Determination of plantation degradation promotes shallow soil water recovery in semi-arid area based on high-density plots investigation

Abstract

Large-scale afforestation poses threats to water resources security in water-limited areas, and the water availability affects plants growth and mortality. Shelterbelts degradation inevitably causes stand structure changes, which affect the soil water content (SWC). In this study, we used high-density sampling method to study the Populus simonii Carr stands located in the only 6.3 km2 Boluosu forest farm in the semiarid region of northern China, including healthy and degraded stands, and cropland and grassland plots as controls. The vertical profiles (0–200 cm) of SWC was measured in each plot in 73 selected locations, soil characteristics and stand structure of typical Populus simonii Carr were measured. The main purpose was to analyze the impact of the Populus simonii Carr degradation on the soil water vertical variation and to combine this information with stand structure and soil characteristics to analyze all their effects together. The results showed that compared with cropland (254.7 ± 14.96 mm) and grassland (237.9 ± 12.62 mm), the soil water storage of healthy Populus simonii Carr (198.91 ± 8.47 mm) decreased by 21.9 % and 16.4 %, respectively. The shallow layer (0–60 cm) SWC increased significantly with degradation degree (P < 0.01), and the shallow layer soil water storage of the degraded Populus simonii Carr (79.7 ± 4.5 mm) was 20 mm (33.5 %) higher than that of healthy Populus simonii Carr (59.7 ± 2.8 mm). There were significant differences in the dominant factors of SWC between healthy and degraded Populus simonii Carr. For healthy Populus simonii Carr, sand content was the dominant factor controlling the SWC and explained 54.6 % of the variations in shallow layer SWC. For degraded Populus simonii Carr, canopy closure was the main factor controlling the SWC and explained 63.3 % of the variations in shallow layer SWC. The study showed that should prioritize plantations with lower water consumption for future afforestation. Additionally, considering the shallow soil water recovery after shelterbelt degradation, the results could provide a scientific support for sustainable management of plantations.

Keywords

• Shelterbelt degradation
• Soil water content
• Stand structure
• Soil characteristics
• Semiarid regions