How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


Effects of Fungi on Biodiversity
References
Read, D.  1998.  Plants on the web.  Nature 396: 22-23.

van der Heijden, M.G.A., Klironomos, J.N., Ursic, M., Moutoglis, P., Streitwolf-Engel, R., Boller, T., Wiemken, A. and Sanders, I.R.  1998.  Mycorrhizal fungal diversity determines plant biodiversity, ecosystem variability and productivity.  Nature 396: 69-72.

What was done
Read (1998) summarized the work of two studies performed by van der Heijden et al. (1998) that investigated the effects of arbuscular mycorrhizal fungi (AMF) diversity on plant productivity and biodiversity in two different artificial ecosystems representative of a European calcareous grassland and a North American abandoned successional field.  In both cases, different numbers of AMF species were added to experimental micro- or macrocosms, which were maintained for one or two growing seasons before final plant material was harvested and analyzed.

What was learned
The experimental results indicated that the biomass production of different plant species varied with the presence of different single species of AMF.  Hence, as greater numbers of different AMF species were added to the artificial ecosystems, they positively impacted the biomass production of more and more plants.  Consequently, both above- and belowground ecosystem biomass increased with increasing numbers of AMF species within the ecosystems.  This effect may have been due, in part, to the observation that plant phosphorus content rose with increasing variety of AMF taxa.  In addition, plant biodiversity was positively correlated with the number of different AMF species: it was approximately 60% greater for ecosystems containing fourteen AMF species than for ecosystems containing only four such species.

What it means
As the CO2 content of the air steadily rises, most plants will experience increased carbohydrate production, a portion of which can be exuded into the soil to stimulate the formation and maintenance of symbiotic relationships with AMF.  This increased flux of carbon into the soil will likely increase the activities of such fungi, including those that make soil nutrients, like phosphorus, more readily available to plants.  In addition, with increased carbohydrate exudation into the soil, greater numbers of AMF can be supported in the plant root zone; and this phenomenon should help to maintain, or possibly increase, plant biodiversity, if the AMF are of different species.  Consequently, the increasing concentration of atmospheric CO2 may well enhance plant biodiversity in earth's many natural ecosystems.

Reviewed 1 December 1998