输水影响下胡杨胸径生长量时空变化

以塔里木河下游14次人工输水对荒漠河岸林修复过程的生态效益评估为长期目标,利用近10 a在塔里木河下游阿拉干断面的大量野外调查数据,探讨了胡杨胸径在不同时间和空间尺度上对人工输水的响应。结果显示,随着输水次数和输水量的稳步增加,河道两边地下水位逐渐抬升,胡杨胸径生长量明显增大；但是,由于不同年间输水次数、输水季节和输水量有差异,各年间胡杨胸径生长量呈现出不同的增加趋势,胸径生长量与河道输水量大小相互对应,累计输水量与胸径生长量成正比,两者之间的指数函数模型拟合度为0.928。随着离河道距离的增加,地下水位抬升不明显,胡杨胸径生长量也逐渐变小,胸径生长量与离河道距离之间的回归模型拟合度为0.965,离河道距离与胸径生长量成反比。离河道距离与不同胸径级胡杨胸径生长量之间的回归模型拟合度(以胸径级增大的趋势)分别为0.876,0.879,0.849和0.837；与胸径级增大的趋势耦合。由此得出,胸径级大的胡杨胸径生长量随离河道距离的变化差异没有比胸径级小的胡杨大,说明胡杨胸径级越大(即胡杨进入老龄阶段),其胸径生长量与地下水埋深之间的关系则不明显。

Spatial-temporal change of DBH of Populus euphratica under artificial water conveyances

In order to assess the benefits of 14 times of ecological water transferring on floodplain forest ecosystems in the lower reaches of the Tarim River, the response of diameter at breast height ( DBH) of Populus euphratica to water transportation project is analyzed based on the long term field survey data obtained in last 10 years at Arghan section. The results showed that, with the increasing amount of transferred water to the lower reaches of Tarim River, the groundwater level around the riverbank has been raised, this result in the obvious increment of the P. euphratica DBH, however, due to the difference of water transferring time and the accumulation of transferred water in different time period, the DBH increment of P. euphratica showed various trend, DBH increment is greater when the accumulated transferred water is larger, the R2 of the exponential model between accumulated water and the DBH increment during each measuring period is 0.928. The regression analysis between the DBH increment and the distance from the river showed that with the increasing distance from the river and the decreasing groundwater level, the DBH increment reduced, the R2 of the regression model is 0. 965. The regression analysis between DBH increment of each DBH class of P. euphratica with the distance from the river showed that P. euphratica within smaller DBH distributed near to the riverbank showed greater DBH increment compared to the one distributed far from the riverbank, while, P. euphratica with bigger DBH increment displayed not obvious correlation with the distance from the river compared to the one with smaller DBH, R2 of the model for each DBH class are 0.876, 0.879, 0.849, 0.837, respectively.