Variation of leaf and fruit descriptors in Q. pubescens-Q. virgiliana complex in Romania Nicolae Sofletea, Lucian Alexandru Curtu, Mihai Cristian Enescu UNIVERSITY TRANSILVANIA of BRASOV
Genus Quercus in Romania: 1,13 mil. ha – 18,2 % of forestry area; Mesothermous and mesophilous species: Q. robur andQ. petraea; Mesothermophilous and mesoxerophilous species: Q. cerris and Q. frainetto; Thermophilous and xerophilous species: Q. pedunculiflora, Q. pubescens andQ. virgiliana
Q. pubescens and Q. virgiliana are located in scattered stands in wood steppe of Dobrogea, Oltenia, Muntenia, Moldova, southern Banat and extrazonal populations in Transilvania A B Q. pubescens (A) and Q,. virgiliana (B) distribution in Romania ( Sanda et al. 2004)
The high adaptability of these taxa to water and temperature stress may be used for buffering the negative effects of climate warming An alternative would be the introduction of the two species in the regions expected to become drier in the future in order to replace the existing species that are no sufficiently adapted to water and temperature stress Consequently, our interest for these taxa will increase in the future
The current taxonomic status of Quercus virgiliana is still unclear: Separate species ? Intraspecific unit of Q . pubescens ? It is even not recognized as a taxon or infrataxon !
The aim of our study was to offer the first data on morphological variability of these taxa in Romania based on leaf and fruit descriptors used in taxonomical determinations by means of statistical tools This data will be used in the future to explore the genetic variability of Romanian populations,for breeding programs, conservation of genetic resources, regulations on the movement of forest reproductive material a.s.o.
Material : The samples were collected in 4 stands situated in different regions ocupied by the two taxa in Romania; 3 are mixed zones with Q. pubescens and Q. virgiliana, nominated in the literature : Macinului Mountains, Ciucurova and Clisura Dunării; the fourth is a NATURA 2000 site for Q.pubescens, Petiş, in central Transilvania A total of 119 trees were analysed; trees situated at 30-50 m between them Branches were collected from the upper part of the crown,with full-developed leaves (at the end of summer – beginning of autumn) 5 leaves/tree and some peduncles of cupula/tree were measured
Methods : • The protocol of leaf morphology assessment was based upon Kremer et al.(2002) and density pubescens after Kissling΄s (1977) grading system • Dimensional characters (measured with an WinFolia scanner for leaves and with a caliper for the length of cupula peduncles) • LL – lamina lenght; PL – petiole length LW – lobe width; SW – sinus width; • WP – length of lamina at largest width • Lped – total length of cupula peduncle in an inflorescence; • lped – length of the peduncle until the first cupula • 2. Observed variables: • BS – basal shape of the lamina (scored as an index: 1 to 9); • PU – abaxial laminar pubescence (scored as an index: 1 – no pubescence to • 6-dense hairiness);
3. Counted variables: NL – number of lobes NV - number of intercalary veins N – number of cupula on an inflorescence 4. Transformed variables: OB – lamina shape (obversity): OB = 100 * WP / LL PR – petiole ratio : PR = 100 * PL / (LL+PL) LDR – lobe depth ratio: LDR = 100 * (LW – SW) / LW LWR – lobe width ratio: LWR = 100 * LW / LL PV – percentage venation: PV = 100 * NV / NL Mean values and standard deviations were estimated for each character Correlations between all characters and LL and PL descriptors were evaluated ANOVA and F statistics have been used for determinig intra and inter- stands variation Principal component analysis (PCA) was applied for determining the influence of the first two synthetic variables
Results: Table 1. Mean values (x), standard deviations (SD) and ANOVA for leaf and fruit descriptors
Conclusions about the morphology: The most intens pubescence was revealed in Petiş Q. pubescens stands The two phytocoenoses situated in Dobrogea (Macinului Mountains and Ciucurova) revealed similaritis for many of the characters: e.g. low cordate-auriculate leaves, low number of intercalary vains, low number of lobes and relatively long petiole; Lped and lped are longer in this area. In the Clisura Dunarii stands NL and BS showed the highest values The most important descriptors for the differentiation between Q. pubescens and Q. virgiliana (LL, PL, NL, Lped and lped) indicate that, the trees sampled belong to Q. pubescens. Only a few number of trees existing in Dobrogea show intermediate traits between the two taxa Only one tree situated in Petiş phytocoenosis showed a very high value for the length of cupula peduncle for Q. pubescens, butother descriptors do not support a Q. virgiliana taxonomic status of this tree.
ANOVA test showed that: Significant differences within phytocoenoses for 12 characters, excepte for: LL, PL, OB and lped Nonsignificant differences among phytocoenoses for all characters
Correlations between descriptors: Table 2. Correlations between leaf and fruit descriptors
The main conclusions regarding the correlations beetwen descriptors: A negative correlation LL - PU [maximum value (r = - 0, 47) in Petiş phytocoenosis] trees with small leaves may be a biotype with a high level of drought resistance A negative and relatively intense correlation LL – PR (r = - 0,31 to – 0,69); this value is significant for the pubescent oak . By contrast, Kremer et al. (2002) reported r = - 0,09 in mixed stands of Q.robur and Q petraea Moderate to very high values for the correlations betweenLL versus LW, SW andWP( r = 0,51...0,92); Kremer et al . (2002) reported similar values ina mixed stand of Q. robur and Q. petraea (r = 0,45...0,73) A positive correlation PL - Lped (r = 0,35); this show that, the two descriptors are useful for the taxonomic discrimination between Q. pubescens and Q. virgiliana: PL and Lped have small values in Q. pubescens and greater in Q. virgiliana
Principal Component Analysis (PCA): The general conclusion resulted from the PCAdiagrames is that in Ciucurova, Petis and Clisura Dunarii phytocoenoses the principal components generate a single morphological group specific to Q. pubescens Our data indicate that only a very small number of trees could be intermediates between Q. pubescens and Q. virgiliana PCA for leaves and fruits descriptors in Petis phytocenosis
In Macinului Mountains phytocoenosis, although the leaf and cupula descriptors do not differentiate clearly the specimens with characters of Q. virgiliana, there is a small tendency to form two morphological groups, especially on fruit descriptors a b Macinului Mountains: a. PCA for leaves b. PCA for fruits
When analysing all of the material, the first two components of PCA explain 45.4% of total variation, from which 26,2 % on the first axis (with great influence caused by LL and WP, followed by SW and PV), respectivelly19,2 % on the second axis (with great influence caused by NV and LDR, followed by PV and PR). In addition, BS and PL in ClisuraDunarii location and LW in Ciucurovaphytocoenosis were responsable for a greater variation at intraphytocoenotic level The trees sampled in different phytocoenoses are dispersed : they do not form separate groups + Clisura Dunării ▪ Ciucurova X Măcinului Mountains ● Petiş PCA for leaves descriptors of all trees in the four phytocoenoses
General conclusions: Almost all of the trees from the four phytocoenoses sampled from the distribution area of Q. virgiliana are tipically forms of Q. pubescens A few oaks showedintermediate characters between the two taxa The correlations between traits do confirm the discriminating power of the Lpeddescriptor (lped descriptor) in identifing of the two taxa The PCA analysis indicate the lack of typical trees of Q. virgiliana in the studied area; this is in accordance with our identification in the field based on a series of the dendrological descriptions (Georgescu and Moraru, 1948; Beldie, 1952; Negulescu and Savulescu, 1957; Dumitriu – Tataranu et al., 1960; Bartha, 2009)
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