Carbon accumulation of tropical peatlands over millennia: a modeling approach

Abstract

Tropical peatlands cover an estimated 440,000 km2 (~10% of global peatland area) and are significant in the global carbon cycle by storing about 40-90 Gt C in peat. Over the past several decades, tropical peatlands have experienced high rates of deforestation and conversion, which is often associated with lowering the water table and peat burning, releasing large amounts of carbon stored in peat to the atmosphere. We present the first model of long-term carbon accumulation in tropical peatlands by modifying the Holocene Peat Model (HPM), which has been successfully applied to northern temperate peatlands. Tropical HPM (HPMTrop) is a one-dimensional, nonlinear, dynamic model with a monthly time step that simulates peat mass remaining in annual peat cohorts over millennia as a balance between monthly vegetation inputs (litter) and monthly decomposition. Key model parameters were based on published data on vegetation characteristics, including net primary production partitioned into leaves, wood, and roots; and initial litter decomposition rates. HPMTrop outputs are generally consistent with field observations from Indonesia. Simulated long-term carbon accumulation rates for 11,000-year-old inland, and 5000-year-old coastal peatlands were about 0.3 and 0.59 Mg C ha(-1) yr(-1), and the resulting peat carbon stocks at the end of the 11,000-year and 5000-year simulations were 3300 and 2900 Mg C ha(-1), respectively. The simulated carbon loss caused by coastal peat swamp forest conversion into oil palm plantation with periodic burning was 1400 Mg C ha(-1) over 100 years, which is equivalent to ~2900 years of C accumulation in a hectare of coastal peatlands.

How temporal patterns in rainfall determine the geomorphology and carbon fluxes of tropical peatlands

“…Several other studies have shown a leveling off of soil CO 2 efflux at very low water tables (25,26), and it is also likely that very high water tables ultimately limit net carbon uptake by trees (primary production) (16). However, including these effects did not affect simulations because these extreme water table heights and depths were neither observed at our site nor predicted by simulations of our site.…”

“…9 A and E), which is a recognized climate feedback for tropical peatlands (12), and also show that artificial drainage for agriculture (Fig. 9D) can dominate all natural feedbacks if not curtailed (4,16). In addition, our simulations demonstrate a third feedback: The increase in rainfall variability from warming climates (33) can cause peat loss if not compensated by an increase in total rainfall ( Fig.…”

“…Hilbert's model inspired a series of increasingly sophisticated models for vegetation dynamics and peat accumulation at a point. The most recent of these point models computes water table depth from monthly rainfall, using a site-specific model (16). Meanwhile, numerical models have been used to simulate peat accumulation under constant rainfall (17,18).…”

Suspended Solids from Drained Peatlands in the East Coastal Zone of New Brunswick: Point Estimates and Climate Effects on the Environment

“…A modelling approach in Ref. [13] also confirms the continuity of these predictions for decades. Soil degradation of peatlands is also one result of the artificial drainage.…”

Greenhouse gas emissions along a peat swamp forest degradation gradient in the Peruvian Amazon: soil moisture and palm roots effects

“…In natural conditions, the portion of SOM that is decomposed and emitted as carbon dioxide (CO 2 ) or methane (CH 4 ) is usually outweighed by the continuous input of fresh litter and roots (Jauhiainen et al 2005;Hergoualc'h and Verchot 2011;Hoyos-Santillan et al 2015). Models such as the Holocene Peat Model-HPM (Frolking et al 2010;Kurnianto et al 2015) use this balance to predict long-term peat accumulation via vegetation-specific characteristics such as decomposition speed and primary production.…”