| The introduction of Rhus typhina native to North America is a species that is deliberately introduced by humans,it has strong ability of asexual reproduction and diffusion,environmental adaptability and resistance to stress,and can present good greening landscape effect.In this study,the alien species of Rhus typhina in Dalian was selected as the research object,using field survey methods and indoor and outdoor experimental methods respectively for asexual reproduction and sexual reproduction of Rhus typhina to carry out specific research on the system,and use the risk assessment system in central Europe(WG-WRA)to evaluate the invasion risk of the Dalian area of Rhus typhina.In the aspect of asexual reproduction,the average growth of Rhus typhina and the number of new-born seedlings propagated by root tillering were statistically analyzed,and the diversity of concomitant species under Rhus typhina and native species was compared and analyzed.In the aspect of sexual reproduction,the seedling emergence of Rhus typhina in different treatments and different temperature soaking were statistically analyzed.The seedling emergence rates of Rhus typhina in different indoor treatments were statistically analyzed;Statistical analysis was made on the numbers of seedlings of Rhus typhina seeds treated in different habitats in the wild;In addition,the emergence rates of Rhus typhina seeds in pots and fields in different habitats were compared on a time scale so as to be able to grasp the characteristics of Rhus typhina breeding time dynamic changes.The main results of this study are as follows:(1)On asexual reproduction,analysis of Rhus typhina asexual reproduction ability,the number of seedling root rice breeding is increasing every year,the investigation of various samples at least can germinate 104 plants,maximum germination of 511 plants,density is increasing at the same time,the sprout is continuously spreading to the edge,covers an area of increasing,the ability to reproduce asexual as the season changes.(2)The diversity of associated species in the understory of the Rhus typhina forest was lower than that of the coniferous species in the native Pinus densiflora,Quercus acutissima and mixed coniferous and broad-leaved forests,suggesting that the Rhus typhina have affected the species diversity in the region.(3)The research on the sexual reproduction of Rhus typhina mainly has three aspects:Firstly,the emergence rate of Rhus typhina seeds greatly changes after soaking in different temperature water.The rise of the seedling rate increases with the increase of temperature.The optimal seedling temperature for untreated seeds,and seeds for direct removal of velvet,and seeds treated with overbased water were 85°C,85°C and 95°C,respectively.Second,the seedlings of Rhus typhina seeds in the indoor potted plants and field habitats in different habitats are low,the emergence rate of the seedlings are about 1% for each treatment,and take a long time;Third,the indoor potted plants in different habitats than the Rhus typhina seed The survival rate of seedlings is high,indoor seedlings all survive,while the wild seed only 1-2 survive,sexual reproduction is low.(4)According to WG-WRA assessment indicators,the risk of Rhus typhina invasion in Dalian is high risk(Grade?),species is likely to become a threat to natural communities if naturalised,and need to be treated and restored.This study is the first study of Rhus typhina in Dalian area,which has reference significance for management departments in managing and preventing invasive species.Meanwhile,it has guiding significance for early warning of potential invasive species. |
PDF Full Text Request