Studies Of Water Heat And CO₂ Flux In Ecosystem And Individual Scale In The Phyllostachys Edulis Forest

Taking Phyllostachys edulis as the research object,we use eddy covariance technique and plant physiological ecology observation to investigate water vapor exchanges process and relationship with environmental factor;Deep analysis variation of water use efficiency in different scales.The main conclusions are as follows:1)The EBR value of Phyllostachys edulis forest was 0.74 and the energy non-closure degree was 26% during the observation period.The net radiation obtained from Phyllostachys edulis forest was mainly used for latent heat flux,sensible heat flux and soil heat flux,accounting for 56.59%,17.57% and 0.26% respectively.For leaf scale,the absorption of light energy for the natural part of the performance of the heat dissipation tend to increase after the rise and then increase in January,April,July and September.In January,the natural heat dissipation value of the highest and were significant differences in other seasons?P<0.05?.In addition,the photochemical dissipation showed the opposite trend,the value of E was not significant change in each month.2)There were obvious diurnal and seasonal changes in water and carbon flux of Phyllostachys edulis forest.The amount of CO₂ exchange was decreased rapidly to be negative value from 5:00 to 7:00am and reach the peak of the day from 10:00 to 12:00am,then become positive value at 17:00¹8:00.In Seasonal scale,Phyllostachys edulis forest play the role of carbon sequestration,the value of carbon flux appears summer>autumn>spring> winter.The daily variation of water vapor flux was showed some of regularity,and the direction of the water vapor transportation from ecosystem to atmosphere.Variation trends of water vapor in different seasons were similar,which were represents the single peak curve and always a peak at 12:00.3)The curves of water use efficiency in the growing season and non-growing season were inverted U-shaped,and the WUE of non-growing season was delayed 1¹.5 h than growing season from positive to negative time and negative positive time ahead of 1h.The effects of light intensity?PAR?,Vapor pressure deficit?VPD?and temperature?Ta?on the water use efficiency of Phyllostachys edulis during the whole year were significant?P <0.01?.The correlation of water use efficiency and soil water content?VWC?was not significant in growing season and both were inversely correlated in non-growing season.Effects of environmental factors on WUE of on-growing period was slightly larger than that of growth period.4)In leaf scale,the trends of water use efficiency and net photosynthetic rate were consistent.When the growth rate of photosynthetic rate was lower than that of transpiration rate,the water use efficiency was began to decreased.There was a significant positive correlation between water use efficiency?WUE?and net photosynthetic rate?Pn??P <0.01?,and negatively correlated with intercellular CO₂ concentration?P<0.01?.The correlation between transpiration rate?Tr?,Tleaf and WUE was not significant.5)The variation of net photosynthetic rate in Phyllostachys edulis forest observation period were stronger.The net photosynthetic rate increased rapidly with the increase of light intensity,When the light intensity reached a certain level,the net photosynthetic rate was no longer increased or even decreased,appeared light saturation phenomenon.Net photosynthetic rate in season show: Summer>Autumn >Spring>Winter.Cond,PAR,Tleaf and Pn showed a significant positive correlation,Ci and Pn showed a Significant negative correlation;Cond,PAR,Tleaf and Tr showed a significant positive correlation,Ci and Pn showed a Significant negative correlation,Significant negative correlation with Ci.6)The trend of CO₂ flux agree well with net photosynthetic in growing period.While there was a positive correlation between Pn*LAI and CO₂ flux.The variation in leaf WUE was similar to ecosystem WUE,at 9:30 to reach the peak then began decline and the second peaks appeared in 15:00.