Seasonal phenology and starch allocation patterns of Cuban bulrush (Oxycaryum cubense) growing in Mississippi, USA

Abstract

Seasonal patterns of biomass and starch allocation for the aquatic invasive species (AIS) Cuban bulrush were quantified in populations from Lake Columbus on the Tennessee-Tombigbee Waterway in Mississippi. Monthly samples of Cuban bulrush were harvested from five plots from May 2019 to April 2021. During each sampling event, water pH, water temperature, air temperature, and photosynthetically active radiation (PAR) were recorded. Average peak total biomass was 309.0 g DW m−2, 290.0 g DW m−2, and 129.3 g DW m−2 in 2019, 2020, and 2021 respectively and usually occurred in late fall or early winter months (November to January). Biomass allocation was greatest for submersed tissues and least for inflorescences. Total, emergent, and submersed biomass had weak negative correlations with water temperature and PAR. Peak total starch content occurred from August to December and was measured at 3.7% DW, 3.2% DW, and 1.3% DW for 2019, 2020, and 2021, respectively. Overall, starch was not disproportionately stored in any one tissue, < 1.5% DW for all plant tissues. Since peak biomass occurred during the coldest months of the study, it suggests the capability of this species to expand northward. Future work should include wider spatial or geographic variation in sampling strategy and incorporate growing degree days (GDD) analysis to enhance the understanding of the relationships between life stages and environmental factors.