Department of Biology, Imperial College, Silwood Park, Ascot, SL5 7PY, UK.
CABI Bioscience: Environment, UK Centre (Ascot), Silwood Park, SL5 7TA, Ascot, UK.
Oecologia. 2001 Apr;127(2):259-265. doi: 10.1007/s004420000579. Epub 2001 Jan 19.
Early-successional old fields are a major component of the European landscape. While a range of factors governing vegetation development in old fields has been identified, empirical and theoretical studies have tended to concentrate on plant competition as the dominant driving force behind succession. We studied the influence of three little researched, yet inter-related, factors on the early stages of an old-field succession: litter cover, soil disturbance and herbivory. Physical and chemical techniques were used to exclude large vertebrates and insects from experimental plots. These treatments had little effect on plant recruitment. A litter-removal experiment, nested within the exclusion treatments, revealed a significant inhibition of forb seedling germination by litter cover. However, the majority of seedlings died during the first month following emergence, whether or not litter was removed. A second experiment, involving the factorial combination of mollusc exclusion and soil disturbance, revealed that the response to disturbance was dependent on life-history characteristics of the plants. However, the dominant factor regulating community composition was seedling herbivory by molluscs. Molluscs caused high rates of forb seedling mortality and promoted the transition from a forb-dominated, to a grass-dominated community. Herbivory is often assumed to influence plant community dynamics through effects on competitive interactions. However, direct effects of herbivory, on the survival of seedlings, may be a significant factor structuring plant communities in ruderal, or other annual dominated systems.
早期演替的旧田地是欧洲景观的主要组成部分。虽然已经确定了一系列控制旧田地植被发育的因素，但实证和理论研究往往集中于植物竞争作为演替的主要驱动力。我们研究了三个研究较少但相互关联的因素对旧田地演替早期阶段的影响：凋落物覆盖、土壤干扰和食草作用。物理和化学技术被用来将大型脊椎动物和昆虫从实验地块中排除。这些处理对植物的繁殖几乎没有影响。在排除处理的嵌套中进行的一项凋落物去除实验表明，凋落物覆盖对草本植物幼苗的发芽有显著抑制作用。然而，无论是否去除凋落物，大多数幼苗在出现后的第一个月内死亡。第二个实验涉及排除软体动物和土壤干扰的组合，揭示了对干扰的反应取决于植物的生活史特征。然而，调节群落组成的主要因素是软体动物对幼苗的食草作用。软体动物导致草本植物幼苗高死亡率，并促进了从以草本植物为主的群落向以草为主的群落的转变。食草作用通常被认为通过对竞争相互作用的影响来影响植物群落动态。然而，食草作用对幼苗存活的直接影响可能是塑造杂草或其他以一年生植物为主的系统中植物群落结构的一个重要因素。
