The spatio-temporal distribution of land cover provides fundamental data for global climate and environmental change research. In recent decades, five global land cover maps have been produced based on remote sensing data sources and methodologies. Related research have shown that the availability and quality of the first four global land cover datasets are poor at the regional or the continental scale for a variety of reasons. There is still no consensus on the accuracy of the latest global land cover map. Based on comparison of the land cover dataset with the statistical cropland data from FAO and the FLUXNET site data, this paper discusses the accuracy of the fifth global land cover map, namely, the GLOBCOVER dataset, at different spatial scales. At the global scale, the cropland area obtained from the GLOBCOVER dataset is greater than that of the FAO statistical data by 47.06–84.49%, and the land cover types of the GLOBCOVER dataset have a 65.02% consistency with that of the FLUXNET site data. At the continental scale, the difference between cropland areas obtained from the GLOBCOVER dataset and the statistical cropland area vary from −43.42% to 502.36%; continents that have a more accurate cropland area compared to the FAO statistical data tend to be less consistent with the FLUXNET site data. In general, North America has a higher accuracy and Oceania has a lower accuracy. At the country scale, the accuracy estimates vary sharply over a wide range: between −100.00% and 190670.37%. It is recommended that future studies should pay careful attention to the data validation step before using the GLOBCOVER dataset for any particular problem. Future studies are also required for the development of a universal land cover classification system and advanced algorithms for remote sensing classification of global land cover maps.
The mitochondrial DNA cytochrome b of 132 collected from 12 localities in the upper to lower reaches of the Yangtze River were amplified and partially sequenced using the PCR technique. The results showed that 27 nucleotide sites were variable along 817 bp length of homologous sequence (3.3%), base substitutions happened mostly at the third codon position. A total of 22 haplotypes were identified, which were characterized with moderate haplotype diversity ( = 0.5417 ± 0.0519), but low nucleotide diversity ( = 0.0019 ± 0.0012). Median-joining network analysis revealed star-shaped patterns with one common central haplotype (H3), whereas mismatch distribution analysis found that the Chinese longsnout catfish fitted a smooth unimodal distribution, which suggested that this species underwent population expansion following bottlenecks and/or they originated from a small number of founding individuals. The time that the total population of Chinese longsnout catfish in the Yangtze River expanded was estimated 169,000–337,000 years before present. The analysis of molecular variance (AMOVA) and phylogenetic reconstructions did not detect significant geographic structure between different river sections, especially between above and below the Gezhouba Dam and the Three Gorges Dam, which suggested that these recently developed dams might have not significantly resulted in population genetic differentiation in the Chinese longsnout catfish.
Based on the analysis of land consolidation engineering effects on biodiversity conservation in hilly areas, this study considers integrating biodiversity conservation into traditional land consolidation projects and integration biodiversity conservation measures into land consolidation engineering from the overall planning, land leveling engineering, farmland water conservancy engineering, roads and landscape construction engineering respectively. It aims to conserve biodiversity and improve eco-environment and arable land quality for increase yields of crops by integration biodiversity conservation ideas and measures into land consolidation activities in advance.
Using a modified belt transect method, we investigated the butterfly communities in five different vertical vegetation belts of Changbai Mountain in China from 1992 to 2009; these belts were broadleaf deciduous forest, coniferous–deciduous mixed forest, coniferous forest, erman’s birch forest and alp tundra. We determined the number of species and abundance of butterflies in each belt and in the coniferous–deciduous mixed forest belt, we also compared these parameters among different months. Preston’s lognormal distribution was used to model the species abundance distributions and five indicators (Shannon–Wiener diversity index ( ′), Pielou uniformity index ( ), Simpson predominance centralization index ( ), Margalef abundance index ( ) and Jaccard similarity coefficients) were used to analyze the butterfly community diversity. We found four main results. (1) Across all five vertical vegetation belts, 9641 butterflies were collected, belonging to 7 families, 98 genera and 196 species. As altitude increased, the number of butterfly genera and species gradually reduced. There was a relationship between the distribution of dominant species and the total species between each belt and the distribution of vascular plants. (2) The species abundance distribution was successfully modeled as a Preston’s lognormal distribution; the best fit was obtained when = 0.326, the determinant coefficient of the equation was 0.74798. The species abundance distribution indicates that Changbai Mountain provides a suitable environment for butterflies; there was high species richness and an even distribution of butterfly species. There were few very common and very rare species, with most species having an intermediate abundance. (3) As altitude increased, ′ and gradually became smaller, while showed the opposite pattern, and did not significantly change. The similarity coefficients analysis demonstrated a clear difference among belts; the farther apart any two belts, the smaller the similarity coefficient, indicating less similarity in the butterfly communities. The similarity coefficient between the deciduous forest and the coniferous–deciduous mixed forest belt was the largest (0.651) while that between the deciduous forest and the alp tundra was the smallest (0.141). (4) Comparison of the butterfly species communities among different months in the coniferous–deciduous mixed forest found that ′ and showed similar directional changes, while the opposite pattern was found with ; the changes in did not necessarily reflect the actual change in diversity.
Juvenile ( = 48, body length, 5.86 ± 0.10 cm, 25 °C) were fasted for 0, 0.5, 1, 2, 4 and 6 weeks. The fast-start performances of the experimental fish were assessed using high-speed video photography and the locomotive kinematics analysis. The morphological parameters including tail height ( ), tail length ( ), lateral body area ( ), median fin area ( ), dorsal cross section area ( ) and tail cross section area ( ) were also measured using TpsDig and the Photoshop. The results showed that 6 week starvation resulted in significant decreases in the escape distance ( ), maximum linear velocity ( ) and maximum linear acceleration ( ) of center of mass in Stage 1 and Stage 2 of fast-start process ( 0.05). The fish did not show any directional preference for left or right during escape turning, and all of the related parameters also remained unchanged among treatment group ( > 0.05). The areas of dorsal body cross-section decreased more acutely ( 0.05). The results indicated that fast-start performance of juvenile is affected by the starvation; metabolic energy related traits such as the maximum linear velocity and the maximum linear acceleration decreased significantly after starvation; whereas traits with no direct link to metabolic energy such as the response time and turning angle remained unchanged during starvation. The lack of starvation induced change in the maneuverability of the fish suggests that fast-start ability related to escape strategy is relatively well conservative in juvenile .
Long-term spatial–temporal dynamics of vegetation coverage is a key problem of issues include global climate change study, regional ecological process monitoring and ecosystem management. Based on SPOT-VGT 10-day composite data over the Circum Bohai Bay Region from 1999 to 2009, this paper performs the Mann–Kendall test and calculates the trend Slope ( ) and Hurst index of time series data to study the temporal trends and long-range dependence of Normalized Difference Vegetation Index (NDVI) on 1 km spatial scale, and plots monthly calendar and seasonal succession map using spatial analysis techniques, and then analyze and reveal the spatial–temporal characteristics of vegetation coverage. Main findings are as follows: (1) dense vegetation coverage mainly distribute in mountainous and hilly areas dominated by forest and shrub, followed by vast plain areas with well developed agricultural industry, and low vegetation coverage mainly distribute along part of coastal beaches, surrounding most of urban areas and large inland water bodies and in the semi-arid agro-pasture intertwined zone at the north-west corner of Hebei province. (2) Overall, vegetation coverage is high in summer–autumn and low in winter–spring and the increasing trend from 1999 to 2009 on monthly, seasonal and annual scales are significant in most areas. An increased seasonal difference is detected because the improving trend of vegetation coverage in growing seasons is more remarkable than that in non-growing seasons. Furthermore, significant long-range dependence of NDVI time series is detected in most areas which indicate that the trend of vegetation coverage change from 1999 to 2009 will definitely persist in the near future. (3) Both variation of vegetation coverage in the past and its long-range dependence show significant spatial differences on macro spatial scale, in detail, improving trend of vegetation coverage in Liaoning province is very significant and it will persist in the near future because more than 85% of the pixels in Liaoning province has positive Slope ( ) and Hurst index great than 0.5, correspondingly, only very mild signal of enlarged seasonal difference is detected in Liaoning province. On the contrary, very large extent of vegetation coverage in Beijing–Tianjin–Hebei area and Shandong province show significant degrading trend and enlarged seasonal difference despite the overall improving trend in these areas in the past 11 years. Areas with degrading trend of vegetation coverage in the past and future trends point to continuing degrading account for 6.71% and 9.84% in Beijing–Tianjin–Hebei area and Shandong province, respectively, while it is below 6.00% in Liaoning province. (4) Areas with degrading trend of vegetation coverage in the past and future trends point to continuing degrading show the overall spatial pattern of scattering on macro scale and aggregating on fine scales, specifically, areas surrounding large inland water bodies, along part of coastal beaches and surrounding urban areas indicates strong tendency of degrading in the past and prospective degrading trend in the near future. (5) Complicated driving forces of vegetation coverage change on macro spatial scale are revealed by the spatial patterns of the coupling index between Slope ( ) and Hurst index, in detail, rapid and extensive urbanization undergone on multi-spatial scales is the most important man-made force of vegetation coverage degrading, large scale agricultural activities overall improve the vegetation coverage and enlarge its seasonal difference; while factors include water level changes near large inland water bodies, water–salt dynamics at coastal beach and so on are the main natural driving forces of vegetation degradation. The findings in this paper are useful for wise regional ecosystem management in Circum Bohai Bay Region.
Lake Taihu, which is the third largest freshwater lakes in China, is a hypertrophic shallow lake in eastern China that has experienced lake-wide cyanobacterial blooms annually during the last few decades. In this study, quantitative real-time PCR assays targeting on phycocyanin intergenic spacer ( - ) and a microcystin synthetase gene were established, respectively. Water samples collected from eight sampling sites (including Zhushan Bay (N5), Meiliang Bay (N2), Gonghu Bay (N4), West lake areas (W2 and W4), south-middle lake areas (S2, S4 and S5)) in August of 2009 and 2010 were analyzed using real time PCR for the distribution and abundance of toxic and total populations. The results showed that exists as a mixed population of potential toxic and non-toxic genotypes, and there was significant spatial changes in the abundance of potential toxic on the basis of quantification by quantitative real-time PCR analysis: the abundance of toxic population in 2009 and 2010 varied from 4.08 × 10 to 8.28 × 10 copies mL , from 4.45 × 10 to 5.22 × 10 copies mL , respectively. Meanwhile the ratio of the subpopulation to the total varied considerably, from 5.7% to 41.1% in 2009 and from 10.3% to 65.8% in 2010 in all sampling sites, and the value is high in Zhushan Bay and Meiliang Bay with the high level of eutrophication. Correlation analysis showed the abundance of toxic and total being strongly related ( 0.05). All data suggest that phosphorus concentration is a critical factor for determining the abundance of toxic population.
Anthropogenic activities and environmental changes have had a significant effect on the fishery ecosystem, biological characteristics, and population dynamics of marine fishes. Overfishing threatens the sustainability of many populations. We evaluated changes in the biological characteristics, distribution, and abundance of using bottom trawl survey data collected from 1985 to 2010 in the central and southern Yellow Sea. The dominant body length of during spring was 80–160 mm in 1986, 60–160 mm in 1998, and 41–80 mm and 111–170 mm in 2010. During summer, the dominant body length was 80–180 mm and 130–169 mm in 2000 and 2007, respectively. During autumn, the dominant body length was 60–160 mm, 100–180 mm, and 90–149 mm in 1985, 2000, and 2009, respectively. During winter, the dominant body length was 80–200 mm, 120–220 mm, and 100–200 mm in 1985, 1999, and 2010, respectively. The dominant body length decreased gradually from 1985 to 2010 (excluding spring, 2010), illustrating the “miniaturization” of the population. Growth was significantly different between male and female individuals, with male individuals forming a “smaller-size type”. The sex ratio of was relatively stable during spring and summer, but significantly different during autumn and winter. The diet of also changed significantly from 1985 to 2010. During 1985–1986, the diet consisted primarily of , and Gammaridae species. , , and were dominant during 1998–2000, whereas was the dominant prey species during 2009–2010. Thus, there was a clear decrease in dietary diversity, with a shift to benthos shrimp, particularly , which accounted for 82.58% of the total diet (by weight) in 2010. The gastric vacuous rate also decreased in every season and the gonad developmental stage changed with each season. The distribution of shifted northward and offshore and became more concentrated. The average catch per haul of decreased in spring and autumn. The average catch per haul ranged from 1.44 kg h to 0.14 kg h in spring and the percentage by weight ranged from 6.53% to 1.28%. The average catch per haul ranged from 3.03 kg h to 0.26 kg h in autumn and the percentage by weight ranged from 8.00% to 0.60%. The average catch per haul increased significantly during summer, ranging from 0.18 kg h to 0.58 kg h , with a percentage by weight of 0.03–0.80%. The average catch per haul was relatively stable in winter (around 1.00 kg h ), but the percentage by weight gradually increased during 1985–2010. Taken together, our results suggested that the population structure, diet composition, and distribution of had been altered during the last three decades. To address this, it is essential to initiate measures to conserve the resource.
The aim of the study was to determine effects of a wildfire on soil nutrients and soil microbial functional diversity in short-term time scales. Burned and unburned control soil samples were collected 1 day, and 2, 4, 8, 10, 12 and 15 months after a shrubbery fire in Yumin county of Xinjiang, Northwest China. Nutrients of soil in each sampling time were detected and soil microbial functional diversity was measured by Biolog Eco plates. Results of the study showed that soil nutrients were significantly affected by fire. Soil pH increased immediately after the wildfire and was higher than that of unburned soil during 15 months post fire. Soil organic matter and total N significantly decreased immediately after the fire and was even lower than control soil at the 15th month post fire. Soil available P level increased sharply during the 4th month after the fire, and later reached to the maximum value with eight times higher than that of unburned soil. Soil available N and available K were more than the control site in 2 months after the fire, then decreased, but available N began to increase, when vegetations restored 1 year after the fire. Soil microbial activity and functional diversity recovered gradually after fire. The average well color development ( ) and functional diversity indices (Shannon index, Simpson index, and McIntosh index) decreased significantly 1 day after the fire, but then increased and were similar to that of undisturbed soil 15 months after the fire, when plant started to regenerate in burned area. The changes in soil nutrients after the fire affected soil microbial activity and functional diversity. Correlation analysis revealed that was negatively correlated with soil pH and positively correlated with soil total N and available N, Shannon and Simpson index had positive significantly correlation with soil total N and McIntosh index had positive significantly correlation with available N. Result of principal component analysis based on the data of carbons metabolism showed that microbial catabolic profiles of burned soils of each sampling time after the wildfire were different and all were distinct from those of unburned soils, which might suggest that microbial community structure of fire-impacted area changed dynamically on monthly scale and was distinct from that of the control site in 15 months after fire, although microbial activity or richness showed similar to pre-fire level at the 15th month post-fire.
Azo dyes, as the largest group of synthetic dyes released from textile and dyestuff industries, have caused serious environmental problems. We investigated the removal ability and physiological response of sunflowers to simulated wastewater containing azo dyes with concentration similar to real wastewater or above. The percent decolorization of the three azo dyes within 4 days varied greatly. For the same dyes, the percent decolorization was descending with the primary dye concentration increasing. The percent decolorization of Bismark browny, Evans blue and Orange G at same concentration was also descending. The average percent decolorization of the three azo dyes at 100 mg/L within 4 days was 62.64%. The physiological effects of the tested azo dyes on sunflowers were also very different. The stress effects of Bismark browny, Evans blue and Orange G at same concentration were also descending. All tested azo dyes reduced significantly normalized relative transpiration (NRT), net photosynthesis rate (Pn), transpiration intensity (Tr) and stomatal conductance (Gs) of sunflowers. The percent of decline of all the indicators such as NRT, Pn, Tr and Gs was less than 50% when concentration of azo dyes was 100 mg/L. The result showed that sunflowers can survive in water containing 100 mg/L all tested azo dyes. We conclude that sunflowers can be used for phytoremediation of wastewater containing azo dyes. 偶氮染料作为纺织和染料工业排放量最大的一类合成染料造成了严重的环境问题。我们研究了向日葵对浓度接近或高于实际废水的模拟含偶氮染料废水的脱色效果及向日葵对废水的光合生理特征响应。在四天里, 向日葵对三种偶氮染料的去处率差异巨大。对同一浓度的俾斯麦棕、依文思蓝和橙黄的去处率递减。对同一染料的去处率随初始浓度的增加而递减。经过四天的处理, 100 mg/L 的三种偶氮染料的平均去除率为62.64%. 测定的偶氮染料对向日葵的生理效应也有很大差异。同一浓度的俾斯麦棕、依文思蓝和橙黄对向日葵的胁迫效应也递减。所测试的偶氮染料显著的降低了向日葵的相对标准蒸腾速率 (NRT), 净光合速率, 蒸腾速率和气孔导度。当染料的浓度为100 mg/L 时, 向日葵的相对标准蒸腾速率 (NRT), 净光合速率, 蒸腾速率和气孔导度等指标下降的幅度均低于 50%. 结果表明向日葵能耐受100 mg/L 的偶氮染料. 可以应用向日葵对含偶氮染料的废水进行植物修复.
Earthquake has great potential to destroy vegetation and water resources. Here, we estimated the ecosystem services before/after “5.12” Wenchuan earthquake in China, in the center zone (ca. 24, 696.94 km ) of the earthquake, the destroyed service value approximately 520.04 × 10 $. Moreover, the losses of biodiversity conservation value were inestimable in this earthquake. The results suggested that earthquake can seriously damage service function of ecosystem. It is a nice opportunity for ecologists to study the recovery of ecosystem services after earthquake disturbance.
The complete mitochondrial genome sequence of the raccoon dog ( ) was determined by using the long and accurate polymerase chain reaction. The entire mitochondrial genome sequence is 16,713 bp in length contains two ribosomal RNA genes, 13 protein-coding genes, 22 transfer RNA genes and 1 control region. Most mitochondrial genes are encoded on the H strand, except for the ND6 gene and 8 tRNA genes. The base compositions of mitochondrial genomes present clearly A–T skew. All the transfer RNA genes can be folded into the typical cloverleaf-shaped structure except tRNA-Ser (AGY), which lacks the dihydrouridine arm. Protein-coding genes mainly initiate with ATG and terminate with TAA. Some reading frame intervals and overlaps are found in the mitochondrial genome. The control region can be divided into three domains: the extended termination associated sequences (ETASs) domain, the central conserved domain and the conserved sequence blocks (CSBs) domain. Three conserved sequence blocks (CSBs) and one extended termination associated sequences (ETAS-1) is found in the control region. The phylogenetic analysis based on the concatenated data set of 14 genes in the mitochondrial genome of Canidae shows that the raccoon dog has close phylogenetic position with the red fox ( ) and they constitute a clade which has an equil evolutionary position with the clade formed by the genera and .
The bacterial community composition and diversity in rock varnish of Turpan Basin were investigated by restriction fragment length polymorphism (RFLP) and clone library of the 16S rRNA gene. 114 positive clones were screened, which could be grouped into 28 phylotypes and then further divided into 23 different operational taxonomic units (OTUs). These were affiliated into 5 phyla (Acidobacteria, Proteobacteria, Chloroflexi, Firmicutes and Cyanobacteria). Clones from actinobacteria were the dominant, accounting for 67.5% of total clones in the library, followed by Proteobacteria (15.8%), Chloroflexi (13.2%), Firmicutes (2.6%) and Cyanobacteria (0.9%). (accounts for 35%) in the phylum Actinobacteria was the dominant genus and contained many species which might be resistant to gamma radiation. A 70% of the library clone sequences showed less 97% similarity to 16S rRNA gene sequences of standard strains obtained by pure culture. Shannon–Wiener index value of this study is 2.52 and is lower than deep-sea sediments, soils, lakes and other environments. Results of this study showed that bacterial diversity in rock varnishes of Turpan Basin was low, but maybe exist a large number of new unknown taxons, especially species that could well adapted to drought and resist radiation.
In the Three Gorges Reservoir Region of China, periodic flooding has led to plant destruction, causing much ecological damage. Re-vegetation with submergence-tolerant species is a possible solution to this problem. At present, many submergence-tolerant species have been selected for such restoration efforts, but it is unclear why these species can survive complete submergence while other species cannot. In this study, we investigated the response of two species – submergence-tolerant Franch. and submergence-intolerant (L.) Presl. – to flooding. Plants were submerged to 2 m for 3, 9, 15, and 30 days, after which malondialdehyde (MDA) (a membrane injury product) and superoxide anion content, as well as superoxide dismutase (SOD) and peroxidase (POD) activity, was measured. We found that (1) MDA levels increased in submerged seedlings but remained constant in ; (2) superoxide anion content and SOD activity in the two species responded similarly to submergence; and (3) POD activity in seedlings was much higher than in . These results demonstrate that plant tolerance to submergence is related to membrane stability, and that POD activity is an important factor in this tolerance.
Shenzhen was a famous typical rapid-urbanization city in China, and this study compares plant species diversity in urban parks from the start of urbanization through 2011. Results show that the plant species biodiversity increased rapidly: the rate changed from 140% to 980% and the average increasing rate was 406.90%, but only 12.59% of plants spread into the park naturally. Shrubs had the highest rate; with change increasing from 20.70% to 43.54%, they replaced trees to become the dominant type. The biodiversity of native plants also increased, but their proportion relative to all species had declined. The homogenization of plant species in the parks increased; more than half of the plant species (62.24%) are located in 5–7 parks at once now, compared with 65.52% of species located in only 2–3 parks at the start of the study. The increase of species was faster than the increase of families; many new species planted belong to a few specific families. The ratio of species to families declined from 0.40 to 0.32. Results indicate that the rapid increase of plant species diversity as well as their homogenization happened in the initial stage of urbanization, and so rapid urbanization might be the major factor in the changes in plant species diversity in municipal parks. Rapid urbanization was an important cause of change in plant species diversity.
Canidae fecal flora reflects the distal gut microbial community structure. was captured on Qilian Mountain in Gansu province of China, and other animals, including , , and , were captured at the nearby Dalai Lake Nature Reserve in Inner Mongolia. Fecal samples were collected 2 h after defecation from five healthy unrelated adult animals of each species. None of the animals had recently fed or been administered any drugs or additives that could influence the composition or diversity of the fecal flora. Using traditional culture-dependent methods, we investigated the composition and diversity of the fecal flora of these five Canidae species. Gram-positive spore bacilli, gram-positive having no spore bacilli, gram-positive coccobacteria, gram-negative coccobacteria and gram-negative bacilli were first identified through microscopic observation and then formal identification tests were carried out, including oxygen needing, methyl red and Acetyl methyl methanol test, catalase, gelatin liquefaction, KNO reduction, indole, fermentation of saccharides and mellows, sodium citrate and NaCl-phily and so on. Based on the results of these physiological and biochemical tests, along with the morphological description, species from approximately 19–21 genera were identified in the feces. The number of genera in the feces was 22 in , 19 in , 21 in , 21 in and 19 in , as well as some unidentified strains. Although, some strains were endemic to the Canidae gut, there were some differences in the community among individuals and species. The Canidae fecal flora comprised 10 –10 colony forming units/g of feces (wet weight). The amount of bacteria reached 1.442 × 10 cfu/g in , 8.330 × 10 cfu/g in , 8.170 × 10 cfu/g in , 8.620 × 10 cfu/g in and 1.485 × 10 cfu/g in . The amount of bacteria was significantly different among species ( < 0.05) but not among different individuals of the same species ( = 0.19; : = 0.898; : = 0.315; : = 0.074; = 0.197). The percentage of shared species among different Canidaes was 65–80%, with the highest percentage between and , and the lowest between and . Although the proportion of shared species between and was 78.95%, the amount of bacteria was markedly different. There was no correlation between the amount and the diversity of bacteria. The most common microbes were , , , , and . Of these, and can be considered as beneficial strains and they were found in all the Canidaes. Our findings suggest that, despite some differences, there is high similarity in the dominant fecal bacteria of different Canidaes.
Analyzing daily air temperature and precipitation observed during 48 years from 1958, we quantified changes in temperature and precipitation with year in Kherlon River Basin of semiarid northern China. In addition, the relationship between the dry biomass measured 23 years from 1983 at a grassland and the corresponding temperature accumulated for higher temperature than 5 °C (AET) and precipitation accumulated after 1 April (CP) was determined. It was estimated that the annual mean air temperatures during non-growing season (October to April) and growing season (May to September) had significantly risen during 50 years from 1958 by 2.38 °C and 1.83 °C, respectively. The year-to-year variation in the annual mean air temperature had a tendency to increase with year during the 48 years. Changes in annual precipitation and precipitation days for any of the entire year (January to December), growing and non-growing seasons with year were not significantly observed. Both the AET and CP (especially CP) during the growing season affected the biomass growth in the semiarid grassland. Prediction of seasonal changes in meteorological tendency as well as that of climate change is important to maintain the production in semiarid grassland and to conserve the plant community and landscape.
Cessation of grazing is an important management practice in restoration of grassland ecosystem productivity and function. However, little is known about the effects of long-term exclusion of grazing on soil bacterial community structure and diversity in grassland ecosystems. This study utilized three grassland sites over two consecutive years (2004 and 2005) in a semi-arid Inner Mongolia steppe; there were a free grazing site (FG), fenced site since 1999 (UG99) and fenced site since 1979 (UG79). Soil moisture content, organic carbon (C) and nitrogen (N), and concentrations were measured across the treatments. Bacterial community structure and diversities were assessed with PCR amplification of genomic DNA extracted from soils and following denaturing gradient gel electrophoresis (DGGE) separation. Results showed that the UG99 soil had higher moisture, organic C, organic N and concentrations than the other soils. Principal components analysis of DGGE patterns showed that soil bacterial community structure sampled in 2004 was different from that in 2005, and the UG99 soil was significantly different from the FG and UG79 soils across the two consecutive years. In addition, the UG99 soil had significantly higher bacterial diversity and evenness compared with the FG and UG79 soils. These results indicate that long-term exclusion of grazing decreases bacterial diversity, which has significant implication for grassland ecosystem management.
The evaluation of microbial molecular diversity has been mainly based on the extraction of total DNA from environmental samples. The indirect extraction methods, which have been used for prokaryotes, have never been used to recover soil microeukaryotic DNA. We evaluated the efficiency of an improved indirect DNA extraction protocol developed herein and the direct lysis (the sodium dodecyl sulfate (SDS)-based method and commercial DNA extraction kit) on estimating the molecular diversity of soil microbial eukaryotes. DNA quality and quantity as well as denaturing gradient gel electrophoresis (DGGE) profiles were determined using three soil samples from different stations. The indirect method detected the highest DGGE bands in spite of the low DNA yield. The commercial kit detected a lower number of DGGE bands than the indirect method. The SDS-based method produced the lowest DGGE bands and DNA purity but the highest yield. Using the indirect method, we further evaluated the effect of freezing and air-dried preservations on estimating the microeukaryotic diversity. In spite of the low DNA yield obtained from the air-dried preservation, no significant differences were found in either the number of DGGE bands or the DNA purity between two manners. Our results indicate that the improved indirect method could obtain a high purity of intracellular DNA and high efficiency in the estimation of molecular diversity of soil microbial eukaryotes.
Maintaining the stability of ecotone is a potential way to stop the expansion of arid areas, but little has known in many key arid ecotones. This study aimed to understand the responses of endemic species to drought conditions in an arid ecotone. A controlled experiment with different drought stress treatments (80%, 40% and 20% field water capacity (FC)) on two endemic species ( and ) was arranged in the ecotone between the Minjiang dry valley and mountain forest. Drought stress dramatically reduced the height, basal diameter, leaf number, biomass production and the accumulations of C, N and P of both species. An increase of belowground proportion was observed indicating higher root/shoot ratio under drought stress conditions, and drought further increased N and P use efficiencies and intrinsic water use efficiency ( ). Compared with under medium drought stress (40%FC), showed less change of morphology characteristics, higher P use efficiency, and due to better N sources. However, showed higher N use efficiency and under severe drought stress condition (20%FC) than . The results suggested that the expanding dry valley could seriously influence endemic species in the ecotone, and N-fixing plant such as could adapt to moderate drought stress better than non-N-fixing plant. 干旱-湿润交错带环境稳定是控制干旱区不断扩散的潜在途径, 但相关研究较为缺乏。为了解岷江干旱河谷－山地森林交错带植物对干旱胁迫的生长适应机制, 以交错带两种典型乡土植物(高山柳 和沙棘 )为研究对象, 研究其在不同程度干旱胁迫条件下的形态生长、生物量生产、N和P积累与利用格局。干旱胁迫明显降低了两种植物的株高、基径和叶片数等形态特征, 减小了生物量生产以及C、N和P的积累, 改变了生物量以及C、N和P的分配格局, 但提高了N和P利用效率。尽管高山柳具有相对较高的N利用效率, 但是沙棘在干旱胁迫条件下可以维持较高的生长和较大的P利用效率, 可以更好地适应于干旱环境。这些结果表明干旱区的持续扩散将严重影响交错带植物的生长, 同时交错带植物也具有相对较强的适应干旱胁迫的潜力, 可以通过改变资源分配格局和提高限制养分利用效率以适应恶劣的生存环境。