Phenology and growth dynamics in Mediterranean evergreen oaks: Effects of environmental conditions and water relations

Budburst date and shoot elongation were measured in two mature Mediterranean evergreen oaks (Quercus suber and Quercus ilex) and their relationships with meteorological and tree water status (predawn leaf water potential) data were analysed. Experimental work took place at two sites: Mitra 2 - Southern Portugal (2002-2003) and Lezirias - Central Portugal (2007-2010). Quercus suber phenology was studied at both sites whereas Q. ilex was only studied at Mitra 2. Quercus suber budburst date occurred at a photoperiod around 13.8 h (± 0.26) - late April/early May - and was highly related to the average daily temperature in the period 25 March - budburst date (ca. 1.5 months prior to budburst), irrespective of site location. In that period, budburst date was much more dependent on average maximum than average minimum daily temperature. Base temperature and thermal time for Q. suber were estimated as 6.2 °C (within the reported literature values) and 323 degree-days, respectively. Q. ilex budburst occurred about 6 weeks earlier than in Q. suber (photoperiod: 12.3 h (±0.3)). Relationships of Q. ilex budburst date and temperature were not studied since only 2 years of data were available for this species. Q. suber shoot elongation underlying mechanisms were quite different in the two sites. At Mitra 2 (Q. suber and Q. ilex), there was a considerable tree water stress during the dry season which restricted shoot elongation. Shoot growth was resumed later in the wet autumn when tree water status recovered again. At the Lezirias site Q. suber water status was not restrictive. Therefore, shoot elongation was mainly dependent on nutrient availability in top soil, as suggested by the strong and positive relationships between annual shoot growth and long-term cumulative rainfall (2-4 months) and short-term average temperature (1 month) prior to budburst. Annual shoot elongation at this well-watered site was higher than in Mitra 2, and variability of growth between trees was enhanced after warm, wet springs when shoot elongation was higher. Results obtained are relevant to the carbon balance, productivity and management of evergreen Mediterranean oak woodlands, particularly under the foreseen climate change scenarios.     

Predicting stand damage and tree survival in burned forests in Catalonia (North-East Spain)

The study developed models for predicting the post-fire tree survival in Catalonia. The models are appropriate for forest planning purposes. Two types of models were developed: a stand-level model to predict the degree of damage caused by a forest fire, and tree-level models to predict the probability of a tree to survive a forest fire. The models were based on forest inventory and fire data. The inventory data on forest stands were obtained from the second (1989–1990) and third (2000–2001) Spanish national forest inventories, and the fire data consisted of the perimeters of forest fires larger than 20 ha that occurred in Catalonia between the 2nd and 3rd measurement of the inventory plots. The models were based on easily measurable forest characteristics, and they permit the forest manager to predict the effect of stand structure and species composition on the expected damage. According to the stand level fire damage model, the relative damage decreases when the stand basal area or mean tree diameter increases. Conversely, the relative stand damage increases when there is a large variation in tree size, when the stand is located on a steep slope, and when it is dominated by pine. According to the tree level survival models, trees in stands with a high basal area, a large mean tree size and a small variability in tree diameters have a high survival probability. Large trees in dominant positions have the highest probability of surviving a fire. Another result of the study is the exceptionally good post-fire survival ability of Pinus pinea and Quercus suber.     

Climate-growth variability in Quercus ilex L. west Iberian open woodlands of different stand density

? We present the longest tree-ring chronology (141 y) of Quercus ilex L. (holm oak), and discuss the species climate-growth relationships and the influence of stand density on tree sensitivity to climate.

? Similarly to Quercus suber L., the most influential climatic variables upon holm oak growth were late spring and early summer precipitation, which enhanced growth, and high temperatures in the previous August and current July, which negatively affected growth.

? High density stands responded to similar climatic factors as low density stands, but their response was generally weaker. Holm oak sensitivity to climate has increased in recent decades, which might be related to increasing temperatures in the region. Sensitivity was higher in low density stands. Additionally, the effect of summer stress on growth seems to have increased during the same period, similarly to other species in the Iberian Peninsula, suggesting that trees are more vulnerable to climatic changes.

? Stand density could buffer the response to climate by smoothing climatic extremes. Nevertheless, the effect of competition might reverse this positive effect at the individual tree level. Precautions should be taken before providing management guidelines regarding the effect of climate change and stand density on holm oak.

     

Variation in the decay resistance of larch to fungi

? Decay resistance of larch (Larix sp.) to fungi was evaluated on heartwood samples belonging to 3 species (L. decidua, L. kaempferi and their hybrid), 3 races of European larch (polonica, sudetica and alpine), 13 wood lots (populations) and 313 trees.

? Larch wood appeared, on average, as moderately durable although a high variability was observed. At the sample level as well as at the mean individual tree level, durability ranged from class 1 to 5 according to EN 350-1 standard. At the population level, larch wood varied from ‘durable’ to ‘slightly durable’. Genetics played a major role in decay resistance at the species, provenance and tree levels. Environmental factors such as the position of heartwood samples and the age of trees were also identified as a source of variability.

? The most durable wood was not necessarily from old native alpine stands of European larch: some young larches from faster growing lowland origins also produced durable wood.

? Genetic improvement of larch wood durability appeared therefore likely by the selection of the best populations for decay resistance as well as from the selection of individuals.

     

Stand structure and successional trends in virgin boreal forest reserves in Sweden

Fire history and stand structure was examined in twelve virgin forest stands situated within forest reserves in northern Sweden. The selected stands represented fire refuges as well as different successional stages after fire. Six of the stands were dominated by Norway spruce (Picea abies L. Karst.), three were dominated by Scots pine (Pinus sylvestris L.), and three were dominated by hairy birch (Betula pubescens Ehrh.) or aspen (Populus tremula L.). In 3 of the southernmost stands, the average fire interval was 34 to 65 years during the late 1600s to late 1800s, but since 1888 no fires had occurred in any of the stands. The absence of fire disturbance since 1888 is probably caused by the fire suppression in the overall landscape. The standing volume of living trees ranged between 87 and 511 m³ ha⁻¹ while the volume of dead trees, including both snags and logs, ranged between 27 and 201 m³ ha⁻¹. The volume of dead trees constituted ca. 30% of the total stem volume. In the conifer dominated stands, there was a statistically significant relationship between total stem volume, including both living and dead trees, and site productivity. A comparison between the amount of dead and living trees indicated substantial changes in tree species composition in several stands. It is suggested that data on the amount of dead trees, especially logs, and its distribution over decay classes could be used to examine the continuity of certain tree species. All stands had a multi-sized tree diameter distribution, which in most cases was similar to a reversed J-shaped distribution. In general spruce was numerous in the seedling cohort and in small diameter classes, indicating that its proportion in the stands was stable, or was increasing at the expense of pioneer tree species such as pine, aspen and silver birch (Betula pendula Roth.). The most numerous species in the seedling cohort, rowan (Sorbus aucuparia L.), was almost totally missing in the tree layer, indicating a high browsing pressure preventing rowan seedlings from growing into trees. The general increase of spruce and the sparse regeneration of pioneer species, in the stands previously affected by fire, are discussed in relation to natural disturbance regimes, biological diversity and nature conservation policies. It is proposed that reintroduction of fire disturbance is a necessity for future management plans of forest reserves. Other management practices to increase species diversity within forest reserves are also discussed.     

Leaf morphology displays no detectable spatial organisation in the relict Quercus afares Pomel compared to the co-occurring parental species Q. canariensis Willd. and Q. suber L

?Context

Oak species display a large within-species diversity combined with significant gene flow between species. Quercus afares Pomel is an endemic species that grows as a small relict population in Northern Tunisia, together with Quercus suber L. and Quercus canariensis Willd. It is considered to be a fixed hybrid between the two latter.

?Aims

We tested (1) whether this population of Q. afares is declining with respect to the neighbouring populations of the two other species and (2) whether the spatial distribution of leaf morphology is random among individuals within this small population of Q. afares or influenced by the neighbouring species.

?Methods

Spatial distribution and diameter at breast height were recorded in the population of Q. afares. We identified two perpendicular transects across the population reaching from areas dominated by Q. canariensis to areas dominated by Q. suber and defined 20 plots along each. Eleven traits were assessed on 10 leaves collected from the upper crown of trees from the three species. A multiple correspondence analysis and an ANOVA were used to test for within and between-species diversity in leaf morphology.

?Results

Q. afares individuals occurred at a low frequency among the two other species. Nevertheless, Q. afares showed no particular evidence of decline with respect to the two other species. Leaf traits displayed a large inter-specific variability with very little overlap between Q. afares and Q. suber and some between Q. afares and Q. canariensis. A high level of diversity was detected for these traits within Q. afares, but we were unable to unravel any spatial organisation of this diversity; in Q. afares, leaf traits varied independently of the presence of neighbouring Q. suber or Q. canariensis.

?Conclusion

Q. afares seems to be a fixed species with specific leaf traits that are independent of that of the species of the neighbouring trees. This population is not suffering a detectable trend towards decline except for the lack of any visible regeneration below any of the three species.     

Root system of Quercus suber L. seedlings in response to herbaceous competition and different watering and fertilisation regimes

Different management practices are commonly applied to increase pasture yield of Mediterranean open woodlands, but the consequences of increasing competition for soil resources with these practices on tree recruitment are still unknown. In a greenhouse study, belowground competition of Quercus suber L. seedlings growing together with natural (Oak_NP) or improved pasture (Oak_IP) was evaluated, and their root systems compared with those of seedlings growing in bare soil (Oak_BS). Two watering levels and two regimes of P₂O₅ fertilisation were also tested. Because of competition, the Oak_IP seedlings had their fine root mass density, coarse root length, and shoot mass reduced by up to 40, 36, and 39%, respectively, when compared to Oak_NP seedlings. Oak_NP and Oak_BS seedlings showed similar average root density parameters and shoot mass values, indicating that Q. suber seedlings growing with natural pasture is a low competitive system. High availability of water and phosphorus did not mitigate the strength of competition between herbaceous plants and oak seedlings, and favoured the pasture to the detriment of the trees. Our findings suggest that P₂O₅ fertilisation and irrigation practices performed to improve herbaceous productivity will negatively influence recruitment of Q. suber seedlings.     

Variation of heartwood phenolics and oak lactones between the species and phenological types of Quercus petraea and Q. robur

Pressler cores were taken of Quercus petraea and Q. robur treesfrom young German provenance stands and mature mixed plantationsin England. The concentration of total phenolics extracted fromthe outer heartwood was measured and significant differencesfound between the two species. Concentrations of oak lactones,measured from provenance samples, also varied significantlybetween the species. However, the difference in total phenolicsbetween species was much lower among the trees from the mixedplantations than from the provenance trials. Q. petraea wascharacterized by lower levels of total phenolics but greaterconcentrations of oak lactones than Q. robur. A comparison betweenlate and early flushing Q. petraea trees found no significantdifference in total phenolics between these phenological types.     

Breeding eastern white pine: A world-wide perspective

Eastern white pine (Pinus strobus L.) has wide genetic variability and high productivity in plantations in North America, Europe and the Far East. In regions where neither white pine blister rust nor the white pine weevil are a problem, as in the central states of the U.S.A. and the warmer parts of Europe, primary attention is given to selection and breeding for vigor. Estimates for trees up to age 18 indicate that a first-generation genetic gain in volume of over 20% can be obtained from open-pollinated family selection within stands. Volume gains of 50% or more over local genotypes have been realized at ages 15–20 through the use of seed from selected southern Appalachian stands and in some individual tree crosses of eastern white pine with blue (Himalayan) pine. In the cool, humid regions of eastern North America and Europe, where blister rust resistance is important, breeding strategies include cloning of resistant P. strobus individuals, use of blue and Balkan pines in breeding programs, and exploitation of low-level rust resistance in low-risk localities. Eastern white pine losses from blister rust can be avoided in Japan and Korea by good plantation management without genetic selection. In some regions where the white pine weevil is the major problem, western white pine is useful both for hybridization and as an alternative, more weevil-resistant species. Analysis of relative photosynthesis of SO₂- and O₃-fumigated clones may be useful as a method of screening for pollution tolerance in regions where air pollution is likely to intensify. Efficient techniques for cloning by rooting of cuttings are now available. Efforts are under way to develop technology for micropropagation for mass production of superior clones. Breeding strategies for the major P. strobus plantation regions of the world are summarized.     

油茶无性系及自然林选优调查分析

在江西省6个县进行油茶无性系及自然林选优调查分析,结果表明,长林、赣无、赣州油系列无性系优树整体表现出较好的经济性状,主要表现为鲜果含油率、平均冠幅产果量及产油量较高,高产优树较多,自然林优树整体表现低于无性系优树,但存在一部分表现高产的优树,无性系优树间、不同地区自然林优树间、同一地区自然林优树间经济性状差异较大,这为油茶选优工作提供了参考依据和空间。今后油茶选优宜重点从现行推广的无性系中进行优中选优,结合在自然林中进行一定的选择,以达到节约成本、提高效率的目标。     

Composition and structure of natural mixed-oak stands in northern and central Portugal

Stand composition and structure of natural mixed-oak stands of common-oak (Quercus robur L.) and pyrenean-oak (Quercus pyrenaica Willd.) were studied. Diverse compositional and structural elements in early and late successional stand stages were analysed. The study was conducted in north and central Portugal where different natural mixed oak forests types are located. The following mixed-oak forest types involving common-oak and pyrenean-oak were studied: common-oak & other hardwoods; common-oak & cork-oak (Quercus suber L.); ash (Fraxinus angustifolia Vahl) & pyrenean-oak; and pyrenean-oak & madrone (Arbutus unedo L.). Measurements were made in early and late successional stand stages on the different mixed oak forest types. Different stand characteristics and indices were used to describe and compare stand structure and composition. The study showed changes in species diversity and stand structure. Most tree species in mature stands are present in early stages but with higher abundance. Shannon diversity index may change between 0.798 and 1.915. Significant differences on species diversity and abundance were found depending on the forest type and successional stage. Mature mixed-oak forests have high species diversity with an abundance of small to medium tree size species. Species distribution and diameter differentiation indices range from 0.30 to 0.70 and 0.52 to 0.82, respectively, revealing significant structural complexity. The average number of standing and downed dead trees was 265 and 83 trees ha⁻¹ for early and late stage, respectively, with 6.9 and 65.4 m³ ha⁻¹. Higher values of stand diversity index were 41 and 53 in more complex and developed forests. Later stand stages have complex structure, with a wider range of tree diameter distribution and higher degree of irregularity.     

Ectomycorrhizal fungal communities of Quercus liaotungensis along different successional stands on the Loess Plateau,China

Although Quercus liaotungensis forest is an important component of Loess Plateau forest ecosystems, little is known about the ectomycorrhizal fungal (EMF) symbiosis of Q. liaotungensis in this ecosystem. Here we investigated EMF communities of Q. liaotungensis along three successional stands on the central Loess Plateau (Yan’an, China): a seedling stand (1 to 3-year-old seedlings under a Populus davidiana forest stand), a young tree stand (20 to 30-year-old Q. liaotungensis forest stand), and a mature tree stand (50 to 70-year-old Q. liaotungensis forest stand). In each stand, the Q. liaotungensis roots were sampled, then EMF communities were examined on the basis of EMF morphotyping, PCR–RFLP, and DNA sequencing. In total, 70 EMF species were observed, and the total richness of estimated species exceeded 100 EMF species. The EMF community was composed of a few common taxa (approx. 7 %) and many rare taxa (approx. 61 %). EMF richness in young and mature trees was higher than in seedlings. EMF communities of young and mature trees were more similar than those of seedlings and trees. Nonmetric multidimensional scaling ordinations of the EMF community revealed more separation among Q. liaotungensis of different age. This study provides preliminary insight into the taxonomic diversity of EMF of Q. liaotungensis along different successional stands on the Loess Plateau.     

Genetic diversity in natural populations of Gmelina arborea: implications for breeding and conservation

Gmelina arborea is a valuable plantation tree species that is native to South and Southeast Asia. In this study, 534 samples representing 19 natural populations in India, China, Thailand and Myanmar were analyzed with 10 polymorphic microsatellite markers. The genetic diversity analysis revealed highly polymorphic loci (N_a?=?16.4), a good level of genetic diversity (H_o?=?0.56; H_e?=?0.83) and the deficiency of heterozygotes in G. arborea populations evidenced by positive fixation index and deviation from Hardy?CWeinberg Equilibrium in all loci and most populations. The Analysis of Molecular Variance attributed 21, 10 and 69% of total genetic diversity to among-region, among-population (within region) and within-population variation. Unweighted Pair Group Method with Arithmetic Mean dendrogram and Principle Coordinate Analysis revealed three separate clusters composed of China, India and Thailand/Myanmar that were consistent with geographical distance and the presence of natural barriers to gene flow. Populations from within India grouped together genetically consistent with geographical locations, with the exception of the Nowgong population (eastern India), that might have originated from the Kasa area (western India) with which it has high genetic similarity. Understanding genetic diversity and structure of G. arborea populations serve as an important reference for tree breeding programs and conservation strategy. Breeding populations of G. arborea should include selections from each of the major geographic regions to maximize genetic diversity and heterosis. Vegetative propagated clones of elite trees can be used for plantation to address the issue of high level of segregation among seed derived plants.     

Characterization of a collection of Chinese fir elite genotypes using sequence-related amplified polymorphism markers

Chinese fir [Cunninghamia lanceolata(Lamb.)Hook] is a major timber tree species in China.In the present study,sequence-related amplified polymorphism(SRAP) markers were used to evaluate the polymorphisms,diversity,and relationships in a collection of Chinese fir elite genotypes(n=103) from the Lechang provenance,an endangered provenance.Thirty-five SRAP primer combinations produced 620 bands among the tested 103 Lechang provenance genotypes and 17 non-Lechang provenance genotypes;577(93.1 %) of these were polymorphic,yielding an average of 16.5 polymorphic bands per primer combination.Of the SRAP primer combinations(n=35),14 ones identified C70.0 % of the 120 genotypes.The Me12–Em19 combination had the strongest discriminatory ability with 93.3 % of the genotypes identified.An UPGMA dendrogram further showed that most of the Lechang provenance genotypes(87.4 %) grouped together(Cluster A).The Lechang genotypes had a considerable amount of genetic variation with genetic similarity from 0.40 to 0.81.The current work may facilitate the management of the endangered Lechang Chinese fir provenance.     

Application of biotechnological tools to Quercus improvement

The genus Quercus, which belongs to the family Fagaceae, is native to the northern hemisphere and includes deciduous and evergreen species. The trees of the different species are very important from both economic and ecological perspectives. Application of new technological approaches (which span the fields of plant developmental biology, genetic transformation, conservation of elite germplasm and discovery of genes associated with complex multigenic traits) to these long-rotation hardwoods may be of interest for accelerating tree improvement programs. This review provides a summary of the advances made in the application of biotechnological tools to specific oak species. Significant progress has been made in the area of clonal propagation via organogenesis and somatic embryogenesis (SE). Standardized procedures have been developed for micropropagating the most important European (Q. robur, Q. petarea, Q. suber) and American (Q. alba, Q. bicolor, Q. rubra) oaks by axillary shoot growth. Although regenerated plantlets are grown in experimental trials, large-scale propagation of oak species has not been carried out. The induction of SE in oaks from juvenile explants is generally not problematic, although the use of explants other than zygotic embryos is much less efficient. During the last decade, enormous advances have been made in inducing SE from selected adult trees, mainly specimens of pedunculate oak (Q. robur) and cork oak (Q. suber). Advances in the understanding of the maturation and germination steps are required for better use of embryogenic process in clonal forestry. Quercus species are late-maturing and late-flowering, exhibit irregular seed set, and produce seeds that are recalcitrant to storage by conventional procedures. Vitrification-based cryopreservation techniques were used successfully in somatic embryos of pedunculate oak and cork oak, and an applied genbank of cork oak selected genotypes is now under development. The feasibility of genetic transformation of pedunculate oak and cork oak somatic embryos by means of co-culture techniques with several strains of Agrobacterium tumefaciens has also been demonstrated. To date, most research on the genomics of Quercus species has concerned population genetics. Approaches using functional genomics to examine the molecular and cellular mechanisms that control organogenesis and or somatic embryogenesis are still scarce, and efforts on the isolation and characterization of genes related to other specific traits should be intensified in the near future, as this would help improve the practical application of clonal forestry in recalcitrant species such as oaks.     

Influence of umbrella pine (<Emphasis Type="Italic">Pinus</Emphasis><Emphasis Type="Italic">pinea</Emphasis> L.) stand type and tree characteristics on cone production

Most umbrella pine (Pinus pinea L.) stands are managed as agroforestry systems, whose main production is fruit, due to the edible and highly nutritious kernels, and are frequently associated to natural or seeded pastures and grazing. The stands have low density, in order to enhance crown growth and fruit production. Nevertheless, cone production, both with regard to number and weight, varies greatly between stands, trees and years. In this study were selected three agroforestry systems, representative of umbrella pine stands whose main production is fruit, and one stand representative of the timber production system, where fruit is the secondary production. It was evaluated the variability in cone production as a function of the tree’s diameter at breast height and crown diameter and the individual tree’s competition status. The results indicate that stands managed in agroforestry systems with lower competition and individuals with larger diameter at breast height and crown diameter tend to produce more and heavier cones per tree. The first two principal components of the principal component analysis explain 84 % of the variance in cone production, trees’ dimensions and competition index. Tree competition status has a negative impact on production per tree.     

Origins and diversity of the Portuguese Landrace of Eucalyptus globulus

The Portuguese Landrace of Eucalyptus globulus is of unknown origin, with the earliest plantings of this tree species dating back to the early 19th century. In Portugal it is currently a major seed source for plantations and is also used in breeding programs. Eucalyptus globulus is native to south-eastern Australia. The substantial genetic differentiation of chloroplast and nuclear DNA markers between different native geographic races of this species allowed us to uncover the Australian origins of the Portuguese Landrace and to study its genetic diversity. To achieve this, we sequenced a highly polymorphic region of chloroplast DNA from 47 Portuguese Landrace individuals, and genotyped 34 of these using seven nuclear microsatellites. We compared these individuals to those in a database comprising chloroplast DNA sequence profiles from 292 native trees and seven nuclear microsatellites from 372 native trees. The majority of the Portuguese Landrace samples had closest affinities, in both marker systems, to native trees from south-eastern Tasmania, but some had affinities to trees from south-eastern Victoria. The discrepancies in the affinities indicated by chloroplast versus nuclear DNA markers could be explained by inter-race hybridisation after introduction. The genetic diversity in the Portuguese Landrace was less than that found in native E. globulus at the species level, but was similar to the average diversity found in native races of the species. This study demonstrates the power of using independent marker systems to identify the origins and diversity of domesticated populations, by comparison with variation in native stands.     

Crown transparency, tree mortality and stem growth of Pinus sylvestris, and colonization of Tomicus piniperda after an outbreak of Gremmeniella abietina

In the year 2000, large areas of forest in Sweden, mainly 30-50 year old Pinus sylvestris (L.) stands, were attacked by the fungus Gremmeniella abietina (Lagerb.) Morelet. The aims of this study were to investigate: (i) the relationship between G. abietina-induced tree crown transparency (CT) and P. sylvestris (L.) tree mortality; (ii) the influence of CT levels on stem growth; (iii) the recovery of the crown; and (iv) the association of CT and colonization by Tomicus piniperda (L.). Thirty-five permanent sample plots were established in five P. sylvestris stands (38-46 years old), infested by G. abietina, and 23 plots in four reference stands, not obviously infested.During the 5 years following the attack, the total mortality amounted to 454 trees ha⁻¹ and 7.8 m² ha⁻¹, on average, in the five infested stands, corresponding to 42% of the trees and 34% of the basal area at the time of the attack. Most of the mortality occurred within 2 years of the attack. The mortality of individual trees (2002-2005) was found to be related to the crown transparency (CT), the position of needle loss within the crown and the tree diameter at breast height. Based on our modeling, the probability of mortality was substantially increased if the initial CT-value was higher than 85%.Growth reductions were detected for individual trees with an initial CT of >c. 40%. In contrast, trees with a low initial CT (<c. 40%) were not affected and even exhibited increased growth. In the five infested stands, the reductions in basal area and volume increment were estimated to be 26-58%, and, 42-73%, respectively, during the five growing seasons after the attacks.The trees in the infested stands that were still alive in spring 2005 had started to recover in terms of CT. Breeding of T. piniperda on the P. sylvestris (L.) stems occurred almost exclusively on stems with a CT > 90%.The data from this study suggest that when a P. sylvestris (L.) stand has been attacked by G. abietina, trees with a CT above 80% should be felled; the remaining trees will have a high probability of survival and resistance to successful breeding by the T. piniperda.     

杉木种源－林分－家系遗传变异研究

运用杉木种源、林分、家系三水平联合试验６年生林分的生长性状和物候观测资料，研究其遗传变异信息。结果显示，种源间、种源内林分间、林分内单株间的胸径、树高、材积都存在极显著差异；在三水平任何层次上的生长性状选择都是有效的，但各层次变异差别很大，其方差分量排序依次为：种源＞林分＞家系，种源、林分、单株材积遗传力分别为０．８４８、０．３９９、０．２３２；选择层次依次是种源、林分、单株。种源（群体）是较稳定的遗传单位，但种源内林分间差异显著，可进一步探讨遗传学上的杉木种源单位的确切范围。种子发芽率、物候因子分析表明，种源间差异显著，林分间差异不显著。     

Analysis of genetic relationship among Arbutus unedo L. genotypes using RAPD and SSR markers

The strawberry tree (Arbutus unedo L.) is an underutilized, drought tolerant, fire resistant species with a south western distribution in Europe, and with ecological and putative socio-economical impact in Portugal and Mediterranean countries. Our aim was to develop an appropriate set of molecular markers to enable genetic diversity to be assessed and to fingerprint Arbutus unedo genotypes for breeding and conservation purposes in Portugal. Twenty-seven trees from a broad geographic range were screened with 20 random amplified polymorphic DNA (RAPD primers) and 11 microsatellite markers (SSR). The RAPDs generated 124 bands, 57.3% of which were polymorphic, with an expected heterozygosity of 27%. We cross-amplified 11 SSR primers developed for Vaccinium spp., and 5 were found to be polymorphic in A. unedo, with 75% of expected heterozygosity, a number of alleles of 11.6, a null allele frequency of 7.6% and a polymorphic information content of 71%. Although the SSRs were more polymorphic and informative than the RAPDs, both markers displayed high genetic variability with the gathered data. No geographic pattern was observed in the genetic variation distribution based on both marker systems, and the lack of correlation between genetic and geographical matrices was confirmed by Mantel tests. Likely, no correlation was found between pairwise SSR and RAPD band-sharing matrices. These results and their implications on A. unedo breeding and conservation programs are discussed.