Brazilian Biorenewables National Laboratory (LNBR), Brazilian Center for Research in Energy and Materials (CNPEM), Rua Giuseppe Maximo Scolfaro 10000, Campinas, São Paulo, 13083-100, Brazil.
School of Agricultural and Veterinarian Sciences (FCAV), São Paulo State University (Unesp), Via de Acesso Prof. Paulo Donato Castellane s/n, Jaboticabal, São Paulo, 14884-900, Brazil.
Sci Rep. 2021 Apr 15;11(1):8325. doi: 10.1038/s41598-021-87479-2.
The spatial structure of soil CO emission (FCO) and soil attributes are affected by different factors in a highly complex way. In this context, this study aimed to characterize the spatial variability patterns of FCO and soil physical, chemical, and microbiological attributes in a sugarcane field area after reform activities. The study was conducted in an Oxisol with the measurement of FCO, soil temperature (Ts), and soil moisture (Ms) in a regular 90 × 90-m grid with 100 sampling points. Soil samples were collected at each sampling point at a depth of 0-0.20 m to determine soil physical (density, macroporosity, and microporosity), particle size (sand, silt, and clay), and chemical attributes (soil organic matter, pH, P, K, Ca, Mg, Al, H + Al, cation exchange capacity, and base saturation). Geostatistical analyses were performed to assess the spatial variability and map soil attributes. Two regions (R1 and R2) with contrasting emission values were identified after mapping FCO. The abundance of bacterial 16S rRNA, pmoA, and nifH genes, determined by real-time quantitative PCR (qPCR), enzymatic activity (dehydrogenase, urease, cellulase, and amylase), and microbial biomass carbon were determined in R1 and R2. The mean values of FCO (2.91 µmol m s), Ts (22.6 °C), and Ms (16.9%) over the 28-day period were similar to those observed in studies also conducted under Oxisols in sugarcane areas and conventional soil tillage. The spatial pattern of FCO was similar to that of macropores, air-filled pore space, silt content, soil organic matter, and soil carbon decay constant. No significant difference was observed between R1 and R2 for the copy number of bacterial 16S rRNA and nifH genes, but the results of qPCR for the pmoA gene presented differences (p < 0.01) between regions. The region R1, with the highest FCO (2.9 to 4.2 µmol m s), showed higher enzymatic activity of dehydrogenase (33.02 µg TPF g dry soil 24 h), urease (41.15 µg NH-N g dry soil 3 h), amylase (73.84 µg glucose g dry soil 24 h), and microbial biomass carbon (41.35 µg C g soil) than R2, which had the lowest emission (1.9 to 2.7 µmol m s). In addition, the soil C/N ratio was higher in R2 (15.43) than in R1 (12.18). The spatial pattern of FCO in R1 and R2 may not be directly related to the total amount of the microbial community (bacterial 16S rRNA) in the soil but to the specific function that these microorganisms play regarding soil carbon degradation (pmoA).
土壤 CO 排放（FCO）的空间结构和土壤属性受到不同因素的高度复杂影响。在这种情况下，本研究旨在描述甘蔗田改革活动后 FCO 以及土壤物理、化学和微生物属性的空间变异模式。该研究在一个氧化土中进行，在一个 90×90 米的规则网格中测量 FCO、土壤温度（Ts）和土壤湿度（Ms），网格中有 100 个采样点。在每个采样点采集 0-0.20 米深的土壤样本，以确定土壤物理性质（密度、大孔和微孔）、粒径（砂、粉砂和粘土）以及化学属性（土壤有机质、pH 值、磷、钾、钙、镁、铝、H+Al、阳离子交换能力和基础饱和度）。进行了地统计学分析以评估土壤属性的空间变异性并进行制图。在制图 FCO 后，确定了具有不同排放值的两个区域（R1 和 R2）。通过实时定量 PCR（qPCR）确定了 R1 和 R2 中细菌 16S rRNA、pmoA 和 nifH 基因的丰度，测定了酶活性（脱氢酶、脲酶、纤维素酶和淀粉酶）和微生物生物量碳。在 28 天期间，FCO（2.91 µmol m s）、Ts（22.6°C）和 Ms（16.9%）的平均值与在甘蔗地区和常规土壤耕作条件下进行的氧化土中也观察到的平均值相似。FCO 的空间模式与大孔、充气孔隙空间、粉砂含量、土壤有机质和土壤碳衰减常数相似。R1 和 R2 之间细菌 16S rRNA 和 nifH 基因的拷贝数没有显著差异，但 pmoA 基因的 qPCR 结果（p < 0.01）存在差异。FCO 最高（2.9 至 4.2 µmol m s）的区域 R1 表现出较高的脱氢酶活性（33.02 µg TPF g 干土 24 h）、脲酶（41.15 µg NH-N g 干土 3 h）、淀粉酶（73.84 µg 葡萄糖 g 干土 24 h）和微生物生物量碳（41.35 µg C g 土壤），而 R2 的排放最低（1.9 至 2.7 µmol m s）。此外，R2 的土壤 C/N 比（15.43）高于 R1（12.18）。R1 和 R2 中 FCO 的空间模式可能与土壤中微生物群落（细菌 16S rRNA）的总量没有直接关系，而是与这些微生物在土壤碳降解方面的特定功能（pmoA）有关。
