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The Dynamics of Living and Dead Fine Roots of Forest Biomes across the Northern Hemisphere
Open AccessArticle

Effects of Summer Drought on the Fine Root System of Five Broadleaf Tree Species along a Precipitation Gradient

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Plant Ecology, Albrecht von Haller Institute for Plant Sciences, University of Goettingen, Untere Karspüle 2, 37073 Goettingen, Germany
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Ecophysiology and Vegetation Ecology, Julius-von-Sachs-Institute of Biological Sciences, University of Würzburg, Julius-von-Sachs-Platz 3, 97082 Würzburg, Germany
*
Author to whom correspondence should be addressed.
Forests 2020, 11(3), 289; https://doi.org/10.3390/f11030289
Received: 21 January 2020 / Revised: 19 February 2020 / Accepted: 25 February 2020 / Published: 3 March 2020
(This article belongs to the Special Issue Fine Root Dynamics in Forests)
While much research has addressed the aboveground response of trees to climate warming and related water shortage, not much is known about the drought sensitivity of the fine root system, in particular of mature trees. This study investigates the response of topsoil (0–10 cm) fine root biomass (FRB), necromass (FRN), and fine root morphology of five temperate broadleaf tree species (Acer platanoides L., Carpinus betulus L., Fraxinus excelsior L., Quercus petraea (Matt.) Liebl., Tilia cordata Mill.) to a reduction in water availability, combining a precipitation gradient study (nine study sites; mean annual precipitation (MAP): 920–530 mm year−1) with the comparison of a moist period (average spring conditions) and an exceptionally dry period in the summer of the subsequent year. The extent of the root necromass/biomass (N/B) ratio increase was used as a measure of the species’ belowground sensitivity to water deficits. We hypothesized that the N/B ratio increases with long-term (precipitation gradient) and short-term reductions (moist vs. dry period) of water availability, while FRB changes only a little. In four of the five species (exception: A. platanoides), FRB did not change with a reduction in MAP, whereas FRN and N/B ratio increased toward the dry sites under ample water supply (exception: Q. petraea). Q. petraea was also the only species not to reduce root tip frequency after summer drought. Different slopes of the N/B ratio-MAP relation similarly point at a lower belowground drought sensitivity of Q. petraea than of the other species. After summer drought, all species lost the MAP dependence of the N/B ratio. Thus, fine root mortality increased more at the moister than the drier sites, suggesting a generally lower belowground drought sensitivity of the drier stands. We conclude that the five species differ in their belowground drought response. Q. petraea follows the most conservative soil exploration strategy with a generally smaller FRB and more drought-tolerant fine roots, as it maintains relatively constant FRB, FRN, and morphology across spatial and temporal dimensions of soil water deficits. View Full-Text
Keywords: Acer platanoides; Carpinus betulus; fine root biomass; fine root necromass; Fraxinus excelsior; necromass/biomass ratio; Quercus petraea; root morphology; Tilia cordata; water availability Acer platanoides; Carpinus betulus; fine root biomass; fine root necromass; Fraxinus excelsior; necromass/biomass ratio; Quercus petraea; root morphology; Tilia cordata; water availability
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Fuchs, S.; Hertel, D.; Schuldt, B.; Leuschner, C. Effects of Summer Drought on the Fine Root System of Five Broadleaf Tree Species along a Precipitation Gradient. Forests 2020, 11, 289.

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