Project description
Background
Iceland offers some uniqe oppertunities to study the effect of terrestrial productivity on aquatic ecosystems. Since human settlement in the 9th century AD, ca. 95% of native forests and woodlands have been cleared, which has led to large-scale vegetation change and soil erosion. Therefore there are extensive lowland areas in Iceland where vegetation (and terresrial productivity) is not in equlibrium with the climatic conditions. This offers possibilities to find catchments (watersheds) with large contrast in terrestrial productivity within relatively small and otherwise comparable areas.

Iceland has Europe's youngest geology with the oldest bedrocks only ca. 15 million years old. The island is split in two by the North Atlantic Ridge where frequent volcanic eruptions take place, on average one in every 5 years. Therefore Iceland's bedrocks can be divided into relatively young and porous lava and palagonite in the volcanic active areas that extend through the country from SW to NE, and older, more solid, basaltic bedrock in the less volcanic active areas found in NW and E Iceland. This difference in geology has profound effects on both terrestrial and aquatic ecosystems.

Hence, both the effect of terrestrial production and of geological age of comparable catchments can be studied in Iceland (Figure 1).


Figure 1. Iceland offers possibilities to make studies on both terrestrial and aquatic ecology along a lowland production transect in the same climate and/or along a transect that compares surfaces of different geological age.

Prior work and main research questions
The terrestrial ecologists active within the ForStreams project had been studying the effect of afforestation and revegetation on terrestrial productivity, carbon cycling and terrestrial biodiversity. Their observation was that when eroded areas or partly eroded areas are afforestated (planted by trees) or revegetated (fertilizer only) much organic matter is stored in the volcanic soil, at least for some decates. When making carbon balance for those areas no infromation was available on how much organic matter/carbon was leaving the ecosystem in disolved form (DOM). They therefore wanted to quantify the fluxes between the terrestrial and aquatic parts of the ecosystems they were studying.

The aquatic ecologists had observed that on a regional scale there seemed to be a strong linkage between vegetation cover of river catchments and the aquatic production, length of food webs and population densities of fish (charr, trout and salmon). This might indicate that the large-scale historic vegetation change descriped earler, also had profound impacts on aquatic ecosystems in Iceland, and also that large scale afforestation or revegetation activities could possibly also have large impacts on stream ecology in those areas. An interesting question remained to be answered: "Can we see simliar differences in stream ecology on a hectar scale (1st order catchments; 20-100 ltr/sec) as is seen in large rivers on a regional scale?" and "Has increased input of OM and DOM in afforestation and revegetation areas impact on stream ecosystems in Iceland?"


Experimental setup

Three vegetation types are compared in the ForStreams project: a) sparsely vegetated areas with low production on eroded or partly eroded catchments in volcanic active areas or older , b) native mountain birch woodlands with intermediate production on near-by catchments and c) forest plantations of exotic conifers with high production in eastern Iceland (Figure 2).



Figure 2. Experimental set-up of the ForStreams study. In southern Iceland we compare 6 first order catchments on eroded lands and mountain birch woodlands. The whole area is in the foothills of the volcano Mt.Hekla and the bedrock is made out of porous palagonite and lava. In eastern Iceland we compare 9 first order catchments on partly eroded lands, in birch woodlands and in coniferous plantations. The bedrock is solid basaltic rock.


Altogether 17 headwater steams are studied in eastern (Figure 3) and southern (Figure 4) Iceland.

Figure 3. (above) Headwater streams included int the ForStreams study in eastern Iceland. Map: Helena Marta Stefánsdóttir and Sigmundur Brink, Agric. Univ. Iceland.

Figure 4. (below) Headwater streams included int the ForStreams study in southern Iceland. Map: Helena Marta Stefánsdóttir and Sigmundur Brink, Agric. Univ. Iceland.