@article {JRN54142, title = {Rangeland ecosystem services: shifting focus from supply to reconciling supply and demand}, journal = {Frontiers in Ecology and the Environment}, volume = {13}, year = {2015}, month = {02/2015}, pages = {44-51}, chapter = {44}, abstract = {

Ecosystem services have been extensively studied in recent decades. Most of the thousands of scholarly papers published on the subject have focused on describing the production, spatial extent, and valuation of such services. Human reliance on ecosystem services is a function of ecosystems{\textquoteright} capacity to supply and societal demand for these benefits. However, considerably more attention has been devoted to the supply side than to the demand for them. Sustainable land management depends on reconciling supply of and demand for ecosystem services among different stakeholders. The emphasis is now shifting from the supply of ecosystem services to attaining a balance between supply and demand. Here, we illustrate the demand for rangeland ecosystem services, describe current changes in societal demand, and present a specific provisioning service to exemplify the dynamic nature of reconciling ecosystem-service supply and demand.

}, keywords = {ecosystem services, land use decisions, rangelands, societal demand, supply and demand}, doi = {10.1890/140156}, url = {/files/bibliography/15-006.pdf}, author = {Laura Yahdjian and O. E. Sala and Kris Havstad} } @article {50004, title = {Nitrogen limitation in arid-subhumid ecosystems: A meta-analysis of fertilization studies}, journal = {Journal of Arid Environments}, volume = {75}, year = {2011}, pages = {675-680}, abstract = {

Evidence supporting water limitation in arid-semiarid ecosystems includes strong correlations between aboveground net primary production (ANPP) and annual precipitation as well as results from experimental water additions. Similarly, there is evidence of N limitation on ANPP in low precipitation ecosystems, but is this a widespread phenomenon? Are all arid-semiarid ecosystems equally limited by nitrogen? Is the response of N fertilization modulated by water availability?

We conducted a meta-analysis of ANPP responses to N fertilization across arid to subhumid ecosystems to quantify N limitation, using the effect-size index R which is the ratio of ANPP in fertilized to control plots. Nitrogen addition increased ANPP across all studies by an average of 50\%, and nitrogen effects increased significantly (P\ =\ 0.03) along the 50{\textendash}650\ mm\ yr-1 precipitation gradient. The response ratio decreased with mean annual temperature in arid and semiarid ecosystems but was insensitive in subhumid systems. Sown pastures showed significant (P\ =\ 0.007) higher responses than natural ecosystems. Neither plant-life form nor chemical form of the applied fertilizer showed significant effects on the primary production response to N addition. Our results showed that nitrogen limitation is a widespread phenomenon in low-precipitation ecosystems and that its importance increases with annual precipitation from arid to subhumid regions. Both water and N availability limit primary production, probably at different times during the year; with frequency of N limitation increasing and frequency of water limitation decreasing as annual precipitation increases. Expected increase N deposition, which could be significant even in arid ecosystems, would increase aboveground net primary production in water-limited ecosystems that account for 40\% of the terrestrial surface.

}, keywords = {arid ecosystems, article, journal, meta-analysis, nitrogen fertilization, primary production, resource limitation}, doi = {10.1016/j.jaridenv.2011.03.003}, url = {files/bibliography/JRN00579.pdf}, author = {Laura Yahdjian and Laureano A. Gherardi and O. E. Sala} } @article {50305, title = {Climate change impacts on South American rangelands}, journal = {Rangelands}, volume = {30}, number = {3}, year = {2008}, note = {//OTHER//LTER V//entered 06/02/2008 per DEP; updated 06/.26/2009 [pdf in file]}, month = {2008}, pages = {34-39}, abstract = {

South America is highly heterogeneous in terms of climate, ecosystems, human population distribution, and cultural traditions. Rangelands are located within regions with climatic conditions from arid to subhumid, and with mean annual precipitation ranges from approximately 150 to 1500 mm (6{\textendash}60 inches). The boundaries of these regions are subject to modification by local soil conditions, evaporative demands, elevation, and topography. Within South America, rangelands cover 33\% of the total land area (Fig. 1), and include grasslands, shrublands, savannas, and hot and cold deserts, but exclude hyperarid deserts.1) In terms of vegetation, rangeland ecosystems of South America have an important herbaceous component, and woody vegetation can range from scattered dwarf shrubs to an almost continuous canopy of small-stature trees. This coexistence of multiple life forms occurs because plants access soil resources differently. Trees, with deeper and more extensive root systems, are able to access deeper soil moisture and nutrients; grasses, with fine, intensive root systems, are better able to exploit resources in the upper soil layers. Fire and flooding play important roles in maintaining the balance between herbaceous and woody vegetation. Frequent flooding leads to open grasslands, whereas better drained areas support savanna species or woodland vegetation. Large grazing mammals, mainly livestock, have a pronounced effect upon the vertical/partitioned structure of savanna grasslands. The herbaceous layer in rangelands with greater rainfall is composed of both C3 and C4 species, which typically have different growth requirements; C3 species achieve maximum productivity in the cooler, early spring, whereas C4 species have maximum productivity in the warmer late spring or early summer. Rangeland in cold climates of the southern South America is populated by C3 species.

}, keywords = {article, climate change, rangeland, journal, rangeland, climate change, South America}, doi = {10.2111/1551-501X(2008)30[34:CCIOSA]2.0.CO;2}, url = {files/bibliography/JRN00495.pdf}, author = {Laura Yahdjian and O. E. Sala} } @article {50304, title = {Do litter decomposition and nitrogen mineralization show the same trend in the response to dry and wet years in the Patagonian steppe?}, journal = {Journal of Arid Environments}, volume = {72}, year = {2008}, note = {//OTHER//LTER V//entered 06/02/2008 per DEP; updated 06/26/2009 [pdf obtained; abstract added]}, month = {2008}, pages = {687-695}, abstract = {

In arid environments, dry and wet years have similar number of small rainfall events but wet years result from the occurrence of a few large rainfall events. What are the implications of these different precipitation patterns on ecosystem functioning? Here, we examined the differential response of soil processes to wet and dry years. Specifically, we assessed litter decomposition and soil N mineralization responses to precipitation excess in the Patagonian steppe, and compared with responses to drought conditions previously reported for this ecosystem.Litter decomposition rates did not differ significantly between simulated wet year and control, while litter decomposition rates decreased under a drought of a similar absolute magnitude. We hypothesize that decomposition rate in this ecosystem may be driven more by number of rainfall events than by total precipitation amount. Net nitrification increased in the simulated wet year but only for a short period of time. Moreover, irrigation positive effects on nitrification were offset by negative effects on net ammonification. Consequently, net N mineralization was not affected by water availability. Our results suggest that the different microorganisms responsible of nitrification and ammonification have differential sensitivity to water availability and that the environmental controls might be overwhelmed by substrate availability in longer time scales. {\textcopyright} 2007 Elsevier Ltd. All rights reserved.

}, keywords = {article, journal, litter decomposition, Patagonian steppe, nitrogen mineralization, Patagonian steppe, Patagonian steppe}, doi = {10.1016/j.jaridenv.2007.09.005}, url = {files/bibliography/JRN00496.pdf}, author = {Laura Yahdjian and O. E. Sala} }