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Eco-economic Threshold Modelling and Parameters Fitting of Grasshoppers in Rangeland

Author: LiuChaoYang
Tutor: ZhangZeHua
School: Chinese Academy of Agricultural Sciences
Course: Agricultural Entomology and Pest Control
Keywords: Grasshopper Eco-economic threshold Grass Precipitation Grass coverage degree
CLC: S812.6
Type: Master's thesis
Year: 2013
Downloads: 2
Quote: 0
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Abstract


The reactions of natural grassland ecosystem are different for various biological disasters. It isnecessary to consider both economic factors and ecological factors during biological disaster treatment.Then it is of great significance to build an eco-ecnomic threshold model taking into account theeconomic and ecological benefits. We studied the compensation, vulnerability and recovery capabilityof the grassland, the effects of precipitation and grass coverage degree on grassland productivity, andgrass occupancy of the insects for biodiversity, then we built an eco-economic threshold model ofgrasshoppers in rangeland based on our research results.According to the life table for natural population and the damage of each instar of Oedaleusdecorus asiaticus Bienko, we simulated infestation. The results showed that with the gradually increaseof the grasshopper infestation, the above-ground standing crop showed a trend of increased and thendecreased. The feeding rate of11.14%is equal compensation point,and feeding rate of22.03%is thecritical point of grass vulnerability. Adult population density of12/m2or15/m2led grasslanddegradation,showing the decreased community dominance, grass coverage degree and productivity andthe increased plant diversity and species richness. The progress of grassland vegetation restoration is theopposite to the above changes. The reproductive indicators and growth indicators of Stipa kryloviiRoshev can be used to evaluate grassland vegetation restoration situation.We set precipitation gradient test and grass coverage degree gradient test, then measured grasslandproductivity and the reproductive indicators and growth indicator of Stipa krylovii Roshev. in differentprecipitation levels and grassland productivity in different levels of grass coverage degree at the end ofJune, July and August.The results showed that grassland productivity and precipitation were positively linear correlation,and the linear equation is P=0.7751×W-22.47(p<0.01, r:0.71), precipitation is conducive to the growthof the Stipa krylovii Roshev reproductive and growth. Grassland productivity and grass coverage degreewere also positively linear correlation, and the linear equation is P=360.89×C(p<0.01,r:0.92).We also studied the insect species and number in non-disaster area of grassland ecosystem andmeasured the grass occupancy of the insects for biodiversity through eco-efficiency conversion method.The results showed that to maintain biodiversity the insects occupy8.69%of grass resource, and theproportion of grass resource needed to keep normal grasshopper populations is6.38%.Based on the above result, we built the eco-ecnomic threshold model taking a variety of factorssuch as subsistence threshold, tolerance threshold, sensitivity index and economic threshold intoconsideration. The model is showed as follows.EET=E×H×C/γ×[(α+β)×γ/FL+CC/EC×P×FL]EET: Eco-economic Threshold; H:The Influence Coefficient of Coverage; C: Historical Average ofGrass Coverage Degree in August; E: Precipitation Factor; FL: Single Population Loss Estimate; CC: Control Cost; Pr: Forage Price; EC: Control Effect;α:Tolerance Coefficient; β:Resource Coefficient; γ:Sensitivity Coefficient.

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CLC: > Agricultural Sciences > Livestock, animal medicine,hunting,silkworm,bee > General Animal Science > Grassland Science,prairie school > Grassland protection
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