The role of soil fertility in invasion of Brazilian pepper (Schinus terebinthifolius) in Everglades National Park, Florida

Brazilian pepper (Schinus terebinthifolius Raddi), an exotic invasive plant, is native to South America. In south Florida, this plant has invaded abandoned agricultural lands, poorly managed pastures, roadsides, and canal banks extensively. The "Hole-in-the Donut (HID)", approximately 4000 ha within the Everglades National Park, is a major site of invasion of this exotic plant. This area was previously short hydroperiod prairie and pineland, but it is now a monospecific stand of Brazilian pepper. It has been hypothesized that this transformation is related to rock-plowing soil (crushing the limestone bedrock to increase soil depth) and to intensive vegetable production 25 to 70 years ago. The objectives of this study were to compare the chemical and physical differences of soils from four land uses (undisturbed land, rock-plowed farm land, non-rock-plowed farm land, and restored land) and the mineral nutrient contents of Brazilian pepper and sawgrass (Cladium jamaicense Crantz). Farming in the HID area changed the soil chemical properties significantly through rock-plowing and the application of agrichemicals necessary for commercial vegetable production. Rock-plowing increased the percenage of rock fragments and the soil pH. Total concentrations of nutrients (N, P, Zn, and Cu) in soils were elevated in both rock-plowed and non-rock-plowed farm lands. Plant-available nutrients in soil of rock-plowed farm land increased about 3 times for P, 6 times for Zn, and 10 times for Cu. As a result of the increased soil fertility, concentrations of P and Zn in Brazilian pepper leaves were 5 and 3 times higher, respectively, than those in sawgrass. High correlation coefficients between leaf P and total and plant-available P in soils indicate that P enrichment in farmed soils facilitated the invasion of Brazilian pepper in this area.