Study On Statusquo And Sustainable Management Of Soil And Water Conservation Forest On Weibei Of Loess Plateau

At the present time, in Weibei of Loess Plateau, the construct of soil and water conservation forest is stepping into a new period and facing new difficulties and challenges. Under new situations and circumstances, how to consolidate afforestation achievements already made and promote sustainable development of soil and water conservation forest has become a very urgent and important task. Taking Yongshou for example, this paper investigate the current situation and existing problems of soil and water conservation forest of Weibei, and put forth some proposal to promote the sustainable management of soil and water conservation forest.The spatial arrangement of soil and water conservation forest in Yongshou is unevenness, the proportion of pure stand is higher than mixed forest. During the whole investigation, the proportion Robinia pseudoacacia is 75.3% in all plots, in the investigation region the kind of forests are monotony, growing conditions of Robinia pseudoacacia and Pinus tabulaeformis Forest are better than mix forest. Base on the state of thickness of dead leaves and soil moisture, we can indicate the benefit of soil and water conservation of mix forest is better than pure stand. In acacia forest, there are quadratic regression relations among the stand age and thickness of dead leaves,soil moisture, correlation coefficients are 0.8315,0.905, there is linear correlation among the thickness of dead leaves and soil moisture, correlation coefficient is 0.7253. In 28-37 year-old Robinia pseudoacacia, the thickness of dead leaves and soil moisture maintained at high levels.Soil moisture may be the most important factor effecting on the growing conditions of Robinia pseudoacacia, the growing conditions of Robinia pseudoacacia in shade slope is better than sunny slope, based on the current annual increment and average annual increment of height,DBH and individual volume, we can indicate the Robinia pseudoacacia in Yongshou can come into a stable growth state when the age is 18-19, that is to say 18-19 is the maturation age of Robinia pseudoacacia. Based on the results of coefficient of skewness (Sk) and coefficient of kurtosis (K), which two characteristic parameters can describe the diameter distribution, we can indicate that the density of acacia forest with the age of 17 and the density of 2140 plant·hm-2 is too higher significantly, under this situation, the growth of DBH and individual volume is inhibited, acacia forest need thinning cutting.The undergrowth plants in Robinia pseudoacacia are richness, 55 species belonging to 22 families and 53 genera are recorded in this statistical investigation, the numbers belongs to the families of Compositae, Rosaceae, Gramineae, Leguminosae and Labiatae take 54.7% in total genera and 56.3% in total species. The diversity of fix forest is higher than pure stand, the species indices of Robinia pseudoacacia is the highest in pure stand. The variation trend of species diversity, abundance index and evenness index are similar.Some suggestion which can promote the sustainable management of forest cultivation: changing the structure of stand, in Robinia pseudoacacia, the age of 17-20 is the most appropriate time to do manual intervention, based on the different forest sites, we can thinning the stand, after the age of 25, we can cut the stand whose canopy density above 0.6 to promoting natural regeneration undergrowth; planting mix forest,converting pure Chinese arborvitae forest whose benefit of soil and water conservation is the lowest into Seabuckthorn and Chinese arborvitae forests, establishing expert group to study the soil and water conservation mix forest; planting density in line with local conditions, benefit of soil and water conservation in 17-18a Robinia pseudoacacia with the density between 700-2200 plant/hm2, the Robinia pseudoacacia whith the density above 2200 plant/hm2 should be skinning skidder; converting some soil and water conservation forest into eco-economical type protection forest; strengthen the management of dead leave undergrowth; increasing the protection for the soil and water conservation forest, promoting the sustainable management of soil and water conservation forest.