Many grasses are infected by systemic fungal endophytes that occur in aboveground plant tissues. Both aboveground endophytic fungi and belowground soil microbes can influence plant growth, but studies on their simultaneous effects on plant growth and competitiveness are limited. This study aims to investigate whether the role of aboveground endophytic fungi in the growth and competitive ability of the host grasses was influenced by soil microbes. In this study, we used Epichloë endophyte-infected and endophyte-free Achnatherum sibiricum as plant materials. A wet sieving method was adopted to obtain microbial inocula with different diversities (com, combined microbe fraction, high diversity; sm, small microbe fraction, low diversity). A three-factor randomized block design was used. The first factor was the endophyte infection status of A. sibiricum. The second factor was the microbial composition of the soil inocula. The third factor was the planting type. Growth and competitive characters were measured after 16 weeks. The results showed that a soil microbe inoculation was detrimental to the growth of A. sibiricum. Epichloë endophytes significantly mitigated the inhibitory effect of soil microbes on A. sibiricum planted alone. When A. sibiricum was planted with Stipa grandis, there was a significant interaction between Epichloë endophytes and soil microbes on the interspecific competition of A. sibiricum. When inoculated with small microbial community fraction, Epichloë endophytes significantly improved the interspecific competitive ability of host plants. When inoculated with combined microbial community fraction, however, Epichloë endophytes had no significant effect on host competition. The results showed that the interaction between Epichloë endophytes and soil microbes contributed more to the interspecific competitive ability than either Epichloë endophytes or soil microbes alone.

Soil microorganisms and their diversity are important bioindicators of soil carbon and nutrient cycling. Land use type is a major determining factor that influences soil microbial community composition in floodplain ecosystems. However, how the structure and diversity of soil microbial communities respond to specific changes in land use, as well as the main drivers of these changes, are still unclear. This study was conducted in the Yellow River floodplain to examine the effects of land use type on soil microbial communities. Four land use types (shrubland, farmland, grassland and forest) were selected, wherein shrubland served as the baseline. We measured soil microbial structure and diversity using phospholipid fatty acids (PLFAs). Land use type significantly affected total, bacterial and fungal PLFAs, and the gram-positive/negative bacterial PLFAs. Compared with shrubland, peanut farmland had higher total and bacterial PLFAs and forest had higher fungal PLFAs. Soil pH and phosphorus were the predominate drivers of microbial PLFAs, explaining 37% and 26% of the variability, respectively. Soil total nitrogen and nitrate nitrogen were the main factors increasing microbial community diversity. Peanut farmland had the highest soil carbon content, soil carbon stock, total PLFAs and microbial diversity, suggesting that farmland has great potential as a carbon sink. Our findings indicated that peanut farmland in the Yellow River floodplain is critical for maintaining soil microbial communities and soil carbon sequestration.

Grazing and mowing are two major land use types in natural grasslands, which have intensive effects on nutrient cycling of grassland ecosystems by deposition of fecaluria nutrient versus removal of hay nutrient. Plant nutrients sensitively respond to the changes in nutrient cycling, while the information on the effects of diverse grazing versus mowing regimes on plant nutrients at different organs or levels are incomplete. A field experiment was conducted to compare the effects of continuous versus rotational grazing, and low versus high mowing frequencies on grassland ecosystems in a semiarid steppe of Inner Mongolia. Plant community characteristics and C, N and P concentrations of dominant species were determined across different managements. We found (i) plant community height and standing biomass significantly decreased with grazing intensity under both continuous and rotational grazing and under annual mowing. (ii) Plant shoot C concentration decreased, whereas N and P concentrations increased with grazing intensity in the two grazing regimes, while these concentrations showed no significant changes in response to the two mowing regimes. (iii) Plant community aboveground C, N and P pools significantly decreased with grazing intensity of both grazing regimes, but did not decrease with mowing frequency in the two mowing regimes. (iv) Plant root C, N and P concentrations showed little significant response to different grazing or mowing regimes, indicating a relatively bigger stability or slower response in plant root nutrients. Our study provides insights into the nutrient cycling in grazing and mowing grassland ecosystems from multiple perspectives.

Fire frequently causes strong disturbance in forests. Belowground fungi are sensitive to forest fire disturbance and can affect vegetation restoration. Our objective was to investigate the responses of belowground fungi under two tree species to forest fire in a mixed forest in Yunnan Plateau. Samples from three ‘sample sites’ (roots, rhizosphere soil and bulk soil) were collected from two plant species, Pinus yunnanensis and Eucalyptus citriodora, and were analyzed for fungal diversity and community composition. Fungi were identified using high-throughput sequencing. Shannon index and principal coordinate analysis were used for diversity and network analysis. LEfSe and FUNGuild were used to analyze the community composition, trophic mode and guild. Alpha diversity in bulk soil was higher than that in rhizosphere soil and roots, while the community composition was significantly different among the three sample sites. Fungal network complexity of E. citriodora was higher than that of P. yunnanensis. The relative abundance of Mucoromycota in the three sample sites was higher for P. yunnanensis than E. citriodora. Most of the top 10 dominant genera of the two plant species were saprotrophic fungi. In the comparison of biomarker, ectomycorrhizal fungi dominated in the roots and rhizosphere soil of P. yunnanensis, while both saprotrophic fungi and symbiotic fungi were in the roots and rhizosphere soil of E. citriodora. Our findings suggest that, following a forest fire, responses of fungal community are species-specific in Yunnan Plateau.

Soil biota, as legacy effects of previous species in natural ecosystems, profoundly affects plant performance in new habitats and, in turn, plant community. However, how soil biota, as legacy effects of agricultural crops, affects the likelihood of establishment of exotic and native plants in newly abandoned farmland remains poorly understood, which may hinder effective management of agricultural weeds. Here, we grew 58 plant species (28 exotic species and 30 native species) common in Central China in sterilized vs. nonsterilized soils collected from a newly abandoned maize field. We (i) estimated the effects of soil biota on plant shoot, root and total mass, (ii) explored the dependence of soil effects on the plants’ phylogenetic distance to maize, origin (native vs. exotic) and life history (annual vs. perennial) and (iii) tested which plant traits could predict soil effects. Soil biota, in general, decreased plant mass, suggesting a dominant role of enemies. The effect of the soil biota on plant total mass was unrelated to the phylogenetic distance of the plants to maize and decreased linearly with increasing plant intrinsic growth ability. Moreover, the soil biota on average had greater negative impacts on the total mass of exotic plants, particularly perennial species, than on that of native plants. Our results suggest that plant intrinsic growth ability, rather than phylogenetic relatedness, is a reliable predictor of soil effects. Additionally, native plants can benefit from plant–soil interactions in competing with exotic perennial plants when initially established in newly abandoned farmlands.

Accelerated global warming in the late 20th century led to frequent forest-decline events in the Northern Hemisphere and increased the complexity of the relationships between tree growth and climate factors. However, few studies have explored the heterogeneity of responses of tree growth to climate factors in different regions of the Northern Hemisphere before and after accelerated warming. In this study, a total of 229 temperature-sensitive tree-ring width chronologies from nine regions on three continents in the Northern Hemisphere were used in the data analysis performed herein. A bootstrapped correlation analysis method was used to investigate whether the tree growth-climate response changed significantly in different regions between the periods before and after rapid warming. Probability density functions and piecewise linear fitting were used to study the fluctuation characteristics of the tree-ring width indices before and after rapid warming. At the end of the 20th century (from 1977 to 2000), rapid warming significantly promoted the radial growth of trees in different regions of the Northern Hemisphere, but tree radial growth was heterogeneous among the different regions from 1950 to 2000. After 1976, except in central North America and northern Europe, the correlation between tree growth and temperature increased significantly in the Northern Hemisphere, especially in Asia. From 1977 to 2000, tree-ring index and temperature divergences were observed in nine regions with a divergence of 2–5 years. From 1950 to 2000, tree growth tracked better average temperature variability in the Northern Hemisphere than regional temperature.

The relationship between biodiversity and ecosystem functioning has become a central issue in any forest ecosystem. However, there are few studies on the interaction of environmental factors based on the history of subtropical forest disturbance. In this study, we intended to disentangle the relationship between different aspects of biodiversity and biomass or biomass change when considering the environmental factors of 34 subtropical forest plots in Zhejiang Province, eastern China. We used linear models to analyze the effects of taxonomic, functional and phylogenetic diversity at the plot level of tree biomass and its growth with or without environmental factors. Taxonomic diversity and functional diversity, rather than phylogenetic diversity, showed significant correlations with biomass and biomass growth. We further found that there was a positive linear relationship between biomass or biomass growth and mean annual temperature and altitude. In addition, the relationship between biomass growth and functional diversity was significantly stronger than the relationship between biomass growth and phylogenetic diversity or taxonomic diversity when environmental factors and stand developmental stages were considered. Our results suggested that the relationship between biodiversity and ecosystem functioning is dependent upon the selection of diversity index and environmental conditions.

Transgenerational effects in plants incur opposing effects on the adaptation to predictable vs. unpredictable environments. While seed-dimorphic plants can produce dimorphic offspring with different adaptive strategies, it remains unclear whether the transgenerational effects and seed dimorphism may interact to dictate offspring adaptation. This study aimed to explore whether and how seed-dimorphic maternal plants impart different transgenerational effects to dimorphic offspring. Synedrella nodiflora was chosen as a study species, which is adaptive to a wide soil water gradient and produces two distinctive types of seeds (light disc vs. heavy ray seeds). In a greenhouse, S. nodiflora was grown for two generations under drought stress to test whether the transgenerational effects on offspring performance and mortality depend on maternal (MS) or offspring seed morph (OS). The potential regulatory mechanisms were explored by measuring seed provisioning and chemical regulators of maternal plants and related reproductive processes. The transgenerational effects depended on both MS and OS. Drought stress induced the maternal plants originated from ray seeds to increase the relative proportion of ray- vs. disc-seed offspring and transmit stronger adaptive transgenerational effects to the former, whereas its effects on the maternal plants originated from disc seeds were exactly opposite. These different effects on offspring corresponded with different seed abscisic acid and soluble sugar contents but not seed provisioning. Dimorphism-dependent transgenerational effects allow large divergence of drought tolerance among offspring, which may be an important but under-explored mechanism to balance the needs of population maintenance and range expansion in seed-dimorphic species.

Fungal communities related to invasive plants may change with an elevational gradient, which may affect the performance and invasiveness of invasive plants. Our recent study revealed that root arbuscular mycorrhizal fungi colonization rate of invasive plant Galinsoga quadriradiata decreased with elevation. However, it is unclear whether it is caused by the changes in the fungal community along elevation. To address this issue, we used high-throughput sequencing techniques, functional groupings and linear statistics to examine how fungal communities in the rhizosphere and roots of G. quadriradiata are changed across the elevation in Qinling and Bashan Mountains, China. Our results revealed that species diversity and composition of the rhizosphere and root fungal communities changed along the elevation. The Shannon–Wiener diversity index in the rhizosphere and roots increased and decreased with elevation, respectively. In contrast, the relative abundance of pathotroph in the rhizosphere decreased while it increased in the roots with elevation. These suggest that, when the invasive plant colonizes into high altitudes, it may not suffer from limited rhizosphere fungal symbionts, but rather the ability of the plant to create and maintain these associations decreases. The invader tends to accumulate more pathogenic fungi in the roots, while the dependence on symbiotic fungi is reduced during expansion into higher elevations. These results highlight that the interactions between invasive plants and fungal community substantially change along elevation, and that belowground interactions may be key in our understanding of how invasive plants derive success in stressful, high-elevation environments.

Evergreen broad-leaved forest (EBLF) is climax vegetation in East China, and Jiangxi Province is located at the center of EBLF. Although many phytosociological studies have provided detailed descriptions on this forest at local and regional scales, knowledge on the high-level classification of EBLF and factors controlling their tree species composition and distribution are still lacking. We aim at providing a high-level classification framework for EBLF in Jiangxi and exploring the roles of topographic and climatic factors in driving their distributions. We investigated 205 EBLF plots covering the main alliances across Jiangxi Province. Two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis (DCA) were used to distinguish the EBLF types. Diagnostic and indicator species were detected. The nonparametric Kruskal–Wallis test was used to compare the differences between the groups of EBLFs. We also used redundancy analysis and variation partitioning to estimate the effects of climatic, geographical and topographical factors on the distribution of EBLFs in Jiangxi. The EBLFs in Jiangxi were classified into four types based on the diagnostic taxa and verified by TWINSPAN, i.e. lowland, ravine monsoon, montane typical and dwarf cloud EBLF types. These four EBLF types are associated with climatic and topographic conditions, and their distribution pattern reflects biogeographic differences. Our study provides an important basis for the syntaxonomic classification of EBLFs and further in-depth studies on humid EBLFs in East China. We also emphasize the importance of conservation practices to protect these forests as diversified Tertiary relict plants.

Two key hypotheses in invasion biology are that certain traits underlie invasiveness in introduced species, and that these traits are selected for during or after introduction. We tested these hypotheses by focusing on two traits likely to confer invasiveness, high increase in growth in response to increase in nutrients and low decrease in growth in response to competition. We compared four species of Carpobrotus that differ in invasiveness, using species from four continents: Africa, Australia, Europe and North America. To test for selection for these traits in Carpobrotus edulis, a highly invasive species, we compared plants from its native range in South Africa to plants from the other three regions, where C. edulis has been introduced. Plants were propagated in a common garden. Offspring were then grown alone with or without added nutrients, and together with another species of Carpobrotus or with the grass Ammophila arenaria (a co-occurring native species in Europe) without added nutrients. Response to nutrients did not differ between species of Carpobrotus, nor was competitive response less negative in more invasive species. However, increase in growth in response to added nutrients was greater in introduced than in native C. edulis. Moreover, fresh mass per ramet at the start of treatments was higher in the two invasive species than in the two non-invasive ones. We provide new evidence that introduction can select for response to nutrient enrichment in invasive species and add to the evidence for an association between size and invasiveness in introduced plants.

River deltas are hot spots of biogeochemical cycling. Understanding sources and driving factors of dissolved organic matter (DOM) in river deltas is important for evaluating the role of river deltas in regulating global carbon flux. In this study, spectroscopic properties of soil DOM were analyzed in both freshwater and tidal areas of the Yellow River Delta. Five fluorescent components of soil DOM (two humic-like DOM, two protein-like DOM and one possible contaminant) were identified by parallel factor analysis and further confirmed by comparison with an online database. Concentration, spectroscopic properties and sources of soil DOM and its components differed between freshwater and tidal areas. DOM concentration was much higher in freshwater areas than in tidal areas. In freshwater areas, soil DOM was mainly derived from phytoplankton and microorganisms, while it was mainly derived from microorganisms and human activities in tidal areas. These differences in DOM between both areas were strongly driven by environmental factors, especially soil carbon (C), nitrogen (N) and its stoichiometric ratio C/N. These explained 80.7% and 69.6% of variations in DOM and chromophoric DOM (CDOM), respectively. In addition, phytoplankton also contributed to soil DOM, CDOM and fluorescent components C1–C4 as identified by significant positive correlations between them. These results imply that both the concentration and composition of soil DOM are strongly driven by soil properties and phytoplankton density in the Yellow River Delta.

Although tropical dry forests are among the most degraded and fragmented biomes in the world, we still have a poor understanding of their basic ecological features and conservation status, particularly in the Neotropics. Here, we assess the diversity, composition, structure and conservation value of tropical dry forests in a highly fragmented landscape in Nicaragua. We established 31 plots and transects in and along river corridors, secondary forests, living fences and pasture-woodlands. We recorded all trees with diameters at breast height ≥ 2.5 cm using Hill numbers (^qD, where q = 0, 1 or 2) and estimated the richness and diversity of trees in each forest type. We calculated the Importance Value Index (IVI) to species and family levels and, finally, performed a Non-Metric Multidimensional Scaling (NMDS) ordination and an Analysis of Similarities (ANOSIM) using the Bray–Curtis index of similarity. Diversity (¹D, ²D) but not species richness (⁰D) differed between forest types (P = 0.01 and 0.66, respectively). IVI was highest for the legume family Fabaceae, followed by the Moraceae and Malvaceae (27.8, 11.1 and 10.5, respectively). Vachellia pennatula, Guazuma ulmifolia and Bursera simaruba had IVIs >30%, the former two being the most abundant trees in all forest types. An analysis of community similarity revealed that each forest type had a distinct composition (P < 0.01, R² = 0.30), thereby underlining the importance of conserving all these different types of land cover.

Compositae family comprises the largest number of species of invasive alien plants (IAPs) in China. Two IAPs can co-invade the same habitat. Drought can alter the litter decomposition of IAPs and soil enzyme activities. This study aims to estimate the independent and combined effects of two composite IAPs (Bidens pilosa and Solidago canadensis) on litter decomposition and soil enzyme activities under drought. A polyethylene litterbags experiment (5 g litters of B. pilosa, 5 g litters of S. canadensis or 5 g litters of B. pilosa and S. canadensis in an equal proportion per polyethylene litterbag) was performed. The polyethylene litterbags were treated with a gradient of drought, i.e. control, light level of drought and heavy level of drought. The decomposition coefficient of the two composite IAPs and soil enzyme activities was determined. The co-invasion of the two composite IAPs posed a synergistic effect on urease activity. The mixed litters of two composite IAPs and the litters of B. pilosa had higher decomposition rates than S. canadensis. Urease activity was increased in light droughts, but it was decreased in heavy drought. Heavy drought reduced the decomposition rate of the mixed litters of two composite IAPs and the litters of B. pilosa. Drought did not affect the decomposition rate of S. canadensis litters. Thus, heavy drought can decrease the nutrient cycling rate under the co-invasion of the two composite IAPs and the independent invasion of B. pilosa rather than the independent invasion of S. canadensis.

While the relationship between genetic diversity and plant productivity has been established for many species, it is unclear whether environmental conditions and biotic associations alter the nature of the relationship. To address this, we investigated the interactive effects of genotypic diversity, drought and mycorrhizal association on plant productivity and plant traits. Our mesocosm study was set up at the Konza Prairie Biological Research Station, located in the south of Manhattan, Kansas. Andropogon gerardii, the focal species for our study, was planted in two levels of genotypic richness treatment: monoculture or three-genotype polyculture. A rainout shelter was constructed over half of the experimental area to impose a drought and Thiophanate-methyl fungicide was used to suppress arbuscular mycorrhizal fungi in selected pots within each genotypic richness and drought treatment. Genotypic richness and mycorrhizal association did not affect above-ground biomass of A. gerardii. Drought differentially affected the above-ground biomass, the number of flowers and bolts of A. gerardii genotypes, and the biomass and the functional traits also differed for monoculture versus polyculture. Our results suggest that drought and genotypic richness can have variable outcomes for different genotypes of a plant species.

Measuring plant heights one by one is an important way to explore the height structure of grassland plant communities, and can be used to analyze the universal rules and regional variations of vegetation growth under environmental change. We chose grasslands in three plateaus, namely Tibetan Plateau (TP), Mongolian Plateau (MP) and Loess Plateau (LP), and set up three grassland transects along the precipitation gradients from meadow, steppe to desert. The mean height of grassland vegetation was 30.38 ± 22.44 cm, and the mean height from TP, MP to LP increased significantly. The aggregation of grassland vegetation exhibited a positive skew distribution (0.91, 3.60), and the community aggregation from TP, MP to LP tended to a normal distribution (0, 3). However, for TP, there was an exponential distribution in community aggregation of meadows, and a uniform distribution in that of desert. The explanatory effect of climate and soil nutrients on the variation of mean height in each region was more than 70%, while the explanatory effect on the community aggregation was the highest at TP, only 29%. From TP, MP to LP, response intensity of mean height to environmental changes increased significantly, and the influence of temperature and precipitation gradually increased, the influence of radiation, wind speed, and nutrients gradually weakened, and the synergy among environmental factors strengthened. Our study shows that normal distribution is a universal rule of grassland height construction, and that the synergy of environmental factors varies from region to region.