Light Response Characteristics of Canopy Photosynthesis of a Tropical Evergreen Broadleaf Forest
[Objective]The light response characteristics of canopy photosynthesis in a tropical evergreen broadleaf forest in Yunnan Province was studied to provide a scientific basis for understanding the spatial and temporal variation characteristics of forest carbon sinks.[Methods]Based on the flux tower data observed from March 2023 to February 2024 in a tropical evergreen broadleaf forest in Puwen Town,Yunnan Province,the Michaelis-Menten equation was used to fit the three photosynthetic parameters of the ecosystems with the time windows of 1 month.And the correlation analysis between ecosystem photosynthetic parameters and environmental factors in corresponding time scale was carried out.[Results]The apparent initial light use efficiency(ɑ)and dark ecosystem respiration(Rd)showed similar seasonal variation characteristics,with the maximum value in October and the minimum value in February.The maximum photosynthesis rate(Pmax)from March to May was low and had no obvious change in other months.The environmental factors that are most correlated with the seasonal variations of ɑ,Rd and Pmax were wind speed,relative air humidity and vapor pressure deficit,respectively.Canopy conductance also had an apparent effect on the seasonal variation of Rd and Pmax.[Conclusion]Three photosynthetic parameters of the tropical evergreen broadleaf forest showed obvious seasonal variations.Rather than photosynthetically active radiation and air temperature,wind speed and water conditions had greater effects on the seasonal variations of photosynthetic parameters.
natural forestecosystem photosynthetic parameterseddy covariancevapor pressure deficitYunnan Province
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