Rosa roxburghii Tratt.is a well-known commercial horticultural crop in China with nutritional and medicinal value.Wild germplasms of this species are mainly distributed in Southwest China but the population is decreas...Rosa roxburghii Tratt.is a well-known commercial horticultural crop in China with nutritional and medicinal value.Wild germplasms of this species are mainly distributed in Southwest China but the population is decreasing due to continuous exploitation,habitat destruction,and fragmentation.Therefore,assessing the genetic diversity and phylogeography is essential for efficient conservation.Herein,two chloroplast intergenic spacers(trnL-trnF and accD-psaI)were investigated in 255 individuals from 29 R.roxburghii populations and 18 haplotypes(H1–H18)were identified.High levels of haplotype diversity(Hd=0.829)and nucleotide diversity(π=1.3×10^(−3))were detected in these populations.Also,the genetic variation representing 86.4%of the total variation was detected by an analysis of molecular variance.A significant correlation was established between genetic divergence and geographic distance by the Mantel test(r=0.204,P=0.04,9999 permutations),suggesting the isolation-by-distance model.A significantly higher Nst than Gst(Nst=0.257,Gst=0.136,P<0.05)indicated the phylogeographic structure of R.roxburghii.Further phylogeographic analysis revealed rapid range expansion in the population,probably between 647073 and 217848 years ago.The primary processes shaping the genetic patterns of the R.roxburghii populations included restricted gene flow with isolation distance within clades 1-8,2-3,and overall,contiguous expansion within clades 1-3 and 3-2,past fragmentation,and/or long-distance colonization within clades 1-9 and 2-2.Conservation priority should be given to the core populations GZ,FQ,DF,DS,xy,AL,LC,PB,and XY in the Yunnan-Guizhou Plateau,NZ and MX in the Qingling-Bashan mountains,and MN in the Hengduan mountains,where an in situ preservation and management strategy should be applied.展开更多
Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an i...Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an innovative composite column.The composite column was comprised of a rectangular steel tube with E.nitens timber infill.The nonlinear compressive behaviour of the composite column filled with E.nitens wood for both dry and wet conditions was examined.The same tests on rectangular steel tubes and bare dry and wet E.nitens samples were also undertaken as a comparison.For samples with different conditions,the ultimate capacity was evaluated and the effect of each condition on the compressive behaviour of the composite column was clarified.The steel tubes showed greater ductile behaviour,and more ductility was found in the wet samples.The steel tubes with E.nitens timber infill samples exhibited a greater linear elastic range connected with higher maximum loads,while the bare timber samples could support only lower maximum loads.The results from this research were promising for the use of rectangular steel tubes with E.nitens timber infill in structural applications.展开更多
基金This study was supported by grants from the National Natural Science Foundation of China(Grant No.31660558)the Department of Science and Technology of Guizhou Province(Grant Nos.20201Y113,20164016 and 20175788)the Construction Program of Biology First-class Discipline in Guizhou(Grant No.GNYL2017009).
文摘Rosa roxburghii Tratt.is a well-known commercial horticultural crop in China with nutritional and medicinal value.Wild germplasms of this species are mainly distributed in Southwest China but the population is decreasing due to continuous exploitation,habitat destruction,and fragmentation.Therefore,assessing the genetic diversity and phylogeography is essential for efficient conservation.Herein,two chloroplast intergenic spacers(trnL-trnF and accD-psaI)were investigated in 255 individuals from 29 R.roxburghii populations and 18 haplotypes(H1–H18)were identified.High levels of haplotype diversity(Hd=0.829)and nucleotide diversity(π=1.3×10^(−3))were detected in these populations.Also,the genetic variation representing 86.4%of the total variation was detected by an analysis of molecular variance.A significant correlation was established between genetic divergence and geographic distance by the Mantel test(r=0.204,P=0.04,9999 permutations),suggesting the isolation-by-distance model.A significantly higher Nst than Gst(Nst=0.257,Gst=0.136,P<0.05)indicated the phylogeographic structure of R.roxburghii.Further phylogeographic analysis revealed rapid range expansion in the population,probably between 647073 and 217848 years ago.The primary processes shaping the genetic patterns of the R.roxburghii populations included restricted gene flow with isolation distance within clades 1-8,2-3,and overall,contiguous expansion within clades 1-3 and 3-2,past fragmentation,and/or long-distance colonization within clades 1-9 and 2-2.Conservation priority should be given to the core populations GZ,FQ,DF,DS,xy,AL,LC,PB,and XY in the Yunnan-Guizhou Plateau,NZ and MX in the Qingling-Bashan mountains,and MN in the Hengduan mountains,where an in situ preservation and management strategy should be applied.
文摘Eucalyptus nitens(E.nitens)has been much used for producing paper but also shows promise for structural applications.In this study,static compressive tests were undertaken to examine its suitability to be used in an innovative composite column.The composite column was comprised of a rectangular steel tube with E.nitens timber infill.The nonlinear compressive behaviour of the composite column filled with E.nitens wood for both dry and wet conditions was examined.The same tests on rectangular steel tubes and bare dry and wet E.nitens samples were also undertaken as a comparison.For samples with different conditions,the ultimate capacity was evaluated and the effect of each condition on the compressive behaviour of the composite column was clarified.The steel tubes showed greater ductile behaviour,and more ductility was found in the wet samples.The steel tubes with E.nitens timber infill samples exhibited a greater linear elastic range connected with higher maximum loads,while the bare timber samples could support only lower maximum loads.The results from this research were promising for the use of rectangular steel tubes with E.nitens timber infill in structural applications.
