Controls and impacts of atmospheric and climate change on terrestrial ecosystems - complex interactions, extreme events and lessons for the future

Claus Beier1
1 Centre for Catchment and Urban Water Research, Norwegian Institute for Water Research, NIVA

Invited Talk 2 in Environmental controls on fluxes and processes in ecosystems

15.07.2014, 12:10-12:40, H18

Atmospheric and climatic change affects key drivers of processes in terrestrial ecosystems and is therefore likely to affect ecosystem structure and functioning. Understanding of these changes have been investigated over recent decades by a large number of field scale ecosystem experiments manipulating water, temperature or CO2, mostly as single factors but in a few cases as multifactor experiments. These experiments often support our hypothesis for above and belowground responses to the individual factors. However, over the past 5 years growing evidence exist that the responses to climate change involving all climate change factors may not be easily upscaled based on single factor responses and/or modelling. This is because of non-linear interactions among the climate change related factors and because impacts of extreme events may not be well known and tested from past experiments.

This is well illustrated by the long term multifactor climate change experiment CLiMA!TE which exposed a shrubland ecosystem to moderate changes in temperature, CO2 and water in all combinations. After 8 years of treatments the results demonstrate that the biological and biogeochemical responses to the individual factors in many cases cancel out each other when the factors are combined. Therefore the effects of the full combination of all climate change factors are often insignificant relative to the untreated control. This is true for both specific plant and soil processes as well as aggregate processes at the system level such as net ecosystem exchange. However, these findings may to some extent reflect the fact that the treatments only applied relatively moderate changes while more extreme changes as forecasted for the future were not tested. Such extreme changes may be of significant importance for long term effects of climate change but these are not well covered by current manipulation methodology in field scale experimentation.

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last modified 2014-04-25