The Variation And Controlling Factors Of Soil Respiration Rate Of Two Diffirent Urban Green Landscapes

The study of soil respiration in terrestrial ecosystems under the background of global warming is the focus of scholars at home and abroad.However,there is still a lack of research on the carbon cycle of urban greening landscape ecosystems.This study selects two urban greening landscapes in Tianjin:Sophora japonica Linn.-Pyrus I f.?GL?and Sophora japonica Linn.-Ginkgo biloba L.?YZ?as research objects,and the soil of two greening landscapes GL and YZ is carried out by using the portable soil carbon flux automatic analyzer ACE.The respiratory rate?Rs?and its influencing factors were measured.The characteristics of soil respiration and its relationship with the main influencing factors were analyzed.The results show that:?1?The soil respiration had significant diurnal variation in two different types of green landscape,which was basically the single-peak pattern.The highest peak appeared at 14:00-18:00,and the lowest one appeared at 2:00-9:00.When the soil moisture was extreme?>50%or<20%?,the diurnal dynamic is non-monomorphic;during the whole observation period,the mean value of daytime and nighttime Rs at GL were 1.74?mol·m^-2·s^-1>1.24?mol·m^-2·s^-1,and the mean value of daytime and nighttime Rs at YZ were 1.65?mol·m^-2·s^-1>1.25?mol·m^-2·s^-1,respectively.The results showed that the soil respiration rate was higher in daytime than at night.The diurnal variation of soil respiration was synergistically affected by soil temperature(T₁₀)and soil moisture?M₅?.The multivariate linear model could better explain the relationship between soil respiration with the soil temperature and soil moisture,T₁₀ and M₅explained 45%⁹0%of Rs variation across days.?2?The seasonal variation of Rs in two different types of green landscape are basically the same,and both of them show an obvious single-peak variation and the peak appear at the same time.The maximum Rs of GL and YZ were 3.62±0.26?mol·m^-2·s^-11 and3.17±0.27?mol·m^-2·s^-1,respectively,and the minimum Rs of GL in mid-May,which was-0.05±0.01?mol·m^-2·s^-1,and the minimum Rs of YZ appeared in mid-April,which was-0.04±0.01?mol·m^-2·s^-1;Simultaneously,there were differences in the variation of Rs between different months.A relatively lower Rs,with less fluctuation,was noted in the November to mid-May:?-0.05±0.01?^1.09±0.16?mol·m^-2·s^-1 for GL and from the end of May to October,Rs was higher and varied greatly:?0.74±0.12?^3.62±0.26?mol·m^-2·s^-1,the range of Rs from the end of May to October was 1.09?mol·m^-2·s^-11 larger than that from November to the middle of May of the following year;from November to April of the following year,the Rs of YZ was lower and the range of monthly variation was?-0.06±0.01?^0.38±0.07?mol·m^-2·s^-1,and from mid-May to October,Rs was large and varied greatly:?0.76±0.17?^3.17±0.27?mol·m^-2·s^-1,the range of Rs from mid-May to October was 1.53?mol·m^-2·s^-1 higher than that from November to April.Rs of two greening landscapes sort by mean:GL?1.02?>YZ?0.92?;In addition,environmental factors that influenced soil respiration are very complicate in these greening landscapes,and two relatively important factors are T₁₀ and M₅.The ability of T₁₀ to explain the Rs seasonal variation of GL and YZ was 80.1%and 54.8%,and that of M₅ to the seasonal variation of Rs was 56.2%and 13.9%,respectively.The multi-factor model including T₁₀ and M₅ can better explain the influence of soil temperature and soil moisture on the seasonal variation of Rs,and its interpretation ability was 87.9%and 55.0%,respectively;?3?The relationship of soil microbes in two different types of green landscape was bacteria>actinomycetes>fungi,which had obvious seasonal variation.The maximum value of GL soil bacteria appeared in July for 77.65×10⁶cfu/g,and YZ reached the maximum value of soil bacteria at 44.25×10⁶cfu/g in June.The maximum value of GL soil actinomycetes appeared in August was 35.75×10⁵cfu/g and YZ appeared in July,which was 136.24×10⁵cfu/g.The maximum values of soil fungi at GL and YZ were 5.04×10⁴cfu/g and 2.32×10⁴ cfu/g in August,respectively.Correlation analysis showed that there was a very significant positive correlation between soil bacteria and soil respiration rate?P<0.01?,and a significant positive correlation between soil actinomycetes with fungi and soil respiration rate?P<0.05?.