人工固沙植被区土壤水分动态及空间分布

Dynamic and Spatial Distribution of Soil Moisture in an Artificially Re-vegetated Desert Area

土壤水分是干旱区固沙植被生长发育最主要的限制因子,了解其动态变化特征对沙区人工植被建设具有重要意义。本研究利用EnviroSMART土壤水分监测系统,于2009—2013年对宁夏沙坡头地区人工固沙植被区的土壤水分动态进行连续监测。结果表明:(1)降水对土壤水分状况及动态变化有较大的影响。土壤水分总体处于过度消耗状态,在非生长季,土壤水分没有明显的回升现象。(2)生长季初期(4—5月)为土壤水分弱消耗阶段;生长旺盛期(6—8月)为土壤水分快速消耗阶段,水分变化波动较剧烈,空间异质性最强;生长季末期(9—10月)的土壤水分处于相对稳定状态。(3)土壤水分随深度增加呈"S"形变化趋势,浅层的土壤含水量明显高于其他深度,200cm深度土壤含水量较低且年际间变化不大(1.53%~2.10%)。湿润年份土壤水分剧烈变化的土层深度为0~100cm,而干旱年份为0~20cm。(4)相对于干旱年份,湿润年份的土壤含水量不但较高,而且水分变化波动较为剧烈。当土壤水分较低时,其变异性会随着土壤水分含量的增加而增加。(5)试验区灌木盖度在5年间呈下降趋势,一年生草本受降水量影响年际变化较大。受降水时空分布影响的土壤水分是沙坡头人工植被演替的重要驱动力。

Soil moisture is the prime limiting factor for vegetation growth and development in arid area.Understanding the dynamic characteristic of soil moisture is important to vegetation construction.From 2009 to 2013,we measured soil moisture dynamics of artificially re-vegetated desert area of Shapotou,Ningxia,China.The results showed that:(1)rainfall was the major factor affecting the soil moisture dynamic.Soil moisture was over-consumed in general,in which there was no significant rise during non-growing season.(2)Soil moisture consumed slowly from April to May,which lost rapidly from June to August,and became relatively steady from September to October.(3)The general trend of soil moisture was 'S' shape with increasing soil depth.Shallow soil moisture content was higher than other layers.The soil moisture content of the 200 cm layer was low and changed little during five years(1.53%-2.10%).(4)Soil moisture was higher and changed more dramatically in wet years than dry years.When soil moisture was lower,the variation increased with soil moisture's increasing.(5)The shrub coverage showed a gradually decreasing trend and the coverage of grass differed greatly among the five years.Over all,soil moisture,affected by temporal and spatial distribution of precipitation,was the major drive force of succession of re-vegetation area in Shapotou.