黄土丘陵沟壑区山地苹果林蒸散特征

以黄土丘陵沟壑区的典型代表米脂为研究区，选取苹果林地生态系统为研究对象，揭示苹果林地的蒸腾蒸发耗散规律及其影响机制，为指导有限水资源条件下苹果产业发展科学布局、优化管理措施及充分挖掘苹果林地的生产潜力提供科学依据.运用热扩散茎流计（TDP）、小型蒸发皿测定了组成苹果林地蒸散的果树蒸腾量和土壤蒸发量，运用水量平衡公式计算了冠层截留量，分析了各气象因子与蒸腾速率的关系，并评估了苹果林地的蒸散量，以期正确认识和评价苹果林地生态水文效应.不同生育期的日均蒸腾速率大小依次为果实膨大期>果实着色期>新梢生长及幼果发育期>萌芽开花期，小时尺度下，不同生育期蒸腾速率到达峰值的时间不同.不同天气条件下，晴天状况下树干蒸腾量明显大于阴天，影响苹果林地蒸腾速率的主要气象因子为太阳辐射和空气温度.果实膨大期及果实着色期为果树耗水的主要时期.降水对蒸腾的影响表现出滞后效应.植被蒸腾量、土壤蒸发量、冠层截留量对蒸散的贡献率由大到小依次为58.9%、26.8%、14.3%.试验期间，降水量大于蒸散量，果园水分收支略有盈余，不同月份土壤水分收支情况不同，应加强萌芽开花期、新梢生长及幼果发育期果园的水分管理. 

Evapotranspiration Characteristics of Apple Forest in Hilly-Gully Region of the Loess Plateau

In this paper, Mizhi County, a typical example of hill-gully region in the Loess Plateau, was selected as the study area to analyze the water balance and evapotranspiration characteristics of apple forestland. The purpose was to understand correctly and evaluate the eco-hydrological effect of apple forest. A thermal dissipation probe (TDP) and micro-lysimeter were used to measure various components of evapotranspiration such as plant transpiration and soil evaporation, and canopy interception was calculated by water balance formula. This study analyzed the relationship between meteorological factors and transpiration rate, evaluated condition of the evapotranspiration of 7-years apple forest. The results show that the average daily transpiration rate in the different growth periods ranked in the order of fruit growth period > fruit coloring stage > new shoots growth and young fruit growth period > germination and flowering period. The time of peak which the transpiration rate reached at different growth stages was different at the hour scale. Under the different weather conditions, the main meteorological factors affecting the transpiration rate of apple forest were solar radiation and air temperature, and the transpiration in sunny days were significantly larger than that of the rainy days. The main periods of water consumption of apple trees were fruit growth period and fruit coloring period. Precipitation shows significant lagging effect on transpiration. The contribution of plant transpiration, soil evaporation and canopy interception to evapotranspiration in the apple forestland ranked in the order of 58.9% > 26.8% > 14.3%, respectively. During the experiment period, the precipitation was more than the evapotranspiration, and the water of apple forest was surplus. The water management of apple forest should be strengthened in germination and flowering period, new shoots growth and young fruit growth periods.