Plant trait response of tundra shrubs to permafrost thaw and nutrient addition

• Main Authors: Iturrate-Garcia, Maitane, Heijmans, Monique M P D, Cornelissen, J Hans C, Schweingruber, Fritz H, Niklaus, Pascal A, Schaepman-Strub, Gabriela
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: Institute of Evolutionary Biology and Environmental Studies; Global Change and Biodiversity; 570 Life sciences; biology; 590 Animals (Zoology); Earth-Surface Processes; Ecology; Evolution; Behavior and Systematics; Betula nana; permafrost; Tundra; Siberia
• Online Access: https://www.zora.uzh.ch/id/eprint/200674/; https://www.zora.uzh.ch/id/eprint/200674/1/bg-17-4981-2020.pdf; https://doi.org/10.5167/uzh-200674; https://doi.org/10.5194/bg-17-4981-2020

Plant traits reflect growth strategies and trade-offs in response to environmental conditions. Because of climate warming, plant traits might change, altering ecosystem functions and vegetation–climate interactions. Despite important feedbacks of plant trait changes in tundra ecosystems with regional climate, with a key role for shrubs, information on responses of shrub functional traits is limited. Here, we investigate the effects of experimentally increased permafrost thaw depth and (possibly thaw-associated) soil nutrient availability on plant functional traits and strategies of Arctic shrubs in northeastern Siberia. We hypothesize that shrubs will generally shift their strategy from efficient conservation to faster acquisition of resources through adaptation of leaf and stem traits in a coordinated whole-plant fashion. To test this hypothesis, we ran a 4 year permafrost thaw and nutrient fertilization experiment with a fully factorial block design and six treatment combinations – permafrost thaw (control, unheated cable, heated cable) × fertilization (no nutrient addition, nutrient addition). We measured 10 leaf and stem traits related to growth, defence and the resource economics spectrum in four shrub species (Betula nana, Salix pulchra, Ledum palustre and Vaccinium vitis-idaea), which were sampled in the experimental plots. The plant trait data were statistically analysed using linear mixed-effect models and principal component analysis (PCA). The response to increased permafrost thaw was not significant for most shrub traits. However, all shrubs responded to the fertilization treatment, despite decreased thaw depth and soil temperature in fertilized plots. Shrubs tended to grow taller but did not increase their stem density or bark thickness. We found a similar coordinated trait response for all four species at leaf and plant level; i.e. they shifted from a conservative towards a more acquisitive resource economy strategy upon fertilization. In accordance, results point towards a lower investment into ...