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  • 1
    Online Resource
    Online Resource
    Fungi regulate the response of the N〈sub〉2〈/sub〉O production process to warming and grazing in a Tibetan grassland
    Copernicus GmbH ; 2018
    In:  Biogeosciences Vol. 15, No. 14 ( 2018-07-20), p. 4447-4457
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 15, No. 14 ( 2018-07-20), p. 4447-4457
    Abstract: Abstract. Lack of understanding of the effects of warming and winter grazing on soil fungal contribution to the nitrous oxide (N2O) production process has limited our ability to predict N2O fluxes under changes in climate and land use management, because soil fungi play an important role in driving terrestrial N cycling. A controlled warming and winter grazing experiment that included control (C), winter grazing (G), warming (W) and warming with winter grazing (WG) was conducted to investigate the effects of warming and winter grazing on soil N2O production potential in an alpine meadow on the Tibetan Plateau. Our results showed that soil bacteria and fungi contributed 46 ± 2 % and 54 ± 2 % to nitrification, and 37 ± 3 % and 63 ± 3 % to denitrification in the control treatment, respectively. We conclude that soil fungi could be the main source of N2O production potential for the Tibetan alpine grasslands. In our results, neither warming nor winter grazing affected the activity of enzymes responsible for overall nitrification and denitrification. However, warming significantly increased the enzyme activity of bacterial nitrification and potential of N2O production from denitrification to 53 ± 2 % and 55 ± 3 %, respectively, but decreased them to 47 ± 2 % and 45 ± 3 %, respectively. Winter grazing had no such effects. Warming and winter grazing may not affect the soil N2O production potential, but climate warming can alter biotic pathways responsible for N2O production process. These findings confirm the importance of soil fungi in the soil N2O production process and how they respond to environmental and land use changes in alpine meadow ecosystems. Therefore, our results provide some new insights into ecological controls on the N2O production process and contribute to the development of an ecosystem nitrogen cycle model.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-15-4447-2018
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2158181-2
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  • 2
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    Online Resource
    Soil microbial community structure and diversity are largely influenced by soil pH and nutrient quality in 78-year-old tree plantations
    Copernicus GmbH ; 2017
    In:  Biogeosciences Vol. 14, No. 8 ( 2017-04-24), p. 2101-2111
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 14, No. 8 ( 2017-04-24), p. 2101-2111
    Abstract: Abstract. Forest plantations have been recognised as a key strategy management tool for stocking carbon (C) in soils, thereby contributing to climate warming mitigation. However, long-term ecological consequences of anthropogenic forest plantations on the community structure and diversity of soil microorganisms and the underlying mechanisms in determining these patterns are poorly understood. In this study, we selected 78-year-old tree plantations that included three coniferous tree species (i.e. slash pine, hoop pine and kauri pine) and a eucalypt species in subtropical Australia. We investigated the patterns of community structure, and the diversity of soil bacteria and eukaryotes by using high-throughput sequencing of 16S rRNA and 18S rRNA genes. We also measured the potential methane oxidation capacity under different tree species. The results showed that slash pine and Eucalyptus significantly increased the dominant taxa of bacterial Acidobacteria and the dominant taxa of eukaryotic Ascomycota, and formed clusters of soil bacterial and eukaryotic communities, which were clearly different from the clusters under hoop pine and kauri pine. Soil pH and nutrient quality indicators such as C : nitrogen (N) and extractable organic C : extractable organic N were key factors in determining the patterns of soil bacterial and eukaryotic communities between the different tree species treatments. Slash pine and Eucalyptus had significantly lower soil bacterial and eukaryotic operational taxonomical unit numbers and lower diversity indices than kauri pine and hoop pine. A key factor limitation hypothesis was introduced, which gives a reasonable explanation for lower diversity indices under slash pine and Eucalyptus. In addition, slash pine and Eucalyptus had a higher soil methane oxidation capacity than the other tree species. These results suggest that significant changes in soil microbial communities may occur in response to chronic disturbance by tree plantations, and highlight the importance of soil pH and physiochemical characteristics in microbially mediated ecological processes in forested soils.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-14-2101-2017
    DOI: 10.5194/bg-14-2101-2017-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
    detail.hit.zdb_id: 2158181-2
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  • 3
    Online Resource
    Online Resource
    Modeling the effects of tree species and incubation temperature on soil's extracellular enzyme activity in 78-year-old tree plantations
    Copernicus GmbH ; 2017
    In:  Biogeosciences Vol. 14, No. 23 ( 2017-12-01), p. 5393-5402
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 14, No. 23 ( 2017-12-01), p. 5393-5402
    Abstract: Abstract. Forest plantations have been widely used as an effective measure for increasing soil carbon (C), and nitrogen (N) stocks and soil enzyme activities play a key role in soil C and N losses during decomposition of soil organic matter. However, few studies have been carried out to elucidate the mechanisms behind the differences in soil C and N cycling by different tree species in response to climate warming. Here, we measured the responses of soil's extracellular enzyme activity (EEA) to a gradient of temperatures using incubation methods in 78-year-old forest plantations with different tree species. Based on a soil enzyme kinetics model, we established a new statistical model to investigate the effects of temperature and tree species on soil EEA. In addition, we established a tree species–enzyme–C∕N model to investigate how temperature and tree species influence soil C∕N contents over time without considering plant C inputs. These extracellular enzymes included C acquisition enzymes (β-glucosidase, BG), N acquisition enzymes (N-acetylglucosaminidase, NAG; leucine aminopeptidase, LAP) and phosphorus acquisition enzymes (acid phosphatases). The results showed that incubation temperature and tree species significantly influenced all soil EEA and Eucalyptus had 1.01–2.86 times higher soil EEA than coniferous tree species. Modeling showed that Eucalyptus had larger soil C losses but had 0.99–2.38 times longer soil C residence time than the coniferous tree species over time. The differences in the residual soil C and N contents between Eucalyptus and coniferous tree species, as well as between slash pine (Pinus elliottii Engelm. var. elliottii) and hoop pine (Araucaria cunninghamii Ait.), increase with time. On the other hand, the modeling results help explain why exotic slash pine can grow faster, as it has 1.22–1.38 times longer residual soil N residence time for LAP, which mediate soil N cycling in the long term, than native coniferous tree species like hoop pine and kauri pine (Agathis robusta C. Moore). Our results will be helpful for understanding the mechanisms of soil C and N cycling by different tree species, which will have implications for forest management.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-14-5393-2017
    DOI: 10.5194/bg-14-5393-2017-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
    detail.hit.zdb_id: 2158181-2
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  • 4
    Online Resource
    Online Resource
    Influences of an entrainment–mixing parameterization on numerical simulations of cumulus and stratocumulus clouds
    Copernicus GmbH ; 2022
    In:  Atmospheric Chemistry and Physics Vol. 22, No. 8 ( 2022-04-25), p. 5459-5475
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 8 ( 2022-04-25), p. 5459-5475
    Abstract: Abstract. Different entrainment–mixing processes can occur in clouds; however, a homogeneous mixing mechanism is often implicitly assumed in most commonly used microphysics schemes. Here, we first present a new entrainment–mixing parameterization that uses the grid mean relative humidity without requiring the relative humidity of the entrained air. Then, the parameterization is implemented in a microphysics scheme in a large eddy simulation model, and sensitivity experiments are conducted to compare the new parameterization with the default homogeneous entrainment–mixing parameterization. The results indicate that the new entrainment–mixing parameterization has a larger impact on the number concentration, volume mean radius, and cloud optical depth in the stratocumulus case than in the cumulus case. This is because inhomogeneous and homogeneous mixing mechanisms dominate in the stratocumulus and cumulus cases, respectively, which is mainly due to the larger turbulence dissipation rate in the cumulus case. Because stratocumulus clouds break up during the dissipation stage to form cumulus clouds, the effects of this new entrainment–mixing parameterization during the stratocumulus dissipation stage are between those during the stratocumulus mature stage and the cumulus case. A large aerosol concentration can enhance the effects of this new entrainment–mixing parameterization by decreasing the cloud droplet size and evaporation timescale. The results of this new entrainment–mixing parameterization with grid mean relative humidity are validated by the use of a different entrainment–mixing parameterization that uses parameterized entrained air properties. This study sheds new light on the improvement of entrainment–mixing parameterizations in models.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-22-5459-2022
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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  • 5
    Online Resource
    Online Resource
    Technical note: Manipulating interactions between plant stress responses and soil methane oxidation rates
    Copernicus GmbH ; 2018
    In:  Biogeosciences Vol. 15, No. 13 ( 2018-07-06), p. 4125-4129
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 15, No. 13 ( 2018-07-06), p. 4125-4129
    Abstract: Abstract. It has recently been hypothesised that ethylene, released into soil by stressed plants, reduces the oxidation of methane by methanotroph. To test this, a field trial was established in which maize plants were grown with and without soil moisture stress, and the effects of addition aminoethoxyvinylglycine (AVG; an ethylene biosynthesis inhibitor) and biochar (increases soil water holding capacity and reduces plant stress) were determined following the static incubation of soil samples. AVG increased methane oxidation rates by 50 % (P=0.039), but only in the absence of irrigation. No other treatment effects were observed. This result provides evidence for a positive feedback system between plant stress, ethylene production, and impacts on methanotrophic activity.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-15-4125-2018
    DOI: 10.5194/bg-15-4125-2018-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2158181-2
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