Branislav Cvjetkovic

Desiccation and Mortality Dynamics in Seedlings of Different European Beech (Fagus sylvatica L.) Populations under Extreme Drought Conditions

European beech (Fagus sylvatica L., hereafter beech), one of the major native tree species in Europe, is known to be drought sensitive. Thus, the identification of critical thresholds of drought impact intensity and duration are of high interest for assessing the adaptive potential of European beech to climate change in its native range. In a common garden experiment with one-year-old seedlings originating from central and marginal origins in six European countries (Denmark, Germany, France, Romania, Bosnia-Herzegovina, and Spain), we applied extreme drought stress and observed desiccation and mortality processes among the different populations and related them to plant water status (predawn water potential, ΨPD) and soil hydraulic traits. For the lethal drought assessment, we used a critical threshold of soil water availability that is reached when 50% mortality in seedling populations occurs (LD50SWA). We found significant population differences in LD50SWA (10.5–17.8%), and mortality dynamics that suggest a genetic difference in drought resistance between populations. The LD50SWA values correlate significantly with the mean growing season precipitation at population origins, but not with the geographic margins of beech range. Thus, beech range marginality may be more due to climatic conditions than to geographic range. The outcome of this study suggests the genetic variation has a major influence on the varying adaptive potential of the investigated populations.

Variation in xylem vulnerability to embolism in European beech from geographically marginal populations

Climate change is expected to increase the frequency and intensity of droughts and heatwaves in Europe, leading to effects on forest growth and major forest dieback events due to hydraulic failure caused by xylem embolism. Inter-specific variability in embolism resistance has been studied in detail, but little is known about intra-specific variability, particularly in marginal populations. We evaluated 15 European beech populations, mostly from geographically marginal sites of the species distribution range, focusing particularly on populations from the dry southern margin. We found small, but significant differences in resistance to embolism between populations, with xylem pressures causing 50% loss of hydraulic conductivity ranging from -2.84 to -3.55 MPa. Significant phenotypic clines of increasing embolism resistance with increasing temperature and aridity were observed: the southernmost beech populations growing in a warmer drier climate and with lower habitat suitability have higher resistance to embolism than those from Northern Europe growing more favourable conditions. Previous studies have shown that there is little or no difference in embolism resistance between core populations, but our findings show that marginal populations have developed ways of protecting their xylem based on either evolution or plasticity.

Provenance by site interaction and stability analysis of European beech (Fagus sylvatica L.) provenances grown in common garden experiments

Abstract Fifteen provenances of European beech (Fagus sylvatica L.) were evaluated for stability and adaptability by height growth at four test sites in Bosnia and Herzegovina (1), Croatia (1) and Serbia (2). Provenance trials were established in spring 2007 by planting 2- and 3-yearold seedlings and arranged in a randomized complete block design. The data from seven 6- year-old and eight 5-year-old provenances were obtained in 2009 and analyzed separately. Finlay and Wilkinson’s regression analysis and Additive main effects and multiplicative interaction model (AMMI model) were used to assess provenance by site interaction (P × S) and to identify beech provenances that have high and stable performance in different environments, at the juvenile stage of development. Analysis of variance showed that effects of provenance, site, and P×S interaction are highly significant (p<0.001) in both age groups. Linear regression model evidenced that most of the provenances had regression coefficients not significantly different from unity (b=1.0), except for provenances Sjeverni Dilj Caglinski (HR24) and Vranica-Bistrica (BA59). The partitioning of the total sum of squares (SS) exhibited that the site effect was the predominant source of variation in both age groups of provenances (50.7% and 38.5%, respectively). Additionally, regression analysis explained 15.8% and 33.2% of provenance by site interaction terms, in provenances age six and five years, respectively, while the AMMI analysis accounted for 62.2% and 78.7% in P×S interaction. The results of AMMI showed that the first principal component (PC1) was statistically significant in both age groups. Adaptability and stability of provenances to the test sites were estimated with AMMI1 and AMMI2 biplots. Provenance Sjeverni Dilj Caglinski (HR24) showed constant performance over tested sites, characterizing with aboveaverage height growth at low yielding environments. Provenances HR25 and BA61 showed the opposite type of adaptation, being adapted to high yielding sites. Provenance Valkonya (HU42) was characterized by IPCA1 score close to zero and above average mean height growth, suggesting general adaptation to the tested environments. The implication of P×S was discussed in light of impact of climate change on beech and selection of most suitable provenances for future reforestation programs.

FENOLOGIJA CVJETANJA TRI VRSTE LIPE (Tilia sp.) NA PODRU

Cilj rada je analiza perioda cvjetanja vrsta roda lipa (Tilia sp.) u toku jedne vegetacione sezone, na podrucju grada Banja Luke. Vrste obuhvacene ovim istraživanjem su: krupnolisna, sitnolisna i srebrnolisna lipa. Terensko istraživanje je sprovedeno na tri lokaliteta: u parku Mladen Stojanovic, Univerzitetskom gradu i na Starcevici. Utvrđene su klimatske, edafske i orografske karakteristike objekta istraživanja. Navedeni lokaliteti, iako se nalaze relativno blizu u istom klimatskom podrucju, pružaju razlicite ekoloske uslove za razvoj i fenologiju istraživanih vrsta. Praceno je pet faza cvjetanja, s ciljem da se utvrdi uticaj stanisnih uslova na fenofazu cvjetanja, te utvrde geneticke razlicitosti analiziranih stabala. Rezultati istraživanja pokazuju da pocetak i trajanje pojedinih faza cvjetanja istraživanih vrsta, u najvecoj mjeri zavise od vrste i stanisnih uslova. Na osnovu izvrsenih fenoloskih osmatranja konstatovane su razlike u trajanju perioda cvjetanja kod analiziranih stabala unutar istog lokaliteta. Dobijeni rezultati mogu biti od koristi kod procjene kvaliteta sjemena i definisanja vremena i nacina njegovog sakupljanja.