Abstract: South Lüliang Mountains of Shanxi is located in the ecotone between south and north warm temperate deciduous broad-leaved forest subzones, according to the China’s vegetation regionalization. By the methods of TWINSPAN and DCCA, this paper studied the ecological gradients of the plant communities in South Lüliang Mountains, in terms of the interactions between plant species and communities and environmental factors. Based on TWINSPAN, 74 quadrats were classified into 18 associations, in which, 4 associations were forest communities, and 14 associations were shrubs. These 18 associations, all in the criteria of secondary vegetation types in south warm temperate zone, represented the major plant communities in South Lüliang Mountains. Field survey also showed that the 18 associations had been subject to anthropogenic disturbances. DCCA ordination of the plots satisfactorily revealed the relationships between the distribution patterns of the plant communities and the environmental components (altitude, slop degree, soil layer depth, litter layer thickness, slope aspect, and human disturbance). The dominant factors controlling the distribution patterns of the plant communities were altitude and human activities, while slope aspect and soil layer depth also had effects on the community characteristics. There existed significant correlations among altitude, human disturbance, and litter layer thickness, which were identified as the dominant factors affecting the community distribution. The integration of the results from TWINSPAN and DCCA analyses clearly showed the vertical distribution of the plant communities in the study area. At the low hills and valleys with an elevation of 690-1 100 m, the dominant plants were Vitex negundo var. heterophylla and Zizinhus jujuba var. spinosa; at the southern and semi-southern slopes with an elevation of 1100-1300 m, mainly distributed Quercus baronii and less distributed Platycladus orientalis and Carpinus turczaniowii; and at the elevation of 1 300-1 570 m, the major communities were the forests dominated by Quercus wutaishanica. The distribution of Q. baronii was the main sign of the ecotone between south and north warm temperate deciduous broad-leaved forest subzones in this area.

Key words: Marine culture, Self-pollution, Red tide, Yellow Sea, Bohai Sea, Eutrophication