Effects of simulated acid rain on soil respiration and its component in a mixed coniferous-broadleaved forest of the three gorges reservoir area in Southwest China

Forest Ecosystems

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[1] 0000 0001 1456 856X, grid.66741.32, School of Soil and Water Conservation, Beijing Forestry University, 100083, Beijing, China;0000 0001 1456 856X, grid.66741.32, Chongqing Jinyun Forest Ecological Station, School of Soil and Water Conservation, Beijing Forestry University, 100083, Beijing, China;

关键词: Simulated acid rain;    Soil respiration;    Q;    C:N ratio;    Enzyme activity;   

DOI  :  10.1186/s40663-019-0192-0

来源: publisher

【 摘 要 】

BackgroundSoil respiration in forest ecosystems is an important part of the forest carbon (C) cycle. Studying the variation patterns of soil respiration under acid rain conditions is critically important for understanding forest C balance and performing rational forest management and operations.MethodsA split-plot design field experiment was performed in a mixed coniferous-broadleaved forest in the Three Gorges Reservoir Area of Jinyun Mountain, Chongqing from January 2016–January 2018. There were 4 main blocks; each was split into untrenched (UT) and trenched (T) treatments. Treatments with four gradient pH levels of 4.5 (control), 4.0, 3.25 and 2.5 were randomly assigned to the untrenched and trenched treatments. The soil CO2 fluxes, soil temperature, and soil moisture content were evaluated under simulated acid rain. Additionally, the effects of soil properties (soil pH, organic C, C:N ratio, microbial biomass, and enzyme activity) on soil respiration were analysed.ResultsThe soil CO2 fluxes exhibited seasonal variation trends. The annual mean soil respiration rates of the UTCK (control), UT4.0, UT3.25, and UT2.5 treatments in untrenched plots were 1.91, 1.91, 1.77, and 1.74 μmol∙m− 2∙s− 1 in 2016 and 1.91, 1.81, 1.55 and 1.37 μmol∙m− 2∙s− 1 in 2017, respectively. The annual mean heterotrophic respiration rates of the TCK (control), T4.0, T3.25, and T2.5 treatments in the trenched plots were 1.39, 1.32, 1.19 and 1.14 μmol∙m− 2∙s− 1 in 2016 and 1.28, 1.18, 1.02 and 0.83 μmol∙m− 2∙s− 1 in 2017, respectively. Acid rain had a significant cumulative effect on soil respiration and heterotrophic respiration (P < 0.01). In 2016, soil respiration was similar in the UTCK versus the UT4.0 treatment but significantly inhibited under higher acidity. In 2017, soil respiration and heterotrophic respiration were significantly decreased by simulated acid rain. The treatments increased the temperature sensitivity of soil respiration but did not significantly affect the soil temperature or moisture content (P > 0.05); moreover, they significantly increased the soil organic C content and C:N ratio, lowered the hydrolysable N and total P concentrations, and lowered the soil pH and fine root biomass at a later experimental stage. Urease and sucrase activities were significantly reduced in the higher-acidity treatments. Soil respiration rate was significantly positively correlated with the soil pH, fine root biomass, and urease and sucrase activity and significantly negatively correlated with the soil organic C and C:N ratio.ConclusionsAcid rain had a significant cumulative and inhibitory effect on soil respiration and heterotrophic respiration, while soil temperature and moisture had a limited effect on soil respiration under simulated acid rain. The variation in soil properties (e.g., soil organic C, C:N ratio, and fine root biomass) caused by acid rain inhibited the microbial utilization of substrates, which was the main cause of the respiration differences.

【 授权许可】

CC BY