Shrubification
Shrubification (Shrub Expansion)[edit]
Shrubification (also referred to simply as shrub expansion) refers to the ongoing expansion of woody vegetation in arctic and alpine environments due to climate change. [1] Shrubification primarily takes place at the forest-tundra ecotone, where vegetation transitions from coniferous trees of the boreal forest to a lichen and grass rich tundra [2]. The forest-tundra ecotone is expected to expand at the expense of reduced tundra landscapes [3]. Vegetation in the forest-tundra ecosystem consists of: patches of boreal conifers, tall shrubs, low shrubs, sedges and krummholz[4] [5]. It’s important for climate scientists to understand the land surface feedbacks that are associated with vegetation changes and ecosystem biogeochemical cycling in order to update existing climate models[6]. Models would be updated with information concerning changes to the global carbon balance, arctic temperatures, and permafrost thickness and distribution caused by shrubification.
Shrubification effects on permafrost[edit]
Shrubification can influence permafrost in one of two ways. The canopy of shrubs can shade the ground from incoming solar radiation, and thus decrease the depth of the active layer [7]. On the other hand, shrubs can also trap snow and isulate soil in during winter months, leading to permafrost thaw [8]. These changes occur simultaneously, and their relative importance is still not fully understood and will vary by region.
Shrubification effects on Arctic Climate[edit]
Increased shrub distribution can affect arctic climate by lowering surface albedo during the snow season, thus increasing the rate of arctic warming [7]. In areas that accumulate enough snow in the wintertime to completely cover shrubs, shrubification would warm the climate by absorbing incoming solar radiation later into the fall, and earlier into the spring.
Shrubification effects on atmospheric greenhouse gases[edit]
The effect of shrubification on the carbon balance remains unclear. It is uncertain whether shrubification will lower atmospheric CO2 through carbon uptake, or increase carbon emissions by accelerating warming, and thus thawing additional permafrost[9]. Shrubification could cause a net decrease in atmospheric CO2 as it is absorbed by shrubs and incorporated into their biomass. Shrubification could also cause a net increase in atmospheric greenhouse gases by warming arctic climate and thereby thawing permafrost. Thawing permafrost releases CO2 into the atmosphere when organic carbon stored in permafrost becomes available to be broken down by bacteria.
References[edit]
- ↑ Mod, Heidi K.; Luoto, Miska (2016). "Arctic shrubification mediates the impacts of warming climate on changes to tundra vegetation". Environmental Research Letters. 11 (12): 124028. doi:10.1088/1748-9326/11/12/124028. ISSN 1748-9326.
- ↑ Ropars, P.; Boudreau, S. (2012). "Shrub expansion at the forest–tundra ecotone: spatial heterogeneity linked to local topography". Environmental Research Letters. 7 (1): 015501. doi:10.1088/1748-9326/7/1/015501. ISSN 1748-9326.
- ↑ Hofgaard, Annika; Harper, Karen; Golubeva, Elena (2012-09-01). "The role of the circumarctic forest–tundra ecotone for Arctic biodiversity". Biodiversity. 13. doi:10.1080/14888386.2012.700560.
- ↑ Roy-Léveillée, Pascale; Burn, C; D. McDonald, I (2014-04-01). "Vegetation-Permafrost Relations within the Forest-Tundra Ecotone near Old Crow, Northern Yukon, Canada". Permafrost and Periglacial Processes. 25. doi:10.1002/ppp.1805.
- ↑ Zeng, Yu; Malanson, George; Butler, David (2007-11-01). "Geomorphological limits to self-organization of alpine forest-tundra ecotone vegetation". Geomorphology. 91: 378–392. doi:10.1016/j.geomorph.2007.04.019.
- ↑ Zhang, Wenxin; Miller, Paul A.; Smith, Benjamin; Wania, Rita; Koenigk, Torben; Döscher, Ralf (2013). "Tundra shrubification and tree-line advance amplify arctic climate warming: results from an individual-based dynamic vegetation model". Environmental Research Letters. 8 (3): 034023. doi:10.1088/1748-9326/8/3/034023. ISSN 1748-9326.
- ↑ 7.0 7.1 Juszak, Inge; M. Erb, Angela; C. Maximov, Trofim; Schaepman-Strub, Gabriela (2014-10-01). "Arctic shrub effects on NDVI, summer albedo and soil shading". Remote Sensing of Environment. 153: 79–89. doi:10.1016/j.rse.2014.07.021.
- ↑ Myers-Smith, Isla H.; Forbes, Bruce C.; Wilmking, Martin; Hallinger, Martin; Lantz, Trevor; Blok, Daan; Tape, Ken D.; Macias-Fauria, Marc; Sass-Klaassen, Ute (2011). "Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities". Environmental Research Letters. 6 (4): 045509. doi:10.1088/1748-9326/6/4/045509. ISSN 1748-9326.
- ↑ Le, Ge, (2016). Carbon Exchange along a Natural Gradient of Deciduous Shrub Coverage in the Low-Arctic (Thesis). Trent University.
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