| Many studies have shown that agricultural intensification and the application of pesticides and fertilizers are one of the main reasons for the decline in biodiversity.The combine of pest control methods and rational design of landscape patterns is an important way to protect biodiversity.As the "resource bank" of predators,alfalfa can provide habitat and food supply,at the same time,mowing can push the predators in alfalfa spread to the adjacent habitat.Rational collocation of alfalfa and other alfalfa can be used fruitfully to increase the species richness and individuals of predators such as spiders,which is significant to pest control.As a polyphagous predator,spiders have the characteristics of rapid movement,wide range of activities,and large predation,which exhibit perfect control of pest.The study on diversity of spider community and response of environment is of great clinical significance in biological pest control.However,the effect of different adjacent habitat,landscape structure on spider community and dynamic spatial change of spider in alfalfa after mowing remains to be further studied.This study used the traps to investigate the polders planted in the four typical agricultural landscape areas of Hongqi Village,Helanshan Farm,Maosheng Grass Company,Heshun Village in Yinchuan District.The effects of different planting patterns on the structure and diversity of ground-dwelling spider community,the edge effects and spillover effects of ground-dwelling spider community in different adjacent crops,and the influence of agricultural landscape structure on spider distribution.The main conclusions are as follows:(1)The ground-dwelling spider community has high species richness and large amount of individuals.Through a four-year field survey,more than 20,000 specimens were collected,and 33 species of spiders were identified.The investigation of the spider community in different cropping patterns,such as adjacent cropping,single cropping and intercropping found that there were dignificant differences in spider community diversity,community structure and individual numer under different planting patterns.Neighboring and intercropping could increase the spider diversity and species richness to improve the stability of the spider community.(2)The Gaussian function was used to dynamically fit the diversity index and number of individuals of ground-dwellin spider community in different planting patterns.The results showed that the fitting curves of Shannon-wiener index,Pielou index and Margalef index were bimodal curves;and witch of Simpson index is the single peak curve.The Shannon-wiener index of the alfalfa-corn field has the shortest peak interval(49.2 d),the alfalfa-orchard field has the longest interval(81.62 d),the alfalfa monoculture field has the largest peak width(123.34 d),and the alfalfa-orchard field is the smallest(101.3 d).The fitting curves of the number of spiders individuals in the alfalfa-wheat and alfalfa-corn field is bimodal,and the other two fields are unimodal.The peak interval of the alfalfa-wheat field fitting curve was 45.65 d,and the alfalfa corn field interval was 22.55 d.(3)Through the investigation of spider communities in the alfalfa-wheat,alfalfa-maize,alfalfa-protective forest and alfalfa-bare land adjacent plots,the result showed that the typs of plant adjacent to the alfalfa can play a relevant role as species richness and community structure on ground-dwelling spider community.The differences in the ground-dwelling spider community in the habitats of different adjacent patterns are mainly reflected in the common species and rare species in the community.Threr is a certain marginal effect between different adjacent habitats.The edge effect of the number of spiders is more significant than the number of spider species and diversity index.The generation o fedge effects is related to the time factor.The time difference between the diversity index of different staggered spider communities and the edge effect of species number is different.(4)The spatial distribution dynamics of spider community under 4 patterns which are alfalfa-wheat,alfalfa-corn,alfalfa-protection forest and alfalfa-bare ground,which were simulated by Kriging interpolation,has showed that mowing was the direct factor causing the spillover effect of spider community in the polder,after castration.There was a significant spillover effect of the spider community diversity index in the four surveyed areas.The spillover effect on the number of spider individuals in the alfalfa-wheat and alfalfa-corn survey sites is more obviously.The spillover effect is mainly cocentrated in the range of 20 m from the staggered zone.The spillover effect still exists after mowing in 7 days.The spider community diversity index has overflowed in the surveyed area of the alfalfa-wheat survey,well other three survey sites do not have this phenomenon.The number of individual spiders is more pronounced than the diversity effect of community diversity.(5)The spider community in alfalfa fields in Hongqi Village,Helanshan Farm,Maosheng Grass Company,Heshun Village were investigated.Through the regression analysis of the number of spider individuals and the landscape index,it is found that:1)the number of individual ground-dwelling spider community in the habitats with the lowest degree of landscape fragmentation is significantly higher than that in the landscape with higher degree of gragmentation;2)the landscape diversity is higher.The number of individuals in spider community in the habitats with smaller average area of plaques is less;3)the response of ground-dwelling spider community in alfalfa field.Obviously,the correlation coefficient between landscape pattern and spider community distribution is the largest in this range;4)the correlation between the landscape fragmentation and the fragmentation index in the 400 m radius landscape scale is higher than that in the 100 m radius landscape scale.The landscape connectivity index has no effect on the spider community. |
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