Study On Forest Growth Characteristics And Saving Water And Protecting Soil Benefits Of Different Robinia Pseudoacacia Cultivars In Three Different Densities

To explore the efficiency of water and soil conservation of different varieties of RobiniaPseudoacacia in hilly areas of eastern Shandong，chooseing appropriate in the hill country ofcentral eastern Shandong tree type, for Shandong province and even in north of China buildsand restore soil and water conservation forest significance.This paper takes the commonRobinia Pseudoacacia and narrow crown Robinia Pseudoacacia planted in Weihai RushanBaisha Zhen Pan Jia Zhuang small watershed in rainy season in2006as the object of study,discussed in Different varieties of Robinia Pseudoacacia, different planting density in order todetermine the growth situation better, soil and water conservation benefit larger varieties,Andquantitative analysisedthe tree growth, litter accumulation, soil physical properties, soilhydrological effect, biomass of understory shrub and herb, shrub and grass vegetationcoverage, photosynthesis and soil nutrient content.Made the following research results andconclusions:（1） The photosynthesis of common Robinia Pseudoacacia and narrow crown RobiniaPseudoacacia have Obvious Diurnal and seasonal variation the diurnal change of Pn ofcommon Robinia Pseudoacacia and narrow crown Robinia Pseudoacacia are unimodal curve.In July the max net photosynthetic rate of narrow crown Robinia Pseudoacacia and commonRobinia Pseudoacacia were16.3μ mol·m^-2s^-1and15.8μ mol·m^-2s^-1;In September the max Netphotosynthetic rate of narrow crown Robinia Pseudoacacia and common RobiniaPseudoacacia were9.3μ mol·m^-2s^-1and8.67μ mol·m^-2s^-1.The Tr and Pn of July were lagerthan the Tr and Pn of September. There was a significant negative correlation between Gs andCi.The WUE of common Robinia Pseudoacacia and narrow crown Robinia Pseudoacaciawere1.74μmol·m-2·s-1and2.32μmol·m-2·s-1.（2） The Litter amount is closely related to the planting density.In accordance with theorder from small to large is A3>A2>A1>B3>B2>A1.Litter undecomposed layer, semi-decomposed layer, decomposed layer and litter layer, there were significant differencesin volumeThe herb coverage is closely related to Planting density.There are significantdifferencesof herb coverage and Planting density. between the common RobiniaPseudoacacia and narrow crown Robinia Pseudoacacia. In accordance with the order fromsmall to large of the herb coverage is A1>A2>B1>B2>B3>A3.The evenness index of A1isthe maximum, B1and A2relatively similar, A3and B3is the smallestThe richness index ofA1is the largest.The biodiversity of A1is the largest.There are significant differencesbetween Herbal Biodiversity of different forest types. In accordance with the order from smallto large of the Herbal Biodiversity is A1>A2>B1>B2>A3>B3.（3） The total soil porosity of narrow crown Robinia Pseudoacacia were lagere thancommon Robinia Pseudoacacia in0-20cm soil of differents densities.The A2is the largestand zhe B3is the smallest. In accordance with the order from small to large isA2>A1>B1>A3>B2>B3. The total soil porosity of narrow crown Robinia Pseudoacacia werelagere than common Robinia Pseudoacacia in20-40cm soil of differents densities. Inaccordance with the order from small to large is A2>B1>A1>A3>B2>B3. In accordance withthe order from small to large of the40-60cm total soil porosity is A2>A1>A3>B2>B1>B3.The non-capillary porosity of narrow crown Robinia Pseudoacacia were lagere than commonRobinia Pseudoacacia in0-20cm soil of differents densities. In accordance with the orderfrom small to large is A1=A2>B1>B2=A3>B3. In accordance with the order from small tolarge of the20-40cm Non-capillary porosity is B1=A2>A1=B2>A3>B3. The capillaryporosity of narrow crown Robinia Pseudoacacia were lagere than common RobiniaPseudoacacia in0-20cm soil of differents densities. In accordance with the order from smallto large is A2>A3>B1>A1>B2>B3. In accordance with the order from small to large of the20-40cm capillary porosity is A2>B1>A3>A1>B2>B3. In accordance with the order fromsmall to large of the20-40cm capillary porosity is A2>A3>A1>B2>B1>B3. Overall thenarrow crown of stand density of1250/hm2locust capillary porosity is the largest. There aresignificant differences between the average infiltration rate of different forest types. Inaccordance with the order from small to large of the average infiltration rate isA2>A1>B1>A3>B2>B3. In accordance with the order from small to large of the soil moistureis A2>A1>B1=A3>B2>B3. The Capillary soil water holding capacity of B1is the largest. In accordance with the order from small to large of the capillary soil water holding capacity isB1>A2>A1>B2>A3>B3. The Soil saturated water of A2is the largest. In accordance with theorder from small to large of the Soil saturated water is A2>A1>B1>B2>B3>A3. Inaccordance with the order from small to large of the Saturated soil water storage isA2>A1>A3>B2>B1>B3.（4） There are significant differences between the chemical properties of soil parametersof different forest types. In accordance with the order from small to large of the Saturated soilwater storage is A3>A2>A1>B3>B2>B1. In accordance with the order from small to large ofthe Soil organic matter is A3>A2>A1>B3>B2>B1. In accordance with the order from smallto large of the Hydrolysable nitrogen in soil is A3>A1>B3>B1>A2>B2. In accordance withthe order from small to large of the Soil phosphorus is A3>A2>A1>B3>B2>B1. There wereno significant differences between B2and B3. In accordance with the order from small tolarge of theSoil and water conservation benefits is A3>A2>A1>B3>B1>B2. This shows thatthe narrow crown Robinia Pseudoacacia of1250/hm2¹667/hm2has the best soil and waterconservation benefits.