Interconnected effects of shrubs, invertebrate‐derived macropores and soil texture on water infiltration in a semi‐arid savanna rangeland

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.

Towards effectively restoring agricultural landscapes in East African drylands: Linking plant functional traits with soil hydrology

“…Aboveground biomass is strongly related to the belowground root biomass (Cheng & Niklas, 2007). We hypothesized that the positive effect of vegetation on soil infiltrability could be caused either by increased aggregate stability due to enhanced SOC content (Lado et al, 2004; Lohbeck et al, 2018), or by increased preferential flow along channels created by roots and tree‐associated soil macrofauna (Bargués Tobella et al, 2014; Dunkerley, 2000; Marquart et al, 2020). As SOC did not have an effect in the optimal infiltration‐model, probably macropores from root channels and tree‐associated soil macrofauna play a key role in explaining our result (Marquart et al, 2020).…”

“…First, trees increase the SOC content (Bayala et al, 2006; Lohbeck et al, 2018), which improves soil structure and aggregation, and ultimately can increase soil infiltrability (Lado et al, 2004). Second, trees may positively affect soil macrofauna abundance and richness due to improved microclimate and soil organic matter content (Zhao & Liu, 2013), and the presence of tree roots and tree‐associated soil macrofauna can enhance macropore preferential flow, resulting in a faster flow of water through the soil (Bargués Tobella et al, 2014; Léonard et al, 2004; Marquart et al, 2020).…”

The regional difference in engineering-control and tillage factors of Chinese Soil Loss Equation

“…Among them, the erosion of erosive rainfall and the displacement of soil particles caused by surface runoff is the most fundamental sources of power for water erosion on slopes (Wang et al 2013;Rutebuka et al 2020;Talchabhadel et al 2020). Soil texture is an important consideration affecting soil permeability (Sajjadi et al 2016;Marquart et al 2020). CRS reflects the frequency of planting and harvesting of crops within a year (Xu and Liu 2014).…”

Ecohydrological connectivity: A unifying framework for understanding how woody plant encroachment alters the water cycle in drylands

“…By adding organic matter and promoting microbial activity, leaf litter acts as a soil amendment, enhancing soil structure and aggregate stability (Bochet et al, 1999). It also provides ideal conditions for soil fauna that-like woody roots-improve macroporosity and infiltrability (Marquart et al, 2020). Some woody plants have a strong legacy effect on soils.…”