Abstract
We analyzed the nutritional composition and isotope ratios (C and N) of big-leaf mahogany (Swietenia macrophylla King) leaves in plantations established on contrasting soils and climates in Central America (State of Quintana Roo, Yucatán, México) and South America (State of Pará, Brazil). The objective was to determine the adaptability of this species to large differences in nutrient availability and rainfall regimes. Nutrient concentrations of leaves and soils were determined spectrophotometrically, and isotope ratios were measured using mass spectrometric techniques.In Pará soils were sandier, and acidic, receiving above 2000 mm of rain, whereas in Quintana Roo soils were predominantly clayey, with neutral to alkaline pH due to the underlying calcareous substrate, with about 1300 mm of rain. Leaf area/weight ratio was similar for both sites, but leaves from Quintana Roo were significantly smaller. Average N and K concentrations of adult leaves were similar, whereas Ca concentration was only slightly lower in Pará in spite of large differences in Ca availability. Leaves from this site had slightly higher P and lower Al concentrations. Differences in water use efficiency as measured by the natural abundance of 13C were negligible, the main effect of lower rainfall in Quintana Roo seemed to be a reduction in leaf area. The N isotope signature (δ15N) was more positive in Pará than in Quintana Roo, suggesting higher denitrification rates in the former. Results reveal a calciotrophic behavior and a remarkable capacity of mahogany to compensate for large differences in soil texture and nutrient availability.
Highlights
Mahogany species (Swietenia spp.) produce high quality wood and have been exploited for more than 200 years from forests of South and Central America and some Caribbean islands (LAMB, 1966; WHITMORE, 2003)
The large geographic range of Big-leaf mahogany in South and Central America (LAMB, 1966; MAYHEW; NEWTON, 1998; GROGAN et al, 2002) suggests that the species may be tolerant to a wide range of environmental conditions
In native forests big-leaf mahogany can survive for several years in a suppressed state in partial shade (GARCÍA et al, 1993; GULLISON et al, 1996), whereas in plantations the species regenerates without apparent restrictions (LUGO; FU, 2003)
Summary
Mahogany species (Swietenia spp.) produce high quality wood and have been exploited for more than 200 years from forests of South and Central America and some Caribbean islands (LAMB, 1966; WHITMORE, 2003). The large geographic range of Big-leaf mahogany in South and Central America (LAMB, 1966; MAYHEW; NEWTON, 1998; GROGAN et al, 2002) suggests that the species may be tolerant to a wide range of environmental conditions. Within its geographic range the species thrives in a variety of soil types differing significantly in fertility (GULLISON et al, 1996; SNOOK, 1996; GROGAN et al, 2002; BROWN et al, 2003; WHITMORE, 2003). There are evidences of genetic differentiation of populations within its geographic range, underscoring the need for protection of natural habitats and development of conservation of the genotypes ex situ (NEWTON et al, 1993; LEMES et al, 2003)
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