【摘要】 为研究长沙地区林地土壤水分运动规律,基于2017年3月—2018年2月长沙地区樟树林土壤水分及0～130 cm土壤水、地下水和降水中稳定同位素监测数据,分析了土壤水中稳定同位素特征及其与降水中稳定同位素的关系.结果表明:（1）土壤水分季节变化表现为丰水期（3—6月,土壤蓄水量大而稳定）、耗水期（7—10月,土壤水分以消耗为主）、补水期（11月—翌年2月,土壤水分以补给为主）3个阶段,土壤含水量由表层至深层呈增加趋势,稳定性增强,土壤含水量的垂向差异依次为耗水期>补水期>丰水期.（2）受到冠层截留和地表枯枝落叶吸持的影响,林地的有效降水为降水量（P）>3.3 mm,并且LMWL_{P>3.3 mm}（降水量>3.3 mm时的当地大气水线）较LMWL的斜率和截距显著增加,与各深度SWL（土壤水线）更接近.（3）由表层至深层,土壤水稳定同位素受降水入渗、新旧水混合和蒸发的影响减小,0～40 cm土壤水中δ¹⁸O均表现为丰水期>补水期>耗水期,而40～130 cm土壤水中δ¹⁸O的季节变化不显著.（4）观测期间不同水体中lc-excess（δD与LMWL的差值）的平均值依次为降水（0）>地下水（-2.80‰）>土壤水（-5.00‰）,土壤水中lc-excess随深度的增加而增大.研究显示:土壤水下渗时新旧水混合是一个持续累积的过程,旧的土壤水逐渐被降水替代;受土壤结构、质地等性质的差异及不同降水事件的影响,土壤水分的补给在剖面上存在时滞.更多还原

【Abstract】 Based on the soil water content and stable isotopes in 0-130 cm soil depth,groundwater and precipitation in a Cinnamomum camphora grove in Changsha from March 2017 to February 2018,the characteristics of stable isotopes in soil water and the relationship between isotopic composition of soil water and precipitation were analyzed in order to reveal the movement of soil water in this area. The results showed that:( 1) The seasonal variations of soil water content during the observation could be divided into three stages,i.e. waterrich period from March to June when soil water storage was large and kept stable,water consumption period from July to October and water replenishment period from November to following February. Soil water content increased from surface to deep soil,and its stability increased. The soil water content showed a larger vertical difference in water-consuming period than that in water-replenishing period and than that in water-rich period.( 2) The daily effective precipitation P at the survey site was larger than 3. 3 mm due to canopy interception and surface litter absorption. The slope and intercept of LMWLP>3. 3 mm( local meteoric water line under P>3. 3 mm),very close to SWL( soil water lines) at different depths,were significantly higher than those of LMWL.( 3) From surface to deep soil,the influences of water infiltration,mixing of old and new soil water and soil evaporation on the stable isotopes in soil water gradually decreased. The average δ18 O in 0-40 cm soil water showed greater values in water-rich period than that in water-replenishing period and than that in waterconsuming period,but insignificant seasonality in 40-130 cm soil water.( 4) The average lc-excess( δD deviations from the LMWL) in different water bodies during the observation period showed higher value in precipitation( 0) than that in groundwater(-2. 80‰) and than that in soil water(-5. 00‰). The lc-excess in soil water increased with depth. Because the mixing of old and new water was a continuous and cumulative process,and was impacted by different soil structures,soil textures and precipitation events,there appeared significant time delays with soil depth in supply of soil water.更多还原