Abstract:

Druing the growing season of 2013, the eddy covariance method was applied to measure the CO2 flux in the coastal Reclaimed wetland of Chongming Dongtan, and the variation characteristic and the effects of related environmental factors were analyzed. The results showed that: druing the whole growing season of 2013, the accumulated CO2 exchange (NEE) value of the net ecosystem was -1 033257 g/m2, and the wetland was characterized by obvious carbon “sink”. The average diurnal variation of NEE varied among months but all appeared as the typical “U” type curve. All the seven months were manifested to be CO2 uptake, and the minimum accumulated NEE value was in July (-274928 g/m2), while the maximum was in September (-67440 g/m2). As far as the ratio of Ecosystem Respiration to Gross Ecosystem Primary Productivity (Z value), April had the minimum Z, while September had the maximum one. In the whole growing season, 722% of GPP was consumed by Reco. There was a rectangular hyperbolic correlation between the photosynthetic active radiation and daytime net ecosystem CO2 exchange (NEEd). The apparent quantum yield (α) and maximum photosynthetic rate (Pmax) reached its maximum in June and August, respectively. Compared with the soil temperature(Ts), the 4m air temperature (Ta4) could explain the variation of nighttime net ecosystem CO2 exchange (NEEn) and NEEd better. There was a significant exponential function correlation between NEEn and Ta4 in every month of the growing season. In July and August, it showed a significant negative correlation between NEEn and Ta4, which means that the increase of Ta4 lead to the inhibition of NEEn, but in other months, it showed a significant positive correlation. Although the discriminant coefficient (R2) between NEEd and Ta4 was small, all of them obey significant quadratic function correlation. But in April, June and September， there were no significant correlation between NEEd and Ts. As far as Q10 vaule, it showed the order of Q10 (Ta4)