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Herbicides Exert Weak and Variable Effects on Microclimate in Early-Seral Forests

Jones, Kristin N., Rivers, James W., Betts, Matthew G.
Northwest science 2018 v.92 no.2 pp. 107-118
air temperature, animals, biodiversity, climate change, coasts, ecosystems, forests, herbicides, intensive forestry, land cover, land use and land cover maps, microclimate, pesticide application, plants (botany), prediction, surface temperature, Oregon
Ecosystem modification driven by anthropogenic land-use and land-cover change is one of the leading drivers of global biodiversity declines. Simultaneously, ongoing climate change is modifying ecosystems and will have far-reaching impacts on the structure and function of ecological communities. Rising surface temperatures are predicted to have negative effects on plants and animals, but such predictions are typically broad and poorly matched to the spatial scale at which most organisms experience the environment. Microclimate thermal regimes are often moderated by land-cover, and intensive forest management practices have the potential to either ameliorate or exacerbate climate change effects on biota. In this study, we examined the degree to which air temperature varied across an experimental gradient of herbicide application intensity within early-seral forests in the Coast Range mountains of western Oregon. We evaluated stand-level air temperatures in regenerating stands subjected to light, moderate, and intensive herbicide treatments, as well as a no-spray control. We examined whether daily temperature measurements (minimum, mean, and maximum) and their associated coefficients of variation were influenced by herbicide treatments. We found that herbicide treatments had some influence on mean and maximum air temperatures, but not on minimum temperature or on measures of temperature variability. However, temperature effects were small (< 0.5 °C), the direction of these effects were inconsistent, and pairwise contrasts often failed to detect significant differences after accounting for multiple comparisons. Our results suggest that post-harvest vegetation management has limited impacts on fine-scale air temperatures and is unlikely to either amplify or buffer the projected effects of climate change within early-seral forests.