Prediction of cutting effects on a population of Chaerophyllum aureum - a demographic approach

A demographic study of the undesirable perennial weed Chaerophyllum aureum in extensified French Pyrenean hay meadows was carried out. For two success ive years the effect of date and intensity of cutting on the population dem ography of this colonizer. Population density is sensitive to cutting pract ices essentially through fecundity, seedling survival rate and seed dispers al between fields. Cutting reduces fecundity by preventing seed formation ( early cutting) or by exportation of some mature seeds with hay (late cuttin g). Nevertheless, the number of seeds transported between field populations by hay harvest, organic manuring and associated cutting practices compensa tes for the lack of seed production in early-cut populations, maintaining t hem at relative high densities. For each of three cutting regimes, the numb er of immigrant and emigrant seeds has been indirectly estimated from a pre diction of population density at equilibrium from demographic parameters me asured in field populations and compared with observed population densities .