DYNAMICS OF A LANDSCAPE MOSAIC - SIZE AND AGE DISTRIBUTIONS, GROWTH AND DEMOGRAPHY OF SEAGRASS CYMODOCEA-NODOSA PATCHES

The patch dynamics (recruitment, growth and mortality) of seagrass Cym odocea nodosa were examined at the landscape scale (i.e. the scale at which disturbances occur) by means of 3-dimensional (X, Y dimensions a nd depth) mapping of shoot internal density and age structure within t he basic units (patches) forming the landscape. Highly skewed patch si ze and age distributions indicated a high exponential patch mortality rate (m = 0.82 +/- 0.07 yr(-1)) and a slightly higher exponential patc h recruitment rate (1.04 yr(-1)) that ensures the maintenance and fast turnover of this population of patches. Patch growth (i.e. increase i n number of shoots per patch) proceeded at an exponential growth rate of 2.28 +/- 0.14 yr(-1), indicating a doubling time of 111 d for the s hoot population within each patch. Moreover, average patch growth rate accelerates with increasing patch size and age. This self-acceleratio n of patch growth means that this seagrass species has a remarkable po tential for rapid space occupation due to its intense clonal growth. T he results obtained emphasize the power of a landscape approach for de scribing the intense dynamics of colonising seagrass populations.