Sapling growth across a gradient of forest disturbance: implications for carbon sequestration
Author:Aubrie De La Cruz
- Robert Fahey, Forest Ecologist, Morton Arboretum
- Christopher Gough, Researcher Assistant Professor and Instructor, Virginia Commonwealth University
Forest ecosystems are natural carbon sinks that help mitigate climate change caused by excessive CO2 emissions. Rapid climate change can stress forest ecosystems and prompt disturbance, making an increase in disturbance frequency likely in the future. Disturbance may alter the capacity of forest carbon sinks thus, it is necessary to study how forest carbon sequestration responds to and recovers from disturbances. We examined how late-successional sapling species (Quercus rubra and Acer rubrum) respond to forest disturbance and facilitate recovery in a temperate deciduous forest of northern lower Michigan. Our research site was an experimentally-treated forest where all early-successional canopy tree species (Populus grandidentata and Betula papyrifera) were stem-girdled to create canopy gaps, simulating a moderate disturbance. Diameter at breast height (DBH) and annual growth metrics were taken for all Quercus and Acer saplings across a gradient of disturbance severity. These data were used to analyze the relationships between annual height and diameter growth across the gradient of canopy gaps, to project which species may become the future canopy dominant and determine how each contributes to forest carbon sequestration recovery. Our results showed that Acer and Quercus saplings were highly responsive to canopy disturbance, but in different ways. As disturbance severity increased, Acer grew taller more quickly when DBH was below 4cm, but Quercus grew wider more quickly when DBH was above 4cm, demonstrating that Acer has a height growth advantage at smaller widths, but Quercus has a diameter growth advantage at larger widths. Additional data need to be gathered to determine if these growth trends hold for all DBHs, to give a better understanding of which species is dominating. This will tell us how these species are contributing to forest carbon storage recovery and help us determine the potential strength of the forest carbon sink in the future.