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Ecology

Centuries-old pioneer

The araucaria coniferous tree, whose lifespan averages 400 years, recovers quickly in deforested areas

Fabio ColombiniPlace in the sun: native Brazilian pine tree needs a lot of light to growFabio Colombini

The forests populated with candlestick-shaped trees that Auguste de Saint-Hilaire became acquainted with in the south of Brazil 200 years ago have become very rare. One century after the French scientist’s trips through the regions of what were then the provinces of Curitiba, Santa Catarina and Rio Grande do Sul, the cutting down of araucaria trees for lumber and for the extraction of the seeds for human consumption have endangered the survival of one of Brazil’s few native pine trees. This has also endangered the survival of the plants and animals that live in the shade of araucaria forests, one of the ecosystems that comprise the Mata Atlantica Rainforest. It is believed that 20 million hectares of araucaria forests once covered the plateaus and mountain ranges of southern and southeastern Brazil until the early twentieth century. Nowadays, according to an extensive survey of the remaining patches of the Mata Atlantica Rainforest, published in 2009 in Biological Conservation, only 12.6 percent of the araucaria trees resist in isolated places such as mountain slopes and mountaintops that are difficult to get to, making it difficult to plant grain or raise cattle. The biggest concern voiced by people who care about the future of the araucárias is that it is not easy for these forests to recover and to maintain their ecological function or benefit from their economic potential.

Ecologist Alexandre Fadigas de Souza, a native of Rio de Janeiro who is currently working at the University of Vale do Rio dos Sinos (Unisinos) in the city of São Leopoldo, state of Rio Grande do Sul, has dedicated five years to the study of the development cycle of these trees and to strategies to regenerate the araucaria. During this relatively short time, he noticed that this majestic tree, the trunk of which can reach a diameter of as much as two meters and provides high-quality wood, whose curved branches rise up to 40 or 50 meters above the ground and over other trees in the forest, plays an important role in the preservation of native vegetation.

Souza regularly visited 26 patches of preserved vegetation and natural forests in the state of Rio Grande do Sul; where the trees had been cut down for timber in varying numbers.

He collected information on the number and size of the araucárias (seedlings, young trees, and adult trees) and on the characteristics of the places where the trees grew in the forests. He added this data to the data collected by the team of forest engineer Solon Jonas Longhi, from the Federal University of Santa Maria, who spent the last ten years keeping track of the growth and mortality rates of the araucárias in the São Francisco de Paula National Forest. When comparing data on the araucárias with that of other trees, Souza concluded that the Brazilian pine was indeed a peculiar species.

Long life
The araucaria is what ecologists refer to as a pioneer species. It is a fast-growing tree and is one of the first plants to populate open spaces such as clearings or abandoned fields, where light is abundant. However, it is not merely any ordinary pioneer. It reaches maturity at a later stage and starts to produce seeds only after 15 years. In addition, most of the other pioneering species die a few decades after maturity, whereas the araucaria lasts for an average of 400 years – some reaching as long as 700 years. During all this time, it creates a favorable environment around it for the growth of more fragile, slow-growing species that form the forest’s second generation of trees. In an article published in Austral Ecology in 2007, Souza describes the araucaria as one of the rarest long-living pioneer trees in Brazilian forests.

During his strolls through forests, Souza discovered that once a forest is formed, it is difficult for the araucaria to produce new adult individuals. He only found samples of young araucárias in open fields and in areas of the forest where the treetops did not entirely block the view of the sky and there was a lot of light, as he wrote in an article published in Acta Oecologica in 2008. There are two reasons for this: first, the young araucárias survive for a very short time in the shade; and second, the pine-shaped seeds, with a diameter of up to 30 centimeters that the tree produces from April to September, are eaten by such native birds as the gralha-azul (azure jay) and by the papagaio-charão (red-spectacled Amazon parrot), and by the common agouti, deer, and collared peccary. “Only 1 percent of the seeds that fall on the ground germinate,” says Souza, who this year was awarded the Fundação Bunge award in the forest sciences category.

Whatever seeds are left over from the animals’ forays become part of the local population’s diet. The seeds, which are carbohydrate- and protein-rich, referred to as pinhão, are used in many dishes typical of the cuisine in the south of Brazil. In 2008, 4.8 thousand tons of pinhão were extracted from the native forests, generating income of R$6.2 million, according to data of the Brazilian Institute of Geography and Statistics. Souza, who analyzed of pinhão sales for the 1977 to 2007 period in the state of Rio Grande do Sul and for the last 14 years on a farm in the state of Santa Catarina, noticed that the production of araucaria seeds does not fluctuate as that of the conifer trees – trees that produce bare seeds grouped in cones – of the Northern Hemisphere. In the Northern Hemisphere, a pine tree does not necessarily produce an abundant harvest of seeds every year. In Brazil, the production of these seeds is more stable. “Production increases somewhat in the year that follows a year when the El Niño phenomenon occurred, as this phenomenon causes heavy rains in the south, while production drops after the droughts provoked by the La Niña phenomenon,” he explains.

The sale of pinhão can be more profitable than the exploitation of araucaria or pinus wood, say Miguel Guerra and his collaborators, who wrote a paper on the exploitation and stewardship of araucárias. The article was published in 2003 in the book Sustentável Mata Atlântica [Sustainable Atlantic Seaboard Forest]. However, it will be necessary to replant forests for economic exploitation to become sustainable. Souza verified that, more than 60 years after the end of the exploitation of the araucaria forests, the original araucaria population had still not recovered entirely.

Scientific article
SOUZA, A. F. et al. Regeneration patterns of a long-lived dominant conifer and the effects of logging in southern South AmericaActa Oecologica. v. 34, p. 221-32. Sep./Oct. 2008.

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