生物炭和地膜覆盖下高粱高光谱特征及其与土壤呼吸的关系

准确估算不同生态系统的土壤呼吸速率对全球碳循环研究具有重要意义。以高粱为研究对象,对生物炭添加和地膜覆盖处理下不同时期高粱的高光谱特征以及土壤呼吸速率进行了定期测定,基于高光谱和土壤呼吸数据建立了他们之间的定量关系,目的是为间接估算土壤呼吸提供方法。田间试验设对照(CK)、生物炭添加(B)、地膜覆盖(P)、生物炭添加+地膜覆盖(B+P)4个处理。结果表明:(1)与对照相比,地膜覆盖使土壤呼吸(Rs)显著增加(p<0.05),添加生物炭后Rs没有明显变化,生长季Rs的平均值大小依次为:9.43μmol/(m2·s)(B+P)>8.88μmol/(m2·s)(P)>7.35μmol/(m2·s)(B)>6.68μmol/(m2·s)(CK)。(2)不同生育期冠层近红外波段反射率表现为,拔节期B+P和P处理显著高于CK和B,但是抽穗期CK和B处理显著高于P和B+P,灌浆期和收获期4个处理之间没明显差异。(3)高粱冠层光谱反射率、一阶微分、光谱特征参数及已有的植被指数均与Rs呈显著相关,最大的相关系数可达0.80以上。(4)综合考虑模型的模拟精度和验证精度,估算高粱土壤呼吸的最佳模型为:Rs=1666.3R’747+1.332R2=0.69,p<0.01,RMSE=2.56μmol/(m2·s)],其验证模型的R2,RMSE,Slope分别为0.75,2.28μmol/(m2·s),0.7158。研究结果可为进一步开展区域农田土壤CO2排放通量的无损监测提供借鉴。

Hyperspectral Characteristics of the Sorghum Field and Their Relations with Soil Respiration Under the Conditions of Plastic Film Mulching and Biochar Application

Accurate estimate of soil respiration(Rs) in different ecosystems has great significance for the global carbon cycle research. Taking sorghum field as the research sample, we carried out the periodical measurement of both soil respiration and canopy hyperspectral characteristics under the conditions of bio-charcoal addition and plastic film mulching, and established the relationship between the Rs and the canopy hyperspectral indices to provide an approach for indirectly estimate total soil emission based on those dataset. Four different field treatments in the experiment were control(CK), biochar(B), plastic film mulching(P), and biochar + plastic film mulching(B+P). The results are showed as follows.(1) Compared with CK treatment, the P treatment significantly promoted Rs(p<0.05), and there was no significant change in Rs for B treatment. The average value of the Rs in the growing season was 9.43 μmol/(m2·s), 8.88 μmol/(m2·s), 7.35 μmol/(m2·s) and 6.68 μmol/(m2·s) in B+P, P, B and CK treatments, respectively.(2) The reflectance of the near-infrared band of the canopy in different growth stages was different. The reflectance values in the B+P and P treatments were significantly higher than those in the CK and B treatments at jointing stage, but the values in CK and B treatments were significantly higher than those in the P and B+P treatments at heading stage, and no significant difference was found among the four treatments during grain filling and harvesting stages.(3) The spectral reflectance, first derivative spectrum, spectral characteristic parameters, and existing vegetation index of the sorghum canopy were significantly correlated with Rs and the highest correlation coefficient was more than 0.80.(4) Comprehensive consideration for the simulation accuracy and verification precision of the model, the best one for the Rs estimation in the sorghum field could be described as Rs =1666.3R′747+1.332 R2=0.69, p<0.01, RMSE=2.56 μmol/(m2·s)], and with respect to the verification model, R2, RMSE and slope were 0.75, 2.28 μmol/(m2·s) and 0.715 8, respectively. The results of the study can provide the technical support for making non-destructive monitor for Rs emission from agricultural ecosystems at large scale.