Xu, X.M. and Ridout, M.S. (2001) Effects of prevailing wind direction on spatial statistics of plant disease epidemics. Journal of Phytopathology, 149 (3-4). pp. 155-166. ISSN 0931-1785.
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A stochastic simulation model was used to study the effects of the strength of prevailing wind (W), the size/shape (Q) of sampling quadrats and their orientation in relation to the prevailing wind direction (D) on spatial statistics describing plant diseases. Spore dispersal followed a half-Cauchy distribution with median distance μ, which depended on simulated wind speed. The relationship of spatial autocorrelation at distance k (ρk) to disease incidence (p) and distance was well described by a four-parameter (α, β1, β2, β3) power-law model; at a given p, ρk declined exponentially with distance. A total of 35 different quadrat sizes, ranging from 4 to 432 plants, were used to sample the simulated epidemics for estimating intraclass correlation (κ). The κ-values decreased exponentially with increasing quadrat size; a binary power law model with three parameters (α1, β4, β5) successfully related κ to p. In general, the effect of W and D was greatest on the parameters α, β1, β2 and β3. The effect of W on α, β1, β2 and β3 depended critically on the spatial pattern of initial infected plants (Y); W had greatest effect for the random pattern. In contrast, the main effect of D and its interaction with W on the parameters α, β1, β2 and β3 were large and consistent over different initial conditions. Variations in α1, β4 and β5 were predominantly due to Y and Q. Only for β5 under the clumped pattern was the effect of W very large. For the parameters α1, β4 and β5 there was a large interaction among W, Q and D for the clumped and regular patterns. As expected, in general, the effect of D increased with increasing prevailing wind strength, quadrat size and quadrat length : width ratio. Using square quadrats reduced significantly the effect of W on the parameters α1, β4 and β5; however, the effect of W on β5 was still very large for the clumped pattern. Sampling perpendicular to the prevailing wind direction generally resulted in larger differences in the nine estimated parameters.
|Subjects:||Q Science > QK Botany|
|Divisions:||Faculties > Science Technology and Medical Studies > School of Mathematics Statistics and Actuarial Science > Statistics|
|Depositing User:||Martin S Ridout|
|Date Deposited:||11 Oct 2008 22:18|
|Last Modified:||14 Jan 2010 14:34|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/9371 (The current URI for this page, for reference purposes)|
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