Tian J(1)(2), Zong N(2), Hartley IP(3), He N(2), Zhang J(4), Powlson D(5), Zhou J(6)(7), Kuzyakov Y(8)(9)(10), Zhang F(1), Yu G(2), Dungait JAJ(3)(11). Author information:
(1)College of Resources and Environmental Sciences, Key Laboratory of Plant-Soil
Interactions, Ministry of Education, National Academy of Agriculture Green
Development, China Agricultural University, Beijing, PR China.
(2)Key Laboratory of Ecosystem Network Observation and Modeling, Institute of
Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences
(CAS), Beijing, PR China.
(3)Geography, College of Life and Environmental Sciences, University of Exeter,
(4)Key Laboratory of Soil Resource Sustainable Utilization for Commodity Grain
Bases of Jilin Province, College of Resource and Environmental Science, Jilin
Agricultural University, Changchun, China.
(5)Department of Sustainable Agriculture Sciences, Rothamsted Research,
(6)Institute for Environmental Genomics, Department of Microbiology and Plant
Biology and School of Civil Engineering and Environmental Sciences, University
of Oklahoma, Norman, OK, USA.
(7)Earth and Environmental Sciences, Lawrence Berkeley National Laboratory,
Berkeley, CA, USA.
(8)Department of Soil Science of Temperate Ecosystems, University of Göttingen,
(9)Agro-Technological Institute, RUDN University, Moscow, Russia.
(10)Institute of Environmental Sciences, Kazan Federal University, Kazan,
(11)Carbon Management Centre, SRUC-Scotland's Rural College, Edinburgh, UK.
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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