Prescribed burning, atmospheric pollution and grazing effects on peatland vegetation composition

1. Peatlands are valued for ecosystem services including carbon storage, water provision and biodiversity. However, there are concerns about the impacts of land management and pollution on peatland vegetation and function. 2. We investigated how prescribed vegetation burning, atmospheric pollution and grazing are related to vegetation communities and cover of four key taxa (Sphagnum spp., Calluna vulgaris, Eriophorum vaginatum and Campylopus introflexus) using two datasets from a total of 2,013 plots across 95 peatland sites in the UK. 3. Non‐metric multidimensional scaling and permutational multivariate analysis of variance showed differences in vegetation community composition between burned and unburned plots at regional and national scales. 4. Analysis showed that burned sites had less Sphagnum and greater C. vulgaris cover on a national scale. On a regional scale, plots burned between 2 and 10 years ago had greater cover of invasive moss C. introflexus and less E. vaginatum than unburned sites. 5. Livestock presence was associated with less Sphagnum and C. vulgaris, while atmospheric pollution was associated with less Sphagnum, but greater C. introflexus cover, and appeared to have more impact on burned sites. 6. Synthesis and applications. Burning, grazing and atmospheric pollution are associated with peatland vegetation composition and cover of key species, including Sphagnum. We suggest that, to promote cover of peat‐forming species, peatlands should not be routinely burned or heavily grazed. Current or historical atmospheric pollution may hinder peat‐forming species, particularly on burned sites

Continuering experimenteel bevloeiingsonderzoek langs de Reest; eindrapport 2006

Doel van het project is het bevloeiingsexperiment te continueren en kennis te genereren over de effecten van bevloeiing op de lange termijn en de effectiviteit van bevloeiing als praktijkgerichte maatregel voor herstel van verdroogde en verzuurde Dotterbloemgraslanden. De resultaten van het onderzoek zullen worden gebruikt voor en beoordeling van de geschiktheid van deze maatregel als proefmaatregel ter bestrijding van verdroging en verzuring van Dotterbloemgraslanden in beekdalen. Hoewel advisering over mogelijkheden en onmogelijkheden voor waterberging geen expliciete projectdoelstelling is, kunnen de verkregen inzichten over effecten van bevloeiing tevens een bijdrage leveren aan de discussie over effecten van waterberging in natuurgebieden (Commissie Waterbeheer 21ste eeuw). Het volgende is onderzocht: slibaanvoer; bemestingsexperimenten; en ontwikkelingen in vegetatieparameters. Vegetatieontwikkeling in het Reestdal. Rapport in het kader van overlevingsplan bos+natuur (obn

The Multiscale Monitoring of Peatland Ecosystem Carbon Cycling in the Middle Taiga Zone of Western Siberia: The Mukhrino Bog Case Study

The peatlands of the West Siberian Lowlands, comprising the largest pristine peatland area of the world, have not previously been covered by continuous measurement and monitoring programs. The response of peatlands to climate change occurs over several decades. This paper summarizes the results of peatland carbon balance studies collected over ten years at the Mukhrino field station (Mukhrino FS, MFS) operating in the Middle Taiga Zone of Western Siberia. A multiscale approach was applied for the investigations of peatland carbon cycling. Carbon dioxide fluxes at the local scale studied using the chamber method showed net accumulation with rates from 110, to 57.8 gC m−2 at the Sphagnum hollow site. Net CO2 fluxes at the pine-dwarf shrubs-Sphagnum ridge varied from negative (−32.1 gC m−2 in 2019) to positive (13.4 gC m−2 in 2017). The cumulative May-August net ecosystem exchange (NEE) from eddy-covariance (EC) measurements at the ecosystem scale was −202 gC m−2 in 2015, due to the impact of photosynthesis of pine trees which was not registered by the chamber method. The net annual accumulation of carbon in the live part of mosses was estimated at 24–190 gC m−2 depending on the Sphagnum moss species. Long-term carbon accumulation rates obtained by radiocarbon analysis ranged from 28.5 to 57.2 gC m−2 yr−1, with local extremes of up to 176.2 gC m−2 yr−1. The obtained estimates of various carbon fluxes using EC and chamber methods, the accounting for Sphagnum growth and decomposition, and long-term peat accumulation provided information about the functioning of the peatland ecosystems at different spatial and temporal scales. Multiscale carbon flux monitoring reveals useful new information for forecasting the response of northern peatland carbon cycles to climatic changes

Salinity-induced increase of the hydraulic conductivity in the hyporheic zone of coastal wetlands

In coastal zones globally, salinization is rapidly taking place due to the combined effects of sea level rise, land subsidence, altered hydrology, and climate change. Although increased salinity levels are known to have a great impact on both biogeochemical and hydrological processes in aquatic sediments, only few studies have included both types of processes and their potential interactions. In the present paper, we used a controlled 3-year experimental mesocosm approach to test salinity induced interactions and discuss mechanisms explaining the observed hydrological changes. Surface water salinity was experimentally increased from 14 to 140 mmol Cl per L (0.9 and 9 PSU) by adding sea salt which increased pore water salinity but also increased sulfate reduction rates, leading to higher sulfide, and lower methane concentrations. By analyzing slug test data with different slug test analysis methods, we were able to show that hydraulic conductivity of the hyporheic zone increased 2.8 times by salinization. Based on our hydrological and biogeochemical measurements, we conclude that the combination of pore dilation and decreased methane production rates were major controls on the observed increase in hydraulic conductivity. The slug test analysis method comparison allowed to conclude that the adjusted Bouwer and Rice method results in the most reliable estimate of the hydraulic conductivity for hyporheic zones. Our work shows that both physical and biogeochemical processes are vital to explain and predict hydrological changes related to the salinization of hyporheic zones in coastal wetlands and provides a robust methodological approach for doing so

Hogere zoutconcentratie leidt tot een verhoogde waterdoorlatendheid van de waterbodem

Door de combinatie van klimaatverandering (zeespiegelstijging en langere droogteperiodes) en ontwatering voor landbouw neemt de kans op stijgende zoutconcentratiesin het oppervlaktewater in laag Nederland toe. Hoewel bekend is dat dit chemische enfysische effecten kan hebben, is de interactie tussen fysische en biogeochemische processen onderbelicht gebleven. In dit artikel wordt een veldexperiment gepresenteerdwaarin de effecten van verhoogde zoutconcentraties op de combinatie van chemischeen fysische processen in een voormalig brak laagveen zijn bestudeerd. Met behulp vanbiogeochemische analyses en de omgekeerde boorgatmethode in de waterbodem wordtaangetoond dat een verhoogde zoutconcentratie in het oppervlaktewater kan leiden toteen verhoogde waterdoorlatendheid van de waterbodem

A deepened water table increases the vulnerability of peat mosses to periodic drought

Here we address the combined impact of multiple stressors that are becoming more common with climate change. To study the combined effects of a lower water table (WT) and increased frequency of drought periods on the resistance and resilience of peatlands, we conducted a mesocosm experiment. This study evaluated how the photosynthesis of lawn Sphagnum mosses responds to and recovers from an experimental periodic drought after exposure to the stresses of a deep or deepened WT (naturally dry and 17-year-long water level drawdown [WLD] in fen and bog environments).We aimed to quantify if deep WTs (1) support acclimation to drought, or (2) increase the base-level physiological stress of mosses or (3) exacerbate the impact of periodic drought.There was no evidence of acclimation in mosses from drier environments; periodic drought decreased the photosynthesis of all Sphagnum species studied. WLDdecreased the photosynthesis of bog-originating mosses prior to periodic drought, indicating that these mosses were stressed by the hydrological change. Deep WTs exacerbated Sphagnum vulnerability to periodic drought, indicating that the combination of drying habitats and increasing frequency of periodic drought could lead to a rapid transition in lawn vegetation. Water-retaining traits may increase Sphagnum resilience to periodic drought. Large capitula size was associated with a higher resistance; the bog originating species studied here lacked large capitula or dense carpet structure and were more vulnerable to drought than the larger fen originating species. Consequently, lawns in bogs may become threatened.Recovery after rewetting was significant for all mosses, but none completely recovered within 3 weeks. The most drought-resilient species had fen origin, indicating that fens are less likely to undergo a sudden transition due to periodic drought.Synthesis: Water level drawdown associated with climate change increases the sensitivity of Sphagnum mosses to periods of drought and moves them closer to their tipping point as species on the edge of their ecological envelope rapidly shut down photosynthesis and recover poorly.202

Aquatic export of young dissolved and gaseous carbon from a pristine boreal fen: Implications for peat carbon stock stability

The stability of northern peatland's carbon (C) store under changing climate is of major concern for the global C cycle. The aquatic export of C from boreal peatlands is recognized as both a critical pathway for the remobilization of peat C stocks as well as a major component of the net ecosystem C balance (NECB). Here, we present a full year characterization of radiocarbon content (14C) of dissolved organic carbon (DOC), carbon dioxide (CO2), and methane (CH4) exported from a boreal peatland catchment coupled with 14C characterization of the catchment's peat profile of the same C species. The age of aquatic C in runoff varied little throughout the year and appeared to be sustained by recently fixed C from the atmosphere (<60 years), despite stream DOC, CO2, and CH4 primarily being sourced from deep peat horizons (2–4 m) near the mire's outlet. In fact, the 14C content of DOC, CO2, and CH4 across the entire peat profile was considerably enriched with postbomb C compared with the solid peat material. Overall, our results demonstrate little to no mobilization of ancient C stocks from this boreal peatland and a relatively large resilience of the source of aquatic C export to forecasted hydroclimatic changes