作 者 ：吴彦,V. G. Onipchenko
期 刊 ：生态学报 2007年 27卷 12期 页码：5120~5129
关键词：青藏高原东缘；雪被；坡向性；植物群落；土壤特性；高山生态；雪被生态；
Keywords:eastern edge of Qinghai-Tibet Plateau, snow-cover, aspect, plant community, soil characteristics, alpine ecology, snow ecology,
摘 要 ：在青藏高原东缘的松潘地区海拔4000 m的高山地带设置5条宽1m、长40~70m的跨山脊南北样带，相邻样带间距为50 m。按1m×1 m面积划分为251个调查样方，于2004~2005年分别进行了地植物学调查、土壤理化性质分析和冬季雪被厚度监测。以物种的相对频度为群落指标，以雪被厚度、土壤厚度、有机质含量、土壤湿度（0.25mm及2mm）、全磷、全钾、铵态氮、水解性酸、pH及坡度等参数为环境指标，运用PC-ORD软件的TWINSPAN对植物群落进行分类、CCA进行排序。结果表明，由南坡向北坡可以划分为亚菊——金露梅高山灌丛草甸、细柄茅——苔草高山草甸、细柄茅、苔草——矮柳高山灌丛草甸群落和杜鹃高山灌丛群落等4种群落类型。由南坡向北坡草本植物盖度由75%下降为39%，灌木盖度由25%增加到54%，在山脊附近50 m左右的局地范围内植被类型表现为明显的南北坡向分异格局。2005年冬季南坡平均雪厚度21cm，山脊处为26 cm，北坡34 cm，由南坡向北坡雪被厚度逐渐增加；雪被厚度与灌木盖度呈正相关（r=+0.40，p<0.01，n=248），与草本植物盖度呈负相关（r=-0.45，p<0.01，n=248）。ANOVA的分析结果显示，土层厚度、风干土含水量、土壤酸度、有机质含量和全磷含量的南北坡向分异明显，由南坡向北坡逐渐增加，与雪被平均厚度存在显著的相关关系，相关系数分别为0.267、0.286、0.199和-0.183 （n=119，p < 0.05）；土壤全钾和铵态氮含量的坡向差异不明显，与雪被厚度的相关性也不显著，相关系数分别为-0068和0.104（n=119，p>0.05）。显示土壤特征的坡向分异规律在某种程度上与雪被的梯度变化存在着共轭关系。群落CCA排序及排序轴与环境指标的相关性分析也表明，坡度、雪被厚度、有机质含量和土壤湿度是导致植物群落坡向分异的主要环境因子，土壤铵态氮和全钾含量对植被坡向分异的影响不明显。
Abstract:Five parallel transects (1m×40m-1m×70m) placed 50m apart, were sampled at the altitude of 4000m from south-slope to north-slope in Songpan county which lies in the eastern edge of the Qinghai-Tibet Plateau. During 2004-2005, all 251 quadrats (1m×1m) were investigated in terms of plant community composition, physicochemical characteristics of soil, and depth of winter snow-cover. The functional module TWINSPAN of software PC-ORD was used to classify the plant communities, based on relative frequency as the community index, and an environmental index comprising depths of snow-cover, soil and organic matter, soil moisture (0.25mm and 2mm）, total P, total K, NH+4-N, hydrolytic acid, pH, slope etc.. CCA was then used to classify plant communities. The results show four community types from south-slope to north-slope: Potentilla -Ajania alpine shrub meadow, Ptilagrostis-Carex alpine meadow, Salix-Carex-Ptilagrostis alpine shrub meadow, and Rhododendron alpine shrub. From south-slope to north-slope, herb cover decreased from 75% to 39%, and shrub cover increased from 25% to 54%. And around the mountain ridge (about 50m) the type of vegetation in south-slope and north-slope shows significant differences. In the winter of 2005, the average snow depth on the south-slope was 21cm, compared to 26cm on the mountain ridge and 34cm on the north-slope. Snow depth was positively correlated with shrub cover (r =+0.40, p<0.01, n=248), but negatively correlated with herb cover (r=-0.45, p<0.01, n=248). ANOVA indicated that soil depth, soil moisture, pH, soil organic matter and total P differed between north and south slopes, tending to increase from south-slope to north-slope, and significantly correlated with the average snow depth (r=0267, 0.286, 0.199 and -0.183, respectively, p<0.05, n=119); soil total K and NH+4-N showed no significant differences with aspect, and no significant correlation with average snow depth (r=-0.068 and 0.104, respectively; p>0.05, n=119). This suggests a complex interaction between aspect, snow depth, and a variety of soil characteristics. The CCA order of community, as well as the correlation analysis of compositor axis and environment index also showed that slope, snow-cover thickness, soil organic matter and soil moisture were the primary factors that induced the different plant community types in south-slope and north-slope, while the impact of soil NH+4-N and total K were not significant.
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