Relationships between soil nutrients and plant species composition in Everglades peatlands

Base cations (Ca, Mg, K, Na) and metals (Al, Fe, Mn) were measured in peatlands of the northern and central Everglades to (i) determine the extent and degree of elemental enrichment of the peat caused by agricultural drainage and (ii) assess the relationship between cattail (Typha latifolia L.) encroachment into sawgrass (Cladium jamaicense Crantz) communities and elemental (cations, metals, P) enrichment of the peat. Soil Ca, Mg, and Na (0-10 cm) decreased, and Al and Fe increased from north to south through the northern and central Everglades. In particular, nutrient-enriched (P) ares of northern WCA 2A had higher concentrations and accumulation rates of Ca, Mg, and Na than areas to the south. A detailed investigation along a P enrichment gradient in northern WCA 2A revealed a gradient of Ca and Na enrichment extending 1.6 to 3.4 km downstream of the Hillsboro canal, the source of agricultural drainage to WCA 2A. Rates of Ca (35 g/m2 per yr) and Na (1.5- 3.2 g/m2 per yr) accumulation were 2 to 10 times greater 1.6 km below the Hillsboro canal than in areas 3.4 to 10.7 km downstream. Correlation analysis revealed that macrophyte species composition along the enrichment gradient was highly correlated with soil P (0-24 cm) but not with soil Na or Ca. The percent frequency of cattail (r = 0.74) and other species (r = 0.66) was positively correlated while sawgrass (r = -0.83) was inversely correlated with soil P content. These findings suggest that cattail encroachment into sawgrass communities is favored by enrichment of the peat with P loadings from agricultural drainage pumped into northern WCA 2A.

Duke Scholars

Author Curtis J. Richardson Environmental Sciences and Policy