Cd contamination determined assembly processes and network stability of AM fungal communities in an urban green space ecosystem.

The effects of cadmium (Cd) contamination on the assembly mechanism and co-occurrence patterns of arbuscular mycorrhizal (AM) fungal communities remain unclear, especially in urban green spaces. This study sequenced AM fungal communities in greenbelt soils in Zhengzhou (China). The effects of Cd contamination on the AM fungal diversity, community assembly processes, and co-occurrence patterns were explored. We found that (1) an increase in Cd contamination changed the community composition, which resulted in a significant improvement in the diversity of specialists of AM fungi and a significant decrease in the diversity of generalists. (2) Deterministic processes dominated the community assembly of specialists and stochastic processes dominated the community assembly of generalists. (3) Specialists played a more important role than generalists in maintaining the stability of AM fungal networks under Cd contamination. Overall, Cd contamination affected the ecological processes of AM fungi in urban green space ecosystems. However, the effects on the assembly processes and network stability of different AM fungi taxa (specialists and generalists) differed significantly. The present study provides deeper insight into the effect of Cd contamination on the ecological processes of AMF and is helpful in further exploring the ecological risk of Cd contamination in urban green spaces.

Microsatellite markers for Dayaoshania cotinifolia (Gesneriaceae), a critically endangered perennial herb.

PREMISE OF THE STUDY: Microsatellite primers were developed for the critically endangered species Dayaoshania cotinifolia (Gesneriaceae) to evaluate population genetic diversity and detect population history. • METHODS AND RESULTS: In our study, 15 primer sets were developed using an enriched genomic library. These are the first microsatellite loci developed for this genus. Genetic diversity was measured using 40 individuals. The number of alleles per locus ranged from one to six, and the incidence of observed heterozygosities was 0.365 and 0.410 in two populations. • CONCLUSIONS: The described markers will be useful in future population genetics studies of this critically endangered species.

Distribution of Woody Plant Species Among Different Disturbance Regimes of Forests in a Temperate Deciduous Broad-Leaved Forest.

Forests in different disturbance regimes provide diverse microhabitats for species growth. However, whether the species distribution of wood plant is random or follows ecological specialization among forests in different disturbance regimes remains to be elucidated. In this study, four 1 hm2 (100 m × 100 m) forest dynamic monitoring plots in different disturbance regimes of forests were randomly selected in a temperate deciduous broad-leaved forest. We examined the specificity of woody plants to forests through network analysis. Torus-translation test was used to analyze the species distribution preference of woody plants to forests in different disturbance regimes. The specialization index of woody plants was 0.3126, and that of shrubs (51.01%) was higher than that of trees (25.16%). Moreover, 66.67% (38/57) of woody plants were associated with different forests. More shrub species (70.00%) had specific preferences than tree species (45.95%) with respect to forests in different disturbance regimes. Our findings suggest that the distribution of woody plants among forests with different disturbance regimes is not random but is specialized. Different woody plants show different community preferences in different disturbance regimes of forests. Shrubs show higher specialization than trees in different disturbance regimes of forests.

Next-generation sequencing yields the complete chloroplast genome of Abies kawakamii.

Abies kawakamii is endemic to the island of Taiwan and has been listed as a threatened species in the Red List. In present study, we reported the complete chloroplast genome of A. kawakamii. The chloroplast genome is 121,290 bp in size. It was composed of 114 genes and they were 68 peptide-encoding genes, 35 tRNA genes, four rRNA genes, six open reading frames and one pseudogene. Loss of ndh genes was identified in the genome of A. kawakamii. Inverted repeat sequences include trnS-psaM-ycf12-trnG and trnG-ycf12-psaM-trnS were recognized in 52-kb inversion points. The phylogenetic analysis confirms that the Abies species are strongly supported as monophyletic. The complete plastome of A. kawakamii will provide potential genetic resources for further conservation and management strategies.

How do similarities in spatial distributions and interspecific associations affect the coexistence of Quercus species in the Baotianman National Nature Reserve, Henan, China.

Congeneric species often have similar ecological characteristics and use similar resources. These similarities may make it easier for them to co-occur in a similar habitat but may also lead to strong competitions that limit their coexistence. Hence, how do similarities in congeneric species affect their coexistence exactly? This study mainly used spatial point pattern analysis in two 1 hm2 plots in the Baotianman National Nature Reserve, Henan, China, to compare the similarities in spatial distributions and interspecific associations of Quercus species. Results revealed that Quercus species were all aggregated under the complete spatial randomness null model, and aggregations were weaker under the heterogeneous Poisson process null model in each plot. The interspecific associations of Quercus species to non-Quercus species were very similar in Plot 1. However, they can be either positive or negative in different plots between the co-occurring Quercus species. The spatial distributions of congeneric species, interspecific associations with non-Quercus species, neighborhood richness around species, and species diversity were all different between the two plots. We found that congeneric species did have some similarities, and the closely related congeneric species can positive or negative associate with each other in different plots. The co-occurring congeneric species may have different survival strategies in different habitats. On the one hand, competition among congenerics may lead to differentiation in resource utilization. On the other hand, their similar interspecific associations can strengthen their competitive ability and promote local exclusion to noncongeneric species to obtain more living space. Our results provide new knowledge for us to better understand the coexistence mechanisms of species.

Drivers of Macrofungi Community Structure Differ between Soil and Rotten-Wood Substrates in a Temperate Mountain Forest in China.

The effects of environmental and dispersal processes on macrofungi community assembly remain unclear. Further, it is not well understood if community assembly differs for different functional guilds of macrofungi, e.g., soil and rotten-wood macrofungi. In this study, using 2433 macrofungi sporocarps belonging to 217 species located within a forest dynamics plot in temperate mountain forest (China), we examined the explanatory power of topography, spatial eigenvectors (representing unknown spatial processes, e.g., dispersal), plant community, and light availability for local spatial variation in the macrofungi community through variance partitioning and partial least squares path modeling. We found spatial eigenvectors and light as the most important factors for explaining species richness and composition of macrofungi. Light was negatively correlated with species richness of macrofungi. Furthermore, species richness and composition of soil macrofungi were best explained by light, and species richness and composition of rotten-wood macrofungi were best explained by spatial eigenvectors. Woody plant community structure was not an important factor for species richness and composition of macrofungi. Our findings suggest that spatial processes, perhaps dispersal limitation, and light availability were the most important factors affecting macrofungi community in temperate deciduous broad-leaved forest. Major differences in influencing factors between soil and rotten-wood macrofungi were observed, with light as the major driver for soil macrofungi and unknown spatial processes as the major driver for rotten-wood macrofungi. These findings shed new light to the processes shaping community assembly in macrofungi in temperate deciduous broad-leaved forest and point to the potential importance of both intrinsic dynamics, such as dispersal, and external forcing, such as forest dynamics, via its effect on light availability.

Macrofungal species distributions depend on habitat partitioning of topography, light, and vegetation in a temperate mountain forest.

The habitat partitioning hypothesis provides a conceptual framework for explaining the maintenance of plant and animal diversity. Its central tenet assumes environmental conditions are spatially structured, and that this structure is reflected in species distributions through associations with different habitats. Studies confirming habitat partitioning effects have focused primarily on spatial distributions of plants and animals, with habitat partitioning hypothesis under explored for macrofungi. Here, we examined the sporocarps of macrofungi in a 5-ha forest dynamics plot in China. We used four different methods to define microhabitats for habitat partitioning analyses based on topography, understory light availability, plant community, or a combination of these factors, and analyzed the effect of microhabitat partitioning on epigeous macrofungal community. Our results showed that the characteristics of the macrofungal assemblages varied among the habitats. A total of 85 species examined were associated with one or more of the habitat types (85/125, 68%). The factors related to the sporocarp composition differed among the various microhabitats. Our findings suggest that different microhabitats favor occurrence of different macrofungal species, and sporocarps -environment relation varied among the different microhabitats at this temperate mountain forest locality. These findings shed new light to the biodiversity conservation in macrofungi in temperate deciduous broad-leaved forest and point to the potential importance of microhabitat partitioning for sporocarp formation.

Stand Structure and Substrate Diversity as Two Major Drivers for Bryophyte Distribution in a Temperate Montane Ecosystem.

Elucidating the major drivers of bryophyte distribution is the first step to protecting bryophyte diversity. Topography, forest, substrates (ground, tree trunks, roots, rocks, and rotten wood), and spatial factor, which factors are the major drivers of bryophyte distribution? In this study, 53 plots were set in 400 m2 along the elevation gradient in Xiaoqinling, China. All bryophytes in the plots were collected and identified. Regression analysis was used to examine the relationship between bryophyte and substrate diversity. We compared the patterns of overall bryophyte diversity and diversity of bryophytes found on the ground, tree, and rock along elevational gradients. Canonical correspondence analysis was applied to relate species composition to selected environmental variables. The importance of topography, forest, substrates, and spatial factors was determined by variance partitioning. A total of 1378 bryophyte specimens were collected, and 240 species were identified. Bryophyte diversity was closely related to substrate diversity. The overall bryophyte diversity significantly increased with elevation; however, the response varied among ground, tree, and rock bryophytes. Tree diversity and herb layer were considered important environmental factors in determining bryophyte distribution. Species abundance was best explained by stand structure (17%), and species diversity was best explained by stand structure (35%) and substrate (40%). Results directly indicated that substrate diversity can improve bryophyte species diversity. The effects of micro-habitat formed by stand structure and substrate diversity were higher than those of spatial processes and topography factors on bryophyte distribution. This study proved that the determinant factors influencing bryophyte diversity reflect the trends in recent forest management, providing a real opportunity to improve forest biodiversity conservation.

Effects of Environment and Space on Species Turnover of Woody Plants across Multiple Forest Dynamic Plots in East Asia.

Species turnover is fundamental for understanding the mechanisms that influence large-scale species richness patterns. However, few studies have described and interpreted large-scale spatial variation in plant species turnover, and the causes of this variation remain elusive. In addition, the determinants of species turnover depend on the dispersal ability of growth forms. In this study, we explored the large-scale patterns of woody species turnover across the latitude gradient based on eight large stem-mapping plots (covering 184 ha forest) in East Asia. The patterns of woody species turnover increased significantly with increasing latitude differences in East Asia. For overall woody species, environment explained 36.30, 37.20, and 48.48% of the total variance in Jaccard's (ßj), Sorenson's, (ßs), and Simpson's dissimilarity (ßsim). Spatial factors explained 47.92, 48.39, and 41.38% of the total variance in ßj, ßs, and ßsim, respectively. The effects of pure spatial and spatially structured environments were stronger than pure environmental effects for overall woody species. Our results support the hypothesis that the effect of neutral processes on woody species turnover is more important than the effect of the environment. Neutral processes explained more variation for turnover of tree species, and environmental factors explained more variation for the turnover of shrub species on a large scale. Therefore, trees and shrubs should be subjected to different protection strategies in future biodiversity conservation efforts.

Evaluation of antioxidant activity of chrysanthemum extracts and tea beverages by gold nanoparticles-based assay.

A gold nanoparticles-based (GNPs-based) assay was developed for evaluating antioxidant activity of chrysanthemum extracts and tea beverages. Briefly, a GNPs growth system consisted of designated concentrations of hydrogen tetrachloroaurate, cetyltrimethyl ammonium bromide, sodium citrate, and phosphate buffer was designed, followed by the addition of 1 mL different level of test samples. After a 10-min reaction at 45°C, GNPs was formed in the reduction of metallic ions to zero valence gold by chrysanthemum extracts or tea beverages. And the resultant solution exhibited a characteristic surface plasmon resonance band of GNPs centered at about 545 nm, responsible for its vivid light pink or wine red color. The optical properties of GNPs formed correlate well with antioxidant activity of test samples. As a result, the antioxidant functional evaluation of chrysanthemum extracts and beverages could be performed by this GNPs-based assay with a spectrophotometer or in visual analysis to a certain extent. Our present method based on the sample-mediated generation and growth of GNPs is rapid, convenient, inexpensive, and also demonstrates a new possibility for the application of nanotechnology in food science. Moreover, this present work provides some useful information for in-depth research of involving chrysanthemum.

Chitosan as an active support for assembly of metal nanoparticles and application of the resultant bioconjugates in catalysis.

Metal nanoparticle-chitosan (NPs-chitosan) bioconjugates were formed by exposure of chitosan to an aqueous solution of metal salts under thermal treatment. The metal nanoparticles that are formed strongly bound to chitosan, which encouraged us to investigate their catalytic performance. It was demonstrated that the metal NPs-chitosan bioconjugates functioned as effective catalysts for the reduction of 4-nitrophenol in the presence of NaBH(4), which was monitored by means of spectrophotometry as a function of reaction time. The silver NPs-chitosan bioconjugates exhibited excellent catalytic activity and were reusable for up to seven cycles. In contrast, the gold NPs-chitosan catalyst displayed poor catalytic activity, even in the second cycle. A highlight of our approach is that chitosan simultaneously acts as an active support for the synthesis and assembly of nanoparticles, and the resultant bioconjugates bear the advantage of easy separation from the reaction medium.

Development and characterization of microsatellite loci in Taihangia rupestris (Rosaceae), a rare cliff herb.

PREMISE OF THE STUDY: Microsatellite primers were developed for the rare Taihangia rupestris (Rosaceae) to evaluate genetic diversity, population genetic structure, mating system, and demographic events of this species. • METHODS AND RESULTS: Ten primer sets were developed using an enriched genomic library and were successfully amplified in T. rupestris var. ciliata and T. rupestris var. rupestris. The number of alleles per locus ranged from 2 to 21; the observed and expected heterozygosities ranged from 0.300 to 0.950 and from 0.328 to 0.956, respectively, in the two varieties. • CONCLUSIONS: The markers described here will be useful for studies of genetic variation, genetic structure, and mating systems of T. rupestris, which are important for the future conservation of this rare species.

The synthesis of chitosan-based silver nanoparticles and their antibacterial activity.

Chitosan-based silver nanoparticles were synthesized by reducing silver nitrate salts with nontoxic and biodegradable chitosan. The silver nanoparticles thus obtained showed highly potent antibacterial activity toward both Gram-positive and Gram-negative bacteria, comparable with the highly active precursor silver salts. Silver-impregnated chitosan films were formed from the starting materials composed of silver nitrate and chitosan via thermal treatment. Compared with pure chitosan films, chitosan films with silver showed both fast and long-lasting antibacterial effectiveness against Escherichia coli. The silver antibacterial materials prepared in our present system are promising candidates for a wide range of biomedical and general applications.

[Chitosan and its applications in synthesis of metal nanomaterials].

Chitosan has natural abundance, unique bioactivity and attractive physicochemical properties. Recent years, the synthesis of chitosan-based metal nanomaterials has attracted increasing attention. The synthesis of metal nanoparticles utilizing biomolecular or organism offers a mild medium, and thus a greater degree of control over the nanoparticles produced, along with higher reproducibility. In particular, preparation of metal nanoparticles based on biomolecular or organism has its unique facility in integrating "minimum feature sizes" into labile biological components to an excellent synergy and bifunctional effect and consequently a more broad application. Herein, we review the new development of chitosan, chitosan-based synthesis of metal nanomaterials, and their application.

[Effects of sand burying on caryopsis germination and seedling growth of Bromus inermis Leyss].

This paper studied the effects of different depth sand burying on the caryopsis germination, seedling emergence and growth of Bromus inermis Leyss., a perennial gramineous grass dominated on Othidag sandy land. The results showed that the maximum burying depth for B. inermis caryopsis germination and seedling emergence was 12 cm and 8 cm, respectively. Below the thresholds, the percentages of caryopsis germination and seedling emergence decreased with increasing depth of sand burying. All the 1- and 2-week-old seedlings of B. inermis could survive when the sand burying depth was up to 33% of their height, and their biomass was no less than the unburied seedlings. When the burying depth increased to 66% of their height, 70% of 1-week-old seedlings and 25% of 2-week-old seedlings could survive, but their growth was impaired. No seedlings could survive when they were wholly buried in sand. When buried by sand, the seedlings allocated more biomass for the development of their aboveground part, which might be an important adaptation strategy of B. inermis to sand burying.