Identification of loci or genes under natural selection is important for both understanding the genetic basis of local adaptation and practical applications, and genome scans provide a powerful means for such identification purposes. In this study, genome-wide simple sequence repeats markers (SSRs) were used to scan for molecular footprints of divergent selection in Eucalyptus grandis, a hardwood species occurring widely in costal areas from 32° S to 16° S in Australia. High population diversity levels and weak population structure were detected with putatively neutral genomic SSRs. Using three F_ST outlier detection methods, a total of 58 outlying SSRs were collectively identified as loci under divergent selection against three non-correlated climatic variables, namely, mean annual temperature, isothermality and annual precipitation. Using a spatial analysis method, nine significant associations were revealed between F_ST outlier allele frequencies and climatic variables, involving seven alleles from five SSR loci. Of the five significant SSRs, two (EUCeSSR1044 and Embra394) contained alleles of putative genes with known functional importance for response to climatic factors. Our study presents critical information on the population diversity and structure of the important woody species E. grandis and provides insight into the adaptive responses of perennial trees to climatic variations.

The superior provenance is a prerequisite for ecological restoration, and a better mastery on the growth rhythms of Ormosia species is fundamental to reforest effectively. For the selection of better provenance and the formulation of artificial cultivation methods, the height and the ground diameter of Ormosia hosiei Hemsl. et Wils., O. xylocarpa Chun ex L. Chen and O. henryi Prain seedlings of different provenances were monitored in the first year. The results showed that their dynamic growths presented a slow-fast-slow trend that fit a “S” growth curve by the logistic mathematical model, and the growth of Ormosia species seedlings of different provenances significantly differed. The accumulated growth increment of O. xylocarpa was the largest (averagely 45.50 cm) and the accumulated growth increment of O. henryi was the least (averagely 20.33 cm). Thus, O. hosiei of Jiujiang provenance, O. xylocarpa of Liping provenance and O. henryi of Longquan provenance have a stronger adaptability for future artificial cultivation in Jiangxi China.

Background: Stable stand structure of mixed plantations is the basis of giving full play to forest ecological function and benefit, and the pure Eucalyptus plantations with large-area and successive planting have presented to be unstable and vulnerable in typhoon-prone area. In this study, we investigated eight 30 m × 30 m plots randomly in pure and mixed eucalyptus forests on growth status, characterized and compared the distribution of non-spatial structure of mixtures with that of mono-species plantation, and evaluated the stand quality and stability from eight indexes including preservation rate, stand density, height, diameter, stem form, degree of slant, tree species composition and age structure, so as to find out the best mixed composition and pattern of eucalyptus and other tree species in typhoon-prone area. Results: Eucalyptus surviving in the mixed forest of Eucalyptus and A. mangium (EA) and the mixed forest of Eucalyptus and P. elliottii × P. caribaea (EP) were 5.0% and 7.6% greater than those in pure Eucalyptus forest (E) respectively, while only the stand preservation rate of EA was greater (+2.9%) than that of pure Eucalyptus forest. The proportions of all mixtures on the height class that greater than 7 m were fewer than that of monoculture. The proportion of EA and EN (mixed forest of Eucalyptus and N.cadamba) on the diameter class that greater than 7 m were 10.6% and 7.8% respectively more than that of monoculture. EN got a highest ratio of branching visibly (41%), EA got a highest ratio of slant stems (8.1%) and EP got a most straight and complete stem form (68.7%). The stand stability of the mixed forest of Eucalyptus and A. mangium presents to be optimal for its subordinate function value (0.76) and status value (ω = 0.607) of real stand were the largest. Conclusion: A. mangium is a most superior tree specie to mix with Eucalyptus for a more stable stand structure in the early growth stage to approach an evident and immense stability and resistance, which is of great significance for the forest restoration of Eucalyptus in response to extreme climate and on the forest management.

Eucalyptus roots form symbiotic relationships with arbuscular mycorrhizal (AM) fungi in soil to enhance adaptation in challenging environments. However, the evolution of the AM fungal community along a chronosequence of eucalypt plantations and its relationship with soil properties remain unclear. In this study, we evaluated the tree growth, soil properties, and root AM fungal colonization of Eucalyptus grandis W. Hill ex Maiden plantations at different ages, identified the AM fungal community composition by high-throughput sequencing, and developed a structural equation model among trees, soil, and AM fungi. Key findings include the following: (1) The total phosphorus (P) and total potassium (K) in the soil underwent an initial reduction followed by a rise with different stand ages. (2) The rate of AM colonization decreased first and then increased. (3) The composition of the AM fungal community changed significantly with different stand ages, but there was no significant change in diversity. (4) Paraglomus and Glomus were the dominant genera, accounting for 70.1% and 21.8% of the relative abundance, respectively. (5) The dominant genera were mainly influenced by soil P, the N content, and bulk density, but the main factors were different with stand ages. The results can provide a reference for fertilizer management and microbial formulation manufacture for eucalyptus plantations.