Contemporary and Historic Population Structure of Abies spectabilis at Treeline in Barun Valley,Eastern Nepal Himalaya

Treeline ecotone dynamics of Abies spectabilis(D. Don) Mirb. in the Barun valley,Makalu Barun National Park, eastern Nepal Himalaya were studied by establishing seven plots(20 m ×variable length) from the forestline to the tree species limit: three plots on the south- and north-facing slopes each(S1-S3, N1-N3), and one plot on the eastfacing slope(E) in the relatively undisturbed forests.A dendroecological method was used to study treeline advance rate and recruitment pattern. In all the plots,most trees established in the early 20 th century, and establishment in the second half of the 20 th century was confined to the forestline area. Treeline position has not advanced substantially in the Barun valley,with only 22 m average elevational shift in the last 130 years, and with average current shifting rate of 14cm/yr. Moreover, no significant relationship was found between tree age and elevation on the south-,north-, and east-facing slopes. The number of seedlings and saplings in near the treeline area was negligible compared to that near the forestline area.Therefore, A. spectabilis treeline response to the temperature change was slow, despite the increasing temperature trend in the region. Beside the temperature change, factors such as high inter-annual variability in temperature, dense shrub cover, and local topography also play an important role in treeline advance and controlling recruitment pattern above the treeline.

Dendroclimatic response of Abies spectabilis at treeline ecotone of Barun Valley, eastern Nepal Himalaya

A dendroclimatic study was conducted in the treeline ecotone of Barun Valley, eastern Nepal, to determine the tree-ring climate response and ring width trend of Abies spectabilis. A 160-year-old chronology, from 1850 to 2010, was developed from 38 tree-ring samples. No higher growth in recent decades was observed in tree-ring width in this area. The mean temperature of the current year in February and in the combined winter months of December, January, and February showed significant positive correlation with tree-ring width, although no significant correlation was found between tree-ring width and the precipitation pattern of the region. This tree-ring climate response result is different from that in other studies in Nepal, which could be attributed to location and elevation.

Predicting upslope expansion of sub-alpine forest in the Makalu Barun National Park, Eastern Nepal, with a hybrid cartographic model

The natural upper boundary of a forest（forest line） in mountain environments is an indicator of climate conditions. An increase in global average temperatures has resulted in an upward advance of the forest line. This advance may result in fragmentation of the alpine ecosystem and a loss of biodiversity. Therefore, it is important to identify potential areas where current forests can advance under scenarios of future climate change. I used expert knowledge and cartographic modeling to create a hybrid cartographic model considering five topographic variables to predict areas where forest line can expand in the future.The prediction accuracy of the model is around 82%. The model is able to predict areas above the current forest line that are suitable or unsuitable for future forest advance.Further inclusion of high-resolution satellite imagery and digital elevation models, as well as field-based information into the model can help to improve the model accuracy.