Wanhui Qian

Background: Mycetia, a subshrub genus within the subfamily Rubioideae (Rubiaceae), is predominantly distributed in tropical Asia, lacking comprehensive plastid genomic resources. This study aimed to characterize the complete plastid genomes of two Mycetia species and explore their structural features and evolutionary relationships. Methods: The plastid genomes of Mycetia hirta and Mycetia sinensis were sequenced and assembled. We analyzed genome structure, simple sequence repeats (SSRs), long repeats, codon usage, nucleotide diversity (π), and Ka/Ks and conducted phylogenetic analysis. Results: Both genomes exhibited a typical quadripartite structure (153,989–154,588 bp; GC content 37.7–37.8%), encoding 126 genes (86 protein-coding, 8 rRNA, and 32 tRNA). Both chloroplast genomes contained 52–60 SSRs and three repeat types with minor interspecific differences. Junction regions and codon usage were highly conserved, with slight variations in RSCU values. The average π was 0.0096, and the non-coding trnE-trnT (π = 0.0817) emerged as a potential DNA barcode. The average Ka/Ks was 0.2900, indicating purifying selection. Phylogenetic analysis confirmed the monophyly of Mycetia within Argostemmateae. Conclusions: This study provides the first comparative plastid genomic analysis for Mycetia, enhancing our understanding of its genetic diversity and supporting future phylogenetic and taxonomic research on the genus.

Landscape health assessments are crucial for balancing conservation and use practices. However, studies considering different land use intensities and grid scales from a functional perspective are limited. This study aimed to develop a landscape classification and indicator system based on functional characteristics using Xiqiao Mountain National Forest Park and Yunyong National Forest Park as research objects. The entropy weight method was used to determine indicator weights, and grid analysis and spatial interpolation were used to analyze the spatial distribution, impact differences, and factors influencing landscape health. The effect of different grid scales on landscape health under varying land use intensities first weakened and then strengthened with increasing grid scales; the optimal grid scales for the two parks were 54 × 54 m and 66 × 66 m, respectively. The forest/non-forest area ratio decreased as the health level of the landscape increased. At the optimal grid scale, the threshold range of the forest/non-forest area ratio for achieving optimal landscape health was 4.46–5.81 and 0.79–0.87 in the two parks, respectively. The results indicate that improved landscape health in suburban forest parks requires the intensive development of construction land, enhanced forest management, and functional synergistic designs to promote coordinated functional development.

It is predicted that global change combined with urbanization will impact increasingly on the society and terrestrial ecosystem in the Guangdong-Hongkong-Macao Greater Bay Area of China (GBA). In this context, the cities in GBA began to plant a variety of urban trees since 2000 which are considered to play an important role in fixing carbon, improving air quality, reducing noise and providing other ecosystem services. However, data on the growth patterns and ecosystem services of the planted trees remains scarce, which hampers a comprehensive understanding of how well the planted trees adapt to the local urban environment. Therefore, we selected three widely planted tree species in Foshan, one of the core cities in GBA and investigated their tree growth and ecosystem services via a harvest campaign and soil analysis. With the same, fast tree growth as natural forests and the greatest above- and below-ground biomass among the three tree species, Ml (Mytilaria laosensis Lec.) showed a distinguished adaption to the local urban environment in terms of growth patterns, carbon fixation, stabilization against typhoon risk and water uptake capacity against potential drought risk in the future. Although Cf (Chinese fir) showed reduced diameter at breast height (DBH) and volume development, it significantly increased the total and available potassium in soils to improve the soil quality. The DBH growth of Sp (Slash pine) decreased between six and 12 years old while it recovered at the age of 12 years, probably suggesting its adaptation might take a longer time. Our results indicated that different trees had different growth patterns and ecosystem services after they were planted in cities. In a harsh urban environment under climate change, precise and comprehensive data on urban trees is necessary, helping to provide different perspectives for urban managers to select appropriate tree species and make policies.