黑河上游青海云杉森林生态系统蒸散发分割

Evapotranspiration partitioning of the Picea crassifolia forest ecosystem in the upper reaches of the Heihe River

通过对黑河上游排露沟流域海拔2 700m和2 900m处青海云杉森林生态系统不同季节的土壤水、植物水和大气水汽等不同水体稳定氧同位素组成(δ18O)的测定,运用Craig-Gordon模型、同位素稳态假设和Keeling Plot模型分别得出土壤蒸发、植物蒸腾和蒸散发的δ18O,结合多元线性混合模型将生态系统蒸散发分割为土壤蒸发和植物蒸腾。结果表明:土壤蒸发水汽的δ18OE、植物蒸腾水汽的δ18OT及蒸散发水汽的δ18OET分别介于-35.9‰^-25.2‰、-9.0‰^-4.2‰和-18.5‰^-10.2‰之间,三者顺序为δ18OT>δ18OET>δ18OE,满足同位素稳态假设。植物蒸腾对蒸散发的贡献率(fT)在52.2%~88.4%之间变化,土壤蒸发对蒸散发的贡献率(fE)在11.6%~47.8%之间变化,fT远大于fE,说明生态系统蒸散发大部分来自于植物蒸腾,即植物蒸腾是青海云杉森林生态系统蒸散发的重要组成部分。fT与气温呈负相关,而与相对湿度呈正相关,说明气温对fT起抑制作用,相对湿度对fT起促进作用,但是相关系数不高,说明fT在自然环境下还可能受除气温和相对湿度外的多种环境因素和生物因素综合影响,具体影响机理有待进一步探究。本研究结果可为进一步研究黑河流域区域内循环和流域尺度水循环研究提供理论依据。

The stable oxygen isotope composition(δ18O)was measured in different water bodies such as soil water,plant water and atmospheric water vapor of Picea crassifolia forest ecosystem in the Pailugou catchment of upper reaches of the Heihe River at2 700m and2 900m altitude,respectively.The Craig-Gordon model,isotope steady state hypothesis and Keeling Plot model were used to obtain theδ18O of evaporation,transpiration and evapotranspiration,respectively.Combined the multiple linear mixed model to partition evapotranspiration into evaporation and transpiration.The results showed that:(1)Theδ18OEof evaporation,theδ18OTof transpiration and theδ18OETof evapotranspiration was between-35.9‰and-25.2‰,-9.0‰and-4.2‰,-18.5‰and-10.2‰,respectively.The order of them wasδ18OT>δ18OET>δ18OE,which according with the assumption of isotope steady state.(2)Contribution rate of evaporation to evapotranspiration(fE)varied from11.6%to47.8%and contribution rate of transpiration to evapotranspiration(fT)varied from52.3%to88.4%.fTwas much larger than fE,indicating that most evapotranspiration came from transpiration.Transpiration was a vital part of evapotranspiration in the Picea crassifolia forest ecosystem.(3)The fTwas negatively correlated with air temperature but positively correlated with relative humidity,indicating air temperature restrained fTand relative humidity promoted fTalthough the correlation was not significant.Addition,fTwas also influenced by various environmental and biological factors except air temperature and relative humidity in natural environment.Temperature and relative humidity are not the only control factors of fT.The results of this study can provide a theoretical basis for further studies on intra-regional circulation and watershed scale water circulation research in Heihe River basin.