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Disturbances such as avalanches, rockfalls, fire, wind and herbivore damage interact and are strongly dependent on climate. |
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Mudflows, debris flows, and landslides Melt of permafrost already has resulted in higher geomorphic activity in many alpine regions, leading to rockfalls and landslides. Especially in combination with intense precipitation events, mudflows and debris flows probably will increase in frequency and intensity. |
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Avalanches Climate warming and land use change are likely to have considerable impacts on frequency and intensity of avalanches. At lower elevations, avalanche frequency may decrease due to a lower probability for snow fall. On the other hand, increased winter precipitation could lead to higher and more intense avalanches at higher elevations and new avalanche paths may be created. |
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Fire Due to higher temperatures and the likely decrease in summer precipitation, fires will become more frequent in alpine environments. The increasing use of alpine areas for recreation also may increase the risk of accidental fires caused by cigarettes or remains of campfires. Additionally, an often observed increase in shrubs represents a higher fuel load and may result in increased frequency and intensity of fires. Increased frequency and intensity of fire events have already been observed in some dryer mountain regions like East Africa, Australia, the Western Rocky Mountains, and within the Mediterranean region. As in the past natural fires have been quite rare in most alpine regions, the vegetation normally is not well adapted and will be transformed. Fire also affects microbial community structure and activity. It usually increases the amount of bare soil and soil temperature. In addition, steep slopes disturbed by fire are more vulnerable to erosion. Fire suppression On the other hand, fire has been a managing tool in several regions. It was used to control shrub and tree invasion into (sub)alpine meadows and initiate regrowth of more palatable and nutrient rich shoots. After a burning ban was issued in Yunnan in 1988, this traditional practices had to be abandoned which resulted in decreased species diversity and reduced livelihood of Tibetan herders. In addition, in some subalpine forests, it has been shown that fire is an important natural factor. Even if quite rare it increases plant species richness at local and landscape scales, and adds to the diversity of plant communities. During a period of total fire suppression in the 20th century in the USA, forests became denser and more susceptible to severe crown fires. Moreover, trees growing in dense stands exhibited a higher vulnerability to pests such as the spruce budworm and mountain pine beetle. Today, a more or less natural fire regime is adopted.
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13 August 2018 |
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