Browsing by Author "Eldridge, David J."

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    Drivers of woody dominance across global drylands
    (American Association for the Advancement of Science, 2024-10-11) Biancari, Lucio; Aguiar, Martín R.; Eldridge, David J.; Oñatibia, Gastón R.; Le Bagousse-Pinguet, Yoann; Saiz, Hugo; Gross, Nicolas; Austin, Amy T.; Ochoa, Victoria; Gozalo, Beatriz; Asensio, Sergio; Guirado, Emilio; Valencia, Enrique; Berdugo, Miguel; Plaza, César; Martínez-Valderrama, Jaime; Mendoza, Betty J.; García-Gómez, Miguel; Abedi, Mehdi; Ahumada, Rodrigo J.; Alcántara, Julio M.; Amghar, Fateh; Anadón, José D.; Aramayo, Valeria; Arredondo, Tulio; Bader, Maaike Y.; Bahalkeh, Khadijeh; Ben Salem, Farah; Blaum, Niels; Boldgiv, Bazartseren; Bowker, Matthew; Branquinho, Cristina; Bu, Chongfeng; Byambatsogt, Batbold; Calvo, Dianela A.; Castillo Monroy, Andrea P.; Castro, Helena; Castro-Quezada, Patricio; Chibani, Roukaya; Conceição, Abel A.; Currier, Courtney M.; Donoso, David A.; Dougill, Andrew; Ejtehadi, Hamid; Espinosa, Carlos I.; Fajardo, Alex; Farzam, Mohammad; Ferrante, Daniela; Fraser, Lauchlan H.; Gaitán, Juan J.; Gherardi, Laureano A.; Gusmán-Montalván, Elizabeth; Hernández-Hernández, Rosa M.; Hölzel, Norbert; Huber-Sannwald, Elisabeth; Hughes, Frederic M.; Jadán, Oswaldo; Jeltsch, Florian; Jentsch, Anke; Ju, Mengchen; Kaseke, Kudzai F.; Kindermann, Liana; Köbel, Melanie; le Roux, Peter C.; Liancourt, Pierre; Linstädter, Anja; Liu, Jushan; Louw, Michelle A.; Maggs-Kölling, Gillian; Malam Issa, Oumarou; Marais, Eugene; Margerie, Pierre; Messeder, João Vitor S.; Mora, Juan P.; Moreno, Gerardo; Munson, Seth M.; Oliva, Gabriel; Pueyo, Yolanda; Quiroga, R. Emiliano; Reed, Sasha C.; Rey, Pedro J.; Rodríguez, Alexandra; Rodríguez, Laura B.; Rolo, Víctor; Ruppert, Jan C.; Sala, Osvaldo; Salah, Ayman; Stavi, Ilan; Stephens, Colton R. A.; Swemmer, Anthony M.; Teixido, Alberto L.; Thomas, Andrew D.; Throop, Heather L.; Tielbörger, Katja; Travers, Samantha K.; van den Brink, Liesbeth; Wagner, Viktoria; Wamiti, Wanyoike; Wang, Deli; Wang, Lixin; Wolff, Peter; Yahdjian, Laura; Zaady, Eli; Maestre, Fernando T.; Earth and Environmental Sciences, School of Science
    Increases in the abundance of woody species have been reported to affect the provisioning of ecosystem services in drylands worldwide. However, it is virtually unknown how multiple biotic and abiotic drivers, such as climate, grazing, and fire, interact to determine woody dominance across global drylands. We conducted a standardized field survey in 304 plots across 25 countries to assess how climatic features, soil properties, grazing, and fire affect woody dominance in dryland rangelands. Precipitation, temperature, and grazing were key determinants of tree and shrub dominance. The effects of grazing were determined not solely by grazing pressure but also by the dominant livestock species. Interactions between soil, climate, and grazing and differences in responses to these factors between trees and shrubs were key to understanding changes in woody dominance. Our findings suggest that projected changes in climate and grazing pressure may increase woody dominance in drylands, altering their structure and functioning.
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    Ploughing and grazing alter the spatial patterning of surface soils in a shrub-encroached woodland
    (2013-06) Daryanto, Stefani; Eldridge, David J.; Wang, Lixin
    Grazing is known to affect the spatial patterning of soil resources through biologically-mediated processes such as the removal of plant biomass and deposition of dung. In dense shrublands, grazing is thought to reinforce the concentration of resources around shrubs (fertile island effect) by enhancing the movement of resources from the interspace to the shrub hummocks. Shrub removal practices such as ploughing, which is commonly used to manage dense shrub patches, has unknown impacts on the distribution of soil properties. In this study we examined the effects of two land management practices, grazing and ploughing, on the spatial distribution of surface soil resources. At the unploughed–ungrazed site, the connectivity (autocorrelation range) of shrub cover was about 3.9 m and there was a well-defined pattern in soil labile C that was related to the distribution of the cover of both shrubs and litter. We also observed a strong pattern of biological crust cover and an autocorrelation range of 2.5 m, similar to that of mineralisable and mineral N. At the unploughed–grazed site, the autocorrelation range of both shrub and crust cover was reduced to 1.9 m and 1.8 m, respectively, although the range of litter cover increased to 4.4 m. Under a treatment of grazing without ploughing, the autocorrelation range of soil labile C was less related to litter cover. Whilst ploughing slightly increased the autocorrelation range of both shrub and litter cover at sites that were grazed, it obliterated any spatial pattern in biological soil crusts. We attribute changes in the spatial patterns of soil N under grazing to inputs of animal dung rather than soil crust cover. Our results indicate that grazing alone, or in combination with ploughing, leads to reduced connectivity of shrub and crust cover, reduction in crust patterning, and marked effects on shrub–litter–nutrient spatial relationships. The results reinforce the notion that management of shrublands by grazing and ploughing is likely to have marked effects on the distribution of surface soils.
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    Shrub encroachment alters the spatial patterns of infiltration
    (2014-04) Eldridge, David J.; Wang, Lixin; Ruiz-Colmenero, Marta
    Encroachment of open woodlands by shrubs is a global phenomenon associated with marked changes in ecosystem structure and function. We measured sorptivity and steady-state infiltration at two supply potentials under shrubs and grasses and in their interspaces where shrubs were encroaching into grassland. Steady-state infiltration (ponded) and sorptivity were greater at the grassland than the shrubland site, and there was substantially greater infiltration under shrubs (48.2 mm h−1) and grasses (50.0 mm h−1) than the corresponding interspaces (17.0 and 32.3 mm h−1 for shrubland and grassland, respectively). The difference between grasses and their interspaces was substantially less (1.5 times) than that between shrubs and their interspaces (three times). Shrub encroachment also affected the spatial patterns of infiltration. Although the autocorrelation range for shrublands coincided almost exactly with the average distance between shrub canopies (3.5 m), the range for grasslands was three times greater (1.5 m) than the mean grass canopy, indicating a greater connectivity of infiltration in the grasslands than the shrublands. Our study indicates that encroachment by shrubs does not change infiltration under individual plants. Rather, it reduces the interspace infiltration rates significantly, resulting in lower estimated site-level infiltration rates in shrublands. Our research suggests therefore that it is the shrubland interspaces that are the likely drivers of reduced infiltration rates when grasslands are encroached, rather than increase in the total cover of shrubs per se. Management strategies that result in greater retention of grass cover and minimize the level of interspace disturbances are likely to result in increased infiltration.
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    Spatial patterns of infiltration vary with disturbance in a shrub-encroached woodland
    (Elsevier, 2013-07-15) Daryanto, Stefani; Eldridge, David J.; Wang, Lixin
    Woody plant encroachment is known to have substantial effects on a range of ecosystem processes. Research worldwide indicates that the area around shrubs and trees has higher levels of infiltration than the interspaces. Little is known, however, about the hydrological consequences of shrub removal on infiltration, and how this might be influenced by grazing. We examined the spatial patterns of infiltration across three treatments relating to shrub removal and grazing: (i) undisturbed (ungrazed, unploughed), (ii) grazed but unploughed, and (iii) grazed and ploughed. In general we found that disturbance was associated with a greater cover of bare soil but lower infiltrability, our laboratory–based measure of infiltration. At the undisturbed site, bare soil was patchy and localized, with an autocorrelation range or connectivity of 1.4 m. The autocorrelation range of infiltrability at this site (A0 = 3 m) was larger than would be predicted from the size of the shrub canopy, and this was attributed to the presence of a well–developed understorey layer and biological soil crust community. At both grazed sites, infiltration was confined to the immediate canopy area of the remaining shrubs (A0 = 1.2 m in the unploughed–grazed site). Additionally, there was increasing connectivity of bare soil with disturbance, up to 6.8 m at the ploughed–grazed site. With increasing disturbance, resource-rich shrub patches are likely to become more developed, further reinforcing their growth and persistence at the expense of the bare interspaces. Our results indicate the importance of shrubs for maintaining landscape connectivity, and the long-term unsustainable practice of removal by ploughing, which is likely to promote shrub dominance rather than suppression.