坡向对东祁连山高寒草甸群落物种功能群及其多样性的影响

Effect of Slope Aspect on Species Functional Groups and Species Diversity in Alpine Meadow of the East of Qilian Mountains

为探究祁连山东缘地区不同坡向的高寒草甸群落物种功能群和多样性差异,该研究选择北坡(N坡)、西北坡(NW坡)、西坡(W坡)、东坡(E坡)、东北坡(NE坡)、西南坡(SW坡)和南坡(S坡)7个坡向类型,调查各坡向的植被特征(高度、盖度和频度),测定土壤因子,分析物种均匀度和多样性指数及其相关性等。结果发现:(1)研究区样地共有植物11科18属21种,主要有豆科(4属4种)、菊科(3属3科)、蔷薇科(1属3种)、莎草科(2属2种)、禾本科(2属2种)和蓼科(1属2种);不同坡向的植物科、属数量变化趋势与种相同,均为东北坡、西南坡、北坡(76.19%)>南坡(66.67%)>东坡(61.90%)>西坡、西北坡(19.05%)。(2)不同坡向的草地群落组成不同,其中东坡、南坡和东北坡主要以草本植物为主,西南坡和北坡为草本和灌丛交错区,西坡和西北坡主要以灌丛为主。(3)不同坡向的物种功能群不同,其中东坡、南坡、东北坡、北坡和西南坡的莎草类重要值最高,西坡和西北坡只有豆科和杂类草,且杂类草重要值最高。(4)不同坡向的优势功能群不同,其中:禾本科植物的重要值大小为阴坡(NE坡)>阳坡(S坡和SW坡)>半阳坡(E坡),莎草科植物重要值大小为半阳坡(E坡)>阳坡(S坡)>阴坡(NE坡和N坡),豆科植物重要值大小为阳坡(S坡)>阴坡(N坡、NW坡和NE坡)>半阳坡(E坡)>半阴坡(W坡),杂类草植物重要值大小为半阴坡(W坡)>阴坡(N坡和NE坡)>半阳坡(E坡)>阳坡(SW坡和S坡)。(5)随着坡向梯度变化,物种丰富度和香农-威纳多样性指数变化一致,其大小均表现为:阴坡>阳坡>半阳坡>半阴坡。(6)冗余分析发现,土壤含水量和碳氮比是影响灌丛植物[瑞香(Daphne odora)、金露梅(Potentilla fruticosa)和头花杜鹃(Rhododendron capitatum)]重要值的重要因素。研究表明,不同坡向的土壤水分、养分和光照等的变化显著影响了高寒草甸植物群落物种功能群及其多样性。

To explore the differences of species functional groups and diversity of alpine meadow communities on different slopes in the eastern margin of Qilian,we investigated the characteristics of vegetation(height,coverage and frequency)on seven slopes(north slope,northwest slope,west slope,east slope,northeast slope,southwest slope,and south slope),determined soil factors,species evenness and diversity index and their correlation.The results showed that:(1)There were 21 families,18 genera and 21 species in the study area,mainly Leguminosae(4 genera and 4 species),Compositae(3 genera and 3 species),Rosaceae(1 genus and 3 species),Cyperaceae(2 genera and 2 species),Gramineae(2 genera and 2 species)and Polygonaceae(1 genus and 2 species).The trend of plant families and genera are similar to species in different slopes,all of which are northeast,southwest and north slopes(76.19%)>south slope(66.67%)>east slope(61.90%)>west slope,northwest slope(19.05%).(2)The composition of grassland communities is different in different slopes,among which the east,south and northeast slopes are mainly herbaceous plants,the southwest and north slopes are herbaceous and shrub interlaced plant,and the west and northwest slopes are mainly shrubs plant.(3)The functional groups are different in different slopes.The important values of sedges on the east,south,north,south and southwest slopes are the highest,while the west and north slopes are only legumes and forbs,which has the highest value.(4)There are different dominant functional groups in different slopes.Important values of gramineous plants were as follows:shady slope(northeast slope)>sunny slope(south slope and southwest slope)>semi-sunny slope(east slope);for leguminous plants:sunny slope(south slope)>shady slope(north slope,northwest slope and northeast slope)>semi-sunny slope(east slope)>semi-shady slope(west slope);for forbs:semi-shady slope(west slope)>shady slope(north and northeast slope)>semi-sunny slope(east slope)>sunny slope(southwest slope and south slope).(5)With the change of slope gradient,the change of species richness and the Shannon-Wiener diversity index are consistent,which are represented as:shady slope>sunny slope>semi-sun slope>semi-shady slope.(6)Redundancy analysis showed that soil water content and C∶N are important factors affecting the important values of shrub plants(Daphne odora,Potentilla fruticosa and Rhododendron capitatum).These results suggest that changes in soil moisture,nutrients and light of different slope orientation have significantly affected the species functional groups and their diversity in alpine meadow vegetation communities.