Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1989 The grasses of Chiquitanía, Santa Cruz, Bolivia Timothy J. Killeen Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Botany Commons Recommended Citation Killeen, Timothy J., "The grasses of Chiquitanía, Santa Cruz, Bolivia " (1989). Retrospective Theses and Dissertations. 9060. https://lib.dr.iastate.edu/rtd/9060 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS The most advanced technology has been used to photo­ graph and reproduce this manuscript from the microfilm master. 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Killeen A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Department: Botany Major: Taxonomy Approved: Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. For the Major Department Signature was redacted for privacy. For the Graduate College Iowa State University Ames, Iowa 1989 ii TABLE OF CONTENTS INTRODUCTION 1 KEY TO GENERA 8 ENUMERATION OF GENERA AND SPECIES 23 LITERATURE CITED 142 ACKNOWLEDGEMENTS 144 1 INTRODUCTION Chiquitania is a region in eastern lowland Bolivia which includes the Provinces of Nuflo de Chavez, Velasco, and Chiquitos in the Department of Santa Cruz. Recognized as a disinct cultural and geographic region, it also has a unique natural history when compared to other parts of eastern Bolivia. Situated on the extreme western edge of the Brazilian (Precambrian) Shield it is characterized by a variable topography (altitude 300-1200 m) that supports a high diversity of forest, savanna, and savanna wetland communities. Chiquitania is bordered on the south by the Serrania de Santiago and the Serrania de Chiquitos (18°10'S), to the west by the alluvial plains of central Santa Cruz (62°40'W), to the East by the Brazilian border, and to the north by the Department of the Beni. Although it was Colonized over 250 years ago by Jesuit missionaries, the vegetation of the region remains largely unaltered as the local inhabitants have utilized the native savanna for cattle production while exploiting the forest for timber, rubber, or wildlife. Shifting agriculture, while common, does not currently pose a threat to the existing forest vegetation. However, the recent introduction of exotic forage grasses adapted to forest soils threatens to disrupt traditional patterns of agriculture. Due to increased productivity and better nutritional quality, these grasses allow for higher stocking rates and the easier management of cattle. Consequently, forest destruction for pasture establishment is occurring at accelerated levels. It is hoped that a better understanding of the native grasses will promote range management techniques which improve the productivity of savanna vegetation, while at the same time helping to preserve some natural communities. This checklist is the partial result of three years of work in the region studying the autecology of the native grasses. Analytic results of the autecological investigations, as well as general descriptions of the vegetation will be reported in future publications. Climate The region has a typical savanna climate or "Aw" in the Koppen classification. The regional airport at Concepcion (16°03'S; 62°10'W; altitude 500 m), has meteorological data spanning 35 years (Guaman ands Valverde 1982). Mean annual precipitation is about 1200 mm with a marked dry season of 5 months during 2 the austral winter. Annual fluctuations vary greatly, ranging from 700 mm to 1500 mm. Mean daily temperature varies only slightly throughout the year, reaching a maximum in November (26°C) and a minimum for the month of June (21°C). Nonetheless, strong cold fronts sweep through the region during the dry season, causing the temperature to drop to 10°C for short periods; while maximum temperatures of about 33°C are common in November at the beginning of the rainy season. Vegetation The vegetation in Chiquitania is similar to that described for the adjacent regions of central Brazil and although Bolivians have developed their own vernacular terms for describing the vegetation in Chiquitania, I use the standard terminology developed by Brazilian ecologists (Eiten 1972, 1978, Ratter et al. 1988). Cerrado refers to a complex of intergrading communities which range from low forest to open grassland which are characterized by the presence of tortuous, woody species with thick stems and coriaceous leaves. Cerrado is the most common savanna vegetation in Chiquitania and is usually restricted to dissected plains or the upper slopes of low hills (500-700 m). Easily recognized due its distinctive physiognomy, these well drained savanna communities are western disjuncts separated from the cerrado province of central Brazil by the more abundant, seasonal forest vegetation. The Bolivians refer to this vegetation as "pampa arbolada" or "arboiada". Floristically and structurally distinct from cerrado is a xerophytic savanna complex known as camoo rupestre. This treeless savanna occurs as islands restricted to ridge tops 800 to 1200 meters above sea level (Eiten 1978). There are a number of campo rupestre localities in eastern Santa Cruz, of which the western escarpment of the Serrania de Caparuch (i.e., Parque Nacional "Prof. Noel Kempff Mercado") is probably the most extensive. The Serrania de San Lorenzo, situated near the town of San Javier, is only 40 km from the western edge of the Brazilian Shield (16°15'S; 62°40'W; altitude 900 m) and is one of the most western campo rupestre localities in South American. This site has yielded two new grass species (and several unique intraspecific forms); undoubtedly, more taxa will be described as the flora of this serrania is documented. The locals refer to this vegetation type as "campo" or "pampa", distinguishing it from cerrado (pampa arbolada) by the lack of woody vegetation. 3 Similarly, the wetland communities common to central Brazil occur throughout Chiquitania. Valley side camoos are treeless savannas which occur along erosional surfaces, wherever there is a fluctuating, perched, water table, which seeps out on gently sloping valley sides (Eiten 1978; Goldsmith 1974). The overflow of rivers on alluvial plains leads to the formation of a pantanal complex of seasonally humid or seasonally inundated savannas (Cole 1986; Eiten 1978). Scattered across these open grasslands are raised earth platforms built up by the action of termites which support cerrado species or low forest. At the base of valley side campos and scattered across the pantanal complexes one finds savanna marsh, a savanna wetland community which retains saturated soils throughout the year. Beck (1984) reports on similar extensive savanna wetlands in the Department of Beni. The residents of Chiquitania generally refer to all savanna wetlands as "curiches". Ruiz (1982) conducted a preliminary inventory of the seasonal forest communities near Concepciôn in the Province of Nuflo de Chavez. The forest types described in his study are semi-deciduous and the density of the understory is inversely correlated with the development of the canopy. High forest was classified as having canopy trees 20-25 meters tall one end of a continuum of forest or forest scrub communities eventually intergrades with cerrado. In contrast, gallery forest is an evergreen community with trees 25-40 m tall, which occupies a narrow strip 50 to 100 m wide on valley floors. Locally, the various gradations of forest are recognized and referred to as "monte alto", "monte bajo", and "monte humedo". In addition, granitic outcrops, locally known as "lajas", exist as islands within cerrado, campo rupestre, savanna wetlands, and seasonal forest. These range in size from small outcrops scattered across the landscape to large domes (inselbergs) which can attain a height of 200 meters and diameter of 400 meters or more. Floristic Relationships of the Grasses of Chiquitania This is the first relatively complete inventory of native grasses from a region in the center of the South American continent.