A Geospatial Modelling Approach to Understand the Spatio-Temporal Impacts of Grazing on Soil Susceptibility to Erosion

Abstract

Grazing management to reduce soil erosion is paramount for preserving and enhancing grassland health under pastoral livestock production systems. However, as the focus of these production systems is to increase productivity, the inclusion of the soil and its complexity in grazing management has been usually neglected. Detailed consideration of the soil spatio-temporal susceptibility to erosion may be best approached with simulation modelling. To understand and explore the spatio-temporal impact of grazing strategies on soil surface erosion, this work used a geospatial model approach in a high-country pastoral livestock production system in New Zealand as a case study. We modelled 45 scenarios characterized by different stock densities and occupation periods applied for each season of the year and for different livestock types: sheep, beef, and deer, producing a total of 540 scenarios. In addition, we included scenarios to represent ungrazed pastures for each season and the current grazing management of the case study station as the baseline for comparisons (resulting in a total of 545 scenarios). Spatio-temporal variation of natural soil superficial erosion from ungrazed pastures appears to be more relevant than the impact of manipulating grazing intensity and indicates that paddocks in our study area have different capacities to support grazing which also changes during seasons. Increases in occupation period seem more detrimental to soil erosion compared to increases in stock density, and cattle are the most detrimental stock type compared to sheep and deer. Our results suggest that grassland health can be enhanced in LUMGS by applying context-adjusted grazing management strategies according to the station spatio-temporal heterogeneity and susceptibility to erosion.

A Geospatial Modelling Approach to Assess the Capability of High-Country Stations in Delivering Ecosystem Services

“…Thus, grazing animals can promote positive effects on the soil, preserve soil health and function and further mitigate flood and sediment delivery, providing that grazing is adjusted in terms of frequency and pressure to the soil treading capacity. As the soil capacity to support treading is spatial and temporally variable, implying that different areas from the same station respond differently to grazing intensity, grazing management needs to be adaptive, flexible, and carefully planned [56].…”

“…Adequate grazing management can contribute to controlling soil erosion and nutrient delivery and accumulation [57]. Naturally, erosion susceptibility is usually high in highcountry stations due to the soil steepness [21,56], and inadequate grazing can further jeopardize soil function and increase soil loss by erosion [52]. For instance, cattle grazing at higher elevations and slopes can cause more soil erosion and nutrient delivery than other stock types [58] due to a higher pressure exerted on the soil during treading that can reduce ground cover and, hence, soil protection against disturbances and erosive forces [51,52].…”

“…For instance, cattle grazing at higher elevations and slopes can cause more soil erosion and nutrient delivery than other stock types [58] due to a higher pressure exerted on the soil during treading that can reduce ground cover and, hence, soil protection against disturbances and erosive forces [51,52]. Thus, grazing management should be based on strategies that suit the natural spatiotemporal variability and capacity of the landscape to erosion and withstand livestock activity [56]. This includes an integrated regime with the selection of the most suitable stock type for a particular area and soil condition and topography [56,57]; an adjusted grazing frequency and pressure to the seasonal growth of plants [57]; and an adequate rest period in between grazing times to allow plants to recover for a complete restoration of roots reserve and accumulation of nutrients for a vigorous regrowth [59,60].…”

“…Thus, grazing management should be based on strategies that suit the natural spatiotemporal variability and capacity of the landscape to erosion and withstand livestock activity [56]. This includes an integrated regime with the selection of the most suitable stock type for a particular area and soil condition and topography [56,57]; an adjusted grazing frequency and pressure to the seasonal growth of plants [57]; and an adequate rest period in between grazing times to allow plants to recover for a complete restoration of roots reserve and accumulation of nutrients for a vigorous regrowth [59,60].…”