• 研究报告 •

### 六盘山南侧不同坡位华北落叶松人工林树干液流特征及其环境影响因子

1. 1内蒙古自治区林业科学研究院， 呼和浩特 010010；2中国林业科学研究院森林生态环境与保护研究所， 北京 100091；3宁夏六盘山森林生态系统定位观测研究站， 宁夏固原 756000）
• 出版日期:2018-07-10 发布日期:2018-07-10

### Sap flow characteristics of Larix principis -rupprechtiiplantation and its impact factors in different slope locations at the south side of Liupan Mountains.

WANG Yun-ni1,2,3, CAO Gong-xiang1, 2, WANG Yan-hui2,3, XU Li-hong2,3, LIU Yong-hong1, WANG Xiao-jiang1*

1. (1InnerMongolia Academy of Forestry, Hohhot 010010, China; 2Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China; 3NingxiaLiupan Mountains Forest Ecosystem Research Station, Guyuan 756000, Ningxia, China).
• Online:2018-07-10 Published:2018-07-10

Abstract: To accurately estimate whole slope-scale or watershedscale forest transpiration from sap flow measurements at plot scale, especially in semi-humid areas with significant spatial variation in environmental factors, it is necessary to examine differences in sap flow at different slope locations and the driving factors. Based on a field study in five larch (Larix principis-rupprechtii) plantation plots established respectively at the upper (P1), middle upper (P2), middle (P3), middle lower (P4) and lower (P5) positions in a southeastfacing slope in Xiangshuihe watershed in the semi-humid region of Liupan Mountains of Ningxia, the sap flow velocity in trees as well as the soil water potential and meteorological factors were simultaneously monitored. During the study period, significant differences among slope positions were found in the daily average sap flow velocity (Js, mL·cm-2·min-1), with an order of P2 (0.0397)>P4 (0.0368)>P3 (0.0325)>P5 (0.0311)>P1 (0.0278). The Js was significantly correlated with the maximum air temperature (Tmax), solar radiation intensity (SR), water vapor pressure deficit (VPD), potential evapotranspiration (PET), soil water potential (Ψ), volumetric soil water content (VSM), but was negatively correlated with minimum air temperature (Tmin), air relative humidity (RH) and precipitation (P). The correlation coefficients were significantly different among different slope positions. There were significant differences in the degree of Js responses to environmental factors among slope positions. Decreasing trends in the response of Js to the daily average air temperature (T), RH, VPD, PET and Ψ  were found by the envelope line analysis with the decreasing slope position. In contrast, increasing trends in the response of Js to the SR and daily average volumetric soil water content (VSM) were observed. Results from regression analysis and partial correlation analysis showed that variations of Js in different slope positions were mainly controlled by PETand VPD. The Js at the upper slope positions was strongly influenced by Ψ and Tmax, while that at the lower slope positions was largely affected by SR and VSM. In general, the slopedifference in Js was caused by soil moisture and meteorological factors. Therefore, it is needed to consider jointly the changes of soil moisture and meteorological factors among the slope positions when we estimate the stand transpiration at the slope scale or watershed scale by upscaling the Js.