Bigleaf mahogany (Swietenia macrophylla King) in southeast Para, Brazil: A life history study with management guidelines for sustained production from natural forests

Bigleaf mahogany demonstrates highly significant association with seasonal streams within the interfluvial landscape of southeast Pará. This distribution pattern is shaped by physical gradients functioning at landscape scales, beginning with topography's influence on hydrologic cycles, soil formation processes, disturbance regimes, and forest composition and structure. Analysis of population structures indicates that recruitment into adult diameter size classes occurs at decadal intervals within watershed-level groups of trees, at single- or multiple-treefall spatial scales, leading to multi-aged aggregations characterized by trees of all sizes and growth rates against a background of continual rather than episodic mortality spread through all size classes. Mahogany's early juvenile phases—seedlings and saplings—proved responsive to differences in soil nutrient status both between topographic extremes and within low-ground areas where adult trees occur at highest densities. Placed within context of more disturbed and irregular low-ground forest canopies compared to those on high ground, growth differences reported here indicate that mahogany's recruitment strategy emphasizes vertical growth performance where resource availabilities are optimal rather than tolerance and or competitive exclusion where growing conditions are not ideal. In nutrient-rich soils, mahogany's vertical growth rates are sufficient to guarantee recruitment at self replacement rates in single- to multiple-treefall gaps. Management systems should emphasize seed tree retention and selection of high quality sites within landscapes for enrichment planting at low densities on 30-year bicyclic harvest schedules assuming a rotation period of 60 years for 60 cm dbh trees grown from seed.