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Peatland restoration is essential to preserve biodiversity and carbon stored in peat soils. Common restoration techniques such as rewetting do not always result in the full recovery of peatland taxonomic and functional properties, threatening the resilience of restored peatlands and their carbon stores. Here, we study the use of peat moss inoculation in stimulating the short-term taxonomic and functional recovery of a wildfire-impacted peatland using mesocosms at high and low water table depth, representing ideal and adverse hydrological conditions respectively. Inoculation in conjunction with high water tables accelerated the recovery of the vascular plant and prokaryote communities. Importantly, Sphagnum—the keystone genus in these peatlands—only established in inoculated mesocosms. Together, this resulted in an increased CO2 uptake by approximately 17 g m−2 day−1 and reduced overall nutrient content in the peat pore water. Synthesis and applications. Our results indicate that inoculation can be used to accelerate the establishment of peatland-specific species. In addition, they suggest the potential to combine peat moss inoculation and hydrological restoration to accelerate the uptake of carbon back into the system post-fire. This offers a basis for future work exploring the long-term use of inoculation to return disturbed peatlands to their pre-degraded state, and a wider application of soil inoculation as a mechanism for functional recovery.

Topsoil removal (TSR) is a management option performed before rewetting drained agricultural peatlands to reduce greenhouse gas (GHG) emissions and remove nutrients. Currently, its common practice to remove 30 to 60 cm of topsoil, which is labor-intensive, costly, and highly disruptive. However, optimal TSR depth for mitigating carbon emissions from rewetted peat soils has neither been determined nor linked to soil biogeochemical factors driving carbon emissions. We performed two mesocosm experiments to address this. In experiment 1, we removed the topsoil of two contrasting drained peat soils before rewetting (i.e., extensively managed, acid peat and intensively managed, near-neutral peat) with a 5 cm interval up to 25 cm TSR. In experiment 2, we combined TSR with the presence and absence of Typha latifolia on intensively managed, near-neutral peat soil. The experiments ran for 22 and three months, respectively, in which we measured carbon dioxide (CO2) and methane (CH4) emissions and porewater chemistry. Our experiments reveal that (i) 5 cm TSR greatly reduced CH4 and CO2 emissions irrespective of peat nutrient status during the 22-month experiment, and (ii) the presence of T. latifolia further reduced CH4 emissions during the 3-month experiment. Specifically, CH4 emissions were six to 10-times lower with 5 cm TSR compared to 0 cm TSR. Peak CH4 emissions occurred after three months with 0 cm TSR and strongly decreased thereafter. Random forest analyses highlighted that variation in CH4 emissions could mainly be explained by cumulative root biomass and porewater alkalinity. Furthermore, 5 cm TSR reduced porewater values of pH, alkalinity, CH4, and ammonium. The effectiveness of TSR in preventing the build-up of phosphorus, iron, and sulfur in porewater was site-specific. Our results show that only 5 to 10 cm TSR may already effectively prevent the adverse effects of rewetting former agriculturally peatlands by reducing undesirable CH4 emissions and avoiding nutrient release. Further, we argue that target setting and site-specific assessments are crucial to optimize the amount of TSR to reduce carbon emissions while minimizing disturbance and costs.

Wind-induced turbulence can strongly impact ecological processes in shallow lake ecosystems. The creation of shelter against wind can be expected to affect both primary producers and herbivores in aquatic food webs. Shelter may benefit particular primary producers more than others by changing relative resource availabilities for different primary producers. Herbivore community compositions may be affected either directly or indirectly as a consequence of changes in their food quantity and quality that, in turn, may affect the transfer efficiency between primary producers and herbivores. A reduction in trophic transfer efficiency resulting from wind-induced turbulence potentially can lead to declines of higher trophic levels, but is generally understudied. Here, we focus on the impact of wind on aquatic primary producers and trophic transfer efficiency. We hypothesised that reducing wind-induced turbulence will stimulate higher trophic production in shallow lakes. However, the multitude of impacts of wind-induced turbulence on aquatic food webs make it challenging to predict the direction of change when creating sheltered conditions. We tested our hypothesis in the shallow waters of a newly constructed archipelago named Marker Wadden in lake Markermeer in the Netherlands. Lake Markermeer has experienced declining numbers of birds and fish. These declines have been related to wind-induced sediment resuspension that potentially limits primary production and trophic transfer efficiency. Marker Wadden is a large-scale restoration project that aims to add sheltered and heterogeneous habitat to the otherwise mostly homogeneous lake, thus targeting the potential problems associated with wind-induced turbulence. We executed a 2-month manipulative field mesocosm experiment in the shallow waters of Marker Wadden to study the effect of reduced wind-induced turbulence (i.e., shelter) on aquatic food webs. Specifically, we studied the effects on primary producers, trophic transfer efficiency between phytoplankton and zooplankton (using zooplankton biomass divided by phytoplankton Chl a as a proxy), and benthic fauna. The experiment consisted of three treatments: no shelter, shelter without macrophytes and shelter with submerged macrophytes (Myriophyllum spicatum) present at the start of the experiment. Our results clearly showed that under unsheltered conditions phytoplankton was the dominant primary producer, whereas in sheltered conditions submerged macrophytes became dominant. Interestingly, submerged macrophytes appeared rapidly in the sheltered treatment where first no macrophytes were visibly present; hence, at the end of the experiment, there was little difference among the sheltered treatments with and without initial presence of submerged macrophytes. Despite that phytoplankton concentrations were 23-fold higher under the unsheltered conditions, this did not result in higher zooplankton biomass. This can be explained by a five-fold greater trophic transfer efficiency between phytoplankton and zooplankton under the sheltered conditions. Furthermore, under the sheltered conditions the Gastropoda density reached 746 individuals m−2, whereas no Gastropoda were found under the no shelter treatment. These findings indicate that for shallow lakes that are negatively affected by wind-induced turbulence, measures aimed at ameliorating this stressor can be effective in facilitating submerged macrophyte recovery, increasing Gastropoda densities and restoring trophic transfer efficiency between phytoplankton and zooplankton. Ultimately, this may support higher trophic levels such as fish and water birds by increasing their food availability in shallow lake ecosystems.