小麦条锈病病害流行空间动态电算模拟的初步探讨——Ⅰ.圆形传播

 在国内已发表的两个小麦条锈病流行电算模拟模型的基础上,将研究的病害传播范围等分成一定大小的正方形小区,并以其为空间传播的计量单元,确定各小区的方位和间距。利用Mackenzie的病害直线传播梯度模型,通过试验建立回归预测式求得b值。并根据子代病叶总数与子代发病中心病情的定量关系,求出中心点病情a。再经过随机数转换和重叠侵染转换,与已有的日传染率、潜育期模型相结合,组建了"XRZD-1"电子计算机模拟模型。通过多次循环可以推算和打印出逐日的各小区病害数量及形象化图形。实现了病害时间动态和空间动态的协同模拟。

COMPUTER SIMULATION OF DISEASE SPREAD FROM THE FOCUS OF WHEAT YELLOW RUST Ⅰ.CIRCULAR SPREAD

Basic model describing the circular spread from the infection focus of wheat yellow rust was developed based on the disease gradient modelXi=a·exp(-bdⁿ).The whole field under study was divided into square compartments with side length being one unit of distance "d",facilating the determination of the distance between each compartment and the focus center.Parameter "b" can be predicted from a regression equation of "b" upon the wind velocity "w",and parameter "a" was deducted based on there lationship between a and b,and the total amount of disease infection.Assuming the velocities of multi-directional wind are more or less the same(ie,in case of circular spread),the number of emerging diseased leaves of each compartment could be calculated according to the equationXi=a·exp(-bdⁿ),and the predicted values were further transformed by random-process and multiple-transformation.By uniting this model with the preexisting temporal model(such as TXLX),a comprehensive model,named XRZD-1,was constructed and run to describe both the temporal and the spatial dynamics of the epidemic in early phase.