| In order to study the soil respiration rate under conditions of warming and straw addition,a series of field experiments were set up from October 2017 to October 2019 to conduct data accumulation and analysis research.The trial site was selected as the agricultural test station of Nanjing University of Information Science and Technology,and two winter wheat-soybean crop rotation trials were conducted and planned for two rotation years.Six treatments were set in the experiment,namely W1S1?warm+no straw application?,W1S2?warm+low straw application amount?,W1S3?warm+high straw application amount?,W2S1?no warm+no straw application?,W2S2?no warm+low straw application amount?,W2S3?no warm+high straw application amount?,of which the low straw application amount is 600 g·m-2,and the high straw application amount is 1200 g·m-2.The soil warming simulation was implemented using a heating tube with infrared radiation function.The soil respiration rate,leaf area index,and relative chlorophyll content were measured using Li-8100A,canopy analyzer,and SPAD-502Plus,and to verify the accuracy of the canopy analyzer the LAI data was also collected by using LAI-2200C.During the 2017?2018 winter wheat-soybean rotation,the average soil respiration rates of six different treatments of winter wheat were 1.69±0.061,2.10±0.083,2.66±0.090,1.41±0.11,1.86±0.18,and 2.27±0.066(?mol·m-2·s-1),the average soil respiration rate in the soybean growing season was 3.00±0.024,3.50±0.028,3.96±0.063,2.73±0.034,3.33±0.060,2.26±0.025,2.71±0.050,3.22±0.051,1.98±0.060,2.50±0.113,2.86±0.049(?mol·m-2·s-1).W1S3>W2S3>W1S2>W2S2>W1S1>W2S1 appeared in six different treatments in the two growing seasons and the annual rotation.Through analysis of variance,it was found that when the temperature conditions are the same,there is a significant difference between the average soil respiration rates under different straw addition gradients?P<0.05?;when the same amount of straw is added,there is also a difference between warming and non-warming treatments.There were significant differences?P<0.05?.Both warming and straw application can significantly increase soil respiration rate.During the second winter wheat-soybean rotation in 2018?2019,the average soil respiration rate of the winter wheat field was 1.92±0.078,2.30±0.066,2.31±0.090,1.33±0.015,1.85±0.058,1.99±0.028(?mol·m-2·s-1).The average soil respiration rate during the soybean growing season was 3.20±0.064,3.99±0.076,4.65±0.056,2.47±0.054,3.64±0.058,4.22±0.070(?mol·m-2·s-1).The average soil respiration rates of the six treatments in the annual rotation were:2.47±0.044,3.02±0.044,3.31±0.045,1.82±0.032,2.62±0.049,2.95±0.015(?mol·m-2·s-1).Under the six different treatments,the following rules are shown:when the temperature conditions are the same,the average soil respiration rate increases with the increase in the amount of straw added;when the amount of straws is the same,the temperature increase treatment increases the average soil respiration rate.Through analysis of variance,it can be seen that when the same amount of straw is added,there is a significant difference between the mean value of soil respiration rate under warming and non-warming treatments?P<0.05?;in the soybean growing season,soil respiration under different straw addition treatments There was also a significant difference between the mean values of the rates?P<0.05?.The overall soil respiration rate of the soybean field was greater than that of the winter wheat field during the two cropping years.The reason for this result is speculated that soybeans grow in summer,the soil temperature is high,the rainfall is sufficient,and the crop root system is vigorous,so the average soil respiration rate is large.There is a very significant correlation between soil respiration rate and soil temperature?P<0.001?,and the two are linear functions.There was also a significant correlation between soil respiration residuals and leaf area index?P<0.001?.There was no significant correlation between chlorophyll content and soil respiration residuals?P>0.05?.In order to study the effects of warming and straw application on soil respiration rate,anyear,a regression equation for soil respiration rate based on soil temperature and leaf area index was established.The coefficient of determination of the equation are:0.640?0.704?0.777?0.763?0.786?0.814.Among them,soil moisture has no significant effect on soil respiration rate and is not taken into account when building the model.The soil respiration model in the second rotation year added the chlorophyll content variable based on the firstrotation year.The coefficient of determination of the equation are:0.651,0.745,0.753,0.675,0.768,0.791.The chlorophyll content under the model of warming+high straw application?W1S3?had no significant effect on the soil pond respiration model.However,soil moisture could be considered in this year's model.The coefficients of determination of soil respiration equations based on comprehensive data of two rotations are:0.579,0.665,0.691,0.662,0.659,0.683,and the fitting effect is good.A comparison of the AIC values?Akaike's informationcriterion?of the three equations shows that the three variables,soil temperature and moisture,and leaf area index,are better variables. |
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