@article {49853, title = {Soil-litter mixing accelerates decomposition in a Chihuahuan Desert grassland}, journal = {Ecosystems}, volume = {16}, year = {2013}, month = {03/2013}, pages = {183-195}, chapter = {183}, abstract = {Decomposition models typically under-predict decomposition relative to observed rates in drylands. This discrepancy indicates a significant gap in our mechanistic understanding of carbon and nutrient cycling in these systems. Recent research suggests that certain drivers of decomposition that are often not explicitly incorporated into models (for example, photodegradation and soil\–litter mixing; SLM) may be important in drylands, and their exclusion may, in part, be responsible for model under-predictions. To assess the role of SLM, litterbags were deployed in the Chihuahuan Desert and interrelationships between vegetation structure, SLM, and rates of decomposition were quantified. Vegetation structure was manipulated to simulate losses of grass cover from livestock grazing and shrub encroachment. We hypothesized that reductions in grass cover would promote SLM and accelerate mass loss by improving conditions for microbial decomposition. Litter mass decreased exponentially, with the greatest losses occurring in concert with summer monsoons. There were no differences in decay constants among grass cover treatments. A significant, positive relationship between mass loss and SLM was observed, but contrary to expectations SLM was independent of grass cover. This suggests that processes operating at finer spatial scales than those in our grass removal treatments were influencing SLM. Shifts in litter lipid composition suggest increased bacterial contribution to decomposition through time. SLM, which is seldom included as a variable controlling decomposition in statistical or mechanistic models, was a strong driver of decomposition. Results are discussed in the context of other known drivers of decomposition in drylands (for example, UV radiation and climate) and more mesic systems.}, keywords = {arid, carbon cycle, decomposition, dryland, dust, erosion, livstock grazing, phospholipid fatty acids, Prosopis, shrub encroachment, soil-litter mixing}, doi = {10.1007/s10021-012-9604-5}, url = {/files/bibliography/13-019.pdf}, author = {Hewins, Daniel B. and Steven R. Archer and Gregory S. Okin and McCulley, Rebecca L. and Heather L. Throop} } @article {49855, title = {Plant responses, climate pivot points, and trade-offs in water-limited ecosystems}, journal = {Ecosphere}, volume = {4}, year = {2013}, abstract = {

Plant species in dryland ecosystems are limited by water availability and may be vulnerable to increases in aridity. Methods are needed to monitor and assess the rate of change in plant abundance and composition in relation to climate, understand the potential for degradation in dryland ecosystems, and forecast future changes in plant species assemblages. I employ nearly a century of vegetation monitoring data from three North American deserts to demonstrate an approach to determine plant species responses to climate and critical points over a range of climatic conditions at which plant species shift from increases to decreases in abundance (climate pivot points). I assess these metrics from a site to regional scale and highlight how these indicators of plant performance can be modified by the physical and biotic environment. For example, shrubs were more responsive to drought and high temperatures on shallow soils with limited capacity to store water and fine-textured soils with slow percolation rates, whereas perennial grasses were more responsive to precipitation in sparse shrublands than in relatively dense grasslands and shrublands, where competition for water is likely more intense. The responses and associated climate pivot points of plant species aligned with their lifespan and structural characteristics, and the relationship between responses and climate pivot points provides evidence of the trade-off between the capacity of a plant species to increase in abundance when water is available and its drought resistance.

}, keywords = {arid, Chihuahuan Desert, climate change, Colorado Plateau, cross-site, desertification, early warning sign, long-term monitoring, plant canopy cover, Sonoran Desert}, doi = {10.1890/ES13-00132.1}, url = {files/bibliography/JRN00612.pdf}, author = {Seth M. Munson} } @article {49881, title = {Animal foraging as a mechanism for sediment movement and soil nutrient development: Evidence from the semi-arid Australian woodlands and the Chihuahuan Desert}, journal = {Geomorphology}, volume = {157-158}, year = {2012}, month = {01/01/2012}, pages = {131-141}, chapter = {131}, abstract = {

An emerging area of interest in geomorphology over the past two decades has been the effects of biota on ecosystemprocesses.We examined the roles of a rangeof vertebrates on soil disturbance in two markedly different environments, the semi-arid woodland of eastern Australia and a Chihuahuan Desert grassland{\textendash}shrubland in the south-western United States. Foraging pits of soil-disturbing vertebrates varied markedly from small scratchings of heteromyid (mainly Dipodomys spp.) rodents (1.8{\texttimes}10-4m3) to deep (1.0{\texttimes}10-2 m3) excavations of the burrowing bettong (Bettongia leuseur) and greater bilby (Macrotis lagotis). Vertebrates moved substantial volumes of soil in both environments, and activity was highly temporally and spatially variable. At large spatial scales, soil disturbance by echidnas (Tachyglossus aculeatus) and Gould{\textquoteright}s sand goannas (Varanus gouldii) was substantially greater in communities dominated by shrubs, and where domestic livestock had been excluded. Heteromyid rodents tended to excavate more foraging pits in coarse-textured vegetation communities (both grasslands and shrublands). In both environments, foraging was concentrated close to perennial plants such as grass tussocks and tree canopies rather than in the interspaces. Foraging pits of Chihuahuan desert animals tended to be higher in labile carbon and support greater levels of infiltration, though this was plant community-dependent. Overall our results indicate that animal foraging is an important geomorphic mechanism capable of mobilizing substantial volumes of soil in arid and semi-arid environments and with potential effects on soil function. {\textcopyright} 2011 Elsevier B.V. All rights reserved.

}, keywords = {arid, Australia, Biopedturbation, foraging, Jornada, patchiness, rodents, soil formation, soil movement, vertebrates}, doi = {10.1016/j.geomorph.2011.04.041}, url = {/files/bibliography/12-016.pdf}, author = {D.J. Eldridge and T. B. Koen and Aaron Killgore and Huang, Niki and Walter G. Whitford} } @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} } @article {49965, title = {Responses of wind erosion to climate-induced vegetation changes on the Colorado Plateau}, journal = {Proceedings of the National Academy of Sciences}, volume = {108}, year = {2011}, pages = {3854-3859}, abstract = {

Projected increases in aridity throughout the southwestern United States due to anthropogenic climate change will likely cause reductions in perennial vegetation cover, which leaves soil surfaces exposed to erosion. Accelerated rates of dust emission from wind erosion have large implications for ecosystems and human wellbeing, yet there is poor understanding of the sources and magnitude of dust emission in a hotter and drier climate. Here we use a two-stage approach to compare the susceptibility of grasslands and three different shrublands to wind erosion on the Colorado Plateau and demonstrate how climate can indirectly moderate the magnitude of aeolian sediment flux through different responses of dominant plants in these communities. First, using results from 20 y of vegetation monitoring, we found perennial grass cover in grasslands declined with increasing mean annual temperature in the previous year, whereas shrub cover in shrublands either showed no change or declined as temperature increased, depending on the species. Second, we used these vegetation monitoring results and measurements of soil stability as inputs into a field-validated wind erosion model and found that declines in perennial vegetation cover coupled with disturbance to biological soil crust resulted in an exponential increase in modeled aeolian sediment flux. Thus the effects of increased temperature on perennial plant cover and the correlation of declining plant cover with increased aeolian flux strongly suggest that sustained drought conditions across the southwest will accelerate the likelihood of dust production in the future on disturbed soil surfaces.

}, keywords = {arid, climate change, Colorado Plateau, horizontal flux, land use, national park, threshold shear velocity, vegetation change, wind erosion}, doi = {10.1073/pnas.1014947108}, url = {files/bibliography/JRN00582.pdf}, author = {Seth M. Munson and Jayne Belnap and Gregory S. Okin} } @conference {50250, title = {Feedbacks between aeolian processes, vegetation productivity, and nutrient flux in deserts}, booktitle = {Geological Society of America Meetings}, series = {Geological Society of America Meetings}, year = {2008}, abstract = {Wind is a key abiotic factor that influences the dynamics of arid and semiarid systems. A series of experiments and models will be presented that show the important feedbacks that exist between Aeolian processes and biotic process in deserts. Wind impacts vegetation by both changing the composition of the soils, mainly by winnowing fines from erosional areas and redeposition of fines in deposition areas, and by direct physical effects on plants. The former leads to significant loss and redistribution of soil organic matter and plant nutrients as well as the disruption of nutrient cycling process. The latter leads to burial, pedestaling, leaf stripping and branch abrasion that lead to increased plant mortality. There is significant evidence that this leads to state changes in deserts, namely replacement of grasses by shrubs, which in turn create landscapes that are far larger emitters of dust. Changes in aridity have, in the past, caused changes variations in dust emission associated with vegetation state changes and, models suggest, aeolian processes will be increasingly important in vegetation change and dust emissions in deserts.}, keywords = {abstract, aeolian, arid, biotic, semiarid, wind}, author = {Gregory S. Okin and Junran Li and Lorelei Alvarez and Debra C. Peters and Paolo D{\textquoteright}Odorico} } @proceedings {50374, title = {Future climate change impacts on New Mexico{\textquoteright}s mountain sources of water}, year = {2007}, month = {11/2007}, pages = {CDROM}, publisher = {Water Resources Research Institute}, edition = {2008}, address = {Santa Fe, New Mexico}, abstract = {The Rio Grande is one of the most important rivers in the western U.S. and is representative of mountain snowmelt basins in arid and semiarid regions around the world. As is true for many arid and semiarid rivers, the total available water supply is already exceeded by water demands. Dependable water supply comes from high elevation snowpacks that contribute 50-75\% of the annual streamflow. Summer rainfall, which is sporadic and frequently of high intensity, supplies the remaining streamflow. Rapid changes in many mountain regions of the world are being experienced due to global climate change and anthropogenic effects. New Mexico water managers and decision makers urgently need knowledge of the potential effects of climate change on the state{\textquoteright}s water resources. Research being done addresses this topic through the development of improved sensing and modeling infrastructure to estimate future changes in water supply from snow-dominated headwater basins. Existing climate change scenarios generated by general circulation and regional climate models are being utilized to develop reasonable forcing variables for basin hydrologic models which will be used as decision-making tools to evaluate the impact of climate changes in the basin. The hydrologic models being employed include the basin-wide Semi-distributed Land Use and Runoff Processes (SLURP) model that serves to integrate models operating on sub-catchments throughout the Rio Grande basin. The Snowmelt Runoff Model (SRM) is used to simulate and forecast flow in the mountainous snowmelt sub-basins and is directly linked to SLURP. SRM also has a formalized climate change algorithm useful in this study. Operating on smaller Rio Grande sub-basins, the TIN-based Real-Time Integrated Basin Simulator (tRIBS) is a distributed hydrologic model for streamflow forecasting and better understanding of processes active in producing runoff. Finally, the RioGEM hydro-economics model is being used to evaluate the benefits from different management strategies in response to hydrologic changes generated by SLURP, SRM, and tRIBS. The results of this project will address the important problem of how global warming will reduce our already overcommitted water supply and what economic and societal impacts will result.}, keywords = {arid, climate, New Mexico, proceedings, Rio Grande, semiarid rivers, sources, water}, url = {/files/bibliography/08-054.pdf}, author = {A. Rango and Enrique Vivoni and Gutzler, D. and Hurd, B. and Brandon T Bestelmeyer} } @article {50439, title = {Introduction to special issue - Landscape linkages and cross scale interactions in arid and semiarid ecosystems}, journal = {Journal of Arid Environments}, volume = {65}, year = {2006}, month = {April 2006}, pages = {193-195}, abstract = {The conversion of grasslands to shrublands in arid and semiarid ecosystems is a serious global problem. Although a great deal of research has been conducted on these conversions, we lack a complete understanding of the processes underlying the transitions. More importantly, our ability to predict when and where desertification will occur and our ability to manage landscapes to prevent degradation and restore degraded landscapes is limited. Research being conducted at the Jornada Experimental Range (JER) is addressing these problems in a new, synthetic way. Since 1981, scientists affiliated with the Jornada Basin Long-Term Ecological Research site in collaboration with scientists from the JER and New Mexico State University generated a number of new ideas and concepts regarding the processes governing desertification that changed our thinking about how these systems operate. Our focus now emphasizes cross-scale spatial and temporal heterogeneity in vegetation patterns and dynamics that have been difficult to explain using traditional approaches. The realization that our current knowledge often cannot explain the existing variability among land units led to the development of a conceptual model by JER scientists that considers nonlinear dynamics and connections among land units across scales. This cross-scale landscape ecology approach will further our understanding of critical processes occurring in arid regions globally and will provide insight to help identify mechanisms to address the pressing issue of desertification.}, keywords = {arid, cross scale, desertification, ecosystems, invasion, landscape, linkages, semiarid, shrub}, doi = {10.1016/j.jaridenv.2005.04.001}, url = {/files/bibliography/06-006.pdf}, author = {Richard E. Estell and E.L. Fredrickson and Debra C. Peters} } @inbook {50446, title = {Water and energy balances within the Jornada Basin}, booktitle = {Structure and Function of a Chihuahuan Desert Ecosystem. The Jornada Basin Long-Term Ecological Research Site}, year = {2006}, month = {July 1, 2006}, pages = {176-188}, publisher = {Oxford University Press}, organization = {Oxford University Press}, chapter = {8}, address = {New York}, abstract = {This chapter describes general characteristics and components of the energy and water balances in arid regions, with specific examples from the Jornada Basin. Various research efforts to characterize the energy and water balances and resultant carbon dioxide fluxes in the Jornada Basin are detailed. We provide a brief overview of how plant physiology interacts with energy and water balances in this region. The purpose of this chapter is to characterize the general abiotic conditions and some physiological traits of plants in this semiarid region.}, keywords = {arid, balances, carbon, dioxide, energy, Jornada, regions, water}, url = {/files/bibliography/06-059.pdf}, author = {V. P. Gutschick and K. A. Snyder}, editor = {Kris Havstad and L. Huenneke and W. H. Schlesinger} } @article {50460, title = {Arid and Semiarid Rangeland Monitoring in North America}, journal = {Secheresse}, volume = {17}, number = {1-2}, year = {2006}, month = {September 2006}, pages = {235-241}, abstract = {Canada, the United States and Mexico all have a long history of rangeland monitoring. However none have developed a nationwide database or even standardized set of protocols. The lack of standardization, inadequately developed relationships between management objectives and monitoring protocols, and an emphasis on data collection rather than analysis and interpretation have limited the value of past monitoring efforts. The future of monitoring is bright in all three countries. New policies reward ranchers who can document positive changes on their land. Non-equilibrium theory developed in Europe, Africa, Australia and North America increase the value of monitoring data. New protocols increasingly focus monitoring on ecological processes.}, keywords = {arid, arid zone, data base, monitoring, rangeland, rangelands, semi-arid}, url = {/files/bibliography/06-033.pdf}, author = {Jeffrey E. Herrick and Moya, E.G. and Walter Willms and Brandon T Bestelmeyer and Sundt, P. and Barnes, W.} } @article {50457, title = {An integrated framework for science-based arid land management}, journal = {Journal of Arid Environments}, volume = {65}, number = {2}, year = {2006}, month = {2006}, pages = {319-335}, abstract = {

Our objective is to develop a science-based management framework for arid and semiarid ecosystems. This framework must facilitate the integration of new knowledge about linkages among landscape units across scales. Science is frequently touted as the solution to dryland management problems, yet most management decisions are, of necessity, based primarily on expert knowledge and experience. This paper describes an integrated framework for organizing, synthesizing, and applying our growing understanding of dryland ecosystems using a flexible, multi-objective assessment, monitoring, and management approach. The framework is dual-purpose: (1) to coordinate the use of existing tools, resources, and diffuse knowledge, and (2) to facilitate the integration and application of new knowledge as it is developed. The framework includes five elements: (1) an ecological, site-based approach for categorizing land based on soils and climate; (2) a repository for organizing existing data and knowledge about each ecological site; (3) conceptual models that organize information on the impacts of management and climate variability; and, protocols for (4) assessing and (5) monitoring key ecosystem attributes fundamental to a variety of management objectives. Within this framework, basic and applied research are explicitly linked to management of arid and semiarid ecosystems to more effectively articulate research questions and set research priorities.

}, keywords = {arid, ecosystems, land mangement, science-based, semiarid}, doi = {10.1016/j.jaridenv.2005.09.003}, url = {/files/bibliography/06-003.pdf}, author = {Jeffrey E. Herrick and Brandon T Bestelmeyer and Steven R. Archer and A.J. Tugel and Joel R. Brown} } @article {50482, title = {Nonlinear dynamics in arid and semi-arid systems: Interactions among drivers and processes across scales}, journal = {Journal of Arid Environments}, volume = {65}, year = {2006}, month = {April 1, 2006}, pages = {196-206}, abstract = {

We discuss a new conceptual framework for arid and semiarid systems that accounts for nonlinear dynamics and cross scale interactions in explaining landscape patterns and dynamics. Our framework includes a spatial and temporal hierarchy, and five key interacting components that connect scales of the hierarchy: (1) historical legacies that include climate, disturbance, and management regimes, (2) dynamic template of patterns in ecological variables and spatial context, (3) vertical and horizontal transport processes (fluvial, aeolian, animal), (4) the rate, direction, and amount of resource redistribution between high and low resource areas, and (5) feedbacks among plants, animals, and soils. We illustrate how this framework can be used to understand, forecast, and manage ecological systems that exhibit nonlinear dynamics across a range of spatial and temporal scales. This paper provides the foundation for a series of papers from the Jornada Experimental Range ARS-LTER research site in southern New Mexico, USA that support this new conceptual framework.

}, keywords = {across scales, arid, drivers, dynamics, nonlinear, semiarid}, doi = {10.1016/j.jaridenv.2005.05.010}, url = {/files/bibliography/06-007.pdf}, author = {Debra C. Peters and Kris Havstad} } @article {50566, title = {Ecohydrological implications of woody plant encroachment}, journal = {Ecology}, volume = {86}, number = {2}, year = {2005}, month = {February 1, 2005}, pages = {308-319}, abstract = {Increases in the abundance or density of woody plants in historically semiarid and arid grassland ecosystems have important implications for hydrology, ecology, and society. Using a simplified water-balance model, we propose a framework for conceptualizing how woody plant encroachment is likely to affect components of the water cycle within these ecosystems. We focus in particular on streamflow and the partitioning of evapotranspiration into E (evaporation) and T (transpiration). On the basis of this framework, we suggest that streamflow and evaporative processes are affected by woody plant encroachment in different ways, depending on the degree of aridity and the availability of subsurface water. Differences in landscape physiography, climate, and runoff mechanisms mediate the influence of woody plants on hydrological processes. Similarly, encroachment of woody plants can be expected to produce relatively large shifts in the ratio of E to T in semiarid ecosystems, whereas such shifts will be small or negligible in both subhumid and xeric ecosystems. This framework for considering the effects of woody plant encroachment highlights important ecological and hydrological interactions that serve as a basis for predicting other ecological aspects of vegetation change,such as potential changes in carbon cycling within an ecosystem. In locations where woody plant encroachment results in increased T and concurrently the availability of soil water is reduced, increased accumulation of carbon in soils can be predicted. Thus, explicitly considering the ecohydrological linkages associated with vegetation change provides additional information on the consequences of woody plant encroachment. http://www.esajournals.org/pdfserv/i0012-9658-086-02-0308.pdf}, keywords = {arid, ecohydrological, ecosystems, evapotranspiration, semiarid, woody plant encroachment}, url = {/files/bibliography/05-006.pdf}, author = {T. Huxman and Wilcox, B.P. and R.L. Scott and K. A. Snyder and Small, E.E. and Hultine, K.R. and Pockman, W.T. and R. B. Jackson} } @article {50629, title = {Fungal endophytes intrinsically associated with micropropagated plants regenerated from native Bouteloua eriopoda Torr. and Atriplex canescens (Pursh) Nutt.}, journal = {In Vitro Cellular and Developmental Biology-Plant}, volume = {40}, number = {6}, year = {2004}, month = {November 1, 2004}, pages = {608-612}, abstract = {Black grama (Bouteloua eriopoda) and fourwing saltbush (Atriplex canescens) are important grass and shrub species in arid rangelands of the northern Chihuahuan Desert. They are naturally colonized by dark septate endophytic fungi that cannot be eliminated by seed disinfestation. Plants were regenerated from both species and appeared to be fungus free in axenic cultures. Analysis of callus and regenerated plants of both species using dual staining with light and scanning electron microscopy revealed fungal endophytes intrinsically associated with cells, roots and leaves of regenerated plants that are also associated with native plants. Fungal layers and biofilms prevent direct exposure of callus, root or leaf tissues to the external environment. Micropropagation is a valuable tool for identifying key fungal endophytes that enhance drought tolerance in native desert plants.}, keywords = {arid, biofilms, drought, mycorrhizae, symbiosis}, url = {/files/bibliography/04-008.pdf}, author = {J.R. Barrow and P. Osuna-Avila and I. Reyes-Vera} } @conference {50647, title = {The high water-holding capacity of petrocalcic horizons}, booktitle = {Soil Science Society of America Annual Meeting}, year = {2004}, month = {October 31-Novem}, address = {Seattle, WA}, abstract = {Petrocalcic soil horizons develop extensively in arid ecosystems around the world, often within the rooting zone of many desert plant species. In coarse textured soils, this results in a dramatic change in moisture holding capacity through the conversion of a horizon dominated by large pores to a fine pore matrix. We conducted a replicated experiment to measure the characteristic moisture release curve for a range of petrocalcic horizon materials. Samples from both the plugged and laminar horizons from two stage V petrocalcic horizons in southern New Mexico were sampled. Tensions closer to zero were measured using a pressure plate; more negative tensions (down to {\textendash}5Mpa) were measured using a chilled mirror water potential device (Decagon Devices WP4). Our method was repeatable and results were fitted using the vanGenuchten equation. Plant available volumetric water holding capacity for desert species (with permanent wilting point set at {\textendash}4Mpa) ranged from 24\% in plugged horizons to 3\% in some laminar horizons in contrast to approximately 5.5\% in a loamy sand. Cementation by calcium carbonate dramatically alters the water-holding characteristics of soils and understanding these horizons is crucial for understanding patterns of soil water in desert systems.}, keywords = {arid, ecosystems, horizons, Petrocalcic, soil, soil water, water-holding capacity}, author = {Danielle Duni and Jeffrey E. Herrick and Curtis H. Monger and Brinegar, H.R.} } @article {50673, title = {Precipitation pulses and carbon fluxes in semiarid and arid ecosystems}, journal = {Oecologia}, volume = {141}, number = {2}, year = {2004}, month = {October 1, 2004}, pages = {254-268}, abstract = {In the arid and semiarid regions of North America, discrete precipitation pulses are important triggers for biological activity. The timing and magnitude of these pulses may differentially affect the activity of plants and microbes, combining to influence the C balance of desert ecosystems. Here, we evaluate how a {\textquoteright}pulse{\textquoteright} of water influences physiological activity in plants, soils, and ecosystems and how characteristics, such as precipitation pulse size and frequency are important controllers of biological and physical processes in arid land ecosystems. We show that pulse size regulates C balance by determining the temporal duration of activity for different components of the biota. Microbial respiration responds to very small events, but the relationship between pulse size and duration of activity likely saturates at moderate event sizes. Photosynthetic activity of vascular plants generally increases following relatively larger pulses or a series of small pulses. In this case, the duration of physiological activity is an increasing function of pulse size up to events that are infrequent in these hydroclimatological regions. This differential responsiveness of photosynthesis and respiration results in arid ecosystems acting as immediate C sources to the atmosphere following rainfall, with subsequent periods of C accumulation should pulse size be sufficient to initiate vascular plant activity. Using the average pulse size distributions in the North American deserts, a simple modeling exercise shows that net ecosystem exchange of CO2 is sensitive to changes in the event size distribution representative of wet and dry years. An important regulator of the pulse response is initial soil and canopy conditions and the physical structuring of bare soil and beneath canopy patches on the landscape. Initial condition influences responses to pulses of varying magnitude, while bare- soil/beneath-canopy patches interact to introduce nonlinearity in the relationship between pulse size and soil water response. Building on this conceptual framework and developing a greater understanding of the complexities of these ecohydrologic systems may enhance our ability to describe the ecology of desert ecosystems and their sensitivity to global change.}, keywords = {arid, biological activity, carbon fluxes, ecosystems, precipitation, pulses, semiarid}, url = {http://www.springerlink.com/media/99a0unmhlkdv8ypgdmwk/contributions/j/c/f/4/jcf4lnwltcxt7wga.pdf}, author = {T. Huxman and K. A. Snyder and Tissue, D. and Leffler, J. and Pockman, W.T. and Sandquist, D.R. and Potts, D.L. and Schwinning, S.} } @article {52290, title = {Brush eradicating, basin pitting, and seeding machine for arid to semiarid rangeland}, journal = {Journal of Range Management}, volume = {26}, number = {3}, year = {1973}, note = {Permission to post articles granted by the Society for Range Management; www.rangelands.org.}, month = {May 1, 1973}, pages = {189-192}, abstract = {A range seeding machine that increased the chances of successful seedling establishment on arid to semiarid rangeland has been designed and tested on 23 plots in southern New Mexico. Working behind a standard rootplow, the machine picks up brush, forms basin pits, firms the soil, plants seed and replaces the brush over the planted area as a mulch. Laboratory and field research was used to demonstrate improved soil conditions for seedling emergence under such a brush mulch. Water retention by basin pits was found to be necessary to decrease runoff of the high intensity, short duration storms typical to this area. About 50\% of the plots planted with this equipment were successfully seeded.}, keywords = {arid, basin pitting, brush eradication, rangeland, seeding machine, semiarid}, url = {/files/bibliography/138.pdf}, author = {Abernathy, G.H. and C.H. Herbel} } @proceedings {52482, title = {Reseeding in the arid southwestern United States}, year = {1965}, month = {1965}, pages = {E-23--E-24}, keywords = {arid, reseeding, southwestern United States}, author = {C.H. Herbel} }