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Research article - Peer-reviewed, 2021

Evaluation of Alnus subcordata for urban environments through assessment of drought and flooding tolerance

Sjoman, Henrik; Levinsson, Anna; Emilsson, Tobias; Ibrahimova, Aida; Alizade, Valida; Douglas, Philip; Wistrom, Bjorn

Abstract

The urban environment is stressful and trees experience multiple stresses, including drought, flooding, and extreme heat, all of which are likely to increase under future climate warming and increasing urbanisation. In the selection of tree species to maximise ecosystem services, tolerance to site characteristics such as flooding and severe drought is of critical importance. This study evaluated the suitability of a rare species, Mims subcordata C.A. Mey (Caucasian alder) from the Hyrcanian forests of southern Azerbai-jan, for its functionality as an urban tree.A total of 48 pot-grown, two-year-old saplings of A. subcordata were tested in a greenhouse experiment using a complete randomised block design. Each block contained four replicates of three treatments (waterlogging, drought, control), with 16 plants per treatment. Height differences between treatments were measured, and water status was estimated by determination of midday leaf water potential (psi(L)) and stomatal conductance (g(s)). To estimate drought tolerance reaction in the treatments, leaf water potential at turgor loss (psi(P0)) was used together with broken-stick modelling of water status over time.A. subcordata plants showed no height increase, while plants in both the waterlogged and control treatments increased in height during the nine-week experiment. Over 63 days of flooding, plant water status was slightly more negative in the waterlogging treatment, but did not deviate essentially from the control. In the drought treatment, plant water status rapidly deviated from the control. There was a significant difference in psi(P0) between treatments, with drought-treated plants showing the lowest value (-2.31 MPa).This study demonstrated that A. subcordata has limited tolerance to drought and seems to rely more on water loss-avoiding strategies. However, the species may be usable at periodically waterlogged sites, due to its high tolerance to flooding. It could therefore be recommended for wet urban environments and stormwater management facilities, for which reliable guidance on suitable trees is currently lacking.

Keywords

climate change; ecosystem services; urban forestry; stress tolerance; adventitious roots

Published in

Dendrobiology
2021, Volume: 85, pages: 39-50
Publisher: BOGUCKI WYDAWNICTWO NAUKOWE