Systematic Study On The Structure And Disturbance Mechanism Of Arthropod Community In Cotton Ifelds

Studies the effect of habitat complexity and fertilization, transgenic Bt cotton and conventional cotton on the structure and dynamics of arthropod community in cotton fields. The main results are as follows:(1)In order to guide ecological control of pest insects, the study for the effect of habitat complexity and fertilization on the structure of arthropod community in cotton field was conducted by treating with different combinations of habitat and fertilization. No straw mulching(A1)and straw mulching(A2) were designed as simple-and complex-structure habitats, respectively. Compound fertilizer90kgN·hm-2(B1), compound fertilizer90kgN·hm-2with biogas fertilizer90kgN·hm-2(B2) and compound fertilizer90kgN·hm-2with urea90kgN·hm-2(B3) were designed as fertilization ways.10cotton plants were sampled in each plot by parallel jumping method. The species and individual number of arthropods from each plant and its ground surface with0.25m2were investigated on a weekly basis. The results showed that the individual number of spiders (A2391.1±70.1/A1226.8±29.3individuals·10plants-1) and the dominant species enemies P. astrigera(A2171.7±13.3/A159.3±9.8individuals·10plants-1) and the dominant index of spiders (A20.527±0.089/A10.258±0.049), the diversity index of pest insects (A21.459±0.067/A11.245±0.249) in straw mulching habitat were much significantly higher than in no straw mulching habitat. The evenness index of pest insects (A20.635±0.040/A10.588±0.100) in straw mulching habitat was significantly higher than in no straw mulching habitat. The individual number of pest insects (A2772.4±206.9/A11156.4±243.7individuals·10plants-1), the target pest insect S. derogata (A2320.8±80.6/A1659.5±254.8individuals·10plants-1), the dominant index of pest insects (A20.311±0.029/A10.400±0.107, the diversity index of spiders(Ai0.997±0.169/A21.584±0.138), the evenness index of spiders (A20.536±0.073/A10.803±0.052) in straw mulching habitat were much significantly lower than in no straw mulching habitat. The individual number of pest insects (B11015.3±344.1/B2714.0±152.2/B31164.0±168.9individuals·10plants-1), the target pest insect S. derogata (B1552.0±253.8/B2280.6±63.7/B3638.0±256.0individuals·10plants-1), the dominant index of pest insects (B10.370±0.055/B20.282±0.022/B30.414±0.111), the diversity index of pest insects (B11.324±0.228/B21.511±0.066/B31.222±0.200), the diversity index of spiders (B11.167±0.374/B21.418±0.373/B31.286±0.262) and the evenness index of pest insects (B10.600±0.039/B20.683±0.043/B30.550±0.081) were much significantly affected by fertilization ways. The dominant index of spiders(B10.457±0.175/B20.353±0.167/B30.368±0.123), the evenness index of spiders (B10.613±0.160/B20.701±0.130/B30.695±0.168) and the diversity index of predatory insects (B11.190±0.153/B21.496±0.179/B31.474±0.125) were significantly affected by fertilization ways. The individual number of pest insects, the pest insect S. derogate, the dominant index of pest insects, the diversity index of pest insects,and the evenness index of pest insects were much significantly affected by the interaction between habitat complexity and fertilization. The species number of spiders was significantly affected by the interaction between habitat complexity and fertilization. Habitat of the dominant species enemies P. astrigera was improved by straw mulching in cotton field, significantly promoting the effect of P. astrigera to control S. derogate. Compound fertilizer with biogas fertilizer did not facilitate the population growth of S. derogate.(2)Using the systematic investigation in fields and community parameters analysis by one way ANOVA, studies for the structure and dynamics of arthropod community in the fields of transgenic Bt cotton Lumianyan34F1(A), conventional cotton Sumian12(B) and Zhongmian19(C) were conducted. The results showed that in the whole cotton growth period the relative abundance of arthropod sub-communities in pest insects, predators and neutral insects were that A92.1%>B85.4%>C77.9%,A1.4%<B1.5%<C2.8%,and A6.5%<B13.1%<C19.3%, respectively. The pest insect species number7.3±0.3species/10plants in A was significantly lower than that11.3±1.3species/10plants in C. The individual number of total community in A was21827.3±7293.4individuals/10plants, which was significantly higher than that12079.±1056.7individuals/10plants in B and7302.3±1423.8individuals/10plants in C. The pest insect individual number in A was20101.3±4198.6individuals/10plants, which was significantly higher than that5690.6±881.1individuals/10plants in C. The predator individual number298.0±12.7individuals/10plants in A was significantly higher than that185.3±17.4individuals/10plants in B. The individual number of dominant species enemy T. octomaculatum in A was33.0±1.0individuals/10plants, which was significantly lower than that45.0±2.6individuals/10plants in C. The individual number of dominant species enemy P. japonica in A was145.6±34.4individuals/10plants, which was significantly higher than that67.6±7.7individuals/10plants in B and59.3±24.1individuals/10plants in C. The individual number of target pest insect A. gossypii in A was18810.6±7105.0individuals/10plants, which was significantly higher than that9164.0±786.0individuals/10plants in B and4790.0±890.9individuals/10plants in C. The dominant index of total community in A was0.7457±0.0413, which was significantly higher than that0.6001±0.0176in B and0.4850±0.0193in C. The diversity index of total community in A was0.5891±0.0805, which was significantly lower than that0.8461±0.0487in B and1.0724±0.0532in C. The pest insects diversity index in A was0.2629±0.0939,which was significantly lower than that0.4691±0.1314in C. The evenness index of total community in A was0.1767±0.0224, which was significantly lower than that0.2465±0.0093in B and0.3078±0.0147in C...