Effects of Winter Inundation on Tundra Vegetation in Iceland: Implications for Hydroelectric Development in the Arctic

Abstract

The diversion of part of the Thjorsa river created a series of lakes and waterways in the central highland of Iceland. Every winter, ice jams have formed, raising lake levels and inundating upshore vegetation. At five sites by two lakes, the vegetation has remained flooded for about 160 d from mid-winter until spring. To monitor the effects of inundation, species frequency in 10- × 10- cm quadrats was recorded on permanent transects prior to disturbance and again after periods of up to 8 yr. At one site, measurements were made annually for the first 6 yr and again 8 yr after disturbance.

Two types of response to winter inundation were distinguished: (1) species showing a steady decrease in frequency and (2) species apparently little affected for a number of years, then suddenly collapsing.

Combining the five sites, the common species were classified according to the strength and nature of their response into four groups: (1) nine sensitive species that rapidly declined or disappeared with repeated submergence, (2) six species showing variable negative response, (3) five species showing little response, and 4) one species showing a positive response. The results show that arctic species which are characteristic of dry or moist habitats are intolerant of inundation, even when it occurs outside of the growing season. This conclusion has implications for hydroelectric development in other arctic areas.