Abstract

This paper presents an integrated response of abiotic and biotic factors to the acidification process in littoral communities in Swedish forest lakes. In structuring the acidified community three major forces can be recognized. Firstly, abiotic variation, including changed water chemistry and habitat structure, has a strong impact on all trophic levels. Low pH and increased toxicity of metals, especially aluminum, are ultimate causes of the extinction and succession of species during acidification. In the acidified community, the abiotic factors affect both the top-down and bottom-up forces, and changes can be triggered at all trophic levels. The second force structuring the community is a bottom-up effect caused by reduced nutrient cycling and a shift in plant heterogeneity. This shift, mainly resulting from a shift in the CO 2-system of the water and increased water transparency, enhances the biomass of primary producers, e.g. Sphagnum and Juncus, and alters habitat heterogeneity in higher trophic levels. The third force structuring the acid community is atop-down effect; the loss of the fourth link in the food chain (fish) alters the impact on the third trophic level. From being mainly regulated by predation from fish, the heterogeneity of the third level will be regulated by abiotic variation and competition in the acid state. This effect cascades down the food web, and the second trophic level, the herbivores, will now be preyed upon by invertebrates instead of fish.

Published in

AMBIO: A Journal of the Human Environment
1993, Volume: 22, number: 5, pages: 290-297
Publisher: ROYAL SWEDISH ACAD SCIENCES

UKÄ Subject classification

Ecology


Permanent link to this page (URI)

https://res.slu.se/id/publ/87566