Primary Study on Diurnal Respiration Variation of Subtropical Manilagrass Lawn Ecosystem

The diurnal variation in respiration of manilagrass lawn ecosystem and its components,soil and aboveground plant,in the Minjiang Park,Fujian,China were measured using a LI-8100 system.All kinds of these respiration showed a single daily peak,with maximal respiration rate appearing at 13:00～14:00.Only in June,the minimal respiration rate of lawn ecosystem was observed at around 7:00,for other months,the lowest rate would appeared at 23:00～2:00.For soil respiration,the minimal rate was observed at 7:00 in April and June,but at 2:00 if the time was August,and in November,no obvious fluctuation and peak value could be observed.With no exception,the daytime ecosystem respiration rate was greater than that at night.The daily CO2 emissions through ecosystem respiration in April,June,August and November were 27.30,43.94,44.79 and 25.18g C m2 d-1,respectively.Soil respiration accounted for 52.93% of ecosystem respiration in June,August and November,and 74.12% in April.Except in November,there was a significantly positive correlation between respiration rate and soil temperature at 5 cm depth.For ecosystem respiration in the lawn,the Q10 value showed an order of AprilNovemberJuneAugust,but of JuneAprilAugustNovember for soil respiration.Except in November,the Q10 value of ecosystem respiration was lower than that of soil respiration.