Impact of afforestation density on soil and water conservation of the semiarid Loess Plateau, China

Abstract

On the Loess Plateau of China, deep rooted, fast-growing species, such as caragana (Caragana korshinskii Kom.), are widely used in afforestation projects. High planting densities and soil water consumption has led to soil desiccation and degradation. We conducted a two-year (2002 to 2003) field experiment assessing the effect of caragana planting density on plant growth and hydrological processes at the Shanghuang Eco-Experimental station. Caragana canopy interception, surface runoff, soil loss, and changes in plant growth and soil water content were determined for five planting densities ranging from 16 to 87 shrubs 100 m⁻² (1,076 ft⁻²). Increases in the caragana canopy within the growing season and greater planting densities resulted in higher canopy interception and in lower runoff and soil loss. The soil water carrying capacity for the caragana amounted to 72 shrubs100 m⁻² when rainfall approaches the long-term average. A sustainable, managed planting density is required that will balance soil water losses due to runoff, the plant's water requirements, and the water supply. In cases where soil desiccation has already occurred, conservation management plans should attempt to recharge the soil water in order to reverse soil degradation.