Importance of colonization and competition in forest landscape response to global climatic change

Abstract

The tree species composition of a forested landscape may respond to climate change through two primary successional mechanisms: (1) colonization of suitable habitats and (2) competitive dynamics of established species. In this study, we assessed the relative importance of competition and colonization in forest landscape response (as measured by the forest type composition change) to global climatic change. Specifically, we simulated shifts in forest composition within the Boundary Waters Canoe Area of northern Minnesota during the period 2000-2400 ad. We coupled a forest ecosystem process model, PnET-II, and a spatially dynamic forest landscape model, LANDIS-II, to simulate landscape change. The relative ability of 13 tree species to colonize suitable habitat was represented by the probability of establishment or recruitment. The relative competitive ability was represented by the aboveground net primary production. Both competitive and colonization abilities changed over time in response to climatic change. Our results showed that, given only moderate-frequent windthrow (rotation period = 500 years) and fire disturbances (rotation period = 300 years), competition is relatively more important for the shortterm (<100 years) compositional response to climatic change. For longer-term forest landscape response (>100 years), colonization became relatively more important. However, if more frequent fire disturbances were simulated, then colonization is the dominant process from the beginning of the simulations. Our results suggest that 54 Climatic Change (2012) 110:53-83 the disturbance regime will affect the relative strengths of successional drivers, the understanding of which is critical for future prediction of forest landscape response to global climatic change.

Sapling growth responses to warmer temperatures ‘cooled’ by browse pressure

“…Eventual overstory composition is the result of species level performance and competitive interactions at multiple early life stages (Pacala et al, 1996;Poorter, 2007). Notable recent studies have found indications that many tree species are not exhibiting northward expan-sions (Zhu et al, 2012) and have shown that other factors, such as competition, likely play a bigger role than climate variation (Clark et al, 2011;Xu et al, 2012). Decreasing growth by both temperate and boreal saplings as they approach their range limits suggests that temperature-mediated competitive dynamics are a key driver of sapling performance, forest composition, and range boundaries across the temperate-boreal transition zone.…”

More than the sum of its parts: how disturbance interactions shape forest dynamics under climate change

“…), and (3) there is a diverse suite of extant tree species that allows for emergent behaviors, as expressed through changes in succession via competition, facilitation, release, and compensatory growth (Xu et al. ).…”

“…(1) to contrast relative tree mortality rates and the extent of disturbance for four individual (single) disturbance regimes (fire, insects, wind, or forest management) vs. all four disturbance regimes operating concurrently (concurrent) under different climate change scenarios, and (2) to determine how climate change interacts with single and concurrent disturbance regimes to affect forest composition. We focused on a large landscape in north-central Minnesota (USA) because (1) all four disturbances are historically important, (2) climate change is expected to be substantial over the next century due to its relatively high latitude , and (3) there is a diverse suite of extant tree species that allows for emergent behaviors, as expressed through changes in succession via competition, facilitation, release, and compensatory growth (Xu et al 2012).…”

How do disturbances and environmental heterogeneity affect the pace of forest distribution shifts under climate change?

“…Dynamic landscape simulations have shown that forest disturbances can have major impacts on carbon storage and species composition under changing climatic conditions (Scheller and Mladenoff 2005). Disturbances provide many opportunities for colonization and establishment, and also affect the competitive balance between early‐ and late‐successional species at stand and landscape scales (Xu et al 2012). Accordingly, we hypothesized that periodic stand disturbances from forest harvesting would accelerate the rate at which forest types gain and lose area at the leading and trailing edges of their distributions, respectively.…”