| This paper studied on 4 deciduous communities with different species and gradient LAI,counted the community parameter,measured the net photosynthetic rate,the transpiration rate and meteorological factors of each species by LI-6400XT during the whole growing season;and then calculated the LAI of the communities with LAI model,established the regression models of the net photosynthetic rate,the transpiration rate and meteorological factors;at last,chose the best regression model to calculate the total amount of carbon-fixing,oxygen-releasing,temperature-reducing and humidity-increasing of every community.The main results were as follows:(1)The Optimal Annual Model on Pn and Tr of LayersThe optimal annual model on Pn of the tree layer is y=0.009x1+0.088x2+0.04x3-2.867,R2=0.433,the prediction accuracy is 95.99%。The optimal annual model on Tr of the tree layer is lny=-54.356/x2+2.096,R2=0.283,the prediction accuracy is 93.37%。The optimal annual model on Pn of the shrub layer is y=0.025x1-1.506*10-5x12+1.421*10-9x13+0.834,R2=0.550,the prediction accuracy is 94.08%。The optimal annual model on Tr of the shrub layer is y=0.002x1+0.151x2-0.06x3+0.555,R2=0.478,the prediction accuracy is 95.32%。The optimal annual model on Pn of the herb layer is y=0.007x1+0.185x2+0.066x3-7.183,R2=0.686,the prediction accuracy is 93.45%.The optimal annual model on Tr of the herb layer is y=-1.321x2+0.025x22+18.804,R2=0.630,the prediction accuracy is 92.71%.Remarks:x1 means PAR,X2means Tair,X3means RH,the same below。(2)The Optimal Seasonal Model on Pn and Tr of Layers①The Tree Layer ModelThe optimal seasonal model on Pn in spring is y=0.011x1+0.117x3-3.275,R2=0.589,the prediction accuracy is 92.45%.The optimal seasonal model on Tr in spring is y=0.002x1-0.051x3+0.101x2+0.453,R2=0.358,the prediction accuracy is 91.14%.The optimal seasonal model on Pn in summer is y=0.018x1-8.751*10-6x12+1.023,R2=0.446,the prediction accuracy is 94.91%.The optimal seasonal model on Tr in summer is lny=ln0.408+0.276*lnx1,R2=0.083,the prediction accuracy is 87.62%.The optimal seasonal model on Pn in autumn is y=0.005x1+0.029x2+0.715,R2=0.300,the prediction accuracy is 92.73%.The optimal seasonal model on Tr in autumn is y=0.079x2+0.001x1-0.02x3-0.179,R2=0.422,the prediction accuracy is 94.17%.②The Shrub Layer ModelThe optimal seasonal model on Pn in spring is lny=ln0.102+0.721*lnx1,R2=0.725,the prediction accuracy is 90.62%.The optimal seasonal model on Tr in spring is y=-0.13x3+0.002x1+8.399,R2=0.583,the prediction accuracy is 88.73%.The optimal seasonal model on Pn in summer is y=0.026x1-1.775*10-5x12+3.874*10-9x13+0.975,R2=0.568,the prediction accuracy is 92.91%.The optimal seasonal model on Tr in summer is y=0.002x1-0.109x3+0.109x2+4.816,R2=0.442,the prediction accuracy is 93.85%.The optimal seasonal model on Pn in autumn is y=0.027x1-2.366*10-5x12+6.438*10-9x13+0.642,R2=0.460,the prediction accuracy is 85.81%.The optimal seasonal model on Tr in autumn is y=0.147x2+0.001x1-0.029x3-0.690,R2=0.653,the prediction accuracy is 93.54%.③The Herb Layer ModelThe optimal seasonal model on Pn in spring is lny=ln0.013+0.973*lnx1,R2=0.619,the prediction accuracy is92.35%.The optimal seasonal model on Tr in spring is y=-1337.523/x1+5.443,R2=0.222,the prediction accuracy is 87.47%.The optimal seasonal model on Pn in summer is lny=-723.816/x1+3.001,R2=0.434,the prediction accuracy is 91.72%.The optimal seasonal model on Tr in summer is lny=4.41*lnx2+ln5.027×10-7,R2=0.460,the prediction accuracy is 89.97%.The optimal seasonal model on Pn in autumn is y=0.187x3+0.006x1+0.23x2-14.298,R2=0.753,the prediction accuracy is 87.56%.The optimal seasonal model on Tr in autumn is y=-2.213x2+0.041x22+30.981,R2=0.523,the prediction accuracy is 88.00%.(3)The formula of carbon-fixing,oxygen-releasing,temperature-reducing and humidity-increasing of deciduous communities based on annual model Wl=2.712×Pn layer×LAI layer;W2=1.972×Pn layer×LAI layer;W3=1.254×106×Trlayer×LAIlayer/(1256×1000)W4=Trlayer×LAI layer×(t+273.16)×2.389×10-3/EXP[21.382-5.3475×1000/(t+273.16)Remarks:W1 means the annual amount of carbon-fixing of unit area(t/hm2.a),W2 means the annual amount of oxygen-releasing of unit area(t/hm2.a),W3 means the daily temperature-reducing of unit area(℃),W4 means the daily humidity-increasing of unit area(%),Pn layer means annual Pn model,Tr layer means annual Tr model,LAI layer means the average of annual LAI.(4)The formula of carbon-fixing,oxygen-releasing,temperature-reducing and humidity-increasing of deciduous communities based on seasonal model In spring:W1=0.380×Pnlayer×LAIlayer;In summer and autumn:W1=1.140×Pnlayer×LAIlayer;In spring:W2=0.276×Pnlayer×LAI layer;In summer and autumn:W2=0.829×Pnlayer×LAIlayer;In spring summer and autumn:W3=1.254×106×Trlayer×LAIlayer/(1256×1000);In spring summer and autumn:W4=Trlayer×LAIlayer×(t+273.16)×2.389×10-3/EXP[21.382-5.3475×1000/(t+273.16)]Remarks:Pn layer means seasonal Pn model,Tr layer means seasonal Tr model,LAI layer means the average of annual LAI.(5)The annual average LAI of sample plot 1 is 0.1212,its annual amount of carbon-fixing,oxygen-releasing,temperature-reducing and humidity-increasing were 2.82t/hm2.a、1.66t/hm2.a、0.63℃、0.82%respectively;the annual average LAI of sample plot 2 is 5.4947,its annual amount of carbon-fixing,oxygen-releasing,temperature-reducing and humidity-increasing were 63.89t/hm2.a、46.46t/hm2.a、7.81℃、11.54%respectively;the annual average LAI of sample plot 3 is 4.0644,its annual amount of carbon-fixing,oxygen-releasing,temperature-reducing and humidity-increasing were 48.84t/hm2.a、35.52t/hm2.a、7.96℃、13.80%respectively;the annual average LAI of sample plot 4 is 3.5303,its annual amount of carbon-fixing,oxygen-releasing,temperature-reducing and humidity-increasing were 39.41t/hm2.a、28.66t/hm2.a、7.79℃、10.89%respectively.(6)Generally speaking,annual models are better than seasonal models when used for calculating the amount of carbon-fixing,oxygen-releasing,temperature-reducing and humidity-increasing of herb layers in deciduous community,seasonal models are better than annual models when used for calculating the amount of carbon-fixing,oxygen-releasing,temperature-reducing and humidity-increasing of tree layers、shrub layers and the whole deciduous community. |
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