Regarding paddy soil colloids as the so-called “organo-mineral colloidal complexes” of A. F. Tyulin, the authors separated the colloidal fractions after his method, and reported the characrzstics of each fraction, and content of humus and some characteristics thereof in the previous paper1). 相似文献
Soil functional microbial taxa and extracellular enzymes are involved in a variety of biogeochemical cycling processes. Although many studies have revealed the vertical change patterns of microbial communities along soil profile, the general understanding of the coupling changes in the functional gene abundances(FGAs) and extracellular enzyme activities(EEAs) in soil profiles is still limited, which hinders us from revealing soil ecosystem processes.Herein, we comparatively investigated the FGAs and EEAs in the diagnostic A, B, and C horizons of soil profiles obtained from two suborders of Isohumosols(Mollisols), Ustic and Udic Isohumosols, in Northeast China based on quantitative real-time polymerase chain reaction and standard fluorometric techniques,respectively. The distribution patterns of both FGAs and EEAs significantly distinguished by the two soil suborders and were also separated from A to C horizon. Additionally, the variations of EEAs and FGAs were greater in Udic Isohumosols compared to Ustic Isohumosols along soil profiles, and greater changes were observed in C horizon than in A horizon. Both FGAs and EEAs correspondently decreased along the soil profiles. However, when normalized by soil organic carbon, the specific EEAs significantly increased in deep soil horizons, suggesting that microorganisms will input more resources to the production of enzymes to ensure microbial nutrient requirements under resource scarcity. More importantly, we revealed that soil microbial nutrient demands were limited by carbon(C) and phosphorus(P), and the C and P limitations significantly increased along soil profiles with a greater C limitation observed in Ustic Isohumosols than in Udic Isohumosols. Overall, our findings provided solid evidence showing the links between FGAs, EEAs, and microbial nutrient limitations, which would be helpful for a better understanding of the ecosystem processes in soil profiles. 相似文献
The objectives were i) to assess indicators for potential nitrogen (N) mineralization and ii) to analyze their relationships for predicting winter wheat (Triticum aestivum L.) growth parameters (yield and N uptake, Nup) in Mollisols of the semi-arid and semi-humid region of the Argentine Pampas. Thirty-six farmer fields were sampled at 0–20 cm. Several N mineralization indicators, wheat grain yield and Nup at physiological maturity stage were assessed. A principal component (PC) analysis was performed using correlated factors to grain yield and Nup. The cluster analysis showed two main groups: high fertility and low fertility soils. In high fertility soils, combining PCs in multiple regression models enhanced the wheat yield and Nup prediction significantly with a high R2 (adj R2 = 0.71–0.83). The main factors that explained the wheat parameters were associated with water availability and N mineralization indicator, but they differ according to soil fertility.
Abbreviations: N: nitrogen; SOM: soil organic matter; POM: particulate organic matter; SOC: soil organic carbon; SON: soil organic nitrogen; POM-C: particulate organic carbon; POM-N: particulate organic nitrogen; Nan: anaerobic nitrogen; Nhyd: hydrolyzable N; NO3-N: cold nitrate; N205: N determined by spectrometer at 205 nm; N260: N determined by spectrometer at 260 nm; Pe: extractable P; Nup: wheat N uptake; NO3-N: inorganic N in the form of nitrate; FR: fallow rainfalls (March-Seeding rainfall); FLR: flowering rainfalls (October-December rainfall); GFR: grain filling rainfall (November rainfall); CCR: crop growing season rainfall (June-December rainfall); PCA: principal component analysis; PC: principal component; MR: multiple regression 相似文献
Biochar is widely used to improve soil physical properties and carbon sequestration.However,few studies focuse on the impact of maize stalk biochar on labile organic carbon(LOC)pool and the relationship between physical properties and LOC fractions.A field positioning experiment was performed in Mollisols region of Northeast China to evaluate the influence of maize stalk biochar on the spatial distribution and temporal changes of physical properties and LOC fractions.Maize stalk biochar treatments included C1(1.5 kg·hm-2),C2(3 kg·hm-2),C3(15 kg·hm-2),C4(30 kg·hm-2),and CK(0).The results showed that maize stalk biochar increased soil water contents(SWC)and soil porosity(SP),but reduced bulk density(BD).Maize stalk biochar reduced dissolved organic carbon(DOC)contents in the 0-20 cm soil layer,ranging from 0.25 g·kg-1 to 0.31 g·kg-1 in harvest period,while increased in the 20-40 cm soil layer.In addition,the application of biochar had a significant impact on the spatial distribution and temporal change of SWC,BD,SP,DOC,hot-water extractable carbon(HWC),acid hydrolyzed organic carbon(AHC I,II),and readily oxidized organic carbon(ROC).High amounts of maize stalk biochar up-regulated the contents of soil organic carbon SOC,HWC,AHC I,AHC II,and ROC.In addition,SWC and SP were the key physical factors to affect LOC fractions.In conclusions,maize stalk biochar could improve physical properties,and then influence LOC fractions,and maize stalk biochar could be used as an organic amendment for restoring degraded soils governed by their rates of addition. 相似文献
Soil morphological, physical and chemical properties are described at four locations along an elevational transect in the northeastern part of the Moldavian Plateau (Romania). These data contribute to the knowledge of the soils of this area and to their classification according to the USDA-Soil Taxonomy, FAO-WRB and the SRTS-Romanian System. The soils were classified as Inceptisols, Alfisols and Mollisols, according to the USDA-Soil Taxonomy; Gleysol, Chernozem and Luvisol, according to the FAO-WRB and Gleiosol, Cernoziom, Preluvosol, Luvosol, according to the SRTS-Romanian System. The selected soils have a range of properties that represent the soilscape of the Moldavian subcarpathian plateau, characterised by a natural forest with oak as the dominant species. The selected soil parameters decreased with increasing elevation; calcium carbonate and clay leaching and accumulation are the main soil formation processes.View The PDF 相似文献
