- S.Ananthanarayanan
Scientists studying the recent outbreak of fungus infection in teak trees in the Khandwa region, Madhya Pradesh have said that a variety of species need to planted, to make sure that teak saplings get the correct nutrition.
How could planting competitors for nutrition help the teak saplings?
The prescription, in fact, was not to have more trees competing, but to have more kind of trees. Having more species would mean less teak trees ion all and the nutrition drawn by each teak tree would then be almost the same. But more
species would help maintain the balance of nutritional components and promote healthy trees all round, teak included.
Sitting duck for parasites
A specialized bio-system, like a plantation of only teak, is a sitting duck for parasites. A natural forest is thus never of just teak, but has the diversity of mutually supporting species, co-operating both against predators as well
as in sustaining the nutritional viability of the land.
A parasite that selectively attacks teak would find the presence of other species an impediment to undisturbed multiplication. Similarly, the teak would protect the other species against parasites that threaten those species. If one
species increased out of proportion, these very parasites would get active and keep down the population of the runaway species. Just as reduction of population of a species would lead to the parasites having a harder time, to live or to find trees to harm,
and the population would rise again.
The mix of species in a natural forest is in continuous adjustment for optimum survival of the mutually co-operating species. Naturally occurring, wild strains of cereal and other food plants are thus likely to survive ups and downs
of climate or inroads of pests or infections. A cultivated strain, specialized through farming, on the other hand, has scant defense against a sudden epidemic or mishap, with the use of fertilizers or insecticides. This is an important reason to make sure
that sufficient acreage of wild and natural vegetation be allowed to survive. This would be the reserve to draw on, to develop specialisd strains again, if the current ones were to be wiped out.
More species ensure balance
In the matter of nutrition also, the same symbiotic protection becomes effective. If a plantation consists largely of a species that draws more of particular nutrients from the ground, those nutrients are likely to be depleted, in time.
But if there is a variety of species, then the mix of nutrients drawn would stabilize after some time. And the mechanisms that replace the nutrients, like nitrogen fixation, seepage, bacterial action, etc., can keep the level of nutrients adequate for the
different, dependant species. Again, if one species increased in number, the particular nutrients it used most would begin to reduce and the growth of the species would slow down. The mix of species in the forest would thus remain stable so long as conditions
like rainfall, sunlight, soil quality remain unchanged.
Simply having a forest with less trees, but of a particular kind would not serve, either. It is still necessary to have diverse species. Having less trees of just one species would result in specific nutrient components being
drawn out. Over time, the land would contain a smaller and smaller component of those nutrients, and the land would be unable to support even the sparse population of the species that needs that component. Having other species present would result in other
nutrient components being drawn out as well and this would maintain the chemical balance of the soil.
This is why all species thrive in highly diverse plantations like rain forests or thick natural collections of plants.
[The writer can be contacted at: simplescience@gmail.com]