Lessons from a 15-year eddy-covariance dataset: could changing soil water content tip the temperate forest carbon balance?
Abstract
Multi-year carbon (C) flux datasets dating back to the 1990s reveal a predominantly increasing trend in temperate forest C sequestration. The magnitude and nature of this trend does not match theoretical and/or global vegetation model predictions, in large part because the dominant biophysical drivers of these fluxes are still in debate, making it difficult to forecast the stability of this sink. Disentangling the primary biophysical variables controlling these fluxes is further complicated by co-occurring forest succession processes, increasing atmospheric carbon dioxide (CO2), vegetation-climate interactions, and disturbance. Here, we utilize a 15-year eddy covariance dataset from a temperate, deciduous forest at the University of Michigan Biological Station (AmeriFlux site US-UMB) to observe gross primary production (GPP), ecosystem respiration (Re), and net ecosystem production (NEP) over time, and to identify the ecological and environmental drivers of these C fluxes. Forest NEP increased by 0.75 Mg-C ha-1 over the last 15 years as GPP rose without a concomitant increase in Re. We found that soil water content, more than temperature and incoming radiation, governed GPP and Re. Multivariate regression and PLS SEM analysis converged to suggest that, despite significant succession-driven shifts in species dominance and rising atmospheric CO2 concentrations throughout the study period, changing environmental variables accounted for most of the C exchange. As soil water content continues to shift with climate change, it is imperative to develop a more comprehensive understanding of its coupling with the temperate forest carbon cycle.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B13B..06S
- Keywords:
-
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 1631 Land/atmosphere interactions;
- GLOBAL CHANGE;
- 1813 Eco-hydrology;
- HYDROLOGY