Poster Session # 14: Forest Ecology.

Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Ramet dynamics of the clonal understory tree, Asimina triloba.

Hosaka, Naomi*,1, 3, Stuefer, Josef2, Whigham, Dennis1, Kachi, Naoki3, 1 Smithsonian Environmental Research Center, Edgewater, Maryland3 Tokyo Metropolitan University, Hachioji, Tokyo, Japan2 University of Nijmegen, Toernooiveld, Nijmegen, The Netherlands

ABSTRACT- Body of Abstract: The ecological feature of clonal growth varies with the life history of plant species and the habitats where they occur. In temperate deciduous forests, clonal growth is common to understorey tree species. We explored three possible features of clonal growth in a natural population of Asimina triloba: risk spreading, securing space occupancy, and foraging for light through ramet dynamics. In one study, four annual censuses of ramet populations in distinct patches were conducted in a shaded understorey to test whether (1) ramet turnover is related to patch size, (2) newly recruited ramets mainly appear inside or outside of existing patches, and (3) the survival of new ramets is lower than the survival of established ramets. In all patches the turnover rates of the ramets were stable and annual natality exceeded mortality during the three years. New ramets occurred inside and outside of the patches and we found no evidence of intra-patch competition between ramets. The ratio of new ramets to the total number of ramets in the patches was relatively constant during the census period. Neither was there a significant relationship between initial ramet size and mortality. These results demonstrate that clonal growth may play a crucial role in the long-term survival of Asimina triloba in the forest understorey. In a second study, annual ramet growth and ramet size structure of patches in an open forest edge site were compared with those of the understorey patches. In the open site, individual ramets showed more vigorous shoot growth, suggesting that improvement of light availability enhances individual ramet growth. Flexible growth of the above ground part of ramets was suggested by a weak correlation between tree-ring and basal diameter of the ramets in the open site. The flexible growth may correspond with heterogeneous light conditions in the forest.

Key words: population size structure, clonal growth, ramet dynamics, understorey