available online at httpj//www.idealibrary.com on I BE bl 0 @ Four sites with contrasting environmental stress in southeastern Brazil: relations of species, life form diversity, and geographic distribution to ecophysiological parameters Some ecophysiological parameters related to plant performance and fitness (carbon and nitrogen isotope composition and total C and N concentrations; in situ chlorophyll fluorescence measurements) were determined for over 30 species in four habitats bordering the montane Atlantic rain forest of Brazil, along a gradient of altitude and rainfall: a dry coastal forest, two areas of sandy coastal plain vegetation (restingas), and a high altitude campo. There was a considerable diversity of ecophysiological behaviour within and between the functional groups we created based on plant life-forms. For instance, both crassulacean acid metabolism (CAM) and C3 species were found in most life-forms sampled and throughout all habitats. Despite the variation in rainfall regimes, average overall water-use efficiency was similar between sites, particularly for C., species, while no clear pattern regarding nitrogen-use emerged in this respect. Acute and chronic photoinhibition were found in many species across this gradient, even in CAM plants. However, on average, chronic photoinhibition and lower energy dissipation capacity were more characteristic of plants from the restinga habitats. This suggests that, although plants colonizing these habitats have evolved features to deal with water shortage, adaptation to high light levels has not been fully achieved yet. The ecophysiological performance of some individual species in distinct habitats and in distinct microhabitats within habitats is also discussed. ! C 2001 The Linnean Society of London ADDITIONAL KEY WORDS: Atlantic forest -carbon isotopes -chlorophyll a fluorescence -dry forest -high altitude vegetation -nitrogen isotopes -sandy coastal vegetation.
Three species of Clusia, namely two CAMspecies (C. hilariana Schlecht. and C. fluminensis Planch. et Triana) and a C 3 -species (C. parviflora Saldanha et Engl.) were studied in different plant communities at the periphery of the Atlantic Forest in the state of Rio de Janeiro, Brazil. The sites chosen were an inselberg (C. parviflora), a range of wet restinga -dry restinga -semideciduous dry forest (C. fluminensis), and a gradient from the sea shore inland with a first sand dune beach ridge -a dry forest -a second beach ridge (C. hilariana). Analyses comprised C and N contents, soluble carbohydrates, soluble nonprotein N compounds and carbon isotope ratios (δ 13 C) in leaves, roots, phloem and wood. Photosynthetic performance was assessed by chlorophyll fluorescence with measurements of instant photosynthetic yield as well as light dependence and potential quantum-use efficiency of photosystem II.The data allow, first, to discuss differences between the ecophysiological performance of C 3 -and CAM-species of Clusia. The C 3 -species, C. parvifolia, had an overall weaker performance than the two CAM-species, where, however, the effects of mode of photosynthesis may have been overlaid by site conditions. Second, it was studied whether ecophysiological performance relates to patterns of local abundance, which was confirmed by showing that the dominant Clusia species of the restingas, C. hilariana, showed the strongest performance overall.Finally, it was studied whether the ecophysiological performance varied in response to site-dependent gradients of environmental water relations, which was confirmed for functions such as photosynthetic capacity, photoinhibition and solute accumulation of C. hilariana and C. fluminensis in relation to moisture of sites.
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