Litterfall and leaf litter processing in riverine forests: effects of the Paraná River flooding regimen

POI DE NEIFF, A.S.G; NEIFF, J.J.; CASCO, S.L.; GALASSI, M.E.; FRANCESCHINI, M.C.

Gramado, Brasil

Congreso; XII Congreso Brasilero de Limnología; 2009

Sociedad Brasilera de Limnología

Leaf litter fall, decomposition, and invertebrate colonization differed in two riverine forests after prolonged inundation or drawdown reflecting strong or weak hydrologic connection to the floodplain of the Paraná River downstream of confluence of the Paraguay River.  The two dominant forest types studied included alder (Tessaria integrifolia) on sand bars near the river and mixed gallery forests up to 2 km from the river of curupí, laurel, inga and sangre de dragón (Sapium haematospermum, Nectandra angustifolia, Inga verna, Croton urucurana, respectively). The leaf litter decomposition rate was significantly faster in the forest with strong hydrologic connection as compared to the forests with weaker connectivity. The more connected riparian forests had the highest level of invertebrate colonization. Many of these invertebrates are not involved in shredding leaf litter, so that collectors dominate these invertebrate assemblages.  The cycling of organic matter depends on three variables including (1) litterfall production, 2) litter quality as related to decomposition rate, and the, (3) the hydrologic connection of the site with the larger fluvial system. In forests with high litter production and low decomposition rate, there was a higher accumulation of detritus than in forests with strong hydrologic connections and faster decomposition rates, e.g., Tessaria integrifolia. Changes in the inundation regime could lead to the loss of the spatial heterogeneity of organic matter accumulation by modifying the composition of the riparian vegetation and the leaf litter quantity.  Therefore, the conservation of these Chaco RAMSAR Wetlands requires the maintenance of connectivity with the river. This research provides evidence that diverse litter inputs may be important in maintaining aquatic diversity, so that riparian restoration strategies in large floodplain rivers should consider this connectivity.