Soil Physical and Chemical Properties of Pure Pinus massoniana and Its Mixed Forests in Different Ages in Southern Guangxi

Six forest stands of 59,34 and 24 year-old Pinus massoniana forests and their mixed forests were selected at the Experimental Center of Tropical Forestry of Chinese Academy of Forestry,and 20 m × 20 m plot was set up and soil samples were taken from 0-60 cm soil layers,to analyze the changes of soil nutrient content under different forest stands and forest ages. The results showed that soil moisture and the bulk density in the mesophytic forest land were higher than those of other forest lands. The highest soil porosity value was observed in the early forest land. Soil p H of different forest was 4. 45-4. 75,indicating the variation was small. Besides,it indicated that the mixed forest was more able to increase the soil fertility than the pure forest because that the variation of soil acidity,organic matter content and total P and K in 34 and24 year-old mixed forests were higher than those in pure forests of the same year old. However,the content of soil available P and K decreased with the increase of soil depth,and varied in terms of forest ages. From the changes of soil indicators in different forest lands,soil nutrients in the 34 year-old P. massoniana forest was superior to that of other forest stands.

Six forest stands of 59, 34 and 24 year-old Pinus massoniana forests and their mixed forests were selected at the Experimental Cen- ter of Tropical Forestry of Chinese Academy of Forestry, and 20 m × 20 m plot was set up and soil samples were taken from 0 - 60 cm soil lay- ers, to analyze the changes of soil nutrient content under dirt）rent forest stands and forest ages. The results showed that soil nmisture and the hulk density in the mesophytic forest land were higher than those of other forest lands. The highest soil porosity value was observed in the early forest land. Soil pH of dirt）rent forest was 4.45 - 4.75, indicating the variation was small. Besides, it indicated that the mixed forest was nmre able to increase the soil fertility than the pure forest because that the variation of soil acidity, organic matter content and total P and K in 34 and 24 year-old mixed forests were higher than those in pure forests of the same year old. However, the content of soil available P and K decreased with the increase of soil depth, and varied in temps of forest ages. From the changes of soil indicators in dirt）rent forest lands, soil nutrients in the 34 year-old P. massoniana forest was superior to that of other forest stands.