Long-term population development and spatial pattern of Carex curvula subspecies

A study of shoot populations of Carex curvula subspecies (Carex curvula ssp. rosae and C. curvula ssp. curvula) compared predictions from a 3-year observation period with renewed observations after 10 years. The study sites were located in the Dolomites (Mount Latemar), Italy, at 2390-2580 m a.s.l. The first observation period (1990-1992) produced findings on shoot numbers in different plots at five sites. These shoot numbers allowed the finite rates of population increase k (characterizing the dynamic state of the populations) to be calculated. The values of k varied modestly within and among populations. The longterm rates of population increase remained close to the equilibrium value of 1.0. The spatial pattern was calculated by means of the patchiness index and patch occupancy. The smaller the plot population, the higher the patchiness and the lower the proportion of occupied patches. To some extent, patchiness can serve as a measure of a population's dynamic state. A correlation between the structural measures (patchiness, patch occupancy) and the rate of population increase k showed that strongly aggregated populations were small and also decreasing in size. The extinction risks for the next 50 years were found to be very low for populations on the pioneer grassland stand whereas most other populations will decrease and probably reach critical thresholds.