Community ecology and species-environment relationships
Tropical rain forests are fascinating environments, renowned for their high species diversity. However, relatively little is known about how plant and animal communities vary in these forests over space and in time, and how compositional changes relate to environmental variation. Because obtaining representative data on all species over large and partly inaccessible areas is a practical impossibility, our ecological studies in the neotropical lowlands mostly focus on two plant groups (pteridophytes and the Melastomataceae), and one animal group (parasitoid wasps, Ichneumonidae). We have collectively spent a lot of time in the field and have collected plant specimens and ancillary environmental data from several hundred standardized inventory transects. The insect samples have been collected by Malaise trapping and canopy fogging from different heights within the rainforest vegetation. On the basis of these large datasets, we are studying the distributions of individual species and the patterns of spatial turnover in community composition, and how they relate to current environmental conditions (such as soils and climate) and the geological history of the area. Variation in floristic composition has also been found to correlate with variation in other taxa, such as mammals. The early focus of the team’s work in the 1980’s and ‘90s was on the western Amazonian lowlands, but in recent years our research has extended to parts of Brazil and Central America. We also carry out research on tropical treeline ecology in the Andes, aiming to understand how climate and human activities have shaped the Andean mountain forest distribution in the past and what is the likely future of these forests, and on epiphytic diversity and their functional importance in tropical mountain cloud forests.
Practical tools for vegetation classification and mapping
Many land use decisions in Amazonian rain forests, including conservation planning, are currently made without reliable information on which species or forest types actually occur where. Accumulating such knowledge has been hampered by difficulties in identifying species and by non-standardized field methods. We develop methods that help to overcome these problems. Pteridophytes and the Melastomataceae have been tested and found useful as indicators of specific environmental conditions and of more general floristic patterns. We are working on illustrated online identification keys to facilitate their use for this purpose. A first version of a key to identify ferns of central Amazonia is available here
. We also work with satellite images and other remotely sensed data to evaluate how best to extrapolate field results to uninventoried areas.
Field work in the tropics often leads to the discovery of new species, and these species need to be described and classified. As the number of described species increases, it also becomes necessary to critically revise their classification and to sort out problems with duplicate or invalid species names. Our team includes both dedicated systematists and such ecologists who started to do taxonomy because internal species tags (such as Miconia sp42) are useless when species-specific ecological results need to be communicated to a wider audience. Organisms that are a focus of our current taxonomical research include parasitoid wasps (Hymenoptera: Ichneumonidae), ferns (especially Marattiaceae and Lindsaeaceae), the shrub family Melastomataceae (especially Adelobotrys), sword plants (Echinodorus, Alismataceae) and wood-rotting Basidiomycetes fungi.
Reconstructing evolutionary history
One of the intriguing questions about the tropical rain forests is how and why all those species originated. We hope to shed light on this question by combining information on present-day geographical and environmental distributions of species with reconstructions of their phylogenetic relationships and of the geological and climatic history of the continent. Our evolutionary studies focus on butterflies (Nymphalidae), ferns (especially Lindsaeaceae and Polybotrya) and the Melastomataceae (Adelobotrys). For example, South America, and particularly the Amazonian lowlands close to the foothills of the Andes mountains, appears to have been an important area for the diversification of the family Nymphalidae.
Geology of the Amazonian lowlands: Neogene to Quaternary palaeoenvironmental and climatic history
As regards Amazonian geology and physical geography, major research activities took place in the 1980s and 1990s on the dynamic processes of the river floodplains and deformation of the Andean foreland and their implications for the biogeography and landscape ecology of the area. These studies still continue yet with minor intensity. Over the last decade, the major focus has been on the Miocene palaeoenvironmental history of western Amazonia.
Ecosystem ecology and carbon dynamics of Amazonian peatlands
We have documented relatively thick peat deposits, whose existence was almost unknown until recently, from western Amazonian floodplains. These deposits have accumulated at very high rates, and thereby have acted as a large carbon sink. We continue to study the thickness, geographical extent and distribution, and carbon sink function of these peatlands, as well as their potential future role as a carbon source under climate change induced drought and changing land-use in Amazonia.
Use, management and conservation of Amazonian rainforests - integrating natural and social sciences
The future of the tropical rain forests is crucially dependent on management decisions taken by a variety of actors, so both socio-economic and political processes need to be understood. Consequently, our multidisciplinary research team also considers the social and political aspects of the use, management and conservation of Amazonian rainforests. Our interests include conservation and land-use planning, regional development, the role of different types of knowledge in natural resource and biodiversity management, biodiversity in social media, as well as environmental information networks. Social and natural sciences are combined, for example, in studies of land use dynamics, hunting, fishing, land entitlement through forestry concessions, and conservation through tourism (with a focus on bird-watching tourism in Peru).
Over the years, team members have been scratching their heads about a wide variety of methodological problems when trying to answer the questions described in the previous topics. Often these have been related to the quality of the data or of their interpretation. For example, we have identified artifactual gradients in reflectance values in Landsat TM imagery, compared different methods for reconstructing phylogenies, discussed how beta diversity can be analysed, and reviewed what different meanings have actually been given to the term "beta diversity".
Members of the Amazon team have many collaboration contacts with colleagues abroad. Currently we run a joint project with the geologists and remote sensing specialists of the Brazilian National Institute for Space Research (INPE - São José dos Campos, SP) in an attempt to understand regional to local scale aspects of the Amazon basin. The project webpage can be accessed here.