Abstract
Rangelands used for cattle grazing in Florida are typically managed under prescribed fire to increase forage production and nutritive value while preventing shrub encroachment. Sustainability of extensively managed, low-input native rangelands is highly dependent on nutrient cycling through plant litter decomposition, which is often constrained by limited N availability. We evaluated the effect of prescribed fire (Unburned vs. Burned), N addition (0 vs. 180 kg N ha−1 yr−1), and species composition (Palmetto [Serenoa repens Bartr.] [100% saw-palmetto], Palmetto-Grass [50−50% mixture of saw-palmetto and grasses], and Grass [chalky bluestem, Andropogon capillipes Nash.; lopsided indiangrass, Sorghastrum secundum {Elliott} Nash]) on aboveground plant litter decomposition and N and P mineralization using field incubated litterbags over 224 d in a split-split plot design with three replicates. Litter disappearance followed a single exponential decay model (P ≤ 0.01) and was mainly driven by plant litter chemical characteristics. At the end of the 224-d incubation, remaining plant litter was less in Palmetto (62%) compared with other treatments (∼72%), possibly due to more favorable chemical characteristics associated with Palmetto treatment (43, 65, and 112 C:N ratio; and 15, 20, and 25 lignin:N ratio for Palmetto, Palmetto-Grass, and Grass, respectively). Remaining N was less (greater N mineralization) in Palmetto (79%) compared with Palmetto-Grass treatment (92%) but was not different from Grass (P ≥ 0.12, 86% remaining N). Greater lignin and proportion of N bound to fiber observed at the end of incubation suggested increased C and N recalcitrance as a result of decomposition. Nutrient inputs through ash or N addition suppressed litter net P and N mineralization. These results suggest litter quality, particularly N concentration and C:N and lignin:N ratios, are the main drivers in nutrient cycling through plant litter decomposition in Florida rangelands.
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