Contrastive Research Of Vegetation On The Southern And Northern Slopes Of Hengshan

Shanxi Hengshan is the threshold between temperate zone prairies and warm temperate zone deciduous broad-leaved forest in the zoning of Chinese vegetation, with its northern and southern slopes belonging to different vegetation zones. Regarding vegetation on both slopes as research object, the article studied their relationships and contractions with the environment, species diversity and niche, etc.As regard to the vegetation's ecological relations, applying TWINSPAN and DCA, the article respectively classified and queued the 65 quadrats with the southern slope and the 73 with the north with a result of 16 and 20 association each, which is confirmed nicely by DCA queuing figures with their first axis standing for elevation temperature and the second for moisture. Analyzing the vegetations of each slope in terms of formation, only four appear on both slopes and with great variability, which show a considerable influence put on their distribution by the factor of water. Also, DCA results show that in the lower elevation, the vegetations are just what they are meant to be according to each vegetation zone, but with the rising of elevation, their types are inclined to be the same.Using richness indices, species diversity indices and evenness indices, the article analyzed the species diversity of vegetations on both slopes, which shows that different community types on the same aspect have considerably different diversity, and the indices go up with the rise of elevation. Comparing their diversity in terms of formation major constructive species, the article found that the same or similar formation have higher diversity indices than their counterparts on the norm with few exceptions due to their unique living environmentUsing Shannon-Wiener niche breadth, the article divided the dominant species on both slopes into 3 ecologic groups, they are: Artemisia brachyloba, Dendranthema chanetii, Carex lanceolate and Sanguisorba alpina on the south, Carex lanceolate, Denfranthema zawwadskii, Poa sphondyloes,Siline jenisseensis and Sanguisorba alpina that occupy a broader niche tfiat spreads. While Potentilla anserine, Spiraea trilobate, Ostryopsis davidiana and Hippophae rbamnoides subsp.sinensis on the south, Stipa bungeana, Puccinellia distans, Artemisia brachyloba, Polygonum viviparuro, Anaphalis hancockii, Spiraea trilobate, Hippophae rhamnoides subsp.sinensis and Populus cathayana etc. occupy a slight iche, which is closely related to their environment.The 16 dominant populations can construct 240 species counterparts, among which 100, that's 41.9% of the total, have niche overlaps, indicating that there exits niche overlap among the 16 species on the south. The 21 dominant populations can construct 420 species counterparts, among which 69, that's 16.4% of the total, have niche overlaps, indicating that there does not exit a apparent niche overlap among the 21 species, but apparent diversification from one another in terms of ecologic niche, and indicating considerable differences as to their utility of recourses. All of above are due to the evenness on the southern slope which on north it is rather stiff, and continuous spreading on the south, while for the north, because of greater variability of elevation, there are often discontinuities which lead to rare niche overlaps.Because of the transformation power of man, the vegetations on both slopes are re-succession ones, and 'are actually processing an reversed evolution, the differences are not apparent as to the comparisons of vegetation divisions of both slopes.