Growth dynamics and biomass allocation of Eleocharis sphacelata at different water depths: observations, modeling, and applications

Imbalanced biomass allocation patterns in emergent aquatic plants to above and below-ground structures as a response to climatic variations and water depth were investigated on the basis of observation of three stable homogeneous populations established under different water regimes and climatic environments in Goulburn and Ourimbah, New South Wales, Australia, from August 2003 to December 2004. The growth of shoots depended on water inundation-drawdown patterns and climatic variations. Shoot density was greater in shallow water but with shorter shoot length and less maximum above-ground biomass density than for plant stands in deep water. Deep-water populations attained higher below-ground biomass with higher above to below-ground biomass ratio than for the shallow-water population. Translocation of carbohydrate reserves between above and below-ground organs in deep-water populations were mostly downward throughout the year whereas the depletion–recharge pattern varied seasonally in shallow water populations. Shoots of deep-water populations grew year-round whereas in shallow water shoots died off after recession of the water level with no re-growth afterward, showing that Eleocharis sphacelata is better adapted to deep water and is stressed under shallow-water conditions. A mathematical model was formulated to describe the growth patterns of E. sphacelata and subsequently to predict the effect of water depth on production. Model simulations are in satisfactory agreement with observed patterns of growth. The model also predicts that maximum production decreases sharply with increasing water depth.