Large-scale climate driven disturbance modifies net carbon pools in a mature temperate forest

Background/Question/Methods

Over the last three decades, the terrestrial biosphere has provided a net sink for approximately 20% of carbon dioxide emitted by the burning of fossil fuels, with the majority estimated to occur in forests. Forests can sequester large amounts of carbon in soils and woody biomass. Similarly, deadwood, including fallen trees, snags, and woody coarse debris make up 8% of the total carbon stock in the world’s forests. Large-scale disturbances, however, have been increasing in intensity and frequency in some regions due to climate change, causing a more chronic stress to forest ecosystems. Temperate forests that have not historically undergone high frequency of severe storms are likely to be more susceptible to these perturbations. This low resistance may limit the ability of these ecosystems to buffer against future emissions. To investigate the impact of a recent large-scale tornado disturbance on the net carbon structure in a temperate forest, we used allometric equations to calculate the aboveground biomass and carbon storage capacity of all woody stems (diameter at breast height > 1 cm) pre- and post-disturbance in 2.56 ha of a mature forest stand. We hypothesized that the wind disturbance substantially modified the distribution of carbon pools within the forest.

Results/Conclusions

Standing biomass of the forest was substantially reduced, and over 60% of trees incurred some damage. Among damaged trees, 90% of the community was completely uprooted, suggesting that these organisms are unlikely to recover, and biomass will contribute to the deadwood carbon budget. Areas with higher aboveground biomass before the disturbance experienced a greater loss in biomass. Morphological differences between species may account for variation in carbon storage throughout the old growth forest. L. tulipifera, also known by its common name as the tulip poplar, tend to be the tallest and largest in easterm deciduous forests, resulting in the highest living aboveground biomass among species. The tulip poplar contributed the most to the total of deadwood biomass generated after the large-scale disturbance. Temperate forests may take up to 15 years to recover from severe storms, and the loss in carbon sequestration capacity is not compensated by the short-term increase in productivity from higher nutrient input from detritus. Understanding how the carbon cycle affects our natural environment is important for the successful implementation of climate change mitigation strategies. Our results help clarify how forest carbon dynamics respond to these upscaling windthrow disturbances, capable of reducing short-term carbon storage in US forests.