Numerical methods illustrating the phytosociology of crops in relation to weed flora.
Frequencies of 207 weed species were recorded in 466 fields of 19 different crops in Denmark. The data were subjected to cluster and factor analyses, in an effort to relate crop types and their weed flora. The weed flora was closely related to crop types. In particular, there was a close relationship between the growth period of crops and their weed flora, especially the frequency of therophytes. The results are discussed in relation to the growth period of the crop, the life form of the weed species and agricultural practice. It is concluded that numerical methods are a useful tool in understanding the phytosociology and ecology of weed flora. From summary.