Abstract
Land use change (LUC), disturbances, and their interactions play an important role in regional forest carbon (C) dynamics. Here we quantified how these activities and events may influence future aboveground biomass (AGB) dynamics in forests using national forest inventory (NFI) and Landsat time series data in the Northern United States (US). Total forest AGB predictions were based on simulations of diameter growth, mortality, and recruitment using matrix growth models under varying levels of LUC and disturbance severity (low (L), medium (M), and high (H)) every five years from 2018 to 2098. Land use change included the integrated effects of deforestation and reforestation/afforestation (forest [F]→agriculture [A], settlements [S, urbanization/other], and A&S→F), specifically, conversion from F→A, F→S, F→A&S, A→F, S→F, and A&S→F. Disturbances included natural and anthropogenic disturbances such as wildfire, weather, insects and disease, and forest harvesting. Results revealed that, when simultaneously considering both medium LUC and disturbances, total forest AGB predictions of LUC + fire, LUC + weather, LUC + insect & disease, and LUC + harvest indicated substantial increases in regional C stocks (± standard deviation) from 1.88 (±0.13) to 3.29 (±0.28), 3.10 (±0.24), 2.91 (±0.19), and 2.68 (±0.17) Pg C, respectively, from 2018 to 2098. An uncertainty analysis with fuzzy sets suggested that medium LUC under disturbances would lead to greater forest AGB C uptake than undisturbed forest C uptake with high certainty, except for LUC + harvest. The matrix models in this study were parameterized using NFI and Landsat data from the past few decades. Thus, our results imply that if recent trends persist, LUC will remain an important driver of forest C uptake, while disturbances may result in C emissions rather than undisturbed forest C uptake by 2098. The combined effects of LUC and disturbances may serve as an important driver of C uptake and emissions in the Northern US well into the 21st century.
Highlights
The accelerating rise of carbon (C) emissions and resulting net increases in atmospheric carbon dioxide (CO2 ) is a substantial forcing factor in global warming [1]
Given the potential for terrestrial C emissions to the atmosphere or C transfer to other ecosystem pools or land use categories caused by land use change (LUC) and disturbances, the objective of this study was to predict the effects of LUC, disturbances, and their interactions on forest aboveground biomass (AGB) C dynamics using national forest inventory (NFI) plots and Landsat time-series data in the Northern United States (US)
There is a confluence of factors that may drive future trajectories of AGB C uptake in forests, especially when disturbances and LUC are considered
Summary
The accelerating rise of carbon (C) emissions and resulting net increases in atmospheric carbon dioxide (CO2 ) is a substantial forcing factor in global warming [1]. The dynamics of the terrestrial C cycle have come under increasing focus because of climate and land use change (LUC, deforestation and reforestation/afforestation). Such changes, when combined with disturbances, are the primary drivers of global changes in forest C stocks [2,3]. Land use change in the US is mainly caused by human activity that has generated substantial impacts on forest C dynamics in terrestrial ecosystems since settlement by Europeans [8,9]. Estimates of the long-term forest C dynamics of the Northern US with impacts of LUC are largely unknown and uncertain [14]
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