Impacts of anthropogenic disturbances on forest succession in the mid-montane forests of Central Himalaya

摘要

We studied the influence of anthropogenic drivers on the distribution and regeneration of tree species in vegetation at different stages of succession from grasslands to oak forests in mid-montane Central Himalaya. We found fire, grazing, and lopping as the main factors hindering a progressive successional regime towards a late-successional oak community. Succession was studied in five vegetation formations (grasslands, pine, pine-oak, open oak, and dense oak), with similar site conditions, representing a theoretical successional sequence from early- to late-successional stages. A structured survey with uniform distribution of sampling plots in the five selected vegetation formations was conducted to gather information abut the vegetation communities. Early-successional grasslands and pine forests were found to harbour high densities of pine and oak seedling and sapling regeneration. However, recurring fires and chronic unsustainable levels of grazing in these vegetation formations obstructed progressive succession by eliminating regenerating seedling and saplings from the forest understorey. Similarly, in intermediate- and late-successional stages (including pine-oak, open oak, and dense oak), overexploitation of existing oaks trees via lopping and grazing of regenerating oak seedlings and saplings hampered oak regeneration and development. The possibility to convert pine forests into oak as well as the conservation of existing oak forests through controlled grazing and lopping are management options that can contribute to an enhanced functioning of forest ecosystems in the study area. We conclude that with strategic management that restricts the current anthropogenic disturbances, the extent of oak forest in the study area can be increased.