@article{MarquartEldridgeTraversetal.2019,
  author    = {Marquart, Arnim and Eldridge, David J. and Travers, Samantha K. and Val, James and Blaum, Niels},
  title     = {Large shrubs partly compensate negative effects of grazing on hydrological function in a semi-arid savanna},
  series = {Basic and applied ecology : Journal of the Gesellschaft f{\"u}r {\"O}kologie},
  volume    = {38},
  journal   = {Basic and applied ecology : Journal of the Gesellschaft f{\"u}r {\"O}kologie},
  publisher = {Elsevier GMBH},
  address   = {M{\"u}nchen},
  issn      = {1439-1791},
  doi       = {10.1016/j.baae.2019.06.003},
  pages     = {58 -- 68},
  year      = {2019},
  abstract  = {Semiarid woodlands and savannas are globally important biomes that provide ecosystem goods and services such as habitat for biota and sinks for carbon, support millions of people that rely primarily on pastoralism, and supply livelihoods for about a third of the global human population. Savannas, however, are prone to degradation by overgrazing, and encroachment by woody plants, reducing their capacity to produce forage that pastoral enterprises depend on. We examined the impacts of livestock grazing and woody encroachment on soil hydrological processes, hypothesizing that heavy grazing by livestock would reduce hydrological function, whereas woody plants would increase hydrological function, therefore, partially offsetting any negative effects of overgrazing by livestock. Understanding the major drivers of soil hydrology in savanna ecosystems is important because water is a critical, yet limited resource in savannas. We found that livestock grazing reduced the early (sorptivity) and late (steady-state infiltration) stages of infiltration under both ponding and tension, and attributed this to a reduction in porosity caused by livestock trampling. Steady-state infiltration and sorptivity under ponding were greater under the canopies of woody shrubs than in open areas, partly compensating for any negative effect of grazing. Structural equation modeling revealed a direct positive effect of shrub height on hydrological functions, and an indirect effect via increases in litter cover. Our results suggest that woody plants can play important roles in driving hydrological function in savannas, counteracting the suppressive effect of livestock overgrazing on infiltration processes. Management strategies in semiarid savannas should aim to reduce trampling by livestock and retain large woody plants in order to maintain hydrological function. (C) 2019 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.},
  language  = {en}
}
@article{MarquartEldridgeGeissleretal.2020,
  author    = {Marquart, Arnim and Eldridge, David J. and Geissler, Katja and Lobas, Christoph and Blaum, Niels},
  title     = {Interconnected effects of shrubs, invertebrate-derived macropores and soil texture on water infiltration in a semi-arid savanna rangeland},
  series = {Land degradation \& development},
  volume    = {31},
  journal   = {Land degradation \& development},
  number    = {16},
  publisher = {Wiley},
  address   = {Chichester, Sussex},
  issn      = {1085-3278},
  doi       = {10.1002/ldr.3598},
  pages     = {2307 -- 2318},
  year      = {2020},
  abstract  = {Many semi arid savannas are prone to degradation, caused for example, by overgrazing or extreme climatic events, which often lead to shrub encroachment. Overgrazing by livestock affects vegetation and infiltration processes by directly altering plant composition (selective grazing) or by impacting soil physical properties (trampling). Water infiltration is controlled by several parameters, such as macropores (created by soil-burrowing animals or plant roots) and soil texture, but their effects have mostly been studied in isolation. Here we report on a study, in which we conducted infiltration experiments to analyze the interconnected effects of invertebrate-created macropores, shrubs and soil texture (sandy soil and loamy sand) on infiltration in two Namibian rangelands. Using structural equation modeling, we found a direct positive effect of shrub size on infiltration and indirectly via invertebrate macropores on both soil types. On loamy sands this effect was even stronger, but additionally, invertebrate-created macropores became relevant as a direct driver of infiltration. Our results provide new insights into the effects of vegetation and invertebrates on infiltration under different soil textures. Pastoralists should use management strategies that maintain a heterogeneous plant community that supports soil fauna to sustain healthy soil water dynamics, particularly on soils with higher loam content. Understanding the fundamental functioning of soil water dynamics in drylands is critical because these ecosystems are water-limited and support the livelihoods of many cultures worldwide.},
  language  = {en}
}