Biological Invasion Risk Estimate To Exotic Species Of Mimosa Sepiaria Benth In Flat Of Hainan Province

Mimosa sepiaria Benth remain with Mimosaceae Mimosa, Its country of originl is tropical America, be regarded as exotic species in hedge creation for various kinds of economic crops groves and fruit orchards. Now it had already spread to wild in Southern china. The thesis aimed to evalut the exotic species of Mimosa sepiaria Benth in Hainan province, by using the methods of physio-ecology,reproductive ecology and community ecology from 3 aspects of ecological adaptability,breeding dispersal characteristics and the harm to local ecosystems. The study could open out the invasive mechanism of Mimosa sepiaria Benth in theory, and also could afford technology on Mimosa sepiaria Benth prevented and cured in practice. The thesis analyzed the adaptability to different environments by studying the seed germination indoor and outdoor to find the key factor which impact on the seed germination of Mimosa sepiaria Benth. The thesis also analyzed the species breeding dispersal properties through the Mimosa sepiaria Benth's sub-soil plant seed ban,seedling proliferation the amount of seed per plant and the actual proliferation of investigation. Additionally, it also analyzed the damage to native ecosystems through the investigation of species diversity and allelopathy research. The main results as follows:1)The seeds of Mimosa Sepiaria Benth could germinate within a wider temperature range(15-40℃),25℃was the most suitable temperature to its germination, while high temperature(≥40℃)strongly inhibited to the germination. With the increase of salt concentration, the germination ratio reduced. The soil-salt concentration of 150mmol·L-1NaCL was the cirtical value to Mimosa sepiaria Benth's germination. But some seeds also could germinate under higher salinity soil stress. The species seeds could excit under lightly water stress. It couldn't germinate as the soil moisture lower than 5% or more than 45%, when the soil moisture is 25%, the germinating rate has increased to 83.33% and the radical growth of it has been best of all. It still has some seed germinated under continuous dark conditions, but the germinating ratio was higher than it was in normal lighting. Seed germination and seeding growth in light conditions were better than in shading conditions.2) Mimosa.sepiaria Benth reproduced sexually and has large number of propagules with high invasion potential. Forest soil seed bank density of Mimosa sepiaria Benth was 1,716 seeds. m-2, average volume of the per plant seed was 17,529, respectively, indicating great potential for regeneration. However, surviving seedlings were much fewer. The species diffused at the speed of middle lever, and its diffusion was mostly by close-proliferation. The lever of the soil seed bank located in more than 3.4 times of the tree's height and the seedling proliferation of the maximum distance was 5.1 times of the height.3) Shannon-wiener index was range between 0.5334-1.3516, Simpson index was range between 0.5159-0.8347, and the Pielou index was range between 0.6468-0.7869. The Shannon-wiener and Pielou index of the sample 4 were higher than other samples, indicating that sample 4 has more vegetation and well-distributed than others. The forest stand of the specie has large crown density, so that some plants hardly to get enough sunshine, only shade-resistance of herbal adapt to grow. This result showed that undergrowth shrub layer and herb layer were sparse and the species diversity was low.4) Different plants had different respondance under the different concentrations of Mimosa Sepiaria Benth leaf leaching liquor. The seedling germination was not increasing along with the leaf extracted concentrations, and the change in different concentration compared with CK showed complexity. Heigh concentration of Mimosa Sepiaria Benth leaf extract treatment on seedling germination and growth of plant has obviously inhibited, and slightly effected in lower concentration. But it has been not effected deal with the soil extract of Mimosa Sepiaria Benth.5) Used the system of indications for accessing the invasion risk of alien woody plant to evaluate the invasion of Mimosa Sepiaria Benth. Assessment of invasion potential of this specie found their invasiveness was moderate, indicating that attention should be given to site selection and plantations. But caution should be taken in introduction and planting of this specie to avoid possible risk of biological invasion.