Question: What is the population viability of a critically
endangered seashore grass, Arctophila fulva var. pendulina.
Location: Liminka Bay, W Finland, 25°21'70 N, 64°51'90 E.
Methods: We constructed a matrix population model based
on colonization and disappearance events and patch size
changes of A. fulva. Patches were divided into hydric and nonhydric
zones according to proximity to the seashore and intensity
of disturbance. Perturbation analyses were carried out in
order to identify transitions critical for population growth.
Seed bank and seed germination studies provided background
information for the model design.
Results: A. fulva patches observed in the more disturbed
hydric zone (closest to the sea) increased in number, as did the
total number of patches. However, the number of patches in
the less disturbed non-hydric zone decreased.
Conclusions: Short-term dynamics of the A. fulva population
at Liminka Bay seem to be determined by environmental
fluctuations, which cause annual variation in transition rates
between patch size classes. The long-term dynamics are probably
governed by initiation of primary succession by isostatic
land uplift. Increased disturbance at the water’s edge may
promote persistence of A. fulva through reduced interspecific
competition. Our results suggest that shoreline disturbance of
the hydric zone is sufficient for maintaining a viable population.
Competitive exclusion of A. fulva in the non-hydric zone
may be delayed by management practices, such as mowing