Morphological characteristics of <Emphasis Type="Italic">Quercus</Emphasis><Emphasis Type="Italic">variabilis</Emphasis> charcoal prepared at different temperatures

The morphology of charcoals was investigated by scanning electron microscopy. Charcoal of Quercus variabilis was prepared in an electric furnace under nitrogen gas atmosphere at 400, 600, 800 and 1,000°C. Charring temperature greatly affects the structure of charcoal. In charcoal prepared at 400°C, most of the morphological characteristics remained relatively unchanged with the exception of the cell-wall layering. The cell walls appeared homogenous and glass-like. Above 400°C, there was an increase in cell-wall thinning and volumetric shrinkage with an increase in the charring temperature. These two factors were responsible for most of the observed changes in structure. Fracture surfaces became increasingly rough and disrupted. Vessel elements were increasingly distorted and tyloses disintegrated with increases in temperature. Parenchyma cells exhibited greater shrinkage except at the pits. This resulted in the appearance of distinctive small protuberances over the surface of the parenchyma cells. Rhomboidal calcium crystals were found to be abundant at all the temperatures studied, but at 800 and 1,000°C the crystals had a sponge-like appearance.     

Geometric morphometric analyses of leaf shapes in two sympatric Chinese oaks: <Emphasis Type="Italic">Quercus dentata</Emphasis> Thunberg <Emphasis Type="Italic">and Quercus aliena</Emphasis> Blume (Fagaceae)

Key message

Geometric morphometric analyses (GMMs) of the leaf shape can distinguish two congeneric oak species Quercus dentata Thunberg and Quercus aliena Blume in sympatric areas.

Contexts

High genetic and morphological variation in different Quercus species hinder efforts to distinguish them. In China, Q. dentata and Q. aliena are generally sympatrically distributed in warm temperate forests, and share some leaf morphological characteristics.

Aims

The aim of this study was to use the morphometric methods to discriminate these sympatric Chinese oaks preliminarily identified from molecular markers.

Methods

Three hundred sixty-seven trees of seven sympatric Q. dentata and Q. aliena populations were genetically assigned to one of the two species or hybrids using Bayesian clustering analysis based on nSSR. This grouping served as a priori classification of the trees. Shapes of 1835 leaves from the 367 trees were analyzed in terms of 13 characters (landmarks) by GMMs. Correlations between environmental and leaf morphology parameters were studied using linear regression analyses.

Results

The two species were efficiently discriminated by the leaf morphology analyses (96.9 and 95.9% of sampled Q. aliena trees and Q. dentata trees were correctly identified), while putative hybrids between the two species were found to be morphologically intermediate. Moreover, we demonstrated that the leaf morphological variations of Q. aliena, Q. dentata, and their putative hybrids are correlated with environmental factors, possibly because the variation of leaf morphology is part of the response to different habitats and environmental disturbances.

Conclusion

GMMs were able to correctly classify individuals from the two species preliminary identified as Q. dentata or Q. aliena by nSSR. The high degree of classification accuracy provided by this approach may be exploited to discriminate other problematic species and highlight its utility in plant ecology and evolution studies.

     

Leaf-level responses to light in two co-occurring <Emphasis Type="Italic">Quercus</Emphasis> (<Emphasis Type="Italic">Quercus ilex</Emphasis> and <Emphasis Type="Italic">Quercus suber</Emphasis>): leaf structure,chemical composition and photosynthesis

We studied morphological, biochemical and physiological leaf acclimation to incident Photon-Photosynthetic-Flux-Density (PPFD) in Quercus ilex (holm oak) and Quercus suber (cork oak) at Mediterranean evergreen oak woodlands of southern Portugal. Specific leaf area (SLA) decreased exponentially with increasing PPFD in both species. Q. ilex had lower SLA values than Q. suber. Leaf nitrogen, cellulose and lignin concentration (leaf area-based) scaled positively with PPFD. Maximum rate of carboxylation (V_cmax), capacity for maximum photosynthetic electron transport (J_max), rate of triose-P utilization (V_TPU) and the rate of nonphotorespiratory light respiration (Rd) were also positively correlated with PPFD in both Quercus species, when expressed in leaf area but not on leaf mass basis. Q suber showed to have higher photosynthetic potential (V_cmax, J_max^m and V_TPU^m) and a higher nitrogen efficient nitrogen use than Q.ilex. Leaf chlorophyll concentration increased with decreasing PPFD, improving apparent quantum use efficiency (Φ) in both Quercus species. We concluded that, in Q.ilex and Q.suber, leaf structural plasticity is a stronger determinant for leaf acclimation to PPFD than biochemical and physiological plasticity.     

Effect of the arbuscular mycorrhizae <Emphasis Type="Italic">Glomus fasciculatum</Emphasis> and <Emphasis Type="Italic">G. macrocarpum</Emphasis> on the growth and nutrient content of <Emphasis Type="Italic">Cassia siamea</Emphasis> in a semi-arid Indian wasteland soil

The effect of two arbuscular mycorrhizal (AM) fungi, Glomus fasciculatum and G. macrocarpum on shoot and root dry weights and nutrient content of Cassia siamea in a semi-arid wasteland soil was evaluated. Under nursery conditions, mycorrhizal inoculation improved growth of seedlings. Root and shoot dry weights were higher in mycorrhizal than non-mycorrhizal plants. The concentration of P, K, Cu, Zn and Na was significantly higher in AM inoculated seedlings than in non-inoculated seedlings. Mycorrhization led to decrease in alkalinity of the rhizosphere soil from pH 8.5 to 7.4. Under nursery conditions, the degree of mycorrhizal dependency increased with age of C. siamea seedling. On transplantation to the field, the survival rate of mycorrhizal seedlings (75%–90%) was higher than that of non-mycorrhizal seedlings (40%). Besides better survival rate, AM inoculation improved the growth performance of seedlings in terms of height and stem diameter. Among the two AM fungi used, the efficiency of Glomus macrocarpum was higher than that of G. fasciculatum under both nursery and field conditions.This revised version was published online in May 2005 with corrected page numbers.     

Successful <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of <Emphasis Type="Italic">Populus tomentosa</Emphasis> with apple <Emphasis Type="Italic">SPDS</Emphasis> gene

The problem of salinized soils has become one of the most serious constraints to agricultural and forest productivity. With the purpose of enhancing salt stress tolerance of Populus tomentosa, we transformed this tree species with spermidine synthase （SPDS） genes derived from an apple by an Agrobacterium-mediated method. Four transgenic clones were confu＇med by PCR and Southern blot analysis. As well, the expression of introduced SPDS genes was analyzed by real-time quantitative PCR.     

Influence of water-stress acclimation and <Emphasis Type="Italic">Tuber melanosporum</Emphasis> mycorrhization on <Emphasis Type="Italic">Quercus ilex</Emphasis> seedlings

Mycorrhizal and non-mycorrhizal holm oak (Quercus ilex L.) seedlings inoculated with black truffle (Tuber melanosporum) were grown under nursery conditions and subjected to drought hardening for 4 months in autumn and winter followed by irrigation for 10 days. Leaf water potential and stomatal conductance were monitored during the 4 months of drought. When the test was completed (March), measurements were made for each treatment (inoculated or non-inoculated), and watering regime (watered and water-stressed). Pressure–volume curves, osmotic potential at full turgor, osmotic potential at zero turgor and the tissue modulus of elasticity near full turgor were calculated. Mycorrhizal colonization and growth, and the content of the main mineral nutrients N, P, K, Ca and Mg were measured. Water stress affected plant growth, caused an elastic adjustment of the plant tissues, and decreased the P and K content, and inoculation improved the nitrogen content. Drought acclimation apparently achieved the goal of improving the drought tolerance of holm oak seedlings, without depressing ectomycorrhizal root colonization by T. melanosporum. José Antonio Rodríguez Barreal—Deceased     

Gas exchange responses of <Emphasis Type="Italic">Eucalyptus</Emphasis>, <Emphasis Type="Italic">C. africana</Emphasis> and <Emphasis Type="Italic">G. robusta</Emphasis> to varying soil moisture content in semi-arid (Thika) Kenya

A dramatic decline in forest cover in eastern Africa along with a growing population means that timber and poles for building and fuelwood are in short supply. To overcome this shortage, the region is increasingly turning to eucalyptus. But eucalyptus raises environmental concerns of its own. Fears that it will deplete water supply, affect wildlife and reduce associated crop yields have caused many countries in the region to discourage farmers from planting this exotic. This paper is part of a series of investigations on the growth and water use efficiency of faster growing eucalyptus hybrids, which was introduced from South Africa to Kenya. The hypothesis is that the new hybrids are more efficient in using water and more suitable for the semi-arid tropics than existing eucalyptus and two popular agroforestry species. Gas exchange characteristics of juvenile Eucalyptus grandis (W. Hill ex Maiden), two eucalyptus hybrids (E. grandis × Eucalyptus camaldulensis Dehnh.), Grevillea robusta (A. Cunn) and Cordia africana (Lam) was studied under field and pot conditions using an infrared gas analyzer was used to measure photosynthetic active radiation (PAR), net photosynthetic rate (A), stomatal conductance (g _s) and transpiration rate (E) at CO₂ concentrations of 360 μmol mol⁻¹ and ambient humidity and temperature. A, E and g _s varied between species, being highest in eucalyptus hybrid GC 15 (24.6 μmol m⁻² s⁻¹) compared to eucalyptus hybrid GC 584 (21.0 μmol m⁻² s⁻¹), E. grandis (19.2 μmol m⁻² s⁻¹), C. africana (17.7 μmol m⁻² s⁻¹) and G. robusta (11.1 μmol m⁻² s⁻¹). C. africana exhibited high E values (7.0 mmol m⁻² s⁻¹) at optimal soil moisture contents than G. robusta (3.9 mmol m⁻² s⁻¹) and eucalyptus (5.3 mmol m⁻² s⁻¹) in field experiment and G. robusta (3.2 mmol m⁻² s⁻¹) and eucalyptus (4.2 mmol m⁻² s⁻¹) in pot-grown trees. At very low soil moisture content, extremely small g _s values were recorded in GC 15 and E. grandis (8 mmol m⁻² s⁻¹) and G. robusta (14 mmol m⁻² s⁻¹) compared to GC 584 (46.9 mmol m⁻² s⁻¹) and C. africana (90.0 mmol m⁻² s⁻¹) indicating strong stomatal control by the species. Instantaneous water use efficiency ranged between 3 and 5 μmol mmol⁻¹ and generally decreased with decline in soil moisture in pot-grown trees but increased with declining soil moisture in field-grown trees.     

Effects of <Emphasis Type="Italic">Eucalypt</Emphasis> and <Emphasis Type="Italic">Acacia</Emphasis> plantations on soil water in Sumatra

Indonesia’s pulp and paper industry needs a large area of sustainably grown plantations to support its continued development. Acacia mangium has been the key species underpinning the pulp and paper industries in Sumatra, however increased disease pressure on A. mangium is expected to require large-scale conversion of Acacia plantations to Eucalyptus in the near future. The effect of such a large scale change in plantation species on soil moisture, for both tree production, and catchment hydrology is unknown. In this study we sought to characterize the impacts of plantation species (Acacia or Eucalyptus) and nitrogen management, on soil moisture, soil water depletion and depth to groundwater under stands of Acacia mangium and Eucalyptus pellita over the first 2–3 years after establishment. The study was conducted in experiments at four sites in Sumatra, Indonesia. Soil moisture and soil water depletion were not influenced by plantation species or fertilizer treatment. Soil moisture content and soil water depletion were strongly influenced by shallow groundwater at two of the four sites, however depth to groundwater did not influence stem growth. Results from the field trials cautiously suggest that large scale conversion of Acacia mangium to Eucalypt species in these regions is unlikely to result in increased moisture stress, nor is conversion of plantation species likely to lead to substantial differences in catchment hydrology. This study demonstrated the importance of conducting multi-site studies when investigating biophysical relationships in forest/plantation systems.     

Potential contribution of <Emphasis Type="Italic">Quercus durata</Emphasis> and <Emphasis Type="Italic">Adenostoma fasciculatum</Emphasis> supplemented with <Emphasis Type="Italic">Medicago sativa</Emphasis> on intake and digestibility in sheep and goats

A digestion trial was conducted to estimate the potential contribution of the chaparral browse Quercus durata (leather oak) and Adenostoma fasciculatum (chamise) on intake and nutrient digestion in goats and sheep. Four wether Kiko goats (avg. wt. 22.9 kg) and four wether Targhee sheep (avg. wt. 39.6 kg) were housed in metabolism cages. Alfalfa pellets were used as a dietary supplement. Digestibility of the shrubs was measured by difference and metabolizable energy (ME) and ME intake (MEI) were calculated from digestibility and plants intake values. Oak and chamise had low crude protein (CP) content (6.5 and 4.3% DM) and high content of extractable condensed tannins (17.8 and 9.8% DM). In vitro organic matter digestibility (OMD) and ME for oak and chamise were 35.6 and 33.1% and 5.0 and 4.7 MJ/kg DM, respectively. In vivo OMD (calculated by difference with alfalfa) and MEI, for browse were greater (P < 0.01) for goats fed chamise compared to sheep. In oak, OMD was similar for both animal species but MEI was greater (P < 0.01) for goats. Greater (P < 0.05) DM and CP intakes (per kg BW^0.75) were observed for goats fed either oak or chamise compared with sheep. When an energy source was given as supplement, the potential contribution of chamise and oak to total ME requirements for maintenance was about 58.3 and 60.4% in goats and about 17.1 and 32.9% in sheep, respectively. In consequence, metabolizable energy supplied by these shrubs may not be adequate for maintenance when, during grazing, they are consumed in high proportions with other chaparral plants that may have lower nutritional value than the alfalfa supplemented in this study. Under an appropriate supplementation program, goats could be more effective than sheep to control fuel load in California chaparral, as they consume more chamise and leather oak and obtain more nutrients from them.     

<Emphasis Type="Italic">Quercus suber</Emphasis> forest and <Emphasis Type="Italic">Pinus</Emphasis> plantations show different post-fire resilience in Mediterranean north-western Africa

Key message

In the African rim of the Western Mediterranean Basin, cork oak forests and pine plantations coexist. Under similar fire regimes, cork oak forest is more resilient in terms of habitat structure (canopy, understory, and complexity of vegetation strata) than pine plantation. By contrast, both woodland types show similar resilience in plant species composition. Resilience in habitat structure varies between the two woodland types because of the resprouting and seeding strategies of cork oak and pine species, respectively. These differences can be relevant for the conservation of biodiversity of forested ecosystems in a future scenario of increased fire frequency and scale in the Mediterranean basin.

Context

Wildfires have major impacts on ecosystems globally. In fire-prone regions, plant species have developed adaptive traits (resprouting and seeding) to survive and persist due to long evolutionary coexistence with fire. In the African rim of the Western Mediterranean Basin, cork oak forest and pine plantation are the most frequently burnt woodlands. Both species have different strategies to respond fire: cork oak is a resprouter while pines are mostly seeders.

Aims

We have examined the hypothesis that pine plantations are less resilient in habitat structure (canopy, understory, diversity of vegetation strata) and plant composition than cork oak woodlands.

Methods

The habitat structure and plant species composition were measured in 30 burnt and 30 unburnt 700-m transects at 12 burnt sites from north-western Africa, where the two forest types can coexist. Habitat structure and plant species composition were compared between burnt and unburnt transects from cork oak and pine plantation woodlands with generalized linear mixed models and general linear models.

Results

The results showed significant interaction effect of fire and forest type, since cork oak forest was more resilient to fire than was pine plantation in habitat structure. By contrast, both forest types were resilient to fire in the composition of the plant communities, i.e., plant composition prior to fire did not change afterwards.

Conclusion

The higher structural resilience of cork oak forest compared to pine plantation is related to the resprouting and seeding strategies, respectively, of the dominant tree species. Differences in the responses to fire need to be considered in conservation planning for the maintenance of the Mediterranean biodiversity in a future scenario of changes in fire regime.

     

Root architecture might account for contrasting establishment success of <Emphasis Type="Italic">Pseudotsuga menziesii</Emphasis> var. <Emphasis Type="Italic">menziesii</Emphasis> and <Emphasis Type="Italic">Pinus sylvestris</Emphasis> in Central Europe under dry conditions

Key message

Pinus sylvestris seedlings quickly expand their roots to deeper soil layers while Pseudotsuga menziesii concentrates its root system in the topsoil, thereby running the risk of desiccation during long dry spells, as indicated by lower survival after simulated summer drought.

Context

Pseudotsuga menziesii (Douglas-fir) is regarded as a promising species to maintain the productivity of Central European lowland forests given the projected increase of long dry spells.

Aims

Will the species be able to regenerate from seed and spread outside plantations in a drier temperate Europe?

Methods

We measured the relative growth rate, biomass allocation, root architecture, and phenotypic plasticity of Pseudotsuga menziesii seedlings sown in a common garden and grown under current precipitation and prolonged drought, respectively. The species’ competitive ability with respect to Pinus sylvestris L., the most drought-tolerant native conifer in Central Europe, was assessed during three growing seasons.

Results

Pinus sylvestris seedlings had higher relative growth rates than did Pseudotsuga menziesii seedlings, first in terms of aboveground biomass and later in terms of shoot height. This resulted in heavier and taller seedlings after three growing seasons under both moist and dry conditions. Shorter vertical roots corresponded with lower survival of Pseudotsuga menziesii seedlings under dry conditions.

Conclusion

Fast root proliferation allows Pinus sylvestris seedlings to reach deeper water pools that are less rapidly depleted during transient drought. By contrast, the shallow root system might put Pseudotsuga menziesii seedlings at the risk of desiccation during prolonged dry spells.

     

Insecticidal properties of <Emphasis Type="Italic">Thymus persicus</Emphasis> essential oil against <Emphasis Type="Italic">Tribolium castaneum</Emphasis> and <Emphasis Type="Italic">Sitophilus oryzae</Emphasis>

Red flour beetle Tribolium castaneum (Herbst) and rice weevil Sitophilus oryzae (L.) are considered to be the major insect pests in storage. Essential oils from aromatic plants are recognized as proper alternatives to fumigants. Thymus persicus (Ronniger ex Rech. f.) is one of these plants that have medicinal properties and is indigenous to Iran. The essential oil was obtained from aerial parts of the plant and analyzed by GC and GC–MS. Carvacrol (44.69%) and thymol (11.05%) were the major constituents of the oil extracted. In this experiment, fumigant toxicity of the essential oil was studied against T. castaneum, S. oryzae at 27 ± 1°C and 60 ± 5% RH in dark condition. The adult insects were exposed to the concentrations of 51.9, 111.1, 207.4 and 370.4 μl/l air to estimate median lethal time (LT₅₀) values. The fumigant toxicity was increased in response to increased essential oil concentrations. The LT₅₀ values at the lowest and the highest concentrations tested were ranged from 28.09 to 13.47 h for T. castaneum, and 3.86 to 2.30 h for S. oryzae. It was found that S. oryzae adults were much more susceptible to the oil than T. castaneum. After 24 h of exposure, the LC₅₀ values (95% fiducial limit) for T. castaneum and S. oryzae were estimated to be 236.9 (186.27–292.81) and 3.34 (2.62–4.28) μl/l air, respectively. These results suggest that T. persicus essential oil merits further study as potential fumigant for the management of these stored-product insects.     

Fine root dynamics in 60-year-old stands of <Emphasis Type="Italic">Fagus sylvatica</Emphasis> and <Emphasis Type="Italic">Picea abies</Emphasis> growing on haplic luvisol soil

Fine root dynamics in mono-specific stands of mature Fagus sylvatica L. and Picea abies Karst. was studied from December 2003 to December 2004 in a stand in Southern Germany. Minirhizotrons were used to draw between species comparisons concerning fine root (≤1 mm) longevity and temporal patterns of fine root dynamics (growth and mortality) as related to seasonal changes in soil water content and soil temperature. In F. sylvatica, median fine root longevity from early seasonal to late-seasonal cohorts was low (77 days). Fine root dynamics scaled positively with seasonal changes in soil water and temperature indicating accelerated fine root turnover during favourable soil conditions. In contrast, fine root longevity in P. abies (273 days) was significantly higher when compared to F. sylvatica and increased from early seasonal to late-seasonal cohorts. Fine root dynamics in P. abies did not correlate with soil environmental conditions. Rather a large proportion of new fine roots occurred during the dry season in superficial soil layers. The data suggest species inherent patterns of fine root longevity and temporal patterns of fine root dynamics.     

Allelopathic effects of <Emphasis Type="Italic">Pinus halepensis</Emphasis> and <Emphasis Type="Italic">Quercus coccifera</Emphasis> on the germination of Mediterranean crop seeds

Agroforestry is a leading alternative for food security and forest conservation. A full understanding of positive and negative, i.e. allelopathic, interactions between crops and forest trees is necessary for producing crops and conserving forests especially within the threatened Mediterranean forest ecosystems. The present study explored the allelopathic effects of green and senescent leaf and soil extracts of two agroforestry trees—Pinus halepensis and Quercus coccifera—on the germination of wheat, barley, lentil, chickpea, and fababean as the major grain crops of Jordan. Results revealed that allelopathic effects reduced seed germination of these crops. Germination reduction reached a maximum of 75% in fababean treated with green extracts of Q. coccifera and differed among crops and extract sources, but not between tree species. Comparing between green and senescent leaf and soil extract, regarding their effect on germination percentage, it was noticed that these effects were similar in some crops and were different in others. Germination responses were generally different between cereals and legumes where cereals tend to be less affected by allelopathic influences than legumes, especially fababean. We suggest using cereals such as wheat and barley in agroforestry practices in the Mediterranean region of Jordan.     

Phenotypic plasticity blurs ecotypic divergence in the response of <Emphasis Type="Italic">Quercus coccifera</Emphasis> and <Emphasis Type="Italic">Pinus halepensis</Emphasis> to water stress

The Mediterranean evergreen woody plants Quercus coccifera and Pinus halepensis grow in a range of environments where selection by drought, heat and high irradiance can drive genetic and phenotypic differentiation of populations. However, the role of these stresses in filtering out maladaptive genotypes remains unknown. We hypothesize that this filtering is an important process for woody Mediterranean species due to their low phenotypic plasticity reported in previous studies. We have studied the response of saplings of Q. coccifera and P. halepensis, originating from two contrasting populations (a rock outcrop and a garrigue formation), to water stress. Isozyme characterization of genetic diversity was done to determine whether populations were genetically distinct. Water response analysis was based on water relations, gas exchange, chlorophyll a fluorescence, pigment content, antioxidant status and morphological and structural parameters. Ecotypic differentiation was found for both Q. coccifera and P. halepensis populations, with a higher population isozyme similarity and a higher frequency of dominance of a few genotypes at the rock outcrop in both the species. P. halepensis exhibited small but significant differences between populations for plastic responses to water, with lower phenotypic plasticity in saplings from the rock outcrop. Although it was not found in Q. coccifera, this pattern suggests that ecotypic differentiation rendering stress-tolerant ecotypes involves a decreased plasticity. Phenotypic plasticity was not high but it explained over 75% of the total variability among individual plants. Thus, and although evidence for ecotypic divergence was found in both the species, saplings were plastic enough to blur ecotypic differentiation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Bioremediation of CCA-treated wood by brown-rot fungi <Emphasis Type="Italic">Fomitopsis palustris</Emphasis>, <Emphasis Type="Italic">Coniophora puteana</Emphasis>, and <Emphasis Type="Italic">Laetiporus sulphureus</Emphasis>

This study evaluated oxalic acid accumulation and bioremediation of chromated copper arsenate (CCA)-treated wood by three brown-rot fungi Fomitopsis palustris, Coniophora puteana, and Laetiporus sulphureus. The fungi were first cultivated in a fermentation broth to accumulate oxalic acid. Bioremediation of CCA-treated wood was then carried out by leaching of heavy metals with oxalic acid over a 10-day fermentation period. Higher amounts of oxalic acid were produced by F. palustris and L. sulphureus compared with C. puteana. After 10-day fermentation, oxalic acid accumulation reached 4.2 g/l and 3.2 g/l for these fungi, respectively. Fomitopsis palustris and L. sulphureus exposed to CCA-treated sawdust for 10 days showed a decrease in arsenic of 100% and 85%, respectively; however, C. puteana remediation removed only 18% arsenic from CCA-treated sawdust. Likewise, chromium removal in F. palustris and L. sulphureus remediation processes was higher than those for C. puteana. This was attributed to low oxalic acid accumulation. These results suggest that F. palustris and L. sulphureus remediation processes can remove inorganic metal compounds via oxalic acid production by increasing the acidity of the substrate and increasing the solubility of the metals.An erratum to this article can be found at     

Comparison of postfire mortality in endemic Corsican black pine (<Emphasis Type="Italic">Pinus nigra</Emphasis> ssp. <Emphasis Type="Italic">laricio</Emphasis>) and its direct competitor (<Emphasis Type="Italic">Pinus pinaster</Emphasis>)

• Introduction   

Laricio pine (Pinus nigra J.F. Arn. ssp. laricio (Poiret) Maire var Corsicana Hyl.) is a form of black pine endemic to Corsica, that may now be under threat due to current fire regimes and competition with maritime pine (Pinus pinaster Aiton).     

Genetic diversity in two threatened species in Vietnam: <Emphasis Type="Italic">Taxus chinensis</Emphasis> and <Emphasis Type="Italic">Taxus wallichiana</Emphasis>

Taxus chinensis and T. wallichiana in have been threatened in their distribution areas in recent decades because of their over-exploitation and reduction and destruction of native habitats. Determining the genetic diversity in populations of the two species will provide guidelines for their protection and preservation. Two hundred and fifteen trees from six populations of T. chinensis and 150 sampled trees of T. wallichiana were sampled. Six microsatellite primer pairs selected from 16 primer pairs were used to investigate genetic variation at the population and species levels. Five yielded polymorphic alleles, and among the 13 putative alleles amplified, 11 were polymorphic (accounting for 76.33 %).Shannon’s information index (I) and percentage of polymorphic bands (PPB) (I = 0.202 and PPB = 67.22 % for T. chinensis; I = 0.217 and PPB = 65.03 % for T. wallichiana). Both species had low levels of genetic diversity (mean H _o = 0.107, H _e = 0.121 for T. chinensis; H _o = 0.095, H _e = 0.109 for T. wallichiana). Genetic differentiation among populations was higher (F _ST = 0.189) for T. chinensis and lower (0.156) for T. wallichiana, indicating limited gene flow (Nm) among populations for T. chinensis (0.68) and T. wallichiana (0.65). Variation among individuals of T. chinensis was 63.59 and 73.12 % for T. wallichiana. Thus, the threatened status of the two conifers is related to a lack of genetic diversity. All populations are isolated in small forest remnants. An ex situ conservation site should be established with a new population for these species that comprises all the genetic groups for the best chance to improve their fitness under environmental stresses.     

Spatial pattern of beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) and oak (<Emphasis Type="Italic">Quercus pubescens</Emphasis> Mill.) seedlings in natural pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.) woodlands

Spatial pattern of recruitment is an important factor influencing population dynamics of plant communities. The spatial pattern is determined by seed dispersal and by the spatial variability of germination and initial survival. In the process of forest expansion following farmland abandonment, mid- and late-successional species are often dispersed in pioneer forests by birds. This could result in an aggregated spatial pattern of seeds that could influence the dynamics of these species in mixed pioneer forests. In the sub-Mediterranean area, mid- and late-successional species such as Quercus pubescens (downy oak) and Fagus sylvatica (European beech) are expected to replace pioneer Pinus species. Using a point sampling method we demonstrated that beech and oak seedlings (height <2 m) have a clumped distribution in the understorey of pine. This could result from an aggregated dispersal by jays (dispersal effect) or from preferential recruitment in particular habitats (habitat effect). To test these hypotheses we proposed a statistical analysis of spatial patterns of regeneration of beech and oak. Ground cover variables (i.e. cover by rock outcrops, herbs, box shrubs, mosses or pine) did not differ significantly around seedlings as compared with random sample plots. Likewise, clumped seedlings had growth similar to isolated seedlings, thus refuting the hypothesis of preferential location in the most favourable microsites. Aggregated dispersal seems to be involved in the process of regeneration. Since beech and oak seedlings have contrasting ecological demands, we discuss the implication of this pattern for the replacement dynamics of pine by these species.