共查询到8条相似文献，搜索用时 15 毫秒
1.
The sorption-desorption behavior of dicyandiamide (DCD) is an important chemical process that affects DCD fate and mobility in soils. Therefore, this study quantified DCD sorption-desorption on a phaeozem (Mollisol), a burozem (Alfisol), a soil with organic matter-removed and peat humus using the batch-equilibration procedure, and identified soil properties that influenced DCD sorption. The sorption on peat humus was higher than that on the phaeozem and the burozem, with much lower sorption observed on the soil with organic matter-removed, indicating that soil organic matter was the main carrier of DCD sorption. Due to its amphipathic property the DCD molecule sorption on the phaeozem and the burozem decreased as pH increased from about 2 to 5, but a further increase in pH led to a rise in DCD sorption.The DCD desorption hysteretic effect for peat humus was greater than that for the phaeozem and the burozem using 0.01 mol L^-1 CaCl2 as the background electrolyte, suggesting that the hydrophobic domains of organic matter may play an important role in DCD sorption. 相似文献
2.
G. Nakos 《Soil biology & biochemistry》1977,9(6):423-426
Laboratory incubation experiments with and without added urea or NH4NO3 were performed on humus from stands of beech (Fagus silvatica) grown on soils from limestone, schists, flysch and peridotites and on humus from oak (Quercus conferta) stands on soils from limestone and schists.Beech and oak humus from stands grown on soils from limestone and flysch showed considerable nitrification with a concurrent high mobilization rate of the nutrient elements Ca, Mg and K, especially in the presence of increasing urea concentrations, but no net humus N mineralization was observed. Beech humus from stands grown on soils from schists and peridotites showed no nitrification and increasing concentrations of added urea did not modify their inability to nitrify. Non-nitrifying types of humus showed considerable ammonification but their Ca, Mg and K mobilization rates were about one-tenth those observed in nitrifying humus and were inversely correlated with urea concentrations.Exchangeable Al3+ and extractable Mn were present in high concentrations in the underlying inorganic soils in all cases where nitrification was absent from the overlying humus but addition of 500 parts Al3+ and 1000 parts Mn/106 separately or in combination to a nitrifying humus failed to inhibit nitrification.An interpretation of these findings is attempted with reference to the possibility of absence of nitrification in climax vegetations and the preference of certain forest species for NH+4 or NO?3. 相似文献
3.
G. Nakos 《Soil biology & biochemistry》1976,8(5):379-383
In incubation experiments in the laboratory interactions of urea or NH4NO3 with humus from stands of fir (Abies cephalonica, Loudon) growing on soils developed from flysch (shales) and limestone and with humus from stands of black pine (pinus nigra, Arn.) growing on soils developed from peridotites, limestone and schists were investigated.Fir humus from stands on flysch and limestone and black pine humus from limestone showed nitrification but it was absent from black pine humus from stands on peridotites and on schists. Humus from stands on schists showed appreciable ammonification. Increasing concentrations of urea did not initiate nitrification in the latter type of humus. No substantial N immobilization was detected in spite of relatively high P immobilization. Increases in concentration of Ca, Mg and K occurring on incubation of humus samples were related to the ability of a humus type to nitrify rather than to concentrations of added urea-N.Urea was hydrolyzed rapidly to NH+4 during contact with various types of humus, resulting in an increase of pH. Production of NH+4 from urea was only minimally affected by drying the humus samples at 70°C for 20 h before incubation but was reduced to 30% at 1–5°C. 相似文献
4.
I. V. Ivanov O. S. Khokhlova V. V. Galitskii O. A. Chichagova E. P. Zazovskaya 《Eurasian Soil Science》2012,45(8):802-810
The dynamics of the 14C content in the humus of chernozems in 1900?C2008 are considered. The elevated 14C content in the atmosphere because of nuclear weapons tests has led to the contamination of humus with bomb radiocarbon. In 1966?C1968, the 14C reserves in the profiles of chernozems exceeded the background ones by 15%; in 1978, by 12%; and, in 1998, by 2%. By the year of 2008, its reserves became equal to the background ones. The 14C distribution along the soil profiles changed. By 1978, the 0- to 30-cm-thick soil layer became free from radiocarbon due to its self-purification; however, at depths of 40?C70 and 100?C115 cm, its weak accumulation was registered. By 2008, the whole soil profile was free from 14C. The main mechanism of the soil self-purification from radiocarbon is suggested to be the constant substitution of fragments of humus compound structures for those of fresh organic matter entering the soils with the 14C content being in equilibrium with the atmospheric one, i.e., due to the renewal of the carbon in the humus. The rate of the carbon renewal and its migration in the soils are assed based on the 14C concentrations in the humus. 相似文献
5.
6.
Keiko Mori Nicolas Bernier Takashi Kosaki Jean-Franois Ponge 《European Journal of Soil Biology》2009,45(4):290-300
Humus forms may vary in different forest stands, but the local influence of trees upon soil microbial and faunal activities is still imperfectly known. Optical methods could help to discern processes of litter transformation and formation of organo-mineral assemblages, allowing a better diagnostic of tree influences upon humus-soil development. The microstratification of humus was studied under a beech (Fagus crenata), a mixed oak forest (Quercus crispula and Quercus serrata), and a cedar (Cryptomeria japonica) plantation. The three sites are located in Kyoto (Japan), and share similar environmental conditions. Litter decomposition rates and soil fauna were also investigated. At the beech site, which had the thickest O horizon, the main process was the gradual fragmentation of litter. This process, together with shallow root and weak fungal development, gave rise to a stable sandwich-like structure in the O horizon. In contrast, the oak site showed a two-step transformation of litter. Initially, litter decomposition was triggered by the activity of white rot fungi, and the discarded litter decayed much more slowly thereafter. The cedar site exhibited a sharp vertical delineation between upper thick Oe horizon developed since plantation time and a relict A horizon. The optical method thus demonstrated differences in soil biological activities and litter transformation patterns under the three sites. 相似文献
7.
B. N. Zolotareva L. A. Fominykh L. T. Shirshova A. L. Kholodov 《Eurasian Soil Science》2009,42(1):36-48
Tundra soils (except for the soils of barren circles) in the moderately and extremely continental tundra areas are characterized
by the pronounced surface accumulation of humic substances. The humate-fulvate nature of humus is typical of the upper horizons
of surface eluvial-gley soils, gley soils, and raw-humus mountainous brown soils; the C ha/C fa ratio in them varies from
0.5 to 0.91. The fulvate-humate nature of humus (C ha/C fa = 1.27–1.50) is typical of cryozems and sandy podburs. The first
and the third fractions of humic substances (hs 1 and hs 3) predominate in the composition of humus. The coefficients of correlation
(R) between the major parameters of soil humus and the physicochemical characteristics of tundra soils have been calculated.
These coefficients between the contents of C org, C ha, C fa, C ha1, and C ha3 and the total acidity are equal to 0.73, 0.76,
0.72, 0.85, and 0.67, respectively; for the exchangeable Mg2+, their values are equal to 0.66, 0.88, 0.85, 0.74, and 0.90, respectively; and for the exchangeable Ca2+, 0.55, 0.47, 0.39, 0.41, and 0.61, respectively (p < 0.05). The composition of exchangeable cations and the total acidity specify the conditions of fractionation of humic substances
in the studied soils. The differentiation of the qualitative composition of humus in the profiles of tundra soils is well
pronounced and is mainly controlled by the distribution of clay and fine silt particles. 相似文献
8.
Abstract Heavy metals may alter the structure and metabolic functions of soil microbial community. The objective of our study was to compare the community level physiological proffies (CLPPs) of microbial communities from forest humus polluted with different amounts of Zn, Pb, and Cd to test whether the addition of soluble Zn and Cd may affect the CLPPs of microbial communities. The samples were taken at 18 locations in southern Poland referred to as unpolluted (UP), slightly polluted (SP), and heavily polluted sites (HP). The contents of heavy metals were measured after wet digestions in concentrated HNO3. Microbial communities were extracted using 0.96% NaCl solution. In order to test heavy metal tolerance of microbial communities from UP sites the extracts from these sites were additionally treated with Zn (50 mg L-1; UP + Zn) and Cd (1 mg L-1; UP + Cd). Metabolic functions of the microbial communities were analyzed using BIOLOG Ecoplates method. The contents of Zn, Pb and Cd were the highest at HP sites (4,740, 1,120, 41.0 mg kg-1, respectively) followed by SP (830, 509, 9.2 mg kg-1, respectively), and UP (173, 93, 2.1 mg kg-1, respectively) sites. Principal components analysis (PCA) indicated that CLPPs at all sites were similar. This suggests that microbial community from SP and HP sites revealed tolerance to heavy metals. Addition of Zn affected CLPPs of microbial communities from UP sites as indicated by significantly (p < 0.05) higher value of PC1 score. The addition of Cd did not affect CLPPs of microbial communities from these sites. 相似文献