黑河河岸植被与环境因子间的相互作用

The relationship between riparian vegetation and environmental factors in Heihe River Basin

2009—2010年,对黑河流域河岸植被分季节进行了详细调查,并实地测定各样点环境因子数据,采用PC-ORD和Canoco软件对数据进行分类排序与环境因子的指示种分析:(1)黑河河岸带植被分为4个植被型和6个群系,位于黑河上游的高山苔草+矮嵩草群系植被种类和数量最为丰富,草本层盖度最大,也是唯一没有乔木分布的群系;金露梅+沙棘+膜荚黄芪+针茅群系是灌木层密度和盖度最大的群系,草本植物种类相对较丰富;位于湿地的沙枣+水柏枝+芦苇+香蒲群系,土壤养分含量最高;(2)影响黑河河岸带植被分布的主要环境因子是海拔、降水、温度、土壤有机质、含水率以及全氮含量,其中,海拔、降水和温度为最重要的影响因子,土壤影响因子中土壤含水率>有机质>全氮,而全磷和速效氮没有显著影响;(3)在黑河河岸带共有20种植物是环境因子指示种,柽柳和苦豆子是温度、降水指示种,胡杨对海拔和降水有很强的指示作用,草本植物中没有土壤含水率和海拔指示种,而在乔灌木中没有土壤有机质指示种,这为气候、土壤条件的变化提供了很好的参考价值。

We conducted vegetation surveys in Heihe River Basin during 2009-2010 and analyzed the data（including plant species and environmental information） using PC-ORD and CANOCO.The results showed that the riparian vegetation in the Heihe River Basin could be divided into four types and six forms.Meadow and steppe were predominant vegetation types in the upper reaches;desert was the main type in the middle and lower reaches;and swamp was the primary type in Zhangye wetland.Plant number and species varied significantly among different vegetation forms.Carex alpine＋Kobresia tibetica form located in the upper reaches of the Heihe had the richest species,the highest quantity and herbaceous coverage;Potentilla fruticosa＋Hippophae rhamnoides＋Astragalus membranaceus＋Stipa capillata form had the richest shrub species and highest shrub coverage;Populus euphratica＋Tamarix chinensis＋Sophora alopecuroides in the downstream had the least plant species,the lowest vegetation coverage and soil nutrient content;and Elaeagnus angustifolia＋Myricaria ＋Phragmites australis＋ Typha orientalis in Wetlands had the highest soil nutrient content,although its species richness and quantity were not the highest.The riparian vegetation had more abundant herbaceous species and greater vegetation cover than other regions of the Heihe River.They share the same tree and shrub species,except that in the lower reaches Populus euphratica can only be observed in riparian zones.In CCA ordination,the first ordination axis reflected trends in environment factors such as elevation,precipitation and temperature.The second axis reflected the trend in soil nutrient content.Along Carex alpina＋Kobresia tibetica,Populus alba＋Achnatherum splendens and Populus alba＋Tamarix chinensis＋ Salsola collina＋ Calamagrostis pseudoholophylla forms,elevation and precipitation gradually decreased and temperature increased.Along Populus euphratica＋Tamarix chinensis＋ Sophora alopecuroides,Potentilla fruticosa＋Hippophae rhamnoides＋ Astragalus membranaceus＋Stipa capillata,Carex alpina＋Kobresia tibetica and Elaeagnus angustifolia＋Myricaria＋Phragmites australis＋Typha orientalis forms,soil nutrient content gradually increased.The main environment factors affecting the distribution of Heihe riparian vegetation were elevation,annual precipitation,annual average temperature,soil organic matter,moisture content and nitrogen content.Elevation,precipitation and temperature were the most important factors,followed by soil moisture content,soil organic matter and total nitrogen.Total phosphorus and available nitrogen did not show significant effect.In different regions,soil factors were different.We found 20 indicator species in the basin.Sophora alopecuroides and Salix purpurea were good temperature and precipitation indicator species;Populus euphratica was a good elevation and precipitation indicator species.There were no herb indicator species for soil moisture and elevation,no tree and shrub indicator species for soil organic matter.All the indicator species for soil organic matter were herbs,which located in wetlands of Zhangye.The indicator species for elevation,precipitation and temperature were mostly found in the low rainfall,low altitude and high temperature areas.Indicator species of riparian plants could reflect river ecological environment.The same as indicator species of aquatic organisms,they provided a good reference in the studies of changes in climate and soil conditions,and could be used as indicators of 3 or 4 ecological division of Heihe River Basin in further study.