Livestock tracks transform resource distribution on terracette landscapes of the Loess Plateau

Striking networks of livestock tracks, or terracettes, molded to the contours are a common feature on hilly rangelands of the semiarid Loess Plateau, one of the regions with the most severe soil erosion in the world. The formation of livestock tracks results in modified micro-topography and ecological processes and leads to strong patterns in spatial distribution of vegetation, water, and nutrients. We investigated the spatial pattern of the topo-edaphic, hydrological, biogeochemical, and biological attributes of these terracette landscapes and explored their potential implications to ecosystem functions. The results showed strong spatial heterogeneity in topo-edaphic and biological structure of these landscapes, organized with three segments of a basic landscape unit-track, shoulder, and interslope. The above-and below-ground biomass and soil nutrients concentrated in the shoulder segment forming a "band of fertility". The network of livestock tracks likely reduced surface runoff and erosion by intercepting runoff and facilitate infiltration, while posing little risk of increasing shallow slope failures given the structure of loess soil. There appears a positive feedback loop for maintaining the structure of terracette landscapes. Trampling by goats maintains the tracks, which leads to spatial heterogeneity in biophysical structure and processes. The network of tracks enabled the goats to travel and graze in ways that reduce energy expenditure and increase foraging efficiency, which leads to strongly preferential use of the tracks by the goats. There are also evidence of a possible process resemble a slope parallel retreat at a micro-scale, which may result in upslope movement of the terracettes. There may be important functional differences between landscapes with and without networks of livestock tracks, in regulating water runoff and soil erosion, forage production, and soil carbon storage. These functional differences may have significant implications to land use policies and practices aiming at soil and water conservation and socioecological sustainability of the Loess Plateau.