Conservative nutrient use by big-leaf mahogany (Swietenia macrophylla king) planted under contrasting environmental conditions

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 13 C were negligible, the main effect of lower rainfall in Quintana Roo seemed to be a reduction in leaf area. The N isotope signature (δ 15 N) 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.Keywords: Big-leaf mahogany; Nutrient relations; N-C isotopes. USO CONSERVATIVO DE NUTRIENTES PELO MOGNO (Swietenia macrophylla King) CULTIVADO SOB CONDIÇÕES AMBIENTAIS CONTRASTANTES RESUMO -Analisou-se a composição nutricional e isotópica (C e N) de folhas de mogno (Swietenia macrophylla

Impacts of Tropical Rainforest Conversion on Soil Nutrient Pools in Viti Levu, Fiji

“…As per Nykvist (2000), logging of tropical forests results in serious deficiencies of soil calcium. However, higher exchangeable soil calcium in plantation as reported in this study may be due to the calciotrophic nature of mahogany; strong affinity for calcium and leaf total Ca/K ratios >1 (Medina et al 2014). The high calcium concentration in mahogany leaves also implies that these trees return substantial amount of calcium back to the soil through litterfall (Danquah et al 2012, Zalamea et al 2016.…”