Seedling recruitment and age-specific survivorship and reproduction in populations of Avena sterilis L. ssp. ludoviciana (Durieu) Nyman.
The demography of the annual grass weed A. sterilis subsp. ludoviciana was studied during 3 consecutive years on populations growing in winter wheat crops in central Spain. Seed banks were determined annually by soil sampling followed by wet sieving. Permanent quadrats were monitored periodically to obtain data on the periodicity of seedling emergence, the fate of seedlings and their reproductive performance. Seedling emergence took place from mid-Oct. to mid-Apr., with a peak in Nov.-Dec. The progress of emergence was described by a logistic model and was closely related to the cumulative rainfall recorded during that period. Total seedling recruitment from the seed bank ranged from 31 to 46% during the 3 seasons. Av. seedling survivorship ranged from 31 to 81% during the 3 seasons. Within each season, survivorship was highly variable for the different cohorts. The major causes of mortality during the life-cycle were pre-sowing tillage, frost and drought stress and inter- and intraspecific competition. Av. adult fecundity varied from 13 to 21 seeds/plant. Within each season, fecundity was highly dependent on the age of the plant. The relationship between plant age and fecundity was well described by a negative exponential model. Overall, the cohorts emerging soon after wheat sowing were the most successful ones, having the largest contribution to the next generation.