BIOMASS, PRODUCTIVITY, LEAF LONGEVITY, AND FOREST STRUCTURE IN THE CENTRAL HIMALAYA

Patterns of leaf characteristics, forest structure, tree species diver sity, biomass, and productivity across a gradient of 3300 m and 15.7 d egrees C in mean annual temperature in Kumaun, in the Indian central H imalaya, were summarized and compared to values from other similar for ests. Throughout the elevational gradient, the annual rainfall was hig h (100-300 cm), but not correlated with elevation. Evergreen species w ith a 1-yr leaf life-span dominated most of the elevational transect; above 1800 m, species with deciduous and multiyear evergreen leaves we re also well represented. Although variability among sites within fore st types was high, a number of consistent patterns were apparent. Fore sts of Pinus roxburghii and those at high elevations were most consist ently different from other forest types. Leaflife-span was not strongl y correlated with leaf mass, specific leaf mass, or leaf production ef ficiency (net primary productivity per unit leaf mass), contrary to re lationships presented in the literature. Tree species richness and bas al area were lower than for most similar types in Nepal. Biomass and p roductivity of the forests in Kumaun were relatively high, compared to mean values for similar forest types elsewhere. Measured values for m ost variables describing these forests (but not all) fell within the r anges for the variables in similar forests worldwide. The maximal valu es for forest biomass remained high, 500-600 Mg/ha, up to 2600 m eleva tion, but declined sharply in birch forest (approximate to 170 Mg/ha) above 3100 m. Net primary productivity (NPP) varied little (15-20 Mg.h a(-1).yr(-1)) below 2700 m, despite a 10 degrees C gradient in mean an nual temperature and marked changes in basal area, tree density, growt h form, and leaf characters. The level of productivity appeared not to be limited by rainfall, forest structure, leaf type, or temperature a bove an annual mean of 11 degrees C. Leaf mass (LM) varied considerabl y among forest types, being 3.7-8.6 Mg/ha for deciduous species, 5.7-8 .9 Mg/ha for P. roxburghii, and 10.0-28.2 Mg/ha for evergreen broad-le aved species. Leaf mass duration (leaf mass x months of the year with leaves present) was related directly to NPP and inversely to leaf prod uction efficiency (NPP/LM). These data add substantially to the data b ase for forest properties, especially for broad-leaved evergreen fores ts.