A poisoned apple: First insights into community assembly and networks of the fungal pathobiome of healthy-looking senescing leaves of temperate trees in mixed forest ecosystem.

Despite the abundance of observations of foliar pathogens, our knowledge is severely lacking regarding how the potential fungal pathobiome is structured and which processes determine community assembly. In this study, we addressed these questions by analysing the potential fungal pathobiome associated with the senescing leaves and needles of 12 temperate tree species. We compared fungal plant pathogen load in the senescing leaves/needles and demonstrated that healthy-looking leaves/needles are inhabited by diverse and distinct fungal plant pathogens. We detected 400 fungal plant pathogenic ASVs belonging to 130 genera. The fungal plant pathogenic generalist, Mycosphaerella, was found to be the potential most significant contributor to foliar disease in seedlings. The analyses of assembly process and co-occurrence network showed that the fungal plant pathogenic communities in different tree types are mainly determined by stochastic processes. However, the homogenising dispersal highly contributes in broadleaf trees, whereas ecological drift plays an important role in coniferious trees. The deterministic assembly processes (dominated by variable selection) contributed more in broadleaf trees as compared to coniferous trees. We found that pH and P level significantly corresponded with fungal plant pathogenic community compositions in both tree types. Our study provides the first insight and mechanistic understanding into the community assembly, networks, and complete taxonomy of the foliar fungal pathobiome in senescing leaves and needles.

Phytoremediation potential of Chromolaena odorata, Impatiens patula, and Gynura pseudochina grown in cadmium-polluted soils.

To assess the cadmium (Cd) phytoremediation of three native plant species from Padeang zinc (Zn) mine area (Chromolaena odorata, Impatiens patula, and Gynura pseudochina), a hydroponic experiment was performed in nutrient solutions containing various concentrations of Cd (0, 5, 10, 20, and 50 mg L-1) for 15 days. In the hydroponic experiment, C. odorata showed significantly higher total Cd content than those grown in 50 mg L-1 Cd solutions. Only C. odorata and I. patula were chosen for the pot experiment. The plants were grown in spiked Cd-contaminated soils for 90 days, with different concentrations of Cd (0, 20, 40, 60, and 80 mg kg-1). The results from the pot experiment revealed that both species accumulated more Cd in their root parts, with translocation factor values < 1. C. odorata exhibited the highest biomass production, relative growth rate, and Cd uptake or removal. The findings of the study clearly demonstrate the best uptake of C. odorata in Cd phytoremediation. Novelty statementEven though Chromolaena odorata, Impatiens patula, and Gynura pseudochina have been reported as a Cd accumulator but the assessment of these species by nutrient medium and the soil was not undertaken so far. The discovery of new Cd-accumulator plants has been hindered by the lack of efficient assessing. To assess the suitability of specific species of tropical plants that are able to uptake high amounts of Cd without risk of toxicity under conditions similar to the actual field study, is a novelty.

Bamboo dominance reduces tree regeneration in a disturbed tropical forest.

Human disturbance may change dominance hierarchies of plant communities, and may cause substantial changes in biotic environmental conditions if the new dominant species have properties that differ from the previous dominant species. We examined the effects of bamboos (Bambusa tulda and Cephalostachyum pergracile) and their litter on the overall woody seedling abundance, species richness and diversity in a mixed deciduous forest in northeastern Thailand. These bamboo species are gaining dominance after human disturbance. Our results show that seedling abundance and species richness were reduced by bamboo canopies. Seedling abundance and species diversity under bamboo canopies were affected by bamboo litter, whereas seedling abundance and species diversity outside bamboo canopies did not respond to the mixed-tree litter manipulation. Removal of bamboo litter increased seedling abundance and species diversity. However, bamboo litter addition did not affect seedling abundance or species diversity compared to either control or litter removal. This may indicate that the effect of natural amount of bamboo litter is as high as for litter addition in preventing seedling establishment by woody species and hence in minimizing resource competition. We conclude that undergrowth bamboos and their litter affect tree seedling regeneration differently from mixed-tree litter, causing changes in plant community composition and species diversity. Increased human disturbance, causing a shift in dominance structure of these forests, may result in a concomitant reduction in their overall woody species abundance, richness and diversity. Thus, management of bamboos by controlling their distribution in areas of high bamboo density can be an important forest restoration method.