The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform

Laurie Scrivener - One of the best experts on this subject based on the ideXlab platform.

Eeva-stiina Tuittila - One of the best experts on this subject based on the ideXlab platform.

  • Varying Vegetation Composition, Respiration and Photosynthesis Decrease Temporal Variability of the CO_2 Sink in a Boreal Bog
    Ecosystems, 2019
    Co-Authors: Aino Korrensalo, Lauri Mehtätalo, Pavel Alekseychik, Salli Uljas, Ivan Mammarella, Timo Vesala, Eeva-stiina Tuittila
    Abstract:

    We quantified the role of spatially varying vegetation composition in seasonal and interannual changes in a boreal bog’s CO_2 uptake. We divided the spatially heterogeneous site into six Microform classes based on plant species composition and measured their net ecosystem exchange (NEE) using chamber method over the growing seasons in 2012–2014. A nonlinear mixed-effects model was applied to assess how the contributions of Microforms with different vegetation change temporally, and to upscale NEE to the ecosystem level to be compared with eddy covariance (EC) measurements. Both ecosystem respiration ( R ) and gross photosynthesis ( P _G) were the largest in high hummocks, 894–964 ( R ) and 969–1132 ( P _G) g CO_2 m^−2 growing season^−1, and decreased toward the wetter Microforms. NEE had a different spatial pattern than R and P _G; the highest cumulative seasonal CO_2 sink was found in lawns in all years (165–353 g CO_2 m^−2). Microforms with similar wetness but distinct vegetation had different NEE, highlighting the importance of vegetation composition in regulating CO_2 sink. Chamber-based ecosystem-level NEE was smaller and varied less interannually than the EC-derived estimate, indicating a need for further research on the error sources of both methods. Lawns contributed more to ecosystem-level NEE (55–78%) than their areal cover within the site (21.5%). In spring and autumn, lawns had the highest NEE, whereas in midsummer differences among Microforms were small. The contributions of all Microforms to the ecosystem-level NEE varied seasonally and interannually, suggesting that spatially heterogeneous vegetation composition could make bog CO_2 uptake temporally more stable.

  • Microform related community patterns of methane cycling microbes in boreal sphagnum bogs are site specific
    FEMS Microbiology Ecology, 2015
    Co-Authors: Heli Juottonen, Mirkka Kotiaho, Devin Robinson, Paivi Merila, Hannu Fritze, Eeva-stiina Tuittila
    Abstract:

    Vegetation and water table are important regulators of methane emission in peatlands. Microform variation encompasses these factors in small-scale topographic gradients of dry hummocks, intermediate lawns and wet hollows. We examined methane production and oxidization among Microforms in four boreal bogs that showed more variation of vegetation within a bog with Microform than between the bogs. Potential methane production was low and differed among bogs but not consistently with Microform. Methane oxidation followed water table position with Microform, showing higher rates closer to surface in lawns and hollows than in hummocks. Methanogen community, analysed by mcrA terminal restriction fragment length polymorphism and dominated by Methanoregulaceae or ‘ Methanoflorentaceae’ , varied strongly with bog. The extent of Microform-related variation of methanogens depended on the bog. Methanotrophs identified as Methylocystis spp. in pmoA denaturing gradient gel electrophoresis similarly showed effect of bog, and Microform patterns were stronger within individual bogs. Our results suggest that methane-cycling microbes in boreal Sphagnum bogs with seemingly uniform environmental conditions may show strong site-dependent variation. The bog-intrinsic factor may be related to carbon availability but contrary to expectations appears to be unrelated to current surface vegetation, calling attention to the origin of carbon substrates for microbes in bogs.

Tim R Moore - One of the best experts on this subject based on the ideXlab platform.

  • Mechanisms for the Development of Microform Patterns in Peatlands of the Hudson Bay Lowland
    Ecosystems, 2019
    Co-Authors: Lorna I. Harris, Nigel T. Roulet, Tim R Moore
    Abstract:

    Spatial surface patterns of hummocks, hollows, ridges, and pools (microtopography) are common features of many northern peatlands and are particularly distinct within the vast peatlands of the Hudson Bay Lowland (HBL), Canada. Hypotheses and models describe how small-scale feedbacks among vegetation, hydrology, and nutrients cause spatial differences in peat accumulation that enable Microforms and surface patterns to develop over time. Empirical tests of the predictions from theoretical models of these proposed feedback mechanisms are limited, particularly in large peatland complexes such as the HBL. We investigate feedbacks controlling peatland structure and function in an ombrogenous bog and a minerogenous fen in the HBL. Our sites represent surface patterns found in many northern peatlands, specifically spatially irregular hummocks and hollows, and parallel ridges and pools that are perpendicular to slope. We found the occurrence of different spatial patterns depends on position within a peat landform, with these differences attributed to the ecohydrological setting. In turn, the ecohydrological setting, with different water table depths, nutrient availability, and species composition, influences the strength and direction of feedback mechanisms at the Microform scale. Our data support the prediction of a positive feedback between plant productivity and acrotelm thickness for peat accumulation and hummock growth and that this may be enhanced by water ponding on slopes to form ridge–pool tracks. We did not find evidence to support the proposed feedback among evapotranspiration-driven transport of water and nutrients for the development of hummocks. Our results suggest a combination of mechanisms operating at various temporal and spatial scales is associated with the development of surface patterns in northern peatlands.

  • variation in co2 exchange over three summers at Microform scale in a boreal bog eastmain region quebec canada
    Journal of Geophysical Research, 2011
    Co-Authors: Luc Pelletier, Michelle Garneau, Tim R Moore
    Abstract:

    [1] We examine variability in carbon dioxide (CO2) exchange as a function of meteorological conditions using static chambers across a peatland microtopographic gradient (high hummock, low hummock, lawn and hollow Microforms) between June and August 2006, 2007, and 2008. Total June to August precipitation increased during the study period with 285 mm in 2006, 320 mm in 2007, and 369 mm in 2008, whereas monthly average temperature was similar among years, with the exception of August 2008, which was 2.4°C warmer than previous years. Significantly different relationships between photosynthetic photon flux density and net ecosystem exchange (NEE) were observed in 2008 on three of the four Microforms corresponding with the different meteorological conditions. The controls on CO2 exchange varied among Microforms: a water table closer to the peat surface increased NEE on the high and low hummocks by increasing maximum rates of photosynthesis (PSNmax) but reduced NEE on the hollow Microform by flooding the surface vegetation and reducing PSNmax. Water table position was a significant control on ecosystem respiration (ER) only on the lawn Microform. We examine relationships between water table position and PSNmax and ER, and propose a theoretical relationship, which supports results from other studies examining water table position and peat accumulation.

Agnes Widder - One of the best experts on this subject based on the ideXlab platform.

Eugene Sawa - One of the best experts on this subject based on the ideXlab platform.