Sal: The Robust Timber Tree

Taxonomists who describe animal or plant species sometimes try to incorporate the species’ characteristic features in the name. Sal is scientifically known as Shorea robusta, and this name has a fascinating origin. Anyone who has seen an old sal tree, with a straight, long trunk reaching heights of 35-40 m cannot remain unimpressed with this magnificent tree — hence the name, robusta. The tree’s genus name comes from Sir John Shore, Governor-general of Bengal (1793–1798) and revenue expert for the East India Company. The tree was first scientifically described by German botanist Carl Friedrich von Gärtner in 1805.

Sal is distributed from the Shivaliks in Haryana throughout northern India, southern Nepal, West Bengal, and from the Northeast to Myanmar. It is also found in Central India (eastern Vindhyas, Satpura ranges, and Eastern Ghats) in Madhya Pradesh, Chhattisgarh, Jharkhand, and Odisha. Sal forests cover nearly 11 million hectares in India, Nepal, and Bangladesh. According to official figures, the highest area under sal (38,300 sq km) is in Odisha, with Madhya Pradesh/Chhattisgarh coming next at 28,000 sq km. Haryana (40 sq km) has the least.

There is a clear-cut natural distribution division of sal and teak (Tectonia grandis) forests: where the sal distribution ends, teak distribution starts. Interestingly, the distribution of red junglefowl (Gallus gallus) ends in Central India with sal distribution, and the range of the grey junglefowl (Gallus sonneratii) starts and goes up to almost the tip of southern India. Like in many biogeographical distributions of two species with no physical barriers, there is always some common ground where both species are found.

Flowers, leaves, and the wood of the sal are considered sacred in Hindu and Buddhist cultures, and it is also important from a medicinal point of view. However, its greatest use is as timber. Its straight, thick trunk of 3-4 m circumference and 30-40 m height is fit for making railway track sleepers, furniture, floors, walls, and traditional household items. Termites, the bane according to many foresters, do not attack it. While working in Dudhwa National Park, I heard the Hindi aphorism, “Sal saoo saal khara, saoo saal pada, saoo saal sada” (sal stands for 100 years, falls and remains for 100 years, and takes 100 years to disintegrate). Incidentally, Dudhwa NP has some of the finest sal stands in India. 

According to Dr M K Ranjitsinh, former bureaucrat and one of India’s topmost conservationists, the terai has very good, old sal trees, and “some patches of sal in the Doon Valley of Uttarakhand were outstanding” before the British started extensive sal timber extraction. On my recent query, he replied, “This tract around Dehra Dun has been the laboratory and playground of foresters, and sal monoculture was actively propagated”. According to him, “Some patches of sal which have never been harvested on the northern flanks of the Maikal Range in Kanha, having been a part of the Banjar Game Reserve in the British era and of the Kanha National Park in the present, are also superb.”

As sal is a valuable timber tree, much research has been done on silvicultural practices (development and care) to increase its timber yield and make it grow quickly. Foresters are worried about its natural regeneration. In many areas, clear felling of old sal was done to allow new growth by seed sowing, but the desired results were not obtained. Attacks by wood borer beetles (Hoplocerambyx spinicornis) is another major problem that came into focus a decade ago when old sal trees started dying in Kanha National Park, Madhya Pradesh. Prolonged droughts, frequent fires, and climate change are other threats impacting sal trees.

In a paper published in Forest Science (2023) entitled “Predicting Impacts of Climate Change on Teak and Sal Forests in Central India Using Maximum Entropy Modelling: an Approach for Future Conservation and Silvicultural Strategies”, Maneesh Kumar Patasaraiya has shown that in Satpura Tiger Reserve, the sal will decline due to climate change in the immediate future (2050) and far future (2070).

Sal seedlings face significant challenges in certain regions due to moisture deficit and dense undergrowth, leading to a high mortality rate. While the initial recruitment of sal seedlings is not problematic, the crucial stage lies in their successful establishment and growth into large-diameter trees. According to some foresters, the decline in moisture levels and the proliferation of undergrowth, including shrubs and weeds, have intensified competition among sal seedlings.

Though it is said that termites do not damage even the fallen sal, some scientific studies have shown that about 350 insect species target the roots, seeds, seedlings, leaves, and full-grown sal trees. A mature sal, or a good stand of sal trees, is an ecological microcosm, with about 64 species of lichens reportedly growing. Many birds nest or roost on sal trees. The great slaty woodpecker (Mulleripicus pulverulentus) is more or less dependent on mature sal forests. This crow-sized woodpecker moves in groups of 6-10 individuals and is on the bucket list of many birdwatchers. Though these massive woodpeckers have been spotted in Dudhwa and Rajaji national parks, they are difficult to locate as they are uncommon even in their main habitats. Despite working in Dudhwa for many years, I have only seen this woodpecker a few times.

Red weaver ants (Oecophylla smaragdina) make nests by swirling large sal leaves into a cup shape. Nesting red weaver ants benefit the tree as they feed on the other insects that may attack sal leaves, flowers, and seeds, thus, the tree and ants maintain a symbiotic relationship. Incidentally, many tribes, particularly in Odisha, Chhattisgarh and Madhya Pradesh, harvest nests of red weaver ants and make a chutney (paste). It is common to see red weaver ants’ nests sold in weekly haats (markets) in many tribal areas. Formic acid from the ant gives the chutney a characteristic tang. Indigenous communities collect fallen leaves and seeds of sal for multiple uses, such as making eco-friendly plates and cups, and the resin is used in traditional medicine. No wonder the sal tree is worshipped by many communities, particularly the Santhals of Odisha.

Throughout the year, sal shows its glory in different forms. New leaves come up in spring, refreshing the forest, followed by flowers in late April and May, giving life to numerous insects and birds. Even the fallen leaves have a mesmerizing effect. The fallen petals, sepals, anthers and whole flowers carpet the floor, and their continuous fall looks like soft snowfall, particularly in the slanting morning sunlight. I have spent many glorious mornings in Dudhwa enjoying this ethereal scene. Once the seeds are ripe, they parachute down like swirling dark raindrops. This characteristic swirl or twisting is due to the seed having five “wings” of unequal shape. In many reserve forests, tribals collect these fallen seeds. In an excellent paper entitled, “Ecological, cultural and medicinal values of sal (Shorea robusta): a multifaceted native tree of India”, Sanjeet Kumar and his team have shown numerous uses of sal leaves, flowers, seeds, trunk, and branches for tribals.

Silviculture (the care of forests) techniques for sal forests have been evolving since the early 20th century, primarily focusing on timber production. However, these forests have historically served multiple purposes, including grazing, fodder collection, fuelwood, and litter gathering. Rather than integrating these diverse uses into forest management strategies, governments have sought to regulate them through forest legislation. This approach has led to ongoing conflicts between local communities and government authorities, contributing to the declining health of sal forests. Promoting sustainable management of sal forests with community involvement is the way forward to protect sal forests.

Photo sources: sal flowers, sal seed, great slaty woodpecker