Modeling the Effects of Climate Change on Forest Succession in Northern Michigan

Abstract

Following a well-known successional dynamic in eastern North America, the species composition in many northern Michigan forests is changing as early successional species that colonized after the logging and fires of the early 20th century reach the end of their life spans. What is not well-understood is how changing climate (predicted to be overall warmer and drier by the end of the 21st century) will also influence future species composition. To address this knowledge gap, in this study I modeled forest composition and succession over a regionally representative northern temperate landscape under different climate scenarios. The study site was the University of Michigan Biological Station (4046 ha) in northern Lower Michigan. My objectives were to: 1) develop the needed input data to parameterize, calibrate, and run the LANDIS-II forest landscape model and its PNet succession module at the landscape level, 2) develop three different future climate scenarios for the study region – a static climate scenario, a moderate warming scenario with up to 4 degrees of warming compared to the current climatology, and a high warming scenario with up to 8 degrees of warming compared to the current climatology, and 3) use the parameterized LANDIS-II/PNet models to predict changes in forest successional composition and biomass under the different climate scenarios, and analyze these by regionally-important species and by landform-level ecosystems. Species biomass and response to climate change varied among landform-level ecosystems. Results showed that under all climate scenarios and landforms, the early successional species of birch and aspen decreased. While later successional species like white pine, red maple, sugar maple, beech, balsam fir, oak, and hickory increased in biomass under all climate scenarios, the increase was greater for sugar maple, fir, hickory, hemlock, and oak under the high warming scenario. Red maple increased the most under both the moderate and the high warming scenarios. The overall changes were largest under the high warming scenario. All other species showed mixed or similar increases under all climate scenarios. There was little expansion of species from one landform-level ecosystem type to another within the UMBS area. These results show the influence of potential climate change, and also the continued importance that non-climactic factors such as land-use history and soil fertility have in determining species locations.