Doctoral defence: Azadeh Rezapour “The impact of climate change on fine root trait responses of deciduous and coniferous trees”

On 31 May at 14:15 Azadeh Rezapour will defend her doctoral thesis “The impact of climate change on fine root trait responses of deciduous and coniferous trees” for obtaining the degree of Doctor of Philosophiae (in Landscape Ecology and EnvironmentProtection).

Supervisors:
Professor Tõnu Oja, University of Tartu 

Opponent:
Senior Scientist Karin Pritsch, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH) (Germany)

Summary
Changes in global temperature, precipitation, air humidity, and N deposition pose challenges to forest ecosystems. Of particular concern are peatland forests. Fine roots (<2 mm in diameter) are divided into absorptive and transport roots. High specific root area and length mean higher resource acquisition. The thesis aimed to analyze fine root acclimation of deciduous and coniferous trees to varying climate and soil. We evaluated fine root C fluxes and morphological variation of hybrid aspen, silver birch, and Scots pine in response to elevated humidity and soil inorganic N; the role of fine root functional groups in carbon exudation; and morphological variation of absorptive roots across the distance from the ditch in drained peatland forests dominated by birch and spruce to identify plasticity in fine root acclimation. Response of fine root biomass and morphology to soil warming at global scale was assessed in meta-analysis. The study showed species-specific responses affecting soil carbon balance. In climate chambers, enhanced humidity reduced transpiration. Enhanced humidity caused growth in pine photosynthesis, decrease in belowground carbon fluxes. Specific root area increased in birch but decreased in pine. The absorptive root morphological responses were uniform in birch and spruce. With increased distance from the ditch, specific root area increased, tissue density decreased. Soil warming increased fine root biomass differently for deciduous and coniferous species. The warming effects on fine root biomass decreased with greater warming magnitude. Rise in soil temperature stimulates root growth. Trees allocate more biomass to fine roots under warmer conditions, morphological plasticity is influenced less. More comprehensive analyses of fine root traits along with root-associated ectomycorrhizal fungi under multifactorial environmental conditions are needed.