Früher Laubfall der Buche während der Sommertrockenheit 2018: Resistenz oder Schwächesymptom?

Wohlgemuth, Thomas; Kistler, Martin; Aymon, Celine; Hagedorn, Frank; Geßler, Arthur; Goßner, Martin M.; Queloz, Valentin; Vögtli, Irina; Wasem, Ulrich; Vitasse, Yann; Rigling, Andreas

doi:10.3188/szf.2020.0257

Cited by 22 publications

(16 citation statements)

References 4 publications

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“…The relative effects of these drivers often depend on the species. For example, severe drought has been shown to hasten leaf senescence of temperate trees at low elevations (Hwang et al ., 2014 ; Xie et al ., 2015 ), which might be a strategy to reduce transpiration (Munné‐Bosch & Alegre, 2004 ) and avoid xylem embolism (Bréda et al ., 2006 ) or the direct consequence of vessel cavitation under extreme severe drought as observed for European beech in central Europe during the summer 2018 (Schuldt et al ., 2020 ; Wohlgemuth et al ., 2020 ). Our results also showed earlier senescence under drought compared with the control‐drought plots for beech and delayed senescence in the irrigated plots.…”

Section: Discussionmentioning

confidence: 99%

Impact of microclimatic conditions and resource availability on spring and autumn phenology of temperate tree seedlings

et al. 2021

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Microclimatic effects (light, temperature) are often neglected in phenological studies and little is known about the impact of resource availability (nutrient and water) on tree's phenological cycles.• Here we experimentally studied spring and autumn phenology in four temperate trees in response to changes in bud albedo (white-vs. black-painted buds), light conditions (nonshaded vs. ~70% shaded), water availability (irrigated, control and reduced precipitation) and nutrients (low vs. high availability). • We found that higher bud albedo or shade delayed budburst (up to +12 days), indicating that temperature is sensed locally within each bud. Leaf senescence was delayed by high nutrient availability (up to +7 days) and shade conditions (up to +39 days) in all species, except oak. Autumn phenological responses to summer droughts depended on species, with a delay for cherry (+ 7 days) and an advance for beech (-7 days). • The strong phenological effects of bud albedo and light exposure reveal an important role of microclimatic variation on phenology. In addition to the temperature and photoperiod effects, our results suggest a tight interplay between source and sink processes in regulating the end of the seasonal vegetation cycle, which can be largely influenced by resource availability (light, water and nutrients).

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Section: Discussionmentioning

confidence: 99%

Impact of microclimatic conditions and resource availability on spring and autumn phenology of temperate tree seedlings

et al. 2021

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“…In 2018, large parts of Central Europe experienced a severe and long‐lasting summer drought with strong impacts on tree and forest functioning (Buras et al ., 2020 ; Schuldt et al ., 2020 ). European beech was especially affected, as indicated by extremely premature leaf senescence (Wohlgemuth et al ., 2020 ). At our site, Ψ soil values below −1 MPa were observed during the drought period indicating soil drought conditions at a level that can lead to xylem embolism in beech (Walthert et al ., 2021 ).…”

Section: Discussionmentioning

confidence: 99%

“…Our beech trees did not quantitatively compensate for restricted topsoil water availability by additional uptake from deeper soil layers. This inability helps to explain the widespread damage of beech during the extremely hot and dry summer of 2018 all over Europe (Schuldt et al ., 2020 ; Wohlgemuth et al ., 2020 ; Walthert et al ., 2021 ) and is in agreement with the supposed drought susceptibility of beech (Rennenberg et al ., 2004 ; Gessler et al ., 2007 ). At our site, however, we also observed a rather fast restoration of water uptake, which also matches the high recovery potential of beech after drought (Rohner et al ., 2021 ).…”

Section: Discussionmentioning

confidence: 99%

Drought reduces water uptake in beech from the drying topsoil, but no compensatory uptake occurs from deeper soil layers

et al. 2021

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The intensity and frequency of droughts events are projected to increase in future with expected adverse effects for forests. Thus, information on the dynamics of tree water uptake from different soil layers during and after drought is crucial.We applied an in situ water isotopologue monitoring system to determine the oxygen isotope composition in soil and xylem water of European beech with a 2-h resolution together with measurements of soil water content, transpiration and tree water deficit. Using a Bayesian isotope mixing model, we inferred the relative and absolute contribution of water from four different soil layers to tree water use.Beech took up more than 50% of its water from the uppermost 5 cm soil layer at the beginning of the 2018 drought, but then reduced absolute water uptake from the drying topsoil by 84%. The trees were not able to quantitatively compensate for restricted topsoil water availability by additional uptake from deeper soil layers, which is related to the fine root depth distribution. Absolute water uptake from the topsoil was restored to pre-drought levels within 3 wk after rewetting.These uptake patterns help to explain both the drought sensitivity of beech and its high recovery potential after drought release.

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“…This was also observed by Wohlgemuth et al . (2020), suggesting that leaf shedding must be considered as a symptom of vulnerability rather than protection against excessive water loss. Similarly, a lower HV is usually linked to significantly higher embolism rates in mature beech trees (Schuldt et al .…”

Section: Introductionmentioning

confidence: 99%

Leaf trait modification in European beech trees in response to climatic and edaphic drought

et al. 2021

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Leaf morphological and physiological traits control the carbon and water relations of mature trees and are determinants of drought tolerance, but it is not well understood how they are modified in response to water deficits. We analysed five sun‐canopy leaf traits (mean leaf size (LS), specific leaf area (SLA), Huber value (HV), water potential at turgor loss point (Ψtlp) and foliar carbon isotope signature (δ13C)) in European beech (Fagus sylvatica L.) across three precipitation gradients sampled in moist (2010), dry (2019) and very dry (2018) summers, and tested their response to short‐term water deficits (climatic water balance (CWB) preceding sample collection) and long‐term water availability (mean annual precipitation (MAP), plant‐available soil water capacity (AWC) and neighbourhood competition). Across the 34 sites, LS varied seven‐fold (3.9−27.0 cm2), SLA four‐fold (77.1−306.9 cm²·g−1) and HV six‐fold (1.0−6.65 cm2·m−2). In the 2018 dataset, LS showed a negative and HV a positive relationship to MAP, which contradicts relations found in multi‐species samples. Average Ψtlp ranged from −1.90 to −2.62 MPa and decreased across the sites with decreasing CWB in the month prior to measurement, as well as with decreasing MAP and AWC in 2019. Studied leaf traits varied considerably between years, suggesting that mast fruiting and the severe 2018 drought caused the formation of smaller leaves. We conclude that sun‐canopy leaf traits of European beech exhibit considerable plasticity in response to climatic and edaphic aridity, and that osmotic adjustment may be an important element in the drought response strategy of this anisohydric tree species.

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Früher Laubfall der Buche während der Sommertrockenheit 2018: Resistenz oder Schwächesymptom?

Cited by 22 publications

References 4 publications

Impact of microclimatic conditions and resource availability on spring and autumn phenology of temperate tree seedlings

Impact of microclimatic conditions and resource availability on spring and autumn phenology of temperate tree seedlings

Drought reduces water uptake in beech from the drying topsoil, but no compensatory uptake occurs from deeper soil layers

Leaf trait modification in European beech trees in response to climatic and edaphic drought

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