The response of soil organic carbon of a rich fen peatland in interior Alaska to projected climate change

It is important to understand the fate of carbon in boreal peatland soils in response to climate change because a substantial change in release of this carbon as CO₂ and CH₄ could influence the climate system. The goal of this research was to synthesize the results of a field water table manipulation experiment conducted in a boreal rich fen into a process‐based model to understand how soil organic carbon (SOC) of the rich fen might respond to projected climate change. This model, the peatland version of the dynamic organic soil Terrestrial Ecosystem Model (peatland DOS‐TEM), was calibrated with data collected during 2005–2011 from the control treatment of a boreal rich fen in the Alaska Peatland Experiment (APEX). The performance of the model was validated with the experimental data measured from the raised and lowered water‐table treatments of APEX during the same period. The model was then applied to simulate future SOC dynamics of the rich fen control site under various CO₂ emission scenarios. The results across these emissions scenarios suggest that the rate of SOC sequestration in the rich fen will increase between year 2012 and 2061 because the effects of warming increase heterotrophic respiration less than they increase carbon inputs via production. However, after 2061, the rate of SOC sequestration will be weakened and, as a result, the rich fen will likely become a carbon source to the atmosphere between 2062 and 2099. During this period, the effects of projected warming increase respiration so that it is greater than carbon inputs via production. Although changes in precipitation alone had relatively little effect on the dynamics of SOC, changes in precipitation did interact with warming to influence SOC dynamics for some climate scenarios.     

Effects of a transient oxic period on mineralization of organic matter to CH4 and CO2 in anoxic peat incubations

Rates of organic matter mineralization in peatlands, and hence production of the greenhouse gases CH₄ and CO₂, are highly dependent on the distribution of oxygen in the peat. Using laboratory incubations of peat, we investigated the sensitivity of the anoxic production of CH₄ and CO₂ to a transient oxic period of a few weeks’ duration. Production rates during 3 successive anoxic periods were compared with rates in samples incubated in the presence of oxygen during the second period. In surface peat (5–10‐cm depth), with an initially high level of CH₄ production, oxic conditions during period 2 did not result in a lower potential CH₄ production rate during period 3, although production was delayed ～1 week. In permanently anoxic, deep peat (50–55‐cm depth) with a comparatively low initial production of CH₄, oxic conditions during period 2 resulted in zero production of CH₄ during period 3. Thus, the methanogens in surface peal—but not in deep peat—remained viable after several weeks of oxic conditions. In contrast to CH₄ production, the oxic period had a negligible effect on anoxic CO₂ production during period 3, in surface as well as deep peat. In both surface and deep peat, CO₂ production was several times higher under oxic than under anoxic conditions. However, for the first 2 weeks of oxic conditions, CO₂ production in the deep peat was very low. Still, deep peat obviously contained facultative microorganisms that, after a relatively short period, were able to maintain a considerably higher rate of organic matter mineralization under oxic than under anoxic conditions.     

Contributions to the Flora of Spitsbergen,especially of Red bay,from the Collections of W. S. Bruce,F.R.S.G.S., Naturalist to the Prince of Monaco's Expeditions of 1898 and 1899

Background: Prescribed burning in peatlands is controversial due to concerns over damage to their ecological functioning, particularly regarding their key genus Sphagnum. However, empirical evidence is scarce.

Aims: The aim of the article is to quantify Sphagnum recovery following prescribed burns.

Methods: We completed nine fires at a raised bog in Scotland, achieving a range of fire severities by simulating drought in some plots. We measured Sphagnum cover and chlorophyll fluorescence F_v/F_m ratio (an estimate of photosynthetic capacity) up to 36 months post-fire.

Results: Cover of dominant Sphagnum capillifolium was similar in unburnt and burnt plots, likely due to its high moisture content which prevented combustion. Burning decreased S. capillifolium F_v/F_m 5 months after fire from 0.67 in unburnt plots to 0.44 in low fire severity plots and 0.24 in higher fire severity (drought) plots. After 22 months, F_v/F_m in burnt plots showed a healthy photosynthetic capacity of 0.76 and no differences between severity treatments. Other Sphagnum species showed similar post-fire recovery though their low overall abundance precluded formal statistical analysis.

Conclusions: S. capillifolium is resilient to low–moderate fire severities and the same may be true for a number of other species. This suggests that carefully applied managed burning can be compatible with the conservation of peatland ecosystem function.     

Vegetation structure and photosynthesis respond rapidly to restoration in young coastal fens

Young coastal fens are rare ecosystems in the first stages of peatland succession. Their drainage compromises their successional development toward future carbon (C) reservoirs. We present the first study on the success of hydrological restoration of young fens. We carried out vegetation surveys at six young fens that represent undrained, drained, and restored management categories in the Finnish land uplift coast before and after restoration. We measured plant level carbon dioxide (CO₂) assimilation and chlorophyll fluorescence (Fv/Fm) from 17 most common plant species present at the sites. Within 5 years of restoration, the vegetation composition of restored sites had started to move toward the undrained baseline. The cover of sedges increased the most in response to restoration, while the cover of deciduous shrubs decreased the most. The rapid response indicates high resilience and low resistance of young fen ecosystems toward changes in hydrology. Forbs had higher photosynthetic and respiration rates than sedges, deciduous shrubs, and grasses, whereas rates were lowest for evergreen shrubs and mosses. The impact of management category on CO₂ assimilation was an indirect consequence that occurred through changes in plant species composition: Increase in sedge cover following restoration also increased the potential photosynthetic capacity of the ecosystem. Synthesis and applications. Restoration of forestry drained young fens is a promising method for safeguarding them and bringing back their function as C reservoirs. However, their low resistance to water table draw down introduces a risk that regeneration may be partially hindered by the heavy drainage in the surrounding landscape. Therefore, restoration success is best safeguarded by managing the whole catchments instead of carrying out small‐scale projects.     

Rapid loss of an ecosystem engineer: Sphagnum decline in an experimentally warmed bog

Sphagnum mosses are keystone components of peatland ecosystems. They facilitate the accumulation of carbon in peat deposits, but climate change is predicted to expose peatland ecosystem to sustained and unprecedented warming leading to a significant release of carbon to the atmosphere. Sphagnum responses to climate change, and their interaction with other components of the ecosystem, will determine the future trajectory of carbon fluxes in peatlands. We measured the growth and productivity of Sphagnum in an ombrotrophic bog in northern Minnesota, where ten 12.8‐m‐diameter plots were exposed to a range of whole‐ecosystem (air and soil) warming treatments (+0 to +9°C) in ambient or elevated (+500 ppm) CO₂. The experiment is unique in its spatial and temporal scale, a focus on response surface analysis encompassing the range of elevated temperature predicted to occur this century, and consideration of an effect of co‐occurring CO₂ altering the temperature response surface. In the second year of warming, dry matter increment of Sphagnum increased with modest warming to a maximum at 5°C above ambient and decreased with additional warming. Sphagnum cover declined from close to 100% of the ground area to <50% in the warmest enclosures. After three years of warming, annual Sphagnum productivity declined linearly with increasing temperature (13–29 g C/m² per °C warming) due to widespread desiccation and loss of Sphagnum. Productivity was less in elevated CO₂ enclosures, which we attribute to increased shading by shrubs. Sphagnum desiccation and growth responses were associated with the effects of warming on hydrology. The rapid decline of the Sphagnum community with sustained warming, which appears to be irreversible, can be expected to have many follow‐on consequences to the structure and function of this and similar ecosystems, with significant feedbacks to the global carbon cycle and climate change.     

Integration of ground survey and remote sensing derived data: Producing robust indicators of habitat extent and condition

The availability of suitable habitat is a key predictor of the changing status of biodiversity. Quantifying habitat availability over large spatial scales is, however, challenging. Although remote sensing techniques have high spatial coverage, there is uncertainty associated with these estimates due to errors in classification. Alternatively, the extent of habitats can be estimated from ground‐based field survey. Financial and logistical constraints mean that on‐the‐ground surveys have much lower coverage, but they can produce much higher quality estimates of habitat extent in the areas that are surveyed. Here, we demonstrate a new combined model which uses both types of data to produce unified national estimates of the extent of four key habitats across Great Britain based on Countryside Survey and Land Cover Map. This approach considers that the true proportion of habitat per km² (Z_i) is unobserved, but both ground survey and remote sensing can be used to estimate Z_i. The model allows the relationship between remote sensing data and Z_i to be spatially biased while ground survey is assumed to be unbiased. Taking a statistical model‐based approach to integrating field survey and remote sensing data allows for information on bias and precision to be captured and propagated such that estimates produced and parameters estimated are robust and interpretable. A simulation study shows that the combined model should perform best when error in the ground survey data is low. We use repeat surveys to parameterize the variance of ground survey data and demonstrate that error in this data source is small. The model produced revised national estimates of broadleaved woodland, arable land, bog, and fen, marsh and swamp extent across Britain in 2007.     

泥炭藓: 一类具有重要生态、经济和科学价值的碳封存植物

全球气候变暖是人类面临最严峻的环境挑战。有效控制碳排放, 充分发挥生态系统的固碳能力是实现碳中和目标的重要手段。作为碳封存能力最强的一种湿地类型, 泥炭地是加快实现碳中和目标的关键陆地生态系统。作为泥炭地“有效的生态系统工程师”, 泥炭藓(Sphagnum)在泥炭地的碳汇功能、过滤淡水及保护土地免受洪水侵袭等方面具有极其重要的作用。100多年来, 泥炭藓广泛应用于医药保健、污染监测和废水处理等领域, 尤其是作为一类最值得信赖的土壤介质和保湿材料一直被广泛用于园艺产业。在全球气候变暖和“双碳”目标的大背景下, 泥炭藓已经成为生命科学和生态学研究的热点。该文主要从泥炭藓的形态、物种多样性和起源、生境与分布、繁殖和保护、培养与种植、环境指示和监测、用途和应用, 以及碳封存、储水和酸化能力等方面进行综述, 旨在为泥炭藓研究、泥炭地的保护和恢复以及泥炭藓开发利用和产业发展提供借鉴与参考。     

Influence of vegetation on the accumulation of peat in southern Quebec

Mirabel bog (southern Quebec) was studied with the aim of specifying the past influence of local vegetation on peat accumulation. This influence was essentially translated by the reduction of minerotrophic inputs and peat accumulation induced by the highering of the peatland surface. Extremely rich initial conditions allow to explain the very high accumulations of the beginning of the Holocene, observed in various plant communities, among which Larix forests with ferns and Carex without modern analogues. Moreover, the structure (forest density) and the composition (dominance of Cyperaceae or Ericaceae) of these communities have locally controlled the dynamic of peat accumulation. These results point out the interest of the confrontation between palynological and macrofossil data and the spatialisation of palaeoecological studies.     

Sensitivity of CO<Subscript>2</Subscript> Exchange of Fen Ecosystem Components to Water Level Variation

Abstract Climate change is predicted to bring about a water level (WL) draw-down in boreal peatlands. This study aimed to assess the effect of WL on the carbon dioxide (CO₂) dynamics of a boreal oligotrophic fen ecosystem and its components; Sphagnum mosses, sedges, dwarf shrubs and the underlying peat. We measured CO₂ exchange with closed chambers during four growing seasons in a study site that comprised different vegetation treatments. WL gradient in the site was broadened by surrounding half of the site with a shallow ditch that lowered the WL by 10–25 cm. We modeled gross photosynthesis (P _G) and ecosystem respiration (R _ECO) and simulated the CO₂ exchange in three WL conditions: prevailing and WL draw-down scenarios of 14 and 22 cm. WL draw-down both reduced the P _G and increased the R _ECO, thus leading to a smaller net CO₂ uptake in the ecosystem. Of the different components, Sphagnum mosses were most sensitive to WL draw-down and their physiological activities almost ceased. Vascular plant CO₂ exchange, en bloc, hardly changed but whereas sedges contributed twice as much to the CO₂ exchange as shrubs in the prevailing conditions, the situation was reversed in the WL draw-down scenarios. Peat respiration was the biggest component in R _ECO in all WL conditions and the increase in R _ECO following the WL draw-down was due to the increase in peat respiration. The results imply that functional diversity buffers the ecosystem against environmental variability and that in the long term, WL draw-down changes the vegetation composition of boreal fens.     

Extent of industrial plantations on Southeast Asian peatlands in 2010 with analysis of historical expansion and future projections

Tropical peatlands cover over 25 Mha in Southeast Asia and are estimated to contain around 70 Gt of carbon. Peat swamp forest ecosystems are an important part of the region's natural resources supporting unique flora and fauna endemic to Southeast Asia. Over recent years, industrial plantation development on peatland, especially for oil palm cultivation, has created intense debate due to its potentially adverse social and environmental effects. The lack of objective up‐to‐date information on the extent of industrial plantations has complicated quantification of their regional and global environmental consequences, both in terms of loss of forest and biodiversity as well as increases in carbon emissions. Based on visual interpretation of high‐resolution (30 m) satellite images, we find that industrial plantations covered over 3.1 Mha (20%) of the peatlands of Peninsular Malaysia, Sumatra and Borneo in 2010, surpassing the area of Belgium and causing an annual carbon emission from peat decomposition of 230–310 Mt CO_2e. The majority (62%) of the plantations were located on the island of Sumatra, and over two‐thirds (69%) of all industrial plantations were developed for oil palm cultivation, with the remainder mostly being Acacia plantations for paper pulp production. Historical analysis shows strong acceleration of plantation development in recent years: 70% of all industrial plantations have been established since 2000 and only 4% of the current plantation area existed in 1990. ‘Business‐as‐usual’ projections of future conversion rates, based on historical rates over the past two decades, indicate that 6–9 Mha of peatland in insular Southeast Asia may be converted to plantations by the year 2020, unless land use planning policies or markets for products change. This would increase the annual carbon emission to somewhere between 380 and 920 Mt CO_2e by 2020 depending on water management practices and the extent of plantations.