Local factors, including geology and topography, play a critical role
By Summit Voice
SUMMIT COUNTY — For residents of high-elevation regions, including Colorado — the impacts of global warming include a potentially radical change in the composition of plant communities. In mountainous areas, the distribution of many species is limited by factors related to elevation, including temperature.
With warmer and drier conditions potentially limiting growth at lower elevations, scientists have already documented the treeline creeping upward in some areas, but there are additional factors to consider, according to a new study from the University of Calgary.
Even in a warmer world, local conditions, including slope steepness, exposure and soil depth – will limit trees being established and growing on mountainsides, the research found.
“You can’t just take a mountain range and say that in every place the tree line is going up,” says Edward Johnson, professor of Biological Sciences and study co-author with then-postdoctoral researcher, Marc Macias-Fauria – now at Oxford University.
The disruption caused by a shifting tree line could fragment alpine ecosystems and potentially threaten certain species. But temperature alone “cannot explain high-elevation tree cover over a more than 100-square-kilometre (study) area in the Canadian Rockies,” the researchers concluded,
“We have to caution that it depends on how much suitable habitat there is above where the tree line is now,” said Johnson, who’s also director of the U of Calgary’s Biogeoscience Institute.
The two researchers looked at tree cover in the Marmot Creek Research Watershed, located next to the Nakiska ski hill in Kananaskis Country west of Calgary.
Using a supercomputer at Oxford University, they ran regional and global computer climate models, and also did remote sensing and on-the-ground investigation of the study area.
They then used the model to forecast tree cover based on moderate climate warning predicted for the late 21st century.
Even with warmer temperatures, “there are lots of places in the present alpine where the conditions are simply not suitable for trees,” Johnson said.
“Between six to 18 percent of the present alpine area is either too steep, has bedrock, cliffs and talus or some other local terrain conditions that will limit trees being established,” he adds.
The researchers now plan to develop a new model that includes all the local geologic/geomorphic factors, and which will identify the inter-related causes of why trees do or do not get established and grow in specific mountain areas.
The study was published this week in the Proceedings of the National Academy of Sciences USA journal.