Simulating Climate, Fire, and Management Influences on Forest Carbon Dynamics in Single- and Multi-Species Forests of the Southwestern and Southeastern US

Abstract:

The interaction of climate, disturbance, and management on forest structure and composition can alter carbon dynamics. Understanding how these factors influence forest carbon dynamics individually and in combination is necessary for making forest projections under altered climatic conditions. Model and emission scenario uncertainty in climate projections presents one challenge. When simulating disturbance, such as fire, projected climate influences both fire behavior and post-wildfire regeneration. The outcome of management actions implemented to alter forest conditions can be influenced by both climate and disturbance. Simulation results in both single- and multi-species forests occupying different future climate space indicate the importance of between climate model variation and variation between emission scenarios. The variation in projected biomass as a function of climate model input is as much as 40%. Response to emission scenario varies as a function of climate space, with increased late-century divergence in net ecosystem exchange (NEE) and biomass. When fire is simulated, climate model influence on biomass ranged from 0-27 Mg ha^-1, while the effect on NEE ranged from -279 to 238 g m^-2. Management implemented to reduce fire risk or provide wildlife habitat influences near- and long-term carbon dynamics as a function of projected climate, with the difference between no management and management for fire risk yielding a range in biomass of 0.6 to 10.78 Mg ha^-1 and relatively little change in NEE (-8 to 21 g m^-2). Given the range of results, including a suite of models and emission scenarios allow for bracketing the range of future forest conditions. However, the mismatch in scales between climate projections and the microclimatic influences on regeneration and the influence of projected climate on wildfire frequency and type add sources of uncertainty to these projections that require additional investigation.