首页 | 本学科首页   官方微博 | 高级检索  
   检索      


Soil warming and CO2 enrichment induce biomass shifts in alpine tree line vegetation
Authors:Melissa A Dawes  Christopher D Philipson  Patrick Fonti  Peter Bebi  Stephan Hättenschwiler  Christian Rixen
Institution:1. WSL Institute for Snow and Avalanche Research – SLF, Davos Dorf, Switzerland;2. Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland;3. Ecosystem Management, Institute of Terrestrial Ecosystems, Zurich, Switzerland;4. Centre d'Ecologie Fonctionnelle & Evolutive (CEFE UMR 5175), CNRS – Université de Montpellier ‐ Université Paul‐Valéry Montpellier ‐ EPHE, Montpellier Cedex 5, France
Abstract:Responses of alpine tree line ecosystems to increasing atmospheric CO2 concentrations and global warming are poorly understood. We used an experiment at the Swiss tree line to investigate changes in vegetation biomass after 9 years of free air CO2 enrichment (+200 ppm; 2001–2009) and 6 years of soil warming (+4 °C; 2007–2012). The study contained two key tree line species, Larix decidua and Pinus uncinata, both approximately 40 years old, growing in heath vegetation dominated by dwarf shrubs. In 2012, we harvested and measured biomass of all trees (including root systems), above‐ground understorey vegetation and fine roots. Overall, soil warming had clearer effects on plant biomass than CO2 enrichment, and there were no interactive effects between treatments. Total plant biomass increased in warmed plots containing Pinus but not in those with Larix. This response was driven by changes in tree mass (+50%), which contributed an average of 84% (5.7 kg m?2) of total plant mass. Pinus coarse root mass was especially enhanced by warming (+100%), yielding an increased root mass fraction. Elevated CO2 led to an increased relative growth rate of Larix stem basal area but no change in the final biomass of either tree species. Total understorey above‐ground mass was not altered by soil warming or elevated CO2. However, Vaccinium myrtillus mass increased with both treatments, graminoid mass declined with warming, and forb and nonvascular plant (moss and lichen) mass decreased with both treatments. Fine roots showed a substantial reduction under soil warming (?40% for all roots <2 mm in diameter at 0–20 cm soil depth) but no change with CO2 enrichment. Our findings suggest that enhanced overall productivity and shifts in biomass allocation will occur at the tree line, particularly with global warming. However, individual species and functional groups will respond differently to these environmental changes, with consequences for ecosystem structure and functioning.
Keywords:dwarf shrub  European larch  free air CO2 enrichment  global change  Larix decidua  mountain pine  Pinus uncinata
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号