Leaf litter decomposition and nutrient dynamics in four southern forested floodplain communities

Decomposition of site-specific litter mixtures was monitored for 100 wk in four floodplain communities: (i) a mixed oak community along the Cache River in central Arkansas, (ii) a sweetgum (Liquid-ambar styraciflua L.)-cherrybark oak (Quercus falcata var. pagodaefolia Ell.) community along Iatt Creek in central Louisiana, (iii) a sweetgum-swamp tupelo [Nyssa sylvatica var. biflora (Wait.) Sarg.] community, and (iv) a laurel oak (Quercus laurifolia Michx.) community along the Coosawhatchie River in southeastern South Carolina. Soil temperature, hydroperiod, and litter quality (C:N, C:P, N:P, lignin:N) were used to interpret differences in the rates of mass loss and nutrient dynamics. After 100 wk, litter mixtures retained 33, 18, 8, and 5% of original mass on the Cache, Coosawhatchie (laurel oak community), Coosawhatchie (sweetgum-swamp tupelo community), and Iatt floodplains. respectively, and these differences appeared related to hydroperiod. Decay rates were comparable to rates reported in similar floodplain environments. Net mineralization of both N and P was observed after 100 wk, but both elements accumulated in litter mixtures periodically. Differences in hydroperiod were observed among the four floodplain communities and decomposition of and nutrient mineralization from litter among them appeared to be inversely related to the number and duration of flood events. Litterbags containing leaf litter of a single-species (i.e.. cherrybark oak) were also monitored on three of the four sites to compare decay rates and nutrient dynamics with the litter mixtures. On the Cache River floodplain, slower decay of poorer quality cherrybark oak litter suggested that litter quality drove decomposition under similar edaphic conditions.