Soil carbon stocks in tropical peatlands have declined recently from water table depth (WTD) drawdown caused by increased frequency and intensity of climate extremes like El Niño and by artificial drainage. Restoration of these carbon stocks under these climatic and anthropogenic disturbances requires improved predictive capacity for hydrological feedbacks to ecological processes. Process-based modeling of tropical peatland ecohydrology could provide us with such capacity, but such modeling has thus far been limited. We aimed at using basic processes for water and O 2 transport and their effects on ecosystem water, carbon, and nitrogen cycling to model seasonal and interannual variations of WTD and surface energy exchange. We tested these processes in a process-based model ecosys in a drained tropical Indonesian peatland from an El Niño year 2002 to a wetter year 2005. WTD was modeled from hydraulically driven water transfers controlled vertically by precipitation versus evapotranspiration (ET) and laterally by discharge versus recharge to or from an external reference WTD. These transfers caused WTD drawdown and soil drying to be modeled during dry seasons, which reduced ET and increased Bowen ratio by lowering stomatal conductance. More pronounced dry seasons in drier years 2002-2004 versus wetter year 2005 caused deeper WTD, more intense peat drying, and greater plant water stress. These modeled trends were well corroborated by site measurements as apparent in regression statistics of modeled versus observed WTD (R 2 > 0.8), latent heat (R 2 > 0.8), and sensible heat (R 2 > 0.7) fluxes. Insights gained from this modeling would aid in predicting the fate of tropical peatlands under future drier climates. Key Points: • Ecosys modeled tropical peatland WTD by a vertical-lateral hydraulic scheme • Deeper WTD caused peat drying and reduced stomatal conductance in dry seasons • Stomatal limitation to transpiration was stronger in drier dry seasons Correspondence to: M. Mezbahuddin, mezbahud@ualberta.ca; symon.mezbahuddin@gov.ab.ca Citation: Mezbahuddin, M., R. F. Grant, and T. Hirano (2015), How hydrology determines seasonal and interannual variations in water table depth, surface energy exchange, and water stress in a tropical peatland: Modeling versus measurements, J. Geophys. Res.Given the effects of WTD drawdown from dry weather and artificial drainage on C storage, predictions of further drier weather by three global circulation models (GCMs) over tropical Southeast Asian peatlands by

Deforestation in Indonesia in recent decades has made increasingly large parts of the region vulnerable to fires. Burning is particularly widespread in deforested peatlands, and it leads to globally significant carbon emissions. Here we use satellite-based observations to assess loss and fragmentation of primary forests and associated changes in fire regimes in Sumatra and Kalimantan between 2001 and 2019. We find that fires did not penetrate undisturbed primary forest areas deeper than two kilometres from the forest edge irrespective of drought conditions. However, fire-resistant forest now covers only 3% of peatlands and 4.5% of non-peatlands; the majority of the remaining primary forests are severely fragmented or degraded due to proximity to the forest edge. We conclude that protection and regeneration of the remaining blocks of contiguous primary forest, as well as peatland restoration, are urgently needed to mitigate the impacts of potentially more frequent fire events under future global warming.

No abstract

No abstract

The present study investigated the rooting ability and growth performance of juvenile single-node leafy stem cuttings of Holarrhena pubescens, collected from two mature mother trees preserved in the hill forests of Chittagong District, Bangladesh. The rooting ability of cuttings was studied with 0, 0.1%, 0.2% and 0.4% indole-3-butyric acid (IBA) treatments. The better rooting response was observed with 0.1% IBA, but was insignifi cant compared to other treatments. The mean number of roots and length of the longest root of cuttings in different treatments showed no signifi cant difference. After transfer to the polythene bags from a nonmist propagator, rooted cuttings treated with 0.4% IBA demonstrated the highest (50.00 ±  0.78%) survival capacity. Regarding initial growth of established rooted cuttings (stecklings) over a 90 d period, the increment of stem length of stecklings under T2 (10 g Urea, 20 g TSP, 10 g MOP dissolved in 2 L water) and leaf area expansion of stecklings under T1 (10 g Urea, 20 g TSP, 10 g MOP dissolved in 1 L water) was signifi cantly higher (p < 0.05) compared with that under T0 (no fertilizer). The increment of collar diameter and root biomass production varied insignifi cantly among different fertilizer concentrations, although stecklings under T2 showed the better performance. The results suggest that rooting juvenile single-node leafy stem cuttings can be an effective mean of regenerating H. pubescens. The application of 0.1% IBA or without IBA is recommended for rooting juvenile leafy stem cuttings. Application of fertilizer appears necessary for subsequent growth of stecklings in polythene bags.