Small herbivores slow down species loss up to 22 years but only at early successional stage

The long-term influence of persistent small herbivores on successional plant community configuration is rarely studied. We used an herbivore exclusion experiment along the successional gradient in a salt-marsh system, to investigate the effects of hares and geese, and hares alone, on plant diversity at five successional stages (the earliest, two early, the intermediate and the late successional stages) in the short and long term, i.e. 7 and 22 years, respectively. Plant diversity declined over time at all successional stages except for the earliest one. Small herbivores slowed down species decline, but only at one early successional stage. Small herbivores slowed down species decline via decreasing dominance of preferred grass Festuca rubra in the short term, and less preferred Elytrigia atherica in the long term. The effects of hares and geese were more pronounced than hares alone, indicating an important additive role of geese, especially in the long term. Synthesis. Small herbivores can have a strong and long-lasting impact on plant diversity, but it highly depends on the abundance of small herbivores, which in turn depends on the quality and abundance of forage plants. A diverse herbivore community may have more positive effects on regulating plant communities.

持续性小型草食动物对演替植物群落构型的长期影响鲜有研究。本研究依托盐沼系统内沿演替梯度布设的草食动物排除实验（herbivore exclusion experiment），分别在短期（7年）与长期（22年）尺度下，探究野兔与雁类、仅野兔两种取食模式对5个演替阶段（初始阶段、两个早期阶段、中间阶段与晚期阶段）植物多样性的影响。结果显示，除初始阶段外，所有演替阶段的植物多样性均随时间推移呈下降趋势。小型草食动物仅能在一个早期演替阶段延缓物种多样性的下降过程。其作用机制为：短期通过降低偏好取食草本紫羊茅（Festuca rubra）的优势度，长期则通过降低低偏好取食草本偃麦草（Elytrigia atherica）的优势度。野兔与雁类共同取食的影响效果显著强于仅野兔取食，表明雁类发挥了重要的叠加作用，尤其在长期尺度下。综合分析表明，小型草食动物对植物多样性可产生强烈且持久的影响，但该影响高度依赖于小型草食动物的种群丰度，而种群丰度又取决于饲用植物的质量与丰度；物种多样的草食动物群落对植物群落的调控或可发挥更积极的作用。