Growth Characteristics Of Different Populations Of Forsythia Suspensa And Their Responses To Polycyclic Aromatic Hydrocarbons Pollution

Forsythia suspensa（Thunb.）Vahl is a deciduous shrub belong to the genus Forsythia of Oleaceae,which is an important medicinal plant.It is one of the 40commonly used Chinese herbal medicines in China.Moreover,Forsythia suspensa is also an important part of forest resources,and it is closely related to human health.Forsythia suspensa can not only be used as a forest medicinal material,but also provide people with medical materials to treat diseases,and improve the ecology and beautify the environment.Forsythia suspensa in shanxi is the most abundant wild resource,with more in Anze,Lingchuan and Pingshun.Furthermore,Shanxi is also a typical coal chemical industry zone.Long-term coal chemical production leads to higher pollution levels of PAHs in the environment.Is the soil environment of wild Forsythia suspensa contaminated?Does it affect the growth characteristics of Forsythia suspensa?Forsythia suspensa community in four different sections of Shanxi Province was used as the research object.125 plots（10 m×10 m）were established by field investigation to analyze the structural characteristics of Forsythia suspensa community,and the surface layer soil（0-25 cm）of the samples was collected,including Forsythia suspensa leaves and fruit samples.The content of 16 excellent polycyclic aromatic hydrocarbons（EPA-PAHs）in the samples were analyzed by chemical extraction and GC-MS instrument analysis.The effects of soil environmental factors and PAHs on the structure and physiological characteristics of Forsythia suspensa community were discussed.The ratio method was used to analyze the source of sample PAHs.According to the total amount and Nemerow comprehensive index method,equivalent toxicity concentration,etc.,the potential ecological risk of Forsythia suspensa growth soil was preliminarily evaluated,and the living environment problems faced by forest medicinal materials were found.The countermeasures for large-scale planting of Forsythia suspensa were proposed.Provide a reference for the development.The main results were as follows:（1）The type of Forsythia suspensa community in the study area was mainly Forsythia suspensa+Rosa xanthina-Carex lanceolata cluster,40.0%of which belong to this type.The environmental factors affecting community structure were different in different intervals.The Lingchuan area wa s mainly affected by altitude;Pingshun,Changzhi and Anze area was mainly affected by soil total phosphorus,available phosphorus and available nitrogen.（2）There was a certain difference in the total amount of soil PAHs（Σ16PAHs）in different intervals.Anze soilΣ16PAHs was between 0.399¹1.6 mg·kg^-1,Changzhi urban area was 0.342¹1.4 mg·kg^-1,Lingchuan area was 0.278².56 mg·kg^-1,and Pingshun area was 0.210¹.08 mg·kg^-1.According to the classification criteria of PAHs contaminated farmland soil proposed by Maliszewska-Kordybach,all samples were higher than the pollution level(>0.200 mg·kg^-1),and 41.4%of the samples exceeded the heavy pollution level(>1.00 mg·kg^-1).（3）There was certain differences in the composition of soil PAHs in different intervals.In the Changzhi City,Lingchuan and Pingshun plots,the soil PAHs were mainly composed of 3 rings,accounting for 86.3%,94.0%,and 50.3%of the total PAHs,respectively.The relative content of 5-ring PAHs in the soil of Anze District was the highest.（25.8%）,followed by 3 rings（25.3%）and 4 rings（22.6%）.（4）Soil PAHs had an effect on the chlorophyll content of Forsythia suspensa,and the chlorophyll content increased within a certain range.The contents of Ace,Acel,Phe,Pyr,Baa,Bbf,Bap,Daa,Bghip and Ind were positively correlated with chlorophyll a（Chla）and chlorophyll b（Chlb）（r>0,P<0.01）.（5）Soil PAHs have a certain influence on the accumulation of saponins and total phenols in Forsythia suspensa.The content of saponin and total phenol in Forsythia suspensa increased in a certain range of PAHs content;the accumulation of Forsythia suspensa in Nap,Ace and Flu was more significant（P<0.05）.Conclusion:（1）The type of Forsythia suspensa community in the study area was mainly Forsythia suspensa+Rosa xanthina-Carex lanceolata cluster.（2）There was a certain degree of PAHs pollution in the soil of f Forsythia suspensa growth area in Shanxi coal chemical industry zone.The pollutants mainly came from the local residents in the production and living process,and the pollutants emitted by biomass and fossil fuel combustion were transmitted through the atmosphere.Settling into the forest and soil.（3）The accumulation of PAHs in Forsythia suspensa leaves and fruits in the four plots was relatively small,and the potential safety risk was relatively low.Soil PAHs had an effect on the photosynthesis rate and secondary metabolic process of Forsythia suspensa,and the soil PAHs content was within a certain range.Caused the increase of chlorophyll content and secondary metabolite content of Forsythia suspensa leaves.