Soil moisture decline following the plantation of Robinia pseudoacacia forests: Evidence from the Loess Plateau

Abstract

<p>Soil moisture is the foundation of ecosystem sustainability in arid and semi-arid regions, and the spatial–temporal details of soil moisture dynamics of afforested areas can benefit for land use management in watershortage regions such as the Loess Plateau of China. In this study, spatial–temporal variations in soil moisture under Robinia pseudoacacia plantations on the Loess Plateau were analyzed. A total of 147 observations of soil moisture content (SMC) data to a depth of 500 cm soil profile were collected in 23 counties via field transect surveys and analyses of published literature. The results suggested that (1) the depth-averaged SMC was generally lower under forest sites than under cropland, both in the shallow layers and in the deep profiles. This finding implied that, compared with the native vegetation, the introduced R. pseudoacacia plantations caused intense reductions in soil moisture. (2) SMC was positively correlated with climatic factors (mean annual precipitation (MAP), mean annual temperature (MAT), and the Palmer drought severity index (PDSI)), indicating that the SMC under R. pseudoacacia plantations was highly consistent with the hydrothermal conditions at the regional scale. (3) The decreasing amplitude of SMC was linearly related to the increasing number of restoration years, especially in the areas below the 500–550 mm precipitation threshold. This finding showed that the restoration ageing sequence was an influential factor that affected the regional SMC variation in R. pseudoacacia plantations on the Loess Plateau. Our results suggest that afforestation activities should be avoided if the local total precipitation is insufficient for replenishing the soil moisture and that local tree species with a lower demand for water resources should be considered a top priority for further afforestation of the Loess Plateau.</p>

Decline in soil moisture due to vegetation restoration on the Loess Plateau of China

“…Ren et al () also compared the effect of afforestation and natural revegetation on soil moisture and suggested that afforestation is the better option for the Loess Plateau only in areas with adequate annual rainfalls. Liang et al () analyzed spatial–temporal variations in soil moisture following the plantation of R. pseudoacacia forests on the Loess Plateau and suggested that afforestation should be avoided in areas where the local total precipitation is insufficient for replenishing the soil moisture. Many vegetation recovery activities, such as planting nonnative trees that consume a large amount of water in dry areas and indiscriminately increasing planting density (Wang & Shao, ) in the process of vegetation construction, have been inappropriate and resulted in a sharp decline in SMC.…”

“…Coupled with the low precipitation, high evaporation, and unsupplied groundwater in the Loess Plateau (Yang et al, ), the soil moisture in this region is insufficient to meet the requirements of vegetation growth. Accordingly, it is vital to select vegetation types based on theoretically matching plant characteristics to the climate conditions and soil properties of certain places (Chen, Shang, Qian, Jing, & Liu, ), and local tree species with a lower demand for water resources should be considered an optimal choice for further afforestation of the Loess Plateau (Liang et al, ).…”

Using Ecosystem Service Bundles to Evaluate Spatial and Tmporal Impacts of Large-scale Landscape Restoration on Ecosystem Services on the Chinese Loess Plateau

“…Another concern is the decrease of water yield, although due to the shrinkage of cropland area by GGP project, the demand for agricultural water use had decreased at the same time. Liang et al (2018) reported a decline of soil moisture after GGP imeplementation, forest has lower moisture content among cropland and grassland, while revegetation on the Loess Plateau is considered as a main driver for the moisture decrease. Clearly, forest expansion had brought more pressure on water supply than grassland on the Loess Plateau with an average annual precipitation from 250 mm ~ mm.…”

Soil moisture variations in response to precipitation in different vegetation types: A multi‐year study in the loess hilly region in China

“…For example, it was reported that black locust and understory species exerted favourable ecological effects in the regions with annual precipitation of more than 500 mm (Jin et al, ). However, in regions with insufficient precipitation, large area degradation and plant mortality occurred under black locust plantations due to severe desiccation (Liang et al, ). Besides, attention should be given to the management of reconstructed vegetation.…”