Plant species diversity of different age Pinus tabulaeformis plantations and its relations with soil fertility
不同种植年代油松林植物多样性及土壤养分变化

By adopting the concept of space as a substitute for time, a field investigation was conducted in the Malan forest region on Loess Plateau to study the plant species diversity of Pinus tabulaeformis plantations at different restoration stages and the changes of soil fertility. The results showed that the species richness, diversity and evenness of P. tabulaeformis plantations increased with the increasing year of restoration, with the largest species richness in about 30 years old plantation and the biggest species evenness and dominance in about 20 years old plantation; the planting of P. tabulaeformis changed the features of plant community, with the species composition and proportion being quite different from those of wasteland, and the 22 and 28 years old P. tabulaeformis plantations had the biggest Sorensen index; planting P. tabulaeformis had definite contribution to soil fertility, e.g., 28 years old P. tabulaeformis plantation had higher contents of soil organic matter and available nitrogen than the others, and with the increasing year of restoration, soil humus layer became thicker and soil pH increased.