基于8hm2样地的天山云杉林蒸腾耗水从单株到林分的转换

为准确地估算天山北坡中部雪岭云杉森林的林分蒸腾耗水量，本研究设置了8hm2固定样地，在每木调查的基础上，通过对7株标准木连续晴天液流的观测，分别得到胸径与液流速率和边材面积的拟合方程，最终计算得到了林分的蒸腾耗水量，确定了估算该森林群落蒸腾耗水的最小取样面积，并且讨论了最小取样面积随样地位置的变化。结果表明：①在自然生长系，雪岭云杉林分最大蒸腾耗水量、平均蒸腾耗水量同植株密度呈Extrem函数分布；当种植密度达到1200株/hm2时，林分最大蒸腾耗水量达到最大，为77.27 t/hm2d；②对林分蒸腾耗水量的测算存在明显的最小取样面积，最小取样面积随取样点的不同而略有差异，取样起始点在本样地的海拔上边界和下边界处时最小取样面积为4 hm2，取样起始点在本样地的中部时最小取样面积为2.56hm2。本研究为更精确地估算天山北坡雪岭云杉森林的蒸腾耗水量提供了理论依据。

Scaling up for transpiration of Pinaceae schrenkiana stands based on 8hm2 permanent plots in Tianshan Mountains

An 8 hm2 Picea Schrenkiana forest permanent plot was established in the northern slope of Tianshan Mountains. Severn individuals of Picea Schrenkiana were chosen in the plot to detect changes of the transpiration by measuring the sap flow velocity (SFV). The quadratic model was used to analyze the relationship between diameter at breast height (DBH) and SFV, while the power model was used to analyze the relationship between DBH and sap wood area. Based on the two models, we calculated the transpiration of the plot, and detected the minimum sampling area of the transpiration. We found that highest transpiration and mean transpiration of the forest are closely related to stand density, which can be fit well in the Extrem function. The maximal transpiration is about 77.27 t/hm2d when stand density increases to 1200 per hm2. In addition, the transpiration of the forest showed significantly positive relationships with sampling size. The sampling size also varies with spatial location of sampling points. The sampling size is about 4 hm2 in the highest and lowest altitude of the plot, and about 2.56 hm2 in the middle altitude.