Forests-Beyond the Wood - V
By Dr. Ranil Senanayake-September 7, 2018, 9:54 pm
The richness of forest ecosystems is not only the trees and the biodiversity that exits within, it also extends to the soil below
The world of soil is bizarre to us who live on the surface. It is opaque to light and mostly solid. Communication is by chemicals, e.g. pheromones or physical, e. g. vibrations. Movement is slow; the faster organisms like worms are the giants of this world, tunnelling through at a fairly rapid rate measured in centimetres per minute. More common are the fungi that move by growing through the soil at rates measured in centimetres per month, or the bacteria, which have rates, measured in centimetres per year.
It is a busy world, one gram of ordinary farmyard soil can contain over 1 billion individual bacteria, over 100 million individual actinomycetes and over 1 kilometre of fungal hyphpae, notwithstanding plants like algae and animals like collembolans, nematodes or worms. This massive diversity provides for the multitude of critical functions, that a living soil provides.
Understanding soil ecosystems and how they work is important for both production and conservation goals. In production systems this information will enable the optimization of inputs and help develop more sustainable agriculture. For instance, while phosphorus is needed as an amendment on most soils to produce good crops, the source of phosphorus used can make a great difference to both productivity and profitability. Phosphorus that has been acted upon by certain soil bacteria can produce a higher volume of crop than that produced by the same amount of phosphorus added as superphosphate. Developed commercially, it has the potential to reduce fertilizer bills significantly. In a submission to US Agriculture In 1938 Dr, William Albrecht a leading US soil scientist, made the following observation:
"Soil organic matter is one of our most important national resources; its unwise exploitation has been devastating; and it must be given its proper rank in any conservation policy as one of the major factors affecting the levels of crop production in the future… The Nation should be made aware of the rapid rate at which the organic matter in the soil is being exhausted. Farm-management practices should be adopted that will at least maintain, and in as many cases as possible even increase, the supply of this natural resource in the soil. The maintenance of soil organic matter might well be considered a national responsibility."
But In 2012 in Sri Lanka, we still have to appreciate this fact. The colonial experience robbed us of that precious organic matter, the felling of forests and clearing of land began with the colonial adventure, in 1820 all land without title ie. The forests and Forest Gardens were deemed 'crown land' and sold to international commercial interests. Emerson Tennent writes that ‘the 'coffee boom' of 1835 saw a rush for investment in land that was only equaled by the rush for land during the gold discoveries in the U.S.’ Thus, the organic soils of the mountains of this country, built over a period of twenty million years, was destroyed in a matter of decades.
The impact of this loss is conveyed by Fredrick Lewis in his book ‘Sixty-Four Years in Ceylon’, he makes this observation on the process of destruction of the mountain forests in the Agra Patna area:
"I know of no more awe-inspiring sight, than that of a thousand acres on fire. Sheets of flame appear to leap into the air, and yell with a sort of devilish delight at their victory over the magnificent trees they are reducing into charred masses of cinder and charcoal. It is more than impressive, it is fearful, yet grand ! After the fire has completed its work, the land is covered with. black logs, lumps of charred timber, masses, and often great fragments of stones, broken by the heat that has swept over them. A deep black covers the landscape; impressive, but depressing.
It was in a burned wilderness like this, that I found my new home. It lay at the extreme end of one of the many blocks of land that had been simultaneously burned off. My path, for road it could not be then called led over hundreds of fallen and charred logs, and followed the valley of the Agra stream.
When morning broke upon the day following the events recorded at the conclusion of the last chapter, I found myself gazing upon a scene not altogether unfamiliar to me. All around me lay hundreds of charred black logs, stumps in fantastic shapes and outlines: fallen branches, broken and distorted by fire: cinder heaps, and little rivulets of sodden ash: all indicative of the fierce, merciless fire that but a few weeks ago, had raged over a spot that so lately had been a beautiful forest land.
It was now a blackened wilderness, to be changed into fields of coffee, by the labour and patience of man. A strange picture; fascinating in one respect: fearful in another and yet so full of a strange mixture of possibilities was this wild heap of ruins, this uncouth mass of slaughtered giants of an inarticulate, yet eloquent world, to be transformed by, industry in the pursuit of fleeting wealth."
The process, eroded and destroyed most of the topsoil, undisturbed since the Jurassic, leaving plantations that cling to the subsoil and yield only with artificial fertilizer that we have to import. As the organic matter receded so did soil cohesion, such that at a slightest downpour, bit of the fields come loose and just fall away. The age and vastness of this incredible soil ecosystem is signified by the number of endemic, soil dwelling reptiles and amphibians, these were the top predators of the soil ecosystem and regarded as indicators of large soil reservoirs. Today, these unique animals are confined to the last patches of remnant forests or pockets of native soil.
Soils also store vast amounts of carbon, more than twice as much as in vegetation or the atmosphere. They do this by respiration processes, which use the energy fixed by photosynthetic activity, to create very long-lived soil carbon compounds synthesis such as humates. The more undisturbed the soil the more carbon it can accumulate and hold. Here, the effective rate of sequestering is dependent on the nature of the soil that it is being produced in.
Thus forested areas or areas with dynamic vegetation create the best soils in nature.
(To be continued )
