Spatially simulating changes of soil water content and their effects on carbon sequestration in Canada's forests and wetlands

The variations of soil water content (SWC) and its influences on the carbon (C) cycle in Canada's forests and wetlands were studied through model simulations using the Integrated Terrestrial Ecosystem Carbon (InTEC) model. It shows that Canada's forests and wetlands experienced spatially and temporally heterogeneous changes in SWC from 1901 to 2000. SWC changes caused average NPP to decrease 40.8 Tg C yr−1 from 1901 to 2000, whereas the integrated effect of non‐disturbance factors (climate change, CO2 fertilization and N deposition) enhanced NPP by 9.9%. During 1981–2000, the reduction of NPP caused by changes in SWC was 58.1 Tg C yr−1 whereas non‐disturbance factors together caused NPP to increase by 16.6%. SWC changes resulted in an average increase of 4.1 Tg C yr−1 in the net C uptake during 1901–2000, relatively small compared with the enhancement in C uptake of 50.2 Tg C yr−1 by the integrated effect of non‐disturbance factors. During 1981–2000, changes in SWC caused a reduction of 3.8 Tg C yr−1 in net C sequestration whereas the integrated factors increased net C sequestration by 54.1 Tg C yr−1. Increase in SWC enhanced C sequestration in all ecozones.