长沙丘陵区油茶林地土壤蒸发的时空变化

Spatiotemporal variation of soil evaporation in Camellia oleifera forest in hilly area of Changsha

2019年4-9月,采用微型蒸渗仪测定长沙丘陵区油茶林地土壤蒸发量;利用ETgage模拟蒸散仪监测林地局部蒸散量,对比分析长沙丘陵地区土壤蒸发量的时空变化,探讨土壤蒸发随气象因素和土壤含水量的变化关系。结果表明:长沙丘陵区油茶林土壤蒸发总量约为192.15 mm,日均为1.05 mm;不同空间位置上,阳面、绝对阴面、相对阴面的土壤蒸发量依次减少,平均值分别为1.14、0.98和0.94 mm/d;空气温度、地温、风速、太阳辐射强度、空气相对湿度对前期(4-5月)土壤蒸发量的影响依次减小,空气温度、空气相对湿度、太阳辐射强度、地温、风速对中期(6-7月)土壤蒸发量的影响依次减小,地温、太阳辐射强度、空气温度、风速、空气相对湿度对后期(8-9月)土壤蒸发量的影响依次减小;前期土壤蒸发量与土壤含水量的相关性较小,中期、后期土壤蒸发量与5 cm土层土壤含水量呈显著正相关,土壤蒸发前缘主要发生于0~5 cm土层;长沙丘陵区油茶林地局部蒸散量约为2.12 mm/d,局部油茶树蒸腾量约为1.11 mm/d,ETgage所测局部蒸散量与微型蒸渗仪测得的蒸发量变化趋势大体相同,且两者呈显著正相关。

From April to September in 2019,the soil evaporation of Camellia oleifera forest in hilly area of Changsha was measured by micro lysimeter,and the local evapotranspiration of forest was monitored by ETgage simulated evapotranspiration sensor.The temporal and spatial changes of soil evaporation in hilly area of Changsha were compared and analyzed,and the relationship between soil evaporation and meteorological factors and soil water content was analyzed.The results showed that the total soil evaporation of Camellia oleifera forest in the hilly area of Changsha was about 192.15 mm,with a daily average of 1.05 mm;in different spatial positions,the soil evaporation on the sunny,absolute and relative shady surfaces decreased in turn,with an average of 1.14,0.98 and 0.94 mm/d,respectively.In the early stage(April to May),the influence of air temperature,ground temperature,wind speed,solar radiation intensity and air relative humidity on soil evaporation decreased in turn;in the middle stage(June to July),the influence of air temperature,air relative humidity,solar radiation intensity,ground temperature and wind speed on soil evaporation decreased in turn;in the later stage(August to September),the influence of ground temperature,solar radiation intensity,air temperature,wind speed and air relative humidity on soil evaporation decreased in turn.The results showed that the correlation between soil evaporation and soil water content was small in the early stage,and there was a significant positive correlation between soil evaporation and soil water content in 5 cm soil layer in the middle and late stage,and the soil evaporation front mainly occurred in 0-5 cm soil layer;the local evapotranspiration of Camellia oleifera forest land in Changsha hilly area was about 2.12 mm/d,and the local transpiration of Camellia oleifera tree was about 1.11 mm/d.The trend of local evapotranspiration measured by ETgage was similar to that measured by micro lysimeter,with a significant positive correlation between the two methods.