环境响应异步性、种间关系及种群增长率差异对河流底栖生物群落稳定性的贡献

Diversity-stability relationship (DSR) is not only a theoretical froniter issue, but also important foundation for ecosystem protection and restoration, thus has been continuously studied in recent decades. Although there were numerous researches in this field, it is difficult to draw general conclusions, due to multifaceted concepts of both stability and biodiversity and separation between theoretical and empircial studies. Mechanism-oriented approach would be a possible way to resolve this debate. However, DSR mechanisms currently were merely deduced from theoretical modeling, and evidences from empirical study is absent. We proposed here to implement an ecological mechanism research on the relationship between species diversity and stability of lotic benthic community. Specifically, biodiversity data on benthic algae and invertebrates, obtained from a natural stream- the Xiangxi River, will be used in a mechanism model to reveal asynchrony of population dynamics within the benthic community. Three kinds of asynchronous processes are to be disentangled: asynchrony in environmental response，interspecific interactions, and difference in population growth rates, and their individual contributions to community stability will be measured. Ecological mechanisms of species diversity stabilizing stream benthic community could be interpreted according to the functions of these three asynchronous processes. Theoretical modeling and empirical data will be combined in the proposed research, our results on DSR hence will an approximation to natural conditions, and be more practical. Moreover, biodiversity and ecological stability in streams are both significantly influenced by streamflow regime, which is never concerned in DSR research hitherto. The proposed research thereby would be conducive to improvement of DSR theory. Our findings also would be informative to developing restoration techeiques for impaired stream ecosystem. Therefore, this research have meaningful scientific value and potential applied implications simultaneously.

生物多样性-稳定性关系是持续受到关注的生态学热点问题，也是生态系统保护与修复技术的重要理论基础。但是，由于稳定性、生物多样性概念的多面性, 以及理论模型与实证研究彼此分离，学术界对它们的关系依然存在争议。机理研究为解决争议提供了新思路，然而目前仅限于理论推导，缺乏基于野外监测的实证研究。本项目拟选择受水流节律影响显著的河流生态系统，以物种多样性丰富、世代周期短的河流底栖生物群落为对象，在开展系统野外监测的基础上，将理论模型与实证研究相结合，分析导致异步性种群动态的环境响应异步性、种间关系及种群增长率差异在维持底栖生物群落稳定中的作用，并比较它们对群落稳定性贡献的差异，从机理上阐释河流底栖生物多样性与群落稳定性的关系。本项目从作用机理角度开展生物多样性-稳定性关系实证研究，有助于完善相关理论体系，具有重要的科学意义；研究结果可为受损河流生态系统修复及可持续管理提供依据，亦有潜在应用价值。

由于生物多样性、稳定性概念的多面性，导致生物多样性-稳定性关系的不统一，进而了引发持续的争论。从机理上而言，不是生物多样性本身影响稳定性，而是生物群落中具有不同生理生态特性的物种（或类群），因为种（群）内关系（表现为密度制约）、种间关系、对环境变化的响应等方面的差异，共同决定了群落的稳定性。该机理从理论模型推导而来，尚待实证研究（特别是针对自然生态系统的研究）检验。.本项目以香溪河连续72个月的监测数据为例，探讨着生藻类群落稳定性的维持机制。对群落时间动态分析发现：藻类群落呈现明显的年内波动特征，物种多样性、群落组成及密度都存在显著的季节变化。然而，从较长时间尺度来看，藻类群落组成围绕着平衡线上下波动，并未出现明显的长期变化趋势。水温、流量、pH、TP、TN是藻类群落时间波动的主要驱动力。.对群落稳定性进行度量发现：藻类群落组成表现出年内季节性周转与年间动态稳定相结合的双重特征；研究期间藻类群落未发生明显的定向变化，说明群落整体保持稳定。零模型检验结果也表明：多数样点藻类群落具有较随机群落显著低的同步性和显著高的稳定性。.进一步分析藻类群落稳定性维持机制发现：组成藻类群落的不同生态共位群内部存在密度制约作用，不同类群间相互关系较弱，环境因子对不同类群的时间动态影响整体较小。因此，香溪河着生藻类群落稳定性主要取决于不同类群内部的密度制约作用。.本项目发现不同共位群内的密度制约作用对维持河流着生群落稳定性的重要性，揭示了群落稳定性的维持机理。此外，发现藻类群落组成季节性周转的重现性可能对维持群落时间稳定性至关重要，为群落稳定性研究提供了新的思路。