Hanley M E, Fenner M, Edwards P J
Department of Biology, University of Southampton, SO16 7PX, UK.
Geobotanisches Institut ETH, Zurichbergstrasse 38, CH-8044, Zurich, Switzerland.
Oecologia. 1996 Apr;106(2):240-246. doi: 10.1007/BF00328604.
Two experiments conducted in spring and autumn 1992 examined the effect of mollusc grazing on seedling regeneration from natural grassland seedbanks by creating artificial gaps in plots in a grassland sward. Molluscs were excluded from half the gaps by application of molluscicide. Mollusc grazing in both the spring and autumn experiment significantly reduced seedling recruitment, though the intensity of grazing was greatest in autumn. Recruitment of five species was markedly influenced by molluscicide application. In spring, plots from which molluscs were excluded contained significantly more seedlings of Chenopodium polyspermum and Ranunculus acris. In the autumn, exclusion of molluscs resulted in increased populations of R. acris, Stellaria graminea and Rumex acetosa. Cerastium holosteoides populations were greatest in autumn grazed plots. Other species, notably the grasses Holcus lanatus and Agrostis capillaris and the legume Trifolium repens were unaffected by molluscicide application. Species diversity was significantly decreased by molluscicide application in the autumn. Gap size significantly affected the recruitment of two species. Ranunculus acris populations were significantly higher in small gaps in both spring and summer, while Chenopodium recruitment in the spring was greater in small gaps. Gap size also significantly influenced the risk of mollusc attack on Ranunculus as molluscs appeared to show an aggregative feeding response in the high seedling density small gaps. Selective grazing of vulnerable seedlings by molluscs may influence the eventual relative proportions of the species present and so provide a potent mechanism in shaping community composition in grasslands.
1992年春、秋两季进行了两项实验，通过在草地草皮上的样地制造人工间隙，研究软体动物啃食对天然草地种子库幼苗更新的影响。通过施用杀软体动物剂，将一半间隙中的软体动物排除在外。春季和秋季实验中，软体动物的啃食均显著减少了幼苗的招募，不过秋季的啃食强度最大。施用杀软体动物剂对五个物种的招募有显著影响。春季，排除了软体动物的样地中，多籽藜和毛茛的幼苗明显更多。秋季，排除软体动物导致毛茛、细叶繁缕和酸模的种群数量增加。全缘卷耳的种群数量在秋季啃食的样地中最多。其他物种，尤其是草地早熟禾、细弱剪股颖和豆科植物白三叶草，不受杀软体动物剂施用的影响。秋季施用杀软体动物剂显著降低了物种多样性。间隙大小对两个物种的招募有显著影响。春季和夏季，毛茛在小间隙中的种群数量显著更高，而春季多籽藜在小间隙中的招募量更大。间隙大小也显著影响了毛茛遭受软体动物攻击的风险，因为软体动物似乎在幼苗密度高的小间隙中表现出聚集取食反应。软体动物对易受攻击的幼苗进行选择性啃食，可能会影响最终现存物种的相对比例，从而为塑造草地群落组成提供一种有力机制。
