Layout 2 - Tropenstation La Gamba

Natural and Cultural
History of the Golfo
Dulce Region, Costa Rica
Historia natural y cultural de la
región del Golfo Dulce, Costa Rica
Anton WEISSENHOFER, Werner HUBER, Veronika MAYER, Susanne PAMPERL,
Anton WEBER, Gerhard AUBRECHT (scientific editors)
Impressum
Katalog / Publication:
Stapfia 88, zugleich Kataloge der Oberösterreichischen Landesmuseen N.S. 80
ISSN:
0252-192X
ISBN:
978-3-85474-195-4
Erscheinungsdatum / Date of delivery:
Medieninhaber und Herausgeber / Copyright:
Direktion:
Leitung Biologiezentrum:
Url:
E-Mail:
9. Oktober 2008
Land Oberösterreich, Oberösterreichische Landesmuseen, Museumstr.14, A-4020 Linz
Mag. Dr. Peter Assmann
Dr. Gerhard Aubrecht
http://www.biologiezentrum.at
[email protected]
In Kooperation mit dem Verein zur Förderung der Tropenstation La Gamba (www.lagamba.at).
Wissenschaftliche Redaktion / Scientific editors: Anton Weissenhofer, Werner Huber, Veronika Mayer, Susanne Pamperl, Anton Weber, Gerhard Aubrecht
Redaktionsassistent / Assistant editor:
Fritz Gusenleitner
Layout, Druckorganisation /
Layout, printing organisation:
Druck / Printing:
Bestellung / Ordering:
Eva Rührnößl
Plöchl-Druck, Werndlstraße 2, 4240 Freistadt, Austria
http://www.biologiezentrum.at/biophp/de/stapfia.php oder / or [email protected]
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Umschlagfoto / Cover:
Blattschneiderameisen. Photo: Alexander Schneider. Layout: E. Rührnößl.
Zitiervorschlag für das Buch / The complete
book may be referenced as follows:
Weissenhofer, A., Huber W., Mayer V., Pamperl S., Weber A. & G. Aubrecht (Hrsg.; 2008): Natural and cultural history of the Golfo Dulce region, Costa Rica. — Stapfia 88: 768 pp.
Zitiervorschlag für Einzelarbeiten / Single
contributions may be referenced as follows:
Ausstellung / Exhibition:
Ort / Address:
Zeitraum / Period:
Weissenhofer A., Huber W. & M. Klingler (2008): Geography of the Golfo Dulce region. — Stapfia 88: #-#.
Der Pfad des Jaguars. Tropenstation La Gamba, Costa Rica
Biologiezentrum der Oberösterreichischen Landesmuseen, J.-W.-Klein-Straße 73, 4040 Linz, Austria
10. Oktober 2008 bis 22. März 2009
Konzept, Organisation und Gestaltung /
Concept, organization, design:
Mag. Stephan Weigl, Mag. Dr. Werner Huber, Mag. Dr. Anton Weissenhofer, Daniel Schaber
Ausstellungstechnik, Mitarbeit /
Exhibition techniques, collaboration:
Jürgen Plass, Roland Rupp, Bruno Tumfart, Erwin Kapl, Josef Schmidt, Roland Zarre, Michaela Minich, Charlotte Füreder, Georg Proske, Franz Rammerstorfer
Museumspädagogik / Museum education:
Leihgeber / Lenders:
Mag. Claudia Kiesenhofer
Naturhistorisches Museum Wien, Mag. Dr. Werner Huber, Mag. Dr. Anton Weissenhofer, Universität Wien;
Mag. Felix Holzmann, Bischofshofen
Due to the orographic formation of its interior and
its humid climate, the Golfo Dulce Region is rich with
biodiversity, containing very dense flora and fauna. After HOLDRIDGE (1971), the region was subdivided into
different zones, including the tropical rainforest, the
tropical wetland forest, and tropical premontane rainforest. The biogeographical situation in this area shows
many similarities to the flora and fauna in the Amazon
and the Colombian Chocó Region and serves as a land
bridge with a valuable genetic base between North and
South America. After unregulated seizure of land by
agricultural settlers, lumberjacks, and large landowners
in the 1940s and 1950s, regulated, state-subsidised settlement reform intended to support agricultural exports
in the 1960s, and intensification of the livestock industry in the 1970s, primary and secondary forest reserves
have shrunk to a minimum. The constant expansion of
monocultures on new land has far-reaching consequences for the local ecosystem.
The conservation and sustainable use of tropical
forests is established in the Forest Declaration, Convention on Climate Protection, and Convention on the
Protection of Species, which demonstrate worldwide
concern for these issues. As a regional example, in the
4,304.80 km2 drainage basin, the ACOSA (Área de
Conservación OSA), which covers an area spanning
the Cantons Osa, Golfito und Corredores, aims to protect species diversity within the 17 game preserves,
which are 44.7% covered by forest, through integration
and an alliance with the Parques Nacionales, Vida Silvestres y Forestales (Fig. 2). The main sector of the Corcovado National Park on the Osa Peninsula covers
424 km2 and the Piedras Blancas National Park covers
148 km2. The altitude ranges from sea level to 745 m on
the Osa Peninsula (Cerro Rincón and Cerro Mueller in
the Fila Matajambre) and to 579 m in the Esquinas forest (Cerro Nicuesa). The Golfo Dulce Forest Reserve
(592 km2) was established between the two parks, thereby forming a natural forest corridor.
References
CHINCHILLA V.E. (1987): Atlas cantonal de Costa Rica. — IFAM. San
José.
HARTSHORN, G.S. (1983): Plants: introduction. — In: JANZEN D.H.
(ed.), Costa Rican natural history. Chicago: Univ. Chicago
Press: 118-157.
HERRERA-MACBRYDE O., MALDONADO V. JIMÉNEZ T.R. & K. THOMSEN
(1997): Osa Península and Corcovado National Park, Costa
Rica. — In: DAVIS S.D., HEYWOOD V.H., HERRERA-MACBRYDE O.,
VILLA-LOBOS J.& A.C. HAMILTON (eds), Centres of plant diversity. A guide and strategy for their conservation. Vol. 3.
WWF, IUCN.
HERWITZ S.R. (1981): Regeneration of selected tropical tree
species in Corcovado National Park, Costa Rica. — Univ.
Calif. Publ. Geogr. 24.
HOLDRIDGE L.R. (1971): Forest environments in tropical life zones.
A pilot study. — Oxford.
MALZER O. (2001): Geological History of Central America and the
Golfo Dulce Region. — Stapfia 78: 34-46.
MORA C.S. (1990): La Geología y sus procesos. — San José.
TOSI J.A. Jr. (1975): The Corcovado Basin on the Osa Península.
— In: TOSI J.A. Jr. (ed.), Potential national parks, nature reserves, and wildlife sanctuary areas in Costa Rica: a survey
of priorities. San José: Centro Científico Tropical. Separate
pp. 12.
Addresses of authors:
Anton WEISSENHOFER
Werner HUBER
Department of Palynology and Structural Botany
Faculty Center of Botany
University of Vienna
Rennweg 14
A-1030 Vienna, Austria
E-mail: [email protected]
[email protected]
Michael KLINGLER
Workgroup Development Studies
and Sustainability Science
Institute of Geography
University of Innsbruck
Innrain 52
A-6020 Innsbruck, Austria
E-mail: [email protected]
21
The river network of the Piedras Blancas National
Park, Costa Rica
La red fluvial del Parque Nacional Piedras Blancas, Costa Rica
J u l i a T S C H E L A U T, C h r i s t i a n P I C H L E R , A n t o n W E I S S E N H O F E R
& Fritz SCHIEMER
Abstract: Research on tropical streams has progressed markedly over the last decade. However, many aspects of biodiversity and
functional processes require more detailed attention. The rivers and streams of the Piedras Blancas National Park in south-western Costa Rica provide a unique opportunity to study near-pristine rainforest streams and tropical freshwater ecology. One of the
primary objectives of the study was to provide a survey of the river network within the Río Esquinas catchment. Rivers were
analysed with regard to abiotic parameters such as morphology, hydrology, hydrochemistry, sedimentology, and to biotic parameters such as canopy cover by the riparian vegetation during the dry and rainy season in 2004. Surveys were carried out on nine
streams and rivers, ranging from 1st order to 4th order, which empty into the Golfo Dulce at the Pacific Ocean. The paper discusses differences between sites according to geology and the seasonal hydrological characteristics of running waters within the catchment. The hydrochemical stream signatures indicate different geological sources within the Río Esquinas catchment. High water
temperatures (> 25°C) are a permanent feature. The streams and rivers exhibit a high annual variation in discharge, turbidity and
hydrochemistry as a result of seasonal rainfall. The mean discharge during the rainy season can be 3 times higher than in the dry
season. Detailed morphometric-hydrological measurements at the Quebrada Negra, a 1st order stream, show a clear picture of a
highly heterogeneous, dynamic and unregulated stream course with a sequence of pool and riffle sections. Rapid water level fluctuations caused by heavy rains are typical. The abundant riparian vegetation is of major significance for the structure and function of the stream ecosystem. The food web structure and trophic interactions of neotropical streams are analysed, taking the results of the Quebrada Negra as an example.
Key words: neotropical streams, seasonality, hydrology, geomorphology, riparian vegetation, nutrient export, food web.
Resumen: La investigación de cursos de agua tropicales ha aumentado en la última década. Sin embargo, muchos aspectos de la
biodiversidad y los procesos funcionales requieren una atención mas detallada. Los ríos y arroyos del Parque Nacional Piedras
Blancas, al sudeste de Costa Rica, ofrecen una oportunidad única para estudiar la ecología de los cursos de agua dulce tropicales
en estado casi inalterado. Uno de los primeros objetivos del estudio fue estudiar la red fluvial de la cuenca del Río Esquinas. Los
ríos fueron analizados teniendo en cuenta factores abióticos como morfología, hidrología, hidroquímica, sedimentología y factores
bioticas como capa de vegetación ripariana durante las estaciones seca y lluviosa de 2004. Se realizó un estudio sobre nueve cursos de agua, del primer al cuarto orden, que desembocan en el área del Golfo Dulce, en el Océano Pacífico. El trabajo trata sobre
las diferencias entre diversos sitios de la cuenca según factores geológicos y las características hidrológicas estacionales de cada
curso de agua. Las características hidroquímicas de los ríos indican diversas fuentes geológicas dentro de la cuenca del río Esquinas.
La alta temperatura del agua (> 25ºC) es una constante de los ríos que se describen aquí. Los cursos de agua muestran una gran
variación anual en descarga, turbidez e hidroquímica debido a las lluvias estacionales. La descarga promedio durante la estación
lluviosa puede llegar al triple de la estación seca. Además se investigaron con mayor detalle las condiciones morfométricas e
hidrológicas del Quebrada Negra, un curso de primer orden. Los resultados muestran que se trata de un curso de agua heterogéneo, dinámico y poco regulado, con una secuencia natural de remansos y rápidos. Las rápidas fluctuaciones de nivel causadas por
las intensas lluvias son típicas. La abundante vegetación riparia mantiene prinicipalmente a las especies típicas de los cursos de
agua de Costa Rica. Se analizan la estructura de la red alimenticia y las interacciones tróficas de los cursos de agua neotropicales
– tomando los resultados del Quebrada Negra como ejemplo.
Palabras clave: agua tropicales, características estacionales, hidrología, geomorfología, vegetación riparia, exportación de nutrientes, red alimenticia.
Stapfia 88,
zugleich Kataloge der
oberösterreichischen
Landesmuseen
Neue Serie 80 (2008):
441-455
Introduction
Studies of neotropical streams and rivers have a long
history, beginning with early explorers and naturalists
who visited these regions and collected aquatic specimens, e.g. von Humboldt and Bonpland (1799-1802),
von Spix and von Martius (1817-1820), Bates (18481859). Later, more extensive collections were made by
professional collectors as well as numerous resident and
visiting scientists (see JACKSON & SWEENEY 1995).
There is a growing interest in the study of neotropical lotic systems, and the number of papers published
each year that address tropical stream research has increased markedly over the last two decades. Although
the advances are evident, JACKSON & SWEENEY (1995)
pointed to the pressing need for more research into the
ecology of zoobenthos, algal and microbial communities. In particular, there is a strong requirement for research into aquatic system processes and their interaction with the terrestrial environment in a catchmentorientated context.
Tropical streams provide the opportunity to study
some general ecological questions e.g. factors that determine patterns of species abundance, distribution and
co-occurrence (ARRINGTON et al. 2005). Patterns determined from temperate zones do not necessarily hold for
tropical systems because of the greater taxonomic and
ecological diversity in the tropics (HOENIGHAUS et al.
2004) and general system differences e.g. in temperature, hydrology and the source of energy for the biota.
The effects of disturbance, predation and environmental complexity (e. g. DUDGEON 1993), the structure of
tropical food webs (e. g. JEPSEN & WINEMILLER 2002)
and the specific role of fish (e. g. FLECKER et al. 2002)
represent research questions of a wider ecological scope.
A characteristic feature of tropical rainforests is
their high diversity and productivity based on a restricted nutrient supply. One resolution of this paradox is the
fast nutrient turnover and high retention capacity. In
this respect, rainforest streams can be considered as the
export routes of nutrients and thus they can be used to
indicate the retention capacities of the system with respect to the nutrient losses that occur. They are therefore good indicators of the retentivity and integrity of
the whole rainforest system (e. g. LEWIS 1987).
Tropical streams form aquatic ecosystems which interconnect intimately with the processes in the riparian
gallery forests and the hyporheic zones flowing beyond
and beside the visible streams. The River Continuum
Concept (RCC), introduced by VANNOTE et al. (1980)
is a tool for displaying and understanding lotic ecosystem dynamics. It explains changes in the structure and
function of communities in low-order rivers and helps
442
predict the way biological communities adapt to such
changing geomorphological and hydrological conditions. This concept was the first unified hypothesis
about how streams and their watersheds work and has
been tested in streams around the world.
This protected area of the Piedras Blancas National
Park, Costa Rica, provides a unique opportunity to
study near-pristine rainforest streams. A continued program of ecological studies of the Río Esquinas catchment and its aquatic subsystems is in progress.
The objective of the present study was to provide an
overview of the overall characteristics of the river network within the Río Esquinas catchment (Fig. 1).
Rivers were analysed with regard to abiotic parameters
such as morphology, hydrology, hydrochemistry, sedimentology and to biotic parameters such as canopy cover by the riparian vegetation. Differences between sites
according to geological factors and the seasonal hydrological characteristics of running waters within the
catchment have been assessed. Research was carried out
at nine study streams and rivers ranging from 1st order
streams to the largest river, the Río Esquinas, a 4th order
river, that empties into the Pacific Ocean at the Golfo
Dulce. Furthermore, the morphometric-hydrological
conditions of the Quebrada Negra, a 1st order stream,
were investigated in more detail. Streams display a more
or less regular alternation between shallow areas of
higher current velocity and mixed gravel-cobble substrate (riffles) and deeper areas of slower velocity and
finer substrate (pools).
The Río Esquinas catchment
A network of rivers, small streams and drainage
channels pass through the national park and its surroundings, which all flow into Río Esquinas (Fig. 1).
“Esquinas” means corner and the river is named after its
meandering course in its downstream section. The river
forms the natural border of the Bosque Esquinas to the
north and west of the national park and drains into the
Pacific Ocean. Extensive mangrove swamps occur along
the tidal estuaries next to its mouth. The banks of the
two main rivers passing through the La Gamba valley,
the Río Bonito and the Río Esquinas, consist of farmland and secondary forest at different stages of regrowth.
Due to logging until the late 20th century, nearly no primary forest is left in the lowland, except small patches
along the coast and deep inside the park. However, the
up-slope areas within the study catchment show almost
no signs of anthropogenic disturbance. Most of the
smaller streams lie within primary rainforest.
The river network, especially the Río Bonito, is
characterised by an almost unaffected geomorphology.
Fig. 1: Río Esquinas catchment with nine
sampling sites and the indicated
subcatchments of Río Bonito and
Quebrada Negra within the Piedras
Blancas National Park and its vicinity.
In its connection with the Río Esquinas, it represents a
very interesting, remarkably preserved, undisturbed and
fully developed, longitudinal morphological river continuum. The upstream area of the Río Bonito, embedded in primary forest, can serve as a valuable reference
section for the investigations of anthropogenic influences for Costa Rican rivers.
Headwater streams, like the Quebrada Mari and
Quebrada Negra, are rocky, shallow, narrow and charac-
terised by a dense riparian vegetation. In contrast, the
canopy cover of high order rivers such as lower meandering parts of Río Esquinas and downstream parts of
Río Bonito is low and the sediments are dominated by
mud and sand. Light levels near the bottom zones are reduced due to an increasing water depth and turbidity.
Figure 2 depicts the downstream decrease in slope
of rivers along their longitudinal course, with steep
headwaters and waterfalls due to the rocky landscape
Table 1: Co-ordinates and brief description of the sampling sites from the nine studied rivers.
river
Quebrada Mari
Quebrada Negra
Quebrada Chorro
Quebrada Gamba
Quebrada Bolsa
Quebrada Sardinal
Río Oro
coordinates
N 08° 42,054', W 083° 12,085'
N 08° 42,425', W 083° 10,552'
N 08° 42,072', W 083° 11,530'
N 08° 42,452', W 083° 11,137'
N 08° 43,407', W 083° 12,773'
N 08° 43,004', W 083° 10,033'
Río Bonito
N 08° 43,868', W 083° 17,723'
Río Esquinas
N 08° 43,868', W 083° 17,723'
description
next to San Miguel, Fila Cruces
next to the Field Station La Gamba
at the waterfall
bridge with railing
bridge in La Gamba
500 m before entering into Río Bonito
bridge on the way from La Gamba to
Interamericana (km 37)
2,5 km upstream the conference with Quebrada
Sardinal
4 km upstream of its mouth before entering into
Golfo Dulce
443
formation, followed by a decline in lowland sections
further downstream. The confluence of various fastflowing, turbulent mountain streams (e. g. Q. Negra, Q.
Gamba, Q. Chorro) results in a fast-flowing river,
which corresponds to the piedmont river type with its
larger flow, a braided course and high gravel transport
(e. g. lower Río Bonito, Fig. 3). The meandering, lower part of the Río Esquinas, winds as a large, smoothlyflowing river through the lowlands to the sea. It is highly influenced by tidal backwaters and the deposition of
sand and fine sediments (up to 10 km inland from the
Pacific Ocean).
The concave longitudinal profile is evident. Whereas
Quebrada Negra shows a steep incline, the slope of Río
Esquinas is low. Along the longitudinal course, discharge
increases in the dry season from 22.5 ls-1 (Q. Negra) to
397 ls-1 (Q. Gamba), 4270 ls-1 (R. Bonito before the confluence with R. Oro) and 10.000 ls-1 (R. Esquinas).
Almost all the characteristics of a river vary with
position along its length. In general, discharge increases
with increasing stream order, resulting in changes in
width, depth and velocity. Particle sizes of river bed material usually shift from an abundance of coarser material upstream to mainly finer material in downstream areas. Sediment size is not only correlated with the stream
order, it also depends upon different physical parameters
(current velocity, incline) of the stream.
Fig. 2: River length [km] versus altitude [m] and flow [ls-1] during the dry
season 2004 of the Quebrada Negra flowing into Quebrada Gamba, Río
Bonito and Río Esquinas. Tributaries like Quebrada Bolsa, Quebrada Chorro
and Río Oro are indicated.
The Golfo Dulce region is one of the most humid
areas in Costa Rica, with more than 6.000 mm of precipitation per year. On the Pacific side of Costa Rica,
distinct dry (December – March) and rainy (May – November) seasons exist. The heaviest rainfalls occur in
September, October and November. February and
March are the driest months, when days can pass without rain. As a result of seasonal rainfall, rivers in this region undergo annual changes in water levels. The dry
and rainy seasons affect various morphological and hydrological parameters, especially stream width, water
depth and discharge. Strong geomorphological changes
of the river bed are visible after periods of seasonal flood
flow events. In the rainy season, frequent (almost daily)
rains and storms can cause bank-full conditions and in
some cases flooding (FÜREDER 1994).
A comparison of cross sections from the dry and
rainy season shows the increase in stream width and water depth during the rainy season. Distinct seasonal differences are evident in Figure 4. Río Oro, Quebrada Sardinal and Río Bonito become strikingly larger and deeper during the rainy season.
Fig. 3: Lower Río Bonito.
444
Streams in Figure 5 are arranged based on Strahler’s
stream order system starting with 1st order streams (Q.
Negra and Q. Mari). Quebrada Chorro, Quebrada Gam-
ba, Quebrada Bolsa, Río Oro and Quebrada Sardinal are
2nd order streams at the respective study sites. Río Bonito was defined as a 3rd order river and Río Esquinas as a
4th order river. The recorded flow at these nine rivers
shows a distinct increase from low order streams to
rivers with higher stream order. The smallest is the
Quebrada Negra with a base flow of 0.031 m3s-1. The
flow of the Río Esquinas was about 300 times as high
(10 m3s-1).
Furthermore, large fluctuations from the dry to the
rainy season are a characteristic feature. Data from the
Quebrada Mari and the Río Esquinas are not available for
the rainy season. Water flow increased in the late rainy
season (September, October). Therefore, differences in
flow depended on sampling date. Values ranged from
0.094 m3s-1 (Q. Negra) to 1.776 m3s-1 (Q. Sardinal).
Sediment size of the river bed differed markedly between the study sites. At seven rivers within the Esquinas catchment, sediment size was estimated visually
in the rainy season (Fig. 6). We used five standard particle size ranges (< 2 mm, 2-6.3 mm, 6.3-20 mm, 20-63
mm, > 63 mm) and noted the proportion of each range
in the stream bed sediment. The sites for this analysis
were chosen at random. The rivers are thus not comparable, but sediment size ranges can be given. The Q25,
the lower quartile, ranged from 1.5 mm to 9.1 mm. This
means that 25% of the sediment sizes were less than 1.5
mm at the site with the finest sediment and smaller
than 9.1 mm at the site with the coarsest soil. The Q50,
the median, ranged from 6.5 mm to 28.9 mm. The Q75,
the upper quartile, extends from 28.5 mm to 91.2 mm.
The Río Oro showed the smallest sediment size, whereas the Quebrada Bolsa had the coarsest sediment.
Fig. 4: Cross sections of Quebrada Sardinal, Río Oro and Río Bonito with
stream width [m] and water level [m] during the dry and rainy season in 2004.
Sampling sites are indicated with red stars in Figure 1.
Geology and chemistry
Tropical rivers generally have lower concentrations
of chemical constituents than temperate rivers, because
tropical rivers are mostly precipitation-dominated.
However local geology is also important. The chemical
composition of stream water reflects and thus reveals geological features of the catchment. The chemical
regime of the water, particularly nutrient dynamics and
export from catchments, provides insights into major
aspects of ecosystem functions (NEWBOLD et al. 1995).
The relationship between solute concentration and
stream flow can help to explain the interplay among
physical, chemical and biological processes within the
catchment. The observed physical and chemical differences in solute concentrations among the studied rivers
within the Río Esquinas catchment seem largely to be a
function of area-specific runoff and geological processes.
Chemical data indicate the same source for Río Es-
Fig. 5: Comparison of the flow [m3s-1] from the nine study rivers during the
dry and the rainy seasons. Arrangement of rivers according to stream order
[1st – 4th]
445
sandstones, often very coarse breccias, but also thinbedded (pelagic to hemipelagic) limestones, mudstones
and radiolarites (maximum thickness 1 metre, deeply
red coloured and sometimes forming jasper) are visible
in the profiles. The La Gamba field station and the Esquinas Rainforest Lodge are both located on this unit.
Light green tuff crops out on the slope north of the station, whereas fine-grained, medium grey basalt and
boulders of basalt breccia are found in the Quebrada
Gamba. Layers of grey-green, fine-grained basalt and
dykes and sills of dolerite appear in the profiles of Quebrada Bolsa (MALZER 2001).
Quebrada Sardinal originates in the adjoining “Rincon Block”, formed almost exclusively by basaltic lavas
with only very minor inclusions of radiolarite; this
stream enters the Golfito Terrane when discharging into Río Bonito.
Fig. 6: Comparison of the sediment size [mm] from seven rivers during the
rainy season. Arrangement of rivers according to stream order [1st – 3th].
Position of sampling sites is indicated in Fig. 1.
quinas and Río Oro within Fila Costena (Fila Cruces),
while all other tributaries originate in Fila Gamba and
Golfito (indicated in Fig. 1).
Fila Golfito and Fila Gamba are formed from Late
Cretaceous and Early Tertiary rocks of a deep marine
sequence of oceanic basaltic flows at the base, followed
by deep sea carbonates and volcaniclastics, including
some lavas and topped by a volcaniclastic sequence
(mainly tuffs) without lava flows. Waterfalls are present
here, but are not as characteristic here as they are of the
Fila Costena. Sediments of the highest layer of this sequence of the “Golfito Terrane” (DI MARCO et al.
1995) are exposed in the Quebrada Bolsa, Chorro and
the lower parts of Quebrada Sardinal. Tuffs, siltstones,
Fig. 7: Ion balances based on concentrations of Ca2+, Mg2+, Na+, alkalinity and
SO42- [mval] for the nine study streams during the dry season in 2004.
446
The Fila Costena, lying to the north and across an
important NW-SE trending fault zone, differs drastically from the Fila Golfito/Fila Gamba area because it belongs to a different megatectonic unit, the “Chorotega
Block”. It is characterised by shallow marine limestones
from the Eocene and shales, sandstones and microconglomerates of Oligocene or Miocene age. There are no
major volcanic and volcanoclastic rocks within reach of
the investigated rivers. An important feature of the Fila
Costena is its steep, rugged, rocky slopes with numerous
waterfalls. This catchment area is clearly dominated by
carbonate rocks (CaCO3) with possible occurrences of
gypsum; high concentrations of CaSO4 are therefore
present here.
Río Oro and Río Esquinas have the highest alkalinity and concentrations of SO42- (Fig. 7). The content of
calcium in the Quebrada Negra, Chorro, Gamba, Sardinal, Bolsa and the Río Bonito is between 14.2 and 25.3
mg l-1. Quebrada Mari (34.8 mg l-1), Río Oro (44.4 /
52.4 mg l-1) and Río Esquinas (44.3 mg l-1) show much
higher concentrations. Moreover, conductivity of
streams originating in the Fila Cruces is also higher (Q.
Mari 260 µS cm-1, Río Oro 372 / 314 µS cm-1 and Río
Esquinas 299 µS cm-1) than in other studied rivers
which have their source in the Golfo Dulce area. The
reported concentrations of nitrate, phosphate, total dissolved nitrogen and total dissolved phosphorus are
clearly correlated with land use. Streams like Quebrada
Gamba, Quebrada Bolsa, Río Bonito and Río Esquinas
drain agricultural land, which has a strong influence on
river chemistry. These rivers are next to plantations (cacao, oil palms and other land use) and have higher nutrient concentrations than those draining forested land.
Lowlands are more heavily farmed and settled than upland regions. The pH value of all studied rivers is about
8, in both the dry and the rainy season.
Riparian Vegetation
This species-rich vegetation determines habitat
structures, access to light and temperature, provides the
organic matter supply (e.g. leaf litter) to the aquatic environment, and reduces the transfer of nutrients and
pollutants. These factors have a major influence on the
structure and function of fish and macroinvertebrate
communities. This special forest type is found along
small rivers with adjacent flat terraces. Trees of the
riverine vegetation are 35-40 m tall and often have massive trunks with widely spreading buttresses (WEISSENHOFER et al. 2001). The riverine vegetation represents
an ecotone — a buffering and intermediate zone between the forest and the aquatic site (SCHIEMER & ZALEWSKI 1992). The abundant riparian vegetation at the
Quebrada Negra consists mostly of species typical for
headstreams and small rivers in the Golfo Dulce region
(see Fig. 8, which represents a vegetation profile at the
Q. Negra).
Trees of the canopy layer include Spondias mombin
(Anacardiaceae), Cordia cymosa (Boraginaceae),
Sloanea medusula (Elaeocarpaceae), Hyeronima alchorneoides (Euphorbiaceae), Lonchocarpus sp. (Fabaceae),
Carapa guianensis (Meliaceae), Castilla tunu (Moraceae)
Virola koschnyi, V. guatemalensis (Myristicaceae) and
Luehea seemannii (Tiliaceae).
Prominent species of the mid-canopy layer are
Guatteria chiriquiensis (Annonaceae), Welfia regia (Arecaceae), Cecropia insignis, C. obtusifolia (Cecropiaceae),
Tetrathylacium macrophyllum (Flacourtiaceae), Cupania
livida (Sapindaceae), Apeiba tibourbou and Trichospermum grewiifolium (Tiliaceae).
The well represented shrub and ground layer contains species like Dieffenbachia oerstedii, Homalomena
wendlandii, Philodendron spp., Spathiphyllum wendlandii
(Araceae), Asterogyne martiana (Arecaceae), Costus pulverulentus, C. laevis (Costaceae), Carludovica drudei, Cyclanthus bipartitus (Cyclanthaceae), Episcia lilacina (Gesneriaceae), various species of Heliconiaceae, Calathea
lutea (Marantaceae), Piper auritum (Piperaceae), Pentagonia wendlandii, Psychotria elata (Rubiaceae), Myriocarpa
longipes, Urera elata (Urticaceae) and the fern
Nephrolepis sp. (Oleandraceae).
Epiphytes are common and conspicuous on exposed
branches, e.g. Columnea flaccida, C. polyantha (Gesneriaceae), but lianas are rare.
Fig. 8: Riparian vegetation
at the Quebrada Negra (~
300 m downstream from the
waterfall and next to the
Esquinas Rainforest Lodge).
1. Cordia cymosa
(Boraginaceae), 2. Carapa
guinensis (Meliaceae), 3.
Luehea semannii (Tiliaceae),
4. Cecropia obtusifolia
(Cecropiaceae), 5. Apeiba
tibourbou (Tiliaceae), 6.
Tetrathylacium
macrophyllum
(Flacourtiaceae), 7. Castilla
tunu (Moraceae), 8. Welfia
regia (Arecaceae), 9.
Lonchocarpus sp. (FabaceaeFaboideae), 10. Virola
guatemalensis
(Myristicaceae), 11. Cecropia
insignis (Cecropiaceae), 12.
Acalypha diversifolia
(Euphorbiaceae), 13.
Myriocarpa longipes
(Urticaceae), 14. Alsophila
firma (Cyatheaceae)
447
At study sites along the larger rivers, the riparian
vegetation is often interrupted due to deforestation or
logging and therefore adjacent areas are mainly dominated by pasture. These sites (Fig. 1), for example, Río
Bonito, Río Oro, Quebrada Bolsa and Río Esquinas, are
less shaded than those of headwater streams.
slower velocity and finer substrate. Natural dynamics of
streams are expressed by these alternating riffle and pool
sections. Pool-riffle sequences are the result of particle
sorting and require a range of sediment sizes to develop.
The intervals of pool-riffle sequences are related to
stream width.
Mangrove forests accompany the sheltered seashore
and estuary of the Río Esquinas, where tidal inundation
of salt water from the sea occurs. This forest type is
floristically poor, thus representing the opposite extreme of the species-rich tropical forest. Rhizophora mangle (Rhizophoraceae) and Pelliciera rhizophorae (Theaceae) are common and form nearly pure stands.
The stream is characterised by a wide diversity of
habitats with different current velocity, depth and substrate, and represents high heterogeneity. Current velocity, stream depth, stream bed width and sediment size
fluctuate within short distances (100 m). Whereas current velocities decrease at pool sequences, riffle sequences are characterised by higher current velocities.
Sites where high velocities were recorded have low average depths. In contrast, low velocities occurred at
deeper sections (Fig. 10).
Quebrada Negra
System-orientated studies concentrated on the Quebrada Negra which is in immediate reach of the Field
Station La Gamba. The upper course of the Quebrada
Negra is an example of a natural, dynamic and unregulated stream course (see Fig. 9), showing both the mean
water depth and the mean current velocity during the
dry season.
Streams are highly heterogeneous environments in
which habitat characteristics vary drastically over small
distances (FENOGLIO et al. 2004). In a naturally flowing
river, stream reaches display a more or less regular alternation between shallow areas of higher current velocity
and mixed gravel-cobble substrate and deeper areas of
Fig. 9: Course of the Quebrada
Negra during the dry season
within the 100 m section, with
bank level [m] and water depth
[m]. Position of the cross
sections and the tropical field
station are indicated.
448
Although water depth and current velocity increased during the rainy season in 2004 due to the higher flow caused by heavy rain, the depth and velocity
profiles nonetheless resemble those of the dry season.
Heavy rainfall during the rainy season caused riverbank
erosion, but the pool and riffle sequences showed no
major shift between the two seasons within the 100 m
course of the Quebrada Negra in 2004.
The hydrograph a continuous record of discharge
plotted against time (ALLAN 1995), in Fig. 11 shows the
response of the flow of the Quebrada Negra to rainfall
from March 2004 to July 2005. With its distinct dry and
rainy seasons, it is a good example for rainforest streams
in Costa Rica. Most Central American rivers do not sustain flood conditions for long periods between successive downpours (BUSSING 1993). The water level on 23
February 2004 was defined as a baseline of zero to provide a measure of range and fluctuation in water levels
over the observation period. Water level zero has a base
flow of 0.020 m3s-1. Within the sampling time, this was
the lowest observed water level. Sudden changes in water level were the rule. High water levels occurred even
in the dry season after rain, but water levels were typically higher in the rainy season in months of heavy and
continuous rain, when the soil was soaked and runoff
was heavy.
The seasonal differences in mean flow discharge are
presented in Figure 12. Flow at different water levels was
assessed by current velocity measurements along depth
profiles at the 55 m cross transect within the 100 m sector. To calculate the mean flow within the two seasons,
the average water level of three months of each season
was taken. The average water level in the dry season
(December, January and February) is 0.4 cm; in the
rainy season (August, September and October) the corresponding value is 5.6 cm. This includes average flows
of about 22 and 60 ls-1, respectively. High-flow episodes
corresponded with a very short time lag to strong rain
events. Figure 13 shows that water level fluctuations follow the precipitation. Each peak of heavy rainfall is followed by a rising water level half an hour later. Turbidity generally increased during flooding but cleared quite
quickly when rain stopped.
Fig. 10: Mean current velocity [ms-1] and mean depth [m] in the dry season
(DS) 2004 within the longitudinal 100 m section.
mostly controlled and often determined by the seasonality of the precipitation. Peaks in leaf fall have been reported during the dry season for Central American forests
(DE LA ROSA 1995). Higher leaf fall during the dry season
is responsible for the larger litter input into the stream.
During the rainy season, most of the leaf litter is transported downstream by flood pulses and higher flow. Riffles and pools show very different leaf accumulations. The
former contain more litter because, at shallow sites,
leaves accumulate at obstacles and form debris dams.
The short-term fluctuations of the Quebrada Negra
are very typical and play a more important role than the
long-term fluctuations. Water levels rise quickly after
the beginning of rain.
Water tends to discharge above ground, and not
much water disappears into the hyporheic interstitial
(underground). Impermeable rocks or soils with large
amounts of clay are one potential explanation for this.
These soils absorb moisture very slowly, especially when
the soils are deep. A smooth running stream can turn
into a torrent very rapidly. Water levels not only rise
quickly, but also drop quickly, which can be explained
by the high resilience of the rainforest. Sudden changes
in water level are the rule for streams and rivers of this
region in Costa Rica.
Headwater streams within rainforests, like the Quebrada Negra, receive low irradiance due to the dense riparian vegetation and therefore have a low primary production. Consequently, much of the energy demand by
consumers is met from allochthonous sources, especially
litter fall. Leaf litter entry into neotropical streams is
Fig. 11: Water level of the Quebrada Negra and precipitation at the tropical
Field Station La Gamba from 23 February 2004 to 1 July 2005.
449
Leaf litter in the Quebrada Negra was recorded as an
indicator for the input of organic carbon to the water.
Figure 14 shows the huge difference between the two
seasons. In the rainy season of 2004, only 4.6 gm-2 were
recorded versus 81.2 gm-2 in the dry season.
Fig. 12: Measured flow [ls-1] of five different water levels [m] and accounted
mean flow [ls-1] of the Q. Negra during the dry and rainy season (based on
mean water level for three-month periods).
The processing of leaf litter in running waters of
temperate regions has been the subject of numerous
studies, but equivalent tropical ecosystems have received little attention (BENSTEAD 1996). In tropical
streams, many leaf types vary in their palatability and
tannin levels (DUDGEON & WU 1999). The decomposition and macroinvertebrate colonisation of leaf litter
from four different plant species of the riparian vegetation were investigated within the course of the study
“Macroinvertebrates and Leaf Litter Decomposition in a
Neotropical Lowland Stream, Quebrada Negra, Costa
Rica” (TSCHELAUT et al. 2008, RIEMERTH et al. 2008).
Some of the most threatened ecosystems on the
planet (e.g. rainforests, coral reefs, freshwater lotic systems) are characterised by extremely complex food webs
(LAYMAN et al. 2005). Figure 15 provides an overview
of the trophic structure of the rainforest streams of the
Esquinas forest. It depicts the trophic interactions and
the major trophic pathways based on community composition and the food habits of the major species.
Algae, fine particular organic matter (FPOM),
coarse particular organic matter (CPOM) and airborne
material are the primary resource basis. The second
trophic level is composed of herbivorous macrozoobenthos and fish. Predatory insects, carnivorous and omnivorous fish represent the third trophic level. Piscivore
fish are on the top of the trophic pyramid. Many species
utilise food from two or more trophic levels.
Fig. 13: Short-term fluctuation and detailed recording of the water level and
precipitation from 13:00 to 17:00 on 8 August 2004 at the Quebrada Negra.
Fig. 14: Mean amount [gm-2] of
collected leaf litter on two sampling
dates (March 5 2004. / August 8 2004)
within the 100 m transect during the
dry and rainy season in 2004.
450
The abundance of macroinvertebrates provides
abundant food for many other predators, including a diverse fish assemblage. Food resources of invertebrate
consumers include periphyton and other surface layer
complexes, macrophytes, detritus and other animals.
We examined the trophic structure of macroinvertebrates using the system of functional feeding groups
(FFG) according to MERRITT & CUMMINS (1996). The
classification of the invertebrate consumers of streams into feeding guilds has proved to be very useful for descriptive and analytical purposes (CUMMINS 1973).
The Quebrada Negra invertebrate fauna is, in terms
of species numbers, mostly made up of collector-gatherers (53.3%), followed by predators (16.5%), filterers
(14.5%), shredders (8.5%) and grazer-scrapers (6.5%).
The functional and taxonomic macroinvertebrate composition is quite similar to that reported from other
Costa Rican lowland streams (PRINGLE & RAMIREZ
1998, ROSEMOND et al. 1998, RAMIREZ & PRINGLE
2001).
Due to the low periphyton production in the Quebrada Negra, scrapers and grazers were poorly represented and constitute only 6.5% of the macroinvertebrate
community.
Ephemeroptera was the most significant group of
collector-gatherers, and within this group the Leptohyphidae (20.1%) and Leptophlebiidae (6.9%) were most
abundant. Predators were the second major feeding
group, dominated by Tanypodinae (7.8%, Diptera, Chironomidae).
Net-spinning caddisflies (Philopotamidae and Hydropsychidae) are passive filter feeders, constructing
nets in exposed locations. Larvae of black flies (Simuliidae) are highly specialised suspension feeders.
Major invertebrates that feed on decaying leaves
(shredders) in our study stream include crane fly larvae
(Tipulidae) and beetles (esp. Ptilodactylidae). Shredders such as Calamoceratidae (caddisflies) were only re-
ported from leaf litter bags within the study “Macroinvertebrates and Leaf Litter Decomposition in a
Neotropical Lowland Stream, Quebrada Negra, Costa
Rica” (TSCHELAUT et al. 2008).
Fish are conspicuous and important components of
tropical river food webs. Fish species almost certainly occupy several of the functional feeding groups and probably exert the greatest impact. Trophic diversification in
tropical river fish assemblages is greater than that of in
similar habitats of temperate regions that contain less
species (WINEMILLER 1991, WINEMILLER & JEPSEN 1998).
Compared to temperate river fish, tropical fish show proportionally more herbivorous, detritivorous and omnivorous feeding behaviours (WINEMILLER 1990, 1991;
WOOTTON & OEMKE 1992). Seasonality plays an important role in tropical river food webs. Flooding brings fish
into contact with a greater abundance and diversity of
allochthonous food resources, especially within forested
watersheds (GOULDING 1980; HENDERSON 1990). In the
Quebrada Negra, population sizes and densities of Poeciliidae decreased from the dry to the rainy season. This
Fig. 15: Simplified food web and major trophic pathways, Quebrada Negra, Costa Rica. Ellipses are the resource basis. Major sampled
species/families with their percentage of total numbers (fish: n = 1373; macroinvertebrates: n = 738) are shown.
451
may reflect seasonal variation in food supply since the
availability of algae and detritus is reduced after floods.
Periphyton production most likely decreased in the rainy
season because of water turbity and decreased light availability. Detrital sources increase in the dry period due to
seasonal leaf fall (CHAPMAN & CHAPMAN 1990).
The survey of rivers lays the basis for further research activities on the aquatic habitats within the
Piedras Blancas National Park. Promising research avenues will be a test of the ecotone and the River Continuum Concept in tropical lotic systems for their global applicability.
The seasonal climate (dry and rainy season) provides good conditions for testing the food web theory
and niche partitioning in neotropical lotic systems. Understanding the ecological energetics will require detailed research on biogeochemical aspects of rainforest
river systems, nutrient retention and nutrient spiralling
and the role of biofilms.
The Piedras Blancas National Park freshwater invertebrate fauna is largely unsurveyed and undescribed.
This protected area in the south of Costa Rica offers an
unique opportunity to study the tropical lotic invertebrate community and to identify the relative role of seasonal changes in physico-chemical factors, and in the
availability and nature of food resources, in explaining
temporal patterns in the functional organisation of
macroinvertebrate communities.
Results from such studies can be used to predict taxa
distribution at local small scales and to identify factors
that can influence micro-distribution patterns in the
lotic system.
Acknowledgements
We thank the staff at the Tropenstation La Gamba
for their support during this research. We thank Otto
Malzer for advice on the geology of this region in Costa
Rica. Mischka Stachowitsch improved the English and
Diego Barletta translated the abstract. Walter Reckendorfer helped with statistics. We thank Hubert Kraill
for the hydrochemical analysis.
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Addresses of authors:
Julia TSCHELAUT
Christian PICHLER
Fritz SCHIEMER
Department of Limnology and Hydrobotany
University of Vienna
Althanstr. 14
A- 1091 Vienna, Austria
E-mail : [email protected]
[email protected]
[email protected]
Anton WEISSENHOFER
Department of Palynology and Structural Botany,
Faculty Center of Botany
University of Vienna,
Rennweg 14
A-1030 Vienna, Austria
E-mail : [email protected]
453
454
d
c
Plate 1: (a) Quebrada Negra, (b) Quebrada Chorro; (c-d) Rio Bonito.
b
a
455
d
c
Plate 2: (a-b) Quebrada Sardinal; (c-d) Rio Esquinas.
b
a
Contents/Indice
Prefaces and introduction — Prólogos y introducción
Dr. Pedro LEON
Coordinator, President Aria’s Initiative on Peace with Nature
11
O. Univ.-Prof. Dr. Georg WINKLER
Rector of the University Vienna
12
Dr. Josef PÜHRINGER
Governor of Upper Austria
13
Introduction
Introduccíon
14
ABIOTIC ASPECTS — FACTORES ABIÓTICOS
Geography — Geografía
Geography of the Golfo Dulce region (survey)
Geografía de la región del Golfo Dulce (sinopsis)
WEISSENHOFER A., HUBER W. & KLINGLER M.
19
Geology — Geología
Outline of the geology of the Golfo Dulce Region (Costa Rica)
and its surroundings in Central America (survey)
Vista de conjunto de la geología de la Región del Golfo Dulce (Costa Rica) y de sus inmediaciones en
América Central (sinopsis)
MALZER O. & FIEBIG M.
23
Geological and mineralogical investigations of the lithologies and their weathering products in
a study area south-west of the field station “La Gamba“, Golfo Dulce, Costa Rica
Investigación geológica y mineralógica de las rocas y sus productos de meteorización, en un área al suroeste
de la estación “La Gamba“, Golfo Dulce, Costa Rica
SCHEUCHER L.E.A., VORTISCH W. & LAGUNA-MORALES J.
31
Anthropogenic and natural radionuclides in soil of a tropical rainforest of Southern Costa Rica
Radionúclidos antropogénicos y naturales en el suelo de un bosque lluvioso tropical del sur de Costa Rica
BOSSEW P., HUBMER A. & STREBL F.
47
Climate — Clima
The climate of the Esquinas rainforest (survey)
El clima del bosque lluvioso Esquinas (sinopsis)
WEISSENHOFER A. & HUBER W.
59
PLANT BIOLOGY — BIOLOGÍA DE PLANTAS
Ecosystems and vegetation — Ecosistemas y vegetación
Ecosystem diversity in the Piedras Blancas National Park and adjacent areas (Costa Rica),
with the first vegetation map of the area
Diversidad de ecosistemas en el Parque Nacional Piedras Blancas y áreas adyacentes (Costa Rica),
con la primera presentación de una mapa vegetacional
WEISSENHOFER A., HUBER W., KOUKAL T., IMMITZER M., SCHEMBERA E., SONTAG S., ZAMORA N. & WEBER A.
65
Plant diversity — Diversidad de plantas
Plant diversity and biogeography of the Golfo Dulce region, Costa Rica (survey)
Diversidad vegetal y biogeografía de la región de Golfo Dulce, Costa Rica (sinopsis)
HUBER W., WEISSENHOFER A., ZAMORA N. & WEBER A.
97
Alien plants and invasion patterns in different habitats of the Golfo Dulce area, Costa Rica
Plantas exóticas y patrones de invasión en diferentes hábitat del área de Golfo Dulce, Costa Rica
HUBER W., WEISSENHOFER A. & ESSL F.
105
Survey of Rubiaceae in the Golfo Dulce area, Costa Rica:
New species, combinations and name changes since 2001
Investigaciones en Rubiaceae en el área de Golfo Dulce, Costa Rica:
nuevas especies, combinaciónes y cambios de nombre desde 2001
WILL S. & KIEHN M.
111
Medicinal plants in La Gamba and in the Esquinas rain forest
Plantas medicinales en La Gamba y de la selva tropical Esquinas
LÄNGER R.
121
Life forms — Formas de vida vegetal
Plant life forms in the Golfo Dulce region and other neotropical rainforests (survey)
Formas de vida vegetal en la región de Golfo Dulce y en otros bosques lluviosos neotropicales (sinopsis)
HIETZ P.
129
Terrestrial litter trappers in the Golfo Dulce region: diversity, architecture and ecology of a poorly
known group of plant specialists
Plantas captadoras de hojarasca en la región de Golfo Dulce: diversidad, arquitectura y ecología de un grupo de
plantas especialistas poco conocido
WEISSENHOFER A., HUBER W., WANEK W. & WEBER A.
143
Ecophysiology — Ecofisiología
Primary production and nutrient cycling in lowland rainforests of the Golfo Dulce region
Producción primaria y ciclo de nutrientes en bosques lluviosos de tierras bajas de la región de Golfo Dulce
WANEK W., DRAGE S., HINKO N., HOFHANSL F., PÖLZ E.-M., RATZER A. & RICHTER A.
155
Fungi and lichens — Hongos y líquenes
Diversity and ecology of fungi in the Golfo Dulce region (survey)
Diversidad y ecología de hongos en la región del Golfo Dulce (sinopsis)
PIEPENBRING M. & RUIZ-BOYER A.
179
The lichens of the Golfo Dulce region (survey)
Líquenes de la región de Golfo Dulce (sinopsis)
BREUSS O.
193
ANIMAL BIOLOGY — BIOLOGÍA DE ANIMALES
Spiders — Arañas
Cupiennius (Araneae, Ctenidae): Biology and sensory ecology of a model Spider
Cupiennius (Araneae, Ctenidae): Biología y ecología sensorica de una araña modelo
BARTH F.G.
211
Key to the genus Cupiennius (Araneae, Ctenidae)
Clave de determinación de genus Cupiennius (Araneae, Ctenidae)
BARTH F.G. & CORDES D.
225
Insects — Insectos
Diversity, biogeography and ecology of insects in the Pacific lowlands of Costa Rica,
with emphasis on La Gamba (survey)
Diversidad, biogeografía y ecología de los insectos en las tierras bajas
del Pacífico de Costa Rica con énfasis en La Gamba (sinopsis)
SCHULZE C.H.
229
Banderillas: Effects of deforestation on dragonflies (Insecta, Odonata) in the Pacific lowland of
Costa Rica
Banderillas: Efectos de la deforestación sobre libélulas (Insecta, Odonata) en la tierra baja Pacífica en Costa Rica
HOFHANSL F.P. & SCHNEEWEIHS S.
237
Longhorn beetles (Coleoptera, Cerambycidae) of the Golfo Dulce region, Costa Rica
Cerambícidos (Coleoptera, Cerambycidae) de la región de Golfo Dulce, Costa Rica
HUBWEBER L.
249
Diversity of Euglossini (Hymenoptera, Apidae) in primary and secondary lowland rainforests
in south-western Costa Rica
Diversidad de Euglossini (Hymenoptera, Apidae) en bosques lluviosos de tierras
bajas primarios y secundarios en el sudoeste de Costa Rica
GRUBER M.H., MORAWETZ L. & WIEMERS M.
257
Stingless bees of the Golfo Dulce region, Costa Rica (Hymenoptera, Apidae, Apinae, Meliponini)
Las abejas sin aguijón de la región de Golfo Dulce, Costa Rica (Hymenoptera, Apidae, Apinae, Meliponini)
JARAU S. & BARTH F.G.
267
Butterfly diversity of the Piedras Blancas National Park and its vicinity –
a preliminary assessment (Lepidoptera: Papilionidae & Hesperioidea)
Diversidad de mariposas del Parque Nacional Piedras Blancas y zonas cercanas –
una evaluación preliminar (Lepidoptera: Papilionidae & Hesperioidea)
WIEMERS M. & FIEDLER K.
277
Feeding behaviours of neotropical butterflies (Lepidoptera, Papilionoidea)
Ingestión de alimentos en mariposas neotropicales (Lepidóptera, Papilionoidea)
KRENN H.W.
295
Amphibians and reptiles — Anfibios y reptiles
The amphibians and reptiles of the Golfo Dulce region (survey)
Los anfibios y reptiles de la región del Golfo Dulce (sinopsis)
HÖBEL G.
305
Plasticity and geographic variation in the reproductive ecology of gladiator frogs,
particularly Hypsiboas rosenbergi
Plasticidad y variación geográfica en la ecología reproductiva de ranas gladiadoras, especialmente Hypsiboas rosenbergi
HÖBEL G.
329
Reproductive behaviour of the glass frog Hyalinobatrachium valerioi
(Anura: Centrolenidae) at the tropical stream Quebrada Negra (La Gamba, Costa Rica)
Comportamiento reproductivo de la rana de cristal Hyalinobatrachium valerioi (Anura: Centrolenidae)
en el arroyo tropical Quebrada Negra (La Gamba, Costa Rica)
VOCKENHUBER E.A., HÖDL W. & KARPFEN U.
335
Birds — Aves
Birds of La Gamba – a call for research and scientific collaboration
Aves de La Gamba – un llamado para investigación y colaboración científica
AUBRECHT G. & SCHULZE C.H.
349
The birds of La Gamba (survey)
Los pajaros de La Gamba (sinopsis)
TEBB G.
353
Habia atrimaxillaris (Dwight & Griscom) 1924 – the black-cheeked ant-tanager.
History of an endemic bird species from SW Costa Rica, from discovery to endangered status
Habia atrimaxillaris (Dwight & Griscom) 1924 – tangara hormiguera cabecinegra.
Historia de una especie de ave endémica del Sudoeste de Costa Rica – desde su descubrimiento a su estatus de peligro
AUBRECHT G.
381
Bird assemblages of forested and human-modified countryside habitats
in the Pacific lowlands of southern Costa Rica
Grupos de aves de hábitat boscosos y rurales en las tierras bajas del Pacífico del sur de Costa Rica
SCHULZE C.H. & RIEDL I.
395
Mammals — Mamíferos
Mammals of the Piedras Blancas National Park, Costa Rica: species composition, habitat associations
and efficiency of research methods – a preliminary overview (survey)
Mamíferos del Parque Nacional Piedras Blancas, Costa Rica: composición de especies, asociaciones de hábitat
y eficiencia de métodos de investigación – una panorámica preliminar (sinopsis)
LANDMANN A., WALDER C., VORAUER A. & EMSER T.
409
Bats of the La Gamba region, Esquinas rain forest, Costa Rica: species diversity, guild structure
and niche segregation
Murciélagos de la región de La Gamba, bosque lluvioso Esquinas, Costa Rica:
diversidad específica, estructura gremial y segregación de nichos
LANDMANN A., WALDER C., VORAUER A., BOHN S. & WEINBEER M.
423
Limnology — Limnología
The river network of the Piedras Blancas National Park, Costa Rica (survey)
La red fluvial del Parque Nacional Piedras Blancas, Costa Rica (sinopsis)
TSCHELAUT J., PICHLER C., WEISSENHOFER A. & SCHIEMER F.
441
Macroinvertebrates and leaf litter decomposition in a neotropical lowland stream,
Quebrada Negra, Costa Rica
Macroinvertebrados y descomposición de residuos de hojas en un curso de agua de tierras bajas neotropical,
Quebrada Negra, Costa Rica
TSCHELAUT J., WEISSENHOFER A. & SCHIEMER F.
457
The role of leaf anatomy and tannins in litter decay in a tropical stream
El rol de la anatomia foliar y de los tanninos en la descomposición de la hojarasca en un arroyo tropical
RIEMERTH A. GUSENLEITNER M. & SCHIEMER F.
467
Freshwater bryozoans in La Gamba (Costa Rica: Piedras Blancas National Park): a general
introduction
Briozoos de agua dulce en La Gamba (Costa Rica: Parque Nacional Piedras Blancas): una introducción
WÖSS E.R.
485
Ecology of fishes of Quebrada Negra, Costa Rica, a first order neotropical lowland stream
Ecología de los peces de Quebrada Negra, Costa Rica, río neotropical de primer orden de tierras bajas
PICHLER C. & SCHIEMER F.
495
PLANT-ANIMAL INTERACTIONS — INTERACCIÓNES DE PLANTAS Y ANIMALES
Pollination — Polinización
Pollination in the plants of the Golfo Dulce area (survey)
Polinización en las plantas del área de Golfo Dulce (sinopsis)
WEBER A.
509
Phenology and pollination of Ceiba pentandra (Bombacaceae) in the wet forest
of south-eastern Costa Rica
Fenología y biología de la polinización de Ceiba pentandra (Bombacaceae) en el bosque húmedo
del sudeste de Costa Rica
ROJAS-SANDOVAL J., BUDDE K., FERNÁNDEZ M., CHACÓN E., QUESADA M. & LOBO J.A.
539
Phenology of tree species of the Osa Peninsula and Golfo Dulce region, Costa Rica
Fenología de especies de árboles de la Península de Osa y la región de Golfo Dulce, Costa Rica
LOBO J., AGUILAR R., CHACÓN E. & FUCHS E.
547
Style release experiments in four species of Marantaceae from the Golfo Dulce area, Costa Rica
Experimentos acerca de la sensibilidad del estilo en cuatro especies de marantáceas del área del Golfo Dulce, Costa Rica
CLASSEN-BOCKHOFF R. & HELLER A.
557
Notes on the pollination of the perfume flowers of Gloxinia perennis (Gesneriaceae)
by euglossine bees
Notas sobre la polinización de las flores perfumadas de Gloxinia perennis (Gesneriaceae) por abejas euglossine
WITSCHNIG G., HICKL C. & WEBER A.
573
Scientific work of Austrian students in the “Austrian rainforest”
(Piedras Blancas National Park, Costa Rica), with special regard to pollination studies
Trabajo científico de los estudiantes en el “Bosque lluvioso de los Austriacos”
(Parque Nacional Piedras Blancas, Costa Rica), con especial consideración en los estudios de polinización
WEBER A.
579
Ants and plants — Hormigas y plantas
A house in the tropics: full pension for ants in Piper plants
Una casa en el tropico: pensión completa para hormigas en plantas de Piper
FISCHER R. & MAYER V.
589
Does nectar production reduce herbivore pressure on Passiflora species (Passifloraceae)
in a tropical rainforest in Costa Rica?
Puede la producción de néctar reducir la presión de herbivoría en especies de Passiflora (Passifloraceae)
en un bosque tropical de Costa Rica?
THURNER M. & MAYER V.
599
HUMAN ASPECTS — ASPECTOS HUMANOS
History and development — Historia y desarrollo
Indigenous societies of the south east of Costa Rica, 15th century
Sociedades indígenas del sudeste de Costa Rica, siglo XVI
BARRANTES CARTÍN C.
609
The stone balls of Palmar
Las esferas de piedra de Palmar
STEPHENS C.
8
631
Impacts of the United Fruit Company in Southwest Costa Rica
Impacto de la United Fruit Company en el Suroeste de Costa Rica
STEPHENS C.
635
Corcovado National Park – almost a banana plantation
El Parque Nacional Corcovado – casi una plantación bananera
STEPHENS C.
645
Case study: economic and structural settlement changes and their consequences in the
community of La Gamba, Golfo Dulce region
Estudio de caso: Cambios estructurales y económicos de la población y sus consecuencias en la
comunidad La Gamba, región del Golfo Dulce
KLINGLER M.
649
History of nature exploration — Historia de exploracíon de la naturaleza
Un ejemplo de intercambio científico entre Europa y América Latina: las investigaciónes
de la expedición científica Austríaca en Costa Rica (1930)
An example of scientific interchange between Europe and Latin America: The investigations of the
Austrian scientific expedition to Costa Rica (1930)
DÍAZ BOLAÑOS R.E.
657
Otto Porsch and the scientific goals and results of the Austrian Costa Rica expedition 1930
Otto Porsch y los objetivos y resultados científicos de la expedición Austriaco-Costarricense de 1930
WEBER A.
667
History of nature conservation — Historia de protección de la naturaleza
Before Corcovado: Early conservation initiatives on the Osa Peninsula (survey)
Antes del Corcovado: Primeras iniciativas pro-conservación en la Peninsula de Osa (sinopsis)
CHRISTEN C.A.
675
Looking back to the foundation of the Corcovado National Park,
a crown jewel of nature in Costa Rica
Una mirada retrospectiva a la fundación del Parque Nacional Corcovado,
una corona de joyas de la naturaleza en Costa Rica
UGALDE A.
683
In defence of local livelihoods, the forest and the Golfo Dulce: the campaign against
”Ston Forestal” in the 1990s and its historical roots
En defens de los medios de vida locales, el bosque y el Golfo Dulce: la campaña contra
Ston Forestal en los 1990 y sus raíces históricas
VAN DEN
HOMBERGH H.
693
Current conservation projects — Projectos actuales de protección de la naturaleza
The Osa biological corridor in the context of the mesoamerican biological corridor
El corredor biológico Osa en el contexto del corredor biológico mesoamericano
GARCÍA R.
701
9
Conectividad entre el Parque Nacional Piedras Blancas y la Fila de Cal
The link between the Piedras Blancas National Park and the Fila de Cal
MORERA C. & ROMERO M.
707
The Biological Corridor Project in the Piedras Blancas National Park, Costa Rica.
A project to preserve the biodiversity by reforestation and alternative culture, with support
of the community La Gamba by new marketing strategies
El proyecto de corredor biológico en el Parque Nacional Piedras Blancas, Costa Rica.
Un proyecto para preservar la biodiversidad mediante la reforestación y cultivos alternativos, con el apoyo
de la comunidad de la Gamba de nuevas estrategias de comercialización
WEISSENHOFER A., BARQUERO M., HUBER W., MAYER V. & NÁJERA UMAÑA J.
715
Reintroducción de la Lapa Roja (Ara macao) en Playa San Josecito, Golfito
Reintroduction of the scarlet macaw (Ara macao) to Playa San Josecito, Golfito
VARELA BENAVIDES I. & JANIK D.
725
The project “Rainforest of the Austrians”
El proyecto “Bosque de los Austriacos”
SCHNITZLER M.
733
The “Tropical Research Station La Gamba” –
science, education and nature conservation in Costa Rica
La “Estación Tropical La Gamba” – sciencia, educación y conservación en Costa Rica
ALBERT R. & WEBER A.
739
Ecotourism and local development — Ecoturismo y desarrollo local
Ecotourism in La Gamba. An economical and ecological alternative for the residents of La Gamba?
Ecoturismo en La Gamba. Una alternativa económica y ecológica para los residentes de La Gamba?
FAHRNBERGER M.
743
Sinergias entre ecoturismo y desarrollo local en la península de Osa, Costa Rica
Synergistic effects of ecotourism and local development on the Osa Peninsula, Costa Rica
MORERA C.
755
APPENDIX — APÉNDICE
Authors’ addresses
Direcciónes de los autores
Vegetation map of the Piedras Blancas Nationalpark, Golfito Forest Reserve and adjacent areas
Mapa de vegetación del Parque Nacional Piedras Blancas, Reserva Forestal Golfito y áreas adyacentes
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