Abstract
Tropical peatlands play a critical role in regional water cycling, yet
most tropical peat swamp forests (PSFs) are anthropogenically disturbed
though modification of the water table (e.g. drainage), deforestation,
and fire events. These disturbances can alter ecosystem processes
including evapotranspiration (ET), thereby creating feedbacks that
degrade peatland ecosystem services and result in significant alteration
of greenhouse gas budgets. However, our understanding of fine-scale
hydrological fluxes in tropical peatland ecosystems is currently
lacking. Here, therefore, we aimed to quantify rates of ET from a
degraded tropical PSF in Central Kalimantan, in the context of broader
peatland hydrology and site meteorology. From March to November 2020, ET
ranged from 1.8–7.3 mm d -1, averaged 4.09 ± 0.06 mm
d -1 and was consistent between months, despite large
fluctuations in precipitation (P) following typical wet/dry seasonality
(e.g., 4.1 ± 0.2 mm d -1 in July, compared to 17.5 ±
4.4 mm d -1 in April). Total ET over the nine-month
study period was 1127 mm; approximately 37% of total precipitation.
Daily ET rates were comparable to previous studies from tropical PSFs,
however, the ratio of ET/P was lower than other tropical PSF sites. We
suggest that the volume of water lost through canal drainage may be
higher at this site than other tropical PSFs, indicating more
substantial hydrological alteration through drainage. We expect that
with continued hydrological restoration (i.e. canal blocking), ET/P may
increase and, if so, could potentially be used as an indicator for
changing peatland condition over time.