Flooding effects on phosphorus dynamics in an Amazonian mangrove forest,TI Flooding effects on phosphorus dynamics in an Amazonian mangrove forest, Northern Brazil

摘要

Aims and methods We examined porewater salinity, soil redox potential (Eh), soil extractable phosphate (extr.-P), leaf phosphorus (leaf-P) and plant growth in relation to inundation frequency (IF) and mangrove species distributions along a 600 m transect in the Bragan a Peninsula, North Brazil. Results The forest species composition changed across the tidal zone with Avicennia germinans dominating (99.1%) the high intertidal (HI) zone where the IF was 41-67 d.y(-1), Rhizophora mangle, Laguncularia racemosa and A. germinans co-occured in the mid intertidal (MI), and a mixed R. mangle (47.1%) - A, germinans (41.2%) stand occupied the low intertidal (LI) zone with an IF of 124-162 d.y(-1). Low IF resulted in high Eh levels (200 mV) in the HI zone relative to the LI where Eh ranged from 0-100 mV. The IF showed a significant positive correlation with extr.-P (r=0,89; p=0.05) and a negative association with Eh (r=-0,75; p=0.05). Conclusion An ANCOVA confirmed that Eh and extr.P were influenced by flooding. Variations in these factors were reflected in patterns of P leaf tissue concentrations across the gradient; however, a MANCOVA showed that leaf-P was not related to tree height, tree volume or basal area. Waterlogging conditions, porewater salinity, and P dynamics in the sediment appear to influence the forest structure. We suggest that P availability plays an important role in controling mangrove species distributions but not their growth.