Permafrost nitrogen status and its determinants on the Tibetan Plateau

Mao, Chengqiong; Kou, Dan; Chen, Leiyi; Qin, Shuqi; Zhang, Dianye; Peng, Yunfeng; Yang, Yuanhe

doi:10.1111/gcb.15205

Cited by 57 publications

(66 citation statements)

References 78 publications

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“…Inorganic nitrogen content was significantly less under year‐round warming (Figure 1c) indicating nitrogen limitation due to climate change in Tibetan alpine meadow ecosystems previously recognized by Ding et al (2019) that may be exacerbated by drought stress. A recent large‐scale field investigation along a 1000‐km transect in the Tibetan Plateau revealed that gross rates of N mineralization were positively associated with soil moisture (Mao et al, 2020). Microbial residues are comparatively rich in nitrogen (Cotrufo et al, 2015) and fungal residues (derived from chitin) are considered to be more persistent than bacterial residues (derived from peptidoglycan; Ding et al, 2019; Six et al, 2006) making the latter more susceptible to nitrogen mining during the growing season.…”

Section: Discussionmentioning

confidence: 99%

Microbial metabolic response to winter warming stabilizes soil carbon

Tian

Zong

Hartley

et al. 2021

Global Change Biology

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Current consensus on global climate change predicts warming trends with more pronounced temperature changes in winter than summer in the Northern Hemisphere at high latitudes. Moderate increases in soil temperature are generally related to faster rates of soil organic carbon (SOC) decomposition in Northern ecosystems, but there is evidence that SOC stocks have remained remarkably stable or even increased on the Tibetan Plateau under these conditions. This intriguing observation points to altered soil microbial mediation of carbon‐cycling feedbacks in this region that might be related to seasonal warming. This study investigated the unexplained SOC stabilization observed on the Tibetan Plateau by quantifying microbial responses to experimental seasonal warming in a typical alpine meadow. Ecosystem respiration was reduced by 17%–38% under winter warming compared with year‐round warming or no warming and coincided with decreased abundances of fungi and functional genes that control labile and stable organic carbon decomposition. Compared with year‐round warming, winter warming slowed macroaggregate turnover rates by 1.6 times, increased fine intra‐aggregate particulate organic matter content by 75%, and increased carbon stabilized in microaggregates within stable macroaggregates by 56%. Larger bacterial “necromass” (amino sugars) concentrations in soil under winter warming coincided with a 12% increase in carboxyl‐C. These results indicate the enhanced physical preservation of SOC under winter warming and emphasize the role of soil microorganisms in aggregate life cycles. In summary, the divergent responses of SOC persistence in soils exposed to winter warming compared to year‐round warming are explained by the slowing of microbial decomposition but increasing physical protection of microbially derived organic compounds. Consequently, the soil microbial response to winter warming on the Tibetan Plateau may cause negative feedbacks to global climate change and should be considered in Earth system models.

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Section: Discussionmentioning

confidence: 99%

Microbial metabolic response to winter warming stabilizes soil carbon

Tian

Zong

Hartley

et al. 2021

Global Change Biology

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“…We selected 24 sites across the central and north of the Tibetan Plateau in 2016 (Figure 1). For each site, five soil cores were gathered within a 10 m × 10 m plot as described in Mao et al (2020). Specifically, soil cores were sampled using a borehole drilling machine with a bore head of 10 cm diameter.…”

Section: Methodsmentioning

confidence: 99%

“…In total, 120 samples were collected from the permafrost layer across 24 sites. Among these sites, the sampling depth varied between 1.5 and 3.5 m due to the fact that the observed ALT ranged from 0.7 to 2.9 m (Mao et al, 2020). Before experimental analyses, the obtained five replicates from each site were cut into segments, and then mixed with an equal quality to form a composite sample.…”

Section: Methodsmentioning

confidence: 99%

Large‐scale evidence for microbial response and associated carbon release after permafrost thaw

Chen

Liu

et al. 2021

Global Change Biology

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Permafrost thaw could trigger the release of greenhouse gases through microbial decomposition of the large quantities of carbon (C) stored within frozen soils. However, accurate evaluation of soil C emissions from thawing permafrost is still a big challenge, partly due to our inadequate understanding about the response of microbial communities and their linkage with soil C release upon permafrost thaw. Based on a large‐scale permafrost sampling across 24 sites on the Tibetan Plateau, we employed meta‐genomic technologies (GeoChip and Illumina MiSeq sequencing) to explore the impacts of permafrost thaw (permafrost samples were incubated for 11 days at 5°C) on microbial taxonomic and functional communities, and then conducted a laboratory incubation to investigate the linkage of microbial taxonomic and functional diversity with soil C release after permafrost thaw. We found that bacterial and fungal α diversity decreased, but functional gene diversity and the normalized relative abundance of C degradation genes increased after permafrost thaw, reflecting the rapid microbial response to permafrost thaw. Moreover, both the microbial taxonomic and functional community structures differed between the thawed permafrost and formerly frozen soils. Furthermore, soil C release rate over five month incubation was associated with microbial functional diversity and C degradation gene abundances. By contrast, neither microbial taxonomic diversity nor community structure exhibited any significant effects on soil C release over the incubation period. These findings demonstrate that permafrost thaw could accelerate C emissions by altering the function potentials of microbial communities rather than taxonomic diversity, highlighting the crucial role of microbial functional genes in mediating the responses of permafrost C cycle to climate warming.

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“…The samples were then analysed with a gas chromatograph (Agilent 6850, Agilent Technologies) and the MIDI Sherlock Microbial Identification System (Microbial ID Inc.) to determine the amount and classification of the PLFAs, respectively. PLFAs specific to fungi (18:2ω6, 9c) and bacteria (i14:0, i15:0, a15:0, i16:0, a17:0, i17:0, 16:1ω7c, cy‐17:0, 18:1ω7and cy19:0; Frostegård & Bååth, 1996; Mao et al., 2020) were used to calculate F/B. With regard to soil extracellular enzyme activity, we measured hydrolase and oxidase activities which were responsible for labile and recalcitrant carbon decomposition (Allison et al., 2008), respectively.…”

Section: Methodsmentioning

confidence: 99%

Changes in above‐/below‐ground biodiversity and plant functional composition mediate soil respiration response to nitrogen input

Zhang

Peng

et al. 2021

Functional Ecology

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Biodiversity loss and changes in plant community composition induced by anthropogenic nitrogen (N) deposition exert profound effects on ecosystem functions. However, limited studies have considered the joint effects of plant community composition, plant species richness, plant functional diversity and soil biodiversity on the dynamics of soil autotrophic and heterotrophic respiration under extra N input. We addressed this issue by conducting a multilevel N‐manipulation experiment in a Tibetan alpine steppe. Based on soil respiration observations as well as biotic and abiotic measurements under this N addition experiment, we quantified the relative and interactive effects of above‐/below‐ground biodiversity, plant community composition and other explanatory variables (environmental factors, plant and microbial properties) on autotrophic and heterotrophic respiration. Our results showed that the effects of N enrichment via plant productivity, root amount, the proportion of sedge biomass and plant functional diversity explained 71% of the N‐induced variations in autotrophic respiration. With regard to heterotrophic respiration, the combination of N addition, soil pH, plant functional diversity and soil biota diversity accounted for 78% of its variations along the N addition gradient. Further analyses showed that above‐/below‐ground diversity loss and changes in plant community composition explained similar variation to that contributed by other factors in both autotrophic and heterotrophic respiration. The declined plant functional diversity and the increased proportion of sedge biomass promoted autotrophic respiration. Conversely, the loss of soil biodiversity together with the decreased plant functional diversity led to the decline of heterotrophic respiration along the experimental N gradient. Our results highlight that the indirect regulation of N input on ecosystem function through changes in plant community composition and above‐/below‐ground biodiversity loss should be considered for better understanding the responses of terrestrial ecosystems to atmospheric N deposition. A free Plain Language Summary can be found within the Supporting Information of this article.

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Permafrost nitrogen status and its determinants on the Tibetan Plateau

Cited by 57 publications

References 78 publications

Microbial metabolic response to winter warming stabilizes soil carbon

Microbial metabolic response to winter warming stabilizes soil carbon

Large‐scale evidence for microbial response and associated carbon release after permafrost thaw

Changes in above‐/below‐ground biodiversity and plant functional composition mediate soil respiration response to nitrogen input

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