Reference Document 5-3
Appendix 5
Winter Temperatures
Winter temperatures are the fastest warming season in most of the United States, and this is no exception for North Carolina’s mountain habitats. Winter conditions (e.g., low temperatures, snowfall) have a major effect on ecological processes such as litter decomposition, mineralization rates, nutrient leaching and gas fluxes in the soil and hydrological processes. Winter conditions are also key drivers of individual species performance and community composition in terrestrial habitats, where many species have evolved life-stage-specific tolerance to winter conditions (e.g., hibernation or dormancy periods) (Williams et al. 2015) . A shortened winter season and warmer winters may cause species range shifts that would allow for warm-adapted species to dominate, and shift distributions of cold-adapted species further northward or upslope (Williams et al. 2015) . For example, overwintering bird populations are responding to warming climate (e.g., poleward shifts) by favoring the formation of winter bird communities dominated by warm-adapted species instead of cold-adapted species (Osland et al., 2021) . Besides shorter winters with less days that drop below freezing, the variability of winter temperatures is increasing, leading to an increase in freeze-thaw events (Leduc and Logan 2025) . Changes in temperature variability during the winter can modify the timing, predictability and sequence of extreme events during the season (Campbell et al. 2005; Williams et al. 2015) . Species with seasonally programmed responses, like winter dormancy (e.g., overwintering bats in caves), risk having their behavioral or physiological mechanisms disrupted and face harmful consequences (Shuter et al. 2012; Williams et al. 2015) . For example, extreme warm periods in late winter can lead to breaking of dormancy in plants, with subsequent extreme events (i.e., temperatures dipping back down to freezing) killing buds and preventing reproduction or growth in the following season. Winter soil freezing also affects insect and microbial communities for the subsequent warm season that affect plants as well (Campbell et al., 2005) . Cave-roosting bats in North Carolina, such as the Indiana bat ( Myotis sodalis ), hibernate in caves all season, but since the white-nose syndrome disease became established in the southeastern US, behaviors such as daytime and cold-weather flight during winter became indicative of infection (Bernard and McCraken 2017) . Cold winter temperatures are important in order for bats to survive white nose syndrome and changes to winter air temperatures affect microclimates of caves, making hibernating infected individuals’ vulnerable (Turner et al. 2021) . The Blue Ridge Ecoregion is driven by consistent cool temperatures and a consistent supply of moisture. This includes moisture provided by snowfall and ground level cloud cover, unique conditions in the SAM. The ecosystem benefits from a closed canopy structure, which allow for cool soil conditions that facilitate red spruce growth. Red spruce have a well-documented ability to rapidly respond to midwinter temperature shifts or “thaws”, but this comes at the expense of its protection from cold injury (Schaberg 2000; DeHayes et al. 2001) . This ability, called dehardening, is normally triggered in conifers by warming temperatures at the winter to spring transition time (Jordan 2018) . However, a sufficiently long midwinter thaw events cam imitates the advent of spring and trigger premature dehardening, and subsequently causing extensive foliar
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2025 NC Wildlife Action Plan
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