Effects of local ecological knowledge, harvest and fire on golden-grass (Syngonanthus nitens, Eriocaulaceae), a non-timber forest product (NTFP) species from the Brazilian savanna.

摘要

The use of fire as a management tool and the harvest of plant parts, known as non-timber forest products, are traditional human activities that impact plant individuals, populations, plant communities and ecosystems. This dissertation focuses on the ecological consequences of harvest and management of golden-grass (Syngonanthus nitens, Eriocaulaceae). Golden-grass flower stalks are harvested to produce handicrafts which represent the most important source of income to hundreds of families in the Cerrado, in central Brazil. I applied an ethnoecological framework to: (i) characterize the local ecological knowledge related to golden-grass harvest and management in Jalapao region, Tocantins state, as well as in regions in Tocantins state to which the handicraft activities have expanded recently; (ii) experimentally test the effects of 'late' harvest, i.e., according to the traditional management practices, and 'early' harvest on golden-grass long-term population growth rates; (iii) experimentally test the effects of fire frequency and fire season on golden-grass populations, since fire is commonly applied in golden-grass management; and (iv) characterize fire behavior and intensity in the wet grasslands where golden-grass occurs. Ecological knowledge, specifically in relation to the timing of harvest is a determining factor for sustainability: harvesting 'late' has no negative effect on golden-grass populations, whereas 'early' harvest leads to accentuated population declines. As stated by experienced harvesters, golden-grass flower production is stimulated one year after fire. Biennial fire regimes, as preferred by experienced harvesters, yields higher long-term population growth rates (lambda) compared to more frequent and sparser fire return intervals. Golden-grass populations were highly affected by variations in rainfall. Survival rates were significantly lower during dry years compared to rainy years, and this caused lambda to decline significantly during dry years. Fires in wet grasslands are less intense and achieve relatively mild temperatures compared to fires in dry physiognomies, both within the Cerrado and in other tropical savannas. This dissertation has direct application to the management of golden-grass and fire in the Cerrado and also contributes to the NTFP and fire literature. Golden-grass harvesting has high potential for supporting conservation of biodiversity and local livelihoods. The sustainability of this activity is directly related to the timing of harvesting.