@article{LuebbeLamarqueDelzonetal.2022,
  author    = {L{\"u}bbe, Torben and Lamarque, Laurent J. and Delzon, Sylvain and Torres Ruiz, Jos{\´e} M. and Burlett, R{\´e}gis and Leuschner, Christoph and Schuldt, Bernhard},
  title     = {High variation in hydraulic efficiency but not xylem safety between roots and branches in four temperate broad-leaved tree species},
  series = {Functional Ecology},
  volume    = {36},
  journal   = {Functional Ecology},
  number    = {3},
  issn      = {0269-8463},
  doi       = {10.1111/1365-2435.13975},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318587},
  pages     = {699 -- 712},
  year      = {2022},
  abstract  = {Xylem hydraulic safety and efficiency are key traits determining tree fitness in a warmer and drier world. While numerous plant hydraulic studies have focused on branches, our understanding of root hydraulic functioning remains limited, although roots control water uptake, influence stomatal regulation and have commonly been considered as the most vulnerable organ along the hydraulic pathway. We investigated 11 traits related to xylem safety and efficiency along the hydraulic pathway in four temperate broad-leaved tree species. Continuous vessel tapering from coarse roots to stems and branches caused considerable reduction in hydraulic efficiency. Wood density was always lowest in roots, but did not decline linearly along the flow path. In contrast, xylem embolism resistance (P50) did not differ significantly between roots and branches, except for one species. The limited variation in xylem safety between organs did not adequately reflect the corresponding reductions in vessel diameter (by ~70\%) and hydraulic efficiency (by ~85\%). Although we did not observe any trade-off between xylem safety and specific conductivity, vessel diameter, vessel lumen fraction and wood density were related to embolism resistance, both across and partly within organs. We conclude that coarse roots are not highly vulnerable to xylem embolism as commonly believed, indicating that hydraulic failure during soil drying might be restricted to fine roots.},
  language  = {en}
}
@article{WeithmannLinkBanzragchetal.2022,
  author    = {Weithmann, Greta and Link, Roman M. and Banzragch, Bat-Enerel and W{\"u}rzberg, Laura and Leuschner, Christoph and Schuldt, Bernhard},
  title     = {Soil water availability and branch age explain variability in xylem safety of European beech in Central Europe},
  series = {Oecologia},
  volume    = {198},
  journal   = {Oecologia},
  number    = {3},
  doi       = {10.1007/s00442-022-05124-9},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324228},
  pages     = {629-644},
  year      = {2022},
  abstract  = {Xylem embolism resistance has been identified as a key trait with a causal relation to drought-induced tree mortality, but not much is known about its intra-specific trait variability (ITV) in dependence on environmental variation. We measured xylem safety and efficiency in 300 European beech (Fagus sylvatica L.) trees across 30 sites in Central Europe, covering a precipitation reduction from 886 to 522 mm year-1. A broad range of variables that might affect embolism resistance in mature trees, including climatic and soil water availability, competition, and branch age, were examined. The average P50 value varied by up to 1 MPa between sites. Neither climatic aridity nor structural variables had a significant influence on P50. However, P50 was less negative for trees with a higher soil water storage capacity, and positively related to branch age, while specific conductivity (Ks) was not significantly associated with either of these variables. The greatest part of the ITV for xylem safety and efficiency was attributed to random variability within populations. We conclude that the influence of site water availability on P50 and Ks is low in European beech, and that the high degree of within-population variability for P50, partly due to variation in branch age, hampers the identification of a clear environmental signal.},
  subject      = {Bodenwasser},
  language  = {en}
}
@article{FuchsHertelSchuldtetal.2020,
  author    = {Fuchs, Sebastian and Hertel, Dietrich and Schuldt, Bernhard and Leuschner, Christoph},
  title     = {Effects of summer drought on the fine root system of five broadleaf tree species along a precipitation gradient},
  series = {Forests},
  volume    = {11},
  journal   = {Forests},
  number    = {3},
  issn      = {1999-4907},
  doi       = {10.3390/f11030289},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-203189},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}