GEOMORPHOLOGY, DISTURBANCE, AND THE SOIL AND VEGETATION OF 2 SUBTROPICAL WET STEEPLAND WATERSHEDS OF PUERTO-RICO

Citation
Fn. Scatena et Ae. Lugo, GEOMORPHOLOGY, DISTURBANCE, AND THE SOIL AND VEGETATION OF 2 SUBTROPICAL WET STEEPLAND WATERSHEDS OF PUERTO-RICO, Geomorphology, 13(1-4), 1995, pp. 199-213
Citations number
59
Categorie Soggetti
Geografhy,"Geosciences, Interdisciplinary",Geology
Journal title
ISSN journal
0169555X
Volume
13
Issue
1-4
Year of publication
1995
Pages
199 - 213
Database
ISI
SICI code
0169-555X(1995)13:1-4<199:GDATSA>2.0.ZU;2-O
Abstract
Relationships between landforms, soil nutrients, forest structure, and the relative importance of different disturbances were quantified in two subtropical wet steepland watersheds in Puerto Rico. Ridges had fe wer landslides and treefall gaps, more above-ground biomass, older age d stands, and greater species richness than other landscape positions. Ridge soils had relatively low quantities of exchangeable bases but h igh soil organic matter, acidity and exchangeable iron. Valley sites h ad higher frequencies of disturbance, less biomass, younger aged stand s, lower species richness and soils with more exchangeable bases. Soil N, P, and K were distributed relatively independently of geomorphic s etting, but were significantly related to the composition and age of v egetation.On a watershed basis, hurricanes were the dominant natural d isturbance in the turnover of individuals, biomass, and forest canopy. However, turnover by the mortality of individuals that die without cr eating canopy openings was faster than the turnover by any natural dis turbance. Only in riparian areas was forest turnover by treefall gaps faster than turnover by hurricanes. The same downslope mass transfer t hat links soil forming processes across the landscape also influences the distribution of landslides, treefall gaps, and the structure and c omposition of the forest. One consequence of these interactions is tha t the greatest aboveground biomass occurs on ridges where the soil nut rient pools are the smallest. Geomorphic stability, edaphic conditions , and biotic adaptations apparently override the importance of spatial variations in soil nutrients in the accumulation of above-ground biom ass at this site.