Study On The Tree Micro-Environment And Structure Of Undergrowth Vegetations In Different Forest Types

The soil water content and light under forest of seventeen years old Robinia pseudoacacia plantaion of four planting density, Ulmus pumila plantation of rwo planting density and Pinus tabulaeformis plantation of two planting density at Loess Platera Semi-ared Area of Shanxi province were observed and determined. Studies were conducted on the growth of trees in different forest stand, the species and their number of undergrowth, and the growth and development of undergrowth. Research can be used to study the indication effect of undergrowth vegetations on conditions both different stand densities and different forest types. The results show as following.⑴In the plantation eco-system, the micro-environment of the tree-grass land was changed as polars existing. The micro-environment factors, including relative light intensity, land temperature and moisture content of soil, their time-changing character and distribution regularity in space were all changed a bit than the outside.⑵Within the forest with low planting density and big nutrition space the soil water content and light decreased with the increasing of planting.⑶Within the stand of Robinia pseudoacacia, as the planting density increase, the phenomenon of dry soil emerges as that occurred in mature plantation in arid and semi-arid areas. The abundance ratio and species diversity also decreased. The species gradually change from mesophyte such as Convolvulus arvensis and Themeda minor to typical xerophyte such as Artemisia sacrorum, Lespedeza dahurica and Adiantam capiuarisveneris. The average soil water content of two planting density Pinus tabulaeformis plantation were lower than other stands, which interpreted that the micro-environment, forest tree growth and development of undergrowth varied with the type of stand and planting density.⑷Evaluated the plantations with ash association coefficient analysis, the result show that the plot 4, Robinia pseudoacacia plantation(1.5m×8m) > the plot 6 Pinus tabulaeformis plantation(1.5m×4m) > the plot 8 Ulmus pumila plantation(1.5m×4m) > the plot 3 Robinia pseudoacacia plantation(1.5m×6m) > the plot 2 Robinia pseudoacacia plantation(1.5m×4m) > the plot 7 Ulmus pumila plantation(1.5m×2m) > the plot 1 Robinia pseudoacacia plantation(1.5m×2m) > the plot 5 Pinus tabulaeformis plantation(1.5m×2m)⑸Most of undergrowth vegetations have lower niche breadth values, but Heteropasppus...