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1. Press–pulse interactions and long‐term community dynamics in a Chihuahuan Desert grassland

   https://doi.org/10.1111/jvs.12881  

   Collins, Scott L. ; Chung, Y. Anny ; Baur, Lauren E. ; Hallmark, Alesia ; Ohlert, Timothy J. ; Rudgers, Jennifer A. ; Valencia, ed., Enrique ( May 2020 , Journal of Vegetation Science)

   Reordering of dominant species is an important mechanism of community response to global environmental change. We asked how wildfire (apulseevent) interacts with directional changes in climate (environmentalpresses) to affect plant community dynamics in a Chihuahuan Desert grassland.

   Sevilleta National Wildlife Refuge, Socorro County, New Mexico, USA.

   Vegetation cover by species was measured twice each year from 1989 to 2019 along two permanently located 400‐m long line intercept transects, one in Chihuahuan Desert grassland, and the second in the ecotone between Chihuahuan Desert and Great Plains grasslands. Trends in community structure were plotted over time, and climate sensitivity functions were used to predict how changes in the Pacific Decadal Oscillation (PDO) affected vegetation dynamics.

   Community composition was undergoing gradual change in the absence of disturbance in the ecotone and desert grassland. These changes were related to the reordering of abundances between two foundation grasses,Bouteloua eriopodaandB. gracilis, that together account for >80% of above‐ground primary production. However, reordering varied over time in response to wildfire (apulse) and changes in the PDO (apress). Community dynamics were initially related to the warm and cool phases of the PDO, but in the ecotone these relationships changed following wildfire, which reset the system.

   Species reordering is an important component of community dynamics in response to ecological presses. However, reordering is a complex, non‐linear process in response to ecological presses that may change over time and interact with pulse disturbances.

    

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2. Press–pulse interactions: effects of warming, N deposition, altered winter precipitation, and fire on desert grassland community structure and dynamics

   https://doi.org/10.1111/gcb.13493  

   Collins, Scott L. ; Ladwig, Laura M. ; Petrie, Matthew D. ; Jones, Sydney K. ; Mulhouse, John M. ; Thibault, James R. ; Pockman, William T. ( September 2016 , Global Change Biology)

   Global environmental change is altering temperature, precipitation patterns, resource availability, and disturbance regimes. Theory predicts that ecological presses will interact with pulse events to alter ecosystem structure and function. In 2006, we established a long‐term, multifactor global change experiment to determine the interactive effects of nighttime warming, increased atmospheric nitrogen (N) deposition, and increased winter precipitation on plant community structure and aboveground net primary production (ANPP) in a northern Chihuahuan Desert grassland. In 2009, a lightning‐caused wildfire burned through the experiment. Here, we report on the interactive effects of these global change drivers on pre‐ and postfire grassland community structure andANPP. Our nighttime warming treatment increased winter nighttime air temperatures by an average of 1.1 °C and summer nighttime air temperature by 1.5 °C. Soil N availability was 2.5 times higher in fertilized compared with control plots. Average soil volumetric water content (VWC) in winter was slightly but significantly higher (13.0% vs. 11.0%) in plots receiving added winter rain relative to controls, andVWCwas slightly higher in warmed (14.5%) compared with control (13.5%) plots during the growing season even though surface soil temperatures were significantly higher in warmed plots. Despite these significant treatment effects,ANPPand plant community structure were highly resistant to these global change drivers prior to the fire. Burning reduced the cover of the dominant grasses by more than 75%. Following the fire, forb species richness and biomass increased significantly, particularly in warmed, fertilized plots that received additional winter precipitation. Thus, although unburned grassland showed little initial response to multiple ecological presses, our results demonstrate how a single pulse disturbance can interact with chronic alterations in resource availability to increase ecosystem sensitivity to multiple drivers of global environmental change.

    

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3. Warming-El Nino-Nitrogen Deposition Experiment (WENNDEx): Soil Temperature, Moisture, and Carbon Dioxide Data from the Sevilleta National Wildlife Refuge, New Mexico

   https://doi.org/10.6073/pasta/9e9f235128c82a46bb073589d91c6989  

   Collins, Scott ( January 2021 , Environmental Data Initiative)

   Humans are creating significant global environmental change, including shifts in climate, increased nitrogen (N) deposition, and the facilitation of species invasions. A multi-factorial field experiment is being performed in an arid grassland within the Sevilleta National Wildlife Refuge (NWR) to simulate increased nighttime temperature, higher N deposition, and heightened El Nino frequency (which increases winter precipitation by an average of 50%). The purpose of the experiment is to better understand the potential effects of environmental drivers on grassland community composition, aboveground net primary production and soil respiration. The focus is on the response of two dominant grasses (Bouteloua gracilis and B eriopoda), in an ecotone near their range margins and thus these species may be particularly susceptible to global environmental change. It is hypothesized that warmer summer temperatures and increased evaporation will favor growth of black grama (Bouteloua eriopoda), a desert grass, but that increased winter precipitation and/or available nitrogen will favor the growth of blue grama (Bouteloua gracilis), a shortgrass prairie species. Treatment effects on limiting resources (soil moisture, nitrogen availability, species abundance, and net primary production (NPP) are all being measured to determine the interactive effects of key global change drivers on arid grassland plant community dynamics and ecosystem processes. This dataset shows values of soil moisture, soil temperature, and the CO2 flux of the amount of CO2 that has moved from soil to air. On 4 August 2009 lightning ignited a ~3300 ha wildfire that burned through the experiment and its surroundings. Because desert grassland fires are patchy, not all of the replicate plots burned in the wildfire. Therefore, seven days after the wildfire was extinguished, the Sevilleta NWR Fire Crew thoroughly burned the remaining plots allowing us to assess experimentally the effects of interactions among multiple global change presses and a pulse disturbance on post-fire grassland dynamics. 

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4. Warming-El Nino-Nitrogen Deposition Experiment (WENNDEx): Soil Nitrogen Data from the Sevilleta National Wildlife Refuge, New Mexico (2006 - 2020)

   https://doi.org/10.6073/pasta/2b7ab47e8e3bfab993e80cdae1c887f5  

   Collins, Scott ; Pockman, William ( January 2020 , Environmental Data Initiative)

   Humans are creating significant global environmental change, including shifts in climate, increased nitrogen (N) deposition, and the facilitation of species invasions. A multi-factorial field experiment is being performed in an arid grassland within the Sevilleta National Wildlife Refuge (NWR) to simulate increased nighttime temperature, higher N deposition, and heightened El Niño frequency (which increases winter precipitation by an average of 50%). The purpose of the experiment is to better understand the potential effects of environmental drivers on grassland community composition, aboveground net primary production and soil respiration. The focus is on the response of two dominant grasses (Bouteloua gracilis and B eriopoda), in an ecotone near their range margins and thus these species may be particularly susceptible to global environmental change. It is hypothesized that warmer summer temperatures and increased evaporation will favor growth of black grama (Bouteloua eriopoda), a desert grass, but that increased winter precipitation and/or available nitrogen will favor the growth of blue grama (Bouteloua gracilis), a shortgrass prairie species. Treatment effects on limiting resources (soil moisture, nitrogen availability, species abundance, and net primary production (NPP) are all being measured to determine the interactive effects of key global change drivers on arid grassland plant community dynamics and ecosystem processes. On 4 August 2009 lightning ignited a ~3300 ha wildfire that burned through the experiment and its surroundings. Because desert grassland fires are patchy, not all of the replicate plots burned in the wildfire. Therefore, seven days after the wildfire was extinguished, the Sevilleta NWR Fire Crew thoroughly burned the remaining plots allowing us to assess experimentally the effects of interactions among multiple global change presses and a pulse disturbance on post-fire grassland dynamics. This data set provides soil N availability in each plot of the warming experiment for the monsoon season (also see SEV176). 

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5. Rodent Parasite Data for the Sevilleta National Wildlife Refuge, New Mexico (1990-1998)

   https://doi.org/10.6073/pasta/b739d2c75e142f5742b7bfe74c97d5c1  

   Duszyinski, Don ( January 2016 , Environmental Data Initiative)

   The 100,000 ha Sevilleta National Wildlife Refuge (SNWR) in central New Mexico lies in a transition zone that straddles several major biomes of the Southwest, including Great Basin Shrub-Steppe, Mogollon Pinon-Juniper Woodland, Great Plains Grassland and Chihuahuan Desert. During 9 years, (1990-1998), collaborating with the University of New Mexico's Long Term Ecological Research (LTER) program, 3,235 rodents (28 species in 4 families) were collected and identified from permanent collecting sites on the 3 major habitat types (grassland, desert/creosote, woodland) on the SNWR. Hosts were necropsied for endoparasites (protozoa [coccidia], helminths) and some ectoparasites. We identified and analyzed all the parasites found in these hosts. By 1998, we had in place the means to easily identify and moniter the parasites from all mammalian hosts caught on the LTER Phase II grant.This is not just another parasite survey; the data we collected was unique for several reasons: 1) This was the first complete inventory of a natural assemblage of parasites from all mammalian (rodent) hosts in 3 different communities, each from a distinctly defined geographic locality (habitat type) over the period of a decade, and beyond; 2) This study was part of a multidisciplinary approach to address conceptual issues of climate change on ecosystem structure and function at multiple scales (individuals, communities, etc) and correlative data from these related studies will strengthen and contribute to the robustness of this data set; 3) As the only parasite study on any of the LTER projects nationwide, it provided an ideal model, and perhaps incentive for parallel longterm studies of parasite communities to be examined in a variety of other habitat types, and from a variety of different perspectives, and other LTER sites in the network.Upon completing the work, we were able to use these long-term data to try to understand the dynamics of natural host-parasite assemblages. Hypotheses were then erected to test/address at least these questions: How do the different parasite communities colonize, mature, climax and senesce over time (or do they?), Do they vary in response to abiotic (climate change) and/or biotic (dispersal, colonization) factors? What temporal and spatial scales, and among what kinds of organisms, do coevolutionary processes influence the community organization of these parasites? Studies of the dynamics of multiple, coexisting species are confined primarily to microtine rodents and have hinted that multiannual cycles tend to be synchronous (Brown and Heske 1990). Are similar patterns seen for the parasites of our desert rodents? Answers to these questions relating to community structure, as well as to questions concerning parasite biodiversity on the SNWR, can be answered paritially or completely by the information we gathered on the parasite species infecting rodents collected on the SNWR. Initial emphasis of our work was on identifying all the parasites collected, by processing 8 consecutive years of parasite data, and on training the undergraduate and graduate students involved in the art of taxonomy and nomenclature of parasitic protozoans and helminths,  to supply some of these answers. 

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