Nutrient distribution and cycling in a sub-alpine coniferous forest ecosystem.
Abstract
The distribution of N, P, K, Ca, Mg and Mn in a 175-year-old Abies amabilis ecosystem is described and estimates of transfers within the system are given.Tree growth, and hence the accumulation rates of nutrients within the trees, was relatively low. The requirement for growth was estimated as approximately 23, 2, 22, 20, 2 and 1 kg ha-1 yr-1 for N, P, K, Ca, Mg and Mn respectively, and uptake was about 12, 1, 25, 23, 5 and 2 kg ha-1 yr-1 for the same nutrients.The biomass and nutrient content of the understorey and lichens was similar and only about 3% of that of the trees.Nutrient returns to the forest floor were 18, 2, 23, 45, 4 and 5 kg ha-1 yr-1 for N, P, K, Ca, Mg and Mn respectively, mostly in the form of litter, except in the case of K and Mg where throughfall was important.Losses from the rooting zone were approximately 3. 0.5, 2, 7, 1 and 0.1 kg ha-1 yr-1 for N, P, K, Ca, Mg and Mn respectively; this slightly exceeded the inputs from rainfall.