环境因子对民勤绿洲荒漠过渡带梭梭人工林蒸散的影响

利用涡度相关系统、土壤水分TDR传感器,于2014年7月—2015年6月连续测定了民勤绿洲荒漠过渡带退化梭梭人工林蒸散量,研究不同天气条件下梭梭人工林的蒸散对外界环境因子的响应.结果表明: 梭梭人工林晴天蒸散量日变化具有明显的季节变化规律.梭梭人工林蒸散量日变化幅度在生长季初期逐渐增大,在生长旺盛期达到最大峰值(0.07 mm·h^-1), 而后逐渐减小,至12月达到最低峰值(0.01 mm·h^-1).不同天气条件下梭梭人工林蒸散日变化波动幅度差异较大,阴天蒸散日变化波动幅度最小,降水后蒸散波动明显增高,强降水(>9 mm·d^-1)后日蒸散量显著增加至雨前的28倍,然后逐渐减少,并持续4个晴朗日后恢复至雨前蒸散量.在整个观测年,梭梭人工林蒸散总量为108 mm,占降水总量的98%,土壤水是梭梭人工林蒸散的水源,为主导因子.净辐射、光合有效辐射、空气温度、水汽压饱和差是决定植被用水和大气边界层水传输的气象动力,为显著影响梭梭人工林蒸散的主要因子.利用日蒸散量与环境因子数据建立了蒸散与土壤含水量和小气候因子的多元回归方程,拟合度(R²)高达0.80.

Effects of environmental factors on evapotranspiration characteristics of Haloxylon ammodendron plantation in the Minqin oasis-desert ectone,Northwest China.

This study continuously measured the evapotranspiration (ET) of degraded Haloxylon ammodendron shrub plantation of Minqin oasis-desert ectone using an eddy covariance system for ET, and TDR for soil moisture profile, analyzing ET in relation to the weather conditions and describing the responses of ET to the microclimate variables in different weather from July 2014 to June 2015. Results showed that the hourly ET dynamics had an apparent seasonal trend in the growing season. This trend gradually increased in the beginning of season from the low level of non-growing season, reached its maximum peak value (0.07 mm·h^-1) in the most physiologically active period, and decreased to the minimum peak value (0.01 mm·h^-1) in December. The diurnal change in ET of the plantation depended on the weather conditions. The ET fluctuated less with a small magnitude in a cloud day, but fluctuated obviously with a greater magnitude after rain if weather was clear. After a strong rainfall (>9 mm·d^-1), ET increased sharply to a high level of 28 folds prior to rain, at which it took four clear days to gradually decease to the pre-rain ET level. The yearly ET over H. ammodendron plantation was 108 mm, equivalent to 98% of annual precipitation. Soil moisture was the water source for ET. Therefore, soil moisture was the dominant factor for theET over the plantation. Net radiation, photosynthesis active radiation, air temperature, and vapor pressure deficit were the microclimate variables to drive the transpiration of vegetation and evaporation over the soil surface, being the major factors forET over the plantation. The regression equation of ET to the dominant factor and major factors had a coefficient of multiple determination (R²) over 0.80.