| Ecological regulation and control of insect pests is always an important frontier area in science and technology for insect pest control.At present,the study system on ecological control of insect pests is developing from a single agroecosystem to regional agricultural landscape ecosystem.Regional ecological regulation and control is an important biological control strategy and the study on the effects of change characteristics of landscape pattern on population dynamics of insect pests and their natural enemies in regional agricultural system are of great significance in theory and practice of insect pest biological control.We mainly studied the relationship among agricultural landscape patterns,wheat fields,wheat aphids and natural enemy ladybeetles in North China.Firstly,based on the remote sensing data of land cover,the landscape pattern metrics were calculated and the changes characteristics of landscape pattern of farmland ecosystems were analyzed in North China.Secondly,on the scale of provincial spatial scope,Shandong Province was taken as the research scope and counties as the research units,and the effects of agricultural landscape pattern on population dynamics of wheat aphids and natural enemy ladybeetles were studied.Thirdly,on the scale of county spatial scope,Yucheng and other four counties was taken as the research scope and local farmland as the research unit,and the effects of local agricultural landscape pattern on population dynamics of wheat aphids and natural enemy ladybeetles were studied at different spatial scales.The above three studies will provide theoretical basis for regional ecological regulation of wheat aphid.The main results are as follows:(1)Change characteristics of landscape pattern in farmland ecosystems in North China:based on the remote sensing data of land cover in the year of 2000,2005 and 2010,we calculated the pattern metrics and conversion matrix of cropland landscape,and analyzed the change characteristics of landscape pattern of farmland ecosystems from 2000 to 2010 on the large spatial scale in six provinces of North China.The results showed that the area of farmland was decreasing,the degree of farmland fragmentation was increasing,and the shape of farmland tends to be simplified from 2000 to 2010.The area of the orchard land isincreasing,the degree of orchard land fragmentation is decreasing,and the shape of the orchard land tends to be complicated.The reduced farmland was mainly transformed into urban land,and the increased farmland mainly comes from water.The reduced orchard land was mainly changed into farmland,and the increased orchard land mainly was from farmland.The changes of orchard land use type mainly were from and into farmland type.Urbanization and other human activities intensified the reduction and fragmentation of farmland.(2)Effects of county agricultural landscape patterns on the population of aphids and ladybeetles in wheat: based on the remote sensing data,land cover classification and the survey data of aphid and ladybeetle abundances in wheat fields,the planting region of wheat was took as a typical example,the landscape pattern metrics were calculated,and the effects of landscape pattern of farmland,non-crop habitat and regional agricultural landscape were analyzed on aphid and ladybeetle abundances using negative binomial generalized linear model.The results showed: 1)the aphid abundance was positively correlated with mean patch area and largest patch index of grassland(P<0.01)and patch density of farmland(P<0.05),and was negatively correlated with mean Euclidean nearest neighbor distance and area-weighted mean patch area of the regional landscape(P<0.01)and area-weighted mean patch area of farmland(P<0.05).The increase in patch area of grassland,fragmentation of the regional landscape and farmland,and the aggregation of the regional landscape promoted an increase in aphid abundance.The model based on patch area and largest patch index of grassland and mean Euclidean nearest neighbor distance of the regional landscape had the best prediction of aphid abundance the Akaike weight of the model was 12%.The patch area of grassland,the fragmentation of farmland,and the spatial distribution and fragmentation of the regional landscape and were important landscape factors affecting the occurrence of wheat aphids.2)The ladybeetle abundance was positively correlated with mean patch area and area-weighted mean patch fractal dimension of grassland and patch richness density of regional landscape(P<0.01),and was negatively correlated with area-weighted mean Euclidean nearest neighbor distance of non-crop habitat(P<0.05).Grassland,clustered non-crop habitats and diverse regional landscapes benefited ladybeetle abundance.The model based on mean patch area of grassland and area-weighted mean Euclidean nearest neighbor distance of non-crop habitat had the best prediction of ladybeetle abundances and the Akaike weight of the model was 21%.Grassland,spatial distribution of non-crop habitats and regional landscape diversity were important landscape factors affecting the occurrence of ladybeetles in wheat fields.(3)Effects of local agricultural landscape patterns on the population of aphids and ladybeetles in wheat: based on the remote sensing data,land cover classification and the survey data of aphid and ladybeetle abundances in wheat fields,we calculated the landscape pattern metrics,and analyzed the correlation between landscape types and aphid and ladybeetle populations and the effects of agricultural landscape pattern on aphid and ladybeetle abundances using negative binomial generalized linear model at the spatial scale of 0.5km,1km,1.5km,2km,2.5km and 3km respectively.The results showed: 1)the aphid abundance model based on aggregation index and farmland,and area-weighted mean patch area and edge density of urban at 1.5km was the best among all competition model at six spatial scales and the Akaike weight of the model was 13%.At 1.5km,the aphid abundance was negatively correlated with aggregation index and farmland,and area-weighted mean patch area and edge density of urban(P<0.01)and clustered farmland patch and the increase of urban patch area did not benefited aphid abundances.2)the ladybeetle abundance model based on mean patch area and mean contiguity of regional landscape and aphid abundances at 1km was the best among all competition model at six spatial scales and the Akaike weight of the model was 35%.At 1km,the ladybeetle abundance was positively correlated with mean patch area of regional landscape(P<0.01)and aphid abundances(P<0.05)and the increase of habitat patch area and aphid abundances benefited ladybeetle abundances.The results showed that by optimizing the habitats layout of agricultural landscape system,the population of ladybeetles could be directly regulated and increased in wheat field,and the population of wheat aphid could be effectively controlled and reduced.In this way the function of natural enemy ladybeetles to control aphids in regional agricultural landscape system could be improved. |
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