Biomass, net primary production and impact of bamboo plantation on soil redevelopment in a dry tropical region

Abstract

Growth and impact of a bamboo (Dendrocalamus strictus (Roxb.) Nees) plantation on mine spoil in a dry tropical region were examined. Culm dynamics, biomass, net primary production, soil microbial biomass and N-mineralization were estimated at ages 3, 4, and 5 years. The recruitment of culm population varied between 18% and 36% and shoot mortality from 6-7% per year. Net accumulation of green culms during 3rd and 4th year was 3999 and between 4th and 5th year 10854 ha⁻¹. Total biomass was 46.9 t ha⁻¹ in the 3-year old to 74.7 t ha⁻¹ in the 5-year old plantation with 35% occurring belowground. Total net primary production (NPP) ranged between 20.7 t ha⁻¹ (3-year old)and 32.0 t ha⁻¹ (5-year old), of which aboveground net production was 17.0 to 24.7 t ha⁻¹ (between 3 to 4, and 4 to 5 years, respectively). Accounting for only 14% of the total biomass, foliage contributed 36% to NPP. Nutrient deposition through leaf litter was 45-79 kg N and 6-11 kg P ha⁻¹. Litter bag experiment indicated 235 days for 50% and more than 1000 days for 95% decomposition. Amounts of N and P deposition and release increased with the age of the plantation. Rate of N-mineralization increased from 3.3 (3 years) to 6.9 μg g⁻¹ month⁻¹ (5 years). The proportion of mineralized-N converted into nitrate decreased with age. Soil microbial C increased from 127-319, microbial-N from 19-38 and microbial-P from 9-16 μg¹ g⁻¹ soil between 3 to 5 years. With increasing age of plantation, a greater proportion of soil C, N and P tended to be immobilized in soil microbial biomass. Net primary production and the soil redevelopment process exhibited a positive feed-back relationship.