An ecological corridor, with both ecological and cultural functions, is a symbol of urban ecological or green civilization, and has therefore become one of the major topics in the fields of landscape ecology, urban ecology, and ecological planning. On the one hand, along with the prominent contradiction between regional ecological protection and economic development, as well as between the growing ecological demands of urban residents and the destruction of natural ecosystems, the construction of urban ecological corridors is very challenging. On the other hand, with contemporary urbanization and ecological civilization development, the standards and requirements for the construction of urban ecological corridors are set higher and higher. Constructing an urban ecological corridor is therefore particularly important, and must adopt a spatial approach that balances the relationship between ecological protection and economic development. In this study, the classification of urban ecological corridors was firstly conducted according to the structural or functional differences. Secondly, research progress on the construction of urban ecological corridors was systematically summarized and the main inadequacies were indicated. Following the analysis of the main methods employed in the construction of urban ecological corridors, existing methods were classified into three kinds, i.e. qualitative analysis, quantitative analysis, and spatial analysis. In addition, the advantages and disadvantages of the methods of subjective judgment, suitability and sensitivity analysis, network analysis, and minimum cost path analysis were compared. To provide theoretical support for the construction and management of urban ecological corridors, four key research directions were also pointed out, i.e. the identification of key nodes of urban ecological corridor, the determination of the width of urban ecological corridor, the measurement of integrated effect of urban ecological corridor, and the multi-scale integration of urban ecological corridor. The present study will aid in accelerating and improving the process of ecological corridors construction in China's new-type urbanization.
Soil physicochemical properties and microbes are essential in terrestrial ecosystems through their role in cycling mineral compounds and decomposing organic matter. This study examined the effect of stand age on soil physicochemical properties and microbial community structure in wolfberry ( L.) fields, in order to reveal the mechanism of soil degradation due to long-term stand of . The objective of the study was achieved by phospholipid fatty acid (PLFA) biomarker analysis of soil samples from fields in Zhongning County, Ningxia Province—the origin of . Five stand ages of were selected, < 1, 3, 6, 9, and 12 years (three plots each). The results showed that soil bulk density increased slightly with increasing stand age, while no clear trend was observed in soil pH or total salinity. As the stand age increased, soil organic matter and nutrients first increased before decreasing, with the highest levels being found in year 9. There was an amazing variety of PLFA biomarkers in soil samples at different stand ages. The average concentrations of total, bacterial, fungal, and actinomycete PLFAs in the surface soil initially decreased and then increased, before decreasing with the stand age in summer. The PLFA concentrations of major microbial groups were highest in year 9, with the total PLFA concentrations being 32.97% and 10.67% higher than those in years < 1 and 12, respectively. Higher microbial PLFA concentrations were detected in summer relative to autumn and in the surface relative to the subsurface soil. The highest ratios of Gram-positive to Gram-negative bacterial (G /G ) and fungal to bacterial (F/B) PLFAs were obtained in year 6, on average 76.09% higher than those at the other four stand ages. The soil environment was most stable in year 6, with no differences between other stand ages. Therefore, soil microbial community structure was strongly influenced by the stand age in year 6 only. The effect of stand age on soil G /G and microbial community structure varied with season and depth; there was little effect for F/B in the 20–40 cm soil layer. Principal component analysis revealed no correlations between microbial PLFA concentrations and total salinity in the soil; negative correlations were noted between soil pH and F/B in summer ( < 0.01), as well as between soil pH and fungal PLFA in autumn ( < 0.05). Moreover, microbial PLFA concentrations were correlated with soil organic matter (mean = 0.7725), total nitrogen (mean = 0.8296), total phosphorus (mean = 0.8175), available nitrogen (mean = 0.7458), and available phosphorus (mean = 0.7795) ( 0.01). On the whole, the soil ecosystem was most stable in year 6, while soil organic matter, nutrients, and microbial PLFA concentrations were maximal in year 9; thereafter, soil fertility indices and microbial concentrations decreased and soil quality declined gradually as the stand age increased. Therefore, farmers should reduce the application rate of fertilizers, especially compound or mixed fertilizers, in fields; organic or bacterial manure can be applied increasingly to improve the soil environment and prolong the economic life of .
In 2006 and 2007, five sampling stations were set up in Xieshui River and its tributaries to study the macro-invertebrate communities, and measure physicochemical parameters and contents of different forms of arsenic. A comparative analysis and multivariate statistical methods were used to explore the effects of arsenic pollution on the macro-invertebrate communities. In this study, sixty species were identified, including 39 aquatic insects, 10 mollusks, 5 oligochaetes, 1 crustacean, and 5 others. Results of the comparative analysis indicated that the macro-invertebrate communities at the station with serious arsenic pollution tended to be simple and showed a significant decreasing in density, biomass, and biodiversity in comparison with the other stations. Arsenic pollution also had a major effect on the dominant species and groups. For instance, EPT taxa disappeared at the station with serious arsenic pollution, and chironomids that belong to the genus were very tolerant to high concentrations of arsenic. Results of the functional feeding groups (FFGs) analysis indicated that the predators were more tolerant to arsenic pollution, while the scrapers, filterers, and collectors were relatively sensitive to arsenic pollution. Results of a non-metric multidimensional scaling (nMDS) analysis showed that when the concentration of inorganic arsenic decreased to the range between the criteria continuous concentration (CCC) and the criteria maximum concentration (CMC), the effects of inorganic arsenic on the macro-invertebrate communities seemed to be insignificant. Results of a BVSTEP (Bio-Env Step-Wise Procedure) analysis showed that water temperature, rotifer density, trivalent arsenic, pentavalent arsenic, and total inorganic arsenic greatly influenced species appearance, while rotifer density and various forms of arsenic had a considerable impact on the species composition.
Gamma radiation, various absorbed doses (0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 krad) effects were evaluated on sunflower ( . L.) germination and growth characteristics. Sunflower healthy seeds were exposed to gamma radiation source Co at nuclear institute for food and agriculture and exposed seeds were grown under controlled laboratory conditions. In comparison to control, gamma radiation absorbed doses affected the measured response positively i.e., radical length, plumule length, number of roots, seedling fresh weight, seedling dry weight, germination percentage, time of germination and diameter of hypocotyl of sunflower enhanced up to 83.15%, 70.32%, 73.03%, 4.80%, 3.26%, 72.0%, − 18.88% and 12.58%, respectively. The time of germination, fresh weight and percent moisture contents enhanced insignificantly, however, the response was higher than control. All gamma radiation absorbed doses showed a stimulatory effect on sunflower germination and seedling growth characteristics. The low gamma radiation absorbed doses were found to be more effective versus higher doses for enhancing the germination and growth characteristics of sunflower. In view of positive effect of gamma radiation of sunflower germination and growth characteristics, it is concluded that this techniques could possibly be used for the enhancement of germination, growth and ultimately yield in sunflower in areas where germination is low due to unfavorable conditions.
A plant's morphology changes throughout its ontogeny. Investigating the allometric relationships between different morphological traits could provide useful information for cultivation of medicinal plants. Here we collected 698 individuals of for allometric analysis from seven populations cultivated in Yunnan, Southwest China. The slopes and intercepts of the allometric relationships were estimated by Standardized Major Axis regression. Significant differences (p < 0.05) were found in each morphological variable considered among populations. Allometric analysis showed that all of the log-log relationships had different slopes or shared a common slope but differed in intercept (p < 0.001). The morphological traits showed flexible allometric relationships. However, the root biomass that considered as a target trait showed the least allometric variability (slope = 1.068–1.378) when compared to other variables. This could be because of the hundreds of years of cultivation and artificial selection.
Microcystin-LR (MC-LR) is the most common hepatotoxic cyanotoxin produced primarily by . Although deaths from microcystin toxication have widely been attributed to hypovolemic shock due to hepatic interstitial hemorrhage, so far, information on coagulation factors of MC-LR has been rare. In our present study, the effects of MC-LR on the coagulation factors expression and pathological changes in zebrafish were investigated. Adult zebrafish were injected intraperitoneally with 200 μg/kg MC-LR and newly hatched larvae were placed in glass wares containing 200 μg MC-LR/L, liver and whole larvae were collected after exposure for 12 h, 24 h, 48 h and 96 h, respectively. mRNA levels of coagulation factor IX (FIX), coagulation factor VII (FVII) and coagulation factor VIIi (FVIIi) in liver of adult fish and total zebrafish larvae were analyzed using quantitative real-time PCR. Significant depression of FIX and FVII were observed in adult zebrafish at different time point, and FVIIi were also significantly decreased except for 12 h post-injection. In addition, the histopathological changes in adult zebrafish liver were observed, and the severe hepatic injuries were found at 96 h. The pathological changes further explained the transcriptional results. The transcriptions of FVII were significantly depressed throughout the entire experiment in zebrafish larvae, and the FIX only significantly depressed after exposure for 48 and 96 h, however, FVIIi just was significantly reduced after 12 h and 24 h stimulation. Whatever the mechanism, the effects of MC-LR on the transcription of these coagulation factors might explain the intrahepatic hemorrhage in liver after exposure to MC-LR, and which would provide new information to elucidate the hepatotoxicity of MC-LR.
Stable isotope analysis has been extensively used as an effective tool in determination of trophic relationship in ecosystems. In freshwater ecosystem, aquatic invertebrates represent main component of a river food web. This study was carried out to determine potential food sources of freshwater organism together with pattern of trophic position along the river food web. In this study, rivers of Belum-Temengor Forest Complex (BTFC) has been selected as sampling site as it is a pristine area that contains high diversity and abundance of organisms and can be a benchmark for other rivers in Malaysia. Stable isotope ratios of carbon ( C) and nitrogen ( N) were applied to estimate trophic position and food web paradigm. Analysis of stable isotopes based on organic material collected from the study area revealed that the highest C value was reported from filamentous algae (− 22.68 ± 0.126 / ) and the lowest C was in allocthonous leaf packs (− 31.58 ± 0.187 / ). Meanwhile the highest N value was in fish (8.45 ± 0.177 / ) and the lowest value of N was in autochthonous aquatic macrophyte (2.00 ± 1.234 / ). Based on the N results, there are three trophic levels in the study river and it is suggested that the trophic chain begins with organic matter followed by group of insects and ends with fish (organic matter < insects < fish).
Grains and milling products constitute a major part of the daily diet of human and animal. The primary factor in grains and by products losses is the depredation of stored-product beetles. The objective of this trial was the evaluation of insecticidal and repellent activity of essential oils (EOs) from three spp ( , ) which grow wild in Iran, against the red flour beetle, (Coleoptera: Tenebrionidae), known as one of the most common stored-product pests worldwide. EOs were extracted from aerial parts of three spp using a Clevenger type apparatus. Their chemical compositions were analyzed by gas chromatography–mass spectrometry (GC/MS). Results indicated that phenolic compounds, such as thymol and carvacrol, are the main constituents of the EOs. Insecticidal activity on the adult was evaluated by direct contact and fumigation bioassays. EO was the most efficient with the lowest estimated LD and LC as 20.11 μg/adult 2.51 mg/L air, respectively. All the tested EOs were strongly repellent to the adult at the tested concentration (1% v/v). Similarly, oil at 1% (v/v) showed the highest repellent activity (98% to 100%) after 4 h of exposure. Considering the potential toxicity and repellency of the mentioned spp EOs to the red flour beetle, future studies could investigate the practical application of this potential bio-insecticide for the control of this pest.
and are widely planted in North China. The needles of and were sampled in the urban, suburban, and rural districts of Tianjin where the atmospheric conditions are significantly different according to the environmental monitoring results. The Cu, Mn, Zn, and Pb concentrations in the samples were examined via ICP. The resistance indexes, and the malonic aldehyde (MDA), soluble sugar, and free proline levels were also determined. The Pearson coefficients between the resistance indexes and the heavy metal contents were analyzed to compare the two plants abilities to accumulate heavy metal and their resistance characteristics. The results indicated that the heavy metal concentrations had the following significant trend: urban areas > suburban areas > rural areas. In urban areas, the Mn, Zn, and Pb concentrations in were as high as 2024.77 mg·kg , 2397.07 mg·kg , and 130.07 mg·kg , significantly higher than in . The Mn, Zn, and Pb concentrations in were extremely significantly positively correlated ( < 0.01), but no significant correlations were noted in . The MDA, soluble sugar, and free proline concentrations in increased as the heavy metal contents rose along the urban–rural gradient, and were positively correlated with the plant heavy metal contents. They were much higher than the contents in where no differences were noted among the sampling sites. In conclusion, the heavy metal resistance methods used by and are different. could absorb and accumulate many heavy metals, mainly through increased physiological resistance to stress. In contrast, resistance relied on avoiding contact with the metals and by reducing absorption. These differences are associated with the biological characteristics of and , and are closely connected with their coniferous and morphological differences.
Water scarcity is the primary cause of land deterioration, so finding new available water resources is crucial to ecological restoration. We investigated a hyper-arid Gobi location in the Dunhuang Mogao Grottoes in this work wherein the burial depth of phreatic water is over 200 m. An air-conditioner was used in a closed greenhouse to condense and measure the yearly amount of phreatic evaporation (PE) from 2010 to 2015. The results shown that the annual quantity of PE is 4.52 mm, and that the PE has sinusoidal characteristics. The average PE is 0.0183 mm d from March to November. Accordingly, by monitoring the annual changes in soil-air temperature and humidity to a depth of 5.0 m, we analyzed the water migration mechanism in the heterothermozone (subsurface zone of variable temperature). The results show that, from March to November, the temperature and absolute humidity (AH) increase. This is due to the flow of solar heat entering the soil — the soil subsequently releases moisture and the soil is in a state of increasing AH so that evaporation occurs. From November to March, the temperature decreases. Now, the soil absorbs water vapor and AH is in a state of decline. Thus, it is temperature alternation in the heterothermozone — due to solar heat transfer — that provides the main driving power for PE. When it drives water vapor to move downwards in the heterothermozone, a small part is reversed upwards and evaporates. Solar radiation intensity dominates the annual sinusoidal PE characteristics.
Amino acid mineralization and its fate in soil have effects on soil nitrogen cycling. Here we used N-labeled alanine and methionine to study differences in their mineralization from soil organic nitrogen under 60% WHC (water holding capacity) and 90% WHC soil conditions. We found that the maximum mineralization rates were at the 24th hours for alanine and at the 5th hours for methionine, and about two times greater rates at 60% WHC than at 90% WHC. The half-live was 24–72 h for alanine and > 72 h for methionine. Half-lives of amino acids occurred sooner under 90% WHC than under 60% WHC. The results suggested that some kind of amino acids do lead the nitrogen cycling in a specific ecosystem or as a sign to trigger soil nitrogen cycling when land utilization was altered or disturbed severely by humans.
and are two species of the rodents family Calomyscidae which are distributed mainly in Iran. Herein, we evaluated the habitat and ecological differences of these two brush-tailed mice in order to test the credibility of a hypothesis stating that species from habitats with different climates and vegetation show greater intraspecific differentiation than those from areas with more similar climates and vegetation. This study was carried out in four rocky regions in Iran between 2013 and 2015. Totally 52 brush-tailed mice were captured from Kopet-Dag, Khaje-Morad, Ark, and Shadan and Olang during the field studies. Maximum parsimony analysis inferred from mitochondrial DNA sequences ( ) was used for species identification, and also comparison of mean Kimura 2-paramater distances was performed. According to the molecular studies, specimens from the first two regions were assigned to and samples from Ark, and Shadan and Olang belonged to . The mean distances within all examined Iranian samples of both and were 2.3% and 0.9%, respectively. Based on our field studies, were captured either from “cold mountainous” climate zone with as main vegetation cover or from “Mediterranean” in which is predominant vegetation. were found in “hot dry desert” and “cold semi-desert” regions both characterized by sp. and vegetation cover. Dog rose seeds were the main food of in Kopet-Dag, whereas brush-tailed mice in the other three regions fed mainly on Mount Atlas pistache fruits. inhabited concealed rock crevices, but were found living in burrows which were digged in the soft soils. Individuals of showed more calm behavior as compared with and (Rodentia) as well as (Lagomorpha) were the most abundant small mammals encountered with , while was the most successful rodent with sympatric colonies with In conclusion, in accordance with the greater genetic distances observed in populations as compared with , more significant differences in the habitat structure were also found for the first species in different parts of its distribution range.
Present study measures the impact of forest disturbance on population structure and regeneration status of a Himalayan banj oak ( ) forest at different aspects and altitudes. The whole study was carried out by placing 300 systematically selected sample plots in banj oak forest. The study revealed that moderately disturbed forest patches were present in all elevation ranges and both north and south facing aspects whereas most of the highly disturbed patches were situated near middle and lower stretches of forests or close to habitations. Density of primary diameter class (5–15 cm) was recorded highest in moderately disturbed zone in upper elevation ranges and north facing aspect and ‘fair’ category of regeneration was most frequent in all elevation ranges and aspects. The paper concludes a positive effect of mid-level disturbance on plant community for better regeneration and study recommends a minimum resource extraction and silvicultural practices in banj-oak belt of Himalaya for a minimum canopy opening which not only be able to provide biomass to local communities for their daily needs but also would be able to maintain and improve forest health.
Studies on ecosystem service function have an important significance for analyzing and understanding global warming. With the introduction of geographic information system (GIS) and remote sensing (RS) technologies for the evaluation of ecosystem service function, the scope for analysis has been widening. Increasing number of researchers use these technologies to quantify the value of ecosystem service functions and reveal their spatial-temporal variability. By using the data for the interpretation of five RS images and net primary productivity (NPP) in Qinghai Lake basin, we assessed the value of vegetation carbon fixation and oxygen release services and revealed their dynamic variation in this basin. The result suggested that the average values of vegetation carbon fixation and oxygen release services in Qinghai Lake basin between 1987 and 2010 were spatially distributed in a ring shape around the Qinghai Lake and decreased from southeastern to the north and northwestern regions; the northwestern areas had the lowest value. The vegetation carbon fixation value between 1987 and 2010 was on an average 28.87 × 10 yuan/a in Qinghai Lake basin, whereas the oxygen release value was 64.41 × 10 yuan/a. Alpine meadow ecosystem showed the highest value of vegetation carbon fixation and oxygen release services function in Qinghai Lake basin, with average values of 18.28 × 10 yuan/a and 40.79 × 10 yuan/a, respectively, followed by those of temperate steppe and sparse vegetation. The vegetation carbon fixation and oxygen release values in Qinghai Lake basin gradually increased from 1987 to 2010, with the maximum value in 2010. By the end of 2010, the values increased by 7.19 × 10 yuan and 16.04 × 10 yuan, respectively. The values slightly decreased in barren land, lakeside marsh, river valley swamp, and sandy areas, but increased to different degrees in other ecosystems. Among them, the largest increase was noted in alpine meadow (4.38 × 10 yuan and 9.78 × 10 yuan, respectively), followed by those in temperate steppe with increased values of 1.12 × 10 yuan and 2.49 × 10 yuan, respectively.