| Panax guinquefolium is a perennial herb of plants,belonging to Araliaceae Panax taxonomically.Its root usually act as the medicine,with various pharmaceutical effects,is a famous and precious Chinese medicine.Panax guinquefolium has been cultivated in China for several decades,it has been found that there are serious problems of continuous cropping obstacle in the process of Panax guinquefolium cultivation.In County of Liuba in Shaanxi province Panax guinquefolium planting base,the local farmers summed up to the "2+2" cultivation mode,reducing the effect of continuous cropping obstacle,but lead to a shortage of suitable land resources,having effect on the sustainable development of Panax guinquefolium industry.In order to fundamentally solve the problem,researching the root of problem "continuous cropping obstacle" is necessary.In order to understand the causes and pathogenesis of the problem,it is necessary to understand and grasp the composition,variation and interaction among soil environmental factors in the normal growth of Panax guinquefolium.This study is based on the ecology "Temporal for Spatial" method,choosing the soil in different years of Panax guinquefolium cultivation as the research object,and using erminal restriction fragment length polymorphism(TRPLP)technique,chloroform fumigation technique and the conventional method to determine soil bacterial and fungal composition,soil microbial biomass carbon,soil nutrients and enzyme activities as indexes separately.The mathematical statistics and the multivariate analysis methods were used to study the relationship among the changes in soil microbial communities,microbial biomass,nutrients and enzyme activities in the process of Panax guinquefolium cultivation,explore the its relationship with the growth of Panax guinquefolium,lay the foundation for further revealing the cause and mechanism of continuous cropping obstacle.The main results are indicated as follows.(1)The effects of the growth of Panax quinquefolium on soil environment.?In general,caused large changes in composition and structure of bacterial and fungal communities;and reduced the soil bacteria and fungi Shannon-Wiener index.?And then increased the soil MBC in general.?The soil nutrients composition has changed in different degree,and the total N,ammonium N and available P increased,pH value decreased,and the total P and organic C were flat.?The soil enzyme activities changed in different degree,the invertase,urease and alkaline phosphatase reduced,and the catalase increased.(2)The changes of soil environment with Panax quinquefolium continuous growth for two years.?The diversity and composition of bacteria and fungi were different.From the first to second years,the bacterial community diversity increased,and the fungal diversity decreased,bacteria and fungi composition structure were changed;from the third to fourth years,the diversity of bacterial and fungal communities were decreased and both of their structure changed.?From the first to second years,the soil MBC was decreased significantly,and the soil MBC increased from third to fourth years.?The contents of total N,total P,ammonium N and available P increased,while pH and organic C decreased from the first year to the second year;the contents of total N,total P,ammonium N and available P decreased,while pH and organic C increased in the period of third to fourth years.?The invertase,urease and alkaline phosphatase activity decreased significantly,and catalase activity increased from the first to second years;the invertase,urease and alkaline phosphatase activity increased significantly,while catalase activity decreased in the period of third to fourth years.(3)The effects of different plant ages of Panax quinquefolium on soil environment.?Compared with the annual plants,the triennial plants increased the diversity of bacteria and reduced the diversity of fungi.?Compared the annuals,the triennial plants reduced the soil MBC significantly.?Compared the annuals,the triennial plants reduced the soil pH,increased the total N,total P,ammonium N and available P content significantly.?Compared the annuals,the triennial plants reduced the invertase,urease and alkaline phosphatase significantly.(4)The rhizosphere effect of Panax guinquefolium on Soil Environment.?Soil bacteria and fungi diversity were higher in rhizosphere soil than non rhizosphere soil.?Rhizosphere soil MBC was greater than the non rhizosphere soil.?In addition to the total N,soil pH,ammonium N,total P,available P and soil fertility index IFI showed that the non rhizosphere was greater than the rhizosphere soil.?The activities of sucrase and catalase were higher in rhizosphere soil than non rhizosphere soil,while urease and alkaline phosphatase were higher in rhizosphere soil than non rhizosphere soil.(5)The growth of Panax quinquefolium cultivation effects on the relationship between soil microbial community and environmental factors.The changes of soil environmental factors were closely related to the changes of soil microbial community composition during the growth of Panax quinquefolium.With the soil bacterial communities were related to different components of bacterial communities S and H,fungal communities S and H,MBC,pH,total N,total P,available P,organic C,invertase,catalase,urease and alkaline phosphatase;and soil fungal community factors were related with bacterial community S,H and J,fungal communities S,H and J,as well as MBC,organic C,total P and urease.The above research results showed that cultivated Panax guinquefolium changed the composition patterns of biological and non biological factors in soil;With the growth two years after sowing and growth two years after transplanting,soil environment have undergone complex changes,and those changes are not conducive to the growth of Panax guinquefolium in the direction of development in general;The effects of Panax guinquefolium on the soil environment were different in different plant ages,and rhizosphere effect of Panax guinquefolium were obvious in most cases. |
PDF Full Text Request