极端干旱区胡杨吸水根系的分布与模拟研究

Distribution of uptake roots of Populus euphratica Oliv in extreme arid region,China

依据2006年7月在极度干旱区内蒙古额济纳旗的实测资料，对胡杨吸水根系根长密度的分布特征进行了分析和拟合，建立了根长密度垂直方向和水平方向的一维、二维分布函数，以期对胡杨根系吸水及胡杨SPAC系统进一步的研究提供有力的试验依据和理论支持。试验结果表明：在垂直方向，吸水根根量主要集中在0～80am的土层内，占吸水根总量的97．60％；在水平方向，0～220am范围内根长密度随距离的增加而逐渐增大；220～400am范围内根长密度随距离的增加而逐渐减小；在0～20am范围内，吸水根系仅占总量的0．47％；在160～220am范围内，吸水根系分布最为密集，占总量的18．57％。统一采用指数函数对胡杨吸水根系根长密度分布函数进行了拟合，拟合函数与实测数据的相关系数平方分别为：0．8884、0．680、0．73和0．685，说明胡杨吸水根系根长密度分布也具有与果树相似的规律，基本符合指数衰减规律。

Populus euphratica Oliv, growing naturally at arid deserts and oases, can endure saline and humid environment and moreover can resist aridity and windstorm. So Populus euphratica Oliv forest is favorable for the balance of the ecosystem in arid deserts and oases, protecting local dwellers and the production of agriculture - stock- breeding. Compared with the research of tree roots and plants root systems in arid region, the researches on the root systems of Populus euphratica Oliv in arid region are especially rare. Calibration of distribution of root systems for plant is very important to establish root water uptake and movement model. And quantification of root distribution also contributes to an improved understanding of chemical fluxes in the vadose zone in both ecological and hydrological studies. So based on the data observed at Ejin Banner, Inner Mongolia, China, in July, 2006, the density distribution of fine roots ofPopulus euphratica Oliv was analyzed and simulated. Both 1-D function （including in vertical and in horizontal direction） and 2-D function of the root length density were established. In vertical direction, most uptake roots distribute soil layer from 0 - 80 cm, which makes up 97.60% of whole uptake roots ; in level direction, the root length density augments with the increase of distance to tree from 0 to 220 cm, while the root length density decreases with the increase of distance to tree from 220 to 400 cm. Fine roots makes up only 0.47% in the tatol, and the distribution of fine root is mostly crowded from 160 to 220 cm, which are 18.57% in the total. All the functions of the root length density were simulated with function of e - exponent, and R2 are 0.8884, （0. 680, 0.73 ） and 0.685, respectively. It shows that the density distribution of fine roots of Populus euphratica Oliv is in accord with the rule of e -exponent. The result is helpful to theoretical research in SPAC （Soil -Plant- Atmosphere Continuum） system of P. euphratica oliv.