Kuiqiao Shi

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (2)3.24 Total impact

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    ABSTRACT: The diurnal and seasonal variation of soil respiration (SR) and their driving environmental factors were studied in a maize ecosystem during the growing season 2005. The diurnal variation of SR showed asymmetric patterns, with the minimum occurring around early morning and the maximum around 13:00h. SR fluctuated greatly during the growing season. The mean SR rate was 3.16μmol CO2m−2s−1, with a maximum of 4.87μmol CO2m−2s−1 on July 28 and a minimum of 1.32μmol CO2m−2s−1 on May 4. During the diurnal variation of SR, there was a significant exponential relationship between SR and soil temperature (T) at 10cm depth: \textSR = a\texte bT {\text{SR}} = \alpha \text{e} ^{\beta T} . At a seasonal scale, the coefficient α and β fluctuated because the biomass (B) increased α, and the net primary productivity (NPP) of maize markedly increased β of the exponential equation. Based on this, we developed the equation \textSR = ( aB + b )\texte ( cNPP + d )T {\text{SR}} = \left( {aB + b} \right)\text{e} ^{\left( {cNPP + d} \right)T} to estimate the magnitude of SR and to simulate its temporal variation during the growth season of maize. Most of the temporal variability (93%) in SR could be explained by the variations in soil temperature, biomass and NPP of maize. This model clearly demonstrated that soil temperature, biomass and NPP of maize combined to drive the seasonal variation of SR during the growing season. However, only taking into account the influence of soil temperature on SR, an exponential equation over- or underestimated the magnitude of SR and resulted in an erroneous representation of the seasonal variation in SR. Our results highlighted the importance of biotic factors for the estimation of SR during the growing season. It is suggested that the models of SR on agricultural sites should not only take into account the influence of soil temperature, but also incorporate biotic factors as they affect SR during the growing season.
    Plant and Soil 01/2007; 291(1):15-26. · 3.24 Impact Factor
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    ABSTRACT: Based on the continuous observation of soil respiration and environmental factors in a maize ecosystem from late April to late September in 2005, the spatial and temporal variation of soil respiration and their controlling factors were analyzed. There was a significant spatial pattern for soil respiration at the plant scale and higher soil respiration rates tended to occur near the maize plant during the growing season. On one measurement moment, root biomass (B) in soil collars exerted significant influence on the spatial pattern of soil respiration under the relatively homogeneous environmental conditions. A linear relationship existed between soil respiration rate and root biomass(1)SR=αB+β.At daily scale, the coefficient α and β in Eq. (1) fluctuated because soil temperature (T) markedly reduced the intercept (β) of the linear equation and significantly increased its slope (α). Based on this, we developed(2)SR=aebTB+cT+d.Eq. (2) indicated that increasing soil temperature ameliorated the positive relationship between soil respiration and root biomass in the daily variation of soil respiration. At seasonal scale, parameter a, b and c in Eq. (2) were affected mainly by soil moisture (W), soil temperature and net primary productivity (NPP), respectively. Thus, we developed(3)SR=(aW+b)ecTB+(dNPP+e)T+fto estimate soil respiration during the growing season. Eq. (3) demonstrated that soil temperature, soil moisture, root biomass and NPP combined affected soil respiration at season scale, and they accounted for 78% of the seasonal and spatial variation of soil respiration during the growing season. Eq. (3) not only took into account the influence of soil temperature and moisture, but also incorporated biotic factors as predictor variables, which would lead to an improvement in predictive capabilities of the model. Moreover, Eq. (3) could simulate instantaneous soil respiration rates from different sampling points and at different temporal scales, so it could explain not only the temporal variation of soil respiration, but also its spatial variation. Although this model might not be broadly applicable, the results suggested that there was significant spatial heterogeneity in soil respiration at the plant scale and root biomass dominated the small-scale spatial patterns of soil respiration. Thus, the models of soil respiration should not only take into account the influence of environmental factors, but also incorporate biotic factors in order to scale-up the chamber measurements of soil respiration to ecosystem level.
    Soil Biology and Biochemistry. 01/2007;