Stresses on extensive grasslands in Iceland - A review

摘要

Grasslands in Iceland are either fertilized hayfields or unfertilized pastures. Stresses to grasses can be physical, chemical, biotic or anthropogenic. All kinds of stresses can be experienced in all seasons of the year and plants will be exposed to anumber of stressors at one time, and interaction between them is highly likely. During summer, stresses caused by grazing and harvesting dominate, and also desiccation, soil compaction, and mineral toxicity or deficiency as well as weeds and pathogens may cause stresses and damage or kill grass plants. Grazing by livestock can be controlled by the farmers, and fortunately grasses tolerate that kind of stress better than other plant types. During winter the buds of grasses are often protected by withered grass and a snow layer and therefore do not experience extremely low air temperatures. The most common and serious plant damage on grasses during winter is ice encasement damage, where water freezes to ice after a warm spell and the ice cover lasts fora long time. Then metabolites are accumulated under the ice to lethal concentrations. Additionally, during winter there are several species of low-temperature fungi, so called snow moulds, which can attack and kill the grasses under the snow.