Open Collections

From deer abundance to soil properties : a case study in the forests of Haida Gwaii

University of British Columbia

The past century witnessed a dramatic increase in deer abundance in North America and Western Europe. Deer overabundance prevented temperate forest regeneration, dramatically reduced their understory vegetation cover and composition, with negative consequences for other trophic layers such as birds and insects. While impacts of abundant deer aboveground have been well documented, effects on the soil of temperate forests remain unclear. Deer interact with the soil through waste deposition, trampling, and reduction of litter quantity and quality through selective foraging. The multiplicity of these pathways makes it difficult to predict the net effect deer will have on soil communities and processes. As a result, current studies in temperate forests have found inconsistent results within, and across, systems. In an attempt to resolve these inconsistencies, we used the unique configuration of the Canadian archipelago of Haida Gwaii which offers a quasi-experimental situation with the presence of islands without and with deer, the latter varying in deer colonisation history. This unique context is complemented by the knowledge gathered in the course of 30 years of studies on the effect of abundant deer aboveground. We measured the effect of deer presence on litter decomposition, soil properties, soil prokaryotic communities and nitrogen cycling rates. We compared three complementary study systems varying in time of deer presence and exclusion. We found that the response of the soil to deer presence was time dependant. Short-term and intermediate effects of deer belowground were the results of the direct interactions deer have with the soil, i.e. waste deposition and trampling. Long-term effects of deer belowground appeared to be the results of both direct interactions, due to trampling, and indirect interactions, due to vegetation shifts. Through the reduction in litter quality by selective browsing, long term deer presence significantly reduced the rate of carbon and nitrogen lost by litter during decomposition. Under long-term deer presence, soil prokaryotic community diversity decreased, and composition was shifted, by trampling. In the absence of deer it had a better ability in decomposing carbon. A preliminary analyse on the nitrogen cycle suggest no effect of deer on the kinetics of nitrogen rates in the forest floor.

Text

2020-02-05

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/73481

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/