Land use type, forest cover and forest edges modulate avian cross-habitat spillover
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Abstract Long‐term watershed experiments provide the opportunity to understand forest hydrology responses to past logging, road construction, forest regrowth, and their interactions with climate and geomorphic processes such as road‐related landslides. We examined a 50‐year record from paired‐watershed experiments in the H. J. Andrews Experimental Forest, Oregon, USA in which 125 to 450‐year‐old conifer forests were harvested in the 1960s and 1970s and converted to planted conifer forests. We evaluated how quickflow and delayed flow for 1222 events in treated and reference watersheds changed by season after clearcutting and road construction, including 50 years of growth of planted forest, major floods, and multi‐decade reductions in snowpack. Quickflow runoff early in the water year (fall) increased by up to +99% in the first decade, declining to below pre‐harvest levels (−1% to −15%) by the third to fifth decade after clearcutting. Fall delayed flow responded more dramatically than quickflow and fell below pre‐treatment levels in all watersheds by the fifth decade, consistent with increased transpiration in the planted forests. Quickflow increased less (+12% to 70%) during the winter and spring but remained higher than pre‐treatment levels throughout the fourth or fifth decade, potentially impacted by post‐harvest burning, roads, and landslides. Quickflow remained highmore »
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Many currently forested areas in the southern Appalachians were harvested in the early 1900s and cleared for agriculture or pasture, but have since been abandoned and reverted to forest (old-field succession). Land-use and land-cover changes such as these may have altered the timing and quantity of water yield (Q). We examined 80 years of streamflow and vegetation data in an experimental watershed that underwent forest–grass–forest conversion (i.e., old-field succession treatment). We hypothesized that changes in forest species composition and water use would largely explain long-term changes in Q. Aboveground biomass was comparable among watersheds before the treatment (208.3 Mg ha−1), and again after 45 years of forest regeneration (217.9 Mg ha−1). However, management practices in the treatment watershed altered resulting species composition compared to the reference watershed. Evapotranspiration (ET) and Q in the treatment watershed recovered to pretreatment levels after 9 years of abandonment, then Q became less (averaging 5.4 % less) and ET more (averaging 4.5 % more) than expected after the 10th year up to the present day. We demonstrate that the decline in Q and corresponding increase in ET could be explained by the shift in major forest species from predominantly Quercus and Carya before treatment to predominantly Liriodendron and Acer through old-field succession. The annual change in Q can be attributed to changesmore »
