Structure and function of oak forest ecosystem of north - eastern India II. Nutrient dynamics

Abstract

This paper deals with nutrient concentra­tion, standing state, uptake, return, turnover time, release and nutrient cycling in the dominant oak tree species of Quercus dealbata, Quercus fenestrate, Quercus griffithii and Rhododendron arboreum in two oak forest sites. Biomass dynamics and net primary productivity have been dealt in earlier paper. In these oak forest sites, the soil, tree layer and litter ac­counted for 65-97.82, 1.44-32.60 and 0.04-1.39 per cent of the total nutrient in the system. The concen­tration of nutrients in the tree species were in the order: leaf > twig > branch > bole. The compartmental distribution of standing state of nutrients in the tree layer were in the order: bole > leaf > branch > twig. The uptake of nutrients by vegetation in the two oak forest sites were 13.31-20.16 N, 12.97-16.38 P, 13.05-19.16 K and 10.11-17.41 Na per cent of the total standing state. Out of the total uptake 11.49-17.31 N, 14.99->7.52 P, 11 52-13.83 K and 5.68-1096 Na per cent were released through the decomposition. Turnover time on standing state for different nutrients varied from 4.98-7.79 years. Turnover time and rate for various nutrients on forest litters ranged from 1.50-1 69 years and 0.58-0.66 in both forest sites. Nutrient use efficiency was higher for sodium and phosphorus in both the forest sites in comparison to nitrogen and potassium.