Thursday, August 9, 2018: 8:20 AM
245, New Orleans Ernest N. Morial Convention Center
Kai Zhu, University of California, Santa Cruz, Jian Zhang, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, China, Shuli Niu, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China, Chengjin Chu, Sun Yat-sen University and Yiqi Luo, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ
Background/Question/Methods North American forests have been widely recognized as a growing carbon sink, absorbing a substantial amount of CO2 from the atmosphere. Two processes are commonly considered to dictate this growing carbon sink: forest recovery induced by land use change or disturbances such as agricultural abandonment, reduced harvesting, and fire suppression; and growth trajectory modified by environmental change such as CO2 fertilization, nitrogen deposition, and climate change. These two growth processes could have contrasting implications to the fate of the carbon sink. To address both processes, we compiled a forest inventory dataset over 26 yr and 140,267 plots in the United States and Canada to quantify aboveground biomass growth with stand age across forest types and climate gradients, using a hierarchical Bayesian approach. Our goals are to understand the fate of forest biomass as a carbon sink and to predict its potential in mitigating global change.
Results/Conclusions
During the current period (2000 – 2016), our model successfully explains the large variations in the aboveground biomass across the stand age and geographic gradients of major forest types in North America. In the idealized case of no further disturbances, we predict that across North America, the forest aboveground biomass grows from 90 Mg ha–1 (2000 – 2016) to 105 Mg ha–1 (2020s), 128 Mg ha–1 (2050s), and 146 Mg ha–1 (2080s) under various climate change scenarios. Climate change modifies the forest recovery trajectory to some extent, but the overall forest growth is limited, showing signs of biomass saturation. The future biomass will only increase 22% (2080s) at most over the current level, implying that the CO2 emission targets might need to be lowered. Our ground-based analysis suggests that active management strategies are needed to sustain the North American forest biomass carbon sink.
