Abstract:In order to predict the non-coevolutionary trend between invasive species with their neighbor species, the seedlings of invasive species Mikania micrantha and three neighboring species, including Ipomoea cairica, Pueraria lobata and Paederia scandens were treated with aqueous leaf extracts, the allelopathic relationship between them were studied. The results showed that the allelopathic effects of M. micrantha on the neighboring species varied with SE=0.50, 0.61, -0.16 for I. cairica, Pueraria lobata and Paederia scandens, respectively, and there was a strong promoting allelopathic effect in intraspecific M. micrantha (SE=0.61), indicating its weak intraspecific competition. The allelopathic effect of intraspecific Pueraria lobata (SE=0.32) was weaker than that of M. micrantha (SE=0.61), and its interspecific allelopathic effect was similar to that of M. micrantha (SE=0.52, 0.50). The allelopathic effect of intraspecific I. cairica (SE=0.06) was weaker than that of M. micrantha and Pueraria lobata (SE=0.32), and its interspecific promoting effect (SE=0.24) was weaker than that of M. micrantha. The intra-and inter-specific allelopathy showed inhibiting effects in Paederia scandens (SE=-0.18, -0.07), demonstrating their strong intra-and inter-specific allelopathic competition. The distribution frequency and abundance of four species in the field were in the order as M. micrantha > Pueraria lobata > I. cairica > Paederia scandens, which is consistent with the results of the allelopathy competitiveness. Therefore, the intra-and inter-specific allelopathy play a very important role in the comprehensive competitiveness of invasive species with their neigboring plants, which sheds the lights on non-coevolutionary trends between the invasive species and their neighboring species.

Abstract:In order to effectively prevent and control invasive alien species (IAS), the associations among community species composition, vegetation structure and environmental factors were analyzed based on nested plot survey of plantations in Luchuan County, Guangxi. Mantel test showed that species composition correlated stronger to vegetation structure (r=0.208, P=0.002) than to other environment factors (r=0.084, P=0.051). MRPP analysis revealed that vegetation structures of plots invaded by Spermacoce alata, or Praxelis clematidea and Ageratum conyzoides were significantly different from that uninvaded by them, but plots invaded by Mikaina micrantha had similar vegetation structure with that uninvaded. From t test, there was not significant correlation between presence-absence of 4 IASs and canopy covers (>3.0 m, P>0.073). When community vegetation density at 1.5 m above-ground increased, the invasion of S. alata, P. clematidea or A. conyzoides might reduce, except of M. micrantha. Vegetation structure as a filter may mainly act on plant seeding time, germination cycle or growth attributes, and invasions of those IASs propagating only by seeds may depend more on disturbances and bare soil; while M. micrantha which conferred with asexual and sexual reproductions and capable of climbing and creeping, may colonize relative randomly in communities of varied vegetation structures.

Abstract:In order to understand the response of trees to elevated CO₂, N addition and Cd stress, the growth characters of Acacia auriculiformis, such as basal diameter, tree height and individual biomass, were studied using an open-top chamber (OTC). The results showed that the basal diameter, height and individual biomass of A. auriculiformis were significantly inhibited under Cd stress, and the inhibition effect was with a lag time. Both elevated CO₂ and N addition remitted the inhibition of Cd stress on A. auriculiformis growth, N addition could promote the base diameter growth of A. auriculiformis, and tree height growth was more sensitive to CO₂ enrichment. Under Cd stress, the biomass accumulation of A. auriculiformis was mainly caused by N addition. So, it was suggested that N fertilization management was an important strategy to promote phytoremediation in the early stage of heavy metal contaminated land remediation.

Abstract:In order to explore the adaptability of Ilex asprella under shading environment, the growth, photosynthetic parameters, and biomass of I. asprella were studied under three light environments, including 85% shading, 56% shading, and full sunlight. The results showed that the contents of chlorophyll a, b, and a+b of I. asprella leaves significantly increased with shading intensity increment, while the content of carotene decreased significantly after one year shading. Compared with control, 56% shading significantly increased the maximum net photosynthetic rate by 17.6% and light saturation point by 25.2%, whereas 85% shading decreased the maximum net photosynthetic rate by 18.2% and light saturation point by 24.1%. The light compensation points significantly decreased under both 85% and 56% shading. The length, width, area, and water content of leaves, specific leaf area increased significantly under shading, but the leaf thickness reduced. The individual biomass and root shoot ratio significantly decreased under shading, but the response of plant height, crown area, and radial growth varied with the shading duration. Therefore, Ilex asprella is shade-tolerant and heliophilous species, it is critical to adjust the light transmittance of the canopy layer when planting in understory layer. Generally, the light transmittance of canopy should be greater than 44%.

Abstract:In order to understand the effect of continuous planting of Eucalyptus grandis on biomass and number of soil microbes, the relationships between soil microbial biomass, number of major microbial groups with soil physicochemical properties in Pinus massoniana forest and E. grandis plantations at different rotations were studied by using space-time interchange method. The results showed that the soil microbial biomass carbon, biomass nitrogen and number of bacteria and fungi in the first rotation plantations of E. grandis had not significant difference from those in P. massoniana forest, but the number of actinomycetes significantly increased. However, with the increasing rotation of Eucalyptus grandis continuous plantations, the soil microbial biomass carbon, biomass nitrogen and the number of bacteria, actinomycetes and fungi decreased. Stepwise regression analysis showed that soil total phosphorus could independently explain 71.7%, 86.1% and 63.0% variation of the microbial biomass nitrogen, the number of bacteria and fungi, respectively. Soil total phosphorus together with total porosity could explain 87.9% variation of microbial biomass carbon, and 89.6% variation of the number of actinomycetes together with total nitrogen. So, it could be concluded that soil total phosphorus well explained the variation of soil microbial characteristics in E. grandis plantations.

Abstract:In order to understand the succession dynamics and biodiversity maintenance mechanism of forest community in karst area, the species composition, flora characteristics, species diversity and population structure of Pinus armandii forest in Caohai National Nature Reserve by using sample-plot survey. The results showed that there were 81 species of seed plants, belonging to 21 families and 39 genera, including 11 species of trees, 32 species of shrubs and 38 species of herbs. The floristic type of families and genera was complex mainly composed by temperate element. The main life-form spectrum was dominated by phanerophytes (46.91%) and hemicryp-tophyte (27.16%). Pinus armandii was the single dominant species with importance value of 58%; the diameter structure was a skewed normal distribution (left-biased type), and the distribution of tree height was focused on 12-21 m, and the distribution of e crown was V type. There was a significant difference in the diversity between tree layer with shrub layer and herb layer. The species richness indexes, S and D_M, and diversity indexes, H and D_S, were in the order of herbaceous layer > shrub layer > tree layer, and the evenness index (J) was shrub layer > herb layer > tree layer. So, the characteristics of P. armandii community and species diversity in Caohai National Nature Reserve have obvious regional features.

Abstract:In order to understand the effect of drought stress on the growth of Phalaenopsis pulcherrima, the changes in contents of photosynthetic pigments, osmotic adjustment substances and non-structural carbohydrates in leaves were studied. The polyethylene glycol 6000 (PEG) solution was used to simulate drought stress. The results showed that plant water content and fresh weight decreased gradually with increment of PEG concentration, and plant water content and fresh weight decreased significantly treated with PEG from 13.75% to 14.84%. The contents of chlorophyll a and b decreased significantly in leaves treated with PEG. With the decreasing of plant water content, the contents of soluble protein and starch (St) decreased gradually, while the soluble sugar (SS), NSC (non-structural carbohydrate), and SS/St in leaves increased at first and then decreased. Therefore, the drought stress simulated by PEG could significantly affect plant water content and accumulation of photosynthetic products in leaves. Under light drought stress, soluble sugar played an important role in resistance to drought, while the physiological metabolism of P. pulcherrima would be seriously influenced under severe drought stress.

Abstract:In order to understand the effect factors on the relationship between plant adaptation mechanism and spatial pattern within population, epigenetic variation characteristics of two populations of Castanopsis chinensis at different succession stages in Dinghushan were analyzed by using DNA methyl-sensitive amplified fragment polymorphism (MSAP). The results showed that the contribution of microhabitats to epigenetic variation decreased from 20.2% in mature forests to 15.7% in over-mature forests, but the influence of topographic factors increased. At the same time, the environmental factors in microhabitats that played a significant role to methylation variation were different between the two forests. So, it was suggested that microhabitat characteristics had partial significant effects on population adaptation mechanism and distribution pattern, and did the succession stage.

Abstract:In order to understand the mechanism of antioxidant responses of mango leaves to enhanced UV-B radiation, the adult trees of Mangifera indica ‘Tainong No. 1’ were treated with enhanced UV-B radiation of 24 and 96 kJ/(m²·d), respectively, with the natural sunlight as control (CK), and the dynamic changes in physiological and biochemical indexes were studied. The results showed that MDA content, relative electrical conductivity, net photosynthetic rate, antioxidant enzyme activities, contents of polyphenols, Vc and mangiferin in leaves treated with 24 kJ/(m²·d) UV-B were not significantly different from CK, while flavonoids and reduced GSH contents were significantly higher than CK. MDA content, relative electrical conductivity, antioxidant enzyme activities, polyphenols, flavonoids, reduced GSH, mangiferin and other reduced protective components were significantly higher than CK treated with 96 kJ/(m²·d) UV-B, while net photosynthetic rate and Vc content were significantly lower than CK. Therefore, the adult mango trees has not been injured under 24 kJ/(m²·d) UV-B, probably through increasing the content of flavonoids and reduced GSH to scavenge reactive oxygen species. The leaves were damaged by reactive oxygen species treated with 96 kJ/(m²·d) UV-B, but it could still reduce the damage by two mechanisms, at first, enhancing the activities of antioxidant enzymes, such as SOD, POD, CAT, and increasing the contents of reducing components, such as polyphenols, flavonoids, reduced GSH, Vc and mangiferin, at the second, mangiferin, flavonoids and reduced GSH could absorb UV-B radiation.

Abstract:To understand the effect of arbuscular mycorrhizal (AM) fungi on secondary metabolism in root and root exudates and plant growth, Citrus reticulata was inoculated by AM fungus Glomus epigaeum, the phenolic, antioxidant enzyme and growth of C. reticulata were studied. After six months cultured in greenhouse, the concentrations of phenolic acids in C. reticulata inoculated with AM fungus significantly increased. However, the components of phenolic acid were different in root and root exudates, the contents of protocatechunic acid and syringic acid in roots was 29.98 and 18.32 μg/g, which were 4.58 and 2.26 times higher than those in control, respectively. The contents of coumaric acid, benzoic acid and phloridzin were 0.36, 6.04 and 12.32 μg/g, respectively, which were 1.71, 1.94 and 1.25 times higher than those in control. Whereas vanillin was only detected in uninoculated roots. The enzyme activities of phenylalnine ammonia-lyase, polyphenol oxidase and peroxidase in C. reticulata inoculated with AM fungus were 38.36, 0.51 and 28.62 U/(g·min), respectively, which were 1.99, 2.83 and 3.10 times higher than those in control. In addition, the height, stem diameter and leaf number of C. reticulata inoculated with arbuscular mycorrhizal fungi also significantly increased. It was suggested that AM colonization could significantly affected the growth and secondary metabolites in C. reticulata.

Abstract:To establish the rapid propagation system of Lavandula angustifolia, the optimal culture condition for seed germination, callus induction, cluster bud differentiation and rooting were studied by using seeds, stems, and leaves as explants. The volatile oil of L. angustifolia were extracted by steam distillation, and components of volatile oil were analyzed by gas chromatography-mass spectrometry. The results showed that the optimal time for soaking seeds was 6 h, and the shortest germination time was 6 days after the seed coat cut open. The optimum medium for seed germination was MS+6-BA 2 mg/L. The optimum medium for callus induction from stem was MS+6-BA 2 mg/L+2,4-D 1 mg/L. The optimum medium for cluster bud differentiation was MS+6-BA 1 mg/L+ NAA 0.5 mg/L. The optimum medium for rooting was 1/2MS+NAA 1 mg/L+6-BA 0.5 mg/L. The essential volatile oils of L. angustifolia cultured in pot and in vitro were different, those in vitro culture contains phytol, caryophyllene, caryophyllene oxide and so on.

Abstract:Porina byssophila, Sarcogyne privigna and Trimmatothelopsis versipellis collected from Mt. Kunyu in Shandong Province, are reported as new record species to China. The detailed description of morphology, anatomy, chemistry and the distribution are also given.

Abstract:Three species of Biatora, including B. alaskana, B. alborufidula and B. longispora, are reported from China for the first time. The morphological, anatomical, and chemical characteristics were described. The key to the known species of Biatora in China is presented.

Abstract:Cuminum borszczowii (Regel et Schmalh.) Koso-Pol. is reported for the first time in China. It is similar to C. cyminum, but differs from the latter by having broadly lanceolate bracts, with wide membranous margins and mericarps covered with densely irregular long hairs. A detailed morphological description and photos of this species are given. Voucher specimens are deposited in the Herbarium of Xinjiang Agricultural University (XJA) and the Herbarium of the Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences (XJBI).

Abstract:The increase of nitrogen deposition has altered ecosystem structure and function. As key bioindicators of soil ecosystems, soil nematodes have important ecological implications. With the globalization of nitrogen deposition, it has attracted widespread attention on how elevated nitrogen inputs affect soil nematode. The response pattern and mechanism of soil nematodes to elevated nitrogen deposition in terrestrial ecosystems (grassland, farmland and forests) were reviewed. In general, elevated nitrogen deposition had no significant effects on the number of soil nematodes, but increased the number of enrichment opportunist (i.e. r-strategy nematodes with low trophic levels) and decreased soil nematode maturity index (MI), indicating that the increase of nitrogen inputs might simplify soil food webs. Moreover, elevated nitrogen deposition could affect the soil nematode community directly by changing soil microenvironment, such as increased NH₄⁺ and NO₃^- concentration and decreased soil pH, or indirectly by changing plant resource inputs and the relationships between the nematodes and other soil biota. In the end, some limitations of previous studies were pointed out, including temporal and special scales, and measurement techniques. To better understand the effects of global environmental changes, it is urgent to explore how multiple global change factors affect soil nematode communities across different terrestrial ecosystems. It was suggested to combine both molecular biology techniques and laboratory incubation methods in the future.