Yong Luo and colleagues recently had their paper published in Journal of Ecology. Read more about their work below.
Global change ecologists have often used trees under weak competition to examine relationships between climatic change and tree growth. Scaling up these results to a forest relies on the assumption that the climatic change-tree growth relationship is not affected by tree-level competition; especially the competition gradient from dominant trees to suppressed trees in a forest stand.
By using permanent sample plot data from the central Canadian boreal forest region, where warming did not result in water deficit, Dr. Yong Luo and his colleagues found that growth increased over time for trees under weak competition, but decreased for those under strong competition. The divergent temporal trends among trees under different levels of competition led to a non-significant change in growth at the plot level. Growth increased with regional warming, atmospheric [CO2] and water availability for trees under weak competition, supporting the hypothesis that tree growth of a boreal forest is limited by heat, water and atmospheric CO2, and climate change has positive effect on tree growth. However, for those under strong competition, the tree growth is generally negatively related to climate variables.
The results suggest that upscaling the growth responses of dominant/codominant trees to climate change to a forest or a region can lead to overestimates. Furthermore, the study suggests that increases in carbon sequestration associated with climatic change-enhanced forest growth may be weak in forests where water deficit is not an issue. Finally, the study sheds light on a mechanism of climate change-associated tree mortality. Trees experiencing weak competition grow more rapidly in response to climate change, in turn enhancing their competitiveness and further suppressing the growth of smaller trees that were already experiencing strong competition.
Yong Luo, Lakehead University & University of British Columbia, Canada
Read the full paper online: Climatic change only stimulated growth for trees under weak competition in central boreal forests