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.

     

Additive tree biomass equations for <Emphasis Type="Italic">Betula platyphylla</Emphasis> Suk. plantations in Northeast China

Key message

A new system of additive tree biomass equations was developed for juvenile white birch plantations based on tree diameter at breast height (DBH) and tree height (HT). Compared with previous equations developed for natural white birch forests, the new system included one more biomass component and provided more accurate predictions.

Context

Accurate estimates of tree component and total biomass are necessary for evaluating alternative forest management strategies for biomass feedstock, carbon sequestration, and products. Previous biomass equations developed for white birch trees in natural stands provided substantially biased predictions for white birch plantations.

Aims

A new system of additive tree biomass equations was developed for juvenile white birch plantations in the northeastern China.

Methods

With destructive biomass sampling data from 501 trees sampled from white birch provenance and family trails at ages 7, 9, 10, and 13 in three provinces, a system of nonlinear additive tree biomass equations based on DBH and tree height was developed using the nonlinear seemingly unrelated regressions (NSUR) approach.

Results

Compared with previously published equations developed for natural white birch forests, the new system provided more accurate predictions of white birch tree component and aboveground and total biomass, especially of branch, foliage, and root biomass.

Conclusion

The new system extended the applicability of biomass equations to white birch plantations in the northeastern China.

     

Short-day photoperiods affect expression of genes related to dormancy and freezing tolerance in Norway spruce seedlings

Key Message

Gene expression analysis showed that prolonged short day (SD) treatment deepened dormancy and stimulated development of freezing tolerance of Picea abies seedlings. Prolonged SD treatment also caused later appearance of visible buds in autumn, reduced risks for reflushing, and promoted earlier spring bud break.

Context

Short day (SD) treatment of seedlings is a common practice in boreal forest tree nurseries to regulate shoot growth and prepare the seedlings for autumn planting or frozen storage.

Aims

The aim of this study was to examine responses of Norway spruce (Picea abies (L.) Karst.) to a range of SD treatments of different length and evaluate gene expression related to dormancy induction and development of freezing tolerance.

Methods

The seedlings were SD treated for 11 h a day during 7, 14, 21, or 28 days. Molecular tests were performed, and the expression profiles of dormancy and freezing tolerance-related genes were analyzed as well as determination of shoot growth, bud set, bud size, reflushing, dry matter content, and timing of spring bud break.

Results

The 7-day SD treatment was as effective as longer SD treatments in terminating apical shoot growth. However, short (7 days) SD treatment resulted in later activation of dormancy-related genes and of genes related to freezing tolerance compared to the longer treatments which had an impact on seedling phenology.

Conclusion

Gene expression analysis indicated an effective stimulus of dormancy-related genes when the SD treatment is prolonged for at least 1–2 weeks after shoot elongation has terminated and that seedlings thereafter are exposed to ambient outdoor climate conditions.

     

Allometry varies among related families of Norway spruce

Key message

Slopes and intercepts of allometric equations for organs’ biomass varied among half-sib families of Norway spruce and between age categories in a family-dependent manner. Genetic variation should be accounted for when applying allometric analysis to mixtures of genetic groups.

Context

Genetic variation in relationships among plant biomass components was rarely addressed in trees, though depending on deployment strategies in tree improvement programs, variation among genetic groups in plant organs’ growth rates, and thus biomass allocation, would affect forest growth and carbon balance.

Aims

We investigated growth and biomass distribution in Norway spruce (Picea abies [L.] H. Karst) half-sib families. We assumed invariance among families in allometric relationships, and stability in growth rates of different organs between ages 2 and 8 years in the subset of those families. We also tested for ontogenetic trend in allometry using the independent dataset of biomass at age 21 years.

Methods

We analyzed allometric relationships among plant components using standardized major axis regression.

Results

Slopes and intercepts of allometric relationships varied among families, indicating variation in both organs’ growth rates and biomass partitioning at a given plant size. Variation in scaling exponents between age categories was also dependent on the family and plant organ considered.

Conclusion

Variation in slopes of allometric relationships indicates that a single scaling coefficient should not be applied when different genetic groups are compared. For the interpretation of age effect on biomass partitioning, both slopes and intercepts of allometric relationships should be examined.

     

Growth phenology in <Emphasis Type="Italic">Pinus halepensis</Emphasis> Mill.: apical shoot bud content and shoot elongation

Key message

The chronology of periods of organogenesis and elongation is highlighted in Pinus halepensis.The two first growth units of an annual shoot are preformed inside the bud during the previous year. The following growth units are formed during the spring or summer of the current year.

Context

Analysis of annual shoot length growth phenology is crucial to assess the impact of climate change on tree production. Little is known about the basic growth characteristics and the phenology of pines.

Aims

The present study disentangles the roles of shoot organogenesis vs elongation in the annual growth cycle of the polycyclic Aleppo pine.

Methods

Growth of young Pinus halepensis trees was monitored monthly for 1 year. At each monitoring date, the bud content and meristem dimensions of the main stem shoots apices were analyzed.

Results

The two first growth units of an annual shoot are preformed inside the bud during the previous year. The following growth units are formed during the spring or summer of the current year. The gap between a shoot organogenesis and its elongation may vary from 1 month, for the last growth unit, to half a year, for the first growth units.

Conclusion

Our results underline the importance of taking seasonal environmental conditions from both the previous and the current year into account, in order to study the plasticity of annual shoot growth and its response to climate change and variability.

     

Initial recovery of compacted soil—planting and technical treatments decrease CO<Subscript>2</Subscript> concentrations in soil and promote root growth

Key message

The combination of technical treatments and planting of alder trees in a compacted forest soil improves the circulation of air and water through the pore system. This leads to decreases in CO ₂ concentrations and increases in root growth in the soil. Both are indicative of an initial recovery of soil structure.

Context

The compaction of forest soils, caused by forest machinery, has as a principal consequence: the destruction of soil structure and thus the reduction of the soil aeration status. Thus, the gas exchange between soil and atmosphere is reduced and the depth propagation of roots is limited, resulting in the shortage of water and nutrient supplies for trees.

Aims

This research aimed at detecting the first stages of recovery of soil structure in a compacted forest soil, which was treated with a combination of techniques (i.e., planting tree species, mulching, addition of lime), which could presumably accelerate the regeneration of soil structure.

Methods

The variation of CO₂ concentrations and the dynamics of root growth were repeatedly measured. Linear mixed models were developed in order to test the effects of the treatments and the planting of trees on soil aeration, as well as to identify the influence of the different environmental effects on CO₂ concentration in soil.

Results

The planting of root-active trees showed significant effects on decreases in CO₂ concentrations. However, during the short-term observation, some negative effects occurred especially for the mulched sites. Nevertheless, all applied technical treatments promoted an improved soil aeration and a higher root growth compared to untreated sites which points to an initial enhanced recovery of soil structure. Pronounced seasonal and interannual variations of soil respiration were highly influenced by soil temperature and soil water content variations.

Conclusion

An initial regeneration of soil structure is indicated by distinct changes of the soil aeration status. This regeneration is partially enhanced by the applied treatments. The quantitative potential of the regeneration techniques needs a longer observation period for mid- and long-term soil recoveries.

     

Climate,tree masting and spatial behaviour in wild boar (<Emphasis Type="Italic">Sus scrofa</Emphasis> L.): insight from a long-term study

Key message

Climate factors affect seed biomass production which in turn influences autumn wild boar spatial behaviour. Adaptive management strategies require an understanding of both masting and its influence on the behaviour of pulsed resource consumers like wild boar.

Context

Pulsed resources ecosystem could be strongly affected by climate. Disantangling the role of climate on mast seeding allow to understand a seed consumer spatial behaviour to design proper wildlife and forest management strategies.

Aims

We investigated the relationship between mast seeding and climatic variables and we evaluated the influence of mast seeding on wild boar home range dynamics.

Methods

We analysed mast seeding as seed biomass production of three broadleaf tree species (Fagus sylvatica L., Quercus cerris L., Castanea sativa Mill.) in the northern Apennines. Next, we explored which climatic variables affected tree masting patterns and finally we tested the effect of both climate and seed biomass production on wild boar home range size.

Results

Seed biomass production is partially regulated by climate; high precipitation in spring of the current year positively affects seed biomass production while summer precipitation of previous year has an opposite effect. Wild boar home range size is negatively correlated to seed biomass production, and the climate only partially contributes to determine wild boar spatial behaviour.

Conclusion

Climate factors influence mast seeding, and the negative correlation between wild boar home range and mast seeding should be taken into account for designing integrated, proactive hunting management.

     

Prevalence of interspecific competition in a mixed poplar/black locust plantation under adverse climate conditions

Key message

In a mixed poplar/black locust plantation in central France, adverse conditions have led to a prevalence of interspecific competition, resulting in a poorer performance than monocultures.

Context

In mixed tree plantations, the presence of woody N₂-fixing species is thought to reduce N needs by fertilization. However, benefits associated to soil nitrogen enrichment have to outweigh the negative effects of interspecific competition. To do so, co-occurring tree species have to be chosen carefully to promote niche sharing between species and reduce competition. Black locust and poplar mixtures therefore seem promising since both species are fast growing and have potentially complementary crown shapes.

Aims

Our objective was to evaluate the impact of the poplar/black locust mixture on the growth, above- and belowground biomass production, and nitrogen allocation of the two species, as compared to their respective monocultures.

Methods

An experimental plantation mixing poplar and black locust was set up in central France. For five growing seasons, growth, nitrogen allocation, and carbon allocation were monitored for the two species growing either in mixture or in monoculture.

Results

After a couple of promising growing seasons, black locust growth and survival slowly declined, mainly in the mixture. At the stand level, biomass production in the mixed plots was nearly 50% below the most productive monoculture (poplar) by age 5 years.

Conclusion

Under adverse conditions, interspecific competition in the mixture was the preponderant interaction, resulting in higher mortality and lower biomass production than the two monocultures.

     

A generalized algebraic difference approach allows an improved estimation of aboveground biomass dynamics of <Emphasis Type="Italic">Cunninghamia lanceolata</Emphasis> and <Emphasis Type="Italic">Castanopsis sclerophylla</Emphasis> forests

Key message

A generalized algebraic difference approach (GADA) developed in this study improved the estimation of aboveground biomass dynamics of Cunninghamia lanceolata (Lamb.) Hook and Castanopsis sclerophylla (Lindl.) Schott forests. This could significantly improve the fieldwork efficiency for dynamic biomass estimation without repeated measurements.

Context

The estimation of biomass growth dynamics and stocks is a fundamental requirement for evaluating both the capability and potential of forest carbon sequestration. However, the biomass dynamics of Cunninghamia lanceolata and Castanopsis sclerophylla using the generalized algebraic difference approach (GADA) model has not been made to date.

Aims

This study aimed to quantify aboveground biomass (AGB, including stem, branch and leaf biomass) dynamics and AGB increment in C. lanceolata and C. sclerophylla forests by combining a GADA for diameter prediction with allometric biomass models.

Methods

A total of 12 plots for a C. lanceolata plantation and 11 plots for a C. sclerophylla forest were selected randomly from a 100 m × 100 m systematic grid placed over the study area. GADA model was developed based on tree ring data for each stand.

Results

GADA models performed well for diameter prediction and successfully predicted AGB dynamics for both stands. The mean AGB of the C. lanceolata stand ranged from 69.4 ± 7.7 Mg ha^?1 in 2010 to 102.5 ± 11.4 Mg ha^?1 in 2013, compared to 136.9 ± 7.0 Mg ha^?1 in 2010 to 154.8 ± 8.0 Mg ha^?1 in 2013 for C. sclerophylla. The stem was the main component of AGB stocks and production. Significantly higher production efficiency (stem production/leaf area index) and AGB increment was observed for C. lancolata compared to C. sclerophylla.

Conclusion

Dynamic GADA models could overcome the limitations posed by within-stand competition and limited biometric data, can be applied to study AGB dynamics and AGB increment, and contribute to improving our understanding of net primary production and carbon sequestration dynamics in forest ecosystems.

     

Drought response of upland oak (<Emphasis Type="Italic">Quercus</Emphasis> L.) species in Appalachian hardwood forests of the southeastern USA

Key message

In Appalachian hardwood forests, density, stem size, and productivity affected growth during drought for red oak, but not white oak species. Minor effects of density suggest that a single low thinning does little to promote drought resilience for oaks in the region.

Context

Management is increasingly focused on promoting resilience to disturbance. Because stand density can modulate climate-growth relationships, thinning may be an adaptation strategy that promotes resistance/resilience to drought.

Aims

We examined how density, manipulated via thinning, stem size, and site productivity, influences the drought response of northern red, black, chestnut, and white oak.

Methods

We modeled the role of density, stem size, and site productivity on resistance, recovery, and resilience during two drought events.

Results

Chestnut and white oak displayed greater resistance, recovery, and/or resilience than did northern red and black oak. For black oak, density and stem size negatively affected resistance during the first and second drought, respectively. Density, stem size, and site productivity had no effect on chestnut and white oak.

Conclusion

The lack of sensitivity of chestnut and white oak to the ranges of density, stem size, and site productivity observed in this study and generally better resistance, recovery, and resilience suggests that management focused on the maintenance of these species, as opposed to a single silvicultural low thinning, may be a possible strategy for sustaining the growth and productivity of oak species in Appalachian hardwood stands. Drought response as affected by alternative thinning interventions should be evaluated.

     

An integrated method for high-resolution definition of new diameter-based fine root sub-classes of <Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.

Key message

Compared to the traditional approach, applying micrometric image analysis to fine root samples of Fagus sylvatica with subsequent data treatment through principal component and cluster analysis yielded specific diameter sizes for fine root sub-classes having better resolution of the corresponding branching orders, and a more coherent relationship with the values of annual production and turnover rate.

Context

Fine root traits are poorly understood, impeding an accurate representation of terrestrial biogeochemical models. Traditionally used, arbitrary diameter thresholds lead to a misestimation of fine root traits such as branching order, environmental relationship, annual production, and turnover rate.

Aims

Here, we present, as modification of the traditional method, an integrated approach to segregate, at high-resolution, fine root populations of Fagus sylvatica into new diameter sub-classes that better correspond with the traits mentioned above.

Methods

Samples, collected with a sequential soil coring method, were subjected to a micrometric image analysis, and resultant data were treated with principal component and cluster analysis.

Results

Results showed that fine roots were distributed into diameter-size sub-classes (0–0.3 mm, 0.3–1 mm, and 1–2 mm) different from those determined by traditional methods (0–0.5 mm, 0.5–1 mm, and 1–2 mm). New sub-classes provided a better resolution of the corresponding branching-orders, and the values of annual production and turnover rate were more coherent with diameter class and soil depth. Moreover, new sub-classes provided a more precise match with soil temperature than traditional methods.

Conclusion

Our method may help to unveil fine root dynamics and development, reduce data analysis time, and make the diameter-based classification more precise and trustworthy even in the case of non-intact samples.

     

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.

     

Selection of arbuscular mycorrhizal fungal strains to improve <Emphasis Type="Italic">Casuarina equisetifolia</Emphasis> L. and <Emphasis Type="Italic">Casuarina glauca</Emphasis> Sieb. tolerance to salinity

Key message

Selection of the best salt-tolerant combination of Casuarina sp. and arbuscular mycorrhizal fungi (AMF) is one of the key criteria for successful setup of saline land rehabilitation program.

Context

Land salinization is a serious problem worldwide that mainly leads to soil degradation and reduces crop productivity. These degraded areas could be rehabilitated by planting salt-tolerant species like Casuarina glauca Sieb. and Casuarina equisetifolia L. These are pioneer plants, able to form symbiotic associations with arbuscular mycorrhizal fungi (AMF), ectomycorrhizal fungi (EMF), and nitrogen-fixing bacteria.

Aims

The aim of this study was to select the highest salt-tolerant combination of Casuarina/AMF that can be used for the rehabilitation of lands degraded by salinity.

Methods

C. equisetifolia and C. glauca were grown in sandy sterile soil in the greenhouse and inoculated separately with Rhizophagus fasciculatus (Thaxt.) C. Walker & A. Schüßler, Rhizophagus aggregatus (N.C. Schenck & G.S. Sm.) C. Walker, and Rhizophagus intraradices (N.C. Schenck & G.S. Sm.) C. Walker & A. Schüßler. After confirming the establishment of a symbiosis, the plants were watered with gradually increasing concentrations of saline solution. After harvest, size and biomass of the seedlings, root colonization by AMF, and AMF metabolic activities were evaluated.

Results

A larger growth was obtained in the two species when the individuals were inoculated with R. fasciculatus. Root colonization rates did not differ among fungal species, but fungal metabolic activities were higher in mycorrhizal roots of C. glauca plants inoculated with R. fasciculatus.

Conclusion

Among the three mycorrhizal fungi, R. fasciculatus was more efficient in association with Casuarinaceae species under salt stress. Our results suggest that selection of appropriate fungal strains is crucial to improve plant performance in saline soils.

     

The effect of surface fire on tree ring growth of <Emphasis Type="Italic">Pinus radiata</Emphasis> trees

Key message

Pinus radiata trees showed significantly reduced basal area increments and increased latewood/earlywood ratios, when their stem was charred by surface fires even if no needle damage occurred. An interaction of fire damage and precipitation on growth was observed.

Context

Heat from forest fires is able to penetrate beyond the bark layer and damage or completely kill a tree’s cambium. Short-term growth reductions following surface fires have been reported for some species. However, most studies have in common that they describe a compound effect of stem and foliage damage.

Aims

This study investigated the impact of surface fires on the radial growth of Pinus radiata, where only the stem of trees was charred, while no needle damage was recorded.

Methods

Tree ring measurements were performed on cores obtained at breast height. Analysis of variance and tests, based on annual basal area increment values were calculated to quantify pre- and post-fire growth differences of tree ring width and latewood/earlywood ratios.

Results

The analysis revealed significant growth reductions following a surface fire on P. radiata in the year on which the fire occurred as well as in the following year. As a consequence of the fire, basal area increment and latewood/earlywood ratios were significantly reduced. An interaction of fire damage and precipitation on growth was observed.

Conclusion

The obtained results show how fires without crown damage can affect growth and tree ring structure of P. radiata trees and indicate that stem char could be associated with a significant decrease in ring width and latewood/earlywood ratio.

     

Radial growth of <Emphasis Type="Italic">Cinnamomum kanehirae</Emphasis> Hayata displays a larger temperature sensitivity in dominant than codominant trees

Key message

The radial wood growth curves of Cinnamomum kanehirae Hayata (an endangered species of subtropical Taiwan) exhibit an S shape. The dominant trees displayed a larger radial growth than the codominant trees, and their growth was more sensitive to air temperature.

Context

Knowledge of wood radial growth is important for evaluating the factors that limit tree growth performance. The relevant experiments have mostly been conducted in cold and temperate ecosystems, but rarely in subtropical ecosystems.

Aims

In this study, we aimed to construct a unified radial growth model for Cinnamomum kanehirae Hayata and to identify its sensitivity to temperature.

Methods

The wood radial increments were quantified for 3 years by either pinning or microcoring. The radial wood growth curves were modelled integratively by semiparametric regression and individually by curve fitting. The effects of tree social class, interannual and environmental factors on radial growth were analysed quantitatively.

Results

A unified S-shaped growth model for C. kanehirae was successfully constructed. By including the social class effect, the model was significantly improved. The maximum radial increment (A) was significantly correlated with the maximum growth rate (μ); both A and μ were significantly higher in dominant than in codominant trees. The time-varying radial growth rate was more sensitive to air temperature in dominant than in codominant trees.

Conclusion

Semiparametric models revealed an S-shaped growth curve of C. kanehirae and confirmed the higher temperature sensitivity of dominant trees compared to codominant trees in humid subtropical areas.

     

Performance of <Emphasis Type="Italic">Quercus suber</Emphasis> L. at nursery stage—application of two bio-inoculants under two distinct environments

Key message

Despite the fact that the technique of application of bioinoculants improved the quality of Quercus suber L. seedlings produced in nurseries, these benefits are dependent on the ecological conditions of the site and the composition of the applied inoculum, which interferes with the profile of the local fungal community.

Context

Quercus suber L. plays a key ecological and socio-economical role in the Iberian Peninsula. Symbiotic ectomycorrhizal fungi-ECM are crucial partners of several tree species, and assessing the efficacy of bioinoculants at nursery stage helps devising tools to increase plant resilience.

Aims

The aim of this study was to compare the effects of two inocula formulations of mixed ECM fungi and bacteria on the quality of seedlings produced in two forest nurseries, differing in environmental conditions and forest embedment.

Methods

Quercus suber L. seedlings were inoculated with a commercial product containing Pisolithus tinctorius (Pers) Coker & Couch, Scleroderma sp., and six bacterial species and with a non-commercial fungal and bacterial dual inoculum (Suillus granulatus (L.) Roussel + Mesorhizobium sp.). Biometric and nutritional parameters and morphological quality indexes were determined on seedlings. The ECM community was assessed by denaturing gradient gel electrophoresis and cloning-sequencing.

Results

In both nurseries, the seedling quality index in inoculated was up to 2-fold higher than in non-inoculated seedlings. Plant biomass differed significantly among nurseries. The inoculum influenced the profile of the fungal community. S. granulatus and P. tinctorius persisted for 6 months in the inoculated seedlings.

Conclusion

The nursery ecosystem influenced plant growth. Inoculation treatments increased plant performance; however, the dual inoculum resulted in more consistent improvements of Q. suber at nursery stage, highlighting the importance of inocula selection.

     

From inventory to consumer biomass availability—the ITOC model

Key message The application of the ITOC model allows the estimation of available biomass potentials from forests on the basis of National Forest Inventory data. The adaptation of the model to country-specific situations gives the possibility to further enhance the model calculations.

Context

With the rising demand for energy from renewable sources, up-to-date information about the available amount of biomass on a sustainable basis coming from forests became of interest to a wide group of stakeholders. The complexity of answering the question about amounts of biomass potentials from forests thereby increases from the regional to the European level.

Aims

The described ITOC model aims at providing a tool to develop a comparable data basis for the actual biomass potentials for consumption.

Methods

The ITOC model uses a harmonized net annual increment from the National Forest Inventories as a default value for the potential harvestable volume of timber. The model then calculates the total theoretical potential of biomass resources from forests. By accounting for harvesting restrictions and losses, the theoretical potential of biomass resources from forests is reduced and the actual biomass potentials for consumption estimated.

Results

The results from ITOC model calculations account for the difference between the amounts of wood measured in the forests and the actual biomass potentials which might be available for consumption under the model assumptions.

Conclusion

The gap between forest resource assessments and biomass potentials which are available for consumption can be addressed by using the ITOC model calculation results.

     

Effects of soil preparation methods and plant types on the establishment of poplars on forest land

Key message

The success of poplar plantations on forest land was affected by soil preparation, plant type, site, and clone. Mounding in combination with large plant types (rooted plants or long cuttings) of site-adapted clones achieved the highest survival and growth.

Context

Poplars (Populus species and hybrids) are fast-growing trees used to make various products. In north European countries, they are mainly grown on agricultural land, but interest in planting poplars on forest land has increased.

Aims

Plant damage and mortality problems occur on forest land, probably due to soil conditions and competing vegetation. It is therefore of interest to investigate whether combinations of soil preparation methods and plant materials can improve establishment.

Methods

At three sites in southern Sweden, the effects of four soil preparation treatments (no soil preparation, patch scarification, mounding, soil inversion) in combination with three plant types (short cuttings, long cuttings, rooted plants) were studied.

Results

Survival and growth were significantly influenced by site, soil preparation method, plant type, and their interactions. Mounding resulted in the best overall performance on all sites. Interactions between site and plant type revealed differences in growth dependent on site conditions, but rooted plants and long cuttings were in general most successful. Patch scarification and short cuttings were associated with lower survival and growth.

Conclusion

Soil preparation is needed to support survival and early growth, but the combination of method and plant type must be adapted to site conditions. The choice of clones should also be considered.

     

Fir expansion not controlled by moderate densities of large herbivores: a Mediterranean mountain grassland conservation issue

Key message

Whilst livestock has maintained grasslands over centuries in south European mountains, current ungulate densities are insufficient to control tree and forest expansion effectively. The present results based on fir population dynamics and radial/height growth raise questions about the sustainable management of new forests that are former mountain grasslands. This empirical case study contributes to debate about methods for long-term management of grasslands in Mediterranean mountains.

Context

Forest expansion following the cessation of grazing is a threat to biodiversity in mountain grasslands that are components of Mediterranean cultural landscapes.

Aims

We hypothesised that ungulates could mitigate tree recruitment, thus conserving mountain grasslands. We tested the efficiency of grazing and browsing by domestic and wild ungulates (sheep, roe and red deer) at inhibiting silver fir (Abies alba Mill.) encroachment in a conservation area, one of the main browsed trees.

Methods

The fir trees’ age structure was analysed by dendrochronology, and the individual growth patterns and scars were recorded in their tree-ring series.

Results

Fir density has increased since the 1960s, simultaneously with the increase in ungulate populations. The scar occurrences only appeared during the 1970s. Most scars were observed on seedlings and small saplings. The impacts of ungulates are observed on the radial and height growth of trees, mostly on trees <?100 cm, but it did not however result in controlling the recruitment of fir.

Conclusion

The hypothesis that a moderate density of ungulates might inhibit tree encroachment is therefore rejected, even in the case of a highly palatable species such as silver fir. Ungulates, solely, would not be an appropriate policy for grassland conservation in Mediterranean mountains.

     

Genetic diversity and genotypic stability in <Emphasis Type="Italic">Prunus avium</Emphasis> L. at the northern parts of species distribution range

Key message

Large genetic variation was found in Prunus avium L. populations from the northern parts of the species distribution range. The ranking of genotypes in terms of growth was stable when tested at three trial sites within the northern parts of the species distribution range.

Context

Peripheral populations especially those in the leading edge are isolated from rest of the areas in the species distribution range. This can make them less genetically diverse yet genetically distinct from the rest of the populations in the species distribution range. Evaluation of their genetic diversity is thus crucial in understanding the local adaptation potential of a species.

Aims

We investigated the genetic diversity and genotype by environment interaction at the northern parts of the distribution range of P. avium.

Methods

Quantitative genetic variation of growth, stem form, and spring phenology were assessed in progenies from 93 plus trees of P. avium selected from 43 locations at the north of the species distribution range in Sweden and tested at two Swedish sites and one Danish site.

Results

We find large quantitative genetic variation in growth and phenology at the northern part of the distribution range of P. avium. Only a limited genotype by environment interaction was observed with no clear indication of local adaptation at the northern parts of the species distribution.

Conclusion

We conclude that P. avium harbors a high level of genetic diversity at the north of its distribution range. Present patterns therefore reflect more likely the recent introduction of the species and dispersal dynamics rather than a long-term loss of diversity along South-North ecological clines during the Holocene. With no indications of genetic depletion in growth or phenology, the gene pool in the breeding program is considered suitable for the future propagation of the species in the tested area.