Successional development of cambará (Vochysia divergens
Pohl)-dominated forest stands
in the Northern Pantanal, Brazil.
J.F. Gottgens - Biology Department, The University of Toledo, Toledo, Ohio
43606
Introduction
In spite of the ecological significance of the Pantanal wetland, we know very little about its ecology. At the landscape level, threats to the structure and composition of the plant communities include high-density cattle grazing, excessive use of fires, drainage practices, use of agri-chemicals on higher elevations, and unexplained invasions of native plant communities by fast-growing pioneer species. These threats are of great concern to conservation organizations, but science-based management and conservation are severely limited by a lack of management-focused research. This summer’s project focused on the spread of an invasive tree species (cambará, Vochysia divergens Pohl, Vochysiaceae) and its impact over time on the structure and composition of the existing woody plant community. Factors promoting the spread and persistence of this species are unknown, although these invasions may be a landscape signal to large-scale changes in the region's environmental conditions.
Cambará, a species of Amazonian origin (Pott and Pott 1994), is characteristic of seasonally inundated areas (Prance and Schaller 1982). It occurs in gallery forests, forest patches, and river floodplains, where it forms dense, monotypic forests, or "cambarazal" (Loureiro et al. 1982). It is most common in areas influenced by drainage of the São Lourenço and Cuiaba rivers and on the terraces along the Cuiaba and Itiquira rivers (Loureiro et al. 1982; Nascimento and Cunha 1989). This fast-growing tree is considered the most aggressive invading species of native grasslands in areas south of Poconé and parts of the Paraguay floodplain (Pott and Pott 1994). As a pioneer, this tree will not grow in its own shade and advances rapidly over adjacent grassland (Pott and Pott 1994). Consequently, ranchers have complained about cambará invasions of pastures. More recently, invasions by cambará of areas as different as native grasslands or gallery forests have been confirmed by regional experts (Pott, CPAP-EMBRAPA; Eberhard, Ecotropica; Damasceno, UFMS). Its expansion, however, has been observed, but not quantified. Cambará can reproduce vegetatively or have its seed transported by wind or water. In spite of its tolerance for seasonal flooding, cambará does not seem to tolerate long periods of inundation or drought (Nascimento and José 1986).
Unfortunately, little information exists on the processes that drive these changes in natural plant communities of the Pantanal. The presence of cambará may be linked to biotic factors (e.g., inter-specific competition) or abiotic factors, such as certain flooding regimes, soil characteristics (Nascimento and José 1986), or fire frequency. Cambará has a high aluminum content in its leaves and has been mentioned as an aluminum accumulating tree (Nascimento and José 1986). Allem and Valls (1987) mention the species’ preference for disturbed areas. Higher flood intensity may favor the species’ expansion by reducing fire activity (Pott, pers. comm). Cambará is sensitive to fire in the young growth stages (up to 2 m), but becomes more fire tolerant as adult when protected by a thicker bark. Cambarazal also shade understory grasses and reduce fuel accumulation (Pott, pers. comm). The tree has short life cycle of approximately 30-40 years, although Dr. Iria H. Ishii (pers. comm.) found a 94-year old tree by dating annual growth rings. In successional seres, cambará initially eliminates herbaceous species, greatly altering plant diversity. Tree diversity is low in the cambará-dominated patches although the nutrient levels in soils in these cambarazal are adequate for the establishment of other species. Later, when the population is mature, shrubs and lianas become established. These are usually zoochorous forest species, including Alchornea, Doliocarpus, Fagara, Odontocarya, and Smilax spp.
Objectives
Our main goal was to quantify changes in the woody plant community structure and composition and measure selected environmental conditions during successional development of a cambarazal. We will then use this information to construct a model of woody plant succession and concurrent environmental change in these communities. Such a model is of theoretical significance because it provides basic ecological information about successional processes in very poorly-known plant communities, including a description of rare or even undocumented species. It is also of applied significance, because it provides resource managers with options to alter successional development of cambará-dominated systems and reduce the spread and impact of this aggressive species. In addition, we wanted to establish a number of permanent study sites for use in future student projects designed to evaluate changes in the plant community over time and to experiment with techniques to control the spread of this species.
Methods
Site description:
This project was carried out at the Fazenda Ipiranga, a traditional cattle ranch of approximately 7,500 ha, located in the northern portion of the Pantanal (in the region of 16º 22’ S/56º34’ W), approximately 17 km south of the town of Pocone. The property is a mosaic of grazed pasture, forests, streams, rivers, and a permanent lake. Water levels on the site fluctuate several meters between the dry southern-hemisphere winter and the wet summer. The Fazenda was particularly suited for this project because it contains areas with cambará-dominated forest patches of different stand-age that have shown an increase in size over the last decade. Additionally, this ranch is one of the main field sites for research projects carried out by the SHIFT Program (Studies on Human Impact on Forests and Floodplains in the Tropics), a German/ Brazilian cooperative research program. Therefore, important baseline data for the site are available, including summaries in workshop proceedings (SHIFT 1995). For instance, Plá and da Silva (1995) inventoried landscape units in the Fazenda Ipiranga using Landsat TM satellite imagery coupled with field checks and produced a thematic map for the site. I have used this ranch for a variety of student projects since 1995. Over the years, I have established a research cooperation with the ranch owner, Mr. João Lozano Eubank de Campos, who has an interest in the development of research efforts on his land. We also collaborate with the Brazilian coordinator for the SHIFT program, Dr. Carolina Joana da Silva, Federal University of Mato Grosso.
Field methods:
Field work was carried out during July and August, 1999 (dry season) and will be continued during the wet season (February and March, 2000). In order to quantify the impact of cambará on the existing woody plant community, we focused on the successional development of cambarazal (Vochysia divergens-dominated forest patches). Data collection methods for the woody vegetation followed the techniques of direct gradient analysis as described by Gauch (1982). As such, we established eight permanently marked 20 x 50 m quadrats (0.1 ha) in four different stand ages of cambará (one replicate for each stand age). The center point for the quadrats was randomly located within clearly defined successional stands, and situated so that the quadrat did not include transitional community boundaries. All trees (>10 cm dbh) and small trees (2.5<dbh<10 cm) were inventoried by species in each quadrat. Saplings (>1 m tall and <2.5 cm dbh) and woody vegetation in the shrub layer (including true shrubs, vines, lianas, and small trees <1 m tall) were counted by species in four 5 x 5 m plots placed at regular intervals along a 50 m tape used to establish the center line of the 0.1 ha quadrat. Estimates of percent cover of herbaceous plants, exposed soil, wood debris, and litter were recorded from ten 1x1 m plots placed at 5 m intervals along the same tape. All cover values were estimated using a cover-class rating scale described by Daubenmire (1968). Voucher specimens for all woody plant species occurring in our study areas were collected and species identifications were made with the use of taxonomic keys of the region and with the assistance of experts at the herbarium in Corumba (Embrapa) and in Cuiaba (Universidade Federal de Mato Grosso).
To estimate the age of the stand, we cored four of the largest cambará trees in each quadrat (two cores per tree) using increment growth cores at breast height. In addition, following the advice of a regional expert (Dr. Iria H. Ishii, pers. comm.), a tree in the direct vicinity of the quadrat was cored, felled, and a sample-section was taken to compare the age record in the cores with the tree section. Cored trees were also measured for canopy height, height to first limb, and crown diameter. Canopy cover was estimated using a spherical crown densiometer at vegetation sampling points along the transects. Composite soil samples were collected from the upper 10 cm and the 10-20 cm interval in each quadrat for the measurement of soil compaction, organic matter content, pH, trace metal concentration, and particle size distribution. In addition, we measured groundwater levels weekly during the sampling period at each quadrat using PVC-pipe wells (5 cm diameter). These measurements will continue on a monthly basis by assistants at our field station using the same PVC wells or a water level gage during the rainy season. Because cambará is said to be able to concentrate aluminum from its environment, we collected leaves (of various ages) and bark from cambará and five other species in our quadrats to measure Al content. The ability to concentrate Al may give cambará a competitive advantage (e.g., protection from grazing) allowing it to outcompete other species.
What is next?
Laboratory work and data analysis associated with this summer’s project will be carried out during the fall 1999 semester. Field work will be continued during the wet season in early 2000. At that time, we will focus on finalizing the taxonomic inventory of the quadrats and identifying remaining unknown woody species that bloom during flooded conditions. In addition, environmental conditions in the quadrats will be monitored, including water level, canopy cover, and the pH, organic matter content, compaction, and trace metal content of the soil.In addition, we will couple a geographical analysis to our field investigations. Maps of the past and present patterns of distribution of cambará will be generated from remote-sensed images and from existing digital maps for the study site (Plá and da Silva 1995). We may use U.S. Air Force photography (1960s), declassified U2 images, SPOT images (since 1986), LANDSAT-5 images (mid-1990s), and images from the recently launched LANDSAT-7 satellite. Image processing (using ERDAS-Imagine software; ERDAS Inc.) will include enhancement, rectification, and classification procedures (DeMers 1997). The potential signal enhancement from the abundant yellow flowers of this tree species, peaking from July through September, will be utilized. Further, ground truthing and establishment of control points during fieldwork will be used to check specific imagery signals for the cambará and verify any discrepancies in vegetation location. The spatial data will be rectified to the Universal Transverse Mercator (UTM) coordinate system to establish a correspondence between new sampling with historical sampling. This is particularly important when comparing the pattern and extent of plant communities over time (DeMers 1996). Maps generated from the remote-sensed imagery in similar studies in the region were rectified with this same procedure (Cunha and Almeida 1995). Processed images will be analyzed with ARC/INFO 7.0 (Environmental Systems Research Institute) at the Department of Geography and Planning of the University of Toledo to detect the distribution of cambará over time. Spatial data of appropriate scale for environmental parameters of relevance for this study (geomorphology, topography, soil type, land-use, hydrology and flooding frequency) will be entered in the ARC-INFO data-base by digitizing images or by using existing digital information (Brasil 1997). Images will be orthometrically-corrected and geo-referenced according to the control points established in the field. Distribution maps of cambará will then be superimposed on the spatial data for the environmental parameters to determine which environmental factors statistically correlate best with the occurrence and spread of the cambará. The overall goal is to quantify the pattern and extent of the expansion of cambará in selected sites of the Fazenda Ipiranga, in the Northern portion of the Pantanal.
References cited
Allem, A.C. and J.F.M. Valls. 1987. Recursos Forrageiros Nativos do Pantanal Mato-Grossense. Brasilia, CENARGEM/EMBRAPA-CPAP, Documento 8: 339 pp.
BRASIL. Ministério do Meio Ambiente, dos Recursos Hídricos e da Amazônia Legal. 1997. Plano de Conservação da Bacia do Alto Paraguay-PCBAP. Brasilia. Vol. I, 72 pp.
Cunha, C. N. and N.N. Almeida. 1995. The Savannas and Forests of the Pantanal of Poconé, MT. I-Northeast Region. Summaries of lectures and posters presented at the II SHIFT- Workshop, Cuiabá 1995. UFMT.
Daubenmire, R. 1968. Plant communities: a textbook of plant synecology. Harper and Row, Publisher, New York.
De Mers, M. N. 1996. Remote Sensing and Geographic Information Systems: Spatial Technologies for Preserving Phytodiversity. In: Sampling the Green World. Innovative Concepts of Collection, Preservation, and Storage of Plant Diversity. T. F. Stuessy and S. H. Sohmer (eds.). New York: Columbia University Press: 289 pp.
De Mers, M. N. 1997. Fundamentals of Geographic Information Systems. John Wiley & Sons, Inc. 486 pp.
Gauch, H. G., Jr. 1982. Multivariate analysis in community ecology. Cambridge University Press, New York.
Loureiro, R. L., Lima, J. P. & Fonzar, B. C. 1982. Vegetação. Estudo Fitogeográfico. Levantamento de Recursos Naturais. Folha SE-21 e parte da Folha SE-20. In: Brasil, Ministério das Minas e Energia, Projeto RadamBrasil. Rio de Janeiro. Vol 27: 333-360
Nascimento, M.T. and D.V. José. 1986. O cambarazal no Pantanal de Mato Grosso. Bol. da FBCN 21: 116-123.
Nascimento, M.T. and C.N. Cunha. 1989. Estrutura e composição florística de um cambarazal no Pantanal de Poconé, MT. Acta Bot. Bras. 3: 3-23.
Plá, V. L. M. and C.J. da Silva. 1995. Lanscape Identification in the Ipiranga farm and surroundings, Pantanal of Poconé, Mato Grosso. Summaries of lectures and posters presented at the II SHIFT- Workshop, Cuiabá 1995. UFMT.
Pott, A. and V.J. Pott. 1994. Plantas do Pantanal. Brasília, EMBRAPA: 320 pp.
Prance, G.T. and G.B. Schaller. 1982. Preliminary study of some vegetation types of the Pantanal, Mato Grosso, Brazil. Brittonia, 34(2): 228-251.
SHIFT. 1995. Summaries of lectures and posters presented at the II SHIFT-Workshop, Cuiabá, July 10-14, 1995, Univ. Fed. Mato Grosso.
Dissemination of Results and Use of Project Outcome in UT Courses
As in the past, I would be happy to share my experiences and the results of this project (and other work I am doing with my students in Brazil) with the campus community. I will continue to incorporate tropical ecology in my courses in Human Ecology (BIO 1130), Aquatic Ecology (BIO 4630/5630/7630), and Current Topics in Community Ecology (BIO 6610/8610) at the University of Toledo. In addition, I will continue to give presentations in related courses taught by colleagues at UT (see below). Results of this project will also be published in scientific papers and presented at conferences and meetings of community organizations. Our recent paper, submitted to BioScience, will be translated into Portuguese and submitted for publication in Brazil. Examples of articles and presentation that appeared recently (or are still "in press"):
Scientific Publications:
Gottgens, J.F., R.H. Fortney, J. Meyer, J.E. Perry, and B.E. Rood. Impacts of the Paraguay-Paraná Hidrovia on the Pantanal of Brazil: Large-scale channelization or a "tyranny of small decisions?" BioScience (accepted)
Gottgens, J.F., R.H. Fortney, J. Meyer, J.E. Perry, and B.E. Rood. 1998. The Paraguay-Paraná waterway ("Hidrovia") and its impact on the Pantanal of Brazil. Bulletin Society Wetland Scientists 15(3): 12-18.
General Publications:
Gottgens, J.F. 1998. Mercury accumulation trends in the Brazilian Pantanal: Core studies and biological samples. Report to the Kohler Foundation and the Center for International Studies and Programs, University of Toledo, Ohio
http://www.geology.utoledo.edu/research/latin-am/LAS%20projects/HG.htm
Gottgens, J.F. 1998. Beyond the test tube: Toledo biologists at work in the Brazilian Pantanal. UT-SciMaTec newsletter.
Nowak, C.J.. Getting their feet wet - but never in over their heads - for science. Article about my research in Brazil for the University of Toledo Alumni magazine (May 1999 issue).
Presentations at Scientific Meetings:
Simmers, B.S., J.F. Gottgens, and C.A. Fernandes. 1997. Mercury accumulation trends in the Northern Pantanal: Core studies and biological samples. 18th Annual Society of Wetland Scientists Conference, Bozeman, Montana.
From science to policy - Society of Wetlands Scientists International Symposium (invited panelist) (1998).
Benedict, M., R.H. Fortney, T.L. Walters, J.F. Gottgens, and B.S. Simmers. 1999. Aquatic plant community composition and distribution along inundation gradients at two ecologically distinct sites in the Pantanal region of Brazil. 20th Annual Society of Wetland Scientists Conference, Norfolk, Virginia.
Simmers, B.S. and J.F. Gottgens. 1999. Mercury accumulation trends from two sites in the Brazilian Pantanal: Core studies and biological samples. 20th Annual Society of Wetland Scientists Conference, Norfolk, Virginia
Presentations to University of Toledo courses or Community Organizations:
Environmental threats to the Brazilian Pantanal, the world’s largest continuous wetland. The Audubon Society of Greater Cleveland, Cleveland Natural Museum of History (1998).
Wetlands research at the University of Toledo. University of Toledo Board of Trustees meeting, Toledo, Ohio (1998).
Environmental threats to the Brazilian Pantanal, the world’s largest continuous wetland. BIOL-2910, Biological Research (1998)
Impacts of the Paraguay-Paraná Hidrovia on the Pantanal of Brazil: Large-scale channelization or a "tyranny of small decisions?" Environmental Law Seminar (Dr. Sandi Zellmer, UT College of Law) (1999).
Impacts of the Paraguay-Paraná Hidrovia on the Pantanal of Brazil: Large-scale channelization or a "tyranny of small decisions?" ENVS-3980, International Environmental Issues, University of Toledo (1999).