Mixed Cover of C3 and CAM Species in a Tropical Coastal Vegetation: a Unique Situation for Efficient Carbon Sequestration
Eduardo
Arcoverde de
Mattos, Depto. de Ecologia, Universidade Federal do Rio de Janeiro, Brazil, eamattos@biologia.ufrj.br
(Presenting)
F.
R.
Scarano, Depto. de Ecologia, Universidade Federal do Rio de Janeiro, Brazil, fscarano@biologia.ufrj.br
The coastal sandy plains of Brazil are frequently covered by open scrub vegetation called restinga. This vegetation shows a mixed cover of species with C3 and CAM photosynthesis. Vegetation patches are often dominated by the obligatory CAM tree Clusia hilariana (Clusiaceae), and CAM bromeliads and cacti are abundant in the herb strata. In our study site, at the northern coast of the state of Rio de Janeiro, the total area covered by vegetation patches ranges from 20 to 60%, for plots set in a 1,600 ha area. Average leaf area index of the vegetation patches varied from 3.0 to 3.5, whereas litter stock was between 1590 to 1936 gm-2. Average leaf mass per area of C3 woody plants was 156 gm-2, whereas in C. hilariana the values found were around 320 gm-2. Photosynthetic capacity of C3 species is between 8 to 18 mmol m-2 s-1, whereas overnight CO2 uptake of C. hilariana is around 7 mmol m-2 s-1. We postulate that this unique situation of dense cover of a CAM tree mixed with C3 woody species, imply in an unusual relatively high 24-hour pattern of carbon sink. Moreover, unfavourable conditions for organic matter decomposition emerge due to low availability of water and nutrients and the low quality of the litter. Thus, we are gathering data to confirm that the restinga vegetation will have a major role to play in carbon sequestration and storage in a future scenario of climate change due to an unusual day-night carbon sink, low decomposition rates and intrinsic abilities of the component species to persist under extreme periods of environmental stresses.
Submetido por Lorena Cordeiro Brewster em 02-ABR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)