Temporal and spatial dynamics of Lithosphermum arvense L. populations on arable fields and the effect of different crop management

Like many other weeds, Lithospermum arvense has strongly declined during the last five decades. Studies on population biology and the effect of crop management (nitrogen, herbicides, one year fallow) were carried out to find reasons for this decline. During three vegetation periods seedling emergence, phenology, growth, reproduction and demography of L. arvense in competition to different crops were studied. A comparison with former investigations on the same experimental sites provides knowledge about long-term dynamics. To obtain information about dispersal and reestablishment, a small initial population was artificially introduced on a field where L. arvense was previously absent. Germination and seedling emergence took place in autumn and early spring. The mean coverage was larger in winter cereals than in spring cereals where the autumn cohort was destroyed by spring tillage. The plasticity in growth (especially shoot length and number of branches) was very high, but even under favourable conditions seed production did not exceed 1000 per plant. The artificially introduced population was dispersed only 2.5 m within two years. Due to short-term seed Viability in the soil and low dispersability, the potential of regeneration must be assessed as low. Nitrogen fertilizer had a positive effect on growth and reproduction. One reason for the success of L. arvense in fertilized crops was the ability to avoid light limitation by increasing the shoot length. The sensivity of L. arvense against different phenoxy acid herbicides was low.