How silvicultural treatments and site quality affect carbon storage on the Penobscot Experimental Forest: A 60-year perspective.

摘要

Developing forest management strategies for addressing global climate change is one of the foremost challenges facing resource managers and policy makers today, but little is known about the impacts of these strategies on carbon cycles in many forest types. To address this issue within the Acadian Forest, I evaluated carbon storage, in 2012, among selection, shelterwood, and commercial clearcut treatments that were initiated in the 1950s on the Penobscot Experimental Forest in central Maine, USA. C pools were also measured in an unmanaged reference stand. Specifically, I investigated (1) the probability of detecting a significant forest management effect on mineral soil carbon content, (2) variability in organic horizon carbon content due to various abiotic and biotic factors, (3) the influence of disturbance, stand development, and site quality on dead wood biomass pools, and (4) differences total ecosystem carbon content plus carbon stored in harvested wood products among treatments after accounting for site quality. In Chapter 1, I found that the probability of detecting a significant forest management effect on mineral soil carbon content was only 6%, which was partially related to high variability in mineral soil carbon content.;In Chapter 2, I found that bryophyte mass only explained a small portion of the high within-plot variation in O horizon C content. In chapter 3, I found that there were significant differences dead wood biomass pools among the selection, shelterwood, and commercial clearcut treatments. The timing of harvest entries in relation to the occurrence and duration of natural disturbances had long-lasting influences on dead wood biomass pools. In chapter 4, I found that, average total ecosystem carbon content plus carbon stored in harvest wood products was highest in the selection and shelterwood treatments, and was lowest in the commercial clearcut treatment. On soils derived from glacial till, locations with higher percentages of coarse fragments in the mineral soil tended to have less total ecosystem carbon content than locations with lower percentages of coarse fragments. Overall, this study highlights the importance of using silvicultural practices as opposed to exploitative harvesting when objectives include maximizing C storage in forests.