Microsite and grazing intensity drive infiltration in a semiarid woodland

Abstract

Human activities such as vegetation removal and overgrazing that result in changes in land cover have substantial impacts on ecosystem processes, including the infiltration of water. Different land cover types (microsites) vary in their capacity to conduct water, but the extent to which infiltration is affected by different herbivores or microsites is largely unknown. We examined the effects of grazing and microsite on infiltration in two extensive woodland communities in semiarid eastern Australia that vary in current condition. Poor condition sites had lower steady-state infiltration under ponding than either average or good condition sites, and this effect was consistent across the two communities. Ponded infiltration and sorptivity beneath grasses, shrubs or trees were about twice that on bare soil, and this corresponded to greater indices of macroporosity. Structural equation modelling showed that shrubs, trees, and grasses had strong positive effects on sorptivity and steady-state infiltration under ponding, whereas grazing had generally negative effects. The suppressive effects of grazing on soil hydrological processes were mainly due to cattle grazing. The positive effects of grasses, shrubs, and trees on hydrology were twice as strong as the negative effects of grazing. Our results also suggest that prolonged overgrazing that leads to reductions in grass cover is likely to have a synergistic reduction in hydrological function in these woodlands by reducing the cover of highly conductive patches and by reducing the extent of macropores.

Light grazing facilitates carbon accumulation in subsoil in Chinese grasslands: A meta‐analysis

“…(c) Grazing increases both soil water and soil N in subsoil (Figure 4c), a finding consistent with some previous reports (Zhang et al., 2019; Zhou et al., 2017). Grazing leads to a more compact surface layer, the inevitable result of trampling, and that compact layer serves as a kind of insulation, preventing water from subsoil from rising to the surface (Vandandorj et al, 2017), and thereby conserving the water present in the deeper layers. Higher water content of the deeper layer, in turn, stimulates roots to go deeper (Hafner et al., 2012; Hamilton & Frank, 2001).…”

Response of Grazing Land Soil Health to Management Strategies: A Summary Review

“…A study conducted on Ethiopian highlands [34] revealed that proper management such as decreasing the grazing intensity or improving plant cover largely alleviates an adverse effect of grazing in steep than flat lands. Prescribed early fire tended to decrease water infiltration [25] and larger size animals can decrease the water infiltration rate more than smaller size animals such as rabbits and kangaroos [12]. Despite this complexity, the majority of earlier studies have demonstrated that heavy grazing has a detrimental impact on soil water infiltration while light and moderate grazing can be beneficial.…”

“…The response of hydrologic processes to grazing methods is influenced by other factors such as management duration [29], topography [34], fire [25], and animal types [12], which are important to consider when determining the grazing intensity and frequency for a specific farm for better water management. For instance, a study on Arizona grasslands observed that grazing exclusion for 54 years had a greater infiltration rate than no-grazing for 25 or 10 years [29].…”

“…When management leads to a decrease in water infiltration, it can cause increased runoff and soil erosion, which are detrimental to ecosystem functions such as livestock productivity [11]. Thus, understanding and improving soil water infiltration is particularly important especially in dry lands [12], which accounts for about 40% of the global land area [13,14]. Past studies investigating the response of soil water infiltration to grazing land management strategies are very few and are often conducted in specific farms or rangelands, which are not representative to the entire grazing lands in the world.…”

Soil and water threats in a changing environment

“…In intensively grazed ecosystems, there are negative effects on soil properties because of the high livestock density. In such conditions, grazing increases soil compaction, eliminates cover protection and reduces key soil properties such as pH, electrical conductivity (Zhang et al, 2017), organic carbon, nitrogen (Byrnes et al, 2017), root biomass (Wang et al, 2017) and hydraulic conductivity (Vandanorj et al, 2017). Also, the use of veterinary antibiotics in cattle increases the content of these elements in the soil via animal droppings (Tasho and Cho, 2017).…”