Boreal tree-rings are influenced by temperature up to two years prior to their formation: a trade-off between growth and reproduction?

Large spatial and between-tree variability has recently been observed in the response of boreal forests to ongoing climate change, spanning from growth stimulation by increasing temperatures to drought limitation. To predict future responses of boreal forests, it is necessary to disentangle the drivers modulating the temperature-growth interaction. To address this issue, we established two inventory plots (at a treeline and closed-canopy forest) and assembled site chronologies in Picea glauca stands at the transition between boreal forest and tundra in Northern Quebec, Canada. In addition to site chronologies, we established a set of chronologies containing, for each year, exclusive subsets of tree-rings with specific cambial age (young/old), tree dimensions (small/large) and tree social status (dominant/suppressed). All chronologies were correlated with climatic data to identify the course of climatic conditions driving variability in tree-ring widths. Our results show that the growth of P. glauca correlates significantly with summer temperature in tree-ring formation years and during up to two prior summers. Tree-ring width is positively influenced by summer temperatures in tree-ring formation year and two years prior to tree-ring formation. In addition, climate-growth correlations indicate a negative effect of summer temperature one year before tree-ring formation at the closed-canopy forest site. The pattern of climate-growth correlations is tightly synchronized with previously published patterns of climate-reproduction correlations of P. glauca, suggesting a growth-reproduction trade-off as a possible factor modulating the response of boreal forests to summer temperatures. Climatic signal does not differ between pairs of chronologies based on subsets of cambial ages, stem dimensions or tree competition status at the treeline site. However, the response to summer temperatures one year before tree-ring formation is significant only in mature (old, large and dominant) individuals at the closed-canopy site. The inverse pattern of temperature-growth correlations during a sequence of three years challenges predictions of how boreal forests respond to climate change.European Union's Horizon 2020 project INTERACT [730938]; Charles University [UNCE/HUM 018

Kvantitativní parametry cév listnáčů jako nástroj pro rekonstrukci fyzickogeografických procesů

Anatomická stavba dřeva je citlivá k vlivům prostředí, což umožňuje následné využití časových řad kvantitativních anatomických parametrů jako zdroje paleoenvironmentálních dat. V této disertační práci jsem studoval odezvu parametrů cév i) dubů letních rostoucích v údolní nivě ke změnám v hladině podzemní vody, klimatu, hydrologických podmínek a k výskytu extrémních hydrologických a meteorologických jevů (sucha, povodně) a ii) bříz bělokorých na mechanické poškození vlivem disturbancí různého typu. Zatímco klimatický signál šířek letokruhů i letokruhové signatury vykazují velkou prostorovou variabilitu, kvantitativní parametry jejich cév mají společný prostorově homogenní signál (pozitivní vliv teploty v létě předchozího roku, v zimě a na začátku jara). Jediný stanovištní rozdíl v klimatickém signálu chronologií založených na cévách je negativní vliv vysoké vlhkosti na velikost cév, pozorovaný pouze v nivě a ne v od řeky vzdálenějších nížinných porostech. To naznačuje, že vývoj efektivních vodivých pletiv dubu je v záplavové zóně limitován vysokou saturací půdního profilu vodou, ačkoliv vysoká dostupnost vody je tam pozitivní z pohledu produktivity. Odezva šířek letokruhů ke změnám v dostupnosti vody není v případě dubů uniformní ani v rámci jednoho porostu vlivem koexistence jedinců se zcela...Trees adjust wood anatomical structure to environmental conditions, predisposing time series of quantitative wood anatomical parameters to be valuable source of palaeoenvironmental information. In this doctoral project we analysed the response of vessel parameters of i) floodplain Quercus robur to groundwater level fluctuation, hydroclimate variability and extreme events (droughts and floods), and of ii) Betula pendula to mechanical damage caused by various disturbances. Although climatic signal as well as pointer years stored in tree-ring width chronologies of Quercus robur largely differ between sites, quantitative vessel parameters contain spatially- homogenous positive signal of previous year summer temperature and current year winter/early spring temperature. The only between-site difference in wood anatomical chronologies is negative effect of moisture on vessel size in floodplain, which does not occur in not-flooded lowland sites. We suggest that while tree productivity benefits from high water availability, the wood anatomical structure of Quercus robur is constrained by high soil water saturation in floodplain zone. In addition, the response of tree-ring widths to moisture availability is not uniform inside single stand, but subgroups of trees with completely opposite response coexist...Katedra fyzické geografie a geoekologieDepartment of Physical Geography and GeoecologyFaculty of SciencePřírodovědecká fakult

Dendrochronological dating of the past avalanche events in the Krkonose Mts.

Avalanches are important natural processes which shape the character of large mountainous areas. The reconstruction of their history has been performed on avalanche tracks in the Důl Bílého Labe Valley, Krkonoše Mts. through application of dendrogeomorphological methods. In total 101 trees from the area of 5 avalanche tracks were cored or cross-sectioned, which helped to identify 1253 growth disturbances (abrupt growth suppressions or releases, increases in tree-ring eccentricity, traumatic resin ducts, reaction wood, callus or determination of the tree death). The analysis spanning period from the 1859 led to the identification of 40 avalanche events, which prolong and complement written evidences of avalanche falls (avalanche cadastre). However, because of limitations of dendrogeomorphology (especially impossibility of dating of small events), these results have character of only minimal number of events. Strong influence of monthly snow melting and snow accumulation on initiation of events was pointed out through the statistical analysis of snowpack changes in relation to the reconstructed avalanche activity. Two main possible natural reasons for avalanche activity initiation were identified - vast spring snow melting and loading with fresh snow. The analysis demonstrates the potential of..

Landslide-induced changes of vessel shape in Betula pendula roth. :a preliminary study

Investigation of relationship between vessel structures and exogenous geomorphic processes like landslides, rockfalls, debris flows as well as snow avalanches are common in present dendrogeomorphology. However, very little is known yet about change of the shape characteristics of vessels of Betula pendula as a result of different mass movements. Analysis of vessel lumen length (LL) and width (LW) change on 49 microsections prepared from 15 landslide-disturbed-birches was the goal of this study. A relationship between LW and LL was reported for the year before (2010) and after (2011) landslide separately using equation of linear regression. To evaluate inter-annual variability of changes in shape parameters of tracheas, the proportions of LW and LL in year 2009 was also described for 8 disturbed trees. Slope of the regression line very well characterizes the relationship between LW and LL and evaluation of inter-annual change between LW and LL was carried out based on annual change index (ACI). ACI was defined as a value of percentage change in the slope of the regression lines before and after the landslide disturbance. There is statistically significant change in vessel shape parameters between the years 2010 and 2011. Overall, the highest values of ACI were calculated in microsections sampled in the direction of slope distribution - side of reaction wood production, where ACI2010/11 average value was higher than 43% which is twice more than values from other samples. Increasing of isodiametricity is also typical, while it was found at 65% of analysed disturbed samples.596

Quantitative vessel parameters of broadleaves as a tool for reconstruction of physical geographical processes

Trees adjust wood anatomical structure to environmental conditions, predisposing time series of quantitative wood anatomical parameters to be valuable source of palaeoenvironmental information. In this doctoral project we analysed the response of vessel parameters of i) floodplain Quercus robur to groundwater level fluctuation, hydroclimate variability and extreme events (droughts and floods), and of ii) Betula pendula to mechanical damage caused by various disturbances. Although climatic signal as well as pointer years stored in tree-ring width chronologies of Quercus robur largely differ between sites, quantitative vessel parameters contain spatially- homogenous positive signal of previous year summer temperature and current year winter/early spring temperature. The only between-site difference in wood anatomical chronologies is negative effect of moisture on vessel size in floodplain, which does not occur in not-flooded lowland sites. We suggest that while tree productivity benefits from high water availability, the wood anatomical structure of Quercus robur is constrained by high soil water saturation in floodplain zone. In addition, the response of tree-ring widths to moisture availability is not uniform inside single stand, but subgroups of trees with completely opposite response coexist..

Dendrochronological dating of catastrophic slope movements

Mass-movements are one example of natural processes that can pose a serious risk for human beings and their possessions. Dendrochronology, a method capable of their reconstruction, can provide parameters of former events, which can be used for planning protective measures. The possibilities for the application of dendrochronological methods have been tested by means of meta-analysis of electronic and printed scientific articles and a case study focused on former avalanche activity in Schustler's avalanche path (Labský důl, Krkonoše Mts.). The main conclusion of the first one is the clear spatial disproportion of the recent dendrogeomorphological research activities - e.g. the dating of avalanches is typical for mountains of Montana (USA); the Alpine region (mainly Switzerland), on the other hand, absolutely dominates in the research of debris-flows. In the case study, the analysis of material with well-chosen indicators led to high accuracy results comparable with the results of scientific articles focused on avalanches, and made the identification of 14 years (in the period 1953-2007) with potential avalanche acitvity possible. Although methods of dendrogeomorphology are usually neglected in the research of avalanches in the Czech republic, their great potential for future applications is shown...

Quantitative vessel parameters of broadleaves as a tool for reconstruction of physical geographical processes

Trees adjust wood anatomical structure to environmental conditions, predisposing time series of quantitative wood anatomical parameters to be valuable source of palaeoenvironmental information. In this doctoral project we analysed the response of vessel parameters of i) floodplain Quercus robur to groundwater level fluctuation, hydroclimate variability and extreme events (droughts and floods), and of ii) Betula pendula to mechanical damage caused by various disturbances. Although climatic signal as well as pointer years stored in tree-ring width chronologies of Quercus robur largely differ between sites, quantitative vessel parameters contain spatially- homogenous positive signal of previous year summer temperature and current year winter/early spring temperature. The only between-site difference in wood anatomical chronologies is negative effect of moisture on vessel size in floodplain, which does not occur in not-flooded lowland sites. We suggest that while tree productivity benefits from high water availability, the wood anatomical structure of Quercus robur is constrained by high soil water saturation in floodplain zone. In addition, the response of tree-ring widths to moisture availability is not uniform inside single stand, but subgroups of trees with completely opposite response coexist..

Landslide-induced changes of vessel shape in Betula pendula Roth. – A preliminary study

Investigation of relationship between vessel structures and exogenous geomorphic processes like landslides, rockfalls, debris flows as well as snow avalanches are common in present dendrogeomorphology. However, very little is known yet about change of the shape characteristics of vessels of Betula pendula as a result of different mass movements. Analysis of vessel lumen length (LL) and width (LW) change on 49 microsections prepared from 15 landslide-disturbed-birches was the goal of this study. A relationship between LW and LL was reported for the year before (2010) and after (2011) landslide separately using equation of linear regression. To evaluate inter-annual variability of changes in shape parameters of tracheas, the proportions of LW and LL in year 2009 was also described for 8 disturbed trees. Slope of the regression line very well characterizes the relationship between LW and LL and evaluation of inter-annual change between LW and LL was carried out based on annual change index (ACI). ACI was defined as a value of percentage change in the slope of the regression lines before and after the landslide disturbance. There is statistically significant change in vessel shape parameters between the years 2010 and 2011. Overall, the highest values of ACI were calculated in microsections sampled in the direction of slope distribution – side of reaction wood production, where ACI2010/11 average value was higher than 43% which is twice more than values from other samples. Increasing of isodiametricity is also typical, while it was found at 65% of analysed disturbed samples. Změny tvarových parametrů cév břízy bělokoré (Betula pendula Roth.) vyvolané svahovými pohyby – Předběžná studie Za účelem ověření vhodnosti břízy bělokoré pro dendrogeomorfologickou analýzu svahových pohybů bylo z prostoru lesního porostu poblíž Jezeří, poničeného sesuvem z ledna 2011, připraveno 67 trvalých preparátů z 24 vytipovaných stromů (15 disturbovaných a 9 referenčních). Pomocí softwaru WinCell Pro 2011a byly na detailních mikrosnímcích anatomické struktury naměřeny šířky (LW) a délky (LL) lumenů dohromady 8236 trachejí v letokruzích vytvořených v letech 2010, 2011 a (za účelem zhodnocení meziroční variability tvaru cév) u vybraných jedinců i v roce 2009. Typický tvar buňky v daném letokruhu byl popsán pomocí směrnice regresní přímky udávající závislost mezi LW a LL a následně byla vypočtena meziroční procentuální změna této směrnice v daném vzorku (Annual Change Index – ACI). Průměrné hodnoty ACI se v případě referenčních a disturbovaných stromů rok před sesuvem (tj. mezi lety 2009 a 2010) pohybují pod hodnotou 23 %, což lze považovat za hranici udávající změny způsobené jinými než vysoce energetickými gravitačními procesy. V případě disturbovaných jedinců mezi lety 2010 a 2011 dosahuje ACI ve směrech A, B, C a D průměrných hodnot 21,1 %, 43,7 %, 21,7 % a 26,2 %. V případě trachejí na straně B (proti svahu, tedy místo působení tahu a tvorby tenzního dřeva) se hodnoty směrnice regresní přímky statisticky významně liší mezi lety 2010 a 2011 (doloženo Wilcoxonovým a Znaménkovým testem – obě p-hodnoty < 0,001) a hodnoty ACI jsou odlišné od hodnot v ostatních orientacích vzorkování u disturbovaných stromů (ANOVA p-hodnota = 0,0459 a následný post-hoc test). Nejvyšší hodnoty ACI2010/11 byly obecně zaznamenány u jedinců s nejzávažnějším typem vnější deformace (např. zasypání báze kmene, exponované kořeny). Závěry této předběžné studie dokládají, že naklonění a další externí deformace kmene břízy bělokoré nacházejí odezvu v tvarových parametrech jejích cév. Nabízí se tak možnost využití trachejí jako indikátoru svahových disturbancí v dalších oblastech antropogenního reliéfu Mostecka i celé ČR; stejně tak však vyvstávají další výzkumné otázky týkající se metody – hlavně pokud se jedná o příčiny nízkého (zhruba do 20 %) ACI zjištěného u referenčních jedinců a v letech bez svahové aktivity.slovenské národnosti. Avšak v této souvislosti je třeba zdůraznit, že vysoká ruralita volebních zisků SMK-MKP je vzhledem k prostorové kompozici jejího elektorátu zapříčiněna především etnickou strukturou obyvatel Slovenska charakterizovanou územní koncentrací občanů maďarské národnosti v jižních částech země. Venkovský profil voličské podpory této strany se tedy programově neváže na prosazování hodnot a potřeb venkovské komunity jako takové. Naopak nejmenší volebně-preferenční nesoulad mezi elektorátem měst a venkovských obcí byl zjištěn v těch částech Slovenska, které vykazují podobné sociální a ekonomické charakteristiky obou prostředí a nacházejí svůj politický rozměr ve volebních inklinacích samotného regionu bez zásadnějšího vlivu zkoumané konfliktní linie. Regionální obraz úrovně sociopolitického štěpení společnosti urbánního a rurální prostředí lze z prostorového hlediska považovat v rámci území Slovenské republiky za dlouhodobě platný. Rovněž můžeme předpokládat, že ke zmírňování společensko- politického rozporu mezi městem a venkovem přispívá relevantním dílem i probíhající proces suburbanizace největších měst Slovenska