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Aims: Peat is used as a major ingredient of growing media in horticulture. Peat extracted from bogs can be acidic and low in nutrient availability and is therefore mixed with liming agents, nutrients, surfactants, perlite and so on. This study aims to estimate the rates at which raw peat and the modified peat (‘growing media’) decompose to release carbon dioxide (CO2), to estimate the release of carbon (C) from liming agents and to estimate how peat biogeochemistry is changed.We obtained 28 and 24 samples of raw peat and 24 growing media from four peat extraction companies in Canada. Growing media were treated with horticultural additives. We incubated the samples under laboratory conditions, measuring CO2 production, tracer using δ13C\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\updelta }^{13}{\text{C}}$$\end{document}-CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document}, pH, C, nitrogen (N) content and humification indices (HIs) from infrared technology called Fourier transform-mid infrared (FT-MIR).C:N ratio, pH, dissolved organic carbon, bulk density and C content differed significantly (P < 0.05) between raw peats and growing media. There was more than a doubling of total CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} production from growing media compared to raw peat. HIs show higher values for the growing media, which could result from spectral band shifts in the growing media because of increased cation availability. δ13C\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\updelta }^{13}{\text{C}}$$\end{document}-CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} as a tracer showed an average 22% of the total CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} production orginated from added carbonate materials.Our results provide the rates (0.15 ± 0.017mgCO2-Cg−1d−1) at which horticultural peat decomposes and on the source of emitted CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document}. This will improve current estimates CO2 emissions from horticultural peat.Methods: Peat is used as a major ingredient of growing media in horticulture. Peat extracted from bogs can be acidic and low in nutrient availability and is therefore mixed with liming agents, nutrients, surfactants, perlite and so on. This study aims to estimate the rates at which raw peat and the modified peat (‘growing media’) decompose to release carbon dioxide (CO2), to estimate the release of carbon (C) from liming agents and to estimate how peat biogeochemistry is changed.We obtained 28 and 24 samples of raw peat and 24 growing media from four peat extraction companies in Canada. Growing media were treated with horticultural additives. We incubated the samples under laboratory conditions, measuring CO2 production, tracer using δ13C\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\updelta }^{13}{\text{C}}$$\end{document}-CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document}, pH, C, nitrogen (N) content and humification indices (HIs) from infrared technology called Fourier transform-mid infrared (FT-MIR).C:N ratio, pH, dissolved organic carbon, bulk density and C content differed significantly (P < 0.05) between raw peats and growing media. There was more than a doubling of total CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} production from growing media compared to raw peat. HIs show higher values for the growing media, which could result from spectral band shifts in the growing media because of increased cation availability. δ13C\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\updelta }^{13}{\text{C}}$$\end{document}-CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} as a tracer showed an average 22% of the total CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} production orginated from added carbonate materials.Our results provide the rates (0.15 ± 0.017mgCO2-Cg−1d−1) at which horticultural peat decomposes and on the source of emitted CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document}. This will improve current estimates CO2 emissions from horticultural peat.Results: Peat is used as a major ingredient of growing media in horticulture. Peat extracted from bogs can be acidic and low in nutrient availability and is therefore mixed with liming agents, nutrients, surfactants, perlite and so on. This study aims to estimate the rates at which raw peat and the modified peat (‘growing media’) decompose to release carbon dioxide (CO2), to estimate the release of carbon (C) from liming agents and to estimate how peat biogeochemistry is changed.We obtained 28 and 24 samples of raw peat and 24 growing media from four peat extraction companies in Canada. Growing media were treated with horticultural additives. We incubated the samples under laboratory conditions, measuring CO2 production, tracer using δ13C\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\updelta }^{13}{\text{C}}$$\end{document}-CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document}, pH, C, nitrogen (N) content and humification indices (HIs) from infrared technology called Fourier transform-mid infrared (FT-MIR).C:N ratio, pH, dissolved organic carbon, bulk density and C content differed significantly (P < 0.05) between raw peats and growing media. There was more than a doubling of total CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} production from growing media compared to raw peat. HIs show higher values for the growing media, which could result from spectral band shifts in the growing media because of increased cation availability. δ13C\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\updelta }^{13}{\text{C}}$$\end{document}-CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} as a tracer showed an average 22% of the total CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} production orginated from added carbonate materials.Our results provide the rates (0.15 ± 0.017mgCO2-Cg−1d−1) at which horticultural peat decomposes and on the source of emitted CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document}. This will improve current estimates CO2 emissions from horticultural peat.Conclusion: Peat is used as a major ingredient of growing media in horticulture. Peat extracted from bogs can be acidic and low in nutrient availability and is therefore mixed with liming agents, nutrients, surfactants, perlite and so on. This study aims to estimate the rates at which raw peat and the modified peat (‘growing media’) decompose to release carbon dioxide (CO2), to estimate the release of carbon (C) from liming agents and to estimate how peat biogeochemistry is changed.We obtained 28 and 24 samples of raw peat and 24 growing media from four peat extraction companies in Canada. Growing media were treated with horticultural additives. We incubated the samples under laboratory conditions, measuring CO2 production, tracer using δ13C\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\updelta }^{13}{\text{C}}$$\end{document}-CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document}, pH, C, nitrogen (N) content and humification indices (HIs) from infrared technology called Fourier transform-mid infrared (FT-MIR).C:N ratio, pH, dissolved organic carbon, bulk density and C content differed significantly (P < 0.05) between raw peats and growing media. There was more than a doubling of total CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} production from growing media compared to raw peat. HIs show higher values for the growing media, which could result from spectral band shifts in the growing media because of increased cation availability. δ13C\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\updelta }^{13}{\text{C}}$$\end{document}-CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} as a tracer showed an average 22% of the total CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document} production orginated from added carbonate materials.Our results provide the rates (0.15 ± 0.017mgCO2-Cg−1d−1) at which horticultural peat decomposes and on the source of emitted CO2\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${{\text{CO}}}_{2}$$\end{document}. This will improve current estimates CO2 emissions from horticultural peat. [ABSTRACT FROM AUTHOR]

Aims: Peatland porewaters frequently contain large concentrations of dissolved organic nitrogen (DON), but small concentrations of inorganic N (NH4+ and NO3−). Our aim was to test whether peatland plants, with low tissue N concentrations (0.7 to 1.7%), have the ability to take up organic forms of N, specifically glycine.Methods: We applied dual-labeled (13C and 15N) glycine to two peatlands: an ombrotrophic bog in eastern Canada and a New Zealand restiad bog undergoing restoration. We compared the δ13C and δ15N values of control and treated above and below-ground plant tissues to establish whether the glycine had been taken up.Results: At the Canadian bog, the moss, shrub and sedge species treated with glycine showed significant increases in δ15N, above and below-ground, and there was evidence of a significant change in δ13C in shrub roots. At the New Zealand peatland, above- and below-ground tissues of the two restiad species and the roots of the sedge species showed significantly increased δ15N, while only the sedge roots showed a significant increase in δ13C.Conclusions: All but one of the nine plant species examined showed significant uptake of 15N in foliage and all roots showed increases in 15N. Variations in uptake appear to be partially related to the plant type and root characteristics. Large variations in C, 13C, N and 15N concentration within treatments precluded strong evidence of whether uptake included intact glycine. [ABSTRACT FROM AUTHOR]

Background and aims: We examined changes in soil organic matter arising from conversion of a 45-year old pasture to a 10 yr. old native tree plantation in Panamá, to evaluate the effect of monoculture and mixtures.Methods: We intensively sampled the soil 0-10 cm depth in the pasture in 2001 and in 22 plantation plots in 2011, ranging from 5 monocultures to 3- and 6-species treatments; samples were also taken from an undisturbed forest site. Soil analyses included organic carbon (SOC) and δ13C.Results: Conversion of the pasture to tree plantation resulted in an overall loss of SOC of 0.6 kg m−2 (18%) in the top 10 cm, but neither tree species nor diversity had a significant effect. End-member δ13C values suggested that the contribution of C3 plants to SOC was increased from 26% in the pasture to 55% after 10 years of plantation and SOC turnover times were calculated to be 21-36 yr.Conclusions: The magnitude of the loss in soil SOC is smaller than the increases in tree biomass (~3 kg C m−2) and litter (~0.3 kg C m−2) in the plantation, but still a significant part of the ecosystem C balance. [ABSTRACT FROM AUTHOR]

Background and aims: The litter-bag technique has become common in the estimation of the rates of decomposition, but in many cases the bags are incubated for only a short period, raising the issue of the extent to which short-term incubations represent long-term litter decomposition. We addressed this using 12 years of data from the CIDET study. Methods: The CIDET study involved placement of 10 foliar litters on the soil surface and wood blocks on the soil surface and buried across temperate to subarctic Canada. Bags were retrieved 10 times over 12 years at 19 sites and the residual litter mass determined. Results: A literature search revealed that 84% of published litter-bag studies in temperate-boreal-subarctic regions were of 3 years duration or less. The strength of the relationship between the mass loss after 1 year and later years at each CIDET site, expressed as the coefficient of determination ( R ) among the 12 litters, decreased with length of incubation, reaching an average of only 0.4 after 12 years. The R value was inversely related to mean annual temperature. The single exponential model of mass remaining ( k) declined with length of incubation, and the rate of decline varied among litter types and sites. For 3 litters at 19 sites, the 3- and 12-year k values were strongly related. Conclusions: These results show that caution should be exercised when extrapolating short-term litter-bag studies (e.g. < 3 years), particularly in temperate climates. [ABSTRACT FROM AUTHOR]

Background and aim: Although ombrotrophic peatlands are nutrient deficient, it is not clear to what extent plants will respond to changes in nutrient availability. Methods: We examined the changes in foliar stoichiometry and species abundance of four shrub species and moss after a decade of nitrogen (N), phosphorus (P) and potassium (K) fertilization at the Mer Bleue bog, eastern Canada. Results: Shrub abundance increased and moss cover decreased after fertilization with 6.4, 5 and 6.3 g m yr of N, P and K, respectively; foliar concentrations of N, P, K and calcium (Ca) and magnesium (Mg) were affected. Stoichiometry showed mainly N limitation after P and K fertilization and P (co)limitation after high levels of N addition in shrubs; moss showed consistent K or KN-co-limitation, even with PK and NPK additions. Shrubs exhibited the strongest homeostasis (the maintenance of an organism's tissue chemical composition with changes in environmental resources) to N, with the homeostatic regulation coefficient ( H) > 9.7, compared to 1.4 in moss. For P and K, shrubs showed weaker homeostasis than N, while moss had a stronger homeostasis. Conclusions: The strong homeostasis of shrubs may be an adaptive strategy to limited availability of soil N and P. [ABSTRACT FROM AUTHOR]

We measured changes in carbon (C), nitrogen (N) and phosphorus (P) concentrations and mass of 10 foliar litters decomposing over 12 years at 21 sites across Canada, ranging from subarctic to temperate, to evaluate the influence of litter quality (nature) and forest floor (nurture) on N and P dynamics. Most litters lost P faster than N, relative to C, except in one litter which had a high initial C:P quotient (2,122). Net N loss occurred at mass C:N quotients of between 33 and 68, positively correlated with the C:N quotient in the original litter, and net P loss likely occurred at C:P quotients between 800 and 1,200. Forest floor properties also influenced N and P dynamics: the higher the C:N or C:P quotient in the surface soil organic matter, the smaller the proportion of initial N or P left in the decomposing litter, relative to C. There was a convergence of C:N and C:P quotients as the litters decomposed, with an overall mass ratio of 427:17:1 when the litters reached 20% original C remaining. These results, covering a wide range of sites and litters and thus decomposition rates, showed that the C:N:P quotients followed similar trajectories and converged as the litters decomposed. The relative loss of N and P was affected by both the initial litter nutrient concentration and the chemistry of the site forest floor, with the former being more important than the latter, resulting in spatial variations in nutrient content of the forest floor. [ABSTRACT FROM AUTHOR]

Fine root production and its relationships to aboveground plant components and environmental drivers such as water table have been poorly quantified in peatland ecosystems, despite being the primary input of labile carbon to peat soils. We studied the relationship between fine root (< 1 mm) production, aboveground biomass and growing season water table within an ombrotrophic peatland in eastern Ontario. We installed 80 in-growth bags (10 cm diameter) to measure fine root production over the full range of 40 cm in water table depth. The point-intersect method was used to estimate peak aboveground biomass components (total, leaf and stem) for the 0.36 m area surrounding each in-growth bag. Mean fine root production was 108 ± 71 g m y and was strongly related to both aboveground biomass and water table. Linear regression analysis showed strong allometric relationships between fine root production and aboveground biomass for shrubs ( r = 0.61, p < 0.001), suggesting that fine root production estimates can be approximated using aboveground biomass data. Water table had a significant effect on the allocation of biomass to fine roots, leaves and stems with a deeper water table significantly increasing both fine root production at depth and at each depth increment. Shrub biomass allocation to leaves and stems similarly shifted, with greater investment in stems relative to leaves with a deeper water table. As a result, greater fine root biomass was produced per unit leaf biomass in areas with a deeper water table, illustrating an important tradeoff between leaf and fine root tissues in drier conditions. Our results indicate that any drop in water table will likely increase aboveground biomass stocks and the influx of labile carbon to peat soils via fine roots and leaves. [ABSTRACT FROM AUTHOR]