北京沙地杨树人工林生态系统水分利用策略

Strategies on Water Utilization of Poplar Plantation Ecosystem in Beijing Sandy Area

以北京沙地107欧美杨人工林为研究对象，采用DELTA V Advantage同位素比率质谱仪测定杨树茎木质部δ（ D）、δ（^18 O）稳定性同位素值，结合自动气象站（ HOBO）连续观测土壤含水量（ SWC）和降水量，利用三源线性混合模型，揭示杨树人工林生态系统水分利用策略。结果表明：（1）夏季土壤含水量均高于秋季，降水在转化为土壤水和地下水的过程中发生同位素分馏。（2）夏秋两季土壤水δ（D）、δ（18O）同位素与土层深度之间均存在显著二次多项式关系，R值均在0．8341以上，表现为越接近土壤表层，土壤水δ（D）、δ（^18O）同位素越偏正。（3）秋季＞100～120 cm土层为土壤水δ（ D）、δ（^18 O）同位素的显著变化层，而夏季没有明显变化层。土壤水稳定性随土层深度的增加而升高。（4）夏季杨树根系主要吸收140 cm以下土壤水和地下水，秋季不仅吸收140 cm以下土壤水和地下水，对浅层土壤水也有少量吸收。可见，在土质疏松和孔隙度大的地区，杨树根系再生能力强且具有明显的趋水性。

With 107 Populus＆#215;euramericanacv plantation in Beijing sandy area, we measured the stableδD andδ18 O isotope value of poplar stem and xylem by using the DELTA V Advantage Isotope Ratio Mass Spectrometer and observed the soil water content （SWC） and rainfall continuously by HOBO.We revealed the strategies on water utilization of polar plantation eco-system with three source linear mixed model.SWC in summer is higher than that in autumn and isotope is fractionated when rainfall is transferring into soil water and underground water .There is an obviousquadratic polynomial relations be-tween soil depth and theδD ,δ^18 O isotope of soil water in summer and autumn with R〉0.834 1, that is, theδD andδ^18 O isotope of soil water tend to be more positive when it is nearer the top soil.In autumn, theδD andδ^18 O isotope of soil wa-ter vary obviously in 100-120 cm soil layer, but there is no difference in summer.The stability of soil water increases with the depth increasing of soil layer.In summer, the root of poplar mainly absorbs the soil water and underground water below 140 cm, and it also absorbs a little water in shallow soil layer in autumn.Therefore, the poplar root system has the abilities of regeneration and hydrotaxis in the areas with loose soil and large soil porosity .