Studied On Site Classification Of Eucalyptus. Grandis Plantation In Sichuan

Eucalyptus, grandis is one of the main planting eucalyptus in Sichuan. In most introduction area, Eucalyptus, grandis demonstrates good adaptability and economic properties. But in different districts, the Eucalyptus.grandis' growth has great differences. So it's necessary for the Eucalyptus.grandis plantation in the main introduction area to study on the site conditions and carry on a site classification, in the hope of finding out the inner link of the Eucalyptus.grandis plantation and it's site conditions, in order to make reasonable management practices which is fit for different site conditions, and improve the Eucalyptus.grandis plantation productivity, then lay the foundation for the Eucalyptus.grandis plantation's integrated development.According to Eucalyptus.grandis distribution situation in Sichuan , 88 piece of standard fields were surveyed by using sample-typical survey in the Eucalyptus.grandis plantation of the main introduction areas in Sichuan, and every kind of site factors were investigated. Based on the principle of leading factors which were on the foundation of synthetical analysis, the leading factors were analyzed and site types were classified by using principle component analysis method and cluster analysis method. The system of site classification was: site area, site region, site sub-region, site type district, group of site type, site type. Site area, site region, site sub-region were advanced regional division units, and linked up with China forestry regional division system. Site type district, group of site type, site type were site classification units, and they were classified by the leading factors of different units.The classification of site type districts the physiognomy of major introduction area was hill, and among hills, there were many small plains. The distribution of water and heat condition was different both kind of physiognomy. So the major introduction area could be classified as hill site type district and plain site type district. In both site type districts, site factors were analyzed by using principle component analysis method, and slope gradient, slope position, soil depth, gravel content, organic matter, total P, available K were chose as leading factors of hill site type districts, and soil texture, soil depth, organic matter, total N,total K, available K were chose as the leading factors of plain site type districts.The classification of group of site types: in each site type district, the leading factors which influenced the reallocation of water and heat condition were different. According to the result of principle component analysis, using slope gradient, slope position as the leading factors of hill site type districts, using soil texture as leading factors of plain soil texture, these two site type districts could be divided into 7 group of site types.The classification of site types: in each group of site type, 17 site types were classified based on the soil's physical and chemical properties of leading factors by using cluster analysis.By using site index, these 17 site types were divided into 3 type of productivity grades: the first grade's site index was 22~24, the second grade's site index was 16~20,the third grade's site index was under 16. Then, through the analysis of typical site types in each productivity grade, proposed that some management practices must be done in Eucalyptus.grandis plantation such as developing vegetations under plantation or constructing mixed plantation, etc, to prevent soil degradation. However, for the worst condition site, the aim of plantation management should be rebuilt the ecosystem or boosted up the stability. Utilizing the function of improving site quantity of plantation and vegetation, and combining with some management practices such as fertilization to increase the input of site, a stable plantation ecosystem should be rebuilt.