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Climate change at northern latitudes: rising atmospheric humidity decreases transpiration, N-uptake and growth rate of hybrid aspen.

Tullus A, Kupper P, Sellin A, Parts L, Sõber J, Tullus T, Lõhmus K, Sõber A, Tullus H - PLoS ONE (2012)

Bottom Line: Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area.The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO(3) (-) in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots.The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO(2) concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place.

View Article: PubMed Central - PubMed

Affiliation: Department of Silviculture, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Tartu, Estonia.

ABSTRACT
At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in response to elevated atmospheric humidity (on average 7% over the ambient level) in a free air experimental facility during three growing seasons (2008-2010) in Estonia, which represents northern temperate climate (boreo-nemoral zone). Data were collected from three humidified (H) and three control (C) plots, and analysed using nested linear models. Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA) in H plots. The magnitude and significance of the humidity treatment effect--inhibition of above-ground growth rate--was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO(3) (-) in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO(2) concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place.

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Height (a), diameter (b) and stem volume (c) increments (ΔH, ΔD and ΔV respectively) of hybrid aspens in control (C) and humidified (H) plots during the study period.The significance of treatment effect (t-test) in individual years is indicated with asterisks and q-values (model) show the summary effect over the years when humidification was applied (age 2–4 years). Whiskers denote ± standard error.
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pone-0042648-g003: Height (a), diameter (b) and stem volume (c) increments (ΔH, ΔD and ΔV respectively) of hybrid aspens in control (C) and humidified (H) plots during the study period.The significance of treatment effect (t-test) in individual years is indicated with asterisks and q-values (model) show the summary effect over the years when humidification was applied (age 2–4 years). Whiskers denote ± standard error.

Mentions: Pairwise comparison of the tree growth characteristics in C and H plots during the individual study years (plot means are given in Table S1) revealed that the growth rate in H plots was higher during the first year of the experiment but remained significantly lower compared to C plots after the second and third year (Fig. 3). The treatment effect on growth was highly significant (q<0.01) also across the whole study period (Fig. 4a). Additionally, tree growth increment in the given year was always strongly dependent on the size of the tree (i.e. the value of the given trait at the end of the previous growing period). The studied tree characteristics were significantly affected also by soil variables, with the strongest effects from [N]S, [P]S and OrgS. There existed a significant interaction between treatment and the size of the tree at the end of previous growing season for predicting the current year increment. Stems of the trees of the same size grew slower in H plots compared to C plots, while such a distinction was greater in bigger trees (Fig. 5).


Climate change at northern latitudes: rising atmospheric humidity decreases transpiration, N-uptake and growth rate of hybrid aspen.

Tullus A, Kupper P, Sellin A, Parts L, Sõber J, Tullus T, Lõhmus K, Sõber A, Tullus H - PLoS ONE (2012)

Height (a), diameter (b) and stem volume (c) increments (ΔH, ΔD and ΔV respectively) of hybrid aspens in control (C) and humidified (H) plots during the study period.The significance of treatment effect (t-test) in individual years is indicated with asterisks and q-values (model) show the summary effect over the years when humidification was applied (age 2–4 years). Whiskers denote ± standard error.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3412825&req=5

pone-0042648-g003: Height (a), diameter (b) and stem volume (c) increments (ΔH, ΔD and ΔV respectively) of hybrid aspens in control (C) and humidified (H) plots during the study period.The significance of treatment effect (t-test) in individual years is indicated with asterisks and q-values (model) show the summary effect over the years when humidification was applied (age 2–4 years). Whiskers denote ± standard error.
Mentions: Pairwise comparison of the tree growth characteristics in C and H plots during the individual study years (plot means are given in Table S1) revealed that the growth rate in H plots was higher during the first year of the experiment but remained significantly lower compared to C plots after the second and third year (Fig. 3). The treatment effect on growth was highly significant (q<0.01) also across the whole study period (Fig. 4a). Additionally, tree growth increment in the given year was always strongly dependent on the size of the tree (i.e. the value of the given trait at the end of the previous growing period). The studied tree characteristics were significantly affected also by soil variables, with the strongest effects from [N]S, [P]S and OrgS. There existed a significant interaction between treatment and the size of the tree at the end of previous growing season for predicting the current year increment. Stems of the trees of the same size grew slower in H plots compared to C plots, while such a distinction was greater in bigger trees (Fig. 5).

Bottom Line: Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area.The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO(3) (-) in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots.The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO(2) concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place.

View Article: PubMed Central - PubMed

Affiliation: Department of Silviculture, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Tartu, Estonia.

ABSTRACT
At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in response to elevated atmospheric humidity (on average 7% over the ambient level) in a free air experimental facility during three growing seasons (2008-2010) in Estonia, which represents northern temperate climate (boreo-nemoral zone). Data were collected from three humidified (H) and three control (C) plots, and analysed using nested linear models. Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA) in H plots. The magnitude and significance of the humidity treatment effect--inhibition of above-ground growth rate--was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO(3) (-) in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO(2) concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place.

Show MeSH