Human pressure on forests, caused by population growth, diffused poverty and lack of alternatives, is increasing, leading to extensive forest degradation and deforestation (Rijal and Meilby, 2012). Salerno et al. (2010) assessed an average decrease of 38% in forest biomass between 1992 and 2008 in the Khumbu Valley. Nonetheless, the development of sustainable
management plans, taking into account both ecological and socio-economic issues, is often limited by the lack of knowledge on forest structure and of awareness about human impact on the ecosystem (Rijal and Meilby, 2012). The measured effects of forest exploitation on stand structure and tree species composition confirmed the recent hypothesis that forest degradation has a stronger impact than deforestation in SNPBZ (Stevens, 2003 and Byers, 2005). Trekking CH5424802 tourism is still increasing in the SNP and is seriously affecting the Sherpas traditional use of natural resources (Byers, 2009 and Spoon, 2011). Forest degradation and shrub removal (especially Juniperus
wallichiana) are the more evident effects of this socio-cultural change. A land cover change analysis recently performed in the area ( Bajracharya et al., 2010) click here revealed that between 1992 and 2006 the most significant shifts were the reduction of mixed forest cover, together with an increase of dwarf shrubs at 3000–4000 m a.s.l. and a reduction of shrubland at higher elevations (4000–5000 m a.s.l.). The overall change in forest and shrub communities was negligible (−4% and −9% respectively) compared to the relevant increase (47%) of dwarf shrubs at 3000–4000 m L-NAME HCl a.s.l. Prior to 1950, the Sherpa people extensively clearcut woodlands
and converted them into pastures and villages. Land use/cover change is a further driver of erosion risk in Himalayas, a region characterized by heavy rainfalls (Valdiya and Bartarya, 1989, Rawat and Rawat, 1994 and Tiwari, 2000). Soil erosion and mass movement are often related to human activities such as deforestation, overgrazing and building construction in vulnerable sites (Shrestha et al., 2004), but natural disturbances can sometimes override human influence (Bruijnzeel and Bremmer, 1989 and Messerli and Hofer, 1992). In the last decades excessive tree felling without any silvicultural rationale, became the most common forest practice and is still widespread. The prohibition to log living trees inside the national park has caused the increasing removal of green limbs and branches (especially of P. wallichiana) causing severe mechanical damage and growth and survival limitations to the trees ( Gautam, 2001, Gautam and Watanabe, 2002, Bhat et al., 2000 and Pandey and Shukla, 2001). In addition, since the removal of deadwood is still allowed within the park, stems are often purposely injured in order to hasten their death.
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