Spatial processes in communities

Patterns and dynamics of boreal forests - Markus Eichhorn

Markus Eichhorn studies the processes that determine the structure and composition of forests. This includes work on scales from individual trees through to whole regions. Individual trees form patterns within forests that vary between the species involved, in different locations and through time. Permanent plots established in the Bystrya Valley of Kamchatka in 1998 are providing data on the structure and dynamics of forests in this region.

Right: Fieldwork in Kamchatka, Far East Russia. The approach to Anaun volcano marks the northern limit of continuous forest on the peninsula. Photo: Valentin Vassilyevich Yakubov.

On a larger scale, the next step is to understand how regional processes determine the composition of local communities of trees, and the various herbs and shrubs that grow beneath them. An analysis of forest communities across Alaska is currently underway.

Competition, coexistence and the maintenance of diversity - Tom Reader

The principal of competitive exclusion (Hardin, 1960) predicts that two species competing for a single limiting resource cannot coexist indefinitely. So the diverse communities of invertebrates that we find exploiting some kinds of resource present us with a problem: how is diversity maintained in the face of intense interspecific competition? Tom Reader is interested in exploring answers to this question in a number of systems, and particularly in the effects of spatial aggregation, resource heterogeneity and predation on diversity.

Above right: Eggs of Lipara lucens (white) and L. rufitarsis (black) are laid on reed stems; intense competition for food means that only one can survive per stem.

The flies in the genus Lipara feed on common reed (Phragmites australis). Several species compete strongly for the same reed stems in wetlands throughout eastern England. Modelling work done in collaboration with Pej Rohani and Stephen Cornell shows that three mechanisms help maintain diversity in this little community: intraspecific aggregation of eggs, resource partitioning at the larval stage, and kleptoparasitism of the superior competitors by the weaker species. Find out more in the following references:

Reader T, Cornell SJ, Rohani P, (2006). Aggregation, intraguild interactions and the coexistence of competitors on small ephemeral patches. Oikos, 115: 321-333. PDF This is a preprint of an Article accepted for publication in Oikos 2006 Blackwell Publishing.

Reader T, (2003). Strong interactions between species of phytophagous fly: a case of intraguild kleptoparasitism. Oikos 103:101-112. PDF This is an electronic version of an Article published in Oikos.

Transmission of malaria and dengue in Thailand - Markus Eichhorn

Malaria and dengue fever are mosquito-borne diseases with immense public health implications for the countries that harbour them. The RISKMODEL project (Predicting the RISKs of MOsquito-borne DisEases from Land use change) is an attempt to provide an integrated model to describe the transmission and epidemiology of these diseases in northern Thailand.

As a member of the project, Markus Eichhorn is investigating the influence of local land-use, detected using remote-sensing techniques, on the abundance and community composition of mosquito vectors collected in ground surveys. Of particular interest are the effects of forests, which are diminishing in extent and becoming increasingly fragmented within the region, and orchards, which are replacing subsistence agriculture as the dominant agricultural practice in many villages.

More information about the broad aims and scope of the project can be found here.

RISKMODEL is funded by the EU under the Quality of Life and Management of Living Resources Programme.

Above right: An example satellite image of one of the study villages. The purple patches indicate orchards, which are expanding in the region, while the green patches represent forests. Figure prepared by Sophie Vanwambeke.

A useful reference: 

Vanwambeke S.O., Lambin E.F., Eichhorn M.P., Flasse S. P., Harbach R.E., Oskam L., Somboon P., van Beers S., van Benthem B.H.B., Walton C. and Butlin R.K. (2007). Impact of land-use change on dengue and malaria in Northern Thailand. Ecohealth 4, 37-51.