Comparison Of Forest Stand Growth, Plant Diversity And Soil Fertility In Different Models To Combat Rocky Desertification

Guangxi province is geographically a typical karst area.The entire mountainous Karst area is 97 700 km~2,accounting for 41%of the total area.Most of the Karst area is located in Mashan Desertification region.The region has a fragile ecological environment,which resulted in frequent human disturbance,land degradation and serious rocky desertification.The ecological environment severely restricts the sustainable development of local economy and exacerbates poverty.This study is based on the artificial afforestation result of Dalbergia odorifera pure forest,Acrocarpus fraxinifolius pure forest and Dalbergia odorifera + Acrocarpus fraxinifolius mingled forest in Mashan region's rocky desertification area.Data obtained from diverse plants of different types of forest,the diversity index of understory plants and the changes of soil fertility were researched and analyzed.Ecological function recovery rate and effect of different rocky desertification control mode were discussed and evaluated for providing theoretical basis for the comprehensive treatment of rocky desertifica-tion in our region.The main findings are as following:(1)There are some differences in survival rate and survival rate of different tree species and different forestt types.The survival rate of Dalbergia odorifera,acrocarpus fraxinifolius low mixed is beneficial to improve the survival rate and preservation rate.(2)The average diameter at breast height and tree height of different tree species and different management modes increased with the increase of the age.In the 4-year stand,annual average diameter breast height and tree height growth of Acrocarpus fraxinifolius pure forest were 1.73cm and 1.87m,corresponding to Dalbergia odorifera pure forest were 1.26cm and 1.33m;in the mingled forest,annual average diameter breast height and tree height growth of Acrocarpus fraxinifolius pure forest were 1.81cm and 2.07m,corresponding to Dalbergia odorifera pure forest were 1.15cm and 1.39m.Acrocarpus fraxinifolius grew better in the mixed forest.(3)Different governance modes have significant effects on the composition and diversity of the plant community.In rocky desertification area,the species diversity index and evenness index of community could be improved significantly,but the individual number of community was significantly decreased.Artificial afforestation will also change the dominant species of shrub layer and herb layer,and increase the risk of invasive alien species.(4)Different governance modes have some improvement on the soil fertility of forest land,especially,the improvement of soil surface layer(0?20cm)was more obvious.The effect of Dalbergia odorifera on soil fertility was better than Acrocarpus fraxinifolius.(5)Using Dalbergia odorifera and Acrocarpus fraxinifolius to control rocky desertification can not only restore the forest landscape,but also improve the ecological function of rocky desertification ecosystem,and it can bring good economic benefits.It is suggested that this technology is vigorously promoted in the South Asian tropical rocky desertification area of Guangxi.Especially,building Dalbergia odorifera + Acrocarpus fraxinifolius mingled forest is better.