岷江上游祁连山圆柏群落结构研究

应用样方调查方法，对祁连山圆柏群落外貌和结构进行研究.结果表明，该群落生活型谱中以地面芽植物为主，但一年生植物也占有较大比率，具有一些温带植物群落特征.该群落垂直结构简单，只有乔、灌、草3层，无层间植物及地被层.乔木层只有祁连山圆柏1种；灌木层以高山绣线菊的重要值最大，为153.3；草本层以丛生苔草重要值最大，达到36.8.在不同坡度样地中，大坡度样地上具有相对较多的幼苗和幼树，而低坡度样地有刺灌木和适口性差的草本较多，这主要是由于坡度不同导致样地上放牧强度不同造成的.由年龄结构和高度结构的分析可以看出，祁连山圆柏种群总体上为衰退种群，如果任由放牧等干扰继续下去，群落将向灌丛草甸方向演替.群落上层盖度对下层盖度影响较大，且各层盖度大小与其多样性之间没有必然联系.

Sabina przewalskii community structure in the upper reaches of Minjiang River

In this paper,the physiognomy and the structure of Sabina przewalskii community were studied by sample plot method.The results showed that in the life spectrum of the community,hemicryptophyte was dominated,but therophytes also occurred frequently,which presented some features of temperate vegetation.The vertical structure of the community was quite simple,consisting of tree layer,shrub layer and herb layer,and there were no interstratum plants and ground layer.Sabina przewalskii was the only species in the tree layer.In fruticose stratum,the important value of Spiraea alpina was 153.3,ranking the first; while in herb layer,the important value of Carex caespifosa ranked the first,amounting to 36.8.Among the three plot groups on different slopes,spiny-shrubs such as Berberis wilsonae and Caragana erinacea grown on small slope were more than those on bigger slope,so did unpalatable grasses such as Pedicularis axillaries and Artemisia tauguticat,which mainly owed to retrogressive succession caused by frequently grazing.The age and height structures of Sabina przewalskii population indicated a declining trend,and the community would develop retrogressively if disturbances (e.g.,grazing) could not be reduced.The disturbance caused by livestock was more obvious in the plot group on small slope than on bigger slope,and livestock mainly destroyed seedlings and small trees,which made tree population be impossible to regenerate.The coverage of upper layers had a notable impact on the lower layers,and there wasn't any correlation between coverage and diversity index (Shannon-Wiener Index) in each layer.