How Forests “handle” Carbon Dioxide

In our century, the twenty-first one, there are many contribution directed to restore and protect forests and in a simple image of natural cycles trees are a main part in the ecosystem balanced system. They are part of the photosynthesis process, producing hydrocarbons (which fuel they growth) and over the course of their lives they store up to 22 tons of carbon dioxide in their trunks, branches and root systems.

At the moment they die, the same exact quantity of greenhouse gases is released as fungi and bacteria penetrate down the wood. Then the next step is to process the carbon dioxide inside it, and breathe it out again. But this natural and very special cycle cannot be replicated (in this particular way) by humans burning wood; and there are people that define both pretty the same thing, without any scientific basis.

We can imagine the whole forest as a gigantic carbon dioxide “vacuum” that imbibe, stores and filters out this gas. Yes, we know also that this carbon dioxide does indeed return to the atmosphere after a tree is dead, but the majority of it is locked in the ecosystem when the crumbling trunk gradually gnawed and munched into smaller pieces.

And as the temperatures falls, life slows down until it comes almost t a standstill, when this carbon dioxide become humus; more concentrated as it ages. This is also the genesis of bituminous and anthracite coal.

The fossil fuel that we need to switch on the car every morning, and to move the transports and machines all over the world are originated by trees that died almost 300 millions years ago.

Today hardly any coal is being formed because forests are constantly being cleared, thanks to modern forest management practices. It happens that when they died of old age their trunk splashed down into stagnant water hardly rotted at all. So, nowadays hardly any coal is being formed because forests cycles are constantly being stressed due to this logging practice.

What is the mechanism of this coal arrest? Well the temperatures are rising and all of this warming rays of sunlight that reach the ground allow the species living there to grow up faster and to adapt on this situation. How do they do it?

They consume humus layers even deep down into the soil, releasing the carbon dioxide they contain into the atmosphere as a gas. The total quantity of climate changing gases that escapes is almost equivalent to the amount of timber forest that has been felled: so carbon stores in the ground below trees in our latitudes are being depleted as fast as they are being formed. Let’s make a step backward.

forest

Carbon dioxide sinks into the mud when plants die because it is stored in the form of carbon compounds, that with the remains of animal bones (formed mainly by calcium carbonate) can fix into the soil and being removed – after hundreds of millions of years – fro the atmosphere. Today we have reversed this trend, emptying the earth’s carbon reservoirs: oil, gas and coal are burned to become heating materials spewing their carbon reserves out into the air.

Sometimes people think that the increased level of carbon dioxide free in the air act as a “fertilizer” for the trees that are growing quickly as they used to.

But not everyone reflect on a simple statement, according to the natural trees process of aging: slow growth is the key to growing old. Growth fueled by the hefty addiction of excess nitrogen from agricultural operations is unhealthy, even if most of people think that young trees are more vigorous and have a fastest growth compared to old ones.

There is a study of N. L. Stephenson et al. (2014) published on Nature that state how forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentration. Our ability to understand and predict changes in the forest carbon cycle (particularly net primary productivity and carbon storage) increasingly relies on models that represent biological processes across several scales of biological organization; from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands,no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Stephenson and its colleagues present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. So, in the case of trees, being old doesn’t mean being weak, bowed and fragile.

Though, it means being full of energy and highly productive regarding the elderly species that in the context of climate change are important allies for humans beings.

So, if we want to use forests as a “weapon” and a tool in this climate change scenario, we need to understand that the more they grow and became old, the more we stay in health allowing then the health of our Planet.

 

LH

 

 

Published by

Lisa Halfon

Deeply passionate in Technology, GeoPhysics, Biology, Science Communication and Life Development. In my blog I write what tickle my mind and may have a public impact

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