Ramet phenology and clonal architectures of the clonal sedge Schoenoplectus americanus (Pers.) Volk. ex Schinz &; R. Keller

The clonal plant Schoenoplectus americanus shows variable belowground clonal architecture as a result of producing two types of ramets: those with very long rhizomes (long rhizome ramet, LRR) and those with very short ones (short rhizome ramet, SRR). In a previous study we demonstrated that the two types of ramets are functionally specialised. The production of SRRs results in the formation of consolidated clonal patches with densely packed shoots, while the production of LRRs results in a more diffuse network of connected rhizomes with widely spaced shoots. We hypothesised that the two types of ramets would be produced at different times during the growing season because of their functional differences. The production of LRRs throughout the growing season would enable the species to continuously explore new habitats while the production of SRRs early in the growing season would enable the species to occupy and consolidate resources in available open patches. We evaluated this hypothesis through field observations in different communities with S. americanus and indeed found that SRRs were produced early in the growing season while LRRs tended to be produced over an extended period of time. Plants in high-quality environments (i.e. higher light conditions) produced more SRRs, and these were formed early in the growing season. In contrast, plants in low-quality environments produced more LRRs, and these were formed continuously over the growing season. We also observed that the shoot longevity was greater for SRR. In high-quality patches, the production of the lower cost SRRs results in a more rapid occupancy of open spaces; in lower quality patches, the production of LRRs throughout the growing season enables plants to explore the immediate environment for higher quality patches.