@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 {JRN55430, title = {Long-term growing season aridity and grazing seasonality effects on perennial grass biomass in a Chihuahuan Desert rangeland}, journal = {Journal of Arid Environments}, volume = {209}, year = {2022}, month = {19 November 2022}, chapter = {104902}, abstract = {Growing season aridity and livestock grazing seasonality can influence primary productivity of perennial grasses in dryland systems. For this study, we used a long-term dataset (1967{\textendash}2004) to investigate the independent and joint effects of growing season aridity and season of grazing (yearlong continuous, fall, winter/spring, or summer season grazing) on the mean annual primary productivity of the perennial grasses Bouteloua eriopoda (black grama), Aristida spp. (threeawn), and Sporobolus spp. (dropseed) in a southwestern United States Chihuahuan Desert rangeland system. Over the 37-year study period, total perennial grass biomass decreased as aridity increased, but the extent of this relationship depended upon season of grazing and specific grass taxon. Aridity-related decreases in total perennial grass biomass were most severe in the summer grazing treatment. Our findings indicate that over time, summer and fall grazing can potentially exacerbate the negative effects of increasing aridity on perennial grass biomass. As arid and semi-arid rangelands globally face increasing aridity associated with a changing climate, land managers can modulate the season of grazing, dependent on dominant taxa present, to minimize these effects. Our study and those from other arid land locations indicate continuous grazing at light to conservative intensities can better sustain key perennial grasses than strategies involving concentrated seasons of grazing. However, growing season aridity levels must also be taken into consideration.}, keywords = {Aridity, black grama, drylands, perennial grass, rotational grazing, Sporobolus}, doi = {10.1016/j.jaridenv.2022.104902}, url = {files/bibliography/22-027.pdf}, author = {Sophia N. Lasch{\`e} and Ryan W.R. Schroeder and Matthew M. McIntosh and Jacob E. Lucero and S. Spiegal and M. Funk and Reldon F. Beck and Jerry L. Holechek and Akasha M. Faist} } @article {JRN55336, title = {Constraints and opportunities for detecting land surface phenology in drylands}, journal = {Journal of Remote Sensing}, volume = {2}, year = {2021}, month = {10/27/2021}, pages = {1-15}, abstract = {Land surface phenology (LSP) enables global scale tracking of ecosystem processes, but its utility is limited in drylands due to low vegetation cover and resulting low annual amplitudes of vegetation indices (VIs). Due to the importance of drylands for biodiversity, food security, and the carbon cycle it is necessary to understand limitations in measuring dryland dynamics. Here, using simulated data and multi-temporal unmanned aerial vehicle (UAV) imagery of a desert shrubland, we explore the feasibility of detecting LSP with respect to fractional vegetation cover, plant functional types, VI uncertainty, and two different detection algorithms. Using simulated data we found that plants with distinct VI signals, such as deciduous shrubs, can require up to 60\% fractional cover to consistently detect LSP. Evergreen plants, with lower seasonal VI amplitude, require considerably higher cover and can have undetectable phenology even with 100\% vegetation cover. Our evaluation of two algorithms showed that neither performed the best in all cases. Even with adequate cover, biases in phenological metrics can still exceed 20 days, and can never be 100\% accurate due to VI uncertainty from shadows, sensor view angle, and atmospheric interference. We showed how high-resolution UAV imagery enables LSP studies in drylands, and highlighted important scale effects driven by within canopy VI variation. With high-resolution imagery the open canopies of drylands are beneficial as they allow for straightforward identification of individual plants, enabling the tracking of phenology at the individual level. Drylands thus have the potential to become an exemplary environment for future LSP research.}, keywords = {constraints, detecting, drylands, land surface phenology, opportunities}, doi = {10.34133/2021/9859103}, url = {files/bibliography/21-048.pdf}, author = {Shawn D. Taylor and Dawn M. Browning and Ruben Baca and Feng Gao} } @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 {JRN54290, title = {An ecosystem services perspective on brush management: research priorities for competing land-use objectives}, journal = {Journal of Ecology}, volume = {102}, year = {2014}, pages = {1394-1407}, abstract = {

1. The vegetation of semi-arid and arid landscapes is often comprised of mixtures of herbaceous and woody vegetation. Since the early 1900s, shifts from herbaceous to woody plant dominance, termed woody plant encroachment and widely regarded as a state change, have occurred world-wide. This shift presents challenges to the conservation of grassland and savanna ecosystems and to animal production in commercial ranching systems and pastoral societies.
2. Dryland management focused on cattle and sheep grazing has historically attempted to reduce the abundance of\  encroaching woody vegetation (hereafter, {\textquoteleft}brush management{\textquoteright}) with the intent of reversing declines in forage production, stream flow or groundwater recharge. Here, we assess the known and potential consequences of brush management actions, both positive and negative, on a broader suite of ecosystem services, the scientific challenges to quantifying these services and the trade-offs among them.
3. Our synthesis suggests that despite considerable investments accompanying the application of brush management practices, the recovery of key ecosystem services may be short-lived or absent. However, in the absence of such\  interventions, those and other ecosystem services may be compromised, and the persistence of grassland and savanna\  ecosystem types and their endemic plants and animals threatened.
4. Addressing the challenges posed by woody plant encroachment will require integrated management systems using diverse theoretical principles to design the type, timing and spatial arrangement of initial management actions and follow-up treatments. These management activities will need to balance cultural traditions and preferences, socio-economic constraints and potentially competing land-use objectives.
5. Synthesis. Our ability to predict ecosystem responses to management aimed at recovering ecosystem services where grasslands and savannas have been invaded by native or exotic woody plants is limited for many attributes (e.g. primary\  production, land surface{\textendash}atmosphere interactions, biodiversity conservation) and inconsistent for others (e.g. forage\  production, herbaceous diversity, water quality/quantity, soil erosion, carbon sequestration). The ecological community is challenged with generating robust information about the response of ecosystem services and their interactions if we are to position land managers and policymakers to make objective, science-based decisions regarding the many trade-offs and competing objectives for the conservation and dynamic management of grasslands and savannas.

}, keywords = {bush clearing, drylands, ecosystem services, shrub encroachment, state change, vegetation change, woody plant encroachment, woody weeds}, doi = {10.1111/1365-2745.12314}, url = {files/bibliography/JRN00621.pdf}, author = {Steven R. Archer and K. Predick} } @article {JRN54130, title = {Quantifying drylands{\textquoteright} drought resistance and recovery: the importance of drought intensity, dominant life history and grazing regime}, journal = {Global Change Biology}, year = {2014}, pages = {1-16}, abstract = {

Projected global change will increase the level of land-use and environmental stressors such as drought and grazing, particularly in drylands. Still, combined effects of drought and grazing on plant production are poorly understood, thus hampering adequate projections and development of mitigation strategies. We used a large, cross-continental database consisting of 174 long-term datasets from \>30 dryland regions to quantify ecosystem responses to drought and grazing with the ultimate goal to increase functional understanding in these responses. Two key aspects of ecosystem stability, resistance to and recovery after a drought, were evaluated based on standardized and normalized aboveground net primary production (ANPP) data. Drought intensity was quantified using the standardized precipitation index. We tested effects of drought intensity, grazing regime (grazed, ungrazed), biome (grassland, shrubland, savanna) or dominant life history (annual, perennial) of the herbaceous layer to assess the relative importance of these factors for ecosystem stability, and to identify predictable relationships between drought intensity and ecosystem resistance and recovery. We found that both components of ecosystem stability were better explained by dominant herbaceous life history than by biome. Increasing drought intensity (quasi-) linearly reduced ecosystem resistance. Even though annual and perennial systems showed the same response rate to increasing drought intensity, they differed in their general magnitude of resistance, with annual systems being ca. 27\% less resistant. In contrast, systems with an herbaceous layer dominated by annuals had substantially higher postdrought recovery, particularly when grazed. Combined effects of drought and grazing were not merely additive but modulated by dominant life history of the herbaceous layer. To the best of our knowledge, our study established the first predictive, cross-continental model between drought intensity and drought-related relative losses in ANPP, and suggests that systems with an herbaceous layer dominated by annuals are more prone to ecosystem degradation under future global change regimes.

}, keywords = {ANPP, climate change, cross-continental, cross-site, drought, drylands, model, recovery, resilience, resistance, stability}, doi = {10.1111/gcb.12777}, author = {Ruppert, Jan C. and Harmoney, Keith and Henkin, Zalmen and Snyman, Hennie A. and Marcelo Sternberg and Walter Willms and Linstadter, Anja} } @article {49944, title = {The ecology of dust}, journal = {Frontiers in Ecology and the Environment}, volume = {8}, year = {2011}, pages = {423-430}, abstract = {Wind erosion and associated dust emissions play a fundamental role in many ecological processes and provide important biogeochemical connectivity at scales ranging from individual plants up to the entire globe. Yet, most ecological studies do not explicitly consider dust-driven processes, perhaps because most relevant research on aeolian (wind-driven) processes has been presented in a geosciences rather than an ecological context. To bridge this disciplinary gap, we provide a general overview of the ecological importance of dust, examine complex interactions between wind erosion and ecosystem dynamics from the scale of plants and surrounding space to regional and global scales, and highlight specific examples of how disturbance affects these interactions and their consequences. It is likely that changes in climate and intensification of land use will lead to increased dust production from many drylands. To address these issues, environmental scientists, land managers, and policy makers need to consider wind erosion and dust emissions more explicitly in resource management decisions.}, keywords = {aeolian processes, biogeochemistry, climate change, disturbance, drylands, dust, dust emissions, dust flux, ecological processes, ecosystem dynamics, land use, resource management, wind erosion}, doi = {10.1890/090050}, author = {J. P. Field and Jayne Belnap and David D. Breshears and J. Neff and Gregory S. Okin and J. J. Whicker and Painter, T. H. and S. Ravi and Reheis, M. C. and Reynolds, R. L.} } @mastersthesis {49948, title = {Land cover classification and change detection in drylands: an evaluation of remote sensing approaches}, volume = {Master of Applied Geography}, year = {2011}, pages = {156}, school = {New Mexico State University}, address = {Las Cruces}, abstract = {Land cover change is occurring at unprecedented rates worldwide and is believed to contribute to environmental concerns such as altered biogeochemical cycles, loss of wildlife habitat, decreases in biodiversity, and reduction of soil productivity. Of particular concern are dryland regions of the world because they are experiencing rapid population growth which is a driver of land cover change. The Southwestern United States is one dryland region which is experiencing rapid population growth and associated expansion of urban land cover. The Mesilla Valley of Southern New Mexico is no exception. In this region, which has experienced rapid growth during the last four decades, it is unclear at what rate land cover is changing and what effects this has had on desert ecosystems. Satellite remote sensing can be of great value for mapping land cover and assessing land cover change. However, accurate land cover mapping of arid and semi-arid environments is challenging due to the natural characteristics of these environments. Few researchers have systematically investigated which combinations of image bands, image derivatives, and hard classification algorithms address the difficulties of mapping land cover in arid environments. This is important because hard classifications are by far the most commonly used technique for mapping land cover and drylands are particularly vulnerable to land cover change due to human population pressures. This study examined a series of hard classification techniques and image feature stacks in order to determine which combinations may provide accurate land cover maps in the Mesilla Valley of New Mexico. The tests were repeated for a second dryland region (Yuma Valley, Arizona) to see if they were generalizable to another dryland region. The feature combination that gave the highest accuracy was used to provide land cover information and land cover change maps of the Mesilla Valley, New Mexico between 1985 and 2009.}, keywords = {drylands, land cover change, land cover classification, Mesilla Valley, remote sensing, technique, Yuma Valley}, author = {Hestir, Kristen Lee} } @article {50121, title = {Vegetation controls on small-scale runoff and erosion dynamics in a degrading dryland environment}, journal = {Hydrological Processes}, volume = {23}, year = {2009}, note = {//USDA//LTER V//entered 06/26/2009}, month = {2009}, pages = {1617-1630}, abstract = {

This paper investigates the controls of vegetation on runoff and erosion dynamics in the dryland environment of Jornada, New Mexico, USA. As the American southwest has seen significant shifts in the dominant vegetation species in the past 150 years, an understanding of the vegetation effects on hydrological and erosional processes is vital for understanding and managing environmental change. Small-scale rainfall simulations were carried out to identify the hydrological and erosional processes resulting from the grassland and shrubland vegetation species. Results obtained using tree-regression analysis suggested that the primary vegetation control on runoff and erosion is the shrub type and canopy density, which directly affects the local microtopographic gradient of mounds beneath the shrubs. Significant interactions and feedbacks were found to occur among the local mound gradient, crust cover, soil aggregate stability and antecedent soil moisture between the different vegetation species for both the runoff and erosion responses. Although some of the shrub species were found to produce higher sediment yields than the grass species, the distinguishing feature of the grassland was the significantly higher enrichment in the fine sediment fraction compared to all other surface cover types. This enrichment in fines has important implications for nutrient movement in such environments. Copyright {\textcopyright} 2009 John Wiley \& Sons, Ltd.

}, keywords = {article, drylands, erosion, hydrology, journal, rainfall simulation, runoff, tree regression, vegetation}, doi = {10.1002/hyp.7293}, url = {files/bibliography/JRN00531.pdf}, author = {Michaelides, Katerina and Lister, Debbie and John Wainwright and A.J. Parsons} }