A global study on the natural dynamics and land-use impacts on tropical
peat soil properties and greenhouse gas effluxes
Abstract
Tropical peatlands are one of the most effective long-term natural
carbon stores on Earth. The drainage, conversion, and degradation of
natural tropical peatlands for agricultural development shifts the
magnitude and direction of their carbon balance, from net carbon sinks
to sources. Yet, there are limited studies that globally synthesize
information to constrain our general understanding of the
characteristics and linkages between peat soil physicochemical
properties and greenhouse gas (GHG) effluxes in tropical peatlands, as
well as how their dynamics may be altered by land-use and land-cover
change (LULCC). Here, we systematically reviewed more than 100 published
field-based papers on soil physicochemical properties such as peat
thickness, ages, bulk density, carbon and nitrogen contents, carbon to
nitrogen ratio, water table, and CO2 and CH4 effluxes across three main
tropical peatland regions, i.e., Latin America, Central Africa, and
Southeast Asia. We report that Southeast Asian peatlands have the
thickest layer with 537±230 cm compared to Latin America (150±104 cm)
and Central Africa (250±160 cm). We also observed a strong natural
variation of soil physicochemical properties within the region, which
may imply variability of produced GHGs. Most managed peatlands have a
higher bulk density compared to undisturbed ones (0.12±0.05 and
0.20±0.18 g cm-3) despite a slightly similar carbon content (44±9 and
47±10 %), which may suggest substantial peat subsidence and losses.
Similarly, LULCC generates more than double increase in
CO2 effluxes despite lowering CH4
effluxes compared to undisturbed peatlands. The global database
constructed through this literature review will be valuable for future
modelling improvement of peatland carbon estimates in the tropics, a
significant carbon-rich system but often overlooked in the terrestrial
climate model. Further, our synthesis and dataset will help provide
science-based guidelines to set and monitor emissions reduction targets
as part of the forestry and land-use sector.