Effects Of Habitats On The Structure And Function Of Arthropod Community In Cotton Fields

In order to determine the effects of habitat on the structure and function of arthropod community in cotton fields,we learned more about the status and roles of habitats in agricultural production and promoted the development of the principle that using natural enemies to control pests in agricultural activities.This paper reaserched the dynamic changes of arthropod community in cotton field under different habitats and the difference of arthropod community structure in cotton field under different habitats as the effect of double factors of the external and interior community habitats.And it also studied the effect of predating the aphids when the predators coexisted in different niche.The results were as follows:1.In the external community habitats we setted two treatments: cotton field without surrounding plants(A1)and cotton fieldswith surrounding plants(A2).In interior community habitats we setted four treatments: bare land(B1),bare land with grass covering(B2),bare land with plastic film(B3),bare land with film and grass covering(B4).Each treatment was taken parallel line jump method to extract six cottons.We investigated and analysiesed systematically all arthropod species and the number of individuals on every 6 plants and the 0.25m2 oil surfaces of plant.The results showed that the individual numbers of neutral insects(A1 402.9±86.6/A2 518.2±176.2 individuals·6 plant-1)?the diversity index of neutral insects(A1 0.477±0.224/A2 0.637±0.197)?the evenness index of neutral insects(A1 0.166±0.080/A2 0.223±0.075)?the dominant index of neutral insects(A1 2.819±2.706/A2 0.770±0.393)?the dominance degree of neutral insects(A1 0.934±0.038/A2 0.904±0.036)and the individual numbers of pests(A1 787.9±204.7/A2 1048.4±196.5 individuals·6 plant-1)?the diversity index of pests(A1 0.334±0.109/A2 0.448±0.218)?the evenness index of pests(A1 0.130±0.041/A2 0.193±0.063)?the dominance degree of pests(A1 0.958±0.016/A2 0.931±0.027)were much significantly affected by external biotope.The individual numbers of predators(A1 117.1±39.1/A2 126.2±19.8 individuals·6 plant-1)was significantly affected by external biotope.The individual numbers of predators(B1 128.0±11.6/B2 144.0±13.4/B3 78.7±28.0/B4 135.8±11.2 individuals·6 plant-1)and the species richness of predators(B1 2.801±0.239/B2 2.345±0.143/B3 2.408±0.185/B4 2.384±0.104),the individual numbers of neutral insects(B1 387.0±130.6/B2 391.2±82.3/B3 511.2±184.0/B4 552.8±131.9 individuals·6 plant-1)and the dominant index of neutral insects(B1 0.817±0.073/B2 1.909±0.926/B3 2.988±3.227/B4 1.465±0.729),the diversity index of neutral insects(B1 0.393±0.139/B2 0.466±0.224/B3 0.230±0.159/B4 0.473±0.078)and the dominance degree of neutral insects(B1 0.962±0.016/B2 0.948±0.021/B3 0.933±0.040/B4 0.936±0.014)were much significantly affected by community interior habitats;The dominant index of predators(B1 0.174±0.072/B2 0.239±0.054/B3 0.155±0.096/B4 0.140±0.034)? the dominance degree of predators(B1 0.280±0.116/B2 0.229±0.039/B3 0.228±0.063/B4 0.193±0.018)and the evenness index of pests(B1 0.123±0.046/B2 0.153±0.052/B3 0.185±0.093/B4 0.183±0.030)were significantly affected by community interior habitats.The dominance degree of predators,the dominant index of predators,the individual number of neutral insects,the dominance degree of of neutral insects,the diversity index of neutral insects,the evenness index of neutral insects,the dominant index of neutral insects,the dominance degree of neutral insects,the diversity index of pests,the dominance degree of pests were much significantly affected by the interaction between external community habitat and community interior habitat.The individual numbers of predators,the species richness of predators,the evenness index of pests were significantly affected by the interaction between external community habitats and community interior habitats.2.Chamber to P.japonica,Harmonia axyridis adults as the object of study predation of the same niche in the natural enemies of cotton aphid,the results showed that: when the two ladybugs are adults,the volume of cotton aphid predator with cotton aphid was increasing by the density increases;when both adult ladybirds coexist,if they can exhibit synergistic effect mainly decided by the prey density.When at a low density(number of 40,60 heads of aphids/plant),the predation of two kinds of ladybirds coexist was much significantly less than the sum of predation that two kinds of ladybirds respectively(P<0.001);at medium density(number of 80 heads of aphids/plant),the predation of two kinds of ladybirds coexist was significantly less than the sum of predation that two kinds of ladybirds respectively(P=0.021);at high density(number of 100,120 heads of aphids/plant),the predation of two kinds of ladybirds coexist was much significantly higher than the sum of predation that two kinds of ladybirds respectively(P=0.006,0.008).3.Chamber to four instar larvae of P.japonica,Harmonia axyridis as the object of study predation of the same niche in the natural enemies of cotton aphid,the results showed that: the predation of four instar larvae of two kinds of ladybugs was increasing by the density increases;the predation of Harmonia axyridis four instar larvae were larger than the Propylaea japonica;when two kinds of ladybug larvae coexist at the same age,if they can exhibit synergistic predation mainly decided by the prey density and their age.When two kinds of ladybug larvae were at first age and aphid density were 50,60,70,80/plant respectively,the predation of two kinds of ladybirds coexist were significantly larger than the sum of predation that two kinds of ladybirds respectively(P= 0.012,0.045,0.046,0.031);when both the larvae in the second instar stage,and aphid density 50,60,70/plant,the predation of two kinds of ladybirds coexist were significantly higher than the sum of predation that two kinds of ladybirds respectively(P=0.040,0.015,0.035),at a density of 80 aphids/plant,the predation of two kinds of ladybirds coexist had reached the density(80/plant);when in the third instar larvae and fourth instar,predation that two kinds of ladybirds respectively were all close to aphid density,while all apids were eaten when two kinds of ladybug larvae coexist.4.Chamber to Propylaea japonica,Tarantula adult as the object of study predation of different niche natural enemies of cotton aphid,the results showed: the predation of P.japonica and tarantula on cotton aphid were increasing as cotton aphid density increases;in each aphid density,the predation of two predators coexist were higher than the sum of predation that two kinds of predators respectively.The gap between the predation of two kinds of predators and the sum of predation that two kinds of predators respectively was increasing as cotton aphid density increases.It shows that the different niche predators of P.japonica and tarantula exhibit synergistic effects on cotton aphids.