Browsing by Author "Ouyang, F."
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- ItemEffects of inter-annual landscape change on interactions between cereal aphids and their natural enemies(Elsevier, 2013) Zhao, Z.H.; Hui, C.; Ouyang, F.; Liu, J.H.; Guan, X.Q.; He, D.H.; Ge, F.The agricultural intensification and the subsequent habitat changes in agroecosystem can strongly affect biological control services. We here examine the influence of inter-annual landscape change in wheat field area on interactions of cereal aphids and their natural enemies, as well as the efficacy of biological control using data collected from a 4-year experiment in Northwest China. Two hypotheses were tested. (i) Population densities decline following an inter-annual expansion of wheat crop proportion cover due to dilution and crowding effects. (ii) Species that are specialists or at higher trophic levels are more sensitive to bottom-up disturbance by inter-annual change in percent cover of wheat crop. Results showed the population densities of one cereal aphid (Macrosiphum avenae), one parasitic wasp (Aphidius avenae), two specialist predators (ladybirds: Hippodamia variegata and H. tredecimpunctata) and one hyperparasitic wasp (Pachyneuron aphidis) declined following the expansion of wheat crop areas, supporting the predictions of inter-annual dilution and crowding effects. In contrast, the populations of one cereal aphid (Schizaphis graminum), one parasitic wasp (A. gifuensis), two generalist predators (spiders: Pardosa astrigera; carabid beetles: Chlaenius pallipes), and two hyperparasitic wasps (Asaphes suspensus, and Alloxysta sp.) did not respond to inter-annual landscape change. The two hypotheses were partially supported but with noticeable exceptions, and the bio-control efficiency declined with the increase of the proportion cover of wheat field in agricultural landscape. Overall, different responses of cereal aphids and their natural enemies make it difficult but still possible to optimize inter-annual landscape change for enhancing the parasitism rate and predator-prey ratio.
- ItemPlant species richness controls arthropod food web: Evidence from an experimental model system(Oxford University Press on behalf of Entomological Society of America, 2019) Zhao, Z.-H.; Hui, C.; Reddy, G.V.P.; Ouyang, F.; Men, X.-Y.; Ge, F.The effects of plant species richness on the function and stability of ecosystems have been an area of focus in recent decades. Arthropod community is one of the most important components in agroecosystems and can provide multiple ecosystem services, including biocontrol and pollination. In particular, species composition and biocontrol function can be sensitive to changes in plant species richness. Here, we designed 50 plots with five levels of plant species richness to examine arthropod distribution and composition over 4 yr. Arthropod richness was found to be positively correlated with plant species richness. High plant species richness can enhance the temporal stability of the arthropod community but can also lead to a decline in the population stability of some species. The species richness and biomass of environmentally friendly insects (EFI), such as honeybees, ants and flies, were found to be positively correlated with those of the natural enemies. As such, high levels of EFI could sustain food web robustness by serving as alternative prey/hosts for natural enemies. The mediation of EFI in the interaction between crops and pests has implications for successful biocontrol practices using natural enemies. Planting diverse plant species with a certain level of spatial turnover could benefit the biocontrol function of natural enemies and safeguard multiple ecosystem services.