CLONAL BIOLOGY OF THE TEMPERATE, CAESPITOSE, GRAMINOID SCHIZACHYRIUM-SCOPARIUM - A SYNTHESIS WITH REFERENCE TO CLIMATE CHANGE

Caespitose graminoids are characterized by the compact spatial arrangement of ramets within clones and the absence of rhizomes or stolons. Resource allocation is principally acropetal with established ramets supporting juvenile ramets during early development. However, after juvenile ramet maturation a responsive resource transfer system is maintained by a low level of continuous resource allocation between parental and juvenile ramets. Isotopic and severing experiments demonstrated that physiological integration in the caespitose graminoid Schizachyrium scoparium is restricted to individual ramet sequences consisting of three connected ramet generations as opposed to all ramets within the clone. This number of ramet generations comprising the physiological individual is determined by demographic variables influencing the recruitment and longevity of individual ramets. Restricted resource allocation among ramet sequences within clones is primarily caused by the disintegration of vascular connections among ramet sequences following death of the seminal ramet. The survival value conferred by a clonal architecture composed of an assemblage of autonomous physiological individuals growing within close proximity requires further evaluation but may center on intra-plant competitive interactions. The response of this large sub-group of clonal plants to climate change will significantly impact community structure and function because of their diversity and dominance in numerous biomes. The impact of climate change on the caespitose graminoid growth form is difficult to anticipate because: 1) caespitose graminoids consist of both C3 and C4 species which will complicate the response of the growth form, 2) our understanding about the clonal biology and population ecology of this growth form is still evolving and 3) the modular construction of this growth form may result in variable responses at the ramet, clone and population levels of organization.