Effects of Accelerated Soil Erosion on Soil Nutrient Loss After Deforestation on the Loess Plateau

Soil erosion and nutrient losses on newly-deforested lands in the Ziwuling Region on the Loess Plateau of China were monitored to quantitatively evaluate the effects of accelerated soil erosion, caused by deforestation, on organic matter, nitrogen and phosphorus losses. Eight natural runoff plots were established on the loessial hill slopes representing different erosion patterns of dominant erosion processes including sheet, rill and shallow gully (similar to ephemeral gully). Sediment samples were collected after each erosive rainfall event. Results showed that soil nutrients losses increased with an increase of erosion intensity. Linear relations between the losses of organic matter, total N, NH4-N, and available P and erosion intensity were found. Nutrient content per unit amount of eroded sediment decreased from the sheet to the shallow gully erosion zones, whereas total nutrient loss increased. Compared with topsoil, nutrients in eroded sediment were enriched, especially available P and NH4-N. The intensity of soil nutrient losses was also closely related to soil erosion intensity and pattern with the most severe soil erosion and nutrient loss occurring in the shallow gully channels on loessial hill slopes. These research findings will help to improve the understanding of the relation between accelerated erosion process after deforestation and soil quality degradation and to design better eco-environmental rehabilitation schemes for the Loess Plateau.

Soil conservation and ecosystem services

Accelerated soil erosion,driven by anthropogenic activities such as conversion of natural ecosystems to agroecosystems and mechanical tillage,has numerous adverse impacts on ecosystem services.In addition to degrading soil quality and reducing agronomic/biomass productivity on-site through a decrease in use-efficiency of inputs,off-site impacts of accelerated erosion include eutrophication and contamination,sedimentation of reservoirs and waterways,and emissions of greenhouse gases(e.g.,CO_(2),CH_(4) and N_(2)O).While advancing food and nutritional security,adoption of restorative land use and recommended management practices are important to strengthening numerous ecosystem services such as improving water quality and renewability,increasing below and above-ground biodiversity,enhancing soil resilience to climate change and extreme events,and mitigating climate change by sequestering C in soil and reducing the emission of CO_(2),CH_(4) and N_(2)O.An effective control of accelerated erosion is essential to sustainable development and improving the environment.