Journal of Conference Abstracts

Counteractions Against Acidification in Forest Ecosystems: Vegetation Dynamics in a Forested Catchment After Dolomite Application in Gjerstad, S Norway

O. Eilertsen¹ (odd.eilertsen@oslo.nina.no), O. E. Stabbetorp¹ (odd.stabbetorp@oslo.nina.no), P. A. Aarrestad² (per.arild.aarrestad@nina.nina.no) & E. Bendiksen¹ (egil.bendiksen@oslo.nina.no)

¹ Norwegian Institute for Nature research, Region Office Oslo, Post box 736 Sentrum, 0105 Oslo, Norway.

² Norwegian Institute for Nature research, Tungasletta 2, 7005 Trondheim, Norway.

The aim of this liming experiment was to reduce soil acidification in a boreal forest in order to improve soil water and runoff water quality, without significant changes in fungi and autotrophic vegetation dynamics. Effects on biotic and abiotic components were assessed between a manipulated, limed catchment (L) (treated with 3 tons dolomite per ha) and an untreated control catchment (C). A pre-treatment gradient analysis of autotrophic vegetation from two boreal forest catchments in Ulltveit, Gjerstad, S Norway, reveals two main complex-gradients; (1) a topography- soil depth gradient running from nutrient poor, lichen rich pine forest (P), through Vaccinium myrtillus-dominated spruce forest, to more nutrient rich spruce forest (S), and (2) a fine-scale paludification gradient within the spruce forest from mesic types (S1) to subxeric types (S2), mainly affecting the species composition of the bottom layer. Thus, the structure of the ground vegetation in the catchments can be regarded as a triangular configuration as appears from a DCA ordination analysis (see Figure).

The analysis was carried out in October 1994, just before application of dolomite to one of the two catchments. Repeated analyses of vegetation were carried out in both catchments in 1995 and 1996. In each catchment 50 permanently marked sample plots, each of 1 m², were analysed to quantify the amount of between-year compositional change, and to elabourate the environmental basis for long-term vegetation change.

Correspondingly, gradient analyses of macro fungi, both mycorrhizal species and saprophytes, were carried out around the same 100 sample plots. The sample plot size was 9 m². The three study years were rather dry, but with different precipitation patterns. This lead to very strong variation in fruiting of different species caused by climatic factors. Frequent species were considered for further comparison between plots with and without liming. Only very few species demonstrated distinctly different trends between the two areas: Three of them increased and four decreased in the limed area. Different trends between the treated plots and the control plots may be due to different species specific responses to liming.

There was no significant difference in species composition between the two catchments in the xeric, nutrient-poor, pine forest and the subxeric to submesic nutrient-rich spruce forest. However, in some intermediate, more mesic and paludified plots limited differences between treatment and control were found. Only a few of the common species showed dynamics that differed from the control catchment. Most of the species that showed changes due to treatment seem to be low-frequency species which separately did not contribute statistically, but together their contribution was considerable.

This project covers the initial phase of a long-term study. So far the balance between sufficient supply of dolomite (to obtain the intended effect on soil and water conditions) and restricted supply of dolomite (to prevent damages on plants) seems to be adequate.