| dc.description.abstract | This thesis quantifies the net change of CO2 (NEE) in an irrigated rice crop cultivation in
RS (Brazil). The research is part of the project CT-HIDRO, which presents as main purpose the
description of surface conditions for different ecosystems in the country. Data were gathered
during the cultivation period, from October 2003 to March 2004. During this time, the average air
temperature and the incident radiation were suitable for the development of the culture in such
an area. The turbulent flows, calculated by the eddy covariance method, overestimated the NEE
value, probably due to the low estimate of breathing tax, because, during some night-times,
sensor registered little turbulence. Moreover, other factor could have interfered in the result of
the flows, for instance, the time in which the flows are calculated. The Webb correction was
applied in the curve of NEE, and a value smaller than 1% was found. Such result didn't modify
the previous result significantly. The behavior of CO2 flow during the whole analyzed period
showed a maximum of -0,47mgCO2 m−2 s −1 in January 2004, what demonstrates the largest
absorption of CO2 from the atmosphere by the plant during the day and a smaller liberation at
night, due to the development phase in which the plant is. In this case, the Webb correction was
also little emphasized, not interfering in the obtained result. The curves that demonstrate the
three phases of development of the rice presented a larger absorption of CO 2 during the
reproductive phase. The behavior of the flow of CO 2 showed a negative flow during the day,
when the plant absorbs CO2 from the atmosphere, and a positive flow during the night, when
the inverse process occurs, what was waited for. The latent heat flow presented larger diary
average values from January to February, always with positive values, consequence of the rice
crop irrigation. Two days with high values of flow of latent heat were obtained, what motivated
the analysis of the energy balance. The closing of the energy balance was not reached in both
days. A possible reason for that could be the low estimate of flows when the eddy covariance
method was applied. | |
