Forest carbon cycling is a political and scientific challenge. From a policy perspective, carbon storage is important to climate mitigation, with the goal of sequestering carbon dioxide (CO2) in forests. From a scientific perspective, the environmental variables that control storage and loss of carbon are of central interest. This dissertation looks at carbon cycling from both perspectives: carbon storage in live biomass to offset emissions and the mechanisms that determine carbon loss from dead biomass. First we compared Massachusetts’ forest carbon sequestration in live biomass to energy-sector CO2 emissions. We found that over 10% of the state’s energy-sector CO2 emissions were sequestered within the state’s forest and nearly half of these forests were at risk of deforestation. From there we looked at the history of a Massachusetts forest to see how a changing composition altered carbon storage in live and dead biomass. We found that this forest increased in above-ground woody biomass carbon storage during the first 40 years, sequestering 3.80 Mg C/ha/yr, but sequestration decreased over the next 20 years. In mature stands, we found that total coarse woody debris biomass in the forest was 13.52 Mg/ha and lignin was 23% of the total biomass. With the knowledge of the woody debris composition, we then asked what would happen to this carbon pool with climate change. We found that soil warming increased mass loss of woody debris by as much as 30%, but that more recalcitrant and larger debris decomposed much slower. We also found that the most lignin-rich species lost lignin the fastest. Last, we asked how a change in woody inputs to the soil from a shifting forest composition would influence soil dynamics under current and future environmental scenarios of warming and nitrogen deposition. We found that a shift from recalcitrant to more labile woody inputs would only increase microbial respiration and activity under future scenarios of warming and nitrogen addition. The research in this dissertation suggests that forests may be able to mitigate CO2 emissions under current forest composition and environmental scenarios, but this could shift dramatically in the next 100 years with a changing environment.
|Commitee:||Ellmore, George, Finzi, Adrien, Reed, Michael|
|School Location:||United States -- Massachusetts|
|Source:||DAI-B 72/05, Dissertation Abstracts International|
|Subjects:||Ecology, Climate Change, Biogeochemistry|
|Keywords:||Carbon cycling, Carbon offsets, Global climate change, Lignin, Temperate forests, Woody debris|
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