trees

Decay rate and substrate quality of fine roots and foliage of two tropical tree species in the Luquillo Experimental Forest, Puerto Rico

Bloomfield, J., K. A. Vogt, and D. J. Vogt. 1993. Decay rate and substrate quality of fine roots and foliage of two tropical tree species in the Luquillo Experimental Forest, Puerto Rico. Plant and Soil 150:233-245.

Abstract: 
Decomposition rates, initial chemical composition, and the relationship between initial chemistry and mass loss of fine roots and foliage were determined for two woody tropical species, Prestoea montana and Dacryodes excelsa, over a gradient of sites in two watersheds in the Luquillo Experimental Forest, Puerto Rico. At all locations, fine roots decayed significantly more slowly than foliage during the initial 6 months. Substrate quality of the initial tissue showed marked differences between roots and foliage when using cell wall chemistry, secondary chemistry and total elemental analysis as indices. Quantity of acid detergent fiber (ADF) (non-digestible cell wall fiber) and lignin content were higher for roots than leaves: D. excelsa roots had 55.3% ADF and 28.7% lignin while leaves had 36.2% ADF and 11.8% lignin; P. montana roots had 68.0% ADF and 26.8% lignin while leaves had 48.5% ADF and 16.1% lignin. Aluminum concentrations were higher in fine roots (843 mg kg -x in D. excelsa, 1500 mg kg -x in P. montana) than leaves (244mg kg -x in D. excelsa, 422mgkg -1 in P. montana), while calcium concentrations were higher in foliage (5.5 mg g-1 in D. excelsa, 7.8 mg g-X in P. montana) than roots (3.4mgg -1 in D. excelsa, 3.1 mgg -x in P. montana). Nitrogen did not show any trend with tissue or species type. A linear model between mass remaining after 6 months and initial tissue chemistry could be developed only for calcium (r 2= 0.64).

Effect of Topography on the Pattern of Trees in Tabonuco (Dacryodes excelsa) Dominated Rain Forest of Puerto Rico

Effect of Topography on the Pattern of Trees in Tabonuco (Dacryodes excelsa) Dominated Rain Forest of Puerto Rico
Khadga Basnet
Biotropica
Vol. 24, No. 1 (Mar., 1992), pp. 31-42

Abstract: 
The structure, composition, and spatial patterns of tree species in two adjacent watersheds of the Luquillo Experimental Forest, Puerto Rico were investigated. Both watersheds had the same vegetational characteristics. Dacryodes excelsa! Sloanea berteriana, and Guarea guidonia were the most important trees in the overstory. A profile diagram, chisquare criterion, and multivariate techniques showed the same result: trees were related significantly to topographic variables. Large trees, especially the dominant species, tabonuco, were associated significantly with ridges and slopes. Size-class distributions of individual species varied as a function of broad ecological factors such as topography and disturbance regime. Past anthropogenic disturbance was still apparent in the pattern of distribution of large trees along the elevational gradients of the watersheds. Dacryodes excelsa is the dominant species, even though Sloanea berteriana has higher representation in smaller size-classes.
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