Response of green alder (Alnus viridis subsp fruticosa) patch dynamics and plant community composition to fire and regional temperature in north-western Canada

被引:108
作者
Lantz, Trevor C. [1 ]
Gergel, Sarah E. [2 ]
Henry, Greg H. R. [3 ]
机构
[1] Univ Victoria, Sch Environm Studies, STN CSC, Victoria, BC V8W 3R4, Canada
[2] Univ British Columbia, Ctr Appl Conservat Res, Vancouver, BC V6T 1Z4, Canada
[3] Univ British Columbia, Dept Geog, Vancouver, BC V6T 1Z2, Canada
基金
加拿大自然科学与工程研究理事会;
关键词
Alnus viridis; climate change; climate feedbacks; disturbance; fire; forest tundra; global change; shrub encroachment; succession; tall shrubs; MACKENZIE DELTA REGION; SOIL BURN SEVERITY; LAND-COVER CHANGE; ARCTIC TUNDRA; CLIMATE-CHANGE; TREE-LINE; VEGETATION RECOVERY; SEWARD PENINSULA; BOREAL FOREST; ACTIVE LAYER;
D O I
10.1111/j.1365-2699.2010.02317.x
中图分类号
Q14 [生态学(生物生态学)];
学科分类号
071012 ; 0713 ;
摘要
Aim Feedbacks between climate warming and fire have the potential to alter Arctic and sub-Arctic vegetation. In this paper we assess the effects and interactions of temperature and wildfire on plant communities across the transition between the Arctic and sub-Arctic. Location Mackenzie Delta region, Northwest Territories, Canada. Methods We sampled air temperatures, green alder (Alnus viridis ssp. fruticosa) cover, growth, reproduction and age distributions, and overall plant community composition on burned and unburned sites across a latitudinal gradient. Results Mean summer temperature across the study area decreased by 3 degrees C per degree of increasing latitude (6 degrees C across the study area). In the northern part of the study area, where seed viability was low, alder was less dominant than at southern sites where seed viability was high. The age structure of alder populations across the temperature gradient was highly variable, except in the northern part of the forest-tundra transition, where populations were dominated by young individuals. Alder growth and reproduction were significantly greater on burned sites (38-51 years following fire) than on unburned sites. North to south across the temperature gradient, vegetation changed from a community dominated by dwarf shrubs and fruticose lichens to one characterized by black spruce (Picea mariana), alder and willows (Salix spp.). Regardless of the position along the temperature gradient, burned sites were dominated by tall shrubs. Main conclusions Temperature limitation of alder abundance and repro-duction, combined with evidence of recent recruitment on unburned sites, indicates that alder is likely to respond to increased temperature. Elevated alder growth and reproduction on burned sites shows that wildfire also has an important influence on alder population dynamics. The magnitude of alder's response to fire, combined with observations that burns at the southern margin of the low Arctic are shrub dominated, suggest that increases in the frequency of wildfire have the potential to alter northern vegetation on decadal scales. By creating new seedbeds, fire provides opportunities for colonization that may facilitate the northward movement of tall shrubs. Feedbacks between the global climate system and low Arctic vegetation make understanding the long-term impact of increasing fire frequency critical to predicting the response of northern ecosystems to global change.
引用
收藏
页码:1597 / 1610
页数:14
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