高寒沙地典型人工林土壤水分动态及其对降雨的响应

Soil Water Dynamics and Its Response to Rainfall in Typical Plantation of Alpine Sandy Land

分析青海共和盆地中间锦鸡儿人工林在不同生长阶段、不同深度的土壤水分动态变化特征,探讨不同深度土壤水分对不同降雨量的响应过程,深入了解高寒沙地植物与降雨关系,为高寒沙区的植被恢复与合理配置提供科学依据。以不同生长阶段(3、5、16、30a)的中间锦鸡儿(Caragana intermedia)人工林为研究对象,利用ECH2O土壤含水量监测系统分别对每个林龄的不同土层深度(10、20、30、40、60、90、120、150cm)土壤水分进行连续监测;利用Dynamet-1k科研级自动气象站记录降雨量,以3场不同降雨事件进行分析,研究其土壤水分对不同降雨量的响应状况。2008年9月-2017年9月间,试验区内降雨主要集中在5-9月,且雨量小频率高,降雨量小于2mm的降雨事件占总降雨事件的48.21%,贡献率仅为9.68%。4种人工林土壤蓄水量的年内变化可分为土壤水分消耗期(9至次年1月)、土壤水分积累期(2-4月,7-8月)和稳定期(5-6月)。5mm以下的降雨能够使30cm以上的土层水分产生波动,5-18mm的降雨量能影响0-40cm的土壤水分,而18mm以上的降雨量能够引起0-60cm土层水分的变化。土壤蓄水量随着土层深度的增加而先减小后增加,林龄越大,土壤水分对于降雨量响应的滞后性越明显,土壤水分增量也相对减少。因此,在高寒沙区造林应注意苗木栽植的密度,在造林过程中加强水土保持措施,降低干旱胁迫对造林成活率的影响。

The soil moisture content of different soil depths (10, 20, 30, 40, 60, 90, 120, 150cm) and precipitation in Caragana intermedia plantations at different growth stages (3, 5, 16, 30a) were observed continuously through the application of ECH2O soil moisture monitoring system and Dynamet-1k automatic weather station, and three rainfall events were analyzed respectively to study soil moisture characteristics and its response to the rainfall in artificial forests in alpine sandy land of Qinghai Province, which contributed to understanding the relationship between plants and rainfall and further provided theoretical basis on restoration and rational allocation of vegetation in the region. The rainfall mainly concentrated in May to September in the alpine sandy land from September 2008 to September 2017 with a high frequency but low amount precipitation. And 48.21% of the total rainfall events were <2 mm with the contribution rate of 9.68% to the total precipitation. According to the annual changes of the soil water storage, a year could be divided into three periods: consumption period of soil moisture (from September to next January), accumulation period of soil moisture (from February to April, from July to August) and stable period of soil moisture (from May to June). The soil moisture of 0.30, 0.40 and 0.60 cm had different degrees response to the rainfall of <5 mm, 5-18 mm and >18 mm separately. Soil water storage decreased first and then increased with the soil depth. The lag of soil moisture response to rainfall increased with the forest age, and the increment of soil moisture content decreased relatively. Therefore, the appropriate planting density should be selected according to the water consumption characteristics of the plantation, and soil and water conservation measures should be strengthened to reduce the impact of drought stress on afforestation survival rate.