Drivers of Leaf Decomposition in Two Wetland Types in the Arkansas River Valley, U.S.A.

White Oak Bayou watershed in the Arkansas River Valley is losing wetlands rapidly that could alter regional carbon cycles. Leaf decomposition of ash and oak were used to assess carbon cycling in five flat and five backwater wetlands within forested (54 %), urban (30 %), and pasture (7 %) catchment. Wetlands were dry in summer and wet the remaining year. Backwaters were expected to have faster decomposition rates from longer wet periods and more nutrients that would increase microbial and macroinvertebrate consumption. Backwaters held more water than flats and decomposition of both tree species was faster in backwaters (k:0.0032 ± 0.0007 day−1) compared to flats (k:0.0026 ± 0.0008 d−1, p = 0.018). Ash (0.0035 ± 0.0006 day−1) decomposed faster than oak (0.0023 ± 0.0005 day−1, p < 0.0001). Variation in ash decomposition rates was explained by inundation time and ammonium concentration. Variation in oak decomposition rates was explained by surrounding forest and nitrite + nitrate concentrations. Minor variations in hydrology affected decomposition rates of fast-breakdown leaf species, while differences in surrounding land use and nutrient concentrations affected rates of slow-breakdown species. Environmental factors altered by changing land use have important consequences for leaf decomposition. This study helps us to understand the influence that anthropogenic changes have on wetland function as urbanization continues to encroach upon wetlands in Arkansas.