Carbon flux response and recovery to drought years in a hemi-boreal peat bog between different vegetation types

Peatlands are a globally important store of approximately 500 Gt carbon (C), with northern blanket bogs accumulating ca. 23 g C m-2 y-1 from undecomposed organic material due to prevailing cool wet conditions. As a sink of carbon dioxide (CO2) they act as an important brake on anthropogenic climate change, but in the warming climate the likelihood of drought will increase. However, it is unknown how drought will affect the GHG balance of peatlands: dryer, warmer conditions will likely reduce net ecosystem exchange (NEE) of CO2 and increase soil respiration, potentially tipping these landscapes from sinks to sources of C. High water tables mean blanket bogs are major source of methane (CH4), an important greenhouse gas (GHG) with a global warming potential (GWP) 34 times that of CO2 over 100 years, but this may change in the future climate. It is further expected that the changing climate will alter blanket bog species composition, which may also influence the GHG balance, due to differences in plant traits such as those which form aerenchyma, e.g. Eriophorum vaginatum (eriophorum) and non-aerenchymatous species, e.g. Calluna vulgaris (heather). In order to understand how these important C stores will respond to climate change, it is vital to measure GHG responses to drought at the species level. &#160;&#160;We used an automated chamber system, SkyLine2D, to measure NEE and CH4 fluxes near-continuously from an ombrotrophic blanket peat bog. Five general ecotypes were identified: sphagnum (Sphagnum spp), eriophorum, heather, water and mixtures of species, with five replicates of each sampled. We followed the fluxes of CO2 throughout 2017- 2019 and CH4 throughout 2017- 2018, hypothesising that GHG fluxes would significantly differ between ecotypes. In 2018, the bog experienced drought conditions, allowing the comparison of NEE between drought and non-drought years, and the potential to recover the following year. Contemporaneous measurements of environmental variables were collected to infer details regarding the drivers of GHG fluxes.We found significant differences in CH4 emissions between ecotypes, F= 2.71, p< 0.02, ordered high to low: eriophorum > sphagnum > water > heather> mix, ranging from ca. 1.5 mg CH4-C m-2 d-1 to 0.5 mg CH4-C m-2 d-1. There were no significant differences in NEE between ecotypes, F= 0.54, p> 0.7, however, under 2018 drought conditions all ecotypes were net sources of CO2. We will also present NEE from 2019, when precipitation levels returned to typical conditions. Our results indicate that drought and shifts in vegetation composition under future climate may alter the C balance of hemi-boreal and potentially act as a positive feedback to climate change in a long-term scenario.

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Carbon Dioxide and Methane Flux Response and Recovery From Drought in a Hemiboreal Ombrotrophic Fen

Frontiers in Earth Science ◽

10.3389/feart.2020.562401 ◽

2021 ◽

Vol 8 ◽

Author(s):

J. B Keane ◽

S. Toet ◽

P. Ineson ◽

P. Weslien ◽

J. E. Stockdale ◽

...

Keyword(s):

Climate Change ◽

Carbon Dioxide ◽

Water Table ◽

Net Ecosystem Exchange ◽

Open Water ◽

Calluna Vulgaris ◽

Methane Flux ◽

High Water ◽

Peat Bogs ◽

Flux Response

Globally peatlands store 500 Gt carbon (C), with northern blanket bogs accumulating 23 g C m−2 y−1 due to cool wet conditions. As a sink of carbon dioxide (CO2) peat bogs slow anthropogenic climate change, but warming climate increases the likelihood of drought which may reduce net ecosystem exchange (NEE) and increase soil respiration, tipping C sinks to sources. High water tables make bogs a globally important source of methane (CH4), another greenhouse gas (GHG) with a global warming potential (GWP) 34 times that of CO2. Warming may increase CH4 emissions, but drying may cause a reduction. Predicted species composition changes may also influence GHG balance, due to different traits such as erenchyma, e.g., Eriophorum vaginatum (eriophorum) and non-aerenchymatous species, e.g., Calluna vulgaris (heather). To understand how these ecosystems will respond to climate change, it is vital to measure GHG responses to drought at the species level. An automated chamber system, SkyLine2D, measured NEE and CH4 fluxes near-continuously from an ombrotrophic fen from August 2017 to September 2019. Four ecotypes were identified: sphagnum (Sphagnum spp), eriophorum, heather and water, hypothesizing that fluxes would significantly differ between ecotypes. The 2018 drought allowed comparison of fluxes between drought and non-drought years (May to September), and their recovery the following year. Methane emissions differed between ecotypes (p < 0.02), ordered high to low: eriophorum > sphagnum > water > heather, ranging from 23 to 8 mg CH4-C m−2 d−1. Daily NEE was similar between ecotypes (p > 0.7), but under 2018 drought conditions all ecotypes were greater sources of CO2 compared to 2019, losing 1.14 g and 0.24 g CO2-C m−2 d−1 respectively (p < 0.001). CH4 emissions were ca. 40% higher during 2018 than 2019, 17 mg compared to 12 mg CH4-C m−2 d−1 (p < 0.0001), and fluxes exhibited hysteresis with water table depth. A lag of 84–88 days was observed between rising water table and increased CH4 emissions. A significant interaction between ecotype and year showed fluxes from open water did not return to pre-drought levels. Our findings suggest that short-term drought may lead to a net increase in C emissions from northern wetlands.

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Plant hydraulic traits reveal islands as refugia from worsening drought

Conservation Physiology ◽

10.1093/conphys/coz115 ◽

2020 ◽

Vol 8 (1) ◽

Cited By ~ 2

Author(s):

Aaron R Ramirez ◽

Mark E De Guzman ◽

Todd E Dawson ◽

David D Ackerly

Keyword(s):

Climate Change ◽

Water Relations ◽

Plant Traits ◽

Regional Climate ◽

Channel Islands ◽

Local Conditions ◽

Early 21St Century ◽

Plant Hydraulics ◽

Drought Conditions ◽

Potential Climate Change

Abstract Relatively mesic environments within arid regions may be important conservation targets as ‘climate change refugia’ for species persistence in the face of worsening drought conditions. Semi-arid southern California and the relatively mesic environments of California’s Channel Islands provide a model system for examining drought responses of plants in potential climate change refugia. Most methods for detecting refugia are focused on ‘exposure’ of organisms to certain abiotic conditions, which fail to assess how local adaptation or acclimation of plant traits (i.e. ‘sensitivity’) contribute to or offset the benefits of reduced exposure. Here, we use a comparative plant hydraulics approach to characterize the vulnerability of plants to drought, providing a framework for identifying the locations and trait patterns that underlie functioning climate change refugia. Seasonal water relations, xylem hydraulic traits and remotely sensed vegetation indices of matched island and mainland field sites were used to compare the response of native plants from contrasting island and mainland sites to hotter droughts in the early 21st century. Island plants experienced more favorable water relations and resilience to recent drought. However, island plants displayed low plasticity/adaptation of hydraulic traits to local conditions, which indicates that relatively conserved traits of island plants underlie greater hydraulic safety and localized buffering from regional drought conditions. Our results provide an explanation for how California’s Channel Islands function as a regional climate refugia during past and current climate change and demonstrate a physiology-based approach for detecting potential climate change refugia in other systems.

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Simulation of Carbon Exchange from a Permafrost Peatland in the Great Hing’an Mountains Based on CoupModel

Atmosphere ◽

10.3390/atmos13010044 ◽

2021 ◽

Vol 13 (1) ◽

pp. 44

Author(s):

Yue Li ◽

Zhongmei Wan ◽

Li Sun

Keyword(s):

Climate Change ◽

Carbon Sink ◽

Ecosystem Respiration ◽

Gross Primary Production ◽

Net Ecosystem Exchange ◽

Carbon Accumulation ◽

Future Climate ◽

Future Climate Change ◽

Growing Seasons ◽

Source Sink

Climate change is accelerating its impact on northern ecosystems. Northern peatlands store a considerable amount of C, but their response to climate change remains highly uncertain. In order to explore the feedback of a peatland in the Great Hing’an Mountains to future climate change, we simulated the response of the overall net ecosystem exchange (NEE), ecosystem respiration (ER), and gross primary production (GPP) during 2020–2100 under three representative concentration pathways (RCP2.6, RCP6.0, and RCP8.5). Under the RCP2.6 and RCP6.0 scenarios, the carbon sink will increase slightly until 2100. Under the RCP8.5 scenario, the carbon sink will follow a trend of gradual decrease after 2053. These results show that when meteorological factors, especially temperature, reach a certain degree, the carbon source/sink of the peatland ecosystem will be converted. In general, although the peatland will remain a carbon sink until the end of the 21st century, carbon sinks will decrease under the influence of climate change. Our results indicate that in the case of future climate warming, with the growing seasons experiencing overall dryer and warmer environments and changes in vegetation communities, peatland NEE, ER, and GPP will increase and lead to the increase in ecosystem carbon accumulation.

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