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Why rainforest soils are generally poor for agriculture
Understanding the basic composition of forest soils helps explain the concept of nutrient cycling in the rainforest; why there are problems with clearing rainforest lands for agriculture; and how soils are an important factor influencing forest complexity. SOIL COMPOSITION
NUTRIENT CYCLING In the rainforest, most of the carbon and essential nutrients are locked up in living vegetation, dead wood, and decaying leaves. As organic material decays, it is recycled so quickly that few nutrients ever reach the soil, leaving it nearly sterile. Decaying matter (dead wood and leaf litter) is processed so efficiently because of the abundance of decomposers including bacteria, fungi, and termites. These organisms take up nutrients that are released as waste and when organisms die. Virtually all organic matter is rapidly processed, even fecal matter and perspiration. It is only a matter of minutes, in many rainforests, before dung is discovered and utilized by various insects. Excretement can be covered with brightly colored butterflies, beetles, and flies, while dung beetles feverishly roll portions of the waste into balls for use later as larval food. I As vegetation dies, the nutrients are rapidly broken down and almost immediately returned to the system as they are taken up by living plants. Uptake of nutrients by plant roots is facilitated by a unique relationship between the roots and a fungi, mycorrhizae. The mycorrhizae attach to plant roots and are specialized to increase the efficiency of nutrient uptake nutrient from the soil. In return, plants provide the fungi with sugars and shelter among their roots. Studies have also shown that mycorrhizae can help a tree resist drought and disease. Tropical rainforest trees are well-adapted to the poor soils of their environment. Since the first 6-8" (15-20 cm) of soil is a compost of decaying leaves, wood, and other organic matter, it is richest pool of nutrients on the ground. Canopy trees are generally shallow rooted to better tap this resource. Being shallow rooted, compounded by the wet soils, has serious disadvantages for tall rainforest trees, especially with the strong winds of the upper canopy that can accompany periodic cyclones. To counter this inherent instability, some rainforest tree species have extensive root systems that run for over 325 feet (100 m). Other trees, especially tall emergent species, have buttress roots, which are large, thin extensions of the trunk that begin some twenty feet from the ground. These structures are thought to also aid in water uptake and storage, increase surface area for gas exchange, and collect leaf litter for additional nutrition. Some trees, expecially palms have developed stilt roots for further support. TAVY - CONVERTING RAINFOREST TO RICE FIELDS
Tavy, as traditionally practiced with long (10 years or more) fallow periods, can probably be an effective strategy for subsistence agriculture in the forests of Madagascar. Increasing the length of the fallow period and leaving intact forest surrounding the cleared patch are key to making tavy a sustainable practice. Unfortunately population/economic pressures and the rapidly disappearing forest cover in eastern Madagascar have made it difficult to carry out tavy in such a manner. The problem is that it is typically in the best short-term interest for Malagasy to clear as much forest as quickly as possible to maximize rice production. For people where day to day subsistence is a question there is little concern for the long-term consequences of their actions. From their perspective, as long as there is more forest land freely availabe for clearing (forests are often considered common property in Madagascar), you might as well take advantage of it before a neighbor does. Tropical Rainforests of Madagascar (previous) | Why rainforest does not regenerate after total clearing (next) More about rainforests Find a mistake? Want to submit pictures or content? Contact WildMadagascar.org Almost all pictures on this site were taken with a Konica Minolta |
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RECENT NEWS Mining and biodiversity offsets in Madagascar 
(08/30/2009) Rio Tinto's ilmenite mine in southeastern Madagascar is among the largest on the planet. At peak capacity, its owners say, it could produce as much as 2 million tons of the stuff—worth roughly $100 a ton—each year, to be shipped off and smelted abroad. What's left of it after refining—some 60 percent of the ore that arrives from Madagascar—will be sold for $2000 a ton as titanium dioxide, a pigment used in everything from white paint and tennis court lines to sunscreen and toothpaste.
Destruction worsens in Madagascar (08/20/2009) Armed bands are decimating rainforest reserves in northeastern Madagascar, killing lemurs and intimidating conservation workers, despite widespread condemnation by international environmental groups. Appalling photos reveal lemur carnage in Madagascar (08/20/2009) New pictures released by Conservation International depict a troubling development in Madagascar: the emergence of a commercial bushmeat market for lemurs. In the aftermath of a March coup that saw Madagascar's president replaced at gunpoint by the capital city's mayor, Madagascar's reserves — especially in the northern part of the country — were ravaged by illegal loggers. Armed bands, financed by foreign timber traders, went into Marojejy and Masoala national parks, harvesting valuable hardwoods including rosewood and ebonies. Without support from the central government — or international agencies that pulled aid following the coup — there was no one to stop the carnage. But now it emerges that timber wasn't the only target. Saving the tsingy forests in Madagascar (08/17/2009) After the success of their Sahafina Forest project, Biodiversity Conservation Madagascar is now branching out to the tsingy forest of Beanka, a project set to launch in October this year. Biodiversity Conservation Madagascar (BCM) has been granted a 25-year lease on a 14,000-hectare area of dry hardwood forest, the Beanka tsingy, situated 75 km east of Maintirano in western Madagascar. 'Tsingy' are spectacular razor-sharp limestone pinnacles found on the west and north of the island, formed by acidic rain erosion. The deciduous forests that inhabit them are characterized by high plant and animal endemism. The Malagasy organization plans to apply the same principles here – protection of the forest, socio-economic development and forest restoration – that brought them success with their last project, the 2,500-hectare forest block of Sahafina on Madagascar’s east coast. Lessons from the crisis in Madagascar, an interview with Erik Patel (08/11/2009) On March 17th of this year the President of Madagascar, Marc Ravalomanana, resigned his post. This made way for Andry Rajoelina, mayor of Madagascar's capital, to install himself as president with help from the military. The unrest and confusion that usually accompanies such a coup brought disaster on many of Madagascar's biological treasures. Within days of Ravalomanana's resignation, armed gangs, allegedly funded by Chinese traders, entered two of Madagascar's world-renowned national parks, Marojejy and Masoala parks, and began to log rosewood, ebonies, and other valuable hardwoods. The pillaging lasted months but the situation began to calm down over the summer. Now that the crisis in Madagascar has abated—at least for the time being—it's time to take stock. In order to do so, Mongabay spoke to Erik Patel, an expert on the Critically Endangered Silky Sifaka and frequent visitor to Madagascar, to find out what the damage looks like firsthand and to see what lessons might be learned. Despite violent protests and coup, Daewoo continues to hold cropland in Madagascar (06/19/2009) Despite violent protests that have left more than 100 dead and led to the ouster of a democratically-elected president, Daewoo Logistics Corp. continues to hold 218,000 hectares of cropland in Madagascar, according to a new campaign by Rainforest Rescue. Conservation success in Madagascar proves illusory in crisis (06/12/2009) Despite the popularity he enjoyed abroad, domestic support for ousted president Marc Ravalomanana eroded rather quickly last February when he went head to head with Andry Rajoelina, the rookie mayor of Madagascar's capital. Rajoelina rallied disparate opposition groups to the cause and soon toppled the incumbent to become, at his own proclamation, President of the "High Authority of Transition." For the country as a whole, the results have not been encouraging. The tourism industry has shriveled to a shadow of itself, important donors have suspended non-humanitarian aid, and a power vacuum has set in in remote regions of the island, wreaking havoc on some of its most fragile and prized ecosystems. Forest Recovery Programs in Madagascar (06/01/2009) Despite being one of the last habitable land masses on earth to be settled by man, Madagascar has lost more of its forests than most countries; less than 10% of its original forest cover now remains, and much of that is degraded. Political turmoil that erupted earlier this year continues to rumble on and the ensuing lawlessness has created the opportunity for illegal logging syndicates to plunder national parks, most notably Marojejy and Masoala, for valuable hardwoods and wildlife. Approximately 200 new frogs discovered in Madagascar threatened by political instability (05/11/2009) Amid the amphibian extinction crisis—where amphibians worldwide are disappearing due to habitat loss, pollution, and a devastating fungal epidemic—the Spanish Scientific Research Council (CSIC) has announced some good news. In a survey of the island-nation of Madagascar they have identified between 129 and 221 new species of frogs. The discovery of so many new species nearly doubles the island's total number of frogs. More news
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