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Relationship Between Soil Respiration And Soil Temperature And Moisture In Tianlong Mountain Grassland And Shrub Communities

Posted on:2019-10-28Degree:MasterType:Thesis
Country:ChinaCandidate:C ZhangFull Text:PDF
GTID:2370330551458726Subject:Ecology
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Soil respiration?Rs?is an important component of carbon cycle in terrestrial ecosystems,and precise quantization the relationship of Rs with environmental fators are meaningful for carbon balance in an area.In this study,based on the field observation data in an interval of twice a month from 2005 to 2016 in two communities?grassland,plot 1;and shrubland,plot2?in Tianlong maintain area,the thesis analyzed relationship between Rs and soil temperature?Ts?and soil water conent?Ws?with 18 different models.And 7 models were choosed according to their simulation accuracy analysed through evaluation index of 18 models.Furthermore,in order to reveal the relationship between Ws thresholds and Rs,these chosed models were used to simulate the soil respiration in different soil water intervals.The results are as follows:?1?The average Rs values during the measurement period of the two plots didn't show significant diffrence,with a value of 3.67?mol CO2 m-2 s-1in the plot 1 and 3.70?mol CO2 m-2 s-1 in the plot 2.Consistent with the seasonal variation trend of Ts,there were significant seasonal variations of Rs,with the maximum in the high temperature and rainy summer and the minimum in the cold winter.There was a obvoius water stress on Rs in late spring and early summer.?2?Explanatory ability of the fitted RsTs equation?21-26%?was lower than that of the fitted RsTs equation?20-31%?in the shrubland.Whereas explanatory ability of the fitted RsTs equation?34-45%?was higher than that of the fitted RsTs equation?6-15%?in the grassland.Among the three fitted models,the best one was Gaussian model,then power,and the last one was exponential one.Explanatory ability of the fitted RsWs equation?20-31%?in the shrubland was higher than that of the shrubland?6-15%?and the decreasing order of the model of the explanatory ability was Rs=exp?a+bWs?,Rs=a+b Ws+cWs2,Rs=a+blnWs,Rs=a+b Ws and Rs=a+bWs3.Compared with the single-variable model the double-variable one including both Ts and Ws variables could explain more Rs seasonal variation.Among the four compound models,multiple linear regression models had the best explanatory power?0.73 in the shrubland and 0.70 in the grassland?,while in the grassland the double-variable power model had the best AIC?823.33?.The other three models showed a similar ability,the R2 of the fitted functions were 0.67 and 0.66?multiple exponential regression model?,0.64 and 0.66?double-variable power model?and 0.64 and 0.66?power-exponential model?.The fact that R2 increase of the double-variable models indicated that the Rs in the two plots was controlled by Ts and Ws together.?3?When the RWC?Ws/water holding capacity,%?was lower than33%in the shrubland and 25%in the grasssland,a significant Ws stress on Rs occurred.When Ws was in the range of 33%?RWC<52%in the shrubland and 25%?RWC<41%in the grasssland,Rs was slightly retracted by low Ws,and when RWC was larger than 52%in the shrubland and 41%in the grasssland no stress effect of Ws on Rs was found.When considering the combined impact of Ts and Ws on Rs for shrubland,when the RWC was more than 52%and Ts was below 18.05?,Ts stress on Rs existed;For the grassland when Ts was less than 14.15?,Rs was controlled by Ts;And when Ts was larger than 14.15?and RWC was lower than 42%,Ws stressed Rs;When RWC was larger than 42%,the effect of Ts and Ws on Rs decreased,mostly because it was affected by other factors.
Keywords/Search Tags:soil respiration, soil moisture thresholds, empirical model, Akaike Information Criterion
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