The ecosystem engineering and trophic effects of the water vole : species loss and ecosystem processes

We investigated the engineering and trophic effects of an endangered burrowing herbivore, the water vole Arvicola terretris in upland environments. Plant community composition and structure was altered around burrows. There were also shifts in the relative composition of plant functional groups. Landscape scale heterogeneity was increased by the metapopulation of structure of water vole colony patches. The intensity of past occupancy was a determinant of community composition and structure in patches. Greater past occupancy and more burrowing disturbance had occurred in more species rich patches. Time since patch abandonment was also an important factor influencing vegetation composition. Burrow systems were extensive and had a drying effect on the surrounding soil belowground. Burrowing also altered soil biological properties. Levels of microbial biomass and activity were enhanced in tunnel walls. We carried out a simulated clipping experiment to determine the relative impacts of above and belowground herbivory. The two treatments had additive negative effects on grasses. Grass species with higher shoot-root ratios were more vulnerable to aboveground herbivory. Belowground clipping had less severe effects on plant growth and reduced the competitive dominance of one species over another. A short term exclosure experiment showed little change in community composition. Total vegetation density was significantly lower where water voles were present but there were no changes of diversity in exclosures. Vegetation in exclosures in an area of high burrow density showed little regrowth, indicating that the effects of burrowing were persistent. The data suggest that the rapid decline of water voles in the UK will reduce habitat heterogeneity and lead to greater abundance of dominant grass species, resulting in lower community diversity.EThOS - Electronic Theses Online ServiceGBUnited Kingdo