黄土丘陵区两典型造林树种生长季树干直径微变化动态及其影响因素

运用DC3型高分辨率树干直径变化记录仪和Granier热扩散探针,对黄土丘陵地区两典型树种辽东栎和刺槐生长季的树干直径微变化和树干液流动态进行连续监测,并同步观测主要环境因子(土壤含水量、太阳辐射、空气温度和相对湿度),分析两树种树干的直径微变化动态特征与蒸腾耗水的关联性及其对环境因子的响应。结果表明: 两树种树干直径和液流通量密度呈现明显的昼夜变化规律,直径日最大收缩量与日均液流通量密度呈显著正相关,树干直径在日尺度上的微变化受当日蒸腾耗水量的影响。对树干直径日最大收缩量和蒸腾驱动因子进行线性拟合,结果显示,树干直径日变化量与主要气象环境因子(日均太阳辐射、日均空气水汽压亏缺、整合变量VT)呈显著正相关。回归曲线斜率表明,辽东栎树干直径日变化量大于刺槐,其直径对气象环境因子的敏感度更大。两树种液流通量密度在较高土壤水分时段高于土壤含水量较低时段,在不同土壤水分条件下辽东栎树干直径日最大收缩量差异显著,刺槐未达到显著水平,这些差异可能与两树种蒸腾调节和树干水分补充等用水策略有关。

Dynamics and influencing factors of stem diameter micro-variations during the growing season in two typical forestation species in the loess hilly region,China.

Using DC3 high-resolution dendrometer and Granier-type thermal dissipation probes, we measured stem diameter micro-variations and xylem sap flow of two typical forestation species, Quercus liaotungensis and Robinia pseudoacacia, for a growing season in the loess hilly region of China. The main environmental factors (soil water content, solar radiation, air temperature and relative humidity) were monitored. The linkage between diameter micro-variations and transpiration water use were analyzed with respect to their responses to environmental factors. The results showed that the variations in stem diameter and sap flux density of both species had obvious diurnal rhythms. The maximum daily shrinkage was positively correlated with daily sap flux density. The micro-variation of stem diameter at the daily scale was affected by transpiration during the day. The maximum daily shrinkage of stem diameter was positively correlated and well fitted with transpiration driving factors (solar radiation, vapor pressure deficit, and the integrated variable VT). The difference in slopes of regression curves suggested that the daily variation of stem diameter in Q. liaotungensis was greater and more sensitive to meteorological factors than that in R. pseudoacacia. The sap flux densities of both tree species were higher during the period with relatively higher soil water content than that with lower soil water content. The difference of maximum daily diameter shrinkage between different soil water conditions was statistically significant in Q. liaotungensis, but not in R. pseudoacacia. These differences may be related to water use strategies, including transpiration regulation and stem water replenishment.