Abstract: This paper focuses on fertility change in paddy soil, green house soils under framed plastic cover, and compares with salt-affected soils. In coastal areas the salt-affected soil were used for paddy,rice pig bring-up and manure collection marsh gas(CH₄) production and vegetable plantation in green house condition. The comprehensive evaluation, with fuzzy evaluation method and principal component analysis(PCA) methods, and with chi-square(χ²) test of co-variance and average vector were applied in 3 areas dominated by paddy soil, greenhouse soil(soil in greenhouse for vegetables), and salt soil respectively. The results show that the differences of soil fertility among 3 soils are extremely evident and that the soil fertility of paddy soil and greenhouse soil have been improved up to the 1st class one according to the regional standard from the 4th one before reclamation.The contents of organic matter,total nitrogen, alkali-soluable nitrogen,available phosphorus and potassium have been obviously increaced and the degree of salinization has been reduced.

Key words: forest, carbon storage, carbon density,  , Linzhi area of Tibet.