The Shola (Tropical Montane Forest)-Grassland Ecosystem Mosaic of Peninsular India: A Review

Abstract

Tropical montane forests (alternatively called tropical montane cloud forests or simply cloud forests) represent some of the most threatened ecosystems globally. Tropical montane forests (TMF) are characterized and defined by the presence of persistent cloud cover. A significant amount of moisture may be captured through the condensation of cloud-borne moisture on vegetation distinguishing TMF from other forest types. This review examines the structural, functional and distributional aspects of the tropical montane forests of peninsular India, locally known as shola, and the associated grasslands. Our review reveals that small fragments may be dominated by edge effect and lack an “interior” or “core”, making them susceptible to complete collapse. In addition to their critical role in hydrology and biogeochemistry, the shola-grassland ecosystem harbor many faunal species of conservation concern. Along with intense anthropogenic pressure, climate change is also expected to alter the dynamic equilibrium between the forest and grassland, raising concerns about the long-term sustainability of these ecosystems

Deep and wide valleys drive nested phylogeographic patterns across a montane bird community

“…The sky islands of the Western Ghats host Tropical Montane Cloud Forests [26], or Sholas as they are known locally, spread across a 700 km range (figure 1) with 17 endemic bird species. Unlike the Andes, where recent topographic changes led to diversification of montane species (for example flycatchers [27] and hummingbirds [28]), the Western Ghats' topography is relatively older (ca 50 Myr, arising owing to a series of uplifts during the Indian plate movement between 160 and 50 Ma [29]), and perhaps existed when songbirds (or oscines) arrived in India (ca 34 Ma) [25].…”

Sky island bird populations isolated by ancient genetic barriers are characterized by different song traits than those isolated by recent deforestation

“…Shola forests, or tropical montane cloud forests (Bunyan, Bardhan, & Jose, 2012), are typically found above 1,400 m ASL on the mountain tops or "sky islands" of the Western Ghats. Each sky island is isolated from neighboring islands by deep valleys characterized by different climate and vegetation, described in Robin et al (2015b).…”

Elements of indigenous socio-ecological knowledge show resilience despite ecosystem changes in the forest-grassland mosaics of the Nilgiri Hills, India

“…E xtensive landscape transformations of natural forest and grasslands into plantations and agricultural lands are an increasingly common global phenomenon, affecting Africa, Australia, southern Asia, Europe, North America and South America (Neke and Du Plessis 2004;Fensham and Fairfax 2003;Zhao et al 2006;Bredenkamp et al 2002;Hoekstra et al 2005;Baldi and Paruelo 2008;Vega et al 2009). Megadiverse countries like India, harbouring about 200,000 (or 13%) of all known species, are threatened largely by vegetation clearing (Bunyan et al 2012;Daniels, 1992;Mohandass and Davidar, 2009). In India, this biodiversity is mostly concentrated in the Western Ghats, a 1600 km long mountain range classified as a biodiversity hotspot with a high degree of endemism of flora and fauna, and with many globally threatened species having a very restricted distribution (Myers et al 2000;Bond and Parr, 2010;Das et al 2006;Gimaret-Carpentier et al 2003;Jose et al 1994).…”

“…The forest-grassland mosaics of the Nilgiri Hills are one of the most diverse and threatened landscapes of the Western Ghats Highlands (Meher-Homji, 1967;Suresh and Sukumar, 1999). Since the mid-nineteen century, land use changes have fragmented the Nilgiri's shola forest-grassland mosaics, and such fragmentation is an increasing focus of ecological studies (Sukumar et al 1995;Bunyan et al 2012;Mohandass and Davidar, 2009;Das et al 2015;Das et al 2017;Davidar et al 2007;Davidar et al 2010;Robin and Nandini, 2012;Thomas and Palmer, 2007;Arasumani et al 2018).…”