TOP-DOWN CONTROL OF SMALL HERBIVORES ON SALT-MARSH VEGETATION ALONG A PRODUCTIVITY GRADIENT

摘要: Exploitation theory predicts strongest plant-herbivore interactions at sites of intermediate productivity. Recent studies illustrate the importance top-down effects by small to intermediate-sized herbivores in structuring salt-marsh communities. How long- term herbivory are modified productivity system is a largely unexplored area. We studied how geese and hares affected plant species replacement erecting exclosures along natural gradient temperate system. After seven years, largest shifts composition were observed when both excluded from plots. Only excluding did not have large impact on replacement, indicating that alone control vegetation. Herbivory slowed down succession retarding establishment spread late-successional low salt marsh. Effects less clear high Vegetation change after was most pronounced unproduc- tive regions As result, different successional trajectories emerged absent or present onset succession. At inter- mediate productivity, where grazing pressure highest, no effect found. hypothesize dominance tolerant these retarded invasion species. The intensity accurately predict To understand herbivore gradients, selectivity patterns bottom-up plants need be considered.