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Diverse native plant communities resist non‐native plants more than species‐poor communities, in part through resource competition. The role of soil biota in diversity–invasibility relationships is poorly understood, although non‐native plants interact with soil biota during invasions. We tested the responses of non‐native plants to soil biota generated by different native plant diversities. We applied well‐watered and drought treatments in both conditioning and response phases to explore the effects of 'historical' and 'contemporary' environmental stresses. When generated in well‐watered soils, the microbial legacies from higher native diversity inhibited non‐native growth in well‐watered conditions. In contrast, when generated in drought‐treated soils, the microbial legacies from higher native diversity facilitated non‐native growth in well‐watered conditions. Contemporary drought eliminated microbial legacy effects on non‐native growth. We provide a new understanding of mechanisms behind diversity–invasibility relationships and demonstrate that temporal variation in environmental stress shapes relationships among native plant diversity, soil biota and non‐native plants. [ABSTRACT FROM AUTHOR]

Aims: Nitrous oxide (N2O) plays an important role in global climate change. Plant expansion can alter soil nutrient cycling and greenhouse gas (GHG) fluxes but the effects of fine root litter mixing from plant expansion on litter decomposition, nutrient cycling, and GHG fluxes are poorly understood. Methods: To evaluate the impacts of fine root litter mixing from plant expansion on GHG budgets, we conducted an in situ study over sixteen months in Japanese cedar (Cryptomeria japonica) plantations experiencing moso bamboo (Phyllostachys edulis) expansions. Litter decomposition and N2O production were quantified in a full-factorial complete-randomized design by comparing fine root litter of Japanese cedar, moso bamboo or their mixtures, with or without nitrogen (N) addition. Results: We found that litter mixing accelerated decomposition, demonstrating a synergistic non-additive effect (19% increase in mass loss). This might have accelerated release of chemicals that inhibit microbial activities because litter mixtures had lower microbial biomass. Soil N2O emissions in the mixed litter treatment were 16.8% and 24.4% lower than those with only cedar or bamboo litter, respectively. N deposition promoted mass loss of mixed litter (28% increase in mass loss) and increased N2O emissions by 36.7%, 60.6% and 33.6% from cedar, mixed and bamboo litter treatments, respectively. Conclusion: The expansion of moso bamboo promotes the return of soil nutrients, reduces N2O emissions, and potentially mitigates GHG emissions. However, with increasing N deposition in the future, moso bamboo expansion will likely contribute to global warming. [ABSTRACT FROM AUTHOR]

Chemical signals are crucial in mediating ecological and evolutionary adaptation of plants to their environments. Indeed, invasive plants may produce greater amounts of chemical metabolites in their new ranges. Some of these chemicals can enhance their mutualistic interactions and improve invasive plant performance, but genetic mechanisms of such adaptations are unexplored.We used Triadica sebifera plants as a model to investigate evolutionary changes in chemical signals that enhance arbuscular mycorrhizal (AM) fungal associations. Previous studies found that T. sebifera plants from invasive populations had higher root exudate concentrations of the flavonoid quercetin and elevated AM fungal colonization compared with those from native populations. Here, we explored genetic variation in strigolactone concentrations in root exudates and their contribution to AM fungal colonization with strigolactone analogue GR24 additions. In addition, we studied how gene expression patterns related to flavonoid and strigolactone biosynthesis varied among invasive and native populations using comparative genomics, transcriptomics and fluorescent real‐time quantitative PCR.We found that plants from invasive populations had higher concentrations of the strigolactone 5‐deoxystrigol in root exudates that were correlated with higher AM fungal colonization rates, relative to those from native populations. Exogenous applications of GR24, a synthetic analogue of 5‐deoxystrigol, increased AM fungal colonization. We found higher expression of a single gene in flavonoid (FLS) and strigolactone (DAD1) biosynthesis pathways increased levels of quercetin and 5‐deoxystrigol in plants from invasive populations, respectively.Synthesis. Understanding the role of genetic evolution in enhancing mutualisms of invasive plants provides new insights into the underlying mechanisms of plant invasion. This study suggests that an invasive plant enhanced its mutualisms by upregulating the expression of key genes related to secondary metabolites in root exudates which stimulate symbiotic relationships with AM fungi. Thus, these findings provide insights into genetic mechanisms that underlie higher AM fungal colonization and enhanced invasive plant performance. [ABSTRACT FROM AUTHOR]

Plants produce secondary chemicals that may vary along with latitude due to changing abiotic and biotic stress gradients and local environmental conditions. Teasing apart the individual and combined effects of these different abiotic, such as soil nutrients, and biotic factors, such as soil biota and herbivores, on secondary chemicals is critical for understanding plant responses to changing environments. We conducted an experiment at different latitudes in China, using tallow tree (Triadica sebifera) seedlings sourced from a population at 31° N. These seedlings were cultivated in gardens located at low, middle and high latitudes, with either local soil or soil from the original seed collection site (origin soil). The seedlings were exposed to natural levels of aboveground herbivores or had them excluded. Plant secondary chemicals (both foliar and root), aboveground herbivores and soil characteristics were measured. Results showed that most leaf and root secondary metabolites depended on the interaction of the experimental site and soil type. Leaf and root phenolic and tannin concentrations were higher at the middle latitude site, especially in the origin soil. Root and foliar flavonoid concentrations increased when aboveground herbivores were excluded. Microbial communities depended strongly on soil treatment. The different responses of tannins versus flavonoids suggest that these two chemical classes differ in their responses to the varying abiotic and biotic factors in these sites along latitudes. Taken together, our results emphasize the importance of considering the interactive effects of local environmental conditions, soil properties and herbivory in regulating plant chemical defenses. [ABSTRACT FROM AUTHOR]

Plants from invasive populations often have higher growth rates than conspecifics from native populations due to better environmental adaptability. However, the roles of improved chlorophyll fluorescence or antioxidant defenses in helping them to grow better under adverse situations are insufficient, even though this is a key physiological question for elucidating mechanisms of plant invasion. Here, we conducted experiments with eight native (China) and eight introduced (USA) populations of Chinese tallow tree (Triadica sebifera). We tested how salinity, nutrients (overall amount or N:P in two separate experiments) and their interaction affected T. sebifera aboveground biomass, leaf area, chlorophyll fluorescence and antioxidant defenses. Plants from introduced populations were larger than those from native populations, but salinity and nutrient shortage (low nutrients or high N:P) reduced this advantage, possibly reflecting differences in chlorophyll fluorescence based on their higher PSII maximum photochemical efficiency (F v/ F m) and PSI maximum photo-oxidizable P700 in higher nutrient conditions. Native population plants had lower F v/ F m with saline. Except in high nutrients/N:P with salinity, introduced population plants had lower electron transfer rate and photochemical quantum yield. There were no differences in antioxidant defenses between introduced and native populations except accumulation of hydrogen peroxide (H2O2), which was lower for introduced populations. Low nutrients and higher N:P or salinity increased total antioxidant capacity and H2O2. Our results indicate that nutrients and salinity induce differences in H2O2 contents and chlorophyll fluorescence characteristics between introduced and native populations of an invasive plant, illuminating adaptive mechanisms using photosynthetic physiological descriptors in order to predict invasions. [ABSTRACT FROM AUTHOR]