Dynamics of Nutrients and Leaf Mass in Central Himalayan Forest Trees and Shrubs

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Abstract
Leaf dynamics, nutrient (N, P, K, Ca, and Na) changes, and retranslocation from the leaves of 13 species [Shorea robusta, Mallotus philippensis, Murraya paniculata, Pinus roxburghii, Symplocos ramosissima, Glochidion velutinum, Myrica esculenta, Myrsine, semiserrata, Lyonia ovalifolia, Viburnum continifolium, Quercus leucotrichophora, Q. floribunda, and Q. lanuginosa] were investigated in four representative forest communities of the Central Himalaya, India. In evergreens of the temperate regions, with leaf longevities of several years, there is negligible movement of subtances from leaves during the first year. For evergreens of the Central Himalaya, by contrast, loss of leaf mass begins in autumn and often continues until summer, when new leaves are formed. The decrease in leaf dry mass during this period was 12.3-34.1% of the maximum leaf mass. The concentration of N, P, and K decreased from the initial peak, stabilized as leaves matured, and declined markedly during senescence, while Ca and Na concentrations increased throughout the life-span of leaves. Leaf mass loss was positively related to most of the nutrient retranslocation percentages. There were significant correlations between retranslocation levels of many nutrients. The dominant canopy species (chir pine), which is adapted to infertile sites, showed conspicuously greater levels of nutrient retranslocation than species adapted fertile sites (oaks). However, species of different growth forms occupying the same sites differed markedly in the extent of nutrient retranslocation.