Tree size mostly drives the variation of xylem traits at the treeline ecotone
The axial structure of the hydraulic system in trees is relatively invariant and insensitive to temperature, while trees plastically adjust the number of cells within the tree ring.
At higher elevations and latitudes in the treeline ecotone, reduction in the heat accrued during the growing season is reflected in gradually decreasing tree size. Due to low temperatures, treeline trees might produce smaller xylem cells and, as a consequence, tree growth could be limited. However, some xylem traits (i.e., cell lumen area) are considered relatively insensitive to climatic factors but highly dependent on tree size because of the natural widening of xylem conduits towards the stem base. We tested the hypothesis that earlywood cell lumen area is essentially invariant and depends largely on tree size. Tracheid traits in four conifer species from the lower (“timberline”) and upper (“treeline”) parts of the treeline ecotone (Picea engelmannii, Picea abies, Pinus cembra and Larix decidua) were measured in the Colorado Front Range (U.S.A.), Krkonoše Mts. (Czech Republic) and Dolomites (Italy). On transversal sections sampled at 1 m of stem height, we measured cell lumen areas, transversal cell size, cell wall thickness, tree-ring width and number of cells per radial file. Cell lumen areas were always greater at the timberline than treeline. When tree height is accounted for, the earlywood cell area did not differ between the two sites, thus showing that difference in temperature did not affect earlywood cell area in any of the four measured species. The number of cells within tree rings exhibited high inter-annual variability according to environmental factors. The fundamental hydraulic structure in trees is relatively rigid and insensitive to temperature, while trees plastically adjust the number of cells within the tree ring as a result of inter-annual climate variability and leaf production.
KeywordsPicea abies Picea engelmannii Pinus cembra Larix decidua Stem allometry Alpine treeline Conduit diameter Cell widening Wood anatomy
The study was supported by Grant Agency of Charles University (GAUK 996216) and largely performed during the stay of J. Kašpar at the University of Padova. Sampling in Front Range was possible thanks to the Fulbright fellowship to V. Treml and logistic support from the Biogeography Lab, University of Colorado. Alison Garside is acknowledged for checking the English.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- Daly C, Halbleib M, Smith JI, Gibson WP, Doggett MK, Taylor GH, Curtis J, Pasteris PP (2008) Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States. Int J Climatol 28:2031–2064. https://doi.org/10.1002/joc.1688 CrossRefGoogle Scholar
- Gärtner H, Schweingruber FH (2013) Microscopic preparation techniques for plant stem analysis. Verlag Dr Kessel, RemagenGoogle Scholar
- Kwiatkowski J (1982) Skutečné srážky v Krkonoších. Opera Corconctica 19:45–64Google Scholar
- Losso A, Anfodillo T, Ganthaler A, Kofler W, Markl Y, Nardini A, Oberhuber W, Purin G, Mayr S (2018) Robustness of xylem properties in conifers: analyses of tracheid and pit dimensions along elevational transects. Tree Physiol 38:212–222. https://doi.org/10.1093/treephys/tpx168 CrossRefPubMedGoogle Scholar
- Olson ME, Anfodillo T, Rosell JA, Petit G, Crivellaro A, Isnard S, León-Gómez C, Alvarado-Cárdenas LO, Castorena M (2014) Universal hydraulics of the flowering plants: vessel diameter scales with stem length across angiosperm lineages, habits and climates. Ecol Lett 17:988–997. https://doi.org/10.1111/ele.12302 CrossRefPubMedGoogle Scholar
- Olson ME, Soriano D, Rosell JA, Anfodillo T, Donoghue MJ, Edwards EJ, León-Gómez C, Dawson T, Julio CM, Castorena M, Echeverría A, Espinosa CI, Fajardo A, Gazol A, Isnard S, Lima RS, Marcati CR, Méndez-Alonzo R (2018) Plant height and hydraulic vulnerability to drought and cold. Proc Natl Acad Sci USA 115:7551–7556. https://doi.org/10.1073/pnas.1721728115 CrossRefPubMedGoogle Scholar
- Pallardy SG (2008) Physiology of woody plants, 3rd edn. Elsevier, AmsterdamGoogle Scholar
- Petit G, von Arx G, Kiorapostolou N, Lechthaler S, Prendin AL, Anfodillo T, Caldeira MC, Cochard H, Copini P, Crivellaro A, Delzon S, Gebauer R, Gričar J, Grönholm L, Hölttä T, Jyske T, Lavrič M, Lintunen A, Lobo-do-Vale R, Peltoniemi M, Peters RL, Robert EMR, Juan SR, Senfeldr M, Steppe K, Urban J, Van Camp J, Sterck F (2018) Tree differences in primary and secondary growth drive convergent scaling in leaf area to sapwood area across Europe. New Phytol 218(4):1383–1392CrossRefGoogle Scholar
- Pohlert T (2014) The Pairwise Multiple Comparison of Mean Ranks Package (PMCMR). R package. https://CRAN.R-project.org/package=PMCMR
- R Development Core Team (2017) R: a language and environment for statistical computing. R Foundation for Statistical Computing, ViennaGoogle Scholar
- Rossi S, Anfodillo T, Cufar K, Cuny HE, Deslauriers A, Fonti P, Frank D, Gricar J, Gruber A, King GM, Krause C, Morin H, Oberhuber W, Prislan P, Rathgeber CBK (2013) A meta-analysis of cambium phenology and growth: linear and non-linear patterns in conifers of the northern hemisphere. Ann Bot 112:1911–1920. https://doi.org/10.1093/aob/mct243 CrossRefPubMedPubMedCentralGoogle Scholar
- Rossi S, Anfodillo T, Čufar K, Cuny HE, Deslauriers A, Fonti P, Frank D, Gričar J, Gruber A, Huang JG, Jyske T, Kašpar J, King G, Krause C, Liang E, Mäkinen H, Morin H, Nöjd P, Oberhuber W, Prislan P, Rathgeber CBK, Saracino A, Swidrak I, Treml V (2016) Pattern of xylem phenology in conifers of cold ecosystems at the Northern Hemisphere. Glob Chang Biol 22:3804–3813. https://doi.org/10.1111/gcb.13317 CrossRefPubMedGoogle Scholar
- Speer JH (2012) Fundamentals of tree-ring research. University of Arizona PressGoogle Scholar
- Tyree MT, Evers FW (1991) The hydraulic architecture of trees and other woody plants. New Phytol 119:345–360. https://doi.org/10.1111/j.1469-8137.1991.tb00035.x CrossRefGoogle Scholar