Population Spatial Dynamics of Larix potaninii in Alpine Treeline Ecotone in the Eastern Margin of the Tibetan Plateau, China

Abstract

Abstract:The high-altitude treeline is known to be sensitive to climate variability, and is thus considered as a bio-monitoring indicator of climate change. However, our understanding of the population dynamics and the cumulative climate-change effects on the alpine treeline ecotone in recent decades is limited. Here, we investigated the population dynamics of Larix potainii on the southand north-facing slopes in the alpine treeline ecotone in the eastern margin of the Tibetan Plateau, China, including treeline position, population density, and tree recruitment. Results showed that on both south-and north-facing slopes, the treeline did not show a significant advancement in the past four decades. The population was dominated by young individuals, which tend to be established in the lower areas. Larix, here, tends to be clustered, especially in the upper areas. However, population density increased dramatically only on north-facing slopes. Larix here suffer from the stressful environment, but the warmer winter due to climate warming could facilitate the vertical growth of seedlings and saplings. Aggregated spatial patterns also provide a positive feedback in ameliorating the harsh environment. The slope-climate-moisture interactions have a pronounced impact on tree recruitment, including snow-limited tree establishment on the north-facing slopes and moisture-limited tree establishment on the south-facing slopes.

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

“…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). Similarly, fewer number (29.1%) of younger age classes individuals of Larix potaninii was reported in some studied plots in Tibet (Cui et al 2017). Previous research from MCA in Nepal documented non-uniform distribution of saplings and seedlings with absence of seedlings and saplings in 60% and 25% of the sampling plots, respectively, both being completely absent from higher elevation (3800-4000 m) (Sujakhu et al 2013).…”

“…In Nepal, trees of Larix occur in scattered stands on open soils of landslide areas (Miehe and Miehe 2000), on the depositional terraces, loose slopes, and other places prone to a higher rate of disturbance (Carpenter and Zomer 1996) including ancient moraines (Sakai and Malla 1981). The microclimate controlled by slope-climate-moisture interactions have found to cause profound impact on tree recruitment of Larix potaninii in alpine treeline ecotone in the eastern margin of the Tibetan Plateau, China (Cui et al 2017). Similarly, tree regeneration and community structure of L. potaninii was found to be influenced by the understory bamboo Fargesia denudata in the Wang Lang Natural Reserve, Sichuan, China (Taylor et al 1996).…”

“…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.…”

Heterogeneous Responses of Alpine Treelines to Climate Warming across the Tibetan Plateau

“…smithii, Abies georgei Orr, Abies fabri and Abies faxoniana) or larch (i.e., Larix potaninii var. macrocarpa) form the primitive treelines on the sunny and shady slopes, respectively [5,19,[33][34][35][36][37]. In the northeastern TP, spruce (Picea likiangensis var.…”

“…The Tibetan Plateau hosts the Northern Hemisphere's highest alpine treelines [17,18], providing an ideal place to investigate relationships between alpine treelines and environmental variables from local to regional scales. Despite a similar warming trend across the plateau, local-scale and regional treeline studies have shown heterogeneous patterns of tree recruitment and treeline shift rates [5,10,[19][20][21][22][23][24]. However, spatiotemporal patterns of alpine treelines at regional scales covering diverse tree species and different climatic zones on the Tibetan Plateau have yet to be evaluated.…”