Characteristics of heat and moisture fluxes and factors affecting them in a conifer-broadleaf mixed forest ecosystem in Jinyun Mountain,Chongqing
[Background]Based on eddy correlation technique,the flux data in the ecosystem of coniferous and broad-leaved mixed forest in Jinyun Mountain Observation Station were processed and analyzed.[Methods]The 30-min flux data and day timescale environmental factor data in the study area was used to analyze the characteristics of heat and moisture fluxes in four seasons and the trends of environmental factors.The above analysis was also used to study the characteristics of heat and moisture fluxes in foggy and non-foggy days,the influence of environmental factors on heat and moisture fluxes.[Results]1)The energy closure rate of the ecosystem was approximately equal to 0.74.2)Each heat and moisture flux showed a single-peaked trend in daily variation.In terms of seasonal change,flux was the highest in summer(daily average value 124.66 W/m2)and the lowest in winter(daily average value 31.68 W/m2).Air temperature and vapor pressure deficit showed a multimodal-peaked trend.Precipitation was concentrated in April,July,August,September and October of one year.Leaf area index showed a single-peaked trend in the growing season(April to October).3)Sensible heat flux in non-foggy days was significantly higher than that in foggy days,net radiation,canopy conductance,air temperature,vapor pressure deficit had significant effects on latent heat flux,and there was no significant relationship between precipitation,wind speed and latent heat flux was found.4)Canopy conductance showed a multi-dimensional complexity.[Conclusions]1)The energy closure state in study area is good,and the data is reliable.2)The change of net radiation caused by the change of solar altitude angle is the leading factor affecting the change of heat and moisture fluxes.Irregular distribution of precipitation and change of leaf area index lead to a multimodal-peaked trend of air temperature and vapor pressure deficit.3)The guidance of fog to soil heat will cause the decrease of sensible heat flux.Higher air temperature affects the rise of sensible heat flux.Generally,sensible heat flux is mainly affected by net radiation,respectively subject to the secondary influence of vapor pressure deficit and soil temperature(foggy environment)and the secondary influence of vapor pressure deficit and wind speed(non-foggy environment).Net radiation,canopy conductance,air temperature,and vapor pressure deficit have significant effects on latent heat flux,and there is no significant relationship between precipitation,wind speed and latent heat flux.4)Canopy conductance are affected by multiple factors(net radiation,vapor pressure deficit,air temperature,soil volumetric water content,precipitation,etc.).
conifer-broadleaf mixed forestsheat and moisture fluxeseddy correlation techniquefogcanopy conductance
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