Research On Interspecific Relationship In Economic Tree And Crop Intercropping System On Loess Region Of Western Shanxi Province

Agroforestry management is widely applied in China Loess Plateau as one of effective measures to reduce soil and water loss, restore ecological balance, raise land utilization rate and increase economic benefits. However, interspecific competition exists in agroforestry system to some extent, the sduty on the relationship among different species in agroforestry system could contribute to intensively understanding the stability of ecosystem structure and function, explore reasonable and efficient utilization ways of resource, provide theoretical basis for managing agroforestry system with high-yield, high-efficiency and stabilization. In order to find suitable intercropping models and management in Loess Plateau, typical economic tree and crop intercropping models in loess region of western Shanxi Province were selected as research objects to study the underground for soil moisture, soil nutrient and walnut roots, the aboveground for photosynthetic active radiation and net photosynthetic rate, yield and economic benefit, and soil moisture, soil nutrient and light distribution at tree-crop interface were analyzed. The objectives of the paper are:1) to minimize the competition between trees and crops and maximize resource utilization,2) to provide a theoretical basis for the agroforestry control and management in this region. The results showed that:(1) Soil moisture distribution in economic tree and crop intercropping system showed that:In temporal, the soil moisture variation of economic tree and crop intercropping was very significant in different phonological phases; In spatial, the variation of soil moisture was different between walnut-crop intercropping and apple-crop intercropping in vertical direction. However, the variation coefficient of soil moisture decreased with soil depth, and soil moisture in the system of walnut-crop intercropping and apple-crop intercropping belonged to intermediate variability; In horizontal direction, soil moisture was related to distance from tree row. The closer to trees sampling points, the lower the soil moistures. The soil moisture in applet-crop intercropping was much less than that in walnut-crop intercropping, and two-dimension isogram of soil moisture content in applet-crop intercropping was more complicated than that in walnut-crop intercropping. By using moving split-window techniques, the distance of edge influence of compound boundary to soil moisture content at soil depth of 0-20 cm and 20-60 cm were [4.0 m,5.5 m] in walnut-crop intercropping.(2) Soil nutrient distribution in economic tree and crop intercropping system showed that:In vertical direction, soil nutrient decreased with increasing soil depth, and vertical decrease gradient of soil nutrient decreased with the increase of the distance from the tree row. In horizontal direction, soil nutrient decreased with the decrease of the distance from the tree row in economic tree area. Soil nutrient increased and its horizontal variation decreased with the increase of the distance from the tree row in crop area. It showed soil nutritent competition between crops and trees of observation range in typical phonological phase.(3) Economic tree roots distribution in economic tree and crop intercropping system showed that: Roots biomass distributions of different diameters were consistent in research ranges. As the main organ of absorption of soil moisture and nutrient, fine roots of walnut trees and apple trees concentrated within the depth of 0-40 cm and 0-60 cm in vertical direction, which accounted for 68.51% and 94.39% of total fine roots biomass respectively. In horizontal direction, fine roots concentrated at [0.5 m,1.5 m] and [0 m,1.5 m] distance from the trees, which accounted for 56.15% and 83.85% of total biomass of fine roots respectively. The root extinction coefficient could be used as a parameter revealing the vertical distribution characteristics of economic tree roots.(4) Light distribution in economic tree and crop intercropping system showed that:The shading areas more depended on accumulation of shading area of per walnut tree in walnut-crop intercropping, and time quantum of canopy shading was relative short. Therefore, shading degree was relative slighter. The light distribution was relative more complicated in apple-crop intercropping, which was influnenced by multiple shading, there was less light on the ground. Therefore, shading degree was relative stronger. The crops were influenced by trees, the photosynthetic active radiation and net photosynthetic rate of crops were significantly decreased by trees, and the decreasing degree is decreased with the increasing of distance from tree rows.(5) The values of EM in economic tree and crop intercropping system were -5.33%,-5.66%, -10.54%, and -12.81% for walnut-peanut, walnut-soybean, apple-peanut and apple-soybean in layer of 0-40 cm respectively, while that were -4.08%,-5.25%,-11.20%, and -16.83% in layer of 0-100 cm respectively, and the values of EN in intercropping with crops were -8.68%,-15.00%,-10.54%, and-12.81% for walnut-peanut, walnut-soybean, apple-peanut and apple-soybean in layer of 0-40 cm respectively, while that were -10.19%,-16.85%,-23.40%, and -25.69% in layer of 0-100 cm respectively. The values of EM in economic tree and crop intercropping were -16.62%,-18.12%,-21.89%, and -26.39% for walnut-peanut, walnut-soybean, apple-soybean and apple-peanut respectively. According to land use efficiency and economic benefits, walnut-peanut, walnut-soybean, apple-peanut, and apple-soybean intercropping models could be used as the main models of economic tree and crop intercropping, and they should be extended in the Loess Plateau. The average value of land use efficiency increased by 70%, and the average economic benefits increased by 14%.