A Research On Yellowing Reason Of Cinnamomum Camphora (L) And Environmental Impact

The yellows of Cinnamomum camphora,one of serious and widespread diseases in urban condition,was studied in Shanghai in this thesis.The health status of Cinnamomum camphora in certain area was surveyed and evaluated.The samples of soils and leaves from Gongqing Forest Park,Tuancheng Road in Chongming Island and the Soong Ching Ling Memorial Residence were collected.The pH value,soil elements and leaf elements were measured under different yellowing grades.The results were analyzed and the cause of yellows was studied step by step.Pot experiments were carried out to examine whether the environmental factors would influence the growth of Cinnamomum camphora.The study of the health status of Cinnamomum camphora in the certain area showed that the incidence of yellows of roadside trees was 36.6%and the incidence of yellows of non-roadside trees was 19.5%.The incidence of yellows first rised and then declined with the increasing of DBH,and it reached the peak when the DBH was 15cm.Among the roadside trees,the proportion of trees whose DBH smaller than 15cm was higher,reaching 58.2%and the incidence of yellows was 50.6%.By studying the growth environment of Cinnamomum camphora in Gongqing Forest Park,Tuancheng Road and the Soong Ching Ling Memorial Residence,the soil status was found that would affect the health status of Cinnamomum camphora.If the depth of soil was greater than 60cm,the growth condition of Cinnamomum camphora was better.If the soil contained more living and construction waste,it would lead to the yellows of Cinnamomurn camphora.Through the measurement and statistical analysis of elements in soils and leaves,the results showed that the lack of iron and sulfur in leaves would cause the yellows,leading to the lack of chlorophyll.Thus this showed the lack of magnesium which was the main components of the chlorophyll.The lack of zinc and manganese in soil may lead to the yellows of Cinnamomum camphora.Pot experiments in laboratory showed that the high pH values would cause the yellows of Cinnamomurn camphora,when pH value was among 9.0-10.0,the total chlorophyll content decreased by 15.2%.Cinnamomum camphora had poor resistance to cold,the trees which grew outdoors in the winter showed the symptom of yellows,total chlorophyll content decreasing by 34.2%,and the missing green of leaf margin was similar to the symptom of the yellows of roadside tree.This showed that the cold weather may have caused the yellows of Cinnamomum camphora,especially having greater influence on the smaller ones.