Nonlinear decoupling of autotrophic and heterotrophic soil respiration in response to drought duration and N addition in
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ORIGINAL PAPER
Nonlinear decoupling of autotrophic and heterotrophic soil respiration in response to drought duration and N addition in a meadow steppe Bo Meng 1,2 & Raúl Ochoa-Hueso 3 & Junqin Li 1 & Shangzhi Zhong 4 & Yuan Yao 1 & Xuechen Yang 1 & Scott L. Collins 2 & Wei Sun 1 Received: 1 June 2020 / Revised: 5 November 2020 / Accepted: 15 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Soil respiration (SRTOT) and its main components, soil heterotrophic (SRH) and autotrophic respiration (SRA), were monitored in response to within-season drought events of increasing duration and soil N enrichment in a semiarid meadow steppe. The experiment consisted of the combination of five drought periods (0 days, 15 days, 30 days, 45 days, and 60 days) and two N addition levels (0 and 10 g N m−2 year−1 applied as urea). Soil respiration decreased after 30 days of drought, with the response being driven by soil heterotrophs. Moreover, N addition increased the sensitivity of soil respiration to soil water content, which we attributed to greater plant C inputs and soil microbial C and N content in the N addition treatment. Our results highlight the role of SRH as a key regulator of C fluxes in nutrient-poor semiarid meadow steppe in response to extreme within-season drought and the role of soil N availability in modulating this response. Keywords Extreme drought . N addition . Soil respiration . Autotrophic respiration . Heterotrophic respiration
Introduction Soil respiration represents one of the main C fluxes between the biosphere and the atmosphere (60 Gt annually), greatly exceeding the amount of C emitted as a result of human activities (8–9 Gt C annually) (Stockmann et al. 2013). Thus, any alteration of this critical component of the global C cycle may have far-reaching interactions with global warming (Goulden et al. 1996; Grace 2004). There are two major components of soil respiration: autotrophic respiration (SRA)
* Wei Sun [email protected] 1
Key Laboratory for Vegetation Ecology, Ministry of Education, Institute of Grassland Science, Northeast Normal University, Changchun 130024, Jilin Province, China
2
Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
3
Department of Biology, IVAGRO, University of Cádiz, Campus de Excelencia Internacional Agroalimentario (ceiA3), Campus del Rio San Pedro, 11510, Puerto Real, Cádiz, Spain
4
Grassland Agri-Husbandry Research Center, College of Grassland Science, Qingdao Agricultural University, Qingdao 255109, China
contributed by plant roots and prototrophic microorganisms, and heterotrophic respiration (SRH) contributed by soil microorganisms and micro- and macrofauna found in the bulk and rhizosphere soils (Hanson et al. 2000; Kuzyakov 2006), both of which are sensitive to changes in environmental conditions and nutrient supply (Moinet et al. 2016; Nguyen et al. 2018; Yan et al. 2010). Understanding the relative response of the two soil respiration components to changing environmental conditions and soil eut
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