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Sample records for primary production gpp

  1. Improving North American gross primary production (GPP) estimates using atmospheric measurements of carbonyl sulfide (COS)

    NASA Astrophysics Data System (ADS)

    Chen, Huilin; Montzka, Steve; Andrews, Arlyn; Sweeney, Colm; Jacobson, Andy; Miller, Ben; Masarie, Ken; Jung, Martin; Gerbig, Christoph; Campbell, Elliott; Abu-Naser, Mohammad; Berry, Joe; Baker, Ian; Tans, Pieter

    2013-04-01

    Understanding the responses of gross primary production (GPP) to climate change is essential for improving our prediction of climate change. To this end, it is important to accurately partition net ecosystem exchange of carbon into GPP and respiration. Recent studies suggest that carbonyl sulfide is a useful tracer to provide a constraint on GPP, based on the fact that both COS and CO2 are simultaneously taken up by plants and the quantitative correlation between GPP and COS plant uptake. We will present an assessment of North American GPP estimates from the Simple Biosphere (SiB) model, the Carnegie-Ames-Stanford Approach (CASA) model, and the MPI-BGC model through atmospheric transport simulations of COS in a receptor oriented framework. The newly upgraded Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) will be employed to compute the influence functions, i.e. footprints, to link the surface fluxes to the concentration changes at the receptor observations. The HYSPLIT is driven by the 3-hourly archived NAM 12km meteorological data from NOAA NCEP. The background concentrations are calculated using empirical curtains along the west coast of North America that have been created by interpolating in time and space the observations at the NOAA/ESRL marine boundary layer stations and from aircraft vertical profiles. The plant uptake of COS is derived from GPP estimates of biospheric models. The soil uptake and anthropogenic emissions are from Kettle et al. 2002. In addition, we have developed a new soil flux map of COS based on observations of molecular hydrogen (H2), which shares a common soil uptake term but lacks a vegetative sink. We will also improve the GPP estimates by assimilating atmospheric observations of COS in the receptor oriented framework, and then present the assessment of the improved GPP estimates against variations of climate variables such as temperature and precipitation.

  2. Global 4 km resolution monthly gridded Gross Primary Productivity (GPP) data set derived from FLUXNET2015

    SciTech Connect

    Kumar, Jitendra; Hoffman, Forrest M.; Hargrove, William W.; Collier, Nathan

    2016-08-01

    This data set contain global gridded surfaces of Gross Primary Productivity (GPP) at 2 arc minute (approximately 4 km) spatial resolution monthly for the period of 2000-2014 derived from FLUXNET2015 (released July 12, 2016) observations using a representativeness based upscaling approach.

  3. Estimation of Crop Gross Primary Production (GPP). 2; Do Scaled (MODIS) Vegetation Indices Improve Performance?

    NASA Technical Reports Server (NTRS)

    Zhang, Qingyuan; Cheng, Yen-Ben; Lyapustin, Alexei I.; Wang, Yujie; Zhang, Xiaoyang; Suyker, Andrew; Verma, Shashi; Shuai, Yanmin; Middleton, Elizabeth M.

    2015-01-01

    Satellite remote sensing estimates of Gross Primary Production (GPP) have routinely been made using spectral Vegetation Indices (VIs) over the past two decades. The Normalized Difference Vegetation Index (NDVI), the Enhanced Vegetation Index (EVI), the green band Wide Dynamic Range Vegetation Index (WDRVIgreen), and the green band Chlorophyll Index (CIgreen) have been employed to estimate GPP under the assumption that GPP is proportional to the product of VI and photosynthetically active radiation (PAR) (where VI is one of four VIs: NDVI, EVI, WDRVIgreen, or CIgreen). However, the empirical regressions between VI*PAR and GPP measured locally at flux towers do not pass through the origin (i.e., the zero X-Y value for regressions). Therefore they are somewhat difficult to interpret and apply. This study investigates (1) what are the scaling factors and offsets (i.e., regression slopes and intercepts) between the fraction of PAR absorbed by chlorophyll of a canopy (fAPARchl) and the VIs, and (2) whether the scaled VIs developed in (1) can eliminate the deficiency and improve the accuracy of GPP estimates. Three AmeriFlux maize and soybean fields were selected for this study, two of which are irrigated and one is rainfed. The four VIs and fAPARchl of the fields were computed with the MODerate resolution Imaging Spectroradiometer (MODIS) satellite images. The GPP estimation performance for the scaled VIs was compared to results obtained with the original VIs and evaluated with standard statistics: the coefficient of determination (R2), the root mean square error (RMSE), and the coefficient of variation (CV). Overall, the scaled EVI obtained the best performance. The performance of the scaled NDVI, EVI and WDRVIgreen was improved across sites, crop types and soil/background wetness conditions. The scaled CIgreen did not improve results, compared to the original CIgreen. The scaled green band indices (WDRVIgreen, CIgreen) did not exhibit superior performance to either the

  4. Estimating gross primary productivity (GPP) of forests across southern England at high spatial and temporal resolution using the FLIGHT model

    NASA Astrophysics Data System (ADS)

    Pankaew, Prasan; Milton, Edward; Dawson, Terry; Dash, Jadu

    2013-04-01

    Forests and woodlands play an important role in CO2 flux and in the storage of carbon, therefore it is important to be able to estimate gross primary productivity (GPP) and its change over time. The MODIS GPP product (MOD17) provides near-global GPP, but at relatively coarse spatial resolution (1km pixel size) and only every eight days. In order to study the dynamics of GPP over shorter time periods and over smaller areas it is necessary to make ground measurements or use a plant canopy model. The most reliable ground-based GPP data are those from the FLUXNET network, which comprises over 500 sites worldwide, each of which measures GPP using the eddy covariance method. Each FLUXNET measurement corresponds to GPP from an area around the sampling tower, the size and shape of which varies with weather conditions, notably wind speed and direction. The FLIGHT forest light simulation model (North, 1996) is a Monte Carlo based model to estimate the GPP from forest canopies, which does not take into account the spatial complexity of the site or the wind conditions at the time. Forests in southern England are small and embedded in a matrix of other land cover types (agriculture, urban etc.), so GPP estimated from FLIGHT needs to be adjusted to match that measured from a FLUXNET tower. The aim of this paper is to develop and test a method to adjust FLIGHT GPP so that it matches FLUXNET GPP. The advantage of this is that GPP can then be estimated over many other forests which do not possess FLUXNET sites. The study was based on data from two mixed broadleaf forests in southern England (Wytham Woods and Alice Holt forest), both of which have FLUXNET sites located within them. The FLUXNET meteorological data were prepared for use in the FLIGHT model by converting broadband irradiance to photosynthetically active radiance (PAR) and estimating diffuse PAR, using methods developed in previous work by the authors. The standard FLIGHT model tended to overestimate GPP in the winter

  5. Estimation of Crop Gross Primary Production (GPP): I. Impact of MODIS Observation Footprint and Impact of Vegetation BRDF Characteristics

    NASA Technical Reports Server (NTRS)

    Zhang, Qingyuan; Cheng, Yen-Ben; Lyapustin, Alexei I.; Wang, Yujie; Xiao, Xiangming; Suyker, Andrew; Verma, Shashi; Tan, Bin; Middleton, Elizabeth M.

    2014-01-01

    Accurate estimation of gross primary production (GPP) is essential for carbon cycle and climate change studies. Three AmeriFlux crop sites of maize and soybean were selected for this study. Two of the sites were irrigated and the other one was rainfed. The normalized difference vegetation index (NDVI), the enhanced vegetation index (EVI), the green band chlorophyll index (CIgreen), and the green band wide dynamic range vegetation index (WDRVIgreen) were computed from the moderate resolution imaging spectroradiometer (MODIS) surface reflectance data. We examined the impacts of the MODIS observation footprint and the vegetation bidirectional reflectance distribution function (BRDF) on crop daily GPP estimation with the four spectral vegetation indices (VIs - NDVI, EVI, WDRVIgreen and CIgreen) where GPP was predicted with two linear models, with and without offset: GPP = a × VI × PAR and GPP = a × VI × PAR + b. Model performance was evaluated with coefficient of determination (R2), root mean square error (RMSE), and coefficient of variation (CV). The MODIS data were filtered into four categories and four experiments were conducted to assess the impacts. The first experiment included all observations. The second experiment only included observations with view zenith angle (VZA) = 35? to constrain growth of the footprint size,which achieved a better grid cell match with the agricultural fields. The third experiment included only forward scatter observations with VZA = 35?. The fourth experiment included only backscatter observations with VZA = 35?. Overall, the EVI yielded the most consistently strong relationships to daily GPP under all examined conditions. The model GPP = a × VI × PAR + b had better performance than the model GPP = a × VI × PAR, and the offset was significant for most cases. Better performance was obtained for the irrigated field than its counterpart rainfed field. Comparison of experiment 2 vs. experiment 1 was used to examine the observation

  6. Temperature acclimation of photosynthesis has only minor effects on gross primary productivity (GPP) in an Earth System Model (ESM)

    NASA Astrophysics Data System (ADS)

    Goll, Daniel; Brovkin, Victor; Kattge, Jens; Zaehle, Soenke; Reick, Christian

    2013-04-01

    The productivity of terrestrial plants influences the dynamics of atmospheric CO2. It is therefore crucial to understand and quantify productivity and predict its future responses to climate change and increasing atmospheric CO2 concentrations. Recently, Booth et al. (2012) found that the temperature dependence of photosynthesis is the most important uncertainty of the climate-carbon cycle feedback in a comprehensive ESM. Using trait data, Kattge and Knorr (2007) found that photosynthesis, in particular the acclimation of the maximum carboxylation rate (Vmax) and electron transport rate (Jmax), acclimates to prevailing temperatures. As a first attempt to address temperature acclimation of photosynthesis on global scale, we replaced the simplified exponential formulation of the temperature dependence of Vmax and Jmax in the Max Planck Institute Earth System Model (MPI-ESM) by a physiologically more plausible and justified model with short-term optimum temperature. For temperature acclimation we then implemented the acclimation descriptions by Kattge and Knorr (2007). We conducted sets of simulations on site scale driven by meteorological observations, and simulations on global scale for present day climate and for a 6 K warmer climate. The physiologically more plausible and justified model with short-term optimum temperature and temperature acclimation yields similar results as the old exponential formulation not accounting for either process. With the new model, global GPP for present day and in the warming scenario is increased by 0.7% and 0.9%, respectively. Acclimation causes a slight shift of productivity from high to low latitudes, too. A slightly larger effect on GPP has the replacement of the exponential formulation with the model with optimum temperature, resulting in a 1.2% decrease in global GPP under both climatic conditions. Acclimation thus compensates for the effects of the physiologically based temperature optimum of photosynthesis. As the effects

  7. Estimation of crop gross primary production (GPP): fAPAR_chl versus MOD15A2 FPAR

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Within leaf chloroplasts chlorophylls absorb photosynthetically active radiation (PAR) for photosynthesis (PSN). The MOD15A2 FPAR (fraction of PAR absorbed by canopy, i.e., fAPARcanopy) product has been widely used to compute absorbed PAR for PSN (APARPSN). The MOD17A2 algorithm uses MOD15A2 FPAR i...

  8. GPP estimates in a biodiesel crop using MERIS products

    NASA Astrophysics Data System (ADS)

    Sánchez, M. L.; Pardo, N.; Pérez, I.; García, M. A.; Paredes, V.

    2012-04-01

    Greenhouse gas emissions in Spain in 2008-2009 were 34.3 % higher than the base-year level, significantly above the burden-sharing target of 15 % for the period 2008-2012. Based on this result, our country will need to make a major effort to meet the committed target on time using domestic measures as well as others foreseen in the Kyoto Protocol, such as LULUFC activities. In this framework, agrofuels, in other words biofuels produced by crops that contain high amounts of vegetable oil such as sorghum, sunflower, rape seed and jatropha, appear to be an interesting mitigation alternative. Bearing in mind the meteorological conditions in Spain, sunflower and rape seed in particular are considered the most viable crops. Sunflower cultivated surface in Spain has remained fairly constant in recent years, in contrast to rapeseed crop surface which, although still scarce, has followed an increasing trend. In order to assess rape seed ability as a CO2 sink as well as to describe GPP dynamic evolution, we installed an eddy correlation station in an agricultural plot of the Spanish plateau. Measurements at the plot consisted of 30-min NEE flux measurements (using a LI-7500 and a METEK USA-1 sonic anemometer) as well as other common meteorological variables. Measurements were performed from March to October. This paper presents the results of the GPP 8-d estimated values using a Light Use Efficiency Model, LUE. Input data for the LUE model were the FPAR 8-d products supplied by MERIS, the PAR in situ measurements, and a scalar f varying, between 0 and 1, to take into account the reduction of the maximum PAR conversion efficiency, ɛ0, under limiting environmental conditions. The f values were assumed to be dependent on air temperature and the evaporative fraction, EF, which was considered as a proxy of soil moisture. ɛ0, a key parameter, which depends on biome types, was derived through the results of a linear regression fit between the GPP 8-d eddy covariance composites

  9. Gross Primary Productivity

    NASA Technical Reports Server (NTRS)

    2002-01-01

    NASA's new Moderate-resolution Imaging Spectroradiometer (MODIS) allows scientists to gauge our planet's metabolism on an almost daily basis. GPP, gross primary production, is the technical term for plant photosynthesis. This composite image over the continental United States, acquired during the period March 26-April 10, 2000, shows regions where plants were more or less productive-i.e., where they 'inhaled' carbon dioxide and then used the carbon from photosynthesis to build new plant structures. This false-color image provides a map of how much carbon was absorbed out of the atmosphere and fixed within land vegetation. Areas colored blue show where plants used as much as 60 grams of carbon per square meter. Areas colored green and yellow indicate a range of anywhere from 40 to 20 grams of carbon absorbed per square meter. Red pixels show an absorption of less than 10 grams of carbon per square meter and white pixels (often areas covered by snow or masked as urban) show little or no absorption. This is one of a number of new measurements that MODIS provides to help scientists understand how the Earth's landscapes are changing over time. Scientists' goal is use of these GPP measurements to refine computer models to simulate how the land biosphere influences the natural cycles of water, carbon, and energy throughout the Earth system. The GPP will be an integral part of global carbon cycle source and sink analysis, an important aspect of Kyoto Protocol assessments. This image is the first of its kind from the MODIS instrument, which launched in December 1999 aboard the Terra spacecraft. MODIS began acquiring scientific data on February 24, 2000, when it first opened its aperture door. The MODIS instrument and Terra spacecraft are both managed by NASA's Goddard Space Flight Center, Greenbelt, MD. Image courtesy Steven Running, MODIS Land Group Member, University of Montana

  10. Towards 250 m mapping of terrestrial primary productivity over Canada

    NASA Astrophysics Data System (ADS)

    Gonsamo, A.; Chen, J. M.

    2011-12-01

    Terrestrial ecosystems are an important part of the climate and global change systems. Their role in climate change and in the global carbon cycle is yet to be well understood. Dataset from satellite earth observation, coupled with numerical models provide the unique tools for monitoring the spatial and temporal dynamics of territorial carbon cycle. The Boreal Ecosystems Productivity Simulator (BEPS) is a remote sensing based approach to quantifying the terrestrial carbon cycle by that gross and net primary productivity (GPP and NPP) and terrestrial carbon sinks and sources expressed as net ecosystem productivity (NEP). We have currently implemented a scheme to map the GPP, NPP and NEP at 250 m for first time over Canada using BEPS model. This is supplemented by improved mapping of land cover and leaf area index (LAI) at 250 m over Canada from MODIS satellite dataset. The results from BEPS are compared with MODIS GPP product and further evaluated with estimated LAI from various sources to evaluate if the results capture the trend in amount of photosynthetic biomass distributions. Final evaluation will be to validate both BEPS and MODIS primary productivity estimates over the Fluxnet sites over Canada. The primary evaluation indicate that BEPS GPP estimates capture the over storey LAI variations over Canada very well compared to MODIS GPP estimates. There is a large offset of MODIS GPP, over-estimating the lower GPP value compared to BEPS GPP estimates. These variations will further be validated based on the measured values from the Fluxnet tower measurements over Canadian. The high resolution GPP (NPP) products at 250 m will further be used to scale the outputs between different ecosystem productivity models, in our case the Canadian carbon budget model of Canadian forest sector CBM-CFS) and the Integrated Terrestrial Ecosystem Carbon model (InTEC).

  11. Joint control of terrestrial gross primary productivity by plant phenology and physiology.

    PubMed

    Xia, Jianyang; Niu, Shuli; Ciais, Philippe; Janssens, Ivan A; Chen, Jiquan; Ammann, Christof; Arain, Altaf; Blanken, Peter D; Cescatti, Alessandro; Bonal, Damien; Buchmann, Nina; Curtis, Peter S; Chen, Shiping; Dong, Jinwei; Flanagan, Lawrence B; Frankenberg, Christian; Georgiadis, Teodoro; Gough, Christopher M; Hui, Dafeng; Kiely, Gerard; Li, Jianwei; Lund, Magnus; Magliulo, Vincenzo; Marcolla, Barbara; Merbold, Lutz; Montagnani, Leonardo; Moors, Eddy J; Olesen, Jørgen E; Piao, Shilong; Raschi, Antonio; Roupsard, Olivier; Suyker, Andrew E; Urbaniak, Marek; Vaccari, Francesco P; Varlagin, Andrej; Vesala, Timo; Wilkinson, Matthew; Weng, Ensheng; Wohlfahrt, Georg; Yan, Liming; Luo, Yiqi

    2015-03-03

    Terrestrial gross primary productivity (GPP) varies greatly over time and space. A better understanding of this variability is necessary for more accurate predictions of the future climate-carbon cycle feedback. Recent studies have suggested that variability in GPP is driven by a broad range of biotic and abiotic factors operating mainly through changes in vegetation phenology and physiological processes. However, it is still unclear how plant phenology and physiology can be integrated to explain the spatiotemporal variability of terrestrial GPP. Based on analyses of eddy-covariance and satellite-derived data, we decomposed annual terrestrial GPP into the length of the CO2 uptake period (CUP) and the seasonal maximal capacity of CO2 uptake (GPPmax). The product of CUP and GPPmax explained >90% of the temporal GPP variability in most areas of North America during 2000-2010 and the spatial GPP variation among globally distributed eddy flux tower sites. It also explained GPP response to the European heatwave in 2003 (r(2) = 0.90) and GPP recovery after a fire disturbance in South Dakota (r(2) = 0.88). Additional analysis of the eddy-covariance flux data shows that the interbiome variation in annual GPP is better explained by that in GPPmax than CUP. These findings indicate that terrestrial GPP is jointly controlled by ecosystem-level plant phenology and photosynthetic capacity, and greater understanding of GPPmax and CUP responses to environmental and biological variations will, thus, improve predictions of GPP over time and space.

  12. Joint control of terrestrial gross primary productivity by plant phenology and physiology

    PubMed Central

    Xia, Jianyang; Niu, Shuli; Ciais, Philippe; Janssens, Ivan A.; Chen, Jiquan; Ammann, Christof; Arain, Altaf; Blanken, Peter D.; Cescatti, Alessandro; Bonal, Damien; Buchmann, Nina; Curtis, Peter S.; Chen, Shiping; Dong, Jinwei; Flanagan, Lawrence B.; Frankenberg, Christian; Georgiadis, Teodoro; Gough, Christopher M.; Hui, Dafeng; Kiely, Gerard; Li, Jianwei; Lund, Magnus; Magliulo, Vincenzo; Marcolla, Barbara; Merbold, Lutz; Olesen, Jørgen E.; Piao, Shilong; Raschi, Antonio; Roupsard, Olivier; Suyker, Andrew E.; Vaccari, Francesco P.; Varlagin, Andrej; Vesala, Timo; Wilkinson, Matthew; Weng, Ensheng; Yan, Liming; Luo, Yiqi

    2015-01-01

    Terrestrial gross primary productivity (GPP) varies greatly over time and space. A better understanding of this variability is necessary for more accurate predictions of the future climate–carbon cycle feedback. Recent studies have suggested that variability in GPP is driven by a broad range of biotic and abiotic factors operating mainly through changes in vegetation phenology and physiological processes. However, it is still unclear how plant phenology and physiology can be integrated to explain the spatiotemporal variability of terrestrial GPP. Based on analyses of eddy–covariance and satellite-derived data, we decomposed annual terrestrial GPP into the length of the CO2 uptake period (CUP) and the seasonal maximal capacity of CO2 uptake (GPPmax). The product of CUP and GPPmax explained >90% of the temporal GPP variability in most areas of North America during 2000–2010 and the spatial GPP variation among globally distributed eddy flux tower sites. It also explained GPP response to the European heatwave in 2003 (r2 = 0.90) and GPP recovery after a fire disturbance in South Dakota (r2 = 0.88). Additional analysis of the eddy–covariance flux data shows that the interbiome variation in annual GPP is better explained by that in GPPmax than CUP. These findings indicate that terrestrial GPP is jointly controlled by ecosystem-level plant phenology and photosynthetic capacity, and greater understanding of GPPmax and CUP responses to environmental and biological variations will, thus, improve predictions of GPP over time and space. PMID:25730847

  13. Retrievals of Chlorophyll Fapar for Improved Crop Gpp Modeling

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Cheng, Y. B.; Wang, Y.; Lyapustin, A.; Yao, T.

    2014-12-01

    Accurate estimation of crop gross primary productivity (GPP) is important. We have recently developed an algorithm to derive fAPAR of chlorophyll (fAPARchl), fAPAR of foliage (fAPARfoliage) and chlorophyll LAI (LAIchl) with PROSAIL2. The MODIS surface reflectance produced with MAIAC were utilized to retrieve fAPARchl, fAPARfoliage and LAIchl for three AmeriFlux sites of maize and soybean. MOD15A2 FPAR and the retrieved fAPARchl were compared with field fAPARcanopy and the fraction of PAR absorbed by green leaves of the vegetation (fAPARgreen). MOD15A2 FPAR overestimated field fAPARcanopy in spring and in fall, and underestimated field fAPARcanopy in midsummer whereas fAPARchl correctly captured the seasonal phenology. The retrieved fAPARchl agreed well with field fAPARgreen at early crop growth stage in June, and was less than field fAPARgreen in late July, August and September, which is consistent with crop physiology theory. GPP estimates with fAPARchl and with MOD15A2 FPAR were compared to tower flux GPP. GPP simulated with fAPARchl was corroborated with tower flux GPP. Improvements in crop GPP estimation were achieved by replacing MOD15A2 FPAR with fAPARchl which also reduced uncertainties of crop GPP estimates by 1.12 - 2.37 g C m-2 d-1. NDVI, EVI, WDRVIgreen, and CIgreen have also been employed to estimate GPP by other scientific teams. We investigated the scaling factors and offsets (i.e., regression slopes and offsets) between fAPARchl and the VIs. The results showed that the scaled EVI obtained the best performance. The performance of the scaled NDVI, EVI and WDRVIgreen was improved across sites, crop types and soil/background wetness conditions, compared to the original un-scaled VIs. The scaled green band indices (WDRVIgreen, CIgreen) did not exhibit superior performance to either the scaled EVI or NDVI in estimating crop daily GPP at these agricultural fields. MOD15A2 LAI and the retrieved LAIchl were implemented into CLM to simulate GPP, respectively

  14. A model-data comparison of gross primary productivity: Results from the North American Carbon Program site synthesis

    NASA Astrophysics Data System (ADS)

    Schaefer, Kevin; Schwalm, Christopher R.; Williams, Chris; Arain, M. Altaf; Barr, Alan; Chen, Jing M.; Davis, Kenneth J.; Dimitrov, Dimitre; Hilton, Timothy W.; Hollinger, David Y.; Humphreys, Elyn; Poulter, Benjamin; Raczka, Brett M.; Richardson, Andrew D.; Sahoo, Alok; Thornton, Peter; Vargas, Rodrigo; Verbeeck, Hans; Anderson, Ryan; Baker, Ian; Black, T. Andrew; Bolstad, Paul; Chen, Jiquan; Curtis, Peter S.; Desai, Ankur R.; Dietze, Michael; Dragoni, Danilo; Gough, Christopher; Grant, Robert F.; Gu, Lianhong; Jain, Atul; Kucharik, Chris; Law, Beverly; Liu, Shuguang; Lokipitiya, Erandathie; Margolis, Hank A.; Matamala, Roser; McCaughey, J. Harry; Monson, Russ; Munger, J. William; Oechel, Walter; Peng, Changhui; Price, David T.; Ricciuto, Dan; Riley, William J.; Roulet, Nigel; Tian, Hanqin; Tonitto, Christina; Torn, Margaret; Weng, Ensheng; Zhou, Xiaolu

    2012-09-01

    Accurately simulating gross primary productivity (GPP) in terrestrial ecosystem models is critical because errors in simulated GPP propagate through the model to introduce additional errors in simulated biomass and other fluxes. We evaluated simulated, daily average GPP from 26 models against estimated GPP at 39 eddy covariance flux tower sites across the United States and Canada. None of the models in this study match estimated GPP within observed uncertainty. On average, models overestimate GPP in winter, spring, and fall, and underestimate GPP in summer. Models overpredicted GPP under dry conditions and for temperatures below 0°C. Improvements in simulated soil moisture and ecosystem response to drought or humidity stress will improve simulated GPP under dry conditions. Adding a low-temperature response to shut down GPP for temperatures below 0°C will reduce the positive bias in winter, spring, and fall and improve simulated phenology. The negative bias in summer and poor overall performance resulted from mismatches between simulated and observed light use efficiency (LUE). Improving simulated GPP requires better leaf-to-canopy scaling and better values of model parameters that control the maximum potential GPP, such asɛmax (LUE), Vcmax (unstressed Rubisco catalytic capacity) or Jmax (the maximum electron transport rate).

  15. Multi-scale analyses reveal robust relations between solar induced fluorescence and gross primary production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Remotely sensed solar induced fluorescence (SIF) has shown great promise for probing spatiotemporal variations in terrestrial gross primary production (GPP), the largest component flux of the global carbon cycle. However, scale mismatches between SIF and ground-based GPP have posed challenges toward...

  16. Estimation of gross primary production capacity from global satellite observations

    NASA Astrophysics Data System (ADS)

    Muramatsu, Kanako; Thanyapraneedkul, Juthasinee; Furumi, Shinobu; Soyama, Noriko; Daigo, Motomasa

    2012-10-01

    To estimate gross primary production (GPP), the process of photosynthesis was considered as two separate phases: capacity and reduction. The reduction phase is influenced by environmental conditions such as soil moisture and weather conditions such as vapor pressure differences. For a particular leaf, photosynthetic capacity mainly depends on the amount of chlorophyll and the RuBisCO enzyme. The chlorophyll content can be estimated by the color of the leaf, and leaf color can be detected by optical sensors. We used the chlorophyll content of leaves to estimate the level of GPP. A previously developed framework for GPP capacity estimation employs a chlorophyll index. The index is based on the linear relationship between the chlorophyll content of a leaf and the maximum photosynthesis at PAR =2000 (μmolm -2s-1) on a light-response curve under low stress conditions. As a first step, this study examined the global distribution of the index and found that regions with high chlorophyll index values in winter corresponded to tropical rainforest areas. The seasonal changes in the chlorophyll index differed from those shown by the normalized difference vegetation index. Next, the capacity of GPP was estimated from the light-response curve using the index. Most regions exhibited a higher GPP capacity than that estimated from Moderate Resolution Imaging Spectroradiometer (MODIS) observations, except in areas of tropical rainforest, where the GPP capacity and the MODIS GPP estimates were almost identical.

  17. Validation and improvement of MODIS Gross Primary Productivity in typical forest ecosystems of East Asia based on eddy covariance measurements

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; He, M.; Ju, W.

    2011-12-01

    Terrestrial carbon cycle plays an important role in global climate change. As a key component of terrestrial carbon cycle, gross primary productivity (GPP) is a major determinant of carbon exchange between the atmosphere and terrestrial ecosystems. Because of the large spatial heterogeneity and temporal dynamics of ecosystems, it is a challenge to estimate GPP at global or regional scales. 8-day MODIS GPP product provides a real time estimate of global GPP. However, many previous studies indicated that MODIS GPP has large uncertainties, which was partly caused by biases in maximum light use efficiency and meteorological data inputs, including VPD, air temperature, and photosynthetically active radiation (PAR). In this study, MODIS GPP of six typical forest ecosystems in East Asia was validated using GPP derived from the eddy covariance flux measurements. The validation indicated that MODIS GPP was significantly underestimated in the forest ecosystems of East Asia. The underestimation is generally more serious in growing seasons than in non-growing seasons and becomes more obvious from the south to the north. By using observed meteorological data, smoothed fPAR and optimized maximum light use efficiency (ɛmax), predicted GPP with MOD17 algorithm consistently matched well with measured GPP. Smoothed fPAR definitely reduced underestimation of annual GPP, and the optimized ɛmax improved annual GPP more significantly, indicating that the errors in MODIS GPP of forest ecosystems in East Asia can be mainly attributed to the uncertainties of ɛmax. Optimized ɛmax are generally higher than that used for producing MODIS GPP product. The optimized ɛmax changes significantly with forest types. It even exhibits distinct seasonal variations for a specific forest. Key words: Gross Primary Productivity, MODIS, Maximum light use efficiency, East Asia, Forest ecosystem Correspondence author:Weimin Ju Email:juweimin@nju.edu.cn

  18. Primary Productivity in Meduxnekeag River, Maine, 2005

    USGS Publications Warehouse

    Goldstein, Robert M.; Schalk, Charles W.; Kempf, Joshua P.

    2009-01-01

    During August and September 2005, dissolved oxygen, temperature, pH, specific conductance, streamflow, and light intensity (LI) were determined continuously at six sites defining five reaches on Meduxnekeag River above and below Houlton, Maine. These data were collected as input for a dual-station whole-stream metabolism model to evaluate primary productivity in the river above and below Houlton. The river receives nutrients and organic matter from tributaries and the Houlton wastewater treatment plant (WWTP). Model output estimated gross and net primary productivity for each reach. Gross primary productivity (GPP) varied in each reach but was similar and positive among the reaches. GPP was correlated to LI in the four reaches above the WWTP but not in the reach below. Net primary productivity (NPP) decreased in each successive downstream reach and was negative in the lowest two reaches. NPP was weakly related to LI in the upper two reaches and either not correlated or negatively correlated in the lower three reaches. Relations among GPP, NPP, and LI indicate that the system is heterotrophic in the downstream reaches. The almost linear decrease in NPP (the increase in metabolism and respiration) indicates a cumulative effect of inputs of nutrients and organic matter from tributaries that drain agricultural land, the town of Houlton, and the discharges from the WWTP.

  19. Global GPP based on Plant Functional Types

    NASA Astrophysics Data System (ADS)

    Veroustraete, Frank; Balzarolo, Manuela

    2016-04-01

    Vegetation variables like Gross Primary productivity (GPP) and the Normalized Difference Vegetation Index (NDVI) are key variables in vegetation carbon exchange studies. Field measurements of the NDVI are time consuming due to landscape heterogeneity across time. Typically a sampling protocol adopted during field campaigns is based on the VALERI protocol in that case toe estimate LAI. Field campaign GPP or NDVI measurements can be scaled up to using in-situ FLUXNET radiation raster maps. Regression analysis can then be applied to construct transfer functions for the determination of GPP raster maps raster imagery from Normalized Difference Vegetation Index (NDVI) raster maps derived from in-situ FLUXNET radiation raster maps. Subsequently, in the VALERI approach the scaling up of raster maps is performed by aggregation of high resolution in-situ FLUXNET radiation raster maps data into high resolution raster maps and subsequently aggregating these to 1x1 km MODIS NDVI raster maps by calculating average NDVI values for the low resolution data. The up-scaled 1x1 km pixels are then used to validate the MODIS GPP and NVI products. Hence up scaling based on in-situ FLUXNET radiation measurements are not a luxury for large and heterogeneous sites. Therefore this paper tackles the problem of up scaling using in-situ FLUXNET radiation measurements. Key Words: FLUXNET, GPP, Plant Functional Types, Up-scaling

  20. A spatial implementation of the BIOME-BGC to model grassland GPP production and water budgets in the Ecuadorian Andean Region

    NASA Astrophysics Data System (ADS)

    Minaya, Veronica; Corzo, Gerald; van der Kwast, Johannes; Mynett, Arthur

    2016-04-01

    Many terrestrial biogeochemistry process models have been applied around the world at different scales and for a large range of ecosystems. Grasslands, and in particular the ones located in the Andean Region are essential ecosystems that sustain important ecological processes; however, just a few efforts have been made to estimate the gross primary production (GPP) and the hydrological budgets for this specific ecosystem along an altitudinal gradient. A previous study, which is one of the few available in the region, considered the heterogeneity of the main properties of the páramo vegetation and showed significant differences in plant functional types, site/soil parameters and daily meteorology. This study extends the work above mentioned and uses spatio-temporal analysis of the BIOME-BGC model results. This was done to simulate the GPP and the water fluxes in space and time, by applying altitudinal analysis. The catchment located at the southwestern slope of the Antisana volcano in Ecuador was selected as a representative area of the Andean páramos and its hydrological importance as one of the main sources of a water supply reservoir in the region. An accurate estimation of temporal changes in GPP in the region is important for carbon budget assessments, evaluation of the impact of climate change and biomass productivity. This complex and yet interesting problem was integrated by the ecosystem process model BIOME-BGC, the results were evaluated and associated to the land cover map where the growth forms of vegetation were identified. The responses of GPP and the water fluxes were not only dependent on the environmental drivers but also on the ecophysiology and the site specific parameters. The model estimated that the GPP at lower elevations doubles the amount estimated at higher elevations, which might have a large implication during extrapolations at larger spatio-temporal scales. The outcomes of the stand hydrological processes demonstrated a wrong

  1. Evaluation and comparison of gross primary production estimates for the Northern Great Plains grasslands

    USGS Publications Warehouse

    Zhang, L.; Wylie, B.; Loveland, T.; Fosnight, E.; Tieszen, L.L.; Ji, L.; Gilmanov, T.

    2007-01-01

    Two spatially-explicit estimates of gross primary production (GPP) are available for the Northern Great Plains. An empirical piecewise regression (PWR) GPP model was developed from flux tower measurements to map carbon flux across the region. The Moderate Resolution Imaging Spectrometer (MODIS) GPP model is a process-based model that uses flux tower data to calibrate its parameters. Verification and comparison of the regional PWR GPP and the global MODIS GPP are important for the modeling of grassland carbon flux. This study compared GPP estimates from PWR and MODIS models with five towers in the grasslands. Among them, PWR GPP and MODIS GPP showed a good agreement with tower-based GPP at three towers. The global MODIS GPP, however, did not agree well with tower-based GPP at two other towers, probably because of the insensitivity of MODIS model to regional ecosystem and climate change and extreme soil moisture conditions. Cross-validation indicated that the PWR model is relatively robust for predicting regional grassland GPP. However, the PWR model should include a wide variety of flux tower data as the training data sets to obtain more accurate results. In addition, GPP maps based on the PWR and MODIS models were compared for the entire region. In the northwest and south, PWR GPP was much higher than MODIS GPP. These areas were characterized by the higher water holding capacity with a lower proportion of C4 grasses in the northwest and a higher proportion of C4 grasses in the south. In the central and southeastern regions, PWR GPP was much lower than MODIS GPP under complicated conditions with generally mixed C3/C4 grasses. The analysis indicated that the global MODIS GPP model has some limitations on detecting moisture stress, which may have been caused by the facts that C3 and C4 grasses are not distinguished, water stress is driven by vapor pressure deficit (VPD) from coarse meteorological data, and MODIS land cover data are unable to differentiate the sub

  2. Dominant role of plant physiology in trend and variability of gross primary productivity in North America

    PubMed Central

    Zhou, Sha; Zhang, Yao; Ciais, Philippe; Xiao, Xiangming; Luo, Yiqi; Caylor, Kelly K.; Huang, Yuefei; Wang, Guangqian

    2017-01-01

    Annual gross primary productivity (GPP) varies considerably due to climate-induced changes in plant phenology and physiology. However, the relative importance of plant phenology and physiology on annual GPP variation is not clear. In this study, a Statistical Model of Integrated Phenology and Physiology (SMIPP) was used to evaluate the relative contributions of maximum daily GPP (GPPmax) and the start and end of growing season (GSstart and GSend) to annual GPP variability, using a regional GPP product in North America during 2000–2014 and GPP data from 24 AmeriFlux sites. Climatic sensitivity of the three indicators was assessed to investigate the climate impacts on plant phenology and physiology. The SMIPP can explain 98% of inter-annual variability of GPP over mid- and high latitudes in North America. The long-term trend and inter-annual variability of GPP are dominated by GPPmax both at the ecosystem and regional scales. During warmer spring and autumn, GSstart is advanced and GSend delayed, respectively. GPPmax responds positively to summer temperature over high latitudes (40–80°N), but negatively in mid-latitudes (25–40°N). This study demonstrates that plant physiology, rather than phenology, plays a dominant role in annual GPP variability, indicating more attention should be paid to physiological change under futher climate change. PMID:28145496

  3. Dominant role of plant physiology in trend and variability of gross primary productivity in North America

    NASA Astrophysics Data System (ADS)

    Zhou, Sha; Zhang, Yao; Ciais, Philippe; Xiao, Xiangming; Luo, Yiqi; Caylor, Kelly K.; Huang, Yuefei; Wang, Guangqian

    2017-02-01

    Annual gross primary productivity (GPP) varies considerably due to climate-induced changes in plant phenology and physiology. However, the relative importance of plant phenology and physiology on annual GPP variation is not clear. In this study, a Statistical Model of Integrated Phenology and Physiology (SMIPP) was used to evaluate the relative contributions of maximum daily GPP (GPPmax) and the start and end of growing season (GSstart and GSend) to annual GPP variability, using a regional GPP product in North America during 2000–2014 and GPP data from 24 AmeriFlux sites. Climatic sensitivity of the three indicators was assessed to investigate the climate impacts on plant phenology and physiology. The SMIPP can explain 98% of inter-annual variability of GPP over mid- and high latitudes in North America. The long-term trend and inter-annual variability of GPP are dominated by GPPmax both at the ecosystem and regional scales. During warmer spring and autumn, GSstart is advanced and GSend delayed, respectively. GPPmax responds positively to summer temperature over high latitudes (40–80°N), but negatively in mid-latitudes (25–40°N). This study demonstrates that plant physiology, rather than phenology, plays a dominant role in annual GPP variability, indicating more attention should be paid to physiological change under futher climate change.

  4. North American Gross Primary Productivity: Regional Characterization and Interannual Variability

    NASA Astrophysics Data System (ADS)

    Baker, I. T.; Denning, A.; Stockli, R.

    2009-12-01

    Seasonality and variability in North American photosynthetic activity are investigated. Using the Simple Biosphere Model (SiB) we simulate 24 years (1983-2006) and evaluate regional and seasonal contribution to annual mean Gross Primary Productivity (GPP) as well as its interannual variability. The largest productivity occurs in tropical Mexico, the southeast U.S. and small areas in the Pacific Northwest. Annual variability is largest in tropical Mexico, the desert Southwest, and the Midwestern corridor that separates the eastern forests from the intermountain west. We find that several areas (Midwest, Northeast, SouthWest, Boreal Canada) have an elevated contribution to interannual variability when compared to other regions, but no single region or season consistently determines continental annual GPP anomaly on an annual basis. GPP variability in NA is highly heterogeneous in space and time. We find that GPP variability is generally dependent upon soil moisture in low- and mid-latitudes, and on temperature in the north. Soil moisture is a better metric than raw precipitation as it integrates precipitation events temporally. EOF analysis shows no significance on an annual basis, but a band from the central plains through New England shows a coherent signal for springtime GPP anomalies. As the springtime anomaly is the largest contributor to the annual GPP variability in almost half of the years simulated (11 of 24), we can posit that this region has significant influence over annual North American GPP variability. However, when regressed against climate modes such as El Nino Southern Oscillation (ENSO), Arctic Oscillation (AO) or Pacific-North America (PNA) patterns, we find that no climate mode can be associated with variability over the entire region highlighted by the EOF analysis. Furthermore, we find that while a general response to temperature is seen (warmer spring implies longer growing season implies anomalous GPP uptake of carbon), in some regions the

  5. Consistency Between Sun-Induced Chlorophyll Fluorescence and Gross Primary Production of Vegetation in North America

    NASA Technical Reports Server (NTRS)

    Zhang, Yao; Xiao, Xiangming; Jin, Cui; Dong, Jinwei; Zhou, Sha; Wagle, Pradeep; Joiner, Joanna; Guanter, Luis; Zhang, Yongguang; Zhang , Geli; Qin, Yuanwei; Wang, Jie; Moore, Berrien, III

    2016-01-01

    Accurate estimation of the gross primary production (GPP) of terrestrial ecosystems is vital for a better understanding of the spatial-temporal patterns of the global carbon cycle. In this study,we estimate GPP in North America (NA) using the satellite-based Vegetation Photosynthesis Model (VPM), MODIS (Moderate Resolution Imaging Spectrometer) images at 8-day temporal and 500 meter spatial resolutions, and NCEP-NARR (National Center for Environmental Prediction-North America Regional Reanalysis) climate data. The simulated GPP (GPP (sub VPM)) agrees well with the flux tower derived GPP (GPPEC) at 39 AmeriFlux sites (155 site-years). The GPP (sub VPM) in 2010 is spatially aggregated to 0.5 by 0.5-degree grid cells and then compared with sun-induced chlorophyll fluorescence (SIF) data from Global Ozone Monitoring Instrument 2 (GOME-2), which is directly related to vegetation photosynthesis. Spatial distribution and seasonal dynamics of GPP (sub VPM) and GOME-2 SIF show good consistency. At the biome scale, GPP (sub VPM) and SIF shows strong linear relationships (R (sup 2) is greater than 0.95) and small variations in regression slopes ((4.60-5.55 grams Carbon per square meter per day) divided by (milliwatts per square meter per nanometer per square radian)). The total annual GPP (sub VPM) in NA in 2010 is approximately 13.53 petagrams Carbon per year, which accounts for approximately 11.0 percent of the global terrestrial GPP and is within the range of annual GPP estimates from six other process-based and data-driven models (11.35-22.23 petagrams Carbon per year). Among the seven models, some models did not capture the spatial pattern of GOME-2 SIF data at annual scale, especially in Midwest cropland region. The results from this study demonstrate the reliable performance of VPM at the continental scale, and the potential of SIF data being used as a benchmark to compare with GPP models.

  6. Large historical growth in global terrestrial gross primary production.

    PubMed

    Campbell, J E; Berry, J A; Seibt, U; Smith, S J; Montzka, S A; Launois, T; Belviso, S; Bopp, L; Laine, M

    2017-04-05

    Growth in terrestrial gross primary production (GPP)-the amount of carbon dioxide that is 'fixed' into organic material through the photosynthesis of land plants-may provide a negative feedback for climate change. It remains uncertain, however, to what extent biogeochemical processes can suppress global GPP growth. As a consequence, modelling estimates of terrestrial carbon storage, and of feedbacks between the carbon cycle and climate, remain poorly constrained. Here we present a global, measurement-based estimate of GPP growth during the twentieth century that is based on long-term atmospheric carbonyl sulfide (COS) records, derived from ice-core, firn and ambient air samples. We interpret these records using a model that simulates changes in COS concentration according to changes in its sources and sinks-including a large sink that is related to GPP. We find that the observation-based COS record is most consistent with simulations of climate and the carbon cycle that assume large GPP growth during the twentieth century (31% ± 5% growth; mean ± 95% confidence interval). Although this COS analysis does not directly constrain models of future GPP growth, it does provide a global-scale benchmark for historical carbon-cycle simulations.

  7. Comparing Temporal Variations in LUE and GPP across Evergreen and Deciduous Forest Types

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; Hilker, T.; Ju, W.; Coops, N. C.; Black, T. A.; Chen, J.

    2015-12-01

    Estimating gross primary production (GPP) is an important goal of global change research. However, the relationship between GPP and its environmental drivers is highly complex and as a result, accurate modeling of GPP is difficult. One possible technique to help constrain the uncertainties is by using remote sensing data to try and determine the factors driving GPP directly from satellite imagery. In this study, we used GPP from flux data (GPP_EC) and meteorological observations of a deciduous (SOA) and a coniferous evergreen forest (DF-49) to optimize light use efficiency of sunlit (LUEsun) and shaded (LUEshaded) canopies. We based our analysis on the two-leave light use efficiency model (TL-LUE) at daily, 8 day, and 16 day scales by using the Markov chain Monte Carlo (MCMC). The photochemical reflectance index (PRI) of sunlit (PRIsun) and shaded (PRIshaded) leaves was calculated from spectral observations and related to tower based GPP at the three temporal scales. We found that the coefficient of determination (R2) between PRIsun and LUEsun, as well as PRIshaded and LUEshaded at the evergreen forest was lower than that at the deciduous forest. The modeled GPP was closely to the GPP_EC at the three temporal scales. The R2 between the GPP_EC and modeled daily GPP was the highest when using daily measures of LUE, and lowest when uisng16-day LUEsun and LUEshaded. The results indicated that LUE is an important parameter when modeling instantaneous GPP and the short term variations of it. The results help to obtain a better understanding of how many satellite observations are needed to reliably constrain existing GPP models from remote sensing data.

  8. Turbidity, light, temperature, and hydropeaking control primary productivity in the Colorado River, Grand Canyon

    USGS Publications Warehouse

    Hall, Robert O.; Yackulic, Charles B.; Kennedy, Theodore A.; Yard, Michael D.; Rosi-Marshall, Emma J.; Voichick, Nicholas; Behn, Kathrine E.

    2015-01-01

    Dams and river regulation greatly alter the downstream environment for gross primary production (GPP) because of changes in water clarity, flow, and temperature regimes. We estimated reach-scale GPP in five locations of the regulated Colorado River in Grand Canyon using an open channel model of dissolved oxygen. Benthic GPP dominates in Grand Canyon due to fast transport times and low pelagic algal biomass. In one location, we used a 738 days time series of GPP to identify the relative contribution of different physical controls of GPP. We developed both linear and semimechanistic time series models that account for unmeasured temporal covariance due to factors such as algal biomass dynamics. GPP varied from 0 g O2 m−2 d−1 to 3.0 g O2 m−2 d−1 with a relatively low annual average of 0.8 g O2 m−2d−1. Semimechanistic models fit the data better than linear models and demonstrated that variation in turbidity primarily controlled GPP. Lower solar insolation during winter and from cloud cover lowered GPP much further. Hydropeaking lowered GPP but only during turbid conditions. Using the best model and parameter values, the model accurately predicted seasonal estimates of GPP at 3 of 4 upriver sites and outperformed the linear model at all sites; discrepancies were likely from higher algal biomass at upstream sites. This modeling approach can predict how changes in physical controls will affect relative rates of GPP throughout the 385 km segment of the Colorado River in Grand Canyon and can be easily applied to other streams and rivers.

  9. Ozone vegetation damage effects on gross primary productivity in the United States

    NASA Astrophysics Data System (ADS)

    Yue, X.; Unger, N.

    2013-12-01

    We apply an off-line process-based vegetation model to assess the impacts of ozone (O3) vegetation damage on gross primary productivity (GPP) in the United States (US) during the past decade (1998-2007). The model's GPP simulation is evaluated at 40 sites of the North American Carbon Program (NACP) synthesis. The ecosystem-scale model version reproduces interannual variability and seasonality of GPP at most sites, especially in croplands. Inclusion of the O3 damage impact decreases biases of simulated GPP at most of the NACP sites. The simulation with the O3 damage effect reproduces 64% of the observed variance in summer GPP and 45% on the annual average. Based on a regional gridded simulation over the US, summertime average O3-free GPP is 5.9 g C m-2 day-1 (9.1 g C m-2 day-1 in the East of 95° W and 3.7 g C m-2 day-1 in the West). O3 damage decreases GPP by 3-7% on average in the eastern US and leads to significant decreases of 13-17% in east coast hotspots. Sensitivity simulations show that a reduction of 25% in surface O3 concentration alleviates the average GPP damages to 1-3%, suggesting a promising prospect for ecosystem health following the emission control.

  10. Ozone vegetation damage effects on gross primary productivity in the United States

    NASA Astrophysics Data System (ADS)

    Yue, X.; Unger, N.

    2014-09-01

    We apply an off-line process-based vegetation model (the Yale Interactive Terrestrial Biosphere model) to assess the impacts of ozone (O3) vegetation damage on gross primary productivity (GPP) in the United States during the past decade (1998-2007). The model's GPP simulation is evaluated at 40 sites of the North American Carbon Program (NACP) synthesis. The ecosystem-scale model version reproduces interannual variability and seasonality of GPP at most sites, especially in croplands. Inclusion of the O3 damage impact decreases biases of simulated GPP at most of the NACP sites. The simulation with the O3 damage effect reproduces 64% of the observed variance in summer GPP and 42% on the annual average. Based on a regional gridded simulation over the US, summertime average O3-free GPP is 6.1 g C m-2 day-1 (9.5 g C m-2 day-1 in the east of 95° W and 3.9 g C m-2 day-1 in the west). O3 damage decreases GPP by 4-8% on average in the eastern US and leads to significant decreases of 11-17% in east coast hot spots. Sensitivity simulations show that a 25% decrease in surface O3 concentration halves the average GPP damage to only 2-4%, suggesting the substantial co-benefits to ecosystem health that may be achieved via O3 air pollution control.

  11. Developing a diagnostic model for estimating terrestrial vegetation gross primary productivity using the photosynthetic quantum yield and Earth Observation data.

    PubMed

    Ogutu, Booker O; Dash, Jadunandan; Dawson, Terence P

    2013-09-01

    This article develops a new carbon exchange diagnostic model [i.e. Southampton CARbon Flux (SCARF) model] for estimating daily gross primary productivity (GPP). The model exploits the maximum quantum yields of two key photosynthetic pathways (i.e. C3 and C4 ) to estimate the conversion of absorbed photosynthetically active radiation into GPP. Furthermore, this is the first model to use only the fraction of photosynthetically active radiation absorbed by photosynthetic elements of the canopy (i.e. FAPARps ) rather than total canopy, to predict GPP. The GPP predicted by the SCARF model was comparable to in situ GPP measurements (R(2)  > 0.7) in most of the evaluated biomes. Overall, the SCARF model predicted high GPP in regions dominated by forests and croplands, and low GPP in shrublands and dry-grasslands across USA and Europe. The spatial distribution of GPP from the SCARF model over Europe and conterminous USA was comparable to those from the MOD17 GPP product except in regions dominated by croplands. The SCARF model GPP predictions were positively correlated (R(2)  > 0.5) to climatic and biophysical input variables indicating its sensitivity to factors controlling vegetation productivity. The new model has three advantages, first, it prescribes only two quantum yield terms rather than species specific light use efficiency terms; second, it uses only the fraction of PAR absorbed by photosynthetic elements of the canopy (FAPARps ) hence capturing the actual PAR used in photosynthesis; and third, it does not need a detailed land cover map that is a major source of uncertainty in most remote sensing based GPP models. The Sentinel satellites planned for launch in 2014 by the European Space Agency have adequate spectral channels to derive FAPARps at relatively high spatial resolution (20 m). This provides a unique opportunity to produce global GPP operationally using the Southampton CARbon Flux (SCARF) model at high spatial resolution.

  12. The impact of forest architecture parameterization on GPP simulations

    NASA Astrophysics Data System (ADS)

    Firanj, Ana; Lalic, Branislava; Podrascanin, Zorica

    2015-08-01

    The presence of a forest strongly affects ecosystem fluxes by acting as a source or sink of mass and energy. The objective of this study was to investigate the influence of the vertical forest heterogeneity parameterization on gross primary production (GPP) simulations. To introduce a heterogeneity effect, a new method for the upscaling of the leaf level GPP is proposed. This upscaling method is based on the relationship between the leaf area index ( LAI) and the leaf area density ( LAD) profiles and the standard sun/shade leaf separation method. The effect of the crown shape and foliage distribution parameterization on the simulated GPP is confirmed in a comparison study between the proposed method and the standard sun/shade upscaling method. The observed values used in the comparison study are assimilated during the vegetation period on three distinguished forest eddy-covariance (EC) measurement sites chosen for the diversity of their morphological characteristics. The obtained results show (a) the sensitivity of the simulated GPP to the leaf area density profile, (b) the capability of the proposed scaling method to calculate the contribution of the different canopy layers to the entire canopy GPP, and (c) a better agreement with the observations of the simulated GPP with the proposed upscaling method compared with the standard sun/shade method.

  13. The global role of ppGpp synthesis in morphological differentiation and antibiotic production in Streptomyces coelicolor A3(2)

    PubMed Central

    Hesketh, Andrew; Chen, Wenqiong Joan; Ryding, Jamie; Chang, Sherman; Bibb, Mervyn

    2007-01-01

    Background Regulation of production of the translational apparatus via the stringent factor ppGpp in response to amino acid starvation is conserved in many bacteria. However, in addition to this core function, it is clear that ppGpp also exhibits genus-specific regulatory effects. In this study we used Affymetrix GeneChips to more fully characterize the regulatory influence of ppGpp synthesis on the biology of Streptomyces coelicolor A3(2), with emphasis on the control of antibiotic biosynthesis and morphological differentiation. Results Induction of ppGpp synthesis repressed transcription of the major sigma factor hrdB, genes with functions associated with active growth, and six of the thirteen conservons present in the S. coelicolor genome. Genes induced following ppGpp synthesis included the alternative sigma factor SCO4005, many for production of the antibiotics CDA and actinorhodin, the regulatory genes SCO4198 and SCO4336, and two alternative ribosomal proteins. Induction of the CDA and actinorhodin clusters was accompanied by an increase in transcription of the pathway regulators cdaR and actII-ORF4, respectively. Comparison of transcriptome profiles of a relA null strain, M570, incapable of ppGpp synthesis with its parent M600 suggested the occurrence of metabolic stress in the mutant. The failure of M570 to sporulate was associated with a stalling between production of the surfactant peptide SapB, and of the hydrophobins: it overproduced SapB but failed to express the chaplin and rodlin genes. Conclusion In S. coelicolor, ppGpp synthesis influences the expression of several genomic elements that are particularly characteristic of streptomycete biology, notably antibiotic gene clusters, conservons, and morphogenetic proteins. PMID:17683547

  14. Change of outlook for the forest productivity estimated with remote sensing using the new Collection 6 GPP/NPP MODIS product

    NASA Astrophysics Data System (ADS)

    Marjanović, Hrvoje; Kern, Anikó; Anić, Mislav; Zorana Ostrogović Sever, Maša; Balenović, Ivan; Alberti, Giorgio; Kovač, Goran; Barcza, Zoltán

    2016-04-01

    Estimates of forest productivity from remote sensing data, such as the MOD17 GPP and NPP values derived from MODIS data, are becoming increasingly important tools for monitoring forest productivity in light of the climate change. Hence, small sensor degradation, like the one in the case of MODIS sensor on-board satellite Terra could lead so significant bias in results and false conclusions of the path that the ecosystem is on. In new Collection 6 (C6) of the MOD17 product, the sensor degradation problem has been addressed compared to the previous version Collection 5.5 (C5.5) products, offering a new outlook on the trends in forest productivity. In our work we compared the C5.5 and C6 for MOD17 GPP and NPP products against estimates from eddy covariance and field measurements ('ground truth') at young Pedunculate oak site in Jastrebarsko forest. In order to assess the outlook of forest productivity at larger scale we intersected in GIS maps of forest areas under management and MODIS pixels with 1km spatial resolution. After selecting only those pixels that have at least 90% forest coverage according to the management plans, we analysed the temporal trends and variability in MODIS derived GPP and NPP both from C5.5 and C6 products. Analysis was performed for four main forests classes according to the dominant tree species (Pedunculate oak, Sessile oak, Common beech and Silver fir).

  15. Net primary production of forests: a constant fraction of gross primary production?

    PubMed

    Waring, R. H.; Landsberg, J. J.; Williams, M.

    1998-02-01

    Considerable progress has been made in our ability to model and measure annual gross primary production (GPP) by terrestrial vegetation. But challenges remain in estimating maintenance respiration (R(m)) and net primary production (NPP). To search for possible common relationships, we assembled annual carbon budgets from six evergreen and one deciduous forest in Oregon, USA, three pine plantations in New South Wales, Australia, a deciduous forest in Massachusetts, USA, and a Nothofagus forest on the South Island of New Zealand. At all 12 sites, a standard procedure was followed to estimate annual NPP of foliage, branches, stems, and roots, the carbon expended in synthesis of these organs (R(g)), their R(m), and that of previously produced foliage and sapwood in boles, branches, and large roots. In the survey, total NPP ranged from 120 to 1660 g C m(-2) year(-1), whereas the calculated fraction allocated to roots varied from 0.22 to 0.63. Comparative analysis indicated that the total NPP/GPP ratio was conservative (0.47 +/- 0.04 SD). This finding supports the possibility of greatly simplifying forest growth models. The constancy of the NPP/GPP ratio also provides an incentive to renew efforts to understand the environmental factors affecting partitioning of NPP above and belowground.

  16. Attributing regional trends of evapotranspiration and gross primary productivity with remote sensing: a case study in the North China Plain

    NASA Astrophysics Data System (ADS)

    Mo, Xingguo; Chen, Xuejuan; Hu, Shi; Liu, Suxia; Xia, Jun

    2017-01-01

    Attributing changes in evapotranspiration (ET) and gross primary productivity (GPP) is crucial for impact and adaptation assessment of the agro-ecosystems to climate change. Simulations with the VIP model revealed that annual ET and GPP slightly increased from 1981 to 2013 over the North China Plain. The tendencies of both ET and GPP were upward in the spring season, while they were weak and downward in the summer season. A complete factor analysis illustrated that the relative contributions of climatic change, CO2 fertilization, and management to the ET (GPP) trend were 56 (-32) %, -28 (25) %, and 68 (108) %, respectively. The decline of global radiation resulted from deteriorated aerosol and air pollution was the principal cause of GPP decline in summer, while air warming intensified the water cycle and advanced the plant productivity in the spring season. Generally, agronomic improvements were the principal drivers of crop productivity enhancement.

  17. Canopy and physiological controls of GPP during drought and heat wave

    NASA Astrophysics Data System (ADS)

    Zhang, Yao; Xiao, Xiangming; Zhou, Sha; Ciais, Philippe; McCarthy, Heather; Luo, Yiqi

    2016-04-01

    Vegetation indices (VIs) derived from satellite reflectance measurements are often used as proxies of canopy activity to evaluate the impacts of drought and heat wave on gross primary production (GPP) through production efficiency models. However, GPP is also regulated by physiological processes that cannot be directly detected using reflectance measurements. This study analyzes the co-limitation of canopy and plant physiology (represented by VIs and climate anomalies, respectively) on GPP during the 2003 European summer drought and heat wave for 15 Euroflux sites. During the entire drought period, spatial pattern of GPP anomalies can be quantified by relative changes in VIs. We also find that GPP sensitivity to relative canopy changes is higher for nonforest ecosystems (1.81 ± 0.32%GPP/%enhanced vegetation index), while GPP sensitivity to physiological changes is higher for forest ecosystems (-0.18 ± 0.05 g C m-2 d-1/hPa). A conceptual model is further built to better illustrate the canopy and physiological controls on GPP during drought periods.

  18. Precipitation and carbon-water coupling jointly control the interannual variability of global land gross primary production

    NASA Astrophysics Data System (ADS)

    Zhang, Yao; Xiao, Xiangming; Guanter, Luis; Zhou, Sha; Ciais, Philippe; Joiner, Joanna; Sitch, Stephen; Wu, Xiaocui; Nabel, Julia; Dong, Jinwei; Kato, Etsushi; Jain, Atul K.; Wiltshire, Andy; Stocker, Benjamin D.

    2016-12-01

    Carbon uptake by terrestrial ecosystems is increasing along with the rising of atmospheric CO2 concentration. Embedded in this trend, recent studies suggested that the interannual variability (IAV) of global carbon fluxes may be dominated by semi-arid ecosystems, but the underlying mechanisms of this high variability in these specific regions are not well known. Here we derive an ensemble of gross primary production (GPP) estimates using the average of three data-driven models and eleven process-based models. These models are weighted by their spatial representativeness of the satellite-based solar-induced chlorophyll fluorescence (SIF). We then use this weighted GPP ensemble to investigate the GPP variability for different aridity regimes. We show that semi-arid regions contribute to 57% of the detrended IAV of global GPP. Moreover, in regions with higher GPP variability, GPP fluctuations are mostly controlled by precipitation and strongly coupled with evapotranspiration (ET). This higher GPP IAV in semi-arid regions is co-limited by supply (precipitation)-induced ET variability and GPP-ET coupling strength. Our results demonstrate the importance of semi-arid regions to the global terrestrial carbon cycle and posit that there will be larger GPP and ET variations in the future with changes in precipitation patterns and dryland expansion.

  19. Precipitation and carbon-water coupling jointly control the interannual variability of global land gross primary production

    PubMed Central

    Zhang, Yao; Xiao, Xiangming; Guanter, Luis; Zhou, Sha; Ciais, Philippe; Joiner, Joanna; Sitch, Stephen; Wu, Xiaocui; Nabel, Julia; Dong, Jinwei; Kato, Etsushi; Jain, Atul K.; Wiltshire, Andy; Stocker, Benjamin D.

    2016-01-01

    Carbon uptake by terrestrial ecosystems is increasing along with the rising of atmospheric CO2 concentration. Embedded in this trend, recent studies suggested that the interannual variability (IAV) of global carbon fluxes may be dominated by semi-arid ecosystems, but the underlying mechanisms of this high variability in these specific regions are not well known. Here we derive an ensemble of gross primary production (GPP) estimates using the average of three data-driven models and eleven process-based models. These models are weighted by their spatial representativeness of the satellite-based solar-induced chlorophyll fluorescence (SIF). We then use this weighted GPP ensemble to investigate the GPP variability for different aridity regimes. We show that semi-arid regions contribute to 57% of the detrended IAV of global GPP. Moreover, in regions with higher GPP variability, GPP fluctuations are mostly controlled by precipitation and strongly coupled with evapotranspiration (ET). This higher GPP IAV in semi-arid regions is co-limited by supply (precipitation)-induced ET variability and GPP-ET coupling strength. Our results demonstrate the importance of semi-arid regions to the global terrestrial carbon cycle and posit that there will be larger GPP and ET variations in the future with changes in precipitation patterns and dryland expansion. PMID:28008960

  20. Precipitation and Carbon-Water Coupling Jointly Control the Interannual Variability of Global Land Gross Primary Production

    NASA Technical Reports Server (NTRS)

    Zhang, Yao; Xiao, Xiangming; Guanter, Luis; Zhou, Sha; Ciais, Philippe; Joiner, Joanna; Sitch, Stephen; Wu, Xiaocui; Nabel, Julian; Dong, Jinwei; Kato, Etsushi; Jain, Atul K.; Wiltshire, Andy; Stocker, Benjamin D.

    2016-01-01

    Carbon uptake by terrestrial ecosystems is increasing along with the rising of atmospheric CO2 concentration. Embedded in this trend, recent studies suggested that the interannual variability (IAV) of global carbon fluxes may be dominated by semi-arid ecosystems, but the underlying mechanisms of this high variability in these specific regions are not well known. Here we derive an ensemble of gross primary production (GPP) estimates using the average of three data-driven models and eleven process-based models. These models are weighted by their spatial representativeness of the satellite-based solar-induced chlorophyll fluorescence (SIF). We then use this weighted GPP ensemble to investigate the GPP variability for different aridity regimes. We show that semi-arid regions contribute to 57% of the detrended IAV of global GPP. Moreover, in regions with higher GPP variability, GPP fluctuations are mostly controlled by precipitation and strongly coupled with evapotranspiration (ET). This higher GPP IAV in semi-arid regions is co-limited by supply (precipitation)-induced ET variability and GPP-ET coupling strength. Our results demonstrate the importance of semi-arid regions to the global terrestrial carbon cycle and posit that there will be larger GPP and ET variations in the future with changes in precipitation patterns and dryland expansion.

  1. Assessment of CO2 fluxes and forest productivity (NPP/GPP) estimates from eddy covariance measurement and field observations

    NASA Astrophysics Data System (ADS)

    Anić, Mislav; Marjanović, Hrvoje; Zorana Ostrogović Sever, Maša; Barcza, Zoltán; Večenaj, Željko

    2016-04-01

    Eddy covariance (EC) measurements were carried out at the Jastrebarsko site, Croatia, in lowland forest dominated by pedunculate oak. For validation of CO2 fluxes measured with EC method bi-weekly field measurements of increment of 640 trees in 24 plots set in a 100m x 100m grid, height increment and litterfall have been used. In our work we compared annual productivity (GPP and NPP) assessments from EC measurements with field measurements. The comparison was made on a seven year dataset of measurements, spanning from 2008 to 2014. Also, flux dependence on groundwater level has been investigated. Results are showing that forest productivity estimates with EC method are in good agreement with the estimates from field measurements in the dry years. Agreement is slightly lower for years with high precipitation.

  2. The 2010 spring drought reduced primary productivity in southwestern China

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Xiao, Jingfeng; Li, Jing; Wang, Kun; Lei, Liping; Guo, Huadong

    2012-12-01

    Many parts of the world experience frequent and severe droughts. Summer drought can significantly reduce primary productivity and carbon sequestration capacity. The impacts of spring droughts, however, have received much less attention. A severe and sustained spring drought occurred in southwestern China in 2010. Here we examine the influence of this spring drought on the primary productivity of terrestrial ecosystems using data on climate, vegetation greenness and productivity. We first assess the spatial extent, duration and severity of the drought using precipitation data and the Palmer drought severity index. We then examine the impacts of the drought on terrestrial ecosystems using satellite data for the period 2000-2010. Our results show that the spring drought substantially reduced the enhanced vegetation index (EVI) and gross primary productivity (GPP) during spring 2010 (March-May). Both EVI and GPP also substantially declined in the summer and did not fully recover from the drought stress until August. The drought reduced regional annual GPP and net primary productivity (NPP) in 2010 by 65 and 46 Tg C yr-1, respectively. Both annual GPP and NPP in 2010 were the lowest over the period 2000-2010. The negative effects of the drought on annual primary productivity were partly offset by the remarkably high productivity in August and September caused by the exceptionally wet conditions in late summer and early fall and the farming practices adopted to mitigate drought effects. Our results show that, like summer droughts, spring droughts can also have significant impacts on vegetation productivity and terrestrial carbon cycling.

  3. Investigating the controls on Gross Primary Productivity of a high elevation tropical montane cloud forest

    NASA Astrophysics Data System (ADS)

    van de Weg, M. J.; Meir, P.; Malhi, Y.; Williams, M.; Silva-Espejo, J.; Grace, J.

    2012-04-01

    Tropical montane cloud forests (TMCF) are a unique, but little understood ecosystem that can be found in tropical mountainous areas around the world. In recent years, the interest in the carbon (C) cycle of TMCFs has increased, especially with regard to possibilities for carbon sequestration and storage practices. Compared with tropical lowland rainforests, these forests have a low aboveground net primary productivity (ANPP), a small standing biomass and a small leaf area index (LAI), while the forests are characterized by the stunted growth form of the trees. However, estimates of gross primary productivity (GPP) of TMCFs are scarce, and there are uncertainties in what factors are most important in controlling TMCF productivity. We investigated the controlling factors on GPP in a TMCF in the Andes in south east Peru (13°11'28"S / 71°35'24"W). First, we measured physiological and structural parameters of the vegetation. On a leaf level, the carboxylation efficiency of Rubisco (V cmax) and the electron transport capacity (Jmax) were as high as those found in tropical lowland forests, but as expected the LAI was smaller. Therefore, in terms of the capacity for TMCF C uptake, the total leaf area is more important in explaining the difference between TMCF GPP and tropical lowland forest GPP, than photosynthetic capacity of the leaf tissue. Furthermore, we used the vegetation parameters, together with meteorological data from the site with a process based simulator (the SPA model) to simulate TMCF GPP and to evaluate the relative importance of the environmental controls on GPP. To our knowledge, this is the first estimate of TMCF GPP that uses parameters and drivers that are derived from the site simulated in the model. Simulated annual GPP was 16.2 ± SE 1.6 t C ha-1 yr-1, which is about half of the GPP commonly observed in neotropical lowland rainforests. Temperature and, to a lesser extent photosynthetic active radiation (PAR), were the strongest environmental

  4. Separating the effects of phenology and diffuse radiation on gross primary productivity in winter wheat

    NASA Astrophysics Data System (ADS)

    Williams, Ian N.; Riley, William J.; Kueppers, Lara M.; Biraud, Sebastien C.; Torn, Margaret S.

    2016-07-01

    Gross primary productivity (GPP) has been reported to increase with the fraction of diffuse solar radiation, for a given total irradiance. The correlation between GPP and diffuse radiation suggests effects of diffuse radiation on canopy light-use efficiency, but potentially confounding effects of vegetation phenology have not been fully explored. We applied several approaches to control for phenology, using 8 years of eddy-covariance measurements of winter wheat in the U.S. Southern Great Plains. The apparent enhancement of daily GPP due to diffuse radiation was reduced from 260% to 75%, after subsampling over the peak growing season or by subtracting a 15 day moving average of GPP, suggesting a role of phenology. The diffuse radiation effect was further reduced to 22% after normalizing GPP by a spectral reflectance index to account for phenological variations in leaf area index LAI and canopy photosynthetic capacity. Canopy photosynthetic capacity covaries with diffuse fraction at a given solar irradiance at this site because both factors are dependent on day of year or solar zenith angle. Using a two-leaf Sun-shaded canopy radiative transfer model, we confirmed that the effects of phenological variations in photosynthetic capacity can appear qualitatively similar to the effects of diffuse radiation on GPP and therefore can be difficult to distinguish using observations. The importance of controlling for phenology when inferring diffuse radiation effects on GPP raises new challenges and opportunities for using radiation measurements to improve carbon cycle models.

  5. Structural uncertainty in model-simulated trends of global gross primary production

    NASA Astrophysics Data System (ADS)

    Hashimoto, H.; Wang, W.; Milesi, C.; Xiong, J.; Ganguly, S.; Zhu, Z.; Nemani, R. R.

    2012-12-01

    Accurate representation of the effect of drought on terrestrial vegetation functioning is important for understanding the interannual variability in global Gross Primary Production(GPP) and for projecting carbon sequestration potential by vegetation. Drought effect is usually modeled as a function of Vapor Pressure Deficit (VPD) and/or soil moisture. Global warming is likely to accelerate increasing trend in VPD, while a relatively stable precipitation is predicted. This difference in projections between VPD and precipitation can cause serious discrepancies in vegetation behavior depending on how the ecosystem models represent the drought effect. In this study, we scrutinized the model responses to drought using the 30-year record of GIMMS 3G dataset (1982-2010). A diagnostic ecosystem model, Terrestrial Observation and Prediction System (TOPS), was used to estimate global GPP from 1982 to 2009 with 9 different experimental simulations. The control run of global GPP increased until around 2000, but stayed flat after 2000. Among the simulations with single climate constraint, only the VPD-driven simulation showed a decrease in 2000s, while the other scenarios simulated an increase in GPP. These different responses in 2000s can be attributed to the difference in the representation of water stress in models, i.e. using VPD and/or precipitation. When we compared the trend of simulated GPP with CO2 growth rate, VPD-driven model had the highest correlation with CO2 growth rate. However, spatial map of trend in simulated GPP using GIMMS 3G data showed more consistent with the GPP driven by soil moisture than the GPP driven by VPD. Thus, the GPP driven by soil moisture is close to satellite observations in TOPS model, and high correlation of VPD-driven simulation with CO2 growth rate can be attributed to spurious correlation that is likely induced by the previously reported high correlations between CO2 growth rate and temperature variability.

  6. A multi-sites analysis on the ozone effects on Gross Primary Production of European forests.

    PubMed

    Proietti, C; Anav, A; De Marco, A; Sicard, P; Vitale, M

    2016-06-15

    Ozone (O3) is both a greenhouse gas and a secondary air pollutant causing adverse impacts on forests ecosystems at different scales, from cellular to ecosystem level. Specifically, the phytotoxic nature of O3 can impair CO2 assimilation that, in turn affects forest productivity. This study aims to evaluate the effects of tropospheric O3 on Gross Primary Production (GPP) at 37 European forest sites during the time period 2000-2010. Due to the lack of carbon assimilation data at O3 monitoring stations (and vice-versa) this study makes a first attempt to combine high resolution MODIS Gross Primary Production (GPP) estimates and O3 measurement data. Partial Correlations, Anomalies Analysis and the Random Forests Analysis (RFA) were used to quantify the effects of tropospheric O3 concentration and its uptake on GPP and to evaluate the most important factors affecting inter-annual GPP changes. Our results showed, along a North-West/South-East European transect, a negative impact of O3 on GPP ranging from 0.4% to 30%, although a key role of meteorological parameters respect to pollutant variables in affecting GPP was found. In particular, meteorological parameters, namely air temperature (T), soil water content (SWC) and relative humidity (RH) are the most important predictors at 81% of test sites. Moreover, it is interesting to highlight a key role of SWC in the Mediterranean areas (Spanish, Italian and French test sites) confirming that, soil moisture and soil water availability affect vegetation growth and photosynthesis especially in arid or semi-arid ecosystems such as the Mediterranean climate regions. Considering the pivotal role of GPP in the global carbon balance and the O3 ability to reduce primary productivity of the forests, this study can help in assessing the O3 impacts on ecosystem services, including wood production and carbon sequestration.

  7. Robustness and Uncertainties of the “Temperature and Greenness” Model for Estimating Terrestrial Gross Primary Production

    PubMed Central

    Dong, Jiaqi; Li, Longhui; Shi, Hao; Chen, Xi; Luo, Geping; Yu, Qiang

    2017-01-01

    Terrestrial gross primary production (GPP) plays a vital role in offsetting anthropogenic CO2 emission and regulating global carbon cycle. Various remote sensing approaches for estimating GPP have attracted considerable scientific attentions, yet their robustness and uncertainties remain unclear. Here we evaluate the performance of the “temperature and greenness” (TG) model, a representative remote sensing model in estimating GPP, using the global FLUXNET GPP based on parameter sensitive analysis and optimization strategies. The results show that the minimum (xn) and optimum (xo) temperatures for photosynthesis are sensitive parameters but maximum temperature (xm) not. Optimized xn and xo differ largely from their defaults for more than half of 12 plant functional types (PFTs). Parameter optimization significantly improves the TG’s performance in forest ecosystems where temperature or solar radiation has significant contribution to GPP. For water-limited ecosystems where GPP are strongly dependent of EVI and EVI are sensitive to precipitation, parameter optimization has limited effects. These results imply that the TG model, and most likely for other kind of GPP models using same methodology, can’t be significantly improved for all PFTs through parameter optimization only, and other key climatic variables should be incorporated into the model for better predicting terrestrial ecosystem GPP. PMID:28272461

  8. Robustness and Uncertainties of the “Temperature and Greenness” Model for Estimating Terrestrial Gross Primary Production

    NASA Astrophysics Data System (ADS)

    Dong, Jiaqi; Li, Longhui; Shi, Hao; Chen, Xi; Luo, Geping; Yu, Qiang

    2017-03-01

    Terrestrial gross primary production (GPP) plays a vital role in offsetting anthropogenic CO2 emission and regulating global carbon cycle. Various remote sensing approaches for estimating GPP have attracted considerable scientific attentions, yet their robustness and uncertainties remain unclear. Here we evaluate the performance of the “temperature and greenness” (TG) model, a representative remote sensing model in estimating GPP, using the global FLUXNET GPP based on parameter sensitive analysis and optimization strategies. The results show that the minimum (xn) and optimum (xo) temperatures for photosynthesis are sensitive parameters but maximum temperature (xm) not. Optimized xn and xo differ largely from their defaults for more than half of 12 plant functional types (PFTs). Parameter optimization significantly improves the TG’s performance in forest ecosystems where temperature or solar radiation has significant contribution to GPP. For water-limited ecosystems where GPP are strongly dependent of EVI and EVI are sensitive to precipitation, parameter optimization has limited effects. These results imply that the TG model, and most likely for other kind of GPP models using same methodology, can’t be significantly improved for all PFTs through parameter optimization only, and other key climatic variables should be incorporated into the model for better predicting terrestrial ecosystem GPP.

  9. Gross primary production of global forest ecosystems has been overestimated

    PubMed Central

    Ma, Jianyong; Yan, Xiaodong; Dong, Wenjie; Chou, Jieming

    2015-01-01

    Coverage rate, a critical variable for gridded forest area, has been neglected by previous studies in estimating the annual gross primary production (GPP) of global forest ecosystems. In this study, we investigated to what extent the coverage rate could impact forest GPP estimates from 1982 to 2011. Here we show that the traditional calculation without considering the coverage rate globally overestimated the forest gross carbon dioxide uptake by approximately 8.7%, with a value of 5.12 ± 0.23 Pg C yr−1, which is equivalent to 48% of the annual emissions from anthropogenic activities in 2012. Actually, the global annual GPP of forest ecosystems is approximately 53.71 ± 4.83 Pg C yr−1 for the past 30 years by taking the coverage rate into account. Accordingly, we argue that forest annual GPP calculated by previous studies has been overestimated due to the exaggerated forest area, and therefore, coverage rate may be a required factor to further quantify the global carbon cycle. PMID:26027557

  10. Exogenous N addition enhances the responses of gross primary productivity to individual precipitation events in a temperate grassland

    PubMed Central

    Guo, Qun; Hu, Zhong-min; Li, Sheng-gong; Yu, Gui-rui; Sun, Xiao-min; Li, Ling-hao; Liang, Nai-shen; Bai, Wen-ming

    2016-01-01

    Predicted future shifts in the magnitude and frequency (larger but fewer) of precipitation events and enhanced nitrogen (N) deposition may interact to affect grassland productivity, but the effects of N enrichment on the productivity response to individual precipitation events remain unclear. In this study, we quantified the effects of N addition on the response patterns of gross primary productivity (GPP) to individual precipitation events of different sizes (Psize) in a temperate grassland in China. The results showed that N enrichment significantly increased the time-integrated amount of GPP in response to an individual precipitation event (GPPtotal), and the N-induced stimulation of GPP increased with increasing Psize. N enrichment rarely affected the duration of the GPP response, but it significantly stimulated the maximum absolute GPP response. Higher foliar N content might play an important role in the N-induced stimulation of GPP. GPPtotal in both the N-addition and control treatments increased linearly with Psize with similar Psize intercepts (approximately 5 mm, indicating a similar lower Psize threshold to stimulate the GPP response) but had a steeper slope under N addition. Our work indicates that the projected larger precipitation events will stimulate grassland productivity, and this stimulation might be amplified by increasing N deposition. PMID:27264386

  11. The potential of carbonyl sulfide as a proxy for gross primary production at flux tower sites

    NASA Astrophysics Data System (ADS)

    Blonquist, J. Mark, Jr.

    Seasonal dynamics of atmospheric carbonyl sulfide (OCS) at regional and continental scales and plant OCS exchange at the leaf level have shown a close relationship with those for CO2. CO2 has both sinks and sources within terrestrial ecosystems, but the primary terrestrial exchange for OCS is thought to be leaf uptake, suggesting potential for OCS uptake as a proxy for gross primary production (GPP). The utility of OCS uptake as a GPP proxy in micrometeorological studies of biosphere-atmosphere CO2 exchange was explored by applying theoretical concepts from earlier OCS studies to estimate GPP. Measured net ecosystem exchange (NEE) was partitioned using the ratio of measured vertical mole fraction gradients of OCS and CO2. At the Harvard Forest AmeriFlux site, measured CO2 and OCS vertical gradients were correlated, and were related to NEE and GPP, respectively. Estimates of GPP from OCS-based NEE partitioning were similar to those from established regression techniques, providing evidence that OCS uptake can potentially serve as a GPP proxy. Measured vertical CO 2 mole fraction gradients at five other AmeriFlux sites were used to project anticipated vertical OCS mole fraction gradients to provide indication of potential OCS signal magnitudes at sites where no OCS measurements were made. Projected OCS gradients at sites with short canopies were greater than those in forests, including measured OCS gradients at Harvard Forest, indicating greater potential for OCS uptake as a GPP proxy at these sites. This exploratory study suggests that continued investigation of linkages between OCS and GPP is warranted.

  12. Ozone vegetation damage effects on gross primary productivity in the United States

    NASA Astrophysics Data System (ADS)

    Yue, X.; Unger, N.

    2013-12-01

    We apply an off-line process-based vegetation model to assess the impacts of ozone vegetation damage on gross primary productivity (GPP) in the contiguous United States during the past decade (1998-2007). The semi-mechanistic parameterization of ozone-induced photosynthesis inhibition from Sitch et al. (2007) is implemented into the vegetation model framework. We first evaluate the model's GPP simulation at 40 sites of the North American Carbon Program (NACP). This ecosystem-scale site-level model is driven with hourly meteorological forcings from the Modern-Era Retrospective Analysis (MERRA) and site-based measurements. The model reproduces interannual variability and seasonality of GPP at most sites, especially in croplands. The annual mean GPP shows a correlation coefficient of 0.68 between simulations and observations. The inclusion of the ozone damage impact improves the simulated GPP at most NACP sites. The simulated annual GPP averaged over all NACP sites changes from 3.8 g C m-2 day-1 to 3.6 g C m-2 day-1, closer to the observations of 3.0 g C m-2 day-1. We then perform a regional gridded simulation at 1.3°×1° resolution over the contiguous U.S. The distributed model is driven with the MERRA meteorology and land cover from the International Satellite Land-Surface Climatology Project (ISLSCP). The simulation shows an average GPP of 5.9 g C m-2 day-1 in summer, with 9.2 g C m-2 day-1 in the East of 95°W and 3.7 g C m-2 day-1 in the West. Hourly surface ozone concentrations are output from simulations representative of the present climatic state performed using the Yale-E2 global carbon-chemistry-climate model. After evaluating the model's surface ozone based on ground observations from ~1200 sites, we probe the response of GPP over the United States to ozone vegetation damage. On average, the summer GPP declines by 2-5% in the contiguous U.S., depending on the sensitivity of GPP to ozone. A larger reduction of 4-7% is estimated in eastern U.S., where both

  13. MODIS-Derived Terrestrial Primary Production

    NASA Astrophysics Data System (ADS)

    Zhao, Maosheng; Running, Steven; Heinsch, Faith Ann; Nemani, Ramakrishna

    Temporal and spatial changes in terrestrial biological productivity have a large impact on humankind because terrestrial ecosystems not only create environments suitable for human habitation, but also provide materials essential for survival, such as food, fiber and fuel. A recent study estimated that consumption of terrestrial net primary production (NPP; a list of all the acronyms is available in the appendix at the end of the chapter) by the human population accounts for about 14-26% of global NPP (Imhoff et al. 2004). Rapid global climate change is induced by increased atmospheric greenhouse gas concentration, especially CO2, which results from human activities such as fossil fuel combustion and deforestation. This directly impacts terrestrial NPP, which continues to change in both space and time (Melillo et al. 1993; Prentice et al. 2001; Nemani et al. 2003), and ultimately impacts the well-being of human society (Milesi et al. 2005). Additionally, substantial evidence show that the oceans and the biosphere, especially terrestrial ecosystems, currently play a major role in reducing the rate of the atmospheric CO2 increase (Prentice et al. 2001; Schimel et al. 2001). NPP is the first step needed to quantify the amount of atmospheric carbon fixed by plants and accumulated as biomass. Continuous and accurate measurements of terrestrial NPP at the global scale are possible using satellite data. Since early 2000, for the first time, the MODIS sensors onboard the Terra and Aqua satellites, have operationally provided scientists with near real-time global terrestrial gross primary production (GPP) and net photosynthesis (PsnNet) data. These data are provided at 1 km spatial resolution and an 8-day interval, and annual NPP covers 109,782,756 km2 of vegetated land. These GPP, PsnNet and NPP products are collectively known as MOD17 and are part of a larger suite of MODIS land products (Justice et al. 2002), one of the core Earth System or Climate Data Records (ESDR or

  14. Estimation and Analysis of Gross Primary Production of Soybean Under Various Management Practices and Drought Conditions

    NASA Astrophysics Data System (ADS)

    Wagle, P.; Xiao, X.; Suyker, A.

    2014-12-01

    Gross primary production (GPP) of croplands may be used to quantify crop productivity and evaluate a range of management practices. Eddy flux data from three soybean (Glycine max L.) fields under different management practices (no-till vs till; rainfed vs irrigated) and Moderate Resolution Imaging Spectroradiometer (MODIS) derived vegetation indices (VIs) were used to evaluate the biophysical performance of VIs and crop phenology, and to model GPP using a satellite-based vegetation photosynthesis model (VPM). The VIs tracked soybean phenology well and delineated the growing season length. The results show that the carbon uptake period and seasonal sums of net ecosystem CO2 exchange (NEE) and GPP can be inferred from the length of the vegetation activity period from satellite remote sensing data. Land surface water index (LSWI) tracked drought-impacted vegetation well. On a seasonal scale, NEE of the soybean sites ranged from -37 to -264 g C m-2. The result suggests that rainfed soybean fields needed about 450-500 mm of well-distributed seasonal rainfall to maximize the net carbon sink. During non-drought conditions, VPM accurately estimated seasonal dynamics and interannual variation of GPP of soybean under different management practices. However, some large discrepancies between GPPVPM and GPPEC were observed under drought conditions as the VI did not reflect the corresponding decrease in GPP. Diurnal GPP dynamics showed a bimodal distribution with a pronounced midday depression at the period of higher water vapor pressure deficit (> 1.2 kPa). A modified Wscalar based on LSWI, to account for the water stress, in VPM helped quantify the reduction in GPP during severe drought and the model's performance improved substantially. The results of this study demonstrate the potential use of remotely sensed VIs for better understanding of carbon dynamics and extrapolation of GPP of soybean croplands.

  15. Effects of foliage clumping on the estimation of global terrestrial gross primary productivity

    NASA Astrophysics Data System (ADS)

    Chen, Jing M.; Mo, Gang; Pisek, Jan; Liu, Jane; Deng, Feng; Ishizawa, Misa; Chan, Douglas

    2012-03-01

    Sunlit and shaded leaf separation proposed by Norman (1982) is an effective way to upscale from leaf to canopy in modeling vegetation photosynthesis. The Boreal Ecosystem Productivity Simulator (BEPS) makes use of this methodology, and has been shown to be reliable in modeling the gross primary productivity (GPP) derived from CO2flux and tree ring measurements. In this study, we use BEPS to investigate the effect of canopy architecture on the global distribution of GPP. For this purpose, we use not only leaf area index (LAI) but also the first ever global map of the foliage clumping index derived from the multiangle satellite sensor POLDER at 6 km resolution. The clumping index, which characterizes the degree of the deviation of 3-dimensional leaf spatial distributions from the random case, is used to separate sunlit and shaded LAI values for a given LAI. Our model results show that global GPP in 2003 was 132 ± 22 Pg C. Relative to this baseline case, our results also show: (1) global GPP is overestimated by 12% when accurate LAI is available but clumping is ignored, and (2) global GPP is underestimated by 9% when the effective LAI is available and clumping is ignored. The clumping effects in both cases are statistically significant (p < 0.001). The effective LAI is often derived from remote sensing by inverting the measured canopy gap fraction to LAI without considering the clumping. Global GPP would therefore be generally underestimated when remotely sensed LAI (actually effective LAI by our definition) is used. This is due to the underestimation of the shaded LAI and therefore the contribution of shaded leaves to GPP. We found that shaded leaves contribute 50%, 38%, 37%, 39%, 26%, 29% and 21% to the total GPP for broadleaf evergreen forest, broadleaf deciduous forest, evergreen conifer forest, deciduous conifer forest, shrub, C4 vegetation, and other vegetation, respectively. The global average of this ratio is 35%.

  16. A continuous measure of gross primary production for the conterminous United States derived from MODIS and AmeriFlux data

    SciTech Connect

    Xiao, Jingfeng; Zhuang, Qianlai; Law, Beverly E.; Chen, Jiquan; Baldocchi, D. D.; Ma, Siyan; Cook, David R.; Oren, Ram; Katul, G. G.; Gu, Lianhong

    2010-03-01

    The quantification of carbon fluxes between the terrestrial biosphere and the atmosphere is of scientific importance and also relevant to climate-policy making. Eddy covariance flux towers provide continuous measurements of ecosystem-level exchange of carbon dioxide spanning diurnal, synoptic, seasonal, and interannual time scales. However, these measurements only represent the fluxes at the scale of the tower footprint. Here we used remotely sensed data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to upscale gross primary productivity (GPP) data from eddy covariance flux towers to the continental scale. We first combined GPP and MODIS data for 42 AmeriFlux towers encompassing a wide range of ecosystem and climate types to develop a predictive GPP model using a regression tree approach. The predictive model was trained using observed GPP over the period 2000 2004, and was validated using observed GPP over the period 2005 2006 and leave-one-out cross-validation. Our model predicted GPP fairly well at the site level. We then used the model to estimate GPP for each 1 km 1 km cell across the U.S. for each 8-day interval over the period from February 2000 to December 2006 using MODIS data. Our GPP estimates provide a spatially and temporally continuous measure of gross primary production for the U.S. that is a highly constrained by eddy covariance flux data. Our study demonstrated that our empirical approach is effective for upscaling eddy flux GPP data to the continental scale and producing continuous GPP estimates across multiple biomes. With these estimates, we then examined the patterns, magnitude, and interannual variability of GPP. We estimated a gross carbon uptake between 6.91 and 7.33 Pg C yr 1 for the conterminous U.S. Drought, fires, and hurricanes reduced annual GPP at regional scales and could have a significant impact on the U.S. net ecosystem carbon exchange. The sources of the interannual variability of U.S. GPP were dominated by these

  17. Temperature sensitivity of stream gross primary production and respiration from the tropics to the arctic

    NASA Astrophysics Data System (ADS)

    Song, C.; Argerich, A.; Baker, C.; Bowden, W. B.; Dodds, W. K.; Douglas, M.; Farrell, K.; Flinn, M. B.; Garcia, E.; Gido, K. B.; Harms, T.; Jones, J.; Koenig, L.; Kominoski, J. S.; McDonald, K. S.; McDowell, W. H.; McMaster, D.; Parker, S.; Rosemond, A.; Rüegg, J.; Sheehan, K.; Trentman, M. T.; Wollheim, W. M.; Ballantyne, F.

    2015-12-01

    Understanding the temperature dependence of gross primary production (GPP) and ecosystem respiration (ER) in streams is critical to predict the carbon balance in stream ecosystems under global warming. We collected dissolved oxygen (DO) concentration, photosynthetically active radiation (PAR), channel hydrology and geomorphology, and temperature from multiple locations throughout stream networks in seven sites across six biomes, specifically tropical forest, temperate deciduous forest, temperate coniferous forest, tallgrass prairie, boreal forest, and arctic tundra. We estimated the activation energy (Ea) of GPP and ER from diel changes in DO, temperature and PAR for each stream reach. We showed the relationship between Ea and environmental variables, such as temperature, light availability and discharge. In addition, we found that Ea of GPP and ER were highly variable from reach to reach within each biome. The estimated Ea of GPP and ER was generally higher than predicted by metabolic theory. Ea of GPP ranges from 20 to 140 KJ/mol and Ea of ER ranges from 50 to 150 KJ/mol. There was no consistent trend of larger Ea for GPP or ER. This suggests that the changes in carbon balance in streams caused directly by warming is likely to be site specific.

  18. Attributing Changes in Gross Primary Productivity from 1901 to 2010

    NASA Astrophysics Data System (ADS)

    Schwalm, C. R.; Huntzinger, D. N.; Michalak, A. M.; Cook, R. B.; El Masri, B.; Hayes, D. J.; Huang, M.; Jacobson, A. R.; Jain, A. K.; Lei, H.; Lu, C.; Tian, H.; Schaefer, K. M.; Wei, Y.

    2014-12-01

    Model-based studies are foundational to perform diagnosis (has there been a change?) and attribution (what caused this change?) in the context of global environmental change. Here we employ a dual method approach using machine learning and simulation differencing across an ensemble of terrestrial biosphere models (TBM) to attribute changes in gross primary productivity (GPP) from 1901 to 2010. The simulations are taken from the Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP). For each TBM MsTMIP prescribes a semi-factorial set of five runs (globally at 0.5º spatial resolution) where time-varying controls on carbon metabolism are sequentially enabled. MsTMIP has a constrained simulation protocol -driving data, vegetation cover, boundary conditions, and steady-state spin up protocol are all standardized- such that only model structure varies and ensemble spread addresses process uncertainty. Applying this dual method to MsTMIP simulation output we attribute changes in GPP to changes in climate, land cover/land use change, atmospheric CO2, nitrogen deposition, near-surface air temperature, precipitation, and downwelling shortwave radiation as well as climate sigma (irreducible climate noise) and nonlinearity (interactions). Globally, the key factor associated with the Anthropocene, namely the sustained increase in atmospheric CO2, dominates changes in GPP across the full time period. Climate factors are of secondary importance and, along with land cover/land use change, may act to decrease GPP depending on decade and reference period. Despite differences in model structure attribution results across the full ensemble are generally consistent. Spatial morphologies, replicating the same dual approach by grid cell, exhibit high variability but with an atmospheric CO2 fertilization effect dominating the tropical zone. Our results suggest that the modern era of global warming, when viewed through the prism of GPP attribution, reaches back at

  19. Modeling Gross Primary Production of Savanna Woodlands in Southern Africa Using MODIS Imagery and CO2 Flux Tower Data

    NASA Astrophysics Data System (ADS)

    Jin, C.; Xiao, X.; Merbold, L.; Arneth, A.; Veenendaal, E.; Kutsch, W.

    2012-12-01

    Accurate estimation of gross primary production (GPP) of savanna ecosystem is valuable for evaluating the role of Africa in the global carbon cycle. An eddy flux observation network has been established to continuously measure the net CO2 fluxes (NEE) across various savanna vegetation types in Africa (CarboAfrica). Several publications have reported the seasonal dynamics and interannual variation of GPP for the savanna vegetation through partitioning of the measured NEE data. The satellite-based Production Efficiency Models (PEM), which calculate GPP as the product of absorbed photosynthetically active radiation (PAR) and light use efficiency (LUE), have been developed to scale up in situ GPP estimation from the eddy flux towers to regional scale. In this study, the Vegetation Photosynthesis Model (VPM) and the Moderate Resolution Imaging Spectroradiometer (MODIS) data were evaluated for their capacity to model GPP for savanna woodlands at two eddy flux towers in Botswana and Zambia, respectively. These two sites have different woodland types and precipitation pattern (Mopane woodlands vs. Miombo woodlands, semi-arid vs. semi-humid). In the VPM model, GPP is simulated as the product of photosynthetically active radiation (PAR), air temperature, Enhanced Vegetation Index (EVI), and Land Surface Water Index (LSWI). The results show that the simulated GPP by the VPM track well the temporal dynamic of GPP estimated from the eddy covariance measurements at these two sites. In addition, the land surface phenology of savanna woodlands, described by the satellite vegetation indices, especially the water-sensitive satellite indices-LSWI, are proved to match the phenology based on vegetation physiology activity measured by eddy covariance towers. The information of the timing and duration of vegetation growing season is useful for assisting the VPM modeling. Further evaluation of VPM simulations for and other savanna ecosystems is necessary before the VPM model is applied to

  20. The ppGpp synthetase gene (relA) of Streptomyces coelicolor A3(2) plays a conditional role in antibiotic production and morphological differentiation.

    PubMed Central

    Chakraburtty, R; Bibb, M

    1997-01-01

    Deletion of most of the coding region of the ppGpp synthetase gene (relA) of Streptomyces coelicolor A3(2) resulted in loss of ppGpp synthesis, both upon entry into stationary phase under conditions of nitrogen limitation and following amino acid starvation during exponential growth, but had no effect on growth rate. The relA mutant, which showed continued rRNA synthesis upon amino acid depletion (the relaxed response), failed to produce the antibiotics undecylprodigiosin (Red) and actinorhodin (Act) under conditions of nitrogen limitation. The latter appears to reflect diminished transcription of pathway-specific regulatory genes for Red and Act production, redD and actII-ORF4, respectively. In addition to the changes in secondary metabolism, the relA mutant showed a marked delay in the onset and extent of morphological differentiation, resulting in a conspicuously altered colony morphology. PMID:9294445

  1. New global observations of the terrestrial carbon cycle from GOSAT: Patterns of plant fluorescence with gross primary productivity

    NASA Astrophysics Data System (ADS)

    Frankenberg, Christian; Fisher, Joshua B.; Worden, John; Badgley, Grayson; Saatchi, Sassan S.; Lee, Jung-Eun; Toon, Geoffrey C.; Butz, André; Jung, Martin; Kuze, Akihiko; Yokota, Tatsuya

    2011-09-01

    Our ability to close the Earth's carbon budget and predict feedbacks in a warming climate depends critically on knowing where, when and how carbon dioxide is exchanged between the land and atmosphere. Terrestrial gross primary production (GPP) constitutes the largest flux component in the global carbon budget, however significant uncertainties remain in GPP estimates and its seasonality. Empirically, we show that global spaceborne observations of solar induced chlorophyll fluorescence - occurring during photosynthesis - exhibit a strong linear correlation with GPP. We found that the fluorescence emission even without any additional climatic or model information has the same or better predictive skill in estimating GPP as those derived from traditional remotely-sensed vegetation indices using ancillary data and model assumptions. In boreal summer the generally strong linear correlation between fluorescence and GPP models weakens, attributable to discrepancies in savannas/croplands (18-48% higher fluorescence-based GPP derived by simple linear scaling), and high-latitude needleleaf forests (28-32% lower fluorescence). Our results demonstrate that retrievals of chlorophyll fluorescence provide direct global observational constraints for GPP and open an entirely new viewpoint on the global carbon cycle. We anticipate that global fluorescence data in combination with consolidated plant physiological fluorescence models will be a step-change in carbon cycle research and enable an unprecedented robustness in the understanding of the current and future carbon cycle.

  2. The Potential of Carbonyl Sulfide as a Tracer for Gross Primary Productivity at Flux Tower Sites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Regional/continental scale studies of atmospheric carbonyl sulfide (OCS) seasonal dynamics and leaf level studies of plant OCS uptake have shown a close relationship to CO2 dynamics and uptake, suggesting potential for OCS as a tracer for gross primary productivity (GPP). Canopy CO2 and OCS differen...

  3. Evaluation of optical remote sensing parameters to improve modeling of gross primary productivity in a heterogeneous agricultural area

    NASA Astrophysics Data System (ADS)

    Schickling, A.; Damm, A.; Schween, J.; Rascher, U.; Crewell, S.; Wahner, A.

    2011-12-01

    Terrestrial photosynthesis greatly determines plant mediated exchange processes in the vegetation atmosphere system and substantially influences patterns in atmospheric carbon dioxide (CO2) concentrations and water vapor. Therefore, an accurate quantification of photosynthetic CO2 uptake, commonly referred to as gross primary productivity (GPP), is a key parameter to distinguish those atmospheric patterns on various spatio-temporal scales. Remote sensing (RS) offers the unique possibility to determine GPP at different spatial scales ranging from the local to the global scale. Attempts to estimate GPP from RS data focus on the light use efficiency (LUE) concept of Monteith which relates GPP to the absorbed photosynthetically active radiation and the efficiency of plant canopies to utilize the absorbed radiation for photosynthesis. To reliably predict GPP on different spatio-temporal scales LUE has to be linked to optical RS parameters which detect changes in photosynthetic efficiency due to environmental conditions. In this study we evaluated two optical RS parameters, namely the sun-induced fluorescence (Fs) and the photochemical reflectance index (PRI), for their potential to serve as a proxy for LUE. The parameters were derived from two ASD FieldSpec spectrometers which were operated in parallel. During several days one instrument was installed on the ground above the vegetation canopy of either a winter wheat or a sugar beet field. The second instrument was operated from a small research aircraft continuously crossing the observation sites at low altitude (< 300 m). GPP was calculated on a diurnal basis including optical parameters in Monteith's LUE concept. The calculated GPP was compared to simultaneously acquired GPP data from eddy covariance measurements. The diurnal behavior of calculated and measured GPP corresponded well indicating that optical RS parameters are able to track the diurnal response of physiological regulation of photosynthesis to changing

  4. Estimating Vegetation Primary Production in the Heihe River Basin of China with Multi-Source and Multi-Scale Data.

    PubMed

    Cui, Tianxiang; Wang, Yujie; Sun, Rui; Qiao, Chen; Fan, Wenjie; Jiang, Guoqing; Hao, Lvyuan; Zhang, Lei

    2016-01-01

    Estimating gross primary production (GPP) and net primary production (NPP) are significant important in studying carbon cycles. Using models driven by multi-source and multi-scale data is a promising approach to estimate GPP and NPP at regional and global scales. With a focus on data that are openly accessible, this paper presents a GPP and NPP model driven by remotely sensed data and meteorological data with spatial resolutions varying from 30 m to 0.25 degree and temporal resolutions ranging from 3 hours to 1 month, by integrating remote sensing techniques and eco-physiological process theories. Our model is also designed as part of the Multi-source data Synergized Quantitative (MuSyQ) Remote Sensing Production System. In the presented MuSyQ-NPP algorithm, daily GPP for a 10-day period was calculated as a product of incident photosynthetically active radiation (PAR) and its fraction absorbed by vegetation (FPAR) using a light use efficiency (LUE) model. The autotrophic respiration (Ra) was determined using eco-physiological process theories and the daily NPP was obtained as the balance between GPP and Ra. To test its feasibility at regional scales, our model was performed in an arid and semi-arid region of Heihe River Basin, China to generate daily GPP and NPP during the growing season of 2012. The results indicated that both GPP and NPP exhibit clear spatial and temporal patterns in their distribution over Heihe River Basin during the growing season due to the temperature, water and solar influx conditions. After validated against ground-based measurements, MODIS GPP product (MOD17A2H) and results reported in recent literature, we found the MuSyQ-NPP algorithm could yield an RMSE of 2.973 gC m(-2) d(-1) and an R of 0.842 when compared with ground-based GPP while an RMSE of 8.010 gC m(-2) d(-1) and an R of 0.682 can be achieved for MODIS GPP, the estimated NPP values were also well within the range of previous literature, which proved the reliability of our

  5. Estimating Vegetation Primary Production in the Heihe River Basin of China with Multi-Source and Multi-Scale Data

    PubMed Central

    Cui, Tianxiang; Wang, Yujie; Sun, Rui; Qiao, Chen; Fan, Wenjie; Jiang, Guoqing; Hao, Lvyuan; Zhang, Lei

    2016-01-01

    Estimating gross primary production (GPP) and net primary production (NPP) are significant important in studying carbon cycles. Using models driven by multi-source and multi-scale data is a promising approach to estimate GPP and NPP at regional and global scales. With a focus on data that are openly accessible, this paper presents a GPP and NPP model driven by remotely sensed data and meteorological data with spatial resolutions varying from 30 m to 0.25 degree and temporal resolutions ranging from 3 hours to 1 month, by integrating remote sensing techniques and eco-physiological process theories. Our model is also designed as part of the Multi-source data Synergized Quantitative (MuSyQ) Remote Sensing Production System. In the presented MuSyQ-NPP algorithm, daily GPP for a 10-day period was calculated as a product of incident photosynthetically active radiation (PAR) and its fraction absorbed by vegetation (FPAR) using a light use efficiency (LUE) model. The autotrophic respiration (Ra) was determined using eco-physiological process theories and the daily NPP was obtained as the balance between GPP and Ra. To test its feasibility at regional scales, our model was performed in an arid and semi-arid region of Heihe River Basin, China to generate daily GPP and NPP during the growing season of 2012. The results indicated that both GPP and NPP exhibit clear spatial and temporal patterns in their distribution over Heihe River Basin during the growing season due to the temperature, water and solar influx conditions. After validated against ground-based measurements, MODIS GPP product (MOD17A2H) and results reported in recent literature, we found the MuSyQ-NPP algorithm could yield an RMSE of 2.973 gC m-2 d-1 and an R of 0.842 when compared with ground-based GPP while an RMSE of 8.010 gC m-2 d-1 and an R of 0.682 can be achieved for MODIS GPP, the estimated NPP values were also well within the range of previous literature, which proved the reliability of our modelling

  6. Gross primary production of a semiarid grassland is enhanced by six years of exposure to elevated atmospheric CO2, warming, and irrigation.

    NASA Astrophysics Data System (ADS)

    Ryan, E.; Ogle, K.; Peltier, D.; Williams, D. G.; Pendall, E.

    2014-12-01

    The goal of this study was to quantify interannual variation of gross primary production (GPP) and evaluate potential drivers of GPP with global change using the Prairie Heating and CO2 Enrichment (PHACE) experiment in semiarid grassland in southeastern Wyoming. PHACE consists of the treatments: control, warming only, elevated CO2 (eCO2) only, eCO2 and warming, and irrigation only. We expected that GPP would be most strongly influenced by interannual variability in precipitation under all PHACE treatments, soil water availability under eCO2, and nitrogen availability. GPP data were obtained from paired measurements of net ecosystem exchange (NEE) and ecosystem respiration (Reco; GPP = Reco - NEE) made on 2-4 week intervals over six growing seasons (2007-2012). Soil temperature (T), soil water content (SWC), vapor pressure deficit (VPD), and photosynthetically active radiation (PAR) were continuously recorded at the plot (T, SWC) and site (VPD, PAR) scales. Annual, plot-level aboveground plant nitrogen content (N) was measured during peak biomass. We fit a non-linear light-response model to the GPP data within a Bayesian framework, and modeled the maximum GPP rate (Gmax) and canopy light-use efficiency (Q) as functions of N and current and antecedent SWC, T, and VPD. The model fit the GPP data well (R2 = 0.64), and regardless of the PHACE treatment the most important drivers of GPP were N (for Gmax), VPD (Gmax and Q), antecedent T (Gmax), and antecedent VPD (Q). Model simulations predicted that annual GPP increased on average by about 16% with eCO2, 14% with warming, 12% with eCO2 and warming, and 23% with irrigation. For four of the six years, annual GPP was significantly affected by either eCO2 alone or when combined with warming. The increase in annual GPP under irrigation was similar to the increase under eCO2 during a dry year (2012), but irrigation stimulated GPP to a greater degree than eCO2 during wet years (2008, 2009). Hence, increases in GPP under eCO2

  7. Comparison of solar-induced chlorophyll fluorescence, light-use efficiency, and process-based GPP models in maize.

    PubMed

    Wagle, Pradeep; Zhang, Yongguang; Jin, Cui; Xiao, Xiangming

    2016-06-01

    Accurately quantifying cropland gross primary production (GPP) is of great importance to monitor cropland status and carbon budgets. Satellite-based light-use efficiency (LUE) models and process-based terrestrial biosphere models (TBMs) have been widely used to quantify cropland GPP at different scales in past decades. However, model estimates of GPP are still subject to large uncertainties, especially for croplands. More recently, space-borne solar-induced chlorophyll fluorescence (SIF) has shown the ability to monitor photosynthesis from space, providing new insights into actual photosynthesis monitoring. In this study, we examined the potential of SIF data to describe maize phenology and evaluated three GPP modeling approaches (space-borne SIF retrievals, a LUE-based vegetation photosynthesis model [VPM], and a process-based soil canopy observation of photochemistry and energy flux [SCOPE] model constrained by SIF) at a maize (Zea mays L.) site in Mead, Nebraska, USA. The result shows that SIF captured the seasonal variations (particularly during the early and late growing season) of tower-derived GPP (GPP_EC) much better than did satellite-based vegetation indices (enhanced vegetation index [EVI] and land surface water index [LSWI]). Consequently, SIF was strongly correlated with GPP_EC than were EVI and LSWI. Evaluation of GPP estimates against GPP_EC during the growing season demonstrated that all three modeling approaches provided reasonable estimates of maize GPP, with Pearson's correlation coefficients (r) of 0.97, 0.94, and 0.93 for the SCOPE, VPM, and SIF models, respectively. The SCOPE model provided the best simulation of maize GPP when SIF observations were incorporated through optimizing the key parameter of maximum carboxylation capacity (Vcmax). Our results illustrate the potential of SIF data to offer an additional way to investigate the seasonality of photosynthetic activity, to constrain process-based models for improving GPP estimates, and to

  8. Seasonality of primary and secondary production in an Arctic river

    NASA Astrophysics Data System (ADS)

    Kendrick, M.; Huryn, A.; Deegan, L.

    2011-12-01

    Rivers and streams that freeze solid for 8-9 months each year provide excellent examples of the extreme seasonality of arctic habitats. The communities of organisms inhabiting these rivers must complete growth and development during summer, resulting in a rapid ramp-up and down of production over the short ice-free period. The effects of recent shifts in the timing of the spring thaw and autumn freeze-up on the duration and pattern of the period of active production are poorly understood. We are currently investigating: 1) the response of the biotic community of the Kuparuk River (Arctic Alaska) to shifts in the seasonality of the ice-free period, and 2) the community response to increases in phosphorous (P) supply anticipated as the volume of the permafrost active-layer increases in response to climate warming. Here algal production supports a 2-tier web of consumers. We tracked primary and secondary production from the spring thaw through mid-August in a reference reach and one receiving low-level P fertilization. Gross primary production/community respiration (GPP/R) ratios for both reaches were increasing through mid-July, with higher GPP/R in response to the P addition. Understanding the degree of synchrony between primary and secondary production in this Arctic river system will enhance further understanding of how shifts in seasonality affect trophic dynamics.

  9. Modelling spatial and temporal dynamics of gross primary production in the Sahel from earth-observation-based photosynthetic capacity and quantum efficiency

    NASA Astrophysics Data System (ADS)

    Tagesson, Torbern; Ardö, Jonas; Cappelaere, Bernard; Kergoat, Laurent; Abdi, Abdulhakim; Horion, Stéphanie; Fensholt, Rasmus

    2017-03-01

    It has been shown that vegetation growth in semi-arid regions is important to the global terrestrial CO2 sink, which indicates the strong need for improved understanding and spatially explicit estimates of CO2 uptake (gross primary production; GPP) in semi-arid ecosystems. This study has three aims: (1) to evaluate the MOD17A2H GPP (collection 6) product against GPP based on eddy covariance (EC) for six sites across the Sahel; (2) to characterize relationships between spatial and temporal variability in EC-based photosynthetic capacity (Fopt) and quantum efficiency (α) and vegetation indices based on earth observation (EO) (normalized difference vegetation index (NDVI), renormalized difference vegetation index (RDVI), enhanced vegetation index (EVI) and shortwave infrared water stress index (SIWSI)); and (3) to study the applicability of EO upscaled Fopt and α for GPP modelling purposes. MOD17A2H GPP (collection 6) drastically underestimated GPP, most likely because maximum light use efficiency is set too low for semi-arid ecosystems in the MODIS algorithm. Intra-annual dynamics in Fopt were closely related to SIWSI being sensitive to equivalent water thickness, whereas α was closely related to RDVI being affected by chlorophyll abundance. Spatial and inter-annual dynamics in Fopt and α were closely coupled to NDVI and RDVI, respectively. Modelled GPP based on Fopt and α upscaled using EO-based indices reproduced in situ GPP well for all except a cropped site that was strongly impacted by anthropogenic land use. Upscaled GPP for the Sahel 2001-2014 was 736 ± 39 g C m-2 yr-1. This study indicates the strong applicability of EO as a tool for spatially explicit estimates of GPP, Fopt and α; incorporating EO-based Fopt and α in dynamic global vegetation models could improve estimates of vegetation production and simulations of ecosystem processes and hydro-biochemical cycles.

  10. The Potential of Carbonyl Sulfide as a Tracer for Gross Primary Productivity at Flux Tower Sites

    NASA Astrophysics Data System (ADS)

    Blonquist, J.; Montzka, S. A.; Yakir, D.; Desai, A. R.; Dragoni, D.; Griffis, T. J.; Monson, R. K.; Munger, J. W.; Scott, R. L.; Bowling, D. R.

    2010-12-01

    Regional/continental scale studies of atmospheric carbonyl sulfide (OCS) seasonal dynamics and leaf level studies of plant OCS uptake have shown a close relationship to CO2 dynamics and uptake, suggesting potential for OCS as a tracer for gross primary productivity (GPP). Canopy CO2 and OCS differences (mole fraction within canopy minus that above canopy) at a temperate deciduous forest (Harvard Forest AmeriFlux site) were analyzed relative to net ecosystem exchange (NEE) and GPP, respectively. Canopy CO2 and OCS vertical gradients (CO2 and OCS differences divided by within and above canopy measurement height differences) were used to calculate ecosystem relative uptake (ERU; relative canopy OCS gradient divided by relative canopy CO2 gradient, where relative gradients are gradients normalized by above canopy mole fractions), from which GPP was estimated using an equation that assumes OCS follows the same physical pathway as CO2 into plant leaves and where GPP / NEE was proportional to OCS gradient / CO2 gradient. Additionally, canopy CO2 differences from five other AmeriFlux sites were analyzed, and OCS differences were projected from these differences (via an assumed ERU) to further evaluate OCS as a potential GPP tracer. At Harvard Forest, canopy CO2 differences were related to NEE (y = 0.041x + 0.046, r2 = 0.14, P < 0.025) and OCS differences were related to GPP (y = 0.43x - 2.0, r2 = 0.18, P < 0.1), indicating the influence of canopy uptake on canopy differences. Relative canopy OCS and CO2 gradients were linearly correlated (slope = 4.4, intercept = -0.00028, r2 = 0.69, P < 0.025), indicating CO2 and OCS dynamics were likely controlled by similar mechanisms. Estimates of GPP derived from OCS and from temperature-based NEE partitioning showed a strong linear relationship (slope = 1.2, intercept = 3.1, r2 = 0.99, P < 0.0005), indicating the potential of OCS as a GPP tracer. As with Harvard Forest, canopy CO2 differences at the other AmeriFlux sites were related

  11. Global estimates of evapotranspiration and gross primary production based on MODIS and global meteorology data

    USGS Publications Warehouse

    Yuan, W.; Liu, S.; Yu, G.; Bonnefond, J.-M.; Chen, J.; Davis, K.; Desai, A.R.; Goldstein, Allen H.; Gianelle, D.; Rossi, F.; Suyker, A.E.; Verma, S.B.

    2010-01-01

    The simulation of gross primary production (GPP) at various spatial and temporal scales remains a major challenge for quantifying the global carbon cycle. We developed a light use efficiency model, called EC-LUE, driven by only four variables: normalized difference vegetation index (NDVI), photosynthetically active radiation (PAR), air temperature, and the Bowen ratio of sensible to latent heat flux. The EC-LUE model may have the most potential to adequately address the spatial and temporal dynamics of GPP because its parameters (i.e., the potential light use efficiency and optimal plant growth temperature) are invariant across the various land cover types. However, the application of the previous EC-LUE model was hampered by poor prediction of Bowen ratio at the large spatial scale. In this study, we substituted the Bowen ratio with the ratio of evapotranspiration (ET) to net radiation, and revised the RS-PM (Remote Sensing-Penman Monteith) model for quantifying ET. Fifty-four eddy covariance towers, including various ecosystem types, were selected to calibrate and validate the revised RS-PM and EC-LUE models. The revised RS-PM model explained 82% and 68% of the observed variations of ET for all the calibration and validation sites, respectively. Using estimated ET as input, the EC-LUE model performed well in calibration and validation sites, explaining 75% and 61% of the observed GPP variation for calibration and validation sites respectively.Global patterns of ET and GPP at a spatial resolution of 0.5° latitude by 0.6° longitude during the years 2000–2003 were determined using the global MERRA dataset (Modern Era Retrospective-Analysis for Research and Applications) and MODIS (Moderate Resolution Imaging Spectroradiometer). The global estimates of ET and GPP agreed well with the other global models from the literature, with the highest ET and GPP over tropical forests and the lowest values in dry and high latitude areas. However, comparisons with observed

  12. Terrestrial ecosystem model performance for net primary productivity and its vulnerability to climate change in permafrost regions

    NASA Astrophysics Data System (ADS)

    Xia, J.; McGuire, A. D.; Lawrence, D. M.; Burke, E.; Chen, X.; Delire, C. L.; Koven, C. D.; MacDougall, A. H.; Peng, S.; Rinke, A.; Saito, K.; Zhang, W.; Alkama, R.; Bohn, T. J.; Ciais, P.; Decharme, B.; Gouttevin, I.; Hajima, T.; Ji, D.; Krinner, G.; Lettenmaier, D. P.; Miller, P. A.; Moore, J. C.; Smith, B.; Sueyoshi, T.; Shi, Z.; Yan, L.; Liang, J.; Jiang, L.; Luo, Y.

    2014-12-01

    A more accurate prediction of future climate-carbon (C) cycle feedbacks requires better understanding and improved representation of the carbon cycle in permafrost regions within current earth system models. Here, we evaluated 10 terrestrial ecosystem models for their estimated net primary productivity (NPP) and its vulnerability to climate change in permafrost regions in the Northern Hemisphere. Those models were run retrospectively between 1960 and 2009. In comparison with MODIS satellite estimates, most models produce higher NPP (310 ± 12 g C m-2 yr-1) than MODIS (240 ± 20 g C m-2 yr-1) over the permafrost regions during 2000‒2009. The modeled NPP was then decomposed into gross primary productivity (GPP) and the NPP/GPP ratio (i.e., C use efficiency; CUE). By comparing the simulated GPP with a flux-tower-based database [Jung et al. Journal of Geophysical Research 116 (2011) G00J07] (JU11), we found although models only produce 10.6% higher mean GPP than JU11 over 1982‒2009, there was a two-fold disparity among models (397 to 830 g C m-2 yr-1). The model-to-model variation in GPP mainly resulted from the seasonal peak GPP and in low-latitudinal permafrost regions such as the Tibetan Plateau. Most models overestimate the CUE in permafrost regions in comparison to calculated CUE from the MODIS NPP and JU11 GPP products and observation-based estimates at 8 forest sites. The models vary in their sensitivities of NPP, GPP and CUE to historical changes in air temperature, atmospheric CO2 concentration and precipitation. For example, climate warming enhanced NPP in four models via increasing GPP but reduced NPP in two other models by decreasing both GPP and CUE. The results indicate that the model predictability of C cycle in permafrost regions can be improved by better representation of those processes controlling the seasonal maximum GPP and the CUE as well as their sensitivity to climate change.

  13. Improved assessment of gross and net primary productivity of Canada's landmass

    NASA Astrophysics Data System (ADS)

    Gonsamo, Alemu; Chen, Jing M.; Price, David T.; Kurz, Werner A.; Liu, Jane; Boisvenue, Céline; Hember, Robbie A.; Wu, Chaoyang; Chang, Kuo-Hsien

    2013-12-01

    assess Canada's gross primary productivity (GPP) and net primary productivity (NPP) using boreal ecosystem productivity simulator (BEPS) at 250 m spatial resolution with improved input parameter and driver fields and phenology and nutrient release parameterization schemes. BEPS is a process-based two-leaf enzyme kinetic terrestrial ecosystem model designed to simulate energy, water, and carbon (C) fluxes using spatial data sets of meteorology, remotely sensed land surface variables, soil properties, and photosynthesis and respiration rate parameters. Two improved key land surface variables, leaf area index (LAI) and land cover type, are derived at 250 m from Moderate Resolution Imaging Spectroradiometer sensor. For diagnostic error assessment, we use nine forest flux tower sites where all measured C flux, meteorology, and ancillary data sets are available. The errors due to input drivers and parameters are then independently corrected for Canada-wide GPP and NPP simulations. The optimized LAI use, for example, reduced the absolute bias in GPP from 20.7% to 1.1% for hourly BEPS simulations. Following the error diagnostics and corrections, daily GPP and NPP are simulated over Canada at 250 m spatial resolution, the highest resolution simulation yet for the country or any other comparable region. Total NPP (GPP) for Canada's land area was 1.27 (2.68) Pg C for 2008, with forests contributing 1.02 (2.2) Pg C. The annual comparisons between measured and simulated GPP show that the mean differences are not statistically significant (p > 0.05, paired t test). The main BEPS simulation error sources are from the driver fields.

  14. An algorithm of gross primary production capacity from GCOM-C1/SGLI

    NASA Astrophysics Data System (ADS)

    Muramatsu, Kanako; Soyama, Noriko; Furumi, Shinobu; Daigo, Motomasa; Mineshita, Yukiko

    An algorithm of gross primary production (GPP) capacity from GCOM-C1/SGLI is presented. GCOM-C1 satellite will be launched in 2016. The characteristics of this method corresponds to photosynthesis process, and was to use light-response curves. The photosynthesis velocity depends on it's capacity and depression because of weather conditions. The capacity part depends on one of plant physiological parameters of chlorophyll contents of a leaf. In the previous study ( J. Thanyapraneedkul et al., 2013 ), the framework of estimation method was developed how to determine the two parameters, initial slope and maximum of GPP capacity in the light saturation, of light-response curves of GPP capacity using FLUX data and satellite data. The initial slope was used as fixed values for each plant functional types. The maximum of GPP capacity at the light saturation was determined from the linear relationship between GPP capacity at 2000 (mumol/m2/s) and Chlorophyll index (CIgreen) using green band developed by Gitelson et al. (1996). The relationship determined for five plant functional types of needleleaf deciduous trees, broadleaf deciduous trees, needleleaf evergreen trees, C3 grass, and crops were determined. For applying the method, other plant functional types were needed. In this study, additional four plant functional types were studied for open shrub, closed shrub, mixed forest and tropical rain forest, and the initial slopes and the relationship between GPP capacity at 2000 (umol/m2/s) and CIgreen for each plant functional types were determined. From the results, the relationship were divided into three groups. One was grass, and open shrubs, and second one was forest types except for tropical rain forest, and third one was tropical rain forest. For each group, the slope of the relationship was almost same value, and only the intercept was different. Whether the rules were extracted for determination of the intercept was discussed and the estimation results of GPP

  15. Instantaneous-to-daily GPP upscaling schemes based on a coupled photosynthesis-stomatal conductance model: correcting the overestimation of GPP by directly using daily average meteorological inputs.

    PubMed

    Wang, Fumin; Gonsamo, Alemu; Chen, Jing M; Black, T Andrew; Zhou, Bin

    2014-11-01

    Daily canopy photosynthesis is usually temporally upscaled from instantaneous (i.e., seconds) photosynthesis rate. The nonlinear response of photosynthesis to meteorological variables makes the temporal scaling a significant challenge. In this study, two temporal upscaling schemes of daily photosynthesis, the integrated daily model (IDM) and the segmented daily model (SDM), are presented by considering the diurnal variations of meteorological variables based on a coupled photosynthesis-stomatal conductance model. The two models, as well as a simple average daily model (SADM) with daily average meteorological inputs, were validated using the tower-derived gross primary production (GPP) to assess their abilities in simulating daily photosynthesis. The results showed IDM closely followed the seasonal trend of the tower-derived GPP with an average RMSE of 1.63 g C m(-2) day(-1), and an average Nash-Sutcliffe model efficiency coefficient (E) of 0.87. SDM performed similarly to IDM in GPP simulation but decreased the computation time by >66%. SADM overestimated daily GPP by about 15% during the growing season compared to IDM. Both IDM and SDM greatly decreased the overestimation by SADM, and improved the simulation of daily GPP by reducing the RMSE by 34 and 30%, respectively. The results indicated that IDM and SDM are useful temporal upscaling approaches, and both are superior to SADM in daily GPP simulation because they take into account the diurnally varying responses of photosynthesis to meteorological variables. SDM is computationally more efficient, and therefore more suitable for long-term and large-scale GPP simulations.

  16. Estimating daytime ecosystem respiration to improve estimates of gross primary production of a temperate forest.

    PubMed

    Sun, Jinwei; Wu, Jiabing; Guan, Dexin; Yao, Fuqi; Yuan, Fenghui; Wang, Anzhi; Jin, Changjie

    2014-01-01

    Leaf respiration is an important component of carbon exchange in terrestrial ecosystems, and estimates of leaf respiration directly affect the accuracy of ecosystem carbon budgets. Leaf respiration is inhibited by light; therefore, gross primary production (GPP) will be overestimated if the reduction in leaf respiration by light is ignored. However, few studies have quantified GPP overestimation with respect to the degree of light inhibition in forest ecosystems. To determine the effect of light inhibition of leaf respiration on GPP estimation, we assessed the variation in leaf respiration of seedlings of the dominant tree species in an old mixed temperate forest with different photosynthetically active radiation levels using the Laisk method. Canopy respiration was estimated by combining the effect of light inhibition on leaf respiration of these species with within-canopy radiation. Leaf respiration decreased exponentially with an increase in light intensity. Canopy respiration and GPP were overestimated by approximately 20.4% and 4.6%, respectively, when leaf respiration reduction in light was ignored compared with the values obtained when light inhibition of leaf respiration was considered. This study indicates that accurate estimates of daytime ecosystem respiration are needed for the accurate evaluation of carbon budgets in temperate forests. In addition, this study provides a valuable approach to accurately estimate GPP by considering leaf respiration reduction in light in other ecosystems.

  17. Improving the estimation of terrestrial gross primary productivity by downscaling global sun-induced chlorophyll fluorescence

    NASA Astrophysics Data System (ADS)

    Cescatti, A.; Duveiller, G.

    2015-12-01

    The synoptic nature of satellite remote sensing makes this technique a key tool to contribute to estimating the amount of Carbon fixed by vegetation at global scale. From the various types of information that can be derived from space, the recent capacity to create global datasets of sun-induced chlorophyll fluorescence (SIF) may prove to be a game-changer. SIF is a signal emitted by the photosynthetic machinery itself that, under the illumination conditions in which it can be estimated by satellite, has been shown to be proportional to gross primary productivity (GPP). However, this relationship is dependent on vegetation types that are typically spatially mixed at the coarse spatial resolution of SIF datasets (at best 0.5°), which in turn is a consequence of the complexity of the SIF retrieval itself. This study demonstrates how 0.5° SIF derived from GOME-2 data can be downscaled to a more adequate spatial resolution of 0.05° by combining 3 explanatory biophysical variables derived from the MODIS sensor (NDVI, land surface temperature and evapotranspiration) under a semi-empirical light-use efficiency framework. The finer spatial resolution results in a cleaner signal when aggregating it per land cover type. The signal is also better correlated in time with GPP estimated from flux towers, reaching the same level of performance than global GPP products calibrated on such flux towers and driven by meteorological and remote sensing variables (other than SIF). Establishing linear relationships between SIF and flux-tower GPP at vegetation type level allows to estimate values of global terrestrial vegetation gross productivity that have different magnitude but similar temporal patterns as other GPP products. Based on downscaled SIF, the mean global GPP values over the period 2007 to 2013 are (for deciduous broadleaf and mixed forests) 13.7, (for evergreen needleleaf forests) 2.5, (for grasslands) 12.5 and (savannahs and woody savannas) 36.8 Pg of Carbon per year.

  18. Modeling the Impacts of Long-Term Warming Trends on Gross Primary Productivity Across North America

    NASA Astrophysics Data System (ADS)

    Mekonnen, Z. A.; Grant, R. F.

    2014-12-01

    There is evidence of warming over recent decades in most regions of North America (NA) that affects ecosystem productivity and the past decade has been the warmest since instrumental records of global surface temperatures began. In this study, we examined the spatial and temporal variability and trends of warming across NA using climate data from the North America Regional Reanalysis (NARR) from 1979 to 2010 with a 3-hourly time-step and 0.250 x 0.250 spatial resolution as part of the Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP). A comprehensive mathematical process model, ecosys was used to simulate impacts of this variability in warming on gross primary productivity (GPP). In a test of model results, annual GPP modeled for pixels which corresponded to the locations of 25 eddy covariance towers correlated well (R2=0.76) with annual GPP derived from the flux towers in 2005. At the continental scale long-term (2000 - 2010) annual average modeled GPP for NA correlated well (geographically weighed regression R2 = 0.8) with MODIS GPP, demonstrating close similarities in spatial patterns. Results from the NARR indicated that most areas of NA, particularly high latitude regions, have experienced warming but changes in precipitation vary spatially over the last three decades. GPP modeled in most areas with lower mean annual air temperature (Ta), such as those in boreal climate zones, increased due to early spring and late autumn warming observed in NARR. However modeled GPP declined in most southwestern regions of NA, due to water stress from rising Ta and declining precipitation. Overall, GPP modeled across NA had a positive trend of +0.025 P g C yr-1 with a range of -1.16 to 0.87 P g C yr-1 from the long-term mean. Interannual variability of GPP was the greatest in southwest of US and part of the Great Plains, which could be as a result of frequent El Niño-Southern Oscillation' (ENSO) events that led to major droughts.

  19. A Continuous Measure of Gross Primary Production for the Conterminous U.S. Derived from MODIS and AmeriFlux Data

    SciTech Connect

    Xia, Jingfeng; Zhuang, Qianlai; Law, Beverly E.; Chen, Jiquan; Baldocchi, Dennis D.; Cook, David R.; Oren, Ram; Richardson, Andrew D.; Wharton, Sonia; Ma, Siyan; Martin, Timothy A.; Verma, Shashi B.; Suyker, Andrew E.; Scott, Russell L.; Monson, Russell K.; Litvak, Marcy; Hollinger, David Y.; Sun, Ge; Davis, Kenneth J.; Bolstad, Paul V.; Burns, Sean P.; Curtis, Peter S.; Drake, Bert G.; Falk, Matthias; Fischer, Marc L.; Foster, David R.; Gu, Lianhong; Hadley, Julian L.; Katul, Gabriel G.; Matamala, Roser; McNulty, Steve; Meyers, Tilden P.; Munger, J. William; Noormets, Asko; Oechel, Walter C.; U, Kyaw Tha Paw; Schmid, Hans Peter; Starr, Gregory; Torn, Margaret S.; Wofsy, Steven C.

    2009-01-28

    The quantification of carbon fluxes between the terrestrial biosphere and the atmosphere is of scientific importance and also relevant to climate-policy making. Eddy covariance flux towers provide continuous measurements of ecosystem-level exchange of carbon dioxide spanning diurnal, synoptic, seasonal, and interannual time scales. However, these measurements only represent the fluxes at the scale of the tower footprint. Here we used remotely-sensed data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to upscale gross primary productivity (GPP) data from eddy covariance flux towers to the continental scale. We first combined GPP and MODIS data for 42 AmeriFlux towers encompassing a wide range of ecosystem and climate types to develop a predictive GPP model using a regression tree approach. The predictive model was trained using observed GPP over the period 2000-2004, and was validated using observed GPP over the period 2005-2006 and leave-one-out cross-validation. Our model predicted GPP fairly well at the site level. We then used the model to estimate GPP for each 1 km x 1 km cell across the U.S. for each 8-day interval over the period from February 2000 to December 2006 using MODIS data. Our GPP estimates provide a spatially and temporally continuous measure of gross primary production for the U.S. that is a highly constrained by eddy covariance flux data. Our study demonstrated that our empirical approach is effective for upscaling eddy flux GPP data to the continental scale and producing continuous GPP estimates across multiple biomes. With these estimates, we then examined the patterns, magnitude, and interannual variability of GPP. We estimated a gross carbon uptake between 6.91 and 7.33 Pg C yr{sup -1} for the conterminous U.S. Drought, fires, and hurricanes reduced annual GPP at regional scales and could have a significant impact on the U.S. net ecosystem carbon exchange. The sources of the interannual variability of U.S. GPP were dominated

  20. Fruit development, not GPP, drives seasonal variation in NPP in a tropical palm plantation.

    PubMed

    Navarro, M N V; Jourdan, C; Sileye, T; Braconnier, S; Mialet-Serra, I; Saint-Andre, L; Dauzat, J; Nouvellon, Y; Epron, D; Bonnefond, J M; Berbigier, P; Rouziere, A; Bouillet, J P; Roupsard, O

    2008-11-01

    We monitored seasonal variations in net primary production (NPP), estimated by allometric equations from organ dimensions, gross primary production (GPP), estimated by the eddy covariance method, autotrophic respiration (R(a)), estimated by a model, and fruit production in a coconut (Cocos nucifera L.) plantation located in the sub-tropical South Pacific archipelago of Vanuatu. Net primary production of the vegetative compartments of the trees accumulated steadily throughout the year. Fruits accounted for 46% of tree NPP and showed large seasonal variations. On an annual basis, the sum of estimated NPP (16.1 Mg C ha(-1) year(-1)) and R(a) (24.0 Mg C ha(-1) year(-1)) for the ecosystem (coconut trees and herbaceous understory) closely matched GPP (39.0 Mg C ha(-1) year(-1)), suggesting adequate cross-validation of annual C budget methods. However, seasonal variations in NPP + R(a) were smaller than the seasonal variations in GPP, and maximum tree NPP occurred 6 months after the midsummer peak in GPP and solar radiation. We propose that this discrepancy reflects seasonal variation in the allocation of dry mass to carbon reserves and new plant tissue, thus affecting the allometric relationships used for estimating NPP.

  1. (Uncertain) Carbonyl Sulfide Plant Fluxes Spatially Constrain (Even More Uncertain) CO2 GPP

    NASA Astrophysics Data System (ADS)

    Hilton, T. W.; Whelan, M.; Kulkarni, S.; Zumkehr, A. L.; Berry, J. A.; Campbell, J. E.

    2015-12-01

    With predictions of future terrestrial carbon dioxide (CO2)gross primary productivity (GPP) remaining stubbornly uncertain,ecosystem carbonyl sulfide (COS) fluxes provide an independent source ofinformation that may be able to reduce that uncertainty. Several openquestions must be addressed before COS may be applied widely as a GPPtracer. Here we employ an atmospheric chemistry and transport model(STEM) and airborne atmospheric COS concentration observations todemonstrate that COS plant uptake spatially constrains CO2 GPP even whenaccounting for soil COS flux uncertainty and COS leaf-scale relativeuptake variability and uncertainty.

  2. Vegetation canopy and physiological control of GPP decline during drought and heat wave

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Xiao, X.; Zhou, S.; McCarthy, H. R.; Ciais, P.; Luo, Y.

    2015-12-01

    Different vegetation indices derived from satellites were often used as a proxy of vegetation activity to monitor and evaluate the impacts of drought and heat wave on ecosystem carbon fluxes (gross primary production, respiration) through the production efficiency models (PEMs). However, photosynthesis is also regulated by a series of physiological processes which cannot be directly observed through satellites. In this study, we analyzed the response of drought and heat wave induced GPP and climate anomaly from 15 Euroflux sites and the corresponding vegetation indices from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. Correlation analysis suggests that the vegetation indices are more responsive to GPP variation in grasslands and open shrublands, but less responsive in forest ecosystems. Physiology control can be up to 20% of the total GPP during the drought period without changing the canopy structure. At temporal scale for each site, VPD and vegetation indices can be used to track the GPP for forest and non-forest, respectively. However, different stand characteristics should be taken into consideration for forest ecosystems. Based on the above findings, a conceptual model is built to illuminate the physiological and canopy control on the GPP during the drought period. Improvement for future PEMs should incorporate better indicators to deal with drought conditions for different ecosystems.

  3. Sea Surface Temperature Influence on Terrestrial Gross Primary Production along the Southern California Current.

    PubMed

    Reimer, Janet J; Vargas, Rodrigo; Rivas, David; Gaxiola-Castro, Gilberto; Hernandez-Ayon, J Martin; Lara-Lara, Ruben

    2015-01-01

    Some land and ocean processes are related through connections (and synoptic-scale teleconnections) to the atmosphere. Synoptic-scale atmospheric (El Niño/Southern Oscillation [ENSO], Pacific Decadal Oscillation [PDO], and North Atlantic Oscillation [NAO]) decadal cycles are known to influence the global terrestrial carbon cycle. Potentially, smaller scale land-ocean connections influenced by coastal upwelling (changes in sea surface temperature) may be important for local-to-regional water-limited ecosystems where plants may benefit from air moisture transported from the ocean to terrestrial ecosystems. Here we use satellite-derived observations to test potential connections between changes in sea surface temperature (SST) in regions with strong coastal upwelling and terrestrial gross primary production (GPP) across the Baja California Peninsula. This region is characterized by an arid/semiarid climate along the southern California Current. We found that SST was correlated with the fraction of photosynthetic active radiation (fPAR; as a proxy for GPP) with lags ranging from 0 to 5 months. In contrast ENSO was not as strongly related with fPAR as SST in these coastal ecosystems. Our results show the importance of local-scale changes in SST during upwelling events, to explain the variability in GPP in coastal, water-limited ecosystems. The response of GPP to SST was spatially-dependent: colder SST in the northern areas increased GPP (likely by influencing fog formation), while warmer SST at the southern areas was associated to higher GPP (as SST is in phase with precipitation patterns). Interannual trends in fPAR are also spatially variable along the Baja California Peninsula with increasing secular trends in subtropical regions, decreasing trends in the most arid region, and no trend in the semi-arid regions. These findings suggest that studies and ecosystem process based models should consider the lateral influence of local-scale ocean processes that could

  4. Sea Surface Temperature Influence on Terrestrial Gross Primary Production along the Southern California Current

    PubMed Central

    Reimer, Janet J.; Vargas, Rodrigo; Rivas, David; Gaxiola-Castro, Gilberto; Hernandez-Ayon, J. Martin; Lara-Lara, Ruben

    2015-01-01

    Some land and ocean processes are related through connections (and synoptic-scale teleconnections) to the atmosphere. Synoptic-scale atmospheric (El Niño/Southern Oscillation [ENSO], Pacific Decadal Oscillation [PDO], and North Atlantic Oscillation [NAO]) decadal cycles are known to influence the global terrestrial carbon cycle. Potentially, smaller scale land-ocean connections influenced by coastal upwelling (changes in sea surface temperature) may be important for local-to-regional water-limited ecosystems where plants may benefit from air moisture transported from the ocean to terrestrial ecosystems. Here we use satellite-derived observations to test potential connections between changes in sea surface temperature (SST) in regions with strong coastal upwelling and terrestrial gross primary production (GPP) across the Baja California Peninsula. This region is characterized by an arid/semiarid climate along the southern California Current. We found that SST was correlated with the fraction of photosynthetic active radiation (fPAR; as a proxy for GPP) with lags ranging from 0 to 5 months. In contrast ENSO was not as strongly related with fPAR as SST in these coastal ecosystems. Our results show the importance of local-scale changes in SST during upwelling events, to explain the variability in GPP in coastal, water-limited ecosystems. The response of GPP to SST was spatially-dependent: colder SST in the northern areas increased GPP (likely by influencing fog formation), while warmer SST at the southern areas was associated to higher GPP (as SST is in phase with precipitation patterns). Interannual trends in fPAR are also spatially variable along the Baja California Peninsula with increasing secular trends in subtropical regions, decreasing trends in the most arid region, and no trend in the semi-arid regions. These findings suggest that studies and ecosystem process based models should consider the lateral influence of local-scale ocean processes that could

  5. Application of MODIS GPP to Forecast Risk of Hantavirus Pulmonary Syndrome Based on Fluctuations in Reservoir Population Density

    NASA Astrophysics Data System (ADS)

    Loehman, R.; Heinsch, F. A.; Mills, J. N.; Wagoner, K.; Running, S.

    2003-12-01

    Recent predictive models for hantavirus pulmonary syndrome (HPS) have used remotely sensed spectral reflectance data to characterize risk areas with limited success. We present an alternative method using gross primary production (GPP) from the MODIS sensor to estimate the effects of biomass accumulation on population density of Peromyscus maniculatus (deer mouse), the principal reservoir species for Sin Nombre virus (SNV). The majority of diagnosed HPS cases in North America are attributed to SNV, which is transmitted to humans through inhalation of excretions and secretions from infected rodents. A logistic model framework is used to evaluate MODIS GPP, temperature, and precipitation as predictors of P. maniculatus density at established trapping sites across the western United States. Rodent populations are estimated using monthly minimum number alive (MNA) data for 2000 through 2002. Both local meteorological data from nearby weather stations and 1.25 degree x 1 degree gridded data from the NASA DAO were used in the regression model to determine the spatial sensitivity of the response. MODIS eight-day GPP data (1-km resolution) were acquired and binned to monthly average and monthly sum GPP for 3km x 3km grids surrounding each rodent trapping site. The use of MODIS GPP to forecast HPS risk may result in a marked improvement over past reflectance-based risk area characterizations. The MODIS GPP product provides a vegetation dynamics estimate that is unique to disease models, and targets the fundamental ecological processes responsible for increased rodent density and amplified disease risk.

  6. Gross primary production variability associated with meteorology, physiology, leaf area, and water supply in contrasting woodland and grassland semiarid riparian ecosystems

    NASA Astrophysics Data System (ADS)

    Jenerette, G. D.; Scott, R. L.; Barron-Gafford, G. A.; Huxman, T. E.

    2009-12-01

    Understanding ecosystem-atmosphere carbon exchanges in dryland environments has been more challenging than in mesic environments, likely due to more pronounced nonlinear responses of ecosystem processes to environmental variation. To better understand diurnal to interannual variation in gross primary productivity (GPP) variability, we coupled continuous eddy-covariance derived whole ecosystem gas exchange measurements with an ecophysiologic model based on fundamental principles of diffusion, mass balance, reaction kinetics, and biochemical regulation of photosynthesis. We evaluated the coupled data-model system to describe and understand the dynamics of 3 years of growing season GPP from a riparian grassland and woodland in southern Arizona. The data-model fusion procedure skillfully reproduced the majority of daily variation GPP throughout three growing seasons. While meteorology was similar between sites, the woodland site had consistently higher GPP rates and lower variability at daily and interannual timescales relative to the grassland site. We examined the causes of this variation using a new state factor model analysis that partitioned GPP variation into four factors: meteorology, physiology, leaf area, and water supply. The largest proportion of GPP variation was associated with physiological differences. The woodland showed a greater sensitivity than the grassland to water supply, while the grassland showed a greater sensitivity to leaf area. These differences are consistent with hypotheses of woody species using resistance mechanisms, stomatal regulation, and grassland species using resilience mechanisms, leaf area regulation, in avoiding water stress and have implications for future GPP sensitivity to climate variability following wood-grass transitions.

  7. Gross primary production responses to warming, elevated CO 2 , and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland

    SciTech Connect

    Ryan, Edmund M.; Ogle, Kiona; Peltier, Drew; Walker, Anthony P.; de Kauwe, Martin G.; Medlyn, Belinda E.; Williams, David G.; Parton, William; Asao, Shinichi; Guenet, Bertrand; Harper, Anna B.; Lu, Xingjie; Luus, Kristina A.; Zaehle, Sönke; Shu, Shijie; Werner, Christian; Xia, Jianyang; Pendall, Elise

    2016-12-19

    Determining whether the terrestrial biosphere will be a source or sink of carbon (C) under a future climate of elevated CO2 (eCO2) and warming requires accurate quantification of gross primary production (GPP), the largest flux of C in the global C cycle. We evaluated six years (2007-2012) of flux-derived GPP data from the Prairie Heating and CO2 Enrichment (PHACE) experiment, situated in a mixed prairie grassland in Wyoming (USA). The GPP data were fitted to a mixed effects model that extended a light response model to include the effects of environmental (soil water content, vegetation greenness, nitrogen) and meteorological data (air temperature, vapor pressure deficit, photosynthetically active radiation) at current and past times. The stimulation of the cumulative six-year GPP by warming (20%, P=0.06) and eCO2 (19%, P=0.14) were primarily driven by enhanced C uptake during spring (96%, P=0.003) and fall (115%, P=0.001), respectively. These enhancements were consistent across each year, suggesting mechanisms for extending the growing season. Vapor pressure deficit from 1-3 days prior was the most significant predictor of temporalvariability in GPP and for explaining treatment differences in GPP, suggesting that atmospheric drought plays an important role for predicting GPP now and under future climate conditions.

  8. Gross primary production responses to warming, elevated CO 2 , and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland

    DOE PAGES

    Ryan, Edmund M.; Ogle, Kiona; Peltier, Drew; ...

    2016-12-19

    Determining whether the terrestrial biosphere will be a source or sink of carbon (C) under a future climate of elevated CO2 (eCO2) and warming requires accurate quantification of gross primary production (GPP), the largest flux of C in the global C cycle. We evaluated six years (2007-2012) of flux-derived GPP data from the Prairie Heating and CO2 Enrichment (PHACE) experiment, situated in a mixed prairie grassland in Wyoming (USA). The GPP data were fitted to a mixed effects model that extended a light response model to include the effects of environmental (soil water content, vegetation greenness, nitrogen) and meteorological datamore » (air temperature, vapor pressure deficit, photosynthetically active radiation) at current and past times. The stimulation of the cumulative six-year GPP by warming (20%, P=0.06) and eCO2 (19%, P=0.14) were primarily driven by enhanced C uptake during spring (96%, P=0.003) and fall (115%, P=0.001), respectively. These enhancements were consistent across each year, suggesting mechanisms for extending the growing season. Vapor pressure deficit from 1-3 days prior was the most significant predictor of temporalvariability in GPP and for explaining treatment differences in GPP, suggesting that atmospheric drought plays an important role for predicting GPP now and under future climate conditions.« less

  9. Parameterizing ecosystem light use efficiency and water use efficiency to estimate maize gross primary production and evapotranspiration using MODIS EVI

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quantifying global carbon and water balances requires accurate estimation of gross primary production (GPP) and evapotranspiration (ET), respectively, across space and time. Models that are based on the theory of light use efficiency (LUE) and water use efficiency (WUE) have emerged as efficient met...

  10. Integrating solar induced flourescence and the photochemical reflectance index for estimating gross primary production in a cornfield

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The utilization of remotely sensed observations for light use efficiency (LUE) and tower-based gross primary production (GPP) estimates was studied in a USDA cornfield. Nadir hyperspectral reflectance measurements were acquired at canopy level during a collaborative field campaign conducted in four ...

  11. Global gross primary productivity and water use efficiency changes under drought stress

    NASA Astrophysics Data System (ADS)

    Yu, Zhen; Wang, Jingxin; Liu, Shirong; Rentch, James S.; Sun, Pengsen; Lu, Chaoqun

    2017-01-01

    Drought can affect the structure, composition and function of terrestrial ecosystems, yet drought impacts and post-drought recovery potentials of different land cover types have not been extensively studied at a global scale. We evaluated drought impacts on gross primary productivity (GPP), evapotranspiration (ET), and water use efficiency (WUE) of different global terrestrial ecosystems, as well as the drought-resilience of each ecosystem type during the period of 2000 to 2011. Using GPP as biome vitality indicator against drought stress, we developed a model to examine ecosystem resilience represented by the length of recovery days (LRD). LRD presented an evident gradient of high (>60 days) in mid-latitude region and low (<60 days) in low (tropical area) and high (boreal area) latitude regions. As average GPP increased, the LRD showed a significantly decreasing trend, indicating readiness to recover after drought, across various land cover types (R 2 = 0.68, p < 0.0001). Moreover, zonal analysis revealed that the most dramatic reduction of the drought-induced GPP was found in the mid-latitude region of the Northern Hemisphere (48% reduction), followed by the low-latitude region of the Southern Hemisphere (13% reduction). In contrast, a slightly enhanced GPP (10%) was evident in the tropical region under drought impact. Additionally, the highest drought-induced reduction of ET was found in the Mediterranean area, followed by Africa. Water use efficiency, however, showed a pattern of decreasing in the Northern Hemisphere and increasing in the Southern Hemisphere. Drought induced reductions of WUE ranged from 0.96% to 27.67% in most of the land cover types, while the increases of WUE found in Evergreen Broadleaf Forest and savanna were about 7.09% and 9.88%, respectively. These increases of GPP and WUE detected during drought periods could either be due to water-stress induced responses or data uncertainties, which require further investigation.

  12. Estimation of gross primary production over burned black spruce forests in interior Alaska using MODIS data

    NASA Astrophysics Data System (ADS)

    Otsuki, M.; Iwata, H.; Harazono, Y.; Iwata, T.

    2012-12-01

    Black spruce forests, which are distributed widely in Alaska and Canada, have been reported to be sinks of carbon dioxide (CO2) under the current climate. However, an increasing trend of wildfire occurrence, and its magnitude, in interior Alaska, may alter the future CO2 budget in regional scale. The goal of this study is to estimate the gross primary production (GPP) in burned area using the light-use efficiency model with MODerate resolution Imaging Spectroradiometer (MODIS) data. Accuracy of GPP estimation was improved by explicitly treating burned area with a new parameterization of light-use efficiency and fraction of absorbed photosynthetically active radiation (FPAR). To parameterize the model, we started a CO2flux observation at a burned black spruce site (65°07N, 147°26W) in interior Alaska in 2008. At this site, a severe wildfire occurred in late June 2004, and almost all vegetation were burned. The vegetation is recovering and saplings of deciduous tree are currently starting to dominate. In order to parameterize the light-use efficiency for burned area, we observed absorption of photosynthetically active radiation (PAR) along with the CO2flux. The obtained maximum light-use efficiency gradually increased over 2009-2011 with the vegetation recovery. In calculating spatial distribution of GPP with satellite data, we estimated PAR distribution using a model developed by Nishida (2006, SOLA). FPAR and the maximum light-use efficiency were estimated from the relationships with satellite NDVI data. A comparison with GPP calculated using MOD15, total GPP can be over estimated by 7% if the burned areas are not considered. This overestimation will lead to a significant error in regional GPP estimation in severe fire years.

  13. Improvement of satellite-based gross primary production through incorporation of high resolution input data over east asia

    NASA Astrophysics Data System (ADS)

    Park, Haemi; Im, Jungho; Kim, Miae

    2016-04-01

    Photosynthesis of plants is the main mechanism of carbon absorption from the atmosphere into the terrestrial ecosystem and it contributes to remove greenhouse gases such as carbon dioxide. Annually, 120 Gt of C is supposed to be assimilated through photosynthetic activity of plants as the gross primary production (GPP) over global land area. In terms of climate change, GPP modelling is essential to understand carbon cycle and the balance of carbon budget over various ecosystems. One of the GPP modelling approaches uses light use efficiency that each vegetation type has a specific efficiency for consuming solar radiation related with temperature and humidity. Satellite data can be used to measure various meteorological and biophysical factors over vast areas, which can be used to quantify GPP. NASA Earth Observing System (EOS) program provides Moderate Resolution Imaging Spectroradiometer (MODIS)-derived global GPP product, namely MOD17A2H, on a daily basis. However, significant underestimation of MOD17A2H has been reported in Eastern Asia due to its dense forest distribution and humid condition during monsoon rainy season in summer. The objective of this study was to improve underestimation of MODIS GPP (MOD17A2H) by incorporating meteorological data-temperature, relative humidity, and solar radiation-of higher spatial resolution than data used in MOD17A2H. Landsat-based land cover maps of finer resolution observation and monitoring - global land cover (FROM-GLC) at 30m resolution were used for selection of light use efficiency (LUE). GPP (eq1. GPP = APAR×LUE) is computed by multiplication of APAR (IPAR×fPAR) and LUE (ɛ= ɛmax×T(°C)scalar×VPD(Pa)scalar, where, T is temperature, VPD is vapour pressure deficit) in this study. Meteorological data of Japanese 55-year Reanalysis (JRA-55, 0.56° grid, 3hr) were used for calculation of GPP in East Asia, including Eastern part of China, Korean peninsula, and Japan. Results were validated using flux tower-observed GPP

  14. Effects of the partitioning of diffuse and direct solar radiation on satellite-based modeling of crop gross primary production

    NASA Astrophysics Data System (ADS)

    Xin, Qinchuan; Gong, Peng; Suyker, Andrew E.; Si, Yali

    2016-08-01

    Modeling crop gross primary production (GPP) is critical to understanding the carbon dynamics of agro-ecosystems. Satellite-based studies have widely used production efficiency models (PEM) to estimate cropland GPP, wherein light use efficiency (LUE) is a key model parameter. One factor that has not been well considered in many PEMs is that canopy LUE could vary with illumination conditions. This study investigates how the partitioning of diffuse and direct solar radiation influences cropland GPP using both flux tower and satellite data. The field-measured hourly LUE under cloudy conditions was 1.50 and 1.70 times higher than that under near clear-sky conditions for irrigated corn and soybean, respectively. We applied a two-leaf model to simulate the canopy radiative transfer process, where modeled photosynthetically active radiation (PAR) absorbed by canopy agreed with tower measurements (R2 = 0.959 and 0.914 for corn and soybean, respectively). Derived canopy LUE became similar after accounting for the impact of light saturation on leaf photosynthetic capacity under varied illumination conditions. The impacts of solar radiation partitioning on satellite-based modeling of crop GPP was examined using vegetation indices (VI) derived from MODIS data. Consistent with the field modeling results, the relationship between daily GPP and PAR × VI under varied illumination conditions showed different patterns in terms of regression slope and intercept. We proposed a function to correct the influences of direct and diffuse radiation partitioning and the explained variance of flux tower GPP increased in all experiments. Our results suggest that the non-linear response of leaf photosynthesis to light absorption contributes to higher canopy LUE on cloudy days than on clear days. We conclude that accounting for the impacts of solar radiation partitioning is necessary for modeling crop GPP on a daily or shorter basis.

  15. Estimating the Capacity of Gross Primary Production from Global Observation Satellite

    NASA Astrophysics Data System (ADS)

    Muramatsu, Kanako; Soyama, Noriko; Thanyaparaneedkul, Juthasinee; Furumi, Shinobu; Daigo, Motomasa

    2012-07-01

    Estimation of Gross Primary Production with high accuracy is important for understanding the carbon cycle. For estimating gross primary production, photosynthesis process was considers into two parts. One is the capacity and another is the reduction which is influenced by environmental conditions such as weather conditions of vapor pressure difference and soil moisture. The capacity estimation part is reported in this conference. For a leaf, it is well known photosynthesis capacity is mainly depend on amount of chlorophyll and enzyme. Chlorophyll contents reflect the color of a leaf. Since we focus on the chlorophyll contents for estimating the capacity of the gross primary production. It was reported by J. Thanyapraneedkul (2012) that vegetation index of the ratio of green band and near infrared was linear relationship with chlorophyll contents of a leaf, and was a linear relationship with the maximum photosynthesis at light saturation of light response curve with less stress conditions using flux data. The index is suitable for global observing satellite, because the spectral bands are available. Using the index and empirical relationship developed by J. Thanyapraneedkul, the light response curve with less stress can be estimated from the vegetation index. In this study, firstly, the global distribution of the index was studied. The regions of high index value in winter time were correspond to tropical rainforest. Next, the capacity of gross primary production was estimated using the light response curve using the index. The GPP capacity of the almost all regions was higher than MODIS GPP. For the tropical rain forest regions, the GPP capacity value was similar with MODIS GPP product.

  16. Sensitivity of Crop Gross Primary Production Simulations to In-situ and Reanalysis Meteorological Data

    NASA Astrophysics Data System (ADS)

    Jin, C.; Xiao, X.; Wagle, P.

    2014-12-01

    Accurate estimation of crop Gross Primary Production (GPP) is important for food securityand terrestrial carbon cycle. Numerous publications have reported the potential of the satellite-based Production Efficiency Models (PEMs) to estimate GPP driven by in-situ climate data. Simulations of the PEMs often require surface reanalysis climate data as inputs, for example, the North America Regional Reanalysis datasets (NARR). These reanalysis datasets showed certain biases from the in-situ climate datasets. Thus, sensitivity analysis of the PEMs to the climate inputs is needed before their application at the regional scale. This study used the satellite-based Vegetation Photosynthesis Model (VPM), which is driven by solar radiation (R), air temperature (T), and the satellite-based vegetation indices, to quantify the causes and degree of uncertainties in crop GPP estimates due to different meteorological inputs at the 8-day interval (in-situ AmeriFlux data and NARR surface reanalysis data). The NARR radiation (RNARR) explained over 95% of the variability in in-situ RAF and TAF measured from AmeriFlux. The bais of TNARR was relatively small. However, RNARR had a systematical positive bias of ~3.5 MJ m-2day-1 from RAF. A simple adjustment based on the spatial statistic between RNARR and RAF produced relatively accurate radiation data for all crop site-years by reducing RMSE from 4 to 1.7 MJ m-2day-1. The VPM-based GPP estimates with three climate datasets (i.e., in-situ, and NARR before and after adjustment, GPPVPM,AF, GPPVPM,NARR, and GPPVPM,adjNARR) showed good agreements with the seasonal dynamics of crop GPP derived from the flux towers (GPPAF). The GPPVPM,AF differed from GPPAF by 2% for maize, and -8% to -12% for soybean on the 8-day interval. The positive bias of RNARR resulted in an overestimation of GPPVPM,NARR at both maize and soybean systems. However, GPPVPM,adjNARR significantly reduced the uncertainties of the maize GPP from 25% to 2%. The results from this

  17. Effects of seasonal and interannual variations in leaf photosynthesis and canopy leaf area index on gross primary production of a cool-temperate deciduous broadleaf forest in Takayama, Japan.

    PubMed

    Muraoka, Hiroyuki; Saigusa, Nobuko; Nasahara, Kenlo N; Noda, Hibiki; Yoshino, Jun; Saitoh, Taku M; Nagai, Shin; Murayama, Shohei; Koizumi, Hiroshi

    2010-07-01

    Revealing the seasonal and interannual variations in forest canopy photosynthesis is a critical issue in understanding the ecological mechanisms underlying the dynamics of carbon dioxide exchange between the atmosphere and deciduous forests. This study examined the effects of temporal variations of canopy leaf area index (LAI) and leaf photosynthetic capacity [the maximum velocity of carboxylation (V (cmax))] on gross primary production (GPP) of a cool-temperate deciduous broadleaf forest for 5 years in Takayama AsiaFlux site, central Japan. We made two estimations to examine the effects of canopy properties on GPP; one is to incorporate the in situ observation of V (cmax) and LAI throughout the growing season, and another considers seasonality of LAI but constantly high V (cmax). The simulations indicated that variation in V (cmax) and LAI, especially in the leaf expansion period, had remarkable effects on GPP, and if V (cmax) was assumed constant GPP will be overestimated by 15%. Monthly examination of air temperature, radiation, LAI and GPP suggested that spring temperature could affect canopy phenology, and also that GPP in summer was determined mainly by incoming radiation. However, the consequences among these factors responsible for interannual changes of GPP are not straightforward since leaf expansion and senescence patterns and summer meteorological conditions influence GPP independently. This simulation based on in situ ecophysiological research suggests the importance of intensive consideration and understanding of the phenology of leaf photosynthetic capacity and LAI to analyze and predict carbon fixation in forest ecosystems.

  18. Mapping cropland GPP in the north temperate region with space measurements of chlorophyll fluorescence

    NASA Astrophysics Data System (ADS)

    Guanter, L.; Zhang, Y.; Jung, M.; Joiner, J.; Voigt, M.; Huete, A. R.; Zarco-Tejada, P.; Frankenberg, C.; Lee, J.; Berry, J. A.; Moran, S. M.; Ponce-Campos, G.; Beer, C.; Camps-Valls, G.; Buchmann, N. C.; Gianelle, D.; Klumpp, K.; Cescatti, A.; Baker, J. M.; Griffis, T.

    2013-12-01

    Monitoring agricultural productivity is important for optimizing management practices in a world under a continuous increase of food and biofuel demand. We used new space measurements of sun-induced chlorophyll fluorescence (SIF), a vegetation parameter intrinsically linked to photosynthesis, to capture photosynthetic uptake of the crop belts in the north temperate region. The following data streams and procedures have been used in this analysis: (1) SIF retrievals have been derived from measurements of the MetOp-A / GOME-2 instrument in the 2007-2011 time period; (2) ensembles of process-based and data-driven biogeochemistry models have been analyzed in order to assess the capability of global models to represent crop gross primary production (GPP); (3) flux tower-based GPP estimates covering the 2007-2011 time period have been extracted over 18 cropland and grassland sites in the Midwest US and Western Europe from the Ameriflux and the European Fluxes Database networks; (4) large-scale NPP estimates have been derived by the agricultural inventory data sets developed by USDA-NASS and Monfreda et al. The strong linear correlation between the SIF space retrievals and the flux tower-based GPP, found to be significantly higher than that between reflectance-based vegetation indices (EVI, NDVI and MTCI) and GPP, has enabled the direct upscaling of SIF to cropland GPP maps at the synoptic scale. The new crop GPP estimates we derive from the scaling of SIF space retrievals are consistent with both flux tower GPP estimates and agricultural inventory data. These new GPP estimates show that crop productivity in the US Western Corn Belt, and most likely also in the rice production areas in the Indo-Gangetic plain and China, is up to 50-75% higher than estimates by state-of-the-art data-driven and process-oriented biogeochemistry models. From our analysis we conclude that current carbon models have difficulties in reproducing the special conditions of those highly productive

  19. Deriving a light use efficiency model from eddy covariance flux data for predicting daily gross primary production across biomes

    USGS Publications Warehouse

    Yuan, W.; Liu, S.; Zhou, G.; Tieszen, L.L.; Baldocchi, D.; Bernhofer, C.; Gholz, H.; Goldstein, Allen H.; Goulden, M.L.; Hollinger, D.Y.; Hu, Y.; Law, B.E.; Stoy, P.C.; Vesala, T.; Wofsy, S.C.

    2007-01-01

    The quantitative simulation of gross primary production (GPP) at various spatial and temporal scales has been a major challenge in quantifying the global carbon cycle. We developed a light use efficiency (LUE) daily GPP model from eddy covariance (EC) measurements. The model, called EC-LUE, is driven by only four variables: normalized difference vegetation index (NDVI), photosynthetically active radiation (PAR), air temperature, and the Bowen ratio of sensible to latent heat flux (used to calculate moisture stress). The EC-LUE model relies on two assumptions: First, that the fraction of absorbed PAR (fPAR) is a linear function of NDVI; Second, that the realized light use efficiency, calculated from a biome-independent invariant potential LUE, is controlled by air temperature or soil moisture, whichever is most limiting. The EC-LUE model was calibrated and validated using 24,349 daily GPP estimates derived from 28 eddy covariance flux towers from the AmeriFlux and EuroFlux networks, covering a variety of forests, grasslands and savannas. The model explained 85% and 77% of the observed variations of daily GPP for all the calibration and validation sites, respectively. A comparison with GPP calculated from the Moderate Resolution Imaging Spectroradiometer (MODIS) indicated that the EC-LUE model predicted GPP that better matched tower data across these sites. The realized LUE was predominantly controlled by moisture conditions throughout the growing season, and controlled by temperature only at the beginning and end of the growing season. The EC-LUE model is an alternative approach that makes it possible to map daily GPP over large areas because (1) the potential LUE is invariant across various land cover types and (2) all driving forces of the model can be derived from remote sensing data or existing climate observation networks.

  20. Evaluating the drought response of CMIP5 models using global gross primary productivity, leaf area, precipitation, and soil moisture data

    NASA Astrophysics Data System (ADS)

    Huang, Yuanyuan; Gerber, Stefan; Huang, Tongyi; Lichstein, Jeremy W.

    2016-12-01

    Realistic representation of vegetation's response to drought is important for understanding terrestrial carbon cycling. We evaluated nine Earth system models from the historical experiment of the Coupled Model Intercomparison Project Phase 5 for the response of gross primary productivity (GPP) and leaf area index (LAI) to hydrological anomalies. Hydrological anomalies were characterized by the standardized precipitation index (SPI) and surface soil moisture anomalies (SMA). GPP and LAI in models were on average more responsive to SPI than in observations revealed through several indicators. First, we find higher mean correlations between global annual anomalies of GPP and SPI in models than observations. Second, the maximum correlation between GPP and SPI across 1-24 month time scales is higher in models than observations. And finally, we found stronger excursions of GPP to extreme dry or wet events. Similar to GPP, LAI responded more to SPI in models than observations. The over-response of models is smaller if evaluated based on SMA instead of SPI. LAI responses to SMA are inconsistent among models, showing both higher and lower LAI when soil moisture is reduced. The time scale of maximum correlation is shorter in models than the observation for GPP, and the markedly different response time scales among models for LAI indicate gaps in understanding how variability of water availability affects foliar cover. The discrepancy of responses derived from SPI and SMA among models, and between models and observations, calls for improvement in understanding the dynamics of plant-available water in addition to how vegetation responds to these anomalies.

  1. Satellites reveal an increase in gross primary production in a greenlandic high arctic fen 1992-2008

    NASA Astrophysics Data System (ADS)

    Tagesson, T.; Mastepanov, M.; Tamstorf, M. P.; Eklundh, L.; Schubert, P.; Ekberg, A.; Sigsgaard, C.; Christensen, T. R.; Ström, L.

    2010-02-01

    Arctic wetlands play a key role in the terrestrial carbon cycle. Recent studies have shown a greening trend and indicated an increase in CO2 uptake in boreal and sub- to low-arctic areas. Our aim was to combine satellite-based normalized difference vegetation index (NDVI) with ground-based flux measurements of CO2 to investigate a possible greening trend and potential changes in gross primary production (GPP) between 1992 and 2008 in a high arctic fen area. The study took place in Rylekaerene in the Zackenberg Research Area (74°28' N 20°34' W), located in the National park of North Eastern Greenland. We estimated the light use efficiency (ɛ) for the dominant vegetation types from field measured fractions of photosynthetic active radiation (FAPAR) and ground-based flux measurements of GPP. Measured FAPAR were correlated to satellite-based NDVI. The FAPAR-NDVI relationship in combination with ɛ was applied to satellite data to model GPP 1992-2008. The model was evaluated against field measured GPP. The model was a useful tool for up-scaling GPP and all basic requirements for the model were well met, e.g., FAPAR was well correlated to NDVI and modeled GPP was well correlated to field measurements. The studied high arctic fen area has experienced a strong increase in GPP between 1992 and 2008. The area has during this period also experienced a substantial increase in local air temperature. Consequently, the observed greening trend is most likely due to ongoing climatic change possibly in combination with CO2 fertilization, due to increasing atmospheric concentrations of CO2.

  2. Multiscale analyses of solar-induced florescence and gross primary production

    NASA Astrophysics Data System (ADS)

    Wood, Jeffrey D.; Griffis, Timothy J.; Baker, John M.; Frankenberg, Christian; Verma, Manish; Yuen, Karen

    2017-01-01

    Solar-induced fluorescence (SIF) has shown great promise for probing spatiotemporal variations in terrestrial gross primary production (GPP), the largest component flux of the global carbon cycle. However, scale mismatches between SIF and ground-based GPP have posed challenges toward fully exploiting these data. We used SIF obtained at high spatial sampling rates and resolution by NASA's Orbiting Carbon Observatory-2 satellite to elucidate GPP-SIF relationships across space and time in the U.S. Corn Belt. Strong linear scaling functions (R2 ≥ 0.79) that were consistent across instantaneous to monthly time scales were obtained for corn ecosystems and for a heterogeneous landscape based on tall tower observations. Although the slope of the corn function was 56% higher than for the landscape, SIF was similar for corn (C4) and soybean (C3). Taken together, there is strong observational evidence showing robust linear GPP-SIF scaling that is sensitive to plant physiology but insensitive to the spatial or temporal scale.

  3. Remote estimation of grassland gross primary production during extreme meteorological seasons

    NASA Astrophysics Data System (ADS)

    Rossini, Micol; Migliavacca, Mirco; Galvagno, Marta; Meroni, Michele; Cogliati, Sergio; Cremonese, Edoardo; Fava, Francesco; Gitelson, Anatoly; Julitta, Tommaso; Morra di Cella, Umberto; Siniscalco, Consolata; Colombo, Roberto

    2014-06-01

    Different models driven by remotely sensed vegetation indexes (VIs) and incident photosynthetically active radiation (PAR) were developed to estimate gross primary production (GPP) in a subalpine grassland equipped with an eddy covariance flux tower. Hyperspectral reflectance was collected using an automatic system designed for high temporal frequency acquisitions for three consecutive years, including one (2011) characterized by a strong reduction of the carbon sequestration rate during the vegetative season. Models based on remotely sensed and meteorological data were used to estimate GPP, and a cross-validation approach was used to compare the predictive capabilities of different model formulations. Vegetation indexes designed to be more sensitive to chlorophyll content explained most of the variability in GPP in the ecosystem investigated, characterized by a strong seasonal dynamic. Model performances improved when including also PARpotential defined as the maximal value of incident PAR under clear sky conditions in model formulations. Best performing models are based entirely on remotely sensed data. This finding could contribute to the development of methods for quantifying the temporal variation of GPP also on a broader scale using current and future satellite sensors.

  4. Productivity, absorbed photosynthetically active radiation, and light use efficiency in crops: implications for remote sensing of crop primary production.

    PubMed

    Gitelson, Anatoly A; Peng, Yi; Arkebauer, Timothy J; Suyker, Andrew E

    2015-04-01

    Vegetation productivity metrics such as gross primary production (GPP) at the canopy scale are greatly affected by the efficiency of using absorbed radiation for photosynthesis, or light use efficiency (LUE). Thus, close investigation of the relationships between canopy GPP and photosynthetically active radiation absorbed by vegetation is the basis for quantification of LUE. We used multiyear observations over irrigated and rainfed contrasting C3 (soybean) and C4 (maize) crops having different physiology, leaf structure, and canopy architecture to establish the relationships between canopy GPP and radiation absorbed by vegetation and quantify LUE. Although multiple LUE definitions are reported in the literature, we used a definition of efficiency of light use by photosynthetically active "green" vegetation (LUE(green)) based on radiation absorbed by "green" photosynthetically active vegetation on a daily basis. We quantified, irreversible slowly changing seasonal (constitutive) and rapidly day-to-day changing (facultative) LUE(green), as well as sensitivity of LUE(green) to the magnitude of incident radiation and drought events. Large (2-3-fold) variation of daily LUE(green) over the course of a growing season that is governed by crop physiological and phenological status was observed. The day-to-day variations of LUE(green) oscillated with magnitude 10-15% around the seasonal LUE(green) trend and appeared to be closely related to day-to-day variations of magnitude and composition of incident radiation. Our results show the high variability of LUE(green) between C3 and C4 crop species (1.43 g C/MJ vs. 2.24 g C/MJ, respectively), as well as within single crop species (i.e., maize or soybean). This implies that assuming LUE(green) as a constant value in GPP models is not warranted for the crops studied, and brings unpredictable uncertainties of remote GPP estimation, which should be accounted for in LUE models. The uncertainty of GPP estimation due to facultative and

  5. Increased peak-growing season GPP in a Greenlandic high-Arctic fen 1992-2008

    NASA Astrophysics Data System (ADS)

    Tagesson, T.; Mastepanov, M.; Tamstorf, M. P.; Eklundh, L.; Schubert, P.; Ekberg, A.; Sigsgaard, C.; Christensen, T. R.; Strom, L.

    2010-12-01

    Arctic ecosystems play a key role in the terrestrial carbon cycle. Recent studies have shown a greening trend and indicated an increase in CO2 uptake in boreal and sub- to low-Arctic areas. Our aim was to combine satellite-based normalized difference vegetation index (NDVI) with ground-based flux measurements of CO2 to investigate possible changes in gross primary production (GPP) for the peak of the growing season between 1992 and 2008 in the high-Arctic. As study area we used a 1.4 km2 rectangle surrounding Rylekaerene, a wet tundra ecosystem situated in the Zackenberg Research Area (74o28 N 20o34 W), North Eastern Greenland. We combined the light use efficiency (LUE) model (GPP= ɛ × PAR × FAPAR, where ɛ is the light use efficiency of the vegetation, PAR is the incoming photosynthetically active radiation and FAPAR the PAR absorbed by the green vegetation) with NDVI data derived from a set of peak growing season satellite images from 1992 to 2008. The LUE-modelled results show a substantial increase in peak-growing season GPP in Rylekaerene during the period. The GPP increase was accompanied by a strong increase in CO2 concentration and air temperature. Possibly, indicating that the increase in GPP was due to the substantial increase in local air temperature, possibly in combination with CO2 fertilization. To model GPP, we first parameterized the LUE-model for the vegetation types dominating the Rylekaerene for the peak of the growing season (peak). Average noon-time PAR measured on the days with satellite images was used as incoming PAR in the model. We found a significant linear relationship between ground-based FAPARpeak and NDVI. The ɛpeak was on average 1.78 g CO2 MJ-1 for this high-Arctic wet tundra ecosystem, which is reasonable for high-Arctic ecosystems. The model was evaluated against field-measured GPP. There were large model uncertainties. This was caused by large natural variation in the field measurements which the model was based upon and

  6. Seasonal controls of canopy chlorophyll content on forest carbon uptake: Implications for GPP modeling

    NASA Astrophysics Data System (ADS)

    Croft, H.; Chen, J. M.; Froelich, N. J.; Chen, B.; Staebler, R. M.

    2015-08-01

    Forested ecosystems represent an important part of the global carbon cycle, with accurate estimates of gross primary productivity (GPP) crucial for understanding ecosystem response to environmental controls and improving global carbon models. This research investigated the relationships between leaf area index (LAI) and leaf chlorophyll content (ChlLeaf) with forest carbon uptake. Ground measurements of LAI and ChlLeaf were taken approximately every 9 days across the 2013 growing season from day of year (DOY) 130 to 290 at Borden Forest, Ontario. These biophysical measurements were supported by on-site eddy covariance flux measurements. Differences in the temporal development of LAI and ChlLeaf were considerable, with LAI reaching maximum values within approximately 10 days of bud burst at DOY 141. In contrast, ChlLeaf accumulation only reached maximum values at DOY 182. This divergence has important implications for GPP models which use LAI to represent the fraction of light absorbed by a canopy (fraction of absorbed photosynthetic active radiation (fAPAR)). Daily GPP values showed the strongest relationship with canopy chlorophyll content (ChlCanopy; R2 = 0.69, p < 0.001), with the LAI and GPP relationship displaying nonlinearity at the start and end of the growing season (R2 = 0.55, p < 0.001). Modeled GPP derived from LAI × PAR and ChlCanopy × PAR was tested against measured GPP, giving R2 = 0.63, p < 0.001 and R2 = 0.82, p < 0.001, respectively. This work demonstrates the importance of considering canopy pigment status in deciduous forests, with models that use fAPARLAI rather than fAPARChl neglecting to account for the importance of leaf photosynthetic potential.

  7. MODIS GPP/NPP for complex land use area: a case study of comparison between MODIS GPP/NPP and ground-based measurements over Korea

    NASA Astrophysics Data System (ADS)

    Shim, C.

    2013-12-01

    The Moderate Resolution Imaging Radiometer (MODIS) Gross Primary Productivity (GPP)/Net Primary Productivity (NPP) has been widely used for the study on global terrestrial ecosystem and carbon cycle. The current MODIS product with ~ 1 km spatial resolution, however, has limitation on the information on local scale environment (< 1km), particularly on the regions with complex land-use types. Here we try to test the performance of MODIS annual GPP/NPP for a case of Korea, where the vegetation types are mostly heterogeneous within a size of MODIS products (~1km). We selected the sites where the ground/tower flux measurements and MODIS retrievals were simultaneously available and the land classification of sites agreed the forest type map (~71m) (1 site over Gwangneung flux tower (GDK) for 2006-2008 and 2 sites of ground measurements over Cheongju (CJ1 and CJ2) for 2011). The MODIS GPP are comparable to that of GDK (largely deciduous forest) within -6.3 ~ +2.3% of bias (-104.5 - 37.9 gCm-2yr-1). While the MODIS NPP of CJ1 at Cheongju (largely Larix leptolepis) underestimated NPP by 34% (-224.5 gCm-2yr-1), the MODIS NPP of CJ2 (largely Pinus densiflora) agreed well with -0.2% of bias (1.6 gCm-2yr-1). The fairly comparable values of the MODIS here however, cannot assure the quality of the MOD17 over the complex vegetation area of Korea since the ground measurements except the eddy covariance tower flux measurements are highly inconsistent. Therefore, the comprehensive experiments to represents GPP/NPP over diverse vegetation types for a comparable scale of MODIS with a consistent measurement technique are necessary in order to evaluate the MODIS vegetation productivity data over Korea, which contains a large portion of highly heterogeneous vegetation area.

  8. Climate-driven uncertainties in modeling terrestrial gross primary production: a site level to global-scale analysis.

    PubMed

    Barman, Rahul; Jain, Atul K; Liang, Miaoling

    2014-05-01

    We used a land surface model to quantify the causes and extents of biases in terrestrial gross primary production (GPP) due to the use of meteorological reanalysis datasets. We first calibrated the model using meteorology and eddy covariance data from 25 flux tower sites ranging from the tropics to the northern high latitudes and subsequently repeated the site simulations using two reanalysis datasets: NCEP/NCAR and CRUNCEP. The results show that at most sites, the reanalysis-driven GPP bias was significantly positive with respect to the observed meteorology-driven simulations. Notably, the absolute GPP bias was highest at the tropical evergreen tree sites, averaging up to ca. 0.45 kg C m(-2)  yr(-1) across sites (ca. 15% of site level GPP). At the northern mid-/high-latitude broadleaf deciduous and the needleleaf evergreen tree sites, the corresponding annual GPP biases were up to 20%. For the nontree sites, average annual biases of up to ca. 20-30% were simulated within savanna, grassland, and shrubland vegetation types. At the tree sites, the biases in short-wave radiation and humidity strongly influenced the GPP biases, while the nontree sites were more affected by biases in factors controlling water stress (precipitation, humidity, and air temperature). In this study, we also discuss the influence of seasonal patterns of meteorological biases on GPP. Finally, using model simulations for the global land surface, we discuss the potential impacts of site-level reanalysis-driven biases on the global estimates of GPP. In a broader context, our results can have important consequences on other terrestrial ecosystem fluxes (e.g., net primary production, net ecosystem production, energy/water fluxes) and reservoirs (e.g., soil carbon stocks). In a complementary study (Barman et al., ), we extend the present analysis for latent and sensible heat fluxes, thus consistently integrating the analysis of climate-driven uncertainties in carbon, energy, and water fluxes

  9. Quantifying subtropical North Pacific gyre mixed layer primary productivity from Seaglider observations of diel oxygen cycles

    NASA Astrophysics Data System (ADS)

    Nicholson, David P.; Wilson, Samuel T.; Doney, Scott C.; Karl, David M.

    2015-05-01

    Using autonomous underwater gliders, we quantified diurnal periodicity in dissolved oxygen, chlorophyll, and temperature in the subtropical North Pacific near the Hawaii Ocean Time-series (HOT) Station ALOHA during summer 2012. Oxygen optodes provided sufficient stability and precision to quantify diel cycles of average amplitude of 0.6 µmol kg-1. A theoretical diel curve was fit to daily observations to infer an average mixed layer gross primary productivity (GPP) of 1.8 mmol O2 m-3 d-1. Cumulative net community production (NCP) over 110 days was 500 mmol O2 m-2 for the mixed layer, which averaged 57 m in depth. Both GPP and NCP estimates indicated a significant period of below-average productivity at Station ALOHA in 2012, an observation confirmed by 14C productivity incubations and O2/Ar ratios. Given our success in an oligotrophic gyre where biological signals are small, our diel GPP approach holds promise for remote characterization of productivity across the spectrum of marine environments.

  10. Integrating Chlorophyll fapar and Nadir Photochemical Reflectance Index from EO-1/Hyperion to Predict Cornfield Daily Gross Primary Production

    NASA Technical Reports Server (NTRS)

    Zhang, Qingyuan; Middleton, Elizabeth M.; Cheng, Yen-Ben; Huemmrich, K. Fred; Cook, Bruce D.; Corp, Lawrence A.; Kustas, William P.; Russ, Andrew L.; Prueger, John H.; Yao, Tian

    2016-01-01

    The concept of light use efficiency (Epsilon) and the concept of fraction of photosynthetically active ration (PAR) absorbed for vegetation photosynthesis (PSN), i.e., fAPAR (sub PSN), have been widely utilized to estimate vegetation gross primary productivity (GPP). It has been demonstrated that the photochemical reflectance index (PRI) is empirically related to e. An experimental US Department of Agriculture (USDA) cornfield in Maryland was selected as our study field. We explored the potential of integrating fAPAR(sub chl) (defined as the fraction of PAR absorbed by chlorophyll) and nadir PRI (PRI(sub nadir)) to predict cornfield daily GPP. We acquired nadir or near-nadir EO-1/Hyperion satellite images that covered the cornfield and took nadir in-situ field spectral measurements. Those data were used to derive the PRI(sub nadir) and fAPAR (sub chl). The fAPAR (sub chl) is retrieved with the advanced radiative transfer model PROSAIL2 and the Metropolis approach, a type of Markov Chain Monte Carlo (MCMC) estimation procedure. We define chlorophyll light use efficiency Epsilon (sub chl) as the ratio of vegetation GPP as measured by eddy covariance techniques to PAR absorbed by chlorophyll (Epsilon(sub chl) = GPP/APAR (sub chl). Daily Epsilon (sub chl) retrieved with the EO-1 Hyperion images was regressed with a linear equation of PRI (sub nadir) Epsilon (sub chl) = Alpha × PRI (sub nadir) + Beta). The satellite Epsilon(sub chl- PRI (sub nadir) linear relationship for the cornfield was implemented to develop an integrated daily GPP model [GPP = (Alpha × PRI(sub nadir) + Beta) × fAPAR (sub chl) × PAR], which was evaluated with fAPAR (sub chl) and PRI (sub nadir) retrieved from field measurements. Daily GPP estimated with this fAPAR (sub chl-) PRI (nadir) integration model was strongly correlated with the observed tower in-situ daily GPP (R(sup 2) = 0.93); with a root mean square error (RMSE) of 1.71 g C mol-(sup -1) PPFD and coefficient of variation (CV) of 16

  11. Net primary productivity of China's terrestrial ecosystems from a process model driven by remote sensing.

    PubMed

    Feng, X; Liu, G; Chen, J M; Chen, M; Liu, J; Ju, W M; Sun, R; Zhou, W

    2007-11-01

    The terrestrial carbon cycle is one of the foci in global climate change research. Simulating net primary productivity (NPP) of terrestrial ecosystems is important for carbon cycle research. In this study, China's terrestrial NPP was simulated using the Boreal Ecosystem Productivity Simulator (BEPS), a carbon-water coupled process model based on remote sensing inputs. For these purposes, a national-wide database (including leaf area index, land cover, meteorology, vegetation and soil) at a 1 km resolution and a validation database were established. Using these databases and BEPS, daily maps of NPP for the entire China's landmass in 2001 were produced, and gross primary productivity (GPP) and autotrophic respiration (RA) were estimated. Using the simulated results, we explore temporal-spatial patterns of China's terrestrial NPP and the mechanisms of its responses to various environmental factors. The total NPP and mean NPP of China's landmass were 2.235 GtC and 235.2 gCm(-2)yr(-1), respectively; the total GPP and mean GPP were 4.418 GtC and 465 gCm(-2)yr(-1); and the total RA and mean RA were 2.227 GtC and 234 gCm(-2)yr(-1), respectively. On average, NPP was 50.6% of GPP. In addition, statistical analysis of NPP of different land cover types was conducted, and spatiotemporal patterns of NPP were investigated. The response of NPP to changes in some key factors such as LAI, precipitation, temperature, solar radiation, VPD and AWC are evaluated and discussed.

  12. Temperature dependence of CO2-enhanced primary production in the European Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Holding, J. M.; Duarte, C. M.; Sanz-Martín, M.; Mesa, E.; Arrieta, J. M.; Chierici, M.; Hendriks, I. E.; García-Corral, L. S.; Regaudie-de-Gioux, A.; Delgado, A.; Reigstad, M.; Wassmann, P.; Agustí, S.

    2015-12-01

    The Arctic Ocean is warming at two to three times the global rate and is perceived to be a bellwether for ocean acidification. Increased CO2 concentrations are expected to have a fertilization effect on marine autotrophs, and higher temperatures should lead to increased rates of planktonic primary production. Yet, simultaneous assessment of warming and increased CO2 on primary production in the Arctic has not been conducted. Here we test the expectation that CO2-enhanced gross primary production (GPP) may be temperature dependent, using data from several oceanographic cruises and experiments from both spring and summer in the European sector of the Arctic Ocean. Results confirm that CO2 enhances GPP (by a factor of up to ten) over a range of 145-2,099 μatm however, the greatest effects are observed only at lower temperatures and are constrained by nutrient and light availability to the spring period. The temperature dependence of CO2-enhanced primary production has significant implications for metabolic balance in a warmer, CO2-enriched Arctic Ocean in the future. In particular, it indicates that a twofold increase in primary production during the spring is likely in the Arctic.

  13. Evaluating post-disaster ecosystem resilience using MODIS GPP data

    NASA Astrophysics Data System (ADS)

    Frazier, Amy E.; Renschler, Chris S.; Miles, Scott B.

    2013-04-01

    An integrated community resilience index (CRI) quantifies the status, exposure, and recovery of the physical, economic, and socio-cultural capital for a specific target community. However, most CRIs do not account for the recovery of ecosystem functioning after extreme events, even though many aspects of a community depend on the services provided by the natural environment. The primary goal of this study was to monitor the recovery of ecosystem functionality (ecological capital) using remote sensing-derived gross primary production (GPP) as an indicator of 'ecosystem-wellness' and assess the effect of resilience of ecological capital on the recovery of a community via an integrated CRI. We developed a measure of ecosystem resilience using remotely sensed GPP data and applied the modeling prototype ResilUS in a pilot study for a four-parish coastal community in southwestern Louisiana, USA that was impacted by Hurricane Rita in 2005. The results illustrate that after such an extreme event, the recovery of ecological capital varies according to land use type and may take many months to return to full functionality. This variable recovery can potentially impact the recovery of certain businesses that rely heavily on ecosystem services such as agriculture, forestry, fisheries, and tourism.

  14. Spatial and temporal variability of canopy GPP within a flux tower footprint

    NASA Astrophysics Data System (ADS)

    Garrity, S. R.; Vierling, L. A.

    2009-12-01

    Gross Primary Productivity (GPP) of plant canopies is strongly related to absorbed photosynthetically active radiation (APAR) and thus canopy structure. Short term canopy GPP responds to variable environmental conditions through alterations in the efficiency with which APAR is used to assimilate carbon and is thus also dependent on accessory pigment ratios and pool sizes. We used spatially distributed measurements of whole canopy transmitted radiation to better understand diurnal and seasonal dynamics of GPP within a flux tower footprint. Our instruments measured transmitted radiation in the Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI) wavelengths. These measurements served as proxies for canopy structure, short term changes in radiation use efficiency (RUE) and longer term changes in pools of photosynthetically important pigments. We found that aggregated measurements of PRI were related to total canopy RUE at both diurnal and seasonal time scales with the highest correlations occurring during periods when light-related stress was greatest. Diurnal and seasonal variability among spatially distributed measurements was in part explained by species composition and canopy structure. At the seasonal time scale we found evidence that suggested the ratios of photosynthetic pigments were related to canopy development and were important for explaining variability in the relationship between APAR and GPP across the growing season.

  15. Assessing soil fluxes of carbonyl sulfide to aid in ecosystem estimates of GPP

    NASA Astrophysics Data System (ADS)

    Whelan, M.; Rhew, R. C.; Campbell, J. E.; Hilton, T. W.; Berkelhammer, M. B.; Zumkehr, A. L.; Berry, J. A.

    2014-12-01

    Measuring the draw down of carbonyl sulfide (chemical formula: COS) over ecosystems can provide a new tool for estimating gross primary production (GPP) at important temporal and spatial scales. COS is a gas ubiquitous in the atmosphere that shares many characteristics with CO2: both are taken up by enzymes in plant leaves at a predictable ratio and in proportion to their ambient concentrations. While CO2 is simultaneously respired by soil and plant roots, the dominant flux of COS is foliar absorption. Previously, ecosystem soil fluxes of COS were thought to be negligible in the application of this COS-GPP proxy. Here we present new data describing controls on soil fluxes as a way to anticipate COS soil exchange over heterogeneous landscapes. Using soil samples from two agricultural sites in the Great Plains and one site in the Colorado Desert, we captured data from the extremes of ecosystem GPP in the United States. We then built a model describing COS soil fluxes with inputs of soil temperature and soil water content based on characterized soil behavior. This study provides an essential refinement in applying COS-GPP estimates over the continents.

  16. Basal Levels of (p)ppGpp in Enterococcus faecalis: the Magic beyond the Stringent Response

    PubMed Central

    Gaca, Anthony O.; Kajfasz, Jessica K.; Miller, James H.; Liu, Kuanqing; Wang, Jue D.; Abranches, Jacqueline; Lemos, José A.

    2013-01-01

    ABSTRACT The stringent response (SR), mediated by the alarmone (p)ppGpp, is a conserved bacterial adaptation system controlling broad metabolic alterations necessary for survival under adverse conditions. In Enterococcus faecalis, production of (p)ppGpp is controlled by the bifunctional protein RSH (for “Rel SpoT homologue”; also known as RelA) and by the monofunctional synthetase RelQ. Previous characterization of E. faecalis strains lacking rsh, relQ, or both revealed that RSH is responsible for activation of the SR and that alterations in (p)ppGpp production negatively impact bacterial stress survival and virulence. Despite its well-characterized role as the effector of the SR, the significance of (p)ppGpp during balanced growth remains poorly understood. Microarrays of E. faecalis strains producing different basal amounts of (p)ppGpp identified several genes and pathways regulated by modest changes in (p)ppGpp. Notably, expression of numerous genes involved in energy generation were induced in the ∆rsh ∆relQ [(p)ppGpp0] strain, suggesting that a lack of basal (p)ppGpp places the cell in a “transcriptionally relaxed” state. Alterations in the fermentation profile and increased production of H2O2 in the (p)ppGpp0 strain substantiate the observed transcriptional changes. We confirm that, similar to what is seen in Bacillus subtilis, (p)ppGpp directly inhibits the activity of enzymes involved in GTP biosynthesis, and complete loss of (p)ppGpp leads to dysregulation of GTP homeostasis. Finally, we show that the association of (p)ppGpp with antibiotic survival does not relate to the SR but rather relates to basal (p)ppGpp pools. Collectively, this study highlights the critical but still underappreciated role of basal (p)ppGpp pools under balanced growth conditions. PMID:24065631

  17. Molecular mutagenesis of ppGpp: turning a RelA activator into an inhibitor

    PubMed Central

    Beljantseva, Jelena; Kudrin, Pavel; Jimmy, Steffi; Ehn, Marcel; Pohl, Radek; Varik, Vallo; Tozawa, Yuzuru; Shingler, Victoria; Tenson, Tanel; Rejman, Dominik; Hauryliuk, Vasili

    2017-01-01

    The alarmone nucleotide (p)ppGpp is a key regulator of bacterial metabolism, growth, stress tolerance and virulence, making (p)ppGpp-mediated signaling a promising target for development of antibacterials. Although ppGpp itself is an activator of the ribosome-associated ppGpp synthetase RelA, several ppGpp mimics have been developed as RelA inhibitors. However promising, the currently available ppGpp mimics are relatively inefficient, with IC50 in the sub-mM range. In an attempt to identify a potent and specific inhibitor of RelA capable of abrogating (p)ppGpp production in live bacterial cells, we have tested a targeted nucleotide library using a biochemical test system comprised of purified Escherichia coli components. While none of the compounds fulfilled this aim, the screen has yielded several potentially useful molecular tools for biochemical and structural work. PMID:28157202

  18. Microbial production of primary metabolites

    NASA Astrophysics Data System (ADS)

    Demain, Arnold L.

    1980-12-01

    Microbial production of primary metabolites contributes significantly to the quality of life. Through fermentation, microorganisms growing on inexpensive carbon sources can produce valuable products such as amino acids, nucleotides, organic acids, and vitamins which can be added to food to enhance its flavor or increase its nutritive value. The contribution of microorganisms will go well beyond the food industry with the renewed interest in solvent fermentations. Microorganisms have the potential to provide many petroleum-derived products as well as the ethanol necessary for liquid fuel. The role of primary metabolites and the microbes which produce them will certainly increase in importance.

  19. Impacts of Light Use Efficiency and fPAR Parameterization on Gross Primary Production Modeling

    NASA Technical Reports Server (NTRS)

    Cheng, Yen-Ben; Zhang, Qingyuan; Lyapustin, Alexei I.; Wang, Yujie; Middleton, Elizabeth M.

    2014-01-01

    This study examines the impact of parameterization of two variables, light use efficiency (LUE) and the fraction of absorbed photosynthetically active radiation (fPAR or fAPAR), on gross primary production(GPP) modeling. Carbon sequestration by terrestrial plants is a key factor to a comprehensive under-standing of the carbon budget at global scale. In this context, accurate measurements and estimates of GPP will allow us to achieve improved carbon monitoring and to quantitatively assess impacts from cli-mate changes and human activities. Spaceborne remote sensing observations can provide a variety of land surface parameterizations for modeling photosynthetic activities at various spatial and temporal scales. This study utilizes a simple GPP model based on LUE concept and different land surface parameterizations to evaluate the model and monitor GPP. Two maize-soybean rotation fields in Nebraska, USA and the Bartlett Experimental Forest in New Hampshire, USA were selected for study. Tower-based eddy-covariance carbon exchange and PAR measurements were collected from the FLUXNET Synthesis Dataset. For the model parameterization, we utilized different values of LUE and the fPAR derived from various algorithms. We adapted the approach and parameters from the MODIS MOD17 Biome Properties Look-Up Table (BPLUT) to derive LUE. We also used a site-specific analytic approach with tower-based Net Ecosystem Exchange (NEE) and PAR to estimate maximum potential LUE (LUEmax) to derive LUE. For the fPAR parameter, the MODIS MOD15A2 fPAR product was used. We also utilized fAPAR chl, a parameter accounting for the fAPAR linked to the chlorophyll-containing canopy fraction. fAPAR chl was obtained by inversion of a radiative transfer model, which used the MODIS-based reflectances in bands 1-7 produced by Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. fAPAR chl exhibited seasonal dynamics more similar with the flux tower based GPP than MOD15A2 fPAR, especially

  20. Evaluation of MODIS GPP over a complex ecosystem in East Asia: A case study at Gwangneung flux tower in Korea

    NASA Astrophysics Data System (ADS)

    Shim, Changsub; Hong, Jiyoun; Hong, Jinkyu; Kim, Youngwook; Kang, Minseok; Malla Thakuri, Bindu; Kim, Yongwon; Chun, Junghwa

    2014-12-01

    Moderate Resolution Imaging Radiometer (MODIS) gross primary productivity (GPP) has been used widely to study the global carbon cycle associated with terrestrial ecosystems. The retrieval of the current MODIS productivity with a 1 × 1 km2 resolution has limitations when presenting subgrid scale processes in terrestrial ecosystems, specifically when forests are located in mountainous areas, and shows heterogeneity in vegetation type due to intensive land use. Here, we evaluate MODIS GPP (MOD17) at Gwangneung deciduous forest KoFlux tower (deciduous forest; GDK) for 2006-2010 in Korea, where the forests comprise heterogeneous vegetation cover over complex terrain. The monthly MODIS GPP data overestimated the GDK measurements in a range of +15% to +34% and was fairly well correlated (R = 0.88) with the monthly variability at GDK during the growing season. In addition, the MODIS data partly represented the sharp GPP reduction during the Asian summer monsoon (June-September) when intensive precipitation considerably reduces solar radiation and disturbs the forest ecosystem. To examine the influence of subgrid scale heterogeneity on GPP estimates over the MODIS scale, the individual vegetation type and its area within a corresponding MODIS pixel were identified using a national forest type map (∼71-m spatial resolution), and the annual GPP in the same area as the MODIS pixel was estimated. This resulted in a slight reduction in the positive MODIS bias by ∼10%, with a high degree of uncertainty in the estimation. The MODIS discrepancy for GDK suggests further investigation is necessary to determine the MODIS errors associated with the site-specific aerodynamic and hydrological characteristics that are closely related to the mountainous topography. The accuracy of meteorological variables and the impact of the very cloudy conditions in East Asia also need to be assessed.

  1. Algorithm developing of gross primary production from its capacity and a canopy conductance index using flux and global observing satellite data

    NASA Astrophysics Data System (ADS)

    Muramatsu, Kanako; Furumi, Shinobu; Daigo, Motomasa

    2015-10-01

    We plan to estimate gross primary production (GPP) using the SGLI sensor on-board the GCOM-C1 satellite after it is launched in 2017 by the Japan Aerospace Exploration Agency, as we have developed a GPP estimation algorithm that uses SGLI sensor data. The characteristics of this GPP estimation method correspond to photosynthesis. The rate of plant photosynthesis depends on the plant's photosynthesis capacity and the degree to which photosynthesis is suppressed. The photosynthesis capacity depends on the chlorophyll content of leaves, which is a plant physiological parameter, and the degree of suppression of photosynthesis depends on weather conditions. The framework of the estimation method to determine the light-response curve parameters was developed using ux and satellite data in a previous study[1]. We estimated one of the light-response curve parameters based on the linear relationship between GPP capacity at 2000 (μmolm-2s-1) of photosynthetically active radiation and a chlorophyll index (CIgreen [2;3] ). The relationship was determined for seven plant functional types. Decreases in the photosynthetic rate are controlled by stomatal opening and closing. Leaf stomatal conductance is maximal during the morning and decreases in the afternoon. We focused on daily changes in leaf stomatal conductance. We used open shrub flux data and MODIS reflectance data to develop an algorithm for a canopy. We first evaluated the daily changes in GPP capacity estimated from CIgreen and photosynthesis active radiation using light response curves, and GPP observed during a flux experiment. Next, we estimated the canopy conductance using flux data and a big-leaf model using the Penman-Monteith equation[4]. We estimated GPP by multiplying GPP capacity by the normalized canopy conductance at 10:30, the time of satellite observations. The results showed that the estimated daily change in GPP was almost the same as the observed GPP. From this result, we defined a normalized canopy

  2. Relationship of the first step in protein synthesis to ppGpp: formation of A(5')ppp(5')Gpp.

    PubMed Central

    Rapaport, E; Svihovec, S K; Zamecnik, P C

    1975-01-01

    In the presence of purified Escherichia coli lysyl-tRNA synthetase [L-lysine:tRNALys ligase (AMP-forming) EC 6.1.1.6], L-lysine, and ATP, addition of the nucleotide ppGpp results in formation of a unique product-A(5')ppp(5') Gpp. The same compound is also formed very rapidly in a cell-free protein-synthesizing system when ppGpp is added. The possible significance of this reaction in the rapid turnover of ppGpp and as a more general mechanism by which an AMP residue is activated and introduced onto a 5'-diphosphorylated species, including the 5'-end of an RNA, is further discussed. PMID:170611

  3. In situ spectral measurements improve the efficiency of light use efficiency models to estimate gross primary productivity in Mediterranean cork oak woodland

    NASA Astrophysics Data System (ADS)

    Cerasoli, S.; Silva, J. M.; Carvalhais, N.; Correia, A.; Costa e Silva, F.; Pereira, J. S.

    2013-12-01

    The Light Use Efficiency (LUE) concept is usually applied to retrieve Gross Primary Productivity (GPP) estimates in models integrating spectral indexes, namely Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI), considered proxies of biophysical properties of vegetation. The integration of spectral measurements into LUE models can increase the robustness of GPP estimates by optimizing particular parameters of the model. NDVI and PRI are frequently obtained by broad band sensors on remote platforms at low spatial resolution (e.g. MODIS). In highly heterogeneous ecosystems such spectral information may not be representative of the dynamic response of the ecosystem to climate variables. In Mediterranean oak woodlands different plant functional types (PFT): trees canopy, shrubs and herbaceous layer, contribute to the overall Gross Primary Productivity (GPP). In situ spectral measurements can provide useful information on each PFT and its temporal variability. The objectives of this study were: i) to analyze the temporal variability of NDVI, PRI and others spectral indices for the three PFT, their response to climate variables and their relationship with biophysical properties of vegetation; ii) to optimize a LUE model integrating selected spectral indexes in which the contribution of each PFT to the overall GPP is estimated individually; iii) to compare the performance of disaggregated GPP estimates and lumped GPP estimates, evaluated against eddy covariance measurements. Ground measurements of vegetation reflectance were performed in a cork oak woodland located in Coruche, Portugal (39°8'N, 8°19'W) where carbon and water fluxes are continuously measured by eddy covariance. Between April 2011 and June 2013 reflectance measurements of the herbaceous layer, shrubs and trees canopy were acquired with a FieldSpec3 spectroradiometer (ASD Inc.) which provided data in the range of 350-2500nm. Measurements were repeated approximately on

  4. Integrating Solar Induced Fluorescence and the Photochemical Reflectance Index for Estimating Gross Primary Production in a Cornfield

    NASA Technical Reports Server (NTRS)

    Cheng, Yen-Ben; Middleton, Elizabeth M.; Zhang, Qingyuan; Huemmrich, Karl F.; Campbell, Petya K. E.; Corp, Lawrence A.; Cook, Bruce D.; Kustas, William P.; Daughtry, Criag S.

    2013-01-01

    The utilization of remotely sensed observations for light use efficiency (LUE) and tower-based gross primary production (GPP) estimates was studied in a USDA cornfield. Nadir hyperspectral reflectance measurements were acquired at canopy level during a collaborative field campaign conducted in four growing seasons. The Photochemical Reflectance Index (PRI) and solar induced chlorophyll fluorescence (SIF), were derived. SIF retrievals were accomplished in the two telluric atmospheric oxygen absorption features centered at 688 nm (O2-B) and 760 nm (O2-A). The PRI and SIF were examined in conjunction with GPP and LUE determined by flux tower-based measurements. All of these fluxes, environmental variables, and the PRI and SIF exhibited diurnal as well as day-to-day dynamics across the four growing seasons. Consistent with previous studies, the PRI was shown to be related to LUE (r2 = 0.54 with a logarithm fit), but the relationship varied each year. By combining the PRI and SIF in a linear regression model, stronger performances for GPP estimation were obtained. The strongest relationship (r2 = 0.80, RMSE = 0.186 mg CO2/m2/s) was achieved when using the PRI and SIF retrievals at 688 nm. Cross-validation approaches were utilized to demonstrate the robustness and consistency of the performance. This study highlights a GPP retrieval method based entirely on hyperspectral remote sensing observations.

  5. Differential regulation by ppGpp versus pppGpp in Escherichia coli.

    PubMed

    Mechold, Undine; Potrykus, Katarzyna; Murphy, Helen; Murakami, Katsuhiko S; Cashel, Michael

    2013-07-01

    Both ppGpp and pppGpp are thought to function collectively as second messengers for many complex cellular responses to nutritional stress throughout biology. There are few indications that their regulatory effects might be different; however, this question has been largely unexplored for lack of an ability to experimentally manipulate the relative abundance of ppGpp and pppGpp. Here, we achieve preferential accumulation of either ppGpp or pppGpp with Escherichia coli strains through induction of different Streptococcal (p)ppGpp synthetase fragments. In addition, expression of E. coli GppA, a pppGpp 5'-gamma phosphate hydrolase that converts pppGpp to ppGpp, is manipulated to fine tune differential accumulation of ppGpp and pppGpp. In vivo and in vitro experiments show that pppGpp is less potent than ppGpp with respect to regulation of growth rate, RNA/DNA ratios, ribosomal RNA P1 promoter transcription inhibition, threonine operon promoter activation and RpoS induction. To provide further insights into regulation by (p)ppGpp, we have also determined crystal structures of E. coli RNA polymerase-σ(70) holoenzyme with ppGpp and pppGpp. We find that both nucleotides bind to a site at the interface between β' and ω subunits.

  6. Primary productivity in the sea

    SciTech Connect

    Falkowski, P.G.

    1980-01-01

    Recent progress in primary productivity is discussed in the book based on 27 symposia texts and 19 poster abstracts. Most papers deal with particular cellular processes in pelagic phytoplankton and their relationship to whole plant photosynthesis and growth. In addition, presentations on the productivity of the seaweed, Laminaria, zooxanthellae and whole corals are included. Other articles discuss predictive modeling, new developments in remote sensing, nutrient regeneration within the sea, grazing effects, and carbon cycling. (JMT)

  7. Atmospheric COS measurements and satellite-derived vegetation fluorescence data to evaluate the terrestrial gross primary productivity of CMIP5 model

    NASA Astrophysics Data System (ADS)

    Peylin, Philippe; MacBean, Natasha; Launois, Thomas; Belviso, Sauveur; Cadule, Patricia; Maignan, Fabienne

    2016-04-01

    Predicting the fate of the ecosystem carbon stocks and their sensitivity to climate change strongly relies on our ability to accurately model the gross carbon fluxes, i.e. photosynthesis and respiration. The Gross Primary Productivity (GPP) simulated by the different terrestrial models used in CMIP5 show large differences however, not only in terms of mean value but also in terms of phase and amplitude, thus hampering accurate investigations into carbon-climate feedbacks. While the net C flux of an ecosystem (NEE) can be measured in situ with the eddy covariance technique, the GPP is not directly accessible at larger scales and usually estimates are based on indirect measurements combining different tracers. Recent measurements of a new atmospheric tracer, the Carbonyl sulphide (COS), as well as the global measurement of Solar Induced Fluorescence (SIF) from satellite instruments (GOSAT, GOME2) open a new window for evaluating the GPP of earth system models. The use of COS relies on the fact that it is absorbed by the leaves in a similar manner to CO2, while there seems to be nothing equivalent to respiration for COS. Following recent work by Launois et al. (ACP, 2015), there is a potential to evaluate model GPP from atmospheric COS and CO2 measurements, using a transport model and recent parameterizations for the non-photosynthetic sinks (oxic soils, atmospheric oxidation) and biogenic sources (oceans and anoxic soils) of COS. Vegetation uptake of COS is modeled as a linear function of GPP and the ratio of COS to CO2 rate of uptake by plants. For the fluorescence, recent measurements of SIF from space appear to be highly correlated with monthly variations of data-driven GPP estimates (Guanter et al., 2012), following a strong dependence of vegetation SIF on photosynthetic activity. These global measurements thus provide new indications on the timing of canopy carbon uptake. In this work, we propose a dual approach that combines the strength of both COS and SIF

  8. Modeling climate change impacts on primary production by the terrestrial biosphere

    NASA Astrophysics Data System (ADS)

    Davis, T. W.; Prentice, I. C.; Evans, B. J.; Gilbert, X.

    2013-12-01

    A modelling system is under development for the global hindcasting and analysis of spatial and temporal patterns in terrestrial gross primary production (GPP). The aim is to produce the simplest possible model that makes good use of observational data (from flux towers, meteorological stations, and remote-sensing satellites) while defensibly representing the principal ecophysiological processes that govern GPP. The first modelling step consists of partitioning high time-resolution carbon dioxide flux data, using in situ photosynthetically active radiation (PAR) measurements. The second step estimates monthly light-use efficiency (LUE) from monthly aggregated GPP and gap-filled, monthly aggregated PAR, and analyses the empirical dependencies of LUE on vegetational and environmental factors in order to yield a simple predictive model for LUE. The third and final stage generates spatial fields of monthly GPP based on remotely sensed reflectances and predicted LUE. The basis of the system is an efficient database structure, which is the "tool chest" for modelling. The tool chest is designed to hold the variety of observational data necessary to complete each stage of the model including point measurements of CO2 fluxes and PAR, and gridded measurements of surface reflectances and downwelling radiation. The Python programming language is used to upload, retrieve and process data. Although the model as currently developed is a data-driven, 'diagnostic' model, the intention is to use its basic elements in the construction of a next-generation vegetation and land-surface model based on a new theoretical approach to predict the light use efficiency of ecosystems. The model will strive for clarity and uniformity so that it may be used by researchers across disciplines. The use of an open-source programming language allows for portability and transparency. The model will invite a range of applications to the analysis of climate and CO2 change impacts on ecosystem processes.

  9. A GPP assimilation model for the southeastern Tibetan Plateau based on CO2 eddy covariance flux tower and remote sensing data

    NASA Astrophysics Data System (ADS)

    Jiang, Yan; Zhang, JiaHua; Xu, XiangDe; Dong, ZhiXin

    2013-08-01

    The gross primary production (GPP) at individual CO2 eddy covariance flux tower sites (GPPTower) in Dali (DL), Wenjiang (WJ) and Linzhi (LZ) around the southeastern Tibetan Plateau were determined by the net ecosystem exchange of CO2 (NEE) and ecosystem respiration (Re). The satellite remote sensing-VPM model estimates of GPP values (GPPMODIS) used the satellite-derived 8-day surface reflectance product (MOD09A1), including satellite-derived enhanced vegetation index (EVI) and land surface water index (LSWI). In this paper, we assembled a subset of flux tower data at these three sites to calibrate and test satellite-VPM model estimated GPPMODIS, and introduced the satellite data and site-level environmental factors to develop four new assimilation models. The new assimilation models’ estimates of GPP values were compared with GPPMODIS and GPPTower, and the final optimum model among the four assimilation models was determined and used to calibrate GPPMODIS. The results showed that GPPMODIS had similar temporal variations to the GPPTower, but GPPMODlS were commonly higher in absolute magnitude than GPPTower with relative error (RE) about 58.85%. While, the assimilation models’ estimates of GPP values (GPPMODEL) were much more closer to GPPTower with RE approximately 6.98%, indicating that the capacity of the simulation in the new assimilation model was greatly improved, the R2 and root mean square error (RMSE) of the new assimilation model were 0.57-4.90% higher and 0.74-2.47 g C m-2 s-1 lower than those of the GPPMODIS, respectively. The assimilation model was used to predicted GPP dynamics around the Tibetan Plateau and showed a reliable result compared with other researches. This study demonstrated the potential of the new assimilation model for estimating GPP around the Tibetan Plateau and the performances of site-level biophysical parameters in related to satellite-VPM model GPP.

  10. Evaluating the potential of Southampton Carbon flux (SCARF) model to predict terrestrial gross primary productivity over Africa.

    NASA Astrophysics Data System (ADS)

    Dash, Jadunandan; Chiwara, Phibion; Milton, Edward; Ardo, Jonas; Saunders, Matthew; Nicolini, Giacomo

    The amount of carbon uptake by vegetation is an important component to understand the functioning of ecosystem processes and their response/feedback to climate. Recently a new diagnostic model called the Southampton Carbon flux (SCARF) model was develop to predict terrestrial gross primary productivity at regional to global scale using satellite data. The model based on the quantum yield of vegetation improves on the previous diagnostic model by (i) using the fraction of photosynthetic active radiation absorbed by the photosynthetic pigment (FAPAR _{ps}) and (ii) using direct quantum yield by classifying the vegetation into C3 or C4 classes. Initial results suggest a very good agreement with expected results for ecosystems where the growth is controlled by temperature (e.g. Northern higher latitude). In this paper we calibrated and validated the model for a range of vegetation types across Africa, in order to test the performance of vegetation over a water limiting ecosystem. The vapour pressure deficit term (VPD) was modified to quantify the water loss and in turn reduced carbon assimilation through Evapotranspiration. The performance of the model was evaluated with GPP measured at eight eddy covariance flux tower data across Africa. Overall, the modelled GPP values show good agreement with observed GPP at most sites (except tropical rainforest site) in terms of their seasonality and absolute values. Mean daily GPP across the investigated period varied significantly across sites depending on the vegetation types from a minimum of 0.64 gC m (2) day (-1) for the dry savannah grassland at Demokeya to a maximum of 7.83 gC m (2) day (-1) for tropical rain forest at Ankasa. The model results have modest to very strong positive agreement with observed GPP at most sites (r (2) values ranging from 0.58 for Kruger and 0.84 for Mongu). Generally, strong correlation is observed in woodlands and grasslands where vegetation follows a prescribed seasonal cycle as determined by

  11. Tree-grass phenology information improves light use efficiency modelling of gross primary productivity for an Australian tropical savanna

    NASA Astrophysics Data System (ADS)

    Moore, Caitlin E.; Beringer, Jason; Evans, Bradley; Hutley, Lindsay B.; Tapper, Nigel J.

    2017-01-01

    The coexistence of trees and grasses in savanna ecosystems results in marked phenological dynamics that vary spatially and temporally with climate. Australian savannas comprise a complex variety of life forms and phenologies, from evergreen trees to annual/perennial grasses, producing a boom-bust seasonal pattern of productivity that follows the wet-dry seasonal rainfall cycle. As the climate changes into the 21st century, modification to rainfall and temperature regimes in savannas is highly likely. There is a need to link phenology cycles of different species with productivity to understand how the tree-grass relationship may shift in response to climate change. This study investigated the relationship between productivity and phenology for trees and grasses in an Australian tropical savanna. Productivity, estimated from overstory (tree) and understory (grass) eddy covariance flux tower estimates of gross primary productivity (GPP), was compared against 2 years of repeat time-lapse digital photography (phenocams). We explored the phenology-productivity relationship at the ecosystem scale using Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation indices and flux tower GPP. These data were obtained from the Howard Springs OzFlux/Fluxnet site (AU-How) in northern Australia. Two greenness indices were calculated from the phenocam images: the green chromatic coordinate (GCC) and excess green index (ExG). These indices captured the temporal dynamics of the understory (grass) and overstory (trees) phenology and were correlated well with tower GPP for understory (r2 = 0.65 to 0.72) but less so for the overstory (r2 = 0.14 to 0.23). The MODIS enhanced vegetation index (EVI) correlated well with GPP at the ecosystem scale (r2 = 0.70). Lastly, we used GCC and EVI to parameterise a light use efficiency (LUE) model and found it to improve the estimates of GPP for the overstory, understory and ecosystem. We conclude that phenology is an important parameter to

  12. Estimation and analysis of gross primary production of soybean under various management practices and drought conditions

    NASA Astrophysics Data System (ADS)

    Wagle, Pradeep; Xiao, Xiangming; Suyker, Andrew E.

    2015-01-01

    Gross primary production (GPP) of croplands may be used to quantify crop productivity and evaluate a range of management practices. Eddy flux data from three soybean (Glycine max L.) fields under different management practices (no-till vs. till; rainfed vs. irrigated) and Moderate Resolution Imaging Spectroradiometer (MODIS) derived vegetation indices (VIs) were used to test the capabilities of remotely sensed VIs and soybean phenology to estimate the seasonal dynamics of carbon fluxes. The modeled GPP (GPPVPM) using vegetation photosynthesis model (VPM) was compared with the GPP (GPPEC) estimated from eddy covariance measurements. The VIs tracked soybean phenology well and delineated the growing season length (GSL), which was closely related to carbon uptake period (CUP, R2 = 0.84), seasonal sums of net ecosystem CO2 exchange (NEE, R2 = 0.78), and GPPEC (R2 = 0.54). Land surface water index (LSWI) tracked drought-impacted vegetation well, as the LSWI values were positive during non-drought periods and negative during severe droughts within the soybean growing season. On a seasonal scale, NEE of the soybean sites ranged from -37 to -264 g C m-2. The result suggests that rainfed soybean fields needed about 450-500 mm of well-distributed seasonal rainfall to maximize the net carbon sink. During non-drought conditions, VPM accurately estimated seasonal dynamics and interannual variation of GPP of soybean under different management practices. However, some large discrepancies between GPPVPM and GPPEC were observed under drought conditions as the VI did not reflect the corresponding decrease in GPPEC. Diurnal GPPEC dynamics showed a bimodal distribution with a pronounced midday depression at the period of higher water vapor pressure deficit (>1.2 kPa). A modified Wscalar based on LSWI to account for the water stress in VPM helped quantify the reduction in GPP during severe drought and the model's performance improved substantially. In conclusion, this study demonstrates

  13. [Characteristics of terrestrial ecosystem primary productivity in East Asia based on remote sensing and process-based model].

    PubMed

    Zhang, Fang-Min; Ju, Wei-Min; Chen, Jing-Ming; Wang, Shao-Qiang; Yu, Gui-Rui; Han, Shi-Jie

    2012-02-01

    Based on the bi-linearly interpolated meteorological reanalysis data from National Centers for Environmental Prediction, USA and by using the leaf area index data derived from the GIMMS NDVI to run the process-based Boreal Ecosystems Productivity Simulator (BEPS) model, this paper simulated and analyzed the spatiotemporal characteristics of the terrestrial ecosystem gross primary productivity (GPP) and net primary productivity (NPP) in East Asia in 2000-2005. Before regional simulating and calculating, the observation GPP data of different terrestrial ecosystem in 15 experimental stations of AsiaFlux network and the inventory measurements of NPP at 1300 sampling sites were applied to validate the BEPS GPP and NPP. The results showed that BEPS could well simulate the changes in GPP and NPP of different terrestrial ecosystems, with the R2 ranging from 0.86 to 0.99 and the root mean square error (RMSE) from 0.2 to 1.2 g C x m(-2) x d(-1). The simulated values by BEPS could explain 78% of the changes in annual NPP, and the RMSE was 118 g C x m(-2) x a(-1). In 2000-2005, the averaged total GPP and total NPP of the terrestrial ecosystems in East Asia were 21.7 and 10.5 Pg C x a(-1), respectively, and the GPP and NPP exhibited similar spatial and temporal variation patterns. During the six years, the total NPP of the terrestrial ecosystems varied from 10.2 to 10.7 Pg C x a(-1), with a coefficient of variation being 2. 2%. High NPP (above 1000 g C x m(-2) x a(-1)) occurred in the southeast island countries, while low NPP (below 30 g C x m(-2) x a(-1)) occurred in the desert area of Northwest China. The spatial patterns of NPP were mainly attributed to the differences in the climatic variables across East Asia. The NPP per capita also varied greatly among different countries, which was the highest (70217 kg C x a(-1)) in Mongolia, far higher than that (1921 kg C x a(-1)) in China, and the lowest (757 kg C x a(-1)) in India.

  14. Gross primary production responses to warming, elevated CO2 , and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland.

    PubMed

    Ryan, Edmund M; Ogle, Kiona; Peltier, Drew; Walker, Anthony P; de Kauwe, Martin G; Medlyn, Belinda E; Williams, David G; Parton, William; Asao, Shinichi; Guenet, Bertrand; Harper, Anna B; Lu, Xingjie; Luus, Kristina A; Zaehle, Sönke; Shu, Shijie; Werner, Christian; Xia, Jianyang; Pendall, Elise

    2016-12-19

    Determining whether the terrestrial biosphere will be a source or sink of carbon (C) under a future climate of elevated CO2 (eCO2 ) and warming requires accurate quantification of gross primary production (GPP), the largest flux of C in the global C cycle. We evaluated 6 years (2007-2012) of flux-derived GPP data from the Prairie Heating and CO2 Enrichment (PHACE) experiment, situated in a grassland in Wyoming, USA. The GPP data were used to calibrate a light response model whose basic formulation has been successfully used in a variety of ecosystems. The model was extended by modeling maximum photosynthetic rate (Amax ) and light-use efficiency (Q) as functions of soil water, air temperature, vapor pressure deficit, vegetation greenness, and nitrogen at current and antecedent (past) timescales. The model fits the observed GPP well (R(2)  = 0.79), which was confirmed by other model performance checks that compared different variants of the model (e.g. with and without antecedent effects). Stimulation of cumulative 6-year GPP by warming (29%, P = 0.02) and eCO2 (26%, P = 0.07) was primarily driven by enhanced C uptake during spring (129%, P = 0.001) and fall (124%, P = 0.001), respectively, which was consistent across years. Antecedent air temperature (Tairant ) and vapor pressure deficit (VPDant ) effects on Amax (over the past 3-4 days and 1-3 days, respectively) were the most significant predictors of temporal variability in GPP among most treatments. The importance of VPDant suggests that atmospheric drought is important for predicting GPP under current and future climate; we highlight the need for experimental studies to identify the mechanisms underlying such antecedent effects. Finally, posterior estimates of cumulative GPP under control and eCO2 treatments were tested as a benchmark against 12 terrestrial biosphere models (TBMs). The narrow uncertainties of these data-driven GPP estimates suggest that they could be useful semi-independent data

  15. Sun-induced chlorophyll fluorescence and photochemical reflectance index improve remote-sensing gross primary production estimates under varying nutrient availability in a typical Mediterranean savanna ecosystem

    NASA Astrophysics Data System (ADS)

    Perez-Priego, O.; Guan, J.; Rossini, M.; Fava, F.; Wutzler, T.; Moreno, G.; Carvalhais, N.; Carrara, A.; Kolle, O.; Julitta, T.; Schrumpf, M.; Reichstein, M.; Migliavacca, M.

    2015-11-01

    This study investigates the performances of different optical indices to estimate gross primary production (GPP) of herbaceous stratum in a Mediterranean savanna with different nitrogen (N) and phosphorous (P) availability. Sun-induced chlorophyll fluorescence yield computed at 760 nm (Fy760), scaled photochemical reflectance index (sPRI), MERIS terrestrial-chlorophyll index (MTCI) and normalized difference vegetation index (NDVI) were computed from near-surface field spectroscopy measurements collected using high spectral resolution spectrometers covering the visible near-infrared regions. GPP was measured using canopy chambers on the same locations sampled by the spectrometers. We tested whether light-use efficiency (LUE) models driven by remote-sensing quantities (RSMs) can better track changes in GPP caused by nutrient supplies compared to those driven exclusively by meteorological data (MM). Particularly, we compared the performances of different RSM formulations - relying on the use of Fy760 or sPRI as a proxy for LUE and NDVI or MTCI as a fraction of absorbed photosynthetically active radiation (fAPAR) - with those of classical MM. Results showed higher GPP in the N-fertilized experimental plots during the growing period. These differences in GPP disappeared in the drying period when senescence effects masked out potential differences due to plant N content. Consequently, although MTCI was closely related to the mean of plant N content across treatments (r2 = 0.86, p < 0.01), it was poorly related to GPP (r2 = 0.45, p < 0.05). On the contrary sPRI and Fy760 correlated well with GPP during the whole measurement period. Results revealed that the relationship between GPP and Fy760 is not unique across treatments, but it is affected by N availability. Results from a cross-validation analysis showed that MM (AICcv = 127, MEcv = 0.879) outperformed RSM (AICcv =140, MEcv = 0.8737) when soil moisture was used to constrain the seasonal dynamic of LUE. However

  16. Interplay of drought and tropical cyclone activity in SE U.S. gross primary productivity

    NASA Astrophysics Data System (ADS)

    Lowman, Lauren E. L.; Barros, Ana P.

    2016-06-01

    Tropical cyclones (TCs), often associated with massive flooding and landslides in the Southeast U.S. (SE U.S.), provide a significant input of freshwater to the hydrologic system, and their timing and trajectory significantly impact drought severity and persistence. This manuscript investigates the sensitivity of gross primary productivity (GPP) in the SE U.S. to TC activity using the 1-D column implementation of the Duke Coupled Hydrology Model with Vegetation (DCHM-V) including coupled water and energy cycles and a biochemical representation of photosynthesis. Decadal-scale simulations of water, energy, and carbon fluxes were conducted at high temporal (30 min) and spatial (4 km) resolution over the period 2002-2012. At local scales, model results without calibration compare well against AmeriFlux tower data. At regional scales, differences between the DCHM-V estimates and the Moderate Resolution Imaging Spectroradiometer GPP product reflect the spatial organization of soil hydraulic properties and soil moisture dynamics by physiographic region, highlighting the links between the water and carbon cycles. To isolate the contribution of TC precipitation to SE U.S. productivity, control forcing simulations are contrasted with simulations where periods of TC activity in the atmospheric forcing data were replaced with climatology. During wet years, TC activity impacts productivity in 40-50% of the SE U.S. domain and explains a regional GPP increase of 3-5 Mg C/m2 that is 9% of the warm season total. In dry years, 23-34% of the domain exhibits a smaller positive response that corresponds to 4-8% of the seasonal carbon uptake, depending on TC timing and trajectory.

  17. Constraining Ecosystem Gross Primary Production and Transpiration with Measurements of Photosynthetic 13CO2 Discrimination

    NASA Astrophysics Data System (ADS)

    Blonquist, J. M.; Wingate, L.; Ogeé, J.; Bowling, D. R.

    2011-12-01

    The stable carbon isotope composition of atmospheric CO2 (δ13Ca) can provide useful information on water use efficiency (WUE) dynamics of terrestrial ecosystems and potentially constrain models of CO2 and water fluxes at the land surface. This is due to the leaf-level relationship between photosynthetic 13CO2 discrimination (Δ), which influences δ13Ca, and the ratio of leaf intercellular to atmospheric CO2 mole fractions (Ci / Ca), which is related to WUE and is determined by the balance between C assimilation (CO2 demand) and stomatal conductance (CO2 supply). We used branch-scale Δ derived from tunable diode laser absorption spectroscopy measurements collected in a Maritime pine forest to estimate Ci / Ca variations over an entire growing season. We combined Ci / Ca estimates with rates of gross primary production (GPP) derived from eddy covariance (EC) to estimate canopy-scale stomatal conductance (Gs) and transpiration (T). Estimates of T were highly correlated to T estimates derived from sapflow data (y = 1.22x + 0.08; r2 = 0.61; slope P < 0.001) and T predictions from an ecosystem model (MuSICA) (y = 0.88x - 0.05; r2 = 0.64; slope P < 0.001). As an alternative to estimating T, Δ measurements can be used to estimate GPP by combining Ci / Ca estimates with Gs estimates from sapflow data. Estimates of GPP were determined in this fashion and were highly correlated to GPP values derived from EC (y = 0.82 + 0.07; r2 = 0.61; slope P < 0.001) and GPP predictions from MuSICA (y = 1.10 + 0.42; r2 = 0.50; slope P < 0.001). Results demonstrate that the leaf-level relationship between Δ and Ci / Ca can be extended to the canopy-scale and that Δ measurements have utility for partitioning ecosystem-scale CO2 and water fluxes.

  18. Global parameterization and validation of a two-leaf light use efficiency model for predicting gross primary production across FLUXNET sites

    NASA Astrophysics Data System (ADS)

    Zhou, Yanlian; Wu, Xiaocui; Ju, Weimin; Chen, Jing M.; Wang, Shaoqiang; Wang, Huimin; Yuan, Wenping; Andrew Black, T.; Jassal, Rachhpal; Ibrom, Andreas; Han, Shijie; Yan, Junhua; Margolis, Hank; Roupsard, Olivier; Li, Yingnian; Zhao, Fenghua; Kiely, Gerard; Starr, Gregory; Pavelka, Marian; Montagnani, Leonardo; Wohlfahrt, Georg; D'Odorico, Petra; Cook, David; Arain, M. Altaf; Bonal, Damien; Beringer, Jason; Blanken, Peter D.; Loubet, Benjamin; Leclerc, Monique Y.; Matteucci, Giorgio; Nagy, Zoltan; Olejnik, Janusz; Paw U, Kyaw Tha; Varlagin, Andrej

    2016-04-01

    Light use efficiency (LUE) models are widely used to simulate gross primary production (GPP). However, the treatment of the plant canopy as a big leaf by these models can introduce large uncertainties in simulated GPP. Recently, a two-leaf light use efficiency (TL-LUE) model was developed to simulate GPP separately for sunlit and shaded leaves and has been shown to outperform the big-leaf MOD17 model at six FLUX sites in China. In this study we investigated the performance of the TL-LUE model for a wider range of biomes. For this we optimized the parameters and tested the TL-LUE model using data from 98 FLUXNET sites which are distributed across the globe. The results showed that the TL-LUE model performed in general better than the MOD17 model in simulating 8 day GPP. Optimized maximum light use efficiency of shaded leaves (ɛmsh) was 2.63 to 4.59 times that of sunlit leaves (ɛmsu). Generally, the relationships of ɛmsh and ɛmsu with ɛmax were well described by linear equations, indicating the existence of general patterns across biomes. GPP simulated by the TL-LUE model was much less sensitive to biases in the photosynthetically active radiation (PAR) input than the MOD17 model. The results of this study suggest that the proposed TL-LUE model has the potential for simulating regional and global GPP of terrestrial ecosystems, and it is more robust with regard to usual biases in input data than existing approaches which neglect the bimodal within-canopy distribution of PAR.

  19. Global parameterization and validation of a two-leaf light use efficiency model for predicting gross primary production across FLUXNET sites: TL-LUE Parameterization and Validation

    SciTech Connect

    Zhou, Yanlian; Wu, Xiaocui; Ju, Weimin; Chen, Jing M.; Wang, Shaoqiang; Wang, Huimin; Yuan, Wenping; Andrew Black, T.; Jassal, Rachhpal; Ibrom, Andreas; Han, Shijie; Yan, Junhua; Margolis, Hank; Roupsard, Olivier; Li, Yingnian; Zhao, Fenghua; Kiely, Gerard; Starr, Gregory; Pavelka, Marian; Montagnani, Leonardo; Wohlfahrt, Georg; D'Odorico, Petra; Cook, David; Arain, M. Altaf; Bonal, Damien; Beringer, Jason; Blanken, Peter D.; Loubet, Benjamin; Leclerc, Monique Y.; Matteucci, Giorgio; Nagy, Zoltan; Olejnik, Janusz; Paw U, Kyaw Tha; Varlagin, Andrej

    2016-04-06

    Light use efficiency (LUE) models are widely used to simulate gross primary production (GPP). However, the treatment of the plant canopy as a big leaf by these models can introduce large uncertainties in simulated GPP. Recently, a two-leaf light use efficiency (TL-LUE) model was developed to simulate GPP separately for sunlit and shaded leaves and has been shown to outperform the big-leaf MOD17 model at 6 FLUX sites in China. In this study we investigated the performance of the TL-LUE model for a wider range of biomes. For this we optimized the parameters and tested the TL-LUE model using data from 98 FLUXNET sites which are distributed across the globe. The results showed that the TL-LUE model performed in general better than the MOD17 model in simulating 8-day GPP. Optimized maximum light use efficiency of shaded leaves (εmsh) was 2.63 to 4.59 times that of sunlit leaves (εmsu). Generally, the relationships of εmsh and εmsu with εmax were well described by linear equations, indicating the existence of general patterns across biomes. GPP simulated by the TL-LUE model was much less sensitive to biases in the photosynthetically active radiation (PAR) input than the MOD17 model. The results of this study suggest that the proposed TL-LUE model has the potential for simulating regional and global GPP of terrestrial ecosystems and it is more robust with regard to usual biases in input data than existing approaches which neglect the bi-modal within-canopy distribution of PAR.

  20. Model-based analysis of environmental controls over ecosystem primary production in an alpine tundra dry meadow

    DOE PAGES

    Fan, Zhaosheng; Neff, Jason C.; Wieder, William R.

    2016-02-10

    We investigated several key limiting factors that control alpine tundra productivity by developing an ecosystem biogeochemistry model. The model simulates the coupled cycling of carbon (C), nitrogen (N), and phosphorus (P) and their interactions with gross primary production (GPP). It was parameterized with field observations from an alpine dry meadow ecosystem using a global optimization strategy to estimate the unknown parameters. The model, along with the estimated parameters, was first validated against independent data and then used to examine the environmental controls over plant productivity. Our results show that air temperature is the strongest limiting factor to GPP in themore » early growing season, N availability becomes important during the middle portion of the growing season, and soil moisture is the strongest limiting factors by late in the growing season. Overall, the controls over GPP during the growing season, from strongest to weakest, are soil moisture content, air temperature, N availability, and P availability. This simulation provides testable predictions of the shifting nature of physical and nutrient limitations on plant growth. The model also indicates that changing environmental conditions in the alpine will likely lead to changes in productivity. For example, warming eliminates the control of P availability on GPP and makes N availability surpass air temperature to become the second strongest limiting factor. In contrast, an increase in atmospheric nutrient deposition eliminates the control of N availability and enhances the importance of P availability. Furthermore, these analyses provide a quantitative and conceptual framework that can be used to test predictions and refine ecological analyses at this long-term ecological research site.« less

  1. Model-based analysis of environmental controls over ecosystem primary production in an alpine tundra dry meadow

    SciTech Connect

    Fan, Zhaosheng; Neff, Jason C.; Wieder, William R.

    2016-02-10

    We investigated several key limiting factors that control alpine tundra productivity by developing an ecosystem biogeochemistry model. The model simulates the coupled cycling of carbon (C), nitrogen (N), and phosphorus (P) and their interactions with gross primary production (GPP). It was parameterized with field observations from an alpine dry meadow ecosystem using a global optimization strategy to estimate the unknown parameters. The model, along with the estimated parameters, was first validated against independent data and then used to examine the environmental controls over plant productivity. Our results show that air temperature is the strongest limiting factor to GPP in the early growing season, N availability becomes important during the middle portion of the growing season, and soil moisture is the strongest limiting factors by late in the growing season. Overall, the controls over GPP during the growing season, from strongest to weakest, are soil moisture content, air temperature, N availability, and P availability. This simulation provides testable predictions of the shifting nature of physical and nutrient limitations on plant growth. The model also indicates that changing environmental conditions in the alpine will likely lead to changes in productivity. For example, warming eliminates the control of P availability on GPP and makes N availability surpass air temperature to become the second strongest limiting factor. In contrast, an increase in atmospheric nutrient deposition eliminates the control of N availability and enhances the importance of P availability. Furthermore, these analyses provide a quantitative and conceptual framework that can be used to test predictions and refine ecological analyses at this long-term ecological research site.

  2. Detecting robust signals of interannual variability of gross primary productivity in Asia from multiple terrestrial carbon cycle models and long-term satellite-based vegetation data

    NASA Astrophysics Data System (ADS)

    Ichii, K.; Kondo, M.; Ueyama, M.; Kato, T.; Ito, A.; Sasai, T.; Sato, H.; Kobayashi, H.; Saigusa, N.

    2014-12-01

    Long term record of satellite-based terrestrial vegetation are important to evaluate terrestrial carbon cycle models. In this study, we demonstrate how multiple satellite observation can be used for evaluating past changes in gross primary productivity (GPP) and detecting robust anomalies in terrestrial carbon cycle in Asia through our model-data synthesis analysis, Asia-MIP. We focused on the two different temporal coverages: long-term (30 years; 1982-2011) and decadal (10 years; 2001-2011; data intensive period) scales. We used a NOAA/AVHRR NDVI record for long-term analysis and multiple satellite data and products (e.g. Terra-MODIS, SPOT-VEGETATION) as historical satellite data, and multiple terrestrial carbon cycle models (e.g. BEAMS, Biome-BGC, ORCHIDEE, SEIB-DGVM, and VISIT). As a results of long-term (30 years) trend analysis, satellite-based time-series data showed that approximately 40% of the area has experienced a significant increase in the NDVI, while only a few areas have experienced a significant decreasing trend over the last 30 years. The increases in the NDVI were dominant in the sub-continental regions of Siberia, East Asia, and India. Simulations using the terrestrial biosphere models also showed significant increases in GPP, similar to the results for the NDVI, in boreal and temperate regions. A modeled sensitivity analysis showed that the increases in GPP are explained by increased temperature and precipitation in Siberia. Precipitation, solar radiation, CO2fertilization and land cover changes are important factors in the tropical regions. However, the relative contributions of each factor to GPP changes are different among the models. Year-to-year variations of terrestrial GPP were overall consistently captured by the satellite data and terrestrial carbon cycle models if the anomalies are large (e.g. 2003 summer GPP anomalies in East Asia and 2002 spring GPP anomalies in mid to high latitudes). The behind mechanisms can be consistently

  3. Analysis of light use efficiency and gross primary productivity based on remote sensing data over a phragmites-dominated wetland in Zhangye, China

    NASA Astrophysics Data System (ADS)

    Jiang, Guoqing; Sun, Rui; Zhang, Lei; Liu, Shaomin; Xu, Ziwei; Qiao, Chen

    2014-11-01

    Light use efficiency (LUE) is a critical parameter for estimating carbon exchange in many ecosystem models, especially those models based on remote sensing algorithms. Estimation and monitoring of LUE and gross primary productivity (GPP) over wetland is very important for the global carbon cycle research and modelling, since the wetland plays a vital role in the ecosystem balance. In this paper, carbon flux data observed with an eddy covariance tower over a reedsdominated wetland in Zhangye, northwest of China, was used to calculate LUE. Through the postprocessing of carbon flux data and estimation of ecosystem respiration, daily GPP was calculated firstly. Combining with fraction of absorbed photosynthetically active radiation (FPAR) inversed from HJ-1 satellite, LUE was determined. The maximum value of LUE was 1.03 g C·MJ-1 occurred in summer. Furthermore, a regional vegetation productivity model based on meteorological data and remote sensing data was used to estimate the wetland GPP. The results show that the modeled GPP results were consistent with in situ data.

  4. An Essential Role for (p)ppGpp in the Integration of Stress Tolerance, Peptide Signaling, and Competence Development in Streptococcus mutans

    PubMed Central

    Kaspar, Justin; Kim, Jeong N.; Ahn, Sang-Joon; Burne, Robert A.

    2016-01-01

    The microbes that inhabit the human oral cavity are subjected to constant fluctuations in their environment. To overcome these challenges and gain a competitive advantage, oral streptococci employ numerous adaptive strategies, many of which appear to be intertwined with the development of genetic competence. Here, we demonstrate that the regulatory circuits that control development of competence in Streptococcus mutans, a primary etiological agent of human dental caries, are integrated with key stress tolerance pathways by the molecular alarmone (p)ppGpp. We first observed that the growth of a strain that does not produce (p)ppGpp (ΔrelAPQ, (p)ppGpp0) is not sensitive to growth inhibition by comX inducing peptide (XIP), unlike the wild-type strain UA159, even though XIP-dependent activation of the alternative sigma factor comX by the ComRS pathway is not impaired in the (p)ppGpp0 strain. Overexpression of a (p)ppGpp synthase gene (relP) in the (p)ppGpp0 mutant restored growth inhibition by XIP. We also demonstrate that exposure to micromolar concentrations of XIP elicited changes in (p)ppGpp accumulation in UA159. Loss of the RelA/SpoT homolog (RSH) enzyme, RelA, lead to higher basal levels of (p)ppGpp accumulation, but to decreased sensitivity to XIP and to decreases in comR promoter activity and ComX protein levels. By introducing single amino acid substitutions into the RelA enzyme, the hydrolase activity of the enzyme was shown to be crucial for full com gene induction and transformation by XIP. Finally, loss of relA resulted in phenotypic changes to ΔrcrR mutants, highlighted by restoration of transformation and ComX protein production in the otherwise non-transformable ΔrcrR-NP mutant. Thus, RelA activity and its influence on (p)ppGpp pools appears to modulate competence signaling and development through RcrRPQ and the peptide effectors encoded within rcrQ. Collectively, this study provides new insights into the molecular mechanisms that integrate

  5. Integrating fAPARchl and PRInadir from EO-1/Hyperion to predict cornfield daily gross primary production (GPP)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurate estimates of terrestrial carbon sequestration is essential for evaluating changes in the carbon cycle due to global climate change. In a recent assessment of 26 carbon assimilation models at 39 FLUXNET tower sites across the United States and Canada, all models failed to adequately compute...

  6. Marginal Lands Gross Primary Production Dominate Atmospheric CO2 Interannual Variations

    NASA Astrophysics Data System (ADS)

    Ahlström, A.; Raupach, M. R.; Schurgers, G.; Arneth, A.; Jung, M.; Reichstein, M.; Smith, B.

    2014-12-01

    Since the 1960s terrestrial ecosystems have acted as a substantial sink for atmospheric CO2, sequestering about one quarter of anthropogenic emissions in an average year. Variations in this land carbon sink are also responsible for most of the large interannual variability in atmospheric CO2 concentrations. While most evidence places the majority of the sink in highly productive forests and at high latitudes experiencing warmer and longer growing seasons, the location and the processes governing the interannual variations are still not well characterised. Here we evaluate the hypothesis that the long-term trend and the variability in the land CO2 sink are respectively dominated by geographically distinct regions: the sink by highly productive lands, mainly forests, and the variability by semi-arid or "marginal" lands where vegetation activity is strongly limited by water and therefore responds strongly to climate variability. Using novel analysis methods and data from both upscaled flux-tower measurements and a dynamic global vegetation model, we show that (1) the interannual variability in the terrestrial CO2 sink arises mainly from variability in terrestrial gross primary production (GPP); (2) most of the interannual variability in GPP arises in tropical and subtropical marginal lands, where negative anomalies are driven mainly by warm, dry conditions and positive anomalies by cool, wet conditions; (3) the variability in the GPP of high-latitude marginal lands (tundra and shrublands) is instead controlled by temperature and light, with warm bright conditions resulting in positive anomalies. The influence of ENSO (El Niño-Southern Oscillation) on the growth rate of atmospheric CO2 concentrations is mediated primarily through climatic effects on GPP in marginal lands, with opposite signs in subtropical and higher-latitude regions. Our results show that the land sink of CO2 (dominated by forests) and its interannual variability (dominated by marginal lands) are

  7. GPP user`s guide - a general-purpose postprocessor for wind turbine data analysis

    SciTech Connect

    Buhl, Jr, M L

    1995-01-01

    GPP (pronounced {open_quotes}jeep{close_quotes}) is a General-Purpose Postprocessor for wind turbine data analysis. The author, a member of the Wind Technology Division (WTD) of the National Renewable Energy Laboratory (NREL), developed GPP to postprocess test data and simulation predictions. GPP reads data into large arrays and allows the user to run many types of analyses on the data stored in memory. It runs on inexpensive computers common in the wind industry. One can even use it on a laptop in the field. The author wrote the program in such a way as to make it easy to add new types of analyses and to port it to many types of computers. Although GPP is very powerful and feature-rich, it is still very easy to learn and to use. Exhaustive error trapping prevents one from losing valuable work due to input errors. GPP will, hopefully, make a significant impact on engineering productivity in the wind industry.

  8. Gross primary production controls the subsequent winter CO2 exchange in a boreal peatland.

    PubMed

    Zhao, Junbin; Peichl, Matthias; Öquist, Mats; Nilsson, Mats B

    2016-12-01

    In high-latitude regions, carbon dioxide (CO2 ) emissions during the winter represent an important component of the annual ecosystem carbon budget; however, the mechanisms that control the winter CO2 emissions are currently not well understood. It has been suggested that substrate availability from soil labile carbon pools is a main driver of winter CO2 emissions. In ecosystems that are dominated by annual herbaceous plants, much of the biomass produced during the summer is likely to contribute to the soil labile carbon pool through litter fall and root senescence in the autumn. Thus, the summer carbon uptake in the ecosystem may have a significant influence on the subsequent winter CO2 emissions. To test this hypothesis, we conducted a plot-scale shading experiment in a boreal peatland to reduce the gross primary production (GPP) during the growing season. At the growing season peak, vascular plant biomass in the shaded plots was half that in the control plots. During the subsequent winter, the mean CO2 emission rates were 21% lower in the shaded plots than in the control plots. In addition, long-term (2001-2012) eddy covariance data from the same site showed a strong correlation between the GPP (particularly the late summer and autumn GPP) and the subsequent winter net ecosystem CO2 exchange (NEE). In contrast, abiotic factors during the winter could not explain the interannual variation in the cumulative winter NEE. Our study demonstrates the presence of a cross-seasonal link between the growing season biotic processes and winter CO2 emissions, which has important implications for predicting winter CO2 emission dynamics in response to future climate change.

  9. Many Means to a Common End: the Intricacies of (p)ppGpp Metabolism and Its Control of Bacterial Homeostasis

    PubMed Central

    Gaca, Anthony O.; Colomer-Winter, Cristina

    2015-01-01

    In nearly all bacterial species examined so far, amino acid starvation triggers the rapid accumulation of the nucleotide second messenger (p)ppGpp, the effector of the stringent response. While for years the enzymes involved in (p)ppGpp metabolism and the significance of (p)ppGpp accumulation to stress survival were considered well defined, a recent surge of interest in the field has uncovered an unanticipated level of diversity in how bacteria metabolize and utilize (p)ppGpp to rapidly synchronize a variety of biological processes important for growth and stress survival. In addition to the classic activation of the stringent response, it has become evident that (p)ppGpp exerts differential effects on cell physiology in an incremental manner rather than simply acting as a biphasic switch that controls growth or stasis. Of particular interest is the intimate relationship of (p)ppGpp with persister cell formation and virulence, which has spurred the pursuit of (p)ppGpp inhibitors as a means to control recalcitrant infections. Here, we present an overview of the enzymes responsible for (p)ppGpp metabolism, elaborate on the intricacies that link basal production of (p)ppGpp to bacterial homeostasis, and discuss the implications of targeting (p)ppGpp synthesis as a means to disrupt long-term bacterial survival strategies. PMID:25605304

  10. Plant invasion impacts on the gross and net primary production of the salt marsh on eastern coast of China: Insights from leaf to ecosystem

    NASA Astrophysics Data System (ADS)

    Ge, Zhen-Ming; Guo, Hai-Qiang; Zhao, Bin; Zhang, Li-Quan

    2015-01-01

    exotic Spartina alterniflora from North America has been rapidly invading the entire Chinese coast, while the impacts of plant invasion on the gross (GPP) and net primary production (NPP) of the coastal salt marshes were less known. In this study, we investigated the photosynthetic performance, leaf characteristics, and primary production of the exotic C4 grass and the dominant native C3 grass (Phragmites australis) in two marsh mixtures (equipped with eddy covariance systems) in the Yangtze Estuary. The light-saturated photosynthetic rate and annual peak leaf area index (LAI) of S. alterniflora was higher than that of P. australis throughout the growing season. The leaf nitrogen content of P. australis declined sharper during the latter growing season than that of S. alterniflora. The leaf-to-canopy production model with species-specific (C3 and C4 types) parameterizations could reasonably simulate the daily trends and annual GPP amount against the 3 year flux measurements from 2005 to 2007, and the modeled NPP agreed with biomass measurements from the two species during 2012. The percentage contributions of GPP between S. alterniflora and P. australis were on average 5.82:1 and 2.91:1 in the two mixtures, respectively. The annual NPP amounts from S. alterniflora were higher by approximately 1.6 times than that from P. australis. Our results suggested that higher photosynthesis efficiency, higher LAI, and longer growing season resulted in greater GPP and NPP in the exotic species relative to the native species. The rapid expansion rate of S. alterniflora further made it the leading contributor of primary production in the salt marsh.

  11. Impact of Chromophoric Dissolved Organic Matter on UV Inhibition of Primary Productivity in the Sea

    NASA Technical Reports Server (NTRS)

    Arrigo, Kevin R.; Brown, Christopher W.

    1996-01-01

    A model was developed to assess the impact of chromophoric dissolved organic matter (CDOM) on phytoplankton production within the euphotic zone. The rate of depth-integrated daily gross primary productivity within the euphotic zone was evaluated as a function of date, latitude, CDONI absorption characteristics, chlorophyll a (chl a) concentration, vertical stratification, and phytoplankton sensitivity to UV radiation (UVR). Results demonstrated that primary production was enhanced in the upper 30 m of the water column by the presence of CDOM, where predicted increases in production due to the removal of damaging UVR more than offset its reduction resulting from the absorption of photosynthetically usable radiation. At greater depths, where little UVR remained, primary production was always reduced due to removal by CDOM of photosynthetically usable radiation. When CDOM was distributed homogeneously within the euphotic zone, the integral over z [(GPP)(sub ez)], was reduced under most bio-optical (i.e. solar zenith angle, and CDOM absorption, and ozone concentration) and photophysiological production at depth was greater than the enhancement of production at the surface.

  12. Gross primary production dynamics assessment of a mediterranean holm oak forest by remote sensing time series analysis

    NASA Astrophysics Data System (ADS)

    Cicuéndez, Víctor; Huesca, Margarita; Rodriguez-Rastrero, Manuel; Litago, Javier; Recuero, Laura; Merino de Miguel, Silvia; Palacios Orueta, Alicia

    2014-05-01

    Agroforestry ecosystems have a significant social, economic and environmental impact on the development of many regions of the world. In the Iberian Peninsula the agroforestry oak forest called "Dehesa" or "Montado" is considered as the extreme case of transformation of a Mediterranean forest by the management of human to provide a wide range of natural resources. The high variability of the Mediterranean climate and the different extensive management practices which human realized on the Dehesa result in a high spatial and temporal dynamics of the ecosystem. This leads to a complex pattern in CO2 exchange between the atmosphere and the ecosystem, i.e. in ecosystem's production. Thus, it is essential to assess Dehesa's carbon cycle to reach maximum economic benefits ensuring environmental sustainability. In this sense, the availability of high frequency Remote Sensing (RS) time series allows the assessment of ecosystem evolution at different temporal and spatial scales. Extensive research has been conducted to estimate production from RS data in different ecosystems. However, there are few studies on the Dehesa type ecosystems, probably due to their complexity in terms of spatial arrangement and temporal dynamics. In this study our overall objective is to assess the Gross Primary Production (GPP) dynamics of a Dehesa ecosystem situated in Central Spain by analyzing time series (2004-2008) of two models: (1) GPP provided by Remote Sensing Images of sensor MODIS (MOD17A2 product) and (2) GPP estimated by the implementation of a Site Specific Light Use Efficiency model based as MODIS model on Monteith equation (1972), but taking into account local ecological and meteorological parameters. Both models have been compared with the Production provided by an Eddy Covariance (EC) flux Tower that is located in our study area. In addition, dynamic relationships between models of GPP with Precipitation and Soil Water Content have been investigated by means of cross

  13. Sun-induced Chlorophyll fluorescence and PRI improve remote sensing GPP estimates under varying nutrient availability in a typical Mediterranean savanna ecosystem

    NASA Astrophysics Data System (ADS)

    Perez-Priego, O.; Guan, J.; Rossini, M.; Fava, F.; Wutzler, T.; Moreno, G.; Carvalhais, N.; Carrara, A.; Kolle, O.; Julitta, T.; Schrumpf, M.; Reichstein, M.; Migliavacca, M.

    2015-07-01

    This study investigates the performances of different optical indices to estimate gross primary production (GPP) of herbaceous stratum in a Mediterranean savanna with different Nitrogen (N) and Phosphorous (P) availability. Sun-induced chlorophyll Fluorescence yield computed at 760 nm (Fy760), scaled-photochemical reflectance index (sPRI), MERIS terrestrial-chlorophyll index (MTCI) and Normalized difference vegetation index (NDVI) were computed from near-surface field spectroscopy measurements collected using high spectral resolution spectrometers covering the visible near-infrared regions. GPP was measured using canopy-chambers on the same locations sampled by the spectrometers. We hypothesized that light-use efficiency (LUE) models driven by remote sensing quantities (RSM) can better track changes in GPP caused by nutrient supplies compared to those driven exclusively by meteorological data (MM). Particularly, we compared the performances of different RSM formulations - relying on the use of Fy760 or sPRI as proxy for LUE and NDVI or MTCI as fraction of absorbed photosynthetically active radiation (fAPAR) - with those of classical MM. Results showed significantly higher GPP in the N fertilized experimental plots during the growing period. These differences in GPP disappeared in the drying period when senescence effects masked out potential differences due to plant N content. Consequently, although MTCI was tightly related to plant N content (r2 = 0.86, p < 0.01), it was poorly related to GPP (r2 = 0.45, p < 0.05). On the contrary sPRI and Fy760 correlated well with GPP during the whole measurement period. Results revealed that the relationship between GPP and Fy760 is not unique across treatments but it is affected by N availability. Results from a cross validation analysis showed that MM (AICcv = 127, MEcv = 0.879) outperformed RSM (AICcv = 140, MEcv = 0.8737) when soil moisture was used to constrain the seasonal dynamic of LUE. However, residual analyses

  14. Observing and modeling dynamics in terrestrial gross primary productivity and phenology from remote sensing: An assessment using in-situ measurements

    NASA Astrophysics Data System (ADS)

    Verma, Manish K.

    Terrestrial gross primary productivity (GPP) is the largest and most variable component of the carbon cycle and is strongly influenced by phenology. Realistic characterization of spatio-temporal variation in GPP and phenology is therefore crucial for understanding dynamics in the global carbon cycle. In the last two decades, remote sensing has become a widely-used tool for this purpose. However, no study has comprehensively examined how well remote sensing models capture spatiotemporal patterns in GPP, and validation of remote sensing-based phenology models is limited. Using in-situ data from 144 eddy covariance towers located in all major biomes, I assessed the ability of 10 remote sensing-based methods to capture spatio-temporal variation in GPP at annual and seasonal scales. The models are based on different hypotheses regarding ecophysiological controls on GPP and span a range of structural and computational complexity. The results lead to four main conclusions: (i) at annual time scale, models were more successful capturing spatial variability than temporal variability; (ii) at seasonal scale, models were more successful in capturing average seasonal variability than interannual variability; (iii) simpler models performed as well or better than complex models; and (iv) models that were best at explaining seasonal variability in GPP were different from those that were best able to explain variability in annual scale GPP. Seasonal phenology of vegetation follows bounded growth and decay, and is widely modeled using growth functions. However, the specific form of the growth function affects how phenological dynamics are represented in ecosystem and remote sensing-base models. To examine this, four different growth functions (the logistic, Gompertz, Mirror-Gompertz and Richards function) were assessed using remotely sensed and in-situ data collected at several deciduous forest sites. All of the growth functions provided good statistical representation of in

  15. Effects of in-situ and reanalysis climate data on estimation of cropland gross primary production using the Vegetation Photosynthesis Model

    SciTech Connect

    Jin, Cui; Xiao, Xiangming; Wagle, Pradeep; Griffis, Timothy; Dong, Jinwei; Wu, Chaoyang; Qin, Yuanwei; Cook, David R.

    2015-11-01

    Satellite-based Production Efficiency Models (PEMs) often require meteorological reanalysis data such as the North America Regional Reanalysis (NARR) by the National Centers for Environmental Prediction (NCEP) as model inputs to simulate Gross Primary Production (GPP) at regional and global scales. This study first evaluated the accuracies of air temperature (TNARR) and downward shortwave radiation (RNARR) of the NARR by comparing with in-situ meteorological measurements at 37 AmeriFlux non-crop eddy flux sites, then used one PEM – the Vegetation Photosynthesis Model (VPM) to simulate 8-day mean GPP (GPPVPM) at seven AmeriFlux crop sites, and investigated the uncertainties in GPPVPM from climate inputs as compared with eddy covariance-based GPP (GPPEC). Results showed that TNARR agreed well with in-situ measurements; RNARR, however, was positively biased. An empirical linear correction was applied to RNARR, and significantly reduced the relative error of RNARR by ~25% for crop site-years. Overall, GPPVPM calculated from the in-situ (GPPVPM(EC)), original (GPPVPM(NARR)) and adjusted NARR (GPPVPM(adjNARR)) climate data tracked the seasonality of GPPEC well, albeit with different degrees of biases. GPPVPM(EC) showed a good match with GPPEC for maize (Zea mays L.), but was slightly underestimated for soybean (Glycine max L.). Replacing the in-situ climate data with the NARR resulted in a significant overestimation of GPPVPM(NARR) (18.4/29.6% for irrigated/rainfed maize and 12.7/12.5% for irrigated/rainfed soybean). GPPVPM(adjNARR) showed a good agreement with GPPVPM(EC) for both crops due to the reduction in the bias of RNARR. The results imply that the bias of RNARR introduced significant uncertainties into the PEM-based GPP estimates, suggesting that more accurate surface radiation datasets are needed to estimate primary production of terrestrial ecosystems at regional and global scales.

  16. Understanding COS Fluxes in a Boreal Forest: Towards COS-Based GPP Estimates.

    NASA Astrophysics Data System (ADS)

    Chen, H.; Kooijmans, L.; Franchin, A.; Keskinen, H.; Levula, J.; Mammarella, I.; Maseyk, K. S.; Pihlatie, M.; Praplan, A. P.; Seibt, U.; Sun, W.; Vesala, T.

    2015-12-01

    Carbonyl Sulfide (COS) is a promising new tracer that can be used to partition the Net Ecosystem Exchange into gross primary production (GPP) and respiration. COS and CO2 vegetation fluxes are closely related as these gases share the same diffusion pathway into stomata, which makes COS a potentially powerful tracer for GPP. While vegetative uptake is the largest sink of COS, the environmental drivers are poorly understood, and soil fluxes represent an important but relatively unconstrained component. Therefore, the realization of the COS tracer method requires proper characterization of both soil and ecosystem fluxes. A campaign to provide better constrained soil and ecosystem COS flux data for boreal forests took place in the summer of 2015 at the SMEAR II site in Hyytiälä, Finland. Eddy covariance flux measurements were made above the forest canopy on an Aerodyne continuous-wave quantum cascade laser (QCL) system that is capable of measuring COS, CO2, CO and H2O. Soil COS fluxes were obtained using modified LI-COR LI-8100 chambers together with high accuracy concentration measurements from another Aerodyne QCL instrument. The same instrument alternately measured concentrations in and above the canopy on a cycle through 4 heights, which will be used to calculate ecosystem fluxes using the Radon-tracer method, providing ecosystem fluxes under low-turbulent conditions. We will compare ecosystem fluxes from both eddy covariance and profile measurements and show estimates of the fraction of ecosystem fluxes attributed to the soil component. With the better understanding of ecosystem and soil COS fluxes, as obtained with this dataset, we will be able to derive COS-based GPP estimates for the Hyytiälä site.

  17. Interpretation of tree-ring data with a model for primary production, carbon allocation and growth

    NASA Astrophysics Data System (ADS)

    Li, G.; Wang, H.; Harrison, S. P.; Prentice, I. C.

    2013-12-01

    We present a simple, generic model of annual tree growth, called ';T'. This model accepts input from a generic light-use efficiency model which is known to provide good simulations of terrestrial carbon exchange. The light-use efficiency model provides values for Gross Primary Production (GPP) per unit of absorbed photosynthetically active radiation (PAR). Absorbed PAR is estimated from the current leaf area. GPP is allocated to foliage, transport-tissue, and fine-root production and respiration, in such a way as to satisfy well-understood dimensional relationships. The result is a model that can represent both ontogenetic effects and the effects of environmental variations and trends on growth. The model has been applied to simulate ring-width series from multiple individual trees in temperature- and drought-limited contexts. Each tree is initialized at its actual diameter at the time when local climate records started. These records are used to drive the trees' subsequent growth. Realistic simulations of the pattern of interannual variability of ring-width are generated, and shown to relate statistically to climate. An upward trend in ring-width during 1958-2007 is shown to be present in the primary observations, and in the simulations; but not in the standard, detrended ring-width series. This approach combines two modelling approaches previously developed in the global carbon cycle and forest science literature respectively. Neither has been widely applied in the context of tree-ring based climate reconstruction. This combination of methods offers promise, however, because it could provide a way to sidestep several known problems. These include: reliance on correlations for the interpretation of ring-width variations in terms of climate; the necessity of detrending using empirical functions (which can remove trends caused by variations in the environment as well as those that are ontogenetic); and the difficulty of assessing effects of extrinsic, non

  18. New global observations of the terrestrial carbon cycle from GOSAT: Patterns of vegetation fluorescence with gross primary productivity

    NASA Astrophysics Data System (ADS)

    Frankenberg, C.; Fisher, J. B.; Lee, J.; Guanter, L.; Van der Tol, C.; Toon, G. C.; kuze, A.; Yokota, T.; Badgley, G. M.; Butz, A.; Jung, M.; Saatchi, S. S.; Worden, J.

    2011-12-01

    Our ability to close the Earth's carbon budget and predict feedbacks in a warming climate depends critically on knowing where, when and how carbon dioxide is exchanged between the land and atmosphere. Terrestrial gross primary production (GPP) constitutes the largest flux component in the global carbon budget, however significant uncertainties remain in GPP estimates and its seasonality. Solar-induced chlorophyll fluorescence is a powerful proxy for assessing biomass photosynthetic activity since photosynthesis and fluorescence are directly coupled processes. This gives rise to re-emission of light between approximately 670 and 780 nm. Passive methods to quantify the fluorescence signal are mainly based on the filling-in of highly saturated O2 absorption structures. This method, however, was mostly applied in field-based measurements and is not directly applicable to space-borne retrievals. We show that variability of aerosols in the atmosphere load and surface pressure cannot be unequivocally disentangled from fluorescence since all these factor impact the absorption depths of O2 lines. This gives rise to biases in the retrieved scattering properties in typical multi-spectral XCO2 retrievals when using the O2 A band but not when focussing solely of solar Fraunhofer lines. We will a) present our retrieval method based on an iterative, non-linear least-squares fitting of Fraunhofer lines, b) discuss the potential impact on XCO2 retrievals and c) show recent fluorescence results from more than one year of GOSAT data. Empirically, we show that global spaceborne observations of solar induced chlorophyll fluorescence exhibit a strong linear correlation with GPP. We found that the fluorescence emission even without any additional meteorological, vegetation type or model information has the same or better predictive skill in estimating GPP as those derived from traditional remotely-sensed vegetation indices using ancillary data and model assumptions. Our results

  19. How tropical cyclone inter-annual timing and trajectory control gross primary productivity in the SE US at seasonal and annual timescales and impacts on mountain forest eco-hydrology

    NASA Astrophysics Data System (ADS)

    Lowman, L.; Barros, A.

    2015-12-01

    Tropical cyclones (TCs) are an important source of freshwater input to the SE US eco-hydrologic function. Soil moisture, a temporal integral of precipitation, is critical to plant photosynthesis and carbon assimilation. In this study, we investigate the impact TCs have on gross primary productivity (GPP) in the SE US using the physically-based Duke Coupled Hydrology Model with Vegetation (DCHM-V) which includes coupled water and energy cycles and a biochemical representation of photosynthesis. A parsimonious evaluation of model-estimated GPP against all available AmeriFlux data in the SE US is presented. We characterize the seasonality of vegetation activity in the SE US by simulating water, energy, and carbon fluxes using the DCHM-V at high spatial (4 km) and temporal (30-min) resolution over the period 2002 - 2012. The model is run offline using atmospheric forcing data from NLDAS-2, precipitation from StageIV, and phenology indices from MODIS FPAR/LAI. Analysis of model results show the tendency for low GPP to occur in the Appalachian Mountains during peak summer months when water stress limits stomatal function. We contrast these simulations with model runs where periods of TC activity are replaced with the monthly climatological diurnal cycle from NARR. Results show that the timing and trajectory of TCs are key to understanding their impact on GPP across the SE US. Specifically: 1) Timing of moisture input from TCs greatly influences the vegetation response. TCs during peak summer months increase GPP and years with TCs falling in peak summer months see much higher annual GPP averages; 2) Years of drought and low plant productivity (2006-2007, 2011-2012) in the SE US tend to have TCs that fall later in the year when the additional moisture input does not have a significant impact on vegetation activity; and 3) TC path impacts regional GPP averages. The mountain region shows large inter- and intra-annual variability in plant productivity and high sensitivity to

  20. Daily GPP estimates in Mediterranean ecosystems by combining remote sensing and meteorological data

    NASA Astrophysics Data System (ADS)

    Gilabert, M. A.; Moreno, A.; Maselli, F.; Martínez, B.; Chiesi, M.; Sánchez-Ruiz, S.; García-Haro, F. J.; Pérez-Hoyos, A.; Campos-Taberner, M.; Pérez-Priego, O.; Serrano-Ortiz, P.; Carrara, A.

    2015-04-01

    The accurate representation of terrestrial CO2 uptake (GPP) using Monteith's approach requires a frequent and site-specific parameterization of the model inputs. In this work, an optimization of this approach has been carried out by adjusting the inputs (fAPAR, PAR and ε) for the study area, peninsular Spain, a typical Mediterranean region. The daily GPP images have been calculated for 2008 and 2011 with a 1-km spatial resolution and validated by comparison with in situ GPP estimates from the eddy covariance data (direct validation) and by inter-comparison with the MODIS GPP product. The direct validation has evidenced an excellent agreement with correlations up to 0.98 in 2008 and 0.92 in 2011 in some sites. The inter-comparison has shown that the two GPP products are consistent temporally. However, a slightly decrease of the correlation has been observed in some areas. The validation has also shown that our optimized GPP product accounts better for the water stress than the MODIS product. The analysis of the explanatory power of the model in terms of its inputs shows, as expected, that PAR and fAPAR are the most relevant inputs. The fAPAR plays a major role on GPP estimation when the vegetation phenology maximum is not reached during solar solstice. Finally, it has been shown that the influence of the water stress, associated with the water shortage typical of Mediterranean landscapes, has to be evaluated accurately in order to explain the GPP inter-annual variability.

  1. The bacterial alarmone (p)ppGpp is required for virulence and controls cell size and survival of Pseudomonas syringae on plants

    PubMed Central

    Chatnaparat, Tiyakhon; Li, Zhong; Korban, Schuyler S.; Zhao, Youfu

    2016-01-01

    Summary The stringent response, mediated by second messenger (p)ppGpp, results in swift and massive transcriptional reprogramming under nutrient limited conditions. In this study, the role of (p)ppGpp on virulence of P. syringae pv. syringae B728a (PssB728a) was investigated. The virulence of the relA/spoT (ppGpp0) double mutant was completely impaired on bean, and bacterial growth was significantly reduced, suggesting that (p)ppGpp is required for full virulence of P. syringae. Expression of T3SS and other virulence genes was reduced in ppGpp0 mutants. In addition, ppGpp deficiency resulted in loss of swarming motility, reduction of pyoverdine production, increased sensitivity to oxidative stress and antibiotic tolerance, as well as reduced ability to utilize γ-amino butyric acid. Increased levels of ppGpp resulted in reduced cell size of PssB728a when grown in a minimal medium and on plant surfaces, while most ppGpp0 mutant cells were not viable on plant surfaces 24 h after spray inoculation, suggesting that ppGpp-mediated stringent response temporarily limits cell growth, and might control cell survival on plants by limiting their growth. These results demonstrated that ppGpp-mediated stringent response plays a central role in P. syringae virulence and survival, and indicated that ppGpp serves as a global signal for regulating various virulence traits in PssB728a. PMID:25626964

  2. Patterns of NPP, GPP, respiration, and NEP during boreal forest succession

    USGS Publications Warehouse

    Goulden, M.L.; Mcmillan, A.M.S.; Winston, G.C.; Rocha, A.V.; Manies, K.L.; Harden, J.W.; Bond-Lamberty, B. P.

    2011-01-01

    We combined year-round eddy covariance with biometry and biomass harvests along a chronosequence of boreal forest stands that were 1, 6, 15, 23, 40, 74, and 154 years old to understand how ecosystem production and carbon stocks change during recovery from stand-replacing crown fire. Live biomass (Clive) was low in the 1 and 6 year old stands, and increased following a logistic pattern to high levels in the 74 and 154year old stands. Carbon stocks in the forest floor (Cforest floor) and coarse woody debris (CCWD) were comparatively high in the 1year old stand, reduced in the 6 through 40year old stands, and highest in the 74 and 154year old stands. Total net primary production (TNPP) was reduced in the 1 and 6year old stands, highest in the 23 through 74year old stands and somewhat reduced in the 154year old stand. The NPP decline at the 154year old stand was related to increased autotrophic respiration rather than decreased gross primary production (GPP). Net ecosystem production (NEP), calculated by integrated eddy covariance, indicated the 1 and 6 year old stands were losing carbon, the 15year old stand was gaining a small amount of carbon, the 23 and 74year old stands were gaining considerable carbon, and the 40 and 154year old stands were gaining modest amounts of carbon. The recovery from fire was rapid; a linear fit through the NEP observations at the 6 and 15year old stands indicated the transition from carbon source to sink occurred within 11-12 years. The NEP decline at the 154year old stand appears related to increased losses from Clive by tree mortality and possibly from Cforest floor by decomposition. Our findings support the idea that NPP, carbon production efficiency (NPP/GPP), NEP, and carbon storage efficiency (NEP/TNPP) all decrease in old boreal stands. ?? 2010 Blackwell Publishing Ltd.

  3. Variability in primary productivity determines metapopulation dynamics

    PubMed Central

    2016-01-01

    Temporal variability in primary productivity can change habitat quality for consumer species by affecting the energy levels available as food resources. However, it remains unclear how habitat-quality fluctuations may determine the dynamics of spatially structured populations, where the effects of habitat size, quality and isolation have been customarily assessed assuming static habitats. We present the first empirical evaluation on the effects of stochastic fluctuations in primary productivity—a major outcome of ecosystem functions—on the metapopulation dynamics of a primary consumer. A unique 13-year dataset from an herbivore rodent was used to test the hypothesis that inter-annual variations in primary productivity determine spatiotemporal habitat occupancy patterns and colonization and extinction processes. Inter-annual variability in productivity and in the growing season phenology significantly influenced habitat colonization patterns and occupancy dynamics. These effects lead to changes in connectivity to other potentially occupied habitat patches, which then feed back into occupancy dynamics. According to the results, the dynamics of primary productivity accounted for more than 50% of the variation in occupancy probability, depending on patch size and landscape configuration. Evidence connecting primary productivity dynamics and spatiotemporal population processes has broad implications for metapopulation persistence in fluctuating and changing environments. PMID:27053739

  4. Quantification and attribution of errors in the simulated annual gross primary production and latent heat fluxes by two global land surface models

    NASA Astrophysics Data System (ADS)

    Li, Jianduo; Wang, Ying-Ping; Duan, Qingyun; Lu, Xingjie; Pak, Bernard; Wiltshire, Andy; Robertson, Eddy; Ziehn, Tilo

    2016-09-01

    Differences in the predicted carbon and water fluxes by different global land models have been quite large and have not decreased over the last two decades. Quantification and attribution of the uncertainties of global land surface models are important for improving the performance of global land surface models, and are the foci of this study. Here we quantified the model errors by comparing the simulated monthly global gross primary productivity (GPP) and latent heat flux (LE) by two global land surface models with the model-data products of global GPP and LE from 1982 to 2005. By analyzing model parameter sensitivities within their ranges, we identified about 2-11 most sensitive model parameters that have strong influences on the simulated GPP or LE by two global land models, and found that the sensitivities of the same parameters are different among the plant functional types (PFT). Using parameter ensemble simulations, we found that 15%-60% of the model errors were reduced by tuning only a few (<4) most sensitive parameters for most PFTs, and that the reduction in model errors varied spatially within a PFT or among different PFTs. Our study shows that future model improvement should optimize key model parameters, particularly those parameters relating to leaf area index, maximum carboxylation rate, and stomatal conductance.

  5. Primary Production in Antarctic Sea Ice

    NASA Technical Reports Server (NTRS)

    Arrigo, Kevin R.; Worthen, Denise L.; Lizotte, Michael P.; Dixon, Paul; Dieckmann, Gerhard

    1997-01-01

    A numerical model shows that in Antarctic sea ice, increased flooding in regions with thick snow cover enhances primary production in the infiltration (surface) layer. Productivity in the freeboard (sea level) layer is also determined by sea ice porosity, which varies with temperature. Spatial and temporal variation in snow thickness and the proportion of first-year ice thus determine regional differences in sea ice primary production. Model results show that of the 40 tera-grams of carbon produced annually in the Antarctic ice pack, 75 percent was associated with first-year ice and nearly 50 percent was produced in the Weddell Sea.

  6. Green light: gross primary production influences seasonal stream N export by controlling fine-scale N dynamics.

    PubMed

    Lupon, Anna; Martí, Eugènia; Sabater, Francesc; Bernal, Susana

    2016-01-01

    Monitoring nutrient concentrations at fine-scale temporal resolution contributes to a better understanding of nutrient cycling in stream ecosystems. However, the mechanisms underlying fine-scale nutrient dynamics and its implications for budget catchent fluxes are still poorly understood. To gain understanding of patterns and controls of fine-scale stream nitrogen (N) dynamics and to assess how they affect hydrological N fluxes, we explored diel variation in stream nitrate (NO3-) concentration along a headwater stream with increasing riparian area and channel width. At the downstream site, the highest day-night variations occurred in early spring, when stream NO3- concentrations were 13% higher at night than at daytime. Such day-night variations were strongly related to daily light inputs (R2 = 0.74) and gross primary production (GPP; R2 = 0.74), and they showed an excellent fit with day-night NO- variations predicted from GPP (R2 = 0.85). These results suggest that diel fluctuations in stream NO3- concentration were mainly driven by photoautotrophic N uptake. Terrestrial influences were discarded because no simultaneous diel variations in stream discharge, riparian groundwater level, or riparian solute concentration were observed. In contrast to the downstream site, no diel variations in NO3- concentration occurred at the upstream site, likely because water temperature was colder (10 degrees C vs. 12 degrees C) and light availability was lower (4 vs. 9 mol x m(-2) x d(-1)). Although daily GPP was between 10- and 100-fold lower than daily respiration, photoautotrophic N uptake contributed to a 10% reduction in spring NO3- loads at the downstream site. Our study clearly shows that the activity of photoautotrophs can substantially change over time and along the stream continuum in response to key environmental drivers such as light and temperature, and further, that its capacity to regulate diel and seasonal N fluxes can be important even in low-productivity streams.

  7. Influence of New Zealand cockles (Austrovenus stutchburyi) on primary productivity in sandflat-seagrass (Zostera muelleri) ecotones

    NASA Astrophysics Data System (ADS)

    Lohrer, Andrew M.; Townsend, Michael; Hailes, Sarah F.; Rodil, Iván F.; Cartner, Katie; Pratt, Daniel R.; Hewitt, Judi E.

    2016-11-01

    New Zealand cockles (Austrovenus stutchburyi) are ecologically important, intertidal bivalves that have been shown to influence nutrient cycles and the productivity of microphytobenthos on sandflats. Here, we investigated the potential for cockles to impact the productivity of seagrass, Zostera muelleri, and examined interactions between these habitat-defining species where they co-occur. We sampled bivalve densities and sizes, sediment properties, and seagrass shoot densities across the boundaries of two seagrass patches on an intertidal sandflat in northern New Zealand, and measured dissolved oxygen and nutrient fluxes in light and dark benthic incubation chambers in conjunction with a 0-97% gradient in seagrass cover. Although gross primary production (GPP, μmol O2 m-2 h-1) increased predictably with the cover of live seagrass, the density of cockles and sediment properties also contributed directly and indirectly. Seagrass cover was positively correlated with cockle density (ranging from 225 to 1350 individuals per m2), sediment mud percentage (0.5-9.5%), and organic matter content (0.5-2.2%), all of which can affect the efflux of ammonium (readily utilisable inorganic nitrogen) from sediments. Moreover, the cover of green seagrass blades plateaued (never exceeded 70%) in the areas of highest total seagrass cover, adding complexity to cockle-seagrass interactions and contributing to a unimodal cockle-GPP relationship.

  8. Simulation of tree-ring widths with a model for primary production, carbon allocation, and growth

    NASA Astrophysics Data System (ADS)

    Li, G.; Harrison, S. P.; Prentice, I. C.; Falster, D.

    2014-12-01

    We present a simple, generic model of annual tree growth, called "T". This model accepts input from a first-principles light-use efficiency model (the "P" model). The P model provides values for gross primary production (GPP) per unit of absorbed photosynthetically active radiation (PAR). Absorbed PAR is estimated from the current leaf area. GPP is allocated to foliage, transport tissue, and fine-root production and respiration in such a way as to satisfy well-understood dimensional and functional relationships. Our approach thereby integrates two modelling approaches separately developed in the global carbon-cycle and forest-science literature. The T model can represent both ontogenetic effects (the impact of ageing) and the effects of environmental variations and trends (climate and CO2) on growth. Driven by local climate records, the model was applied to simulate ring widths during the period 1958-2006 for multiple trees of Pinus koraiensis from the Changbai Mountains in northeastern China. Each tree was initialised at its actual diameter at the time when local climate records started. The model produces realistic simulations of the interannual variability in ring width for different age cohorts (young, mature, and old). Both the simulations and observations show a significant positive response of tree-ring width to growing-season total photosynthetically active radiation (PAR0) and the ratio of actual to potential evapotranspiration (α), and a significant negative response to mean annual temperature (MAT). The slopes of the simulated and observed relationships with PAR0 and α are similar; the negative response to MAT is underestimated by the model. Comparison of simulations with fixed and changing atmospheric CO2 concentration shows that CO2 fertilisation over the past 50 years is too small to be distinguished in the ring-width data, given ontogenetic trends and interannual variability in climate.

  9. Simulation of tree ring-widths with a model for primary production, carbon allocation and growth

    NASA Astrophysics Data System (ADS)

    Li, G.; Harrison, S. P.; Prentice, I. C.; Falster, D.

    2014-07-01

    We present a simple, generic model of annual tree growth, called "T". This model accepts input from a first-principles light-use efficiency model (the P model). The P model provides values for Gross Primary Production (GPP) per unit of absorbed photosynthetically active radiation (PAR). Absorbed PAR is estimated from the current leaf area. GPP is allocated to foliage, transport-tissue, and fine root production and respiration, in such a way as to satisfy well-understood dimensional and functional relationships. Our approach thereby integrates two modelling approaches separately developed in the global carbon-cycle and forest-science literature. The T model can represent both ontogenetic effects (impact of ageing) and the effects of environmental variations and trends (climate and CO2) on growth. Driven by local climate records, the model was applied to simulate ring widths during 1958-2006 for multiple trees of Pinus koraiensis from the Changbai Mountain, northeastern China. Each tree was initialised at its actual diameter at the time when local climate records started. The model produces realistic simulations of the interannual variability in ring width for different age cohorts (young, mature, old). Both the simulations and observations show a significant positive response of tree-ring width to growing-season total photosynthetically active radiation (PAR0) and the ratio of actual to potential evapotranspiration (α), and a significant negative response to mean annual temperature (MAT). The slopes of the simulated and observed relationships with PAR0 and α are similar; the negative response to MAT is underestimated by the model. Comparison of simulations with fixed and changing atmospheric CO2 concentration shows that CO2 fertilization over the past 50 years is too small to be distinguished in the ring-width data given ontogenetic trends and interannual variability in climate.

  10. Measured and modeled interactive effects of potassium deficiency and water deficit on gross primary productivity and light-use efficiency in Eucalyptus grandis plantations.

    PubMed

    Christina, Mathias; Le Maire, Guerric; Battie-Laclau, Patricia; Nouvellon, Yann; Bouillet, Jean-Pierre; Jourdan, Christophe; de Moraes Gonçalves, José Leonardo; Laclau, Jean-Paul

    2015-05-01

    Global climate change is expected to increase the length of drought periods in many tropical regions. Although large amounts of potassium (K) are applied in tropical crops and planted forests, little is known about the interaction between K nutrition and water deficit on the physiological mechanisms governing plant growth. A process-based model (MAESPA) parameterized in a split-plot experiment in Brazil was used to gain insight into the combined effects of K deficiency and water deficit on absorbed radiation (aPAR), gross primary productivity (GPP), and light-use efficiency for carbon assimilation and stem biomass production (LUEC and LUEs ) in Eucalyptus grandis plantations. The main-plot factor was the water supply (undisturbed rainfall vs. 37% of throughfall excluded) and the subplot factor was the K supply (with or without 0.45 mol K m(-2 ) K addition). Mean GPP was 28% lower without K addition over the first 3 years after planting whether throughfall was partly excluded or not. K deficiency reduced aPAR by 20% and LUEC by 10% over the whole period of growth. With K addition, throughfall exclusion decreased GPP by 25%, resulting from a 21% decrease in LUEC at the end of the study period. The effect of the combination of K deficiency and water deficit was less severe than the sum of the effects of K deficiency and water deficit individually, leading to a reduction in stem biomass production, gross primary productivity and LUE similar to K deficiency on its own. The modeling approach showed that K nutrition and water deficit influenced absorbed radiation essentially through changes in leaf area index and tree height. The changes in gross primary productivity and light-use efficiency were, however, driven by a more complex set of tree parameters, especially those controlling water uptake by roots and leaf photosynthetic capacities.

  11. Grazer Effects on Stream Primary Production and Nitrate Utilization: Estimating Feedbacks Under Reduced Nitrate Levels at High-Temporal Resolutions from the Patch to Reach-Scale

    NASA Astrophysics Data System (ADS)

    Reijo, C. J.; Cohen, M. J.

    2015-12-01

    While nutrient enrichment is often identified as the leading cause for changes in stream gross primary production (GPP) and shifts in vegetative communities, other factors such as grazers influence overall stream structure and function. Evidence shows that grazers are a top-down control on algae in streams; however, the specific feedbacks between overall stream metabolism, grazer effects, and nutrient cycling have been variable and little is known about these interactions at nutrient levels below ambient. To further our understanding of these linkages, a nutrient depletion chamber was created and paired with high-resolution in situ sensors to estimate stream metabolism and characterize nitrate uptake (UNO3) pathways (i.e. plant uptake and denitrification). The Plexiglas chamber blocks flow and nutrient supply, inserts into upper sediments, allows light in and sediment-water-air interactions to occur. At Gum Slough Springs, FL, nitrate was reduced from ambient levels (1.40 mg N/L) to below regulatory thresholds (ca. 0.20 mg N/L) within one week. Paired chambers with and without the presence of snails (Elimia floridensis) were deployed across submerged aquatic vegetation (SAV; Vallisneria americana) and algae (Lyngbya) substrates. Results show that GPP and UNO3 were higher under SAV (70 g O2/m2/d and 300 mg NO3/m2/d, respectively) and a general lack of nutrient limitation even at low [NO3]. Grazer effects differed by vegetation type as it alleviated the reduction of NO3 levels and GPP under SAV but enhanced the decrease of algal GPP and NO3 levels over time. Continued work includes estimating grazer effects on denitrification, quantifying snail nutrient excretion contributions, and scaling up all estimates from the patch to reach level. Overall, this study will further our understanding of grazer-production-nutrient interactions within stream systems, making it possible to predict changes in feedbacks when one part of the biotic or abiotic ecosystem is altered.

  12. (p)ppGpp, a Small Nucleotide Regulator, Directs the Metabolic Fate of Glucose in Vibrio cholerae*

    PubMed Central

    Oh, Young Taek; Lee, Kang-Mu; Bari, Wasimul; Raskin, David M.; Yoon, Sang Sun

    2015-01-01

    When V. cholerae encounters nutritional stress, it activates (p)ppGpp-mediated stringent response. The genes relA and relV are involved in the production of (p)ppGpp, whereas the spoT gene encodes an enzyme that hydrolyzes it. Herein, we show that the bacterial capability to produce (p)ppGpp plays an essential role in glucose metabolism. The V. cholerae mutants defective in (p)ppGpp production (i.e. ΔrelAΔrelV and ΔrelAΔrelVΔspoT mutants) lost their viability because of uncontrolled production of organic acids, when grown with extra glucose. In contrast, the ΔrelAΔspoT mutant, a (p)ppGpp overproducer strain, exhibited better growth in the presence of the same glucose concentration. An RNA sequencing analysis demonstrated that transcriptions of genes consisting of an operon for acetoin biosynthesis were markedly elevated in N16961, a seventh pandemic O1 strain, but not in its (p)ppGpp0 mutant during glucose-stimulated growth. Transposon insertion in acetoin biosynthesis gene cluster resulted in glucose-induced loss of viability of the ΔrelAΔspoT mutant, further suggesting the crucial role of acetoin production in balanced growth under glucose-rich environments. Additional deletion of the aphA gene, encoding a negative regulator for acetoin production, failed to rescue the (p)ppGpp0 mutant from the defective glucose-mediated growth, suggesting that (p)ppGpp-mediated acetoin production occurs independent of the presence of AphA. Overall, our results reveal that (p)ppGpp, in addition to its well known role as a stringent response mediator, positively regulates acetoin production that contributes to the successful glucose metabolism and consequently the proliferation of V. cholerae cells under a glucose-rich environment, a condition that may mimic the human intestine. PMID:25882848

  13. Relationships between primary production and crop yields in semi-arid and arid irrigated agro-ecosystems

    NASA Astrophysics Data System (ADS)

    Jaafar, H. H.; Ahmad, F. A.

    2015-04-01

    In semi-arid areas within the MENA region, food security problems are the main problematic imposed. Remote sensing can be a promising too early diagnose food shortages and further prevent the population from famine risks. This study is aimed at examining the possibility of forecasting yield before harvest from remotely sensed MODIS-derived Enhanced Vegetation Index (EVI), Net photosynthesis (net PSN), and Gross Primary Production (GPP) in semi-arid and arid irrigated agro-ecosystems within the conflict affected country of Syria. Relationships between summer yield and remotely sensed indices were derived and analyzed. Simple regression spatially-based models were developed to predict summer crop production. The validation of these models was tested during conflict years. A significant correlation (p<0.05) was found between summer crop yield and EVI, GPP and net PSN. Results indicate the efficiency of remotely sensed-based models in predicting summer yield, mostly for cotton yields and vegetables. Cumulative summer EVI-based model can predict summer crop yield during crisis period, with deviation less than 20% where vegetables are the major yield. This approach prompts to an early assessment of food shortages and lead to a real time management and decision making, especially in periods of crisis such as wars and drought.

  14. Leaf chlorophyll constraint on model simulated gross primary productivity in agricultural systems

    NASA Astrophysics Data System (ADS)

    Houborg, Rasmus; McCabe, Matthew F.; Cescatti, Alessandro; Gitelson, Anatoly A.

    2015-12-01

    Leaf chlorophyll content (Chll) may serve as an observational proxy for the maximum rate of carboxylation (Vmax), which describes leaf photosynthetic capacity and represents the single most important control on modeled leaf photosynthesis within most Terrestrial Biosphere Models (TBMs). The parameterization of Vmax is associated with great uncertainty as it can vary significantly between plants and in response to changes in leaf nitrogen (N) availability, plant phenology and environmental conditions. Houborg et al. (2013) outlined a semi-mechanistic relationship between Vmax25 (Vmax normalized to 25 °C) and Chll based on inter-linkages between Vmax25, Rubisco enzyme kinetics, N and Chll. Here, these relationships are parameterized for a wider range of important agricultural crops and embedded within the leaf photosynthesis-conductance scheme of the Community Land Model (CLM), bypassing the questionable use of temporally invariant and broadly defined plant functional type (PFT) specific Vmax25 values. In this study, the new Chll constrained version of CLM is refined with an updated parameterization scheme for specific application to soybean and maize. The benefit of using in-situ measured and satellite retrieved Chll for constraining model simulations of Gross Primary Productivity (GPP) is evaluated over fields in central Nebraska, U.S.A between 2001 and 2005. Landsat-based Chll time-series records derived from the Regularized Canopy Reflectance model (REGFLEC) are used as forcing to the CLM. Validation of simulated GPP against 15 site-years of flux tower observations demonstrate the utility of Chll as a model constraint, with the coefficient of efficiency increasing from 0.91 to 0.94 and from 0.87 to 0.91 for maize and soybean, respectively. Model performances particularly improve during the late reproductive and senescence stage, where the largest temporal variations in Chll (averaging 35-55 μg cm-2 for maize and 20-35 μg cm-2 for soybean) are observed. While

  15. QUANTIFYING UNCERTAINTY IN NET PRIMARY PRODUCTION MEASUREMENTS

    EPA Science Inventory

    Net primary production (NPP, e.g., g m-2 yr-1), a key ecosystem attribute, is estimated from a combination of other variables, e.g. standing crop biomass at several points in time, each of which is subject to errors in their measurement. These errors propagate as the variables a...

  16. Landscape-scale GPP and carbon density inform patterns and impacts of an invasive tree across wet forests of Hawaii.

    PubMed

    Barbosa, Jomar M; Asner, Gregory P; Hughes, R Flint; Johnson, M Tracy

    2017-03-01

    Plant invasion typically occurs within a landscape-scale framework of abiotic and biotic conditions, often resulting in emergent feedbacks among environment, ecosystem functions, and the dominance of invasive species. Understanding the mechanisms underlying successful invasions is an important component of conservation and management efforts, but this has been poorly investigated in a spatially explicit manner. Knowing where and why invasion patterns change throughout the landscape enables managers to use context-specific controls on the spread of invasive species. Using high-resolution airborne imaging spectroscopy, we studied plant performance in growth within and across landscapes to examine the dominance and spatial distribution of an invasive tree, Psidium cattleianum (strawberry guava), in heterogeneous environmental conditions of a submontane Hawaiian tropical forest. We assessed invader performance using the GPP ratio index, which is the relative difference in remotely sensed estimates of gross primary productivity between canopies of guava and canopies of the invaded plant community. In addition, we used airborne LiDAR data to evaluate the impacts of guava invasion on the forest aboveground carbon density in different environments. Structural equation modeling revealed that substrate type and elevation above sea level interact and amplify landscape-scale differences in productivity between the invasive species and the host plant community (GPP ratio); differences that ultimately control levels of dominance of guava. We found shifts in patterns of forest carbon storage based on both gradual increase of invader dominance and changes in environmental conditions. Overall, our results demonstrate that the remotely sensed index defined as the GPP ratio provided an innovative spatially explicit approach to track and predict the success of invasive plants based in their canopy productivity, particularly within a landscape-scale framework of varying environmental

  17. Impacts of Temperature on Primary Productivity and Respiration in Naturally Structured Macroalgal Assemblages

    PubMed Central

    Tait, Leigh W.; Schiel, David R.

    2013-01-01

    Rising global temperatures caused by human-mediated change has already triggered significant responses in organismal physiology, distribution and ecosystem functioning. Although the effects of rising temperature on the physiology of individual organisms are well understood, the effect on community-wide processes has remained elusive. The fixation of carbon via primary productivity is an essential ecosystem function and any shifts in the balance of primary productivity and respiration could alter the carbon balance of ecosystems. Here we show through a series of tests that respiration of naturally structured algal assemblages in southern New Zealand greatly increases with rising temperature, with implications for net primary productivity (NPP). The NPP of in situ macroalgal assemblages was minimally affected by natural temperature variation, possibly through photo-acclimation or temperature acclimation responses, but respiration rates and compensating irradiance were negatively affected. However, laboratory experiments testing the impacts of rising temperature on several photosynthetic parameters showed a decline in NPP, increasing respiration rates and increasing compensating irradiance. The respiration Q10 of laboratory assemblages (the difference in metabolic rates over 10°C) averaged 2.9 compared to a Q10 of 2 often seen in other autotrophs. However, gross primary productivity (GPP) Q10 averaged 2, indicating that respiration was more severely affected by rising temperature. Furthermore, combined high irradiance and high temperature caused photoinhibition in the laboratory, and resulted in 50% lower NPP at high irradiance. Our study shows that communities may be more severely affected by rising global temperatures than would be expected by responses of individual species. In particular, enhanced respiration rates and rising compensation points have the potential to greatly affect the carbon balance of macroalgal assemblages through declines in sub-canopy NPP

  18. Sensitivity of Global Terrestrial Gross Primary Production to Hydrologic States Simulated by the Community Land Model Using Two Runoff Parameterizations

    SciTech Connect

    Lei, Huimin; Huang, Maoyi; Leung, Lai-Yung R.; Yang, Dawen; Shi, Xiaoying; Mao, Jiafu; Hayes, Daniel J.; Schwalm, C.; Wei, Yaxing; Liu, Shishi

    2014-09-01

    The terrestrial water and carbon cycles interact strongly at various spatio-temporal scales. To elucidate how hydrologic processes may influence carbon cycle processes, differences in terrestrial carbon cycle simulations induced by structural differences in two runoff generation schemes were investigated using the Community Land Model 4 (CLM4). Simulations were performed with runoff generation using the default TOPMODEL-based and the Variable Infiltration Capacity (VIC) model approaches under the same experimental protocol. The comparisons showed that differences in the simulated gross primary production (GPP) are mainly attributed to differences in the simulated leaf area index (LAI) rather than soil moisture availability. More specifically, differences in runoff simulations can influence LAI through changes in soil moisture, soil temperature, and their seasonality that affect the onset of the growing season and the subsequent dynamic feedbacks between terrestrial water, energy, and carbon cycles. As a result of a relative difference of 36% in global mean total runoff between the two models and subsequent changes in soil moisture, soil temperature, and LAI, the simulated global mean GPP differs by 20.4%. However, the relative difference in the global mean net ecosystem exchange between the two models is small (2.1%) due to competing effects on total mean ecosystem respiration and other fluxes, although large regional differences can still be found. Our study highlights the significant interactions among the water, energy, and carbon cycles and the need for reducing uncertainty in the hydrologic parameterization of land surface models to better constrain carbon cycle modeling.

  19. Ecosystem Disturbance Effects on Land Surface Temperature, Forest Carbon Stocks, and Primary Productivity in the Western United States

    NASA Astrophysics Data System (ADS)

    Cooper, L. A.; Ballantyne, A.; Holden, Z. A.; Landguth, E.

    2015-12-01

    Disturbance plays an important role in the structure, composition, and nutrient cycling of forest ecosystems. Climate change is resulting in an increase in disturbance frequency and intensity, making it critical that we quantify the physical and chemical impacts of disturbances on forests. The impacts of disturbance are thought to vary widely depending on disturbance type, location, and climate. More specifically, fires, insect infestations, and other types of disturbances differ in their timing, extent, and intensity making it difficult to assess the true impact of disturbances on local energy budgets and carbon cycling. Here, we provide a regional analysis of the impacts of fire, insect attack, and other disturbances on land surface temperature (LST), carbon stocks, and gross primary productivity (GPP). Using disturbances detected with MODIS Enhanced Vegetation Index (EVI) time series between 2002 and 2012, we find that the impacts of disturbance on LST, carbon stocks, and GPP vary widely according to local climate, vegetation, and disturbance type and intensity. Fires resulted in the most distinct impacts on all response variables. Forest responses to insect epidemics were more varied in their magnitude and timing. The results of this study provide an important estimation of the variability of climate and ecosystem responses to disturbance across a large and heterogeneous landscape. With disturbance projected to increase in both frequency and intensity around the globe in the coming years, this information is vitally important to effectively manage forests into the future.

  20. Chemolithotrophic primary production in a subglacial ecosystem.

    PubMed

    Boyd, Eric S; Hamilton, Trinity L; Havig, Jeff R; Skidmore, Mark L; Shock, Everett L

    2014-10-01

    Glacial comminution of bedrock generates fresh mineral surfaces capable of sustaining chemotrophic microbial communities under the dark conditions that pervade subglacial habitats. Geochemical and isotopic evidence suggests that pyrite oxidation is a dominant weathering process generating protons that drive mineral dissolution in many subglacial systems. Here, we provide evidence correlating pyrite oxidation with chemosynthetic primary productivity and carbonate dissolution in subglacial sediments sampled from Robertson Glacier (RG), Alberta, Canada. Quantification and sequencing of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) transcripts suggest that populations closely affiliated with Sideroxydans lithotrophicus, an iron sulfide-oxidizing autotrophic bacterium, are abundant constituents of microbial communities at RG. Microcosm experiments indicate sulfate production during biological assimilation of radiolabeled bicarbonate. Geochemical analyses of subglacial meltwater indicate that increases in sulfate levels are associated with increased calcite and dolomite dissolution. Collectively, these data suggest a role for biological pyrite oxidation in driving primary productivity and mineral dissolution in a subglacial environment and provide the first rate estimate for bicarbonate assimilation in these ecosystems. Evidence for lithotrophic primary production in this contemporary subglacial environment provides a plausible mechanism to explain how subglacial communities could be sustained in near-isolation from the atmosphere during glacial-interglacial cycles.

  1. Chemolithotrophic Primary Production in a Subglacial Ecosystem

    PubMed Central

    Hamilton, Trinity L.; Havig, Jeff R.; Skidmore, Mark L.; Shock, Everett L.

    2014-01-01

    Glacial comminution of bedrock generates fresh mineral surfaces capable of sustaining chemotrophic microbial communities under the dark conditions that pervade subglacial habitats. Geochemical and isotopic evidence suggests that pyrite oxidation is a dominant weathering process generating protons that drive mineral dissolution in many subglacial systems. Here, we provide evidence correlating pyrite oxidation with chemosynthetic primary productivity and carbonate dissolution in subglacial sediments sampled from Robertson Glacier (RG), Alberta, Canada. Quantification and sequencing of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) transcripts suggest that populations closely affiliated with Sideroxydans lithotrophicus, an iron sulfide-oxidizing autotrophic bacterium, are abundant constituents of microbial communities at RG. Microcosm experiments indicate sulfate production during biological assimilation of radiolabeled bicarbonate. Geochemical analyses of subglacial meltwater indicate that increases in sulfate levels are associated with increased calcite and dolomite dissolution. Collectively, these data suggest a role for biological pyrite oxidation in driving primary productivity and mineral dissolution in a subglacial environment and provide the first rate estimate for bicarbonate assimilation in these ecosystems. Evidence for lithotrophic primary production in this contemporary subglacial environment provides a plausible mechanism to explain how subglacial communities could be sustained in near-isolation from the atmosphere during glacial-interglacial cycles. PMID:25085483

  2. Modelling the Gross Primary Productivity of West Africa with the Regional Biomass Model RBM+, using optimized 250 m MODIS FPAR and fractional vegetation cover information

    NASA Astrophysics Data System (ADS)

    Machwitz, Miriam; Gessner, Ursula; Conrad, Christopher; Falk, Ulrike; Richters, Jochen; Dech, Stefan

    2015-12-01

    Global warming associated with climate change is one of the greatest challenges of today's world. Increasing emissions of the greenhouse gas CO2 are considered as a major contributing factor to global warming. One regulating factor of CO2 exchange between atmosphere and land surface is vegetation. Measurements of land cover changes in combination with modelling the Gross Primary Productivity (GPP) can contribute to determine important sources and sinks of CO2. The aim of this study is to accurately model the GPP for a region in West Africa with a spatial resolution of 250 m, and the differentiation of GPP based on woody and herbaceous vegetation. For this purpose, the Regional Biomass Model (RBM) was applied, which is based on a Light Use Efficiency (LUE) approach. The focus was on the spatial enhancement of the RBM from the original 1000-250 m spatial resolution (RBM+). The adaptation to the 250 m scale included the modification of two main input parameters: (1) the fraction of absorbed Photosynthetically Active Radiation (FPAR) based on the 1000 m MODIS MOD15A2 FPAR product which was downscaled to 250 m using MODIS NDVI time series; (2) the fractional cover of woody and herbaceous vegetation, which was improved by using a multi-scale approach. For validation and regional adjustments of GPP and the input parameters, in situ data from a climate station and eddy covariance measurements were integrated. The results of this approach show that the input parameters could be improved significantly: downscaling considerably reduces data gaps of the original FPAR product and the improved dataset differed less than 5.0% from the original data for cloud free regions. The RMSE of the fractional vegetation cover varied between 5.1 and 12.7%. Modelled GPP showed a slight overestimation in comparison to eddy covariance measurements. The in situ data was exceeded by 8.8% for 2005 and by 2.0% for 2006. The model results were converted to NPP and also agreed well with previous NPP

  3. Decreasing net primary production due to drought and slight decreases in solar radiation in China from 2000 to 2012

    NASA Astrophysics Data System (ADS)

    Wang, J.; Dong, J.; Yi, Y.; Lu, G.; Oyler, J.; Smith, W. K.; Zhao, M.; Liu, J.; Running, S.

    2017-01-01

    Terrestrial ecosystems have continued to provide the critical service of slowing the atmospheric CO2 growth rate. Terrestrial net primary productivity (NPP) is thought to be a major contributing factor to this trend. Yet our ability to estimate NPP at the regional scale remains limited due to large uncertainties in the response of NPP to multiple interacting climate factors and uncertainties in the driver data sets needed to estimate NPP. In this study, we introduced an improved NPP algorithm that used local driver data sets and parameters in China. We found that bias decreased by 30% for gross primary production (GPP) and 17% for NPP compared with the widely used global GPP and NPP products, respectively. From 2000 to 2012, a pixel-level analysis of our improved NPP for the region of China showed an overall decreasing NPP trend of 4.65 Tg C a-1. Reductions in NPP were largest for the southern forests of China (-5.38 Tg C a-1), whereas minor increases in NPP were found for North China (0.65 Tg C a-1). Surprisingly, reductions in NPP were largely due to decreases in solar radiation (82%), rather than the more commonly expected effects of drought (18%). This was because for southern China, the interannual variability of NPP was more sensitive to solar radiation (R2 in 0.29-0.59) relative to precipitation (R2 < 0.13). These findings update our previous knowledge of carbon uptake responses to climate change in terrestrial ecosystems of China and highlight the importance of shortwave radiation in driving vegetation productivity for the region, especially for tropical forests.

  4. Changes of net primary productivity in China during recent 11 years detected using an ecological model driven by MODIS data

    NASA Astrophysics Data System (ADS)

    Liu, Yibo; Ju, Weimin; He, Honglin; Wang, Shaoqiang; Sun, Rui; Zhang, Yuandong

    2013-03-01

    Net primary productivity (NPP) is an important component of the terrestrial carbon cycle. Accurately mapping the spatial-temporal variations of NPP in China is crucial for global carbon cycling study. In this study the process-based Boreal Ecosystem Productivity Simulator (BEPS) was employed to study the changes of NPP in China's ecosystems for the period from 2000 to 2010. The BEPS model was first validated using gross primary productivity (GPP) measured at typical flux sites and forest NPP measured at different regions. Then it was driven with leaf area index (LAI) inversed from the Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance and land cover products and meteorological data interpolated from observations at 753 national basic meteorological stations to simulate NPP at daily time steps and a spatial resolution of 500 m from January 1, 2000 to December 31, 2010. Validations show that BEPS is able to capture the seasonal variations of tower-based GPP and the spatial variability of forest NPP in different regions of China. Estimated national total of annual NPP varied from 2.63 to 2.84Pg C·yr-1, averaging 2.74 Pg C·yr-1 during the study period. Simulated terrestrial NPP shows spatial patterns decreasing from the east to the west and from the south to the north, in association with land cover types and climate. South-west China makes the largest contribution to the national total of NPP while NPP in the North-west account for only 3.97% of the national total. During the recent 11 years, the temporal changes of NPP were heterogamous. NPP increased in 63.8% of China's landmass, mainly in areas north of the Yangtze River and decreased in most areas of southern China, owing to the low temperature freezing in early 2008 and the severe drought in late 2009.

  5. Assessing boreal forest photosynthetic dynamics through space-borne measurements of greenness, chlorophyll fluorescence and model GPP

    NASA Astrophysics Data System (ADS)

    Walther, Sophia; Guanter, Luis; Voigt, Maximilian; Köhler, Philipp; Jung, Martin; Joiner, Joanna

    2015-04-01

    sophia.walther@gfz-potsdam.de The seasonality of photosynthesis of boreal forests is an essential driver of the terrestrial carbon, water and energy cycles. However, current carbon cycle model results only poorly represent interannual variability and predict very different magnitudes and timings of carbon fluxes between the atmosphere and the land surface (e.g. Jung et al. 2011, Richardson et al. 2012). Reflectance-based satellite measurements, which give an indication of the amount of green biomass on the Earth's surface, have so far been used as input to global carbon cycle simulations, but they have limitations as they are not directly linked to instantaneous photosynthesis. As an alternative, space-borne retrievals of sun-induced chlorophyll fluorescence (SIF) boast the potential to provide a direct indication of the seasonality of boreal forest photosynthetic activity and thus to improve carbon model performances. SIF is a small electromagnetic signal that is re-emitted from the photosystems in the chloroplasts, which results in a direct relationship to photosynthetic efficiency. In this contribution we examine the seasonality of the boreal forests with three different vegetation parameters, namely greenness, SIF and model simulations of gross primary production (gross carbon flux into the plants by photosynthesis, GPP). We use the enhanced vegetation index (EVI) to represent green biomass. EVI is calculated from NBAR MODIS reflectance measurements (0.05deg, 16 days temporal resolution) for the time from January 2007-May 2013. SIF data originate from GOME-2 measurements on board the MetOp-A satellite in a spatial resolution of 0.5deg for the time from 2007-2011 (Joiner et al. (2013), Köhler et al. (2014)). As a third data source, data-driven GPP model results are used for the time from 2006-2012 with 0.5deg spatial resolution. The method to quantify phenology developed by Gonsamo et al. (2013) is applied to infer the main phenological phases (greenup/onset of

  6. PRIMARY PRODUCTION ESTIMATES IN CHESAPEAKE BAY USING SEAWIFS

    EPA Science Inventory

    The temporal and spatial variability in primary production along the main stem of Chesapeake Bay was examined from 1997 through 2000. Primary production estimates were determined from the Vertically Generalized Production Model (VGPM) (Behrenfeld and Falkowski, 1997) using chloro...

  7. Coupling gross primary production and transpiration for a consistent estimate of canopy water use efficiency

    NASA Astrophysics Data System (ADS)

    Yebra, Marta; van Dijk, Albert

    2015-04-01

    Water use efficiency (WUE, the amount of transpiration or evapotranspiration per unit gross (GPP) or net CO2 uptake) is key in all areas of plant production and forest management applications. Therefore, mutually consistent estimates of GPP and transpiration are needed to analysed WUE without introducing any artefacts that might arise by combining independently derived GPP and ET estimates. GPP and transpiration are physiologically linked at ecosystem level by the canopy conductance (Gc). Estimates of Gc can be obtained by scaling stomatal conductance (Kelliher et al. 1995) or inferred from ecosystem level measurements of gas exchange (Baldocchi et al., 2008). To derive large-scale or indeed global estimates of Gc, satellite remote sensing based methods are needed. In a previous study, we used water vapour flux estimates derived from eddy covariance flux tower measurements at 16 Fluxnet sites world-wide to develop a method to estimate Gc using MODIS reflectance observations (Yebra et al. 2013). We combined those estimates with the Penman-Monteith combination equation to derive transpiration (T). The resulting T estimates compared favourably with flux tower estimates (R2=0.82, RMSE=29.8 W m-2). Moreover, the method allowed a single parameterisation for all land cover types, which avoids artefacts resulting from land cover classification. In subsequent research (Yebra et al, in preparation) we used the same satellite-derived Gc values within a process-based but simple canopy GPP model to constrain GPP predictions. The developed model uses a 'big-leaf' description of the plant canopy to estimate the mean GPP flux as the lesser of a conductance-limited and radiation-limited GPP rate. The conductance-limited rate was derived assuming that transport of CO2 from the bulk air to the intercellular leaf space is limited by molecular diffusion through the stomata. The radiation-limited rate was estimated assuming that it is proportional to the absorbed photosynthetically

  8. Observations of Ocean Primary Productivity Using MODIS

    NASA Technical Reports Server (NTRS)

    Esaias, Wayne E.; Abbott, Mark R.; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    Measuring the magnitude and variability of oceanic net primary productivity (NPP) represents a key advancement toward our understanding of the dynamics of marine ecosystems and the role of the ocean in the global carbon cycle. MODIS observations make two new contributions in addition to continuing the bio-optical time series begun with Orbview-2's SeaWiFS sensor. First, MODIS provides weekly estimates of global ocean net primary productivity on weekly and annual time periods, and annual empirical estimates of carbon export production. Second, MODIS provides additional insight into the spatial and temporal variations in photosynthetic efficiency through the direct measurements of solar-stimulated chlorophyll fluorescence. The two different weekly productivity indexes (first developed by Behrenfeld & Falkowski and by Yoder, Ryan and Howard) are used to derive daily productivity as a function of chlorophyll biomass, incident daily surface irradiance, temperature, euphotic depth, and mixed layer depth. Comparisons between these two estimates using both SeaWiFS and MODIS data show significant model differences in spatial distribution after allowance for the different integration depths. Both estimates are strongly dependence on the accuracy of the chlorophyll determination. In addition, an empirical approach is taken on annual scales to estimate global NPP and export production. Estimates of solar stimulated fluorescence efficiency from chlorophyll have been shown to be inversely related to photosynthetic efficiency by Abbott and co-workers. MODIS provides the first global estimates of oceanic chlorophyll fluorescence, providing an important proof of concept. MODIS observations are revealing spatial patterns of fluorescence efficiency which show expected variations with phytoplankton photo-physiological parameters as measured during in-situ surveys. This has opened the way for research into utilizing this information to improve our understanding of oceanic NPP

  9. Stomata-controlled nighttime COS fluxes in a boreal forest: implications for the use of COS as a GPP tracer

    NASA Astrophysics Data System (ADS)

    Kooijmans, Linda M. J.; Maseyk, Kadmiel; Seibt, Ulli; Vesala, Timo; Mammarella, Ivan; Baker, Ian T.; Franchin, Alessandro; Kolari, Pasi; Sun, Wu; Keskinen, Helmi; Levula, Janne; Chen, Huilin

    2016-04-01

    Carbonyl Sulfide (COS) is a promising new tracer that can be used to partition the Net Ecosystem Exchange into gross primary production (GPP) and respiration. COS and CO2 vegetation fluxes are closely related as these gases share the same diffusion pathway into stomata. This close coupling is the fundamental principle for the use of COS as tracer for GPP. Nonetheless, in contrast to CO2 , the uptake of COS by vegetation is not light-dependent, and therefore the vegetative uptake of COS can continue during the night as long as stomata are open. Nighttime stomatal conductance is observed in a variety of studies, and also nighttime depletion of COS concentrations is reported several times but it is not confirmed with field measurements that the depletion of COS in the night is indeed driven by stomatal opening. In the summer of 2015 a campaign took place at the SMEAR II site in Hyytiälä, Finland to provide better constrained COS flux data for boreal forests using a combination of COS measurements, i.e. atmospheric profile concentrations up to 125 m, eddy-covariance fluxes and soil chamber fluxes, and collocated measurements of stomatal conductance and 222Radon. A high correlation between concentrations of 222Radon and COS implies that the radon-tracer method is a valuable tool to derive nighttime ecosystem COS fluxes. We find that soils contribute to 17% of the total ecosystem COS flux during nighttime in the peak growing season. Nighttime ecosystem COS fluxes show a correlation with stomatal conductance (R2 = 0.3), indicating that nighttime COS fluxes are primarily driven by vegetation. The COS vegetation fluxes will be compared with calculated fluxes from the Simple Biosphere model. Furthermore, the nighttime vegetative COS uptake covers a substantial fraction (25%) of the daily maximum COS uptake by vegetation. Accurate quantification of nighttime COS uptake is required to be able to use COS as a useful tracer for GPP.

  10. A Transcriptional Regulator and ABC Transporters Link Stress Tolerance, (p)ppGpp, and Genetic Competence in Streptococcus mutans▿ †

    PubMed Central

    Seaton, Kinda; Ahn, Sang-Joon; Sagstetter, Ann M.; Burne, Robert A.

    2011-01-01

    Streptococcus mutans, a primary agent of dental caries, has three (p)ppGpp synthases: RelA, which is required for a mupirocin-induced stringent response; RelP, which produces (p)ppGpp during exponential growth and is regulated by the RelRS two-component system; and RelQ. Transcription of relPRS and a gene cluster (SMu0835 to SMu0837) located immediately upstream was activated in cells grown with aeration and during a stringent response, respectively. Bioinformatic analysis predicted that SMu0836 and SMu0837 encode ABC exporters, which we designated rcrPQ (rel competence-related) genes, respectively. SMu0835 (rcrR) encodes a MarR family transcriptional regulator. Reverse transcriptase PCR (RT-PCR) and quantitative RT-PCR analysis showed that RcrR functions as an autogenous negative regulator of the expression of the rcrRPQ operon. A mutant in which a polar insertion replaced the SMu836 gene (Δ836polar) grew more slowly and had final yields that were lower than those of the wild-type strain. Likewise, the Δ836polar strain had an impaired capacity to form biofilms, grew poorly at pH 5.5, and was more sensitive to oxidative stressors. Optimal expression of rcrPQ required RelP and vice versa. Replacement of rcrR with a nonpolar antibiotic resistance marker (Δ835np), which leads to overexpression of rcrPQ, yielded a strain that was not transformable with exogenous DNA. Transcriptional analysis revealed that the expression of comYA and comX was dramatically altered in the Δ835np and Δ836polar mutants. Collectively, the data support the suggestion that the rcrRPQ gene products play a critical role in physiologic homeostasis and stress tolerance by linking (p)ppGpp metabolism, acid and oxidative stress tolerance, and genetic competence. PMID:21148727

  11. The productivity of primary care research networks.

    PubMed Central

    Griffiths, F; Wild, A; Harvey, J; Fenton, E

    2000-01-01

    Primary care research networks are being publicly funded in the United Kingdom to promote a culture of research and development in primary care. This paper discusses the organisational form of these networks and how their productivity can be evaluated, drawing on evidence from management science. An evaluation of a research network has to take account of the complexity of the organisation, the influence of its local context, and its stage of development. Output measures, such as number of research papers, and process measures, such as number of research meetings, may contribute to an evaluation. However, as networking relies on the development of informal, trust-based relationships, the quality of interactions within a network is of paramount importance for its success. Networks can audit and reflect on their success in promoting such relationships and a more formal qualitative evaluation by an independent observer can document their success to those responsible for funding. PMID:11141879

  12. Estimating crop net primary production using inventory data and MODIS-derived parameters

    SciTech Connect

    Bandaru, Varaprasad; West, Tristram O.; Ricciuto, Daniel M.; Izaurralde, Roberto C.

    2013-06-03

    National estimates of spatially-resolved cropland net primary production (NPP) are needed for diagnostic and prognostic modeling of carbon sources, sinks, and net carbon flux. Cropland NPP estimates that correspond with existing cropland cover maps are needed to drive biogeochemical models at the local scale and over national and continental extents. Existing satellite-based NPP products tend to underestimate NPP on croplands. A new Agricultural Inventory-based Light Use Efficiency (AgI-LUE) framework was developed to estimate individual crop biophysical parameters for use in estimating crop-specific NPP. The method is documented here and evaluated for corn and soybean crops in Iowa and Illinois in years 2006 and 2007. The method includes a crop-specific enhanced vegetation index (EVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS), shortwave radiation data estimated using Mountain Climate Simulator (MTCLIM) algorithm and crop-specific LUE per county. The combined aforementioned variables were used to generate spatially-resolved, crop-specific NPP that correspond to the Cropland Data Layer (CDL) land cover product. The modeling framework represented well the gradient of NPP across Iowa and Illinois, and also well represented the difference in NPP between years 2006 and 2007. Average corn and soybean NPP from AgI-LUE was 980 g C m-2 yr-1 and 420 g C m-2 yr-1, respectively. This was 2.4 and 1.1 times higher, respectively, for corn and soybean compared to the MOD17A3 NPP product. Estimated gross primary productivity (GPP) derived from AgI-LUE were in close agreement with eddy flux tower estimates. The combination of new inputs and improved datasets enabled the development of spatially explicit and reliable NPP estimates for individual crops over large regional extents.

  13. Leaf demography and physiology of the Tapajós National Forest: could phenology cause a forest-level increase in gross primary productivity during the dry season?

    NASA Astrophysics Data System (ADS)

    Albert, L.; Wu, J.; Prohaska, N.; Camargo, P. B. D.; Cosme, R., Jr.; Huxman, T. E.; Saleska, S. R.

    2014-12-01

    Tropical forests such as the forests of the Amazon basin are a significant component of the earth's carbon budget, yet how these forests respond to seasonal changes in weather, along with the extent to which tree biology synchronizes with seasonal cycles, are poorly understood. For evergreen forests in equatorial Amazon that experience dry seasons, most global vegetation models project a dry-season decrease in gross primary productivity (GPP). However, eddy covariance observations and remote sensing assessments suggest a late-dry season increase in GPP. Most global vegetation models assume that there is no seasonal variation in leaf phenology (cycles of leaf flush and senescence), or in leaf physiology. We conducted a case study in the Tapajos National Forest KM67 site, near Santarém, Brazil, to investigate whether leaf aging and seasonal shifts in leaf demography could cause an increase in GPP during the dry season. In a series of fieldwork campaigns beginning in August 2012, we monitored leaf demographic composition (leaf age categories) from 1-m branches collected from 20 trees representing abundant species, and we assessed how photosynthesis varies with leaf age for a subset of these trees. Our results show that photosynthetic capacity (e.g. Vcmax) is higher for leaves that matured during the most recent dry season than for older leaves from previous periods of growth. For many trees, leaf demography shifted during the dry season such that recently matured leaves replaced old leaves. For instance, leaf demography of an Erisma uncinatum, the most abundant canopy tree species at our site, had significantly more recently matured leaves, and significantly fewer old leaves, during surveys late in the dry season (after mid-October) than early in the dry season (prior to mid-September). These results suggest that shifts in leaf demography together with the effects of leaf age on leaf physiology can increase GPP during the dry season at the KM67 site. Thus, leaf

  14. A Simulation of the Importance of Length of Growing Season and Canopy Functional Properties on the Seasonal Gross Primary Production of Temperate Alpine Meadows

    PubMed Central

    Baptist, Florence; Choler, Philippe

    2008-01-01

    Background and Aims Along snowmelt gradients, the canopies of temperate alpine meadows differ strongly in their structural and biochemical properties. Here, a study is made of the effects of these canopy dissimilarities combined with the snow-induced changes in length of growing season on seasonal gross primary production (GPP). Methods Leaf area index (LAI) and community-aggregated values of leaf angle and leaf nitrogen content were estimated for seven alpine plant canopies distributed along a marked snowmelt gradient, and these were used as input variables in a sun–shade canopy bulk-photosynthesis model. The model was validated for plant communities of early and late snowmelt sites by measuring the instantaneous CO2 fluxes with a canopy closed-chamber technique. A sensitivity analysis was conducted to estimate the relative impact of canopy properties and environmental factors on the daily and seasonal GPP. Key Results Carbon uptake was primarily related to the LAI and total canopy nitrogen content, but not to the leaf angle. For a given level of photosynthetically active radiation, CO2 assimilation was higher under overcast conditions. Sensitivity analysis revealed that increase of the length of the growing season had a higher effect on the seasonal GPP than a similar increase of any other factor. It was also found that the observed greater nitrogen content and larger LAI of canopies in late-snowmelt sites largely compensated for the negative impact of the reduced growing season. Conclusions The results emphasize the primary importance of snow-induced changes in length of growing season on carbon uptake in alpine temperate meadows. It was also demonstrated how using leaf-trait values of the dominants is a useful approach for modelling ecosystem carbon-cycle-related processes, particularly when continuous measurements of CO2 fluxes are technically difficult. The study thus represents an important step in addressing the challenge of using a plant functional

  15. Diagnosing the Dynamics of Observed and Simulated Ecosystem Gross Primary Productivity with Time Causal Information Theory Quantifiers.

    PubMed

    Sippel, Sebastian; Lange, Holger; Mahecha, Miguel D; Hauhs, Michael; Bodesheim, Paul; Kaminski, Thomas; Gans, Fabian; Rosso, Osvaldo A

    2016-01-01

    Data analysis and model-data comparisons in the environmental sciences require diagnostic measures that quantify time series dynamics and structure, and are robust to noise in observational data. This paper investigates the temporal dynamics of environmental time series using measures quantifying their information content and complexity. The measures are used to classify natural processes on one hand, and to compare models with observations on the other. The present analysis focuses on the global carbon cycle as an area of research in which model-data integration and comparisons are key to improving our understanding of natural phenomena. We investigate the dynamics of observed and simulated time series of Gross Primary Productivity (GPP), a key variable in terrestrial ecosystems that quantifies ecosystem carbon uptake. However, the dynamics, patterns and magnitudes of GPP time series, both observed and simulated, vary substantially on different temporal and spatial scales. We demonstrate here that information content and complexity, or Information Theory Quantifiers (ITQ) for short, serve as robust and efficient data-analytical and model benchmarking tools for evaluating the temporal structure and dynamical properties of simulated or observed time series at various spatial scales. At continental scale, we compare GPP time series simulated with two models and an observations-based product. This analysis reveals qualitative differences between model evaluation based on ITQ compared to traditional model performance metrics, indicating that good model performance in terms of absolute or relative error does not imply that the dynamics of the observations is captured well. Furthermore, we show, using an ensemble of site-scale measurements obtained from the FLUXNET archive in the Mediterranean, that model-data or model-model mismatches as indicated by ITQ can be attributed to and interpreted as differences in the temporal structure of the respective ecological time

  16. Vegetation Responses to Future Climates: Global Variability in Water Use Efficiency and Primary Productivity in a CMIP5 Multimodel Ensemble

    NASA Astrophysics Data System (ADS)

    Bernardes, S.; Campbell, P. K. E.; Zhang, Q.; Middleton, E.

    2015-12-01

    Climate projections for the 21st century predict substantial changes in temperature and in the quantity and spatiotemporal distribution of precipitation for large regions on the planet. Reductions in water availability resulting from decreased precipitation and increased water demand by the atmosphere can negatively affect plant metabolism, reduce carbon uptake, and limit services of entire ecosystems. Future increases in temperature and in atmospheric carbon dioxide concentrations may help offset some of these impacts on vegetation. In particular, plants may adjust their water use efficiency (WUE, plant production per water loss by evapotranspiration) in response to changing environmental conditions. We assessed an ensemble of thirteen models from the Coupled Model Intercomparison Project 5 (CMIP5) and analyzed future changes in climate variables, carbon mass in vegetation, vegetation primary productivity and WUE. The analysis considered two representative concentration pathways (RCP4.5 and RCP8.5) for the period 2006-2099 and compared projections to historical values (1850-2005). Results include differences between historical and projected conditions for global, regional and latitudinal distributions of model outputs, for both RCPs. We observed significant intermodel variability when representing changes in WUE over the century, including high model sensitivity to different greenhouse concentration scenarios. Model agreement varied with RCP (higher agreement for RCP4.5), as well as regionally (higher agreement in Southeast Asia, lower agreement in arid areas, including the Sahara and Western Australia). The majority of models point to an increase in GPP and WUE for most of the planet under both concentration pathways, with changes ranging from zero to 100% of their historical values. These increases were observed to be consistently higher for RCP8.5. In addition, higher increases in GPP and WUE are predicted to occur over higher latitudes in the northern

  17. Diagnosing the Dynamics of Observed and Simulated Ecosystem Gross Primary Productivity with Time Causal Information Theory Quantifiers

    PubMed Central

    Sippel, Sebastian; Mahecha, Miguel D.; Hauhs, Michael; Bodesheim, Paul; Kaminski, Thomas; Gans, Fabian; Rosso, Osvaldo A.

    2016-01-01

    Data analysis and model-data comparisons in the environmental sciences require diagnostic measures that quantify time series dynamics and structure, and are robust to noise in observational data. This paper investigates the temporal dynamics of environmental time series using measures quantifying their information content and complexity. The measures are used to classify natural processes on one hand, and to compare models with observations on the other. The present analysis focuses on the global carbon cycle as an area of research in which model-data integration and comparisons are key to improving our understanding of natural phenomena. We investigate the dynamics of observed and simulated time series of Gross Primary Productivity (GPP), a key variable in terrestrial ecosystems that quantifies ecosystem carbon uptake. However, the dynamics, patterns and magnitudes of GPP time series, both observed and simulated, vary substantially on different temporal and spatial scales. We demonstrate here that information content and complexity, or Information Theory Quantifiers (ITQ) for short, serve as robust and efficient data-analytical and model benchmarking tools for evaluating the temporal structure and dynamical properties of simulated or observed time series at various spatial scales. At continental scale, we compare GPP time series simulated with two models and an observations-based product. This analysis reveals qualitative differences between model evaluation based on ITQ compared to traditional model performance metrics, indicating that good model performance in terms of absolute or relative error does not imply that the dynamics of the observations is captured well. Furthermore, we show, using an ensemble of site-scale measurements obtained from the FLUXNET archive in the Mediterranean, that model-data or model-model mismatches as indicated by ITQ can be attributed to and interpreted as differences in the temporal structure of the respective ecological time

  18. On the relationship between leaf photosynthetic capacity and leaf chlorophyll and implications for simulating GPP in space and time

    NASA Astrophysics Data System (ADS)

    Houborg, R.; Cescatti, A.; Migliavacca, M.

    2012-12-01

    Advancing the use of remote sensing data for retrieving key vegetation physiological controls is of critical importance for modeling spatio-temporal variations in gross primary productivity (GPP) with high fidelity. Key land-surface model controls on GPP, such as the maximum rate of carboxylation (Vcmax) that governs leaf photosynthetic efficiency, are typically assigned fixed literature-based values for broad categories of vegetation types although in reality temporal and spatial variability can be significant in response to differences in plant phenology and physiological condition, nutrient availability and climate. Vcmax defines the biochemical capacity of leaves to assimilate CO2 and is related to the nitrogen content of leaves, which is indirectly related to leaf reflectance and transmittance spectra. However, the fact that Vcmax is a leaf level parameter complicates larger scale parameterizations based on remote sensing observations due to confounding influences from the canopy and soil. Thus a key challenge is to separate the leaf contribution associated with changes in Vcmax from the total remote sensing signal. Chlorophylls are vital pigments for photosynthesis and directly controls leaf absorption in the visible waveband region. Here we report on the utility of satellite-based leaf chlorophyll (Chl) retrievals for quantifying Vcmax variability in space and time, and look into a mechanistic methodology for exploiting Chl information within the Community Land Model (CLM4) for improved predictability of GPP. Chl is retrieved from Landsat imagery by inversion of leaf optics and canopy reflectance models within the framework of REGFLEC (REGularized canopy reFLECtance tool). The potential of Chl retrievals for constraining model simulations of GPP is evaluated at multiple flux tower sites.ig. 1 Benefit of using satellite-based leaf chlorophyll (Chl) for parameterizing Vcmax and constraining modeled carbon fluxes over the growing season at a corn site in

  19. A Model-Data Fusion Approach for Constraining Modeled GPP at Global Scales Using GOME2 SIF Data

    NASA Astrophysics Data System (ADS)

    MacBean, N.; Maignan, F.; Lewis, P.; Guanter, L.; Koehler, P.; Bacour, C.; Peylin, P.; Gomez-Dans, J.; Disney, M.; Chevallier, F.

    2015-12-01

    Predicting the fate of the ecosystem carbon, C, stocks and their sensitivity to climate change relies heavily on our ability to accurately model the gross carbon fluxes, i.e. photosynthesis and respiration. However, there are large differences in the Gross Primary Productivity (GPP) simulated by different land surface models (LSMs), not only in terms of mean value, but also in terms of phase and amplitude when compared to independent data-based estimates. This strongly limits our ability to provide accurate predictions of carbon-climate feedbacks. One possible source of this uncertainty is from inaccurate parameter values resulting from incomplete model calibration. Solar Induced Fluorescence (SIF) has been shown to have a linear relationship with GPP at the typical spatio-temporal scales used in LSMs (Guanter et al., 2011). New satellite-derived SIF datasets have the potential to constrain LSM parameters related to C uptake at global scales due to their coverage. Here we use SIF data derived from the GOME2 instrument (Köhler et al., 2014) to optimize parameters related to photosynthesis and leaf phenology of the ORCHIDEE LSM, as well as the linear relationship between SIF and GPP. We use a multi-site approach that combines many model grid cells covering a wide spatial distribution within the same optimization (e.g. Kuppel et al., 2014). The parameters are constrained per Plant Functional type as the linear relationship described above varies depending on vegetation structural properties. The relative skill of the optimization is compared to a case where only satellite-derived vegetation index data are used to constrain the model, and to a case where both data streams are used. We evaluate the results using an independent data-driven estimate derived from FLUXNET data (Jung et al., 2011) and with a new atmospheric tracer, Carbonyl sulphide (OCS) following the approach of Launois et al. (ACPD, in review). We show that the optimization reduces the strong positive

  20. Continued increases in Arctic Ocean primary production

    NASA Astrophysics Data System (ADS)

    Arrigo, Kevin R.; van Dijken, Gert L.

    2015-08-01

    Dramatic declines in sea-ice cover in the Arctic Ocean in recent decades have the potential to fundamentally alter marine ecosystems. Here we investigate changes in sea ice between the years 1998 and 2012 at regional and basin scales and how these have impacted rates of phytoplankton net primary production (NPP). Annual NPP increased 30% over the Arctic Ocean during our study period, with the largest increases on the interior shelves and smaller increases on inflow shelves. Increased annual NPP was often, but not always, associated with reduced sea-ice extent and a longer phytoplankton growing season (fewer days of ice cover). Spatial patterns of increased annual NPP suggest that increased nutrient fluxes may also play an important role. Outflow shelves either exhibited no change in annual NPP during our study period or a significant decline, perhaps indicating that nutrients had been consumed by increased NPP farther upstream.

  1. Primary and Bacterial Production in Two Dimictic Indiana Lakes

    PubMed Central

    Lovell, Charles R.; Konopka, Allan

    1985-01-01

    The relationship between primary and bacterial production in two dimictic Indiana lakes with different primary productivities was examined during the summer stratification period in 1982. Primary production rates were calculated from rates of H14CO3− incorporation by natural samples, and bacterial production was calculated from rates of [3H-methyl]thymidine incorporation by natural samples. Both vertical and seasonal distributions of bacterial production in the more productive lake (Little Crooked Lake) were strongly influenced by primary production. A lag of about 2 weeks between a burst in primary production and the subsequent response in bacterial production was observed. The vertical distribution of bacterial production in the water column of the less productive lake (Crooked Lake) was determined by the vertical distribution of primary production, but no clear relationship between seasonal maxima of primary and bacterial production in this lake was observed. High rates of bacterial production in Crooked Lake during May indicate the importance of allochthonous carbon washed in by spring rains. Bacterial production accounted for 30.6 and 31.8% of total (primary plus bacterial) production in Crooked Lake and Little Crooked Lake, respectively, from April through October. High rates of bacterial production during late September and October were observed in both lakes. Calculation of the fraction of bacterial production supported by phytoplankton excretion implies an important role for other mechanisms of supplying carbon, such as phytoplankton autolysis. Several factors affecting the calculation of bacterial production from the thymidine incorporation rates in these lakes were examined. PMID:16346742

  2. Combining remote sensing and eddy covariance data to monitor the gross primary production of an estuarine wetland ecosystem in East China.

    PubMed

    Wu, Mingquan; Muhammad, Shakir; Chen, Fang; Niu, Zheng; Wang, Changyao

    2015-04-01

    Wetland ecosystems are very important for ecological diversity and have a strong ability to sequester carbon. Through comparisons with field measured eddy covariance data, we evaluated the relationships between the light use efficiency (LUE) index and the enhanced vegetation index (EVI), normalized difference vegetation index (NDVI), and land surface temperature (LST). Consequently, we have proposed a new model for the estimation of gross primary production (GPP) for wetland ecosystems using Moderate Resolution Imaging Spectroradiometer (MODIS) products, including these vegetation indices, LST and the fraction of photosynthetically active radiation (FAPAR) absorbed by the active vegetation. This model was developed and validated for a study site on Chongming Island, Shanghai, China. Our results show that photosynthetically active radiation (PAR) was highly correlated with the LST, with a coefficient of determination (R(2)) of 0.59 (p < 0.001). Vegetation indices, such as EVI, NDVI and LST, were highly correlated with LUE. We found that the product of vegetation indices (VIs) and a modified form of LST (Te) can be used to estimate LUE, with an R(2) of 0.82 (P < 0.0001) and an RMSE of 0.054 kg C per mol PAR. This new model can provide reliable estimates of GPP (R(2) of 0.87 and RMSE of 0.009 kg C m(-2) 8 d(-1) (P < 0.0001)).

  3. Understanding the output of a Smith-Root GPP electrofisher

    USGS Publications Warehouse

    Miranda, L.E.; Spencer, A.B.

    2005-01-01

    There is confusion among biologists about the use of the percent of range control in the GPP series of Smith-Root electrofishers. We evaluated the output of a GPP 7.5 electrofisher to examine how adjustments to the percent of range control affect voltage, pulse width, duty cycle, and waveform. We found that contrary to how most users interpret the labels on the GPP unit, adjustments to the percent of range control are linked only indirectly to changes in peak voltage. Suggestions for dealing with the restrictions of the GPP units are offered. ?? Copyright by the American Fisheries Society 2005.

  4. Herbivory and Stoichiometric Feedbacks to Primary Production.

    PubMed

    Krumins, Jennifer Adams; Krumins, Valdis; Forgoston, Eric; Billings, Lora; van der Putten, Wim H

    2015-01-01

    Established theory addresses the idea that herbivory can have positive feedbacks on nutrient flow to plants. Positive feedbacks likely emerge from a greater availability of organic carbon that primes the soil by supporting nutrient turnover through consumer and especially microbially-mediated metabolism in the detrital pool. We developed an entirely novel stoichiometric model that demonstrates the mechanism of a positive feedback. In particular, we show that sloppy or partial feeding by herbivores increases detrital carbon and nitrogen allowing for greater nitrogen mineralization and nutritive feedback to plants. The model consists of differential equations coupling flows among pools of: plants, herbivores, detrital carbon and nitrogen, and inorganic nitrogen. We test the effects of different levels of herbivore grazing completion and of the stoichiometric quality (carbon to nitrogen ratio, C:N) of the host plant. Our model analyses show that partial feeding and plant C:N interact because when herbivores are sloppy and plant biomass is diverted to the detrital pool, more mineral nitrogen is available to plants because of the stoichiometric difference between the organisms in the detrital pool and the herbivore. This model helps to identify how herbivory may feedback positively on primary production, and it mechanistically connects direct and indirect feedbacks from soil to plant production.

  5. Virulence in Pectobacterium atrosepticum is regulated by a coincidence circuit involving quorum sensing and the stress alarmone, (p)ppGpp.

    PubMed

    Bowden, Steven D; Eyres, Alison; Chung, Jade C S; Monson, Rita E; Thompson, Arthur; Salmond, George P C; Spring, David R; Welch, Martin

    2013-11-01

    Pectobacterium atrosepticum (Pca) is a Gram-negative phytopathogen which causes disease by secreting plant cell wall degrading exoenzymes (PCWDEs). Previous studies have shown that PCWDE production is regulated by (i) the intercellular quorum sensing (QS) signal molecule, 3-oxo-hexanoyl-l-homoserine lactone (OHHL), and (ii) the intracellular 'alarmone', (p)ppGpp, which reports on nutrient limitation. Here we show that these two signals form an integrated coincidence circuit which ensures that metabolically costly PCWDE synthesis does not occur unless the population is simultaneously quorate and nutrient limited. A (p)ppGpp null ΔrelAΔspoT mutant was defective in both OHHL and PCWDE production, and nutritional supplementation of wild type cultures (which suppresses (p)ppGpp production) also suppressed OHHL and PCWDE production. There was a substantial overlap in the transcriptome of a (p)ppGpp deficient relA mutant and of a QS defective expI (OHHL synthase) mutant, especially with regards to virulence-associated genes. Random transposon mutagenesis revealed that disruption of rsmA was sufficient to restore PCWDE production in the (p)ppGpp null strain. We found that the ratio of RsmA protein to its RNA antagonist, rsmB, was modulated independently by (p)ppGpp and QS. While QS predominantly controlled virulence by modulating RsmA levels, (p)ppGpp exerted regulation through the modulation of the RsmA antagonist, rsmB.

  6. Primary production in the northern Red Sea

    NASA Astrophysics Data System (ADS)

    Qurban, Mohammed Ali; Balala, Arvin C.; Kumar, Sanjeev; Bhavya, P. S.; Wafar, Mohideen

    2014-04-01

    Rates of uptake of carbon and nitrogen (ammonium, nitrate and urea) by phytoplankton, along with concentrations of nutrients and chlorophyll a, in the Saudi Arabian waters of the northern Red Sea (23 °N-28 °N) were measured in autumn, 2012. Concentrations of nitrate, nitrite and phosphate within the euphotic zone were in trace amounts while those of silicon were in excess of 0.5 μmol L- 1. Concentrations of chlorophyll (Chl a) were very low within the euphotic zone (0.01-0.6 μg L- 1 at discrete depths and 1.53-21.5 mg m- 2 as column-integrated values). A deep chlorophyll maximum and a nitrite maximum were present between 60 and 80 m at almost all of the stations occupied. Rates of carbon uptake at discrete depths ranged from 0.02 to 3 μg C L- 1 h- 1. Chl-normalized carbon uptake rates related with ambient light in a Michaelis-Menten kinetic pattern. About 80% of the carbon uptake was attributable to the < 20 μm fraction. Ammonium and urea were the nitrogen compounds taken up in preference by phytoplankton and accounted for close to 90% of the total N uptake. Considered together, these results indicate that the waters of the northern Red Sea are oligotrophic and that the primary production is strongly N-controlled. Analyses of the data and interpretation of the results led to the following speculations: (1) the perceived north-south gradient in Chl a (and possibly in primary production) in the Red Sea is maintained by circulation of Chl- and nutrient-rich waters through a series of gyres, (2) there is a greater role for heterotrophy and microbial loop in the trophic dynamics, and (3) in situ nitrification in the euphotic zone is an important source of N for phytoplankton and consequently export of carbon to deep sea could be lesser than that indicated by f-ratios.

  7. Primary productivity in the Golden Horn.

    PubMed

    Gönüllü, M Talha; Avşar, Yaşar; Bayhan, Hürrem; Sakar, Süeyman; Arslankaya, Ertan; Apaydin, Omer; Kurt, Uĝur

    2005-10-01

    The shores of the Golden Horn--once most important seaport of the region--represented throughout history a romantic and recreational venue. This tributary to the Bosphorus, however, became seriously polluted with the extensive industrialization and rapid population growth in Istanbul over the past century. Two main tributaries, the Alibeykoy and the Kagithane, dumped both liquid and solid waste from residential areas and industry (small and large-scale) into the Golden Horn. As a result of this pollution, the landward three to four kilometers of the estuary became swamped with sediment. The dominance of anaerobic activity resulted in a highly unpleasant smell, and the shallow depth as one progressed up the bay restricted navigation. In early 1997 The Istanbul Metropolitan Municipality began a dredging operation and gradually diverted all domestic and industrial wastewater discharge from the Golden Horn. Since then there have been remarkable improvements in water quality. This paper presents the state of eutrophication through the water body of the Golden Horn; parameters such as DO, TKN, NH(3)-N, NO(3)-N, the total phosphorus (TP) and dissolved phosphorus (PO(4)-P), phytoplankton and chlorophyll-a have been were analyzed in samples of water taken from various points in the Golden Horn. The presence of DO and the phytoplankton, both indicators of primary productivity in an aquatic body, has been evaluated in relation to former conditions.

  8. Parameterization of Oceanic Convection In Primary Production

    NASA Astrophysics Data System (ADS)

    Wehde, Henning

    The influence of Oceanic Convection in Primary Production was investigated in a numerical model study. Lagrangian tracers were introduced to a 2.5 dimensional non- hydrostatic convection model. Model domain is a vertical ocean slice with an isotropic grid size of 5 meters, vanishing gradients normal to the plane and cyclic lateral bound- ary conditions. The horizontal dimension is chosen according to the expected convec- tive aspect ratios that vary between 1 and 3. For each tracer a simple phytoplankton model predicts growth dependent on light conditions. The mean amount of light avail- able for growth for a plankton cell depends on the thickness of the mixed layer and the convective activity. The model was applied to several shelf and open ocean strat- ifications and forced with varying atmospheric conditions to study the sensitivity and to quantify the contact duration and return frequency of plankton into the euphotic zone. The phytoplankton concentration is closely related to the depth of the convec- tively mixed layer. The oceanic convection forms the actual mixed layer depth and was found to heavily influence the contact duration and return frequency of a plank- ton cell into the euphotic zone. Phytoplankton is dispersed by convection in vertical orbit cells. The vertical motion allow for the frequent return of plankton cells to the euphotic zone.

  9. A simplified gross primary production and evapotranspiration model for boreal coniferous forests - is a generic calibration sufficient?

    NASA Astrophysics Data System (ADS)

    Minunno, F.; Peltoniemi, M.; Launiainen, S.; Aurela, M.; Lindroth, A.; Lohila, A.; Mammarella, I.; Minkkinen, K.; Mäkelä, A.

    2015-07-01

    The problem of model complexity has been lively debated in environmental sciences as well as in the forest modelling community. Simple models are less input demanding and their calibration involves a lower number of parameters, but they might be suitable only at local scale. In this work we calibrated a simplified ecosystem process model (PRELES) to data from multiple sites and we tested if PRELES can be used at regional scale to estimate the carbon and water fluxes of Boreal conifer forests. We compared a multi-site (M-S) with site-specific (S-S) calibrations. Model calibrations and evaluations were carried out by the means of the Bayesian method; Bayesian calibration (BC) and Bayesian model comparison (BMC) were used to quantify the uncertainty in model parameters and model structure. To evaluate model performances BMC results were combined with more classical analysis of model-data mismatch (M-DM). Evapotranspiration (ET) and gross primary production (GPP) measurements collected in 10 sites of Finland and Sweden were used in the study. Calibration results showed that similar estimates were obtained for the parameters at which model outputs are most sensitive. No significant differences were encountered in the predictions of the multi-site and site-specific versions of PRELES with exception of a site with agricultural history (Alkkia). Although PRELES predicted GPP better than evapotranspiration, we concluded that the model can be reliably used at regional scale to simulate carbon and water fluxes of Boreal forests. Our analyses underlined also the importance of using long and carefully collected flux datasets in model calibration. In fact, even a single site can provide model calibrations that can be applied at a wider spatial scale, since it covers a wide range of variability in climatic conditions.

  10. Global patterns in human consumption of net primary production

    NASA Astrophysics Data System (ADS)

    Imhoff, Marc L.; Bounoua, Lahouari; Ricketts, Taylor; Loucks, Colby; Harriss, Robert; Lawrence, William T.

    2004-06-01

    The human population and its consumption profoundly affect the Earth's ecosystems. A particularly compelling measure of humanity's cumulative impact is the fraction of the planet's net primary production that we appropriate for our own use. Net primary production-the net amount of solar energy converted to plant organic matter through photosynthesis-can be measured in units of elemental carbon and represents the primary food energy source for the world's ecosystems. Human appropriation of net primary production, apart from leaving less for other species to use, alters the composition of the atmosphere, levels of biodiversity, energy flows within food webs and the provision of important ecosystem services. Here we present a global map showing the amount of net primary production required by humans and compare it to the total amount generated on the landscape. We then derive a spatial balance sheet of net primary production `supply' and `demand' for the world. We show that human appropriation of net primary production varies spatially from almost zero to many times the local primary production. These analyses reveal the uneven footprint of human consumption and related environmental impacts, indicate the degree to which human populations depend on net primary production `imports' and suggest policy options for slowing future growth of human appropriation of net primary production.

  11. Global Patterns in Human Consumption of Net Primary Production

    NASA Technical Reports Server (NTRS)

    Imhoff, Marc L.; Bounoua, Lahouari; Ricketts, Taylor; Loucks, Colby; Harriss, Robert; Lawrence William T.

    2004-01-01

    The human population and its consumption profoundly affect the Earth's ecosystems. A particularly compelling measure of humanity's cumulative impact is the fraction of the planet's net primary production that we appropriate for our Net primary production-the net amount of solar energy converted to plant organic matter through photosynthesis-can be measured in units of elemental carbon and represents the primary food energy source for the world's ecosystems. Human appropriation of net primary production, apart from leaving less for other species to use, alters the composition of the atmosphere, levels of biodiversity, flows within food webs and the provision of important primary production required by humans and compare it to the total amount generated on the landscape. We then derive a spatial ba!mce sheet of net primary production supply and demand for the world. We show that human appropriation of net primary production varies spatially from almost zero to many times the local primary production. These analyses reveal the uneven footprint of human consumption and related environmental impacts, indicate the degree to which human populations depend on net primary production "imports" and suggest policy options for slowing future growth of human appropriation of net primary production.

  12. Global patterns in human consumption of net primary production.

    PubMed

    Imhoff, Marc L; Bounoua, Lahouari; Ricketts, Taylor; Loucks, Colby; Harriss, Robert; Lawrence, William T

    2004-06-24

    The human population and its consumption profoundly affect the Earth's ecosystems. A particularly compelling measure of humanity's cumulative impact is the fraction of the planet's net primary production that we appropriate for our own use. Net primary production--the net amount of solar energy converted to plant organic matter through photosynthesis--can be measured in units of elemental carbon and represents the primary food energy source for the world's ecosystems. Human appropriation of net primary production, apart from leaving less for other species to use, alters the composition of the atmosphere, levels of biodiversity, energy flows within food webs and the provision of important ecosystem services. Here we present a global map showing the amount of net primary production required by humans and compare it to the total amount generated on the landscape. We then derive a spatial balance sheet of net primary production 'supply' and 'demand' for the world. We show that human appropriation of net primary production varies spatially from almost zero to many times the local primary production. These analyses reveal the uneven footprint of human consumption and related environmental impacts, indicate the degree to which human populations depend on net primary production 'imports' and suggest policy options for slowing future growth of human appropriation of net primary production.

  13. Importance of coastal primary production in the northern Baltic Sea.

    PubMed

    Ask, Jenny; Rowe, Owen; Brugel, Sonia; Strömgren, Mårten; Byström, Pär; Andersson, Agneta

    2016-10-01

    In this study, we measured depth-dependent benthic microalgal primary production in a Bothnian Bay estuary to estimate the benthic contribution to total primary production. In addition, we compiled data on benthic microalgal primary production in the entire Baltic Sea. In the estuary, the benthic habitat contributed 17 % to the total annual primary production, and when upscaling our data to the entire Bothnian Bay, the corresponding value was 31 %. This estimated benthic share (31 %) is three times higher compared to past estimates of 10 %. The main reason for this discrepancy is the lack of data regarding benthic primary production in the northern Baltic Sea, but also that past studies overestimated the importance of pelagic primary production by not correcting for system-specific bathymetric variation. Our study thus highlights the importance of benthic communities for the northern Baltic Sea ecosystem in general and for future management strategies and ecosystem studies in particular.

  14. Modelling Lake Primary Production Based on Satellite Data

    NASA Astrophysics Data System (ADS)

    Soomets, Tuuli; Kutser, Tiit; Danckaert, Thomas

    2015-12-01

    The productivity of the lakes has a marked importance in the estimation of their ecological state and for predicting their development in the future. Combining modelling with Earth Observation data facilitates a new perspective for lake primary production studies. In this study the primary production was modelled for a 3 different large lakes (Geneva, Peipsi and Võrtsjärv) using MERIS images. We used a semi-empirical model that estimates primary production as a function of photosynthetically absorbed radiation and quantum yield of carbon fixation. The necessary input parameters of the model (concentration of chlorophyll a, downwelling irradiance, and the diffuse attenuation coefficient) were obtained from MERIS products. The primary production maps allow us to study temporal and spatial changes in those lakes.

  15. Interannual Variation in Phytoplankton Primary Production at a Global Scale

    NASA Technical Reports Server (NTRS)

    Rousseaux, Cecile Severine; Gregg, Watson W.

    2013-01-01

    We used the NASA Ocean Biogeochemical Model (NOBM) combined with remote sensing data via assimilation to evaluate the contribution of four phytoplankton groups to the total primary production. First, we assessed the contribution of each phytoplankton groups to the total primary production at a global scale for the period 1998-2011. Globally, diatoms contributed the most to the total phytoplankton production ((is)approximately 50%, the equivalent of 20 PgC·y1). Coccolithophores and chlorophytes each contributed approximately 20% ((is) approximately 7 PgC·y1) of the total primary production and cyanobacteria represented about 10% ((is) approximately 4 PgC·y1) of the total primary production. Primary production by diatoms was highest in the high latitudes ((is) greater than 40 deg) and in major upwelling systems (Equatorial Pacific and Benguela system). We then assessed interannual variability of this group-specific primary production over the period 1998-2011. Globally the annual relative contribution of each phytoplankton groups to the total primary production varied by maximum 4% (1-2 PgC·y1). We assessed the effects of climate variability on group-specific primary production using global (i.e., Multivariate El Niño Index, MEI) and "regional" climate indices (e.g., Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO)). Most interannual variability occurred in the Equatorial Pacific and was associated with climate variability as indicated by significant correlation (p (is) less than 0.05) between the MEI and the group-specific primary production from all groups except coccolithophores. In the Atlantic, climate variability as indicated by NAO was significantly correlated to the primary production of 2 out of the 4 groups in the North Central Atlantic (diatoms/cyanobacteria) and in the North Atlantic (chlorophytes and coccolithophores). We found that climate variability as indicated by SAM had only a limited effect

  16. A (p)ppGpp-null mutant of Haemophilus ducreyi is partially attenuated in humans due to multiple conflicting phenotypes.

    PubMed

    Holley, Concerta; Gangaiah, Dharanesh; Li, Wei; Fortney, Kate R; Janowicz, Diane M; Ellinger, Sheila; Zwickl, Beth; Katz, Barry P; Spinola, Stanley M

    2014-08-01

    (p)ppGpp responds to nutrient limitation through a global change in gene regulation patterns to increase survival. The stringent response has been implicated in the virulence of several pathogenic bacterial species. Haemophilus ducreyi, the causative agent of chancroid, has homologs of both relA and spoT, which primarily synthesize and hydrolyze (p)ppGpp in Escherichia coli. We constructed relA and relA spoT deletion mutants to assess the contribution of (p)ppGpp to H. ducreyi pathogenesis. Both the relA single mutant and the relA spoT double mutant failed to synthesize (p)ppGpp, suggesting that relA is the primary synthetase of (p)ppGpp in H. ducreyi. Compared to the parent strain, the double mutant was partially attenuated for pustule formation in human volunteers. The double mutant had several phenotypes that favored attenuation, including increased sensitivity to oxidative stress. The increased sensitivity to oxidative stress could be complemented in trans. However, the double mutant also exhibited phenotypes that favored virulence. When grown to the mid-log phase, the double mutant was significantly more resistant than its parent to being taken up by human macrophages and exhibited increased transcription of lspB, which is involved in resistance to phagocytosis. Additionally, compared to the parent, the double mutant also exhibited prolonged survival in the stationary phase. In E. coli, overexpression of DksA compensates for the loss of (p)ppGpp; the H. ducreyi double mutant expressed higher transcript levels of dksA than the parent strain. These data suggest that the partial attenuation of the double mutant is likely the net result of multiple conflicting phenotypes.

  17. Seasonal trends of spectral indexes for monitoring GPP in a Mediterranean cork oak savanna

    NASA Astrophysics Data System (ADS)

    Cerasoli, S.; Silva, J. M. N.; Carvalhais, N.; Silva, F.; López, G.; Pereira, J. M. C.; Pereira, J. S.

    2012-04-01

    It is nowadays clear that the inclusion of spectral indexes into biogeochemical models can greatly improve actual estimates of gross primary productivity (GPP) at local and global scale. Several vegetation indexes can be obtained by the reflectance of light at specific wavelengths. Among them, the Normalized Vegetation Index (NDVI), the Enhanced Vegetation Index (EVI) and the Photochemical Reflectance Index (PRI) were found suitable to represent different characteristics of ecosystems strictly related with GPP, such as biomass and photosynthetic capacity (NDVI, EVI) or radiation use efficiency (PRI). In Mediterranean cork oak savannas, characterized by high heterogeneity, the application of spectral indexes derived from coarse spatial resolution remotely sensed data (e.g. MODIS imagery) to represent the performance of the whole ecosystem is complex. A better knowledge of the variability of vegetation indexes for specific vegetation types, assessed in fieldwork, is fundamental to the interpretation of the same indexes obtained with satellite data and a key step through the integration of such indexes into biogeochemical models. We consider three different vegetation types: trees, grasses and shrubs, concurring to the overall ecosystem carbon budget in Mediterranean cork oak savannas. Since April 2011, reflectance measurements were performed in the range of 300-2500nm by the use of a handheld hyperspectral spectroradiometer (FieldSpec3, ASD Inc. CO, USA) in several species of the three vegetation types in a cork oak savanna eddy covariance site located in central Portugal. Measurements were always performed around solar noon and repeated approximately every two weeks. Several vegetation indexes were calculated. All indexes showed clear differences among vegetation types and among species. Marked seasonal trends were identified for grasses and shrubs, clearly related with the onset of dry summer conditions. Both NDVI and EVI decreased in grasses from April to the

  18. Intertidal invertebrates locally enhance primary production.

    PubMed

    Pfister, Catherine A

    2007-07-01

    The contribution of autochthonous vs. allochthonous inputs to productivity is an important determinant of ecosystem function across multiple habitats. In coastal marine systems, nutrients are thought to come primarily from the upwelling of deep, nutrient-rich water. Using experimental manipulations of a dominant tide pool animal, the mussel Mytilus californianus, I show that the presence of mussels greatly increases the supply of inorganic nitrogen and phosphorus. Mussels further had a direct effect on productivity: benthic microalgal abundance increased by a factor of 4-8, while the growth of a red alga was four times greater in the presence of mussels. The increase in nitrite and nitrate associated with mussels further suggests nitrifying activity by microbes. These findings have broad implications for coastal marine systems, including that regenerated nutrients may contribute more to productivity than previously recognized and that the presence of animal-generated nutrients sets the stage for numerous positive interactions.

  19. Modeling gross primary production of agro-forestry ecosystems by assimilation of satellite-derived information in a process-based model.

    PubMed

    Migliavacca, Mirco; Meroni, Michele; Busetto, Lorenzo; Colombo, Roberto; Zenone, Terenzio; Matteucci, Giorgio; Manca, Giovanni; Seufert, Guenther

    2009-01-01

    In this paper we present results obtained in the framework of a regional-scale analysis of the carbon budget of poplar plantations in Northern Italy. We explored the ability of the process-based model BIOME-BGC to estimate the gross primary production (GPP) using an inverse modeling approach exploiting eddy covariance and satellite data. We firstly present a version of BIOME-BGC coupled with the radiative transfer models PROSPECT and SAILH (named PROSAILH-BGC) with the aims of i) improving the BIOME-BGC description of the radiative transfer regime within the canopy and ii) allowing the assimilation of remotely-sensed vegetation index time series, such as MODIS NDVI, into the model. Secondly, we present a two-step model inversion for optimization of model parameters. In the first step, some key ecophysiological parameters were optimized against data collected by an eddy covariance flux tower. In the second step, important information about phenological dates and about standing biomass were optimized against MODIS NDVI. Results obtained showed that the PROSAILH-BGC allowed simulation of MODIS NDVI with good accuracy and that we described better the canopy radiation regime. The inverse modeling approach was demonstrated to be useful for the optimization of ecophysiological model parameters, phenological dates and parameters related to the standing biomass, allowing good accuracy of daily and annual GPP predictions. In summary, this study showed that assimilation of eddy covariance and remote sensing data in a process model may provide important information for modeling gross primary production at regional scale.

  20. Modeling GPP in Semi-arid Inner Mongolia using MODIS Imagery and Tower-based Fluxes

    NASA Astrophysics Data System (ADS)

    John, R.; Chen, J.; Noormets, A.; Xu, J.

    2011-12-01

    Semi-arid Inner Mongolia is experiencing climate change with associated land cover/use change that includes an increase in irrigated agriculture and population growth. We evaluate temporal scaling up of carbon fluxes from eddy covariance (EC) tower observations in different water-limited land cover/use and biome types. The Vegetation Photosynthesis model (VPM) and modified VPM (MVPM), driven by Enhanced Vegetation Index (EVI) and Land Surface Water Index (LSWI) for 2006-2007 that were derived from MODIS surface reflectance product (MOD09A1) was used to scale up and validate temporal changes in GPP from the EC towers during 2006 & 2007 growing seasons. The VPM model predicted the annual GPP (GPPvpm) reasonably well at the Duolun cropland (R2 = 0.67 & 0.71) and Xilinhaote typical steppe (R2 = 0.80 & 0.73). The predictive power of VPM varied in the desert steppe, at an irrigated poplar stand (R2 = 0.74 & 0.68) and nearby shrubland in Kubuqi (R2 = 0.31 & 0.49). The comparison between GPPtower and GPPmvpm predicted GPP showed good agreement for the Xilinhaote typical steppe (R2 = 0.84 & 0.70) in 2006-2007, Duolun typical steppe (R2 = 0.63), and cropland (R2 = 0.63) in 2007. The predictive power of MVPM decreased slightly in the desert steppe, at the irrigated poplar stand (R2 = 0.55 & .47) and the shrubland (R2 = 0.20 & 0.41). The results of this study demonstrate the feasibility of scaling up GPP from EC towers to the regional scale. The inter & intra-annual changes in dynamics of GPP in Inner Mongolia are especially relevant given the extreme climate events on the Mongolian Plateau. We seek to study the effects of drought in the Mongolian plateau through the mapping of anomalies in different vegetation indices (EVI, NDVI, SAVI) as well as functional variables (GPP, ET) during the MODIS decade (2001-2010). Our research question is: What is the biome response to the severe dzuds (extreme winters) and summer droughts? We then compared the MODIS data to spatially

  1. Global Regulation by (p)ppGpp and CodY in Streptococcus mutans▿ †

    PubMed Central

    Lemos, José A.; Nascimento, Marcelle M.; Lin, Vanessa K.; Abranches, Jacqueline; Burne, Robert A.

    2008-01-01

    The RelA, RelP, and RelQ enzymes are responsible for the production of the alarmone (p)ppGpp in Streptococcus mutans. A strain lacking all three synthetases (ΔrelAPQ) does not grow in minimal medium lacking the branched-chain amino acids (BCAA) leucine or valine but grows well if isoleucine is also omitted. Here, we investigated whether there was a correlation between growth in the absence of leucine and valine with (p)ppGpp pools and the activation of CodY. By using a combination of single, double, and triple mutants lacking the (p)ppGpp synthetase enzymes, we demonstrated that the ability to grow in the absence of leucine or valine required basal levels of (p)ppGpp production by RelP and RelQ. The introduction of a codY mutation into the ΔrelAPQ strain fully restored growth in medium lacking leucine or valine, revealing that the growth-defective phenotype of ΔrelAPQ was directly linked to CodY. Lowering GTP levels through the addition of decoyinine did not alleviate CodY repression or affect the expression of genes involved in BCAA biosynthesis, suggesting that S. mutans CodY is not activated by GTP. The results of phenotypic studies revealed that the codY mutant had a reduced capacity to form biofilms and that its growth was more sensitive to low pH, showing a role for CodY in two key virulence properties of S. mutans. Microarray results revealed the extent of the CodY regulon. Notably, the identification of putative CodY-binding boxes upstream of genes that were downregulated in the codY mutant indicates that CodY may also function as a transcriptional activator in S. mutans. PMID:18539745

  2. (p)ppGpp-dependent and -independent pathways for salt tolerance in Escherichia coli.

    PubMed

    Tarusawa, Takefusa; Ito, Shion; Goto, Simon; Ushida, Chisato; Muto, Akira; Himeno, Hyouta

    2016-07-01

    Addition of some kinds of translation inhibitors targeting the ribosome such as kasugamycin to the culture medium as well as removal of a ribosome maturation factor or a ribosomal protein provides Escherichia coli cells with tolerance to high salt stress. Here, we found that another kind of translation inhibitor, serine hydroxamate (SHX), which induces amino acid starvation leading to (p)ppGpp production, also has a similar effect, but via a different pathway. Unlike kasugamycin, SHX was not effective in (p)ppGpp-null mutant cells. SHX and depletion of RsgA, a ribosome maturation factor, had an additive effect on salt tolerance, while kasugamycin or depletion of RsgA did not. These results indicate the presence of two distinct pathways, (p)ppGpp-dependent and -independent pathways, for salt tolerance of E. coli cell. Both pathways operate even in the absence of σ(S), an alternative sigma factor involved in the stationary phase or stress response. Hastened activation of the exocytoplasmic stress-specific sigma factor, σ(E), after salt shock was observed in the cells treated with SHX, as has been observed in the cells treated with a translation inhibitor or depleted of a ribosome maturation factor.

  3. Primary production of the cryptoendolithic microbiota from the Antarctic Desert

    NASA Technical Reports Server (NTRS)

    Vestal, J. R.; Friedmann, E. I. (Principal Investigator)

    1988-01-01

    Primary production in the Antarctic cryptoendolithic microbiota can be determined from biomass and photosynthetic 14CO2 incorporation measurements. Even though good nanoclimate data are available, it is difficult to determine the amount of time when abiotic conditions permit metabolism. Making appropriate assumptions concerning the metabolism of the cryptoendolithic microbiota during periods of warmth, light and moisture, the primary production of the biota was calculated to be on the order of 0.108 to 4.41 mgC/m2/yr, with a carbon turnover time from 576 to 23,520 years. These production values are the lowest found on planet Earth.

  4. Global climate change and terrestrial net primary production

    NASA Technical Reports Server (NTRS)

    Melillo, Jerry M.; Mcguire, A. D.; Kicklighter, David W.; Moore, Berrien, III; Vorosmarty, Charles J.; Schloss, Annette L.

    1993-01-01

    A process-based model was used to estimate global patterns of net primary production and soil nitrogen cycling for contemporary climate conditions and current atmospheric CO2 concentration. Over half of the global annual net primary production was estimated to occur in the tropics, with most of the production attributable to tropical evergreen forest. The effects of CO2 doubling and associated climate changes were also explored. The responses in tropical and dry temperate ecosystems were dominated by CO2, but those in northern and moist temperate ecosystems reflected the effects of temperature on nitrogen availability.

  5. Primary production of the cryptoendolithic microbiota from the Antarctic Desert.

    PubMed

    Vestal, J R

    1988-01-01

    Primary production in the Antarctic cryptoendolithic microbiota can be determined from biomass and photosynthetic 14CO2 incorporation measurements. Even though good nanoclimate data are available, it is difficult to determine the amount of time when abiotic conditions permit metabolism. Making appropriate assumptions concerning the metabolism of the cryptoendolithic microbiota during periods of warmth, light and moisture, the primary production of the biota was calculated to be on the order of 0.108 to 4.41 mgC/m2/yr, with a carbon turnover time from 576 to 23,520 years. These production values are the lowest found on planet Earth.

  6. Evaluation of the new MODIS fAPARchl product

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Cheng, Y.; Lyapustin, A.; Wang, Y.; Suyker, A.; Middleton, E.

    2013-12-01

    Accurately simulating the absorbed photosynthetically active radiation (PAR) for vegetation photosynthesis (APARPSN) and gross primary production (GPP) in terrestrial ecosystem models and land surface models is critical because errors in simulated APARPSN and GPP propagate through the models to introduce additional errors in simulated biomass and other fluxes. For the last three decades, fraction of PAR absorbed by a whole canopy (fAPARcanopy) and the normalized difference of vegetation index (NDVI) have been widely used to eatimate APARPSN and GPP. For the last decade, the enhanced vegetation index (EVI), the wide dynamic range vegetation index (WDRVI), the clorophyll index (CI), and the MOD15A2 FPAR have also been extensively utilized in estimating GPP. However, only the PAR absorbed by photosynthetic pigments (mainly chlorophyll, chl), not by the whole canopy, is used for vegetation photosynthesis. The MAIAC produced MODIS surface reflectance data were used in our study to calculate the vegetation indices and fAPARchl. This study explores the empirical relationships between fAPARchl vs. the four VIs (NDVI, EVI, WDRVI, and CI), and investigate how much uncertainty of the estimation of APARPSN and GPP will be reduced by using fAPARchl instead of fAPARcanopy. Our results show that using the site-specific empirical relationships between fAPARchl vs. the VIs can improve estimates of GPP. But the coefficients vary with locations/sites. Compared to MOD15A2 FPAR, the fAPARchl product significantly improves the accuracy and reduce the uncertainty of estimates of GPP

  7. Net primary productivity, allocation pattern and carbon use efficiency in an apple orchard assessed by integrating eddy covariance, biometric and continuous soil chamber measurements

    NASA Astrophysics Data System (ADS)

    Zanotelli, D.; Montagnani, L.; Manca, G.; Tagliavini, M.

    2013-05-01

    Carbon use efficiency (CUE), the ratio of net primary production (NPP) over gross primary production (GPP), is a functional parameter that could possibly link the current increasingly accurate global GPP estimates with those of net ecosystem exchange, for which global predictors are still unavailable. Nevertheless, CUE estimates are actually available for only a few ecosystem types, while information regarding agro-ecosystems is scarce, in spite of the simplified spatial structure of these ecosystems that facilitates studies on allocation patterns and temporal growth dynamics. We combined three largely deployed methods, eddy covariance, soil respiration and biometric measurements, to assess monthly values of CUE, NPP and allocation patterns in different plant organs in an apple orchard during a complete year (2010). We applied a measurement protocol optimized for quantifying monthly values of carbon fluxes in this ecosystem type, which allows for a cross check between estimates obtained from different methods. We also attributed NPP components to standing biomass increments, detritus cycle feeding and lateral exports. We found that in the apple orchard, both net ecosystem production and gross primary production on a yearly basis, 380 ± 30 g C m-2 and 1263 ± 189 g C m-2 respectively, were of a magnitude comparable to those of natural forests growing in similar climate conditions. The largest differences with respect to forests are in the allocation pattern and in the fate of produced biomass. The carbon sequestered from the atmosphere was largely allocated to production of fruit: 49% of annual NPP was taken away from the ecosystem through apple production. Organic material (leaves, fine root litter, pruned wood and early fruit falls) contributing to the detritus cycle was 46% of the NPP. Only 5% was attributable to standing biomass increment, while this NPP component is generally the largest in forests. The CUE, with an annual average of 0.71 ± 0.12, was higher

  8. Human Appropriation of Net Primary Production - Can Earth Keep Up?

    NASA Technical Reports Server (NTRS)

    Imhoff, Marc L.

    2006-01-01

    The amount of Earth's vegetation or net primary production required to support human activities is powerful measure of aggregate human impacts on the biosphere. Biophysical models applied to consumption statistics were used to estimate the annual amount of net primary production in the form of elemental carbon required for food, fibre, and fuel-wood by the global population. The calculations were then compared to satellite-based estimates of Earth's average net primary production to produce a geographically explicit balance sheet of net primary production "supply" and "demand". Humans consume 20% of Earth's net primary production (11.5 petagrams carbon) annually and this percentage varies regionally from 6% (South America) to over 70% (Europe and Asia), and locally from near 0% (central Australia) to over 30,000% (New York City, USA). The uneven footprint of human consumption and related environmental impacts, indicate the degree to which human populations are vulnerable to climate change and suggest policy options for slowing future growth of NPP demand.

  9. Nuclide production by primary cosmic-ray protons

    SciTech Connect

    Reedy, R.C.

    1986-01-01

    The production rates of cosmogenic nuclides in the solar system and in interstellar space were calculated for the primary protons in the galactic and solar cosmic rays. At 1 AU, the long-term average fluxes of solar protons usually produce many more atoms of a cosmogenic nuclide than the primary protons in the galactic cosmic rays (GCR), the exceptions being nuclides made only by high-energy reactions (like /sup 10/Be). Because the particle fluxes inside meteorites and other large objects in space include many secondary neutrons, the production rates are much higher and ratios inside large objects are often very different from those by just the primary GCR protons in small objects. The production rates of cosmogenic nuclides are calculated to vary by about factors of 2.5 during at typical 11-year solar cycle, in agreement with measurements of short-lived radionuclides in recently fallen meteorites. The production of cosmogenic nuclides by the GCR particles outside the heliosphere is higher than that by the modulated GCR primaries normally in the solar system. However, there is considerable uncertainty in the fluxes of interstellar protons and, therefore, in the production rates of cosmogenic nuclides in interstellar space. Production rates and ratios for cosmogenic nuclides would be able to identify particles that were small in space or that were exposed to an unmodulated spectrum of GCR particles. 25 refs., 2 figs., 2 tabs.

  10. Carbon Use Efficiency, and Net Primary Productivity of Terrestrial Vegetation

    NASA Astrophysics Data System (ADS)

    Choudhury, Bhaskar J.

    The carbon use efficiency (CUE), defined as the ratio of net carbon gain to gross carbon assimilation during a period, is a highly significant determinant of primary production of terrestrial plant communities. Available data for CUE is summarized. Then, a model for gross assimilation has been run using satellite and ancillary data to calculate annual net carbon gain or net primary productivity for the global land surface during four year period (1987-1990). The results are compared with other estimates. Interannual variability of 30-50% is found in some of the latitude bands

  11. Primary production control of methane emission from wetlands

    NASA Technical Reports Server (NTRS)

    Whiting, G. J.; Chanton, J. P.

    1993-01-01

    Based on simultaneous measurements of CO2 and CH4 exchange in wetlands extending from subarctic peatlands to subtropical marshes, a positive correlation between CH4 emission and net ecosystem production is reported. It is suggested that net ecosystem production is a master variable integrating many factors which control CH4 emission in vegetated wetlands. It is found that about 3 percent of the daily net ecosystem production is emitted back to the atmosphere as CH4. With projected stimulation of primary production and soil microbial activity in wetlands associated with elevated atmospheric CO2 concentration, the potential for increasing CH4 emission from inundated wetlands, further enhancing the greenhouse effect, is examined.

  12. Multi-objective assessment of three remote sensing vegetation products for streamflow prediction in a conceptual ecohydrological model

    NASA Astrophysics Data System (ADS)

    Naseem, Bushra; Ajami, Hoori; Liu, Yi; Cordery, Ian; Sharma, Ashish

    2016-12-01

    This study assesses the implications of using three alternate remote sensing vegetation products in the simulation of streamflow using a conceptual ecohydrologic model. Vegetation is represented as a dynamic component in this model which simulates two response variables, streamflow and one of the following three vegetation attributes: Gross Primary Productivity (GPP), Leaf Area Index (LAI) or Vegetation Optical Depth (VOD). Model simulations are performed across 50 catchments with areas ranging between 50 and 1600 km2 in the Murray-Darling Basin in Australia. Moderate Resolution Imaging Spectroradiometer (MODIS) LAI and GPP products, passive microwave observations of VOD and streamflow are used for model calibration and/or validation. Single-objective model calibration based on one of the vegetation products (GPP, LAI and VOD) shows that GPP is the best vegetation simulating product. On the contrary, LAI produces the best streamflow during validation when the optimized parameters are applied for streamflow estimation. To obtain the best compromise solution for simultaneous simulation of streamflow and a vegetation product, a multi-objective optimization is applied on GPP and streamflow, VOD and streamflow and LAI and streamflow. Results show that LAI and then VOD are the two best products in simulating streamflow across these catchments. Improved simulation of VOD and LAI in a multi-objective setting is partly related to the higher temporal resolution of these datasets and inclusion of processes for converting GPP to net primary productivity and biomass. It is suggested that further development of these remote sensing products at finer spatial and temporal resolutions may lead to improved streamflow prediction, as well as a better simulation capability of the ecohydrological system being modeled.

  13. Evaluation of primary production in Lake Erie by multiple proxies.

    PubMed

    Ostrom, Nathaniel E; Carrick, Hunter J; Twiss, Michael R; Piwinski, Leah

    2005-06-01

    Direct measurements of rates of primary production in Lake Erie are few and uncertainties surround rate measurements based on radiocarbon and the light-dark bottle incubation methods. For these reasons, we conducted a series of simultaneous primary productivity measurements in Lake Erie in July and August of 2003, based on incubation with [14C]-NaHCO3, the light-dark bottle method, and incubation with (18)O enriched water. Significant differences in the rates of primary production obtained by incubations with [(18)O]-H2O (0.19-34.60 mmol-O2 m(-3) h(-1)), [14C]-NaHCO3 (0.03-90.50 mmol-C m(-3) h(-1)), and light-dark bottles (0.06-60.78 mmol-O2 m(-3) h(-1)) were evident in six out of nine comparisons. Within the epilimnion, [(18)O]-H2O rates of primary production were significantly different from rates based on [14C]-NaHCO3 and light-dark bottles in all four comparisons and lower rates were obtained in three out of four comparisons. Eutrophic conditions in Sandusky Bay, Lake Erie were evident from the high primary production rates of 20.50-34.60 mmol-O2 m(-3) h(-1) ([(18)O]-H2O), 34.39-90.50 mmol-C m(-3) h(-1) ([14C]-NaHCO3), and 46.66-60.78 mmol-O2 m(-3) h(-1) (light-dark bottle). The photosynthetic quotient (PQ), or ratio of O2 production to CO2 consumption during photosynthesis, averaged 0.64+/-0.33 and 1.93+/-1.93, respectively, based on a comparison of [(18)O]-H2O to [14C]-NaHCO3 rates or light-dark bottle to [14C]-NaHCO3 production rates, respectively, demonstrating that photosynthesis in Lake Erie communities primarily follows expected stochiometric trends. The average of the ratio of production rates based on incubation with [(18)O]-H2O relative to those obtained by the light-dark incubation method was 0.66+/-0.33, indicating a tendency for the [(18)O]-H2O method to provide slightly lower estimates of production in Lake Erie. Lower estimates of primary production based on [(18)O]-H2O incubation relative to the other two approaches is most likely a consequence

  14. Comparisons of MODIS vegetation index products with biophysical and flux tower measurements

    NASA Astrophysics Data System (ADS)

    Sirikul, Natthanich

    Vegetation indices (VI) play an important role in studies of global climate and biogeochemical cycles, and are also positively related to many biophysical parameters and satellite products, such as leaf area index (LAI), gross primary production (GPP), land surface water index (LSWI) and land surface temperature (LST). In this study we found that VI's had strong relationships with some biophysical products, such as gross primary production, yet were less well correlated with biophysical structural parameters, such as leaf area index. The relationships between MODIS VI's and biophysical field measured LAI showed poor correlation at semi-arid land and broadleaf forest land cover type whereas cropland showed stronger correlations than the other vegetation types. In addition, the relationship between the enhanced vegetation index (EVI)-LAI and normalized difference vegetation index (NDVI)-LAI did not show significant differences. Comparisons of the relationships between the EVI and NDVI with tower-measured GPP from 11 flux towers in North America, showed that MODIS EVI had much stronger relationships with tower-GPP than did NDVI, and EVI was better correlated with the seasonal dynamics of GPP than was NDVI. In addition, there were no significant differences among the 1x1, 3x3 and 7x7 pixel sample sizes. The comparisons of VIs from the 3 MODIS products from which VI's are generated (Standard VI (MOD13)), Nadir Adjusted Surface Reflectance (NBAR (MOD43)), and Surface Reflectance (MOD09)), showed that MODIS NBAR-EVI (MOD43) was best correlated with GPP compared with the other VI products. In addition, the MODIS VI - tower GPP relationships were significantly improved using NBAR-EVI over the more complex canopy structures, such as the broadleaf and needleleaf forests. The relationship of tower-GPP with other MODIS products would be useful in more thorough characterization of some land cover types in which the VI's have encountered problems. The land surface temperature

  15. Magnesium for automotive applications: Primary production cost assessment

    NASA Astrophysics Data System (ADS)

    Das, Sujit

    2003-11-01

    Production technologies must be cost effective for primary magnesium to become an economically viable alternative material for wide spread automotive applications. In this article, the prices at which magnesium becomes competitive with aluminum and steel are examined, including magnesium production cost estimates for current and future scenarios using electrolytic and thermal processes. The economic viability of the industry for automotive applications is also examined in the context of magnesium market price, taking into consideration the dynamics of its supply and demand as well.

  16. Decadal Changes in Global Ocean Annual Primary Production

    NASA Technical Reports Server (NTRS)

    Gregg, Watson; Conkright, Margarita E.; Behrenfeld, Michael J.; Ginoux, Paul; Casey, Nancy W.; Koblinsky, Chester J. (Technical Monitor)

    2002-01-01

    The Sea-viewing Wide Field-of-View Sensor (SeaWiFS) has produced the first multi-year time series of global ocean chlorophyll observations since the demise of the Coastal Zone Color Scanner (CZCS) in 1986. Global observations from 1997-present from SeaWiFS combined with observations from 1979-1986 from the CZCS should in principle provide an opportunity to observe decadal changes in global ocean annual primary production, since chlorophyll is the primary driver for estimates of primary production. However, incompatibilities between algorithms have so far precluded quantitative analysis. We have developed and applied compatible processing methods for the CZCS, using modern advances in atmospheric correction and consistent bio-optical algorithms to advance the CZCS archive to comparable quality with SeaWiFS. We applied blending methodologies, where in situ data observations are incorporated into the CZCS and SeaWiFS data records, to provide improvement of the residuals. These re-analyzed, blended data records provide maximum compatibility and permit, for the first time, a quantitative analysis of the changes in global ocean primary production in the early-to-mid 1980's and the present, using synoptic satellite observations. An intercomparison of the global and regional primary production from these blended satellite observations is important to understand global climate change and the effects on ocean biota. Photosynthesis by chlorophyll-containing phytoplankton is responsible for biotic uptake of carbon in the oceans and potentially ultimately from the atmosphere. Global ocean annual primary decreased from the CZCS record to SeaWiFS, by nearly 6% from the early 1980s to the present. Annual primary production in the high latitudes was responsible for most of the decadal change. Conversely, primary production in the low latitudes generally increased, with the exception of the tropical Pacific. The differences and similarities of the two data records provide evidence

  17. Deep-sea primary production at the Galapagos hydrothermal vents

    SciTech Connect

    Karl, D.M.; Wirsen, C.O.; Jannasch, H.W.

    1980-03-21

    Dense animal populations surrounding recently discovered hydrothermal vents at the Galapagos Rift sea-floor spreading center, 2550 meters deep, are probably sustained by microbial primary production. Energy in the form of geothermically reduced sulfur compounds emitted from the vents is liberated during oxidation and used for the reduction of carbon dioxide to organic matter by chemosynthetic bacteria.

  18. Forecasting annual aboveground net primary production in the intermountain west

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For many land manager’s annual aboveground net primary production, or plant growth, is a key factor affecting business success, profitability and each land manager's ability to successfully meet land management objectives. The strategy often utilized for forecasting plant growth is to assume every y...

  19. Carbon dioxide supersaturation promotes primary production in lakes.

    PubMed

    Jansson, Mats; Karlsson, Jan; Jonsson, Anders

    2012-06-01

    A majority of the world's lakes are supersaturated with respect to carbon dioxide (CO(2) ). By experimental manipulation of the CO(2) concentration in supersaturated boreal lakes, we demonstrate that phytoplankton primary production was up to 10 times higher in supersaturated lake water in comparison with water with CO(2) at equilibrium concentrations and that CO(2) , together with nutrients, explained most of the variation in pelagic primary production and phytoplankton biomass over a wide variety of unproductive lakes. These results suggest that phytoplankton can be co-limited by CO(2) and nutrients in unproductive lakes. As import of terrestrial organic carbon and its subsequent microbial mineralisation in lakes is a driving force of CO(2) -supersaturation our results suggest that lake productivity and carbon cycling may respond to variations in terrestrial organic carbon export, (e.g. caused by land use or climate change) in ways not described before.

  20. Scaling from Flux Towers to Ecosystem Models: Regional Constraints on GPP from Atmospheric Carbonyl Sulfide

    NASA Astrophysics Data System (ADS)

    Abu-Naser, M.; Campbell, J.; Berry, J. A.; Seibt, U.; Maseyk, K. S.; Torn, M. S.; Biraud, S. C.; Fischer, M. L.; Billesbach, D. P.; Baker, I. T.; Collatz, G. J.; Chen, H.; Montzka, S. A.; Sweeney, C.

    2012-12-01

    Process-level information on terrestrial carbon fluxes are typically observed at small spatial scales (e.g. eddy flux towers) but critical applications exist at much larger spatial scales (e.g. global ecosystem models). New methodologies are needed to fill this spatial gap. Recent work suggests that analysis of atmospheric carbonyl sulfide (COS) could fill this gap by providing constraints on GPP fluxes at large scales. This proposal is based on evidence that COS plant uptake is quantitatively related to photosynthesis and that COS plant uptake is the dominant COS budget flux influencing atmospheric concentrations over northern extratropical continents. Previous atmospheric analysis of COS has focused on continental or larger scales and only one ecosystem model. Here we explore the spatial and temporal COS variation within North America and their relationship to a range of ecosystem models using regional and global atmospheric transport models. Airborne COS observations are examined from the NOAA-ESRL network including 13 North American airborne sites and a total of 1,447 vertical profiles from years 2004 to 2012. In addition to COS plant uptake, we examined the influence of atmospheric transport treatments, boundary conditions, soil fluxes (mechanistic and empirical), and anthropogenic emissions. The atmospheric COS simulations were consistent with the primary observed spatial and temporal variations in the US mid-continent. This consistency is supportive of ecosystem models because the dominant input for these atmospheric COS simulations is ecosystem model GPP data. However, only the COS simulations driven by a subset of the ecosystem models were able to reproduce the observed COS seasonality in a semiarid cultivated region (ARM/SGP). This subset of ecosystem models produced GPP seasonality that was similar to eddy flux estimates, suggesting a role for COS observations in extending flux tower data to regional spatial scales.

  1. Mercury emission to atmosphere from primary Zn production in China.

    PubMed

    Li, Guanghui; Feng, Xinbin; Li, Zhonggen; Qiu, Guangle; Shang, Lihai; Liang, Peng; Wang, Dingyong; Yang, Yongkui

    2010-09-15

    Emissions of mercury (Hg) to air have regional and global impacts through long range transport in the atmosphere. Primary Zn production is regarded as an important anthropogenic Hg source in China, but research on its Hg emission is limited. To gain a better understanding of Hg emissions from Zn production activities in China, field investigations at four industrial-scale Zn production plants using electrostatic process with Hg removal (HP-WR), electrostatic process without Hg removal (HP-WOR), retort Zn production (RZ), imperial smelting process (ISP), and one artisanal Zn smelting process (AZ) were carried out. In the investigation, Hg emission factors are defined as how much Hg was emitted to the atmosphere per ton Zn produced during various Zn production methods and were estimated by using mass balance method. The results showed that the estimated Hg emission factors of Zn production were 5.7+/-4.0 g Hg t(-1) Zn for HP-WR, 31+/-22 g Hg t(-1) Zn for HP-WOR, 34+/-71 g Hg t(-1) Zn for RZ, 122+/-122 g Hg t(-1) Zn g t(-1) for ISP, and 75+/-115 g Hg t(-1) Zn for AZ. Approximately 80.7-104.2 t year(-1) of Hg was emitted to atmosphere from primary Zn production during the period of 2002-2006 in China.

  2. A mechanistic description of the global COS cycle consistent with atmospheric measurements and its potential to evaluate gross primary production of vegetation models

    NASA Astrophysics Data System (ADS)

    Launois, Thomas; Peylin, Philippe; Belviso, Sauveur; Bopp, Laurent; Ogée, Jérôme; Wingate, Lisa; Cuntz, Matthias

    2016-04-01

    Accurate estimates of the gross carbon fluxes - photosynthesis and respiration - are essential to predict the ecosystem carbon fluxes and stocks and their evolution in a changing climate. The gross primary productivity (GPP) in the current dynamic global vegetation models (DGVMs), however, shows large differences in terms of mean values, phase and amplitude. As large scale measurements of the GPP are not possible, their estimates are usually based on indirect tracers. Carbonyl sulfide (COS) has been proposed as a tracer of GPP since COS and CO2 are dominantly taken up by plants via the same enzyme during photosynthesis. Thus leaf uptakes of COS and CO2 are often found to be proportional, with a coefficient of proportionality (LRU) that is species-dependant according to laboratory measurements. However contrarily to CO2, atmospheric records of COS over the last decades show a strong seasonal cycle but with no significant trend, which implies roughly equilibrated sources and sinks of COS at the global scale. Most recent estimates of COS uptake by plants using this LRU concept led to larger sinks over land than initially estimated. In order to maintain a closed atmospheric budget, a compensatory COS source had to be found, with the ocean being suggested as the most likely candidate. In this work, we propose a new mechanistically-based parameterization of the major sources and sinks of COS, allowing to close the global atmospheric budget. For the ocean, we used the ocean general circulation and biogeochemistry model NEMO-PISCES to assess the marine source of COS. Using the simulated organic compounds at the surface, we derived a direct source of COS through the COS photo-production as well as an indirect source through the emissions of sulfur compounds (DMS). The resulting simulated global fluxes correspond to a net source of COS of around 800 GgS yr-1, spatially and temporally consistent with the suggested missing source. For the land, we considered most anoxic soils

  3. Assessment of the magnesium primary production technology. Final report

    SciTech Connect

    Flemings, M.C.; Kenney, G.B.; Sadoway, D.R.; Clark, J.P.; Szekely, J.

    1981-02-01

    At current production levels, direct energy savings achievable in primary magnesium production are 1.2 milliquads of energy per annum. Were magnesium to penetrate the automotive market to an average level of 50 pounds per vehicle, the resultant energy savings at the production stage would be somewhat larger, but the resulting savings in gasoline would conserve an estimated 325 milliquads of energy per year. The principal barrier to more widespread use of magnesium in the immediate future is its price. A price reduction of magnesium of 10% would lead to widespread conversion of aluminum die and permanent mold castings to magnesium. This report addresses the technology of electrolytic and thermic magnesium production and the economics of expanded magnesium production and use.

  4. Factors affecting the estimate of primary production from space

    NASA Technical Reports Server (NTRS)

    Balch, W. M.; Byrne, C. F.

    1994-01-01

    Remote sensing of primary production in the euphotic zone has been based mostly on visible-band and water-leaving radiance measured with the coastal zone color scanner. There are some robust, simple relationships for calculating integral production based on surface measurements, but they also require knowledge for photoadaptive parameters such as maximum photosynthesis which currently cannot be obtained from spave. A 17,000-station data set is used to show that space-based estimates of maximum photosynthesis could improve predictions of psi, the water column light utiliztion index, which is an important term in many primary productivity models. Temperature is also examined as a factor for predicting hydrographic structure and primary production. A simple model is used to relate temperature and maximum photosynthesis; the model incorporates (1) the positive relationship between maximum photosynthesis and temperature and (2) the strongly negative relationship between temperature and nitrate in the ocean (which directly affects maximum growth rates via nitrogen limitation). Since these two factors relate to carbon and nitrogen, 'balanced carbon/nitrogen assimilation' was calculated using the Redfield ratio, It is expected that the relationship between maximum balanced carbon assimilation versus temperature is concave-down, with the peak dependent on nitrate uptake kinetics, temperature-nitrate relationships,a nd the carbon chlorophyll ration. These predictions were compared with the sea truth data. The minimum turnover time for nitrate was also calculated using this approach. Lastly, sea surface temperature gradients were used to predict the slope of isotherms (a proxy for the slope of isopycnals in many waters). Sea truth data show that at size scales of several hundred kilometers, surface temperature gradients can provide information on the slope of isotherms in the top 200 m of the water column. This is directly relevant to the supply of nutrients into the surface

  5. Primary production in the Delta: Then and now

    USGS Publications Warehouse

    Cloern, James E.; Robinson, April; Richey, Amy; Grenier, Letitia; Grossinger, Robin; Boyer, Katharyn E.; Burau, Jon; Canuel, Elizabeth A.; DeGeorge, John F.; Drexler, Judith Z.; Enright, Chris; Howe, Emily R.; Kneib, Ronald; Mueller-Solger, Anke; Naiman, Robert J.; Pinckney, James L.; Safran, Samuel M.; Schoellhamer, David H.; Simenstad, Charles A.

    2016-01-01

    To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function. Primary production is a crucial ecosystem process, which directly limits the quality and quantity of food available for secondary consumers such as invertebrates and fish. The Delta has a low rate of primary production, but it is unclear whether this was always the case. Recent analyses from the Historical Ecology Team and Delta Landscapes Project provide quantitative comparisons of the areal extent of 14 habitat types in the modern Delta versus the historical Delta (pre-1850). Here we describe an approach for using these metrics of land use change to: (1) produce the first quantitative estimates of how Delta primary production and the relative contributions from five different producer groups have been altered by large-scale drainage and conversion to agriculture; (2) convert these production estimates into a common currency so the contributions of each producer group reflect their food quality and efficiency of transfer to consumers; and (3) use simple models to discover how tidal exchange between marshes and open water influences primary production and its consumption. Application of this approach could inform Delta management in two ways. First, it would provide a quantitative estimate of how large-scale conversion to agriculture has altered the Delta's capacity to produce food for native biota. Second, it would provide restoration practitioners with a new approach—based on ecosystem function—to evaluate the success of restoration projects and gauge the trajectory of ecological recovery in the Delta region.

  6. Satellites for the study of ocean primary productivity

    NASA Technical Reports Server (NTRS)

    Smith, R. C.; Baker, K. S.

    1983-01-01

    The use of remote sensing techniques for obtaining estimates of global marine primary productivity is examined. It is shown that remote sensing and multiplatform (ship, aircraft, and satellite) sampling strategies can be used to significantly lower the variance in estimates of phytoplankton abundance and of population growth rates from the values obtained using the C-14 method. It is noted that multiplatform sampling strategies are essential to assess the mean and variance of phytoplankton biomass on a regional or on a global basis. The relative errors associated with shipboard and satellite estimates of phytoplankton biomass and primary productivity, as well as the increased statistical accuracy possible from the utilization of contemporaneous data from both sampling platforms, are examined. It is shown to be possible to follow changes in biomass and the distribution patterns of biomass as a function of time with the use of satellite imagery.

  7. Regulation of primary productivity rate in the equatorial Pacific

    SciTech Connect

    Barber, R.T. ); Chavez, F.P. )

    1991-12-01

    Analysis of the Chl-specific rate of primary productivity (P{sup B}) as a function of subsurface nutrient concentration at >300 equatorial stations provides an answer to the question: What processes regulate primary productivity rate in the high-nutrient, low-chlorophyll waters of the equatorial Pacific In the western Pacific where there is a gradient in 60-m (NO{sub 3}) from 0 to {approximately}12 {mu}M, the productivity rate is a linear function of nutrient concentration; in the eastern Pacific where the gradient is from 12 to 28 {mu}M, the productivity rate is independent of nutrient concentration and limited to {approximately}36 mg C(mg Chl){sup {minus}1} d{sup {minus}1}, or a mean euphotic zone C-specific growth rate ({mu}) of 0.47 d{sup {minus}1}. However, rates downstream of the Galapagos Islands are not limited; they are 46.4 mg C(mg Chl){sup {minus}1} d{sup {minus}1} and {mu} = 0.57 d{sup {minus}1}, very close to the predicted nutrient-regulated rates in the absence of other limitation. This pattern of rate regulation can be accounted for by a combination of eolian Fe, subsurface nutrients, and sedimentary Fe derived from the Galapagos platform. In the low-nutrient western Pacific the eolian supply of Fe is adequate to allow productivity rate to be set by subsurface nutrient concentration. In the nutrient-rich easter equatorial region eolian Fe is inadequate to support productivity rates proportional to the higher nutrient concentrations, so in this region eolian Fe is rate limiting. Around the Galapagos Islands productivity rates reach levels consistent with nutrient concentrations; sedimentary Fe from the Galapagos platform seems adequate to support increased nutrient-regulated productivity rates in this region.

  8. Improving ecosystem productivity modeling through spatially explicit estimation of optimal light use efficiency

    NASA Astrophysics Data System (ADS)

    Madani, Nima; Kimball, John S.; Affleck, David L. R.; Kattge, Jens; Graham, Jon; Bodegom, Peter M.; Reich, Peter B.; Running, Steven W.

    2014-09-01

    A common assumption of remote sensing-based light use efficiency (LUE) models for estimating vegetation gross primary productivity (GPP) is that plants in a biome matrix operate at their photosynthetic capacity under optimal climatic conditions. A prescribed constant biome maximum light use efficiency parameter (LUEmax) defines the maximum photosynthetic carbon conversion rate under these conditions and is a large source of model uncertainty. Here we used tower eddy covariance measurement-based carbon (CO2) fluxes for spatial estimation of optimal LUE (LUEopt) across North America. LUEopt was estimated at 62 Flux Network sites using tower daily carbon fluxes and meteorology, and satellite observed fractional photosynthetically active radiation from the Moderate Resolution Imaging Spectroradiometer. A geostatistical model was fitted to 45 flux tower-derived LUEopt data points using independent geospatial environmental variables, including global plant traits, soil moisture, terrain aspect, land cover type, and percent tree cover, and validated at 17 independent tower sites. Estimated LUEopt shows large spatial variability within and among different land cover classes indicated from the sparse tower network. Leaf nitrogen content and soil moisture regime are major factors explaining LUEopt patterns. GPP derived from estimated LUEopt shows significant correlation improvement against tower GPP records (R2 = 76.9%; mean root-mean-square error (RMSE) = 257 g C m-2 yr-1), relative to alternative GPP estimates derived using biome-specific LUEmax constants (R2 = 34.0%; RMSE = 439 g C m-2 yr-1). GPP determined from the LUEopt map also explains a 49.4% greater proportion of tower GPP variability at the independent validation sites and shows promise for improving understanding of LUE patterns and environmental controls and enhancing regional GPP monitoring from satellite remote sensing.

  9. Looking deeper into the soil: biophysical controls and seasonal lags of soil CO2 production and efflux.

    PubMed

    Vargas, Rodrigo; Baldocchi, Dennis D; Allen, Michael F; Bahn, Michael; Black, T Andrew; Collins, Scott L; Yuste, Jorge Curiel; Hirano, Takashi; Jassal, Rachhpal S; Pumpanen, Jukka; Tang, Jianwu

    2010-09-01

    We seek to understand how biophysical factors such as soil temperature (Ts), soil moisture (theta), and gross primary production (GPP) influence CO2 fluxes across terrestrial ecosystems. Recent advancements in automated measurements and remote-sensing approaches have provided time series in which lags and relationships among variables can be explored. The purpose of this study is to present new applications of continuous measurements of soil CO2 efflux (F0) and soil CO2 concentrations measurements. Here we explore how variation in Ts, theta, and GPP (derived from NASA's moderate-resolution imaging spectroradiometer [MODIS]) influence F0 and soil CO2 production (Ps). We focused on seasonal variation and used continuous measurements at a daily timescale across four vegetation types at 13 study sites to quantify: (1) differences in seasonal lags between soil CO2 fluxes and Ts, theta, and GPP and (2) interactions and relationships between CO2 fluxes with Ts, theta, and GPP. Mean annual Ts did not explain annual F0 and Ps among vegetation types, but GPP explained 73% and 30% of the variation, respectively. We found evidence that lags between soil CO2 fluxes and Ts or GPP provide insights into the role of plant phenology and information relevant about possible timing of controls of autotrophic and heterotrophic processes. The influences of biophysical factors that regulate daily F0 and Ps are different among vegetation types, but GPP is a dominant variable for explaining soil CO2 fluxes. The emergence of long-term automated soil CO2 flux measurement networks provides a unique opportunity for extended investigations into F0 and Ps processes in the near future.

  10. NEE and GPP dynamic evolution at two biomes in the upper Spanish plateau

    NASA Astrophysics Data System (ADS)

    Sánchez, María Luisa; Pardo, Nuria; Pérez, Isidro Alberto; García, Maria de los Angeles

    2014-05-01

    In order to assess the ability of dominant biomes to act as a CO2 sink, two eddy correlation stations close to each other in central Spain have been concurrently operational since March 2008 until the present. The land use of the first station, AC, is a rapeseed rotating crop consisting of annual rotation of non-irrigated rapeseed, barley, peas, rye, and sunflower, respectively. The land use of the second, CIBA, is a mixture of open shrubs/crops, with open shrubs being markedly dominant. The period of measurements covered variable general meteorological conditions. 2009 and 2012 were dominated by drought, whereas 2010 was the rainiest year. Annual rainfall during 2008 and 2009 was close to the historical averaged annual means. This paper presents the dynamic evolution of NEE-8d and GPP-8d observed at the AC station over five years and compares the results with those concurrently observed at the CIBA station. GGP 8-d estimates at both stations were determined using a Light Use Efficiency Model, LUE. Input data for the LUE model were the FPAR 8-d products supplied by MODIS, PAR in situ measurements, and a scalar f, varying between 0 and 1, to take account of the reduction in maximum PAR conversion efficiency, ɛ0, under limiting environmental conditions. f values were assumed to be dependent on air temperature and evaporative fraction, EF, which was considered a proxy of soil moisture. ɛ0, a key parameter, which depends on land use types, was derived through the results of a linear regression fit between the GPP 8-d eddy covariance composites observed and the LUE concurrent 8-d model estimates. Over the five-year study period, both biomes behaved as CO2 sinks. However, the ratio of the NEE-8d total accumulated at AC and CIBA, respectively, was close to a factor two, revealing the effectiveness of the studied crops as CO2 sinks. On an annual basis, accumulated NEE-8d exhibited major variability in both biomes. At CIBA, the results were largely dominated by the

  11. 40 CFR 63.11164 - What General Provisions apply to primary zinc production facilities?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primary zinc production facilities? 63.11164 Section 63.11164 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Zinc Production Facilities § 63.11164 What General Provisions apply to primary zinc production facilities? (a) If you own...

  12. 40 CFR 63.11164 - What General Provisions apply to primary zinc production facilities?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... primary zinc production facilities? 63.11164 Section 63.11164 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Zinc Production Facilities § 63.11164 What General Provisions apply to primary zinc production facilities? (a) If you own...

  13. 40 CFR 63.11164 - What General Provisions apply to primary zinc production facilities?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... primary zinc production facilities? 63.11164 Section 63.11164 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Zinc Production Facilities § 63.11164 What General Provisions apply to primary zinc production facilities? (a) If you own...

  14. 40 CFR 63.11164 - What General Provisions apply to primary zinc production facilities?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... primary zinc production facilities? 63.11164 Section 63.11164 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Zinc Production Facilities § 63.11164 What General Provisions apply to primary zinc production facilities? (a) If you own...

  15. 40 CFR 63.11164 - What General Provisions apply to primary zinc production facilities?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary zinc production facilities? 63.11164 Section 63.11164 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Zinc Production Facilities § 63.11164 What General Provisions apply to primary zinc production facilities? (a) If you own...

  16. 40 CFR 63.11166 - What General Provisions apply to primary beryllium production facilities?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... primary beryllium production facilities? 63.11166 Section 63.11166 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Beryllium Production Facilities § 63.11166 What General Provisions apply to primary beryllium production facilities? (a) You...

  17. 40 CFR 63.11166 - What General Provisions apply to primary beryllium production facilities?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... primary beryllium production facilities? 63.11166 Section 63.11166 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Beryllium Production Facilities § 63.11166 What General Provisions apply to primary beryllium production facilities? (a) You...

  18. 40 CFR 63.11166 - What General Provisions apply to primary beryllium production facilities?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primary beryllium production facilities? 63.11166 Section 63.11166 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Beryllium Production Facilities § 63.11166 What General Provisions apply to primary beryllium production facilities? (a) You...

  19. 40 CFR 63.11166 - What General Provisions apply to primary beryllium production facilities?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary beryllium production facilities? 63.11166 Section 63.11166 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Beryllium Production Facilities § 63.11166 What General Provisions apply to primary beryllium production facilities? (a) You...

  20. 40 CFR 63.11166 - What General Provisions apply to primary beryllium production facilities?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... primary beryllium production facilities? 63.11166 Section 63.11166 Protection of Environment ENVIRONMENTAL... Primary Nonferrous Metals Area Sources-Zinc, Cadmium, and Beryllium Primary Beryllium Production Facilities § 63.11166 What General Provisions apply to primary beryllium production facilities? (a) You...

  1. Measuring forest structure along productivity gradients in the Canadian boreal with small-footprint Lidar.

    PubMed

    Bolton, Douglas K; Coops, Nicholas C; Wulder, Michael A

    2013-08-01

    The structure and productivity of boreal forests are key components of the global carbon cycle and impact the resources and habitats available for species. With this research, we characterized the relationship between measurements of forest structure and satellite-derived estimates of gross primary production (GPP) over the Canadian boreal. We acquired stand level indicators of canopy cover, canopy height, and structural complexity from nearly 25,000 km of small-footprint discrete return Light Detection and Ranging (Lidar) data and compared these attributes to GPP estimates derived from the MODerate resolution Imaging Spectroradiometer (MODIS). While limited in our capacity to control for stand age, we removed recently disturbed and managed forests using information on fire history, roads, and anthropogenic change. We found that MODIS GPP was strongly linked to Lidar-derived canopy cover (r = 0.74, p < 0.01), however was only weakly related to Lidar-derived canopy height and structural complexity as these attributes are largely a function of stand age. A relationship was apparent between MODIS GPP and the maximum sampled heights derived from Lidar as growth rates and resource availability likely limit tree height in the prolonged absence of disturbance. The most structurally complex stands, as measured by the coefficient of variation of Lidar return heights, occurred where MODIS GPP was highest as productive boreal stands are expected to contain a wider range of tree heights and transition to uneven-aged structures faster than less productive stands. While MODIS GPP related near-linearly to Lidar-derived canopy cover, the weaker relationships to Lidar-derived canopy height and structural complexity highlight the importance of stand age in determining the structure of boreal forests. We conclude that an improved quantification of how both productivity and disturbance shape stand structure is needed to better understand the current state of boreal forests in

  2. Differential effects of nutrient-limited primary production on primary, secondary or tertiary consumers.

    PubMed

    Malzahn, Arne M; Hantzsche, Florian; Schoo, Katherina L; Boersma, Maarten; Aberle, Nicole

    2010-01-01

    Nutritional imbalances between predator and prey are the rule rather than the exception at the lower end of food webs. We investigated the role of different grazers in the propagation of nutritionally imbalanced primary production by using the same primary producers in a three-trophic-level food chain and a four-trophic-level food chain experimental setup. The three-trophic-level food chain consisted of a classic single-cell primary producer (Rhodomonas salina), a metazoan grazer (the copepod Acartia tonsa) and a top predator (the jellyfish Gonionemus vertens), while we added a protozoan grazer (Oxyrrhis marina) as primary consumer to the food chain to establish the four-trophic-level food chain. This setup allowed us to investigate how nutrient-limitation effects change from one trophic level to another, and to investigate the performance of two components of our experimental food chains in different trophic positions. Stoichiometry and fatty acid profiles of the algae showed significant differences between the nutrient-depleted [no N and no P addition (-P), respectively] and the nutrient-replete (f/2) treatments. The differences in stoichiometry could be traced when O. marina was the first consumer. Copepods feeding on these flagellates were not affected by the nutritional imbalance of their prey in their stoichiometry, their respiration rates nor in their developmental rates. In contrast, when copepods were the primary consumer, those reared on the -P algae showed significantly higher respiration rates along with significantly lower developmental rates. In neither of our two experimental food chains did the signals from the base of the food chains travel up to jelly fish, our top predator.

  3. Molecular biology in studies of oceanic primary production

    SciTech Connect

    LaRoche, J.; Falkowski, P.G.; Geider, R.

    1992-07-01

    Remote sensing and the use of moored in situ instrumentation has greatly improved our ability to measure phytoplankton chlorophyll and photosynthesis on global scales with high temporal resolution. However, the interpretation of these measurements and their significance with respect to the biogeochemical cycling of carbon relies on their relationship with physiological and biochemical processes in phytoplankton. For example, the use of satellite images of surface chlorophyll to estimate primary production is often based on the functional relationship between photosynthesis and irradiance. A variety of environmental factors such as light, temperature, nutrient availability affect the photosynthesis/irradiance (P vs I) relationship in phytoplankton. We present three examples showing how molecular biology can be used to provide basic insight into the factors controlling primary productivity at three different levels of complexity: 1. Studies of light intensity regulation in unicellular alga show how molecular biology can help understand the processing of environmental cues leading to the regulation of photosynthetic gene expression. 2. Probing of the photosynthetic apparatus using molecular techniques can be used to test existing mechanistic models derived from the interpretation of physiological and biophysical measurements. 3. Exploratory work on the expression of specific proteins during nutrient-limited growth of phytoplankton may lead to the identification and production of molecular probes for field studies.

  4. Molecular biology in studies of oceanic primary production

    SciTech Connect

    LaRoche, J.; Falkowski, P.G. ); Geider, R. . Coll. of Marine Studies)

    1992-01-01

    Remote sensing and the use of moored in situ instrumentation has greatly improved our ability to measure phytoplankton chlorophyll and photosynthesis on global scales with high temporal resolution. However, the interpretation of these measurements and their significance with respect to the biogeochemical cycling of carbon relies on their relationship with physiological and biochemical processes in phytoplankton. For example, the use of satellite images of surface chlorophyll to estimate primary production is often based on the functional relationship between photosynthesis and irradiance. A variety of environmental factors such as light, temperature, nutrient availability affect the photosynthesis/irradiance (P vs I) relationship in phytoplankton. We present three examples showing how molecular biology can be used to provide basic insight into the factors controlling primary productivity at three different levels of complexity: 1. Studies of light intensity regulation in unicellular alga show how molecular biology can help understand the processing of environmental cues leading to the regulation of photosynthetic gene expression. 2. Probing of the photosynthetic apparatus using molecular techniques can be used to test existing mechanistic models derived from the interpretation of physiological and biophysical measurements. 3. Exploratory work on the expression of specific proteins during nutrient-limited growth of phytoplankton may lead to the identification and production of molecular probes for field studies.

  5. Connected speech production in three variants of primary progressive aphasia.

    PubMed

    Wilson, Stephen M; Henry, Maya L; Besbris, Max; Ogar, Jennifer M; Dronkers, Nina F; Jarrold, William; Miller, Bruce L; Gorno-Tempini, Maria Luisa

    2010-07-01

    Primary progressive aphasia is a clinical syndrome defined by progressive deficits isolated to speech and/or language, and can be classified into non-fluent, semantic and logopenic variants based on motor speech, linguistic and cognitive features. The connected speech of patients with primary progressive aphasia has often been dichotomized simply as 'fluent' or 'non-fluent', however fluency is a multidimensional construct that encompasses features such as speech rate, phrase length, articulatory agility and syntactic structure, which are not always impacted in parallel. In this study, our first objective was to improve the characterization of connected speech production in each variant of primary progressive aphasia, by quantifying speech output along a number of motor speech and linguistic dimensions simultaneously. Secondly, we aimed to determine the neuroanatomical correlates of changes along these different dimensions. We recorded, transcribed and analysed speech samples for 50 patients with primary progressive aphasia, along with neurodegenerative and normal control groups. Patients were scanned with magnetic resonance imaging, and voxel-based morphometry was used to identify regions where atrophy correlated significantly with motor speech and linguistic features. Speech samples in patients with the non-fluent variant were characterized by slow rate, distortions, syntactic errors and reduced complexity. In contrast, patients with the semantic variant exhibited normal rate and very few speech or syntactic errors, but showed increased proportions of closed class words, pronouns and verbs, and higher frequency nouns, reflecting lexical retrieval deficits. In patients with the logopenic variant, speech rate (a common proxy for fluency) was intermediate between the other two variants, but distortions and syntactic errors were less common than in the non-fluent variant, while lexical access was less impaired than in the semantic variant. Reduced speech rate was

  6. Global impact of tropical cyclones on primary production

    NASA Astrophysics Data System (ADS)

    Menkes, Christophe E.; Lengaigne, Matthieu; Lévy, Marina; Ethé, Christian; Bopp, Laurent; Aumont, Olivier; Vincent, Emmanuel; Vialard, Jérôme; Jullien, Swen

    2016-05-01

    In this paper, we explore the global responses of surface temperature, chlorophyll, and primary production to tropical cyclones (TCs). Those ocean responses are first characterized from the statistical analysis of satellite data under ~1000 TCs over the 1998-2007 period. Besides the cold wake, the vast majority of TCs induce a weak chlorophyll response, with only ~10% of induced blooms exceeding 0.1 mg m-3. The largest chlorophyll responses mostly occur within coastal regions, in contrast to the strongest cold wakes that generally occur farther offshore. To understand this decoupling, we analyze a coupled dynamical-biogeochemical oceanic simulation forced by realistic wind vortices applied along observed TC tracks. The simulation displays a realistic spatial structure of TC-induced blooms and its observed decoupling with TC cold wakes. In regions of strong TC energy input, the strongest cold wakes occur in regions of shallow thermocline (<60 m) and the strongest blooms in regions of shallow nitracline and/or subsurface chlorophyll maximum (<60 m). Shallow thermoclines are found over many open ocean regions, while regions of shallow nitracline and/or subsurface chlorophyll maximum are most prominent in near-coastal areas, explaining the spatial decoupling between the cold and bloom wakes. The overall TC contribution to annual primary production is weak and amounts to ~1%, except in a few limited areas (east Eurasian coast, South tropical Indian Ocean, Northern Australian coast, and Eastern Pacific Ocean in the TC-prone region) where it can locally reach up to 20-30%. Nearly 80% of this TC-induced annual primary production is the result of the biogeochemical response to the 30% strongest TCs.

  7. Evaluating North American net primary productivity with satellite observations

    NASA Technical Reports Server (NTRS)

    Goward, Samuel N.; Dye, Dennis G.

    1987-01-01

    An ecological model is developed to estimate annual net primary productivity (NPP) in 12 North American biomes. The model combines existing models which address canopy photosynthesis in response to light, temperature, and moisture availability, and account for respiration. Climate data, solar radiation data, and spectral vegetation index data are utilized. Estimates of NPP from the model compare well with data in the literature, but a systematic error is suspected. Difficulties encountered in specifying certain model parameters are discussed as possible sources of this error. The results of this study suggest the promise of remotely sensed measurements for macroscale evaluation and modeling of NPP.

  8. Nutrient cycling by fish supports relatively more primary production as lake productivity increases.

    PubMed

    Vanni, Michael J; Bowling, Anna M; Dickman, Elizabeth M; Hale, R Scott; Higgins, Karen A; Horgan, Martin J; Knoll, Lesley B; Renwick, William H; Stein, Roy A

    2006-07-01

    Animals can be important in nutrient cycling in particular ecosystems, but few studies have examined how this importance varies along environmental gradients. In this study we quantified the nutrient cycling role of an abundant detritivorous fish species, the gizzard shad (Dorosoma cepedianum), in reservoir ecosystems along a gradient of ecosystem productivity. Gizzard shad feed mostly on sediment detritus and excrete sediment-derived nutrients into the water column, thereby mediating a cross-habitat translocation of nutrients to phytoplankton. We quantified nitrogen and phosphorus cycling (excretion) rates of gizzard shad, as well as nutrient demand by phytoplankton, in seven lakes over a four-year period (16 lake-years). The lakes span a gradient of watershed land use (the relative amounts of land used for agriculture vs. forest) and productivity. As the watersheds of these lakes became increasingly dominated by agricultural land, primary production rates, lake trophic state indicators (total phosphorus and chlorophyll concentrations), and nutrient flux through gizzard shad populations all increased. Nutrient cycling by gizzard shad supported a substantial proportion of primary production in these ecosystems, and this proportion increased as watershed agriculture (and ecosystem productivity) increased. In the four productive lakes with agricultural watersheds (>78% agricultural land), gizzard shad supported on average 51% of phytoplankton primary production (range 27-67%). In contrast, in the three relatively unproductive lakes in forested or mixed-land-use watersheds (>47% forest, <52% agricultural land), gizzard shad supported 18% of primary production (range 14-23%). Thus, along a gradient of forested to agricultural landscapes, both watershed nutrient inputs and nutrient translocation by gizzard shad increase, but our data indicate that the importance of nutrient translocation by gizzard shad increases more rapidly. Our results therefore support the

  9. Physical control of primary production on the Faroe Shelf

    NASA Astrophysics Data System (ADS)

    Eliasen, Solva; Margretha Larsen, Karin; Hansen, Bogi

    2014-05-01

    The Faroe Islands are surrounded by a shelf with tidally mixed water, partly isolated from the open ocean by a tidal front. The on-shelf areas support a relatively uniform shelf ecosystem, distinct from the off-shelf waters. Earlier studies have shown high inter-annual variability in biological production on-shelf, with high correlation between fluctuations in the various trophic levels. It seems as if phytoplankton production is the prime driver in the ecosystem since grazing pressure by the zooplankton community during the spring bloom is not large enough to postpone and/or suppress the phytoplankton spring bloom. This indicates that physical effects are the dominant control of the primary production on the Faroe Shelf. For a well-mixed shelf water mass, solar radiation is an obvious candidate as a controlling factor, but inter-annual variations in light intensity show no correlation with primary production. Instead, it appears that variations in the horizontal exchange rate on-shelf and between on-shelf and off-shelf waters can explain the main features in both the inter-annual and shorter term variations of the spring bloom on-shelf. Two competing forcing factors seem to control the exchange rate: the homogenizing tidal currents and the air-sea heat exchange, which tends to induce both vertical and horizontal density gradients. In the presentation, a simple model is proposed to explain how the variations in these two factors affect the horizontal exchange rate and through that the spring bloom on the Faroe shelf.

  10. ppGpp couples transcription to DNA repair in E. coli.

    PubMed

    Kamarthapu, Venu; Epshtein, Vitaly; Benjamin, Bradley; Proshkin, Sergey; Mironov, Alexander; Cashel, Michael; Nudler, Evgeny

    2016-05-20

    The small molecule alarmone (p)ppGpp mediates bacterial adaptation to nutrient deprivation by altering the initiation properties of RNA polymerase (RNAP). ppGpp is generated in Escherichia coli by two related enzymes, RelA and SpoT. We show that ppGpp is robustly, but transiently, induced in response to DNA damage and is required for efficient nucleotide excision DNA repair (NER). This explains why relA-spoT-deficient cells are sensitive to diverse genotoxic agents and ultraviolet radiation, whereas ppGpp induction renders them more resistant to such challenges. The mechanism of DNA protection by ppGpp involves promotion of UvrD-mediated RNAP backtracking. By rendering RNAP backtracking-prone, ppGpp couples transcription to DNA repair and prompts transitions between repair and recovery states.

  11. Recent functional insights into the role of (p)ppGpp in bacterial physiology

    PubMed Central

    Hauryliuk, Vasili; Atkinson, Gemma C.; Murakami, Katsuhiko S.; Tenson, Tanel; Gerdes, Kenn

    2015-01-01

    The alarmone (p)ppGpp is involved in regulating growth and several different stress responses in bacteria. In recent years, substantial progress has been made in our understanding of the molecular mechanisms of (p)ppGpp metabolism and (p)ppGpp-mediated regulation. In this Review, we summarize these recent insights, with a focus on the molecular mechanisms governing the activity of the RelA/SpoT Homologue (RSH) proteins, which are key players that regulate the cellular leves of (p)ppGpp, the structural basis of transcriptional regulation by (p)ppGpp and the role of (p)ppGpp in GTP metabolism and in the emergence of bacterial persisters. PMID:25853779

  12. Excretion of caffeine and its primary degradation products into bile.

    PubMed

    Holstege, A; Kurz, M; Weinbeck, M; Gerok, W

    1993-01-01

    Caffeine, widely consumed in beverages, is known to alter several biliary parameters that can affect gallstone pathogenesis. To address the question whether methylxanthines can act on the luminal side of biliary epithelial cells, we measured caffeine and its primary demethylation products in human bile. Eight patients had an external biliary drainage due to bile duct or gallbladder disease. Two of the patients suffered from histologically confirmed liver cirrhosis. The levels of caffeine, paraxanthine, theobromine, and theophylline were monitored over 10 h in plasma and bile before and after a prior oral dose of caffeine (5 mg/kg b. wt.). Methylxanthines were enriched by an organic extraction procedure and separated by reversed-phase high-performance liquid chromatography. Time-concentration curves in bile paralleled the time-course of methylxanthine levels in blood plasma. Accordingly, values in bile and blood plasma were highly correlated for each methylxanthine measured. Within 1 h after the oral test dose, peak levels of caffeine were obtained in both fluids. Biliary concentrations were either almost equal (caffeine) or lower (dimethylxanthines) than their respective values in blood plasma. The results of our study indicate that minor amounts of caffeine and its primary degradation products are excreted via the bile allowing local interference with epithelial cell metabolism of bile ducts and gallbladder.

  13. Indicators of Early Research Productivity Among Primary Care Fellows

    PubMed Central

    Steiner, John F; Lanphear, Bruce P; Curtis, Peter; Vu, Kieu O

    2002-01-01

    OBJECTIVE Little is known about the impact of fellowship training in primary care on subsequent research productivity. Our goal was to identify characteristics of research fellows and their training associated with subsequent publications and research funding. DESIGN Mail survey in 1998. SETTING AND PARTICIPANTS 1988–1997 graduates of 25 National Research Service Award primary care research fellowships in the United States. OUTCOME MEASURES 1) Publishing 1 or more papers per year since the beginning of fellowship, or 2) serving as principal investigator (PI) on a federal or non-federal grant. RESULTS One hundred forty-six of two hundred fifteen program graduates (68%) completed the survey. The median age was 38 years, and 51% were male. Thirty-two percent had published 1 or more papers per year, and 44% were PIs. Male gender (odds ratio [OR], 3.6; 95% confidence interval [95% CI], 1.4 to 9.2), self-reported allocation of 40% or more of fellowship time to research (OR, 4.4; 95% CI, 1.8 to 11.2), and having an influential mentor during fellowship (OR, 5.0; 95% CI, 1.5 to 17.2) were independently associated with publishing 1 or more papers per year. Fellows with funding as a PI were also more likely to have an influential mentor (OR, 3.0; 95% CI, 1.3 to 7.2). CONCLUSION Primary care fellows who had influential mentors were more productive in research early after fellowship. Awareness of the indicators of early research success can inform the policies of agencies that fund research training and the curricula of training programs themselves.

  14. Gross primary productivity of the true steppe in central Asia in relation to NDVI: scaling up CO2 fluxes

    USGS Publications Warehouse

    Gilmanov, Tagir G.; Johnson, Douglas A.; Saliendra, Nicanor Z.; Akshalov, Kanat; Wylie, Bruce K.

    2004-01-01

    Compared to other characteristics of CO2 exchange, gross primary productivity (P g ) is most directly related to photosynthetic activity. Until recently, it was considered difficult to obtain measurement-based P g . The objective of our study was to evaluate if P g can be estimated from continuous CO2 flux measurements using nonlinear identification of the nonrectangular hyperbolic model of ecosystem-scale, light-response curves. Estimates of P g and ecosystem respiration (R e ) were obtained using Bowen ratio– energy-balance measurements of CO2 exchange in a true-steppe ecosystem in northern Kazakhstan during four growing seasons (1998–2001). The maximum mean weekly apparent quantum yield (αmax) was 0.0388 mol CO2 mol photons and the maximum mean weekly P g was 28 g CO2/m2/day in July 2000. The highest mean weekly R e max (20 g CO2m2/day) was observed in July of both 1999 and 2000. Nighttime respiration calculated from daily respiration corrected for length of the dark period and temperature (using Q 10 = 2) was closely associated with measured nighttime respiration (R 2 = 0.67 to 0.93). The 4-year average annual gross primary production (GPP) was 1617 g CO2/m2/ year (range = 1308–1957). Ten-day normalized difference vegetation index corrected for the start of the season (NDVIsos) was closely associated with 10-day average P g (R 2 = 0.66 to 0.83), which was higher than R 2 values for regressions of mean 10-day net daytime fluxes on NDVIsos (0.55–0.72). This demonstrates the advantage of usingP g in scaling up flux-tower measurements compared to other characteristics (net daytime flux or net 24-h flux).

  15. A symbol-by-symbol decoding algorithm of 3GPP MBMS Raptor

    NASA Astrophysics Data System (ADS)

    Shi, Dongxin; Sun, Xiangran; Yang, Zhanxin; Niu, Lipi

    2013-03-01

    This paper presents a symbol-by-symbol decoding algorithm of 3GPP MBMS Raptor. We redefine the initial matrix of 3GPP MBMS Raptor, and add some ancillary information to help make up for destruction of linear relationship in matrix caused by advanced Gauss elimination in 3GPP MBMS Raptor. So we can realize a correct decoding by symbolby- symbol, while 3GPP can not. The proposed algorithm is adapted to an erasure channel with large symbols, low code rate, big time delay or high error probability , and it can greatly improve decoding efficiency.

  16. Phytoplankton primary production in the world's estuarine-coastal ecosystems

    NASA Astrophysics Data System (ADS)

    Cloern, J. E.; Foster, S. Q.; Kleckner, A. E.

    2014-05-01

    Estuaries are biogeochemical hot spots because they receive large inputs of nutrients and organic carbon from land and oceans to support high rates of metabolism and primary production. We synthesize published rates of annual phytoplankton primary production (APPP) in marine ecosystems influenced by connectivity to land - estuaries, bays, lagoons, fjords and inland seas. Review of the scientific literature produced a compilation of 1148 values of APPP derived from monthly incubation assays to measure carbon assimilation or oxygen production. The median value of median APPP measurements in 131 ecosystems is 185 and the mean is 252 g C m-2 yr-1, but the range is large: from -105 (net pelagic production in the Scheldt Estuary) to 1890 g C m-2 yr-1 (net phytoplankton production in Tamagawa Estuary). APPP varies up to 10-fold within ecosystems and 5-fold from year to year (but we only found eight APPP series longer than a decade so our knowledge of decadal-scale variability is limited). We use studies of individual places to build a conceptual model that integrates the mechanisms generating this large variability: nutrient supply, light limitation by turbidity, grazing by consumers, and physical processes (river inflow, ocean exchange, and inputs of heat, light and wind energy). We consider method as another source of variability because the compilation includes values derived from widely differing protocols. A simulation model shows that different methods reported in the literature can yield up to 3-fold variability depending on incubation protocols and methods for integrating measured rates over time and depth. Although attempts have been made to upscale measures of estuarine-coastal APPP, the empirical record is inadequate for yielding reliable global estimates. The record is deficient in three ways. First, it is highly biased by the large number of measurements made in northern Europe (particularly the Baltic region) and North America. Of the 1148 reported values of

  17. Phytoplankton primary production in the world's estuarine-coastal ecosystems

    USGS Publications Warehouse

    Cloern, James E.; Foster, S.Q.; Kleckner, A.E.

    2014-01-01

    Estuaries are biogeochemical hot spots because they receive large inputs of nutrients and organic carbon from land and oceans to support high rates of metabolism and primary production. We synthesize published rates of annual phytoplankton primary production (APPP) in marine ecosystems influenced by connectivity to land – estuaries, bays, lagoons, fjords and inland seas. Review of the scientific literature produced a compilation of 1148 values of APPP derived from monthly incubation assays to measure carbon assimilation or oxygen production. The median value of median APPP measurements in 131 ecosystems is 185 and the mean is 252 g C m−2 yr−1, but the range is large: from −105 (net pelagic production in the Scheldt Estuary) to 1890 g C m−2 yr−1 (net phytoplankton production in Tamagawa Estuary). APPP varies up to 10-fold within ecosystems and 5-fold from year to year (but we only found eight APPP series longer than a decade so our knowledge of decadal-scale variability is limited). We use studies of individual places to build a conceptual model that integrates the mechanisms generating this large variability: nutrient supply, light limitation by turbidity, grazing by consumers, and physical processes (river inflow, ocean exchange, and inputs of heat, light and wind energy). We consider method as another source of variability because the compilation includes values derived from widely differing protocols. A simulation model shows that different methods reported in the literature can yield up to 3-fold variability depending on incubation protocols and methods for integrating measured rates over time and depth. Although attempts have been made to upscale measures of estuarine-coastal APPP, the empirical record is inadequate for yielding reliable global estimates. The record is deficient in three ways. First, it is highly biased by the large number of measurements made in northern Europe (particularly the Baltic region) and North America. Of the 1148

  18. 9 CFR 113.51 - Requirements for primary cells used for production of biologics.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 9 Animals and Animal Products 1 2013-01-01 2013-01-01 false Requirements for primary cells used... VECTORS STANDARD REQUIREMENTS Ingredient Requirements § 113.51 Requirements for primary cells used for production of biologics. Primary cells used to prepare biological products shall be derived from...

  19. 9 CFR 113.51 - Requirements for primary cells used for production of biologics.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 9 Animals and Animal Products 1 2014-01-01 2014-01-01 false Requirements for primary cells used... VECTORS STANDARD REQUIREMENTS Ingredient Requirements § 113.51 Requirements for primary cells used for production of biologics. Primary cells used to prepare biological products shall be derived from...

  20. 9 CFR 113.51 - Requirements for primary cells used for production of biologics.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false Requirements for primary cells used... VECTORS STANDARD REQUIREMENTS Ingredient Requirements § 113.51 Requirements for primary cells used for production of biologics. Primary cells used to prepare biological products shall be derived from...

  1. 9 CFR 113.51 - Requirements for primary cells used for production of biologics.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 1 2011-01-01 2011-01-01 false Requirements for primary cells used... VECTORS STANDARD REQUIREMENTS Ingredient Requirements § 113.51 Requirements for primary cells used for production of biologics. Primary cells used to prepare biological products shall be derived from...

  2. 9 CFR 113.51 - Requirements for primary cells used for production of biologics.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Requirements for primary cells used... VECTORS STANDARD REQUIREMENTS Ingredient Requirements § 113.51 Requirements for primary cells used for production of biologics. Primary cells used to prepare biological products shall be derived from...

  3. Net ecosystem CO2 exchange of a primary tropical peat swamp forest in Sarawak, Malaysia

    NASA Astrophysics Data System (ADS)

    Tang Che Ing, A.; Stoy, P. C.; Melling, L.

    2014-12-01

    Tropical peat swamp forests are widely recognized as one of the world's most efficient ecosystems for the sequestration and storage of carbon through both their aboveground biomass and underlying thick deposits of peat. As the peat characteristics exhibit high spatial and temporal variability as well as the structural and functional complexity of forests, tropical peat ecosystems can act naturally as both carbon sinks and sources over their life cycles. Nonetheless, few reports of studies on the ecosystem-scale CO2 exchange of tropical peat swamp forests are available to-date and their present roles in the global carbon cycle remain uncertain. To quantify CO2 exchange and unravel the prevailing factors and potential underlying mechanism regulating net CO2 fluxes, an eddy covariance tower was erected in a tropical peat swamp forest in Sarawak, Malaysia. We observed that the diurnal and seasonal patterns of net ecosystem CO2 exchange (NEE) and its components (gross primary productivity (GPP) and ecosystem respiration (RE)) varied between seasons and years. Rates of NEE declined in the wet season relative to the dry season. Conversely, both the gross primary productivity (GPP) and ecosystem respiration (RE) were found to be higher during the wet season than the dry season, in which GPP was strongly negatively correlated with NEE. The average annual NEE was 385 ± 74 g C m-2 yr-1, indicating the primary peat swamp forest functioned as net source of CO2 to the atmosphere over the observation period.

  4. Primary productivity and its correlation with rainfall on Aldabra Atoll

    NASA Astrophysics Data System (ADS)

    Shekeine, J.; Turnbull, L. A.; Cherubini, P.; de Jong, R.; Baxter, R.; Hansen, D.; Bunbury, N.; Fleischer-Dogley, F.; Schaepman-Strub, G.

    2015-01-01

    Aldabra Atoll, a UNESCO World Heritage Site since 1982, hosts the world's largest population of giant tortoises. In view of recent rainfall declines in the East African region, it is important to assess the implications of local rainfall trends on the atoll's ecosystem and evaluate potential threats to the food resources of the giant tortoises. However, building an accurate picture of the effects of climate change requires detailed context-specific case-studies, an approach often hindered by data deficiencies in remote areas. Here, we present and analyse a new historical rainfall record of Aldabra atoll together with two potential measures of primary productivity: (1) tree-ring measurements of the deciduous tree species Ochna ciliata and, (2) satellite-derived NDVI (normalized difference vegetation index) data for the period 2001-2012. Rainfall declined by about 6 mm yr-1 in the last four decades, in agreement with general regional declines, and this decline could mostly be attributed to changes in wet-season rainfall. We were unable to cross-date samples of O. ciliata with sufficient precision to deduce long-term patterns of productivity. However, satellite data were used to derive Aldabra's land surface phenology (LSP) for the period 2001-2012 which was then linked to rainfall seasonality. This relationship was strongest in the eastern parts of the atoll (with a time-lag of about six weeks between rainfall changes and LSP responses), an area dominated by deciduous grasses that supports high densities of tortoises. While the seasonality in productivity, as reflected in the satellite record, is correlated with rainfall, we did not find any change in mean rainfall or productivity for the shorter period 2001-2012. The sensitivity of Aldabra's vegetation to rainfall highlights the potential impact of increasing water stress in East Africa on the region's endemic ecosystems.

  5. Remotely-sensed detection of effects of extreme droughts on gross primary production.

    PubMed

    Vicca, Sara; Balzarolo, Manuela; Filella, Iolanda; Granier, André; Herbst, Mathias; Knohl, Alexander; Longdoz, Bernard; Mund, Martina; Nagy, Zoltan; Pintér, Krisztina; Rambal, Serge; Verbesselt, Jan; Verger, Aleixandre; Zeileis, Achim; Zhang, Chao; Peñuelas, Josep

    2016-06-15

    Severe droughts strongly impact photosynthesis (GPP), and satellite imagery has yet to demonstrate its ability to detect drought effects. Especially changes in vegetation functioning when vegetation state remains unaltered (no browning or defoliation) pose a challenge to satellite-derived indicators. We evaluated the performance of different satellite indicators to detect strong drought effects on GPP in a beech forest in France (Hesse), where vegetation state remained largely unaffected while GPP decreased substantially. We compared the results with three additional sites: a Mediterranean holm oak forest (Puéchabon), a temperate beech forest (Hainich), and a semi-arid grassland (Bugacpuszta). In Hesse, a three-year reduction in GPP following drought was detected only by the Enhanced Vegetation Index (EVI). The Photochemical Reflectance Index (PRI) also detected this drought effect, but only after normalization for absorbed light. In Puéchabon normalized PRI outperformed the other indicators, while the short-term drought effect in Hainich was not detected by any tested indicator. In contrast, most indicators, but not PRI, captured the drought effects in Bugacpuszta. Hence, PRI improved detection of drought effects on GPP in forests and we propose that PRI normalized for absorbed light is considered in future algorithms to estimate GPP from space.

  6. Remotely-sensed detection of effects of extreme droughts on gross primary production

    PubMed Central

    Vicca, Sara; Balzarolo, Manuela; Filella, Iolanda; Granier, André; Herbst, Mathias; Knohl, Alexander; Longdoz, Bernard; Mund, Martina; Nagy, Zoltan; Pintér, Krisztina; Rambal, Serge; Verbesselt, Jan; Verger, Aleixandre; Zeileis, Achim; Zhang, Chao; Peñuelas, Josep

    2016-01-01

    Severe droughts strongly impact photosynthesis (GPP), and satellite imagery has yet to demonstrate its ability to detect drought effects. Especially changes in vegetation functioning when vegetation state remains unaltered (no browning or defoliation) pose a challenge to satellite-derived indicators. We evaluated the performance of different satellite indicators to detect strong drought effects on GPP in a beech forest in France (Hesse), where vegetation state remained largely unaffected while GPP decreased substantially. We compared the results with three additional sites: a Mediterranean holm oak forest (Puéchabon), a temperate beech forest (Hainich), and a semi-arid grassland (Bugacpuszta). In Hesse, a three-year reduction in GPP following drought was detected only by the Enhanced Vegetation Index (EVI). The Photochemical Reflectance Index (PRI) also detected this drought effect, but only after normalization for absorbed light. In Puéchabon normalized PRI outperformed the other indicators, while the short-term drought effect in Hainich was not detected by any tested indicator. In contrast, most indicators, but not PRI, captured the drought effects in Bugacpuszta. Hence, PRI improved detection of drought effects on GPP in forests and we propose that PRI normalized for absorbed light is considered in future algorithms to estimate GPP from space. PMID:27301671

  7. Remotely-sensed detection of effects of extreme droughts on gross primary production

    NASA Astrophysics Data System (ADS)

    Vicca, Sara; Balzarolo, Manuela; Filella, Iolanda; Granier, André; Herbst, Mathias; Knohl, Alexander; Longdoz, Bernard; Mund, Martina; Nagy, Zoltan; Pintér, Krisztina; Rambal, Serge; Verbesselt, Jan; Verger, Aleixandre; Zeileis, Achim; Zhang, Chao; Peñuelas, Josep

    2016-06-01

    Severe droughts strongly impact photosynthesis (GPP), and satellite imagery has yet to demonstrate its ability to detect drought effects. Especially changes in vegetation functioning when vegetation state remains unaltered (no browning or defoliation) pose a challenge to satellite-derived indicators. We evaluated the performance of different satellite indicators to detect strong drought effects on GPP in a beech forest in France (Hesse), where vegetation state remained largely unaffected while GPP decreased substantially. We compared the results with three additional sites: a Mediterranean holm oak forest (Puéchabon), a temperate beech forest (Hainich), and a semi-arid grassland (Bugacpuszta). In Hesse, a three-year reduction in GPP following drought was detected only by the Enhanced Vegetation Index (EVI). The Photochemical Reflectance Index (PRI) also detected this drought effect, but only after normalization for absorbed light. In Puéchabon normalized PRI outperformed the other indicators, while the short-term drought effect in Hainich was not detected by any tested indicator. In contrast, most indicators, but not PRI, captured the drought effects in Bugacpuszta. Hence, PRI improved detection of drought effects on GPP in forests and we propose that PRI normalized for absorbed light is considered in future algorithms to estimate GPP from space.

  8. Widespread methanotrophic primary production in lowland chalk rivers.

    PubMed

    Shelley, Felicity; Grey, Jonathan; Trimmer, Mark

    2014-05-22

    Methane is oversaturated relative to the atmosphere in many rivers, yet its cycling and fate is poorly understood. While photosynthesis is the dominant source of autotrophic carbon to rivers, chemosynthesis and particularly methane oxidation could provide alternative sources of primary production where the riverbed is heavily shaded or at depth beneath the sediment surface. Here, we highlight geographically widespread methanotrophic carbon fixation within the gravel riverbeds of over 30 chalk rivers. In 15 of these, the potential for methane oxidation (methanotrophy) was also compared with photosynthesis. In addition, we performed detailed concurrent measurements of photosynthesis and methanotrophy in one large chalk river over a complete annual cycle, where we found methanotrophy to be active to at least 15 cm into the riverbed and to be strongly substrate limited. The seasonal trend in methanotrophic activity reflected that of the riverine methane concentrations, and thus the highest rates were measured in mid-summer. At the sediment surface, photosynthesis was limited by light for most of the year with heavy shading induced by dense beds of aquatic macrophytes. Across 15 rivers, in late summer, we conservatively calculated that net methanotrophy was equivalent to between 1% and 46% of benthic net photosynthetic production within the gravel riverbed, with a median value of 4%. Hence, riverbed chemosynthesis, coupled to the oxidation of methane, is widespread and significant in English chalk rivers.

  9. Estimating Net Primary Productivity Using Satellite and Ancillary Data

    NASA Technical Reports Server (NTRS)

    Choudhury, Bhaskar J.

    2002-01-01

    The net primary productivity (C) or the annual rate of carbon accumulation per unit ground area by terrestrial plant communities is the difference of gross photosynthesis (A(sub g)) and respiration (R) per unit ground area. Available field observations show that R is a large and variable fraction of A(sub g), although it is generally recognized that there are considerable difficulties in determining these fluxes, and thus pose challenge in assessing the accuracy. Further uncertainties arise in extrapolating field measurements (which are acquired over a hectare or so area) to regional scale. Here, an approach is presented for determining these fluxes using satellite and ancillary data to be representative of regional scale and allow assessment of interannual variation. A, has been expressed as the product of radiation use efficiency for gross photosynthesis by an unstressed canopy and intercepted photosynthetically active radiation, which is then adjusted for stresses due to soil water shortage and temperature away from optimum. R has been calculated as the sum of growth and maintenance components (respectively, R(sub g) and R(sub m)).The R(sub m) has been determined from nitrogen content of plant tissue per unit ground area, while R(sub g) has been obtained as a fraction of the difference of A(sub g) and R(sub m). Results for five consecutive years (1986-1990) are presented for the Amazon-Tocontins, Mississippi, and Ob River basins.

  10. Climate change enhances primary production in the western Antarctic Peninsula.

    PubMed

    Moreau, Sébastien; Mostajir, Behzad; Bélanger, Simon; Schloss, Irene R; Vancoppenolle, Martin; Demers, Serge; Ferreyra, Gustavo A

    2015-06-01

    Intense regional warming was observed in the western Antarctic Peninsula (WAP) over the last 50 years. Here, we investigate the impact of climate change on primary production (PP) in this highly productive region. This study is based on temporal data series of ozone thickness (1972-2010), sea ice concentration (1978-2010), sea-surface temperature (1990-2010), incident irradiance (1988-2010) and satellite-derived chlorophyll a concentration (Chl-a, 1997-2010) for the coastal WAP. In addition, we apply a photosynthesis/photoinhibition spectral model to satellite-derived data (1997-2010) to compute PP and examine the separate impacts of environmental forcings. Since 1978, sea ice retreat has been occurring earlier in the season (in March in 1978 and in late October during the 2000s) while the ozone hole is present in early spring (i.e. August to November) since the early 1990s, increasing the intensity of ultraviolet-B radiation (UVBR, 280-320 nm). The WAP waters have also warmed over 1990-2010. The modelled PP rates are in the lower range of previously reported PP rates in the WAP. The annual open water PP in the study area increased from 1997 to 2010 (from 0.73 to 1.03 Tg C yr(-1) ) concomitantly with the increase in the production season length. The coincidence between the earlier sea ice retreat and the presence of the ozone hole increased the exposure to incoming radiation (UVBR, UVAR and PAR) and, thus, increased photoinhibition during austral spring (September to November) in the study area (from 0.014 to 0.025 Tg C yr(-1) ). This increase in photoinhibition was minor compared to the overall increase in PP, however. Climate change hence had an overall positive impact on PP in the WAP waters.

  11. Catalytic mechanism and allosteric regulation of an oligomeric (p)ppGpp synthetase by an alarmone

    PubMed Central

    Steinchen, Wieland; Schuhmacher, Jan S.; Altegoer, Florian; Fage, Christopher D.; Srinivasan, Vasundara; Linne, Uwe; Marahiel, Mohamed A.; Bange, Gert

    2015-01-01

    Nucleotide-based second messengers serve in the response of living organisms to environmental changes. In bacteria and plant chloroplasts, guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp) [collectively named “(p)ppGpp”] act as alarmones that globally reprogram cellular physiology during various stress conditions. Enzymes of the RelA/SpoT homology (RSH) family synthesize (p)ppGpp by transferring pyrophosphate from ATP to GDP or GTP. Little is known about the catalytic mechanism and regulation of alarmone synthesis. It also is unclear whether ppGpp and pppGpp execute different functions. Here, we unravel the mechanism and allosteric regulation of the highly cooperative alarmone synthetase small alarmone synthetase 1 (SAS1) from Bacillus subtilis. We determine that the catalytic pathway of (p)ppGpp synthesis involves a sequentially ordered substrate binding, activation of ATP in a strained conformation, and transfer of pyrophosphate through a nucleophilic substitution (SN2) reaction. We show that pppGpp—but not ppGpp—positively regulates SAS1 at an allosteric site. Although the physiological significance remains to be elucidated, we establish the structural and mechanistic basis for a biological activity in which ppGpp and pppGpp execute different functional roles. PMID:26460002

  12. Molecular Mechanism and Evolution of Guanylate Kinase Regulation by (p)ppGpp

    SciTech Connect

    Liu, Kuanqing; Myers, Angela R.; Pisithkul, Tippapha; Claas, Kathy R.; Satyshur, Kenneth A.; Amador-Noguez, Daniel; Keck, James L.; Wang, Jue D.

    2015-02-01

    The nucleotide (p)ppGpp mediates bacterial stress responses, but its targets and underlying mechanisms of action vary among bacterial species and remain incompletely understood. Here, we characterize the molecular interaction between (p)ppGpp and guanylate kinase (GMK), revealing the importance of this interaction in adaptation to starvation. Combining structural and kinetic analyses, we show that (p)ppGpp binds the GMK active site and competitively inhibits the enzyme. The (p)ppGpp-GMK interaction prevents the conversion of GMP to GDP, resulting in GMP accumulation upon amino acid downshift. Abolishing this interaction leads to excess (p)ppGpp and defective adaptation to amino acid starvation. A survey of GMKs from phylogenetically diverse bacteria shows that the (p)ppGpp-GMK interaction is conserved in members of Firmicutes, Actinobacteria, and Deinococcus-Thermus, but not in Proteobacteria, where (p)ppGpp regulates RNA polymerase (RNAP). We propose that GMK is an ancestral (p)ppGpp target and RNAP evolved more recently as a direct target in Proteobacteria.

  13. Near-UV stress in salmonella typhimurium: 4-thiouridine in tRNA, ppGpp, and ApppGpp as components of an adaptive response

    SciTech Connect

    Kramer, G.F.; Baker, J.C.; Ames, B.N.

    1988-05-01

    We have examined the role of 4-thiouridine in the responses of Salmonella typhimurium to near-UV irradiation. Mutants lacking 4-thiouridine (nuv) and mutants defective in the synthesis of ppGpp (guanosine 5'-diphosphate-3'-diphosphate) (relA) were found to be sensitive to killing by near-UV. Near-UV induced the synthesis of a set of proteins that were not induced in the nuv mutant. Some of these proteins were identified as oxidative defense proteins, and others were identified as ppGpp-inducible proteins. Over 100-fold increases in ApppGpp (adenoisine 5', 5'''-triphosphoguanosine-3'''-diphosphate, the adenylylated form of ppGpp) were observed in wild-type cells after near-UV irradiation but not in the 4-thiouridine-deficient mutant. These data support a model in which ppGpp and ApppGpp, a dinucleotide proposed to be synthesized by tRNA-aminoacyl synthetases as a response to the cross-linking of 4-thiouridine in tRNA by near-UV, induce the synthesis of proteins necessary for resistance to near-UV irradiation.

  14. Degradation of net primary production in a semiarid rangeland

    NASA Astrophysics Data System (ADS)

    Jackson, Hasan; Prince, Stephen D.

    2016-08-01

    Anthropogenic land degradation affects many biogeophysical processes, including reductions of net primary production (NPP). Degradation occurs at scales from small fields to continental and global. While measurement and monitoring of NPP in small areas is routine in some studies, for scales larger than 1 km2, and certainly global, there is no regular monitoring and certainly no attempt to measure degradation. Quantitative and repeatable techniques to assess the extent of deleterious effects and monitor changes are needed to evaluate its effects on, for example, economic yields of primary products such as crops, lumber, and forage, and as a measure of land surface properties which are currently missing from dynamic global vegetation models, assessments of carbon sequestration, and land surface models of heat, water, and carbon exchanges. This study employed the local NPP scaling (LNS) approach to identify patterns of anthropogenic degradation of NPP in the Burdekin Dry Tropics (BDT) region of Queensland, Australia, from 2000 to 2013. The method starts with land classification based on the environmental factors presumed to control (NPP) to group pixels having similar potential NPP. Then, satellite remotely sensing data were used to compare actual NPP with its potential. The difference in units of mass of carbon and percentage loss were the measure of degradation. The entire BDT (7.45 × 106 km2) was investigated at a spatial resolution of 250 × 250 m. The average annual reduction in NPP due to anthropogenic land degradation in the entire BDT was -2.14 MgC m-2 yr-1, or 17 % of the non-degraded potential, and the total reduction was -214 MgC yr-1. Extreme average annual losses of 524.8 gC m-2 yr-1 were detected. Approximately 20 % of the BDT was classified as "degraded". Varying severities and rates of degradation were found among the river basins, of which the Belyando and Suttor were highest. Interannual, negative trends in reductions of NPP occurred in 7 % of the

  15. Metabolic initiation of differentiation and secondary metabolism by Streptomyces griseus: significance of the stringent response (ppGpp) and GTP content in relation to A factor.

    PubMed Central

    Ochi, K

    1987-01-01

    I investigated the significance of the intracellular accumulation of guanosine 5'-diphosphate 3'-diphosphate (ppGpp) and of the coordinated decrease in the GTP pool for initiating morphological and physiological differentiation of Streptomyces griseus, a streptomycin-producing strain. In solid cultures, aerial mycelium formation was severely suppressed by the presence of excess nutrients. However, decoyinine, a specific inhibitor of GMP synthetase, enabled the cells to develop aerial mycelia in the suppressed cultures at concentrations which only partially inhibited growth. A factor (2S-isocapryloyl-3S-hydroxymethyl-gamma-butyrolactone) added exogenously had no such effect. Decoyinine was also effective in initiating the formation of submerged spores in liquid culture. The ability to produce streptomycin did not increase but decreased drastically on the addition of decoyinine. This sharp decrease in streptomycin production was accompanied by a decrease in intracellular accumulation of ppGpp. A relaxed (rel) mutant was found among 25 thiopeptin-resistant isolates which developed spontaneously. The rel mutant had a severely reduced ability to accumulate ppGpp during a nutritional shift-down and also during postexponential growth and showed a less extensive decrease in the GTP pool than that in the rel+ parental strain. The rel mutant failed to induce the enzymes amidinotransferase and streptomycin kinase, which are essential for the biosynthesis of streptomycin. The abilities to form aerial mycelia and submerged spores were still retained, but the amounts were less, and for both the onset of development was markedly delayed. The decreased ability to produced submerged spores was largely restored by the addition of decoyinine. This was accompanied by an extensive GTP pool decrease. The rel mutant produced A factor normally, indicating that synthesis of A factor is controlled neither by ppGpp nor by GTP. Conversely, a mutant defective in A-factor synthesis accumulated

  16. Stratospheric sulfate geoengineering enhances terrestrial gross primary productivity

    NASA Astrophysics Data System (ADS)

    Xia, L.; Robock, A.; Tilmes, S.; Neely, R. R., III

    2015-09-01

    Stratospheric sulfate geoengineering could impact the terrestrial carbon cycle by enhancing the carbon sink. With an 8 Tg yr-1 injection of SO2 to balance a Representative Concentration Pathway 6.0 (RCP6.0) scenario, we conducted climate model simulations with the Community Earth System Model, with the Community Atmospheric Model 4 fully coupled to tropospheric and stratospheric chemistry (CAM4-chem). During the geoengineering period, as compared to RCP6.0, land-averaged downward visible diffuse radiation increased 3.2 W m-2 (11 %). The enhanced diffuse radiation combined with the cooling increased plant photosynthesis by 2.4 %, which could contribute to an additional 3.8 ± 1.1 Gt C yr-1 global gross primary productivity without nutrient limitation. This increase could potentially increase the land carbon sink. Suppressed plant and soil respiration due to the cooling would reduce natural land carbon emission and therefore further enhance the terrestrial carbon sink during the geoengineering period. This beneficial impact of stratospheric sulfate geoengineering would need to be balanced by a large number of potential risks in any future decisions about implementation of geoengineering.

  17. Spatial scaling of net primary productivity using subpixel landcover information

    NASA Astrophysics Data System (ADS)

    Chen, X. F.; Chen, Jing M.; Ju, Wei M.; Ren, L. L.

    2008-10-01

    Gridding the land surface into coarse homogeneous pixels may cause important biases on ecosystem model estimations of carbon budget components at local, regional and global scales. These biases result from overlooking subpixel variability of land surface characteristics. Vegetation heterogeneity is an important factor introducing biases in regional ecological modeling, especially when the modeling is made on large grids. This study suggests a simple algorithm that uses subpixel information on the spatial variability of land cover type to correct net primary productivity (NPP) estimates, made at coarse spatial resolutions where the land surface is considered as homogeneous within each pixel. The algorithm operates in such a way that NPP obtained from calculations made at coarse spatial resolutions are multiplied by simple functions that attempt to reproduce the effects of subpixel variability of land cover type on NPP. Its application to a carbon-hydrology coupled model(BEPS-TerrainLab model) estimates made at a 1-km resolution over a watershed (named Baohe River Basin) located in the southwestern part of Qinling Mountains, Shaanxi Province, China, improved estimates of average NPP as well as its spatial variability.

  18. Natural organic matter as global antennae for primary production.

    PubMed

    Van Trump, J Ian; Rivera Vega, Fransheska J; Coates, John D

    2013-05-01

    Humic substances (HS) are high-molecular-weight complex refractory organics that are ubiquitous in terrestrial and aquatic environments. While resistant to microbial degradation, these compounds nevertheless support microbial metabolism via oxidation or reduction of their (hydro)quinone moieties. As such, they are known to be important electron sinks for respiratory and fermentative bacteria and electron sources for denitrifying and perchlorate-reducing bacteria. HS also strongly promote abiotic reduction of Fe(III) when irradiated with light. Here, we show that HS-enhanced Fe(III) photoreduction can also drive chemolithotrophic microbial respiration by producing Fe(II), which functions as a respiratory electron donor. Due to their molecular complexity, HS absorb most of the electromagnetic spectrum and can act as broad-spectrum antennae converting radiant energy into bioavailable chemical energy. The finding that chemolithotrophic organisms can utilize this energy has important implications for terrestrial, and possibly extraterrestrial, microbial processes and offers an alternative mechanism of radiation-driven primary productivity to that of phototrophy.

  19. Net Primary Production of boreal forests in the Krasnoyarsk Territory

    NASA Astrophysics Data System (ADS)

    Larko, Alexander; Chernetskiy, Maxim; Shevyrnogov, Anatoly

    One of the most important characteristics used in the biosphere change control is net primary production dynamics. (NPP) NPP shows the amount of pure carbon fixed in plants for a definite time period, essentially, this indicator reflects the intensity of a carbon biochemical cycle. Being the main indicator of the ecosystem condition, NPP has great significance, since it is also an indicator of biosphere carbon flux intensity. Its use is important for ecological investigations, carbon cycle calculation and the distribution of natural recourses. Ground true ecosystems determine most of seasonal and annual changes in the atmospheric CO2 concentration. Satellite methods of investigation are known to be effectively used for the calculation of the global NPP distribution. In its turn, the study of boreal forest NPP dynamics is required to introduce clarity into global models and to understand their role in the carbon cycle. At present, there is a number of calculation models for obtaining NPP. In the given work, an estimate of NPP for boreal forests of the Krasnoyarsk Territory is made. For the calculation, the GloPEM model employing TERRA/MODIS and TOMS data has been used. The obtained data have been compared with satellite temperature and ground true climatic data and, also, with the forest vegetation maps. The maps contained data about the biomass amount and the forest species composition, which allowed one to obtain the results showing the nonuniformity of NPP distribution depending on the climatic conditions, species composition and the latitude of the objects under study.

  20. The linkages between photosynthesis, productivity, growth and biomass in lowland Amazonian forests.

    PubMed

    Malhi, Yadvinder; Doughty, Christopher E; Goldsmith, Gregory R; Metcalfe, Daniel B; Girardin, Cécile A J; Marthews, Toby R; Del Aguila-Pasquel, Jhon; Aragão, Luiz E O C; Araujo-Murakami, Alejandro; Brando, Paulo; da Costa, Antonio C L; Silva-Espejo, Javier E; Farfán Amézquita, Filio; Galbraith, David R; Quesada, Carlos A; Rocha, Wanderley; Salinas-Revilla, Norma; Silvério, Divino; Meir, Patrick; Phillips, Oliver L

    2015-06-01

    Understanding the relationship between photosynthesis, net primary productivity and growth in forest ecosystems is key to understanding how these ecosystems will respond to global anthropogenic change, yet the linkages among these components are rarely explored in detail. We provide the first comprehensive description of the productivity, respiration and carbon allocation of contrasting lowland Amazonian forests spanning gradients in seasonal water deficit and soil fertility. Using the largest data set assembled to date, ten sites in three countries all studied with a standardized methodology, we find that (i) gross primary productivity (GPP) has a simple relationship with seasonal water deficit, but that (ii) site-to-site variations in GPP have little power in explaining site-to-site spatial variations in net primary productivity (NPP) or growth because of concomitant changes in carbon use efficiency (CUE), and conversely, the woody growth rate of a tropical forest is a very poor proxy for its productivity. Moreover, (iii) spatial patterns of biomass are much more driven by patterns of residence times (i.e. tree mortality rates) than by spatial variation in productivity or tree growth. Current theory and models of tropical forest carbon cycling under projected scenarios of global atmospheric change can benefit from advancing beyond a focus on GPP. By improving our understanding of poorly understood processes such as CUE, NPP allocation and biomass turnover times, we can provide more complete and mechanistic approaches to linking climate and tropical forest carbon cycling.

  1. Effective Symbiosis between Rhizobium etli and Phaseolus vulgaris Requires the Alarmone ppGpp

    PubMed Central

    Moris, Martine; Braeken, Kristien; Schoeters, Eric; Verreth, Christel; Beullens, Serge; Vanderleyden, Jos; Michiels, Jan

    2005-01-01

    The symbiotic interaction between Rhizobium etli and Phaseolus vulgaris, the common bean plant, ultimately results in the formation of nitrogen-fixing nodules. Many aspects of the intermediate and late stages of this interaction are still poorly understood. The R. etli relA gene was identified through a genome-wide screening for R. etli symbiotic mutants. RelA has a pivotal role in cellular physiology, as it catalyzes the synthesis of (p)ppGpp, which mediates the stringent response in bacteria. The synthesis of ppGpp was abolished in an R. etli relA mutant strain under conditions of amino acid starvation. Plants nodulated by an R. etli relA mutant had a strongly reduced nitrogen fixation activity (75% reduction). Also, at the microscopic level, bacteroid morphology was altered, with the size of relA mutant bacteroids being increased compared to that of wild-type bacteroids. The expression of the σN-dependent nitrogen fixation genes rpoN2 and iscN was considerably reduced in the relA mutant. In addition, the expression of the relA gene was negatively regulated by RpoN2, the symbiosis-specific σN copy of R. etli. Therefore, an autoregulatory loop controlling the expression of relA and rpoN2 seems operative in bacteroids. The production of long- and short-chain acyl-homoserine-lactones by the cinIR and raiIR systems was decreased in an R. etli relA mutant. Our results suggest that relA may play an important role in the regulation of gene expression in R. etli bacteroids and in the adaptation of bacteroid physiology. PMID:16030240

  2. Environmental Humidity Regulates Effects of Experimental Warming on Vegetation Index and Biomass Production in an Alpine Meadow of the Northern Tibet

    PubMed Central

    Fu, Gang; Shen, Zhen Xi

    2016-01-01

    Uncertainty about responses of vegetation index, aboveground biomass (AGB) and gross primary production (GPP) limits our ability to predict how climatic warming will influence plant growth in alpine regions. A field warming experiment was conducted in an alpine meadow at a low (4313 m), mid- (4513 m) and high elevation (4693 m) in the Northern Tibet since May 2010. Growing season vapor pressure deficit (VPD), soil temperature (Ts) and air temperature (Ta) decreased with increasing elevation, while growing season precipitation, soil moisture (SM), normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), AGB and GPP increased with increasing elevation. The growing season Ta, Ts and VPD in 2015 was greater than that in 2014, while the growing season precipitation, SM, NDVI, SAVI, AGB and GPP in 2015 was lower than that in 2014, respectively. Compared to the mean air temperature and precipitation during the growing season in 1963–2015, it was a warmer and wetter year in 2014 and a warmer and drier year in 2015. Experimental warming increased growing season Ts, Ta,VPD, but decreased growing season SM in 2014–2015 at all the three elevations. Experimental warming only reduced growing season NDVI, SAVI, AGB and GPP at the low elevation in 2015. Growing season NDVI, SAVI, AGB and GPP increased with increasing SM and precipitation, but decreased with increasing VPD, indicating vegetation index and biomass production increased with environmental humidity. The VPD explained more variation of growing season NDVI, SAVI, AGB and GPP compared to Ts, Ta and SM at all the three elevations. Therefore, environmental humidity regulated the effect of experimental warming on vegetation index and biomass production in alpine meadows on the Tibetan Plateau. PMID:27798690

  3. Environmental Humidity Regulates Effects of Experimental Warming on Vegetation Index and Biomass Production in an Alpine Meadow of the Northern Tibet.

    PubMed

    Fu, Gang; Shen, Zhen Xi

    2016-01-01

    Uncertainty about responses of vegetation index, aboveground biomass (AGB) and gross primary production (GPP) limits our ability to predict how climatic warming will influence plant growth in alpine regions. A field warming experiment was conducted in an alpine meadow at a low (4313 m), mid- (4513 m) and high elevation (4693 m) in the Northern Tibet since May 2010. Growing season vapor pressure deficit (VPD), soil temperature (Ts) and air temperature (Ta) decreased with increasing elevation, while growing season precipitation, soil moisture (SM), normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), AGB and GPP increased with increasing elevation. The growing season Ta, Ts and VPD in 2015 was greater than that in 2014, while the growing season precipitation, SM, NDVI, SAVI, AGB and GPP in 2015 was lower than that in 2014, respectively. Compared to the mean air temperature and precipitation during the growing season in 1963-2015, it was a warmer and wetter year in 2014 and a warmer and drier year in 2015. Experimental warming increased growing season Ts, Ta,VPD, but decreased growing season SM in 2014-2015 at all the three elevations. Experimental warming only reduced growing season NDVI, SAVI, AGB and GPP at the low elevation in 2015. Growing season NDVI, SAVI, AGB and GPP increased with increasing SM and precipitation, but decreased with increasing VPD, indicating vegetation index and biomass production increased with environmental humidity. The VPD explained more variation of growing season NDVI, SAVI, AGB and GPP compared to Ts, Ta and SM at all the three elevations. Therefore, environmental humidity regulated the effect of experimental warming on vegetation index and biomass production in alpine meadows on the Tibetan Plateau.

  4. [Migration of monomers and primary aromatic amines from nylon products].

    PubMed

    Mutsuga, Motoh; Yamaguchi, Miku; Ohno, Hiroyuki; Kawamura, Yoko

    2010-01-01

    Migration of 2 kinds of monomer and 21 kinds of primary aromatic amines (PAAs) from 21 kinds of nylon products such as turners, ladles and wrap film were determined. Samples were classified as regards materials by mean of pyrolysis-GC/MS. One sample was classified as nylon 6, 15 samples as nylon 66 and three samples as nylon 6/66 copolymers, while two samples were laminate of nylon 6 with polyethylene or polypropylene. All of the nylon 66 samples contained a small amount of ε-caprolactam (CPL), which is the nylon 6 monomer. Migration levels of monomers and PAAs at 60°C for 30 min into 20% ethanol were measured by LC/MS/MS. CPL was detected at the level of 0.015-38 µg/mL from all samples, excluding one wrap film sample, and 1,6-hexamethylenediamine was detected at the level of 0.002-0.013 µg/mL from all nylon 66 samples and one nylon 6/66 sample. In addition, 0.006-4.3 µg/mL of 4,4'-diaminodiphenylmethane from three samples, 0.032-0.23 µg/mL of aniline from four samples, 0.001 µg/mL of 4-chloroaniline from two samples, and 0.002 µg/mL of 2-toluidine and 0.066 mg/mL of 1-naphthylamine from one sample each were detected. The migration levels at 95 or 121°C were about 3 and 10 times the 60°C levels, respectively.

  5. Recent Changes in Primary Production in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Arrigo, K. R.

    2015-12-01

    Over the last decade and a half, the continued loss of sea is in the Arctic ocean has led to a dramatic increase in marine net primary production (NPP). Increased annual NPP is often, but not always, associated with reduced sea-ice extent and a longer phytoplankton growing season (fewer days of ice cover). However, spatial patterns of enhanced annual NPP suggest that increased nutrient fluxes may also play a role. For instance, the greatest increases in Arctic NPP have been observed on the interior shelves in waters near the shelfbreak. These are areas where additional nutrients may become increasingly available as the sea ice retreats toward the pole, facilitated by increased shelfbreak upwelling. The eastern Arctic, which receives a large fraction of the high-nutrient Pacific water, exhibits an unusual pattern whereby increased annual NPP in more upstream waters of the Chukchi and Beaufort seas is offset by lower annual NPP in downstream regions of the Greenland Sea. The reason for the decline in NPP in downstream waters is unclear, especially if upstream nutrient supplies and NPP are increasing. Perhaps higher NPP on the Chukchi shelf has caused an increase in the rate of sediment denitrification, resulting in larger losses of fixed nitrogen. This would require that the large increase in annual NPP in the Beaufort Sea be driven by some other nutrient source, perhaps local shelfbreak upwelling. More efficient utilization of these nutrients, due perhaps to longer growing seasons, could eventually reduce inventories downstream, resulting in no change in annual NPP in the Baffin sector and a decline over the outflow shelves near Greenland. This is consistent with the observation that large increases in Chukchi Sea NPP preceded significant declines in Greenland Sea waters by more than a year. More work needs to be done to understand the factors responsible for both the large-scale and the small-scale patterns in annual NPP.

  6. Estimating Net Primary Productivity Using Satellite and Ancillary Data

    NASA Technical Reports Server (NTRS)

    Choudhury, B. J.; Houser, Paul (Technical Monitor)

    2001-01-01

    The net primary productivity (C) or annual rate of carbon accumulation per unit ground area by terrestrial plant communities is the difference of the rate of gross photosynthesis (A(sub g)) and autotrophic respiration (R) per unit ground area. Although available observations show that R is a large and variable fraction of A(sub g), viz., 0.3 to 0.7, it is generally recognized that much uncertainties exist in this fraction due to difficulties associated with the needed measurements. Additional uncertainties arise when these measurements are extrapolated to regional or global land surface using empirical equations, for example, using regression equations relating C to mean annual precipitation and air temperature. Here, a process-based approach has been taken to calculate A(sub g) and R using satellite and ancillary data. A(sub g) has been expressed as a product of radiation use efficiency, magnitude of intercepted photosynthetically active radiation (PAR), and normalized by stresses due to soil water shortage and air temperature away from the optimum range. A biophysical model has been used to determine the radiation use efficiency from the maximum rate of carbon assimilation by a leaf, foliage temperature, and the fraction of diffuse PAR incident on a canopy. All meteorological data (PAR, air temperature, precipitation, etc.) needed for the calculation are derived from satellite observations, while a land use, land cover data (based on satellite and ground measurements) have been used to assess the maximum rate of carbon assimilation by a leaf of varied cover type based on field measurements. R has been calculated as the sum of maintenance and growth components. The maintenance respiration of foliage and live fine roots at a standard temperature of different land cover has been determined from their nitrogen content using field and satellite measurements, while that of living fraction of woody stem (viz., sapwood) from the seasonal maximum leaf area index as

  7. Distinct roles of ppGpp and DksA in Legionella pneumophila differentiation

    PubMed Central

    Dalebroux, Zachary D.; Yagi, Brian F.; Sahr, Tobias; Buchrieser, Carmen; Swanson, Michele S.

    2010-01-01

    SUMMARY To transit between hosts, intracellular Legionella pneumophila transform into a motile, infectious, transmissive state. Here we exploit the pathogen’s life cycle to examine how guanosine tetraphosphate (ppGpp) and DksA cooperate to govern bacterial differentiation. Transcriptional profiling revealed that during transmission alarmone accumulation increases the mRNA for flagellar and Type IV-secretion components, secreted host effectors, and regulators, and decreases transcripts for translation, membrane modification and ATP synthesis machinery. DksA is critical for differentiation, since mutants are defective for stationary phase survival, flagellar gene activation, lysosome avoidance, and macrophage cytotoxicity. The roles of ppGpp and DksA depend on the context. For macrophage transmission, ppGpp is essential, whereas DksA is dispensable, indicating ppGpp can act autonomously. In broth, DksA promotes differentiation when ppGpp levels increase, or during fatty acid stress, as judged by flaA expression and evasion of degradation by macrophages. For flagella morphogenesis, DksA is required for basal fliA (σ28) promoter activity. When alarmone levels increase, DksA cooperates with ppGpp to generate a pulse of Class II rod RNA or to amplify the Class III sigma factor and Class IV flagellin RNAs. Thus, DksA responds to the level of ppGpp and other stress signals to coordinate L. pneumophila differentiation. PMID:20199605

  8. Vegetation Productivity Consequences of Sprawl in the Eastern United States

    NASA Astrophysics Data System (ADS)

    Zhao, T.; Brown, D. G.; Fang, H.; Liu, T.; Zhang, T.

    2009-12-01

    Urban, suburban, and exurban areas expanded rapidly in the United States during the 1990s, replacing the rural land that lay outside existing metropolitan areas, cities, and towns. The conversion of rural landscapes to urban infrastructures and land uses has significant consequences for the regional vegetation productivity, but these consequences are not yet fully understood. A previous study in the Detroit-Ann Arbor-Flint Consolidated Metropolitan Statistical Areas (CMSA) in Michigan showed that exurbanization and suburbanization, i.e., development at relatively low densities, occupied four times the area of urbanization (development at the highest densities). While urbanization was associated with a net carbon source from the landscape in this CMSA, exurban development from the previous rural areas enhanced the uptake of carbon on land measured by gross primary production (GPP). In this study, similar research approaches were extended to all areas east of the Mississippi River in the United States. Two research questions were of particular interest: 1) Are patterns of sprawl consistent throughout the various regions that make up the Eastern US? and 2) Are relationships between types of sprawl and changes in GPP retain consistent over a large geographic extent? In this study, development was quantitatively evaluated based on Census housing-unit data collected in 1990 and 2000. Changes in GPP over the same time period were estimated based on satellite-derived land cover and vegetation greenness, climate data, and empirical light-use-efficiency parameters for various land-cover types. Results indicated that patterns of sprawl are regionally distinctive; and that relationships between sprawl and changes in GPP are relatively consistent, except for the effects of exurbanization on GPP, which tend to vary by ecoregion.

  9. Positive feedback between chironomids and algae creates net mutualism between benthic primary consumers and producers.

    PubMed

    Herren, Cristina M; Webert, Kyle C; Drake, Michael D; Jake Vander Zanden, M; Einarsson, Árni; Ives, Anthony R; Gratton, Claudio

    2017-02-01

    The chironomids of Lake Mývatn show extreme population fluctuations that affect most aspects of the lake ecosystem. During periods of high chironomid densities, chironomid larvae comprise over 90% of aquatic secondary production. Here, we show that chironomid larvae substantially stimulate benthic gross primary production (GPP) and net primary production (NPP), despite consuming benthic algae. Benthic GPP in experimental mesocosms with 140,000 larvae/m(2) was 71% higher than in mesocosms with no larvae. Similarly, chlorophyll a concentrations in mesocosms increased significantly over the range of larval densities. Furthermore, larvae showed increased growth rates at higher densities, possibly due to greater benthic algal availability in these treatments. We investigated the hypothesis that larvae promote benthic algal growth by alleviating nutrient limitation, and found that (1) larvae have the potential to cycle the entire yearly external loadings of nitrogen and phosphorus during the growing season, and (2) chlorophyll a concentrations were significantly greater in close proximity to larvae (on larval tubes). The positive feedback between chironomid larvae and benthic algae generated a net mutualism between the primary consumer and primary producer trophic levels in the benthic ecosystem. Thus, our results give an example in which unexpected positive feedbacks can lead to both high primary and high secondary production.

  10. Examination of silicate limitation of primary production in Jiaozhou Bay, China. I. Silicate being a limiting factor of phytoplankton primary production

    NASA Astrophysics Data System (ADS)

    Yang, Dong-Fang; Zhang, Jing; Lu, Ji-Bin; Gao, Zhen-Hui; Chen, Yu

    2002-09-01

    Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou Bay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO{3/-}-N, NO{2/-}-N, NH{4/+}-N, SiO{3/2-}-Si, PO{4/3-}-P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq. (1) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temperature; that the main factor controlling the primary production is Si; that water temperature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecological niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature's effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay, the biogeochemical sediment process of the silicon, the phytoplankton predominant species and the phytoplankton structure. The authors considered silicate a limiting factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and uptake by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrinsic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high

  11. Photoneutron production in the primary barriers of medical accelerator rooms.

    PubMed

    McGinley, P H

    1992-04-01

    Several radiation surveys, at medical linear accelerator facilities where lead or steel had been used with concrete to fabricate the primary barriers, revealed the existence of a sizable neutron field outside the shielding. This neutron field is produced by photoneutrons generated in the metal portion of the shield when the primary x-ray beam is aimed at the barrier. A method was developed to calculate the neutron dose-equivalent rate expected outside a primary shield when it is irradiated by a high-energy x-ray beam. It was found that the minimum photoneutron dose was produced when the metal part of the shield was positioned inside the treatment room in front of the concrete and also by using steel in place of lead. A thickness of less than or equal to 17 cm of metal on the inner surface of the shield produced only a slight increase in the neutron dose equivalent outside the barrier.

  12. Overload Control for Signaling Congestion of Machine Type Communications in 3GPP Networks

    PubMed Central

    Lu, Zhaoming; Pan, Qi; Wang, Luhan; Wen, Xiangming

    2016-01-01

    Because of the limited resources on radio access channels of third generation partnership projection (3GPP) network, one of the most challenging tasks posted by 3GPP cellular-based machine type communications (MTC) is congestion due to massive requests for connection to radio access network (RAN). In this paper, an overload control algorithm in 3GPP RAN is proposed, which proactively disperses the simultaneous access attempts in evenly distributed time window. Through periodic reservation strategy, massive access requests of MTC devices are dispersed in time, which reduces the probability of confliction of signaling. By the compensation and prediction mechanism, each device can communicate with MTC server with dynamic load of air interface. Numerical results prove that proposed method makes MTC applications friendly to 3GPP cellular network. PMID:27936011

  13. Short-term to seasonal variability in factors driving primary productivity in a shallow estuary: Implications for modeling production

    NASA Astrophysics Data System (ADS)

    Canion, Andy; MacIntyre, Hugh L.; Phipps, Scott

    2013-10-01

    The inputs of primary productivity models may be highly variable on short timescales (hourly to daily) in turbid estuaries, but modeling of productivity in these environments is often implemented with data collected over longer timescales. Daily, seasonal, and spatial variability in primary productivity model parameters: chlorophyll a concentration (Chla), the downwelling light attenuation coefficient (kd), and photosynthesis-irradiance response parameters (Pmchl, αChl) were characterized in Weeks Bay, a nitrogen-impacted shallow estuary in the northern Gulf of Mexico. Variability in primary productivity model parameters in response to environmental forcing, nutrients, and microalgal taxonomic marker pigments were analysed in monthly and short-term datasets. Microalgal biomass (as Chla) was strongly related to total phosphorus concentration on seasonal scales. Hourly data support wind-driven resuspension as a major source of short-term variability in Chla and light attenuation (kd). The empirical relationship between areal primary productivity and a combined variable of biomass and light attenuation showed that variability in the photosynthesis-irradiance response contributed little to the overall variability in primary productivity, and Chla alone could account for 53-86% of the variability in primary productivity. Efforts to model productivity in similar shallow systems with highly variable microalgal biomass may benefit the most by investing resources in improving spatial and temporal resolution of chlorophyll a measurements before increasing the complexity of models used in productivity modeling.

  14. Primary productivity in the southeast Pacific Ocean: Effect of enhanced ultraviolet-B radiation

    SciTech Connect

    Behrenfeld, M. ); Hardy, J.T. ); Gucinski, H.; Wones, A.G. )

    1990-01-09

    Experiments were conducted to determine the effects of predicted increases in solar UV-B radiation, resulting from stratospheric ozone depletion, on the primary production of natural marine phytoplankton assemblages over a wide latitudinal gradient. Primary production was measured every 2 to 4[degrees] latitude in the southeast Pacific using the carbon-14 technique. Fluorescent sunlamps were used to enhance the dose of UV-B radiation above ambient during shipboard incubations. Enhanced UV-B radiation caused a significant mean decrease of 34% in surface water primary production. Decreases in primary production increased with increasing assimilation efficiencies. Results indicate that predicted increases in ambient solar UV-B radiation could result in mean annual decreases of near-surface oceanic primary production of less than 1% near the equator to more than 34% at high southern latitudes.

  15. Role of (p)ppGpp in Viability and Biofilm Formation of Actinobacillus pleuropneumoniae S8

    PubMed Central

    Li, Gang; Xie, Fang; Zhang, Yanhe; Bossé, Janine T.; Langford, Paul R.; Wang, Chunlai

    2015-01-01

    Actinobacillus pleuropneumoniae is a Gram-negative bacterium and the cause of porcine pleuropneumonia. When the bacterium encounters nutritional starvation, the relA-dependent (p)ppGpp-mediated stringent response is activated. The modified nucleotides guanosine 5’-diphosphate 3’-diphosphate (ppGpp) and guanosine 5’-triphosphate 3’-diphosphate (pppGpp) are known to be signaling molecules in other prokaryotes. Here, to investigate the role of (p)ppGpp in A. pleuropneumoniae, we created a mutant A. pleuropneumoniae strain, S8ΔrelA, which lacks the (p)ppGpp-synthesizing enzyme RelA, and investigated its phenotype in vitro. S8ΔrelA did not survive after stationary phase (starvation condition) and grew exclusively as non-extended cells. Compared to the wild-type (WT) strain, the S8ΔrelA mutant had an increased ability to form a biofilm. Transcriptional profiles of early stationary phase cultures revealed that a total of 405 bacterial genes were differentially expressed (including 380 up-regulated and 25 down-regulated genes) in S8ΔrelA as compared with the WT strain. Most of the up-regulated genes are involved in ribosomal structure and biogenesis, amino acid transport and metabolism, translation cell wall/membrane/envelope biogenesis. The data indicate that (p)ppGpp coordinates the growth, viability, morphology, biofilm formation and metabolic ability of A. pleuropneumoniae in starvation conditions. Furthermore, S8ΔrelA could not use certain sugars nor produce urease which has been associated with the virulence of A. pleuropneumoniae, suggesting that (p)ppGpp may directly or indirectly affect the pathogenesis of A. pleuropneumoniae during the infection process. In summary, (p)ppGpp signaling represents an essential component of the regulatory network governing stress adaptation and virulence in A. pleuropneumoniae. PMID:26509499

  16. Application of a satellite-based terrestrial carbon flux model for quantifying recent climate and fire disturbance impacts on northern ecosystem productivity

    NASA Astrophysics Data System (ADS)

    Yi, Y.; Kimball, J. S.; Jones, L. A.; Reichle, R. H.; Nemani, R. R.

    2012-12-01

    Quantifying variability and underlying environmental constraints on carbon (CO2) sequestration in northern (≥ 45 °N) ecosystems is important for improving predictions of future climate change. We applied a satellite-based terrestrial carbon flux model for daily estimation of net ecosystem CO2 exchange (NEE) and component carbon fluxes across a pan-boreal/Arctic domain. The model includes a light use efficiency algorithm for estimating vegetation gross primary production (GPP) using operational satellite NDVI records, while ecosystem respiration is derived using a three-pool soil decomposition model adapted to utilize potential inputs from satellite microwave retrieved soil moisture and temperature as primary environmental constraints to soil respiration. Initial validation against tower eddy-covariance measurement based carbon fluxes for northern tower sites showed favorable results for GPP (R ≥ 0.7, RMSE < 2.5 g C/m2/day), and overall consistency for NEE (R > 0.5) at predominantly undisturbed sites. However, the terrestrial carbon uptake during the peak growing season was generally underestimated by the model especially for deciduous broadleaf forests, mainly due to under prediction of GPP over dense canopy areas and model steady-state assumptions of dynamic equilibrium between vegetation productivity and respiration processes. A model framework integrating satellite-based burned area products and vegetation indices was then developed to represent non-steady-state fire disturbance and recovery effects and the simulations largely tracked NEE recovery indicated by tower CO2 flux measurements over three boreal fire chronosequence networks. The regional simulations indicated that large drought and fire events were generally associated with large GPP reductions and net ecosystem carbon losses, though NEE was generally less sensitive to fire disturbance due to similar behavior in GPP and respiration components. These results are being used to inform development of

  17. Regulation of σ factor competition by the alarmone ppGpp

    PubMed Central

    Jishage, Miki; Kvint, Kristian; Shingler, Victoria; Nyström, Thomas

    2002-01-01

    Many regulons controlled by alternative σ factors, including σS and σ32, are poorly induced in cells lacking the alarmone ppGpp. We show that ppGpp is not absolutely required for the activity of σS-dependent promoters because underproduction of σ70, specific mutations in rpoD (rpoD40 and rpoD35), or overproduction of Rsd (anti-σ70) restored expression from σS-dependent promoters in vivo in the absence of ppGpp accumulation. An in vitro transcription/competition assay with reconstituted RNA polymerase showed that addition of ppGpp reduces the ability of wild-type σ70 to compete with σ32 for core binding and the mutant σ70 proteins, encoded by rpoD40 and rpoD35, compete less efficiently than wild-type σ70. Similarly, an in vivo competition assay showed that the ability of both σ32 and σS to compete with σ70 is diminished in cells lacking ppGpp. Consistently, the fraction of σS and σ32 bound to core was drastically reduced in ppGpp-deficient cells. Thus, the stringent response encompasses a mechanism that alters the relative competitiveness of σ factors in accordance with cellular demands during physiological stress. PMID:12023304

  18. [THE ROLE OF (p)ppGpp MOLECULES IN FORMATION OF "STRICT RESPONSE" IN BACTERIA AND BIOSYNTHESIS OF ANTIBIOTICS AND MORPHOLOGICAL DIFFERENTIATION IN ACTINOMYCETES].

    PubMed

    Klymyshin, D; Stephanyshyn, O; Fedorenko, V

    2016-01-01

    Strict response is a pleiotropic physiological response of cells caused by lack of aminoacetylated tRNAs. Experimentally, this response occurs due to the lack of amino acids in the environment and the limitation of tRNA aminoacylation even in the presence of the corresponding amino acids in the cell. Many features of this response indicate its dependence on the accumulation of ppGpp molecules. There is a correlation between the growth rate of actinomycetes and biosynthesis of their secondary metabolites. Introduction of additional relA gene copies of ppGpp synthetase can affect the production of antibiotics in streptomycetes. The article presents the authors' own experimental data, dedicated to the influence of heterologous relA gene expression in Streptomyces nogalater cells.

  19. An Exploration of Behavioral Health Productivity and Billing Practices Within Pediatric Primary Care.

    PubMed

    Cederna-Meko, Crystal L; Ellens, Rebecca E H; Burrell, Katherine M; Perry, Danika S; Rafiq, Fatima

    2016-11-01

    OBJECTIVES : To provide descriptive information on behavioral health (BH) productivity and billing practices within a pediatric primary care setting. METHODS : This retrospective investigation reviewed 30 months of electronic medical records and financial data. RESULTS : The percent of BH provider time spent in direct patient care (productivity) was 35.28% overall, with a slightly higher quarterly average (M  =  36.42%; SD  =  6.46%). In the 646.75 hr BH providers spent in the primary care setting, $52,050.00 was charged for BH services delivered ($80.48 hourly average). CONCLUSIONS : BH productivity and billing within pediatric primary care were suboptimal and likely multifactorially derived. To promote integrated primary care sustainability, the authors recommend three future aims: improve BH productivity, demonstrate the value-added contributions of BH services within primary care, and advocate for BH-supporting health care reform.

  20. An Exploration of Behavioral Health Productivity and Billing Practices Within Pediatric Primary Care

    PubMed Central

    Ellens, Rebecca E. H.; Burrell, Katherine M.; Perry, Danika S.; Rafiq, Fatima

    2016-01-01

    Objectives To provide descriptive information on behavioral health (BH) productivity and billing practices within a pediatric primary care setting. Methods This retrospective investigation reviewed 30 months of electronic medical records and financial data. Results The percent of BH provider time spent in direct patient care (productivity) was 35.28% overall, with a slightly higher quarterly average (M  =  36.42%; SD  =  6.46%). In the 646.75 hr BH providers spent in the primary care setting, $52,050.00 was charged for BH services delivered ($80.48 hourly average). Conclusions BH productivity and billing within pediatric primary care were suboptimal and likely multifactorially derived. To promote integrated primary care sustainability, the authors recommend three future aims: improve BH productivity, demonstrate the value-added contributions of BH services within primary care, and advocate for BH-supporting health care reform. PMID:27498983

  1. The Impact of Submesoscale Physics on Primary Productivity of Plankton

    NASA Astrophysics Data System (ADS)

    Mahadevan, Amala

    2016-01-01

    Life in the ocean relies on the photosynthetic production of phytoplankton, which is influenced by the availability of light and nutrients that are modulated by a host of physical processes. Submesoscale processes are particularly relevant to phytoplankton productivity because the timescales on which they act are similar to those of phytoplankton growth. Their dynamics are associated with strong vorticity and strain rates that occur on lateral scales of 0.1-10 km. They can support vertical velocities as large as 100 m d-1 and play a crucial role in transporting nutrients into the sunlit ocean for phytoplankton production. In regimes with deep surface mixed layers, submesoscale instabilities can cause stratification within days, thereby increasing light exposure for phytoplankton trapped close to the surface. These instabilities help to create and maintain localized environments that favor the growth of phytoplankton, contribute to productivity, and cause enormous heterogeneity in the abundance of phytoplankton, which has implications for interactions within the ecosystem.

  2. The Impact of Submesoscale Physics on Primary Productivity of Plankton.

    PubMed

    Mahadevan, Amala

    2016-01-01

    Life in the ocean relies on the photosynthetic production of phytoplankton, which is influenced by the availability of light and nutrients that are modulated by a host of physical processes. Submesoscale processes are particularly relevant to phytoplankton productivity because the timescales on which they act are similar to those of phytoplankton growth. Their dynamics are associated with strong vorticity and strain rates that occur on lateral scales of 0.1-10 km. They can support vertical velocities as large as 100 m d(-1) and play a crucial role in transporting nutrients into the sunlit ocean for phytoplankton production. In regimes with deep surface mixed layers, submesoscale instabilities can cause stratification within days, thereby increasing light exposure for phytoplankton trapped close to the surface. These instabilities help to create and maintain localized environments that favor the growth of phytoplankton, contribute to productivity, and cause enormous heterogeneity in the abundance of phytoplankton, which has implications for interactions within the ecosystem.

  3. Influence of Submarine Groundwater Discharge on Primary Productivity in the Semi-Enclosed Bay in Japan

    NASA Astrophysics Data System (ADS)

    Sugimoto, R.; Nishi, S.; Taniguchi, M.; Tominaga, O.

    2014-12-01

    In recent years, a number of studies have shown that submarine groundwater discharge is an alternative nutrient pathway and can drive primary production in coastal seas. However, very little is known about an exact relationship between input of groundwater and response of primary production. To clarify the relationship, we conducted the field survey in the semi-enclosed coastal bay in Japan (Obama Bay). There are abundant amounts of groundwater resources in the basin. Firstly, we conducted 222Rn continuous measurement along the coast in March 2013 to obtain the spatial difference of groundwater impact. As a result, 222Rn activity clearly showed that groundwater discharge concentrates in the western part of the bay head. We thus conducted in-situ measurements of primary productivity using stable 13C tracer method and environmental parameters (ex. 222Rn activity, light intensity, temperature and nutrient concentrations) at 6 stations within the western bay head in July and August 2013. Primary productivity within the western bay head changed from 11.0 to 49.5 μg C L-1 hr-1 in July and from 9.3 to 32.4 μg C L-1 hr-1 in August. Moreover, there was significant relationship between primary productivity and 222Rn concentration in both months. Although light intensity and water temperature were different in each station and month, concentrations of nutrients limited primary productivity. These results showed that nutrient supply from SGD would affect crucial impact on primary productivity in Obama Bay.

  4. Interannual Variation in Phytoplankton Class-Specific Primary Production at a Global Scale

    NASA Technical Reports Server (NTRS)

    Rousseaux, Cecile Severine; Gregg, Watson W.

    2014-01-01

    We used the NASA Ocean Biogeochemical Model (NOBM) combined with remote sensing data via assimilation to evaluate the contribution of 4 phytoplankton groups to the total primary production. First we assessed the contribution of each phytoplankton groups to the total primary production at a global scale for the period 1998-2011. Globally, diatoms were the group that contributed the most to the total phytoplankton production (50, the equivalent of 20 PgC y-1. Coccolithophores and chlorophytes each contributed to 20 (7 PgC y-1 of the total primary production and cyanobacteria represented about 10 (4 PgC y(sub-1) of the total primary production. Primary production by diatoms was highest in high latitude (45) and in major upwelling systems (Equatorial Pacific and Benguela system). We then assessed interannual variability of this group-specific primary production over the period 1998-2011. Globally the annual relative contribution of each phytoplankton groups to the total primary production varied by maximum 4 (1-2 PgC y-1. We assessed the effects of climate variability on the class-specific primary production using global (i.e. Multivariate El Nio Index, MEI) and regional climate indices (e.g. Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO)). Most interannual variability occurred in the Equatorial Pacific and was associated with climate variability as indicated by significant correlation (p 0.05) between the MEI and the class-specific primary production from all groups except coccolithophores. In the Atlantic, climate variability as indicated by NAO was significantly correlated to the primary production of 2 out of the 4 groups in the North Central Atlantic (diatomscyanobacteria) and in the North Atlantic (chlorophytes and coccolithophores). We found that climate variability as indicated by SAM had only a limited effect on the class-specific primary production in the Southern Ocean. These results provide a modeling and

  5. Modelling productivity in a mixed C3 and C4 Australian savanna using a soil-plant-atmosphere model

    NASA Astrophysics Data System (ADS)

    Macinnis-Ng, Cate; Whitley, Rhys; Hutley, Lindsay; Beringer, Jason; Zeppel, Melanie; Williams, Mathew; Medlyn, Belinda; Eamus, Derek

    2010-05-01

    The Soil-Plant-Atmosphere (SPA) model of Williams et al. (1996) is a mechanistic model which simulates ecosystem carbon and water fluxes over multiple canopy and soil layers at fine temporal scale. To-date, this model has not included consideration of C4 vegetation that is typically present in tropical savannas. We added a C4 photosynthesis routine to the model to allow estimation of the gross primary productivity (GPP) of a mixed (C3 and C4) tropical savanna in northern Australia. Much of Australia's savanna consists of a seasonal C4 grass understorey with a C3 open tree canopy, including evergreen, semi-deciduous and deciduous species. The tall annual grasses make up approximately half of the leaf area index (LAI) in the wet season (November to March) when 90% of annual rain falls but they die back in every dry season (April to October). The seasonal cycle of leaf area and foliar N distributions were defined for each canopy layer and each layer was designated as C3 or C4 for application of the applicable photosynthesis model. The SPA model was then run over a 5 year period (2001-2005) and compared to measured eddy covariance data. There was good agreement between modelled and measured GPP values. The model explained between 80 - 87% of the variance and had a low root-mean-square error (RMSE) of between 0.0206 - 0.5742 g C m-2 d-1. The contribution of the grass to total annual GPP was approximately 66%, highlighting the importance of including the C4 grasses in the model. Approximately 60% of the total (trees and grasses) annual GPP occurred during the wet season. Landscape quantum yields were calculated as the response of GPP to PAR between 50 and 250 µmol m-2 s-1 and compared for wet and dry seasons, in both morning and afternoons. This was highest for the wet season mornings (0.0282 mol CO2 per mol photon) and lowest for dry season afternoons. A sensitivity analysis of GPP revealed that daily GPP was most sensitive to changes in understorey LAI and foliar N

  6. Interannual Variation in Phytoplankton Class-specific Primary Production at a Global Scale

    NASA Technical Reports Server (NTRS)

    Rousseaux, Cecile; Gregg, Watson

    2014-01-01

    Phytoplankton is responsible for over half of the net primary production on earth. The knowledge on the contribution of various phytoplankton groups to the total primary production is still poorly understood. Data from satellite observations suggest that for upwelling regions, photosynthetic rates by microplankton is higher than that of nanoplankton but that when the spatial extent is considered, the production by nanoplankton is comparable or even larger than microplankton. Here, we used the NASA Ocean Biogeochemical Model (NOBM) combined with remote sensing data via assimilation to evaluate the contribution of 4 phytoplankton groups to the total primary production. Globally, diatoms were the group that contributed the most to the total phytoplankton production (approx. 50%) followed by coccolithophores and chlorophytes. Primary production by diatoms was highest in high latitude (>45 deg) and in major upwelling systems (Equatorial Pacific and Benguela system). We assessed the effects of climate variability on the class-specific primary production using global (i.e. Multivariate El Nino Index, MEI) and 'regional' climate indices (e.g. Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO)). Most interannual variability occurred in the Equatorial Pacific and was associated with climate variability. These results provide a modeling and data assimilation perspective to phytoplankton partitioning of primary production and contribute to our understanding of the dynamics of the carbon cycle in the oceans at a global scale.

  7. Primary production and canopy cover in bitterbrush-cheatgrass communities

    SciTech Connect

    Rickard, W.H.; Sauer, R.H.

    1982-01-01

    Aboveground grass and forb production averaged 126 g m/sup -2/ yr/sup -1/ and ranged between 10 and 195 grams over a four year period 1975-1978. The low production year was 1977, a year of extreme drought. Production was not significantly different between unburned sites and burned sites five years post burning (1970). Canopy cover and species composition were similar on burned and unburned sites except for the shrubs, bitterbrush (Purshia tridentata) and sagebrush (Artemisia tridentata), which were killed by burning. There was no indication that shrubs were invading the burned areas as seedlings or vegetatively through sprouting. The implications of burning and mule deer (Odocoileus hemionus) management are briefly discussed.

  8. Comparison of marine productivity among Outer Continental Shelf planning areas. Supplement: An evaluation of benthic habitat primary productivity. Final report

    SciTech Connect

    Balcom, B.J.; Foster, M.A.; Fourqurean, J.J.; Heine, J.N.; Leonard, G.H.

    1991-01-01

    Literature on current primary productivity was reviewed and evaluated for each of nine benthic communities or habitats, estimates of daily and annual benthic primary productivity were derived within each community, the benthic primary estimates were related to an estimate of areal extent of each community within or adjacent to each OCS planning area. Direct comparisons between habitats was difficult because of the varying measures and methodologies used. Coastal marshes were the most prevalent habitat type evaluated. Mangrove and coral reef habitats were highly productive but occur within few planning areas. Benthic diatoms and blue-green algae are less productive in terms of estimated annual productivity on a per square meter basis; these habitats have the potential to occur across wide areas of the OCS and should not be overlooked.

  9. Inflectional morphology in primary progressive aphasia: an elicited production study.

    PubMed

    Wilson, Stephen M; Brandt, Temre H; Henry, Maya L; Babiak, Miranda; Ogar, Jennifer M; Salli, Chelsey; Wilson, Lisa; Peralta, Karen; Miller, Bruce L; Gorno-Tempini, Maria Luisa

    2014-09-01

    Inflectional morphology lies at the intersection of phonology, syntax and the lexicon, three language domains that are differentially impacted in the three main variants of primary progressive aphasia (PPA). To characterize spared and impaired aspects of inflectional morphology in PPA, we elicited inflectional morphemes in 48 individuals with PPA and 13 healthy age-matched controls. We varied the factors of regularity, frequency, word class, and lexicality, and used voxel-based morphometry to identify brain regions where atrophy was predictive of deficits on particular conditions. All three PPA variants showed deficits in inflectional morphology, with the specific nature of the deficits dependent on the anatomical and linguistic features of each variant. Deficits in inflecting low-frequency irregular words were associated with semantic PPA, with lexical/semantic deficits, and with left temporal atrophy. Deficits in inflecting pseudowords were associated with non-fluent/agrammatic and logopenic variants, with phonological deficits, and with left frontal and parietal atrophy.

  10. Inflectional morphology in primary progressive aphasia: An elicited production study

    PubMed Central

    Wilson, Stephen M.; Brandt, Temre H.; Henry, Maya L.; Babiak, Miranda; Ogar, Jennifer M.; Salli, Chelsey; Wilson, Lisa; Peralta, Karen; Miller, Bruce L.; Gorno-Tempini, Maria Luisa

    2014-01-01

    Inflectional morphology lies at the intersection of phonology, syntax and the lexicon, three language domains that are differentially impacted in the three main variants of primary progressive aphasia (PPA). To characterize spared and impaired aspects of inflectional morphology in PPA, we elicited inflectional morphemes in 48 individuals with PPA and 13 healthy age-matched controls. We varied the factors of regularity, frequency, word class, and lexicality, and used voxel-based morphometry to identify brain regions where atrophy was predictive of deficits on particular conditions. All three PPA variants showed deficits in inflectional morphology, with the specific nature of the deficits dependent on the anatomical and linguistic features of each variant. Deficits in inflecting low-frequency irregular words were associated with semantic PPA, with lexical/semantic deficits, and with left temporal atrophy. Deficits in inflecting pseudowords were associated with non-fluent/agrammatic and logopenic variants, with phonological deficits, and with left frontal and parietal atrophy. PMID:25129631

  11. Fission Product Migration in Primary System and Containment

    SciTech Connect

    2015-04-01

    Version 00 ART MOD2 aims at a comprehensive analysis for the FP behaviour in primary system and in containment during severe accidents and therefore the code considers the removal of radio-nuclides of up to 60 materials including chemical compounds by natural deposition and by the engineered safety features (ESF) such as spray systems. As for the natural deposition of radio-nuclides, the code can consider the phenomena such as gravitational settling, thermophoresis, diffusiophoresis, Brownian diffusion, diffusion under laminar or turbulent flows, resuspension, condensation, chemisorption and revaporization. The code also models the aerosol growth by agglomeration of aerosols and condensation/evaporation of volatile material at the aerosol surface. Recently, the models for iodine chemistry in containment sump water was incorporated into ART MOD2 ART MOD2 was modified in January 2015 to correct coding errors and improve the vibration of the calculation result of water (H2O) vapor.

  12. Will Global Change Effect Primary Productivity in Coastal Ecosystems?

    NASA Technical Reports Server (NTRS)

    Rothschild, Lynn J.; Peterson, David L. (Technical Monitor)

    1997-01-01

    Algae are the base of coastal food webs because they provide the source of organic carbon for the remaining members of the community. Thus, the rate that they produce organic carbon to a large extent controls the productivity of the entire ecosystem. Factors that control algal productivity range from the physical (e.g., temperature, light), chemical (e.g., nutrient levels) to the biological (e.g., grazing). Currently, levels of atmospheric carbon dioxide surficial fluxes of ultraviolet radiation are rising. Both of these environmental variables can have a profound effect on algal productivity. Atmospheric carbon dioxide may increase surficial levels of dissolved inorganic carbon. Our laboratory and field studies of algal mats and phytoplankton cultures under ambient and elevated levels of pCO2 show that elevated levels of inorganic carbon can cause an increase in photosynthetic rates. In some cases, this increase will cause an increase in phytoplankton numbers. There may be an increase in the excretion of fixed carbon, which in turn may enhance bacterial productivity. Alternatively, in analogy with studies on the effect of elevated pCO2 on plants, the phytoplankton could change their carbon to nitrogen ratios, which will effect the feeding of the planktonic grazers. The seasonal depletion of stratospheric ozone has resulted in elevated fluxes of UVB radiation superimposed on the normal seasonal variation. Present surface UV fluxes have a significant impact on phytoplankton physiology, including the inhibition of the light and dark reactions of photosynthesis, inhibition of nitrogenase activity, inhibition of heterocyst formation, reduction in motility, increased synthesis of the UV-screening pigment scytonemin, and mutation. After reviewing these issues, recent work in our lab on measuring the effect of UV radiation on phytoplankton in the San Francisco Bay Estuary will be presented.

  13. Novel approach for computing photosynthetically active radiation for productivity modeling using remotely sensed images in the Great Plains, United States

    USGS Publications Warehouse

    Singh, Ramesh K.; Liu, Shu-Guang; Tieszen, Larry L.; Suyker, Andrew E.; Verma, Shashi B.

    2012-01-01

    Gross primary production (GPP) is a key indicator of ecosystem performance, and helps in many decision-making processes related to environment. We used the Eddy covariancelight use efficiency (EC-LUE) model for estimating GPP in the Great Plains, United States in order to evaluate the performance of this model. We developed a novel algorithm for computing the photosynthetically active radiation (PAR) based on net radiation. A strong correlation (R2=0.94,N=24) was found between daily PAR and Landsat-based mid-day instantaneous net radiation. Though the Moderate Resolution Spectroradiometer (MODIS) based instantaneous net radiation was in better agreement (R2=0.98,N=24) with the daily measured PAR, there was no statistical significant difference between Landsat based PAR and MODIS based PAR. The EC-LUE model validation also confirms the need to consider biological attributes (C3 versus C4 plants) for potential light use efficiency. A universal potential light use efficiency is unable to capture the spatial variation of GPP. It is necessary to use C3 versus C4 based land use/land cover map for using EC-LUE model for estimating spatiotemporal distribution of GPP.

  14. Primary production and biovolume of various phototrophic plankton size fractions in three southeastern United States reservoirs

    SciTech Connect

    Tison, D.; Wilde, E.W.

    1981-04-01

    Plankton size classes of < 3 ..mu..m consisting largely of unicellular cyanobacteria accounted for 15 to 40% of the total primary production and generally represented < 5% of the total phototrophic plankton biovolume in three South Carolina reservoirs.

  15. Cationic bactericidal peptide 1018 does not specifically target the stringent response alarmone (p)ppGpp

    PubMed Central

    Andresen, Liis; Tenson, Tanel; Hauryliuk, Vasili

    2016-01-01

    The bacterial stringent response is a key regulator of bacterial virulence, biofilm formation and antibiotic tolerance, and is a promising target for the development of new antibacterial compounds. The intracellular nucleotide (p)ppGpp acts as a messenger orchestrating the stringent response. A synthetic peptide 1018 was recently proposed to specifically disrupt biofilms by inhibiting the stringent response via direct interaction with (p)ppGpp (de la Fuente-Núñez et al. (2014) PLoS Pathogens). We have interrogated the specificity of the proposed molecular mechanism. When inhibition of Pseudomonas aeruginosa planktonic and biofilm growth is tested simultaneously in the same assay, peptides 1018 and the control peptide 8101 generated by an inversion of the amino acid sequence of 1018 are equally potent, and, importantly, do not display a preferential activity against biofilm. 1018 inhibits planktonic growth of Escherichia coli equally efficiently either when the alleged target, (p)ppGpp, is essential (MOPS media lacking amino acid L-valine), or dispensable for growth (MOPS media supplemented with L-valine). Genetic disruption of the genes relA and spoT responsible for (p)ppGpp synthesis moderately sensitizes – rather than protects – E. coli to 1018. We suggest that the antimicrobial activity of 1018 does not rely on specific recognition of the stringent response messenger (p)ppGpp. PMID:27819280

  16. Methylmercury Bioaccumulation in Stream Food Webs Declines with Increasing Primary Production.

    PubMed

    Walters, David M; Raikow, David F; Hammerschmidt, Chad R; Mehling, Molly G; Kovach, Amanda; Oris, James T

    2015-07-07

    Opposing hypotheses posit that increasing primary productivity should result in either greater or lesser contaminant accumulation in stream food webs. We conducted an experiment to evaluate primary productivity effects on MeHg accumulation in stream consumers. We varied light for 16 artificial streams creating a productivity gradient (oxygen production =0.048-0.71 mg O2 L(-1) d(-1)) among streams. Two-level food webs were established consisting of phytoplankton/filter feeding clam, periphyton/grazing snail, and leaves/shredding amphipod (Hyalella azteca). Phytoplankton and periphyton biomass, along with MeHg removal from the water column, increased significantly with productivity, but MeHg concentrations in these primary producers declined. Methylmercury concentrations in clams and snails also declined with productivity, and consumer concentrations were strongly correlated with MeHg concentrations in primary producers. Heterotroph biomass on leaves, MeHg in leaves, and MeHg in Hyalella were unrelated to stream productivity. Our results support the hypothesis that contaminant bioaccumulation declines with stream primary production via the mechanism of bloom dilution (MeHg burden per cell decreases in algal blooms), extending patterns of contaminant accumulation documented in lakes to lotic systems.

  17. Methylmercury bioaccumulation in stream food webs declines with increasing primary production

    USGS Publications Warehouse

    Walters, David; D.F. Raikow,; C.R. Hammerschmidt,; M.G. Mehling,; A. Kovach,; J.T. Oris,

    2015-01-01

    Opposing hypotheses posit that increasing primary productivity should result in either greater or lesser contaminant accumulation in stream food webs. We conducted an experiment to evaluate primary productivity effects on MeHg accumulation in stream consumers. We varied light for 16 artificial streams creating a productivity gradient (oxygen production =0.048–0.71 mg O2 L–1 d–1) among streams. Two-level food webs were established consisting of phytoplankton/filter feeding clam, periphyton/grazing snail, and leaves/shredding amphipod (Hyalella azteca). Phytoplankton and periphyton biomass, along with MeHg removal from the water column, increased significantly with productivity, but MeHg concentrations in these primary producers declined. Methylmercury concentrations in clams and snails also declined with productivity, and consumer concentrations were strongly correlated with MeHg concentrations in primary producers. Heterotroph biomass on leaves, MeHg in leaves, and MeHg in Hyalella were unrelated to stream productivity. Our results support the hypothesis that contaminant bioaccumulation declines with stream primary production via the mechanism of bloom dilution (MeHg burden per cell decreases in algal blooms), extending patterns of contaminant accumulation documented in lakes to lotic systems.

  18. Effect of cobalt on the primary productivity of Spirulina platensis

    SciTech Connect

    Sharma, R.M.; Panigrahi, S.; Azeez, P.A.

    1987-10-01

    Cobalt, a micronutrient for biological organisms, is a metal of wide use. Main sources of Co to the environment are combustion of fossil fuels, smelters, cobalt processing facilities, sewage and industrial wastes. Atomic power plants and nuclear weapon detonations form an important source of radioisotopes of this metal to the environment. Cobalt has been included in the 14 toxic trace elements of critical importance from the point of view of environmental pollution and health hazards. Cobalt deficiency leads to diseases like stunted growth. At toxic level, Co inhibits heme biosynthesis and enzyme activities. The present study reports the effect of cobalt on biomass productivity of blue-green alga Spirulina platensis.

  19. Patchiness of phytoplankton and primary production in Liaodong Bay, China

    PubMed Central

    Laws, Edward A.; Zhang, Haibo; Ye, Siyuan; Yuan, Hongming; Liu, Haiyue

    2017-01-01

    A comprehensive study of water quality, phytoplankton biomass, and photosynthetic rates in Liaodong Bay, China, during June and July of 2013 revealed two large patches of high biomass and production with dimensions on the order of 10 km. Nutrient concentrations were above growth-rate-saturating concentrations throughout the bay, with the possible exception of phosphate at some stations. The presence of the patches therefore appeared to reflect the distribution of water temperature and variation of light penetration restricted by water turbidity. There was no patch of high phytoplankton biomass or production in a third, linear patch of water with characteristics suitable for rapid phytoplankton growth; the absence of a bloom in that patch likely reflected the fact that the width of the patch was less than the critical size required to overcome losses of phytoplankton to turbulent diffusion. The bottom waters of virtually all of the eastern half of the bay were below the depth of the mixed layer, and the lowest bottom water oxygen concentrations, 3–5 mg L–1, were found in that part of the bay. The water column in much of the remainder of the bay was within the mixed layer, and oxygen concentrations in both surface and bottom waters exceeded 5 mg L–1. PMID:28235070

  20. Conformational states of Ras complexed with the GTP analogue GppNHp or GppCH2p: implications for the interaction with effector proteins.

    PubMed

    Spoerner, Michael; Nuehs, Andrea; Ganser, Petra; Herrmann, Christian; Wittinghofer, Alfred; Kalbitzer, Hans Robert

    2005-02-15

    The guanine nucleotide-binding protein Ras occurs in solution in two different states, state 1 and state 2, when the GTP analogue GppNHp is bound to the active center as detected by (31)P NMR spectroscopy. Here we show that Ras(wt).Mg(2+).GppCH(2)p also exists in two conformational states in dynamic equilibrium. The activation enthalpy DeltaH(++)(12) and the activation entropy DeltaS(++)(12) for the transition from state 1 to state 2 are 70 kJ mol(-1) and 102 J mol(-1) K(-1), within the limits of error identical to those determined for the Ras(wt).Mg(2+).GppNHp complex. The same is true for the equilibrium constants K(12) = [2]/[1] of 2.0 and the corresponding DeltaG(12) of -1.7 kJ mol(-1) at 278 K. This excludes a suggested specific effect of the NH group of GppNHp on the equilibrium. The assignment of the phosphorus resonance lines of the bound analogues has been done by two-dimensional (31)P-(31)P NOESY experiments which lead to a correction of the already reported assignments of bound GppNHp. Mutation of Thr35 in Ras.Mg(2+).GppCH(2)p to serine leads to a shift of the conformational equilibrium toward state 1. Interaction of the Ras binding domain (RBD) of Raf kinase or RalGDS with Ras(wt) or Ras(T35S) shifts the equilibrium completely to state 2. The (31)P NMR experiments suggest that, besides the type of the side chain of residue 35, a main contribution to the conformational equilibrium in Ras complexes with GTP and GTP analogues is the effective acidity of the gamma-phosphate group of the bound nucleotide. A reaction scheme for the Ras-effector interaction is presented which includes the existence of two conformations of the effector loop and a weak binding state.

  1. Tight coupling of primary production and marine mammal reproduction in the Southern Ocean.

    PubMed

    Paterson, J Terrill; Rotella, Jay J; Arrigo, Kevin R; Garrott, Robert A

    2015-05-07

    Polynyas are areas of open water surrounded by sea ice and are important sources of primary production in high-latitude marine ecosystems. The magnitude of annual primary production in polynyas is controlled by the amount of exposure to solar radiation and sensitivity to changes in sea-ice extent. The degree of coupling between primary production and production by upper trophic-level consumers in these environments is not well understood, which prevents reliable predictions about population trajectories for species at higher trophic levels under potential future climate scenarios. In this study, we find a strong, positive relationship between annual primary production in an Antarctic polynya and pup production by ice-dependent Weddell seals. The timing of the relationship suggests reproductive effort increases to take advantage of high primary production occurring in the months after the birth pulse. Though the proximate causal mechanism is unknown, our results indicate tight coupling between organisms at disparate trophic levels on a short timescale, deepen our understanding of marine ecosystem processes, and raise interesting questions about why such coupling exists and what implications it has for understanding high-latitude ecosystems.

  2. Tight coupling of primary production and marine mammal reproduction in the Southern Ocean

    PubMed Central

    Paterson, J. Terrill; Rotella, Jay J.; Arrigo, Kevin R.; Garrott, Robert A.

    2015-01-01

    Polynyas are areas of open water surrounded by sea ice and are important sources of primary production in high-latitude marine ecosystems. The magnitude of annual primary production in polynyas is controlled by the amount of exposure to solar radiation and sensitivity to changes in sea-ice extent. The degree of coupling between primary production and production by upper trophic-level consumers in these environments is not well understood, which prevents reliable predictions about population trajectories for species at higher trophic levels under potential future climate scenarios. In this study, we find a strong, positive relationship between annual primary production in an Antarctic polynya and pup production by ice-dependent Weddell seals. The timing of the relationship suggests reproductive effort increases to take advantage of high primary production occurring in the months after the birth pulse. Though the proximate causal mechanism is unknown, our results indicate tight coupling between organisms at disparate trophic levels on a short timescale, deepen our understanding of marine ecosystem processes, and raise interesting questions about why such coupling exists and what implications it has for understanding high-latitude ecosystems. PMID:25854885

  3. Role of eddy pumping in enhancing primary production in the ocean

    NASA Technical Reports Server (NTRS)

    Falkowski, Paul G.; Kolber, Zbigniew; Ziemann, David; Bienfang, Paul K.

    1991-01-01

    Eddy pumping is considered to explain the disparity between geochemical estimates and biological measurements of exported production. Episodic nutrient injections from the ocean into the photic zone can be generated by eddy pumping, which biological measurements cannot sample accurately. The enhancement of production is studied with respect to a cyclonic eddy in the subtropical Pacific. A pump-and-probe fluorimeter generates continuous vertical profiles of primary productivity from which the contributions of photochemical and nonphotochemical processes to fluorescence are derived. A significant correlation is observed between the fluorescence measurements and radiocarbon measurements. The results indicate that eddy pumping has an important effect on phytoplankton production and that this production is near the maximum relative specific growth rates. Based on the production enhancement observed in this case, eddy pumping increases total primary production by only 20 percent and does not account for all enhancement.

  4. DksA and (p)ppGpp have unique and overlapping contributions to Haemophilus ducreyi pathogenesis in humans.

    PubMed

    Holley, Concerta L; Zhang, Xinjun; Fortney, Kate R; Ellinger, Sheila; Johnson, Paula; Baker, Beth; Liu, Yunlong; Janowicz, Diane M; Katz, Barry P; Munson, Robert S; Spinola, Stanley M

    2015-08-01

    The (p)ppGpp-mediated stringent response is important for bacterial survival in nutrient limiting conditions. For maximal effect, (p)ppGpp interacts with the cofactor DksA, which stabilizes (p)ppGpp's interaction with RNA polymerase. We previously demonstrated that (p)ppGpp was required for the virulence of Haemophilus ducreyi in humans. Here, we constructed an H. ducreyi dksA mutant and showed it was also partially attenuated for pustule formation in human volunteers. To understand the roles of (p)ppGpp and DksA in gene regulation in H. ducreyi, we defined genes potentially altered by (p)ppGpp and DksA deficiency using transcriptome sequencing (RNA-seq). In bacteria collected at stationary phase, lack of (p)ppGpp and DksA altered expression of 28% and 17% of H. ducreyi open reading frames, respectively, including genes involved in transcription, translation, and metabolism. There was significant overlap in genes differentially expressed in the (p)ppGpp mutant relative to the dksA mutant. Loss of (p)ppGpp or DksA resulted in the dysregulation of several known virulence determinants. Deletion of dksA downregulated lspB and rendered the organism less resistant to phagocytosis and increased its sensitivity to oxidative stress. Both mutants had reduced ability to attach to human foreskin fibroblasts; the defect correlated with reduced expression of the Flp adhesin proteins in the (p)ppGpp mutant but not in the dksA mutant, suggesting that DksA regulates the expression of an unknown cofactor(s) required for Flp-mediated adherence. We conclude that both (p)ppGpp and DksA serve as major regulators of H. ducreyi gene expression in stationary phase and have both overlapping and unique contributions to pathogenesis.

  5. Production of primary mirror segments for the Giant Magellan Telescope

    NASA Astrophysics Data System (ADS)

    Martin, H. M.; Allen, R. G.; Burge, J. H.; Davis, J. M.; Davison, W. B.; Johns, M.; Kim, D. W.; Kingsley, J. S.; Law, K.; Lutz, R. D.; Strittmatter, P. A.; Su, P.; Tuell, M. T.; West, S. C.; Zhou, P.

    2014-07-01

    Segment production for the Giant Magellan Telescope is well underway, with the off-axis Segment 1 completed, off-axis Segments 2 and 3 already cast, and mold construction in progress for the casting of Segment 4, the center segment. All equipment and techniques required for segment fabrication and testing have been demonstrated in the manufacture of Segment 1. The equipment includes a 28 m test tower that incorporates four independent measurements of the segment's figure and geometry. The interferometric test uses a large asymmetric null corrector with three elements including a 3.75 m spherical mirror and a computer-generated hologram. For independent verification of the large-scale segment shape, we use a scanning pentaprism test that exploits the natural geometry of the telescope to focus collimated light to a point. The Software Configurable Optical Test System, loosely based on the Hartmann test, measures slope errors to submicroradian accuracy at high resolution over the full aperture. An enhanced laser tracker system guides the figuring through grinding and initial polishing. All measurements agree within the expected uncertainties, including three independent measurements of radius of curvature that agree within 0.3 mm. Segment 1 was polished using a 1.2 m stressed lap for smoothing and large-scale figuring, and a set of smaller passive rigid-conformal laps on an orbital polisher for deterministic small-scale figuring. For the remaining segments, the Mirror Lab is building a smaller, orbital stressed lap to combine the smoothing capability with deterministic figuring.

  6. Predicting diffuse light-enhancement of GPP from plant functional traits: A multi-site synthesis

    NASA Astrophysics Data System (ADS)

    O'Halloran, T. L.; Barr, J. G.; Cook, B.; Goeckede, M.; Law, B. E.; Kueppers, L. M.; Riley, W. J.

    2013-12-01

    Diffuse light enhances canopy-scale photosynthesis because isotropic diffuse light penetrates deeper into the canopy, involves more leaf area in photosynthesis, and prevents the top of the canopy from becoming light saturated. However, the observational and modeling communities still have little understanding of how the 'Diffuse light Enhancement Effect' (DEE) varies across plant functional types or is constrained by factors such as nitrogen availability and plant structure. So far, variability in the strength of DEE across plant functional types (PFTs) remains poorly constrained, but canopy models indicate leaf area index (LAI) is a primary controller. While the very few existing multi-site, measurement-based syntheses of the DEE have provided valuable information on the variability of the DEE across a few plant functional types, no study has correlated measured metrics of DEE magnitude with direct measurements of canopy physical traits across a wide range of plant functional types. Here we report a new metric that is suitable for quantifying the DEE in both flux measurements and land surface models. We also present, for the first time, an examination of the relationship between the DEE metric and plant functional traits. Results from our 70+ site AmeriFlux and FLUXNET synthesis indicate that LAI is the strongest controller of the DEE across sites and PFTs, with less significant influences from foliar nitrogen, canopy height, and mean annual precipitation. Our results will enable direct evaluation and improvement of remote sensing algorithms and light use efficiency models (e.g. MODIS GPP), which to this point regard diffuse light fraction as a source of noise. Additionally, improving resolution of the DEE in prognostic land surface models, such as the Community Land Model (CLM), will greatly improve our ability to forecast future feedbacks to terrestrial carbon sequestration from changes in cloudiness and aerosol amount.

  7. MODIS EVI as a proxy for net primary production across precipitation regimes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Above ground net primary production (ANPP) is a measure of the rate of photosynthesis in an ecosystem, and is indicative of its biomass productivity. Prior studies have reported a relationship between ANPP and annual precipitation which converged across biomes in dry years. This deserves further s...

  8. ESTUARINE PHYTOPLANKTON PRIMARY PRODUCTION AND SIZE AS DETERMINED REMOTELY FROM AIRCRAFT AND COASTAL OBSERVATION

    EPA Science Inventory

    We used remotely sensed estimates of chlorophyll a and sea surface temperature, incorporated into the Chesapeake Bay Productivity Model (Harding et al., 2002), to estimate the spatial and temporal variation of phytoplankton net primary production and species size in the Narragans...

  9. Patterns of new versus recycled primary production in the terrestrial biosphere

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrogen (N) and phosphorus (P) availability regulate plant productivity throughout the terrestrial biosphere, influencing the patterns and magnitude of net primary production (NPP) by land plants both now and into the future. These nutrients enter ecosystems via geologic and atmospheric pathways, a...

  10. Modeled diversity effects on microbial ecosystem functions of primary production, nutrient uptake, and remineralization.

    PubMed

    Goebel, Nicole L; Edwards, Christopher A; Follows, Michael J; Zehr, Jonathan P

    2014-01-01

    Ecosystem-wide primary productivity generally increases with primary producer diversity, emphasizing the importance of diversity for ecosystem function. However, most studies that demonstrate this positive relationship have focused on terrestrial and aquatic benthic systems, with little attention to the diverse marine pelagic primary producers that play an important role in regulating global climate. Here we show how phytoplankton biodiversity enhances overall marine ecosystem primary productivity and other ecosystem functions using a self-organizing ecosystem model. Diversity manipulation numerical experiments reveal positive, asymptotically saturating relationships between ecosystem-wide phytoplankton diversity and functions of productivity, nutrient uptake, remineralization, and diversity metrics used to identify mechanisms shaping these relationships. Increase in productivity with increasing diversity improves modeled ecosystem stability and model robustness and leads to productivity rates that exceed expected yields primarily through niche complementarity and facilitative interactions between coexisting phytoplankton types; the composition of traits in assemblages determines the magnitude of complementarity and selection effects. While findings based on these aggregate measures of diversity effects parallel those from the majority of experimental outcomes of terrestrial and benthic biodiversity-ecosystem function studies, we combine analyses of community diversity effects and investigations of the underlying interactions among phytoplankton types to demonstrate how an increase in recycled production of non-diatoms through an increase in new production of diatoms drives this diversity-cosystem function response. We demonstrate the important role that facilitation plays in the modeled marine plankton and how this facilitative interaction could amplify future climate-driven changes in ocean ecosystem productivity.

  11. Primary production and sinking export during fall in the Hudson Bay system, Canada

    NASA Astrophysics Data System (ADS)

    Lapoussière, Amandine; Michel, Christine; Gosselin, Michel; Poulin, Michel; Martin, Johannie; Tremblay, Jean-Éric

    2013-01-01

    Primary production and organic material sinking export were investigated in the Hudson Bay system (i.e., Hudson Bay, Hudson Strait and Foxe Basin) under ice-free conditions during early fall 2005, using the 14C-uptake method and short-term free-drifting particle interceptor traps deployed below the euphotic zone at 50 m. Principal component analysis revealed spatial patterns of primary production and chlorophyll a (chl a) biomass in the euphotic zone that were shaped by hydrographic conditions and nutrient concentrations linked to freshwater/seawater influence. Primary production rates varied widely, from 70 to 435 mg C m-2 d-1, while the range of particulate organic carbon (POC) sinking fluxes was narrow, from 50 to 77 mg C m-2 d-1. Consequently, high ratios of POC sinking export to primary production (i.e., export ratios; range of 0.38-0.69) were observed at stations where primary production was low and dominated by small cells, and where heterotrophic protist dominated in biomass. These results show that at short temporal scales neither protist community structure nor biomass or production rates could be used to predict the magnitude of POC sinking export from the euphotic zone.

  12. Simplified, rapid, and inexpensive estimation of water primary productivity based on chlorophyll fluorescence parameter Fo.

    PubMed

    Chen, Hui; Zhou, Wei; Chen, Weixian; Xie, Wei; Jiang, Liping; Liang, Qinlang; Huang, Mingjun; Wu, Zongwen; Wang, Qiang

    2017-04-01

    Primary productivity in water environment relies on the photosynthetic production of microalgae. Chlorophyll fluorescence is widely used to detect the growth status and photosynthetic efficiency of microalgae. In this study, a method was established to determine the Chl a content, cell density of microalgae, and water primary productivity by measuring chlorophyll fluorescence parameter Fo. A significant linear relationship between chlorophyll fluorescence parameter Fo and Chl a content of microalgae, as well as between Fo and cell density, was observed under pure-culture conditions. Furthermore, water samples collected from natural aquaculture ponds were used to validate the correlation between Fo and water primary productivity, which is closely related to Chl a content in water. Thus, for a given pure culture of microalgae or phytoplankton (mainly microalgae) in aquaculture ponds or other natural ponds for which the relationship between the Fo value and Chl a content or cell density could be established, Chl a content or cell density could be determined by measuring the Fo value, thereby making it possible to calculate the water primary productivity. It is believed that this method can provide a convenient way of efficiently estimating the primary productivity in natural aquaculture ponds and bringing economic value in limnetic ecology assessment, as well as in algal bloom monitoring.

  13. A reassessment of primary production and environmental change in the Bering Sea

    NASA Astrophysics Data System (ADS)

    Brown, Zachary W.; van Dijken, Gert L.; Arrigo, Kevin R.

    2011-08-01

    Regarded as one of the world's most productive marine environments, the Bering Sea is widely thought to be rapidly warming and losing sea ice. Such changes would be expected to have dramatic impacts on primary producers, with cascading effects on upper trophic levels, including this region's vast commercial fisheries resources. Here, we use satellite-derived sea ice concentration, sea surface temperature, and ocean color data as input to a primary productivity algorithm to take stock of environmental change and primary production in the Bering Sea. Results show that, rather than declining, mean annual sea ice extent in the Bering Sea has exhibited no significant change over the satellite sea ice record (1979-2009). Furthermore, significant warming during the satellite sea surface temperature record (1982-2009) is mainly limited to the summer months, when all regions of the Bering Sea warmed. This warming suggests increasing stratification during the phytoplankton growth season. Despite certain hot spots of primary production and a strong pulse in the spring, the rate of annual area-normalized primary production in the Bering Sea (124 g C m-2 yr-1) is below the global mean (140 g C m-2 yr-1). Between 1998 and 2007, basin-wide annual primary production ranged from 233 to 331 Tg C yr-1 under the influence of highly variable sea ice and temperature conditions. By comparing warm, low-ice years (2001-2005) with cold, high-ice years (1998-2000 and 2006-2007), we speculate that Bering Sea primary productivity is likely to rise under conditions of future warming and sea ice loss.

  14. Production and carbon allocation in monocultures and mixed-species plantations of Eucalyptus grandis and Acacia mangium in Brazil.

    PubMed

    Nouvellon, Yann; Laclau, Jean-Paul; Epron, Daniel; Le Maire, Guerric; Bonnefond, Jean-Marc; Gonçalves, José Leonardo M; Bouillet, Jean-Pierre

    2012-06-01

    Introducing nitrogen-fixing tree species in fast-growing eucalypt plantations has the potential to improve soil nitrogen availability compared with eucalypt monocultures. Whether or not the changes in soil nutrient status and stand structure will lead to mixtures that out-yield monocultures depends on the balance between positive interactions and the negative effects of interspecific competition, and on their effect on carbon (C) uptake and partitioning. We used a C budget approach to quantify growth, C uptake and C partitioning in monocultures of Eucalyptus grandis (W. Hill ex Maiden) and Acacia mangium (Willd.) (treatments E100 and A100, respectively), and in a mixture at the same stocking density with the two species at a proportion of 1 : 1 (treatment MS). Allometric relationships established over the whole rotation, and measurements of soil CO(2) efflux and aboveground litterfall for ages 4-6 years after planting were used to estimate aboveground net primary production (ANPP), total belowground carbon flux (TBCF) and gross primary production (GPP). We tested the hypotheses that (i) species differences for wood production between E. grandis and A. mangium monocultures were partly explained by different C partitioning strategies, and (ii) the observed lower wood production in the mixture compared with eucalypt monoculture was mostly explained by a lower partitioning aboveground. At the end of the rotation, total aboveground biomass was lowest in A100 (10.5 kg DM m(-2)), intermediate in MS (12.2 kg DM m(-2)) and highest in E100 (13.9 kg DM m(-2)). The results did not support our first hypothesis of contrasting C partitioning strategies between E. grandis and A. mangium monocultures: the 21% lower growth (ΔB(w)) in A100 compared with E100 was almost entirely explained by a 23% lower GPP, with little or no species difference in ratios such as TBCF/GPP, ANPP/TBCF, ΔB(w)/ANPP and ΔB(w)/GPP. In contrast, the 28% lower ΔB(w) in MS than in E100 was explained both by

  15. Primary production dynamics in a pristine groundwater influenced coastal lagoon of the Yucatan Peninsula

    NASA Astrophysics Data System (ADS)

    Medina-Gómez, Israel; Herrera-Silveira, Jorge A.

    2006-06-01

    Dzilam lagoon is a shallow (0.6 m mean depth) ecosystem with 9.4 km 2 surface area, located in the north coast of the Yucatan Peninsula, and connected to the Gulf of Mexico through a permanent inlet. Freshwater input is possible through numerous sinkholes distributed throughout the lagoon, which also represent a continuous source of nitrate and silicate. The low anthropogenic influence has maintained a pristine condition in Dzilam lagoon, manifested in a spatial heterogeneity of water quality and primary production strongly related to the environmental fluctuations. To determine the annual variability of primary production and identify the factors controlling it, 12 monthly samplings were undertaken at six stations, from September 1998 to August 1999. Thus, physical-chemical parameters, inorganic nutrients concentrations, chlorophyll- a, phytoplankton production and seagrass biomass were measured. The water residence time in Dzilam lagoon is higher during dry season due to the significant evaporation rate, and shorter in rainy season because of increase in precipitation and volume of groundwater discharge. The multivariate analysis results suggest that the salinity gradient, changes in aquatic vegetation biomass, and the remineralized nutrients in sediments constitute key processes depicting the water quality and net primary production in Dzilam lagoon. Furthermore, the biogeochemical benthic processes, combined with a longer stay of phytoplankton cells within the lagoon, enhanced primary production in the water column during dry season, as opposite as rainy period, when the inferior water residence time yielded lower production values. The seagrasses ( Halodule wrightii and Ruppia maritima) showed the highest biomass (110.5 g dw/m 2/d) in dry season, while the lowest recordings were observed during cold fronts, with a salient belowground contribution (rhizomes and roots). Seagrasses and phytoplankton participation to the total primary production in Dzilam lagoon

  16. The magic spot: identification of the binding site for ppGpp on E. coli RNA polymerase

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Despite more than 40 years of study of the global regulatory nucleotide ppGpp ("magic spot") in Escherichia coli, its target site on RNA polymerase (RNAP), and therefore its mechanism of action, is unknown. We report here a binding site for ppGpp on E. coli RNAP, identified by crosslinking, protease...

  17. MS_RHII-RSD, a Dual-Function RNase HII-(p)ppGpp Synthetase from Mycobacterium smegmatis

    PubMed Central

    Murdeshwar, Maya S.

    2012-01-01

    In the noninfectious soil saprophyte Mycobacterium smegmatis, intracellular levels of the stress alarmones guanosine tetraphosphate and guanosine pentaphosphate, together termed (p)ppGpp, are regulated by the enzyme RelMsm. This enzyme consists of a single, bifunctional polypeptide chain that is capable of both synthesizing and hydrolyzing (p)ppGpp. The relMsm knockout strain of M. smegmatis (ΔrelMsm) is expected to show a (p)ppGpp null [(p)ppGpp0] phenotype. Contrary to this expectation, the strain is capable of synthesizing (p)ppGpp in vivo. In this study, we identify and functionally characterize the open reading frame (ORF), MSMEG_5849, that encodes a second functional (p)ppGpp synthetase in M. smegmatis. In addition to (p)ppGpp synthesis, the 567-amino-acid-long protein encoded by this gene is capable of hydrolyzing RNA·DNA hybrids and bears similarity to the conventional RNase HII enzymes. We have classified this protein as actRelMsm in accordance with the recent nomenclature proposed and have named it MS_RHII-RSD, indicating the two enzymatic activities present [RHII, RNase HII domain, originally identified as domain of unknown function 429 (DUF429), and RSD, RelA_SpoT nucleotidyl transferase domain, the SYNTH domain responsible for (p)ppGpp synthesis activity]. MS_RHII-RSD is expressed and is constitutively active in vivo and behaves like a monofunctional (p)ppGpp synthetase in vitro. The occurrence of the RNase HII and (p)ppGpp synthetase domains together on the same polypeptide chain is suggestive of an in vivo role for this novel protein as a link connecting the essential life processes of DNA replication, repair, and transcription to the highly conserved stress survival pathway, the stringent response. PMID:22636779

  18. Diversity in guanosine 3',5'-bisdiphosphate (ppGpp) sensitivity among guanylate kinases of bacteria and plants.

    PubMed

    Nomura, Yuhta; Izumi, Atsushi; Fukunaga, Yoshinori; Kusumi, Kensuke; Iba, Koh; Watanabe, Seiya; Nakahira, Yoichi; Weber, Andreas P M; Nozawa, Akira; Tozawa, Yuzuru

    2014-05-30

    The guanosine 3',5'-bisdiphosphate (ppGpp) signaling system is shared by bacteria and plant chloroplasts, but its role in plants has remained unclear. Here we show that guanylate kinase (GK), a key enzyme in guanine nucleotide biosynthesis that catalyzes the conversion of GMP to GDP, is a target of regulation by ppGpp in chloroplasts of rice, pea, and Arabidopsis. Plants have two distinct types of GK that are localized to organelles (GKpm) or to the cytosol (GKc), with both enzymes being essential for growth and development. We found that the activity of rice GKpm in vitro was inhibited by ppGpp with a Ki of 2.8 μM relative to the substrate GMP, whereas the Km of this enzyme for GMP was 73 μM. The IC50 of ppGpp for GKpm was ∼10 μM. In contrast, the activity of rice GKc was insensitive to ppGpp, as was that of GK from bakers' yeast, which is also a cytosolic enzyme. These observations suggest that ppGpp plays a pivotal role in the regulation of GTP biosynthesis in chloroplasts through specific inhibition of GKpm activity, with the regulation of GTP biosynthesis in chloroplasts thus being independent of that in the cytosol. We also found that GKs of Escherichia coli and Synechococcus elongatus PCC 7942 are insensitive to ppGpp, in contrast to the ppGpp sensitivity of the Bacillus subtilis enzyme. Our biochemical characterization of GK enzymes has thus revealed a novel target of ppGpp in chloroplasts and has uncovered diversity among bacterial GKs with regard to regulation by ppGpp.

  19. Definition of primary mode of action of a combination product. Final rule.

    PubMed

    2005-08-25

    The Food and Drug Administration (FDA) is amending its combination product regulations to define "mode of action'' (MOA) and "primary mode of action" (PMOA). Along with these definitions, the final rule sets forth an algorithm the agency will use to assign combination products to an agency component for regulatory oversight when the agency cannot determine with reasonable certainty which mode of action provides the most important therapeutic action of the combination product. Finally, the final rule will require a sponsor to base its recommendation of the agency component with primary jurisdiction for regulatory oversight of its combination product by using the PMOA definition and, if appropriate, the assignment algorithm. The final rule is intended to promote the public health by codifying the agency's criteria for the assignment of combination products in transparent, consistent, and predictable terms.

  20. Responses of primary production, leaf litter decomposition and associated communities to stream eutrophication.

    PubMed

    Dunck, Bárbara; Lima-Fernandes, Eva; Cássio, Fernanda; Cunha, Ana; Rodrigues, Liliana; Pascoal, Cláudia

    2015-07-01

    We assessed the eutrophication effects on leaf litter decomposition and primary production, and on periphytic algae, fungi and invertebrates. According to the subsidy-stress model, we expected that when algae and decomposers were nutrient limited, their activity and diversity would increase at moderate levels of nutrient enrichment, but decrease at high levels of nutrients, because eutrophication would lead to the presence of other stressors and overwhelm the subsidy effect. Chestnut leaves (Castanea sativa Mill) were enclosed in mesh bags and immersed in five streams of the Ave River basin (northwest Portugal) to assess leaf decomposition and colonization by invertebrates and fungi. In parallel, polyethylene slides were attached to the mesh bags to allow colonization by algae and to assess primary production. Communities of periphytic algae and decomposers discriminated the streams according to the trophic state. Primary production decomposition and biodiversity were lower in streams at both ends of the trophic gradient.

  1. GPP Webinar: The Solar Roadmap—Navigating the Evolving Solar Energy Market

    EPA Pesticide Factsheets

    GPP and State & Local Climate and Energy Branch webinar on the Solar Roadmap and the evolving solar energy market. This webinar discussed local and state government’s success stories and opportunities for progress in renewable energy goals using the Solar

  2. Good Publication Practice for Communicating Company-Sponsored Medical Research: GPP3.

    PubMed

    Battisti, Wendy P; Wager, Elizabeth; Baltzer, Lise; Bridges, Dan; Cairns, Angela; Carswell, Christopher I; Citrome, Leslie; Gurr, James A; Mooney, LaVerne A; Moore, B Jane; Peña, Teresa; Sanes-Miller, Carol H; Veitch, Keith; Woolley, Karen L; Yarker, Yvonne E

    2015-09-15

    This updated Good Publication Practice (GPP) guideline, known as GPP3, builds on earlier versions and provides recommendations for individuals and organizations that contribute to the publication of research results sponsored or supported by pharmaceutical, medical device, diagnostics, and biotechnology companies. The recommendations are designed to help individuals and organizations maintain ethical and transparent publication practices and comply with legal and regulatory requirements. These recommendations cover publications in peer-reviewed journals and presentations (oral or poster) at scientific congresses. The International Society for Medical Publication Professionals invited more than 3000 professionals worldwide to apply for a position on the steering committee, or as a reviewer, for this guideline. The GPP2 authors reviewed all applications (n = 241) and assembled an 18-member steering committee that represented 7 countries and a diversity of publication professions and institutions. From the 174 selected reviewers, 94 sent comments on the second draft, which steering committee members incorporated after discussion and consensus. The resulting guideline includes new sections (Principles of Good Publication Practice for Company-Sponsored Medical Research, Data Sharing, Studies That Should Be Published, and Plagiarism), expands guidance on the International Committee of Medical Journal Editors' authorship criteria and common authorship issues, improves clarity on appropriate author payment and reimbursement, and expands information on the role of medical writers. By following good publication practices (including GPP3), individuals and organizations will show integrity; accountability; and responsibility for accurate, complete, and transparent reporting in their publications and presentations.

  3. Consumers regulate nutrient limitation regimes and primary production in seagrass ecosystems.

    PubMed

    Allgeier, Jacob E; Yeager, Lauren A; Layman, Craig A

    2013-02-01

    Consumer-mediated nutrient supply is increasingly recognized as an important functional process in many ecosystems. Yet, experimentation at relevant spatial and temporal scales is needed to fully integrate this bottom-up pathway into ecosystem models. Artificial reefs provide a unique approach to explore the importance of consumer nutrient supply for ecosystem function in coastal marine environments. We used bioenergetics models to estimate community-level nutrient supply by fishes, and relevant measures of primary production, to test the hypothesis that consumers, via excretion of nutrients, can enhance primary production and alter nutrient limitation regimes for two dominant primary producer groups (seagrass and benthic microalgae) around artificial reefs. Both producer groups demonstrated marked increases in production, as well as shifts in nutrient limitation regimes, with increased fish-derived nutrient supply. Individuals from the two dominant functional feeding groups (herbivores and mesopredators) supplied nutrients at divergent rates and ratios from one another, underscoring the importance of community structure for nutrient supply to primary producers. Our findings demonstrate that consumers, through an underappreciated bottom-up mechanism in marine environments, can alter nutrient limitation regimes and primary production, thereby fundamentally affecting the way these ecosystems function.

  4. Evaluation of bio-optical algorithms to remotely sense marine primary production from space

    NASA Technical Reports Server (NTRS)

    Berthelot, Beatrice; Deschamps, Pierre-Yves

    1994-01-01

    In situ bio-optical measurements from several oceanographic campaigns were analyzed to derive a direct relationship between water column primary production P (sub t) ocean color as expressed by the ratio of reflectances R (sub 1) at 440 nm and R (sub 3) at 550 nm and photosynthetically available radiation (PAR). The study is restricted to the Morel case I waters for which the following algorithm is proposed: log (P(sub f)) = -4.286 - 1.390 log (R(sub 1)/R(sub3)) + 0.621 log (PAR), with P(sub t) in g C m(exp -2)/d and PAR in J m(exp -2)/d. Using this algorithm the rms accuracy of primary production estimate is 0.17 on a logarithmic scale, i.e., a factor of 1.5. Using spectral reflectance measurements in the entire visible spectral range, the central wavelength, spectral bandwidth, and radiometric noise level requirements are investigated for the channels to be used by an ocean color space mission dedicated to estimating global marine primary production and the associated carbon fluxes. Nearly all the useful information is provided by two channels centered at 440 nm and 550 nm, but the accuracy of primary production estimate appears weakly sensitive to spectral bandwidth, which, consequently, may be enlarged by several tens of nanometers. The sensitivity to radiometric noise, on the contrary, is strong, and a noise equivalent reflectance of 0.005 degraded the accuracy on the primary production estimate by a factor 2 (0.14-0.25 on a logarithmic scale). The results should be applicable to evaluating the primary production of oligotrophic and mesotrophic waters, which constitute most of the open ocean.

  5. Primary productivity and nitrogen assimilation with identifying the contribution of urea in Funka Bay, Japan

    NASA Astrophysics Data System (ADS)

    Kudo, Isao; Hisatoku, Takatsugu; Yoshimura, Takeshi; Maita, Yoshiaki

    2015-06-01

    Primary production is supported by utilization of several forms of nitrogen (N), such as nitrate, ammonium, and urea. Nevertheless, only few studies have measured the concentration and uptake of urea despite its importance as a nitrogenous nutrient for phytoplankton. We measured primary productivity monthly at four depths within the euphotic zone using a clean technique and the 13C method by a 24 h in situ mooring incubation over a year in Funka Bay, a subarctic coastal area in Japan, to make better updated estimates (re-evaluation) of annual primary production. Nitrogenous (N) nutrient assimilation rates (nitrate, ammonium and urea) were also measured to elucidate the relative contributions of these nutrients to autotrophic production and to distinguish between new and regenerated production. The estimated annual primary production was 164 g C m-2, which was 40-60% higher than the previously reported values in the bay. Use of a clean technique and more frequent measurement during the spring bloom may have contributed to the higher rates. The production during the spring bloom was 56.5 g C m-2, accounting for 35% of the annual production. The maximum daily productivity occurred in the bloom at 1.4 g C m-2 d-1, which is one of the highest values among the world embayments. The annual primary production in the bay was classified as mesotrophic state based on the classification by Cloern et al. (2014). The assimilation rate of nitrate was maximal at 54 nmol N L-1 h-1 during the bloom. During the post-bloom periods with nitrate depleted conditions, assimilation rates of ammonium and urea increased and accounted for up to 85% of the total N assimilation. The assimilation rate of urea was almost comparable to that of ammonium throughout the year. Taking urea into account, the f-ratio ranged from 0.15 under the nitrate-depleted conditions to 0.8 under the spring bloom conditions. These ratios were overestimated by 50% and 10%, respectively, if urea uptake was eliminated

  6. Study on photosynthetic parameters and primary production of marine phytoplankton in Minnan-Taiwan Shoal

    NASA Astrophysics Data System (ADS)

    Wang, Xian; Li, Wen-Quan

    1994-03-01

    Carbon assimilation rates were determined in situ in the Minnan-Taiwan Shoal with the C-14 tracer method. Seasonal variations of photosynthetic parameters of marine phytoplankton were measured together with determination of Chl a and carbon content. Experimental results indicated that the average carbon-specific carbon accumulation rate is 0.85 d-1, mean primary productivity is 0.55 g C (m2d)-1. Temperature effect on the growth of the algae can be described by the model of Goldman and Carpenter. Supplementation of nutrients brought up by the upwelling in summer caused the observably high primary productivities in autumn.

  7. Baroclinic Features In The Irish Sea: Modelling Their Impact On Primary Production

    NASA Astrophysics Data System (ADS)

    Holt, J. T.; Proctor, R.

    Seasonal cycles in the Irish Sea have been simulated with a 3-dimensional hydrody- namic model capable of resolving the internal baroclinic radius of deformation. The main features of the hydrodynamics are reproduced, most notably the thermally strat- ifed 'gyre' region west of the Isle of Man and the associated tidal fronts. Ecosystem dynamics have been coupled to the hydrodynamics with the emphasis on primary production. Additional 1-dimensional coupled model experiments indicate the role that the 3-dimensional baroclinic processes play in determining primary production and show why 1-dimensional model simulations need to be treated with care in areas where baroclinic currents exist.

  8. Eutrophication and consumer control of new England salt marsh primary productivity.

    PubMed

    Bertness, Mark D; Crain, Caitlin; Holdredge, Christine; Sala, Nicholas

    2008-02-01

    Although primary productivity in salt marshes is thought to be controlled by physical forces, recent evidence suggests that human disturbances can drive a switch to consumer control in these ecologically valuable ecosystems. We tested the hypothesis that nitrogen enrichment can trigger consumer control in salt marshes in Narragansett Bay, Rhode Island, with (1) a field experiment in which we manipulated nutrient availability (with nutrient additions) and insect herbivory (with insecticide application), (2) a survey of 20 salt marshes that examined the relationship between marsh nutrient status and herbivore pressure, and (3) insect herbivore removal at high and low nutrient input sites to directly test the hypothesis that nutrient enrichment is increasing insect herbivory in these marshes. Experimental nitrogen eutrophication initially increased plant productivity but eventually led to reduced plant biomass due to insect herbivory, and our surveys revealed that marsh nitrogen supply was a good predictor of herbivore damage to plants. Insects had minimal impacts on primary productivity in pristine marshes, but suppressed primary productivity in eutrophic salt marshes by 50-75%. Thus, eutrophication is currently triggering consumer suppression of primary productivity in New England salt marshes and may ultimately jeopardize the ecological and societal services these systems provide.

  9. The effects of temporal variability of mixed layer depth on primary productivity around Bermuda

    NASA Technical Reports Server (NTRS)

    Bissett, W. Paul; Meyers, Mark B.; Walsh, John J.; Mueller-Karger, Frank E.

    1994-01-01

    Temporal variations in primary production and surface chlorophyll concentrations, as measured by ship and satellite around Bermuda, were simulated with a numerical model. In the upper 450 m of the water column, population dynamics of a size-fractionated phytoplankton community were forced by daily changes of wind, light, grazing stress, and nutrient availability. The temporal variations of production and chlorophyll were driven by changes in nutrient introduction to the euphotic zone due to both high- and low-frequency changes of the mixed layer depth within 32 deg-34 deg N, 62 deg-64 deg W between 1979 and 1984. Results from the model derived from high-frequency (case 1) changes in the mixed layer depth showed variations in primary production and peak chlorophyll concentrations when compared with results from the model derived from low-frequency (case 2) mixed layer depth changes. Incorporation of size-fractionated plankton state variables in the model led to greater seasonal resolution of measured primary production and vertical chlorophyll profiles. The findings of this study highlight the possible inadequacy of estimating primary production in the sea from data of low-frequency temporal resolution and oversimplified biological simulations.

  10. Diatom Abundance in Surface Sediments: A Quantitative Proxy for Primary Productivity at the Global Level?

    NASA Astrophysics Data System (ADS)

    Abrantes, F. F. G.; Lopes, C.; Romero, O. E.; Matos, L.; Rufino, M. M.; Magalhaes, V. H.; Cermeno, P.

    2014-12-01

    Diatom abundance and assemblage composition has for long been considered one of the best proxies for primary production, in particular for low latitude coastal upwelling areas, where they constitute the dominant phytoplankton. To investigate productivity conditions at those upwelling systems at any time and at the global level would be of great use for C export estimations and climate modeling, since primary production and C export in those systems is of major importance in controlling Earth's climate. To assess the value of the diatom sediment record at the global level, total abundance of marine diatoms was determined for 730 sites distributed by the five most important coastal upwelling systems of the modern ocean, and compared to several meaningful ecological parameters. Investigations of the satellite estimated primary productivity; upwelling index; water column physical properties and nutrient content, reveal a clear relation between sediment diatom abundance and primary production - although different between areas. Furthermore, upwelled waters [Si] appear as a determinant factor of the observed global diatom distribution.

  11. Primary productivity by phytoplankton in the tidal, fresh Potomac River, Maryland, May 1980 to August 1981

    USGS Publications Warehouse

    Cohen, R.R.; Pollock, S.O.

    1983-01-01

    Primary productivity by phytoplankton was measured on samples collected from the Potomac Tidal River, Maryland. The studies were performed monthly from May 1980 to September 1981. Additional studies were done once a week in August 1980, twice a week from August 4 to 8, 1980 and twice in September 1980. Depth-integrated samples were collected at five stations and incubated in boxes that were exposed to natural sunlight. The boxes were covered with neutral density filters transmitting 100 , 65, 32, 16, and 6 percent surface light. River water was pumped continuously over the samples. The extinction of light in the water column by phytoplankton was measured when samples were collected. Experiments were performed to select a method for routine productivity analysis. No difference was found between productivity: (1) determined in situ and in boxes; (2) measured in 300 ml and (4) calculated from short term (4 hours) and long term (10-24 hours) incubations. There were higher productivity differences in samples that were rotated among different light intensities every 15 minutes (simulating mixing) than those remaining stationary. Respiration was significantly less in samples pumped through a hose from those collected using a depth-integrating sampler. Depth-integrated primary productivity was determined from the productivity data using an equation modified from one reported in the literature. Depth-integrated gross primary productivity was highest in August 1980 and 1981 and lowest in January 1980. (USGS)

  12. Synthetic growth phenotypes of E.coli lacking ppGpp and transketolase A (tktA) are due to ppGpp-mediated transcriptional regulation of tktB

    PubMed Central

    Harinarayanan, Rajendran; Murphy, Helen; Cashel, Michael

    2008-01-01

    Summary Many physiological adjustments to nutrient changes involve ppGpp. Recent attempts to deduce ppGpp regulatory effects using proteomics or gene profiling can rigorously identify proteins or transcripts, but the functional significance is often unclear. Using a random screen for synthetic lethals we found a ppGpp-dependent functional pathway that operates through transketolase-B (TktB), and which is “buffered” in wildtype strain by the presence of an isozyme, transketolase-A (TktA). Transketolase activity is required in cells to make erythrose-4-phosphate, a precursor of aromatic amino acids and vitamins. By studying tktB-dependent nutritional requirements as well as measuring activities using PtalA-tktB′-lacZ transcriptional reporter fusion we show positive transcriptional regulation of the talA-tktB operon by ppGpp. Our results show the existence of RpoS-dependent and independent modes of positive regulation by ppGpp. Both routes of activation are magnified by elevating ppGpp levels with a spoT mutation (spoT-R39A) defective in hydrolase but not synthetase activity or with the stringent suppressor mutations rpoB-A532Δ or rpoB-T563P in the absence of ppGpp. PMID:18532980

  13. Nutrient concentrations and primary productivity at the Peros Banhos and Salomon atolls in the Chagos Archipelago

    NASA Astrophysics Data System (ADS)

    Rayner, R. F.; Drew, E. A.

    1984-02-01

    Coral atolls are areas of high biological productivity even though they are usually located in regions of the tropical ocean characterized by low primary production and extremely low levels of vital dissolved nutrient materials. Recent studies have indicated the possible importance of in situ dinitrogen fixation on shallow reef flats in supplementing low oceanic nitrate levels and thus contributing to the maintenance of high reef productivity. Variations in the structure of atolls may have a direct bearing on the accumulation of fixed nitrogen and other nutrient materials, and consequently on lagoonal and reefal primary productivity. This paper investigates the effect of differing atoll configurations by comparing neighbouring, but structurally dissimilar, mid-ocean atolls. The findings are discussed in terms of ecosystem function and possible influences on the structural evolution of atolls.

  14. Benthic primary production in an upwelling-influenced coral reef, Colombian Caribbean

    PubMed Central

    Bayraktarov, Elisa; Hauffe, Torsten; Pizarro, Valeria; Wilke, Thomas; Wild, Christian

    2014-01-01

    In Tayrona National Natural Park (Colombian Caribbean), abiotic factors such as light intensity, water temperature, and nutrient availability are subjected to high temporal variability due to seasonal coastal upwelling. These factors are the major drivers controlling coral reef primary production as one of the key ecosystem services. This offers the opportunity to assess the effects of abiotic factors on reef productivity. We therefore quantified primary net (Pn) and gross production (Pg) of the dominant local primary producers (scleractinian corals, macroalgae, algal turfs, crustose coralline algae, and microphytobenthos) at a water current/wave-exposed and-sheltered site in an exemplary bay of Tayrona National Natural Park. A series of short-term incubations was conducted to quantify O2 fluxes of the different primary producers during non-upwelling and the upwelling event 2011/2012, and generalized linear models were used to analyze group-specific O2 production, their contribution to benthic O2 fluxes, and total daily benthic O2 production. At the organism level, scleractinian corals showed highest Pn and Pg rates during non-upwelling (16 and 19 mmol O2 m−2 specimen area h−1), and corals and algal turfs dominated the primary production during upwelling (12 and 19 mmol O2 m−2 specimen area h−1, respectively). At the ecosystem level, corals contributed most to total Pn and Pg during non-upwelling, while during upwelling, corals contributed most to Pn and Pg only at the exposed site and macroalgae at the sheltered site, respectively. Despite the significant spatial and temporal differences in individual productivity of the investigated groups and their different contribution to reef productivity, differences for daily ecosystem productivity were only present for Pg at exposed with higher O2 fluxes during non-upwelling compared to upwelling. Our findings therefore indicate that total benthic primary productivity of local autotrophic reef communities is

  15. Observed aerosol-induced radiative effect on plant productivity in the eastern United States

    NASA Astrophysics Data System (ADS)

    Strada, S.; Unger, N.; Yue, X.

    2015-12-01

    We apply satellite observations of aerosol optical depth (AOD) in conjunction with flux tower-derived estimates of gross primary productivity (GPP) to probe the relationship between atmospheric aerosol loading and carbon uptake rate at 10 select sites (4 deciduous broadleaf, 3 cropland, 1 evergreen needle leaf, 1 mixed forest and 1 grassland) on hourly time scales in the growing season in the eastern United States. For deciduous and mixed forests, the aerosol light scattering increases GPP with a maximum effect observed under polluted conditions (AOD >0.6), when diffuse radiation is 40-60%. During midday hours, high AOD conditions (>0.4) enhance plant productivity by ∼13% in deciduous forests. In contrast, we find that high diffuse light fraction does not increase the carbon uptake rate in croplands and grasslands; for these ecosystems, we estimate that high AOD conditions reduce GPP by ∼17% during midday hours. Our findings are consistent with previous studies that have attributed these contrasting response sensitivities to the complex and closed canopy architecture of forests versus crops and grasslands. C4 but not C3 crops may benefit from pollution-induced changes in diffuse and direct light. Further research is needed to investigate the role of local meteorology as a possible confounder in the connection between atmospheric aerosols and plant productivity.

  16. Primary production in the tropical continental shelf seas bordering northern Australia

    NASA Astrophysics Data System (ADS)

    Furnas, Miles J.; Carpenter, Edward J.

    2016-10-01

    Pelagic primary production (14C uptake) was measured 81 times between 1990 and 2013 at sites spanning the broad, shallow Northern Australian Shelf (NAS; 120-145°E) which borders the Australian continent. The mean of all areal production measurements was 1048±109 mg C m-2 d-1 (mean±95% CI). Estimates of areal primary production were correlated with integral upper-euphotic zone chlorophyll stocks (above the 50% and 20% light penetration depths) accessible to ocean color remote sensing and total water column chlorophyll standing crop, but not surface (0-2 m) chlorophyll concentrations. While the NAS is subject to a well characterized monsoonal climate regime (austral summer-NW monsoon -wet: austral winter- SE monsoon -dry), most seasonal differences in means of regional-scale chlorophyll standing crop (11-33 mg Chl m-2 for 12 of 15 season-region combinations) and areal primary production (700-1850 mg C m- day-1 for 12 of 15 season-region combinations) fell within a 3-fold range. Apart from the shallow waters of the Torres Strait and northern Great Barrier Reef, picoplankton (<2 μm size fraction) dominated chlorophyll standing crop and primary production with regional means of picoplankton contributions ranging from 45 to >80%. While the range of our post-1990 areal production estimates overlaps the range of production estimates made in NAS waters during 1960-62, the mean of post-1990 estimates is over 2-fold greater. We regard the difference to be due to improvements in production measurement techniques, particularly regarding the reduction of potential metal toxicity and incubations in more realistic light regimes.

  17. Carbonyl sulfide (OCS) as a proxy for GPP: Complications derived from studies on the impact of CO2, soil humidity and sterilization on the OCS exchange between soils and atmosphere

    NASA Astrophysics Data System (ADS)

    Bunk, Rüdiger; Behrendt, Thomas; Yi, Zhigang; Kesselmeier, Jürgen

    2016-04-01

    Carbonyl sulfide is discussed to be used as a proxy for gross primary productivity (GPP) of forest ecosystems. However, soils may interfere. Soils play an important role in budgeting global and local carbonyl sulfide (OCS) fluxes, yet the available data on the uptake and emission behavior of soils in conjunction with environmental factors is limited. The work of many authors has shown that the OCS exchange of soils depends on various factors, such as soil type, atmospheric OCS concentrations, temperature or soil water content (Kesselmeier et al., J. Geophys. Res., 104, No. D9, 11577-11584, 1999; Van Diest & Kesselmeier, Biogeosciences, 5, 475-483, 2008; Masyek et al., PNAS, 111, No 25, 9064-9069, doi: 10.1073/pnas.1319132111, 2014; Whelan and Rhew, J. Geophys. Res. Biogeosciences., 120, 54-62, doi: 10.1002/2014JG002661, 2015) and the light dependent and obviously abiotic OCS production as reported by Whelan and Rhew (2015). To get a better constraint on the impact of some environmental factors on the OCS exchange of soils we used a new laser based integrated cavity output spectroscopy instrument (LGR COS/CO Analyzer Model 907-0028, Los Gatos, Mountain View, California, USA) in conjunction with an automated soil chamber system (as described in Behrendt et al, Biogeosciences, 11, 5463-5492, doi: 10.5194/bg-11-5463-2014, 2014). The OCS exchange of various soils under the full range of possible soil humidity and various CO2 mixing ratios was examined. Additionally OCS exchange of chloroform sterilized subsamples was compared to their live counterparts to illuminate the influence of microorganisms. Results were quite heterogeneous between different soils. With few exceptions, all examined soils show dependence between OCS exchange and soil humidity, usually with strongest uptake at a certain humidity range and less uptake or even emission at higher and lower humidity. Differences in CO2 mixing ratio also clearly impacts on OCS exchange, but trends for different soils

  18. Twenty-million-year relationship between mammalian diversity and primary productivity.

    PubMed

    Fritz, Susanne A; Eronen, Jussi T; Schnitzler, Jan; Hof, Christian; Janis, Christine M; Mulch, Andreas; Böhning-Gaese, Katrin; Graham, Catherine H

    2016-09-27

    At global and regional scales, primary productivity strongly correlates with richness patterns of extant animals across space, suggesting that resource availability and climatic conditions drive patterns of diversity. However, the existence and consistency of such diversity-productivity relationships through geological history is unclear. Here we provide a comprehensive quantitative test of the diversity-productivity relationship for terrestrial large mammals through time across broad temporal and spatial scales. We combine >14,000 occurrences for 690 fossil genera through the Neogene (23-1.8 Mya) with regional estimates of primary productivity from fossil plant communities in North America and Europe. We show a significant positive diversity-productivity relationship through the 20-million-year record, providing evidence on unprecedented spatial and temporal scales that this relationship is a general pattern in the ecology and paleo-ecology of our planet. Further, we discover that genus richness today does not match the fossil relationship, suggesting that a combination of human impacts and Pleistocene climate variability has modified the 20-million-year ecological relationship by strongly reducing primary productivity and driving many mammalian species into decline or to extinction.

  19. Bacterial and primary production in the pelagic zone of the Kara Sea

    NASA Astrophysics Data System (ADS)

    Sazhin, A. F.; Romanova, N. D.; Mosharov, S. A.

    2010-10-01

    Data on the bacterial and primary production, which were obtained simultaneously for the same water samples, are presented for three regions of the Kara Sea. The samples were collected for the transect westwards of the Yamal Peninsula, along the St. Anna Trough, and the transect in Ob Bay. Direct counts of the DAPI-stained bacterial cells were performed. The bacterial production and grazing rates were determined using a direct method when metabolic inhibitors vancomycin and penicillin were added. The primary production rates were estimated using the 14C method. The average primary production was 112.6, 58.5, and 28.7 mg C m-2 day-1, and the bacterial production was 12.8, 48.9, and 81.6 mg C m-2 day-1 along the Yamal Peninsula, the St. Anna Trough, and Ob Bay, respectively. The average bacterial carbon demand was 34.6, 134.5, and 220.4 mg C m-2 day-1 for these regions, respectively. The data obtained lead us to conclude that the phytoplankton-synthesized organic matter is generally insufficient to satisfy the bacterial carbon demand and may be completely assimilated via the heterotrophic processes in the marine ecosystems. Therefore, the bacterial activity and, consequently, the amount of the synthesized biomass (i.e., the production) both depend directly on the phytoplankton’s condition and activity. We consider these relationships to be characteristics of the Kara Sea’s biota.

  20. Twenty-million-year relationship between mammalian diversity and primary productivity

    PubMed Central

    Fritz, Susanne A.; Eronen, Jussi T.; Schnitzler, Jan; Hof, Christian; Janis, Christine M.; Mulch, Andreas; Böhning-Gaese, Katrin; Graham, Catherine H.

    2016-01-01

    At global and regional scales, primary productivity strongly correlates with richness patterns of extant animals across space, suggesting that resource availability and climatic conditions drive patterns of diversity. However, the existence and consistency of such diversity–productivity relationships through geological history is unclear. Here we provide a comprehensive quantitative test of the diversity–productivity relationship for terrestrial large mammals through time across broad temporal and spatial scales. We combine >14,000 occurrences for 690 fossil genera through the Neogene (23–1.8 Mya) with regional estimates of primary productivity from fossil plant communities in North America and Europe. We show a significant positive diversity–productivity relationship through the 20-million-year record, providing evidence on unprecedented spatial and temporal scales that this relationship is a general pattern in the ecology and paleo-ecology of our planet. Further, we discover that genus richness today does not match the fossil relationship, suggesting that a combination of human impacts and Pleistocene climate variability has modified the 20-million-year ecological relationship by strongly reducing primary productivity and driving many mammalian species into decline or to extinction. PMID:27621451

  1. Twenty-million-year relationship between mammalian diversity and primary productivity

    NASA Astrophysics Data System (ADS)

    Fritz, Susanne A.; Eronen, Jussi T.; Schnitzler, Jan; Hof, Christian; Janis, Christine M.; Mulch, Andreas; Böhning-Gaese, Katrin; Graham, Catherine H.

    2016-09-01

    At global and regional scales, primary productivity strongly correlates with richness patterns of extant animals across space, suggesting that resource availability and climatic conditions drive patterns of diversity. However, the existence and consistency of such diversity-productivity relationships through geological history is unclear. Here we provide a comprehensive quantitative test of the diversity-productivity relationship for terrestrial large mammals through time across broad temporal and spatial scales. We combine >14,000 occurrences for 690 fossil genera through the Neogene (23-1.8 Mya) with regional estimates of primary productivity from fossil plant communities in North America and Europe. We show a significant positive diversity-productivity relationship through the 20-million-year record, providing evidence on unprecedented spatial and temporal scales that this relationship is a general pattern in the ecology and paleo-ecology of our planet. Further, we discover that genus richness today does not match the fossil relationship, suggesting that a combination of human impacts and Pleistocene climate variability has modified the 20-million-year ecological relationship by strongly reducing primary productivity and driving many mammalian species into decline or to extinction.

  2. Global Net Primary Production Predicted from Vegetation Class, Precipitation, and Temperature.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Net Primary Production (NPP), the difference between CO2 fixed by photosynthesis and CO2 lost to autotrophic respiration, is one of the most important components of the carbon cycle. Our goal was to develop a simple regression model to estimate global NPP using climate and land cover data. Approxima...

  3. Increased Light-Use Efficiency Sustains Net Primary Productivity of Shaded Coffee Plants In Agroforestry System.

    PubMed

    Charbonnier, Fabien; Roupsard, Olivier; le Maire, Guerric; Guillemot, Joannès; Casanoves, Fernando; Lacointe, André; Vaast, Philippe; Allinne, Clémentine; Audebert, Louise; Cambou, Aurélie; Clément-Vidal, Anne; Defrenet, Elsa; Duursma, Remko A; Jarri, Laura; Jourdan, Christophe; Khac, Emmanuelle; Leandro, Patricia; Medlyn, Belinda E; Saint-André, Laurent; Thaler, Philippe; Van den Meersche, Karel; Barquero Aguilar, Alejandra; Lehner, Peter; Dreyer, Erwin

    2017-04-06

    In agroforestry systems, shade trees strongly affect the physiology of the undergrown crop. However, a major paradigm is that the reduction in absorbed photosynthetically active radiation is, to a certain extent, compensated by an increase in light-use efficiency, thereby reducing the difference in net primary productivity between shaded and non-shaded plants. Due to the large spatial heterogeneity in agroforestry systems and the lack of appropriate tools, the combined effects of such variables have seldom been analysed, even though they may help understand physiological processes underlying yield dynamics. In this study, we monitored net primary productivity, during two years, on scales ranging from individual coffee plants to the entire plot. Absorbed radiation was mapped with a 3D-model (MAESPA). Light-use efficiency and net assimilation rate were derived for each coffee plant individually. We found that although irradiance was reduced by 60% below crowns of shade trees, coffee light-use efficiency increased by 50%, leaving net primary productivity fairly stable across all shade levels. Variability of aboveground net primary productivity of coffee plants was caused primarily by the age of the plants and by intraspecific competition among them (drivers usually overlooked in the agroforestry literature) rather than by the presence of shade trees.

  4. Resource and Production, A Primary Unit in Cultural Geography. Pupil Text and Workbook and Teacher Manual.

    ERIC Educational Resources Information Center

    Imperatore, William

    This is an instructional unit in cultural geography for the primary grades. The major objective of the unit, which is comprised of a Pupil Text/Workbook and Teacher Manual, is to develop the geographic concepts labeled resource and production. Teaching strategies used include the Pestalozzian method of asking leading questions to draw the students…

  5. Enhanced biogas production using cow manure to stabilize co-digestion of whey and primary sludge.

    PubMed

    Shilton, A; Powell, N; Broughton, A; Pratt, C; Pratt, S; Pepper, C

    2013-01-01

    Increasing biogas production from municipal anaerobic digesters via additional loading with industrial/agricultural wastes offers a low-cost, sustainable energy generation option of significant untapped potential. In this work, bench-top reactors were used to mimic a full-scale primary sludge digester operating at an organic loading rate (OLR) of 2.4 kg COD/m3 d and a 20 d hydraulic retention time (HRT). Co-digestion of whey with primary sludge was sustained at a loading rate of 3.2 kg COD/m3 d (17 d HRT) and boosted gas production to 151% compared to primary sludge digestion alone. Addition of chemical alkalinity enabled co-digestion of whey with primary sludge to be maintained at an elevated OLR of 6.4 kg COD/m3 d (11 d HRT) with gas production increased to 208%. However, when the chemical addition was simply replaced by cow manure, stable operation was maintained at OLRs of 5.2-6.9 kg COD/m3 d (11-14 d HRT) with gas production boosted up to 268%.

  6. Critical soil water period for primary production in Chihuahuan Desert ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In desert ecosystems where water is the main limiting factor, it is expected that net primary production (NPP) is largely determined by precipitation. However, precipitation alone often explains only a small portion of the variation in NPP, and the critical precipitation period for NPP varies by pla...

  7. Legacies of precipitation fluctuations on primary production: Theory and data synthesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Variability of aboveground net primary production (ANPP) of arid to sub-humid ecosystems displays a closer association with precipitation when considered across space, based on multiyear averages for different locations, than through time, based on year to year change at single locations. Here, we p...

  8. Legacies of precipitation fluctuations on primary production: theory and data synthesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Variability of above-ground net primary production (ANPP) of arid to sub-humid ecosystems displays a closer association with precipitation when considered across space (based on multiyear averages for different locations) than through time (based on year-to-year change at single locations). Here, we...

  9. Modeling the Response of Nutrient Concentrations and Primary Productivity in Lake Michigan to Nutrient Loading Scenarios

    EPA Science Inventory

    A water quality model, LM3 Eutro, will be used to estimate the response of nutrient concentrations and primary productivity in Lake Michigan to nutrient loading scenarios. This work is part of a larger effort, the Future Midwestern landscapes study, that will estimate the produc...

  10. A comparison of global estimates of marine primary production from ocean color

    NASA Astrophysics Data System (ADS)

    Carr, Mary-Elena; Friedrichs, Marjorie A. M.; Schmeltz, Marjorie; Noguchi Aita, Maki; Antoine, David; Arrigo, Kevin R.; Asanuma, Ichio; Aumont, Olivier; Barber, Richard; Behrenfeld, Michael; Bidigare, Robert; Buitenhuis, Erik T.; Campbell, Janet; Ciotti, Aurea; Dierssen, Heidi; Dowell, Mark; Dunne, John; Esaias, Wayne; Gentili, Bernard; Gregg, Watson; Groom, Steve; Hoepffner, Nicolas; Ishizaka, Joji; Kameda, Takahiko; Le Quéré, Corinne; Lohrenz, Steven; Marra, John; Mélin, Frédéric; Moore, Keith; Morel, André; Reddy, Tasha E.; Ryan, John; Scardi, Michele; Smyth, Tim; Turpie, Kevin; Tilstone, Gavin; Waters, Kirk; Yamanaka, Yasuhiro

    2006-03-01

    The third primary production algorithm round robin (PPARR3) compares output from 24 models that estimate depth-integrated primary production from satellite measurements of ocean color, as well as seven general circulation models (GCMs) coupled with ecosystem or biogeochemical models. Here we compare the global primary production fields corresponding to eight months of 1998 and 1999 as estimated from common input fields of photosynthetically-available radiation (PAR), sea-surface temperature (SST), mixed-layer depth, and chlorophyll concentration. We also quantify the sensitivity of the ocean-color-based models to perturbations in their input variables. The pair-wise correlation between ocean-color models was used to cluster them into groups or related output, which reflect the regions and environmental conditions under which they respond differently. The groups do not follow model complexity with regards to wavelength or depth dependence, though they are related to the manner in which temperature is used to parameterize photosynthesis. Global average PP varies by a factor of two between models. The models diverged the most for the Southern Ocean, SST under 10C, and chlorophyll concentration exceeding 1 mg Chl m-3. Based on the conditions under which the model results diverge most, we conclude that current ocean-color-based models are challenged by high-nutrient low-chlorophyll conditions, and extreme temperatures or chlorophyll concentrations. The GCM-based models predict comparable primary production to those based on ocean color: they estimate higher values in the Southern Ocean, at low SST, and in the equatorial band, while they estimate lower values in eutrophic regions (probably because the area of high chlorophyll concentrations is smaller in the GCMs). Further progress in primary production modeling requires improved understanding of the effect of temperature on photosynthesis and better parameterization of the maximum photosynthetic rate.

  11. Food webs obscure the strength of plant diversity effects on primary productivity.

    PubMed

    Seabloom, Eric W; Kinkel, Linda; Borer, Elizabeth T; Hautier, Yann; Montgomery, Rebecca A; Tilman, David

    2017-04-01

    Plant diversity experiments generally find that increased diversity causes increased productivity; however, primary productivity is typically measured in the presence of a diverse food web, including pathogens, mutualists and herbivores. If food web impacts on productivity vary with plant diversity, as predicted by both theoretical and empirical studies, estimates of the effect of plant diversity on productivity may be biased. We experimentally removed arthropods, foliar fungi and soil fungi from the longest-running plant diversity experiment. We found that fungi and arthropods removed a constant, large proportion of biomass leading to a greater reduction of total biomass in high diversity plots. As a result, the effect of diversity on measured plant productivity was much higher in the absence of fungi and arthropods. Thus, diversity increases productivity more than reported in previous studies that did not control for the effects of heterotrophic consumption.

  12. Sea-ice algal primary production and nitrogen uptake rates off East Antarctica

    NASA Astrophysics Data System (ADS)

    Roukaerts, Arnout; Cavagna, Anne-Julie; Fripiat, François; Lannuzel, Delphine; Meiners, Klaus M.; Dehairs, Frank

    2016-09-01

    Antarctic pack ice comprises about 90% of the sea ice in the southern hemisphere and plays an important structuring role in Antarctic marine ecosystems, yet measurements of ice algal primary production and nitrogen uptake rates remain scarce. During the early austral spring of 2012, measurements for primary production rates and uptake of two nitrogen substrates (nitrate and ammonium) were conducted at 5 stations in the East Antarctic pack ice (63-66°S, 115-125°E). Carbon uptake was low (3.52 mg C m-2 d-1) but a trend of increased production was observed towards the end of the voyage suggesting pre-bloom conditions. Significant snow covers reaching, up to 0.8 m, induced strong light limitation. Two different regimes were observed in the ice with primarily nitrate based 'new' production (f-ratio: 0.80-0.95) at the bottom of the ice cover, due to nutrient-replete conditions at the ice-water interface, and common for pre-bloom conditions. In the sea-ice interior, POC:PN ratios (20-70) and higher POC:Chl a ratios suggested the presence of large amounts of detrital material trapped in the ice and here ammonium was the prevailing nitrogen substrate. This suggests that most primary production in the sea-ice interior was regenerated and supported by a microbial food web, recycling detritus.

  13. Prioritising Carbon Sequestration Areas in Southern Queensland using Time Series MODIS Net Primary Productivity (NPP) Imagery

    NASA Astrophysics Data System (ADS)

    Apan, A.; Suarez Cadavid, L. A.; Richardson, L.; Maraseni, T.

    2014-11-01

    The aim of this study was to develop a method that will use satellite imagery to identify areas of high forest growth and productivity, as a primary input in prioritising revegetation sites for carbon sequestration. Using the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data, this study analysed the annual net primary production (NPP) values (gC/m2) of images acquired from 2000 to 2013, covering the Condamine Catchment in southeast Queensland, Australia. With the analysis of annual rainfall data during the same period, three transitions of "normal to dry" years were identified to represent the future climate scenario considered in this study. The difference in the corresponding NPP values for each year was calculated, and subsequently averaged to the get the "Mean of Annual NPP Difference" (MAND) map. This layer identified the areas with increased net primary production despite the drought condition in those years. Combined with key thematic maps (i.e. regional ecosystems, land use, and tree canopy cover), the priority areas were mapped. The results have shown that there are over 42 regional ecosystem (RE) types in the study area that exhibited positive vegetation growth and productivity despite the decrease in annual rainfall. However, seven (7) of these RE types represents the majority (79 %) of the total high productivity area. A total of 10,736 ha were mapped as priority revegetation areas. This study demonstrated the use of MODIS-NPP imagery to map vegetation with high carbon sequestration rates necessary in prioritising revegetation sites.

  14. Primary productivity and the carrying capacity for herring in NE Pacific marine ecosystems

    NASA Astrophysics Data System (ADS)

    Perry, R. Ian; Schweigert, Jacob F.

    2008-05-01

    The carrying capacity for Pacific herring ( Clupea pallasi) and its relationship to primary productivity was examined for eight populations in the NE Pacific and eastern Bering Sea. Data on biomass (ages 3 and older) and catches of herring in British Columbia (Georgia Strait, west coast Vancouver Island, Central Coast, Queen Charlotte Islands, Prince Rupert) and Alaska (Sitka, Prince William Sound, eastern Bering Sea) during the second half of the 20th Century derived from analytical stock assessments were used to calculate annual surplus production of herring. There was considerable interannual variability in herring productivity among all populations, however, only three (Georgia Strait, Prince Rupert, Prince William Sound) showed significant differences in mean productivity on decadal time scales (productivity regimes). Carrying capacity for the most recent productivity regime for each population was estimated using the Schaefer surplus production model. Mean annual primary productivity was estimated from remotely-sensed (SeaWiFS) chlorophyll data for British Columbia and Sitka ecosystems, and from in situ chlorophyll data for Prince William Sound and the eastern Bering Sea. The carrying capacity for herring populations in the NE Pacific ranged from 28,000 to 250,000 tonnes, and to 325,000 tonnes in the eastern Bering Sea. When considered on the basis of their distributional area, the west coast of Vancouver Island and Georgia Strait populations had the highest carrying capacity per unit area (9.3-13.8 tonnes km -2) and the eastern Bering Sea had the lowest (0.7 tonnes km -2). There is a significant positive linear relationship between the productivity of herring populations at carrying capacity and primary productivity on a per unit area basis. Although similar direct relationships have been observed between phytoplankton standing stock (as chlorophyll biomass) and total catches of resident fish populations from these regions, such a direct relationship was

  15. Estimation of Mangrove Net Primary Production and Carbon Sequestration service using Light Use Efficiency model in the Sunderban Biosphere region, India

    NASA Astrophysics Data System (ADS)

    Sannigrahi, Srikanta; Sen, Somnath; Paul, Saikat

    2016-04-01

    Net Primary Production (NPP) of mangrove ecosystem and its capacity to sequester carbon from the atmosphere may be used to quantify the regulatory ecosystem services. Three major group of parameters has been set up as BioClimatic Parameters (BCP): (Photosynthetically Active Radiation (PAR), Absorbed PAR (APAR), Fraction of PAR (FPAR), Photochemical Reflectance Index (PRI), Light Use Efficiency (LUE)), BioPhysical Parameters (BPP) :(Normalize Difference Vegetation Index (NDVI), scaled NDVI, Enhanced Vegetation Index (EVI), scaled EVI, Optimised and Modified Soil Adjusted Vegetation Index (OSAVI, MSAVI), Leaf Area Index (LAI)), and Environmental Limiting Parameters (ELP) (Temperature Stress (TS), Land Surface Water Index (LSWI), Normalize Soil Water Index (NSWI), Water Stress Scalar (WS), Inversed WS (iWS) Land Surface Temperature (LST), scaled LST, Vapor Pressure Deficit (VPD), scaled VPD, and Soil Water Deficit Index (SWDI)). Several LUE models namely Carnegie Ames Stanford Approach (CASA), Eddy Covariance - LUE (EC-LUE), Global Production Efficiency Model (GloPEM), Vegetation Photosynthesis Model (VPM), MOD NPP model, Temperature and Greenness Model (TG), Greenness and Radiation model (GR) and MOD17 was adopted in this study to assess the spatiotemporal nature of carbon fluxes. Above and Below Ground Biomass (AGB & BGB) was calculated using field based estimation of OSAVI and NDVI. Microclimatic zonation has been set up to assess the impact of coastal climate on environmental limiting factors. MODerate Resolution Imaging Spectroradiometer (MODIS) based yearly Gross Primary Production (GPP) and NPP product MOD17 was also tested with LUE based results with standard model validation statistics: Root Mean Square of Error (RMSE), Mean Absolute Error (MEA), Bias, Coefficient of Variation (CV) and Coefficient of Determination (R2). The performance of CASA NPP was tested with the ground based NPP with R2 = 0.89 RMSE = 3.28 P = 0.01. Among the all adopted models, EC

  16. Trends in primary production in the California Current detected with satellite data

    NASA Astrophysics Data System (ADS)

    Kahru, Mati; Kudela, Raphael; Manzano-Sarabia, Marlenne; Mitchell, B. Greg

    2009-02-01

    Several ocean primary production algorithms using satellite data were evaluated on a large archive of net primary production (NPP) and chlorophyll-a (Chl-a) measurements collected by the California Cooperative Fisheries Investigations program in the California Current. The best algorithm matching in situ data was found by empirically adjusting the Behrenfeld-Falkowski Vertically Generalized Production Model. Satellite-derived time series of NPP were calculated for the California Current area. Significant increase in NPP and Chl-a annual peak levels, i.e., the "bloom magnitude," were found along the coasts of the California Current as well as other major eastern boundary currents for the period of modern ocean color data (1997-2007). The reasons for this increase are not clear but are associated with various environmental conditions.

  17. Production of avian influenza virus vaccine using primary cell cultures generated from host organs.

    PubMed

    Babar, Mustafeez Mujtaba; Riaz, Muhammad Suleman; Zaidi, Najam-us-Sahar Sadaf; Afzal, Farhan; Farooq, Muhammad Sabir

    2013-06-01

    The global availability of a therapeutically effective influenza virus vaccine during a pandemic remains a major challenge for the biopharmaceutical industry. Long production time, coupled with decreased supply of embryonated chicken eggs (ECE), significantly affects the conventional vaccine production. Transformed cell lines have attained regulatory approvals for vaccine production. Based on the fact that the avian influenza virus would infect the cells derived from its natural host, the viral growth characteristics were studied on chicken embryo-derived primary cell cultures. The viral propagation was determined on avian origin primary cell cultures, transformed mammalian cell lines, and in ECE. A comparison was made between these systems by utilizing various cell culture-based assays. In-vitro substrate susceptibility and viral infection characteristics were evaluated by performing hemagglutination assay (HA), 50 % tissue culture infectious dose (TCID₅₀) and monitoring of cytopathic effects (CPE) caused by the virus. The primary cell culture developed from chicken embryos showed stable growth characteristics with no contamination. HA, TCID₅₀, and CPE exhibited that these cell systems were permissive to viral infection, yielding 2-10 times higher viral titer as compared to mammalian cell lines. Though the viral output from the ECE was equivalent to the chicken cell culture, the time period for achieving it was decreased to half. Some of the prerequisites of inactivated influenza virus vaccine production include generation of higher vial titer, independence from exogenous sources, and decrease in the production time lines. Based on the tests, it can be concluded that chicken embryo primary cell culture addresses these issues and can serve as a potential alternative for influenza virus vaccine production.

  18. Invariable biomass-specific primary production of taxonomically discrete picoeukaryote groups across the Atlantic Ocean.

    PubMed

    Grob, Carolina; Hartmann, Manuela; Zubkov, Mikhail V; Scanlan, Dave J

    2011-12-01

    Oceanic photosynthetic picoeukaryotes (< 3 µm) are responsible for > 40% of total primary production at low latitudes such as the North-Eastern tropical Atlantic. In the world ocean, warmed by climate changes, the expected gradual shift towards smaller primary producers could render the role of photosynthetic picoeukaryotes even more important than they are today. Little is still known, however, about how the taxonomic composition of this highly diverse group affects primary production at the basin scale. Here, we combined flow cytometric cell sorting, NaH¹⁴CO₃ radiotracer incubations and class-specific fluorescence in situ hybridization (FISH) probes to determine cell- and biomass-specific inorganic carbon fixation rates and taxonomic composition of two major photosynthetic picoeukaryote groups on a ∼7500-km-long latitudinal transect across the Atlantic Ocean (Atlantic Meridional Transect, AMT19). We show that even though larger cells have, on average, cell-specific CO₂ uptake rates ∼5 times higher than the smaller ones, the average biomass-specific uptake is statistically similar for both groups. On the other hand, even at a high taxonomic level, i.e. class, the contributions to both groups by Prymnesiophyceae, Chrysophyceae and Pelagophyceae are significantly different (P < 0.001 in all cases). We therefore conclude that these group's carbon fixation rates are independent of the taxonomic composition of photosynthetic picoeukaryotes across the Atlantic Ocean. Because the above applies across different oceanic regions the diversity changes seem to be a secondary factor determining primary production.

  19. A multi-sensor remote sensing approach for measuring primary production from space

    NASA Technical Reports Server (NTRS)

    Gautier, Catherine

    1989-01-01

    It is proposed to develop a multi-sensor remote sensing method for computing marine primary productivity from space, based on the capability to measure the primary ocean variables which regulate photosynthesis. The three variables and the sensors which measure them are: (1) downwelling photosynthetically available irradiance, measured by the VISSR sensor on the GOES satellite, (2) sea-surface temperature from AVHRR on NOAA series satellites, and (3) chlorophyll-like pigment concentration from the Nimbus-7/CZCS sensor. These and other measured variables would be combined within empirical or analytical models to compute primary productivity. With this proposed capability of mapping primary productivity on a regional scale, we could begin realizing a more precise and accurate global assessment of its magnitude and variability. Applications would include supplementation and expansion on the horizontal scale of ship-acquired biological data, which is more accurate and which supplies the vertical components of the field, monitoring oceanic response to increased atmospheric carbon dioxide levels, correlation with observed sedimentation patterns and processes, and fisheries management.

  20. The Influence of Sea Ice on Primary Production in the Southern Ocean: A Satellite Perspective

    NASA Technical Reports Server (NTRS)

    Smith, Walker O., Jr.; Comiso, Josefino C.

    2007-01-01

    Sea ice in the Southern Ocean is a major controlling factor on phytoplankton productivity and growth, but the relationship is modified by regional differences in atmospheric and oceanographic conditions. We used the phytoplankton biomass (binned at 7-day intervals), PAR and cloud cover data from SeaWiFS, ice concentrations data from SSM/I and AMSR-E, and sea-surface temperature data from AVHRR, in combination with a vertically integrated model to estimate primary productivity throughout the Southern Ocean (south of 60"s). We also selected six areas within the Southern Ocean and analyzed the variability of the primary productivity and trends through time, as well as the relationship of sea ice to productivity. We found substantial interannual variability in productivity from 1997 - 2005 in all regions of the Southern Ocean, and this variability appeared to be driven in large part by ice dynamics. The most productive regions of Antarctic waters were the continental shelves, which showed the earliest growth, the maximum biomass, and the greatest areal specific productivity. In contrast, no large, sustained blooms occurred in waters of greater depth (> 1,000 m). We suggest that this is due to the slightly greater mixed layer depths found in waters off the continental shelf, and that the interactive effects of iron and irradiance (that is, increased iron requirements in low irradiance environments) result in the limitation of phytoplankton biomass over large regions of the Southern Ocean.

  1. Carbon production and export from Biscayne Bay, Florida. I. Temporal patterns in primary production, seston and zooplankton

    NASA Astrophysics Data System (ADS)

    Roman, Michael R.; Reeve, M. R.; Froggatt, J. L.

    1983-07-01

    Five stations along a transect from the western shore of Biscayne Bay, Florida to the Florida Current were sampled monthly for one year. The variability and amount of seston particulate organic carbon, adenosine triphosphate, chlorophyll a, primary production and zooplankton decreased along the seaward transect. The greater inshore biomass and variability of seston were the result of the allochthonous input of detritus and inorganic nutrients via terrestrial runoff. Annual primary production in this subtropical coastal lagoon ranged from 13 to 46 g C m -2 yr -1. Chlorophyll a in the bay ranged from 1 to 3 mg chlorophyll a m -2. In contrast, chlorophyll a in the surface centimetre of the sediment ranged from 50 to 300 mg chlorophyll a m -2. In this clear, shallow (2 to 3 m), oligotrophic lagoon, over 90% of total primary production is by submerged macrophytes and benthic algae. The high zooplankton biomass in the bay is most likely sustained by macrophyte detritus and the resuspension of benthic diatoms by the high winds associated with summer squalls and winter cold fronts.

  2. Studies of slow-positron production using low-energy primary electron beams.

    SciTech Connect

    Lessner, E.

    1999-04-20

    Slow-positron beams produced from negative-work-function solid-state moderators have found numerous applications in condensed matter physics. There are potential advantages in using low-energy primary electron beams for positron production, including reduced radiation damage to single-crystal moderators and reduced activation of nearby components. We present numerical calculations of positron yields and other beam parameters for various target-moderator configurations using the Argonne Wakefield Accelerator (AWA) [1] and Advanced Photon Source (APS) [2] electron linacs [3] as examples of sources for the primary electron beams. The status of experiments at these facilities is reviewed.

  3. Annual primary production: Patterns and mechanisms of change in a nutrient-rich tidal ecosystem

    USGS Publications Warehouse

    Jassby, Alan D.; Cloern, James E.; Cole, B.E.

    2002-01-01

    Although nutrient supply often underlies long-term changes in aquatic primary production, other regulatory processes can be important. The Sacramento-San Joaquin River Delta, a complex of tidal waterways forming the landward portion of the San Francisco Estuary, has ample nutrient supplies, enabling us to examine alternate regulatory mechanisms over a 21-yr period. Delta-wide primary productivity was reconstructed from historical water quality data for 1975–1995. Annual primary production averaged 70 g C m−2, but it varied by over a factor of five among years. At least four processes contributed to this variability: (1) invasion of the clam Potamocorbula amurensis led to a persistent decrease in phytoplankton biomass (chlorophyll a) after 1986; (2) a long-term decline in total suspended solids—probably at least partly because of upstream dam construction—increased water transparency and phytoplankton growth rate; (3) river inflow, reflecting climate variability, affected biomass through fluctuations in flushing and growth rates through fluctuations in total suspended solids; and (4) an additional pathway manifesting as a long-term decline in winter phytoplankton biomass has been identified, but its genesis is uncertain. Overall, the Delta lost 43% in annual primary production during the period. Given the evidence for food limitation of primary consumers, these findings provide a partial explanation for widespread Delta species declines over the past few decades. Turbid nutrient-rich systems such as the Delta may be inherently more variable than other tidal systems because certain compensatory processes are absent. Comparisons among systems, however, can be tenuous because conclusions about the magnitude and mechanisms of variability are dependent on length of data record.  

  4. Forest productivity and water stress in Amazonia: observations from GOSAT chlorophyll fluorescence.

    PubMed

    Lee, Jung-Eun; Frankenberg, Christian; van der Tol, Christiaan; Berry, Joseph A; Guanter, Luis; Boyce, C Kevin; Fisher, Joshua B; Morrow, Eric; Worden, John R; Asefi, Salvi; Badgley, Grayson; Saatchi, Sassan

    2013-06-22

    It is unclear to what extent seasonal water stress impacts on plant productivity over Amazonia. Using new Greenhouse gases Observing SATellite (GOSAT) satellite measurements of sun-induced chlorophyll fluorescence, we show that midday fluorescence varies with water availability, both of which decrease in the dry season over Amazonian regions with substantial dry season length, suggesting a parallel decrease in gross primary production (GPP). Using additional SeaWinds Scatterometer onboard QuikSCAT satellite measurements of canopy water content, we found a concomitant decrease in daily storage of canopy water content within branches and leaves during the dry season, supporting our conclusion. A large part (r(2) = 0.75) of the variance in observed monthly midday fluorescence from GOSAT is explained by water stress over moderately stressed evergreen forests over Amazonia, which is reproduced by model simulations that include a full physiological representation of photosynthesis and fluorescence. The strong relationship between GOSAT and model fluorescence (r(2) = 0.79) was obtained using a fixed leaf area index, indicating that GPP changes are more related to environmental conditions than chlorophyll contents. When the dry season extended to drought in 2010 over Amazonia, midday basin-wide GPP was reduced by 15 per cent compared with 2009.

  5. Forest productivity and water stress in Amazonia: observations from GOSAT chlorophyll fluorescence

    PubMed Central

    Lee, Jung-Eun; Frankenberg, Christian; van der Tol, Christiaan; Berry, Joseph A.; Guanter, Luis; Boyce, C. Kevin; Fisher, Joshua B.; Morrow, Eric; Worden, John R.; Asefi, Salvi; Badgley, Grayson; Saatchi, Sassan

    2013-01-01

    It is unclear to what extent seasonal water stress impacts on plant productivity over Amazonia. Using new Greenhouse gases Observing SATellite (GOSAT) satellite measurements of sun-induced chlorophyll fluorescence, we show that midday fluorescence varies with water availability, both of which decrease in the dry season over Amazonian regions with substantial dry season length, suggesting a parallel decrease in gross primary production (GPP). Using additional SeaWinds Scatterometer onboard QuikSCAT satellite measurements of canopy water content, we found a concomitant decrease in daily storage of canopy water content within branches and leaves during the dry season, supporting our conclusion. A large part (r2 = 0.75) of the variance in observed monthly midday fluorescence from GOSAT is explained by water stress over moderately stressed evergreen forests over Amazonia, which is reproduced by model simulations that include a full physiological representation of photosynthesis and fluorescence. The strong relationship between GOSAT and model fluorescence (r2 = 0.79) was obtained using a fixed leaf area index, indicating that GPP changes are more related to environmental conditions than chlorophyll contents. When the dry season extended to drought in 2010 over Amazonia, midday basin-wide GPP was reduced by 15 per cent compared with 2009. PMID:23760636

  6. Effects of bark beetle-caused tree mortality on biogeochemical and biogeophysical MODIS products

    NASA Astrophysics Data System (ADS)

    Bright, Benjamin C.; Hicke, Jeffrey A.; Meddens, Arjan J. H.

    2013-07-01

    affect forest-atmosphere exchanges of carbon, water, and energy, thereby influencing weather and climate. Bark beetle outbreaks are one such disturbance type that alters biogeochemical and biogeophysical processes in forests. Few studies have documented bark beetle impacts to leaf area index (LAI), gross primary productivity (GPP), evapotranspiration (ET), land surface temperature (LST), and surface albedo with satellite observations. Our objective was to use Landsat-derived estimates of bark beetle-caused tree mortality and Moderate Resolution Imaging Spectroradiometer (MODIS) land surface products to estimate beetle-caused changes in LAI, GPP, ET, LST, and surface albedo in northern Colorado. Following bark beetle-caused tree mortality, decreases occurred in LAI (0.02-0.80 m2m-2, 1-40%), annual GPP (50-248 gC m-2 yr-1, (5-26%), and daily summer ET (0.20-0.70 mm day-1, 13-44%), whereas increases occurred in August LST (1-3.9 K) and February albedo (0.03-0.09, 19-52%). We found greater responses of these variables in areas of greater mortality severity. The extent and severity of tree mortality in northern Colorado caused substantial changes in land surface variables (9-23%) when averaged across all forested areas of our study area. Our results demonstrate that land surface variables are sensitive to bark beetle-caused tree mortality and that bark beetle outbreaks can significantly impact biogeochemical and biogeophysical processes.

  7. Seasonality of oceanic primary production and its interannual variability from 1998 to 2007

    NASA Astrophysics Data System (ADS)

    Brown, Christopher W.; Schollaert Uz, Stephanie; Corliss, Bruce H.

    2014-08-01

    The seasonality of primary productivity plays an important role in nutrient and carbon cycling. We quantify the seasonality of satellite-derived, oceanic net primary production (NPP) and its interannual variability during the first decade of the SeaWiFS mission (1998 to 2007) using a normalized seasonality index (NSI). The NSI, which is based upon production half-time, t(1/2), generally becomes progressively more episodic with increasing latitude in open ocean waters, spanning from a relatively constant rate of primary productivity throughout the year (mean t(1/2) ~5 months) in subtropical waters to more pulsed events (mean t(1/2) ~3 months) in subpolar waters. This relatively gradual, poleward pattern in NSI differs from recent estimates of phytoplankton bloom duration, another measure of seasonality, at lower latitudes (~40°S-40°N). These differences likely reflect the temporal component of production assessed by each metric, with NSI able to more fully capture the irregular nature of production characteristic of waters in this zonal band. The interannual variability in NSI was generally low, with higher variability observed primarily in frontal and seasonal upwelling zones. The influence of the El Niño-Southern Oscillation on this variability was clearly evident, particularly in the equatorial Pacific, where primary productivity was anomalously episodic from the date line east to the coast of South America in 1998. Yearly seasonality and the magnitude of annual production were generally positively correlated at mid-latitudes and negatively correlated at tropical latitudes, particularly in a region bordering the Pacific equatorial divergence. This implies that increases of annual production in the former region are attained over the course of a year by shorter duration but higher magnitude NPP events, while in the latter areas it results from an increased frequency or duration of similar magnitude events. Statistically significant trends in the seasonality

  8. Bio-optical modeling of primary production on regional scales: the Bermuda BioOptics project

    NASA Astrophysics Data System (ADS)

    Siegel, D. A.; Westberry, T. K.; O'Brien, M. C.; Nelson, N. B.; Michaels, A. F.; Morrison, J. R.; Scott, A.; Caporelli, E. A.; Sorensen, J. C.; Maritorena, S.; Garver, S. A.; Brody, E. A.; Ubante, J.; Hammer, M. A.

    Regional to global scale estimates of primary production must rely on remotely sensed quantities. Here, we characterize in situ light-primary production relationships and assess the predictive capability of several global primary production models using a 6-yr time series collected as part of the US JGOFS Bermuda Atlantic Time Series (BATS). The consistency and longevity of this data set provide an excellent opportunity to evaluate bio-optical modeling methodologies and their predictive capabilities for estimating rates of water-column-integrated primary production, ∫PP, for use with satellite ocean-color observations. We find that existing and regionally tuned parameterizations for vertically integrated chlorophyll content and euphotic zone depth do not explain much of the observed variability at this site. Fortunately, the use of these parameterizations for light availability and harvesting capacity has little influence upon modeled rates of ∫PP. Site-specific and previously published global models of primary production both perform poorly and account for less than 40% of the variance in ∫PP. A sensitivity analysis is performed to demonstrate the importance of light-saturated rates of primary production, P sat∗, compared with other photophysiological parameters. This is because nearly one-half of ∫PP occurs under light-saturated conditions. Unfortunately, we were unable to derive a simple parameterization for P sat∗that significantly improves prediction of ∫PP. The failure of global ∫PP models to encapsulate a major portion of the observed variance is due in part to the restricted range of ∫PP observations for this site. A similar result is found comparing global chlorophyll-reflectance algorithms to the present observations. More importantly, we demonstrate that there exists a time-scale (roughly 200 d) above which the modeled distributions of ∫PP are consistent with the observational data. By low-pass filtering the observed and modeled

  9. Relationships between primary production and irradiance in coral reef algal communities

    SciTech Connect

    Not Available

    1985-07-01

    Shallow water algal turf communities are the major primary producers on coral reefs. High rates of primary production are maintained despite extremely high light intensities and exposure to ultraviolet wavelengths. The relationships between the light intensity and primary production in these assemblages are typical of algae adapted to a high light environment (low ..cap alpha.. (initial slope), high I/sub k/ (saturating light intensity), and high I/sub c/ (compensation point light intensity)). Seasonal variations in algal standing crop due to herbivory and daylength result in some characteristic photoadaptive changes in ..cap alpha.. I/sub k/, and I/sub c/ and changes in Pnet/sub max/ rates (maximum net photosynthetic rate achieved at light saturation) on both a chlorophyll ..cap alpha.. and an areal basis. Exposure to UV wavelength results in significantly higher respiration rates but no changes in ..cap alpha.., Pnet/sub max/, or I/sub k/, when compared with these parameters for the same algal communities incubated at the same light intensities without UV wavelengths. The apparent lack of photoinhibition in these algae allows calculation of the daily integrated production from the P vs. I parameters. This integrated production is highest in July (3.1 +/- 0.2 g C m/sup -2/d/sup -1/) and is reduced by 30% from this maximum in December (2.1 +/- 0.1 g C m/sup -2/d/sup -1/).

  10. Assessing the impact of urbanization on regional net primary productivity in Jiangyin County, China.

    PubMed

    Xu, C; Liu, M; An, S; Chen, J M; Yan, P

    2007-11-01

    Urbanization is one of the most important aspects of global change. The process of urbanization has a significant impact on the terrestrial ecosystem carbon cycle. The Yangtze Delta region has one of the highest rates of urbanization in China. In this study, carried out in Jiangyin County as a representative region within the Yangtze Delta, land use and land cover changes were estimated using Landsat TM and ETM+ imagery. With these satellite data and the BEPS process model (Boreal Ecosystem Productivity Simulator), the impacts of urbanization on regional net primary productivity (NPP) and annual net primary production were assessed for 1991 and 2002. Landsat-based land cover maps in 1991 and 2002 showed that urban development encroached large areas of cropland and forest. Expansion of residential areas and reduction of vegetated areas were the major forms of land transformation in Jiangyin County during this period. Mean NPP of the total area decreased from 818 to 699 gCm(-2)yr(-1) during the period of 1991 to 2002. NPP of cropland was only reduced by 2.7% while forest NPP was reduced by 9.3%. Regional annual primary production decreased from 808 GgC in 1991 to 691 GgC in 2002, a reduction of 14.5%. Land cover changes reduced regional NPP directly, and the increasing intensity and frequency of human-induced disturbance in the urbanized areas could be the main reason for the decrease in forest NPP.

  11. Microbial primary production on an Arctic glacier is insignificant in comparison with allochthonous organic carbon input.

    PubMed

    Stibal, Marek; Tranter, Martyn; Benning, Liane G; Rehák, Josef

    2008-08-01

    Cryoconite holes are unique freshwater environments on glacier surfaces, formed when solar-heated dark debris melts down into the ice. Active photoautotrophic microorganisms are abundant within the holes and fix inorganic carbon due to the availability of liquid water and solar radiation. Cryoconite holes are potentially important sources of organic carbon to the glacial ecosystem, but the relative magnitudes of autochthonous microbial primary production and wind-borne allochthonous organic matter brought are unknown. Here, we compare an estimate of annual microbial primary production in 2006 on Werenskioldbreen, a Svalbard glacier, with the organic carbon content of cryoconite debris. There is a great disparity between annual primary production (4.3 mug C g(-1) year(-1)) and the high content of organic carbon within the debris (1.7-4.5%, equivalent to 8500-22 000 mug C g(-1) debris). Long-term accumulation of autochthonous organic matter is considered unlikely due to ablation dynamics and the surface hydrology of the glacier. Rather, it is more likely that the majority of the organic matter on Werenskioldbreen is allochthonous. Hence, although glacier surfaces can be a significant source of organic carbon for glacial environments on Svalbard, they may be reservoirs rather than oases of high productivity.

  12. Efficiency of chlorophyll in gross primary productivity: A proof of concept and application in crops.

    PubMed

    Gitelson, Anatoly A; Peng, Yi; Viña, Andrés; Arkebauer, Timothy; Schepers, James S

    2016-08-20

    One of the main factors affecting vegetation productivity is absorbed light, which is largely governed by chlorophyll. In this paper, we introduce the concept of chlorophyll efficiency, representing the amount of gross primary production per unit of canopy chlorophyll content (Chl) and incident PAR. We analyzed chlorophyll efficiency in two contrasting crops (soybean and maize). Given that they have different photosynthetic pathways (C3 vs. C4), leaf structures (dicot vs. monocot) and canopy architectures (a heliotrophic leaf angle distribution vs. a spherical leaf angle distribution), they cover a large spectrum of biophysical conditions. Our results show that chlorophyll efficiency in primary productivity is highly variable and responds to various physiological and phenological conditions, and water availability. Since Chl is accessible through non-destructive, remotely sensed techniques, the use of chlorophyll efficiency for modeling and monitoring plant optimization patterns is practical at different scales (e.g., leaf, canopy) and under widely-varying environmental conditions. Through this analysis, we directly related a functional characteristic, gross primary production with a structural characteristic, canopy chlorophyll content. Understanding the efficiency of the structural characteristic is of great interest as it allows explaining functional components of the plant system.

  13. Climate change decouples oceanic primary and export productivity and organic carbon burial

    PubMed Central

    Lopes, Cristina; Kucera, Michal; Mix, Alan C.

    2015-01-01

    Understanding responses of oceanic primary productivity, carbon export, and burial to climate change is essential for model-based projection of biological feedbacks in a high-CO2 world. Here we compare estimates of productivity based on the composition of fossil diatom floras with organic carbon burial off Oregon in the Northeast Pacific across a large climatic transition at the last glacial termination. Although estimated primary productivity was highest during the Last Glacial Maximum, carbon burial was lowest, reflecting reduced preservation linked to low sedimentation rates. A diatom size index further points to a glacial decrease (and deglacial increase) in the fraction of fixed carbon that was exported, inferred to reflect expansion, and contraction, of subpolar ecosystems that today favor smaller plankton. Thus, in contrast to models that link remineralization of carbon to temperature, in the Northeast Pacific, we find dominant ecosystem and sea floor control such that intervals of warming climate had more efficient carbon export and higher carbon burial despite falling primary productivity. PMID:25453073

  14. Climate change decouples oceanic primary and export productivity and organic carbon burial

    NASA Astrophysics Data System (ADS)

    Lopes, Cristina; Kucera, Michal; Mix, Alan C.

    2015-01-01

    Understanding responses of oceanic primary productivity, carbon export, and burial to climate change is essential for model-based projection of biological feedbacks in a high-CO2 world. Here we compare estimates of productivity based on the composition of fossil diatom floras with organic carbon burial off Oregon in the Northeast Pacific across a large climatic transition at the last glacial termination. Although estimated primary productivity was highest during the Last Glacial Maximum, carbon burial was lowest, reflecting reduced preservation linked to low sedimentation rates. A diatom size index further points to a glacial decrease (and deglacial increase) in the fraction of fixed carbon that was exported, inferred to reflect expansion, and contraction, of subpolar ecosystems that today favor smaller plankton. Thus, in contrast to models that link remineralization of carbon to temperature, in the Northeast Pacific, we find dominant ecosystem and sea floor control such that intervals of warming climate had more efficient carbon export and higher carbon burial despite falling primary productivity.

  15. Climate change decouples oceanic primary and export productivity and organic carbon burial.

    PubMed

    Lopes, Cristina; Kucera, Michal; Mix, Alan C

    2015-01-13

    Understanding responses of oceanic primary productivity, carbon export, and burial to climate change is essential for model-based projection of biological feedbacks in a high-CO2 world. Here we compare estimates of productivity based on the composition of fossil diatom floras with organic carbon burial off Oregon in the Northeast Pacific across a large climatic transition at the last glacial termination. Although estimated primary productivity was highest during the Last Glacial Maximum, carbon burial was lowest, reflecting reduced preservation linked to low sedimentation rates. A diatom size index further points to a glacial decrease (and deglacial increase) in the fraction of fixed carbon that was exported, inferred to reflect expansion, and contraction, of subpolar ecosystems that today favor smaller plankton. Thus, in contrast to models that link remineralization of carbon to temperature, in the Northeast Pacific, we find dominant ecosystem and sea floor control such that intervals of warming climate had more efficient carbon export and higher carbon burial despite falling primary productivity.

  16. Importance of seep primary production to Lophelia pertusa and associated fauna in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Becker, Erin L.; Cordes, Erik E.; Macko, Stephen A.; Fisher, Charles R.

    2009-05-01

    To investigate the importance of seep primary production to the nutrition of Lophelia pertusa and associated communities and examine local trophic interactions, we analyzed stable carbon, nitrogen, and sulfur compositions in seven quantitative L. pertusa community collections. A significant seep signature was only detected in one of the 35 species tested ( Provanna sculpta, a common seep gastropod) despite the presence of seep fauna at the three sample sites. A potential predator of L. pertusa was identified ( Coralliophila sp.), and a variety of other trophic interactions among the fauna occupying the coral framework were sug