Assessing vegetation changes in timberline ecotone of Nanda Devi National Park, Uttarakhand

Changes in the timberline ecotone vegetation of Nanda Devi National Park (NDNP) was studied over a period of 30 years (1980–2010). Our study based on remote sensing analysis of Landsat MSS and TM images suggests no geographical shift in the upper limit of timberline, while the subalpine forest's canopy has increased substantially. Decrease in heterogeneous reflectance pattern near upper boundary of timberline ecotone (above 3600 m asl) suggest more homogenous growth at this elevation. Though the scale of the study is not sufficient to detect minor changes our objective here is to know if the timberline vegetation of NDNP has gone under rapid change in last three decades. Two different methods post classification comparison and vegetation index differencing, used in this study have widely been used for vegetation change detection but very few studies have reported the performance of these methods for highly rugged terrain. Our approach in this study is to test the applicability of these methods in the specific environment of western Himalaya. Given the fact that the findings of the study could be the result of incorporation of various methodological errors we analyzed the descriptive statistics (mean and standard deviation) of vegetation index to interpret the nature of change.

► Temporal change in the timberline ecotone vegetation of NDNP was studied.
► No evidence of geographical shift in the upper limit of timberline was found.
► However, substantial increase in the subalpine forest's canopy was found.
► Decrease in the heterogeneity of reflectance pattern indicates no new regeneration.
► Among different method used ratio band (NIR/R) performed better than MSAVI2 and NDVI.