Modeling Soil and Biomass Carbon Responses to Declining Water Table in a Wetland-Rich Landscape

Abstract

Peatlands and forested wetlands can cover a large fraction of the land area and contain a majority of the regional carbon pool in wet northern temperate landscapes. We used the LANDIS-II forest landscape succession model coupled with a model of plant community and soil carbon responses to water table changes to explore the impacts of declining water table on regional carbon pools in a peatland-and wetland-rich landscape in northern Wisconsin, USA. Simulations indicated that both biomass accumulation and soil decomposition would increase as a consequence of drying. In peatlands, simulated water table declines of 100 cm led to large increases in biomass as well as shortterm increases in soil carbon, whereas declines of 40 cm led to continuous declines in soil carbon and smaller increases in biomass, with the net result being a loss of total carbon. In non-peat wetlands, biomass accumulation outweighed soil carbon loss for both scenarios. Long-term carbon cycle responses were not significantly affected by the time scale of water table decline. In general, peatland carbon storage over the first 50-150 years following drainage was neutral or increasing due to increased plant growth, whereas carbon storage over longer time scales decreased due to soil carbon loss. Although the simplicity of the model limits quantitative interpretation, the results show that plant community responses are essential to understanding the full impact of hydrological change on carbon storage in peatland-rich landscapes, and that measurements over long time scales are necessary to adequately constrain landscape carbon pool responses to declining water table.

Subtle shifts in microbial communities occur alongside the release of carbon induced by drought and rewetting in contrasting peatland ecosystems

“…However, climate change represents a serious threat to temperate peatlands; for example, within the UK the area covered by blanket peat is projected to decline, with the potential for peatlands to change from carbon sinks to carbon sources 15 . Likewise, the amount of carbon stored within peatlands in Canada 16 , the USA 17 and across the Northern hemisphere 18 is also predicted to decline.…”

Parameter interactions and sensitivity analysis for modelling carbon heat and water fluxes in a natural peatland, using CoupModel v5

“…Another limitation of previous peatland modelling studies is the use of local sensitivity analyses, changing only one parameter or one input driver at a time (e.g. Hilbert et al, 2000;Yu et al, 2001;Zhang et al, 2002;Wania et al, 2009;Frolking et al, 2010;Tang et al, 2010;St-Hilaire et al, 2010). This approach does not account for possible interactions and non-linearity in equations (e.g.…”

Modelling Sphagnum moisture stress in response to projected 21st‐century climate change

“…While not accounting for Sphagnum mosses directly, Sulman et al . () model landscape vegetation succession, in part, by combining species mortality rates and establishment probability with differences in moisture constraints on productivity, maximum productivity and flood tolerance.…”

“…Moreover, with a systematic decrease in soil-moisture storage, shifts in the vegetation community are likely over long timescales. While not accounting for Sphagnum mosses directly, Sulman et al (2013) model landscape vegetation succession, in part, by combining species mortality rates and establishment probability with differences in moisture constraints on productivity, maximum productivity and flood tolerance.…”