Treeline dynamics with climate change at the central Nepal Himalaya

Treeline shifting in tandem with climate change has widely been reported from various parts of the world. In Nepal, several impacts of climate change on the physical environment have been observed, but study on the biological impacts is lacking. This dendrochronological study was carried out at the treeline in the high mountain slope of Kalchuman Lake (3750-4003 m a.s.l.) area of Manaslu Conservation Area in the central Nepal Himalaya to explore the impact of climate change on the treeline dynamic. Two belt transect plots (size: 20 m wide, > 250 m long) were laid which included treeline as well as tree species limit. Ecological mapping of all individuals of dominant trees Abies spectabilis and Betula utilis was done and their tree cores were collected. Stand character and age distribution revealed an occurrence of more matured B. utilis (max. age 198 years) compared to A. spectabilis (max. age 160 years). A. spectabilis contained an overwhelmingly high population (89) of younger plants (< 50 years) indicating its high recruitment rate. Population age structure along the elevation gradient revealed an upward shifting of A. spectabilis at the rate of 2.61 m year-1 since AD 1850. The upper distribution limit of B. utilis was found to be stagnant in the past few decades. An increment in plant density as well as upward shifting in the studied treeline ecotones was observed. The temporal growth of A. spectabilis was correlated negatively with the monthly mean and minimum temperature of June to September of the current and previous year. The regeneration of A. spectabilis, on the other hand, was positively correlated with August precipitation and monthly maximum temperature of the month of the current year. The growth and regeneration of A. spectabilis was more sensitive to maximum and minimum temperature rather than average temperature. The growth of the B. utilis was mainly limited by moisture stress during the pre-monsoon season. As these two species presented species-specific responses to climate change with differential pattern in regeneration condition, much wider differences are anticipated in their population status as climate continues to change throughout the century

High Altitude Wetlands of Nepal

Currently there is no precise definition available in the scientific literature for the term high altitude wetlands (HAWs), however Chatterjee et al. (2010) describe HAWs as "areas of swamp, marsh, meadow, fen, peat land, or water located at an altitude above 3,000 m, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish, or saline and are generally located at altitude between continuous natural forest border and the permanent snow." HAWs include different categories of water bodies, such as lakes, ponds, rivers, glaciers, and glacial lakes. They are characterized by a unique diversity of water sources, habitats, species, and communities and generally have not been subjected to rampant human interference compared to other wetland ecosystems. Nepal is blessed with the highest peak in the world, Mt. Everest, along with another ten of the fourteen highest peaks, all over 8,000 m. These mountains are the source of many glaciers and lakes in the high altitude regions across the country. Most of the high altitude wetlands in South Asia, including Nepal, lie within the Hindu Kush Himalayan Region that extends over 3,500 km and covers approximately 3.5 million sq. km., acting as a fresh water reservoir to the major river basins such as the Ganges, Indus, Yangtze, Mekong, Amu Darya, and Hilmand (Gujja 2005)