Scientific forest management is an emerging need for managing existing natural forests of Nepal on the basis of silvicultural intervention. The study was carried out in Lumbini Collaborative Forest at Rupandehi District of Nepal, where Sal (Shorea robusta) forests are being managed under Irregular Shelterwood System with eighty years of cutting cycle since 2011-2012. The study was purposed to find out the intial effects of silvicultural intervention on plant species diversity and regeneration of Sal forest. The vegetative sampling was done using quadrate method based on the principle of simple random sampling both in the managed as well as the unmanaged parts of forest. The study found out remarkable increase in regeneration as well as decrease in plant diversity in the managed first and second-year stands (Block I and Block II respectively) as compared to the unmanaged stand (Block III) at its initial level of implementation. The mean value of diversity, richness, evenness, dominance index and regeneration of S. robusta varied significantly (p≤0.05) between the managed blocks (stands). The seedling density of S. robusta was found higher in the managed blocks (Block I and Block II) as compared to the unmanaged one (Block III) in terms of height class. The study recommends implementation of Irregular Shelterwood System for managing the existing degraded Sal forests of the Terai region of Nepal, however, its long term effects on plant species diversity should be further studied in detail.

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ABSTRACT:The individual tree growth models are important decision-making tools in forestry. Age dependent and age independent individual tree basal area growth models were developed for Chir pine (Pinus roxberghii Sarg.) in one of the western districts, Rukum district, in Nepal. Data from thirty-five destructively sampled trees, which were representative of all possible stand densities, site productivities, age classes, and size classes of Chir pine forests in the district, were used. Sample trees were felled and diameters and ages were measured on the cut surface of the stump (at 30 cm above the ground). Since measurements from the same stump of a tree were strongly correlated, the autoregressive error structure modelling approach was applied while specifying the model in order to reduce bias. All parameter estimates of the models were significant (P < 0. 01) and the models described most of the variations of basal area growth (R 2 adj > 0.86). Residual graphs showed no serious systematic bias for all observed age classes and diameter classes. The age independent growth model showed relatively better fit statistics (R 2 adj = 0.8751, RMSE = 4.8494) than its age dependent counterpart (R 2 adj = 0.8668, RMSE = 5.0158). Because of being more precise and simpler, the age independent model is recommended to apply to both even-aged and uneven-aged stands of Chir pine in the district.

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