鄱阳湖湿地植物根性状及与地上部分关联研究

Plant functional traits could significantly affect ecosystem functions and indicate the response of vegetation to environmental change. So far, researches on plant functional traits were concentrated on above-ground parts in terrestrial ecosystem. The below-ground root traits are still poorly understood, which not only substantially hindered the modeling of below-ground processes and the responses of ecosystem to environmental change, but also affected further development and verification of resource economy spectrum theory. In this study, the typical Poyang Lake wetlands located at the front edge of Ganjiang delta will be selected as research sits. Subsequently, the plant community investigation will be conducted along water table gradient in growing season, and then root, stem and leaf traits (e.g., specific root length, specific leaf area, tissues density and tissues nutrients) of dominant and accompanying species will be measured. In addition, root, stem and leaf traits of dominant plant community will be dynamically monitored. Based on root order, we will compare the root traits difference between dominant and accompanying species, and analyze the responses of root traits to water table changes. Additionally, the relationship between various root traits, as well as root and leaf traits will be discussed. The result of this study will not only help to improve the knowledge of heterogeneity of root system, but also clarify the mutualistic mechanism of plant species in Poyang Lake wetlands. Furthermore, this study will reveal the interaction between above-ground and below-ground parts of wetland ecosystem, and provide basic data for the extension of resource economy spectrum theory to below-ground roots.

生态学的一半在地下，植物根系功能性状研究的不足不仅严重制约了对于地下生态过程及其机理的理解和认识，还制约了资源经济谱系理论的进一步拓展与验证。本项目拟选择鄱阳湖湿地典型区—赣江三角洲前缘地带，于植物生长季沿水位梯度对常见植物群落优势种与伴生种进行根系和地上茎、叶等功能性状测定，并结合优势植物群落根系与地上部分性状的年际动态监测，从根序的角度研究湿地植物优势种与伴生种之间的根性状差异，分析根性状对水位变化的响应，探讨根性状之间的关系以及与地上部分相应性状的关联。项目研究结果一方面将有助于深入认识根系系统的异质性，为阐明大型通江湖泊湿地生态系统物种共存的机理、揭示湿地生态系统地下与地上部分的相互作用机制提供科学依据，另一方面还将为资源经济谱系理论拓展至地下根系提供数据支持。

生态学的一半在地下，植物根系功能性状研究的不足严重制约了对于地下生态过程及其机理的理解和认识。本项目选取鄱阳湖南矶湿地典型区，采集了22种常见湿地植物的根系与叶片样品，并对4种优势植物进行了动态监测，从根序的角度分析了根系结构和化学组成等性状特征与动态变化，探讨了地下根系与地上叶片相应性状之间的关联。结果表明：22植物一级根、二级根和三级根比根长变化范围分别为41.52-812.38m·g-1、10.21-879.45m·g-1和0.59-160.23m·g-1，平均值随根序的升高而降低。根组织密度在一级根、二级根和三级根中的变化范围分别是0.05-0.55g·cm-3、0.01-0.43g·cm-3和0.03-0.59g·cm-3，平均值表现为三级根>一级根>二级根。根系全C、全N和全P含量变化范围分别为：267.15-423.22 mg·g-1、2.22-31.05 mg·g-1和0.31-2.70 mg·g-1。全C随根序的升高而增加，全N、全P则随根序升高而降低。根系全C、全N和全P含量皆低于叶片的相应养分含量。根序、物种及其交互作用均显著影响根系的结构性状与化学性状，根系分级在地下根系功能性状研究中十分必要。比根长与根组织密度在一级根、二级根和三级根中均表现出极显著负相关（P<0.01），而各等级细根的比根长、根组织密度与相对应的全C、全N和全P含量之间未发现显著相关性（P>0.05）。比叶面积分别与一级根（r=0.41，P<0.05）、二级根（r= 0.50，P<0.05）及三级根比根长（r=0.58，P<0.05）呈现显著正相关，与不同等级根系的全C、全N和全P含量之间亦存在不同程度的相关性。叶片全C 含量仅与一级根（r=0.46,P<0.01）、二级根（r=0.33,P<0.01）存在显著正相关；叶片全N含量与一级根（r=0.25, P<0.01）、二级根之间存在极显著的相关性（r=0.35,P<0.01），与三级根全N含量之间相关性显著（r=0.28, P<0.05）；叶片全P含量与各等级根系之间的相关性不显著。受生长季温度及水位变化影响，4种优势植物比根长、根组织密度、分枝比、分支强度以及全C、全N、全P含量均表现出明显的季节变化规律。此外，根系养分化学计量关系中N:P随时间变化的稳定性高于C:N和C:P；群落尺度的C:N:P稳定性高于个体水平。