title: Spatial models reveal the microclimatic buffering capacity of old-growth forests.
abstract: Climate change is predicted to cause widespread declines in biodiversity, but these predictions are derived from coarse-resolution climate models applied at global scales. Such models lack the capacity to incorporate microclimate variability, which is critical to biodiversity microrefugia. In forested montane regions, microclimate is thought to be influenced by combined effects of elevation, microtopography, and vegetation, but their relative effects at fine spatial scales are poorly known. We used boosted regression trees to model the spatial distribution of fine-scale, under-canopy air temperatures in mountainous terrain. Spatial models predicted observed independent test data well (r = 0.87). As expected, elevation strongly predicted temperatures, but vegetation and microtopography also exerted critical effects. Old-growth vegetation characteristics, measured using LiDAR (light detection and ranging), appeared to have an insulating effect; maximum spring monthly temperatures decreased by 2.5°C across the observed gradient in old-growth structure. These cooling effects across a gradient in forest structure are of similar magnitude to 50-year forecasts of the Intergovernmental Panel on Climate Change and therefore have the potential to mitigate climate warming at local scales. Management strategies to conserve old-growth characteristics and to curb current rates of primary forest loss could maintain microrefugia, enhancing biodiversity persistence in mountainous systems under climate warming.
authors.affiliation: Forest Biodiversity Research Network, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Sarah J K
authors.initials: SJ
authors.lastname: Frey
authors.affiliation: Forest Biodiversity Research Network, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Adam S
authors.identifier: 0000-0002-8344-3354
authors.initials: AS
authors.lastname: Hadley
authors.affiliation: U.S. Forest Service, Pacific Northwest Research Station, Corvallis, OR 97331, USA.
authors.forename: Sherri L
authors.identifier: 0000-0002-4223-3465
authors.initials: SL
authors.lastname: Johnson
authors.affiliation: Forest Biodiversity Research Network, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Schulze
authors.affiliation: Geography, College of Earth, Ocean, and Atmospheric Sciences (CEOAS), Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Julia A
authors.identifier: 0000-0001-9429-8925
authors.initials: JA
authors.lastname: Jones
authors.affiliation: Forest Biodiversity Research Network, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Betts
mesh_terms: D044822:Biodiversity; D057231:Climate Change; D065928:Forests; D008834:Microclimate; D012621:Seasons; D013696:Temperature
keywords: Boosted regression trees; forest structure; microclimate; microrefugia; mountains