Characteristics of soil freeze–thaw cycles and their effects on water enrichment in the rhizosphere

Abstract

The freeze–thaw process can lead to water enrichment in freezing layers of soil, and may have beneficial effects on vegetation restoration efforts in sandy land habitats. This study determined the characteristics of soil water migration in dunes and interdune areas during freeze–thaw process, and discussed its potential application to the restoration and recovery of sandy land plant communities. In this research, the mobile sand dunes and interdune lowlands were chosen as the study objects in Horqin Sandy Land, north China. We investigated the soil temperature and moisture content on depths of 20cm, 50cm, 100cm and 150cm during soil freeze–thaw period (from September 20, 2010 to April 9, 2011), and determined the migrated water during freezing–thawing processes on soil of sand dunes and interdune lowlands, and discussed its potential application on plant recovery processes. Results showed that the soil freeze–thaw process occurred mostly at a depth of 0–100cm, and the longest period of soil that remained frozen is 104days at a depth of 20cm and the shortest period is 39days at a depth of 100cm in sand dunes. The number of freeze–thaw cycles was not different between sand dune and interdune area over winter. Most freeze–thaw cycles occurred in the thawing process, and mostly at a depth of 0–50cm. The freeze–thaw cycles of interdune areas only occurred in the thawing process, but the freeze–thaw cycles of sand dunes occurred both in the process of freezing and thawing. More water of the interdune areas apparently migrated than did in the sand dunes. The range of soil water storage content at depths of 0 to 100cm increased to 92.4mm on interdune, and 10.8mm on sand dunes during the freeze–thaw process. A negative correlation was found between soil temperature and moisture at depths of 100cm and 150cm, and while a positive correlation existed at depths of 20cm and 50cm. The freeze–thaw process can lead to water enrichment in freezing layer of soil on sand dunes and interdune. Soil texture affected the quantity of soil water migrating during the freeze/thaw process, and more water migrated in interdune areas than in sand dune habitat.