Sensitive indicators of soil nutrients from reservoir effects in the hot-dry valleys of China

Abstract

The construction of giant reservoirs can affect the hydroclimatic cycles and related soil nutrient recycling. The current understanding of variations in soil nutrients driven by reservoir impoundment is limited because soil often reacts slowly to changes and the impoundment effects can be masked by various factors, making detection difficult. The soils in the hot-dry valleys suffer from a savanna-like hot and dry climate, making it an ideal area for studying the effect of reservoir impoundment on the soil. Here we collected 138 soil samples in April and November along the cascading reservoirs located in the hot-dry valleys of China, including Xiangjiaba, Xiluodu, Baihetan, and Wudongde reservoirs. Results showed that (1) the reservoir impoundment does alter the soil nutrients. The contribution of the impoundment to the variation of soil nutrients was 3.82% in April and 6.44% in November. (2) Compared to April, a relatively dry and cold November is preferred for revealing the reservoir impact on soil nutrients in the hot-dry valleys. (3) Available nitrogen and available phosphorus, followed by soil organic matter, are potential sensitive indicators that can be used to reflect the reservoir impoundment effects. Additionally, pH may be a potential indicator, particularly in the head reservoir area. It is important to note that the effect of reservoir impoundment on soil nutrients is easily masked. This study encourages dam operating agencies, policymakers, and researchers to regard reservoirs as integral parts of the forcings that modify soil nutrients and is an essential step in gaining an insight into the impact of hydropower development on surrounding terrestrial ecosystem services related to soil nutrients.