Forest Ecology - Markus Eichhorn

Herbivory of tropical rain forest tree seedlings

One of the great mysteries of ecology is how so many species are maintained in tropical rain forests. More tree species can be found in a single hectare of rain forest in Borneo than in the whole of Europe or North America. How can so many species co-exist? The answer is not simple, and is likely to be found in the complex web of interactions between tree species and their environment.

The BITRF (Biological Interactions in Tropical Rain Forests) project was established to investigate the influences of many factors on the growth and survival of trees seedlings in Sabah, Malaysia. These included the influence of soil conditions, light availability, pathogens, herbivores and mycorrhizae. The seedling stage is thought to be the crucial phase in structuring rain forests, as a large number of species compete to fill gaps in the canopy, of which usually only one will survive to become a reproductive adult tree.

Right: What determines which of these seedlings will fill the gap in the canopy above? Photo: Jake Snaddon
 
Within this project, Markus Eichhorn is investigating the interactions between tree seedlings and their insect herbivores. This includes the effects that herbivores have upon the seedlings, in terms of their rates of damage, growth and survival, but also how characteristics of the seedlings such as their defences (chemical and mechanical) and nutritional value influence the communities of insect herbivores and their feeding.

Results have indicated that rates of herbivory vary little within tree species, regardless of where they grow, but can differ widely between species. Levels of defensive chemicals seem to be the main determinants of herbivory rate rather than leaf toughness or nutritional content. Contrary to the traditional view of complex insect herbivore assemblages in tropical rain forests, it would appear that the majority of damage is caused by a limited number of generalist herbivores in this system.

Project website (somewhat out of date)

BITRF was funded by the British Ecological Society

Some useful references:

Eichhorn M.P., Fagan K.C, Dent D.H., Compton S.G. and Hartley S.E. (2007). Explaining leaf herbivory rates on tree seedlings in a Malaysian rain forest. Biotropica, 39, 416-421.

Eichhorn M.P., Compton S.G. and Hartley S.E. (2006). Seedling species determines rates of leaf herbivory in a Malaysian rain forest. Journal of Tropical Ecology, 22, 513-519.

See also Spatial community ecology.

Agroforestry in Europe

Many systems of farming with trees have existed in Europe for thousands of years, including the dehesas of south-western Spain and Portugal, the olive groves of the Mediterranean and the Streuobst of central Europe. In recent years, an emerging interest in sustainable farming has recognised the benefits of agroforestry in erosion protection, drainage control and diversification of rural incomes, as well as more unexpected features such as improved nutrient use efficiency and a reduced reliance on pesticides. Novel systems are being developed in addition to studies investigating traditional methods. Markus Eichhorn is interested in how ancient systems might inform future agricultural sustainability.

Above right: An experimental agroforestry system at Vézénobres, France. Here rape is grown between rows of poplar. Photo: Christian Dupraz.

Below right: A dehesa landscape in Extremadura, Central Spain (photo: Gerardo Moreno). Evergreen oak trees are scattered across grazing land which is periodically ploughed and cultivated on a regular cycle. More bird species are found within the dehesas than any other habitat in Europe. 

For more information, see the SAFE (Silvoarable Agroforestry For Europe) website.

The SAFE project was funded by the EU under its Quality of Life programme.

A useful reference:

Eichhorn M.P., Paris P., Herzog F., Incoll L.D., Liagre F., Mantzanas K., Mayus M., Moreno G., Papanastasis V.P., Pilbeam D.J., Pisanelli A. and Dupraz C. (2006). Silvoarable systems in Europe – past, present and future prospects. Agroforestry Systems, 67, 29-50.