The Effect Of Bichor And Film Mulching On High Spectral Characteristics Of Sorghum And Its Soil Respiration

Climate warming begeted by greenhouse gases has become the most serious environmental problem all over the world.There is no doubt that a significant relationship existing between the arisesing of this problem and industrial production and emissions.While the effect of CO₂ generated by agricultural production impacting on the greenhouse can not be ignored.Soil respiration is the main way to produce CO₂.Based on the canopy hyperspectral reflectance and soil respiration rate measured in Dongyang experimental Center of Shanxi Academy of Agricultural Sciences,we analyzed the seasonal changes of both hyperspectral parameters and soil respiration rate of sorguhm sites under seven different treatments including?check test?CK?,?general fertilizer treatment?NPK?,?general fertilizer plus one biochar treatment?NPK+B?,?general fertilizer plus three biochar treatment?NPK+3B?,?general fertilizer plus straw treatment?NPK+S?,?general fertilizer plus mulching film treatment?NPK+P?and?general plus mulching film and one biochar treatment?NPK+B+P?.And also based on the soil temperature and soil moisture as well as the hyperspectral parameters we constructed soil respiration models with single and compounded variables.The results were as follows.?1?The results from the variations and comparison of canopy reflectance,first order differential spectrum,red edge parameters and vegetation indices showed that for the mentioned items,there were significant difference over the different growing seasons for CK,NPK+3B,NPK+B,NPK,NPK+S,NPK+P and NPK+P+B treatments.Overall,the growing situations between the treatments of CK,NPK and NPK+B were similar,and the beginning time of four phenological periods of jointing stage,heading stage,milking stage and mature stage was the lastest.The growing situation of the NPK+3B,NPK+S treatments were similar,and the beginning time of the four phenological periods was one week earlier than that of CK,NPK,NPK+B treatments.And the growing situation of the NPK+3B,NPK+S treatments were similar,and the beginning time of the four phenological periods was one week earlier than that of NPK+3B ? NPK+S treatments and the four phenological periods of NPK+P+B was earlier than that of NPK+P.?2?From jointing stage to mature stage,peak value of soil respiration appeared in heading stage in all seven treatments,and the soil respiration was 11.51 ± 4.61,10.00 ± 1.95,10.17 ± 1.78,10.01 ± 1.72,11.31 ± 1.07,14.60 ± 3.14 and 17.38±3.31 ?mol CO₂ m^-2 s^-1 for CK,NPK+3B,NPK+B,NPK,NPK+S,NPK+P and NPK+P+B,respectively.?3?There were no significant difference in the overall soil respiration among seven treatments,and the order from low to high among the treatments was NPK+P+B(9.65±4.83 ?mol CO₂ m^-2 s^-1),NPK+P(8.75±4.62?mol CO₂ m^-2 s^-1),NPK+S(7.68±4.43 ?mol CO₂ m^-2 s^-1),CK(7.11±5.19 ?mol CO₂ m^-2 s^-1),NPK+B(6.77±4.60 ?mol CO₂ m^-2 s^-1),NPK+3B(6.49±4.31?mol CO₂ m^-2 s^-1),NPK(6.32±3.78 ?mol CO₂ m^-2 s^-1).The average soil respiration rate of NPK+P+B and NPK+P treatments was 52.7%and 38.4%higher than that of NPK treatment,and 42.5%and 29.2%higher than that of NPK+B.The respiration rate in NPK+B,NPK+3B treatment was 7.1%and 2.7%higher than that in NPK,and 21.5%in NPK+S higher than that in NPK,NPK+B,NPK+3B.?4?The relationship between soil respiration and soil temperature was an exponential for all the seven treatments,and soil temperature could explain the seasonal variation of 43%,50%,53%,66%,65%,61%and 38%in soil respiration for CK,NPK+3B,NPK+B,NPK,NPK+S,NPK+P and NPK+P+B treatments,respectively.No significant correlation was found between soil respiration and soil moisture for all the seven treatment.A compounded model including two variables of soil temperature and soil moisture explained percent of seasonal changes of soil respiration from 43%to 58%only for CK treatment,and for other six treatments the R2 of the fitted double variable model decreased to some extent.However,the AIC and RMSE values were larger than that from the single variable model.?5?No significant relationship was found between soil respiration and canopy spectral reflectance in visible light waveband under seven treatments,but significant was founded between soil respiration and near-infrared band.The best fitted band for CK,NPK+3B,NPK+B,NPK,NPK+S,NPK+P and NPK+P+B was 856 nm,901 nm,778 nm,855 nm,807 nm,867 nm and 779 nm,respectively.But for the first-order value the best was 892 nm,891 nm,809 nm,746 nm,641 nm,744 nm,630 nm,respectively.?6?Among nine vegetation indexes and three red edge parameters,the correlation coefficients of respiration with difference Vegetation Index?DVI?,ratio Index?RVI?,enhanced Vegetation Index?EVI?,red edge slope(D?_red)in CK treatment was the best,so was DVI in NPK+3B treatment and with red edge area(S?_red);RVI in NPK+B with D?_red;EVI in NPK with D?_red(S?_red);DVI in NPK+S with S?_red;EVI in NPK+P with D?_red;Plant Senescence Reflectance Index?PRSI?in NPK+P+B with S?_red.The efficiency of the compounded models based on hyperspectral parameters was better than single models,with the coefficients of determination of more than 0.85.?7?The increased R² values of the fitted double model between soil respiration with biotic and abiotic and the decreased RMSE and AIC indicated that the modeling efficiency was improved greatly.The results showed that by the using of remote sense techniques we could gain soil respiration data easily at larger scale.