Phenological patterns in an arable land weed community related to disturbance

The emergence pattern and life cycle of four major species growing in a non–irrigated almond tree grove were analysed in relation to ploughing frequencies and environmental factors. At the community level, the overall emergence pattern was found to be much the same whether or not the soil was disturbed. Nevertheless, soil disturbance in late winter and early spring produced peaks of seedling emergence and brought about an increase in germination. Winter annuals such as Lolium rigidum Gaudin and Diplotaxis erucoides (L.) DC., which emerged in the autumn, started to grow rapidly in winter and spring and were able to pre–empt the environmental resources of the habitat and suppress spring–germinating plants such as Chenopodium album L. and Amaranthus blitoides S. Watson. Late–winter and early–spring disturbances favoured the dominance of summer annuals such as C. album and A. blitoides S. Watson. The different ploughing regimes applied during the first year had effects on plant development and seed production which brought about changes in plant population size during the second year.