中文摘要：

【目的】探讨北京山区典型乔木侧柏和栓皮栎的水分利用情况,为北京山区植被建设提供参考和理论依据。【方法】通过测定其木质部水分及其不同水源的稳定氢氧同位素值,利用多源线性混合模型（iso-source）,再结合茎干液流计（TDP）,分析不同水源对2种植物的贡献率和贡献量。【结果】结果表明：1）2个树种在旱季和雨季的茎干液流通量排序为：旱季侧柏（5.87 kg）〈旱季栓皮栎（9.42 kg）〈雨季侧柏（13.42 kg）〈雨季栓皮栎（18.26 kg）。2）侧柏在旱季主要利用深层60-80 cm的土壤水分和地下水,利用率分别为19.8%和51.4%,日平均利用量为1.16和3.02 kg;在雨季主要利用表层0-20 cm的土壤水分和地下水,利用率分别为51.4%和27.7%,日平均利用量为6.90和3.72 kg。3）栓皮栎在旱季表层0-20 cm的土壤水分和深层60-80 cm的土壤水分利用率贡献最大,分别为53.5%和20.2%,日平均利用量为5.04和1.90 kg;在雨季的水分利用率贡献最大的还是集中在表层0-20cm的土壤水和地下水分,利用率分别为51.8%和38.1%,日平均利用量为9.46和6.96 kg。【结论】从侧柏和栓皮栎的水分利用特征来看,2个树种对各水源的利用深度相似,在造林树种选择时,应避免混交产生竞争。在季节性干旱的北京山区水分匮缺,在造林时应优先选择蒸腾耗水较小的侧柏树种。

英文摘要：

【Objective】In order to provide reference and theoretical basis for vegetation construction in Beijing mountain areas,this study investigated water utilization of typical arbors of Platycladus orientalis and Quercus variabilis in Beijing mountainous area. 【Method 】We measured stable isotopic values of hydrogen and oxygen of water in the xylem and different water sources by using multi-source linear mixed models（ Iso-Source）. In combination with the thermal dissipation probe measurement（ TDP）,we analyzed the contribution rate and amount of different water sources to the two tree species. 【Result】Results show that： 1） in dry and rain period,the sap fluid flux was in the order of： P. orientalis in dry period（ 5. 87 kg）〈 Q. variabilis in dry period（ 9. 42 kg） 〈P. orientalis in rain period（ 13. 42 kg）〈 Q.variabilis in rain period（ 18. 26 kg）. 2） P. orientalis up-took water from 60-80 cm soil layer and underground water in the dry season,and the contribution rate was 19. 8% and 51. 4%,respectively,and the average daily use rate was 1. 16 kg and1. 16 kg. In the rainy season,P. orientalis consumed top layer（ 0-20 cm） soil water and groundwater,and the utilization rate was 51. 4% and 27. 7%,respectively,and the average daily use was 6. 90 kg and 3. 72 kg. 3） Q.variabilis up-took water from 0-20 cm and 60-80 cm soil layers in dry period,and the utilization rate of 53. 5% and20. 2%,respectively,and the average daily use was 5. 04 kg and 1. 9 kg. In the rainy season time,Q. variabilis up-took water from 0-20 cm soil layer and shallow underground water,and the utilization rate was 51. 8% and 38. 1%,respectively,and the average daily use was 9. 46 kg and 6. 96 kg. 【Conclusion】In terms of the water use characteristicsof P. orientalis and Q. variabilis,two species had similar utilization of water source depth. Thus in afforestation,the two species should not be mixed together to avoid competition for water sources. In Beijing mountainous area with seasonal drought,less w