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Nutrient dynamics of the highly productive C 4 macrophyte Echinochloa polystachya on the Amazon floodplain
Author(s) -
PIEDADE M. T. F.,
JUNK W. J.,
LONG S. P.
Publication year - 1997
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1046/j.1365-2435.1997.00066.x
Subject(s) - floodplain , nutrient , biology , macrophyte , echinochloa , amazon rainforest , biomass (ecology) , botany , cecropia , agronomy , ecology , weed
1.Echinochloa polystachya forms extensive monotypic stands on the lower levels of the Amazon floodplains. During its annual growth cycle c. 100t (dry mass) ha –1 of biomass is formed as the floodplain is being submerged (December–September) and a phase of death and decomposition occurs when the water has retreated (October–November). This study examines the mineral nutrient dynamics of this plant and its potential significance to the nutrient status of the floodplain. 2.Echinochloa polystachya was sampled monthly from a study site in the central Amazon. N, P and K contents for different plant organs were determined and net uptake calculated from concurrent measurements of dry matter production and turnover. 3. Leaf N, P and K contents were c. 20, 1·7 and 19gkg –1 , values typical of nutrient‐replete stands of C 4 plants. Stem concentrations were c. 12% of those of the leaves. Net N and P uptake followed the rise in the river level, whilst K appeared independent of water level. 4. The vegetation accumulated 377, 51 and 1136kgha –2 of N, P and K, respectively, during the growth phase. Over a possible 5000km 2 of these stands in the Várzea, this represents a massive sequestration of nutrients in the flood phase and a high release during the following low‐water period. It is suggested that the E. polystachya stands could have a role in maintaining the nutrient status of the Amazon floodplain.