• Energy Research

AbstractQuestion: What is the relative importance of competition and physical factors in restricting the occurrence of different fen species to certain zones of the riparian landscape?Location: Biebrza National Park, NE Poland.Methods: We carried out a two‐season reciprocal transplantation experiment: sod‐blocks were replaced between a low‐productive groundwater‐fed small‐sedge fen and a high‐productive fluviogenous tall‐sedge fen. Five treatments were applied to the transplanted sods: (1) no manipulation; (2) fertilization with NPK to exclude the effect of nutrient limitation; (3) clipping vegetation around the transplant to exclude competition for light; (4) clipping + fertilizing; (5) sods were also transplanted within their own environment.Results: After two seasons, the small‐sedge sods transplanted into the high‐productive zone had a biomass two times lower than that of the control transplants, mainly due to a decrease in small sedges and bryophytes. Tall sedges of the high‐productive zone did not respond significantly to transplantation in the low‐productive zone. Removal of the surrounding vegetation largely enhanced the growth of small sedges and bryophytes and, to a lesser degree, of tall sedges. Fertilization, on the other hand, resulted in increased growth of tall sedges, grasses and non‐graminoid herbs.Conclusion: Species characteristic of low‐productive fen communities are competitively excluded from the high‐productive zone through light competition. In contrast, the performance of tall sedges in the low‐productive zone is lowered by nutrient limitation. In the long run this may lead to a complete disappearance of these species from this zone. We did not find evidence that the physical stress of flooding has a direct effect on the performance and distribution of species. Results from the experiment suggest that productivity gradients and their influence on competition intensity are of primary importance for structuring vegetation patterns in lowland riparian fens.

AbstractQuestion: What is the relative importance of competition and physical factors in restricting the occurrence of different fen species to certain zones of the riparian landscape?Location: Biebrza National Park, NE Poland.Methods: We carried out a two‐season reciprocal transplantation experiment: sod‐blocks were replaced between a low‐productive groundwater‐fed small‐sedge fen and a high‐productive fluviogenous tall‐sedge fen. Five treatments were applied to the transplanted sods: (1) no manipulation; (2) fertilization with NPK to exclude the effect of nutrient limitation; (3) clipping vegetation around the transplant to exclude competition for light; (4) clipping + fertilizing; (5) sods were also transplanted within their own environment.Results: After two seasons, the small‐sedge sods transplanted into the high‐productive zone had a biomass two times lower than that of the control transplants, mainly due to a decrease in small sedges and bryophytes. Tall sedges of the high‐productive zone did not respond significantly to transplantation in the low‐productive zone. Removal of the surrounding vegetation largely enhanced the growth of small sedges and bryophytes and, to a lesser degree, of tall sedges. Fertilization, on the other hand, resulted in increased growth of tall sedges, grasses and non‐graminoid herbs.Conclusion: Species characteristic of low‐productive fen communities are competitively excluded from the high‐productive zone through light competition. In contrast, the performance of tall sedges in the low‐productive zone is lowered by nutrient limitation. In the long run this may lead to a complete disappearance of these species from this zone. We did not find evidence that the physical stress of flooding has a direct effect on the performance and distribution of species. Results from the experiment suggest that productivity gradients and their influence on competition intensity are of primary importance for structuring vegetation patterns in lowland riparian fens.

Ground- and surface-water-fed peatlands (i.e., fens) of temperate Europe face high anthropogenic nutrient loads from atmospheric deposition, agricultural catchment areas, and from peat decomposition, if drained. As a result, nitrogen loads may exceed a fen's natural nutrient removal capacity, leading to increased eutrophication of adjacent water bodies. Therefore, it is important to address possible means to decrease a fen's nutrient load, including nutrient uptake by fen plants. To assess how much fen plants can contribute to nutrient removal by uptake, nutrient stocks of above- and below-ground biomass need to be quantified. Therefore, we investigated nitrogen, phosphorous, and potassium uptake capacities of sedges (Carex species), which are common dominants in fen plant communities. We grew specimens of five Carex species with varying preferences in nutrient availability under controlled, different nutrient levels. We show that Carex above-ground biomass harvest can remove up to one third of a system's total nitrogen even at high loads of about 40 g nitrogen m-2. Species-specific differences in biomass production, rather than preferences in nutrient availability under natural conditions, were drivers of standing nutrient stocks: Highly productive species, i.e., C. acutiformis and C. rostrata, had highest nutrient standing stocks across all nutrient levels. Amounts of nutrients stored in shoots increased almost linearly with increasing nutrient levels, whereas below-ground nutrient stocks species-specifically increased, saturated, or decreased, with increasing nutrient levels. As a rough estimate, depending on the species, 6-16 cycles of annual above-ground harvest would suffice to decrease nitrogen concentrations from the highest to the lowest level used in this study. Overall, our results indicate that Carex biomass harvest can be an efficient means to counteract anthropogenic nitrogen eutrophication in fens.

Ground- and surface-water-fed peatlands (i.e., fens) of temperate Europe face high anthropogenic nutrient loads from atmospheric deposition, agricultural catchment areas, and from peat decomposition, if drained. As a result, nitrogen loads may exceed a fen's natural nutrient removal capacity, leading to increased eutrophication of adjacent water bodies. Therefore, it is important to address possible means to decrease a fen's nutrient load, including nutrient uptake by fen plants. To assess how much fen plants can contribute to nutrient removal by uptake, nutrient stocks of above- and below-ground biomass need to be quantified. Therefore, we investigated nitrogen, phosphorous, and potassium uptake capacities of sedges (Carex species), which are common dominants in fen plant communities. We grew specimens of five Carex species with varying preferences in nutrient availability under controlled, different nutrient levels. We show that Carex above-ground biomass harvest can remove up to one third of a system's total nitrogen even at high loads of about 40 g nitrogen m-2. Species-specific differences in biomass production, rather than preferences in nutrient availability under natural conditions, were drivers of standing nutrient stocks: Highly productive species, i.e., C. acutiformis and C. rostrata, had highest nutrient standing stocks across all nutrient levels. Amounts of nutrients stored in shoots increased almost linearly with increasing nutrient levels, whereas below-ground nutrient stocks species-specifically increased, saturated, or decreased, with increasing nutrient levels. As a rough estimate, depending on the species, 6-16 cycles of annual above-ground harvest would suffice to decrease nitrogen concentrations from the highest to the lowest level used in this study. Overall, our results indicate that Carex biomass harvest can be an efficient means to counteract anthropogenic nitrogen eutrophication in fens.

AbstractThe EU Nature Restoration Law (NRL) is critical for the restoration of degraded ecosystems and active afforestation of degraded peatlands has been suggested as a restoration measure under the NRL. Here, we discuss the current state of scientific evidence on the climate mitigation effects of peatlands under forestry. Afforestation of drained peatlands without restoring their hydrology does not fully restore ecosystem functions. Evidence on long-term climate benefits is lacking and it is unclear whether CO2 sequestration of forest on drained peatland can offset the carbon loss from the peat over the long-term. While afforestation may offer short-term gains in certain cases, it compromises the sustainability of peatland carbon storage. Thus, active afforestation of drained peatlands is not a viable option for climate mitigation under the EU Nature Restoration Law and might even impede future rewetting/restoration efforts. Instead, restoring hydrological conditions through rewetting is crucial for effective peatland restoration.

AbstractThe EU Nature Restoration Law (NRL) is critical for the restoration of degraded ecosystems and active afforestation of degraded peatlands has been suggested as a restoration measure under the NRL. Here, we discuss the current state of scientific evidence on the climate mitigation effects of peatlands under forestry. Afforestation of drained peatlands without restoring their hydrology does not fully restore ecosystem functions. Evidence on long-term climate benefits is lacking and it is unclear whether CO2 sequestration of forest on drained peatland can offset the carbon loss from the peat over the long-term. While afforestation may offer short-term gains in certain cases, it compromises the sustainability of peatland carbon storage. Thus, active afforestation of drained peatlands is not a viable option for climate mitigation under the EU Nature Restoration Law and might even impede future rewetting/restoration efforts. Instead, restoring hydrological conditions through rewetting is crucial for effective peatland restoration.