Alterations Following a Fire in a Forest Community of Alto Rio Xingu
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Forest Ecology and Management 184 (2003) 239–250 Alterations following a fire in a forest community of Alto Rio Xingu Nata´lia Macedo Ivanauskasa,*, Reinaldo Monteirob, Ricardo Ribeiro Rodriguesc aDepartamento de Biologia, Universidade do Estado de Mato Grosso, Caixa Postal 08, 78.690-000, Nova Xavantina-MT, Brazil bDepartamento de Botaˆnica, Instituto de Biocieˆncias, Universidade Estadual Paulista, 13506-900 Rio Claro, SP, Brazil cDepartamento de Cieˆncias Biolo´gicas, Escola Superior de Agricultura ‘‘Luiz de Queiroz’’, 13418-900 Piracicaba, SP, Brazil Received 5 August 2002; received in revised form 28 September 2002; accepted 1 April 2003 Abstract This study records the consequences of fire upon the soil and structure of the Amazonian Forest of Gau´cha do Norte, Mato Grosso state, Brazil (138120S and 538200W). For this, the number of individuals sampled in 1 ha of the forest, during a phytosociological survey completed 2 days before the accidental fire, was compared with the survivors recorded afterwards in the reinventory of the area taken 2 days and 10 months after the fire. For the surveys, the area of 1 ha was subdivided into 50 plots of 10 m  20 m, and all the individuals with circumference at breast height ðCBHÞ15 cm were sampled. Chemical analysis of the 30 soil samples collected 2 days before the fire were compared with those obtained 15 days and 1 year after the fire. It was seen that, soon after the fire, there was a significant increase in the nutrient levels in the soil, an increase in the pH and a decrease in the aluminum toxicity. However, after 1 year, losses by lixiviation resulted in a nutrient reserve in the soil of less than that before the fire. The tree mortality was extremely high (23.98%), particularly amongst the younger individuals of the population (93.68% of the total of deaths in the period). There was no significant reduction in the forest richness analyzed: 60% of the species had reduced populations after the fire, but just four species were locally extinct. Results, however, demonstrated a role for fire in the selection of resistant species or those adapted to fires, since some species demonstrated a greater tolerance to the fire than others. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Amazonia; Tropical evergreen forest; Forest vegetation; Forest soil; Fire effect 1. Introduction during the last 6000 years, at a time in which the climate was drier and the vegetation was sclero- Fire has been influencing the structure and compo- morphic (Uhl and Kauffman, 1990; Holdsworth and sition of Amazonian forests for thousands of years. In Uhl, 1998). Nowadays, the microclimate and the high the northeast of the Amazon basin, the presence of rainfall create non-inflammable conditions, making charcoal in the soil indicates the occurrence of fire fires—in the majority of non-perturbed rain forests with high and closed canopies—virtually impossible * Corresponding author. Present address: R. Heitor Bariani, 511 (Pires and Koury, 1958; Uhl and Kauffman, 1990). Tatuape´, 03080-020 Sa˜o Paulo, SP, Brazil. Tel.: þ55-11-295-6872. In contrast with scrub land, the evergreen forest E-mail address: [email protected] (N.M. Ivanauskas). demonstrates few evolutionary adaptations for fire 0378-1127/$ – see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0378-1127(03)00156-7 240 N.M. Ivanauskas et al. / Forest Ecology and Management 184 (2003) 239–250 survival. The extremely low capacity of the primary forests were substituted with pasture, the volume of forest to survive even low intensity fires suggests that vapor emitted into the atmosphere would be severely the occurrence of fire is extremely rare in this eco- reduced, since pastures present an evapotranspiration system (Kauffman and Uhl, 1990). Thus, frequent fires of 15% below that of the forests (Jipp et al., 1998). may cause the extinction of the current vegetation or The cool temperature and the high humidity make the conversion of the remaining tropical forest into the majority of non-perturbed rain forests non-inflam- sclerophilic rain forest (Melick and Ashton, 1991). mable, since they make difficult the drying of com- The tropical rain forest is being radically trans- bustible mass (litter layer) that does not reach the formed as a result of human activity, creating a mosaic ignition point (Uhl et al., 1990). Unfortunately, the of exploited forests, cultured fields and secondary Amazon forests are losing their capacity to act as great forests (Uhl and Kauffman, 1990). In the substitution ‘‘fire breakers’’ along the country side (Nepstad et al., or management of forest areas, fire is used as a cultural 1994), one of the most important ecological services and traditional agricultural tool by a large variety of of the forest, making megafire phenomena more and ethnic groups (Goldammer, 1988). more probable. The increase in rural occupation has resulted in an Under a drier climate, therefore, the factor which alarming rise in fire pressure upon the remaining most threatens the biodiversity of the Amazon, in the forests (Goldammer, 1988), accelerating the processes near future, seems to be fire. This threat may be greater of degradation and transforming non-inflammable in the eastern region of the Amazon, where the forests tropical forests into inflammable secondary commu- suffer seasonal droughts, and at the frontiers of Ama- nities. Exploited ecosystems represent a new and zonian occupation, established principally by the use of unique environment for fire in the Amazon; the com- fire for deforestment (Moutinho and Nepstad, 1999). bustible mass is high, the modification of the micro- Thus, the permanence of the forests of the eastern climate promotes rapid drying of this combustible Amazon represents a guarantee of preservation, not mass and anthropogenic ignitions are common (Uhl only of the climate and biodiversity, but also of the and Kauffman, 1990). productive activity and the quality of life of the local Undoubtedly, the frequency and wide spread use of populations (Moutinho and Nepstad, 1999). The for- fire in the Amazon is dramatically altering the succes- ests which undergo seasonal drought, which cover a sional patterns, the structure and the composition of third of the Amazonian area, should therefore be the forest (Kauffman and Uhl, 1990). If the use of fire prioritized by conservation plans. is not controlled, such as rigid control and adequate As a recurring perturbation, fire has an unparalleled legislation, the fires will tend to increase in size, potential to deplete and alter the forests of the eastern becoming more dangerous. This fire regime may Amazon region (Cochrane and Schulze, 1999). From irreversibly change the basic characteristics of the this point of view, forecasts of the responses of forests Amazon forest (Uhl et al., 1990). to the increase in environmental degradation become Inside the Amazon forest, half the rain which falls more and more relevant. The understanding of how upon the forest is generated by the forest itself. In a natural communities regenerate following perturba- paradoxical manner, a large part of the vapor emitted tional, anthropical or natural actions and information to the atmosphere by the forest comes from the regions to determine which species will resist and, maybe which undergo seasonal droughts, principally in the more importantly, which organisms will be lost are east and south of the Amazon, the forests undergo 3–5 therefore of absolute necessity (Kauffman, 1991; months of severe drought during which the quantity of Castellani and Stubblebine, 1993). rain fall is much lower than the quantity of water This study presents comparative data of the soil, of emitted by the forest into the atmosphere via evapo- the structure and the floristic composition of a stretch transpiration (Gash, 1996). This phenomenon is made of forest in the eastern Amazon region, subject to possible by the fact that the forests have a system of seasonal drought, before and after it was affected by an roots capable of absorbing water at depths of more accidental fire of low intensity. The objective of this than 10 m during the annual dry seasons (Nepstad investigation is to analyze the impact of fire upon this et al., 1994; Moutinho and Nepstad, 1999). If these community. N.M. Ivanauskas et al. / Forest Ecology and Management 184 (2003) 239–250 241 Fig. 1. Location of Gau´cha do Norte, state of Mato Grosso, Brazil. 2. Methods and the neighboring municipalities of Paranatinga (with access via the MT-020) and Canarana and Nova 2.1. Study area Ubirata˜ (via the BR-242). With the growth of the municipality and the build- The municipality of Gau´cha do Norte (Fig. 1) ing of highways, the cutting and burning of forests has occupies an area of 16958.69 km2 and houses a popu- increased at an alarming rate. In turn, fires have lation of 3277 inhabitants, part of the population being become more frequent and, during the dry period of indigenous and the remainder being migrants from the 1999, extensive areas of forest were burnt. south of the Brazil, the latter arriving by way of The regional climate is Aw type by the Ko¨eppen businesses colonizing the region during the last 20 classification (Ometto, 1981). The mean annual tem- years. perature is 26 8C and the average annual rainfall is The northern region of the municipality is part of an 1508 mm; there is a dry season from May to October. indigenous area of the Xingu Indigenous Park (Parque The study was carried out on a stretch of evergreen Ind´ıgena do Xingu) and the local forest can be found in seasonal forest which lies on oxisol on the private a well-preserved state. The southern region, in con- property of Lauri Stoffel (138120S and 538200W).