Establishment Of Risk Assessment System For Alien Plants In Jiangsu, Zhejiang And Shanghai

In recent years, with the development of economic,social and foreign exchange, alien plant invasions become more and more evident. As foreign exchange, economic and trade center of China, the number of alien invasive plants in Jiangsu, Zhejiang and Shanghai increased dramatically, so a Risk Assessment System for exotic plants in this area should be established to prevent plant invasions effectively. Based on the current theory of invasion ecology, the investigation of herbs in Jiangsu, Zhejiang and Shanghai, the relationship between attributes of plants and invasiveness, distribution of plants and environmental factors, the indices in relation to plant invasiveness were identified, thus a risk assessment sysment for exotic plants in Jiangsu, Zhejiang and Shanghai were established. The main results are:1. The species of alien plants in Jiangsu, Zhejiang and Shanghai were surveyed with the square plot method in different habitats. Based on our investigation, together with the literature, 171 alien plant species, belonging to 74 genera and 38 families, were confirmed. Among them,Compositae (47 species), Gramineae (29), Leguminosae (13), Maranthaceae (10) are the dominant families. In this region, the proportion of tropical distribution of these 171 alien plant species was higher, floristic characteristic was younger. Totally about 85% of the alien plants originate from America (56%) and Europe (29%), so appropriate measures to control the introduction of the plants from America and Europe are essential.2. Based on the ecological important value of 431 plants in 498 sites, their niche breadth was calculated based on the Shannon equation. Galium aparine var. tenerum, Conyza bonariensis, Conyza canadensis, Solidago canadensis and Erigeron annuus had the highest frequency and a broad distribution; Solidago canadensis, Galium aparine var. tenerum, Vicia sativa, Humulus scandens, Geranium carolinianum and Conyza bonariensis, had the largest total important values, being 23.099,20.802,16.865,16.635,11.642 and 11.447, respectively; Galium aparine var. tenerum, Conyza bonariensis, Solidago canadensis, Conyza canadensis, Erigeron anuus and Aster subulatus had the largest niche breadth, being 5.193,5.044,4.804, 4.817,4.542,4.041, respectively, which means that these plants are higher invasive because of their ability to adapt to diverse habitats. Therefor, the degree of diverse habitats for a apecies could be used as an indicator to build risk assessment system.3. Pearson correlations between the ecological important value and the disturbance intensity were calculated to elucidate the ability to adapt the disturbed environment for a species.The results showed:Setaria viridis, Eleusine indica, Digitaria sanguinalis, Solidago canadensis, Aster subulatus, Xanthium sibiricum had the largest correlation coefficients, being 0.313,0.265,0.251,0.227,0.222 and 0.213, respectively; while Aster ageratoides Aster ageratoides (-0.250), Houttuynia cordata (-0.239), Glycine soja (-0.238), Lysimachia christinae (-0.235), Cyclosorus acuminatus (-0.225) and Gynostemma pentaphyllum (-0.225) had the largest negective correlation coefficients, being less than -0.225. According to the investigation in the field, as well as the check of related literature, the larger the correlation coefficient was, the more suitable for a species to grow in the disturbed ebvironment, and thus the plant had laeger invasiveness.4. A total of 26 characters of 421 plants in Jiangsu, Zhejiang and Shanghai were recorded, and the relationship between these characters with their invasiveness (namely the correlation coefficient between the ecological important value and the disturbance intensity for a species) were analyzed. Our results showed that the invasive plants tend to have annual or biennial life form, toxic. These plants also adapted to xeric or suuny habitats. They are likely to have wind pollinated bieesual flowers, actinomorphic flowers and produce many small mucilaginous or armed seeds. They are unlikely to have thorns, or reproduce vegetatively.5.Invasive plants are generally characterized by having smaller DNA C-values, dormancy and irregular germination seeds; higher polyploid and allelochemicals to inhibit seed germination and seedling growth of indigenous plants. Sum up the above, a risk assessment system was established about invasive plants in Jiangsu, Zhejiang and Shanghai. This system includes five one-level indexes and 27 two-level indexes, the weighted value of each index is the final assessment scores. A species whose assessment scores from 0 to 29 is acceptable, allowing it to introduce, those from 30 to 59 is of certain risk, certain measures should be taken after introduction to control their escape and spread, and those from 60 to 100 is of high risk, and are unacceptable, we must prohibit them from introduction. Finally,54 exotic plants in Jiangsu, Zhejiang and shanghai were selected to authenticate this system.