Rhizosphere effects of moso bamboo and dominant tree species of secondary broadleaved forest on soil organic carbon mineralization.

The rhizosphere effect of plants affects soil organic carbon (SOC) mineralization. It is still unclear for the mechanism by which the rhizosphere effect of dominant plants in secondary broadleaved forest habitats invaded by moso bamboo affects SOC mineralization. Taking broadleaved tree species (Quercus glauca and Cunninghamia lanceolata) and moso bamboo, dominating respectively in uninvaded secondary broadleaved forest and bamboo forest formed after the invasion as test materials, we investigated rhizosphere effect of plants on the SOC mineralization in laboratory incubation experiments. The results showed that carbon mineralization rates of Phyllostachys edulis (PE), Quercus glauca (QG) and Cunninghamia lanceolata (CL) rhizosphere soils were 20%, 26%, and 21% higher than bulk soils, respectively. Carbon mineralization of bulk soils of QG and CL was 22% and 26% higher, while that of rhizosphere soils was 14% and 11% higher than PE, respectively. The contents of water-soluble organic carbon and organic carbon in rhizosphere soils of the three species were significantly higher than those of bulk soil, and the abundance of rhizosphere soil bacteria was higher than that of non-rhizosphere. The contents of microbial biomass carbon, water-soluble organic carbon, and total nitrogen were important factors influencing carbon mineralization in rhizosphere, while water-soluble organic carbon and microbial metabolic quotient were important factors influencing carbon mineralization in non-rhizosphere. On the whole, the rhizosphere effect increased total SOC mineralization, driving by changes in microbial biomass carbon, water-soluble organic carbon, and total nitrogen content. The results could provide a theoretical basis for plant-soil interaction on soil carbon cycling in bamboo invasion habitats.

Phylogenomics and integrative taxonomy reveal two new species of Amana (Liliaceae).

Until now the genus Amana (Liliaceae), known as 'East Asian tulips', has contained just seven species. In this study, a phylogenomic and integrative taxonomic approach was used to reveal two new species, Amana nanyueensis from Central China and A. tianmuensis from East China. A. nanyueensis resembles Amana edulis in possessing a densely villous-woolly bulb tunic and two opposite bracts, but differs in its leaves and anthers. Amana tianmuensis resembles Amana erythronioides in possessing three verticillate bracts and yellow anthers, but differs in aspects of its leaves and bulbs. These four species are clearly separated from each other in principal components analysis based on morphology. Phylogenomic analyses based on plastid CDS further support the species delimitation of A. nanyueensis and A. tianmuensis and suggests they are closely related to A. edulis. Cytological analysis shows that A. nanyueensis and A. tianmuensis are both diploid (2n = 2x = 24), different from A. edulis, which is either diploid (northern populations) or tetraploid (southern populations, 2n = 4x = 48). The pollen morphology of A. nanyueensis is similar to other Amana species (single-groove germination aperture), but A. tianmuensis is quite different because of the presence of a sulcus membrane, which creates the illusion of double grooves. Ecological niche modelling also revealed a niche differentiation between A. edulis, A. nanyueensis and A. tianmuensis.

[Reconstructing mean temperature of April-July in 1809-2018 based on tree-ring of Pinus taiwanensis in the Tianmu Mountain, East China]. / åŸºäºŽé»„å±±æ¾æ ‘è½®é‡å»ºåŽä¸œå¤©ç›®å±±åœ°åŒº1809­2018å¹´4­7月平均气温.

We established 340-year chronologies of total ring width, early wood width, and late wood width with tree-ring samples of Pinus taiwanensis at high altitude collected from the western Tianmu Mountain in northern Zhejiang Province. According to the criterion that subsample signal strength (SSS) should be larger than 0.8, the reliable period was from 1810 to 2019. Through the correlation analysis between chronologies and climatic factors, we examined the responses of tree ring growth to climate. The results showed that radial growth of P. taiwanensis was more sensitive to temperature than to precipitation. Comprehensively considering the correlation analysis results for the raw and first-order difference series, early wood width was significantly correlated with the early growing season mean and maximum temperatures of the prior year, while late wood width with prior May and current September mean and maximum temperatures. The correlation pattern of total ring width was similar to that of early wood width, although at a low level. The optimal correlation was between early wood width and prior April-July mean temperature. Based on this relationship, April-July mean temperature of the Tianmu Mountain, East China was reconstructed for the period of 1809-2018 with an explained variance of 61.5%. Both the raw and first-order difference series passed the split sample calibration-verification test. The warm periods were 1809-1833 and 1965-2018, with a cold period in 1834-1964. Temperature had risen rapidly since the 1960s. From the standpoint of low frequency, it reached an unprecedented level since the 1980s over the past 210 years. Spatial correlation analysis showed that the reconstructed temperature series could represent temperature variations of East China, which had a good agreement with a reconstructed regional temperature series from East China. Our results showed that P. taiwanensis had a great potential for paleoclimate reconstruction in East China.

[Effect of UV-B radiation on the chemical composition and subsequent decomposition of Cyclobalanopsis glauca leaf litter].

A experiment on leaf litter decomposition was carried out to evaluate the effects of UV-B radiation on the chemical composition and subsequent decomposition of leaf litter in humid subtropical forest systems. The leaf litter was derived from Cyclobalanopsis glauca seedlings exposed to elevated and ambient ultraviolet B (UV-B) radiation treatments during growth for one year. The results showed that UV-B treatment significantly increased the original N, K and P content of leaf litter by 154.9%, 29.8% and 9.7%, respectively, and decreased the ratios of C: N, lignin: N and C: P of leaf litter by 60.5%, 61.7% and 8.5%, respectively (P < 0.05), but had no significant effect on C and lignin content. The decomposition of leaf litter derived from seedlings exposed to elevated UV-B treatment during growth was faster, but did not show significant difference from that of ambient UV-B treatment. Exposure to elevated UV-B radiation during growth did not significantly influence the K release, but promoted the P release and retarded the N accumulation during leaf litter decomposition. Our result will contribute to the better understanding of the role of UV-B radiation in moist subtropical forest ecosystem.

Development of the first chloroplast microsatellite loci in Ginkgo biloba (Ginkgoaceae).

PREMISE OF THE STUDY: To investigate population genetics, phylogeography, and cultivar origin of Ginkgo biloba, chloroplast microsatellite primers were developed. • METHODS AND RESULTS: Twenty-one chloroplast microsatellite markers were identified referring to the two published chloroplast genomes of G. biloba. Polymorphisms were assessed on four natural populations from the two refugia in China. Eight loci were detected to be polymorphic in these populations. The number of alleles per locus ranged from three to seven, and the unbiased haploid diversity per locus varied from 0.441 to 0.807. • CONCLUSIONS: For the first time, we developed 21 chloroplast microsatellite markers for G. biloba, including 13 monomorphic and eight polymorphic ones within the assessed natural populations. These markers should provide a powerful tool for the study of genetic variation of both natural and cultivated populations of G. biloba, as well as cultivars.

Demographic genetic structure of Cryptomeria japonica var. sinensis in Tianmushan Nature Reserve, China.

Genetic changes over space and time provide insights into the relative roles of evolutionary factors in shaping genetic patterns within plant populations. However, compared with spatial genetic structure, few studies have been conducted on genetic changes over time. In this study, we used six polymorphic microsatellite loci to assess genetic variation of six size-classes of the population of Liushan, Cryptomeria japonica var. sinensis, in the Tianmushan National Nature Reserve, whose origin was debatable. The mean number of alleles per locus and expected heterozygosity were 4.583 and 0.599 9 respectively, lower than other conifers with the same life history characteristics. FST was 0.002+/-0.003, and the pairwise test revealed no significant differentiation in any pair of size classes. Significant heterozygosity excesses were detected in five size classes except the oldest one, indicating bottleneck event(s). The above results support the hypothesis that Tianmushan population was introduced and followed by natural regeneration.

Genetic diversity and geographic differentiation in the threatened species Dysosma pleiantha in China as revealed by ISSR analysis.

Dysosma pleiantha, an important threatened medicinal plant species, is restricted in distribution to southeastern China. The species is capable of reproducing both sexually and asexually. In this study, inter-simple sequence repeat marker data were obtained and analyzed with respect to genetic variation and genetic structure. The extent of clonality, together with the clonal and sexual reproductive strategies, varied among sites, and the populations under harsh ecological conditions tended to have large clones with relatively low clonal diversity caused by vegetative reproduction. The ramets sharing the same genotype show a clumped distribution. Across all populations surveyed, average within-population diversity was remarkably low (e.g., 0.111 for Nei's gene diversity), with populations from the nature reserves maintaining relatively high amounts of genetic diversity. Among all populations, high genetic differentiation (AMOVA: Phi(ST) = 0.500; Nei's genetic diversity: G (ST) = 0.465, Bayesian analysis: Phi(B) = 0.436) was detected, together with an isolation-by-distance pattern. Low seedling recruitment due to inbreeding, restricted gene flow, and genetic drift are proposed as determinant factors responsible for the low genetic diversity and high genetic differentiation observed.

Species-specific SCAR markers for authentication of Sinocalycanthus chinensis.

Sinocalycanthus chinensis, an endangered species endemic to China, is cultivated as an ornamental landscape tree in China. However, S. chinensis, Chimonanthus species and Calycanthus floridus are difficult to be distinguished in seedling market because of their similar morphological characters. In this study, ISSR (inter-simple sequence repeats) were applied to detect S. chinensis from its closely related species. A unique 748-bp band was found in all accessions of S. chinensis. SCAR (sequence characterized amplified regions) markers were created by cloning and sequencing the specific band, and designing a pair of primers to amplify the band of 748 bp. Diagnostic PCRs were performed using the primer pair with the total DNAs of S. chinensis, Chimonanthus species and C. floridus as templates, with only S. chinensis being able to be amplified. This amplification is not only rapid (results can be obtained in less than 3 h), but is also easy to perform. Hence it is a feasible method for identifying S. chinensis in seedling market.