Allometric scaling of dry weight and leaf area for Spartina densiflora and Spartina alterniflora in two Southwest Atlantic Saltmarshes

Abstract

Southwest Atlantic saltmarshes are characterized by the presence of Spartina alterniflora in the lower intertidal zones and Spartina densiflora in the middle to high tidal elevations. Because of its dominance and productivity and its central role in carbon and energy fluxes, Spartina spp. biomass and primary production have been extensively studied by different techniques. Since nondestructive techniques require relationships between tiller biomass and morphometric parameters, in this work we established allometric relations among biomass, leaf area, and size, in populations of S. densiflora and S. alterniflora from Mar Chiquita and Bahía Blanca, Argentina. We collected 743 standing tillers of S. densiflora and 663 of S. alterniflora from different dates, conditions (green, flowered, and dead), and sources (high and low marsh). We obtained strong correlations between all the morphometric parameters. Leaf area and leaf length were strongly related (R2 = 0.84 for S. densiflora and 0.91 for S. alterniflora). Leaf area per tiller and tiller biomass strongly regressed on tiller height (R2 = 0.97 and 0.91 for S. densiflora and 0.88 and 0.90 for S. alterniflora, respectively) thereby facilitating estimations of these parameters. The predictive power of the biomass vs. tiller height equations was satisfactory when applied for different data types (date, condition, and source), suggesting that the models can be widely used for estimating the biomass of a tiller from its length. Moreover, the predictive power of the equations was high even for standing dead tillers, allowing us to use the same equation along the tiller's span life and facilitating detritus production estimations. The allometric relations established in this study may be used to estimate Spartina biomass and leaf area at the study sites, with strong implications in the monitoring and assessment of saltmarshes.