Timberline structure and woody taxa regeneration towards treeline along latitudinal gradients in Khangchendzonga National Park, Eastern Himalaya

Abstract

With main purpose of developing a coherent baseline information of timberline forests of Sikkim, Eastern Himalaya, we investigated, (i) forest structure and composition, (ii) regeneration status of dominant timberline tree species between timberline and treeline, (iii) influence of environmental variables in species composition, and (iv) relationship between environmental variables and ecological attributes. The study was conducted along the timberline stretch of Dzongri landscape nested within the Khangchendzonga National Park (UNESCO’s World Heritage Site, 2016), a core zone of Khangchendzonga Biosphere Reserve (in UNESCO WNBRs, 2018), Sikkim, India. We employed quadrat method to sample 9 contiguous sites to capture all possible variations in timberline composition. Transect method was used to study the regeneration of woody taxa between timberline to treeline. In total, 20 woody species belonging to 10 genera and 6 families were recorded. Among these, Abies densa, Rhododendron lanatum and Sorbus microphylla exhibited higher dominance, comprising of 50% of the total importance value index (IVI) weightage. Betula utilis the common treeline species in much of the western and central parts of Himalaya was absent here. Tree density in studied timberline was significantly higher than its western Himalayan counterparts of Indian Himalayan region. Environmental variables viz., elevation, slope, and humus were observed determinants of species composition across the study area. The species dominance correlated negatively (p<0.01; n = 9) with species diversity and richness. We observed an irregular spatial pattern of timberline across the 9 study sites, and the extent of timberline elements (seedling; sapling; live tree or dead tree) ranged between 5.3m to 187.7m higher than the current timberline at different sites. The present trends suggest that upslope advancement is unlikely to occur in near future, while treeline densification is anticipated. Further investigations are suggested to develop a holistic understating of these timberline patterns across the Indian Himalayan region.

Population structure and regeneration of Himalayan endemic Larix species in three high-altitude valleys in Nepal Himalaya

“…The regeneration of the plant is the key ecological process in a forest ecosystem in which seeding and sprouting of woody species are involved (Pratt et al 2012). One of the most important problems that mountainous forests are experiencing is poor regeneration (Karauchi et al 2000), which is especially observed in subalpine forests in Eastern Himalaya (Tambe et al 2011;Pandey et al 2018) as well as in Western Himalaya (Rai et al 2012). Poor regeneration and naturally slow growing nature of Larix griffithiana are documented in subalpine forests in Sikkim Himalaya (Tambe et al 2011) and absence of seedlings and saplings of the species has been recorded in temperate forests in Lachung Range of the Sikkim Himalaya (Subba et al 2015).…”

“…Sustainability of populations with inadequate number or lack of regenerating individuals has been reported to be challenging for several species of subalpine trees. Examples include Larix potaninii in China (Taylor et al 1996;Cui et al 2017;Liang and Wei 2020), Larix griffithiana in Sikkim, India (Tambe et al 2011;Subba et al 2015), and Bhutan (Moktan 2010); and for many other species in the eastern Himalaya (Pandey et al 2018), Nepal Himalaya (Vetaas 2000;Shrestha et al 2007;Kunwar 2011;Sujakhu et al 2013;Maren et al 2015;Suwal et al 2016), and western Himalaya (Rai et al 2012). Therefore, for the effective conservation of the typical Himalayan vegetation of Larix forests, efforts need to be concentrated both locally and regionally.…”

Dynamics of 18 (&lt;i&gt;Sophora japonica&lt;/i&gt;) Tree Community’s Crown Volume along Elevation Gradient in &lt;i&gt;Ye County&lt;/i&gt;

“…In resent years, more and more researches explained the correlation between tree community's crown volume and elevation [7]- [13]. These researches include dynamics of community's crown volume traits [1], tree community's crown volume structure [2], tree community's crown volume growth [3] [4] [5], tree leaf structure of community's crown volume [6], community canopy crown volume and structure [7]- [11] along elevation gradient. Thus, the results indicate that elevation was the dominant environment driver of crown volume of 18 (Sophora japonica) tree communities increased along elevation gradient.…”

“…The correlations between tree community's structure and elevation include tree community traits [1], tree community structure [2], tree community growth [3], DOI: 10.4236/oje.2019.97017 210 Open Journal of Ecology tropical tree community growth [4], tree community [5], tree community's leaf structure [6], and community canopy structure [7] in the environmental (size-dependent changes [1], latitudinal [2], climate warming [3], elevation [4], climate variations [5], ecological environment [6] [7]) dynamics along elevation in the forestry ecosystems. However, there is the correlation between crown volume of (Sophora japonica) tree communities and elevation along elevation gradient in Ye County.…”

How people perceive resilience of Himalayan pheasants, Phasianidae, in relation to climate warming in Eastern Himalaya

“…Climate warming is critically viewed in response to the loss of alpine biodiversity (Gentili et al, 2015). In mountain regions, upward movements of plant species and timberlines are predicted to reach «sky islands» (Gottfried et al, 2012;Pandey et al, 2018). The increase in mean annual temperatures is not uniform around the globe.…”