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1.
A study was carried out to investigate the potential gross nitrogen (N) transformations in natural secondary coniferous and evergreen broad-leaf forest soils in subtropical China. The simultaneously occurring gross N transformations in soil were quantified by a 15N tracing study. The results showed that N dynamics were dominated by NH4+ turnover in both soils. The total mineralization (from labile and recalcitrant organic N) in the broad-leaf forest was more than twice the rate in the coniferous forest soil. The total rate of mineral N production (NH4+ + NO3−) from the large recalcitrant organic N pool was similar in the two forest soils. However, appreciable NO3− production was only observed in the coniferous forest soil due to heterotrophic nitrification (i.e. direct oxidation of organic N to NO3−), whereas nitrification in broad-leaf forest was little (or negligible). Thus, a distinct shift occurred from predominantly NH4+ production in the broad-leaf forest soil to a balanced production of NH4+ and NO3− in the coniferous forest soil. This may be a mechanism to ensure an adequate supply of available mineral N in the coniferous forest soil and most likely reflects differences in microbial community patterns (possibly saprophytic, fungal, activities in coniferous soils). We show for the first time that the high nitrification rate in these soils may be of heterotrophic rather than autotrophic nature. Furthermore, high NO3− production was only apparent in the coniferous but not in broad-leaf forest soil. This highlights the association of vegetation type with the size and the activity of the SOM pools that ultimately determines whether only NH4+ or also a high NO3− turnover is present.  相似文献   

2.
Since recent studies reveal citric acid to be favorable for estimating plant‐available P in soils, we investigated if it can also be used for assessing other nutrients. According to our results, it provides stronger correlations with the tree nutrition for Mg (beech, spruce), Ca+K (beech) and Fe (spruce) than the standard methods for determining exchangeable cations. Thus, when estimating plant‐available P by citric acid‐extraction, these cations should be additionally measured in ICP analysis.  相似文献   

3.
Titanium dioxide (TiO2)–silicon dioxide (SiO2) thin films were synthesized using the peroxo titanic acid approach (PTA) combined with the sol–gel method at low temperature around 100°C. The effects of type and amount of dopants of ferric (Fe3+) or thiourea (N-S) and co-dopants of Fe3+ and N-S on the films physicochemical properties and on the photocatalytic degradation of the methylene blue and formaldehyde under UV and visible light irradiation were investigated. Physicochemical properties of photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, wavelength-dispersive X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV–Vis spectroscopy. The results showed that the TiO2 crystal phases obtained from this method were exclusively anatase and the needle-like crystals have an average diameter of 10–25 nm. Compared with the single dopant of 1.0 wt.% Fe3+ or 0.125 wt.% N-S that was the optimal concentration for photocatalytic degradation of methylene blue and formaldehyde, the co-dopants of 0.125 wt.% N-S + 1.0 wt.% Fe3+ furthermore increased the degradation efficiency. Co-dopants of 0.125 wt.% N-S + 1.0 wt.% Fe3+ in TiO2–SiO2 films were considered to play synergistic roles in narrowing TiO2 band gap resulting in the higher methylene blue and formaldehyde degradation efficiency. Since the crystal grain size of TiO2–SiO2 films synthesized by the PTA method is small, in the visible light region, the high transmittance was attainable to 80% with no-doped and dropped to 50–60% with doped thin films.  相似文献   

4.

Purpose

Enzyme activities in decomposing litter are directly related to the rate of litter mass loss and have been widely accepted as indicators of changes in belowground processes. Studies of variation in enzyme activities of soil–litter interface and its effects on decomposition are lacking. Evaluating enzyme activities in this layer is important to better understand energy flow and nutrient cycling in forest ecosystems.

Materials and methods

Litter decomposition and the seasonal dynamics of soil–litter enzyme activities were investigated in situ in 20- (younger) and 46-year-old (older) Pinus massoniana stands for 540 days from August 2010 to March 2012 by litterbag method. We measured potential activities of invertase, cellulase, urease, polyphenol oxidase, and peroxidase in litter and the upper mineral soils, and evaluated their relationships with the main environment factors.

Results and discussion

Remaining litter mass was 57.6 % of the initial weights in the younger stands and 61.3 % in the older stands after 540-day decomposition. Levels of enzyme activity were higher in the litter layer than in the soil layer. Soil temperature, litter moisture, and litter nitrogen (N) concentration were the most important factors affecting the enzyme activities. The enzyme activity showed significantly seasonal dynamics in association with the seasonal variations in temperature, water, and decomposition stages. Remaining litter dry mass was found to be significantly linearly correlated with enzyme activities (except for litter peroxidase), which indicates an important role of enzyme activity in the litter decomposition process.

Conclusions

Our results indicated the important effects of biotic (litter N) and abiotic factors (soil temperature and litter moisture) on soil–litter interface enzyme activities. Overall significant linear relationship between remaining dry mass and enzyme activities highlighted the important role of enzyme activity in affecting litter decomposition processes, which will further influence nutrient cycling in forest ecosystems. Our results contributed to the better understanding of the mechanistic link between upper soil–litter extracellular enzyme production and litter decomposition in forest ecosystems.
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5.
Mixtures of peat and substrate clays are commonly used as growth media for horticultural plant production. A quality protocol for substrate clays defines a threshold value of active manganese (Mnact = sum of exchangeable and easily reducible Mn) in substrate clays of < 500 mg kg–1 to prevent toxic reactions of plants. This threshold value was tested in experiments with peat‐clay blends under various growth conditions, and nutrient solution experiments were additionally conducted to investigate the effects of silicic acid and dissolved organic matter on the occurrence of Mn toxicity. Common bean (Phaseolus vulgaris L.) and hydrangea (Hydrangea macrophylla) plants were cultivated in different peat‐clay substrates and in peat under different moisture and pH levels. The clays varied in their Mnact content from 4–2354 mg kg–1. The results of the substrate experiments reveal that a threshold value for Mn in substrate clays is not justified, as plants grown in all peat‐clay substrates did not develop any Mn toxicity even at high substrate moisture or low pH conditions which are known to increase the Mn availability. The extraction of active Mn did not well reflect the Mn concentrations in plant dry matter and substrate solution. As plants tolerated high Mn concentrations in the substrate solution compared to the nutrient solution without toxicity symptoms, the influence of silicic acid and dissolved organic matter (DOM) on Mn toxicity was characterized in a nutrient‐solution experiment. Manganese toxicity was clearly diminished by silicic acid application, but not by DOM. The former effect probably explains the tolerance of bean plants in peat substrates where high silicon concentrations in the substrate solution were observed. Peat‐clay blends even provided up to five times more silicon to plants than pure peat.  相似文献   

6.
The textile industries are characterized as one of the biggest consumers of potable water and chemical products throughout its process, being responsible for the elevated wastewater generation with intense coloration and wide polluting potential. In this context, the present study proposes the development and application of a new coagulant material for textile wastewater treatment. The proposed coagulant (α-Fe2O3-MO) was composed by hematite nanoparticles (α-Fe2O3) obtained by a simple non-pollutant methodology, associated with Moringa oleifera (MO) seeds saline extract compounds. Coagulation/flocculation (CF) efficiency was evaluated by removal of physicochemical parameters such as apparent color, turbidity, and compounds with absorption at UV254nm (UV254nm) through CF tests carried out on Jar test equipment and sedimentation carried out in the presence and absence of external magnetic field (600 k Am?1). Kinetics sedimentation was from 0 to 90 min. The use of this new coagulant allowed the removal of 92.37% for apparent color, 91.43% for turbidity, and 46.09% for UV254nm, indicating that the proposed coagulant association was efficient in the treatment of this type of wastewater under external magnetic field with only 10 min of sedimentation. In addition, the resulting sludge from CF process was tested as base material for a new coagulant synthesis, demonstrating great reuse potential. Therefore, the new proposed coagulant, composed of α-Fe2O3 and the compounds present in the seed extract of MO, has applicability for textile wastewater treatment demonstrating high removal rate for all evaluated parameters with cost reduction in the proposed treatment for this wastewater.  相似文献   

7.
The stocks of organic carbon and mean rates of the CO2 emission during the growing season (May–September) and the entire year were estimated in a sequence of grass ecosystems along the transect encompassing chestnut and meadow-chestnut steppe soils, marsh and meadow alluvial soils, and a haloxerophytic community on a typical solonchak. The total stocks of organic carbon comprised 6.17–9.70 kg С/m2 in steppe, 7.41–10.04 kg С/m2 in floodplain, and 4.74 kg С/m2 in haloxerophytic ecosystems. The portion of humus carbon in the upper 50-cm-thick soil layer comprised 79–92% of the total carbon stock. The mean daily CO2 emission (С–CO2/(m2 day)) from alluvial soils was moderate (3.3–4.9) or low (1.5–2.5). The dependence of the CO2 emission on the moistening of steppe soils, temperature of alluvial soils, and temperature and moistening of solonchak was revealed. In comparison with the CO2 emission from the zonal chestnut soil, its mean values during the growing season and the entire year were 1.2 times higher for the meadowchestnut soil, 3.3 times higher for the marsh alluvial soil, 2.3 times higher for the meadow alluvial soil, and 1.7 times higher for the solonchak. The portion of the CO2 emission beyond the growing season in the mean annual emission averaged 19.8–24.2% and depended on the type of grass ecosystem and on weather conditions of particular years. The sink of carbon in the grass ecosystems exceeded carbon emission, especially in the steppe ecosystems.  相似文献   

8.
Allium siculum Ucria is a perennial bulbous plant that occurs in Bulgaria as A. siculum subsp. dioscoridis (Sm.) K. Richt. The plant is locally known as “samardala”. Its herbage is used traditionally by local communities in Bulgaria as edible green and for preparation of salty spice mixtures. The study was focused on the documentation of traditional knowledge about samardala, covering local collection and cultivation practices, processing methods and consumption preferences. The respondents (aged 30–86 years, 50% over 65) were local producers and small-scale salesmen of the herbage and samardala-containing spices. To assess the health features of samardala spices the total phenol and flavonoid content was measured in home-consumed or marketed flavoured salts. Overall appreciation of the plant and related food products was found to be very high; presenting a considerable engagement of the locals in plant cultivation and gathering, laborious processing and consumption. Traditional ecological knowledge about the biology, phenology and ecology of the samardala plant and methods for its processing is still preserved by elderly people who rely mostly on their own cultivated plants. Although the introduction of modern appliances has altered the method of production, its main stages and the recipes are preserved. Modernization of the processing method has not affected the quality of the products and faster processing could be a contributing factor for the higher content of biologically active substances. Phenolic content was about twice as low as the flavonoid content, following the same pattern for all tested flavoured salts. Measures for better management of natural populations and promotion of cultivation practices of A. siculum subsp. dioscoridis would ensure the sustainable quality of traditional products as well as conservation of the natural plant resources.  相似文献   

9.

Purpose  

Polycyclic musk compounds (PMC) are used as fragrances in cosmetics and detergents and enter rivers via domestic wastewater and sewage treatment plants. Soils can be contaminated by PMC through application of sewage sludge. Accumulation of PMC occurs in sediments and biota due to their persistence and lipophilicity. Dissolved organic matter (DOM) is of special relevance for their transport and behavior in the environment as it acts as solubilizer and carrier in aquatic and terrestrial systems. With the distribution coefficient KDOC, one can predict their affinity to DOM. Different approaches exist to determine KDOC, resulting in a range of coefficients for a number of organic pollutants. The objective of this study was to determine KDOC values for PMC using solid-phase microextraction (SPME).  相似文献   

10.
A simulation model of the 90Sr dynamics in the soil and stand components of deciduous forest ecosystems with a 1-day step was developed; this model was used to conduct numerical experiments to clarify the mechanisms of the 90Sr behavior. The algorithm allows one to take into account the effect of meteorological, phenological, and physiological factors on the behavior of the radionuclide and simulate different fallout conditions. The results of simulation can be used in the valuation of deciduous forest products. The model is applicable for studying the redistribution of calcium in the stand of deciduous forest ecosystems.  相似文献   

11.
To determine whether senescing leaves provoke an active nitrogen (N) remobilization that results in the reduction of nitrogenase activity, 60% of Medicago truncatula lower leaves were either darkened or individually excised for two weeks. Although a considerable amount of N was remobilized, N2 fixation activity was found to be increased to maintain the N source/sink balance, indicating an absence of the negative N‐feedback regulation of nitrogenase activity in the senescing M. truncatula.  相似文献   

12.
用PCR方法从酵母(Saccharomyces cerevisiae ) AH109中扩增出α-半乳糖苷酶的Mel1基因，将其克隆至整合型载体pGAPZαA中构建成组成型分泌表达酶产物的重组质粒pGAPZα-Mel1。将线性化的重组质粒pGAPZα-Mel1电击转化至毕赤酵母(Pichia pastoris ) KM71，在含有100 mg/mL zeocin和预先涂布有X-α-gal的YPDS平板上选择蓝色阳性菌落。发酵培养酵母的上清经SDS-PAGE分析，在53 kD处有特异带；经非变性PAGE凝胶电泳，与显色底物的反应，检测到α-半乳糖苷酶活性带。重组菌pGAPZα-Mel1 /KM71摇瓶发酵6 d后，培养液α-半乳糖苷酶粗酶活性为12 U/mL。  相似文献   

13.
A standard method for the detection and isolation of microplastics is required to adequately investigate plastic ingestion by juvenile fish. Dissections of juvenile fish guts require precise handling, which can affect the processing time if sample numbers are high. To investigate the efficacy of nitric acid (HNO3) in aiding the isolation of microplastics using whole fish, we digested juvenile glassfish, Ambassis dussumieri (Cuvier, 1828), at room temperature and at 80 °C. For a complete digestion, overnight incubation in 10 mL of 55% analytical-reagent (AR) HNO3 was sufficient for a whole fish of 1 g at room temperature. When coupled with elevated temperature, the digestion time is shortened to a few minutes and larger fish of 3 g can be digested in 30 min. Four of the five types of plastic survived the process, with nylon being the exception. This is a shortfall to the method; however, until a better method replaces it, we still value the use of HNO3 for its simple, inexpensive, swift and complete digestions of whole fish. Four fish species from two feeding guilds were digested using this method to validate its use. The number of plastic particles ingested did not differ between benthic and pelagic species and microplastic fibres comprised the majority of the plastic types found.  相似文献   

14.
In vitro, high nitrate (NO3 ?) concentrations significantly inhibit N2O reductase activity. However, little information is available on the in situ temporal effects of excessive N fertilization on soil N2O reductase activity and the regulation of the N2O/(N2 + N2O) product ratio in agricultural soil. This study examined the monthly in situ dynamics of NO3 ? concentration, N2O reductase activity, and N2O/(N2 + N2O) product ratio for 2 years in loamy soil that had received either continuous N fertilizer at 400 kg N ha?1 year?1 for 15 years (N400) or no N fertilizers (CK). N2O reductase activity was significantly lower under the N400 treatment than under the CK and correlated negatively with soil NO3 ? concentration. The decrease in N2O reductase activity resulted in the N2O/(N2 + N2O) product ratio increasing. These results demonstrate that excessive N fertilization has the potential to increase N2O emissions by reducing N2O reductase activity in soils. These results highlight the need for N2O mitigation options to embrace the reduction of soil NO3 ? concentrations.  相似文献   

15.

Amomum tsao-ko Crevost & Lemarié is an important crop that has been widely used in traditional Chinese medicine and daily diets for a long time. In this study, the genetic diversity and relationships of eight cultivated populations of A. tsao-ko grown in Southwest China were examined using sequence-related amplified polymorphism (SRAP) and inter-simple sequence repeat (ISSR) markers. The results showed that 139 (99.29%) of 140 and 185 (99.46%) of 186 bands were polymorphic by SRAP and ISSR primers amplification, respectively. The polymorphic information content of detected bands were 0.270 (SRAP) and 0.232 (ISSR), respectively. The average Nei’s gene diversity (H?=?0.217) and Shannon’s information index (I?=?0.348) at the species level generated by SRAP primer were higher than those by ISSR analysis (H?=?0.158, I?=?0.272). Genetic differentiation coefficients and molecular variance analysis (AMOVA) indicated that the genetic variance of A. tsao-ko mainly occurred within populations rather than among populations. The high genetic identity among populations was revealed by SRAP (0.937) and ISSR (0.963). Using UPGMA cluster analysis, principal coordinate analysis, and population structure analysis, the accessions were categorized into two major groups. Overall, results obtained here will be useful for A. tsao-ko germplasm characterization, conservation, and utilization.

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16.
Aegilops triuncialis L. (2n = 4x = 28, genome formula UUCC) has been used to obtain one of the “Arsenal collection”, the distant hybridization of Triticum aestivum L. The introgression line 124/00i, which was derived from the cross of T. aestivum ‘Rodina' with γ-irradiated pollen of an accession of Ae. triuncialis. However, undesirable genes can be incorporated into the cultivated varieties from Ae. triuncialis. The spikes of Ae. triuncialis disarticulate from stems at a single node at the bottom of the spikes. It was defined as a synaptospermic diaspore. However, the spike of 124/00i unexpectedly disarticulate below each spikelet showing wedge type of disarticulation. The brittle rachis gene Br 124 (B rittle r achis of 124 /00 i ) of 124/00i was allelic to Br2 located on the short arm of chromosome 3A. From the microsatellite mapping, the Br 124 gene was bracketed by Xbarc19 (20.3 cM) and Xgwm779.1(14.3 cM) on the short arm of chromosome 3A. The present study suggested that the dominant mutation from synaptospermic diaspore to wedge type disarticulation occurred in the gamete of Ae. triuncialis when Ae. triuncialis pollen was treated with γ-irradiation.  相似文献   

17.
依据已报道的蜘蛛（Nephila clavipes）牵丝蛋白部分cDNA序列，设计合成两种不同结构的拟蜘蛛牵丝蛋白基因单体，大小分别为360和390 bp。多聚化得到8倍体和16倍体后，克隆到表达载体pET-30a，得到4种表达载体，转化大肠杆菌（Escherichia coli）BL21(DE3)诱导表达。用自制的抗蜘蛛牵丝蛋白血清Western blot检测，表达产物呈梯度排列，主带与预计大小一致。蜘蛛牵丝蛋白表达量最高为800 mg/L。  相似文献   

18.

Purpose

The area of southeastern Serbia, the P?inja and South Morava River Basins, is under the influence of very strong erosion, and the aim of this study was to investigate the vertical and spatial distribution of the 137Cs in the eroded soils of this area.

Materials and methods

Vertical soil profiles were collected with 5-cm increments from the uppermost layer down to 20, 25, 30, 40, and 50 cm of depth, depending on the thickness of the soil layers, i.e., down to the underlying parent rocks. Measurements of 137Cs activity concentration were performed by using the HPGe gamma-ray spectrometer ORTEC-AMETEK (34 % relative efficiency and high resolution 1.65 keV at 1.33 MeV for 60Co), from its gamma-ray line at 661.2 keV.

Results and discussion

The mean 137Cs activity concentration across all 18 soil profiles (for all soil layers) was found to be 20 Bq kg?1. In the greatest number of soil profiles, the 137Cs activity concentration was generally highest in the first soil layer (0–5 cm) and decreased with soil depth, while in a few soil profiles, the peak of either the 137Cs activity concentration occurred in the second soil layer (5–10 cm) or the 137Cs activity concentration was almost equal throughout the entire soil profile. The mean 137Cs activity concentration in the first soil layer (0–5 cm) was found to be 61 Bq kg?1, and the high coefficient of variation of 92 % pointed out high spatial variability and large range of the 137Cs activity concentrations in the study area.

Conclusions

The obtained results indicate that in the greatest number of soil profiles, 137Cs is present in the upper layers, with concentration decreasing with depth, as is typical in uncultivated soil. Its spatial distribution was very uneven among the surface soil layers of the investigated sites. One of the main reasons for such pattern of 137Cs in the study area may be soil erosion. Additional investigations which would support this hypothesis are required.
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19.
A set of experimental introgression lines of Triticum aestivum L. cv. Novosibirskaya 67 (N67)—Triticum polonicum L. line IC 12196 was developed using a small-scale bulk breeding method. The linkage map in chromosome 7A was constructed using F2 hybrids of N67/IC12196 and 34 microsatellite markers. The P gene was flanked by the centromeric markers, Xgwm890 (18.6 cM) and Xbarc108 (20.0 cM) on the long arm of chromosome 7A. Among 124 introgression lines, 118 lines were hexaploid (2n = 6x = 42), and 6 were tetraploid (2n = 4x = 28). Among hexaploid accessions, 68 were long-glumed, whereas 50 were normal-glumed. Thirty-four polymorphic microsatellite markers were scored for either the N67 alleles or IC 12196 alleles in 124 introgression lines derived from N67/IC 12196. The UPGMA dendrogram showed five clusters; Cluster 1 mainly contained hexaploid introgression lines with long glumes. Although the alleles around the P locus were recombined with IC1296 alleles, the distal end of the chromosome contained N67 alleles. Cluster 2 mainly contained normal glumed, hexaploid introgression lines. These predominantly had the N67 alleles on the long arm of chromosome 7A and the short arm proximal to the centromere. Cluster 3 contained long-glumed, hexaploid wheat lines with relatively high level of recombination. Cluster 4 contained non-parental alleles. Cluster 5 contained the group of tetraploid wheat lines. These tetraploid lines have IC12196 alleles on both arms of chromosome 7A. The frequency spectrum of parental alleles and chromosomal blocks among introgression lines suggested that T. aestivum – T. polonicum hybridization can rapidly give rise to a new landrace due to selective introgression of the P gene.  相似文献   

20.
Australian examples of surplus killing by mammalian predators were collated. These included surplus killing of native mammals and birds by foxes (Vulpes vulpes) and stock, native mammals and native birds by dingoes (Canis lupus dingo). We found no examples of surplus killing by feral cats (Felis catus). Incidents collated include historical anecdotes of surplus killing by foxes as they colonised the Australian mainland, recent examples where foxes killed threatened native species at sites despite intensive management to exclude foxes, and recent examples of the killing of native species on formerly fox-free islands to which foxes gained entry. Episodes of surplus killings by foxes, other than predation on captive or closely confined animals, appeared different in kind and frequency to those documented for co-evolved predator-prey systems on the large continental landmasses. They did not appear to be uncommon events associated with synchronised births of prey species, unusual or extreme weather that disadvantaged prey species, or seasonal food caching by a predator. Rather, surplus killing events appeared to reflect ineffective anti-predator defences by prey species when encountering a novel and efficient predator to which they have had no evolutionary exposure. We suggest that surplus killing by foxes may have been a feature of, and major contributor to, the rapid mainland extinction or contraction in range of many native species in Australia. In contrast to foxes, examples of surplus killing by dingoes relate mostly to domestic stock (calves and sheep). The arrival of dingoes to the Australian continent preceded that of foxes by 3500-4000 years, but they appear not to have had the dire impact on native mammals that we attribute to foxes. This may be due to fundamental differences in hunting styles and prey size and to their sparse populations in pre-European Australia. Active persecution of non-commensal dingoes by Aborigines, the lack of free-water, and the absence of European rabbits (Oryctolagus cuniculus) as an alternative food supply would have limited their numbers and their impact on native mammals.  相似文献   

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