Leaf chemistry plays a central role in structuring phyllosphere microbiomes. Plant populations often evolve genetic differences in leaf chemistry across region due to both abiotic and biotic selection pressures, including insect herbivory. Plants in invasive populations may reassociate with native specialist insects, providing an ideal system to examine how herbivory-mediated changes in plant chemistry affect phyllosphere microbiome. Here, we conducted a common garden experiment using Ambrosia artemisiifolia populations differing in leaf chemistry and reassociation history with a specialist beetle—Ophraella communa. We found that plant populations with a longer reassociation history exhibited stronger herbivore resistance and supported phyllosphere communities with higher alpha diversity and more complex composition. These changes were associated with shifts in concentrations of plant metabolites and the expression levels of corresponding biosynthetic genes. The abundance of the fungal pathogens, Golovinomyces, decreased with increasing herbivore resistance, while Pestaliopsis showed the opposite trend. Although reassociation history was linked to population latitude, climatic and soil conditions at the sites of origin also contributed to between-population variation in leaf chemistry and phyllosphere fungal community composition. Our study suggests that genetic differences in leaf chemistry among plant populations can strongly affect herbivore resistance and phyllosphere fungal communities. The observed alignment of reassociation history, chemical traits and phyllosphere fungal communities suggests that herbivore-mediated selection may be a key driver of microbial community evolution in invasive plants.

Land tillage disturbances and nutrient enrichment profoundly alter ecosystem processes and functions. Previous studies have explored the effects of tillage disturbance and nutrient enrichment on plant communities and soil properties. However, integrated studies of the effects of tillage disturbance and nutrient enrichment on multiple below-ground ecological processes and functions are needed. Here, we conducted a field experiment in the Hulunber grassland, establishing four treatments (control, tillage disturbance (D), nutrient enrichment (NPKμ) and tillage disturbance plus nutrient enrichment (NPKμD)) to examine their influences on plant communities, soil microbial communities, and carbon mineralization. Compared with the D treatment, the NPKμD treatment increased plant community biomass through a significant 13-fold rise in annual and biennial plant biomass (P < 0.01). Both the D treatment and NPKμD treatment significantly decreased the Shannon index of plant communities (P < 0.05). Microbial network complexity increased under NPKμ treatment whereas the D treatment reduced it. Both D treatment and NPKμ treatments significantly reduced soil carbon mineralization, and NPKμ exacerbated the negative effects of tillage disturbance (P < 0.05). Partial Least Squares Path Modeling showed that plant diversity, biomass and soil properties influenced soil carbon mineralization directly and indirectly via soil bacterial and fungal communities. Our findings suggest that nutrient enrichment promotes the recovery of plant community productivity after disturbance, while the recovery of plant diversity and soil microbial community structure may require a longer period. Therefore, achieving comprehensive ecological integrity characterized by stable plant community structure and healthy soil microbial communities requires long-term dynamic monitoring and targeted management strategies.

Warm temperate forests have the large potential to sequester atmospheric carbon dioxide (CO₂), while the interannual variability (IAV) of net forest ecosystem carbon exchange (NEE) in the global carbon cycle is still not fully understood. In this study, we conducted eddy-covariance measurement to investigate the IAV of carbon fluxes and concurrent influencing factors in a warm temperate natural oak forest from 2017 to 2022. Our results showed the natural oak forest was a strong CO₂ sink with an increase of 27.79 g C m⁻² a⁻¹ in annual carbon sequestration, resulting from a larger increase in annual gross primary production (GPP) than that of annual ecosystem respiration (Re). Precipitation in spring (PPT_spring) negatively influenced annual GPP, soil water content in spring (SWC_spring) negatively influenced annual Re, while the water conditions had lesser effect on annual NEE attributing to the synchronous changes of annual GPP and annual Re. Increase of temperature in autumn (Ta_autumn) delayed the end date of the growing season, leading to the increase in annual carbon sequestration. In addition, carbon fluxes did not significantly decrease under dramatic reduction of summer precipitation, indicating that warm temperate natural oak forest had a high resistance to seasonal drought. Our study helped us to better understand the mechanisms underlying forest carbon fluxes in response to drought in the context of future climate change.

Carbon (C) quality of non-leaf litter is closely related to decomposition rate and plays a vital role in terrestrial ecosystem C sequestration. However, to date, the global patterns and influencing factors of non-leaf litter C quality remain unclear. Here, using meta-analysis method, we quantified the characteristics and driving factors of the initial C quality of non-leaf litter (bark, branch, flower, fruit, root, stem, and wood) with 996 observations collected from 279 independent publications, including the concentrations of total C, lignin, cellulose, and hemicellulose. Results showed that (1) only total C and cellulose concentrations significantly varied among different types of non-leaf litter; (2) C quality is higher (i.e., lower concentration) in bark, branch, root, stem and wood litter from angiosperms than gymnosperms, from herbaceous than woody plants, from broadleaved than coniferous trees, and from arbuscular mycorrhizal (AM) than ectomycorrhizal (ECM) plants (except for hemicellulose concentration); and (3) the impacts of different geographic features on C quality of non-leaf litter differed among different litter types, while soil properties generally exhibited strong impacts. Overall, our results clearly show the global patterns of C quality and associated influencing factors for different types of non-leaf litter, which would be helpful for a better understanding of role of non-leaf litter in terrestrial ecosystem C cycling and for the improvement of C cycling models.

Xanthium italicum is a globally distributed invasive weed that causes significant ecological and agricultural damage in the invaded areas. Although multiple mechanisms have been reported to contribute to its invasive success, the extent to which intraspecific differentiation and phenotypic plasticity facilitate this process in invaded habitats remains insufficiently understood. In this study, we conducted a common garden experiment with three nitrogen treatments: no nitrogen addition (NN), low nitrogen (LN: 2 g urea per pot), and high nitrogen (HN: 4 g urea per pot). Ten populations of invasive X. italicum (ten individuals per population, 100 individuals total) and native Xanthium sibiricum (excluded from the NN treatment due to seed limitations) were grown under each nitrogen treatments. Under the NN treatment, we detected significant phenotypic differences among different invasive X. italicum populations across six growth traits (root length, shoot length, crown breadth, base diameter, relative chlorophyll content, and biomass). Furthermore, when subjected to the LN and HN treatments, invasive X. italicum exhibited significantly higher phenotypic plasticity compared with that of native X. sibiricum in biomass and base diameter. Our findings suggest that phenotypic plasticity and intraspecific differentiation may play important roles in facilitating the invasive success of X. italicum in China, potentially increasing the risk of further biological invasion.

Groundwater depth is a key environmental factor influencing the composition and structure of plant communities in coastal ecosystems. However, effects of the groundwater depth on the characteristics of shrub-grass communities in muddy coastal zones remain poorly understood. In this study, we conducted a field experiment to evaluate effects of the different groundwater depth (0.54, 0.83, 1.18, 1.62, and 2.04 m), on soil salinity, soil moisture, community diversity, distribution pattern and growth of the dominant Tamarix chinensis in the muddy coastal zone of Bohai Bay. Our results demonstrated that (1) the soil moisture and salinity gradually decreased with increasing groundwater depth (P < 0.001); Compared to the 0.54 m groundwater depth, soil moisture at depths of 0.83, 1.18, 1.62, and 2.04 m decreased by 16.02%, 24.83%, 54.40%, and 61.24%, and soil salinity decreased by 43.17%, 50.82%, 63.93%, and 73.41%, compared to 0.54 m, respectively. (2) The Simpson, Shannon-Wiener, Pielou and Margalef indices of the T. chinensis communities peaked at the 1.62 m groundwater table depth; (3) The dominant shrub T. chinensis population exhibited an aggregated distribution and optimal growth of T. chinensis shrubs occurring within the groundwater table depth range of 1.18 to 1.62 m; (4) The groundwater depth affected the diversity of the plant community primarily by influencing soil salinity rather than soil moisture; the dominant shrub T. chinensis promoted diversity of plant community, but this facilitation effect was inhibited by soil salinity. Our results suggest that the optimal groundwater depth for maintaining biodiversity falls within the range of 1.18 to 1.62 m. Shallow groundwater diminishes biodiversity both directly through soil salinization and indirectly by impairing T. chinensis’ facilitation of biodiversity. Therefore, regulating optimal groundwater table depth and protecting T. chinensis are critical for biodiversity conservation and ecosystem recovery in muddy coastal areas.

Soil nutrient heterogeneity is common in nature, but few studies have tested the effects of soil nutrient heterogeneity on plant productivity in natural communities. Such effects are of particular interest in habitats where heterogeneity may be increasing due to global warming, as in high-elevation grassland on the Qinghai-Tibetan Plateau. In a three-year study, we added N, P and K to 2 m × 2 m plots in grassland to establish five homogeneous and six heterogeneous treatments that varied in patch size, patch contrast (difference in nutrient levels between patches), and number of patch types (with different nutrient levels). We measured aboveground biomass of grasses, other graminoids, legumes and forbs. Biomass of grasses was higher (over 300 g m^–2) and that of legumes was lower (about 25 g m^–2) at higher nutrient availability in homogeneous treatments. Within heterogeneous plots, grasses similarly had about 25% higher biomass and legumes had about 60% lower biomass in patches with higher nutrients, mainly at the larger patch size and sometimes more so when patch contrast was greater. Accounting for 47%–61% of the total aboveground biomass, grasses showed a roughly similar pattern to that of the whole community. An increase in soil nutrient heterogeneity is unlikely to affect plant aboveground biomass in this grassland, although it can increase biomass of grasses and decrease that of legumes. Soil nutrient heterogeneity might partly mitigate these effects if large patches without elevated nutrients persist.

Atmospheric nitrogen (N) deposition includes inorganic N (IN) and organic N (ON). IN enrichment trends to reduce species richness greater than ON, likely lowering ecosystem stability, as species richness and ecosystem stability are usually positively related. However, previous field experiments evaluating N deposition effects on ecosystem stability used either IN or ON additions, likely biasing results. We assessed the effects of IN:ON ratios (0:10, 3:7, 5:5, 7:3, and 10:0) at 10 g N m^–2 year^–1 on the temporal stability of plant community productivity in a temperate meadow grassland using 6-year (2017–2022) data from a long-term N addition experiment established in 2014. Species richness, species asynchrony, population stability, and dominant species stability were investigated to explore mechanisms underlying community stability changes. We found that IN:ON ratio showed no significant effect on community stability, although all N addition significantly reduced community stability (averaged 26.7% reduction). However, IN decreased species richness more than ON (54.1% reduction in 10:0 vs. 31.8% reduction in 0:10). IN:ON ratio showed no significant effect on species asynchrony, population stability or dominant species stability. Species asynchrony and dominant species stability were both positively related to community stability, while population stability showed no significant association. It implies that species asynchrony and dominant species stability maintained community stability across IN:ON ratios. Overall, our findings suggest that, despite IN reducing species richness greater than ON, it may be reasonable to assess N deposition effects on ecosystem stability using either IN or ON addition.

Soil dissolved organic matter (DOM) is vital in terrestrial ecosystem carbon (C) cycling; however, the regulatory effects of forest types and elevations on soil DOM dynamics in mountain ecosystems remain incompletely understood. Here, we investigated DOM content, spectroscopic characteristics, molecular traits and their potential drivers along an elevational gradient (2600-3500 m) in the Hengduan Mountains. Our results showed that soil dissolved organic C (DOC) content was higher in broad-leaf forest soil (at 2900 m and 3500 m) than in coniferous forest soil (at 2600 m and 3200 m) irrespective of elevation, with a greater amount in wet season than in dry season. Humification index (HIX) trends aligned with the DOC content, while the aromaticity index (AI) showed an inverse relationship. These patterns were linked to the quality of litter carbon sources. Molecular-level analysis of DOM suggested that lignins/CRAM-like structure compounds and tannins predominated in soil DOM, indicating that the molecular composition of soil DOM was typical of plant-derived sources in our study region. Additionally, the relative abundance of lignin compounds decreased gradually with increasing elevation during the dry season. We detected that soil properties (especially, NH₄⁺-N content) predominantly mediated DOM dynamics in dry season, whereas litter traits (i.e., leaf-DOC content) were the key factors across elevations in wet season. Overall, our results revealed litter traits and soil properties predominantly regulated soil DOM mechanism along elevational gradient, indicating that soil DOM dynamics associated with tree species in alpine mountain ecosystems may differentially influence soil C sequestration under future climate change scenarios.