基于同位素技术分析不同生长季节杨树水分利用

Water use strategy of poplar(Populus alba) in different growing seasons based on isotopic analysis

本文利用碳、氢、氧同位素示踪技术,将直接判断法、多元线性混合模型相结合,分析正蓝旗地区杨树不同季节的吸水来源和水分利用效率。结果表明:杨树吸水来源具有明显季节性规律,生长前期和末期(4、5、10月),主要利用0~50 cm浅层土壤水和150 cm以下的深层土壤水或地下水;生长中期(6、7、8、9月)主要利用0~150 cm土壤中的降水水源。该地区杨树的水分利用效率较高,5—9月水分利用效率为208.68、133.90、62.01、61.92、257.55 mmol C·mol-1H2O。当雨季浅层土壤水无法满足杨树的需水量时,杨树吸收较深层的土壤水,并逐渐提高水分利用效率;有降水时,杨树开始从最上层的土壤水中吸收降雨水源并逐渐降低水分利用效率。以上结果表明,半干旱地区杨树具有较高的水分利用效率,同时可以调节自身吸水来源和用水效率,朝着最有利于生长发展的方向最大程度上利用水分。

Carbon, hydrogen and oxygen isotope tracer techniques were used to analyze theseasonal dynamics of water sources and water use efficiency of poplar （Populus alba） in Zhenglanqi, with direct judgment method and multivariate mixed linear model. The results showed that there was obviously seasonal dynamics in poplar’s water sources. In early and late stages of growing season （April-May, October）, poplar used both shallow soil water （0-50 cm） and deep soil water or underground water under 150 cm. In middle stage of growing season （June to September）, poplar primarily used precipitation which infiltrated to 0 to 150 cm soil. Water use efficiency of poplar was relatively higher, with 35.90, 13.90, 20.65, 28.93 and 63.88 mmol C·mol-1 H2O from May to September, respectively. Poplar could use deep soil water and increase water use efficiency when shallow soil water could not satisfy its water requirement in rainy season. When there was enough precipitation, poplar use soil water from the top layer, and water use efficiency decreased gradually as well. These results indicated that poplar had higher water use efficiency due to its ability to use alternative water sources and controlling its water use rate in semiarid area. These strategies assist poplar to reach the greatest water use efficiency favoring their growth.