| Based on the measurements of eddy covariance (EC), the water vapor flux, carbon flux ofPhyllostachys edulis and Phyllostachys praecox forest ecosystem were analyzed from January toDecember of2011in Anji County, and10/2010~9/2011in Taihuyuan town of Li′an city,both ofwhich were in Zhejiang Province of the subtropical China. Besides, combined with therelationship of the rate of photosynthesis (Pn), transpiration (Tr), and water use efficiency (WUE)with photosynthetically active radiation (PARi) and stomatal conductance (Cond), the paperinvestigated the water use efficiency and the relationship between carbon and water. And theresults displayed that1) On the leaf scale, the Pnand WUE of Moso bamboo were higher than those of LeiBamboo on the typical sunny day of September, October and in different season. And the WUEof former was4.61μmol mmol-1, the maximum value was7.68μmol mmol-1in Octoberhigher than in September (the average value was3.58μmol mmol-1, the maximum value was5.09μmol mmol-1. while the latter was4.19μmolCO2mmol-1H2O) in September, slightlylarger than in October (4.03μmolCO2mmol-1H2O). The relationship of moso bambooseasonal WUE was Winter (13.839μmolCO-12mmolH2O)> Summer (6.26μmolCO2mmol-1H2O)> Autumn (5.38μmolCO2mmol-1H2O)> Spring (4.29μmolCO2mmol-1H2O).while Lei bamboo was lower,the details were as follows,Autumn (4.96μmolCO2mmol-1H2O)> Winter (4.53μmolCO2mmol-1H2O)> Spring (4.45μmolCO2mmol-1H2O)>Summer (3.97μmolCO2mmol-1H2O).2) On the ecosystem scale, the curve of water use efficiency in moso bamboo forest was a Ushape, regularity obviously during the daytime. The curve in June and September was relativelyflat. However, the curve changed fluctuations from December to February. At about ten, thepeak value occurred. The maximum WUE value was in December (the average daytimemaximum value was19.89mgCO2g-1H2O, the instantaneous maximum was29.58mgCO2g-1H2O).the minimum in August (the average daytime maximum value was6.57mgCO2g-1H2O, the instantaneous maximum was11mgCO2g-1H2O). On seasonal scale, the curve inWinter was the most complex, volatile change in the most gentle, while in Spring and Autumnthe curve changed similarity and gently. The maximum was in Winter (the mean value was 17.53mgCO-2g1H2O, the instantaneous value was23.72mgCO-2g1H2O), the minimum inSummer (the mean value was5.62mgCO2g-1H2O, the instantaneous value was8mgCO2g-1H2O).while the WUE curve of Lei bamboo from June to August were all gentle.Which were small fluctuations. Especially the curve in September had two peaks obviously. Therest changed relatively regularity, with a plurality of peak. And the peaks were all about fromeight to ten. The maximum was in September (the mean value was11.85mgCO2g-1H2O, theinstantaneous value was15.80mgCO-2g1H2O), the minimum in August (the mean value was3.76mgCO2g-1H2O, the instantaneous value was5.04mgCO2g-1H2O). On seasonal scale, theWUE maximum was in Autumn (the mean value was8.61mgCO-2g1H2O, the instantaneousvalue was11.76mgCO2g-1H2O), the minimum in Summer (he mean value was4.39mgCO2g-1H2O, the instantaneous value was5.44mgCO2g-1H2O).3) During the seasonal scale, the changing curves of carbon flux and water vapor flux inMoso bamboo forest and Lei bamboo forest were all obvious, basically in the same trend duringthe daytime. The curve of carbon flux was a U shape and the water vapor flux was a single peaktype.4) During the daytime from June to September in Moso bamboo forest and Lei bambooforest, the relationship between WUE and net radiation were both significant positivecorrelation and the relationship between WUE and vapor pressure deficit were both significantnegative correlation. The carbon flux was extremely significant linear relationship with thewater vapor flux, indicating the presence of coupling between the two. However, due to thereason of water and heat resources distribution differences to some extent, there were also thedecoupling phenomenon.5) According to the analysis of WUE with net radiation, vapor pressure deficit, temperature,the results showed both of them were extremely significant level. All of which the mostsignificant correlation was with net radiation. Which showed that net radiation was dominantduring the factors. Besides,the correlation with soil water content (SWC-5cm、SWC-50cm、SWC-100cm) was not significant either.6) In conclusion, the physiological mechanism of carbon-water coupling in moso bambooand Lei bamboo forest ecosystem were three sides. Firstly, net radiation was the driving force ofthe cycle of carbon and water in the forest ecosystem. Secondly, stomata was the same channel of carbon flux and water flux.Thirdly, vapor pressure difference, temperature and otherenvironment factors had the same effect on the carbon and water. Last but not the least, canopyof bamboo forest had the stability relationship between photosynthesis and transpiration. |
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