Effects of colony nesting of Great blue heron( Ardea herodias) on vegetation compositionand soil nutrient concentration on Southeastern Vancouver Island

摘要

Effects of colony nesting of Great blue herons on understorey cover and species composition, and levels of δ15N,NO3-N and PO4-P in soil were studied in a big leaf maple forests at Chase River and Clamshell Road, VancouverIsland. Species composition did differ between study sites which had different nest densities but a dominant specieswas not changed. Total understorey cover and number of species declined with increasing nest density, and someburned plants were observed under the highest nest density. The level of 15N enrichment in the soil as well as soilaccumulations of NO3-N and PO4-P all related closely to increases in nest density. We conclude that the soil underthe colony has undergone eutrophication by heron excrement, and the local vegetation has responded negatively.However, it was certain that Great blue herons played an important role to link marine and terrestrial ecosystems incoastal British Columbia.