黄土高原苹果园生草复合系统种间营养竞争/协同机制研究

Interspecific relationship research is always the keynote of Agroforestry research. Current studies about the underground interspecific relationship is still weak. So far, in the Apple-Grass intercropping system, the mechanism about how apple trees and pasture components affect their mutual nutrition competition or synergism by the root distribution with morphological change and physiological change is still not clear. Therefore, the popularization and application of Growing-herbage-in-orchard has been extremely limited. In this project, Apple-Grass intercropping system in the Chinese Loess Plateau are selected as subject investigated. Based on field experiment and indoor rhizobox experiment, methods of Minirhizotron, C-13 Isotope determination and Drilling method are adopted to conduct the coupling relationship research related to the chemical composition, photosynthate allocation, and respiration consumption of the underground root system. Also, how this coupling relationship affects the root distribution and morphology change will be illustrated, and then, the physiological processes and mechanism of root distribution with their morphological change of different components in the system will be clarified. Subsequently, the interactive relationship of the root distribution, morphological change, physiological change and nutrient absorption, the feedback effect of soil nutrient in the Apple-Grass intercropping system are to be elaborated using a successive, systematic and quantitative methodology. Finally, the mechanism about how the root of apple trees and pasture affect the interspecific nutrition competition or synergism by changing their morphology, distribution and physiology will be explored. The result of this project will support a new theory for the interspecific nutrition competition or synergism in the Apple-Grass intercropping system. Moreover, it has an expansive application prospect due to the remarkable characteristics of optimizing and managing the Apple-Grass intercropping system functions, establishing an efficient and sustainable Growing-herbage-in-orchard technology, realizing a high economic and ecological benefits synchronously.

种间关系研究是农林复合系统研究的核心问题，目前对地下部种间关系研究还相当薄弱，至今对果园生草复合系统中，果树与牧草组分怎样通过改变根系的形态、分布及生理变化，进而影响种间营养竞争/协同机制不十分清楚，限制了果园生草技术推广应用。本项目以黄土高原苹果园生草复合系统为对象，以田间和室内箱栽试验为基础，采用微根管法、C-13同位素法、根钻法等方法，通过对根系化学组成、光合产物分配及呼吸消耗的耦合关系，以及三者之间耦合关系如何影响根系形态与分布研究，查明各组分根系形态与分布变化的生理学过程与机制；采用连续的、系统的、定量方法，研究果树与牧草组分根系形态、分布及生理变化与营养吸收及土壤营养反馈作用之间的互动关系，明确三者的之间耦合关系对种间营养竞争/协同影响。本研究不仅为果园复合系统种间竞争/协同机理提供了新理论，同时对优化果园生草复合系统功能、建立高效果园生草技术，实现果园经济与生态效益同步提高。

果园生草是一种新型果园土壤管理模式，但对其种间营养竞争/协同机制不十分清楚，限制了果园生草技术应用。项目采用挖掘法、C-13同位素法等多种方法，系统研究了黄土高原苹果园生草复合系统果树与牧草组分根系形态、分布及生理变化，以及根系分布及生理变化与营养吸收及土壤营养反馈之间的关系，阐明果园生草复合系统种间营养竞争/协同机制。. 种间互作促进了复合系统苹果≤2mm径级根生长及I级根序发育；在根系垂直分布上，复合系统各组分根系主要分布在0-30cm土层，苹果组分各径级根在不同发育时期不同程度的向深处位移，在水平方向上，复合系统生草区苹果根系RBD、RLD、RSAD总体小于不生草区，生草区苹果D1和D2径级根分布比例在春稍和秋稍生长期均提高；提高了复合系统苹果I级根序根系活力和II级根序树根活力和活跃吸收面积，显著提高了春稍和秋稍生长期复合系统苹果d≤2mm径级根系活力。. 13C 稳定同位素标记结果表明：种间互作显著改变了复合系统苹果光合产物分配格局，更多光合产物分配到地下根系，主要分配给 20 cm 土层以下根系和直径 0-1 mm 细根，增加了苹果径级在 0-1 mm 细根呼吸速率和氮含量，并使苹果根系纤维素含量上升，木质素含量下降。. 在苹果不同发育阶段，间种间互作改变了复合系统土壤养分的空间变异性，种间养分竞争主要表现在0-20cm土层，复合系统生草区与非生草区界面养分变化强烈。RDA二维关系分析结果表明：根长密度与根系活力与全氮、速效磷、速效钾和有机碳呈显著正相关。. 种间互作降低了复合系统苹果组分N、P、K元素累积量，主要对N、P累积量产生了影响，秋梢和落叶期表现更明显，提高了复合系统白三叶组分N、P、K元素累积量，在秋梢期表现更明显；苹果组分N、P累积量随着白三叶组分N、P累积量升高而降低，尤其在秋梢期更为明显，且复合系统中白三叶组分对N的竞争比率值高于对P的竞争。本研究可为对优化果园生草复合系统功能、建立高效果园生草技术提供科学依据，具有重要应用前景。