藏东南不同下垫面栽培草地土壤温湿度的特征分析

Analysis of soil temperature and moisture characteristics of artificial grasslands with different underlying surfaces in southeast Tibet

为揭示藏东南不同下垫面土壤温湿度的特征,本研究以西藏芒康县拉乌山为研究对象,采集2015年11月至2017年12月的10 cm土壤温湿度数据,对植被覆盖(植被区)、砾石+植被覆盖(砾石区)的栽培草地和裸地(无覆盖)3种下垫面条件下的土壤温湿度数据进行比较研究。结果表明:1)拉乌山3种下垫面10 cm土壤温度基本上按正弦曲线变化,与太阳辐射趋势较一致,最大值和最小值分别出现在7月和1月;砾石区土壤温度年较差最大,分别为25.46和23.38℃,植被区土壤温度年较差最小,分别为17.17和16.65℃;砾石区土壤温度日变化呈正弦曲线变化,裸地和植被区在11:00-13:00有轻微的上下波动。2)季节尺度上,土壤湿度主要受降水年变化的影响,呈“W”形发生周期性波动;日尺度上,砾石区夏秋季峰值出现在午夜和傍晚,植被区和裸地均无明显日变化。3)非生长季(11月初至4月下旬),砾石区存在不稳定冻结、不稳定消融和日冻融现象,而植被区和裸地冻融过程相对简单;生长季(5月中旬至10月中旬),砾石区土壤温湿度显著大于植被区(P<0.05),水热条件优于植被区。综上可知,藏东南高寒草原地区砾石+植被覆盖是一种较理想的调节土壤水热条件的措施,可为草地植被恢复工作提供理论依据。

To explore soil temperature and moisture characteristics of artificial grasslands on different underlying surfaces in Southeast Tibet,temperature and moisture data at a depth of 10 cm were collected from Mount Lawu,Mangkang County,Tibet,between November 2015 and December 2017.Data of three underlying surfaces for artificial grasslands,namely vegetation mulching(vegetation area),gravel+vegetation mulching(gravel area),and no mulching(bare land),were collected and compared.The results are as follows.1)The trend of soil temperature at a depth of 10 cm was sinusoidal on all three underlying surfaces,which is consistent with the trend of solar radiation.The maximum and minimum values were recorded in July and January,respectively.Annual variation in soil temperature was the greatest(25.46 and 23.38℃,respectively)in gravel area and the smallest(17.17 and 16.65℃,respectively)in vegetation area.The trend of daily variation in soil temperature was sinusoidal in gravel area,and soil temperature in bare land and vegetation area fluctuated slightly from 11:00 to 13:00.2)On the seasonal scale,soil moisture was mainly affected by annual variation in precipitation,and it fluctuated periodically,assuming a W-shaped trend.On the daily scale,peak soil moisture values in summer and autumn were recorded in the midnight and evening,respectively,in gravel area,but there were no obvious daily changes in soil moisture in vegetation area and bare land.3)In non-vegetative growth season(early November to late April),unstable,daily freezing and thawing were observed in gravel area,while the freezing and thawing process was relatively simple in vegetation area and bare land.In vegetative growth season(mid-May to mid-October),soil temperature and moisture were significantly higher(P<0.05),and the hydrothermal conditions were better in gravel area than in vegetation area.These results indicate that gravel+vegetation mulching is an ideal underlying surface to regulate soil moisture and temperature conditions in artificial grasslands.These data can provide theoretical basis for grassland restoration.