Diurnal Dynamic Patterns of Soil Respiration for Poplar Plantations and its Different Measuring Methods

The dynamic closed-chamber IRGA method was used to determine the diurnal(24 h) dynamic pattern of soil respiration,and daily soil respiration rates calculated with this method were compared to those measured with the static alkali absorption(AA) method for four poplar plantation(Populus×euramericana cv.)patterns and agriculture system in the northern area of Jiangsu province.The results were as follows:①Daily soil respiration rates measured with IRGA and AA methods were 3 065～5 880 mg CO2-C/(m2·d) and 1 060～1 697 mgCO2-C/(m2·d) respectively.The result measured with IRGA method was significantly higher than that measured with AA method,with AA method averaging 33.8% of that measured with IRGA method.Linear relationship between results measured with AA method and IRGA method was significant and the regression equation was IRGA=3.823 1AA-1118.②Root respiration accounted for 47.9% and 13.5% of total soil respiration in P1 and P2 patterns,respectively.③Diurnal fluctuations in soil respiration rate showed a single-peaked curve and highest soil respiration rate occurred at 13:00～17:00.The dynamics of soil respiration rate was well consistent to that of soil temperature.