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1. Belowground responses to altered precipitation regimes in two semi-arid grasslands

   https://doi.org/10.6073/pasta/2d233f4ba9af3a13b564a1c6364704c7  

   Holguin, Jennifer; Collins, Scott L; McLaren, Jennie R (January 2022, Environmental Data Initiative)

   Predicted climate change extremes, such as severe and prolonged drought, may profoundly impact biogeochemical processes like carbon and nitrogen cycling in water-limited ecosystems. To increase our understanding of how extreme climate events impact belowground ecosystem processes, we investigated the effects of five years of severe growing season drought and two-month delay in monsoon precipitation on belowground productivity and biogeochemical processes in two semi-arid grasslands. This experiment takes place during the fifth year of the Extreme Drought in Grassland Experiment (EDGE) at the Sevilleta National Wildlife Refuge (SNWR), a Long-Term Ecological Research in central New Mexico, USA. The two grassland sites a Chihuahuan Desert grassland dominated by Bouteloua eriopoda and Great Plains grassland dominated by B. gracilis are ~5km apart in the SWNR. The EDGE platform was established in the spring of 2012 (pre-treatment). Each site contains three treatments (ten replicates): ambient rainfall, extreme growing season drought, and delayed monsoon. The extreme drought treatment reduces growing season rainfall (April through September) each year by 66%, which equates to a 50% reduction of annual precipitation while maintaining natural precipitation patterns. There are 10 replicates per treatment within each site. All plots are 3 x 4 m in size and are paired spatially into blocks with treatments assigned randomly within a block. We measured an array of belowground and biogeochemical variables. Each variable was measured either once, twice, or three times (specific information on sampling scheme for each measured variable in methods section). Belowground net primary productivity, standing crop root biomass, total organic carbon, and total nitrogen were measured once. Extractable organic carbon, extractable total nitrogen, microbial biomass carbon, microbial biomass nitrogen and extracellular enzymes were measured twice. Available soil nitrate, available soil ammonium, and available soil phosphate were measured three times. 

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2. Small rainfall events increase belowground production in Chihuahuan Desert grassland

   https://doi.org/10.1002/ecy.70206  

   Collins, Scott L; Brown, Renée F (September 2025, Ecology)

   Abstract Dryland productivity is highly sensitive to precipitation variability, and models predict that rainfall variability will increase in the future. Numerous studies have documented the relationship between productivity and precipitation, but most focus on aboveground production (ANPP), while the effects on belowground production (BNPP) remain poorly understood. Furthermore, previous research suggests that ANPP and BNPP are uncoupled within ecosystems, but the degree to which rainfall variability affects the interplay between aboveground and belowground production is unknown. We conducted a long‐term rainfall manipulation experiment in Chihuahuan Desert grassland to investigate how the size and frequency of growing season rain events affected BNPP and its relationship to ANPP. Experimental plots received either 12 small‐frequent rain events or 3 large‐infrequent events during the monsoon season for a total of 60 mm of added rainfall per treatment per year. All plots, including three controls, received ambient rainfall throughout the year. Total BNPP ranged from a low of 94.7 ± 38.2 g m²year⁻¹under ambient conditions to a high of 183.7 ± 44.6 g m²year⁻¹under the small‐frequent rainfall treatment. Total BNPP was highest under small‐frequent rain events, and there was no difference in BNPP between 0–15 and 15–30 cm soil depths in either rainfall treatment. ANPP and BNPP were uncorrelated within rainfall treatments, but weakly positively correlated across all plots and years. Our results contribute to a growing body of research on the importance of small rain events in drylands and provide further evidence regarding the weak coupling between aboveground and belowground processes. 

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3. Extreme Drought Decreases the Stability of Above‐ but Not Below‐Ground Productivity Across Eurasian Steppes

   https://doi.org/10.1111/gcb.70303  

   Yan, Yingjie; Xu, Chong; Hautier, Yann; Wang, Hongqiang; Ke, Yuguang; Wu, Honghui; Wang, Jinsong; Cheng, Changjin; Zuo, Xiaoan; Luo, Wentao; et al (June 2025, Global Change Biology)

   ABSTRACT Ecological stability plays a crucial role in determining the sustainability of ecosystem functioning and nature's contribution to people. Although the disruptive effects of extreme drought on ecosystem structure and functions are widely recognized, their effect on the stability of above‐ and belowground productivity remains understudied. We assessed the effects of drought on ecosystem stability using a 3‐year drought experiment established in six Eurasian steppe grasslands. The treatments imposed included ambient precipitation, chronic drought (66% reduction in precipitation throughout the growing season), and intense drought (complete exclusion of precipitation for two months during the growing season). We found that drought, irrespective of how it was imposed, reduced the stability of aboveground net primary productivity (ANPP) but had little impact on belowground net primary productivity (BNPP) stability. Reduced ANPP stability under drought was primarily attributed to changes in subordinate species stability, with mean annual precipitation (MAP) and its variability, historical drought frequency, and the aridity index (AI) also influencing responses to extreme drought. In contrast, BNPP stability was not related to any community factor investigated, but it was influenced by MAP variability and AI. Our findings that above‐ and belowground productivity stability in grasslands are differentially sensitive to multi‐year extreme drought under both common (MAP and AI) as well as unique drivers (plant community changes) highlight the complexity of predicting carbon cycle dynamics as hydrological extremes become more severe. 

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4. SEV-LTER quadrat plant species cover and height all sites and experiments

   https://doi.org/10.6073/pasta/de4f0ae6a2d304db6a8033a6340501e7  

   Baur, Lauren; Collins, Scott; Muldavin, Esteban; Rudgers, Jennifer A; Pockman, William T. (January 2021, Environmental Data Initiative)

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

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5. SEV-LTER quadrat plant species biomass all sites and experiments

   https://doi.org/10.6073/pasta/90f40fe4a7ab5ed5bcab35272d6e9d84  

   Baur, Lauren; Collins, Scott; Muldavin, Esteban; Rudgers, Jennifer A; Pockman, William T. (January 2022, Environmental Data Initiative)

   {"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."]} 

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