Using the shelterwood method to mitigate water table rise after forest harvesting

The groundwater level of a conifer stand established on a lowland in eastern Canada was periodically measured using water wells installed in an experimental design composed of. four. completely randomized blocks and five levels of cutting (0, 40, 50, 60, and 100% of basal, area (BA) removed). The three partial cutting treatments were applied following the principles of low thinning, but with the seed cutting objectives of the shelterwood method. Before cutting, highly similar values for groundwater level were recorded for plots targeted to receive the planned treatments During the first growing season after cutting, the water table rise was linearly related to the percentage of cutting, and this effect was more apparent it the lower levels recorded for the control water table. This finding is partly explained by the leaf biomass of residual trees that intercepted an increasing proportion of rainfall with decreasing cutting intensity. Five years after cutting, although the water table of clearcut experimental units (EU) was still higher than that of the controls, it was no longer related to cutting intensity. During the 5 years following cutting, the slopes of the relationship between the water table depth of the control plots and those of any treatment gradually approached the value calculated before,cutting. This water table recovery was related to the increasing leaf biomass of the regeneration stratum over time, rather than to the crown expansion of residual trees. The shelterwood method should be considered for forest management of wetlands, since it mitigates water table rise after, the first cut and promotes a vigorous regeneration stratum which should also mitigate water table rise following the. final cut. (C) 2002 Elsevier Science B.V. All rights reserved.