@article {JRN55373, title = {Mechanisms and drivers of alternative shrubland states}, journal = {Ecosphere}, volume = {13}, year = {2022}, month = {03 April 2022}, pages = {e3987}, abstract = {Grassland-to-shrubland state change has been widespread in arid lands globally. Long-term records at the Jornada Basin USDA-LTER site in the North American Chihuahuan Desert document the time series of transition from grassland dominance in the 1850s to shrubland dominance in the 1990s. This broadscale change ostensibly resulted from livestock overgrazing in conjunction with periodic drought and represents the classic {\textquotedblleft}grassland-to-shrubland{\textquotedblright} regime shift. However, finer-scale observations reveal a more nuanced view of this state change that includes transitions from dominance by one shrub functional type to another (e.g., based on leaf habit [evergreen vs. deciduous], N2 fixation potential, and drought tolerance). We analyzed the Jornada Basin historic vegetation data using a fine-scale grid and classified the dominant vegetation in the resulting 890 cells on each of four dates (1858, 1915, 1928, and 1998). This analysis allowed us to quantify on contrasting soil geomorphic units the rate and spatial distribution of: (1) state change from grasslands to shrublands across the Jornada Basin, (2) transitions between shrub functional groups, and (3) transitions from shrub-to-grass dominance. Results from our spatially explicit, decadal timescale perspective show that: (1) shrubland ecosystems developing on former grasslands were spatially and temporally more dynamic than has been generally presumed, (2) in some locations, shrublands initially developing on grasslands subsequently transitioned to ecosystems dominated by a different shrub functional type, with these changes in shrub composition likely involving changes in soil properties, and (3) some shrub-dominated locations have reverted to grass dominance. Accordingly, traditional, broad characterizations of {\textquotedblleft}grassland-to-shrubland{\textquotedblright} state change may be too simplistic. An accounting of these complexities and transitions from one shrub functional group to another is important for projecting state change consequences for ecosystem processes. Understanding the mechanisms, drivers, and influence of interactions between patterns and processes on transitions between shrub states defined by woody plant functional types will be germane to predicting future landscape change.}, keywords = {desertification, drylands, plant functional types, regime shifts, shrub growth form, shrubland transitions, Special Feature: Dynamic Deserts}, doi = {10.1002/ecs2.3987}, url = {files/bibliography/22-005.pdf}, author = {Steven R. Archer and Debra C. Peters and N. Dylan Burruss and Jin Yao} } @article {JRN55413, title = {Simulated distribution of Eragrostis lehmanniana (Lehmann lovegrass): Soil{\textendash}climate interactions complicate predictions}, journal = {Ecosphere}, volume = {13}, year = {2022}, month = {3/7/2022}, pages = {e3974}, abstract = {The invasive perennial grass Eragrostis lehmanniana has expanded rapidly throughout the Sonoran Desert (SD) while remaining sparse and patchily distributed in the neighboring Chihuahuan Desert (CD). As temperatures and patterns in precipitation change, identifying the drivers limiting spread in the CD is needed. Our objectives were (1) to identify the climatic and edaphic factors limiting recruitment of E. lehmanniana throughout the CD and (2) to predict the edaphic and climatic locations in the CD where this species is expected to have higher probabilities of recruitment under future climatic conditions. Recruitment was simulated at 57 locations throughout the CD with a daily, multilayer soil water model (SOILWAT) that was parameterized and tested to develop recruitment parameters for E. lehmanniana using long-term data from research stations in the SD and CD. Logistic regression was used to predict recruitment across the CD using climate and soil factors to create a map of simulated recruitment under current and alternative climate scenarios. Simulated recruitment under current climate was low for most of the CD. However, localized areas with high probabilities (>0.8) occurred along the western transition between the CD and the SD, and in the southern extent of the CD. In general, the CD climate is too cool and dry for rapid and widespread invasion. However, increases to temperature and precipitation are likely to increase recruitment success. Interactions among soil, tempera-ture, and precipitation were important to increases in recruitment of E. lehmanniana and are expected to lead to heterogeneous increases in abundance as climate continues to change. This patchy increase in abundance will result in changes in its geographic distribution that will make predictions in the future challenging.}, keywords = {Chihuahuan Desert, climate change, Geographic distribution, numerical model, recruitment, seedling establishment, Special Feature: Dynamic Deserts}, doi = {10.1002/ecs2.3974}, url = {files/bibliography/22-022.pdf}, author = {N. Dylan Burruss and Debra.C.P. Peters and Haitao Huang and Jin Yao} } @article {JRN55133, title = {Constraints on shrub cover and shrub-shrub competition in a U.S. southwest desert}, journal = {Ecosphere}, volume = {10}, year = {2019}, month = {02/2019}, pages = {1-16}, chapter = {1}, abstract = {

The cover of woody perennial plants (trees and shrubs) in arid ecosystems is at least partially constrained by water availability. However, the extent to which maximum canopy cover is limited by rainfall, and the degree to which soil water holding capacity and topography impacts maximum shrub cover are not well understood. Similar to many other deserts in the U.S. southwest, plant communities at the Jornada Basin Long-Term Ecological Research (LTER) site in the northern Chihuahuan Desert have experienced a long-term state-change from perennial grassland to shrubland dominated by woody plants. To better understand this transformation, and the environmental controls and constraints on shrub cover, we created a shrub cover map using high spatial resolution images and explored how maximum shrub cover varies with landform, water availability, and soil characteristics. Our results indicate that when clay content is below ~18\%, the upper limit of shrub cover is positively correlated with plant available water as mediated by surface soil clay influence on water retention. At surface soil clay contents \>18\%, maximum shrub cover decreases, presumably because the amount of water percolating to depths preferentially used by deep-rooted shrubs is diminished. In addition, the relationship between shrub cover and density suggests that self-thinning occurs in denser stands in most landforms of the Jornada Basin, indicating that shrub-shrub competition interacts with soil properties to constrain maximum shrub cover in the northern Chihuahuan Desert.

}, keywords = {Jornada Basin Long-Term Ecological Research (LTER), shrub-shrub competition, Southwest U.S. drylands, Special Feature: Dynamic Deserts, woody plant encroachment}, doi = {doi.org/10.1002/ecs2.2590}, url = {files/bibliography/19-014.pdf}, author = {W Ji and Niall Hanan and Dawn M. Browning and Curtis H. Monger and Debra C. Peters and Brandon T Bestelmeyer and Steven R. Archer and Ross, C. Wade and Lind, Brianna M. and Julius Anchang and Kumar, Sanath S. and Prihodko, Lara} } @article {JRN54924, title = {Synchronous species responses reveal phenological guilds: implications for management}, journal = {Ecosphere}, volume = {9}, year = {2018}, month = {09/2018}, pages = {1-23}, chapter = {1}, abstract = {

Phenological studies are critical for understanding the ability of terrestrial ecosystems to respond to changes in climate. Monitoring seasonal transitions at the species or community level across large areas is challenging and expensive. One approach for lowering costs is to identify phenological guilds{\textemdash}groups of species that exhibit similar timing of seasonal transitions{\textemdash}and limit monitoring to a smaller number of species within a guild. In this study, we evaluated 23 consecutive years of monthly observations of individual species at 15 long-term study sites at the Jornada Basin USDA-Long-Term Ecological Research site to identify patterns in the onset of three phenophases{\textemdash}leaf-out, flower, and fruit{\textemdash}of 16 widely occurring species in the arid southwestern United States and to investigate the existence of phenological guilds. We conducted univariate analyses of distributions in the timing of leaf, flower, and fruit production across time and space and multivariate cluster analysis of the time series to identify coherent groups of species{\textendash}site instances that exhibit coherence in timing of phenophase onsets (i.e., guilds). The six species of C3 shrubs demonstrated greater consistency in timing of all phenophases relative to C4 grasses. Further, we found that in all species, leaf-out occurred prior to the onset of the summer monsoon rains. Cluster analysis revealed six groups of species{\textendash}site observations demonstrating high within-year concordance in timing of leaf-out and first fruit across variable site conditions and rainfall years. The six groups for timing of first fruit differed from those for first leaf in that they exhibited greater multi-species membership and within-year variability in timing. We propose that use of phenological guilds can improve the efficiency of ecosystem monitoring, predictive models of ecosystem cues driving phenological events, and land management outcomes.

}, keywords = {Chihuahuan Desert, drylands, first fruit, first leaf, long-term ecological research, pattern recognition, phenological functional group, plant phenology, Special Feature: Dynamic Deserts, start of season}, doi = {doi.org/10.1002/ecs2.2395}, url = {files/bibliography/18-017.pdf}, author = {Dawn M. Browning and Theresa Crimmins and D. K. James and S. Spiegal and Matthew Levi and John P. Anderson and Debra C. Peters} } @article {JRN54904, title = {Soil water dynamics at 15 locations distributed across a desert landscape: insights from a 27-yr dataset}, journal = {Ecosphere}, volume = {9}, year = {2018}, month = {07/2018}, pages = {36 pp}, abstract = {

Desert ecosystems are primarily limited by water availability. Within a climatic regime, topography, soil characteristics, and vegetation are expected to determine how the combined effects of precipitation, temperature, and evaporative demand of the atmosphere shape the spatial and temporal patterns of water within the soil profile and across a landscape. To forecast how desert landscapes may respond to future climatic conditions, it is imperative to improve our understanding of these ecohydrologic processes. Here, we report on 27 yr of monthly soil volumetric water content (VWC) measurements and associated soils data from a site in the northern Chihuahuan Desert of North America. The dataset includes VWC and soil properties measured to 3 m in depth across 15 locations that encompass a range of Chihuahuan Desert vegetation types. We use this unique dataset (1) to generate insights into general temporal and depth patterns in VWC, (2) to analyze how VWC corresponds to measures of climatic conditions, and (3) to qualitatively evaluate the relative importance of soils, topographic setting, and vegetation type in mediating temporal patterns in VWC. Analyses of this unique dataset emphasize the importance of soil and topographic setting in determining depth and temporal patterns in VWC across time. Results emphasize the episodic nature of deep wetting events in our study system{\textemdash}essentially limited to three large events over the 27-yr record driven primarily by wetter than normal winters. Comparison of soil water dynamics between mesquite shrub coppice dunes and interspace soils suggests the {\textquotedblleft}island of fertility{\textquotedblright} concept does not extend to soil water. Median VWC was strongly coupled to climatic conditions over surprisingly long windows at most locations (6{\textendash}18 months), suggesting that soil water at depth is decoupled from short climatic pulses. However, VWC dynamics and VWC{\textendash}climate relationships varied among locations, depths, and seasons, with unexpected similarities in ecohydrologic dynamics observed among very different vegetation types (e.g., an eroded creosote shrubland and a playa grassland). These results further underscore the importance of ecohydrological investigations in these ecosystems, given forecasts for a warmer and more variable climate in deserts globally.

}, keywords = {Chihuahuan Desert, coppice dunes, critical zone, deep recharge, desertification, ecohydrology, grassland, landscape context, neutron moisture meter, shrubland, soil water, Special Feature: Dynamic Deserts, vadose zone}, doi = {e02335. 10.1002/ecs2.2335}, url = {files/bibliography/18-013.pdf}, author = {Danielle Duni and Matthew D. Petrie and Debra C. Peters and John P. Anderson and K. Crossland and Jeffrey E. Herrick} } @article {JRN54901, title = {Shrub encroachment, productivity pulses, and core-transient dynamics of Chihuahuan Desert rodents}, journal = {Ecosphere}, volume = {9}, year = {2018}, month = {07/2018}, pages = {Article e02330}, abstract = {

Drylands worldwide are experiencing shrub encroachment into grasslands with potential consequences for biodiversity and ecosystem services. Climate change could increase the rate of shrub encroachment, amplify precipitation variability, and thus alter bottom-up processes for animal communities. Desert rodents are important biodiversity elements of arid grasslands and shrublands that exert strong effects on soil, vegetation, and other animal species. We used long-term data from the Jornada Basin Long Term Ecological Research site in the Chihuahuan Desert of southern New Mexico to ask whether bottomup control of desert rodents changes across shrub encroachment gradients. Our design included spatial blocks with replicated ecological states representing transitions from black grama (Bouteloua eriopoda) to honey mesquite (Prosopis glandulosa). Grassland-to-shrubland transitions did not produce degraded ecosystems, on average, with reduced net primary production or decreased rodent biomass. However, more rodent biomass was supported on unencroached grasslands following droughts whose frequency and severity may increase in southwestern United States. Hence, the observed evenness in rodent biomass across ecological states should be sensitive to climate change. The best predictors of rodent biomass also differed markedly for two trophic groups. This outcome was explained by considering core-transient dynamics. Granivores were mostly core species that regularly occurred on sites and responded to lagged net primary production at local scales, whereas folivores included transient species (especially Sigmodon hispidus) that responded to lagged precipitation at broader scales via spillover dynamics. Bottom-up processes for desert rodents across shrub invasion gradients were understood by integrating lagged responses to productivity pulses with core-transient structuring of communities.

}, keywords = {bottom-up control, Chihuahuan Desert, net primary production, precipitation variability, prosopis glandulosa, rodent communities, shrub encroachment, Special Feature: Dynamic Deserts}, doi = {e02330. 10.1002/ecs2.2330}, url = {files/bibliography/18-009.pdf}, author = {Robert L. Schooley and Brandon T Bestelmeyer and A. Campanella} } @article {JRN54812, title = {Percolation observations in an arid piedmont watershed and linkages to historical conditions in the Chihuahuan Desert}, journal = {Ecosphere}, volume = {8}, year = {2017}, pages = {Article e02000}, abstract = {

A critical hydrologic process in arid and semiarid regions is the interaction between ephemeral channels and groundwater aquifers. Generally, it has been found that ephemeral channels contribute to groundwater recharge when streamflow infiltrates into the sandy bottoms of channels. This process has traditionally been studied in channels that drain large areas (tens to hundreds of square kilometers). Since the water table in arid and semiarid regions is typically far from the surface, measured streamflow losses or percolation into the deep vadose zone is equated to groundwater recharge. In this study, we use a water balance approach to estimate deep percolation in a first-order, instrumented watershed (4.7 ha) on a piedmont slope of the Jornada Experimental Range (JER) in the Chihuahuan Desert. Results indicate that runoff generated within the piedmont slope contributes significantly to deep percolation. During the short-term 6-yr study period, we estimated 385 mm of total percolation, 62 mm/yr, or a ratio of percolation to rainfall of 0.26. Based on the instrument network, we identified that percolation occurs inside channel areas when these receive overland sheetflow from hillslopes. We observed less streamflow leaving the watershed as compared to percolation during the study period, leading to an outlet streamflow to rainfall ratio of 0.02. Using long-term data sets available from the JER, we estimate that over the last 100 yr, 48 mm/yr of percolation occurs at the study site, a ratio of percolation to rainfall of 0.19. We then scale this up to determine the contribution of similarly sized watersheds on the piedmont slopes of the JER. These observations highlight the importance of arid piedmont slopes for generating groundwater recharge, in particular during above-average rainfall periods.

}, keywords = {Chihuahuan Desert, dryland ecohydrology, groundwater recharge, long term ecological research, Special Feature: Dynamic Deserts, watershed instrumentation}, doi = {10.1002/ecs2.2000 }, url = {files/bibliography/JRN00659.pdf}, author = {A. P. Schreiner-McGraw and Enrique Vivoni} }