在一项为期25年的草原研究中,测试连接是否能稳定超级社区并挽救日益减少的多样性
Susan Harrison1, Rebecca A Nelson1,2
1Department of Environmental Science and Policy, University of California Davis, Davis, CA 95616.
概括
超社区理论表明,分散稳定了生态系统. 然而,这项为期25年的草原研究发现,连接性并不能防止物种消失,也不能稳定面临环境变化和方向转移的社区.
科学领域:
- 生态生态学 生态生态学
- 社区生态学社区生态学
- 景观生态学 景观生态学
背景情况:
- 超社区理论认为,分散可以稳定当地社区对抗环境变化.
- 连接性,定义为分布半径内的息地,是元社区动态的一个关键因素.
- 草原生态系统容易受到环境变化和物种组成的变化的影响.
研究的目的:
- 测试景观连接在25年内对草原元社区的稳定效应.
- 研究连接性和时间变异性,物种多样性保留和物种丰富性之间的关系.
- 确定连接性是否影响物种交换,以及这些影响是否受到放牧历史的调节.
主要方法:
- 使用了25年的数据集,来自2800公的景观中的80个草原.
- 基于分散相关半径内的源草原息地数量的量化景观连接性.
- 分析了总覆盖面和生物质的时间变化,物种多样性保留,物种丰富性和物种周转率.
- 在分析中考虑了牲畜放牧历史.
主要成果:
- 连接性和覆盖面或生物质的时间变化之间没有发现显著的关系.
- 连接性并没有提高随着时间的推移物种多样性的保留.
- 没有观察到连接性和物种丰富之间预测的单模式关系.
- 检测到连接性和物种周转率之间的积极关系,但在考虑放牧历史后消失了.
- 草原表现出朝着更高的异国情调的一年草和减少物种丰富度的方向转变,而不管连接或放牧.
结论:
- 景观连接并没有稳定当地草原社区,这些社区正在经历方向性环境变化.
- 观察到的物种组成 (热友化) 和丰度减少的变化发生在独立于连接性的情况下.
- 畜牧放牧历史显著影响了物种周转,掩盖了潜在的连接效应.
- 超社区理论对通过分散稳定性的预测可能不会在经历强烈方向环境转移的系统中成立.
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