| Study on stress tolerance and insect resistance of transgenic plants has become one of the hot issues in biology.Along with the worldwide increase of planting area of the insect-resistant transgenic cotton(Gossypium)and insect-resistant poplar(Populus),it’s urgent to study the Arthropod changes on community structure and function in poplar-cotton eco-systems.So far,researchers have done some researches on Arthropod changes from the view of community structure and characteristics,most of which focused on a single forest land or a single crop farmland,and researches on ecological status of compound agroforestry ecosystem were very rare.Especially the study of using the transgenic poplar-cotton eco-systems as research object remains blank at home and abroad.In order to clarify community structure characteristics of the transgenic poplar-cotton eco-systems,we have studied the composition,structure characteristics,structural stability,structural clustering,community similarity,temporal dynamics of the arthropod animal community on the basis of the theory of community ecology using statistical ecology and applying mathematics method,over a period of three years.The study area is located in Wu Cun Lin Chang state field,Yi He Zhuang County,Zhuozhou City,Hebei province in China,where the field of consistent natural climate and ecological conditions was selected as the test area.Here we performed a systematic survey on the diversity and population of arthropod community in four different combination of poplar-cotton eco-systems,including non-transgenic poplar and non-transgenic cotton fields(I);non-transgenic poplar and transgenic cotton fields(Bt cotton)(II);Bt transgenic poplar(high insect resistant strain Pb29)and non-transgenic cotton(III);and transgenic poplar and transgenic cotton fields(IV)The main results were as followes:1.Impacts of insect-resistant transgenic poplar-cotton eco-systems on the arthropod community structure.Transgenic composite system significantly inhibited target insect pests(Lepidoptera: Lepidoptera)while the individual number of sucking insects did’t change significantly.There is no significant difference in the numbers ofthe parasitic natural enemy,neutral insects and quantity of other defoliators in different composite systems.2.Impacts of insect-resistant transgenic poplar-cotton eco-systems on the nutritive layer of arthropod community: Compared with non-transgenic eco-system,the basal species richness and most functional group were higher in transgenic poplar-cotton eco-systems,the order was Ⅲ > Ⅰ > Ⅳ > Ⅱ.Transgenic hybrid system has good effect on controlling lepidopterous pests.In view of the middle or top species,the number of middle species and most functional groups in transgenic Bt cotton adjacent to transgenic poplar topped the list except for a small part of community groups,accounting for a larger proportion.With the extension of transgenic poplar planting time,community structure within the system gradually improved and became stable for development direction.3.Impacts of insect-resistant transgenic poplar-cotton eco-systems on the seasonal dynamics of arthropod community: Individual numbers of arthropod community first increased and then decreased in the overall trend for every system;Variety of arthropod community diversity index of Shannon-Wiener was in consistent trend and kinds of arthropod community diversity index of animal is near,although the number of arthropod animal species varied in different months of one year between the emergence of a large or small fluctuations.In the entire investigation period,the changes in the same year trend of arthropod community in every animal Pielou index is largely the same.In2009-2011 seasonal years,arthropod community of different systems are clustered into3 classes,they are different in different year,suggesting that the arthropod community was functioning differently.4.Impacts of insect-resistant transgenic poplar-cotton eco-systems on the structure stability of arthropod community: the trend of stability index of different years is different.In 2009,the order of the stability index of the systems are: II> III> IV> I;in2010,the order of the stability index of the systems are: IV> III> I> II;in 2011,the order of the stability index of the systems are: IV> I> III> II.Comprehensively,arthropod community was relatively stable in 2009 and 1010,than 2011 at the same time in the seasonal years.Due to the complexity of the system,this issue needs to be discussed after further monitoring.5.Otimal timing segregation of insect-resistant transgenic poplar-cotton eco-systems on the basis of the comprehensive index for the transgenic poplar-cotton eco-systems: in2009,systems of I,II and IV arthropod animal communities gently decreased in the total variation after the 3 period among the four plots,,so the community divided into three stages,system III arthropod animal communities decreased in the 4 period after subtle variation,so the community will be divided into four stages.In 2010 and2011,the community will be divided into three stages.Animal pattern of arthropod community in animal study area was variable during the time development in same seasonal year,these divisions result corresponds to the arthropod community in different environment of the animal growth stage and arthropod animal communities have different performance according to the characteristics of each stage.This can be used in the preservation and protection of diversity of the arthropod community.6.Comparison of the characteristics of arthropod community index of insect-resistant transgenic poplar-cotton eco-systems: there were no significant difference in parameters of system and time factors(P>0.05)in the same year;while there were significant differences in systems are I,but not three other systems in the interannual between 2009-2011.Our results from three years’ data showed that the basal species richness in transgenic poplar-cotton eco-systems is slightly higher than the control system,and the number of functional groups in transgenic poplar-cotton eco-systems were higher than those of the control system.Except for the neutral insects,functional group structure in transgenic poplar-cotton eco-systems was better than the non transgenic composite system.The characteristic index of transgenic poplar cotton system Ⅳ is more suitable than others,so the arthropod community structure of animal within the system will be more stable.These results clearly showed that the transgenic poplar cotton system does not cause the reduction of total number of species,on contrary,this transgenic system may play important practical role in the conservation of the species and population structure improvement.The internal relations of arthropod communities in transgenic poplar-cotton eco-systems was more complex than as we anticipated and their changing rule also need further analysis and research.However,the results of this study still can provide somereference and scientific basis for reasonable planting and promotion of the transgenic poplar and cotton of the compound agroforestry ecosystem. |
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