乘积优势度法在农田杂草群落研究中的应用

The Multiplied Dominance Ratio Method in the Study of Crop-weed Communities

提出用盖度、相对高度和频度的乘积计算杂草群落中某个种的优势度,表达植物种地上部分所占的三维空间。运用乘积优势度(MDR)可对农田杂草群落的种类组成进行定量分析,区别杂草群落,进行草害调查。方法简便、快速,所得结果的可靠程度大于传统方法,今后还可应用于种群变迁与群落演替趋势的监测和预测。

There are difficulties in quantitative study of weed communities and weediness. According to M. Numata(1962), the floristic compostion of weed communities can be expressed by the summed dominance ratio (SDR). However, the author found in 1988 by observation and statistics that the SDR value of a weed species with low coverage would be exaggerated, and that of wheat with high coverage be lowered, giving significant errors. H. Walter (1983) stated that weediness, an estimate of the competitive potential of a weed infestation, is a combination of plant cover and height, but he did not well define it. The author suggested in 1988 a multiplied dominance ratio (MDR) method and applied it in the study of weed communities in wheat in Southern Jiangsu (see Tables 1,2). The MDR value is obtained by multiplying coverage (C') , relative height (H')and frequency (F'), i. e. , MDR2 ( % ) = (C'X H') X 100, MDR3 ( % ) = (C'X H'X F') X 100 and MDR'(relative MDR) of a given species= (MDR of the species)/(S MDR of major species) X100. MDR represents the three dimensional space occupied by the above ground parts of the species ; the MDR2 value may thus represent the weediness of the weed species. This method, when used in the quantitative analysis of floristic composition, classification of weed communities and assessment of weediness, is more convenient, rapid and reliable than traditional methods. It has been applied successfully in the investigation of dominant species in weed communities and in the assessment of weed damage in rice, wheat, cotton, maize, soybean, vegetables and lawns in Wuxi and Huaiyin districts of Jiangsu in 1988-1990. It can also be used to monitor and predict the trend of population shifts and succession of weed communities.