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1.
A new approach for determining the trend of changes in the rate of degradation of arable soils is suggested. It is based on the assessment of volumes of soil material eroded from arable fields and accumulated on the bottoms of first-order valleys during two time intervals: 1954(1963)?1986 and 1986?2015. For dating of this material, 137Cs of global fallout and Chernobyl fallout are used. This approach in combination with a detailed morphometric characterization of the valley bottoms, the pathways of sediment transport from the fields, and the morphology and composition of the sediments accumulated on the bottoms makes it possible to give reliable estimates of the volumes of soil loss from tilled slopes. The benchmarks of 1963 and 1986 are related to maximum 137Cs fallout during nuclear bomb testing and immediately after the Chernobyl accident. As an example, the rates of formation of stratozems (stratified aggraded soils formed due to accumulation of eroded sediments) within the first-order catchment of the Veduga River basin (Voronezh oblast, Russia) are analyzed. The results of the study indicate that the mean annual rate of soil loss from arable fields of the catchment in 1986–2015 was at least two times lower than that in the preceding period from 1954 (the beginning of the global fallout) to 1986 (the Chernobyl accident).  相似文献   

2.
Tunisia, other countries in northwestern Africa, and the Iberian Peninsula, represent a center of diversity of Daucus. The genus traditionally has included about 20–25 species worldwide, but a recent molecular study redefined and expanded Daucus to include representatives from nine other genera. By this classification, Daucus now contains about 40 species, with some of them having winged fruits in addition to its traditionally recognized spiny fruits. The taxonomy of Daucus in Tunisia has recently been studied with morphological data, concluding that D. carota subsp. capillifolius is a subspecies that co-occurs and crosses with subsp. carota. The present study extends these findings with additional data from Genotyping-by-Sequencing (GBS) from 33 Tunisian accessions of D. carota (93 individuals with two to three replicates per accession), including the first collections of subsp. gummifer from Tunisia. Placed in the context of additional GBS data, D. carota subsp. gummifer has separate origins from other collections of subsp. carota in Tunisia and/or immediately adjacent areas to the north in Italy or its surrounding islands. Our results add support to the utility of large SNP datasets for species-level phylogenetic studies in Daucus.  相似文献   

3.
The floodplain of the Morava River in Strá?nické Pomoraví, south-east Moravia, Czech Republic contains a very valuable record of regional environmental change, which goes back to several thousand years. Its interpretation has been limited by poor stratigraphic correlation and dating of the sediments. We present a geochemical solution to this challenge. We studied 8 outcrops of floodplain deposits from 4 localities along a 6 km long part of the current meander belt of the Morava River in Strá?nické Pomoraví using geochemical proxy analyses, magnetic susceptibility measurements, 14C dating of wood remnants, and sediment micromorphology. The proxy methods are based on elemental analysis (EDXRF) and analysis of the cation exchange capacity of clay minerals; granulometric analyses provided the basis for lithological and facies assignment of the sediments. Our geochemical and mineralogical interpretations have further been tested by microstratigraphically studying the optical properties of the fine fraction. Horizons older than about 3 centuries were 14C dated using wood remnants and the age of deposits from the last century was determined on the base of several proxies reflecting their industrial contamination by heavy metals and magnetic particles. The mean depositional rate over the period from about 1000 to about 1900 AD ranged from 0.2 to 0.6 mm y− 1, depending on the sedimentary facies. The coeval lithological change in the majority of the studied sections indicated a change of the meander belt structure at between ~ 1200 AD and ~ 1600 AD probably as a consequence of changes of channel structure. The alluvial deposition in the 20th century was strongly affected by the river regulation.  相似文献   

4.

Purpose

The mineralization/immobilization of nutrients from the crop residues is correlated with the quality of the plant material and carbon compartments in the recalcitrant and labile soil fractions. The objective of this study was to correlate the quality and quantity of crop residues incubated in the soil with carbon compartments and CO2-C emission, using multivariate analysis.

Materials and methods

The experiment was conducted in factorial 4?+?2?+?5 with three replicates, referring to three types of residues (control, sugarcane, Brachiaria, and soybean), and two contributions of the crop residues in constant rate, CR (10 Mg ha?1 residue), and agronomic rate, AR (20, 8, and 5 Mg ha?1 residue, respectively, for sugarcane, soybean, and Brachiaria), evaluated five times (1, 3, 6, 12, and 48 days after incubation). At each time, we determined the CO2-C emission, nitrogen and organic carbon in the soil, and the residues. In addition, the microbial biomass and water-soluble, labile, and humic substance carbons fractionated into fulvic acids, humic acids and humin were quantified.

Results and discussion

Higher CO2-C emissions occurred in the soil with added residue ranging from 0.5 to 1.1 g CO2-C m?2 h?1 in the first 6 days of incubation, and there was a positive correlation with the less labile organic soil fractions as well as residue type. In the final period, after 12 days of soil incubation, there was a higher relation of CO2-C emission with carbon humin. The sugarcane and soybean residue (20 Mg ha?1) promoted higher CO2-C emission and the reduction of carbon residue. The addition of residue contributed to an 82.32 % increase in the emission of CO2-C, being more significant in the residue with higher nitrogen availability.

Conclusions

This study shows that the quality and quantity of residue added to soil affects the carbon sequestration and CO2-C emission. In the first 6 days of incubation, there was a higher CO2-C emission ratio which correlates with the less stable soil carbon compartments as well as residue. In the final period of incubation, there is no effect of quality and quantity of residue added to soil on the CO2-C emission.
  相似文献   

5.
The snake melon, Cucumis melo subsp. melo Flexuosus Group, is a cucurbit crop that was grown and esteemed in Mediterranean lands in antiquity and classical times. Images of snake melons appear in ancient Egyptian wall paintings and sculptures and in mosaics from the Roman Empire. The sikyos of Greek, the cucumis of Latin, and the qishu’im of Hebrew, thought by many to be cucumbers, Cucumis sativus, have now been identified as snake melons. Less iconographic and written evidence exists concerning the appreciation of snake melons during the medieval period. The present work focuses on some philologically based evidence of the importance of snake melons leading into and including the medieval period, with two specific objectives. One was to trace the records of the Hebrew epithet piqqus, which applied to removal of the hairs of young cucurbit fruits, and the Arabic epithet faqqous, used historically and to the present day to designate snake melons. Another objective was to re-affirm how piqqus was actually conducted, as mandated in the second-century code of Jewish Oral Law known as the Mishna. Various conjugational forms of the Hebrew word piqqus were found in writings dating from 200 CE to approximately 600 CE. Evidence is presented that further establishes the exact meaning of piqqus as the rubbing off of the hairs of young cucurbit fruits. The Arabic word faqqous was found in writings dating from the beginning of the tenth century and through to the end of the medieval period in the fifteenth century, the writers hailing from Andalusia in the west to Iraq in the east. These writings suggest that the snake melon was a familiar vegetable across a wide geographic belt throughout the medieval period.  相似文献   

6.
This study reports on the concentrations, distribution, and availability of heavy metals in the children’s playground soils of Athens. Playgrounds were chosen because they are open city areas; they show relatively even spatial distribution within the district of Athens and are used by a great number of young children and their escorts on a regular basis. Samples were collected from 70 playground surface soils, representing more than 70% of the city’s playgrounds. Cu, Zn, Pb, Cr, Ni, Co, Mn, and Fe were extracted by aqua regia and by diethylene triamine pentaacetic acid (DTPA) to estimate total and available metal forms, respectively. Their mean total concentrations were 43, 174, 110, 80, 82, 22, 312, and 17?×?103?mg kg?1, respectively. The DTPA-extracted fraction showed much lower values, with means of 2.5, 7.8, 5.8, 1.5, 1.3, 0.4, 8.4, and 2.0 mg kg?1 respectively, which, however, should be carefully monitored since they relate directly to the bioavailable fraction of heavy metals. Though mean values of metal concentrations are not particularly high, the calculated enrichment factors indicate site-specific cases of high enrichment with heavy metals. Considering that the bioavailable fraction of a metal is possibly a more appropriate indicator for the recent soil pollution history, availability ratios were calculated and their distribution was visualized over the entire city profile using the appropriate GIS software. It was shown that recent metal pollution events appear to have affected mostly playground sites in the southern and eastern part of the municipality.  相似文献   

7.
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   

8.
This study aimed to elucidate the response of diversity and activity of soil invertebrates to elevated soil metal concentrations that were a result of sewage sludge application. Field sampling of soil invertebrates was carried out from 2002 to 2004 at an experimental site established in 1982 to test the effects on crop production of metal contamination from sewage sludge applications with elevated concentrations of zinc (Zn), copper (Cu) and nickel (Ni) with certain treatments exceeding the current UK statutory limits for the safe use of sludge on land. At metal concentrations within the limits, none of the invertebrates sampled showed adverse effects on their abundance or overall community diversity (from Shannon–Weiner index). At concentrations above the limits, individual taxa showed sensitivity to different metals, but overall diversity was not affected. Earthworm abundance was significantly reduced at total Cu concentrations at and above 176 mg kg?1, while nematode and enchytraeid abundances were sensitive to Cu and high Zn concentrations. Correspondingly, litter decomposition was lower in Zn and Cu treatments although there was no direct relationship between decomposition and soil invertebrate abundance or diversity. Such enduring changes in both soil biodiversity and biological activity around the current UK regulatory limits warrant further investigation to determine whether they indicate detrimental damage to soil functioning over the long‐term.  相似文献   

9.
10.
The Qinling Mountains form the geo-ecological boundary between subtropical and warm-temperate zones in China and represent the northern boundary for the range of native Actinidia chinensis. To protect, explore and make use of natural resources more effectively, factors influencing genetic diversity of species must be determined. Whether the complex demography of the Qinling Mountains significantly influences gene flow of Actinidia species remains unknown. We assessed genetic diversity and structure of A. chinensis populations in the Qinling Mountains using genomic- and EST-SSR markers. We also conducted barrier analysis to detect genetic discontinuity and isolated pools within structured populations. A total of 179 alleles were detected in six natural A. chinensis populations with an average of 14.9 alleles per locus. Overall, genetic differentiation among A. chinensis populations was low but was stronger than that of populations on either the northern or southern slopes. Analysis of molecular variance showed that 25.97% of the total variance occurred among populations, whereas 74.03% of the total variance occurred within populations. The strongest gene flow occurred between the PX population on the southern slope and the LX population on the northern slope. A UPGMA dendrogram revealed that LX and PX populations were clustered together in one group. The other populations were clustered into another group. A Mantel test revealed no significant correlation between genetic and geographical distances. Clear genetic structure was revealed, and four geographic barriers were identified within and among five areas located in the western, central and eastern Qinling Mountains. Gene flow among populations was restricted by the primary ridges of the Qinling Mountains extending west to east, with branches advancing north to south.  相似文献   

11.
A total of sixty-five accessions from the Spanish region of Castilla y León including those authorized in the VQPRD areas were characterized for six SSR loci. All the samples but one unknown were identified by comparison to other databases. Thirty synonymous samples and three cases of homonymy were found out, confirming in most cases ampelographic expectations. Five unique genotypes belonging to local varieties in risk of extinction were detected. Several parameters were calculated to assess the usefulness of the chosen loci in this work. A dendrogram representing the genetic similarities among the accessions was constructed using the neighbor-joining method to investigate possible parentage relationships in the sample, and to explain them from an historical and cultural point of view.  相似文献   

12.
The variability of 14 landraces belonging to a Madrilean village historically specialized on melon cultivation, Villaconejos, was evaluated based on 58 quantitative and qualitative morphological traits. These landraces were compared to a reference array composed of 14 accessions which represented the main varieties cultivated in Spanish fields. Individual data related to plant, fruit, seed and phenology have been analysed using a multivariate analysis. This analysis showed intra- and inter-varietal diversity, as emphasized the most discriminant morphological traits in order to define similarities. Villaconejos accessions were morphologically distinct from the reference accessions (RA). Only the landraces belonging to Piel de Sapo market class showed common morphological affinities with the RA, grouping with them. The majority of Villaconejos traditional varieties clustered in five different groups, with no RA within, showing distinctive morphological singularities not described previously. Two of these groups showed some particularities in fruit traits, which are appreciated as quality marks for Spanish consumers. These results indicate that these accessions must be conserved as valuable genetic resources to enrich the Inodorus genetic bases for future breeding proposes worldwide. Furthermore, it should be considered the opportunity of promoting their cultivation under the shelter of a Protected Geographical Indication as a high quality melon. Finally, the discovering of such a high variability presented in a very small area, gives a clue for focusing, with an elevated probability of success, future surveys in similar ancestral European villages which in the past times, also supplied more populated cities with their farming products.  相似文献   

13.
The increasing use of nanoparticles (nps) in consumer and industrial applications raises concerns about their potential risks to ecosystems and biological systems. The nps can cause negative effects on bacteria, algae, and animals. However, only little is known about their effects on higher plants and the underlying mechanisms. Zea mays L. “Ayrro” was used to investigate effects of ZnO (30–40 nm), TiO2 (5–15 nm), and Ag (15 nm) nps, in comparison their corresponding bulk counterparts, on germination and early seedling growth. Treatment with nps affected growth positively (ZnO) or negatively (TiO2, Ag) in a dose-dependent manner. Effects of the corresponding bulk counterparts were either similar (TiO2) or opposite (ZnO), or even absent (Ag). To separate direct np effects (“nano effects”) from effects of ions released from nps, roots of 5-week-old plants were either treated with Ag nps or Ag+ ions with the same effective concentrations of dissolved free Ag+ ions, each with or without CaCl2 to precipitate free Ag+ ions as AgCl. Both Ag treatments reduced transpiration and assimilation rate. After addition of CaCl2, these negative effects disappeared, indicating that acute negative effects can be largely attributed to free Ag+ ions, rather than to specific nano effects. Further research with longer exposure times and different growth media could provide further insights in the analysis of np effects on plants.  相似文献   

14.
Sediment profiles from the floodplain of Morava River in the Czech Republic have been collected from exposed river banks (4–6 m long sections) and cores (2–4 m deep) and investigated using a set of geochemical proxies validated by granulometry and conventional geochemical analysis, outlined in our previous paper. The work was conducted to evaluate the increase in sedimentation rate during Medieval and modern time periods. Correlation of sediments along the current channel belt allows identification of two most important synchronous changes in the channel structure over the past 1300 years: in the 13th century and at the end of the 16th century. These changes could be related to central European climatic extremes rather than to land cover/land use practises. Analysis of the pollen record in peaty deposits at the floodplain edge allows excluded dramatic deforestation in Medieval times. Maps of the area from the last five centuries revealed direct and indirect signs of past avulsions and clearly show how the original multichannel system was transformed into a single meandering channel in the early 20th century. The extrapolated aggradation rate (net vertical accretion of floodplain fines except for levee sediments) increased from 0.2–0.3 cm/year in 700 AD to 0.3–0.4 cm/year in 2000 AD depending on the grain size of the sediment. This is the smallest yet reported enhancement of siliclastic deposition, although Morava River watershed has been intensively used for agriculture and its land cover has changed in a manner similar to west and central European rivers.  相似文献   

15.
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   

16.
Kura clover (Trifolium ambiguum M.B.) is a perennial rhizomatous forage legume whose use is currently limited by difficulties in its establishment in part attributable to nodulation problems and very specific rhizobial requirements. A limited number of Kura clover-nodulating rhizobial strains are currently available and many have a limited effectiveness. In this study, 128 rhizobia were isolated from four sites in the center of origin of Kura clover (i.e., two in Azerbaijan, one in Armenia, and one in Northwest Iran) using the three ploidy levels of Kura clover (diploid, tetraploid, and hexaploid), red clover (Trifolium pratense L.), and white clover (Trifolium repens L.) plants as trap hosts. Rhizobia were fingerprinted using repetitive extragenic palindromic polymerase chain reaction (BOXA1R primer) and their genetic diversity was measured using the Shannon-Weaver diversity index. The nodulation specificity and phenotypic diversity of a subset of 13 isolates was determined. Genetic diversity among the 128 isolates was large and similar for rhizobia grouped according to their geographic origin or original host plant. Phenotypic diversity was significant; percentage of similarity among 13 isolates ranging between 38 and 92%. Nodulation specificity of the Kura clover-nodulating rhizobial isolates studied was less complex and not as clearly delineated as previously reported. Some strains originally isolated from Kura clover could effectively nodulate more than one ploidy level of Kura clover and even one or both of two other Trifolium species (i.e., red clover and white clover). Three strains formed effective nodules on both Kura clover and white clover; however, none promoted plant growth of both species to levels currently obtained with commercial inoculants when evaluated in a growth chamber. Rhizobial isolates that are highly effective with both species have yet to be identified.  相似文献   

17.

Purpose  

Iron’s fluctuation between the II (ferrous) and III (ferric) oxidation states has been coined as the “FeIII–FeII redox wheel.” Numerous studies have coupled the “iron redox wheel” with the biogeochemical cycle of carbon (C), nitrogen (N), sulfur (S), or phosphorus (P) individually in soils or sediments, but evidence suggests that the FeIII–FeII redox wheel drives the biogeochemical cycles interactively in a fluctuating redox microenvironment. The interactions of the FeIII–FeII redox wheel with the biogeochemical cycles of C, N, S, and P in the fluctuating redox environments were reviewed in this paper.  相似文献   

18.
The leguminous Andean root crop ahipa has become scarce and the current status of in situ conservation in Bolivia is concerning. Agro-biodiversity changes affect the use, conservation and socio-economic trends for ahipa (Pachyrhizus ahipa) and to substantiate this, a comparison of two cropping periods were made. Aspects of root production and the shift from cultivation of ahipa to cash crops such as maize were compared for two periods: (a) 1994/96 and (b) 2012. Our study showed that the price of ahipa had not increased in 70% of the urban markets; hence, there is little incentive to retain the cultivation of ahipa. We found that rural ahipa growers selected the largest seeds, but did not select seeds by colour. The mixed seed colour predominated the conservation of ahipa. Laborious yield enhancing practices required in field management and low market value endanger future conservation of the ahipa. We conclude that additional research is needed in order to safeguard the extant variation of ahipa, i.e. nutritional value, taste, stress tolerance and market potential.  相似文献   

19.
The greatest extent of genetic variation and outcrossing for Lycopersicon pimpinellifolium occurs in northern Peru. This is also the area most affected by EI Niño Southern Oscillation (ENSO). Using morphological and the molecular markers SSRs and AFLPs, we studied the genetic structure of L. pimpinellifolium populations collected after the ENSO event of 1997–1998. This was the most intense in the last century and caused a vast increase in the size of L. pimpinellifolium populations. Populations in the area surveyed were not regionally differentiated. We did not find any cline or eco-geographic association for genetic diversity, and positive correlations between genetic and geographic distances were found only at very short distances. Flooding and water streams caused by ENSO might have facilitated a periodical seed migration from distant areas. Gene flow between populations could then occur, facilitated by the increase in the population sizes of plants and pollinators and by the high levels of stigmatic exsertion. Results revealed a significant lack of heterozygotes in comparison with those expected in a panmictic population without consanguinity. A high degree of endogamy was found in all populations. In this context, endogamy can be explained by the occurrence of crosses between relatives rather than by autogamy. In an area intensely disturbed by ENSO, we found a population that had not been reported by earlier collectors in this region. This yellow-fruited population remained morphologically and molecularly differentiated from all L. pimpinellifolium and L. esculentum populations analyzed.  相似文献   

20.
A methodological approach to the physically sound mathematical simulation of the hydrothermal regime for a complex soil cover on an agricultural field scale was proposed. To realize the approach, it is necessary (1) to restore the hydrothermal regime of two contrasting soils using a physically sound mathematical model on the basis of the experimental thermophysical and hydrophysical characteristics, (2) to adapt and optimize the model using the available experimental regime data, (3) to determine the hydrophysical and thermophysical properties for the entire plot under study using pedotransfer functions, and (4) to restore the hydrothermal regime of the entire soil plot using a mathematical model and the meteorological data for a specific time period. The proposed procedure allows simulating the hydrothermal regime of an agrogray soil complex in the Vladimir Opol??e region with a normalized standard error of about 8%. The analysis of the hydrothermal regime for the soil cover of the studied plot calculated from the meteorological data for the period from May to August of 2009 showed that the lower temperature values were confined to the areas of the agrogray soils with the second humus horizon: their average temperature was lower than the temperature of the agrogray soils by 0.44, 0.93, and 1.32°C at depths of 20, 40, and 70 cm, respectively, and the differences between their sums of the active temperatures for the considered period of 2009 reached 89 and 74°C at depths of 20 and 40 cm, respectively.  相似文献   

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