Abstract
BackgroundForest disturbance induced changes in the coupling of forest carbon and water have important implications for ecosystem functioning and sustainable forest management. However, this is rarely investigated at the large watershed scale with cumulative forest disturbance. We used a combination of techniques including modeling, statistical analysis, and machine learning to investigate the effects of cumulative forest disturbance on water use efficiency (WUE, a proxy for carbon and water coupling) in the 19,200 km2 Chilcotin watershed situated in the central interior of British Columbia, Canada. Harvesting, wildfire, and a severe Mountain Pine Beetle (MPB) infestation have gradually cumulated over the 45-year study period, and the watershed reached a cumulative equivalent clear-cut area of 10% in 1999 and then 40% in 2016.ResultsSurprisingly, with the dramatic forest disturbance increase from 2000 to 2016 which was mainly due to MPB, watershed-level carbon stocks and sequestration showed an insignificant reduction. This resilience was mainly due to landscape-level carbon dynamics that saw a balance between a variety of disturbance rates and types, an accumulation of older stand types, and fast growing young regenerated forests. Watershed-level carbon sequestration capacity was sustained, measured by Net Primary Production (NPP). A concurrent significant decrease in annual evapotranspiration (ET), led to a 19% increase in WUE (defined as the ratio of NPP to ET), which is contrary to common findings after disturbance at the forest stand-level. During this period of high disturbance, ET was the dominant driver of the WUE increase.ConclusionsWe conclude that disturbance-driven forest dynamics and the appropriate scale must be considered when investigating carbon and water relationship. In contrast to the stand-level trade-off relationship between carbon and water, forested watersheds may be managed to maintain timber, carbon and water resources across large landscapes.
Highlights
Forest disturbance induced changes in the coupling of forest carbon and water have important impli‐ cations for ecosystem functioning and sustainable forest management
Tau is the z-statistic from the Mann–Kendall test indicating the direction of change of the variable; p-value is the level of significance from the Mann–Kendall test; and bolded italics indicate significant trends at a significance level of 0.05), CECA cumulative clear-cut area, AGBIO above ground biomass, DOM dead organic matter, TEC total ecosystem carbon, Net Primary Production (NPP) net primary production, NBP net biome production, Annual Mean Daily Temperature (Tmean) annual average daily temperature, Annual Minimum Daily Temperature (Tmin) annual minimum daily temperature, Annual Maximum Daily Temperature (Tmax) annual maximum daily temperature, P precipitation, Potential Evapotran‐ spiration (PET) potential evapotranspiration, evapotran‐ spiration (ET) evapotranspiration, Q mean annual streamflow, Water use efficiency (WUE) water use efficiency (AGBIO, TEC, and DOM) all significantly (P < 0.001) increased over the period from 1971 to 1999
Watershed-level DOM increased significantly after the high levels of Mountain Pine Beetle (MPB) mortality in the early 2000s, as MPB killed living biomass in trees, converting it to DOM [55]. This suggests that there is a relationship between forest disturbance and some carbon sub-pools, and the conversion from AGBIO to DOM caused by MPB infestation was the key reason for insignificant reduction in the total amount of carbon stored in the watershed (TEC) despite severe cumulative disturbance
Summary
Forest disturbance induced changes in the coupling of forest carbon and water have important impli‐ cations for ecosystem functioning and sustainable forest management. This is rarely investigated at the large watershed scale with cumulative forest disturbance. We used a combination of techniques including modeling, statis‐ tical analysis, and machine learning to investigate the effects of cumulative forest disturbance on water use efficiency (WUE, a proxy for carbon and water coupling) in the 19,200 km Chilcotin watershed situated in the central interior of British Columbia, Canada. WUE is used to evaluate the potential impacts of climate change on food production [10, 11], water supply [7], and forest or land use management [12,13,14]. Among the existing studies on WUE at various spatial scales, large watershed- or landscape-level studies are rare, likely due to the difficulty of conducting field measurements [24]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
