Both trait-neutrality and filtering effects are validated by the vegetation patterns detected in the functional recovery of sand grasslands

Neutral theory of species assembly means that species assembly is governed by stochastic dispersal processes and fluctuations in established populations. An alternative theory suggests that assembly is strongly determined by functional trait filtering governed by abiotic and biotic filtering selecting species from the local species pool. To test these assumptions, in the current paper we analysed vegetation changes in the first 12 years of succession after heavy goose grazing on acidic sand. With trait-based analyses using permanent plots we addressed the following hypotheses: (i) High fluctuations in the trait values are typical in the first years; later a temporally divergent change in the trait patterns of sites with different vertical position became characteristic. (ii) In the functional diversity of regenerative and vegetative traits we expected different temporal patterns. We confirmed the first hypothesis, as in the first few years most traits displayed high fluctuations with no clear patterns. Our findings weakly supported the second hypothesis; while there were distinct patterns detected in the functional richness of traits, functional divergence and evenness displayed no clear distinctive patterns. We can conclude that both trait neutrality and filtering effects operate in the vegetation changes of the first period of secondary succession.

物种集合中性理论（Neutral theory of species assembly）认为，物种集合过程由随机扩散过程与定居种群的波动共同主导。另有替代理论提出，物种集合过程主要受功能性状过滤（functional trait filtering）调控：即通过非生物过滤与生物过滤从本地物种库中筛选适配物种。为检验这两种理论假设，本文分析了酸性沙地经高强度鹅放牧后，次生演替前12年的植被动态变化。本研究依托永久样地开展基于性状的分析，旨在验证以下两项假说：（i）性状值的剧烈波动多出现于演替初期；后续阶段，不同垂直位置样地的性状格局将呈现随时间分化的特征。（ii）更新性状与营养生长性状的功能多样性将表现出不同的时间动态模式。研究结果验证了第一项假说：演替最初几年间，多数性状均呈现剧烈波动且无明确格局。第二项假说仅得到弱支持：尽管在性状功能丰富度中可观测到显著格局，但功能分异度与功能均匀度并未呈现清晰的特异性模式。综上，在次生演替初期的植被动态中，中性理论与性状过滤效应均发挥了调控作用。