Evaluating a 50 Year Record of Forest Encroachment in Rocky Mountain Alpine Meadows

95th Ecological Society of America (ESA) Annual Meeting, Pittsburgh, PA, 01-06 August 2010

Sunita Yadav and Stephen F. Matter

“The potential impact of global warming is predicted to be strongest at higher altitude and latitude. Alpine meadows are already limited in their spatial extent and are especially vulnerable to rising temperatures which may cause them to retract substantially or completely disappear due to invasion by woody forest species. It is generally believed, that during periods of warmer than average temperatures, tree-line increases in altitude. In our study, we analyzed the record from 1952 to 2009 of forest encroachment in the Alberta Rocky Mountains. We quantified the extent of meadow areas along two ridges in the front ranges of the Canadian Rockies to explore land cover change. Historical aerial photographs, image processing, and geographic information systems (GIS) tools were used to quantify the extent of forest encroachment over the past 50 years. Using an orthorectified base map, we co-registered the aerial photographs and classified forest and meadow areas. Actual areal extent was calculated in a GIS program.  The results clearly show a significant decrease in meadow area with the majority of the reduction occurring within the past two decades. The consequences of such dramatic landscape change have cascading effects on meadow populations leading to reduced overall species diversity and smaller individual species populations due to fragmentation and isolation. Further work on this system involves studying the effects of this fragmentation on the population structure of a Sedum species occurring in these meadows.”