Figure 15. Conceptual diagram of the factors driving sequestration of CO₂ at Harvard Forest. The forest is aggrading due to the legacies of prior land use and the hurricane of 1938. Factors such as lengthening the growing season, atmospheric nutrient inputs, forest management, and higher atmospheric CO₂ accelerate uptake of CO₂. Air pollution, introduced pests, and timber harvest reduce CO₂ sequestration.