Makalu-Barun National Park and Conservation Area, recently established in Nepal, protects a broad range of eastern Himalayan forest types, ranging from near-tropical dipterocarp monsoon forest (400 m) to subalpine conifer stands (4000 m). Forests span five bioclimatic zones (tropical, subtropical, lower and upper temperate, and subalpine), but ecotones are poorly defined. Below 2000 m forests are strongly affected by subsistence agriculture, although some ecologically significant stands remain at those altitudes. Above 2000 m, a cool, humid climate suppresses agricultural activity and forests are usually extensive. An interesting transition occurs in the temperate zone from forests dominated by broadleaf evergreen ( Quercus -Lauraceae) to broadleaf deciduous ( Acer-Magnolia ) taxa. Subalpine stands show an increased dominance by conifers ( Juniperus, Abies ) along a transect from outer, southern slopes to the inner valleys. Aspect is ecologically important at all altitudes, but controls different ecological variables (seasonal moisture availability, temperature, snow cover) at different altitudes. The Makalu-Barun area exhibits the high regional diversity expected of a physiographically complex, low-latitude mountain region.