Food security, an important part of human well being, is a major concern for most if not all developing country. Madagascar’s rainforests are constantly and severely threatened by local communities which have, most of time, no other choice than using natural resources for a living.
« Carbon storage » as an ecosystemical service is a non destructive way to valorize the forests. However defining the valuable carbon stock is tricky and even the scientific community must face strong difficulties to give a precise accounting of the carbon stock. Carbon is stored in different pools and the most detailed and studied one is the most apparent: the above ground biomass. However, carbon is also stored in roots and in soil, also called “below ground carbon”, which are both a huge stock.
Just like an iceberg, the biggest part of the carbon stock is below the surface. But unlike an iceberg we cannot see easily what is below the ground surface and we cannot tell just by sight which quantity of carbon is in that forest soil. The purpose of the project is to give a direct and precise assessment of the carbon above and below the ground. By doing this, our workpackage which is a part of the p4ges project funded by ESPA program, can give to the decision makers of the country the current best carbon accounting of the rainforest corridor « Ankeniheny Zahamena » and contribute to poverty alleviation.
How do we proceed?
For aboveground, to determine the carbon stock of the forest we have measured the carbon content of the trees. And because there are millions of trees in the rainforests we cannot measure all of them one by one. That is why it is important to select some representative area. In this area, we determined the specific composition of the forest (which species do we find?) and the carbon content. For this, saplings are collected, weighed and sampled in a circle of 2 m radius. For big trees, their diameters and their heights are recorded to calculate the above ground carbon. And to have more precised data, we have selected some dominant species, weighted and sampled their trunks, leaves and branches. We then apply the obtained model to the entire forest. This can be done because the forests are arrangements and repetition of some species. In other terms, if there are a million trees in a forest, we won’t have a million different tree species but a repetition of a pattern of a several species.
That was for the easy part, the above ground carbon.
For the root-carbon, the difficult one, a direct measurement had to be done. For this, we first need to cut the tree (some trees to serve the cause of the science) because we must free all the roots from the ground by excavation, to weight, measure and sample them.
Because some trees have hundreds of root ramifications and some ramifications can be as long as 15 meters, root-carbon quantification is a very massive and time consuming work. But with our project, a reliable prediction model of the root carbon, taking account the shoot parameters (a visible part of the trees) can be developed. The obtained data can be used to predict on the future the root-carbon without such a destructive work. Thus, we don’t have to cut more trees than necessary. We then use the predetermined composition to extrapolate accurately the carbon content of the roots.
For the soil carbon, soil samples were collected on pits at different depths (up to 100cm) with cylinder in order to measure soil bulk density. Then, soils were analyzed for soil organic content (via the Walkley and Black and Mid Infra Red Spectroscopy), humidity and density in the laboratory.
Why is it important?
There is a considerable amount of carbon inside the tropical rainforests like the Ankeniheny-Zahamena corridor. Our project aimed to quantify the entire potential of the forest using direct and indirect measurement methods on the visible and buried part of the forest.
Global and national scale studies on carbon quantification give only a few references on root carbon stock. The existing studies relate to artificial forests or other non-forest land uses. Our project can help to compensate the lack of knowledge on carbon quantification in the root compartment which contains a large amount of carbon. This will allow consideration of this compartment in carbon accounting and will have an important impact on future REDD project.
With the equipment at our disposal and the amount of work required to obtain precised data, we are working hard to produce results that meet scientific requirements to provide to decision makers reliable and precised elements.
In our project, we work with various actors from the local community through various scientists, to the decision-maker, both at national and international level. We can say for example the preparation of Madagascar to the COP21 summit, a major event on the climate change topic, via the organization of a side event supported by the international community.
Carbon can be stored. It is a way to reduce the deforestation’s greenhouse gas emissions and by the way help people to find some revenues without destroying the rainforests. This project is the first step to get closer to this objective.
Blogpost and picture submitted by Mieja Razafindrakoto (Laboratoires des RadioIsotopes, Madagascar) – mieja.razafindrakoto(at)gmail.com
Picture courtesy Carbon team of the p4ges project
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