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Turkish Journal of Agriculture and Forestry

DOI

10.3906/tar-1408-115

Abstract

The thinning of stream buffer zones (SBZs) is gaining popularity as a silvicultural management practice in order to reduce the risk of wildfire and insect hazard, provide economic return, and improve the effectiveness of SBZs. In this study, streamflow over a 1-year period was monitored at 2 small paired watersheds (treated vs. reference). The short-term impacts of a partial cutting within a SBZ as well as the relative effects of pastoral, forested, and clearcut areas on changes in downstream hydrology were examined. Upstream pastoral areas had a higher water yield than downstream forested sections during the no-harvest (calibration) period of 6 months. The partial cut (about 50% of the basal area) within the SBZ changed the hydrologic pattern by remarkably increasing the water yield on the treated downstream sections during the 6-month-long postharvest period. The harvest operation also caused an increase in direct runoff at 2 downstream sections, WT2 and WT3 (~200% and ~100%, respectively). No significant changes were observed in the water yield pattern of the control watershed. Because harvested areas within the SBZs constitute a fraction of the monitored sub-watersheds and only partial harvesting (~50% of the basal area) was implemented, the observed increase in flow at the treated downstream sections (100% and 250%, respectively) is unprecedented. The partial harvesting within the SBZs also resulted in a significantly flashier hydrological system. Because silvicultural treatments are part of regular, repeated management operations, these short term (in this study, 6-month-long) but substantial changes in water yield, direct runoff, and flashiness could have important implications for water quality, water resources, and downstream biota.

Keywords

Partial cutting, streamside buffer zone, watershed, water yield

First Page

764

Last Page

774

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