| Summary: | Iceland has the lowest vegetation cover in Europe, and a large part of the country is degraded. The main drivers are sheep grazing, along with cold climate and volcanic activity. Grazing can negatively impact the flowering and seed production of plants. Because sheep selectively graze flowers and because when plants are grazed, they might allocate resources to regrow after grazing, leaving fewer resources for reproduction. Over 60% of the country is estimated to be used for sheep grazing. Around half of all grazing areas are in the grazing commons in the highlands of Iceland. The conditions of the grazing commons vary greatly from fully vegetated too almost completely barren and highly degraded. Plants in highly degraded areas can experience stress, and when plants are under stress the mortality risk is higher which might cause them to allocate resources to sexual reproduction rather than growth. Thus, degradation might increase seed production in plants. This project aims to determine the effects of degradation and sheep grazing on flowering and seed production in plants in the Icelandic highlands. Data was gathered during two consecutive growing seasons in a grazing exclusion experiment in two habitats at contrasting degradation stages in Auðkúluheiði, NW Iceland. One habitat a vegetated, dwarf-shrub heath and another is an eroded desert. In both years of sampling, plant flowering was estimated, in both fenced and control plots in each habitat. In addition, seed collection was performed in the later sampling year, with seeds collected from two species. The results of this study suggest that plants in severely degraded areas in the Icelandic highlands put more effort into flowering and seed production than plants in vegetated habitats. A possible explanation might be that plant species favouring sexual reproduction are more common in areas of high degradation than in areas of low degradation. The results also indicate that in areas in the low stages of degradation, grazing exclusions increase flowering, while ...
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