北京松山落叶阔叶林生态系统水分利用效率变化特征及影响因素

Water-Use Efficiency Exchange and Its Affecting Factors in a DeciduousBroad-Leaved Forest in Songshan,Beijing,China

基于松山通量观测站点2019年4~10月份通量数据,定量分析了松山落叶阔叶林生态系统水分利用效率(WUE)特征及影响因素。利用涡度相关技术对北京松山落叶阔叶林生态系统的水通量进行长期原位连续监测,利用微气象监测系统对空气温度(T_(a))、土壤温度(T_(s))、光合有效辐射(PAR)、降雨量(P)、饱和水气压差(VPD)等环境因子进行同步连续观测。结果表明:WUE年平均值为1.68 g C kg^(-1) H_(2)O,在北京时间6:00~8:00达到最大值(5~14 g C kg^(-1) H_(2)O),随后降低至1~4 g C kg^(-1)H_(2)O保持稳定,WUE稳定值相较于刚日出时降低了30%~70%。WUE在季节尺度上无明显的变化规律,在日尺度上具有明显变化规律。WUE与T_(a)和T_(s)具有显著正相关关系,与PAR具有显著二次曲线关系,随PAR的升高而存在拐点,不同设定条件下拐点不同,与VPD表现为显著负相关关系,为评估该地区水分利用情况提供一定的数据支撑。

Characteristics and influencing factors of water use efficiency(WUE)in songshan deciduous broad-leaved forest ecosystem are analyzed based on the flux data from April to October 2019 at songshan Flux Observation station,which certains data support for the assessment of water use in this region. The eddy-covariance (EC) method was used for long-term in-situ monitoring of water flux in Beijing Songshan deciduous broad-leaved forest ecosystem, and the micro-meteorological monitoring system was used for synchronous and continuous observation of environmental factors such as air temperature, soil temperature, photosynthetically active radiation active radiation, precipitation and vapor pressure deficit.Based on flux data and micrometeorological data, the characteristics and influencing factors of water use efficiency in Songshan deciduous broad-leaved forest ecosystem in Beijing were analyzed. The results show that the annual mean value of WUE was 1.68 g C/kg H_(2)O, which reached the maximum value (5-14 g C/kg H_(2)O) at 6:00-8:00 Beijing time, and then decreased to 1-4 g C/kg H_(2)O,which remained stable. The WUE stable value decreased by 30-70% compared with that at sunrise. It is conclued that WUE has no obvious changes on seasonal scale, but has obvious changes on daily scale.WUE has a significant positive correlation with air temperature and soil temperature, a significant quadratic relationship with photosynthetically active radiation,and there is an inflection point with the increase of PAR. The inflection point is different under different setting conditions, and it has a significant negative correlation with vapor pressure deficit.