Intensification enhances litter carbon and nitrogen decomposition dynamics in subtropical grazinglands

Abstract

Abstract Increased grazing land management intensification through the selection of productive species and the use of N affects the amount and quality of C and N inputs to the soil. This study evaluated the short‐term impacts of litter quality on litter decomposition and C and N distribution among soil size–density fractions. A 168‐d litter bag mesocosm experiment and a 120‐d incubation study evaluated the decomposition of three perennial species [rhizoma peanut (Arachis glabrata Benth., RP), bahiagrass (Paspalum notatum Flügge; BG), and saw‐palmetto (Serenoa repens Bartr., SP)] on grazing land soils with contrasting C concentrations (3.4 and 18 g C kg−1; Buck Island Ranch and Ona, respectively). Soil did not affect litter decomposition. There was less remaining biomass at the end of incubation for RP and BG (58%) than SP (79%). Nitrogen immobilization occurred on SP litter, probably because of its high initial lignin/N and fiber‐bound N/N ratios (43 and 384 g kg−1 organic matter, respectively). Litter had no effect on soil C and N concentrations in size–density fractions; however, greater proportions of C and N (∼47 and 59%, respectively) were found in the light‐free fraction. Nitrogen addition promoted C and N accumulation in the mineral fraction. These results suggest plant litter chemical characteristics played a more important role on litter decomposition than soil C and N concentrations. Management intensification through changes in plant species and N fertilization had positive effects on C and N dynamics in coarse‐textured soils, with enhanced decomposability of cultivated forage species relative to native vegetation.