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{"Abstract":["This dataset includes estimated plant aboveground live biomass data\n measured in 1 m x 1 m quadrats at several sites and experiments\n under the Sevilleta LTER program. Quadrat locations span four\n distinct ecosystems and their ecotones: creosotebush dominated\n Chihuahuan Desert shrubland (est. winter 1999), black\n grama-dominated Chihuahuan Desert grassland (est. winter 1999), blue\n grama-dominated Plains grassland (est. winter 2002), and\n pinon-juniper woodland (est. winter 2003). Data on plant cover and\n height for each plant species are collected per individual plant or\n patch (for clonal plants) within 1 m x 1 m quadrats. These data\n inform population dynamics of foundational and rare plant species.\n Biomass is estimated using plant allometries from non-destructive\n measurements of plant cover and height, and can be used to calculate\n net primary production (NPP), a fundamental ecosystem variable that\n quantifies rates of carbon consumption and fixation. Estimates of\n plant species cover, total plant biomass, or NPP can inform\n understanding of biodiversity, species composition, and energy flow\n at the community scale of biological organization, as well as\n spatial and temporal responses of plants to a range of ecological\n processes and direct experimental manipulations. The cover and\n height of individual plants or patches are sampled twice yearly\n (spring and fall) in permanent 1m x 1m plots within each site or\n experiment. This dataset includes core site monitoring data (CORE,\n GRIDS, ISOWEB, TOWER), observations in response to wildfire (BURN),\n and experimental treatments of extreme drought and delayed monsoon\n rainfall (EDGE), physical disturbance to biological soil crusts on\n the soil surface (CRUST), interannual variability in precipitation\n (MEANVAR), intra-annual variability via additions of monsoon\n rainfall (MRME), additions of nitrogen as ammonium nitrate\n (FERTILIZER), additions of nitrogen x phosphorus x potassium\n (NutNet), and interacting effects of nighttime warming, nitrogen\n addition, and El Niño winter rainfall (WENNDEx). To build allometric\n equations that relate biomass to plant cover or volume, the dataset\n "SEV-LTER quadrat plant cover and height data all sites and\n experiments" is used with a separate dataset of selectively\n harvested plant species "SEV-LTER Plant species mass data for\n allometry." Together, these datasets produced \u201cSEV-LTER quadrat\n plant species biomass all sites and experiments\u201d using the scripts\n posted with the allometry dataset. Data from the CORE sites in this\n dataset were designated as NA-US-011 in the Global Index of\n Vegetation-Plot Databases (GIVD). Data from the TOWER sites in this\n dataset are linked to Ameriflux sites:\n ameriflux.lbl.gov/doi/AmeriFlux/US-Seg and\n ameriflux.lbl.gov/sites/siteinfo/US-Ses."]} 

{"Abstract":["The U.S. Fish and Wildlife's plan to apply a prescribed burn to a\n large portion of McKenzie Flats was deemed an opportunity to study\n the effects of fire on vegetation at the boundary between shrubland\n and grassland. This study actually was undertaken on an area that\n had prescribed fire applied to 8 of 16 (300 m x 300 m) plots 10\n years before in 1993. This previous study had also examined the\n effects of fencing to exclude the indigenous prong-horn antelope. In\n the 2003 study the prescribed fire was applied to the northeastern\n half of the 16 plots while the southwestern plots were intentionally\n protected. Sampling prior to the prescribed burn included\n quantification of cover of grass species in quadrats within all of\n the 16 plots. Measurements were made using "niner" quadrat\n frames that are 30 cm x 30 cm frames that are divided into 9\n 1-decimeter squares. Counts of grass species were made just prior to\n the June 2003 burn. Following the prescribed burn, quadrats were\n remeasured in the fall of 2003 to quantify mortality of grass\n species. These measurements were taken through the fall of 2012 and\n the fall of 2018. Measurements were not taken for 2014-2017."]} 

The U.S. Fish and Wildlife's plan to apply a prescribed burn to a large portion of McKenzie Flats was deemed an opportunity to study the effects of fire on the vegetation at the boundary between shrubland and grassland. This study actually was undertaken on an area that had prescribed fire applied to 8 of 16 (300 m x 300 m) plots 10 years before in 1993. This previous study had also examined the effects of fencing to exclude the indigenous prong-horn antelope. In the 2003 study the prescribed fire was applied to the northeastern half of the 16 plots while the southwestern plots were intentionally protected. Sampling prior to the prescribed burn included quantification of fuel load (ie. the standing biomass of all grasses and forbs in the area to be burned). These measurements were made using Daubenmire quadrat frames that are 5 cm x 20 cm and delineate a 0.1 square meter area. Four samples were taken adjacent to the six 3 m x 4 m quadrats in each of the eight plots that were to be burned. Quadrat frames were laid down over the vegetation and all vegetation rooted within the frame was clipped at ground level. This material was bagged, oven-dried and weighed. Following the prescribed burn, re-measurements were made every fall of from 2004 until 2012 when vegetation had reached its annual peak biomass. Data were not collected from 2014-2017, but were collected again in 2018. 

Disturbance from fire can affect the abundance and distribution of shrubs and grasses in arid ecosystems. In particular, fire may increase grass and forb production while hindering shrub encroachment. Therefore, prescribed fires are a common management tool for maintaining grassland habitats in the southwest. However, Bouteloua eriopoda (black grama), a dominant species in Chihuahuan Desert grassland, is highly susceptible to fire resulting in death followed by slow recovery rates. A prescribed fire on the Sevilleta National Wildlife refuge in central New Mexico in 2003 provided the opportunity to study the effects of infrequent fires on vegetation in this region. This study was conducted along a transition zone where creosote bushes (Larrea tridentata) are encroaching on a black grama grassland. Before and after the fire, above ground plant productivity and composition were monitored from 2003 to present. Following the prescribed fire, there were fewer individual grass clumps and less above ground grass cover in burned areas compared to unburned areas. This decrease in productivity was primarily from a loss of B. eriopoda. Specifically, B. eriopoda density and cover were significantly lower following the fire with a slow recovery rate in the five years following the fire. Other grasses showed no such adverse response to burning. Data were collected from 2004-2013 and 2018. Data were not collected for 2014-2017. 

Two of the most pervasive human impacts on ecosystems are alteration of global nutrient budgets and changes in the abundance and identity of consumers. Fossil fuel combustion and agricultural fertilization have doubled and quintupled, respectively, global pools of nitrogen and phosphorus relative to pre-industrial levels. In spite of the global impacts of these human activities, there have been no globally coordinated experiments to quantify the general impacts on ecological systems. This experiment seeks to determine how nutrient availability controls plant biomass, diversity, and species composition in a desert grassland. This has important implications for understanding how future atmospheric deposition of nutrients (N, S, Ca, K) might affect community and ecosystem-level responses. This study is part of a larger coordinated research network that includes more than 40 grassland sites around the world. By using a standardized experimental setup that is consistent across all study sites, we are addressing the questions of whether diversity and productivity are co-limited by multiple nutrients and if so, whether these trends are predictable on a global scale. 

{"Abstract":["The varied topography and large elevation gradients that\n characterize the arid and semi-arid Southwest create a wide range of\n climatic conditions - and associated biomes - within relatively\n short distances. This creates an ideal experimental system in which\n to study the effects of climate on ecosystems. Such studies are\n critical given that the Southwestern U.S. has already experienced\n changes in climate that have altered precipitation patterns (Mote et\n al. 2005), and stands to experience dramatic climate change in the\n coming decades (Seager et al. 2007; Ting et al. 2007). Climate\n models currently predict an imminent transition to a warmer, more\n arid climate in the Southwest (Seager et al. 2007; Ting et al.\n 2007). Thus, high elevation ecosystems, which currently experience\n relatively cool and mesic climates, will likely resemble their lower\n elevation counterparts, which experience a hotter and drier climate.\n In order to predict regional changes in carbon storage, hydrologic\n partitioning and water resources in response to these potential\n shifts, it is critical to understand how both temperature and soil\n moisture affect processes such as evaportranspiration (ET), total\n carbon uptake through gross primary production (GPP), ecosystem\n respiration (Reco), and net ecosystem exchange of carbon, water and\n energy across elevational gradients. We are using a sequence of six\n widespread biomes along an elevational gradient in New Mexico --\n ranging from hot, arid ecosystems at low elevations to cool, mesic\n ecosystems at high elevation to test specific hypotheses related to\n how climatic controls over ecosystem processes change across this\n gradient. We have an eddy covariance tower and associated\n meteorological instruments in each biome which we are using to\n directly measure the exchange of carbon, water and energy between\n the ecosystem and the atmosphere. This gradient offers us a unique\n opportunity to test the interactive effects of temperature and soil\n moisture on ecosystem processes, as temperature decreases and soil\n moisture increases markedly along the gradient and varies through\n time within sites. This dataset examines how different stages of\n burn affects above-ground biomass production (ANPP) in a mixed\n desert-grassland. Net primary production is a fundamental ecological\n variable that quantifies rates of carbon consumption and fixation.\n Estimates of NPP are important in understanding energy flow at a\n community level as well as spatial and temporal responses to a range\n of ecological processes. Above-ground net primary production is the\n change in plant biomass, represented by stems, flowers, fruit and\n foliage, over time and incorporates growth as well as loss to death\n and decomposition. To measure this change the vegetation variables\n in this dataset, including species composition and the cover and\n height of individuals, are sampled twice yearly (spring and fall) at\n permanent 1m x 1m plots. The data from these plots is used to build\n regressions correlating biomass and volume via weights of select\n harvested species obtained in SEV157, "Net Primary Productivity\n (NPP) Weight Data." This biomass data is included in SEV292,\n "Flux Tower Seasonal Biomass and Seasonal and Annual NPP\n Data.""]} 

{"Abstract":["This dataset contains pinon-juniper woodland quadrat data and is\n part of a long-term study at the Sevilleta LTER measuring net\n primary production (NPP) across four distinct ecosystems:\n creosote-dominant shrubland (Site C, est. winter 1999), black\n grama-dominant grassland (Site G, est. winter 1999), blue\n grama-dominant grassland (Site B, est. winter 2002), and\n pinon-juniper woodland (Site P, est. winter 2003). Net primary\n production is a fundamental ecological variable that quantifies\n rates of carbon consumption and fixation. Estimates of NPP are\n important in understanding energy flow at a community level as well\n as spatial and temporal responses to a range of ecological\n processes. Above-ground net primary production is the change in\n plant biomass, represented by stems, flowers, fruit and and foliage,\n over time and incorporates growth as well as loss to death and\n decomposition. To measure this change the vegetation variables in\n this dataset, including species composition and the cover and height\n of individuals, are sampled twice yearly (spring and fall) at\n permanent 1m x 1m plots within each site. A third sampling at Site C\n is performed in the winter. The data from these plots is used to\n build regressions correlating biomass and volume via weights of\n select harvested species obtained in SEV157, "Net Primary\n Productivity (NPP) Weight Data." This biomass data is included\n in SEV182, "Seasonal Biomass and Seasonal and Annual NPP for\n Core Research Sites.""]} 

{"Abstract":["Begun in spring 2013, this project is part of a long-term study at\n the Sevilleta LTER measuring net primary production (NPP) across\n three distinct ecosystems: creosote-dominant shrubland (Site C),\n black grama-dominant grassland (Site G), and blue grama-dominant\n grassland (Site B). Net primary production is a fundamental\n ecological variable that quantifies rates of carbon consumption and\n fixation. Estimates of NPP are important in understanding energy\n flow at a community level as well as spatial and temporal responses\n to a range of ecological processes. Above-ground net primary\n production is the change in plant biomass, represented by stems,\n flowers, fruit and foliage, over time and incorporates growth as\n well as loss to death and decomposition. To measure this change the\n vegetation variables in this dataset, including species composition\n and the cover and height of individuals, are sampled twice yearly\n (spring and fall) at permanent 1m x 1m plots within each site. A\n third sampling at Site C is performed in the winter. The data from\n these plots is used to build regressions correlating biomass and\n volume via weights of select harvested species obtained in SEV999,\n "Net Primary Productivity (NPP) Weight Data." This biomass\n data is included in SEV999, "Seasonal Biomass and Seasonal and\n Annual NPP for Core Grid Research Sites.""]} 

{"Abstract":["This dataset contains pinon-juniper woodland biomass data and is\n part of a long-term study at the Sevilleta LTER measuring net\n primary production (NPP) across four distinct ecosystems:\n creosote-dominant shrubland (Site C, est. winter 1999), black\n grama-dominant grassland (Site G, est. winter 1999), blue\n grama-dominant grassland (Site B, est. winter 2002), and\n pinon-juniper woodland (Site P, est. winter 2003). Net primary\n production is a fundamental ecological variable that quantifies\n rates of carbon consumption and fixation. Estimates of NPP are\n important in understanding energy flow at a community level as well\n as spatial and temporal responses to a range of ecological\n processes. Above-ground net primary production is the change in\n plant biomass, represented by stems, flowers, fruit and and foliage,\n over time and incoporates growth as well as loss to death and\n decomposition. To measure this change the vegetation variables in\n this dataset, including species composition and the cover and height\n of individuals, are sampled twice yearly (spring and fall) at\n permanent 1m x 1m plots within each site. A third sampling at Site C\n is performed in the winter. Volumetric measurements are made using\n vegetation data from permanent plots (SEV278, "Pinon-Juniper\n (Core Site) Quadrat Data for the Net Primary Production Study")\n and regressions correlating species biomass and volume constructed\n using seasonal harvest weights from SEV157, "Net Primary\n Productivity (NPP) Weight Data.""]} 

EDGE is located at six grassland sites that encompass a range of ecosystems in the Central US - from desert grasslands to short-, mixed-, and tallgrass prairie. We envision EDGE as a research platform that will not only advance our understanding of patterns and mechanisms of ecosystem sensitivity to climate change, but also will benefit the broader scientific community. Identical infrastructure for manipulating growing season precipitation will be deployed at all sites. Within the relatively large treatment plots (36 m2), we will measure with comparable methods, a broad spectrum of ecological responses particularly related to the interaction between carbon fluxes (NPP, soil respiration) and species response traits, as well as environmental parameters that are critical for the integrated experiment-modeling framework, as well as for site-based analyses. By designing EDGE as a research platform open to the broader scientific community, with subplots in all replicates (n = 180 plots) set-aside for additional studies, and by making data available to the broader ecological community EDGE will have value beyond what we envision here.