Phenology is the study of the relationships between various climatic factors and occurrence of successive stages in the life cycle of plants or animals (McCarty, 1986). Early attempts to describe phenological events date back to seventeenth century, Carl Von Linné in 1751 noted phenological stages of the species collected (Bergmeier, 1998). The scientific approach to phenological investigation is a fairly recent development. Since 1947, several authors have intensively studied agronomic crops (Kirby et al., 1999; Baker and Reddy 2001) and weeds phenology. Swanton et al. (1999 and 2000) reported the life cycle for Setaria viridis L. and Echinochloa crus-galli (L.) Beauv. Huang et al. (2001) studied pattern of Sinapis arvensis L. growth stages. Among weed species whose phenology was described recently and whose one or several stages phenologic were quantified using ecological factors such as the temperature, we quote: Galium aparine L (Vander Weide, 1992), Solanum nigrum L. (McGiffen and Masiunas, 1992), Cynodon dac-tylon (Satorre et al., 1996), Ranunculus repens L. (Harris et al., 1998), and Alopecurus myosuro'ides Huds. (Chauvel, 2000).
The knowledge of phenological aspects is an essential element for any plan of integrated weed management. Timing of phenological events is one of the most important factors determining the success of plants in capturing resources. Therefore, understanding the factors that control phenological variability is crucial for the design of durable weed management practices. In Algeria, the low grain yield (700 kg ha-1) is partly due to the erratic and low rainfall and also due to the use of unimproved production practices, which do not give attention to the control of weeds. The wheat yield losses caused by weed flora in the Setifian region vary from 30% to 60% depending on weed density and environmental conditions. The objectives of this research were to determine phenological characteristics of 14 cereal weeds and their relations with the climatic variations.
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.