The open hills: understanding the Nilgiris’ shola–grassland mosaic

Grassland slopes and pockets of shola forest in the Nilgiris, photographed in February 2009. Anand Osuri / Wikimedia Commons, CC BY-SA 4.0. Displayed to fit; no editorial edits.

In this archive photograph, taken in the Nilgiris in February 2009, pale grassy ridges roll towards the horizon. Dark patches of trees gather in the folds between them. Follow those edges with your eye: the change from grass to woodland can be surprisingly clear. That meeting of textures is the beginning of a story about the high hills.

Ecologists call this a shola–grassland mosaic. The name brings the two habitats together, asking us to give the open slopes as much attention as the trees. For a visitor used to looking for a summit or a distant view, it offers a quieter pleasure: learning to read the ground in between.

A landscape in two textures

Sholas are patches of evergreen mountain forest, often with comparatively short trees, set among grasslands in the higher Western Ghats. Researchers describe woodland occupying depressions and valleys, with grassland across the surrounding slopes. Seen from a distance, the forest canopy creates dark, uneven shapes against the finer texture of the grass.

These are ancient ecosystems, with rare and locally restricted plants and animals. Their importance lies partly in that close arrangement of different habitats. A photograph can help us recognise the pattern, though it cannot identify every tree or grass within it. The useful first question is simply where one vegetation type ends and the other begins.

The cold that helps hold an edge

Why does woodland stop where it does? One revealing answer comes from experiments by ecologists Atul Joshi, Jayashree Ratnam and Mahesh Sankaran, reported in the Journal of Ecology. They studied tree germination and seedling survival in a high-elevation forest–grassland mosaic in the Western Ghats, including the effects of warming.

Seeds could germinate in grassland. Surviving the cold was the difficulty: native tree seedlings suffered high mortality after winter frosts and freezing temperatures, while seedlings in adjoining forest escaped those freezing conditions. Invasive Acacia seedlings survived the grassland winter more successfully. The findings show how a boundary visible across a hillside can depend on the fate of very small plants.

This is an explanation of an ecological process, rather than a forecast for a particular morning in Ooty. It adds another dimension to the view: the open hill has its own conditions, and the trees respond to them.

What a grassland needs

The presence of additional trees can therefore change the character of this landscape. Research in the Nilgiri Biosphere Reserve has examined grasslands invaded by black wattle, Scotch broom and gorse. These plants can fix nitrogen, and the study found changes in the availability and cycling of nutrients in the soil beneath invaded patches.

That matters because restoration reaches beyond removing what is visible above ground. In a separate restoration framework, Manaswi Raghurama and Mahesh Sankaran emphasise the recovery of soil processes, the establishment of native grasses and other herbaceous plants, and the prevention of renewed invasion. Caring for the mosaic means understanding what belongs in each part of it.

For the traveller, this is a useful adjustment of perspective. An open stretch of native grassland deserves attention in its own right. Its texture, plant life and relationship with the neighbouring forest are all part of the hills’ ecological character.

A slower way to look

When a landscape view is available from a permitted path or viewing place, begin with its shapes. Trace the curve of a ridge, then look for the darker woodland below. Notice whether the edge is sharp or irregular. A wide photograph can hold those relationships more clearly than a tightly framed portrait of a single tree.

Keep that attention gentle: follow local access instructions, remain on permitted routes and leave plants undisturbed. There is no need to enter a forest patch to appreciate how it sits within the larger scene. For a stay at Tiverton, this offers a small theme to carry through the day: give the grassy hillside time, and let the whole landscape come into focus.

Further reading: NCBS annual report 2015–16, Shola-grassland mosaics of Southern India; Joshi, Ratnam and Sankaran: frost and tree establishment; Raghurama and Sankaran: invasive plants and soil nutrients; Raghurama and Sankaran: restoring forest–grassland mosaics.