Abstract
The objective of this study was to investigate the effect of general factors such as crop, regional climate or country on the weed flora and weed abundance in rainfed crops in tropical regions. For this purpose, we used 24 weed survey datasets from 4 climates, 11 crops and 11 countries in the tropics. These datasets are available in public access on the CIRAD Amatrop dataverse. This represents a set of 6 069 weed surveys, covering a total of 1 388 taxa. The data were analysed using different complementary approaches, including infestation diagrams, species correlation and co-occurrence matrices, corrected ecological profiles, and PCAIV. The results show that in the tropics there is a background of fairly common and ubiquitous species that are found in varying abundance in almost all situations. Ageratum conyzoides is the only Major general species, while Rottboellia cochinchinensis, Digitaria horizontalis, Bidens pilosa, Cyperus rotundus, Commelina benghalensis, Euphorbia heterophylla, Eleusine indica, Euphorbia hirta and Tridax procumbens are General species, present in more than 15% of the records. The climate factor, depending on rainfall and altitude, which influences temperature, selects certain indicator species for different situations. The crop factor does not have a particular selective effect and the country highlights local flora. Crops are themselves dependent on climate. It is nevertheless possible to know which species are most likely to be found in a plot of a crop, under a given climate and in a given country. However, it seems that it is the combination of the edaphic and climatic nature of the plot that most accurately determines the floristic composition of the weed flora, although we were unable to analyse this due to the lack of complete information on these factors for all the datasets used. Finally, out of the 1 388 taxa taken into account, only about 300 species constitute the core of the weeds of tropical rainfed crops, because of their frequency, their abundance or their character as indicators of particular agro-ecological conditions.