西藏东南部急尖长苞冷杉蒸腾耗水及其驱动因子分析

目的 探讨不同径级急尖长苞冷杉个体蒸腾耗水规律,并分析其与主要气象因子的相关性,为明确西藏亚高山区林木生长规律提供重要参考。方法 应用树干液流测定系统在西藏色季拉山天然急尖长苞冷杉林内对8株不同径级急尖长苞冷杉个体进行蒸腾耗水的连续测定,并同步监测5个气象因子。结果 急尖长苞冷杉树干液流速率日变化为单峰曲线,7月、8月和9月8株样木平均液流速率分别为137.09、142.71和184.43 g/h,日活动时间为10:00—22:00,其峰值出现在16:00左右。急尖长苞冷杉树干蒸腾耗水速率与大气温度和光合有效辐射呈极显著正相关关系,与饱和水汽压差显著正相关,与大气湿度极显著负相关,与风速无关;蒸腾耗水与各因子相关系数绝对值排序为大气湿度>大气温度>光合有效辐射>饱和水汽压差。急尖长苞冷杉边材面积和日蒸腾耗水量均与胸径呈极显著的二次曲线关系,决定系数分别为0.999和0.937。结论 急尖长苞冷杉蒸腾耗水日变化呈“N”形变化,受大气温湿度和光合有效辐射等环境因子影响显著;随胸径增加,单株日蒸腾耗水量迅速升高。

Analyses of transpiration water consumption of Abies georgei var. smithii and its driving factors in southeastern Tibet

【Objective】 The transpiration water consumption of Abies georgei var. smithii individuals with different diameters at breast height (DBH) was studied, and its correlations with meteorological factors were analyzed. This information could provide an important reference for understanding the forest growth rule in the sub-high mountain area of Tibet Autonomous Region. 【Method】 A stem sap flow measurement system was used to measure the transpiration water consumption of A. georgei var. smithii in the Sejila Mountains of southeastern Tibet. Eight individuals of A. georgei var. smithii with different DBH were measured, as well as five meteorological factors. 【Result】 The diurnal variation of the sap flow displayed a single peaked curve on sunny days, and the average stem sap flow rates of the eight samples were 137.09, 142.71 and 184.43 g/h in July, August and September, respectively. The activity period of sap flow was from 10:00 to 22:00, and its peak value occurred at approximately 16:00. The transpiration water consumption per unit sapwood area was significantly positively correlated with air temperature and photosynthetic active radiation, and was positively correlated with saturated vapor pressure difference (VPD), but was negatively correlated with air relative humidity, and had no relation with wind speed. The ranking of correlation coefficients was air relative humidity > air temperature > photosynthetic active radiation > VPD. The DBH was significantly correlated with sapwood area (R ²=0.999) and transpirtation water consumption per day (R²=0.937). 【Conclusion】 The diurnal variation in the transpiration water consumption of A. georgei var. smithii was of “N” type, which was significantly affected by environmental factors, such as air temperature, humidity, and photosynthetic active radiation. The daily transpiration water consumption per plant increased rapidly with the increase in DBH.