Jacquemont’s Acacia (Bhuri Babool)

Jacquemont’s acacia (Acacia jacquemontii, now also written Vachellia jacquemontii, locally bhuri or khor) is the multi-stemmed, thorny nitrogen-fixer that colonises bare sand first. It runs through the Thar and Cholistan dunes and across the sandy plains of Punjab and Sindh, where it is often the first woody plant to take hold and hold the sand in place.1 For a grower starting on shifting dune or hard desert margin, it is the pioneer that begins building soil where there is none — a plant that asks for nothing and leaves the ground better than it found it.

Where it thrives

This is an erect, rigid, deep-rooted xerophytic shrub of arid and semi-arid country, effectively endemic to the Thar biome and recorded by the Flora of Pakistan in Sindh, Punjab, and Balochistan.1 It is well suited to sandy and loamy desert soils, including the infertile, alkaline sands of the Thar and the Thal, the roughly 2.5-million-hectare desert tract of the Punjab.2 Full sun, deep sand, and very little rain are exactly its conditions, and its deep root system lets it ride out long droughts that would kill a shallow-rooted shrub. It is a true desert plant: it does not need irrigation, fertile soil, or shelter, which is precisely why it can go in first where nothing else will establish.

Role in the system

As a pioneer legume its first contribution is fertility. It nodulates and fixes atmospheric nitrogen, and the work matters because the soils it grows on are some of the poorest in the country. On the stressful alkaline ground of the Thar it is nodulated by diverse, promiscuous Ensifer rhizobia — strains tough enough to function under that stress — so it builds nitrogen where most legumes would fail to nodulate at all.3 Its deep roots and low, branching crown stabilise sand dunes and break the wind, and its litter starts the slow work of making soil organic matter.1 The sequence on bare sand is straightforward: establish it first, let it fix nitrogen and pin the dune for a few years, then plant longer-lived trees into the shelter and improved soil it has created. It is the first tenant that makes the ground habitable for the rest of a guild.

What you get

The wood is valued as firewood because it burns hot, a real return where fuel is scarce and people otherwise burn dung that the soil needs, and the leaves are browsed by goats and camels, giving dry-country fodder off otherwise unproductive sand.2 The bark carries local medicinal use as well, and the shrub yields a minor gum like other acacias. The larger return, though, is the service work that does not show up as a harvest: nitrogen added, sand held, wind cut, and shade thrown for seedlings. That is what makes the next, more productive stage of planting possible at all.

Establishment

Raise it from seed collected off healthy desert stands. The seed coat is hard, so scarify it — nick or briefly soak it — before sowing to break dormancy and get even germination. Where the local soil has never carried this acacia and lacks the right rhizobia, raise seedlings in soil taken from an existing nodulated stand, or inoculate, so the nitrogen-fixing partnership is in place from the start. Once established it is self-reliant and needs no further care.

Sources

1. Flora of Pakistan. “Acacia jacquemontii Benth.” eFloras.org, Missouri Botanical Garden & Harvard University Herbaria.
2. Wikipedia contributors. “Vachellia jacquemontii.” Wikipedia.
3. Gehlot, H. S., et al. (2016). “Molecular characterization of nitrogen fixing microsymbionts from root nodules of Vachellia (Acacia) jacquemontii, a native legume from the Thar Desert of India.” Plant and Soil, Springer.