Soil Respiration And Its Affecting Factors In Different Aged Chinese Fir Plantations

Forest soil respiration is an important part of the soil respiration in terrestrial ecosystems,the variation of which will bring far-reaching influence on the balance of global carbon. Precisemeasurement of soil respiration and quantify the relationship between soil respiration andenvironmental factors is the most basal and exigent problem in global change research.In this paper, diurnal changes of soil respiration in different aged Chinese fir plantaions, aswell as seasonal changes of soil respiration,mineral soil respiration and root respiration and theiraffecting factors such as air temperature,soil temperature and soil moisture were analyzed byLI-8100 automated soil CO₂ flux system.The results showed that: (1) There were no significant diurnal or daily dynamics of soilrespiration rate in different aged Chinese fir plantations. Daily variations of soil respiration ratewere from 3.91 to 4.36μmol·m^-2·s^-1 in 21-year-old Chinese fir, from 3.64 to 4.58μmol·m^-2·s^-1 in41-year-old Chinese fir, from 3.82 to 5.11μmol·m^-2·s^-1 in 88-year-old Chinese fir, from 4.12 to5.79μmol·m^-2·s^-1 in deforested land in July. (2) The maximum flux occurred in July or in Augustand the minimum flux occurred in December. Seasonal variations of soil respiration rate werefrom 0.63 to 3.21μmol·m^-2·s^-1 in 7-year-old Chinese fir, from 0.78 to 3.38μmol·m^-2·s^-1 in16-year-old Chinese fir, from 0.99 to 3.51μmol·m^-2·s^-1 in 21-year-old Chinese fir, from 0.97 to5.14μmol·m^-2·s^-1 in 28-year-old Chinese fir, from 1.04 to 3.66μmol·m^-2·s^-1 in 41-year-oldChinese fir, from 0.75 to 4.30μmol·m^-2·s^-1 in 88-year-old Chinese fir and from 0.66 to 3.78μmol·m^-2·s^-1 in deforested land. Seasonal variations of mineral soil respiration rate were from0.47 to 2.56μmol·m^-2·s^-1 in 7-year-old Chinese fir, from 0.80 to 2.23μmol·m^-2·s^-1 in 16-year-oldChinese fir, from 0.73 to 2.17μmol·m^-2·s^-1 in 21-year-old Chinese fir, from 0.55 to 3.07μmol·m^-2·s^-1 in 28-year-old Chinese fir, from 0.80 to 2.55μmol·m^-2·s^-1 in 41-year-old Chinese fir,from 0.81 to 2.15μmol·m^-2·s^-1 in 88-year-old Chinese fir and from 0.49 to 3.21μmol·m^-2·s^-1 indeforested land. Seasonal variations of root respiration rate were from 0.14 to 1.43μmol·m^-2·s^-1in 7-year-old Chinese fir, from 0.18 to 1.43μmol·m^-2·s^-1 in 16-year-old Chinese fir, from 0.19 to1.29μmol·m^-2·s^-1 in 21-year-old Chinese fir, from 0.25 to 2.47μmol·m^-2·s^-1 in 28-year-oldChinese fir, from 0.20 to 1.56μmol·m^-2·s^-1 in 41-year-old Chinese fir, from 0.34 to 1.89 μmol·m^-2·s^-1 in 88-year-old Chinese fir and from 0.15 to 1.83μmol·m^-2·s^-1 in deforested land.(3)The main factors that controlling soil respiration, mineral soil respiration and root respirationwere soil temperature and air temperature above ground. There were extremely significantexponential correlations between soil respiration,mineral soil respiration,root respiration andsoil temperature(P＜0.01). Soil temperature explained from 85.59% to 97.98% changes of rootrespiration, explained from 72.50% to 92.64% changes of soil respiration, explained from39.68% to 76.31% changes of mineral soil respiration。There were significant exponentialcorrelations between soil respiration,mineral soil respiration,root respiration and air temperature,while there were weakly correlations between soil respiration,mineral soil respiration,rootrespiration and soil moisture. (4)The Q₁₀ values were from 1.83 to 2.75 for soil respiration, werefrom 1.61 to 2.70 for mineral soil respiration and from 2.24 to 3.49 for root respiration.