| Based on Sino-Italian environmental cooperation project, the experiments were carried out in Qingzhou demonstrational site of Shandong province from 2002 to 2003. The purpose of study was to understand the characteristics of soil biota community and food web in soil ecosystem of greenhouse, and how they responded to the conditions of alternative technologies of methyl bromide in soil fumigation. Three parts were involved in the study. Firstly, how was the disturbance of soil disinfections practices to chemical characteristics, microorganisms, four fungi-Fusarium spp., Trichoderma spp., Phytophthora spp., Pythium spp., soil mites and collembolan? Secondly, how was effect of tomato resistant rootstock (Beaufort SIS-1, Lycopersicon lycopersicum x L.hirsutum) as one of promising alternative technologies of methyl bromide on the above biotic indicators? Thirdly, what was the structure of food web in greenhouse agro-ecosystem, how to construct Organisms-oriented model, how was temporal dynamics of food web and its response to soil disinfections practices and tomato resistant rootstock? The principal results are as follows.As compared to control and SS+BCA, Four disinfections practices such as methyl bromide (MB) and metham sodium (MS), significantly (P<0.05) repressed root-knot nematode disease {Meloidogyne spp.). Fives disinfections practices including SS+BCA, made abundance of soil microorganisms, four fungi, and mites decline, so did the biodiversity and species number of soil mites (P<0.05 ). The inferior species were more sensitive to soil disinfections practices. The abundance of dominant species in mite community, however, decreased after soil disinfections in relative long period, so as to cut the peak of mites dynamics occurring in control plot. Hierarchical Cluster Analysis of mite community dynamics proved the above results. The density of collembolan in the soil of greenhouse was kept in low level during the whole tomato growth, which indicted collembolan was weakly affected by soil disinfections. Evidence in the study showed methyl bromide and its alternatives technologies impacted soil chemical characteristics, possibly changed nutrients release directly, affected indirectly the characteristics of microorganisms and microvores even predators communities in soil ecosystem.As compared to susceptible cultivar Maofen (Lycopersicum esculentum Mill), tomato resistant rootstock significantly controlled plant diseases such as Meloidogyne spp., Rhizoctonia solani, abrupt damping off, ToMV, as a result significantly declined the dead rate of seedlings, the disease index of root-knot nematode (P<0.05) . Furthermore, Beaufort SIS-1 repressed the population increase of four fungi, decreased the densities of mites and collembolan, cut the peak of mites dynamics occurring in Maofen plot, kept the stability of collembolan community. The difference between Beaufort SIS-1 and soil disinfections was that tomato resistant rootstock significantly enhanced the biodiversity level and evenness index (P<0.05 ) because it promoted the change of community structure and distribution of species of soil mites with the time going on.Conversion of abundance of soil biota into biomass carbon after functional groups classification based on the feeding habits was proved much necessary to know the position and function of functional groups in food web. Bacteria-based food web was found predominant in the soil ecosystem of greenhouse, with a high percent of soil microbiomass and protozoa biomass as the bottom of Pyramid,while the biomass of soil mite, nematodes and collembolan as the top of Pyramid. Food web is the channel of organic carbon cycle below ground. The establishment of Organisms-oriented model (Food web model) contributed to make us know the way of organic carbon cycle below ground, and the position and function of functional groups in food web were understood qualitatively and quantitatively. Detritus food chains involved bacteria-based food chain and fungi-based food chain; the former containing more biomass carbon than the later inc... |
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