黄土坡面果粮复合系统根系结构及生态位特征研究

Agroforestry system is an effective way to solve the cause-and-effect vicious circle between ecological disaster and undeveloped economy in the loess Plateau. In agroforestry system, moisture and nutrient, especially moisture is the major competitive object between crops and trees and the plants absorb moisture and nutrient mainly through root system. Research on root system and niche characteristics of trees in agroforestry system can open out the mechanism of plants arrangement in the loess area. This paper choose the typical economic trees of almond and apple tree in this region and thoroughly study its root system and niche characteristics as well as the moisture distribution characteristics beside the interface of crops and trees..It is concluded that in agroforestry system, the dense layer of root system distribution and absorbing root system is deeper than that in pure forest, which will contribute to the utilizing of moisture and nutrient in deeper soil layer and then lighten the competition between crops and trees..Except that old apple tree impact more on the crops growing on the farmland beside the upper ridge of contour ditch on the gentle slope, almond impact more than apple tree on crops growing on the farmland beside the upper and lower ridge of contour ditch. Also niche overlapping between almond and wheat is greater than that of apple tree in time aspect. So as a hedgerow tree be used on contour ditch, apple tree is obviously better than almond..The competition characteristics of Absorbing moisture and nutrient between trees and crops is decided by its niche characteristics respectively. In the 0-100 cm soil layer beside the interface of forest and crops, niche breadth of forest reduce and that of crops increase gradually with the distance from hedgerow. Under the condition of without irrigation in the loess area, 1H range from hedgerow is the competitive region of moisture and nutrient between trees and crops and 0-40 cm soil layer is the major competitive layer, as well as the area beside 0.5H from hedgerow is the most acute competitive region. Tree is predominant in competition and will affect crops negatively。.In the fruit tree hedgerow on contour ditch with slope type of AF, result of the entering of forest, the moisture content beside the interface of forest and crops is less than that in the middle of farmland and this kind of moisture in deficit is different with the change of slope and forest age..Influenced by the landform, fruit tree hedgerow mainly absorb moisture from the farmland beside the lower ridge of contour ditch on steep slope and impact more on the crops growing on the lower farmland of contour ditch than that on the upper land; The situation of the gentle slope is contrariwise to this..In the agroforestry system which is composed by young fruit tree and crops, the max moisture deficit is occurred on the 0-20 cm soil layer both on the 0.5H distance from the upper and lower ridge of contour ditch, which is different from the 40-100 cm soil layer of old fruit trees. This phenomenon shows that the old fruit tree make full use of the deeper moisture than the young one.. In the fruit tree hedgerow on contour ditch with slope type of AF, fruit trees hedgerow use the slope and land space and increase the moisture use efficiency through intercepting precipitation. After many years fixed observation, it is found that the utilizing of deeper moisture don't result in the continually moisture wane in the deeper soil layer and this is a new soil moisture balance system been formed after the hedgerow entering. That is the moisture content beside the interface of tree and crops is less than that in the middle area of farmland.. The moisture regulating measures for the fruit tree hedgerow on contour ditch with slope type of AF include spatial and temporal redistribution of rainfall using moisture basin, moisture saving irrigation, and coverage to reduce the soil moisture evaporation. Irrigation quota and coverage methods are key measures and the best combination is medium or high quota

以黄土坡面果粮复合系统为研究对象，试验研究不同复合类型及水肥条件下树木根系的生长发育规律及树木和农作物水养分生态位特征；测定分析树木根系的分维结构，研究分形模拟重构技术；分析树木根系分维结构与生态位的关系，并建立生态位的分维模型；据此模拟试验和预测黄土坡面不同复合类型及水肥管理条件下果（杏、梨、苹果、花椒）粮（小麦、玉米）复合系统的合理结构配置，揭示干旱半干旱地区高效可持续经营的农林复合系统合理结构的机理，为黄土坡面农林复合系统植物种群选择及其结构合理配置提供理论依据。