Herbaceous ornamental plants with conspicuous aesthetic traits contribute to plant invasion risk in subtropical urban parks.

Global ornamental horticulture is a major pathway for plant invasions, while urban parks are key areas for introducing non-native ornamental plants. To react appropriately to the challenges (e.g., biological invasion issues) and opportunities (e.g., urban ecosystem services) of herbaceous ornamentals in urban parks, we conducted a comprehensive invasive risk assessment in 363 urban parks in Chongqing, a subtropical city in China. The results found more than 1/3 of the 119 non-native species recorded in urban parks had a high invasion risk, and more than five species had potential invasion risk in 96.29% of the study area, indicating herbaceous ornamentals in urban parks are potentially a pool of invasive species that deserves attention. Moreover, humans have chosen herbaceous ornamentals with more aesthetic characteristics in urban parks, where exotic species were more prominent than native species in floral traits, such as more conspicuous flowers and longer flowering periods. The findings can inform urban plant management, provide an integrated approach to assessing herbaceous ornamentals' invasion risk, and offer insights into understanding the filtering effects of human aesthetic preferences.

Characterizing composition profile and diversity patterns of spontaneous urban plants across China's major cities.

Spontaneous urban plants (SUPs) constitute an important component of urban vegetation, but they have received less attention in urban biodiversity and ecological research, especially at the regional scale. We comprehensively reviewed the occurrence records of SUPs in 59 major cities across China's geographical regions. We systematically analyzed floristic composition profiles and diversity patterns of SUPs at the regional scale and explored their influencing factors. The study identified 1211 SUP species through an extensive search of existing field research studies and fieldwork. The species composition pattern of SUPs, displaying a spatial association with climatic zones, was mainly affected by climatic factors and also anthropogenic factors. At different geographic scales, the life-form characteristics revealed some patterns, with more diverse perennials at the regional scale. The abundance of SUPs and the high proportion of native species suggested that limited urban habitats can still contribute to the enrichment and accumulation of urban biodiversity. However, in the context of globalization, continual species exchanges between neighboring regions at different scales may significantly exacerbate urban-biota homogenization. In conclusion, our study provided a regional-scale case of a synoptic SUP profile. The results furnished a scientific basis for understanding the general patterns of SUPs. The findings could inform sustainable solutions for urban ecological planning and management of spontaneous nature in cities.

Human activities and species biological traits drive the long-term persistence of old trees in human-dominated landscapes.

Old trees have many ecological and socio-cultural values. However, knowledge of the factors influencing their long-term persistence in human-dominated landscapes is limited. Here, using an extensive database (nearly 1.8 million individual old trees belonging to 1,580 species) from China, we identified which species were most likely to persist as old trees in human-dominated landscapes and where they were most likely to occur. We found that species with greater potential height, smaller leaf size and diverse human utilization attributes had the highest probability of long-term persistence. The persistence probabilities of human-associated species (taxa with diverse human utilization attributes) were relatively high in intensively cultivated areas. Conversely, the persistence probabilities of spontaneous species (taxa with no human utilization attributes and which are not cultivated) were relatively high in mountainous areas or regions inhabited by ethnic minorities. The distinctly different geographic patterns of persistence probabilities of the two groups of species were related to their dissimilar responses to heterogeneous human activities and site conditions. A small number of human-associated species dominated the current cohort of old trees, while most spontaneous species were rare and endemic. Our study revealed the potential impacts of human activities on the long-term persistence of trees and the associated shifts in species composition in human-dominated landscapes.

Short-term decline of Castanopsis fargesii adult trees promotes conspecific seedling regeneration: The complete process from seed production to seedling establishment.

Declining forests usually face uncertain regeneration dynamics and recovery trajectories, which are challenging to forest management. In this study, we investigated the decline pattern of Castanopsis fargesii and examined the effects on conspecific seedling regeneration. We found that 61.45% of adult individuals were in decline and the smaller DBH size classes of trees (10-40 cm) had a greater probability of decline. Most of the intermediate decline (94.52%) and nondecline individuals (95.23%) did not worsen, and the crowns of 21.91% of the intermediate decline trees were recovered during 2013-2018. Adult tree decline had a negative effect on seed production (mean mature seed density of nondecline, intermediate decline, and high decline individuals was 167.3, 63.3, and 2.1 seeds/m2, respectively), but no effect on key seed traits. The seed survival rate of declining trees was greater than that of nondeclining trees at both the seed production and seed dispersal stages. The seed to seedling transition rates in canopy gaps, decline habitats, and nondecline habitats were 7.94%, 9.47%, and 109.24%, respectively. The survival rate and height growth of newly germinated seedlings were positively correlated with the light condition, which was notably accelerated in the canopy gaps. Taken together, these results indicate that the reduction in seed production of some adult trees had a weakly negative effect on new seedling recruitment, while the improved environmental condition after the decline significantly enhanced the survival and growth of both advanced and new germinated seedlings. Looking at the overall life history, the short-term defoliation and mortality of some C. fargesii adult trees can be regarded as a natural forest disturbance that favors conspecific seedling regeneration. High-intensity management measures would be unnecessary in cases of an emerging intermediate decline in this forest.

Modulating the activities of human mesenchymal stem cells (hMSCs) and C3A/HepG2 hepatoma cells by modifying the surface characteristics of poly(3-hydroxybutyrate-co-3-hydroxyhexnoate) (PHBHHx).

The new biodegradable polyester poly(3-hydroxybutyrate-co-3-hydroxyhexnoate) (PHBHHx) has a potential application in tissue engineering. The aim of this study was to present a deeper picture of the relationship between the cellular behavior and the surface characteristics of PHBHHx films. The pristine PHBHHx film was prepared by adopting the compression-molding method, and then the acrylic acid molecules were grafted on PHBHHx membrane surface by UV irradiation. The hydrophilic nature and surface roughness of various PHBHHx films were controlled by adjusting the acrylic acid concentration and the UV irradiation time. Although the surface characteristics of various PHBHHx films could not affect the metabolic activity of hMSCs, the performance of morphology of hMSCs was deeply affected by the hydrophilic nature and the orientation of surface scars. The hydrophilic nature would effectively improve the spread of hMSCs, and the orientation of surface scars would guide the growth direction of cytoskeleton (actin) inside hMSCs. In contrast, the behaviors of C3A/HepG2 hepatoma cells presented an opposite outcomes. Those surface characteristics were obviously associated with the performance of metabolic activity of C3A cells, but not with the morphology of C3A cells. Both hMSCs and C3A cells have unique cellular characteristics; therefore, their responses to environmental stimulations are significantly different.