Short-term microbial effects on n-alkane during the early phase degradation and consequential modification of biomarkers in a lowland subtropical rainforest in southern Taiwan: A litterbag experiment.

Accurate reconstructions of past environments are critical and urgent because they can help understand how modern environments might respond to current climatic and land-use changes. However, the effect of microbial degradation and consequential modification in plant-derived-biomarkers during the early degradation phase is not yet apparent, that might bias the paleoenvironmental investigation. In this regard, a litterbag experiment was conducted to reveal the microbial effects on n-alkane-associated biomarker changes associated with three habitats (ravine, windward, and leeward) in a lowland subtropical rainforest in southern Taiwan. Freshly collected leaves of plant species Iles rotunda, Ficus benjamina, and Castanopsis carlesii were distributed in the habitat leaf litterbag experiment for 15 and 75 days incubation, respectively. The results revealed that the average leaf decomposition rate was 19.4% ± 6.4% during the first 15 days and 39% ± 11% within 75 days incubation for all leaves. The overall leaf mass degradation of I. rotunda, F. benjamina and C. carlesii in the ravine after 75 days was 58%, 51% and 41%, respectively, which were higher than those in the windward (28%, 36% and 38%) and leeward habitats (35%, 26% and 42%, respectively) indicating higher decomposition rate in the ravine habitat than the others. The predominant n-alkanes in I. rotunda were C31 and C29, whereas in F. benjamina these were C31, C29, and C33, and in C. carlesii it was C31. After 75 days, the ravine habitat showed a 60% decrease in the total n-alkane concentration compared to windward and leeward habitats, suggesting the microbial community associated with the ravine habitat has a higher efficiency of degrading n-alkanes. However, the biomarkers such as carbon preference index (CPI), average carbon length (ACL) and the C31/C29 ratio did not show statistical difference in all habitats from 15 to 75 days incubation. The next-generation sequencing revealed that microbial communities changed significantly from 15 to 75 days in all habitats. The alkB gene-containing bacteria and their family lineages increased substantially during the first 15 days incubation in all habitats. Furthermore, several bacterial genera were exclusively present in the ravine habitat, whereas some were only in the leeward and windward habitats. Despite the heterogeneity of microbial proliferation, difference in biomass and n-alkane degradation among the three habitats, most of the n-alkane-associated biomarkers remained the same. Therefore, we concluded that the microbial effects on n-alkane degradation during the early phase in plant leaves had little influence on the results of most n-alkane biomarkers.

Contribution of tree community structure to forest productivity across a thermal gradient in eastern Asia.

Despite their fundamental importance the links between forest productivity, diversity and climate remain contentious. We consider whether variation in productivity across climates reflects adjustment among tree species and individuals, or changes in tree community structure. We analysed data from 60 plots of humid old-growth forests spanning mean annual temperatures (MAT) from 2.0 to 26.6 °C. Comparing forests at equivalent aboveground biomass (160 Mg C ha-1), tropical forests ≥24 °C MAT averaged more than double the aboveground woody productivity of forests <12 °C (3.7 ± 0.3 versus 1.6 ± 0.1 Mg C ha-1 yr-1). Nonetheless, species with similar standing biomass and maximum stature had similar productivity across plots regardless of temperature. We find that differences in the relative contribution of smaller- and larger-biomass species explained 86% of the observed productivity differences. Species-rich tropical forests are more productive than other forests due to the high relative productivity of many short-stature, small-biomass species.

Arbuscular mycorrhizal trees influence the latitudinal beta-diversity gradient of tree communities in forests worldwide.

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity.

Mahonia oiwakensis Extract and Its Bioactive Compounds Exert Anti-Inflammatory Activities and VEGF Production Through M2-Macrophagic Polarization and STAT6 Activation.

Macrophages play an indispensable role in the host immune defense. Macrophages can undergo polarization into classically (M1) and alternatively (M2) activated macrophages. M1 macrophages activate immune and inflammatory response, while M2 macrophages are involved in tissue remodeling. Mahonia oiwakensis (Mo) is a herbal medicine in Asia used for its anti-inflammatory and analgesic properties; however, the mechanism is unclear. This study analyzed the effect of Mo extracts and its effects on the polarization of both macrophage RAW264.7 cells and mouse splenic macrophages. Water (Mo-W) and EtOH extracts (Mo-E) did not change the viability of RAW264.7 cells, whereas Mo-E inhibited nitric oxide (NO) production. The major compounds, berberine and palmatine, decreased the viability and NO levels of cells. The secretion of inflammatory cytokines CXCL16, IL-6, L-selectin, MCP1, RANTES, and sTNF-R1 was downregulated, whereas the production of vascular endothelial growth factor (VEGF) was upregulated by Mo-E, berberine, and palmatine treatments. Mo-E, berberine, and palmatine stimulated the expression of macrophage CD68 and M2-type CD204 markers, decreased M1-mediated p-STAT1 and NF-κB, and increased M2-mediated p-STAT6 expression. Similar effects on M2 polarization were also observed in splenic macrophages from mice. In conclusion, Mo-E, berberine, and palmatine modulated macrophages through the suppression of M1-mediated inflammation and the recruitment of M2-mediated VEGF secretion and STAT6 expression.