Zhang Huan, Cao Jun, Wang Hua Bing, Song Bo, Jia Guo Dong, Liu Zi Qiang, Yu Xin Xiao, Zeng Jia
College of Water and Soil Conservation, Beijing Forestry University/Key Laboratory of Soil and Water Conservation and Desertification Combating, Ministry of Education, Beijing 100083, China.
Miyun Gardening and Greening Bureau, Beijing 101500, China.
Ying Yong Sheng Tai Xue Bao. 2018 May;29(5):1381-1388. doi: 10.13287/j.1001-9332.201805.026.
In Zhangbei County, Hebei Province, poplar-dominated shelterbelts are degraded to different extents. Water availability is the main limiting factor for plant survival in arid areas. The purpose of this study was to reveal the relationship between water availability and poplar degradation. Based on the hydrogen and oxygen stable isotope techniques, we explored the water sources of Populus simonii under different degradation degrees by comparing the isotopic values of P. simonii xylem water with that in potential water source, and calculated the utilization ratio of each water source. The results showed that the water sources of poplar trees varied with degradation degree. The water sources of P. simonii gradually transferred from the deep layer to the surface layer with the increases of degradation. P. simonii with no degradation mainly absorbed soil water in the range of 320-400 cm, with the utilization rate being 25.1%. P. simonii with slight degradation mainly used soil water at depth of 120-180, 180-240 and 240-320 cm. The total utilization rate of three layers was close to 50.0%, with less utilization of water from other layers. The moderately degraded P. simonii mainly used soil water at depth of 20-40, 40-60 and 60-80 cm. The utilization rate of each layer was 17.5%-20.9%, and the contribution rate of soil water under 120 cm was less than 10.0%. The severely degraded P. simonii mainly used water from surface soil layer (0-20 cm), with the utilization rate being 30.4%, which was significantly higher than that of other water sources. The water sources of poplar shelter forests were gradually shallower during the process of degradation. However, the low soil water content in the shallow layer could not meet the normal water demand of poplar, which would accelerate the degradation and even decline of poplar.
在河北省张北县，以杨树为主的防护林带出现了不同程度的退化。水分可利用性是干旱地区植物生存的主要限制因素。本研究的目的是揭示水分可利用性与杨树退化之间的关系。基于氢氧稳定同位素技术，通过比较小叶杨木质部水与潜在水源的同位素值，探究不同退化程度下小叶杨的水源，并计算各水源的利用率。结果表明，杨树的水源随退化程度而变化。随着退化程度的增加，小叶杨的水源逐渐从深层转移到表层。未退化的小叶杨主要吸收320 - 400厘米范围内的土壤水，利用率为25.1%。轻度退化的小叶杨主要利用120 - 180、180 - 240和240 - 320厘米深度的土壤水。三层的总利用率接近50.0%，对其他层水的利用率较低。中度退化的小叶杨主要利用20 - 40、40 - 60和60 - 80厘米深度的土壤水。各层利用率为17.5% - 20.9%，120厘米以下土壤水的贡献率小于10.0%。重度退化的小叶杨主要利用表层土壤（0 - 20厘米）的水，利用率为30.4%，显著高于其他水源。杨树防护林带在退化过程中水源逐渐变浅。然而，浅层土壤水分含量低，无法满足杨树正常的水分需求，这将加速杨树的退化甚至衰退。
