Anatomical and ecophysiological responses of Quercus pubescens Willd. to different soil water availability from the submediterranean phytogeographic region of Slovenia

Lavrič, Martina (avtor), Gričar, Jožica (mentor), Vodnik, Dominik (komentor)

Intra-annual variations in leaf development, radial growth (including the secondary phloem part), sap flow and non-structural carbohydrates (NSCs) have been rarely studied in deciduous trees from drought-prone environments. In order to better understand the chronological order and temporal course of these processes, we monitored leaf phenology, xylem and phloem formation (in different tree parts), sap flow (HRM method), variations in NSC amounts and relationship between various wood-anatomical parameters and climatic factors in Quercus pubescens Willd. from Podgorski Kras in Slovenia during study period 2014–2016. For this purpose two research areas (RA) were selected, where at RA2 two adjacent plots differing in bedrock and soil type (flysch with eutric cambisol, high water retention - F; limestone with rendzic leptosol, low water retention - L) were sampled. We found that initial earlywood vessels were fully lignified and ready for water transport before bud opening at the beginning of April. Buds started to open in the second half of April and full leaf unfolding occurred by the end of May. Sap flow was increasing contemporarily with leaf development and LAI values. In the initial three weeks of radial growth, phloem growth preceded that of xylem. Cambial cell production was one month longer at the stem base than in branches. In addition, the xylem ring was wider than the phloem ring in all three parts. The amount of NSCs significantly differed among the tissue parts and sampling dates but not between the plots. Starch amounts were the highest in xylem and the amounts of free sugars were highest in inner phloem + cambium. Trees on F were more buffered against drier hydroclimatic conditions due to a higher availability of soil water. In the period of severe drought, sap flow density in trees growing on L was decoupled from the changes of vapour pressure deficit, due to increased employment of water conservation strategies (decreases in stomatal conductance). This was further translated into stomatal limitation of photosynthesis and contributed to reduced radial stem growth that revealed smaller yearly xylem increments in L trees and anatomical acclimations of conductive tissues, supporting/preserving trees' hydraulic function. Xylem ring width, early- and latewood widths, diameter, area and number of earlywood vessels were mainly related to temperature. Our study confirmed that the temporal sequence of leaf development and radial growth are not contemporary. Soil water availability substantially influenced secondary growth in the stem, whereas NSC amounts seemed to be less affected. It has been demonstrated that latewood width and earlywood vessel characteristics are promising wood-anatomical parameters containing complementary information on the impact of weather conditions on radial growth. We concluded that climate is not the only driver for radial growth of Q. pubescens at the selected locations; soil type with respect to water retention potential is also important environmental feature that needs to be considered in wood formation studies and growth models in the future.

• Jezik: Angleški jezik
• Ključne besede: pubescent oak, submediterranean climate, karst, drought, radial growth, sap flow, leaf development, non-structural carbohydrates, stem, branch, xylem, phloem, cambium, earlywood, vessel, stomatal conductance
• Vrsta gradiva: Doktorsko delo/naloga
• Tipologija: 2.08 - Doktorska disertacija
• Organizacija: BF - Biotehniška fakulteta
• Založnik: [M. Lavrič]
• Leto izida: 2019
• PID: 20.500.12556/RUL-112569
• UDK: 581:5:633.872(497.4)(043.3)
• COBISS.SI-ID: 936311
• Datum objave v RUL: 25.10.2019

Sekundarni jezik

• Jezik: Slovenski jezik
• Naslov: Anatomski in ekofiziološki odzivi puhastega hrasta (Quercus pubescens Willd.) na vsebnost vode v tleh v submediteranskem fitogeografskem območju Slovenije

Izvleček

Medletna dinamika v razvoju listov, debelinski rasti (vključno z razvojem sekundarnega floema), ksilemskem toku vode in količinah nestrukturnih ogljikovih hidratov (NOH) je redko preučevana pri listavcih v okolju, ki je izpostavljeno suši. Z namenom boljšega razumevanja kronološkega zaporedja in časovnega poteka teh procesov smo spremljali fenologijo listov, nastanek ksilema in floema (v različnih delih drevesa), ksilemski tok vode (HRM metoda), razporeditev NOH in povezanost med različnimi lesno-anatomskimi parametri in podnebnimi dejavniki pri puhastem hrastu (Quercus pubescens Willd.) na Podgorskem Krasu (JZ Slovenija) v obdobju 2014-2016. V ta namen smo izbrali dva raziskovalna območja (RO), kjer smo na RO2 vzorčili dve bližnji ploskvi, ki sta se razlikovali v matični podlagi in tipu tal (evtrična rjava tla na flišu, visoko zadrževanje vode - F; rendzina na apnencu, slaba sposobnost zadrževanja vode - L). Ugotovili smo, da so bile prve traheje v ranem lesu popolnoma lignificirane in pripravljene za transport vode pred odpiranjem brstov na začetku aprila. V drugi polovici aprila so se brsti začeli odpirati in polno olistanje dreves je nastopilo konec maja. Ksilemski tok vode je naraščal sočasno z razvojem listov in vrednostmi LAI. V prvih treh tednih debelinske rasti je rast floema potekala pred rastjo ksilema. Začetek in konec nastanka kambijevih celic sta bila sinhronizirana na obeh lokacijah v vejah, vendar sta bila različna v deblu (za mesec daljše). Ksilemski prirastek v deblu in v vejah je bil širši od floemskega prirastka. Količina NOH se je bistveno razlikovala med posameznimi tkivi in datumi vzorčenja, ne pa med ploskvama. Količina škroba je bila najvišja v ksilemu in količina topnih sladkorjev v notranjem floemu + kambiju. Hrasti na mokrem rastišču F so bili bolj zaščiteni pred sušnimi hidroklimatskimi razmerami. V obdobju močne suše, ksilemski tok vode v hrastih na L ni bil odvisen od sprememb v deficitu tlaka vodne pare, ampak je na njegovo dinamiko vplivala povečana uporaba strategij hrasta za ohranjanje vode, kot je zmanjšanje stomatalne prevodnosti. To je vplivalo na omejevanje fotosinteze in prispevalo k zmanjšanju debelinske rasti debla. Anatomske študije so pokazale manjše letne prirastke ksilema pri hrastih s ploskve L in anatomske aklimacije prevodnih tkiv, ki podpirajo/ohranjajo hidravlično funkcijo dreves. Končna širina branike, širina kasnega in ranega lesa ter premer, površina in število trahej ranega lesa so bili povezani predvsem s temperaturo. Potrdili smo, da časovno zaporedje razvoja listov in debelinske rasti ni usklajeno. Razpoložljivost vode v tleh je bistveno vplivala na sekundarno rast v deblu, medtem ko na količine NOH ni bilo zaznati vpliva. Ugotovili smo, da so širina kasnega lesa in značilnosti trahej ranega lesa primerni lesno-anatomski parametri, ki vsebujejo komplementarne informacije o vplivu vremenskih razmer na debelinsko rast. Potrdili smo, da podnebje ni edino, ki vpliva na debelinsko rast puhastega hrasta na izbranih lokacijah. Talni tip z vidika sposobnosti zadrževanja vode je tudi pomembna okoljska značilnost, ki jo je potrebno upoštevati pri preučevanju rasti in funkcionalnosti dreves v različnih okoljskih razmerah ter modelih debelinske rasti v prihodnosti.

• Ključne besede: puhasti hrast, submediteransko podnebje, kras, suša, debelinska rast, ksilemski tok vode, razvoj listov, nestrukturni ogljikovi hidrati, deblo, veja, ksilem, floem, kambij, rani les, traheja, stomatalna prevodnost