Biomass and nutrient distribution in a highland bamboo forest in southwest Ethiopia: implications for management

The Masha natural bamboo forest was stocked with 8840 trees ha−1, uniformly distributed with a mean height of 16.8 m, diameter of 7.6 cm and leaf area index (LAI) of 9.7. Age-structure was 13% of <1 year, 24% of 1-3 years and 63% of >3 years. Culm contributed 82%, branch 13% and leaf 5% to the 110 t ha−1 total above ground biomass, while trees mature for harvest (>3 year) made up 73%. The culm component of the mature trees was 60% of the above ground biomass, whereas the biomass of current shoots (<1 year) constituted only 7%. Annual shoot production was 8 t ha−1 and contained 44 kg ha−1 of N, 6 kg ha−1 of P, 122 kg ha−1 of K and 1 kg ha−1 of Ca. Significant variations in nutrient concentration of plant tissues were found among age-classes and between seasons. More than 8 t ha−1 year−1 plant litter containing 115 kg N, 8 kg P, 56 kg K and 22 kg Ca returned to the soil surface mainly during the humid season. Resorption efficiency of the foliage was 43% for K, 37% for P and 19% for N. Soil nutrient concentrations declined sharply with soil depth and a large fraction of the total soil nutrient pool was located in the organic layer; the soil was poor in P and K. Management approaches to improve the production efficiency of the forest and the quality of the harvested biomass are discussed.