Understanding Disturbance Regimes from Patterns in Forest Biomass

Abstract

Natural and anthropogenic disturbances are important drivers of tree mortality, shaping the structure, composition, and biomass distribution of forest ecosystems. Differences in disturbance regimes, characterized by the frequency, extent, and intensity of disturbance events, result in structurally different landscapes. Characterizing different disturbance regimes through landscape-scale forest structure provides a unique perspective for diagnosing the impacts and potential carbon-climate feedbacks from terrestrial ecosystems. In this study, we design a model-based experiment to investigate the links between disturbance regimes and spatial biomass patterns. We generate over 850 thousand biomass patterns, from 2,142 combinations of μ, α, and β under different primary productivity and background mortality scenarios. We characterize the emergent biomass patterns via synthesis statistics, including central tendency statistics; different moments of the distribution; information-based and texture features. We further follow a multi-output regression approach that takes the biomass synthesis statistics and gross primary production (GPP) as independent variables to retrieve the three disturbance regimes parameters. Results show confident inversion of all three “true” disturbance parameters, with Nash-Sutcliffe efficiency of 94.8% for μ, 94.9% for α, and 97.1% for β. Overall, these results demonstrate the association between biomass patterns and disturbance statistics that emerge from different underlying disturbance regimes. By doing so, it overcomes the known issue of equifinality between mortality rates and total biomass. Given the increasing availability of Earth observation of biomass, our findings open a new avenue to better understand and parameterize disturbance regimes and their links with vegetation dynamics under climate change. Ultimately, at a large scale, this approach would improve our current understanding of controls and feedback at the biosphere-atmosphere interface in the current Earth system models.