[目的]分析不同时间尺度下不同林龄苹果林蒸腾量与环境因子的关系,建立蒸腾量与环境因子的关系模型,研究蒸腾量、降水量、土壤储水量之间的关系以及不同林龄苹果林蒸腾占蒸散的比例,为果树生长重要时期提出减少土壤蒸发、控制果树蒸腾和提高果树水分利用效率的方法提供参考.[方法]在黄土高原沟壑区的典型代表长武塬,选取10龄和20龄苹果林生态系统为研究对象,用热扩散探针法对2015年苹果树生长季日、月尺度下苹果树干液流速率进行连续监测,用位于距样地50 m处的自动气象观测站连续监测获取气象数据,同时进行土壤水分含量以及土壤蒸发量的测定.[结果]1)日尺度下,苹果林蒸腾与空气温度和水汽压差均呈现正相关关系,但当VPD＞1 kPa时,2个林龄的苹果林日蒸腾量均有所下降;月尺度下,与蒸腾相关的环境因子仍为空气温度和水汽压差.2)在月尺度下,按土壤储存与消耗的水量可以将试验期分为3个时期:土壤水分迅速耗水期(5-7月)、土壤水分平稳期(8月)、土壤水分缓慢消耗期(9-10月).10龄苹果林蒸腾耗水主要集中在0～ 300 cm土层,而20龄苹果林蒸腾所需水分来源于0～ 600 cm土层,在极度缺水的7月份,300～600 cm土层的贡献更多.3)20龄苹果林Tr/ET为29.25％～67.51％,10龄苹果林Tr/ET为36.44％～ 62.06％,2个林龄的Tr/ET整体表现为先升高后降低.20龄苹果林Tr/ET在8月达到峰值后急剧下降,而10龄苹果林经过1个缓慢下降的过渡期后,从9月份开始急剧下降.[结论]随着时间尺度的增大,进入蒸腾量与环境因子回归方程的环境因子个数减少且水汽压差在日、月尺度下均为不同林龄苹果林蒸腾的主导因子.10龄苹果林蒸腾耗水主要集中在0～300 cm土层,而20龄苹果林蒸腾所需水分来源于0～600 cm土层,在极度缺水的7月份,300～600 cm土层的贡献更多.8月下旬之后,应对20龄苹果林采取适当的保墒措施以减少土壤蒸发,但对10龄苹果林而言,相应的保墒措施可以在9月份之后进行,以期为翌年苹果树健康生长提供优质的土壤水分条件.%[Objective] This study investigated the characteristics of transpiration and the Tr/ET of the apple forests,and analyzed the relationship between transpiration of apple trees and environmental factors under different time scales,to provide a scientific basis for reducing the soil evaporation,controlling the transpiration and improving the efficiency of water use.[Method] This study was conducted in the Changwu Tableland,a typical representation of the Loess Plateau region.The thermal diffusion probe method was used to measure the sap flow of apple trees in 20a and 10a apple forests in 2015 at daily and monthly scales,and meteorological data were collected in an automatic meteorological observation station located at 50 m from the experimental plot,and at the same time,the soil moisture content and soil evaporation were determined.[Result] 1) On the day scale,there was a positive significant correlation between the transpiration of apple forests and air temperature (Ta) and VPD.However,the daily transpiration of the two apple forests declined when VPD ＞ 1 kPa.The monthly transpiration was also significantly correlated to air temperature (Ta) and VPD.2) On the month scale,the experiment can be divided into three periods according to the soil water storage and consumption:the rapid soil moisture consumption period (May-Jul.),the soil moisture stable period (Aug.) and the slow soil moisture consumption period (Sep.-Oct.).Water consumption by transpiration of the 10-year-old apple forest mainly came from the soil layers of 0-300 cm,while the water consumption of the 20-year-old apple forest came from 0-600 cm.In the extremely dry month (Jul.),the water mainly came from the soil layers of 300-600 cm.3) The Tr/ET of the 20-year-old apple forest was 29.25-67.51％ and that of the 10-year-old apple forest was 36.44-62.06％.The Tr/ET of the different age apple forests showed the trend that increased first and then decreased.The Tr/ET of 20-year-old apple forest declined sharply after reaching a peak in August,while the 10-year-old apple forest declined sharply in September after a transition period.[Conclusion] With the increase of time scales,the number of environmental factors associated with the sap flow velocity was gradually reduced,but VPD was the dominant factor at each time scale.The water source of transpiration of the 10-year-old apple tree was mainly concentrated in the 0-300 cm soil layers,while that of the 20-year-old apple tree was from the 0-600 cm soil layers.In the extreme water deficit July,the more water came from 300-600 cm soil layers in the 20-year-old apple forest.After the end of August,some appropriate conservation measures on soil moisture should be taken to reduce evaporation for the 20-year-old apple forest,while the corresponding measures can be carried out in September for the 10-year-old forest.Those measures would provide a relatively sufficient soil moisture for healthy growth of apple trees in the next year.
展开▼
