塔里木河中游荒漠河岸林物种多样性对地下水埋深变化的响应

于塔里木河中游地区选取30个样地,并采集相应地区30眼地下水位监测井的数据。根据监测井的地下水位检测数据,将地下水位按不同埋藏深度划分为0~2 m、2~4 m、4~6 m、6~8 m、8~10 m、>10 m共6个梯度,对不同地下水埋深下的样地群落盖度、物种多样性进行分析,以探讨主要植物分布频率与地下水埋深的关系,明确塔里木河中游地区荒漠河岸林植被的合理生态水位,为塔里木河中游地区乃至全流域的生态系统恢复提供依据。结果显示:（1）塔里木河中游地区共出现植物15种,其优势种植物为胡杨。（2）随着地下水位的降低,植被的盖度逐渐减小;当地下水位介于2~4 m时,植被的盖度平均为39.14%,当地下水埋深介于6~8 m时,植被的覆盖度小于20%;当地下水位低于10 m时,植被的平均覆盖度仅为7.65%。（3）随着地下水位的降低,研究区内的各类物种多样性指数均呈先增加后降低的趋势,一般在地下水埋深2~4 m时物种的多样性最高,其次为4~6 m和0~2 m;当地下水位在6 m以下时,物种的多样性锐减,地下水位低于10 m时,物种仅存柽柳和胡杨,多样性降至很小。（4） 塔里木河中游地区植物所要求的地下水平均深度为:胡杨4.58 m、柽柳3.53 m、芦苇2.34 m、骆驼刺4.10 m、花花柴3.18 m、黑刺2.98 m,只有芦苇适宜较浅的地下水埋深（≤2.5 m）,其余的均宜在3~4 m左右。研究表明,在塔里木河中游地区,最适宜植物生长的地下水位为2~4 m,能够保证植物正常生长的合理地下水埋深区间为2~6 m。因此,要使塔里木河中游地区的植被得到恢复并确保其正常生长,区域内的地下水位应确保在6 m以上。

Response of the Species Diversity of Desert Riparian Forest to the Changes of Groundwater Depth in Middle Reaches of Tarim River

In this study,we collected the data from 30 plots and 30 groundwater level monitoring wells in the middle reaches of Tarim River.According to the data from monitoring wells,we divided the groundwater levels into 6 gradients:0~2 m,2~4 m,4~6 m,6~8 m,8~10 m,>10 m.Then we analyse the coverage of vegetation and biodiversity at different groundwater levels,in order to investigate the relationship between the frequency of plants distribution and groundwater level,as well as to determine the reasonable ecological water level of the desert riparian forest in middle reaches of Tarim basin,and to provide a basis to ecosystem restoration in middle reaches even the whole basin-wide of Tarim basin.The result shows that:(1)There are 15 species in middle reaches of Tarim basin and the dominant species is Populus euphratica.(2)With the reduction of groundwater depth,the coverage of vegetation decreases gradually;As the groundwater level between 2~4 m,the average coverage is 39.14%;When the groundwater level between 6~8 m,the coverage of vegetation is less than 20%;The coverage is only 7.65% when groundwater level less than 10 m.(3)Along with the lowering of groundwater level,the changing trend of species diversity is increased firstly,and then decreased;The species diversity is maximum when groundwater level between 2~4 m,followed by 4~6 m and 0~2 m;When groundwater depth under 6 m,the species diversity decreases rapidly.The species diversity is precious little when groundwater level under 10 m,only P.euphratica and Tamarix chinensis still remaining.(4)Average depth of groundwater level for the species in middle reaches of Tarim river are:P.euphratica 4.58 m,T.chinensis 3.53 m,P.communis 2.34 m,Alhagi sparsifolia 4.10 m,Karelinia caspica 3.18 m,Lycium ruthenicum 2.98 m;P.communis can be suitable for the shallow level of groundwater only,the suitable water level of the rest is about 3~4 m.In summary,in the middle reaches of Tarim River,the most suitable groundwater level to the growth of plants is 2~4 m and the reasonable groundwater level to ensure the normal growth of plants is 2~6 m.It indicates that the groundwater level should be above 6 m in order to ensure the restoration of vegetation and the normal growth as well.