Integrating peatlands and permafrost into a dynamic global vegetation model: 2. Evaluation and sensitivity of vegetation and carbon cycle processes

Abstract

[1] Peatlands and permafrost are important components of the carbon cycle in the northern high latitudes. The inclusion of these components into a dynamic global vegetation model required changes to physical land surface routines, the addition of two new peatland-specific plant functional types, incorporation of an inundation stress mechanism, and deceleration of decomposition under inundation. The new model, LPJ-WHy v1.2, was used to simulate net ecosystem production (NEP), net primary production (NPP), heterotrophic respiration (HR), and soil carbon content. Annual peatland NEP matches observations even though the seasonal amplitude is overestimated. This overestimation is caused by excessive NPP values, probably due to the lack of nitrogen or phosphorus limitation in LPJ-WHy. Introduction of permafrost reduces circumpolar (45-90°N) NEP from 1.65 to 0.96 Pg C a À1 and leads to an increase in soil carbon content of almost 40 Pg C; adding peatlands doubles this soil carbon increase. Peatland soil carbon content and hence HR depend on model spin-up duration and are crucial for simulating NEP. These results highlight the need for a regional peatland age map to help determine spin-up times. A sensitivity experiment revealed that under future climate conditions, NPP may rise more rapidly than HR resulting in increases in NEP.

Present state of global wetland extent and wetland methane modelling: methodology of a model inter-comparison project (WETCHIMP)

“…These modifications lower the water table position in hummocks compared to lawns. The vegetation for hummocks is restricted to Sphagnum mosses, whereas lawns are able to grow any plant functional type depending on the water table position (Wania et al, 2009b). Methane emissions from the two parallel runs are averaged under the assumption that hummocks and hollows cover approximately the same surface area.…”

Multiple greenhouse-gas feedbacks from the land biosphere under future climate change scenarios

“…Terrestrial processes are simulated with the LPX-Bern 1.0 model (Land surface processes and exchanges, Bern version 1.0), which unifies representations for natural 13 , agricultural 14,20 and peatland 15,17,18 coupled C and N (ref. 16) dynamics and predicts the release/uptake of CO 2 , N 2 O and CH 4 .…”

“…LPX-Bern 13-18 is applied here to simulate the coupled cycling of carbon and nitrogen and the emissions of GHGs from agricultural and natural land and from peat. Sitescale evaluations of this model have been presented earlier 7,[15][16][17][18][19][20] . For this test, we force LPX-Bern with observational data for climate 21 , cCO 2 (ref.…”

“…Addressing the historical atmospheric GHG budgets serves as a test for the sensitivity of simulated GHG emissions to the combination of climate, cCO 2 and external forcings. LPX-Bern [13][14][15][16][17][18] is applied here to simulate the coupled cycling of carbon and nitrogen and the emissions of GHGs from agricultural and natural land and from peat. Sitescale evaluations of this model have been presented earlier 7,[15][16][17][18][19][20] .…”

Modeling Carbon Fluxes Using Multi-Temporal MODIS Imagery and CO2 Eddy Flux Tower Data in Zoige Alpine Wetland, South-West China

“…Several studies indicate that plant aboveground net primary production (ANPP) has variable responses to warming in arctic and alpine regions, with reported increases, decreases, or no change (Houborg and Soegaard 2004;Wan et al 2005;Klein et al 2007;Post and Pedersen 2008). Wania et al (2009) modeled strong increases in Arctic annual NPP using a dynamic global vegetation model (DGVM). In their case, the NPP trend was also related to strong sensitivity to changes in air temperature.…”