Greenhouse gas dynamics in degraded and restored tropical peatlands

Agricultural and other land uses on ombrotrophic lowland tropical peat swamps typically lead to reduced vegetation biomass and water table drawdown. We review what is known about greenhouse gas (GHG) dynamics in natural and degraded tropical peat systems in south-east Asia, and on this basis consider what can be expected in terms of GHG dynamics under restored conditions. Only limited in situ data are available on the effects of restoration and the consequences for peat carbon (C) dynamics. Hydrological restoration seeks to bring the water table closer to the peat surface and thus re-create near-natural water table conditions, in order to reduce wildfire risk and associated fire impacts on the peat C store, as well as to reduce aerobic peat decomposition rates. However, zero emissions are unlikely to be achieved due to the notable potential for carbon dioxide (CO2) production from anaerobic peat decomposition processes. Increased vegetation cover (ideally woody plants) resulting from restoration will increase shading and reduce peat surface temperatures, and this may in turn reduce aerobic decomposition rates. An increase in litter deposition rate will compensate for C losses by peat decomposition but also increase the supply of labile C, which may prime decomposition, especially in peat enriched with recalcitrant substrates. The response of tropical peatland GHG emissions to peatland restoration will also vary according to previous land use and land use intensity.Peer reviewe

Effects of water level and nutrients on spatial distribution of soil mesofauna in peatlands drained for forestry in Finland

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Restoration of peatlands and greenhouse gas balances

In this chapter the impact of peatland restoration on greenhouse gas fluxes is discussed based on a literature review. Casestudies are presented covering different peatland types, different regions and different starting conditions

To treat or not to treat? The seedling performance of native tree species for reforestation on degraded tropical peatlands of SE Asia

Degraded tropical peatlands in Southeast Asia are a major challenge for reforestation. Often treeless, drained and several times burnt, these peatland areas are nutrient-poor hostile environments prone to droughts, heavy flooding and extreme diurnal temperature changes. In order to succeed in establishment of a viable tree stand, careful selection of species and management techniques is needed. In this study we investigated the suitability of five native tree species for reforestation of tropical peatlands with three site preparation treatments for potentially enhancing seedling success: weeding, mounding and fertilizing. The study area was a clear-cut, drained and repeatedly burnt former tropical peat swamp forest in Central Kalimantan, Indonesia. Seedlings were grown in a field nursery, planted in the field and their growth and survival were monitored regularly for 1.5 years. Seedling growth in response to environmental variables and treatments was studied by linear mixed models and seedling survival with Cox regression models. In most cases, weeding and fertilizing proved beneficial for the growth and survival of the seedlings, whereas mounding only had a minor impact on seedling performance. The seedlings of Shorea balangeran performed the best and can be recommended for reforestation of heavily degraded areas. Alstonia pneumatophora and Dacryodes rostrata performed relatively well depending on the treatments, whereas Dyera polyphylla had mixed results with problems in seedling production, and Campnosperma squamatum performed rather poorly. The effects of wildfires which engulfed the study area two years after planting were also monitored and are discussed.Peer reviewe

Ecohydrological and vegetational changes in a restored bog and fen

The vegetation of two boreal mires drained for forestry was studied prior to and after restoration (removal of tree stand and filling in of ditches). The restoration induced a rapid rise in the water table level and caused relatively rapid changes in plant species composition and cover. On the minerotrophic fen site, the number of forest species declined and the cover of Eriophorum vaginatum increased five-fold, reaching over 50% cover in three years. On the ombrotrophic bog site, the terrestrial lichens disappeared, while the cover of Empetrum nigrum, Calluna vulgaris, E. vaginatum, and Sphagnum balticum increased. Changes in water table level and vegetation indicate a change towards a functional mire ecosystem

Nitrous oxide fluxes from tropical peat with different disturbance history and management

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Carbon dioxide and methane fluxes from different surface types in a created urban wetland

Many wetlands have been drained due to urbanization, agriculture, forestry or other purposes, which has resulted in a loss of their ecosystem services. To protect receiving waters and to achieve services such as flood control and storm water quality mitigation, new wetlands are created in urbanized areas. However, our knowledge of greenhouse gas exchange in newly created wetlands in urban areas is currently limited. In this paper we present measurements carried out at a created urban wetland in Southern Finland in the boreal climate. We conducted measurements of ecosystem CO2 flux and CH4 flux (FCH4) at the created storm water wetland Gateway in Nummela, Vihti, Southern Finland, using the eddy covariance (EC) technique. The measurements were commenced the fourth year after construction and lasted for 1 full year and two subsequent growing seasons. Besides ecosystemscale fluxes measured by the EC tower, the diffusive CO2 and CH4 fluxes from the open-water areas (FwCO(2) and FwCH(4), respectively) were modelled based on measurements of CO2 and CH4 concentration in the water. Fluxes from the vegetated areas were estimated by applying a simple mixing model using the above-mentioned fluxes and the footprintweighted fractional area. The half-hourly footprint-weighted contribution of diffusive fluxes from open water ranged from 0% to 25.5% in 2013. The annual net ecosystem exchange (NEE) of the studied wetland was 8.0 g C-CO2 m(-2) yr(-1), with the 95% confidence interval between 18:9 and 34.9 g C-CO2 m(-2) yr(-1), and FCH4 was 3.9 g C-CH4 m(-2) yr(-1), with the 95% confidence interval between 3.75 and 4.07 g C-CH4 m(-2) yr(-1). The ecosystem sequestered CO2 during summer months (June-August), while the rest of the year it was a CO2 source. CH4 displayed strong seasonal dynamics, higher in summer and lower in winter, with a sporadic emission episode in the end of May 2013. Both CH4 and CO2 fluxes, especially those obtained from vegetated areas, exhibited strong diurnal cycles during summer with synchronized peaks around noon. The annual FwCO(2) was 297.5 g C-CO2 m(-2) yr(-1) and FwCH(4) was 1.73 g C-CH4 m(-2) yr(-1). The peak diffusive CH4 flux was 137.6 nmol C-CH4 m(-2) s(-1), which was synchronized with the FCH4. Overall, during the monitored time period, the established storm water wetland had a climate-warming effect with 0.263 kgCO(2)-eqm(-2) yr(-1) of which 89% was contributed by CH4. The radiative forcing of the open-water areas exceeded that of the vegetation areas (1.194 and 0.111 kgCO(2)-eqm(-2) yr(-1), respectively), which implies that, when considering solely the climate impact of a created wetland over a 100-year horizon, it would be more beneficial to design and establish wetlands with large patches of emergent vegetation and to limit the areas of open water to the minimum necessitated by other desired ecosystem services.Peer reviewe