Abstract:In order to reveal the plant resources and ecological environment changes in Guangzhou, the vascular plants and vegetation in hotspot areas were investigated from 2017 to 2019. A total of 3 508 species of vascular plants belonging to 1 362 genera and 230 families were recorded, of which 174 species in 78 genera and 25 families are lycophytes and ferns, 34 species in 20 genera and 8 families are gymnosperms, and 3 300 species in 1 264 genera and 197 families are angiosperms. There are 20 national and 5 provincial key protected plants, and 131 alien invasive plants. It also shows that the flora of seed plants has the transitional characteristics from tropical to subtropical and the typical families includes Lauraceae, Fagaceae, Pentaphylacaceae, Phyllanthaceae, Aquifoliaceae, Celastraceae and Theaceae. The vegetation investigation and evaluation indicated that the community composition and structure of different vegetation types had gone through a positive and healthy developmental tendency and the forest vegetation has been succeeding toward the zonal climax community types under the circumstance of strict ecological protection and sustainable utilization. These results present the comprehensive basic data on the current status of plant diversity and the dynamics of vegetation changes in the recent 10 years, which are important for making biodiversity conservation and development strategies and keeping the local biosecurity in Guangzhou.

Abstract:Based on field investigation and literature consultation, seventy three species of alien invasive plants belonging to 59 genera of 27 families were identified in Guangzhou. Of them, nineteen alien invasive species belonging to Asteraceae, eight to Poaceae, and seven to Fabaceae and Amaranthaceae respectively, and they take up 56.2% of the total number of the invasive plants in Guangzhou. With respect to the life form of alien invasive plants distributed in Guangzhou, the most dominant plant are terrestrial herbs (58 species), then shrubs (10 species), aquatic herbs (3 species) and trees (2 species), which distributed in the area of heavily disturbed and low altitude. In addition, based on the growing, dispersal status and other ecological features of the invasive plants in the field, eleven alien invasive species were evaluated to be at the highest degree of threat to the local biodiversity, twenty five at the medium, and 37 at the lowest. Constitutional analysis of the original locality of the alien invasive species revealed that 61 species were from tropical America and took up 83.6% of the total species in Guangzhou. Comparing with other domestic regions in terms of the number of the alien invasive plants, Guangzhou and Guangxi share the most and have 62 species. However, concerning the species that have caused serious threat to local biodiversity, Guangzhou shared eight species with Hong Kong, seven species with Shenzhen, and six species with Guangxi. Moreover, we also evaluated the potential threat for those alien plants that grow in Guangzhou and have caused serious biodiversity damages in other domestic regions. Our result reveals that the government should pay much attention to monitoring these invasive species so as to prevent them from dispersing and causing ecology disaster in Guangzhou. Furthermore, the invasive pathways and preventive strategies of alien plants are also summarized here.

Abstract:The characteristics of nitrogen metabolism and soil nitrogen of four invasive plants (Ipomoea cairica, Wedelia trilobata, Synedrella nodiflora, Lantana camara) and one native plant (Paederia scandens, control plant) had been studied. The results showed that the activity of nitrate reductase in invasive plant tissue, the contents of NH4-N and NO3-N and the activities of protease and urease in their rhizosphere soil were higher than those of Paederia scandens by 1.65~4.34 times, 1.56~2.15 times, 1.72~3.11 times, 1.43~3.23 times and 1.41~3.33 times, respectively. But the nitrate content in invasive plant tissue fell to 17.5%~50.6% that of Paederia scandens. Furthermore, the correlation analysis indicated that the activity of nitrate reductase in invasive plant tissue was positively and significantly related to total nitrogen, NH4-N, NO3-N and the activities of protease and urease in their rhizosphere soil. The invasion of exotic plants speeded up nitrogen metabolism, enhanced nitrogen bioavailability, improved the efficiency of nitrogen assimilation, and coordinated plant nitrogen metabolism with soil nitrogen metabolism. All these benefited their growth when invasive plants competed against native ones for nitrogen, which might be a contributing factor to their successful invasion.

Abstract:There are 114 species of invasive plants belonging to 80 genera, 36 families in Guangxi Province. The most abundant family is Compositae including 26 species. The plants all immigrated from aboard and 87 species (76.3%) are mainly from America. There are 90 species of Herbs amounting to 78.9% of the total species. The plants were introduced intentionally or unconsciously. They, especially poisonous or virulent weeds, have produced large negative effects on agriculture, forestry, human health and ecological environment in Guangxi. The effective approaches to defend against invasive plants are as follows: to investigate and evaluate invasive species, to recover native vegetation and species diversity, to implement risk analysis of invasive plants.