Studies Of Water Heat And CO₂ Flux In Field And Individual Scale In The North China Plain

With global warming and water resource shortage prominent phenomenon, water cycles of ecosystems has been paid more and more attention. As a special field of terrestrial ecosystems, it supports a certain contributions to the global carbon and water cycles. Finding the environmental factors and the dynamical mechanisms for water, heat, carbon flux in farmland ecosystem and revealing the distribution of farmland ecosystems from different scales are the main contents of ecosystem environments.In this paper, the distribution of water, heat, carbon flux of farmland ecosystem was studied with eddy covariance technique. Then analysis the physiological and ecological processes of crop were with the LI-6400 photosynthetic instrument. At last, find the relationship between carbon and water indicators on different scales. Specific results are as follows:1) The variation of energy balance: The most of energy from the fields are used for the exchange of water vapor and latent heat flux, and they had reached 34.6%, 20.3% of the net radiation.2) The CO₂ and water vapor flux reached the highest at the filling stage. The proportion of sensible heat flux was increased as the enhancing of turbulence between the atmosphere and the underlying surface after the mature period.3) The water use efficiency of summer maize arrived at the highest value at filling stage. The values in the morning are higher than the afternoon's during the diurnal fluctuation of water use efficiency, and the peak was appeared at 8:30 am.4) The stomatal conductance is the most important index on photosynthesis among physiological and ecological factors, and the correlation coefficients were 0.85. The net photosynthetic rate, transpiration rate and stomatal conductivity, have different affections to the leaf WUE, but the correlation were connected to the climate change factors.5) The trend of CO₂ flux agree well with net photosynthetic.While there was a positive correlation between Pn*LAI and CO₂ flux. The relativity between Pn*LAI and CO₂ flux under summer maize was higher than winter wheat stages, more over the relativity of the day at 14:00 is bigger than 16:00 in both maize and wheat stages.6) The variation in leaf WUE was similar to crop WUE, and the WUE of corn season was as twice as wheat season's.