水分梯度下黑河流域荒漠植物群落多样性特征

摘要

The responses of species diversity to the large-scale environment represent an important issue in plant ecology.In arid regions,the influence of the unique environmental conditions of inland river basins on species diversity remains uncertain.We examined the characteristics of plant community alpha and beta diversity under different moisture gradients in plant communities of the arid desert of the Heihe basin,Northwest China.The results showed that:(1) the type of desert plant community changed with moisture gradients.The communities which were most distinguished based on important value by increasing precipitation gradients were communities dominated by Haloxylon ammodendron,Nitraria sibirica,Nitraria praevisa,Artemisia desertorum,Kalidium gracile,Salsola passerina,and Kalidium cuspidatum.The communities of Populus euphratica,Tamarix ramosissima,Karelinia caspia,and Reaumuria songarica were distributed along the moisture gradient,with species listed in order of increasing distance of their communities from rivers.(2) The species diversity indexes of desert plant communities were low;the maximum Margalef,Shannon-Wiener,and Simpson values were only 0.985,1.641,and 0.596,respectively.The structure and composition of the studied communities were simple,and the communities were relatively stable.Moreover,monotypic (oligotypic) community types were prevalent.(3) Under the gradient of regional increasing precipitation,α diversity showed a trend towards increasing and then decreasing;there was a high-value area around the community of Salsola passerina (190 mm),but then values decreased rapidly.The Sφrensen index reached a maximum in the communities of Kalidium gracile (166 mm) and Salsola passerina (190 mm),while the Cody index remained relatively small.This suggests that the species richness was highest in the Salsola passerina community (190 mm).The β diversity reached minimum values in the Kalidium gracile (166 mm) and Salsola passerina (190 mm) communities.The species replacement rate was also the lowest in these communities,indicating that these communities were relatively stable.(4) The α diversity showed a trend towards "M" type change with increasing distance from the river,and reached two peaks at around the community of Tamarix ramosissima (1km) and the community of Tamarix ramosissima (4.1 km).There were two smaller Sφrensen index values approximately 1-1.5 km and 4.1-4.8 km,and the Cody index value showed a trend opposite to that of the Sφrensen index.Furthermore,the β diversity values were high,which suggests that these were transitional zones.We concluded that the diversity index based on important value was more applicable in arid desert areas and that the species diversity of the desert plant community showed no linear increase with increasing moisture.These results are important for maintaining and managing the diversity of desert plant communities.%物种多样性对大尺度环境条件的响应是植物生态学的热点问题,干旱区内陆河流域的特殊环境条件如何影响物种多样性仍存在较大的不确定性.以黑河流域荒漠植物群落为对象,探讨了荒漠植物群落α多样性和β多样性对不同水分梯度的响应.结果表明:(1)荒漠植物群落随水分条件不同而变化,在区域降水梯度上,依次分布有梭梭[Haloxylon ammodendron (C.A.Mey.) Bunge]、西伯利亚白刺(Nitraria sibirica Pall.)、毛瓣白刺(Nitraria praevisa Bobr.)、沙蒿(Artemisia desertorum Spreng.)、细枝盐爪爪(Kalidium gracile Fenzl)、珍珠猪毛菜(Salsola passerina Bunge)和尖叶盐爪爪[Kalidium cuspidatum(Ung.Sternb.) Grub.]群落;随距黑河河道距离增加,主要分布有胡杨(Populus euphratica Oliv.)、多枝柽柳(Tamarix ramosissima Lebed.)、花花柴[Karelinia caspia(Pall.) Less.]和红砂[Reaumuria songarica(Pall.)Maxim.]群落.(2)荒漠植物群落物种多样性指数偏低,Margalef指数、Shannon-Weiner指数和Simpson指数最大值仅为0.985、1.641、0.596,群落结构简单,物种组成单一,单寡种优势群落现象极为明显,群落相对稳定.(3)在区域降水梯度上,α多样性指数大致呈先增加后降低的变化趋势,在珍珠猪毛菜群落(190 mm)达到峰值后迅速下降,Sφrensen相似指数在细枝盐爪爪群落(166 mm)与珍珠猪毛菜群落(190 mm)之间达到最大值,Cody指数相对较小,表明珍珠猪毛菜群落(190 mm)物种丰富度最高,细枝盐爪爪群落(166 mm)与珍珠猪毛菜群落(190 mm)之间β多样性最小,物种更替速率最慢,群落处于较稳定阶段.(4)随距黑河河道距离增加,α多样性指数大体呈“M”型变化,在多枝柽柳群落(l km)和多枝柽柳群落(4.1 km)存在两个峰值,此处物种多样性相对较高,Sφrensen指数在1-1.5 km和4.1-4.8 km之间出现两个较小值,Cody指数出现两个峰值,两者之间β多样性最大,为物种更替速率相对较快的过渡地带.对荒漠植被,以重要值为指标计测多样性指数较为可行,荒漠植物群落的物种多样性并不是随水分的增加而直线增加,这对维持和管理荒漠植物群落的多样性具有重要意义.