The Process of Soil Desiccation under Haloxylon ammodendron Plantations: A Case Study of the Alxa Legue Desert, China.

Bing Jia,Chunyan Zhao,Chunlin Wang,Jie Qin,Xiaohui He,Dongmeng Zhou,Xinglin Zhu,Jianhua Si

doi:10.3390/plants11030235

Abstract

Haloxylon ammodendron is a desert shrub widely used as a windbreak and for sand fixation, and it has achieved remarkable results in China. However, in desert areas, large-scale afforestation increases soil water consumption and forms a dried soil layer (DSL), the development of which seriously threatens the sustainable development of the ecosystem. In this study, soil moisture in the 0–400 cm soil profile was measured in selected 5-, 11-, 22-, 34-, and 46-year-old plantations of Haloxylon ammodendron plantations in Alxa Legue, China, and three soil desiccation evaluation indices were calculated—the soil desiccation index (SDI), DSL thickness (DSLT), and DSL soil water content (DSL-SWC)—to analyze the change pattern of the soil water content for different stand ages. The results showed that the shallow water layer (0–200 cm) was depleted sharply in the first five years of Haloxylon ammodendron plantation growth, but no DSL developed; the inflection point of soil water content change appeared after 10 years of growth, after which the shallow soil water was depleted and the drying process of the deep soil water content was significantly faster than that in the early growth period. The deep soil layer (200–400 cm) was depleted seriously after 22 years of afforestation, the soil drying phenomenon was obvious, and the DSL developed from the 172 cm soil layer. After 46 years of afforestation, the DSL was fully developed and the DSL-SWC was only 0.034 cm3 cm−3. Priority should thus be given to the use of less water-consuming shrub species; alternatively, after 5 years of growth of Haloxylon ammodendron plantations, certain water control measures should be taken to maintain the soil water balance.

Highlights

Afforestation, as an important measure to control sand damage, has a long history in China and is recognized as one of the most effective approaches to constraining windblown sand disasters [1]
If the water lost by transpiration from artificial afforestation and soil evaporation exceeds that gained by precipitation, the soil moisture content will be reduced, and regional water shortages will be aggravated [10,11,12]
The specific objectives of this study are as follows: (1) to study large-scale Haloxylon ammodendron plantations with regard to the soil moisture depletion and desiccation process, along with the formation and development of the dried soil layer (DSL), and (2) to determine the changes in the soil moisture content with forest age after Haloxylon ammodendron plantations

Summary

Introduction

Afforestation, as an important measure to control sand damage, has a long history in China and is recognized as one of the most effective approaches to constraining windblown sand disasters [1]. Planting trees can reduce surface runoff [2,3,4] and improve soil porosity and water conductivity, thereby changing the infiltration rate [5,6,7]. [8] reported that where natural runoff is 30% of precipitation, planting trees can reduce runoff by half or more. Wu et al [9] showed that root decay in large-scale afforestation could maintain a relatively high and stable infiltration rate by reduced root density. If the water lost by transpiration from artificial afforestation and soil evaporation exceeds that gained by precipitation, the soil moisture content will be reduced, and regional water shortages will be aggravated [10,11,12]

Objectives

Methods

Results

Discussion

Conclusion