Spatial Heterogeneity in Ecologically Important Climate Variables at Coarse and Fine Scales in a High-Snow Mountain Landscape

Abstract

Climate plays an important role in determining the geographic ranges of species. With rapid climate change expected in the coming decades, ecologists have predicted that species ranges will shift large distances in elevation and latitude. However, most range shift assessments are based on coarse-scale climate models that ignore fine-scale heterogeneity and could fail to capture important range shift dynamics. Moreover, if climate varies dramatically over short distances, some populations of certain species may only need to migrate tens of meters between microhabitats to track their climate as opposed to hundreds of meters upward or hundreds of kilometers poleward. To address these issues, we measured climate variables that are likely important determinants of plant species distributions and abundances (snow disappearance date and soil temperature) at coarse and fine scales at Mount Rainier National Park in Washington State, USA. Coarse-scale differences across the landscape such as large changes in elevation had expected effects on climatic variables, with later snow disappearance dates and lower temperatures at higher elevations. However, locations separated by small distances (∼20 m), but differing by vegetation structure or topographic position, often experienced differences in snow disappearance date and soil temperature as great as locations separated by large distances (>1 km). Tree canopy gaps and topographic depressions experienced later snow disappearance dates than corresponding locations under intact canopy and on ridges. Additionally, locations under vegetation and on topographic ridges experienced lower maximum and higher minimum soil temperatures. The large differences in climate we observed over small distances will likely lead to complex range shift dynamics and could buffer species from the negative effects of climate change.

Forest fragmentation alters winter microclimates and microrefugia in human‐modified landscapes

“…Both plot‐ and landscape‐scale characteristics had important effects on microclimate variability within forest fragments embedded within human‐modified landscapes (Bonan ). Given the simple topography of our study area, it was surprising that relative elevation had the largest effect size ranging from 0.5 and 2°C, and was comparable to the effect sizes of other studies in mountainous terrains (Ashcroft and Gollan , Ford et al ). Compared to more mountainous areas the velocity of climate change is expected to occur faster in low‐lying regions (Loarie et al ), yet within our study region we found that even subtle variations in microtopography promoted warmer minimum temperatures in forest patches of higher elevation.…”

“…We found that environmental characteristics at both the plot‐ and landscape‐scale were strong drivers of winter microclimates in remnant forest patches. Most studies of microclimates emphasize the role of vegetation and topography (Ashcroft and Gollan , Ford et al ), and although we found strong support for these relationships (e.g. basal area, relative elevation), we also found that characteristics of the surrounding landscape had strong influences on microclimates.…”

Climate Change Refugia, Fire Ecology and Management

“…Fuel reduction could have unintended consequences, since trees moderate climate. Trees filter solar radiation, providing a buffer between CAPs and the atmosphere; removing trees can increase maximum surface temperatures 10 to 40˝C [26]. Oddly, fire suppression which increases tree density may have also made CAPs climates cooler.…”

“…Refugia populations are at a greater risk from changing fire patterns [21] due to their predisposition to local extinction because of their small, isolated nature, especially if the plants are fire avoiders [24]. Fire could alter species occurrence directly by killing vegetation or indirectly by altering vegetation's moderating effect on climate [25,26] and the selection pressures on vegetation [27]. In more extreme cases fire can locally extirpate plants if fires are more frequent [28], less frequent [29], or more severe than historical fire regimes [30].…”

Within‐lake habitat heterogeneity mediates community response to warming trends

“…Benefits of fine‐scale heterogeneity have been recognized in terrestrial landscapes as functions of vegetation cover and small‐scale topographical features (Ford et al. ) and in rivers due to dendritic structure and landscape gradients (Brown , Thompson and Townsend ), but lakes have received less attention as systems with spatial heterogeneity on scales relevant to mobile organisms. Failure to recognize and account for this heterogeneity within lakes can mislead our understanding of biological responses to environmental changes (Luoto and Heikkinen ).…”