Nutrient Losses Through Complete Harvesting From Some Monoculture Plantations of Punjub

Abstract

In the forest ecosystems nutrients are added to the forest floor by litter fall, decaying roots, animal excreta and canopy wash. These nutrients are finally decomposed and released into soil and ultimately taken up by the plants and retained in the plant biomass. Some released nutrients are stored in the soil and some are lost by leaching, erosion and harvesting of the plants. Thus it is through this dynamic and rather complex system of bio-geo-chemical cycling that the soil organic matter and nutrient supplies are replenished and maintained thereby ensuring continuous productivity of the site. The present study was conducted in Eucalyptus hybrid, Dalbergia sissoo and Acacia catechu plantations of different ages at different sites in 10 Forest Divisions of Punjab. Biomass of all plant parts of these 3 species have been calculated and nutrient concentration in all plant parts have also been analysed to work out the nutrient accumulation in each plant part (Rawat, 2006). Trees accumulate nutrients over a period of their growth, which upon harvesting are lost from the site. The extent of loss depends upon the harvesting and utilization intensity. The nutrients accumulated in each plant part are removed after harvesting. Thus, nutrient accumulation in different tree parts of these species are considered to be the net loss of nutrients after harvesting. The net loss of N (nitrogen) in case of E. hybrid was found to be up to 675.93 kg ha-1 (about 33.6%); in D. sissoo it was up to 2087 kg ha-1 (42 %) and in A. catechu it was up to 1041 kg ha-1 (35.6 %). Similarly loss of P (phosphorus) was up to 52.65 (2.6%) in E. hybrid, 98.05 (1.99%) in D. sissoo and 92.75 (2.76%) in A. catechu. Loss of K (potassium) was up to 547.47 (27.2%) in E. hybrid, 1305.4 (20.8%) in D. sissoo and 767.05 (22.8%) in A. catechu. Calcium loss was up to 1010.22 (59.7%) in E. hybrid, 3306.38 (52.8%) in D. sissoo and 1385.41 (41.1%) in A. catechu and loss of magnesium up to 62.98 (5.7%) in E. hybrid, 141.20 (2.8%) in D. sissoo and 80.13 (2.4%) in A. catechu. The results clearly show substantial losses of nutrients after harvesting from these plantations. Thus harvesting may seriously deplete the pool of nutrients in a stand without any doubt.