If you are interested in initiating such a collaborative research effort and experiencing the stimulating atmosphere of international research at IIASA, please contact us at eep@iiasa.ac.at.

In this context, particularly attractive opportunities are offered via IIASA's Young Scientist Summer Program (YSSP). Each year, the program allows an international selection of about 50 students and young scientists to participate in the Institute's research programs for a period of three months from June to August.

For previous years please visit our Webarchive

2012

Detailed description of all projects (PDF)

Project: Modeling soil microbial dynamics in carbon and nitrogen cycling
Name: Sarah Evans
Affiliation: Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, USA

The cycling of carbon and nitrogen in soils is controlled by microorganisms. How such microbial communities respond to novel climates regimes in the future will thus affect carbon and nitrogen fluxes, which in turn can change greenhouse-gas fluxes, soil fertilities, and other aspects of ecosystem functioning. Current models are limited in accurately predicting biogeochemical pulses during large rainfall events after droughts. As future climate regimes are expected to be characterized by an increased frequency of droughts and floods, overcoming this limitation, by better understanding the underlying microbial mechanisms, is important for predicting future ecosystem dynamics. Specifically, sudden changes in soil moisture resulting from droughts and floods induce moisture stress on microorganisms, which is bound to influence the distribution of microbial functional groups and traits. Changes in soil moisture also affect physical processes, like the diffusion of substrate, enzymes, and microbial cells, which must be in contact for microbial metabolism and many gas fluxes to proceed. Methodological challenges hinder investigating these mechanisms experimentally, leaving much unexplained variability in current biogeochemical models. In this project, we use an individual-based model of soil microbial communities developed at IIASA to examine how droughts and floods affect enzyme activity and the distribution of microbial traits, and how changes in these factors affect carbon and nitrogen cycling at larger scales. This work will inform efforts to more accurately predict biogeochemical fluxes under future rainfall regimes, as well as improve our understanding of the role of soil microorganisms in larger-scale ecosystem dynamics. Details

Project: A management model for Alpine fish populations under temperature stress
Name: Harald Ficker
Affiliation: Institute for Limnology of the Austrian Academy of Sciences, Mondsee, Austria

The last century has seen an overexploitation of many economically relevant fishes in marine and freshwater habitats, leading to dwindling catches and the collapse of many stocks. Management practices involving juvenile stocking or fishing restrictions based on size classes and bag limits have not always been successful in restoring populations. One reason is that, mostly due to life-history variability in highly abundant early life stages, interannual population fluctuations are often pronounced. Another reason is that life-history dynamics are affected by harvesting and that harvesting, in turn, is affected by life-history dynamics. It is necessary to account for these two complicating factors when assessing the ultimate effects of management interventions. In this project, we do so using a model based on stochastic population projection matrices calibrated with empirical catch data for a whitefish population (coregonids) in Lake Irrsee, Austria. We consider populations with stable, as well as with non-equilibrium, demographic distributions. Since life-history rates and their fluctuations depend on water temperature, which is currently slowly increasing in Alpine lakes, we will use this model to investigate the joint impacts of climate change, management, and harvesting on Alpine fish populations. Details

Project: Effects of climate-induced changes in river flows on temperate seabass
Name: Taiki Fuji
Affiliation: Graduate School of Agriculture, Kyoto University, Japan

Anthropogenic impacts are increasingly altering the native environment of many fishes. Developing sustainable fisheries-management practices that are capable of mitigating the detrimental effects of these changes require a good understanding of the mechanisms driving the dynamics of fish populations and their interactions with the changing environment. Rivers are known to be important in the ecology of coastal marine fishes: first, rivers change coastal water flows and the transport of fish larvae, and second, rivers function as nurseries for juvenile fish. The temperate seabass Lateolabrax japonicus is an important coastal fishery species in Japan, which utilizes both rivers and the sea as nurseries. To predict how this species will be affected by the anticipated degradation of river nurseries and changes in river discharge brought about by human activities, we develop and analyze a model of its population dynamics. It is expected that this study will help elucidate the role of rivers in the population dynamics of estuarine fishes. Details

Project: Curbing corruption in public good games
Name: Joung Hun Lee
Affiliation: Department of Biology, Kyushu University, Fukuoka, Japan

By distorting group-beneficial resource allocation, corruption prevents the efficient governance of public goods. Corruption can be reduced, and public goods can thus be managed successfully, if appropriate systems for monitoring and sanctioning are put in place. The purpose of this project is to analyze which conditions facilitate the curbing of corruption. Using evolutionary game theory, we investigate a scenario in which members of a group are encouraged by an endogenous or exogenous social institution to contribute towards a public good. Each group member decides whether or not to contribute, and if no contribution is made, whether or not to attempt bribing the institution. The institution provides positive and/or negative incentives accordingly, with successful bribes causing non-contributing members to receive the same incentives as contributing members. Bribes are unsuccessful if they are rejected by the institution or if they are detected by other group members or an outside observer. On this basis, we identify conditions under which bribing strategies thrive or perish. We compare governance systems in which the enforcement of contributions is imposed from the outside or is jointly established by the group members, and in which the detection of bribes is operated from the outside or is jointly accomplished by the group members. Based on this analysis, we may consider extensions to multiple groups, multi-part institutions, multi-tier institutions, or dynamic public goods. Details

Project: The evolution of malaria incubation time
Name: Kyeongah Nah
Affiliation: Bolyai Institute, University of Szeged, Hungary

Malaria is one of the most dangerous infectious diseases, responsible for a significant fraction of human deaths in a large part of the world. Yet, past eradication efforts have failed. To design effective eradication campaigns, the infection cycle must be well understood. Malaria’s infectious agents (parasites of one of several species of the genus Plasmodium) are transmitted between mosquitos and humans through mosquito bites: after transmission, symptoms occur only after a certain incubation period. In particular, Plasmodium vivax - the malaria-inducing parasite species most prevalent in temperate zones - remains dormant in the human liver for longer periods than other species, which makes its combatting especially difficult. While incubation periods of P. vivax malaria in Korea show a clearly bimodal distribution, with short-term and long-term incubation periods, the reasons for this bimodality are not known. Using adaptive dynamics theory, we study the evolution of incubation times and investigate the evolutionary constraints guiding the emergence of bimodality. Based on the evolutionary insights gained in this first step, we identify and investigate the simplest suitable transmission model for P.vivax malaria that is in agreement with observed data. Details

Project: Ecosystem vulnerability to species loss
Name: Victoria Veshchinskaya
Affiliation: Department of Optimal Control, Lomonosov Moscow State University, Russia

Species losses have always occurred as a natural phenomenon, but the pace at which species are going extinct has recently accelerated dramatically as a result of human activities. The disappearance of a species can have far-reaching and often unexpected consequences for other species, since changes can propagate throughout ecosystems. The principal aim of this project is to investigate the consequences of species losses in ecosystems. In this project, we develop and analyze a dynamic ecosystem network model, calibrated to a set of real ecosystems, to predict the cascading changes that can follow the extinction of a species. The impacts of such primary species losses are measured in terms of secondary species losses and biomass changes. Fundamental descriptors of ecosystem structure (such as the number of coexisting species, their connectivity, the ecosystem’s maximum tropic level) are assessed for their capacity to predict indicators of ecosystem vulnerability to species loss (such as the average number of species losses, the average biomass loss or gain, the average time to extinction). Particular emphasis is given to the relationship between an ecosystem’s structural complexity and vulnerability. It is anticipated that the results will be useful for ecosystem management and will contribute to community ecology’s long-standing complexity-stability debate. Details

2011

Detailed description of all projects (PDF)

Project: Effects of temperature and precipitation on vegetation structure
Name: Gustavo Burin Ferreira
Affiliation: Department of Botany, University of São Paulo, Brazil

With human activities altering the Earth’s natural environments at an accelerating rate, it is important to understand how Earth’s living organisms will respond to the ensuing environmental changes. Plant species might be particularly susceptible to environmental changes as they lack the option of migrating to environments to which they are best adapted. Studies of non-perennial traits, such as leaves, phenological characters, and physiological rates have helped to reveal how the Earth’s vegetation is responding to the most recent changes in climatic conditions. However, it is difficult to extrapolate future climatic impacts from present responses, and it is also challenging to disentangle responses caused by anthropogenic climatic changes from those that would be occurring also under natural conditions. To address these questions, a longer record of how vegetation has changed in response to climatic conditions is needed: such a long-term record can be obtained by studying tree rings, and dendrochronology (from the Greek dendron = tree, chronos = time, and logos = knowledge) is a well-established science that can be used to infer growth rates under different environmental conditions. Guided by dendrochronological data for two tree species in Brazil, I will aim to incorporate temperature- and precipitation-dependence in an established model of plant growth developed by a former YSSP participant (Falster et al. 2010). The model will then be used to study how salient aggregate properties of vegetation, such as net primary productivity and total biomass, are expected to be affected by future changes in temperature and precipitation. Details

Project: Comparing methods for identifying optimal forest management
Name: Mario Cammarano
Affiliation: Institute of Agro-Environmental and Forest Biology, Rome, Italy

The past few decades have seen a considerable increase in the number and level of detail of individual-based models (IBMs) of forest dynamics. These models forecast dynamics by predicting each individual’s birth, dispersal, reproduction, and death and how these events are affected by spatial competition for resources with neighbors. Individual-based forest simulators have also been used for forest management. Despite their usefulness, IBMs have one important disadvantage: they require too much computational resources to be used at a large scale. For this reason, a number of approaches has recently been developed based on differential equations, rather than on more complex algorithms. A notable advance in this area has been the development of the perfect-plasticity approximation (PPA; Strigul et al. 2008), which builds on the assumption that trees experience full light above the canopy height, defined as the maximum height at which the canopy can be closed, and reduced light below the canopy height. In turn, this height is a dynamic quantity, which depends on demographic parameters. The PPA is a promising tool for understanding forest dynamics. Until now, however, it has been developed and studied only for natural forests. In this project, we will explore its validity for describing managed forests under different types of harvesting. This will be done in three steps. First, we will develop a spatially explicit IBM of forest dynamics that accounts for crown plasticity and management. Second, we will derive a PPA corresponding to this IBM. Finally, we will compare and critically evaluate the results of these two approaches. Details

Project: Biodiversity dynamics under intransitive competition and habitat destruction
Name: Matthew J. Labrum
Affiliation: Department of Mathematics, Washington State University, Pullman, USA

As world population increases, anthropogenic habitat destruction becomes more prevalent and poses an increasing threat to biodiversity. To identify species at risk of extinction, it is important to understand the interplay between species interactions and habitat destruction. While recent modeling efforts have made great strides towards understanding the principal factors causing the extinction of species in response to habitat destruction, a common simplifying assumption made in these models is a hierarchical ranking of competitive abilities among the species occupying a focal habitat. Empirical studies, however, have suggested that this assumption is not always valid. I therefore aim to investigate the ecological consequences of incorporating intransitive competition in a habitat-destruction model. As previous studies have shown that spatial scales affect the outcomes of intransitive competition, both spatial and non-spatial models will be analyzed. Model outcomes will be contrasted with those resulting for a perfect hierarchical ranking of competitive abilities among species. Of particular interest is the extent to which intransitivity in competitive interactions affects biodiversity dynamics and extinction risks, and how the frequency and spatial extent of habitat destruction alter these results. Details

Project: Indirect reciprocity with costly information
Name: Mitsuhiro Nakamura
Affiliation: Department of Mathematical Informatics, University of Tokyo, Japan

Humans are reciprocal animals cooperating with each other even though such behavior is costly. Indirect reciprocity is a mechanism for sustaining cooperation when individuals rarely interact with the same partners; such situations are increasingly ubiquitous in human societies (e.g., anonymous encounters in online marketplaces). For indirect reciprocity, reputation plays a key role: individuals help others with a good reputation, but not those with a bad reputation. Sharing information about reputations is therefore crucial for indirect reciprocity. In practice, however, it often seems costly to share information about the reputation of individuals. For example, while Amazon.com adopts a feedback mechanism to assess each seller, customers often do not submit such feedback because for them this involves extra work. More in general, collecting, sharing, and maintaining information is costly, so the availability and quality of information may suffer from a tragedy of the commons. Individuals, or a marketplace as a whole, may try to address these challenges by charging fees before allowing individuals to access reputation information, which can lead to the emergence of a reputation market operating alongside the dynamics of indirect reciprocity. During the YSSP, I will study cooperation dynamics under indirect reciprocity based on costly reputation information. I will identify the conditions that sustain cooperation and examine the following specific aspects. (1) Individuals may exchange reputation information either through pairwise interactions or through a centralized institution, so I will examine which mode is more efficient. (2) I will study competition among information providers and clarify conditions for the emergence of hubs among them. (3) I will study how conditions for cooperation change when erroneous reputation information can spread via gossip, or when information sellers have an incentive to cheat information buyers by providing them with inaccurate or false information. Details

Project: Biodiversity dynamics in stream communities
Name: Tuyen Van Nguyen
Affiliation: Department of Mathematics & Department of Biology, Pusan National University, Republic of Korea

The rapid development in Asian countries has led to unprecedented economic growth, but endangered the stability of ecosystems. Aquatic ecosystems, in particular, are very vulnerable to certain anthropogenic disturbances, like pollution from industrial plants, which threatens their ability to provide food and clean water. Benthic macroinvertebrates and aquatic insects are regarded as one of the most suitable ecological indicators for water quality and play a fundamental functional role in aquatic food webs. In this project, I will analyze the response of benthic macroinvertebrate communities to disturbances using an individual-based eco-evolutionary model that describes essential life events (birth, death, movement, drifting, and adult flight), includes the effects of competition within the community, and enables local adaptation to, or tolerance for, extrinsic environmental factors (e.g., oxygen, temperature, pollution). I expect that my results will contribute to the prediction of community compositions in response to disturbances and thus facilitate the establishment of efficient assessment methods and management plans for aquatic ecosystems. Details

Project: Financial-market stability in the presence of heterogeneous adaptive agents
Name: Ziqiang Wu
Affiliation: College of Management and Economics, Tianjin University, China

Financial markets provide an efficient way to trade assets of various kinds. Asset prices determine investor decisions and depend on them in turn, leading to complex dynamics that are prone to drastic fluctuations in both asset price and investor wealth; an issue that, although not new, has recently attracted a lot of public attention. Investors themselves are intrinsically heterogeneous and adaptive with respect to their decision-making strategies, and while the market may reward “following the herd” for a while, any strategy is ultimately bound to fail when it is universally adopted. I will analyze the interplay between investor types and financial-market dynamics by studying a modified version of the agent-based Santa Fe Institute artificial stock market model, augmented to allow for the emergence of different investor personalities and to include a mechanism for social learning. I will study the emerging investor-type patterns, and try to draw qualitative conclusions about conditions that promote, or threaten, the stability of financial markets. Details

Last edited: 04 October 2012