Patterns of growth and reproduction in a perennial tundra forb (Geum rossii): effects of clone area and neighborhood

The relationships of clone area and neighborhood to ramet size, reproductive effort, and spatial distribution within Geum rossii clones were studied in an alpine ecosystem on the Beartooth Plateau, Montana. Clones growing on an early seral site in relative isolation were compared to clones on a late seral site within dense, heterogeneous neighborhoods. Individual clones of G. rossii required a minimum clone area of about 200 cm2 before maximum ramet size and reproductive effort were achieved. Mean ramet size and reproductive effort were fairly constant among clones larger than 200 cm2 on both the early and later seral sites. Within clones the size and reproductive effort of ramets were positively related. Pattern analysis revealed that ramets became more widely and irregularly spaced as clone area increased on the early seral site. This may have been a geometric function of an increase in the space required as clones aged and became larger. On the late seral site, clones were characterized by ramets that were widely and erratically spaced, that had low leaf numbers and mass, and that had low reproductive effort. For clones of comparable area on the early seral site, ramets were more closely and uniformly spaced, and leaf number, mass, and reproduction per ramet were higher. Conservative patterns of growth and reproduction make G. rossii well suited to dominate in dense, heterogeneous neighborhoods of late seral sites and to colonize mineral soils of early seral sites. Similar to other clonal species, site characteristics and the type of neighborhood determine the trade-off between the physical occupation of space and the allocation to ramet growth and reproduction in G. rossii. Key words: Geum rossii, alpine, reproductive effort, growth, clone area, pattern analysis, succession, neighborhood.