Many of the world's peatlands have been affected by water table drawdown and subsequent loss of organic matter. Rewetting has been proposed as a measure to restore peatland functioning and to halt ...carbon loss, but its effectiveness is subject to debate. An important prerequisite for peatland recovery is a return of typical microbial communities, which drive key processes. To evaluate the effect of rewetting, we investigated 13 fen peatland areas across a wide (>1500 km) longitudinal gradient in Europe, in which we compared microbial communities between drained, undrained, and rewetted sites. There was a clear difference in microbial communities between drained and undrained fens, regardless of location. Community recovery upon rewetting was substantial in the majority of sites, and predictive functional profiling suggested a concomitant recovery of biogeochemical peatland functioning. However, communities in rewetted sites were only similar to those of undrained sites when soil organic matter quality (as expressed by cellulose fractions) and quantity were still sufficiently high. We estimate that a minimum organic matter content of ca. 70% is required to enable microbial recovery. We conclude that peatland recovery after rewetting is conditional on the level of drainage-induced degradation: severely altered physicochemical peat properties may preclude complete recovery for decades.
Plant species diversity in Eurasian wetlands and grasslands depends not only on productivity but also on the relative availability of nutrients, particularly of nitrogen and phosphorus. Here we show ...that the impacts of nitrogen:phosphorus stoichiometry on plant species richness can be explained by selected plant life-history traits, notably by plant investments in growth versus reproduction. In 599 Eurasian sites with herbaceous vegetation we examined the relationship between the local nutrient conditions and community-mean life-history traits. We found that compared with plants in nitrogen-limited communities, plants in phosphorus-limited communities invest little in sexual reproduction (for example, less investment in seed, shorter flowering period, longer lifespan) and have conservative leaf economy traits (that is, a low specific leaf area and a high leaf dry-matter content). Endangered species were more frequent in phosphorus-limited ecosystems and they too invested little in sexual reproduction. The results provide new insight into how plant adaptations to nutrient conditions can drive the distribution of plant species in natural ecosystems and can account for the vulnerability of endangered species.
Mesotrophic rich fens, that is, groundwater-fed mires, may be long-lasting, as well as transient ecosystems, displaced in time by poor fens, bogs, forests or eutrophic reeds. We hypothesized that fen ...stability is controlled by plant stress caused by waterlogging with calcium-rich and nutrient-poor groundwater, which limits expansion of hummock mosses, tussock sedges and trees. We analysed 32 European Holocene macrofossil profiles of rich fens using plant functional traits (PFTs) which indicate the level of plant stress in the environment: canopy height, clonal spread, diaspore mass, specific leaf area, leaf dry matter content, Ellenberg moisture value, hummock-forming ability, mycorrhizal status and plant functional groups. Six PFTs, which formed long-term significant trends during mire development, were compiled as rich fen stress indicator (RFSI). We found that RFSI values at the start of fen development were correlated with the thickness of subsequently accumulated rich fen peat. RFSI declined in fens approaching change into another mire type, regardless whether it was shifting into bog, forest or eutrophic reeds. RFSI remained comparatively high and stable in three rich fens, which have not terminated naturally until present times. By applying PFT analysis to macrofossil data, we demonstrated that fens may undergo a gradual autogenic process, which lowers the ecosystem’s resistance and enhances shifts to other mire types. Long-lasting rich fens, documented by deep peat deposits, are rare. Because autogenic processes tend to alleviate stress in fens, high levels of stress are needed at initial stages of rich fen development to enable its long persistence and continuous peat accumulation.
Large-scale re-establishment of wetland buffer zones (WBZ) along rivers is regarded as an effective measure in order to reduce non-point source nitrogen (N) and phosphorus (P) pollution in ...agricultural catchments. We estimated efficiency and costs of a hypothetical establishment of WBZs along all watercourses in an agricultural landscape of the lower Narew River catchment (north-eastern Poland, 16,444 km2, amounting to 5% of Poland) by upscaling results obtained in five sub-catchments (1087 km2). Two scenarios were analysed, with either rewetting selected wetland polygons that collect water from larger areas (polygonal WBZs) or reshaping and rewetting banks of rivers (linear WBZs), both considered in all ecologically suitable locations along rivers. Cost calculation included engineering works necessary in order to establish WBZs, costs of land purchase where relevant, and compensation costs of income forgone to farmers (needed only for polygonal WBZs). Polygonal WBZs were estimated in order to remove 11%–30% N and 14%–42% P load from the catchment, whereas linear WBZs were even higher with 33%–82% N and 41%–87% P. Upscaled costs of WBZ establishment for the study area were found to be 8.9 M EUR plus 26.4 M EUR per year (polygonal WBZ scenario) or 170.8 M EUR (linear WBZ scenario). The latter value compares to costs of building about 20 km of an express road. Implementation of buffer zones on a larger scale is thus a question of setting policy priorities rather than financial impossibility.
In peatland restoration we often lack an information whether re-established ecosystems are functionally similar to non-degraded ones. We re-analysed the long-term outcomes of restoration on ...vegetation and plant functional traits in 38 European fens restored by rewetting (18 sites) and topsoil removal (20 sites). We used traits related to nutrient acquisition strategies, competitiveness, seed traits, and used single- and multi-trait metrics. A separate set of vegetation records from near-natural fens with diverse plant communities was used to generate reference values to aid the comparisons. We found that both restoration methods enhanced the similarity of species composition to non-degraded systems but trait analysis revealed differences between the two approaches. Traits linked to nutrient acquisition strategies indicated that topsoil removal was more effective than rewetting. After topsoil removal competitive species in plant communities had decreased, while stress-tolerant species had increased. A substantial reduction in nutrient availability ruled out the effect of initial disturbance. An ability to survive and grow in anoxic conditions was enhanced after restoration, but the reference values were not achieved. Rewetting was more effective than topsoil removal in restricting variation in traits values permitted in re-developing vegetation. We found no indication of a shift towards reference in seed traits, which suggested that dispersal constraint and colonization deficit can be a widespread phenomena. Two functional diversity indices: functional richness and functional dispersion showed response to restoration and shifted values towards reference mires and away from the degraded systems. We concluded that targeting only one type of environmental stressor does not lead to a recovery of fens, as it provides insufficient level of stress to restore a functional ecosystem. In general, restoration efforts do not ensure the re-establishment and long-term persistence of fens. Restoration efforts result in recovery of fen ecosystems, confirmed with our functional trait analysis, although more rigid actions are needed for restoring fully functional mires, by achieving high and constant levels of anoxia and nutrient stresses.
Semi-natural grasslands are some of the most threatened habitats on the planet, due to the abandonment of small-scale farming and its replacement with intensive agriculture. The fragmented landscape ...of today has created dispersal limitation that makes improbable the natural dispersal of target species into the remaining patches of grassland. This paper reviews the current status of species introduction into semi-natural grasslands, and summarises the results of published literature in this field. Our review shows that restoration through species introduction is an effective method of establishing dispersal limited species. However, the field of species introduction in restoration ecology has yet to make use of the value that Functional Diversity can add to restoration. No single study in our search has followed up species introduction by measuring any of the currently available indices of functional diversity. This approach is necessary to gain knowledge on what traits are likely to be sorted out in species introduction cases in various environments.
For more than two decades, wetland restoration has been successfully applied in Denmark as a tool to protect watercourses from elevated nutrient inputs from agriculture, but little is known about how ...the flora and fauna respond to restoration. The main objective of this study was therefore to: (1) examine plant community characteristics in 10 wetland sites in the River Odense Kratholm catchment, restored between 2001 and 2011 by re-meandering the stream and disconnecting the tile drains, and (2) explore whether the effects of restoration on plant community characteristics change with the age of the restoration. Specifically, we hypothesised that plant community composition, species richness and diversity would improve with the age of the restoration and eventually approach the state of natural wetland vegetation. We found that the prevailing plant communities could be characterised as humid grasslands, moist fallow fields and improved grasslands, whereas the abundance of natural wetland plant communities (e.g., rich fens, fen-sedge beds and humid grasslands) was lower in both the recently restored as well as in older restored wetlands. Additionally, species richness and diversity did not seem to improve with the age of the restoration. We suggest that the continued high nutrient input at the restored sites in combination with restricted dispersal of wetland plant species may hamper the recovery of natural plant communities and that the sites therefore may stay botanically poor for many decades.
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•We investigated plant communities in wetlands 7-17 years after restoration.•Plant communities did not approach those characterising natural riparian wetlands.•Target species dispersal from source populations may restrict restoration success.•Continuous high nutrient input may be another major constraint for recovery.
Wetland buffer zones (WBZs) are riparian areas that form a transition between terrestrial and aquatic environments and are well-known to remove agricultural water pollutants such as nitrogen (N) and ...phosphorus (P). This review attempts to merge and compare data on the nutrient load, nutrient loss and nutrient removal and/or retention from multiple studies of various WBZs termed as riparian mineral soil wetlands, groundwater-charged peatlands (i.e. fens) and floodplains. Two different soil types (‘organic’ and ‘mineral’), four different main water sources (‘groundwater’, ‘precipitation’, ‘surface runoff/drain discharge’, and ‘river inundation’) and three different vegetation classes (‘arboraceous’, ‘herbaceous’ and ‘aerenchymous’) were considered separately for data analysis. The studied WBZs are situated within the temperate and continental climatic regions that are commonly found in northern-central Europe, northern USA and Canada. Surprisingly, only weak differences for the nutrient removal/retention capability were found if the three WBZ types were directly compared. The results of our study reveal that for example the nitrate retention efficiency of organic soils (53 ± 28%; mean ± sd) is only slightly higher than that of mineral soils (50 ± 32%). Variance in load had a stronger influence than soil type on the N retention in WBZs. However, organic soils in fens tend to be sources of dissolved organic N and soluble reactive P, particularly when the fens have become degraded due to drainage and past agricultural usage. The detailed consideration of water sources indicated that average nitrate removal efficiencies were highest for ground water (76 ± 25%) and lowest for river water (35 ± 24%). No significant pattern for P retention emerged; however, the highest absolute removal appeared if the P source was river water. The harvesting of vegetation will minimise potential P loss from rewetted WBZs and plant biomass yield may promote circular economy value chains and provide compensation to land owners for restored land now unsuitable for conventional farming.
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•The efficiency of wetland buffer zones for nutrient retention was reviewed.•Organic and mineral soils as nutrient filters or sources were compared.•Processes driving phosphorus and nitrogen fluxes were described.•The indirect and direct impact of vegetation were unraveled.•Implications for wetland restoration and open research questions were specified.
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•Tracked vehicles are increasingly used for conservational mowing of fens to maintain open landscape biodiversity.•We show that caterpillar tracks may flatten mire surface, pressing ...tussocks and hummocks into the peat.•Fens managed by tracked mowers differ in plant functional traits and have less rare plant species than unmanaged plots.•We warn against using large tracked mowers in fens when high botanical diversity is of primary interest.
Cessation of traditional mowing management has been the main threat to fen biodiversity for many decades; shrubs and trees expand and target plant and animal species decline. In Biebrza National Park (BNP), the EU’s largest conservation area of alkaline fens, abandonment has affected more than 300km2. To combat unwanted succession, tracked mowers were developed based on snow grooming vehicles and are increasingly used in BNP and some other European fens. While effects on bird populations seemed promising, the impact on botanical diversity remained yet unknown. We assessed the effects of this management on vegetation by comparing 12 pairs of mown and unmown plots (percentage cover recorded from 4m2 for all species and 25m2 for rare species) spread over several km2. We found that tracked vehicles suppressed some species, which are likely to facilitate others by providing shelters above groundwater level (hummock mosses, tussock sedges and shrubs) and enhanced species with effective clonal spread and high specific leaf area. An even stronger increase was observed in forbs, which share effective clonal spread and flood tolerance (high Ellenberg F value). Analysis of functional diversity indices based on all measured traits showed a decrease of functional divergence due to mowing (indicating convergence of traits) and no response of functional richness, evenness and functional dispersion. Mowing has also decreased the number of rare species. We associate these changes with the reduction of micro-topography by caterpillar tracks. Tracked mowers should therefore be avoided in those fens, in which microtopography contributes to unique botanical diversity.
The aim of this study was to understand the variation in traits relevant for desiccation avoidance among bryophyte species dominant in rich fens and to assess whether these traits explain the ...formation of a hummock-hollow gradient within peatlands. In samples of 10 species (
Aulacomnium palustre, Calliergonella cuspidata, Climacium dendroides, Hamatocaulis vernicosus, Helodium blandowii, Marchantia polymorpha, Plagiomnium ellipticum, Sphagnum teres, S. warnstorfii, Tomentypnum nitens
) collected in rich fens of NE Poland, we calculated: canopy bulk density of wet (CDW) and dry (CDD) colonies, maximum water content of bryophyte colonies (WC
max
), desiccation rate (K), shoot area index (SAI), canopy dry mass per surface-projected area (CMA), and specific leaf area of a whole living bryophyte part (SLA). The hummock-forming frequency was quantified for each species in the field.
Sphagna
had the highest WC
max
, SAI and CDW,
T. nitens
and
C. dendroides
had the lowest WC
max
and SLA,
P. ellipticum
had the highest K, the lowest CMA and CDD. Hummock-forming frequency was positively correlated with CMA and generally negatively related to K, with exception of
H. vernicosus
showing a high water-retaining ability (low K) despite a hollow or lawn form of growth.
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