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Streptomyces from unexplored or underexplored environments may be an essential source of discoveries of bioactive molecules. One such example is Streptomyces qaidamensis S10T, which was isolated from a sand sample collected in Qaidam Basin, Qinghai Province, China. Here, we report on (±)-differolide, an antioxidant isolated from S. qaidamensis, and verified with scavenging experiments on 2,2-diphenyl-1-picrylhydrazyl (DPPH). The biosynthetic gene cluster responsible for synthesizing the compound was also identified using comparative genomic methods. These results provide a basis for further study of the biological activities of (±)-differolide, which also make it possible to develop as an antioxidant medicine. [ABSTRACT FROM AUTHOR]

[Display omitted] • We uncovered significant legacy effects of extreme drought on Qinghai spruce growth. • Management practices improved Qinghai spruce growth resilience to drought. • Management practices mitigated drought legacy effects on Qinghai spruce growth. • Management effects were weaker in multi-year than single-year drought events. Understanding the impact of management upon post-drought tree growth recovery and drought legacy effects is among the fundamental challenges hindering the improvement of forest conservation strategies in the face of increasingly frequent, longer, and intensified extreme droughts under ongoing climate change. Yet surprisingly little is known to date about how management practices can influence drought legacy effects; and previous studies of management impacts on forest resilience to drought have reached inconsistent and contentious conclusions. This study sought to tackle these pressing questions and gain insight by analyzing tree-ring datasets from non-managed and managed Qinghai spruce forests in northwestern China. The results show improved growth resilience to drought of those trees under management practices. Moreover, Qinghai spruce radial growth in non-managed forest exhibited significant legacy effects of extreme drought, whereas such legacy effects were mitigated in managed forest. Nevertheless, both the resilience augmentation and the mitigation of drought legacy effects by management were much weaker in the face of a three-year persistent drought than a single-year event. Hence, we may conclude that current management practices are advantageous and necessary for forest conservation under exacerbated drought conditions, for which strategies and measures should be better thought out and tailored to specific situations, rather than being "one-size-fits-all", to better serve the goals of forest managers and conservationists. [ABSTRACT FROM AUTHOR]

[Display omitted] • Forest stand age influences the growth resilience of Qinghai spruce to drought. • Older growth forests show greater resistance to drought than younger growth forests. • Post-drought recovery is weaker in older growth forests than younger ones. • Stand age-related resilience differences are diminished at drier sites. The growth resilience of forests to extreme drought event has become an urgent topic in global change ecology because of exacerbated water constraints upon trees' growth over the last few decades. Yet, surprisingly little is empirically known about the contribution of stand age, a key factor influencing forest structure and ecological processes, to variation in growth resilience among stands. This study revealed discrepancies in the drought resilience of forests of different stand ages by analyzing an extensive tree-ring dataset from Qinghai spruce (Picea crassifolia Kom.), a typical moisture-sensitive tree species in northwestern China. We found that older growth Qinghai spruce forest stands have higher resistance to droughts than do younger growth ones. Conversely, however, the post-drought recoveries of these older growth forest stands are lower than those of the younger growth stands. Patterns in the variation of resilience indices were consistent between two contrasting hydrological niche regions, whereas the stand age-related discrepancies in drought resilience became significantly smaller going from the wetter region to the drier region. These findings imply that, instead of a "one-size-fits-all" strategy, more meticulous and more targeted strategies are needed to enhance forest management and strengthen forest conservation given the experienced and projected climate trends, which feature increasing precipitation but higher extreme-drought frequency across this spruce tree's habitat and distribution in northwestern China. [ABSTRACT FROM AUTHOR]

• Radial growth of Qinghai spruce differed with stand age. • Stand age effect on radial growth is not consistent. • Stand age effect of growth was lower at drier sites. • Stand age growth concordance was negatively correlated with site moisture. Although stand age has been shown to strongly affect forest ecosystem processes, little is known about the role that forest stand age plays in tree radial growth processes. The knowledge on geographical patterns of the stand age effect on radial growth along climatic gradients is also scarce. Based on dendrological methods and tree-ring cores from 2276 trees at 14 sampling plots, we confirmed that differences in stand age could result in radial growth dissimilarities of Qinghai spruce (Picea crassifolia Kom.), a moisture-sensitive forest tree species endemic to the Tibetan Plateau. However, the effect that stand age has on the radial growth of Qinghai spruce is not consistent. There is evident dissimilarity in the radial growth dynamics of Qinghai spruce from different-aged forest stands in semi-humid regions, but this dissimilarity is minimal in regions under higher drought limitation. Additionally, we observed significant negative correlations in temporal changes of growth concordance of Qinghai spruce from different-aged stands and regional moisture conditions at each study site. It can therefore be concluded that Qinghai spruce will exhibit greater stand age related growth dissimilarities under lower drought limitation. Findings from this study can improve our understanding of biogeographical patterns of moisture-sensitive tree growth that will be necessary to improve future projections of forest dynamics and to guide forest management under a changing climate. [ABSTRACT FROM AUTHOR]

• We made a systematic assessment of Qinghai spruce growth along a moisture gradient. • Tree growth status was assessed using dendrological method with 4219 tree-ring cores. • Qinghai spruce showed divergent growth dynamics across various hydrological niches. • Differences in growth-climate response can explain Qinghai spruce growth divergences. Understanding the spatial–temporal tree growth variability and its associative climatic response is fundamental in the assessment of forest vulnerability and the appraisal of forest risk under climate change. Based on 4219 tree-ring cores from 23 sample plots, this study demonstrates divergent radial growth dynamics of Qinghai spruce (Picea crassifolia Kom.) across a moisture gradient. On the one hand, contrary to the warming-induced growth enhancement of trees in cold regions reported in previous studies, our study find that Qinghai spruce growth has persistently declined under recent warming trends in multiple cold and moist sites that are representative of the Tibetan Plateau, China. On the other hand, Qinghai spruce growth exhibited W-shaped dynamic trajectories that were similar to changes in regional precipitation at all warmer and drier sites investigated in this study. Along with differences in regional evaporative change, differences in the growth-climate response can explain divergences in Qinghai spruce growth observed throughout various hydrological niches. Drought is believed to be the primary limiting factor of Qinghai spruce growth in all regions, resulting in a lower radial growth rate in warmer and drier regions. However, Qinghai spruce growth exhibited a higher dependency on the negatively-affected temperature in cold and moist regions, while the growth dependency respective to the positively-affected precipitation was higher than the temperature in warmer and drier regions. Results from this study are intended to add to the growing knowledgebase of forest response under persistent climate change. [ABSTRACT FROM AUTHOR]

[Display omitted] • Forest managements reshaped the phyllosphere bacterial community. • The α -diversity increased, and β -diversity decreased. • The community stability and resistance increased, while the complexity decreased. • The keystone species altered following forest management. • Select-driven community assembly mechanisms increased in the managed forest. Research has shown that forest management can improve the post-drought growth and resilience of Qinghai spruce in the eastern Qilian Mountains, located on the northeastern Tibetan Plateau. However, the impact of such management on the tree-associated phyllosphere microbiome is not yet fully understood. This study provides new evidence of positive forest management effects on the phyllosphere microbiome after extreme drought, from the perspectives of community diversity, structure, network inference, keystone species, and assembly processes. In managed Qinghai spruce forest, the α -diversity of the phyllosphere bacterial communities increased, whereas the β -diversity decreased. In addition, the phyllosphere bacterial community became more stable and resistant, yet less complex, following forest management. Keystone species inferred from a bacterial network also changed under forest management. Furthermore, forest management mediated changes in community assembly processes, intensifying the influence of determinacy, while diminishing that of stochasticity. These findings support the hypothesis that management can re-assemble the phyllosphere bacterial community, enhance community stability, and ultimately improve tree growth. Overall, the study highlights the importance of forest management on the phyllosphere microbiome and furnishes new insights into forest conservation from the perspective of managing microbial processes and effects. [ABSTRACT FROM AUTHOR]