Spatial continuity and local conditions determine spatial pattern of dried soil layers on the Chinese Loess Plateau

Abstract

Many efforts of restoring vegetation have ignored the feedbacks between biotic and abiotic factors that have developed in water-limited ecosystem. Dried soil layers (DSLs) have formed extensively on the Chinese Loess Plateau (CLP). The objective of this study was to identify the primary factors controlling spatial pattern of DSLs on the CLP. Two DSL indices (DSL thickness (DSLT) and soil water content in a DSL (DSL-SWC)) were estimated by measuring SWC to a depth of 5 m at 86 sites along a south-north transect on the CLP in 2013. The correlation between the spatial pattern of DSLs and environmental factors was determined with redundancy analysis (RDA). DSLs had formed at most of the sites (66 of the 86 sites) along the transect. The sites without DSLs were primarily in an irrigated agricultural zone. DSLT was >400 cm and generally increased from south to north, and DSL-SWC was 2.54% (v/v) in the semi-arid zone of the transect. The connected features of DSLs between connected neighboring sampling units exhibited a much wider extent. A total of nine environmental variables were the primary contributors to the spatial pattern of the DSLs, explaining approximately 47.3% of the variability. Local conditions were responsible for the higher proportion of explained variability than climatic factors. In addition, field capacity was the most important factor in all environmental factors, which may have influenced water-holding capacity. This study concludes that spatial continuity and local conditions determine the spatial pattern of DSLs at a regional scale. Understanding the characteristic of DSLs is useful for efficiency of vegetation restoration and soil water management.