopeusing ground-based data. We find an SiO abundance of 3 × 10-6, and an NH3 abundance of 1.7 × 10-5, confined to a small envelope. If we include uncertainties

  11. Sulphur molecules in the circumstellar envelopes of M-type AGB stars

    NASA Astrophysics Data System (ADS)

    Danilovich, T.; De Beck, E.; Black, J. H.; Olofsson, H.; Justtanont, K.

    2016-04-01

    Aims: The sulphur compounds SO and SO2 have not been widely studied in the circumstellar envelopes of asymptotic giant branch (AGB) stars. By presenting and modelling a large number of SO and SO2 lines in the low mass-loss rate M-type AGB star R Dor, and modelling the available lines of those molecules in a further four M-type AGB stars, we aim to determine their circumstellar abundances and distributions. Methods: We use a detailed radiative transfer analysis based on the accelerated lambda iteration method to model circumstellar SO and SO2 line emission. We use molecular data files for both SO and SO2 that are more extensive than those previously available. Results: Using 17 SO lines and 98 SO2 lines to constrain our models for R Dor, we find an SO abundance of (6.7 ± 0.9) × 10-6 and an SO2 abundance of 5 × 10-6 with both species having high abundances close to the star. We also modelled 34SO and found an abundance of (3.1 ± 0.8) × 10-7, giving an 32SO/34SO ratio of 21.6 ± 8.5. We derive similar results for the circumstellar SO and SO2 abundances and their distributions for the low mass-loss rate object W Hya. For the higher mass-loss rate stars, we find shell-like SO distributions with peak abundances that decrease and peak abundance radii that increase with increasing mass-loss rate. The positions of the peak SO abundance agree very well with the photodissociation radii of H2O. We also modelled SO2 in two higher mass-loss rate stars but our models for these were less conclusive. Conclusions: We conclude that for the low mass-loss rate stars, the circumstellar SO and SO2 abundances are much higher than predicted by chemical models of the extended stellar atmosphere. These two species may also account for all the available sulphur. For the higher mass-loss rate stars we find evidence that SO is most efficiently formed in the circumstellar envelope, most likely through the photodissociation of H2O and the subsequent reaction between S and OH. The S

  12. New insights into the dust formation of oxygen-rich AGB stars

    NASA Astrophysics Data System (ADS)

    Karovicova, I.; Wittkowski, M.; Ohnaka, K.; Boboltz, D. A.; Fossat, E.; Scholz, M.

    2013-12-01

    Context. Asymptotic giant branch (AGB) stars are one of the major sources of dust in the universe. The formation of molecules and dust grains and their subsequent expulsion into the interstellar medium via strong stellar winds is under intense investigation. This is in particular true for oxygen-rich stars, for which the path of dust formation has remained unclear. Aims: We conducted spatially and spectrally resolved mid-infrared multi-epoch interferometric observations to investigate the dust formation process in the extended atmospheres of oxygen-rich AGB stars. Methods: We observed the Mira variable AGB stars S Ori, GX Mon, and R Cnc between February 2006 and March 2009 with the MIDI instrument at the VLT interferometer. We compared the data to radiative transfer models of the dust shells, where the central stellar intensity profiles were described by dust-free dynamic model atmospheres. We used Al2O3 and warm silicate grains, following earlier studies in the literature. Results: Our S Ori and R Cnc data could be well described by an Al2O3 dust shell alone, and our GX Mon data by a mix of an Al2O3 and a silicate shell. The best-fit parameters for S Ori and R Cnc included photospheric angular diameters ΘPhot of 9.7 ± 1.0 mas and 12.3 ± 1.0 mas, optical depths τV(Al2O3) of 1.5 ± 0.5 and 1.35 ± 0.2, and inner radii Rin of 1.9 ± 0.3 RPhot and 2.2 ± 0.3 RPhot, respectively. Best-fit parameters for GX Mon were ΘPhot = 8.7 ± 1.3 mas, τV(Al2O3) = 1.9 ± 0.6, Rin(Al2O3) = 2.1 ± 0.3 RPhot, τV(silicate)= 3.2 ± 0.5, and Rin(silicate)= 4.6 ± 0.2 RPhot. Our data did not show evidence of intra-cycle and cycle-to-cycle variability or of asymmetries within the error-bars and within the limits of our baseline and phase coverage. Conclusions: Our model fits constrain the chemical composition and the inner boundary radii of the dust shells, as well as the photospheric angular diameters. Our interferometric results are consistent with Al2O3 grains condensing close to

  13. Searching for heavily obscured post-AGB stars and planetary nebulae. II. Near-IR observations of IRAS sources

    NASA Astrophysics Data System (ADS)

    Ramos-Larios, G.; Guerrero, M. A.; Suárez, O.; Miranda, L. F.; Gómez, J. F.

    2012-09-01

    The most massive AGB stars are expected to result in heavily obscured post-AGB stars, proto-PNe and PNe with highly axisymmetric morphologies. To investigate this evolutionary connection, we have selected a sample of 165 presumably obscured IRAS post-AGB star and PN candidates and obtained near-IR JHK images for 164 of them. These images, in conjunction with DSS, 2MASS, Spitzer GLIMPSE, MSX, AKARI, and IRAS archival data, have allowed us to identify the near-IR counterparts of 154 of these sources, providing reliable finding charts and coordinates. Near-IR narrow-band Brγ, H2, and K continuum images were acquired for 6 of these sources that were found to be resolved in near-IR JHK images. Among the extended post-AGB source and PN candidates, three are round and seven have bipolar morphologies. Five of the extended sources are ionized and may have thus entered the PN stage. We note that all extended sources with water maser emission have bipolar morphology. We have investigated the Galactic distribution of sources with the largest flux drop from the 9 μm AKARI band to the near-IR J band and found that the width of the distribution in Galactic latitude is consistent with those of bipolar PNe and DUPLEX (DUst-Prominent Longitudinally EXtended) sources. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile (081.D-0812), observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and on observations with AKARI, a JAXA project with the participation of ESA.

  14. Radial velocity variable, hot post-AGB stars from the MUCHFUSS project. Classification, atmospheric parameters, formation scenarios

    NASA Astrophysics Data System (ADS)

    Reindl, N.; Geier, S.; Kupfer, T.; Bloemen, S.; Schaffenroth, V.; Heber, U.; Barlow, B. N.; Østensen, R. H.

    2016-03-01

    In the course of the MUCHFUSS project we recently discovered four radial velocity (RV) variable, hot (Teff≈ 80 000-110 000 K) post-asymptotic giant branch (AGB) stars. Among them, we found the first known RV variable O(He) star, the only second known RV variable PG 1159 close binary candidate, as well as the first two naked (i.e., without planetary nebula (PN)) H-rich post-AGB stars of spectral type O(H) that show significant RV variations. We present a non-LTE spectral analysis of these stars along with one further O(H)-type star whose RV variations were found to be not significant. We also report the discovery of a far-infrared excess in the case of the PG 1159 star. None of the stars in our sample displays nebular emission lines, which can be explained well in terms of a very late thermal pulse evolution in the case of the PG 1159 star. The "missing" PNe around the O(H)-type stars seems strange, since we find that several central stars of PNe have much longer post-AGB times. Besides the non-ejection of a PN, the occurrence of a late thermal pulse, or the re-accretion of the PN in the previous post-AGB evolution offer possible explanations for those stars not harbouring a PN (anymore). In the case of the O(He) star J0757, we speculate that it might have been previously part of a compact He transferring binary system. In this scenario, the mass transfer must have stopped after a certain time, leaving behind a low-mass close companion that may be responsible for the extreme RV shift of 107.0 ± 22.0 km s-1 that was measured within only 31 min.

  15. Terrestrial laser scanning for plant height measurement and biomass estimation of maize

    NASA Astrophysics Data System (ADS)

    Tilly, N.; Hoffmeister, D.; Schiedung, H.; Hütt, C.; Brands, J.; Bareth, G.

    2014-09-01

    Over the last decades, the role of remote sensing gained in importance for monitoring applications in precision agriculture. A key factor for assessing the development of crops during the growing period is the actual biomass. As non-destructive methods of directly measuring biomass do not exist, parameters like plant height are considered as estimators. In this contribution, first results of multitemporal surveys on a maize field with a terrestrial laser scanner are shown. The achieved point clouds are interpolated to generate Crop Surface Models (CSM) that represent the top canopy. These CSMs are used for visualizing the spatial distribution of plant height differences within the field and calculating plant height above ground with a high resolution of 1 cm. In addition, manual measurements of plant height were carried out corresponding to each TLS campaign to verify the results. The high coefficient of determination (R² = 0.93) between both measurement methods shows the applicability of the presented approach. The established regression model between CSM-derived plant height and destructively measured biomass shows a varying performance depending on the considered time frame during the growing period. This study shows that TLS is a suitable and promising method for measuring plant height of maize. Moreover, it shows the potential of plant height as a non-destructive estimator for biomass in the early growing period. However, challenges are the non-linear development of plant height and biomass over the whole growing period.

  16. Biomass estimation with high resolution satellite images: A case study of Quercus rotundifolia

    NASA Astrophysics Data System (ADS)

    Sousa, Adélia M. O.; Gonçalves, Ana Cristina; Mesquita, Paulo; Marques da Silva, José R.

    2015-03-01

    Forest biomass has had a growing importance in the world economy as a global strategic reserve, due to applications in bioenergy, bioproduct development and issues related to reducing greenhouse gas emissions. Current techniques used for forest inventory are usually time consuming and expensive. Thus, there is an urgent need to develop reliable, low cost methods that can be used for forest biomass estimation and monitoring. This study uses new techniques to process high spatial resolution satellite images (0.70 m) in order to assess and monitor forest biomass. Multi-resolution segmentation method and object oriented classification are used to obtain the area of tree canopy horizontal projection for Quercus rotundifolia. Forest inventory allows for calculation of tree and canopy horizontal projection and biomass, the latter with allometric functions. The two data sets are used to develop linear functions to assess above ground biomass, with crown horizontal projection as an independent variable. The functions for the cumulative values, both for inventory and satellite data, for a prediction error equal or smaller than the Portuguese national forest inventory (7%), correspond to stand areas of 0.5 ha, which include most of the Q.rotundifolia stands.

  17. Measuring bulrush culm relationships to estimate plant biomass within a southern California treatment wetland

    USGS Publications Warehouse

    Daniels, Joan S. (Thullen); Cade, Brian S.; Sartoris, James J.

    2010-01-01

    Assessment of emergent vegetation biomass can be time consuming and labor intensive. To establish a less onerous, yet accurate method, for determining emergent plant biomass than by direct measurements we collected vegetation data over a six-year period and modeled biomass using easily obtained variables: culm (stem) diameter, culm height and culm density. From 1998 through 2005, we collected emergent vegetation samples (Schoenoplectus californicus andSchoenoplectus acutus) at a constructed treatment wetland in San Jacinto, California during spring and fall. Various statistical models were run on the data to determine the strongest relationships. We found that the nonlinear relationship: CB=β0DHβ110ε, where CB was dry culm biomass (g m−2), DH was density of culms × average height of culms in a plot, and β0 and β1 were parameters to estimate, proved to be the best fit for predicting dried-live above-ground biomass of the two Schoenoplectus species. The random error distribution, ε, was either assumed to be normally distributed for mean regression estimates or assumed to be an unspecified continuous distribution for quantile regression estimates.

  18. Exploring the Onset of the Contribution of the First AGB Stars to the Galactic Chemical Enrichment using Isotopic Ratios

    NASA Astrophysics Data System (ADS)

    Goswami, A.

    2015-08-01

    There is uncertainty over the time at which the first intermediate and low-mass stars reach the AGB phase and begin to influence their environments with the products of nucleosynthesis. While some studies have indicated that enrichment from AGB stars sets in at a time corresponding to -2.4 < [Fe/H] < -2.1, others suggest a time as early as [Fe/H] ≍ -2.75. These suggestions come from observations of s-process heavy elements in old metal-poor stars. Measurements of stellar isotopic ratios, such as the Mg isotope ratios, can also be a useful probe to explore the contribution of AGB stars to the Galactic chemical inventory. However, measurements of isotopic ratios require spectra with high resolution (R > 90 000) and high S/N ratios (> 200) which require very long exposure times with the existing observing facilities. Upcoming large telescopes of 25 to 42-m size equipped with high resolution spectrographs will provide the resolution and sensitivity required for measurements of isotopic ratios that are fundamental indicators of nucleosynthesis.

  19. The Effects of Stellar Chemistry on the Broad 9-15 Micron Spectral Feature of O-rich AGB Stars

    NASA Astrophysics Data System (ADS)

    Arrant, David J.; Speck, A.

    2013-01-01

    Dust plays an important role in many astrophysical processes. Asymptotic giant branch (AGB) stars expel gas from their surfaces; as it moves away from the star, it cools and condenses to produce dust. Carbon monoxide (CO) is extremely stable and will trap most of the oxygen and carbon. The lesser abundant of carbon and oxygen will be entirely trapped in CO, while the more abundant will have excess atoms available to form dust. AGB stars are divided into carbon-rich (C-rich) stars or oxygen-rich (O-rich) stars. O-rich AGB stars with low mass-loss rates show a 9-15 micron feature, which is attributed to various dust species, such as silicates and oxides. This broad feature is fitted with two overlapping Gaussian functions. The parameters of the Gaussian fits are compared to stellar chemistry properties, such as the elemental abundances (C, N, O, Fe, Ti, Ni, Y, Zr, and Nd) and ratios (C/N, C/O, C/Fe…) in order to assess the effect of chemistry on dust formation.

  20. Post-AGB Stars in Nearby Galaxies as Calibrators for HST

    NASA Technical Reports Server (NTRS)

    Bond, Howard E.

    2003-01-01

    This report summarizes activities carried out with support from the NASA Ultraviolet, Visible, and Gravitational Astrophysics Research and Analysis Program under Grant NAG 5-6821. The Principal Investigator is Howard E. Bond (Space Telescope Science Institute). STScI Postdoctoral Associates Laura K. Fullton (1998), David Alves (1998-2001), and Michael Siegel (2001) were partially supported by this grant. The aim of the program is to calibrate the absolute magnitudes of post-asymptotic- giant-branch (post-AGB or PAGB) stars, which we believe will be an excellent new "standard candle" for measuring extragalactic distances. The argument is that, in old populations, the stars that are evolving through the PAGB region of the HR diagram arise from only a single main-sequence turnoff mass. In addition, theoretical PAGB evolutionary tracks show that they evolve through this region at constant luminosity; hence the PAGB stars should have an extremely narrow luminosity function. Moreover, as the PAGB stars evolve through spectral types F and A (en route from the AGB to hot stellar remnants and white dwarfs), they have the highest luminosities attained by old stars (both bolometrically and in the visual band). Finally, PAGB stars of these spectral types are very easily identified. because of their large Balmer jumps, which are due to their very low surface gravities. Our approach is first to identify PAGB stars in Milky Way globular clusters and in other Local Group galaxies, which are at known distances, and thus to measure accurate absolute magnitudes for the PAGB stars. With this Milky Way and Local Group luminosity calibration, we will then be in a position to find PAGB stars in more distant galaxies from the ground, and ultimately from the Hubble Space Telescope. and thus derive distances. These PAGB stars are, as noted above, the visually brightest members of Population II, and hence will allow distance measurements to galaxies that do not contain Cepheids, such as

  1. Dust-driven winds of AGB stars: The critical interplay of atmospheric shocks and luminosity variations

    NASA Astrophysics Data System (ADS)

    Liljegren, S.; Höfner, S.; Nowotny, W.; Eriksson, K.

    2016-04-01

    Context. Winds of AGB stars are thought to be driven by a combination of pulsation-induced shock waves and radiation pressure on dust. In dynamic atmosphere and wind models, the stellar pulsation is often simulated by prescribing a simple sinusoidal variation in velocity and luminosity at the inner boundary of the model atmosphere. Aims: We experiment with different forms of the luminosity variation in order to assess the effects on the wind velocity and mass-loss rate, when progressing from the simple sinusoidal recipe towards more realistic descriptions. This will also give an indication of how robust the wind properties derived from the dynamic atmosphere models are. Methods: Using state-of-the-art dynamical models of C-rich AGB stars, a range of different asymmetric shapes of the luminosity variation and a range of phase shifts of the luminosity variation relative to the radial variation are tested. These tests are performed on two stellar atmosphere models. The first model has dust condensation and, as a consequence, a stellar wind is triggered, while the second model lacks both dust and wind. Results: The first model with dust and stellar wind is very sensitive to moderate changes in the luminosity variation. There is a complex relationship between the luminosity minimum, and dust condensation: changing the phase corresponding to minimum luminosity can either increase or decrease mass-loss rate and wind velocity. The luminosity maximum dominates the radiative pressure on the dust, which in turn, is important for driving the wind. An earlier occurrence of the maximum, with respect to the propagation of the pulsation-induced shock wave, then increases the wind velocity, while a later occurrence leads to a decrease. These effects of changed luminosity variation are coupled with the dust formation. In contrast there is very little change to the structure of the model without dust. Conclusions: Changing the luminosity variation, both by introducing a phase shift

  2. Dust-driven winds of AGB stars: The critical interplay of atmospheric shocks and luminosity variations

    NASA Astrophysics Data System (ADS)

    Liljegren, S.; Höfner, S.; Nowotny, W.; Eriksson, K.

    2016-05-01

    Context. Winds of AGB stars are thought to be driven by a combination of pulsation-induced shock waves and radiation pressure on dust. In dynamic atmosphere and wind models, the stellar pulsation is often simulated by prescribing a simple sinusoidal variation in velocity and luminosity at the inner boundary of the model atmosphere. Aims: We experiment with different forms of the luminosity variation in order to assess the effects on the wind velocity and mass-loss rate, when progressing from the simple sinusoidal recipe towards more realistic descriptions. This will also give an indication of how robust the wind properties derived from the dynamic atmosphere models are. Methods: Using state-of-the-art dynamical models of C-rich AGB stars, a range of different asymmetric shapes of the luminosity variation and a range of phase shifts of the luminosity variation relative to the radial variation are tested. These tests are performed on two stellar atmosphere models. The first model has dust condensation and, as a consequence, a stellar wind is triggered, while the second model lacks both dust and wind. Results: The first model with dust and stellar wind is very sensitive to moderate changes in the luminosity variation. There is a complex relationship between the luminosity minimum, and dust condensation: changing the phase corresponding to minimum luminosity can either increase or decrease mass-loss rate and wind velocity. The luminosity maximum dominates the radiative pressure on the dust, which in turn, is important for driving the wind. An earlier occurrence of the maximum, with respect to the propagation of the pulsation-induced shock wave, then increases the wind velocity, while a later occurrence leads to a decrease. These effects of changed luminosity variation are coupled with the dust formation. In contrast there is very little change to the structure of the model without dust. Conclusions: Changing the luminosity variation, both by introducing a phase shift

  3. Biomass yield as affected by wheat harvest method

    SciTech Connect

    Allen, R.R.; Hollingsworth, L.D.

    1982-12-01

    Wheat biomass yield and the portions recoverable by different harvesting methods were investigated at Bushland, TX. Where all above-ground dry matter was removed by hand and threshed with a small bundle thresher; the grain, straw and chaff portions averaged about 40, 50, and 10, respectively, of the total biomass. When clipping samples at a simulated combine harvesting height (13-14 inches), the remaining stubble amounts ranged from 1500 to 3000 pounds per acre when grain yield levels averaged 3000 to 6000 pounds per acre. In treatments where the stubble was swathed and baled after conventional combine harvesting, the straw yields ranged from 2000 to 2800 pounds per acre. The bales accounted for 34 to 46 of the ''material other than grain.'' There was about 2000 pounds per acre of stubble remaining below the 3 to 4 inch swather cutting height. In treatments where the combine cutter-bar was operated near ground level (2 to 3 inches) and all straw discharge was caught (whole plant combining), the catchings ranged from 65 to 89 of the ''material other than grain.'' The catching weights ranged from 3900 to 6000 pounds per acre.

  4. Lidar-based biomass assessment for the Yukon River Basin

    NASA Astrophysics Data System (ADS)

    Peterson, B.; Wylie, B. K.; Stoker, J.; Nossov, D.

    2010-12-01

    Climate change is expected to have a significant impact on high-latitude forests in terms of their ability to sequester carbon as expressed as pools of standing total biomass and soil organic matter. Above ground biomass is an important driver in ecosystem process models used to assess, predict, and understand climate change impacts. Therefore, it is of compelling interest to acquire accurate assessments of current biomass levels for these high-latitude forests, a particular challenge because of their vastness and remoteness. At this time, remote sensing is the only feasible method through which to acquire such assessments. In this study, the use of lidar data for estimating shrub and tree biomass for the Yukon Flats region of Alaska’s Yukon River Basin (YRB) is demonstrated. The lidar data were acquired in the late summer and fall of 2009 as were an initial set of field sampling data collected for training and validation purposes. The 2009 field campaigns were located near Canvasback Lake and Boot Lake in the YRB. Various tallies of biomass were calculated from the field data using allometric equations (Bond-Lamberty et al. 2002, Yarie et al. 2007, Mack et al. 2008). Additional field data were also collected during two 2010 field campaigns at different locations in the Yukon Flats. Linear regressions have been developed based on field-based shrub and tree biomass and various lidar metrics of canopy height calculated for the plots (900 m^2). A multiple linear regression performed at the plot level resulted in a strong relationship (R^2=0.88) between observed and predicted biomass at the plot level. The coefficients for this regression were used to generate a shrub and tree biomass map for the entire Yukon Flats study area covered by lidar. This biomass map will be evaluated using additional field data collected in 2010 as well as other remote sensing data sources. Furthermore, additional lidar metrics (e.g. height of median energy) are being derived from the raw

  5. Biomass for Electricity Generation

    EIA Publications

    2002-01-01

    This paper examines issues affecting the uses of biomass for electricity generation. The methodology used in the National Energy Modeling System to account for various types of biomass is discussed, and the underlying assumptions are explained.

  6. Energy from Biomass.

    ERIC Educational Resources Information Center

    Carioca, J. O. B.; And Others

    1987-01-01

    Discusses how biomass in the form of fuelwood, crop residues, and animal dung can be converted into fuels such as biogas and ethanol to replace or supplement fossil fuels. Argues for future decentralized, integrated biomass energy development. (TW)

  7. Pretreated densified biomass products

    SciTech Connect

    Dale, Bruce E; Ritchie, Bryan; Marshall, Derek

    2014-03-18

    A product comprising at least one densified biomass particulate of a given mass having no added binder and comprised of a plurality of lignin-coated plant biomass fibers is provided, wherein the at least one densified biomass particulate has an intrinsic density substantially equivalent to a binder-containing densified biomass particulate of the same given mass and h a substantially smooth, non-flakey outer surface. Methods for using and making the product are also described.

  8. BIOMASS DRYING TECHNOLOGIES

    EPA Science Inventory

    The report examines the technologies used for drying of biomass and the energy requirements of biomass dryers. Biomass drying processes, drying methods, and the conventional types of dryers are surveyed generally. Drying methods and dryer studies using superheated steam as the d...

  9. Small Modular Biomass Systems

    SciTech Connect

    2002-12-01

    This fact sheet provides information about modular biomass systems. Small modular biomass systems can help supply electricity to rural areas, businesses, and the billions of people who live without power worldwide. These systems use locally available biomass fuels such as wood, crop waste, animal manures, and landfill gas.

  10. Biomass Program Biopower Factsheet

    SciTech Connect

    2010-03-01

    Generating electricity and thermal energy from biomass has the potential to help meet national goals for renewable energy. The forest products industry has used biomass for power and heat for many decades, yet widespread use of biomass to supply electricity to the U.S. power grid and other applications is relatively recent.

  11. THE SPECTRAL ENERGY DISTRIBUTION OF POST-STARBURST GALAXIES IN THE NEWFIRM MEDIUM-BAND SURVEY: A LOW CONTRIBUTION FROM TP-AGB STARS

    SciTech Connect

    Kriek, Mariska; Conroy, Charlie; Labbe, Ivo; Whitaker, Katherine E.; Van Dokkum, Pieter G.; Brammer, Gabriel B.; Muzzin, Adam; Franx, Marijn; Quadri, Ryan F.; Illingworth, Garth D.; Rudnick, Gregory

    2010-10-10

    Stellar population synthesis (SPS) models are a key ingredient of many galaxy evolution studies. Unfortunately, the models are still poorly calibrated for certain stellar evolution stages. Of particular concern is the treatment of the thermally pulsing asymptotic giant branch (TP-AGB) phase, as different implementations lead to systematic differences in derived galaxy properties. Post-starburst galaxies are a promising calibration sample, as TP-AGB stars are thought to be most prominently visible during this phase. Here, we use post-starburst galaxies in the NEWFIRM medium-band survey to assess different SPS models. The available photometry allows the selection of a homogeneous and well-defined sample of 62 post-starburst galaxies at 0.7 {approx_lt} z {approx_lt} 2.0, from which we construct a well-sampled composite spectral energy distribution (SED) over the range 1200-40000 A. The SED is well fit by the Bruzual and Charlot SPS models, while the Maraston models do not reproduce the rest-frame optical and near-infrared parts of the SED simultaneously. When the fitting is restricted to {lambda} < 6000 A, the Maraston models overpredict the near-infrared luminosity, implying that these models give too much weight to TP-AGB stars. Using the flexible SPS models by Conroy et al. and assuming solar metallicity, we find that the contribution of TP-AGB stars to the integrated SED is a factor of {approx}3 lower than predicted by the latest Padova TP-AGB models. Whether this is due to lower bolometric luminosities, shorter lifetimes, and/or heavy dust obscuration of TP-AGB stars remains to be addressed. Altogether, our data demand a low contribution from TP-AGB stars to the SED of post-starburst galaxies.

  12. Moving toward a Biomass Map of Boreal Eurasia based on ICESat GLAS, ASTER GDEM, and field measurements: Amount, Spatial distribution, and Statistical Uncertainties

    NASA Astrophysics Data System (ADS)

    Neigh, C. S.; Nelson, R. F.; Sun, G.; Ranson, J.; Montesano, P. M.; Margolis, H. A.

    2011-12-01

    The Eurasian boreal forest is the largest continuous forest in the world and contains a vast quantity of carbon stock that is currently vulnerable to loss from climate change. We develop and present an approach to map the spatial distribution of above ground biomass throughout this region. Our method combines satellite measurements from the Geoscience Laser Altimeter System (GLAS) that is carried on the Ice, Cloud and land Elevation Satellite ( ICESat), with the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM), and biomass field measurements collected from surveys from a number of different biomes throughout Boreal Eurasia. A slope model derived from the GDEM with quality control flags, and Moderate-resolution Imaging Spectroradiometer (MODIS) water mask was implemented to exclude poor quality GLAS shots and stratify measurements by MODIS International Geosphere Biosphere (IGBP) and World Wildlife Fund (WWF) ecozones. We derive equations from regional field measurements to estimate the spatial distribution of above ground biomass by land cover type within biome and present a map with uncertainties and limitations of this approach which can be used as a baseline for future studies.

  13. Understanding Biomass Feedstock Variability

    SciTech Connect

    Kevin L. Kenney; Garold L. Gresham; William A. Smith; Tyler L. Westover

    2013-01-01

    If the singular goal of biomass logistics and the design of biomass feedstock supply systems is to reduce the per-ton supply cost of biomass, these systems may very well develop with ultimate unintended consequences of highly variable and reduced quality biomass feedstocks. This paper demonstrates that, due to inherent species variabilities, production conditions and differing harvest, collection and storage practices, this is a very real scenario that biomass producers and suppliers as well as conversion developers should be aware of. Biomass feedstock attributes of ash, carbohydrates, moisture and particle morphology will be discussed. We will also discuss specifications for these attributes, inherent variability of these attributes in biomass feedstocks, and approaches and solutions for reducing variability for improving feedstock quality.

  14. Understanding Biomass Feedstock Variability

    SciTech Connect

    Kevin L. Kenney; William A. Smith; Garold L. Gresham; Tyler L. Westover

    2013-01-01

    If the singular goal of biomass logistics and the design of biomass feedstock supply systems is to reduce the per ton supply cost of biomass, these systems may very well develop with ultimate unintended consequences of highly variable and reduced quality biomass feedstocks. This paper demonstrates that due to inherent species variabilities, production conditions, and differing harvest, collection, and storage practices, this is a very real scenario that biomass producers and suppliers as well as conversion developers should be aware of. Biomass feedstock attributes of ash, carbohydrates, moisture, and particle morphology will be discussed. We will also discuss specifications for these attributes, inherent variability of these attributes in biomass feedstocks, and approaches and solutions for reducing variability for improving feedstock quality.

  15. Detailed homogeneous abundance studies of 14 Galactic s-process enriched post-AGB stars: In search of lead (Pb)

    NASA Astrophysics Data System (ADS)

    De Smedt, K.; Van Winckel, H.; Kamath, D.; Siess, L.; Goriely, S.; Karakas, A. I.; Manick, R.

    2016-03-01

    Context. This paper is part of a larger project in which we systematically study the chemical abundances of Galactic and extragalactic post-asymptotic giant branch (post-AGB) stars. The goal at large is to provide improved observational constraints to the models of the complex interplay between the AGB s-process nucleosynthesis and the associated mixing processes. Aims: Lead (Pb) is the final product of the s-process nucleosynthesis and is predicted to have large overabundances with respect to other s-process elements in AGB stars of low metallicities. However, Pb abundance studies of s-process enriched post-AGB stars in the Magellanic Clouds show a discrepancy between observed and predicted Pb abundances. The determined upper limits based on spectral studies are much lower than what is predicted. In this paper, we focus specifically on the Pb abundance of 14 Galactic s-process enhanced post-AGB stars to check whether the same discrepancy is present in the Galaxy as well. Among these 14 objects, two were not yet subject to a detailed abundance study in the literature. We apply the same method to obtain accurate abundances for the 12 others. Our homogeneous abundance results provide the input of detailed spectral synthesis computations in the spectral regions where Pb lines are located. Methods: We used high-resolution UVES and HERMES spectra for detailed spectral abundance studies of our sample of Galactic post-AGB stars. None of the sample stars display clear Pb lines, and we only deduced upper limits of the Pb abundance by using spectrum synthesis in the spectral ranges of the strongest Pb lines. Results: We do not find any clear evidence of Pb overabundances in our sample. The derived upper limits are strongly correlated with the effective temperature of the stars with increasing upper limits for increasing effective temperatures. We obtain stronger Pb constraints on the cooler objects. Moreover, we confirm the s-process enrichment and carbon enhancement of two

  16. Detailed homogeneous abundance studies of 14 Galactic s-process enriched post-AGB stars: In search of lead (Pb)

    NASA Astrophysics Data System (ADS)

    De Smedt, K.; Van Winckel, H.; Kamath, D.; Siess, L.; Goriely, S.; Karakas, A. I.; Manick, R.

    2016-03-01

    Context. This paper is part of a larger project in which we systematically study the chemical abundances of Galactic and extragalactic post-asymptotic giant branch (post-AGB) stars. The goal at large is to provide improved observational constraints to the models of the complex interplay between the AGB s-process nucleosynthesis and the associated mixing processes. Aims: Lead (Pb) is the final product of the s-process nucleosynthesis and is predicted to have large overabundances with respect to other s-process elements in AGB stars of low metallicities. However, Pb abundance studies of s-process enriched post-AGB stars in the Magellanic Clouds show a discrepancy between observed and predicted Pb abundances. The determined upper limits based on spectral studies are much lower than what is predicted. In this paper, we focus specifically on the Pb abundance of 14 Galactic s-process enhanced post-AGB stars to check whether the same discrepancy is present in the Galaxy as well. Among these 14 objects, two were not yet subject to a detailed abundance study in the literature. We apply the same method to obtain accurate abundances for the 12 others. Our homogeneous abundance results provide the input of detailed spectral synthesis computations in the spectral regions where Pb lines are located. Methods: We used high-resolution UVES and HERMES spectra for detailed spectral abundance studies of our sample of Galactic post-AGB stars. None of the sample stars display clear Pb lines, and we only deduced upper limits of the Pb abundance by using spectrum synthesis in the spectral ranges of the strongest Pb lines. Results: We do not find any clear evidence of Pb overabundances in our sample. The derived upper limits are strongly correlated with the effective temperature of the stars with increasing upper limits for increasing effective temperatures. We obtain stronger Pb constraints on the cooler objects. Moreover, we confirm the s-process enrichment and carbon enhancement of two

  17. Genome size and ploidy influence angiosperm species' biomass under nitrogen and phosphorus limitation.

    PubMed

    Guignard, Maïté S; Nichols, Richard A; Knell, Robert J; Macdonald, Andy; Romila, Catalina-Andreea; Trimmer, Mark; Leitch, Ilia J; Leitch, Andrew R

    2016-06-01

    Angiosperm genome sizes (GS) range c. 2400-fold, and as nucleic acids are amongst the most phosphorus- (P) and nitrogen (N)-demanding cellular biomolecules, we test the hypothesis that a key influence on plant biomass and species composition is the interaction between N and P availability and plant GS. We analysed the impact of different nutrient regimes on above-ground biomass of angiosperm species with different GS, ploidy level and Grime's C-S-R (competitive, stress-tolerant, ruderal) plant strategies growing at the Park Grass Experiment (Rothamsted, UK), established in 1856. The biomass-weighted mean GS of species growing on plots with the addition of both N and P fertilizer were significantly higher than that of plants growing on control plots and plots with either N or P. The plants on these N + P plots are dominated by polyploids with large GS and a competitive plant strategy. The results are consistent with our hypothesis that large genomes are costly to build and maintain under N and P limitation. Hence GS and ploidy are significant traits affecting biomass growth under different nutrient regimes, influencing plant community composition and ecosystem dynamics. We propose that GS is a critical factor needed in models that bridge the knowledge gap between biodiversity and ecosystem functioning. PMID:26875784

  18. Radial-Velocity Analysis of the Post-AGB Star, HD101584

    NASA Astrophysics Data System (ADS)

    Díaz, F.; Hearnshaw, J.; Rosenzweig, P.; Guzman, E.; Sivarani, T.; Parthasarathy, M.

    2007-08-01

    This project concerns the analysis of the periodicity of the radial velocity of the peculiar emission-line supergiant star HD 101584 (F0 Ia), and also we propose a physical model to account for the observations. From its peculiarities, HD 101584 is a star that is in the post-AGB phase. This study is considered as a key to clarify the multiple aspects related with the evolution of the circum-stellar layer associated with this star's last phase. The star shows many lines with P Cygni profiles, including H-alpha, Na D lines in the IR Ca triplet, indicating a mass outflow. For HD 101584 we have performed a detailed study of its radial-velocity variations, using both emission and absorption lines over a wide range of wavelength. We have analyzed the variability and found a periodicity for all types of lines of 144 days, which must arise from the star's membership in a binary system. The data span a period of five consecutive years and were obtained using the 1-m telescope of Mt John Observatory, in New Zealand., with the echelle and Hercules high resolution spectrographs and CCD camera. HD101584 is known to be an IRAS source, and our model suggests it is a proto-planetary nebula, probably with a bipolar outflow and surrounded by a dusty disk as part of a binary system. We have found no evidence for HD101584 to contain a B9 star as found by Bakker et al (1996). A low resolution IUE spectrum shows the absence of any strong UV continuum that would be expected for a B star to be in this system.

  19. A Luminous Yellow Post-AGB Star in the Galactic Globular Cluster M79

    NASA Astrophysics Data System (ADS)

    Bond, Howard E.; Ciardullo, Robin; Siegel, Michael H.

    2016-02-01

    We report the discovery of a luminous F-type post-asymptotic-giant-branch (PAGB) star in the Galactic globular cluster (GC) M79 (NGC 1904). At visual apparent and absolute magnitudes of V=12.20 and {M}V=-3.46, this “yellow” PAGB star is by a small margin the visually brightest star known in any GC. It was identified using CCD observations in the uBVI photometric system, which is optimized to detect stars with large Balmer discontinuities, indicative of very low surface gravities. Follow-up observations with the SMARTS 1.3 and 1.5 m telescopes show that the star is not variable in light or radial velocity, and that its velocity is consistent with cluster membership. Near- and mid-infrared observations with 2MASS and WISE show no evidence for circumstellar dust. We argue that a sharp upper limit to the luminosity function exists for yellow PAGB stars in old populations, making them excellent candidates for Population II standard candles, which are four magnitudes brighter than RR Lyrae variables. Their luminosities are consistent with the stars being in a PAGB evolutionary phase, with core masses of ˜ 0.53 {M}⊙ . We also detected four very hot stars lying above the horizontal branch (“AGB-manqué” stars); along with the PAGB star, they are the brightest objects in M79 in the near-ultraviolet. In the Appendix, we give periods and light curves for five variables in M79: three RR Lyrae stars, a Type II Cepheid, and a semiregular variable. Based in part on observations with the 1.3 and 1.5 m telescopes operated by the SMARTS Consortium at Cerro Tololo Interamerican Observatory.

  20. NanoSIMS studies of Ba isotopic compositions in single presolar silicon carbide grains from AGB stars and supernovae

    NASA Astrophysics Data System (ADS)

    Marhas, K. K.; Hoppe, P.; Ott, U.

    2007-08-01

    We have studied 74 single presolar silicon carbide grains with sizes between 0.2 and 2.6 μm from the Murchison and Murray meteorites for Ba isotopic compositions using NanoSIMS. We also analyzed 7 SiC particles either consisting of sub-micron-size SiC grains or representing a morphologically and isotopically distinct subgroup. Of the 55 (likely) mainstream grains, originating from asymptotic giant branch (AGB) stars, 32 had high enough Ba contents for isotopic analysis. For 26 of them, CsHx interferences were either negligible or could be corrected with confidence. They exhibit typical s-process Ba isotopic patterns with slightly higher than solar 134Ba/136Ba and lower than solar 135,137,138Ba/136Ba ratios. Results are generally well explained in the context of neutron capture nucleosynthesis in low mass (1-3 M⊙) AGB stars and provide constraints on AGB models, by reducing the needed 13C spread from factor of ˜20 down to 2. Out of the 19 supernova X grains, three had sufficient concentrations for isotopic analysis. They tend to exhibit higher than solar 134Ba/136Ba and 138Ba/136Ba ratios, close to solar 137Ba/136Ba, and 135Ba/136Ba lower than solar but higher than in mainstream grains. This signature could indicate a mixture of n-burst type Ba with either "normal Ba" more s-process-rich than solar, or normal Ba plus weak s-process Ba. In the n-burst component Cs may have to be separated from Ba at ˜10 years after the SN explosion. Depending on predictions for its composition, another possibility is early separation (at ˜1 year) coupled with addition of some unfractionated n-burst matter. Abundances of trace elements (Sr, Zr, Cs, La, and Ce) analyzed along with Ba signify that implantation may have been an important process for their introduction.

  1. Detection of HCN and C2H2 in ISO Spectra of Oxygen-Rich AGB Stars

    NASA Technical Reports Server (NTRS)

    Carbon, Duane F.; Chiar, Jean; Goorvitch, David; Kwak, Dochan (Technical Monitor)

    2002-01-01

    Cool oxygen-rich AGB stars were not expected to have organic molecules like HCN in either their photospheres or circumstellar envelopes (CSEs). The discovery of HCN and CS microwave emission from the shallowest CSE layers of these stars was a considerable surprise and much theoretical effort has been expended in explaining the presence of such organics. To further explore this problem, we have undertaken a systematic search of oxygen-rich AGB stellar spectra in the Infrared Space Observatory (ISO) data archive. Our purposes are to find evidence regarding critical molecular species that could be of value in choosing among the proposed theoretical models, to locate spectral features which might give clues to conditions deeper in the CSEs, and to lay the groundwork for future SIRTF (Space Infrared Telescope Facility) and SOFIA (Stratospheric Observatory for Infrared Astronomy) observations. Using carefully reduced observations, we have detected weak absorption features arising from HCN and possibly C2H2 in a small number of oxygen-rich AGB stars. The most compelling case is NML Cyg which shows both HCN (14 microns) and CO2 (15 microns). VY CMa, a similar star, shows evidence for HCN, but not CO2. Two S-type stars show evidence for the C-H bending transitions: W Aql at 14 microns (HCN) and both W Aql and S Cas at 13.7 microns (C2H2). Both W Aql and S Cas as well as S Lyr, a SC-type star, show 3 micron absorption which may arise from the C-H stretch of HCN and C2H2. In the case of NML Cyg, we show that the HCN and CO2 spectral features are formed in the CSE at temperatures well above those of the outermost CSE layers and derive approximate column densities. In the case of the S-stars, we discuss the evidence for the organic features and their photospheric origin.

  2. Gasification of Woody Biomass.

    PubMed

    Dai, Jianjun; Saayman, Jean; Grace, John R; Ellis, Naoko

    2015-01-01

    Interest in biomass to produce heat, power, liquid fuels, hydrogen, and value-added chemicals with reduced greenhouse gas emissions is increasing worldwide. Gasification is becoming a promising technology for biomass utilization with a positive environmental impact. This review focuses specifically on woody biomass gasification and recent advances in the field. The physical properties, chemical structure, and composition of biomass greatly affect gasification performance, pretreatment, and handling. Primary and secondary catalysts are of key importance to improve the conversion and cracking of tars, and lime-enhanced gasification advantageously combines CO2 capture with gasification. These topics are covered here, including the reaction mechanisms and biomass characterization. Experimental research and industrial experience are investigated to elucidate concepts, processes, and characteristics of woody biomass gasification and to identify challenges. PMID:26247289

  3. Complex pendulum biomass sensor

    DOEpatents

    Hoskinson, Reed L.; Kenney, Kevin L.; Perrenoud, Ben C.

    2007-12-25

    A complex pendulum system biomass sensor having a plurality of pendulums. The plurality of pendulums allow the system to detect a biomass height and density. Each pendulum has an angular deflection sensor and a deflector at a unique height. The pendulums are passed through the biomass and readings from the angular deflection sensors are fed into a control system. The control system determines whether adjustment of machine settings is appropriate and either displays an output to the operator, or adjusts automatically adjusts the machine settings, such as the speed, at which the pendulums are passed through the biomass. In an alternate embodiment, an entanglement sensor is also passed through the biomass to determine the amount of biomass entanglement. This measure of entanglement is also fed into the control system.

  4. Optically visible post-AGB/RGB stars and young stellar objects in the Small Magellanic Cloud: candidate selection, spectral energy distributions and spectroscopic examination

    NASA Astrophysics Data System (ADS)

    Kamath, D.; Wood, P. R.; Van Winckel, H.

    2014-04-01

    We have carried out a search for optically visible post-asymptotic giant branch (post-AGB) candidates in the Small Magellanic Cloud (SMC). First, we used mid-IR observations from the Spitzer Space Telescope to select optically visible candidates with excess mid-IR flux and then we obtained low-resolution optical spectra for 801 of the candidates. After removing poor-quality spectra and contaminants, such as M-stars, C-stars, planetary nebulae, quasi-stellar objects and background galaxies, we ended up with a final sample of 63 high-probability post-AGB/RGB candidates of A-F spectral type. From the spectral observations, we estimated the stellar parameters: effective temperature (Teff), surface gravity (log g) and metallicity ([Fe/H]). We also estimated the reddening and deduced the luminosity using the stellar parameters combined with photometry. For the post-AGB/RGB candidates, we found that the metallicity distribution peaks at [Fe/H] ≈ -1.00 dex. Based on a luminosity criterion, 42 of these 63 sources were classified as post-red giant branch (post-RGB) candidates and the remaining 21 as post-AGB candidates. From the spectral energy distributions, we were able to infer that 6 of the 63 post-AGB/RGB candidates have a surrounding circumstellar shell suggesting that they are single stars, while 27 of the post-AGB/RGB candidates have a surrounding disc, suggesting that they lie in binary systems. For the remaining 30 post-AGB/RGB candidates the nature of the circumstellar environment was unclear. Variability is displayed by 38 of the 63 post-AGB/RGB candidates with the most common variability types being the Population II Cepheids (including RV-Tauri stars) and semiregular variables. This study has also revealed a new RV Tauri star in the SMC, J005107.19-734133.3, which shows signs of s-process enrichment. From the numbers of post-AGB/RGB stars in the SMC, we were able to estimate evolutionary rates. We find that the number of post-AGB and post-RGB candidates that

  5. Process for treating biomass

    DOEpatents

    Campbell, Timothy J.; Teymouri, Farzaneh

    2015-08-11

    This invention is directed to a process for treating biomass. The biomass is treated with a biomass swelling agent within the vessel to swell or rupture at least a portion of the biomass. A portion of the swelling agent is removed from a first end of the vessel following the treatment. Then steam is introduced into a second end of the vessel different from the first end to further remove swelling agent from the vessel in such a manner that the swelling agent exits the vessel at a relatively low water content.

  6. Engine fuels from biomass

    NASA Astrophysics Data System (ADS)

    Parker, H. W.

    1981-01-01

    Sources of biomass fuels for engines are compared to other synfuels. Biomass can be converted to gaseous and liquid engine fuels by the same processes utilized for coal conversion such as gasification, direct liquefaction, and indirect liquefaction. Alternatively, biomass can be converted into liquid fuels by fermentation to methane or ethanol. The quantities of biomass derived engine fuels potentially available in the next decade are relatively small, and the anticipated costs are significantly greater than for liquid engine fuels made from coal or oil shale.

  7. Biomass Processing Photolibrary

    DOE Data Explorer

    Research related to bioenergy is a major focus in the U.S. as science agencies, universities, and commercial labs seek to create new energy-efficient fuels. The Biomass Processing Project is one of the funded projects of the joint USDA-DOE Biomass Research and Development Initiative. The Biomass Processing Photolibrary has numerous images, but there are no accompanying abstracts to explain what you are seeing. The project website, however, makes available the full text of presentations and publications and also includes an exhaustive biomass glossary that is being developed into an ASAE Standard.

  8. Process for treating biomass

    SciTech Connect

    Campbell, Timothy J; Teymouri, Farzaneh

    2015-11-04

    This invention is directed to a process for treating biomass. The biomass is treated with a biomass swelling agent within the vessel to swell or rupture at least a portion of the biomass. A portion of the swelling agent is removed from a first end of the vessel following the treatment. Then steam is introduced into a second end of the vessel different from the first end to further remove swelling agent from the vessel in such a manner that the swelling agent exits the vessel at a relatively low water content.

  9. Gasification-based biomass

    SciTech Connect

    None, None

    2009-01-18

    The gasification-based biomass section of the Renewable Energy Technology Characterizations describes the technical and economic status of this emerging renewable energy option for electricity supply.

  10. AN INFRARED CENSUS OF DUST IN NEARBY GALAXIES WITH SPITZER (DUSTiNGS). II. DISCOVERY OF METAL-POOR DUSTY AGB STARS

    SciTech Connect

    Boyer, Martha L.; Sonneborn, George; McQuinn, Kristen B. W.; Gehrz, Robert D.; Skillman, Evan; Barmby, Pauline; Bonanos, Alceste Z.; Gordon, Karl D.; Meixner, Margaret; Groenewegen, M. A. T.; Lagadec, Eric; Lennon, Daniel; Marengo, Massimo; McDonald, Iain; Zijlstra, Albert; Sloan, G. C.; Van Loon, Jacco Th.

    2015-02-10

    The DUSTiNGS survey (DUST in Nearby Galaxies with Spitzer) is a 3.6 and 4.5 μm imaging survey of 50 nearby dwarf galaxies designed to identify dust-producing asymptotic giant branch (AGB) stars and massive stars. Using two epochs, spaced approximately six months apart, we identify a total of 526 dusty variable AGB stars (sometimes called ''extreme'' or x-AGB stars; [3.6]-[4.5] > 0.1 mag). Of these, 111 are in galaxies with [Fe/H] < –1.5 and 12 are in galaxies with [Fe/H] < –2.0, making them the most metal-poor dust-producing AGB stars known. We compare these identifications to those in the literature and find that most are newly discovered large-amplitude variables, with the exception of ≈30 stars in NGC 185 and NGC 147, 1 star in IC 1613, and 1 star in Phoenix. The chemical abundances of the x-AGB variables are unknown, but the low metallicities suggest that they are more likely to be carbon-rich than oxygen-rich and comparisons with existing optical and near-IR photometry confirm that 70 of the x-AGB variables are confirmed or likely carbon stars. We see an increase in the pulsation amplitude with increased dust production, supporting previous studies suggesting that dust production and pulsation are linked. We find no strong evidence linking dust production with metallicity, indicating that dust can form in very metal-poor environments.

  11. Development of a Model for Estimation of Acacia Senegal Tree Biomass Using Allometry and Aster Satellite Imagery at Ennuhud, West Kordofan State, Sudan

    NASA Astrophysics Data System (ADS)

    Elamin, Hatim; Elnour Adam, Hassan; Csaplovics, Elmar

    The current paper deals with the development of a biomass model for Acacia senegal trees by applying allometric equations for ground data combined with ASTER satellite data sets. The current study is conducted around Ennuhud area which is located in Ennuhud locality in West Kordofan State, Sudan. Primary data are obtained by application of random sampling around Ennuhud town where Acacia senegal tree species is abundant. Ten sample units are taken. Each unit contains five sample plots (15x15 m), one in the centre and the others in the four directions 100 m away from the centre forming a total of 50 sample plots. The tree coordinates, diameter/diameters (diameter at breast height ≥ 5 cm), height and crown diameters will be recorded. Sensor data were acquired from ASTER remote sensing satellite (29.03.2007 & 26.01.2011) and integrated with the in-situ data. The expected findings allow for the calculation of the mean diameter of trees. The tree above ground biomass (TAGB), tree below ground biomass (TBGB) and the tree total biomass (TTB) of Acacia senegal are computed consequently. Remotely sensed data are integrated with the ground data for creating the data base for calculating the correlation of the relationship between the two methods of data collection. The application of allometric equations is useful as a non-destructive method for biomass estimation by the application of remote sensing is recommended for biomass modelling over large areas. Keywords: Biomass model, Acacia senegal tree, remote sensing, Ennuhud, North Kordofan

  12. Developing synergy regression models with space-borne ALOS PALSAR and Landsat TM sensors for retrieving tropical forest biomass

    NASA Astrophysics Data System (ADS)

    Sinha, Suman; Jeganathan, C.; Sharma, L. K.; Nathawat, M. S.; Das, Anup K.; Mohan, Shiv

    2016-06-01

    Forest stand biomass serves as an effective indicator for monitoring REDD (reducing emissions from deforestation and forest degradation). Optical remote sensing data have been widely used to derive forest biophysical parameters inspite of their poor sensitivity towards the forest properties. Microwave remote sensing provides a better alternative owing to its inherent ability to penetrate the forest vegetation. This study aims at developing optimal regression models for retrieving forest above-ground bole biomass (AGBB) utilising optical data from Landsat TM and microwave data from L-band of ALOS PALSAR data over Indian subcontinental tropical deciduous mixed forests located in Munger (Bihar, India). Spatial biomass models were developed. The results using Landsat TM showed poor correlation (R 2 = 0.295 and RMSE = 35 t/ha) when compared to HH polarized L-band SAR (R 2 = 0.868 and RMSE = 16.06 t/ha). However, the prediction model performed even better when both the optical and SAR were used simultaneously (R 2 = 0.892 and RMSE = 14.08 t/ha). The addition of TM metrics has positively contributed in improving PALSAR estimates of forest biomass. Hence, the study recommends the combined use of both optical and SAR sensors for better assessment of stand biomass with significant contribution towards operational forestry.

  13. Developing synergy regression models with space-borne ALOS PALSAR and Landsat TM sensors for retrieving tropical forest biomass

    NASA Astrophysics Data System (ADS)

    Sinha, Suman; Jeganathan, C.; Sharma, L. K.; Nathawat, M. S.; Das, Anup K.; Mohan, Shiv

    2016-06-01

    Forest stand biomass serves as an effective indicator for monitoring REDD (reducing emissions from deforestation and forest degradation). Optical remote sensing data have been widely used to derive forest biophysical parameters inspite of their poor sensitivity towards the forest properties. Microwave remote sensing provides a better alternative owing to its inherent ability to penetrate the forest vegetation. This study aims at developing optimal regression models for retrieving forest above-ground bole biomass (AGBB) utilising optical data from Landsat TM and microwave data from L-band of ALOS PALSAR data over Indian subcontinental tropical deciduous mixed forests located in Munger (Bihar, India). Spatial biomass models were developed. The results using Landsat TM showed poor correlation ( R 2 = 0.295 and RMSE = 35 t/ha) when compared to HH polarized L-band SAR ( R 2 = 0.868 and RMSE = 16.06 t/ha). However, the prediction model performed even better when both the optical and SAR were used simultaneously ( R 2 = 0.892 and RMSE = 14.08 t/ha). The addition of TM metrics has positively contributed in improving PALSAR estimates of forest biomass. Hence, the study recommends the combined use of both optical and SAR sensors for better assessment of stand biomass with significant contribution towards operational forestry.

  14. Biomass Research Program

    SciTech Connect

    Kenney, Kevin; Wright, Christopher; Shelton-Davis, Colleen

    2011-01-01

    INL's mission is to achieve DOE's vision of supplying high-quality raw biomass; preprocessing biomass into advanced bioenergy feedstocks; and delivering bioenergy commodities to biorefineries. You can learn more about research like this at the lab's facebook site http://www.facebook.com/idahonationallaboratory.

  15. Global biomass opportunities

    SciTech Connect

    Sheinkopf, K.

    1993-10-01

    Low cost and plentiful resources make biomass a viable choice for power projects worldwide. Nevertheless, the potential does not alleviate the development obstacles. The developing world appears to hold the greatest promise for using biomass technologies - primarily Latin America, Africa, China, and other parts of Asia and Oceania.

  16. Biomass Research Program

    ScienceCinema

    Kenney, Kevin; Wright, Christopher; Shelton-Davis, Colleen

    2013-05-28

    INL's mission is to achieve DOE's vision of supplying high-quality raw biomass; preprocessing biomass into advanced bioenergy feedstocks; and delivering bioenergy commodities to biorefineries. You can learn more about research like this at the lab's facebook site http://www.facebook.com/idahonationallaboratory.

  17. CEN 34 - high-mass YSO in M 17 or background post-AGB star?

    NASA Astrophysics Data System (ADS)

    Chen, Zhiwei; Nürnberger, Dieter E. A.; Chini, Rolf; Liu, Yao; Fang, Min; Jiang, Zhibo

    2013-09-01

    We investigate the proposed high-mass young stellar object (YSO) candidate CEN 34, thought to be associated with the star-forming region M 17. Its optical to near-infrared (550-2500 nm) spectrum reveals several photospheric absorption features, such as Hα, the Ca ii triplet, and the CO bandhead, but lacks emission lines. The spectral features in the range 8375-8770 Å are used to constrain an effective temperature Teff = 5250 ± 250 K (early-/mid-G) and a log g = 2.0 ± 0.3 (supergiant). The spectral energy distribution (SED) displays a faint infrared excess that resembles that of a high-mass YSO or an evolved star of intermediate mass. Moreover, the observed temperature and surface gravity are identical for high-mass YSOs and evolved stars. The radial velocity of CEN 34 relative to the local standard of rest (VLSR) as obtained from various photospheric lines is of the order of -60 km s-1 and thus distinct from the +25 km s-1 found for several OB stars in the cluster and for the associated molecular cloud. The SED modeling yields 10-4 M⊙ of circumstellar material, which contributes only a tiny fraction to the total visual extinction (11 mag). The distance of CEN 34 is between 2.0 kpc and 4.5 kpc. In the case of a YSO, a dynamical ejection process is proposed to explain the VLSR difference between CEN 34 and M 17. Additionally, to match the temperature and luminosity, we speculate that CEN 34 had accumulated the bulk of its mass with an accretion rate >4 × 10-3M⊙/yr over a very short time span (~103 yrs), and it is currently undergoing a phase of gravitational contraction without any further mass gain. However, all the aforementioned characteristics of CEN 34 are compatible with an evolved star of 5-7 M⊙ and an age of 50-100 Myr, so it is most likely a background post-AGB star with a distance between 2.0 kpc and 4.5 kpc. We consider the latter classification as the more likely interpretation. Further discrimination of the two possible scenarios should come

  18. The planetary nebulae and H II regions in NGC 6822 revisited. Clues to AGB nucleosynthesis

    NASA Astrophysics Data System (ADS)

    García-Rojas, Jorge; Peña, Miriam; Flores-Durán, Sheila; Hernández-Martínez, Liliana

    2016-02-01

    Aims: The chemical behaviour of an ample sample of planetary nebulae (PNe) in NGC 6822 is analysed. Methods: Spectrophotometric data of 11 PNe and two H ii regions were obtained with the OSIRIS spectrograph attached to the Gran Telescopio Canarias. Data for other 13 PNe and three H ii regions were retrieved from the literature. Physical conditions and chemical abundances of O, N, Ne, Ar, and S were derived in a consistent way for 19 PNe and 4 H ii regions. Results: Abundances in the PNe sample are widely distributed showing 12 + log (O/H) from 7.4 to 8.2 and 12 + log (Ar/H) from 4.97 to 5.80. Two groups of PNe can be differentiated: one old with low metallicity (12 + log (O/H) <8.0 and 12 + log (Ar/H) < 5.7) and another younger one with metallicities similar to the values for H ii regions. The old objects are distributed in a larger volume than the young ones. An important fraction of PNe (over 30%) was found to be highly N-rich (Peimbert Type I PNe). Such PNe occur at any metallicity. In addition, about 60% of the sample presents high ionization (He++/He ≥ 0.1), possessing a central star with effective temperature higher than 100 000 K. Possible biases in the sample are discussed. From comparison with stellar evolution models by Karakas (2010) and Fishlock et al. (2014) of the observed N/O abundance ratios, our PNe should have had initial masses that are lower than 4 M⊙, although if the comparison is made with Ne vs. O abundances, the initial masses should have been lower than 2 M⊙. It appears that these models of stars of 2-3 M⊙ are producing too much 22Ne in the stellar surface at the end of the AGB. On the other hand, the comparison with another set of stellar evolution models with a different treatment of convection and on the assumptions about the overshoot of the convective core during the core H-burning phase, provided there is reasonable agreement between the observed and predicted N/O and Ne/H ratios if initial masses of more massive stars are

  19. SPITZER survey of dust grain processing in stable discs around binary post-AGB stars

    NASA Astrophysics Data System (ADS)

    Gielen, C.; van Winckel, H.; Min, M.; Waters, L. B. F. M.; Lloyd Evans, T.

    2008-11-01

    Aims: We investigate the mineralogy and dust processing in the circumbinary discs of binary post-AGB stars using high-resolution TIMMI2 and SPITZER infrared spectra. Methods: We perform a full spectral fitting to the infrared spectra using the most recent opacities of amorphous and crystalline dust species. This allows for the identification of the carriers of the different emission bands. Our fits also constrain the physical properties of different dust species and grain sizes responsible for the observed emission features. Results: In all stars the dust is oxygen-rich: amorphous and crystalline silicate dust species prevail and no features of a carbon-rich component can be found, the exception being EP Lyr, where a mixed chemistry of both oxygen- and carbon-rich species is found. Our full spectral fitting indicates a high degree of dust grain processing. The mineralogy of our sample stars shows that the dust is constituted of irregularly shaped and relatively large grains, with typical grain sizes larger than 2 μm. The spectra of nearly all stars show a high degree of crystallinity, where magnesium-rich end members of olivine and pyroxene silicates dominate. Other dust features of e.g. silica or alumina are not present at detectable levels. Temperature estimates from our fitting routine show that a significant fraction of grains must be cool, significantly cooler than the glass temperature. This shows that radial mixing is very efficient is these discs and/or indicates different thermal conditions at grain formation. Our results show that strong grain processing is not limited to young stellar objects and that the physical processes occurring in the discs are very similar to those in protoplanetary discs. Based on observations obtained at the European Southern Observatory (ESO), La Silla, observing program 072.D-0263, on observations made with the 1.2 m Flemish Mercator telescope at Roque de los Muchachos, Spain, the 1.2 m Swiss Euler telescope at La Silla

  20. Dust formation in the oxygen-rich AGB star IK Tauri

    NASA Astrophysics Data System (ADS)

    Gobrecht, D.; Cherchneff, I.; Sarangi, A.; Plane, J. M. C.; Bromley, S. T.

    2016-01-01

    interferometric observations. The derived dust-to-gas mass ratio for IK Tau is in the range 1-6 × 10-3 and agrees with values derived from observations of O-rich Mira-type stars. Conclusions: Our results confirm the importance of periodic shocks in chemically shaping the inner wind of AGB stars and providing gas conditions conducive to the efficient synthesis of molecules and dust by non-equilibrium processes. They indicate that the wind acceleration will possibly develop in the radius range 4-8 R⋆ in IK Tau.

  1. Examining the Impact of Early AGB Nucleosynthesis on the Apparent Cosmological Variation in the Fine Structure Constant

    NASA Astrophysics Data System (ADS)

    Ashenfelter, Timothy; Mathews, Grant; Olive, Keith

    2004-10-01

    Evidence from a large sample of quasar absorption-line spectra in damped Lyman-α systems has shown potential cosmological variation of the fine structure constant α. The most statistically significant portion of this sample involves the comparison of Mg and Fe wavelength shifts using the many-multiplet (MM) method. However, this method is sensitive to the heavy isotopes, especially in Mg. We implement recent yields of intermediate mass (IM) stars, which evolve beyond the CNO cycle, to show that the ensuing isotope distribution of Mg can account for the observed variation in α provided early star-formation was particularly rich in IM stars. During the Asymptotic Giant Branch (AGB) phase of IM stars, heavy Mg isotopes are robustly produced via hot-bottom burning and thermal pulsing in helium burning shell. We incorporate these recently appreciated processes in the galactic chemical evolution models of these damped Lyman-α systems (early galaxies) and delve into the consequences of this chemical evolution alternative to an α variation. We find that this analysis adds to the mounting evidence that the low-metallicity Universe was strongly influenced by IM stars beyond the standard power law distribution of stellar masses. Because these AGB stars have a significant influence on other abundances, especially nitrogen, we use measurements of N, Si Fe, C, and O to constrain our models. In this way, we obtain an alternative explanation of the α variation that is consistent with observations.

  2. Hydrodynamic simulations of the interaction between an AGB star and a main-sequence companion in eccentric orbits

    NASA Astrophysics Data System (ADS)

    Staff, Jan E.; De Marco, Orsola; Macdonald, Daniel; Galaviz, Pablo; Passy, Jean-Claude; Iaconi, Roberto; Low, Mordecai-Mark Mac

    2016-02-01

    The Rotten Egg Nebula has at its core a binary composed of a Mira star and an A-type companion at a separation >10 au. It has been hypothesized to have formed by strong binary interactions between the Mira and a companion in an eccentric orbit during periastron passage ˜800 yr ago. We have performed hydrodynamic simulations of an asymptotic giant branch (AGB) star interacting with companions with a range of masses in orbits with a range of initial eccentricities and periastron separations. For reasonable values of the eccentricity, we find that Roche lobe overflow can take place only if the periods are ≪100 yr. Moreover, mass transfer causes the system to enter a common envelope phase within several orbits. Since the central star of the Rotten Egg nebula is an AGB star, we conclude that such a common envelope phase must have lead to a merger, so the observed companion must have been a tertiary companion of a binary that merged at the time of nebula ejection. Based on the mass and time-scale of the simulated disc formed around the companion before the common envelope phase, we analytically estimate the properties of jets that could be launched. Allowing for super-Eddington accretion rates, we find that jets similar to those observed are plausible, provided that the putative lost companion was relatively massive.

  3. Modelling a set of C-rich AGB stars: the cases of RU Vir and R Lep

    NASA Astrophysics Data System (ADS)

    Rau, G.; Paladini, C.; Hron, J.; Aringer, B.; Groenewegen, M. A. T.; Nowotny, W.

    We study the atmospheres of a set of carbon-rich asymptotic giant branch AGB stars to improve our understanding of the dynamic processes happening there. We compare in a systematic way spectrometric, photometric and mid-infrared (VLTI/MIDI) interferometric measurements with different types of model atmospheres: (1) hydrostatic models + MOD-dusty models added a posteriori; (2) self-consistent dynamic model atmospheres. These allow us to interpret in a coherent way the dynamic behavior of gas and dust. The results underline that the joint use of different kinds of observations, as photometry, spectroscopy and interferometry, is essential for understanding the atmospheres of pulsating C-rich AGB stars. For our first target, the carbon-rich Mira star RU Vir, the dynamic model atmospheres fit well the ISO/SWS spectrum in the wavelength range lambda = [2.9, 13.0] mu m. However, the object turned out to be somehow ''peculiar''. The other target we present is R Lep. Here the agreement between models and observations is much better although the MIDI data at 11.4 mu m cannot be properly modelled.

  4. VizieR Online Data Catalog: Water maser emission toward post-AGB and PN (Gomez+, 2015)

    NASA Astrophysics Data System (ADS)

    Gomez, J. F.; Rizzo, J. R.; Suarez, O.; Palau, A.; Miranda, L. F.; Guerrero, M. A.; Ramos-Larios, G.; Torrelles, J. M.

    2015-09-01

    The observed sources are listed in Table 1. They comprise most of the sources in Ramos-Larios et al. (2009A&A...501.1207R). They are post-AGB stars and PN candidates with the IRAS color criteria of Suarez et al. (2006A&A...458..173S) and with signs of strong optical obscuration. We have also included some optically visible post-AGB stars from Suarez et al. (2006A&A...458..173S) that were not included in our previous water maser observations of Suarez et al. (2007A&A...467.1085S, 2009A&A...505..217S) or for which those observations had poor sensitivity. We observed the 616-523 transition of H2O (rest frequency = 22235.08MHz) using three different telescopes: the DSS-63 antenna (70m diameter) at the Madrid Deep Space Communications Complex (MDSCC) near Robledo de Chavela (Spain), the 64m antenna at the Parkes Observatory of the Australia Telescope National Facility (ATNF), and the 100m Robert C. Byrd Green Bank Telescope (GBT) of the National Radio Astronomy Observatory. The observed positions, rms noise per spectral channel, and observing dates are listed in Table 1. (3 data files).

  5. Biomass power in transition

    SciTech Connect

    Marshall, D.K.

    1996-12-31

    Electricity production from biomass fuel has been hailed in recent years as an environmentally acceptable energy source that delivers on its promise of economically viable renewable energy. A Wall Street Journal article from three years ago proclaimed wood to be {open_quotes}moving ahead of costly solar panels and wind turbines as the leading renewable energy alternative to air-fouling fossils fuels and scary nuclear plants.{close_quotes} Biomass fuel largely means wood; about 90% of biomass generated electricity comes from burning waste wood, the remainder from agricultural wastes. Biomass power now faces an uncertain future. The maturing of the cogeneration and independent power plant market, restructuring of the electric industry, and technological advances with power equipment firing other fuels have placed biomass power in a competitive disadvantage with other power sources.

  6. Rheology of concentrated biomass

    NASA Astrophysics Data System (ADS)

    Samaniuk, J. R.; Wang, J.; Root, T. W.; Scott, C. T.; Klingenberg, D. J.

    2011-12-01

    Economic processing of lignocellulosic biomass requires handling the