核桃-小麦复合系统中细根生长动态及竞争策略

以核桃(Juglans regia)-小麦(Triticum aestivum)间作复合系统为研究对象,用微根窗和根钻相结合的方法采样,研究复合系统中核桃和小麦细根年内年际的生长动态和竞争适应策略,为农林复合系统的经营管理和竞争模型的建立提供理论依据和技术支持。结果表明,间作核桃和小麦根系均在上半年有一个大的生长高峰(5月和4月),在下半年有一个小的生长高峰(9月和11月),二者的竞争主要发生在上半年的大生长高峰期。在各年份各土层,间作核桃的根长密度均低于单作核桃,且在从第7年开始存在显著差异。在0—20 cm土层间作小麦根长密度在第3—7年间获得迅速提高,从第7年开始显著高于单作小麦,但在20 cm以下土层则相反。间作使核桃和小麦细根生态位实现了分离,11年的观察期内间作核桃比单作核桃细根的垂直分布中心下移了6.59 cm,间作小麦比单作小麦的上移了8.59 cm。在根系竞争策略方面,小麦根系是通过短期内的快速生长,迅速占据土壤空间获得竞争优势;而核桃根系是通过根系的逐年积累,逐步占据土壤空间从而获得竞争优势。可以干扰核桃根系积累过程的"竞争-干扰-再平衡"农林复合经营管理策略可以让复合系统中核桃和小麦保持各自竞争优势的情况下实现共存。在根系形态方面,自身细根直径较小者小麦在剧烈竞争区域以增加细根直径减小比根长来适应竞争,而自身细根直径较大者核桃则相反。

Growth dynamics and competitive strategies of fine roots in a walnut-wheat agroforestry system

The competition and ecological plasticity of fine roots between intercropping trees and alley crops are vital for the sustainable management in agroforestry system. To understand the interspecific competition and the adaptive strategy of fine roots in agroforestry system, both minirhizotron and soil core methods were used in investigating the dynamic of fine roots in the walnut-wheat (Juglans regia-Triticum aestivum) intercropping system at Weibei loess area. The monocultural systems were compared with the intercropping one. The results showed that there were two growth peaks of both walnut and wheat roots in the agroforestry system. One was from April to May and the other was from September to November. During April and May, large root biomass was gained and the major interspecific competition took place between walnuts and wheats. The root length density of walnut in the intercropping system was lower than walnut monoculture system at all the soil layers during all the growth periods. A significant difference was found since the 7^th year after planting. In surface soil (0-20 cm), the root length density of wheat increased rapidly from the 3^th to 7^th year in the intercropping system, and became significantly greater than the wheat monoculture since the 7^th year. However, the opposite trend was observed in the soil layer below 20 cm. The root ecological niche of walnut and wheat separated in the intercropping system. The roots vertical distribution center of walnut and wheat moved down for 6.59 cm and moved up for 8.59 cm than that in the walnut and wheat monoculture systems, respectively. In the aspect of root competition strategy, the wheat took competitive advantage through rapid growth and occupied more space in a short term than the walnut, however, the walnut trees took the space by accumulating their roots year by year and gradually took the advantageous place in the intercropping system. Walnut and wheat coexisted in the agroforestry system following the "competition-disturbance-rebalance" management strategy, which can interfere with the accumulation process of walnut root. In root morphology respect, wheat, whose fine root diameter was smaller at the beginning, tended to increase fine root diameter and reduce specific root length. However, the opposite trend was found for the walnut in the agroforestry system.