title: Performance of an age series of Alnus-cardamom plantations in the Sikkim Himalaya: nutrient dynamics.
abstract: Nutrient cycling, nutrient use efficiency and nitrogen fixation in an age series of Alnus-cardamom plantations were studied in the eastern Himalaya. The impact of stand age (5, 10, 15, 20, 30 and 40 years) on the nutrient dynamics of mixtures of N2-fixing (Alnus nepalensis) and non-N2-fixing (large cardamom) plants was assessed. Foliar nutrient concentrations of Alnus decreased with advancing age groups of plantations and showed an inverse relationship with stand age. Annual N fixation increased from the 5-year-old stand (52 kg ha(-1)), peaking in the 15-year-old stand (155 kg ha(-1)) and then decreased with increasing plantation age. Nitrogen and phosphorus uptake was lowest in the 40-year-old stand, and highest in the 15- and 5-year-old stand, respectively. Nutrient storage in understorey cardamom was very high: up to 31 % N and 59 % P of the stand total in the 15-year-old stand. Nutrient use efficiency was higher (with faster turnover times) in younger stands and decreased (with slower turnover times) in older plantations. Nitrogen retranslocation showed a strong positive relationship with stand age, while that of P was inversely related to stand age. Nutrient standing stock, uptake and return were also highest in the 15-year-old stand. Nitrogen and P cycling in Alnus-cardamom plantations was functionally balanced. Nutrient cycling and dynamics indicated that Alnus-cardamom plantations performed sustainably up to 15-20 years. The management practice should be altered to incorporate replantation after this age.
authors.affiliation: G. B. Pant Institute of Himalayan Environment and Development, Gangtok, Sikkim, India.
authors.forename: G
authors.initials: G
authors.lastname: Sharma
authors.forename: R
authors.initials: R
authors.lastname: Sharma
authors.forename: E
authors.initials: E
authors.lastname: Sharma
authors.forename: K K
authors.initials: KK
authors.lastname: Singh
mesh_terms: D000465:Algorithms; D029661:Alnus / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D001692:Biological Transport; D018533:Biomass; D003247:Conservation of Natural Resources / Q000379:methods; D017753:Ecosystem; D028523:Elettaria / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D016468:Forestry / Q000379:methods; D007194:India; D016014:Linear Models; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation / Q000502:physiology*; D010758:Phosphorus / Q000378:metabolism*; D018514:Plant Structures / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism; D013997:Time Factors
chemical_list: D010758:Phosphorus; D009584:Nitrogen