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Hog deer (Axis porcinus) were once widespread throughout much of lowland Southern Asia, but numbers rapidly declined during the last two decades. In Cambodia, the species was considered extinct until 2006 when a small number of individuals (presumedly spp. annamiticus) was rediscovered along the western bank of the Mekong River, near Kratie. Since reliable data on this population are lacking, we conducted two camera trap surveys to investigate hog deer habitat use, activity patterns and density. In the first survey, camera traps were placed in a random regular grid covering all main habitat types in the region, enabling us to verify hog deer presence/absence and identify habitat use. We found that hog deer were confined to a remnant patch of tall moist grassland of approximately 2 km(2), at least in the dry season. The follow-up survey was conducted exclusively in this tall grassland patch, in which we estimated hog deer activity patterns and density using kernel density estimation and a simplified version of the random encounter model (REM). Cameras were active for a total of 1770 camera trap days, during which 609 independent hog deer encounters were recorded. Density was estimated to be 41.8 (CI: 37.93-45.72) individuals km(-2), equating to an estimated abundance of 84 individuals. Hog deer activity was mainly crepuscular and nocturnal. We conclude that the recently rediscovered hog deer population in Kratie province is extremely vulnerable to extinction due to its small size and its complete dependency on a tiny remnant patch of core habitat. Conservation and restoration actions to preserve and restore prime habitat are urgently required to prevent local extinction.

Drainage-induced shifts in physicochemical peat properties are irreversible on a decadal time span. We investigated whether carbon emissions from fen peat can be estimated using two proxies: current water levels and peat properties (as affected by drainage history, i.e. degradation legacy). We collected bare peat monoliths from a long-term drained and an undrained fen. In a crossed design, half of the monoliths was kept wet and the other half was drained. Highest carbon dioxide (CO2) emissions came from the originally undrained peat under low water levels (607 mmol m-2 d-1). Overall, CO2 emissions were primarily determined by drainage history, with 141 % higher emissions from the originally undrained peat. In addition, low current water levels correlated with 42 % higher emissions. Highest methane (CH4) emissions were measured in the originally undrained peat under high water levels (123 mmol m-2 d-1). Overall, CH4 emissions were primarily determined by current water levels, with 430 % higher emissions under high water levels. In addition, the originally undrained peat had 180 % higher emissions. The lower C efflux from originally drained peat correlated with lower concentrations of methanogens and of easily-degradable carbon substrate (cellulose). We conclude that substrate limitation in long-term drained fens ensures low baseline carbon emissions, which provides opportunities for renewed carbon sequestration by rewetting.

Peatland degradation is tightly connected to hydrological changes and microbial metabolism. To better understand these metabolism processes, more information is needed on how microbial communities and substrate cycling are affected by changing hydrological regimes. These activities should be imprinted in stable isotope bulk values (δ 15N, δ 13C) due to specific isotopic fractionation by different microbial communities, their metabolic pathways and nutrient sources. We hypothesize that stable isotope values and microbial abundance are correlated and act as indicators of different hydrological regimes. We sampled an East–West transect across European fens in 14 areas and conducted a stable isotope (δ 13C, δ 15N) and membrane fatty acid (mFA) analysis. Within each area an undrained, drained and rewetted site was selected. Rewetted sites were separated based on when rewetting occurred. We found differences in the upper layers of all sites in microbial-derived mFAs and stable isotope values corresponding to hydrological regimes. The highest and lowest quantities of microbial-derived mFAs were measured in undrained and drained sites, respectively. Fungal-derived mFAs were especially lower in drained sites. Simultaneously, δ15N stable isotope values were highest in drained sites. In addition, stable isotope values and microbial-derived mFAs showed distinct depth trends. In undrained sites stable isotopes values slightly increased with depth. In drained sites, δ15N values decreased downwards, whereas δ13C values increased. Overall microbial-derived mFAs decreased with depth. These patterns presumably result from anoxic conditions and high peat recalcitrance in the deeper layers. In sites with short time of rewetting, the microbial-derived mFAs and stable isotope values were similar to values of drained sites, while with increasing rewetting time values shifted to those of undrained sites. We conclude that biomarkers indicate that stable isotope values reflect specific microbial metabolic processes, which differ with hydrological regimes, and thus could indicate both drainage and rewetting in fens.

Een eeuwenlange historie van antropogene ontwatering en versnippering heeft diepe sporen achtergelaten in het Europese beekdallandschap. Ongestoorde beekdalvenen komen nauwelijks meer voor, en de venen die nog resteren hebben vaak grote veranderingen doorgemaakt in biogeochemie en vegetatie. Veenherstel door grootschalige vernatting is nu de enige weg voorwaarts, maar het is de vraag of deze maatregel toereikend is voor biogeochemisch herstel.

In this study we address the question of the extent to which iron may be a limiting factor in restoring rich fens in the temperate climate zone of Europe. Rewetted fens that were heavily degraded in the past by draining over a long period, were compared with pristine fens or fens with slightly altered hydrological systems. The chemical composition of peat and of pore water was analysed and related to the composition of the vegetation of the fens. The species composition and chemistry of the topsoil of restored fens differed markedly from that of the other fens, while the chemistry of the pore water from deeper layers showed only minor differences. Multivariate analysis revealed that differences in species composition between both categories were strongly related to the concentration of Fe in the pore water in the topsoil. Restored sites with high iron concentrations in the pore water (> 100 mu mol.L-1) lacked many vascular plants and mosses typical of peat forming fens. Iron and inorganic phosphorus pools in the topsoil of most restored fens were much greater than in the reference fens. A higher soil phosphorus pool originated mainly from the iron-bound fraction. We conclude that these differences are strongly governed by local processes and not by regional differences in climate, which were associated with geographical distribution of the different fens studied. The strong accumulation of iron and phosphorus in restored fens is attributed to a long history of drainage, which enhanced the accumulation of oxidized iron in the topsoil and also lowered the concentrations of calcium, magnesium and sulphur through drainage-caused reoccurring oxidation-reduction and leaching processes. A high iron and associated high phosphorous content appears to be an important and possibly irreversible bottleneck to restoring biodiversity and accumulation of peat with a low degree of humification in degraded fens. If a degraded fen has a low iron content then it is more likely to be restorable.