In the semiarid loess hilly region of China, where groundwater lies too deep to sustain plant life, the soil water regime faces a unique challenge. According to researchers Yang Wenzhi and Han Shifeng, the water within these soils is predominantly in a suspended state, leading to what they describe as an “automorphic-evaporative type” of soil water regime. This means that water is constantly moving upward through evaporation, leaving the soil increasingly arid over time.
The implications of this aridization are stark. The researchers highlight four key characteristics of the soil water background in this region: significant variations in soil water content across different landforms, highly active upward evaporation, low water content under field steady moisture conditions, and difficulties in storing water in deep soil layers. These factors create a challenging environment for plant growth, particularly when man-made vegetation is introduced. The absorption of water by trees and shrubs leads to the formation of a “complex dry soil layer” or “overlapping dry soil layer,” where soil moisture struggles to recover even after rainfall.
Yang Wenzhi and Han Shifeng argue that the northwestern part of the loess hilly region, located in the steppe zone, is particularly harsh for plantation due to its increasingly arid climate. Here, shrubs that are well-adapted to dry conditions are the most suitable choice. In contrast, the central and southern parts of the region, which fall within the forest steppe zone, could benefit from a mixed forest type to combat soil erosion and address fuel shortages.
For the energy sector, these findings suggest a need to rethink land use strategies in the loess hilly region. The researchers propose converting wasteland into man-made grassland as an optimal method for efficient soil water use. This approach not only improves soil fertility but also boosts grass yield, offering potential benefits for bioenergy production. As the study, published in *Shuitu baochi yanjiu* (translated as *Soil and Water Conservation Research*), underscores, understanding and adapting to the unique soil water dynamics in this region could pave the way for more sustainable land management practices, with far-reaching implications for both agriculture and renewable energy sectors.