| 1. |
- Nilsson, Christer, et al.
(författare)
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The role of hydrochory in structuring riparian and wetland vegetation
- 2010
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Ingår i: Biological Reviews. - 1464-7931 .- 1469-185X. ; 85:4, s. 837-858
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Tidskriftsartikel (refereegranskat)abstract
- Hydrochory, or the passive dispersal of organisms by water, is an important means of propagule transport, especially forplants. During recent years, knowledge about hydrochory and its ecological consequences has increased considerablyand a substantial body of literature has been produced. Here, we review this literature and define the state of the art ofthe discipline. A substantial proportion of species growing in or near water have propagules (fruits, seeds or vegetativeunits) able to disperse by water, either floating, submerged in flowing water, or with the help of floating vessels.Hydrochory can enable plants to colonize sites out of reach with other dispersal vectors, but the timing of dispersaland mechanisms of establishment are important for successful establishment. At the population level, hydrochorymay increase the effective size and longevity of populations, and control their spatial configuration. Hydrochory isalso an important source of species colonizing recruitment-limited riparian and wetland communities, contributing tomaintenance of community species richness. Dispersal by water may even influence community composition in differentlandscape elements, resulting in landscape-level patterns. Genetically, hydrochory may reduce spatial aggregation ofgenetically related individuals, lead to high gene flow among populations, and increase genetic diversity in populationsreceiving many propagules. Humans have impacted hydrochory in many ways. For example, dams affect hydrochoryby reducing peak flows and hence dispersal capacity, altering the timing of dispersal, and by presenting physical barriersto dispersal, with consequences for riverine plant communities. Hydrochory has been inferred to be an important vectorfor the spread of many invasive species, but there is also the potential for enhancing ecosystem restoration by improvingor restoring water dispersal pathways. Climate change may alter the role of hydrochory by modifying the hydrology ofwater-bodies as well as conditions for propagule release and plant colonization.
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| 2. |
- Bejarano, Maria D., et al.
(författare)
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The effects of hydropeaking on riverine plants : a review
- 2018
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Ingår i: Biological Reviews. - : WILEY. - 1464-7931 .- 1469-185X. ; 93:1, s. 658-673
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Forskningsöversikt (refereegranskat)abstract
- Hydropeaking refers to frequent, rapid and short-term fluctuations in water flow and water levels downstream and upstream of hydropower stations. Such fluctuations are becoming increasingly common worldwide and are known to have far-reaching effects on riverine vegetation. Novel hydrology caused by hydropeaking has no natural correspondence in freshwater systems, and hence few species have adaptations to all its aspects. Here, we review the literature on hydropeaking effects on riverine plants and define the state of the information on this human alteration of riverine ecosystems. We focus on riparian plants, but also draw on information from aquatic plant species, which exhibit a wide variety of adaptations to inundation and associated processes. Riparian plants face both physiological and physical constraints because of the shifts between submergence and drainage, and erosion of substrates. At the population level, hydropeaking may favour dispersal within, but not between, reservoirs, but may hamper germination, establishment, growth and reproduction. At the community level, strong filtering towards easily dispersed, flexible, flood-tolerant and amphibious plants is expected, although few species share these traits. Hence, most riparian plant species are expected to disappear or be pushed towards the upper boundaries of the regulated river margin. Future research should examine more closely global variation in hydropeaking effects, including other taxonomic groups of species and the diversity of hydropeaking regimes. There is also a need for studies focusing on identifying the boundaries within which hydropeaking could operate without impairing plant life.
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| 3. |
- Lind, Lovisa, et al.
(författare)
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The role of ice dynamics in shaping vegetation in flowing waters
- 2014
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Ingår i: Biological Reviews. - : John Wiley & Sons. - 1464-7931 .- 1469-185X. ; 89:4, s. 791-804
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Tidskriftsartikel (refereegranskat)abstract
- Ice dynamics is an important factor affecting vegetation in high-altitude and high-latitude streams and rivers. During the last few decades, knowledge about ice in streams and rivers has increased significantly and a respectable body of literature is now available. Here we review the literature on how ice dynamics influence riparian and aquatic vegetation. Traditionally, plant ecologists have focused their studies on the summer period, largely ignoring the fact that processes during winter also impact vegetation dynamics. For example, the freeze-up period in early winter may result in extensive formation of underwater ice that can restructure the channel, obstruct flow, and cause flooding and thus formation of more ice. In midwinter, slow-flowing reaches develop a surface-ice cover that accumulates snow, protecting habitats under the ice from formation of underwater ice but also reducing underwater light, thus suppressing photosynthesis. Towards the end of winter, ice breaks up and moves downstream. During this transport, ice floes can jam up and cause floods and major erosion. The magnitudes of the floods and their erosive power mainly depend on the size of the watercourse, also resulting in different degrees of disturbance to the vegetation. Vegetation responds both physically and physiologically to ice dynamics. Physical action involves the erosive force of moving ice and damage caused by ground frost, whereas physiological effects - mostly cell damage - happen as a result of plants freezing into the ice. On a community level, large magnitudes of ice dynamics seem to favour species richness, but can be detrimental for individual plants. Human impacts, such as flow regulation, channelisation, agriculturalisation and water pollution have modified ice dynamics; further changes are expected as a result of current and predicted future climate change. Human impacts and climate change can both favour and disfavour riverine vegetation dynamics. Restoration of streams and rivers may mitigate some effects of anticipated climate change on ice and vegetation dynamics by, for example, slowing down flows and increasing water depth, thus reducing the potential for massive formation of underwater ice.
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