@article {JRN55095, title = {Plant phenology: Taking the pulse of rangelands}, journal = {Rangelands}, volume = {41}, year = {2019}, month = {06/2019}, pages = {129-134}, chapter = {129}, abstract = {Plant phenology{\textemdash}the timing of seasonal life cycle events{\textemdash}is a primary control on ecosystem productivity and an integrative indicator of species{\textquoteright} responses to the environment. Plant phenology data can be used to design better management systems by adjusting the timing of grazing, fire and other disturbances relative to the growth stage of key species and in planning restoration activities such as herbicide applications or targeted grazing. Repeated observations needed to understand phenology can be collected at various spatial scales with a variety of methods from field-based observations of individual plants to broad-scale observations of landscape {\textquotedblleft}greenness{\textquotedblright} from satellite imagery. Digital cameras mounted on towers (phenocams) provide a more cost-effective way to collect data to capture vegetation {\textquotedblleft}greenness.{\textquotedblright} Phenocam greenness values are used to generate plant canopy- and community-level metrics in real-time for a fraction of the cost of on-the-ground field observations. Phenocam greenness metrics also serve to link plant- or community-scale phenology observations collected in the field with those from satellite remote sensing and can reveal the plant species or functional groups contributing to satellite NDVI. Phenocam image time series also help interpret rangeland monitoring data by placing data in the context of inter- and intra-annual variability.}, keywords = {grasslands, invasive species, management tools, monitoring, phenocams, plant phenology}, doi = {doi.org/10.1016/j.rala.2019.02.001}, url = {files/bibliography/19-011.pdf}, author = {Dawn M. Browning and K. A. Snyder and Jeffrey E. Herrick} } @article {JRN55005, title = {Digital soil mapping for predicting and managing fire in rangelands}, journal = {Fire Ecology}, year = {2018}, month = {12/2018}, pages = {1-12}, chapter = {1}, abstract = {

Background: Soil properties have important effects on fire occurrence and spread, but soils are often overlooked in
fire prediction models. Quantifying soil-fire linkages is limited by information in conventional soil maps, but digital
soil mapping products (e.g., detailed soil property maps) could improve both wildfire prediction models and post-fire
management decisions.
Results: Of our estimated 3.7 Mkm2 of rangeland in the continental US and Alaska, an average of 38 000 km2 burned
per year between 2008 and 2017. To highlight the role of soils in fire ecology, we present 1) a conceptual framework
explaining why soil information can be useful for fire models, 2) a comprehensive suite of literature examples that used
soil property information in traditional soil survey for predicting wildfire, and 3) specific examples of how more detailed
soil information can be applied for pre- and post-fire decisions.
Conclusions: Digital soil mapping can improve fire prediction models and inform post-fire management decisions

}, keywords = {digital soil mapping, fire effects, grasslands, shrublands, soil moisture, spatial modeling, wildfire}, doi = {doi.org/10.1186/s42408-018-0018-4}, url = {files/bibliography/19-006.pdf}, author = {Matthew Levi and Brandon T Bestelmeyer} } @article {JRN54650, title = {Nematode exclusion and recovery in experimental soil microcosms}, journal = {Soil Biology and Biochemistry}, volume = {108}, year = {2017}, pages = {78-83}, abstract = {

Experimental manipulations of soil fauna are a powerful tool for assessing causal relationships between belowground biodiversity and key ecosystem properties. However, preparing soil microcosm treatments without soil fauna for ecological experiments can be problematic. Methods to exclude nematodes, a ubiquitous and functionally important component of terrestrial ecosystems, have been developed for a few specific ecosystems, some of them involving the application of nematicides that may have interactive effects throughout the soil food web. Our goal was to develop a method to remove nematodes from soils of three Long Term Ecological Research (LTER) grassland sites, ranging from desert to moist, without use of chemicals and with moderate disturbance. Moreover, we aimed at testing whether the nematode removal would remain effective up to several weeks later. The following treatments were applied to ~3- kg soil microcosms in the laboratory: (1) a 72 h heating (65 C) - freezing (-20 C) - heating (65 C) cycle using soil maintained at its original water content, and pre-wetting soil 24 h before heating (65 C) for either (2A) 48 h or (2B) 24 h.We measured treatment effects on total abundance and trophic structure of the nematode community. To investigate whether nematodes would recolonize eight weeks after treatments, we conducted a greenhouse experiment where individual seedlings of the dominant grass species for each ecosystem were transplanted to treated and non-treated (control) soils. A heat-freezeheat cycle of 72 h using soil in its original field water content killed 60, 95, and 99\% of the nematodes for the desert, semi-arid, and moist tallgrass prairie soils, respectively. Pre-wetting soil before heating increased mortality to 99\% for all ecosystems after only 24 h at 65 C. Root-feeders were the most resistant nematode trophic group. Eight weeks after treatments, there was no significant nematode recolonization for the pre-wetted 48 h heated soils from the three sites, while for the semi-arid and moist sites there was a slight recovery in abundance in soil from the 24 h heating treatment. Therefore, a treatment at 65 C for 48 h using pre-wetted soil is recommended for eight-week long manipulative experiments in order to assure the effectiveness of the nematode removal throughout the experiment. {\textcopyright} 2017 Elsevier Ltd. All rights reserved.

}, keywords = {grasslands, intersite, LTER, nematode removal, soil defaunation, soil microcosm}, doi = {10.1016/j.soilbio.2017.02.001}, url = {files/bibliography/JRN00658.pdf}, author = {A. C. Franco and Knox, Matthew A. and Andriuzzi, Walter S. and Cecilia M. de Tomasel} } @article {JRN53932, title = {The changing role of shrubs in rangeland-based livestock production systems: Can shrubs increase our forage supply?}, journal = {Rangelands}, volume = {36}, year = {2014}, month = {04/2014}, pages = {25-31}, chapter = {25}, abstract = {

Projected global increases in ruminant numbers and loss of native grasslands will present a number of challenges for livestock agriculture. Escalated demand for livestock products may stimulate interest in using shrubs on western rangelands. A paradigm shift is needed to change the role of shrubs in rangeland ecosystems. Progress has occurred in identifying mechanisms to increase shrub use, but more solutions are needed to convert woody plants into red meat. Strategies for increasing shrub use could be important for rural communities to adapt to changing climate and shrub cover and for the livestock industry to adapt to predicted growth.

}, keywords = {cattle, goats, grasslands, secondary plant metabolites, sheep, woody plants}, url = {/files/bibliography/14-009.pdf}, author = {Richard E. Estell and Kris Havstad and Andr{\'e}s F. Cibils and D.M. Anderson and Scott T. Schrader} } @article {JRN52693, title = {Mechanisms of grass response in grasslands and shrublands during dry or wet periods}, journal = {Oecologia}, volume = {174}, year = {2014}, pages = {1323-1334}, chapter = {1323}, abstract = {

Multi-year climatic periods are expected to increase with global change, yet long-term data are often insufficient to document factors leading to ecological responses. We used a suite of long-term datasets (1993-2010) to examine the processes underlying different relationships between aboveground net primary production (ANPP) and precipitation in wet and dry rainfall periods in shrublands and grasslands in the Chihuahuan Desert. We hypothesized that trends in ANPP can be explained by different processes associated with their dominant grasses [Bouteloua eriopoda (grasslands); Sporobolus flexuosus (shrublands)], and with ecosystem properties that influence soil water dynamics with feedbacks to ANPP. We compared datasets on recruitment and growth for seven years with no trend in precipitation followed by a four-year drought and five consecutive wet years. We integrated these data in a simulation model to examine the importance of positive feedbacks. In grasslands, ANPP was linearly related to precipitation regardless of rainfall period, primarily as a result of stolon recruitment by B. eriopoda. A lag in responses suggests the importance of legacies associated with stolon density. In shrublands, ANPP was only related to rainfall in the wet period when it increased nonlinearly as the number of wet years increased. Seed availability increased in the first year, and seedling establishment occurred two to four years later. Increases in biomass, litter, and simulated transpiration beginning in the third year corresponded with increases in ANPP. Understanding the processes underlying ecosystem dynamics in multi-year dry or wet periods is expected to improve predictions under directional increases or decreases in rainfall.

}, keywords = {Bouteloua eriopoda, Demographic processes, grasslands, Plant-soil water feedbacks, Sporobolu flexuosus}, doi = {10.1007/s00442-013-2837-y}, url = {/files/bibliography/14-004.pdf}, author = {Debra C. Peters and Jin Yao and Dawn M. Browning and A. Rango} } @article {49841, title = {Changes in ecological stability across realistic biodiversity gradients depend on spatial scale}, journal = {Global Ecology and Biogeography}, volume = {22}, year = {2013}, pages = {19-28}, abstract = {

Aim: It is unclear how the stability of natural ecosystems and populations varies with biodiversity at spatial scales relevant to resource managers. This study evaluates whether theory and prior experiments adequately predict how stability varies with a measure of biodiversity, plant species richness, at multiple scales in naturally assembled ecosystems and assesses mechanisms through which biodiversity is proposed to affect stability.

Location: Chihuahuan desert. Historically, grasslands represented the dominant vegetation type in this landscape and shrubs were uncommon. Desertification has degraded many native grassland regions into one of several alternate states dominated by different shrub species and these regions differ in biodiversity.

Methods: Researchers at the Jornada long-term ecological research site have amassed 12 years of data on the primary productivity of individual plant species in 735 permanent 1-m2 plots distributed among 15 regions that were all historically grasslands. I used this information to describe the relationship between biodiversity and stability at the local (1 m2) and regional (3721 m2) scale and to evaluate mechanisms through which biodiversity is proposed to affect stability.

Results: At the local scale, ecosystem stability increased linearly with biodiversity while population stability tended to decline with biodiversity. At the regional scale, both ecosystem and population stability increased as a saturating function of biodiversity. Scale-dependent change in the biodiversity{\textendash}stability relationship can be explained by the spatial insurance hypothesis, asynchrony in the local productivity dynamics of the average species, and a change in species evenness with scale that weakens statistical averaging.

Main conclusions: Results from small-scale experimental studies may not directly translate to larger spatial scales but they appear to predict patterns in natural communities at small spatial scales. These results suggest that the maintenance of high biodiversity over a large spatial area is essential for maintaining ecosystem services and reducing the potential for further species extinctions.

}, keywords = {Chihuahuan Desert, ecosystem dynamics, grasslands, population dynamics, scale dependence, synchrony}, doi = {10.1111/j.1466-8238.2012.00779.x}, url = {files/bibliography/JRN00607.pdf}, author = {Chalcraft, David R.} } @inbook {49858, title = {Desertification of Rangelands}, booktitle = {Climate Vulnerability: Understanding and Addressing Threats to Essential Resources}, series = {Climate Vulnerability}, volume = {4}, number = {4}, year = {2013}, pages = {239-258}, publisher = {Academic Press}, organization = {Academic Press}, edition = {First}, abstract = {Desertification, the broad-scale conversion of perennial grasslands to dominance by xerophytic shrubs, and the attendant consequences to ecosystem services has affected arid and semiarid regions globally over the past several centuries. This state change is expected to continue in the future as environmental drivers continue to change. It is generally well-recognized that desertification is a cumulative threat that explicitly includes both climatic (e.g., drought) and land-use drivers (e.g., livestock overgrazing and inappropriate conversions of rangeland to cropland).\  However, a basis for ranking the relative importance of these drivers is lacking for many locations. In addition, the emergence of additional drivers (e.g., non-native forbs and grasses modifying historic fire regimes), will result in even more complex dynamics in the future. Clearly, directional changes in climate can have unanticipated effects, in particular for dryland regions with low and variable precipitation and high temperatures in the growing season. However, any change in climate will be operating across diverse landscapes that include a mosaic of human-dominated and natural states, each governed by different drivers and susceptible to different threats. Accounting for the separate and interactive effects of these threats on grassland-shrubland transitions will be necessary as we move forward into a difficult to predict, if not unknown, environmental world.}, keywords = {biodiversity, climate, desertification, dryland ecosystems, feedbacks, grasslands, invasive species, land management, land use, land-atmosphere interactions, shrublands, state change, thresholds, water, wind}, doi = {10.1016/B978-0-12-384703-4.00426-3}, url = {/files/bibliography/13-014.pdf}, author = {Debra C. Peters and Steven R. Archer and Brandon T Bestelmeyer and Brooks, Andrew and Joel R. Brown and Comrie, Andrew and Gimblett, H. Randy and Goldstein, Joshua H. and Kris Havstad and Lopez-Hoffman, L. and Curtis H. Monger and Gregory S. Okin and A. Rango and O. E. Sala and Craig Tweedie and Enrique Vivoni} } @article {49900, title = {Directional climate change and potential reversal of desertification in arid and semiarid ecosystems}, journal = {Global Change Biology}, volume = {18}, year = {2012}, month = {01/2012}, pages = {151-163}, chapter = {151}, abstract = {Our objective was to determine if long-term increases in precipitation can maintain grasslands susceptible to desertification, and initiate a reversal of historic regime shifts on desertified shrublands. Perennial grass production and species richness in a multi-year wet period were hypothesized to be greater than expected based on precipitation in a sequence of dry years. These responses were expected to differ for grasslands and shrublands with different dominant species and topo-edaphic properties. Long-term trends in desertification were documented using vegetation maps beginning in 1858, 1915, 1928, and 1998). These trends were compared with herbaceous and woody species responses to a sequence of dry (1994\–2003) and wet years (2004\–2008) for two grassland (uplands, playas) and three desertified shrubland types (honey mesquite, creosotebush, tarbush) in the Chihuahuan Desert. Analyses showed that both types of grasslands decreased in spatial extent since 1858 whereas areas dominated by mesquite or creosotebush increased. Production of upland grasslands in the wet period was greater than expected based on responses during the dry period whereas the relationships between species richness and precipitation was the same for both periods. Precipitation was not important to responses in playa grasslands in either period. For all ecosystem types, the production response in wet years primarily was an increase in herbaceous plants, and the most pronounced responses occurred on sandy sites (upland grasslands, mesquite shrubland). Results suggest that multiple wet years are needed to initiate a sequence of grass establishment and survival processes that can maintain upland grasslands without management inputs and lead to a state change reversal in desertified shrublands. Restoration strategies need to take advantage of opportunities provided by future climates while recognizing the importance of ecosystem type.}, keywords = {extreme events, grasslands, regime shift, shrublands, spatial content, wet-dry climatic periods}, doi = {10.1111/j.1365-2486.2011.02498.x}, url = {/files/bibliography/12-002.pdf}, author = {Debra C. Peters and Jin Yao and O. E. Sala and John P. Anderson} } @article {JRN54212, title = {Long-term experimental loss of foundation species: consequences for dynamics at ecotones across heterogeneous landscapes}, journal = {Ecosphere}, volume = {3}, year = {2012}, month = {03/2012}, pages = {1-23}, chapter = {Article 27}, abstract = {

Biome transition zones where species co-exist near their geographic limits are expected to be among the most responsive to changes in climate that result in mortality of foundation species. Long-term (.13 years) patterns in dominance and cover of functional types were examined following the annual experimental removal of one of three foundation species at an arid-semiarid biome transition zone.\  Objectives were to identify key processes influencing these patterns, and to predict future landscape-scale dynamics following mortality of different foundation species. Aboveground biomass of dominant species was removed from 334 m plots. Cover by species on control and removal plots was estimated annually in communities with a single dominant species, and in ecotonal communities with two dominant species across two types of ecotones (semiarid grassland-arid grassland, arid grassland-arid shrubland).\  For most species and functional types, trends in cover through time were related to the remaining species assemblages rather than to variable climatic conditions. In ecotonal communities, resident co-dominant species increased to dominance following the loss of a foundation species with little change in community composition. In mono-dominated communities, dominant species loss resulted in a shift to species that are currently sub-dominants of the same functional type as the species that was removed. \ Subdominant perennial grass and shrub species increased rapidly following removals in most grassland locations.\  Annuals and perennial forbs had variable cover values through time that were not clearly related to pulses in precipitation and were not synchronized across locations. The most common response regardless of the identity of the foundation species removed or the community type was an increase in cover by subdominant grasses and by the arid grass species (Bouteloua eriopoda). The rate of increase by B. eriopoda depended on initial cover, and resulted from both vegetative growth and seedling recruitment from other locations. Seed dispersal and seedling recruitment from other locations were not found for the semiarid grass, Bouteloua gracilis or the arid shrub, Larrea tridentata. Because B. eriopoda is more susceptible to shrub invasion, drought, and livestock grazing than the other two foundation species, widespread loss of either of the other species and subsequent increase in B. eriopoda is expected to result in an increase in landscape scale vulnerability to these environmental drivers. The extent and magnitude of this change invulnerability will depend on the ability of B. eriopoda to respond based on the micro-environmental conditions of the site regardless of which species (B. gracilis, L. tridentata) is lost.

}, keywords = {arid, biome transitions, Chihuahuan Desert, dominant species, experimental removals, grasslands, mortality, semiarid, Shorrgrass Steppe, shrublands}, doi = {10.1890/ES11-00273.1}, url = {/files/bibliography/12-042.pdf}, author = {Debra C. Peters and Jin Yao} } @proceedings {49981, title = {Plant-soil feedbacks and the reversal of desertification with climate change}, year = {2011}, month = {04/2011}, pages = {292-296}, publisher = {International Rangeland Congress}, address = {Rosario, Argentina}, abstract = {Our objective was to provide a conceptual framework for perennial grass recovery in a series of wet years, which includes both plant-soil feedbacks that increase available water to grasses and effects of precipitation on a sequence of recovery-related processes. We tested hypotheses based on this framework for grasslands and shrublands in the Chihuahuan Desert, the largest desert in North America. Results show that a sequence of 5 wet years following 14 years of variable rainfall increased production in resource conserving ecosystem types greater than predicted based on rainfall alone. The increase in production was primarily by herbaceous plants, which captured water locally to increase plant available water to both existing plants and new recruits. The sequence of wet years allowed a series of linked plant processes to occur that resulted in the establishment and survival of perennial grasses and forbs. We predict that a continued series of wet years will maintain the herbaceous component of these systems, and may act to reverse desertification on degraded shrublands, and to maintain perennial grasslands without management inputs. Degraded shrublands located on slopes susceptible to runoff of water responded linearly to annual precipitation in multiple wet years, and are expected to be resistant to a shift back towards grasslands under a directional increase in precipitation.}, keywords = {Chihuahuan Desert, grasslands, precipitation, regime shift, shrublands}, url = {/files/bibliography/11-017.pdf}, author = {Debra C. Peters and Jin Yao and John P. Anderson and O. E. Sala} } @article {50052, title = {The contribution of brown vegetation to vegetation dynamics}, journal = {Ecology}, volume = {91}, year = {2010}, pages = {743-755}, chapter = {743}, abstract = {

Indices of vegetation dynamics that include both green vegetation (GV) and non-photosynthetic vegetation (NPV), that is, brown vegetation, were applied to MODIS surface reflectance data from 2000 to 2006 for the southwestern United States. These indices reveal that the cover of NPV, a measure of vegetation brownness and a component of ecosystems worldwide, is highly variable in both space and time in the study region. In the more mesic regions of the study area, the timing of peaks in NPV appears to result from simple senescence of GV at the end of the growing season. In these regions, the amplitude of GV cyclicity dominates the total vegetation signal. In contrast, in arid and semiarid regions, the amplitude of cyclicity of NPV dominates the total vegetation signal, showing the vegetation of these regions to be unexpectedly dynamic. Shrublands of southwestern United States exhibit temporal behavior in which the annual peak in NPV cover precedes the annual peak in GV cover by a few months. Several explanations for this behavior are offered. This study shows the importance of vegetation indices that include NPV, or vegetation brownness, in understanding terrestrial ecosystem dynamics, as well as the response to change for these ecosystems.

}, keywords = {deserts, grasslands, green photosynthetic, non photosynthetic, phenology remote sensing, savannas, shrublands, stress vegetation dynamics, vegetation, woodlands}, doi = {10.1890/09-0302.1}, url = {/files/bibliography/10-051.pdf}, author = {Gregory S. Okin} } @conference {50082, title = {Does livestock grazing influence spatial patterns of woody plant proliferation?}, booktitle = {Ecological Society of America Abstracts}, year = {2009}, month = {August 2009}, pages = {COS 127-10}, abstract = {Patterns of woody plant proliferation in grasslands and savannas influence rates of erosion, spread of disturbance, and nutrient pools.~ Spatial pattern is the outcome of plant dispersal, recruitment, competition/facilitation, and disturbance. We quantified effects of livestock grazing, a widely cited driver of shrub encroachment, on the spatial patterns of velvet mesquite (Prosopis velutina) distribution and recruitment in southeastern Arizona. ~Field surveys of plant canopy size and location spanning 74 years (1932, 1948, and 2006) were conducted on areas grazed by livestock since the late 1800s and on areas protected from livestock since 1932.~ Point pattern analysis and Moran{\textquoteright}s I were used to quantify changes in distribution and spatial autocorrelation over time.}, keywords = {erosion, grasslands, nutrient, savannas, spatial pattern}, author = {Dawn M. Browning and Steven R. Archer and Janet Franklin and Guertin, D. P.} } @conference {50081, title = {Grazing effect on woody plant recruitment in a Sonoran Desert grassland across space and time}, booktitle = {US International Association for Landscape Ecology}, year = {2009}, month = {04/2009}, publisher = {US, IALE}, organization = {US, IALE}, address = {Snowbird, Utah}, abstract = {

Livestock grazing is a commonly cited factor contributing to shrub encroachment in savannas and grasslands. Patterns of woody plant proliferation are known to influence rates of erosion and spread of disturbance and are of practical importance to livestock management with regard to forage distribution and abundance. However, the effects of grazing on woody plant population dynamics and stand structure are poorly understood, owing to a paucity of long-term, spatially-explicit data. We explored the spatial patterns of distribution and recruitment for velvet mesquite (Prosopis velutina) using field surveys spanning 74 years (1932, 1948, and 2006) on areas grazed by livestock since the late 1800s and protected from livestock since 1932. Univariate analyses with Ripley\’s K and neighborhood density functions (NDF) revealed mesquite plants were randomly distributed in 1932. In 1948, following 16 years of protection from livestock, plants on the protected area were clustered at all distances (1 to 20m), while mesquite on the grazed area were clustered at short distances (1 to 4m) only. In 2006, mesquite on the protected area remained clustered at all distances, with a marked peak in clustering at short distances (1 to 4m), whereas mesquite on the grazed area were randomly distributed. Bivariate analyses with Ripley\’s K and NDF indicated that juvenile mesquite plants (\<1m height) were significantly clustered around adult plants from 2 to 5m on the protected area in 2006; but there were no significant patterns of association between juveniles and adults on the grazed area through time. Previous analyses revealed that spatial autocorrelation in mesquite density did not deviate from random on the grazed area, whereas associations on the protected area became increasingly positive. Grazing influenced recruitment-driven changes in population structure from 1932 to 2006 and protection from livestock facilitated formation of high density shrub clusters and open areas generating high spatial heterogeneity.

}, keywords = {erosion, grasslands, livestock management, point pattern analysis, proliferation, Santa Rita Experimental Range, savannas, shrub encroachment, spatial ecology, velvet mesquite, woody}, author = {Dawn M. Browning and Janet Franklin and Steven R. Archer} } @inbook {50085, title = {Grasslands in the Borderlands. Understanding coupled natural-human systems and transboundary conservation}, booktitle = {Conservation of Shared Environments. Learning from the United States and Mexico}, year = {2009}, month = {2009}, pages = {188-203}, publisher = {University of Arizona Press}, organization = {University of Arizona Press}, chapter = {12}, address = {Tucson, AZ}, abstract = {Grasslands are one of the shared ecosystems that dominate the heart of the North American continent. Among these are the Chihuahuan Desert grasslands that are undergoing a rapid transition to desertified, arid scrub conditions. Policy-driven landuse changes are reducing their capacity to maintain biodiversity, ecosystem services, and human well-being. In northwestern Chihuahua, and adjoining New Mexico, Arizona and Texas, degradation occurred differentially on either side of the border with degradation in the United States preceding that in Mexico, but becoming more pronounced in some parts of Mexico during the last two decades. Degradation patterns in the United States can inform Mexican conservation efforts, while relatively intact Mexican ecosystems provide valuable insights into functional grassland systems. Our collaborative socio-ecological study of the patterns and processes governing ecological change is guiding grassland recovery with the goal of maintaining biodiversity that appears necessary to reinstate lost ecosystem services and grassland productivity on which human population{\textquoteright}s in the transbounday region depend. As this chapter discusses, prairie dogs in this region exhibit the characteristics of a keystone species and are important ecosystem engineers that maintain northern Chihuahuan grasslands. They are critical for the maintenance of biodiversity and support grassland ecosystem functioning, resulting in important benefits for humans. The natural process of prairie dogs supporting ecosystem function creates ecosystem services essential for human well-being. This process is disrupted by poor land management (i.e., governmental policies that promote cattle overgrazing) resulting in environmental degradation that results in a loss of biodiversity, alteration of ecosystem function, and reduction of ecosystem services. In this chapter we present an approach to overcome the negative cycle of overgrazing, and discuss how this approach could be implemented bi-nationally.}, keywords = {borderlands, grasslands, Mexico, US}, url = {/files/bibliography/09-028.pdf}, author = {G. Ceballos and List, R. and A.D. Davidson and E.L. Fredrickson and Sierra Corona, R. and Martinez, L. and Jeffrey E. Herrick and Pacheco, J.}, editor = {Lopez-Hoffman, L. and McGovern, E.D. and Varady, R.G. and Flessa, K.W.} } @article {50230, title = {Shrub encroachment in North American grasslands: Shifts in growth form dominance rapidly alters control of ecosystem carbon inputs}, journal = {Global Change Biology}, volume = {14}, year = {2008}, month = {January 30, 2008}, pages = {615-623}, publisher = {Blackwell Publishing}, abstract = {

Shrub encroachment into grass-dominated biomes is occurring globally due to a variety of anthropogenic activities, but the consequences for carbon (C) inputs, storage and cycling remain unclear. We studied eight North American graminoid-dominated ecosystems invaded by shrubs, from arctic tundra to Atlantic coastal dunes, to quantify patterns and controls of C inputs via aboveground net primary production (ANPP). Across a 4-fold range in mean annual precipitation (MAP), a key regulator of ecosystem C input at the continental scale, shrub invasion decreased ANPP in xeric sites, but dramatically increased ANPP (\>1000 g/m2) at high MAP, where shrub patches maintained extraordinarily high leaf area. Concurrently, the relationship between MAP and ANPP shifted from being non-linear in grasslands to linear in shrublands. Thus, relatively abrupt (\<50 yrs) shifts in growth form dominance, without changes in resource quantity, can fundamentally alter continental-scale pattern of C inputs and control by MAP in ways that exceed the direct effects of climate change alone.

}, keywords = {aboveground net primary production, carbon, climate change, encroachment, grass-dominated biomes, grasslands, growth form, LAI, MAP, North American, shrub, shrublands}, doi = {10.1111/j.1365-2486.2007.01512.x }, url = {/files/bibliography/08-005.pdf}, author = {A. K. Knapp and J. M. Briggs and S.L. Collins and Steven R. Archer and M.S. Bret-Harte and Ewers, B. and Debra C. Peters and Young, D. and Shaver, G. and Cleary, M.B.} } @conference {50338, title = {Ecosystem services to and from North American arid grasslands}, booktitle = {IV Simposium Internacional de Pastezales}, year = {2007}, month = {August 22-24, 20}, pages = {1}, address = {San Luis Potosi, Mexico}, abstract = {Arid grasslands throughout North America are characterized by low and variable precipitation, nutrient-poor soils, and high spatial and temporal variability in plant production. These grasslands have provided a variety of goods and services, with the provisioning of food and fiber dominating through much of the 20th century. More recently, poor economic returns, increased regulations, an aging rural population, expanding urbanization, and/or increasingly diverse interests of land owners have pressured the traditional services originating from the rangeland livestock industry. A shift to other provisioning, regulating, cultural, and supporting services has occurred or is occurring in many regions. This shift has important implications for other services of increasing interest, such as biodiversity and carbon sequestration. We have always recognized that these lands can supply societal demands such as clean water and a safe food supply. Irrespective of the services and goods supplied, the use of ecologically-based principles remains at the core of land management. However, expectations need to be based on a thorough understanding of the inherent limits of these lands. One service to these lands that needs to be provided by managers is the use of practices that either maintains ecological functions or that restores functions to systems that have been substantially degraded over past decades. With proper policies, supporting science, and ecologically based management techniques, these grasslands may provide these historical and more unique goods and services in a sustainable fashion, though in different proportions than in the past.}, keywords = {grasslands, North America}, author = {Kris Havstad} } @conference {50424, title = {Shrub encroachment across North America: A multi-site synthesis of patterns, mechanisms, and consequences}, booktitle = {91st Ecological Society of America Meetings}, year = {2006}, month = {August 6-11, 200}, pages = {99}, address = {ProCite field[13]: Memphis, TN}, abstract = {In North America, the expansion of shrubs within ecosystems previously dominated by herbaceous species has been documented in barrier islands off the Virginia coast, mesic grasslands of the Great Plains, sub-tropical savannas of Texas, desert grasslands of the Southwest, across the Intermountain West and in the Artic tundra. We synthesized data from four LTER sites and seven sites in total (in Virginia, Kansas, Texas, New Mexico, Wyoming and Alaska) to assess the mechanisms and consequences of this widespread pattern of growth-form substitution. Mean annual temperature at these sites ranged from -12.5C at the tundra site (Arctic LTER) to 22C at the La Copita, TX site and mean annual precipitation (MAP) ranging from 259mm at the WY site to 1065mm at the Virginia Coast Reserve LTER site. Overall, ANPP was increased when shrubs invaded herbaceous-dominated ecosystems, but this pattern was driven by large increases at the mesic sites. At the driest sites (NM and WY), ANPP decreased with shrub expansion. Across all sites, MAP was more strongly correlated with shrub ANPP (r2 = 0.71) than herbaceous ANPP (r2 = 0.55). In contrast to ANPP responses, species richness declined with the expansion of shrubs into these herbaceous-dominated ecosystems. These shifts in ecosystem structure clearly affect function across these biomes, with potentially dramatic and long-term regional implications given the extent of this phenomenon and the low probability of a return to dominance by herbaceous species in many of these ecosystems.}, keywords = {grasslands, shrub, sythesis}, author = {J. M. Briggs and A. K. Knapp and Steven R. Archer and M.S. Bret-Harte and S.L. Collins and Ewers, B. and Debra C. Peters and Young, D.} } @article {50428, title = {Mapping woody plant cover in desert grasslands using canopy reflectance modeling and MISR data}, journal = {Geophysical Research Letters}, volume = {33}, number = {L17402}, year = {2006}, month = {September 2006}, pages = {1-5}, abstract = {

A simplified geometric-optical model (SGM) was inverted using red band reflectance data acquired at 275 m in nine viewing angles from the Multiangle Imaging SpectroRadiometer (MISR) flown on NASA\’s Terra satellite, to provide estimates of fractional woody plant cover for large areas (over 3519 km2) in parts of the Chihuahuan Desert in New Mexico, USA. The use of the model in these semi-arid environments was enabled by the derivation of a priori estimates of the soil/understory background reflectance response. This was made possible by determining relationships between the kernel weights from a LiSparse-RossThin model adjusted against the same MISR data \– together with spectral reflectance data derived from MISR\’s nadir-viewing camera \– and the parameters of the Walthall model used to represent the background. Spatial distributions of retrieved fractional woody plant cover match those of \% tree cover in the global MODIS Vegetation Continuous Fields product but also include shrubs. Good relationships wereobtained with fractional shrub cover measured in pastures in the USDA, ARS Jornada Experimental Range but tree cover in higher elevation and riparian zones was dramatically overestimated as a result of the fixing of crown height and shape parameters.

}, keywords = {grasslands, MISR, woody plant}, doi = {10.1029/2006GL027148}, url = {/files/bibliography/06-040.pdf}, author = {M. Chopping and L. Su and Andrea S. Laliberte and A. Rango and Debra C. Peters and J. V. Martonchik} } @article {50591, title = {Using historic data to assess effectiveness of shrub removal in southern New Mexico}, journal = {Journal of Arid Environments}, volume = {62}, number = {1}, year = {2005}, month = {July 1, 2005}, pages = {75-91}, abstract = {

In the late 1930{\textquoteright}s, the presence of a highly organized labor force, the Civilian Conservation Corps (CCC), in the Jornada Basin of southern New Mexico provided the capability for rangeland scientists to conduct experiments to determine the effectiveness of various techniques for remediating or reversing the encroachment of shrubs into grasslands. Unfortunately, soon after the treatments were performed, the CCC disbanded and most records of the treatments were lost. Despite sketchy documentation, some rangeland treatments left legacies on the landscape, and effects on water retention, erosion, and vegetation dynamics remained long after the CCC work ended. The discovery of historical documents from long-closed files and aerial photography in widely scattered archives allowed some of the experiments to be located and reexamined. Two research areas established in the mid-1930s were of particular interest, namely a tarbush (Flourensia cernua) site where shrubs were grubbed and quadrats established and a creosote (Larrea tridentata) site where both creosote and tarbush shrubs were grubbed. Here we outline how these sites were rediscovered, how historical measurements were repeated for the first time since the late l930s, and conclusions drawn regarding specific rangeland remediation strategies and vegetation dynamics. Our results show that shrub populations recovered from a radical removal treatment in less than 65 years. Remediation of these sites so that grass will recover to pre-shrub-dominated amounts will require measures additional to just removal of shrubs in order to restore hydrologic function. The fact that we were able to relocate, revisit, and resample these treatment areas provided unique opportunities to understand the long-term vegetation dynamics of these arid ecosystems. It is evident that woody plant populations have a high degree of resilience, that density dependence or interference appears to limit plant size in arid shrub communities, and that shrub populations had not reached any stable equilibrium state at the time of treatment in the 1930s. These insights would have been impossible to gain from short-term studies and without long-term studies initiated in the 1930s combined with recent discoveries of original documentation and historical aerial photography. http://authors.elsevier.com/sd/article/S0140196304002411

}, keywords = {aerial, grasslands, historical, photography, remediation, shrubs}, doi = {10.1016/j.jaridenv.2004.11.001}, url = {/files/bibliography/05-002.pdf}, author = {A. Rango and L. Huenneke and M. Buonopane and Jeffrey E. Herrick and Kris Havstad} } @article {50641, title = {Scale dependence in the species-richness-productivity relationship: the role of species turnover}, journal = {Ecology}, volume = {85}, number = {10}, year = {2004}, note = {//NMSU,USDA//LTER IV//Entered 11/14/2006.}, month = {2004}, pages = {2701-2708}, abstract = {

Recent research in aquatic systems suggests that productivity{\textendash}richness relationships change with spatial scale and that species turnover (i.e., spatial and temporal variation in species composition) plays an important role in generating this scale dependence. The generality of such scale dependence and the effects of variation in temporal scale remain unknown. We examined the extent to which the richness{\textendash}productivity relationship in terrestrial plant communities depends on spatial or temporal scale and evaluated how spatial and temporal turnover (i.e., species turnover in space and time) generates scale dependence in these relationships using data from two Long-Term Ecological Research (LTER) sites (Jornada and Konza). We found a weak hump-shaped relationship (Jornada) and no relationship (Konza) between richness and productivity at the smallest focal scale (1 m2 at Jornada and 50 m2 at Konza) at each site, but strong hump-shaped relationships at the largest focal scale (49 m2 at Jornada and 200 m2 at Konza) for each site. Relationships between spatial turnover and productivity at each site mirrored the productivity{\textendash}richness relationships that emerged at the larger spatial scale (i.e., a significant hump-shaped pattern). In contrast, temporal turnover was unrelated to productivity, and hence increasing temporal scale did not appreciably change the form of the productivity{\textendash}richness relationship. Our study suggests that the way in which productivity{\textendash}richness relationships change with spatial or temporal scale depends on the form and strength of the underlying relationship between species turnover and productivity. Moreover, we contend that a dominant effect of increasing productivity is the generation of dissimilarity in species composition among localities that comprise a region, rather than increasing the number of species that occur within local communities. Thus, understanding the mechanisms that cause species turnover to vary with productivity is critical to understanding scale dependence in richness{\textendash}productivity relationships.

}, keywords = {article, biodiversity, environmental heterogeneity, grasslands, journal, LTER, productivity, scale, species composition, species richness, species turnover, stability, terrestrial plants}, doi = {10.1890/03-0561}, url = {files/bibliography/JRN00418.pdf}, author = {Chalcraft, David R. and John W. Williams and M. D. Smith and Michael R. Willig} } @article {50974, title = {Local and regional-scale responses of ant diversity to a semiarid biome transition}, journal = {Ecography}, volume = {24}, number = {4}, year = {2001}, month = {December 1, 2001}, pages = {381-392}, abstract = {

The locations of biome transitions and ecotones are frequently defined by the rapid shift from one form of dominant vegetation to another. The composition of animal taxa is predicted to shift parallel with that of dominant plants, and species diversity is predicted to be greater in transitional zones than in adjacent areas. We asked whether ant species diversity and composition supported these predictions across a biome transition between shortgrass steppe and Chihuahuan Desert vegetation. Neither species richness nor diversity was highest at the biome transition region as a whole or within habitats in the biome transition. The biome transition region was not intermediate in ant species composition or in the representation of different faunal complexes. The community similarity between matched habitats shared between the biome transition zone and adjacent regions was less than that between distinct habitats occurring within regions. A zoogeographic transition for ants may occur to the nort of the phytogeographic transition and may be coincident with the northern limits of monsoonal precipitation patterns. In contrast, the phytogeographic transition may be related to less extreme climatic variation within the monsoonal region occurring further south.

}, keywords = {ants, Desert insects, grasslands, Habitats, Insect communities, shrublands, species diversity, Steppes, Taxa}, doi = {10.1034/j.1600-0587.2001.d01-194.x}, url = {/files/bibliography/01-015.pdf}, author = {Brandon T Bestelmeyer and J.A. Wiens} } @conference {51084, title = {Effects of shrubs and disturbances on pattern and process in Chihuahuan Desert grasslands}, booktitle = {85th Annual Meeting, Ecological Society of America}, year = {2000}, month = {August 6, 2000}, pages = {393}, address = {Snowbird, UT}, abstract = {

Disturbances can cause patchiness in the vegetation at different spatial and temporal scales. In arid environments, dominant species of the vegetation are similar to disturbances in that they create patches with a modified biotic and abiotic environment. Shrub invasion in arid environments has caused a shift in the dominant life form, which is expected to have important implications for the occurrence of subdominant plants. The objective of this study was to understand and predict changes in the relative abundance of subdominant species when an evergreen shrub (Larrea tridentata) invades desert grasslands dominated by Bouteloua eriopoda, and to compare those changes to other disturbances that affect the vegetation. We used a spatially-explicit individual-plant based model (ECOTONE) to simulate responses of desert grassland species to shrub invasion using a hierarchical patch dynamics approach. The effects of changes in light, water, and nutrients caused either by disturbance or shrub invasion on subdominant species were evaluated. We found that the effects of shrub invasion on species composition were comparable to other disturbances. However, contrary to other disturbances, changes in processes induced by shrub invasion appear to be self-reinforcing, whereas species recover after disturbances. As a consequence, initially positive effects of shading by shrubs on the abundance of subdominant species ultimately caused a loss of subdominant plants as shrub cover increased. These results correspond to field data collected at a desert grassland-shrubland ecotone at the Sevilleta LTER in New Mexico. Our study demonstrates the similarity and differences of invasive species to disturbances.

}, keywords = {Chihuahuan Desert, disturbances, grasslands, Sevilleta LTER, shrub invasion}, author = {Hochstrasser, T. and Debra C. Peters} } @conference {51148, title = {Invasion of grasslands by exotic perennial weeds: Allelopathy and soil texture effects}, booktitle = {84th Annual Meeting of the Ecological Society of America}, volume = {80}, year = {1999}, month = {1999}, pages = {94}, address = {Spokane, WA}, abstract = {Invasion of native ecosystems by exotic perennial weeds is an increasingly important ecological problem, yet the key processes involved remain poorly understand for many species. Our objective was to evaluate the importance of allelopathy to the invasion by Acroptilon repens (Russian knapweed) into native semiarid grasslands. Based upon the inverse texture hypothesis, we expected the strength of the allelopathic affect to be related to soil texture and its effects on soil water availability. We used an individual plant-based simulation model (ECOTONE) to evaluate the importance of allelopathy to invasion by Russian knapweed into shortgrass communities in eastern Colorado over a range of soil textures. We found that allelopathy was more important for fine-textured soils where allelochemicals became concentrated in the rooting zone of grasses compared to soils with high sand contents where leaching of allelochemicals occurred. Rates of invasion nwere faster and more complete dominance by Russian knapweed occurred on fine- compared to coarse-textured soils. Our results have important implications for the management and sustainability of these grasslands under the threat of invasion by perennial weeds.}, keywords = {Allelopathy, grasslands, invasion, perennial weeds, soil texture}, author = {Sarah Goslee and Debra C. Peters and Beck, K.G.} } @article {52508, title = {Grazing values and management of black grama and tobosa grasslands and associated shrub ranges of the Southwest}, year = {1962}, month = {1962}, pages = {56 }, abstract = {Optimum production of livestock on black grama and tobosa grasslands and associated shrub ranges of the Southwest depends on proper management of the forage resource. In this region, periods of low precipitation are frequent and fluctuations in seasonal and annual amounts are extreme. Under these circumstances, range livestock operators are faced with perplexing problems of how to maintain stability and continuity of their enterprises. Too often ranchers and land managers are handicapped by not having long-term records of forage production to give them a better idea of range potential. Studies of management practices and effects of weather on black grama and tobosa grasslands and associated shrub ranges have been underway in southern New Mexico since 1912. The Jornada Experimental Range was established that year as a 193,394-acre tract 23 miles northeast of Las Cruces. Because its vegetation, soils, and climate are sufficiently comparable to that of more than 26 million acres of black grama, tobosa and associated shrub ranges in the Southwest, research results can be applied directly to much of this area. Many of the principles of management also are adaptable to other semidesert grass-shrub ranges in Arizona and Texas. The experimental work on the Jornada has been a combination of empirical studies on large range pastures and detailed studies of climate, soils and important forage plants and range types (Campbell, 1940). These studies have two main objectives: (1) to gain an understanding of the forage resource, and (2) to determine the methods of management best suited to the region.}, keywords = {black grama, forage production, government publication, grasslands, livestock production, shrub ranges, tobosa}, url = {/files/bibliography/087.pdf}, author = {Paulsen, H.A., Jr. and F.N. Ares} }