基于同位素与液流的沙地杨树人工林水分利用策略

Strategy of Water Utilization for Poplar Plantation Based on Isotope and Stem Sap Flow

采用同位素比率质谱仪和热扩散式探针于生长季分别测定杨树茎木质部、各来源水δD、δ18O稳定性同位素和树干液流，结合自动气象站观测各环境和气象因子，并利用线性混合模型，分析杨树林水分利用策略。结果表明，土层深度与土壤水δD和δ18O同位素间呈二次多项式关系，R2分别为0．8543和0．8166；杨树东侧耗水速率开始增加及降低时间分别早于西侧30、10min，昼夜间耗水无明显停止界限，杨树单木日耗水量与树干胸径和边材面积呈极显著相关（Sig=0．01）；沙地杨树林平均单木水分消耗量约为6．26kg／d；杨树西侧根主要吸收40～120cm土层的土壤水和地下水来补给水分消耗，东侧根除了吸收40～120cm土层的土壤水和地下水补给外，亦少量利用0～40cm浅层土壤水。

DELTA V Advantage Isotope Ratio Mass Spectrometer and TDP were adopted to measure and determine poplar＇s stem xylem, source of water δD, δ18O stable isotope and stem sap flow respectively in growing season combining with HOBO to monitor SWC and precipitation as well as other environmental and meteorological factors along with utilizing linear mixing model to analyze the water use strategies for poplar woods in different locations at different times. The results showed that there existed a distinct quadratic polynomial relation between soil depth and soil water δD and δ18O isotope, with R2 of 0. 8543 and 0. 8166 respectively; the times when water consumption rate at east side of poplar started to increase and reduce were early about 30 minutes and 10 minutes than those in west side respectively. There were great- ly significant correlation between daily water consumption of individual poplar tree and DBH and sapwood area （Sig=O. 01） ; the water consumption of individual sand poplar tree was about 6.26 kg/d; the root of poplar at east side mainly replenished its water consumption by absorbing soil water in 40-120 cm and un- derground water while the root of poplar at west side replenished its water consumption by absorbing soil water in 40-120 cm and underground water, as well as a little soil water in 0-40 cm.