Litter Nutrient Dynamics of Shorea robusta Gaertn. Plantation at Doon Valley (Uttaranchal) India

Present paper deals with patterns in leaf fall, its accretion, decomposition, nutrient return, release and accumulation in Sal plantation of Doon valley. Leaf fall contributed 83.87% (8286.87 kg/ha/yr) to the total litter fall (11271 kg/ha/yr). The peak period of leaf fall was March-April (40-45%). In June-July heavy seed fall occurred. The value of decomposition constant (k) was 1.668 for leaf litter while it was 0.947 for twig litter. Higher values for decomposition rate was recorded during rainy season. Temperature, rainfall, number of rainy days and soil moisture is positively related with decomposition rate. Nutrient concentration is generally higher in leaf litter than of twig litter. Ca and N contributed higher proportion in total nutrient return, release and accumulation. In general, the magnitude of total nutrient return was in order to the total litter fall. The higher nutrient return was associated with higher litter fall and litter nutrient concentrations. Further, the order of importance in terms of magnitude of nutrient return was Ca ≥ N ≥ Mg ≥ K ≥ P. The higher rate of return and release of nutrients were due to higher litter input and its subsequent decomposition. The higher release of Nand Ca can be attributed to their higher returns. Significant variations in all the nutrients were noticed. Nand P showed higher variations. These variations are also correlated with magnitude of leaf fall showing efficient biochemical cycling. The present mature Sal stand showed efficient nutrient cycling, which may due to the availability of nutrients, plant growth form, age and stature. The higher rate of litter production and its subsequent decomposition under tropical climate contributed rapid turn-over of nutrients and affects the nutrient cycling, in cases, where growth period and uptake are not synchronized with leaf fall and its subsequent decomposition. Hence, during the raising the Sal plantations, it is advisable to mix the desired deciduous tree and shrub species at the initial phase of the plantation growth, so that higher returned nutrients can be conserved through absorption by the species of the other growth forms due to differences in their growth periods.