Changes of Soil Nutrients Under Different Vegetation Restoration Patterns and Age Limit in Karst Mountain

In 2002, 2005, 2009, and August 2016, soil samples from the upper, middle and lower parts of 11 fixed vegetation restoration sites in Fadou were determined by 4 surveys. The changes of 11 kinds of vegetation of different species of tree (grass) and the changes of soil nutrients and restoration of forestland under restoration years were analyzed. The results showed that along the 14 years succession, there was close correlation between restoration time and soil nutrient parameters such as organic matter, available N, available P, available K and pH. Soil organic matter content increased significantly after vegetation restoration and restoration effect was obvious. Soil available N content can also be significantly restored. The content of available P in soil was changed slowly, increased rapidly and then decreased, and the content of available P in soil was not recovered obviously. Soil K content showed a "slow down-sharp drop-slow increase" changes, the recovery effect was not obvious. After 7 years, the soil pH value showed a clear downward trend. After 14 years, the soil pH value in the woodland was effectively reduced and stabilized. Restricted nutrient available P and available K recoveried significantly lag behind the recovery of organic matter and available N, indicating that restrictive nutrients to be significantly restored to take longer. Based on the change and restoration of soil nutrients in the course of vegetation restoration, 6 species of fragrant wood, such as Manglietia aromatica + Cupressus lusitanica and Pistacia weinmannifolia, were optimized for artificial vegetation restoration in Yunnan karst mountainous areas.