title: Strong topographic sheltering effects lead to spatially complex treeline advance and increased forest density in a subtropical mountain region.
abstract: Altitudinal treelines are typically temperature limited such that increasing temperatures linked to global climate change are causing upslope shifts of treelines worldwide. While such elevational increases are readily predicted based on shifting isotherms, at the regional level the realized response is often much more complex, with topography and local environmental conditions playing an important modifying role. Here, we used repeated aerial photographs in combination with forest inventory data to investigate changes in treeline position in the Central Mountain Range of Taiwan over the last 60 years. A highly spatially variable upslope advance of treeline was identified in which topography is a major driver of both treeline form and advance. The changes in treeline position that we observed occurred alongside substantial increases in forest density, and lead to a large increase in overall forest area. These changes will have a significant impact on carbon stocking in the high altitude zone, while the concomitant decrease in alpine grassland area is likely to have negative implications for alpine species. The complex and spatially variable changes that we report highlight the necessity for considering local factors such as topography when attempting to predict species distributional responses to warming climate.
authors.affiliation: Tropical Ecology and Conservation Group, Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Greenwood
authors.forename: Jan-Chang
authors.initials: JC
authors.lastname: Chen
authors.forename: Chaur-Tzuhn
authors.initials: CT
authors.lastname: Chen
authors.forename: Alistair S
authors.initials: AS
authors.lastname: Jump
mesh_terms: D000531:Altitude; D057965:Carbon Sequestration / Q000502:physiology; D003198:Computer Simulation; D065928:Forests; D005843:Geography; D008954:Models, Biological; D011156:Population Density; D013624:Taiwan; D013696:Temperature; D014197:Trees / Q000254:growth & development*
keywords: Abies kawakamii; Taiwan; aerial photography; alpine habitat; central mountain range; climate change; forest density; fragmentation; topography