Tree range expansion in eastern North America fails to keep pace with climate warming at northern range limits

Abstract

Rising global temperatures are suggested to be drivers of shifts in tree species ranges. The resulting changes in community composition may negatively impact forest ecosystem function. However, long-term shifts in tree species ranges remain poorly documented. We test for shifts in the northern range limits of 16 temperate tree species in Quebec, Canada, using forest inventory data spanning three decades, 15° of longitude and 7° of latitude. Range shifts were correlated with climate warming and dispersal traits to understand potential mechanisms underlying changes. Shifts were calculated as the change in the 95th percentile of latitudinal occurrence between two inventory periods (1970-1978, 2000-2012) and for two life stages: saplings and adults. We also examined sapling and adult range offsets within each inventory, and changes in the offset through time. Tree species ranges shifted predominantly northward, although species responses varied. As expected shifts were greater for tree saplings, 0.34 km yr , than for adults, 0.13 km yr . Range limits were generally further north for adults compared to saplings, but the difference diminished through time, consistent with patterns observed for range shifts within each life stage. This suggests caution should be exercised when interpreting geographic range offsets between life stages as evidence of range shifts in the absence of temporal data. Species latitudinal velocities were on average <50% of the velocity required to equal the spatial velocity of climate change and were mostly unrelated to dispersal traits. Finally, our results add to the body of evidence suggesting tree species are mostly limited in their capacity to track climate warming, supporting concerns that warming will negatively impact the functioning of forest ecosystems.

Climate change and tree harvest interact to affect future tree species distribution changes

“…Thus, our results suggest that range shifts of most tree species will not keep pace with climate change. This finding is in line with many previous studies that suggest most of tree species will not move fast enough to track and adjust to the pace and magnitude of climate change (Sittaro et al., ) and biotic factors (e.g. dispersal, colonization) dominate the leading edge limits (Putnam & Reich, ; Saltré, Duputié, Gaucherel, & Chuine, ).…”

“…However, we found that tree harvest generally did not interact with climate change to facilitate or ameliorate extinctions. This was because tree species may take centuries to respond to changing climates due to inherent demographic inertia that enables tree species resist extinction during unfavourable climatic conditions (Sittaro et al., ). As a result, our 100‐year simulation period may not be long enough for interactive effects to manifest.…”

Divergent responses to climate change and disturbance drive recruitment patterns underlying latitudinal shifts of tree species

“…The latitudinal shift patterns we observed for four northern temperate hardwood tree species were generally consistent with climate change predictions of northward shifts at the northern range limit (Périé & de Blois, ) and with those of previous studies (Boisvert‐Marsh et al, ; Sittaro et al, ). They also reveal shifts that result from spatially explicit responses, with different combinations of climate change and disturbance variables influencing the probability of sapling occurrence gains depending on location within the study area.…”

Projected Future Distribution of Tsuga canadensis across Alternative Climate Scenarios in Maine, U.S

“…Recent research found that the rate of tree species latitudinal migrations were, on average, <50% of that required to keep pace with the spatial velocity of climate change [31] suggesting that migration success of individual species will require active management. The management of Tsuga canadensis in particular, may include site preparation [30] and the removal of the pervasive competitor, Fagus grandifolia saplings, which are shade tolerant and also susceptible to beech bark disease [5].…”