Genetic variation in susceptibility to pine wilt disease of maritime pine (<Emphasis Type="Italic">Pinus pinaster</Emphasis> Aiton) half-sib families

Key message

This paper presents a greenhouse study for assessing the genetic variation in maritime pine (Pinus pinaster Aiton) in response to pinewood nematode (Bursaphelenchus xylophilus (Steiner et Buhren) Nickle), which is a causal agent of pine wilt disease. Fifteen out of 96 half-sib families were selected as less susceptible. This experiment is an important first step for creating a resistance breeding program.

Context

Pine wilt disease is caused by the pinewood nematode (Bursaphelenchus xylophilus (Steiner et Buhren) Nickle), a quarantine pest, and is a concern to maritime pine (Pinus pinaster) in Portugal due to its economic, environmental, and social impacts. This disease is regarded as a major threat to European forests.

Aims

This paper aimed to evaluate the genetic variation in maritime pine families that were inoculated with pinewood nematode, identify the most resistant families, and establish the guidelines for a resistance improvement program.

Methods

Two-year-old half-sib progenies obtained from 96 plus trees were inoculated. The plants were monitored for survival on four different dates. The statistical analysis followed the mixed model theory.

Results

Genetic variability of the susceptibility to pine wilt disease was observed. At 157 days after inoculation, the 15 highest genetic ranking families out of 96 were selected, having a predicted survival mean of 15.6% instead of 11.0% on average for the all 96 families.

Conclusion

This study allows for the implementation of an improvement program to help control pine wilt disease.

     

The Level II aggregated forest soil condition database links soil physicochemical and hydraulic properties with long-term observations of forest condition in Europe

Key message

Aggregated, consolidated, and derived soil physicochemical data of 286 ICP Forests Level II plots were completed with soil hydraulic properties for integrated use with forest monitoring data. Database access should be requested at http://icp-forests.net . Metadata associated available at https://metadata-afs.nancy.inra.fr/geonetwork/apps/georchestra/?uuid=153e599e-6624-4e2b-b862-8124386ea9cd&hl=eng

Context

The ICP Forests database is one of the most comprehensive forest ecosystem datasets in Europe and contains the accumulated results of more than two decades of harmonised forest monitoring all over Europe.

Aims

The aim of this paper is to share knowledge on the ICP Forests Level II soil data for broader use among forest scientists.

Methods

After standard analysis, quality checks, aggregation, and calculation of derived variables (e.g. nutrient stocks, base saturation, C:N ratio, and water retention parameters), data have been gathered into a static database (AFSCDB.LII.2.2), which will be updated to new versions as soon as new measurements become available.

Results

The database provides a basis for the combined evaluation of up to 130 unique soil variables of 286 plots with dynamic data on tree growth, ground vegetation, foliar chemistry, crown condition, tree phenology, leaf area index, ozone injury, litterfall, soil solution chemistry, deposition, ambient air quality, and meteorological data assessed on the same plots.

Conclusion

The unprecedented comprehensiveness and level of detail in this newly aggregated database may overcome existing restrictions so far impeding the realisation of large-scale forest ecosystem studies in Europe.

     

Forward selection in a maritime pine polycross progeny trial using pedigree reconstruction

Key message

Molecular markers were used for paternity recovery in a maritime pine ( Pinus pinaster Ait.) polycross trial, facilitating forward selection. Different breeding strategies for seed orchard establishment were evaluated by comparing genetic gains and diversity. This work opens up new perspectives in maritime pine breeding.

Context

Polycross mating designs are widely used in forest tree breeding to evaluate parental breeding values for backward selection. Alternatively, polycross progeny trials may be used to select the best trees on the basis of individual breeding values and molecular pedigree analysis.

Aims

This study aimed to test such a forward selection strategy for the maritime pine breeding program.

Methods

In a maritime pine polycross trial, progeny with higher breeding values for growth and stem straightness was first preselected with or without relatedness constraints. After paternity recovery, the preselected trees were ranked on the basis of their breeding values, estimated from the recovered full pedigree. Finally, the best candidates were selected with three different strategies (forward, backward, mixed) and three levels of coancestry constraints to establish a virtual clonal seed orchard.

Results

Complete pedigrees were successfully recovered for most of the preselected trees. There was no major difference in expected genetic gains between the two preselection strategies which differed for relatedness constraints. Genetic gains were slightly higher for forward selection than for classical backward selection.

Conclusion

This seminal study opens up new perspectives for using forward selection within the French maritime pine breeding program.

     

Dynamics of diameter and height increment of Norway spruce and Scots pine in southern Finland

Key message

Onset and cessation of radial and height increment of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in southern Finland were independent phenomena. They both contributed to the increment period duration, which was a more crucial factor defining the magnitude of annual radial and height increment.

Context

Phenology of diameter and height increment is a critical component of growth, also contributing to damage and survival of trees.

Aims

We quantified annual variation in intra-annual tracheid production and height increment of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.).

Methods

The number of tracheids and the day of the year for the onset and cessation of tracheid production were monitored from microcores collected repeatedly during growing seasons 2001–2012 in southern Finland. Weekly height increment was also measured in an adjacent sapling stand in 2008–2012.

Results

The first tracheids in pine were found around mid-May and in spruce a week later. The cessation of the tracheid production occurred during the last week of August for both tree species. Increment onset and cessation were independent phenomena, both contributing to the magnitude of tracheid production via increment period duration, which appeared to be a more crucial factor defining the number of tracheids. Duration of the height increment period was also related to shoot length but the connection was less tight than the link between the duration of tracheid production and the number of tracheids. A thermal threshold around 100 d.d. (degree days) was found for the onset of radial increment. No single environmental factor triggered the cessation of tracheid production, but in some years, soil water availability appeared to play a role.

Conclusion

The results indicate that extending growing seasons due to the climatic warming may increase growth in the Finnish forests.

     

Crown bulk density and fuel moisture dynamics in <Emphasis Type="Italic">Pinus pinaster</Emphasis> stands are neither modified by thinning nor captured by the Forest Fire Weather Index

Key message

No temporal change was recorded during summer in fuel availability in Pinus pinaster stands, contrary to predictions from the Forest Fire Weather Index. Also, thinning had no mid-term effect on fuel moisture or canopy structure.

Context

Forest fires are a major problem in Mediterranean countries. Management actions, such as fuel reductions, are one of the main tools to diminish fire risk, but the midterm efficacy of such tools remains largely untested with empirical data.

Aims

Here, we test for midterm effects of thinning on fuel moisture and crown bulk density in P. pinaster stands and whether temporal variations in fuel moisture correlated with predictions from the Fire Weather Index, a commonly used index on fire risk, and its components.

Methods

We compared fuel moisture over a fire season and crown bulk density in nine pairs of thinned/unthinned plots 7 years after treatments were applied.

Results

We observed that fuel moisture remained stable during a fire season, as a likely result of drought-induced physiological adjustments, including stomatal regulation and others, which allow leaves to maintain a large humidity even during drought, and that thinning had no midterm effect on fuel moisture or crown bulk density. Moreover, the Fire Weather Index and its components displayed different temporal dynamics than those observed in fuel moisture.

Conclusion

These results are important as they indicate that thinning may only have a limited, short-term impact towards diminishing the potential for crown fire spread in these stands and that current indices to evaluate fire risk may require a re-evaluation.

     

Is forest insurance a relevant vector to induce adaptation efforts to climate change?

? Key message

Insurance might be an efficient tool to strengthen adaptation of forest management to climate change. A theoretical model under uncertainty is proposed to highlight the effect, on adaptation decisions, of considering adaptation efforts in forest insurance contracts. Results show that insurance is relevant to increase adaptation efforts under some realistic conditions on forest owner’s uncertainty and risk preferences, and on the observability or not of adaptation efforts.

? Context

One of the challenges of forest adaptation to climate change is to encourage private forest owners to implement adaptation strategies.

? Aims

We suggest the analysis of forest insurance contracts against natural hazards as a vector to promote the implementation of adaptation efforts by private forest owners.

? Methods

We propose a theoretical model of insurance economics under risk and under uncertainty.

? Results

Our results indicate that when climate change makes the probability of the occurrence of the natural event uncertain, then it may be relevant to include adaptation efforts in the insurance contract, leading to an increase in the adaptation efforts of risk-averse and uncertainty-averse forest owners. In addition, we show that the relevance of insurance as a vector to promote adaptation efforts is greater when the forest owner’s effort is unobservable by the insurer as compared to a situation of perfectly observable effort.

? Conclusion

Under some realistic assumptions, the forest insurance contract seems to be a relevant tool to encourage forest owners to adapt to climate change.

     

Modelling wood formation and structure: power and limits of a morphogenetic gradient in controlling xylem cell proliferation and growth

Key message

The emergence of the characteristic tree-ring pattern during xylogenesis is commonly thought to be controlled by a gradient of morphogen (auxin, TDIF peptide...). We show that this hypothesis accounts for several developmental aspects of wood formation, but not for the final anatomical structure.

Context

Wood formation is a dynamic cellular process displaying three generic features: (i) meristematic cell proliferation is restricted to the small cambial zone, preventing exponential xylem radial growth along the growing season; (ii) developmental processes result in a stable zonation of the developing xylem; (iii) the resulting mature wood cells form the typical tree-ring structure made of early and late wood with a gradient of cell sizes, an important trait for wood functioning in trees and for lumber quality. The mechanisms producing these spatial-temporal patterns remain largely unknown. According to the often-cited morphogenetic-gradient hypothesis, a graded concentration profile of a signalling molecule (e.g. auxin, TDIF) controls xylogenesis by providing positional information to differentiating cells.

Aims

We assessed the predictions of the morphogenetic-gradient theory.

Methods

We developed a computational model of wood formation implementing hypotheses on how a morphogen flows through the developing xylem and controls cell division and growth and we tested it against data produced by studies monitoring wood formation in conifers.

Results

We demonstrated that a morphogenetic gradient could indeed control xylem radial growth and wood-forming tissue zonation. However, it failed to explain the pattern of final cell sizes observed in tree-rings. We discussed the features that candidate additional regulatory mechanisms should meet.

     

Comparing morphology and physiology of southeastern US <Emphasis Type="Italic">Pinus</Emphasis> seedlings: implications for adaptation to surface fire regimes

Key message

The suite of traits expressed as seedlings by coastal and mountain longleaf pine and south Florida slash pine suggest they can survive fire in the seedling stage. In contrast, loblolly pine and typical slash pine tolerate fire when mature but do not exhibit traits that allow them to survive fire when young, representing a different strategy for survival in frequently burned communities.

Context

Fire is an important driver in the distribution and abundance of southern US pine species, and seedling fire tolerance often determines individual survival under frequent fire regimes.

Aims

We investigated seedling growth, biomass allocation, needle distribution, bark thickness, and total non-structural carbohydrate (TNC) storage in taproots and related them to the expression of fire-tolerance for five species or types, including loblolly pine (Pinus taeda L.), two longleaf pine (P. palustris Mill.) types representing two distinct ecological communities (coastal and mountain) and two slash pine (P. elliottii Englem.) varieties.

Methods

We analyzed the relationship of seedling growth, biomass characteristics, and total non-structural carbohydrate storage between species by using analysis of variance.

Results

Both coastal and mountain longleaf pines had thick bark, long, densely arranged needles, and a grass-stage. South Florida slash pine shared the same suite of traits but, contrary to previous reports, displayed reduced height growth rather than a grass-stage. In contrast, loblolly pine and typical slash pine had faster height growth, more branching, lower needle density, and thinner bark. Both longleaf pines and south Florida slash pine also had higher TNC storage in taproots than either loblolly or typical slash pines.

Conclusion

The relative strength of expression of these fire-adaptation traits among the five species types generally matches the fire-return intervals associated with each species’ habitat, suggesting the importance of fire regimes in determining the distribution and abundance of the studied species.

     

Beech coppice conversion to high forest: results from a 31-year experiment in Eastern Pre-Alps

Key message

Selective thinning is a more viable method for beech coppice conversion to high forest when compared with thinning from below as it enhances tree growth, reduces mortality of the remaining trees, and allows to obtain stands with a higher mechanical stability and larger crowns.

Context

Beech forests in North-East Italy have been largely managed as coppice. Due to socio-economic changes, a large conversion to high forests program started in the second half of the past century.

Aims

A long-term experiment testing the effects on tree growth and stability of two different conversion methods (thinning from below—method A; selective thinning—method B) was implemented.

Methods

Both silvicultural treatments started in 1979 with a first thinning followed by a second one in 1997. All trees were periodically measured in order to assess mortality, stability, and growth during the period 1979–2010. In 2010, an assessment of stem quality and crown size was also performed.

Results

Both methods were economically viable, but method B acted with a higher intensity both in 1979 and in 1997, thus making the harvest more profitable for the owners. Moreover, method B enhanced tree growth, especially in the period after the first thinning, reduced mortality, and allowed to obtain stands with a higher mechanical stability and with larger crowns.

Conclusion

It would be possible to adopt some of the criteria prescribed with method B in future thinnings over the large areas actually managed with method A, as prescribed by the law.

     

Carbon stock density in planted versus natural <Emphasis Type="Italic">Pinus massoniana</Emphasis> forests in sub-tropical China

Key message

Carbon stock density was quite similar in planted vs natural forest of Masson’s pine ( Pinus massoniana Lamb.) in China across three ages (7, 15, and 50 years). The stock in the standing trees was larger in planted than in natural forests, but this difference was compensated by larger stocks in the soil and the debris of natural forests.

Context

Most studies on the carbon stocks are focused on management strategies to maximize carbon stocks. We still lack data comparing planted vs natural conifer forests.

Aims

We compared carbon storage in the different compartment (vegetation, soil, debris) along a chronosequence of Masson’s pine plantations vs natural forests.

Methods

We investigated 58 Masson’s pine (Pinus massoniana Lamb.) forest stands (20 m?×?50 m plots), that differ in stand management (planted and natural forests) and age (young, middle-aged, and mature ages) and then calculated the carbon stock densities of vegetation biomass (tree, shrub, and herb), debris, and soil.

Results

The carbon stock densities in the planted and natural Masson’s pine forest ecosystems ranged from 78 to 210 Mg ha^?1 and from 97 to 177 Mg ha^?1 respectively. The carbon stock densities in the vegetation were significantly greater in planted forests than in natural forests. A lower carbon stock density in debris and soil alleviated the increase of biomass carbon stock densities in planted vs natural forests, leading to similar carbon stock densities at ecosystem level. The carbon stock densities in the vegetation increased with age, whereas those of debris and soil remained stable.

Conclusions

Planted forests of Masson’s pine sequester similiar amounts of carbon at ecosystem level to those in natural forests, reinforcing the idea that planted pine forests can contribute to the mitigation of greenhouse gas emission.

     

Mixing oak and pine trees does not improve the functional response to severe drought in central French forests

Key message

Mixing sessile oak and Scots pine in central France to reduce intraspecific competition for water resources did not improve the ability of these two species to withstand severe drought during the summer.

Context

In order to reduce the impact of increasingly extreme droughts on forests, managers must adapt their practices to future climate conditions. Maintaining a greater diversity of tree species in temperate forest ecosystems is one of the recommended options.

Aims

We addressed how interactions between sessile oak and Scots pine in mixed forests in central France affect their functional response to drought.

Methods

We characterized the carbon isotope composition (δ¹³C) in the tree growth rings formed during wet (2001, 2007) or dry (2003, 2004) summers for each of the two species growing both in pure and in mixed stands in order to compare the effect of stand composition on variations in carbon isotope discrimination (Δ¹³C) among contrasted years.

Results

The severe drought in 2003 induced a strong decrease in Δ¹³C for all trees and in all stands as compared to 2001. This decrease was greater in pine than in oak. There was no significant difference between pure and mixed stands in the response of either species to drought.

Conclusion

Mixing sessile oak and Scots pine in stands in central France does not improve the ability of either species to withstand severe drought during the summer.

     

Disturbance severity and canopy position control the radial growth response of maple trees (<Emphasis Type="Italic">Acer</Emphasis> spp.) in forests of northwest Ohio impacted by emerald ash borer (<Emphasis Type="Italic">Agrilus planipennis</Emphasis>)

Key message

Radial growth of silver and red maples was investigated across three forests in northwest Ohio following the outbreak of the invasive emerald ash borer. The growth response of maples was driven by an advancement in canopy class and disturbance severity.

Context

Forest disturbances resulting in species-specific diffuse mortality cause shifts in aboveground and belowground competition. This competition may differentially affect non-impacted trees, depending on crown class, disturbance severity, and species-specific responses.

Aims

The purpose of this study is to elucidate the primary drivers of silver and red maple (Acer saccharinum and A. rubrum) growth following emerald ash borer (EAB, Agrilus planipennis)-induced ash tree (Fraxinus spp.) mortality in riparian forests of northwest Ohio.

Methods

Using dendroecological approaches, we analyzed the pattern of radial growth in red and silver maples in conjunction with the EAB outbreak.

Results

This study revealed growth rates of maples increased 72% following EAB arrival and trees advancing in crown class grew 41% faster than those not advancing. The growth response varied by initial crown class, with trees in the intermediate class responding most dramatically. Furthermore, the positive correlation between relative basal area of ash and the radial growth response of maples indicates the important role of disturbance severity in post-disturbance dynamics.

Conclusion

These findings suggest that, although advancement in crown class may allow predictions of “winners” in forest succession post-disturbance, even trees not changing crown class benefit from decreased competition. Results from this study provide a detailed account of radial growth responses in maples following EAB-induced ash mortality and lend insight into the future canopy composition of ash-dominated riparian forests.

     

Hierarchical model-based inference for forest inventory utilizing three sources of information

? Key message

The study presents novel model-based estimators for growing stock volume and its uncertainty estimation, combining a sparse sample of field plots, a sample of laser data, and wall-to-wall Landsat data. On the basis of our detailed simulation, we show that when the uncertainty of estimating mean growing stock volume on the basis of an intermediate ALS model is not accounted for, the estimated variance of the estimator can be biased by as much as a factor of three or more, depending on the sample size at the various stages of the design.

? Context

This study concerns model-based inference for estimating growing stock volume in large-area forest inventories, combining wall-to-wall Landsat data, a sample of laser data, and a sparse subsample of field data.

? Aims

We develop and evaluate novel estimators and variance estimators for the population mean volume, taking into account the uncertainty in two model steps.

? Methods

Estimators and variance estimators were derived for two main methodological approaches and evaluated through Monte Carlo simulation. The first approach is known as two-stage least squares regression, where Landsat data were used to predict laser predictor variables, thus emulating the use of wall-to-wall laser data. In the second approach laser data were used to predict field-recorded volumes, which were subsequently used as response variables in modeling the relationship between Landsat and field data.

Results

? The estimators and variance estimators are shown to be at least approximately unbiased. Under certain assumptions the two methods provide identical results with regard to estimators and similar results with regard to estimated variances.

? Conclusion

We show that ignoring the uncertainty due to one of the models leads to substantial underestimation of the variance, when two models are involved in the estimation procedure.

     

Genetic variation and genotype by environment interaction in the susceptibility of <Emphasis Type="Italic">Abies nordmanniana</Emphasis> (Steven) Spach to the fungus <Emphasis Type="Italic">Neonectria neomacrospora</Emphasis> (Booth &amp; Samuels) Mantiri &amp; Samuels

Key message

Pronounced clonal variation and moderate to high broad-sense heritability estimates of susceptibility to Neonectria neomacrospora were found in Abies nordmanniana in three sites. Significant genotype by environment (G × E) interaction was detected across sites.

Context

Nordmann fir, a widely used Christmas tree species in Europe, has, since 2011, been increasingly damaged by a canker disease caused by Neonectria neomacrospora.

Aims

The objective was to study the genetic variation and genotype by environment interaction in the susceptibility of Nordmann fir to N. neomacrospora.

Methods

Damage caused by N. neomacrospora was evaluated using a visual scale in three Nordmann fir clonal seed orchards in Denmark, partly containing the same clones.

Results

Damage due to N. neomacrospora was substantial at all three sites, and no clone was completely resistant to N. neomacrospora, but a large genetic variation in the susceptibility was detected among clones. Estimates of single-site individual broad-sense heritability for susceptibility varied between 0.38 and 0.47. The average type-B genetic correlation for damage score across sites was 0.34.

Conclusion

Genetic variation was very pronounced, and significant G × E interactions were detected for susceptibility. Further investigations of narrow-sense heritability, expression of the trait in younger material, and identification of the cause of G × E for N. neomacrospora susceptibility in Nordmann fir across different sites are recommended.

     

Differences in carbon isotope discrimination and whole-plant transpiration efficiency among nine Australian and Sahelian <Emphasis Type="Italic">Acacia</Emphasis> species

· Key message

We observed coordinated differences in water-use efficiency, ¹³ C isotope composition, and whole-plant transpiration efficiency among nine Acacia species, although the up scaling from leaf to whole-plant level resulted in different relationships in Sahelian and Australian species.

· Context

The genus Acacia sensu lato contains a large variety of tropical to Mediterranean species adapted to habitats ranging from mesic to arid in Africa and Australia.

· Aims

We checked whether transpiration efficiency differed among a range of nine Sahelian and Australian species and whether it was related to the degree of aridity of the original area or to their type of foliage (pinnate leaves or phyllodes).

· Methods

Intrinsic water-use efficiency (W _I) was recorded from leaf gas exchange and whole-plant transpiration efficiency (TE) from biomass production and water consumption of potted seedlings. Both W _I and TE were compared to ¹³C discrimination (Δ¹³C) computed from either bulk foliage or extracted cellulose.

· Results

At leaf level, Δ¹³C matched closely W _I across species, while at the whole-plant level, the relationship between TE and either Δ¹³C or W _I differed between the Sahelian and the Australian species. Large interspecific differences were found but they were not related to the aridity of the origin nor to the type of foliage.

· Conclusion

Δ¹³C captured well the variability of W _I among several Acacia species while species differences in carbon-use efficiency (the fraction of carbon assimilated recovered in plant biomass) or the relative nocturnal transpiration may disrupt the relationship between TE and Δ¹³C.

     

Patterns of within-stem variations in wood specific gravity and water content for five temperate tree species

? Key message

Intensive measurements of basic specific gravity and relative water content of lumens show that within-stem variations strongly depend on species and cannot be summarised through the typical patterns reported in the literature; breast height measurements are not always representative of the whole stem.

? Context

Knowledge of the distribution of wood properties within the tree is essential for understanding tree physiology as well as for biomass estimations and for assessing the quality of wood products.

? Aims

The radial and vertical variations of basic specific gravity (BSG) and relative water content of lumens (RWC _L ) were studied for five species: Quercus petraea/robur, Fagus sylvatica, Acer pseudoplatanus, Abies alba and Pseudotsuga menziesii. The observations were compared with typical patterns of variations reported in the literature.

? Methods

Wood discs were sampled regularly along tree stems and X-rayed in their fresh and oven-dry states.

? Results

At breast height, BSG was found to clearly increase radially (pith to bark) for two species and to decrease for one species. For F. sylvatica and A. alba, the radial variations of BSG were rather U-shaped, with in particular inner wood areas showing respectively lower and higher BSG than the corresponding mature wood. RWC _L increased generally from inner to outer area but wet sapwood was clearly distinguishable only for the coniferous species. Vertical variations of BSG and RWC _L were strongly dependant on the species with usually non-linear patterns.

? Conclusion

The observed variations of BSG were only partially in agreement with the reported typical radial patterns. Despite the vertical variations, the mean BSG of a cross-section at breast height appeared to be a good estimator of the mean BSG of the whole stem (although the difference was statistically significant for coniferous species), whereas breast height measurement of RWC _L was not representative of the whole stem.

     

<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.

     

The effects of forest type on soil microbial activity in Changbai Mountain,Northeast China

Key message

Forty years after clear-cutting mixed old-growth forest (broadleaf/Korean pine) in the Changbai Mountain area (Northeast China), a mixed forest with natural broadleaf regeneration and larch plantation displayed larger microbial biomass and activity in the soil than either a naturally regenerated birch forest or a monospecific spruce plantation.

Context

Clear-cutting with limited restoration effort was until the end of the twentieth century the norm for managing primary forests in Northeast China. Forest restoration plays an important role in the recovery of soil quality after clear-cutting, but the effects of different regeneration procedures on forest soil quality remain poorly known in Northeast China.

Aims

We assessed the effects of three regeneration procedures, i.e., (i) naturally regenerated birch forest, (ii) spruce plantation, and (iii) naturally regenerated broadleaf species interspersed with planted larch on soil quality and microbial activity in the Changbai Mountain area. An old-growth mixed broadleaf/Korean pine forest was used as a reference.

Methods

Physical and chemical properties and microbial biomass were recorded in the soil. Basal respiration and carbon mineralization were measured with a closed-jar alkali-absorption method.

Results

Microbial biomass was smaller in the birch forest and spruce plantation than in the old-growth and the mixed broadleaf/larch forests. Moreover, microbial biomass, microbial quotient, and potentially mineralizable carbon were larger in the mixed broadleaf/larch than in the birch forest, while no difference was found between spruce plantation and birch forest for microbial biomass and microbial quotient. Basal respiration and metabolic quotient were larger in the birch forest as compared to the three other forest types, indicating a larger energy need for maintenance of the microbial community and lower microbial activity in the naturally regenerated birch forest.

Conclusion

Mixed broadleaf/larch forest displayed a larger microbial biomass and higher substrate use efficiency of the soil microbial community than either naturally regenerated birch forest or spruce plantation. The combined natural and artificial regeneration procedure (mixed broadleaf-larch forest) seems better suited to restore soil quality after clear-cutting in the Changbai Mountain.

     

Within- and between-tree variation of wood density components in <Emphasis Type="Italic">Pinus nigra</Emphasis> at six sites in Portugal

Key message

In Europe, P. nigra wood presents a density pattern of longitudinal variation with an increase from east to west. However, no latitudinal tendencies were detected. Compared to other Portuguese resinous species, P. nigra revealed higher density, identical radial growth and intra-ring heterogeneity, which presents advantages for industry purposes. The environmental factors (Sites effect) manifest more strongly in the latewood components while the Trees/Sites effect is more strongly expressed in the earlywood components.

Context

Although P. nigra Arnold is one of the most important conifers in Europe, little is known about the wood’s characteristics in the southwest European region.

Aims

Our aims are to outline a first approach to study the growth and wood quality in P. nigra in Portugal comparing to other European natural stands and other resinous species.

Methods

Inter- and intra-wood density variation of P. nigra from six Portuguese sites was studied using microdensitometry. Analysis of variance (ANOVA) was performed in three subsets: 50 common rings, core (juvenile wood) and peripheral analysis (mature wood).

Results

The average ring density was 0.588 g cm^?3, with maximum values in the north and low altitudes. Regarding growth traits, no latitudinal and altitudinal tendencies were detected. Compared to the main timber species in Portugal (P. pinaster Aiton), P. nigra showed similar radial growth, higher density but lower intra-ring density homogeneity. The Sites effect mainly influenced latewood density components, while the Trees/Sites effect primarily influenced earlywood components. The Rings effect was found to be relatively low, with a density decrease in the tree’s first years followed by an increase in the periphery. Growth traits showed a reduction from pith to bark.

Conclusion

Considering the quality (density) and growth features of the Black pine, this species could be useful for the reforestation of mountainous Southern Europe areas that are not favourable for other species.

     

Genetic structure and phylogeography of <Emphasis Type="Italic">Juniperus phoenicea</Emphasis> complex throughout Mediterranean and Macaronesian regions: different stories in one

Key message

The genetic structure of Juniperus phoenicea in the Mediterranean Basin is inferred using amplified fragment length polymorphism markers (AFLP) markers. As other Mediterranean conifers, J. phoenicea populations show moderate levels of genetic diversity and interpopulational differentiation. The pattern of distribution of genetic diversity seems highly influenced by the climatic fluctuations which occurred in the Pleistocene.

Context

It has been stated that the genetic structure of Mediterranean conifers is mediated by the historical climatic changes and the geological rearrangements which occurred in the Mediterranean Basin. J. phoenicea provides an excellent example to test how its genetic structure is influenced by these events.

Aims

In this work, we study the amount and distribution of genetic diversity of J. phoenicea complex, in order to evaluate its taxonomic status and to reveal underlying phylogeographic patterns.

Methods

The molecular diversity was analyzed for 805 individuals from 46 populations throughout its distribution range using AFLP markers. Principal coordinate analysis, analysis of molecular variance (AMOVA), and Bayesian-based analysis were applied to examine the population structure.

Results

AFLP markers revealed moderate levels of intrapopulation genetic diversity, pairwise genetic differentiation, and a clear pattern of isolation by distance. Bayesian analysis of population structure showed five clusters related to the taxonomic status of J. phoenicea and J. turbinata, and a geographic pattern of genetic structure in J. turbinata.

Conclusion

All the analysis separate J. phoenicea from J. turbinata. For J. turbinata, up to four groups can be distinguished from a phylogeographic point of view. The genetic structure of J. turbinata seems highly influenced by climatic and geologic fluctuations occurring since the Oligocene.