Invasive Species Compendium

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Abstract

Demography of Lolium rigidum in winter barley crops: analysis of recruitment, survival and reproduction.

Abstract

Demographic studies were conducted with Lolium rigidum growing in winter barley crops at five sites in central and eastern Spain, over a period of 2 or 3 years (1993-95). Although 3-fold differences (34-97%) in annual recruitment were recorded in the various experiments, most of the values were close to the overall average (67%). Seedling emergence took place in a very short period of time after sowing, with 90% emergence generally being reached after a thermal time of 242 d°C (provided soil moisture was adequate at sowing). Seedling survival was very high (78-95%) in most experiments, with no clear relationship between this parameter and any of the environmental variables studied. Survival curves were relatively linear, with plant mortality increasing gradually throughout the life cycle of the plant. There were 34-fold differences (from 7 to 237 seeds per plant) in the fecundities recorded in the various experiments. Variation in fecundity resulted partly from differences in crop and weed densities and total precipitation received during the growth cycle. The annual rate of population growth was estimated based on the above-mentioned parameters. The potential for population growth was high (average λ=6.21), but large differences were obtained for the different sites and years.