THE POPULATION-DYNAMICS OF VULPIA-FASCICULATA - A 9-YEAR STUDY

Vulpia fasciculata was monitored for 9 yr on fixed dunes in N Wales. During the first 4 yr, the number of individuals on each plot varied little, but numbers then declined rapidly to extinction, associated with an increase in the cover of perennial vegetation and a decline in the cover of bare sand. Fecundity of individuals varied between years but generally increased with the decline in density. The decline was associated with a decrease in the local movement of surface-blown sand and an increase in mortality amongst the seedlings which germinated on the sand surface. Populations can only be expected to persist where the percentage of bare sand remains >50%. -from Author