Populus, a core genus of Salicaceae, plays a significant ecological role as a source of pioneer species in boreal forests. However, interspecific hybridization and high levels of morphological variation among poplars have resulted in great difficulty in classifying species for systematic and comparative evolutionary studies. Here, we present phylogenetic analyses of 24 newly sequenced Populus plastomes and 36 plastomes from GenBank, which represent seven genera of Salicaceae, in combination with a matrix of eighteen morphological characters of 40 Populus taxa to reconstruct highly supported relationships of genus Populus. Relationships among the 60 taxa of Salicaceae strongly supported two monophyletic genera: Populus and Salix. Chosenia was nested within the genus Salix, and five clades within Populus were divided. Clade I included the three taxa P. euphratica, P. pruinosa, and P. ilicifolia. Clade II contained thirteen taxa [P. adenopoda, P. alba, P. bolleana, P. davidiana, P. hopeiensis, P. nigra, P. qiongdaoensis, P. rotundifolia, P. rotundifolia var. duclouxiana, P. tremula, P. tremula × alba, P. tomentosa, and P. tomentosa (NC)]. Clade III included the ten taxa P. haoana, P. kangdingensis, P. lasiocarpa, P. pseudoglauca, P. qamdoensis, P. schneideri, P. simonii, P. szechuanica, P. szechuanica var. tibetica, and P. yunnanensis. Clade IV included P. cathayana, P. gonggaensis, P. koreana, P. laurifolia, P. trinervis, P. wilsonii, and P. xiangchengensis. The last clade comprised P. angustifolia, P. balsamifera, P. deltoides, P. deltoides × nigra, P. fremontii, P. mexicana, and P. trichocarpa. This phylogeny is also supported by morphological traits, including bark smoothness, bud size, petiole shape, leaf inflorescence, male anther length and male anther tip.

Pinus yunnanensis Franch. is an particular conifer tree species in Yunnan-Guizhou plateau in southwest China. The morphological and anatomical traits of needles are important to evaluate geographic variation and population dynamics of conifer species. Seedlings from seven populations of P. yunnanensis were analyzed, looking at 22 morphological and anatomical needle traits. The results showed that variations among and within populations were significantly different for all traits and the variance components within populations were generally higher than that among populations in the most tested needle traits. The proportions of three-needle fascicle were significantly different among populations. The traits related to needle size in both morphology and anatomy were positive with latitude and negative with annual temperature and precipitation. Ratio indices, including mesophyll area/vascular bundle area, mesophyll area/resin canals area, vascular bundle area/resin canals area and mesophyll area/(resin canals area and vascular bundle area), were negatively correlated with elevation and positively correlated with the annual mean temperature, showing some fitness feature for the populations. Needle traits were more significantly correlated with longitude than with other four environmental factors. Needle length was significantly correlated with almost all environmental factors. First four principal components accounted for 81.596 % of the variation with eigenvalues [1; the differences among populations were mainly dependent on needle width, stomatal density, section areas of vascular bundle, total resin canals, and mesophyll, as well as area ratio traits. Seven populations were divided into three categories by Euclidean distance. Variations in needle traits among the populations have shown systematic microevolution in terms of geographic impact on P. yunnanensis. This study would provide empirical data to characterize adaptation and genetic variation of P. yunnanensis, which would be helpful for management of genetic resources and reasonable utilization of them in future.

Populus tomentosa , of section Populus , is distributed mainly in northern China. This species has high resistance to many diseases and insects, and it plays key roles in shelterbelts and urban afforestation in northern China. It has long been suspected to be a hybrid, but its parents remain unknown. In the present study, we report four newly sequenced complete cp genomes from section Populus and comparative genomic analyses of these new sequences and three published cp genome sequences. The seven cp genomes ranged from 155,853 bp ( P . tremula var. davidiana ) to 156,746 bp ( P . adenopoda ) in length, and their gene orders, gene numbers and GC contents were similar. We analyzed SNPs, indels, SSRs and repeats among the seven cp genomes, and eight small inversions were detected in the ndhC-trnV , rbcL-accD , petA-psbJ , trnW-trnP , rpl16-rps3 , trnL-ycf15 , ycf15-trnL , and ndhF-trnL intergenic regions. Furthermore, seven divergent regions ( trnH-psbA , matK , psbM-psbD , ndhC-trnV , ycf1 , ndhF-ccsA and ccsA-ndhD ) were found in more highly variable regions. The phylogenetic tree reveals that P . tomentosa is closely related to P . alba and P . alba var. pyramidalis . Hence, P . alba was involved in the formation of P . tomentosa .

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Background: The impacts of selective logging on ecosystem multifunctionality (EMF) remain largely unexplored. In this study, we analyzed the response of nine variables related to four ecosystem functions (i.e. nutrient cycling, soil carbon stocks, decomposition, and wood production) to ve selective logging intensities in a Pinus yunnanensis-dominated forest. We included a control group with no harvest to evaluate the potential shifts in EMF of the P. yunnanensis forests. We also assessed the relationship between above-and belowground biodiversity and EMF under these different selective logging intensities. Additionally, we evaluated the effects of biotic and abiotic factors on EMF using a structural equation modeling (SEM) approach. Results: Individual ecosystem functions (EFs) all had a signi cant positive correlation with selective logging intensity. Different EFs showed different patterns with the increase of selective logging intensity. We found that EMF tended to increase with logging intensity, and that EMF signi cantly improved when the stand was harvested at least twice. Both functional diversity and soil moisture had a signi cant positive correlation with EMF, but soil fungal operational taxonomic units (OTUs) had a signi cant negative correlation with EMF. Based on SEM, we found that selective logging improved EMF mainly by increasing functional diversity. Conclusion: Our study demonstrates that selective logging is a good management technique from an EMF perspective, and thus provide us with potential guidelines to improve forest management in P.