Northern Forest Trees Under Increasing
Atmospheric Humidity
Elina Oksanen, Jenna Lihavainen, Markku Keinänen, Sarita Keski-Saari,
Sari Kontunen-Soppela, Arne Sellin, and Anu Sõber
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
2 High Humidity Affects Physiology, Biochemistry and the Structure of Plants . . . . . . . . . . . . 320
2.1 Stomata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
2.2 Transpiration and Mineral Nutrient Uptake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
2.3 Growth and Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
2.4 Biochemical and Molecular Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
2.5 Interaction with Abiotic Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
3 High Humidity Experiments with Forest Trees and Forest Ecosystems . . . . . . . . . . . . . . . . . . . 323
3.1 Free Air Humidity Manipulation (FAHM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
3.2 Ecophysiological Responses in the FAHM Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
3.3 Metabolic Responses in the FAHM Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
3.4 Laboratory Studies Confirming the Field Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
3.5 The Key Role of Leaf Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
4 Future Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
Abstract Several climate change scenarios predict increasing precipitation for
northern latitudes and several other regions in the globe, leading to increase in
atmospheric water vapour content [expressed as increased relative humidity (RH)
or as decreased water vapour pressure deficit (VPD)] and environmental wetness.
Plants are known to be sensitive to high humidity (low VPD) as indicated by changes
in stomatal function, transpiration, mineral nutrient uptake, growth, development,
sugar metabolism and leaf epicuticular wax composition in several species and
studies. To understand the impact of increasing humidity (lower VPD) on forest
ecosystems, a long-term and large-scale field experiment (FAHM, Free Air
E. Oksanen (*), J. Lihavainen, M. Keinänen, S. Keski-Saari, and S. Kontunen-Soppela
Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu,
Finland
e-mail: elina.oksanen@uef.fi
A. Sellin and A. Sõber
Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
© Springer International Publishing AG 2018
Progress in Botany (2019) 80: 317–336, DOI 10.1007/124_2017_15,
Published online: 30 January 2018
317
Atmospheric Humidity
Elina Oksanen, Jenna Lihavainen, Markku Keinänen, Sarita Keski-Saari,
Sari Kontunen-Soppela, Arne Sellin, and Anu Sõber
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
2 High Humidity Affects Physiology, Biochemistry and the Structure of Plants . . . . . . . . . . . . 320
2.1 Stomata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
2.2 Transpiration and Mineral Nutrient Uptake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
2.3 Growth and Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
2.4 Biochemical and Molecular Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
2.5 Interaction with Abiotic Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
3 High Humidity Experiments with Forest Trees and Forest Ecosystems . . . . . . . . . . . . . . . . . . . 323
3.1 Free Air Humidity Manipulation (FAHM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
3.2 Ecophysiological Responses in the FAHM Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
3.3 Metabolic Responses in the FAHM Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
3.4 Laboratory Studies Confirming the Field Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
3.5 The Key Role of Leaf Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
4 Future Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
Abstract Several climate change scenarios predict increasing precipitation for
northern latitudes and several other regions in the globe, leading to increase in
atmospheric water vapour content [expressed as increased relative humidity (RH)
or as decreased water vapour pressure deficit (VPD)] and environmental wetness.
Plants are known to be sensitive to high humidity (low VPD) as indicated by changes
in stomatal function, transpiration, mineral nutrient uptake, growth, development,
sugar metabolism and leaf epicuticular wax composition in several species and
studies. To understand the impact of increasing humidity (lower VPD) on forest
ecosystems, a long-term and large-scale field experiment (FAHM, Free Air
E. Oksanen (*), J. Lihavainen, M. Keinänen, S. Keski-Saari, and S. Kontunen-Soppela
Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu,
Finland
e-mail: elina.oksanen@uef.fi
A. Sellin and A. Sõber
Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
© Springer International Publishing AG 2018
Progress in Botany (2019) 80: 317–336, DOI 10.1007/124_2017_15,
Published online: 30 January 2018
317