Silviculture Research Papers - Academia.edu (original) (raw)

Sal (Shorea robusta) is one of the most important timber-yielding trees in India, spread over an estimated area of 13 million hectares. Sal occurs gregariously on the southern slopes of the Himalayas and is also distributed on the plains and lower foothills of the Himalayas including the valleys. Regeneration is considered as a key process for the existence of a species in the community as it maintains desired composition and stocking. Presence of ample number of seedlings and saplings in a given population indicates successful regeneration. This study is a comparative assessment of the natural regeneration of Sal under protected and unprotected conditions and consequently aims at identifying the environmental and anthropogenic factors influencing the regeneration of Sal. It is essential to study the influence of protection and conservation on the regeneration potential of Sal for the efficient management and silviculture of these forests. The major factors influencing the regeneration of Sal were identified as soil characteristics, structure and floristic composition of the forest, relationship of Sal with its associate species, canopy density, light conditions, rainfall, temperature, frost, drought, forest fires and other important anthropogenic factors such as grazing, firewood collection, seed collection, lopping and harvesting of non-timber forest products. The degree of disturbances faced by the protected and unprotected forests were sharply contrasting, enabling an efficient comparative study. The study was carried out in two different forest patches, one under complete protection and the other exposed to anthropogenic disturbance. However, as the two patches are in close proximity, climatic conditions are identical. The two sites are located in the Doon Valley region, on the Himalayan foothills in the Uttarakhand State of India and under the management of Kalsi Forest Division. Nearly 80% of the Doon Valley forests are Sal forests. Phytosociological analysis and soil sampling was carried out in the months of January and February 2015. The sampling and data collection was done by dividing the forest structure into three layers, trees, shrubs and herbs. Saplings and seedlings were included in the shrub and herb layers respectively. This data was then quantitatively analysed to calculate the density, frequency, abundance, Importance Value Index, basal area and Whitford Index separately for the three layers. The data was also analysed for α-diversity and estimation of other diversity, similarity, richness, dominance indices and evenness. Sal was the only species found in the tree layer, indicating its complete dominance in this layer. 21 species were found in the shrub layer of the protected site, while 19 species were found in the unprotected site. However, the density of Sal saplings was found to be 340 individuals/ha in the unprotected site, significantly higher than the protected site having 120 individuals/ha. The major species found to be competing extensively with Sal were Clerodendrum viscosum, Mallotus philippensis, Murraya koenigii, Jasminum sp and Lantana camara, thus hindering its regeneration. The most significant results were obtained from the herb layer, as the density of Sal seedlings was found to be only 20 individuals/ha in the unprotected site, while the protected site had 80 individuals/ha, clearly indicating the lack of Sal regeneration under disturbed conditions in the unprotected site. Echinocarpus, Oplismenus compositus and Rungia pectinata were observed to be the species competing with the Sal seedlings in the herb layer. The graphical representation of the density of Sal trees, saplings and seedlings of both the sites clearly indicates the better regeneration of Sal under protected conditions. Although the regeneration of Sal is better in the protected site, it is not as high as expected, due to the high canopy density obstructing the sunlight and rainwater reaching the lower layers and the forest floor and excessive growth of competitive species. This indicates that protection should be coupled with appropriate silvicultural and forest management strategies to maximise the natural regeneration. The correlation analysis of the physico-chemical properties of soil with the floristic composition of the shrub layer shows that pH is the only negatively correlated soil property and acidic soils are necessary for the healthy growth and composition of Sal forests.