Effects of silvicultural regimes on dynamics of genetic and ecological diversity of european beech forests

An inventory of the genetic diversity in European beech (Fagus sylvatica L.) populations was conducted using four highly polymorphic microsatellite and ten isozyme markers. In total data of 1058 trees were obtained, originating from 10 stands, which were stored in a database. These data allowed us to examine the impact of forest management on genetic diversity and mating in these beech stands. For this we performed a pair-wise comparison of the stands which differ in management intensity. As reference natural stands under low management intensity were chosen. Different parameters of genetic diversity, mating system and for estimating genetic differentiation were obtained such as allelic richness (A), effective number of alleles (Ae), number of rare alleles (Arare), observed (Ho) and expected heterozygosity (He), panmictic index (Fis) and Fst. From the results of the genetic inventory we were able to draw conclusions about the effect of management on genetic diversity. Our results indicated that the shelter wood system is adequate to maintain the genetic diversity in beech. It is likely that this type of management has no or minimum impact on the diversity, at least for the genetic markers used, in beech because the management mimics natural regeneration processes. Additionally, the genetic data were useful for describing the geographical genetic structure of this European species.

We used 143 individuals from a F1 beech full-sib family. Two linkage maps (one for each parent) were constructed (see linkage map result). In the same pedigree we investigated the association with genetic markers of several quantitative traits: leaf area, leaf number and shape in 2 different years, specific leaf area, leaf carbon-isotope discrimination and tree height. A composite interval-mapping approach was used to estimate the number of QTLs, the amount of variation explained by each of them, and their position on the genetic linkage maps. Eight QTLs associated with leaf traits were found that explained between 15% and 35% of the trait variation, five on the female map and three on the male map. A database of physiological and morphological parameters has been prepared and is vailable. The idividual oriented parameters describe: maximum transpiration, stomatal conductance, sensitivity to soil drought, phenology, Fv/Fm, nitrogen content and LMA.

We built the first linkage map for beech (Fagus sylvatica). Based on a total of 312 markers (28 RAPDs, 274 AFLPs, 10 SSRs) scored in 143 individuals from a F1 full-sib family. Two maps (one for each parent) were constructed according to a two-way pseudo-testcross mapping strategy. In the male map 119 markers could be clustered in 11 major groups (971 cM), while in the female map 132 markers were distributed in 12 major linkage groups (844 cM). In addition, four and one minor linkage groups (doublets and triplets) were obtained for the male and female map respectively. The two maps cover about 82% and 78% of the genome. Based on the position of 15 AFLP and 2 SSR loci segregating in both parents, seven homologous linkage groups could be identified.

Primers for the amplification of microsatellites were obtained by sequencing clones of an enriched library constructed for Fagus sylvatica. Microsatellites are markers displaying high variation and extremely useful for several applications in population and conservation genetics, in particular for the analysis of gene flow. Moreover, these markers can be applied for certification purposes, in particular of provenances and/or seed lots and wood material. These new microsatellites developed for beech are already available to scientists and end users thanks to scientific publications where all details about their characteristics and protocols for their screening are reported. Details about the methodology for the amplification of microsatellite markers are provided in a scientific publication. This publication includes: 1) composition of the amplification reaction; 2) thermal profile for the amplification; 3) methodology to visualize SSRs; 4) characteristics of the SSRs. The protocol was developed for the amplification of microsatellites having characteristics necessary to correctly perform paternity analysis, namely absence of null alleles, reproducibility and lack of linkages. Considering that microsatellites useful for paternity analysis must not be linked and must be Mendelian inherited, a segregation and linkage analysis was performed. Mendelian inheritance and absence of linkages between markers was confirmed. Markers having these characteristics have several useful applications in different fields of forest genetics.

A beech field test was established in 1997 in northeast France. It included 48 open-pollinated families replicated 4 times and 8 grafted copies of the respective mother trees. Bud burst was observed in spring of 2002 and 2003 on seedlings and grafts. Several ecophysiological traits were observed on part of the grafted clonal test in June 2000. Significant heritability values confirm that beech bud burst is under strong genetic control as many other species of temperate climate. Among ecophysiological traits, Vcmax (maximum rate of RubisCO activity), G1 (slope of stomatal conductance model according to Leuning et al. [8]) and An/gs (ratio of light-saturated net photosynthesis and stomatal conductance measured at CO2 concentration of 350 µmol mol-1) showed slight genetic control. But none of these traits displayed any significant heritability. This trial is probably the first attempt on beech to introduce copies of parent trees in the progeny test to reduce the age effect on heritability estimates.

This study on plant performance resulted in an assessment of ecological variation on plant growth, phenology, ecophysiological processes on seedlings and saplings (offspring) of selected European beech populations under different silvicultural regimes. Seven seed sources of four beech provenances originating from Austrian, French, German and Italian sites were studied. Leaf photosynthetic and stomatal conductance response curves to a number of environmental conditions including light, temperature, CO2 concentrations were measured on seedlings and saplings under field conditions and under controlled conditions. Photosynthesis was analysed in accordance with the Farquhars model. Differences in ecophysiological responses among and within beech genotypes from different sites were analysed. Phenological characteristics, bud-burst and leaf unfolding, were assessed and the variation of growth parameters (plant height, stem diameter, biomass allocation) were studied in experimental mini-plots under field-like environmental conditions and in greenhouse experiments under controlled environment. The photosynthetic key parameters Vcmax and Jmax were closely related to the foliage nitrogen content (Nleaf) and with morphological characteristics such as leaf mass area (LMA). The optimum temperature was analyzed from the An-Ci curves at different temperature levels. Linear dependencies of temperature optima for the photosynthetic parameters, maximal carboxylation rate of RubisCO (Vcmax) and potential rate of electron transport (Jmax) to leaf mass area (LMA) were detected. The optimal temperature (Topt) for Vcmax and Jmax varied with leaf structural properties (LMA) and ranged from 32.0 to 38.1°C (Vcmax) and from 30.5 to 36.3 °C (Jmax). The variation of bud-burst timing among the different European beech populations observed at the same study site (under identical environmental conditions) demonstrates the influence of genetic traits. Significant differences in bud-durst dates between the European beech populations and no differences between seed sources of the different management regimes (l: low management intensity and h: high management intensity) could be detected. Beech populations with earlier bud-burst timing showed enhanced growth. Tree height and stem diameter development varied significantly between families and populations.

Guidelines aim at compiling information originating from the project and other results to evaluate the applicability to forestry practice of different outputs of the project. They are management guidelines and recommendations on the effect of different management systems on the evolution genetic resources. Part one includes the contribution of genetic knowledge to different stages of beech stand development: plantation, natural regeneration, thinning, and conservation of genetic resources. Part two presents the genetic basis of seed collection. Part three includes the economic assessment of recommendations. Part four is a business evaluation of guidelines.

Mating system parameters have been estimated in different Fagus sylvatica stands. Paternity and parentage analysis were performed. These parameters are implemented in simulation models. Gene flow studies revealed that a high proportion of pollen is coming from outside the analysed stands. Pollen dispersal curves indicate different dispersal distances in the beech stands. Seed dispersal curves showed that a high frequency of seeds is dispersed to a distance up to 80-100 meters, with peaks at 30-40 meters. Few direct measurements of seed dispersal within populations have been performed so far. Therefore these results can be considered very innovative. Both pollen and seed dispersal curves represent important parameters to be implemented into simulation models. Analysis about the presence of spatial structure within stand was performed in 10 Fagus sylvatica populations characterized by different management intensity. Some positive spatial autocorrelation was observed in all unmanaged stands while no structure was observed in almost all managed stands. The presence of positive autocorrelation is an important aspect to be taken into consideration in the stand management. In particular, the collection of seeds to be used to produce seedlings for reforestation should be performed from trees at least 30-40 meters apart: this would avoid using seed lots having a too high proportion of inbreeds. Silvicultural treatments seem to play a role in reducing (or even cancelling) the spatial structure within stands. This information can be extremely useful for planning efficiently the managemnt of beech stands and for establish criteria for seed collection.

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