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1.
Key message
The use of increasing debarking during the first harvest of cork oak trees ( Quercus suber L.) had no effect on the secondary cork calliper (thickness) in one of the trials and had a small negative effect in a second trial. Little evidence was found that debarking coefficient is a useful index for the management of cork oak stands.Context
The Portuguese national legislation defines, without the support of scientific data or knowledge, maximum values of debarking coefficients (ratio of debarking height and perimeter at breast height measured over cork). For the first debarking, this value is limited to 2.0.Aims
The aim of this study was to determine the impact of increasing cork debarking coefficient on the calliper of the secondary cork extraction.Methods
Trees were located in two sites, in distinct regions characterized by low or high productivity classes. Three debarking coefficients were considered: 1.5, 2.0 and 2.5. The debarking coefficient for the first cork extraction was randomly selected for each tree. During the second debarking, a cork sample was taken from each tree. The samples were used for assessing secondary cork calliper. Differences in cork calliper were analysed using both correlation analysis and modelling approaches.Results
Debarking intensity increase had a small negative effect on secondary cork thickness in the most inland site, while no effect was detected in the more coastal site.Conclusion
In our experiment, debarking intensity had a significant but small effect in one site and no effect in other sites. Debarking coefficients not only should be defined according to legal constraints but also instead should be adapted considering tree and site characteristics.2.
Belkheir Dehane Carmen Hernando Mercedes Guijarro Javier Madrigal 《Annals of Forest Science》2017,74(3):60
Key message
The high flammability of some companion species in Quercus suber forests, estimated in laboratory tests, could potentially generate an increase in fire vulnerability and in fire risk.Context
Recurrent wildfire is one of the main causes of forest degradation, especially in the Mediterranean region. Increased fire frequency and severity due to global change could reduce the natural resilience of cork oak to wildfire in the future. Hence, it is important to evaluate the flammability of companion species in cork oak forests in the particularly dry bioclimatic conditions of North Africa.Aims
This study aimed to assess and compare flammability parameters at laboratory scale among ten companion frequent species in cork oak forests.Methods
Fuel samples were collected in a cork oak (Quercus suber L) forest in the southern part of the mountains of Tlemcen (Western Algeria). A series of flammability tests were carried out using a Mass Loss Calorimeter device (FTT ®). A cluster analysis to classify flammability of the selected species was conducted using the K-means algorithm.Results
The results revealed differences in the four flammability parameters (ignitability, sustainability, combustibility and consumability), in both fresh and dried fine fuel samples from Quercus suber, Pinus halepensis, Quercus ilex, Quercus faginea, Erica arborea, Arbutus unedo, Pistacia lentiscus, Calicotome spinosa, Juniperus oxycedrus and Tetraclinis articulata. Application of the K-means clustering algorithm showed that C. spinosa, T. articulata, J. oxycedrus and P. halepensis are highly flammable because of their high combustibility and sustainability.Conclusion
The findings identify species that could potentially increase the vulnerability of cork oak forests to forest fires.3.
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.4.
Giovânia C. Araújo Nadine R. Sousa Miguel A. Ramos Alberto L. Vega Paula M. L. Castro 《Annals of Forest Science》2018,75(1):29
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.5.
Damien Bonal Mathilde Pau Maude Toigo André Granier Thomas Perot 《Annals of Forest Science》2017,74(4):72
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.6.
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.7.
Key message
Coppice stands result in slightly higher stump waste compared with planted stands, when felled mechanically by a harvester.Context
The large demand for wood fibre requires efficient production and cost-effective practices throughout the supply chain.Aims
The purpose of the study was to quantify the amount of volume lost to excessive stump height in coppiced and planted stands.Methods
Stump height was measured on similar eucalypt stands that differed only for their origin: coppiced or planted. The study sample comprised of 543 planted stems and 851 coppice stems; of which 365 grew as double stems and 486 as single.Results
Stump waste was highest for coppiced double stumps, smallest for coppiced single stumps and intermediate for planted tree stumps. All differences were statistically significant, but the difference between coppiced single stumps and planted tree stumps was much smaller (20%) than the difference between coppiced double stumps and the rest (220–260%). Regression analysis showed that stump waste volume increased with tree volume, and this effect was twice as large for coppiced double stumps compared with the other treatments. Stump waste seemed very small in both relative and absolute terms and is unlikely to offset the large benefits accrued through coppice management and mechanization.Conclusion
Comparison with previous stump height studies indicates that the results obtained in this experiment for planted eucalypt may have general value and could be extended to other coppice stands, although with caution.8.
Key message
Segregating stands and logs based on internal wood properties is likely to lead to improvements in value for forest and mill owners, but some situations were found where no segregation was the best alternative. Where segregation was the best alternative, segregating logs at the landing, or stands based on pre-harvest inventory assessments, led to the greatest value improvements.Context
The benefits of segregating stands, stems and logs based on wood properties are not clear due to the high variability of wood properties, poor market signals for wood with superior properties and poor understanding of the costs across the value chain.Aims
The aim of this study was to determine if the benefits of segregating stands and logs outweighed the additional costs.Methods
A techno-economic model (SEGMOD) was constructed that allowed comparisons of segregation at different approaches in the supply chain. The model was populated with Pinus radiata (D.Don) stand, cost and price data from companies operating in four forestry regions of New Zealand. A total of 255 segregation scenarios were modelled, which included variations in segregation approach, stand type, stand location, terrain type, market focus and market horizon.Results
Segregating logs based on internal wood properties led to improvements in stumpage and mill door value for most of the scenario sets evaluated. The No Segregation option was found (infrequently) to be best in unpruned stands. Segregating logs based on pre-harvest inventory assessments or at the landing would appear to be the best approach.Conclusion
The economic benefits of segregating stands and logs for forest and mill owners outweighed the additional costs in most of the scenarios evaluated.9.
Key message
The concept of expected losses is an appropriate measure for integrating risk in the determination of the optimal rotation period and choice of tree species.Context
Natural threats are challenging forest management decisions. Essential decisions about the optimal length of a harvest period are often taken without considering risks.Aims
Here, a practical and easy to apply way to integrate risk in these decisions is shown. Furthermore, it is seen how the rotation period changes according to the risk-type and risk-level.Methods
The marginal principle of Preßler’s indicator rate is developed further by including the concept of expected losses, leading to an optimal harvest age under risk. The application of the new formula is shown by a simulation, which also visualises the influence on the optimal rotation age.Results
Whether risk influences the optimal harvest age compared to a risk free solution, depends on the relationship between expected losses in terms of land rent of the succeeding stand and expected losses in terms of value growth of the existing stand. If they are equal, the rotation age stays. If the expected loss on value growth is bigger than on land rent, the rotation period will be shorter, while it will be longer if the relation is inverse.Conclusion
The concept of expected losses can be applied to practically determine the optimal rotation period under risk.10.
Mohamed Boulmane Hayat Oubrahim Mohammed Halim Mark R. Bakker Laurent Augusto 《Annals of Forest Science》2017,74(3):57
Key message
Short-rotation forestry using eucalyptus in degraded oak forests in the semi-arid area of NW Morocco can be a useful strategy to avoid further degradation and carbon loss from this ecosystem, but it might be constrained by nutrient and water supply in the long term.Context
Land degradation and deforestation of natural forests are serious issues worldwide, potentially leading to altered land use and carbon storage capacity.Aims
Our objectives were to investigate if short-rotation plantations can restore carbon pools of degraded soils, without altering soil fertility.Methods
Carbon and nutrient pools in above- and below-ground biomass and soils were assessed using stand inventories, harvested biomass values, allometric relationships and selective sampling for chemical analyses.Results
Carbon pools in the total ecosystem were low in the degraded land and in croplands (6–13 Mg ha?1) and high in forests (66–94 in eucalyptus plantations; 86–126 in native forests). The soil nutrient status of eucalyptus stands was intermediate between degraded land and native forests and increased over time after eucalyptus introduction. All harvest scenarios for eucalyptus are likely to impoverish the soil but, for the moment, the soil nutrient status has not been affected.Conclusion
Afforestation of degraded land with eucalyptus can be a useful restoration tool relative to carbon storage and soil fertility, provided that non-intensive forestry is applied.11.
Fernando Silla Álvaro Camisón Andrea Solana Héctor Hernández Guillermo Ríos Miguel Cabrera Dámaris López Albert Morera-Beita 《Annals of Forest Science》2018,75(4):95
Key message
Quercus secondary forests show a gradual transition toward mixed forests, with sweet chestnut ( Castanea sativa ) becoming increasingly abundant in the western Spanish Central System. Additionally, in chestnut-dominated stands, it shows a certain resistance to competitive displacement by Quercus pyrenaica . Our results partially refute the traditional view that C. sativa is unable to recruit in the absence of cultural inputs.Context
Sweet chestnut, Castanea sativa, is a component of European broadleaf forests and is one of the most managed trees. Due to a reduction in cultural inputs, chestnut-dominated stands tend to be invaded by other species, and it is unclear how chestnut is able to persist in natural mixed forests.Aims
Our work aimed to identity the main factors that limit the establishment of C. sativa and to analyze the recruitment and mortality processes of C. sativa trees.Methods
The age, growth ring patterns, regeneration density, and the spatial structure of trees and saplings in 11 plots in the Spanish Central System were analyzed.Results
Chestnut seedling density increased with C. sativa basal area, but transition toward the sapling stage appeared limited owing to light availability. In Quercus pyrenaica secondary forests, sparse canopies did not constrain chestnut regeneration, and in old chestnut stands, C. sativa showed a certain resistance to competitive displacement. By contrast, mixed young coppices showed a high mortality, most likely due to competition with other vigorous resprouters.Conclusion
Quercus secondary forests showed a gradual transition toward mixed forests with sweet chestnut becoming increasingly more abundant. In old stands, C. sativa is likely to persist under a gap-phase mode of regeneration. Our results partially refute the traditional view that C. sativa is unable to recruit in the absence of cultural inputs.12.
Huawei Ji Jiahao Wen Baoming Du Ningxiao Sun Björn Berg Chunjiang Liu 《Annals of Forest Science》2018,75(2):59
Key message
Foliar phosphorus (P) resorption in Quercus variabilis Blume was significantly lower at a P-rich than at a P-deficient site. Moreover, P resorption strongly decreased, and nitrogen:phosphorus and carbon:phosphorus resorption ratios increased with soil P content. This demonstrates a strong link between foliar P resorption and P content in soils, and emphasizes the importance of P resorption in leaves of trees growing in soils with contrasted P content.Context
Subtropical ecosystems are generally characterized by P-deficient soils. However, P-rich soils develop in phosphate rock areas.Aims
We compared the patterns of nutrient resorption, in terms of ecological stoichiometry, for two sites naturally varying in soil P content.Methods
The resorption efficiency (percentage of a nutrient recovered from senescing leaves) and proficiency (level to which nutrient concentration is reduced in senesced leaves) of 12 elements were determined in two oak (Q. variabilis) populations growing at a P-rich or a P-deficient site in subtropical China.Results
P resorption efficiency dominated the intraspecific variation in nutrient resorption between the two sites. Q. variabilis exhibited a low P resorption at the P-rich site and a high P resorption at the P-deficient site. Both P resorption efficiency and proficiency strongly decreased with soil P content only and were positively related to the N:P and C:P ratios in green and senesced leaves. Moreover, resorption efficiency ratios of both N:P and C:P were positively associated with soil P.Conclusion
These results revealed a strong link between P resorption and P stoichiometry in response to a P deficiency in the soil, and a single- and limiting-element control pattern of P resorption. Hence, these results provide new insights into the role of P resorption in plant adaptations to geologic variations of P in the subtropics.13.
Ingrid Seynave Alain Bailly Philippe Balandier Jean-Daniel Bontemps Priscilla Cailly Thomas Cordonnier Christine Deleuze Jean-François Dhôte Christian Ginisty François Lebourgeois Dominique Merzeau Eric Paillassa Sandrine Perret Claudine Richter Céline Meredieu 《Annals of Forest Science》2018,75(2):48
Key message
The diversity of forest management systems and the contrasted competition level treatments applied make the experimental networks of the GIS Coop, a nationwide testing program in the field of emerging forestry topics within the framework of the ongoing global changes.Context
To understand the dynamics of forest management systems and build adapted growth models for new forestry practices, long-term experiment networks remain more crucial than ever.Aims
Two principles are at the basis of the experimental design of the networks of the Scientific Interest Group Cooperative for data on forest tree and stand growth (GIS Coop): contrasted and extreme silvicultural treatments in diverse pedoclimatic contexts.Methods
Various forest management systems are under study: regular and even-aged stands of Douglas fir, sessile and pedunculate oaks, Maritime and Laricio pines, mixed stands of sessile oak, European silver fir, and Douglas fir combined with other species. Highly contrasted stand density regimes, from open growth to self-thinning, are formalized quantitatively.Results
One hundred and eighty-five sites representing a total of 1206 plots have been set up in the last 20 years, where trees are measured regularly (every 3 to 10 years). The major outputs of these networks for research and management are the calibration/validation of growth and yield models and the drawing up of forest management guides.Conclusion
The GIS Coop adapts its networks so that they can contribute to develop growth models that explicitly integrate pedoclimatic factors and thus also contribute to research on the sustainability of ecosystems under environmental and socio-economic changes.14.
José Ramón González-Olabarria Jordi Garcia-Gonzalo Blas Mola-Yudego Timo Pukkala 《Annals of Forest Science》2017,74(3):52
Key message
We generate flexible management rules for black pine stands, adaptable to alternative stand management situations and entailing thinnings, final-felling, and salvage cuts, based on the results on 270 stand level optimizations.Context
Forest management instructions often rely on the anticipated prediction of the stand development, which poses a challenge on variable economic and environmental conditions. Instead, an alternative approach to better adapt forest management decisions to changing conditions is defining flexible rules based on thresholds that trigger management operations.Aims
This article develops rules for the adaptive management of P. nigra stands in Catalonia (Spain) addressing the risk of fire and post-fire forest management.Methods
The stochastic version of the simulation-optimization system RODAL was used to optimize the management of forest stands in three sites under different fire probability levels. A total of 270 optimizations were done varying site fertility, fire probability, and economic factors. The results of the optimizations were used as the basis of flexible forest management rules for adaptive stand management.Results
The developed management rules defined the basal area limit for thinning, the thinning intensity, the mean tree diameter at which regeneration cuttings should start, and the basal area below which a salvage cutting should be done. Fire risk was not a significant predictor of the models for thinning and final cutting rules.Conclusion
The presented rules provide a flexible tool for forest management during the stand development and under changing conditions when the management objective is to maximize economic profitability of timber production.15.
Joanna Mucha Andrzej M. Jagodziński Bartosz Bułaj Piotr Łakomy Adrian M. Talaśka Jacek Oleksyn Marcin Zadworny 《Annals of Forest Science》2018,75(1):22
Key message
Quercus robur seedling mass was affected more by planting density than by taproot pruning. Root pruning enhanced stem biomass at the expense of roots in later growth stages. Alteration of biomass allocation due to nursery practices may result in greater susceptibility to injury and death of the seedlings under unfavorable environmental conditions.Context
Plants adjust their growth and modulate the resource allocation in response to applied treatments and environmental conditions.Aims
The aim was to examine how taproot pruning in seedlings grown at different densities affected long-term growth of Quercus robur.Methods
Seedlings, sown as acorns at two planting densities, with or without pruned roots were harvested in the second, fourth, and fifth years of growth. The effect of root pruning on biomass allocation was determined by measuring leaf, stem, and root mass fractions; carbohydrate concentrations in the roots; and C/N ratios. Specific leaf area and root length were also determined to assess morphological adaptations to growth conditions.Results
Total seedling mass was affected more by planting density than by taproot pruning. After 4 years of growth, root mass fractions were lower and stem mass fractions were greater in seedlings planted at a higher density. Five-year old root-pruned seedlings also had a lower root mass fraction and higher stem mass fractions than unpruned seedlings. Specific root length was not affected by root pruning or planting density.Conclusion
Decrease of relative root biomass with simultaneous increase of stem biomass may be a long-term consequence of taproot pruning of Q. robur, and the effects may manifest years after the seedling stage.16.
Barbara Mariotti Giorgio Alberti Alberto Maltoni Andrea Tani Pietro Piussi 《Annals of Forest Science》2017,74(2):44
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.17.
Emila Akroume Bernd Zeller Marc Buée Philippe Santenoise Laurent Saint-André 《Annals of Forest Science》2016,73(4):1005-1013
Key message
Near- and mid-infrared spectroscopy allows for the detection of local patterns of forest soil properties. In combination with dendrometric data, it may be used as a prospective tool for determining soil heterogeneity before setting up long-term forest monitoring experiments.Context
Forest soils and stands generally exhibit higher spatial heterogeneity than other terrestrial ecosystems. This variability needs be taken into account before setting up long-term forest monitoring experiments to avoid multiple interactions between local heterogeneity and the factors tested in the experiment.Aims
We hypothesized that raw near- and mid-infrared spectra can be used as an integrated proxy of a large set of soil properties. The use of this method, in combination with dendrometric data, should provide a quick and cost-effective tool for optimizing the design of experimental forest sites.Methods
We assessed the local soil heterogeneity at 11 experimental sites in oak and beech stands, which belong to a new forest long-term ecological research (LTER) network. We used near- and mid-infrared spectroscopy in soil and litter samples. The spectra were subjected to principal components analyses (PCA) to determine the intra-site variability of the soil and litter layers.Results
Based on mapped PCA coordinates and basic dendrometric data, it was possible to design the experiment and minimize the interactions between the treatment layout and the tested variables. The method was validated with chemical analyses of the soil. No interaction was detected at the set-up of the experiment between the treatment layout and chemical soil properties (C, N, C/N ratio, pH, CEC, Al, Mg, P2O5, Fe, Mn, Na, and K).Conclusion
Near-infrared (NIR) and mid-infrared (MIR) spectroscopy is a useful tool for characterizing the overall heterogeneity of soil chemical properties. It can be used without any preliminary calibration. In combination with dendrometric data, it provides a reliable method for optimizing LTER plots in different types of ecosystems.18.
Susanne Brandl Tobias Mette Wolfgang Falk Patrick Vallet Thomas Rötzer Hans Pretzsch 《Annals of Forest Science》2018,75(2):56
Key message
Static site indices determined from stands’ top height are derived from different forest inventory sources with height and age information and thus enable comparisons and modeling of a species’ productivity encompassing large environmental gradients.Context
Estimating forest site productivity under changing climate requires models that cover a wide range of site conditions. To exploit different inventory sources, we need harmonized measures and procedures for the productive potential. Static site indices (SI) appear to be a good choice.Aims
We propose a method to derive static site indices for different inventory designs and apply it to six tree species of the German and French National Forest Inventory (NFI). For Norway spruce and European beech, the climate dependency of SI is modeled in order to estimate trends in productivity due to climate change.Methods
Height and age measures are determined from the top diameters of a species at a given site. The SI is determined for a reference age of 100 years.Results
The top height proves as a stable height measure that can be derived harmoniously from German and French NFI. The boundaries of the age-height frame are well described by the Chapman-Richards function. For spruce and beech, generalized additive models of the SI against simple climate variables lead to stable and plausible model behavior.Conclusion
The introduced methodology permits a harmonized quantification of forest site productivity by static site indices. Predicting productivity in dependence on climate illustrates the benefits of combined datasets.19.
Gerald Dirnberger Angela-Elisabeth Kumer Eduard Schnur Hubert Sterba 《Annals of Forest Science》2017,74(1):8
Key message
Trees with otherwise equal dimensions have different leaf areas if they are located in different stand types. While leaf area of European larch is affected by mixture proportion, leaf area of Norway spruce is affected by stand density.Context
Leaf area is a key parameter for evaluating growth efficiency of trees, and therefore needs to be measured as consistently and accurately as possible. This is even more important when comparing monospecific and mixed stands.Aims
The aim of the study is to find combinations of parameters and allometric relationships that can be used to estimate accurately the leaf area of individual trees.Methods
Allometries of the measured leaf area of 194 trees in 12 stands were analysed in order to find variables affecting leaf area. Existing functions from the literature were validated. Finally, models were fitted to find the most appropriate method for estimating leaf area of mixed and monospecific stands of Norway spruce and European larch.Results
Allometric relationships of leaf area to other measurable characteristics of trees vary in different stand types. Besides individual tree dimensions such as diameter and crown surface area, leaf area of Norway spruce is related to stand density, whereas the leaf area of European larch is dependent on the admixture of Norway spruce in the stand.Conclusion
In contrast to models for estimating individual tree leaf area of Norway spruce, models for leaf area of European larch have to consider mixture proportions in order to correctly interpret the growth efficiency of mixed stands.20.
Pau Brunet-Navarro Frank J. Sterck Jordi Vayreda Jordi Martinez-Vilalta Godefridus M.J. Mohren 《Annals of Forest Science》2016,73(4):1025-1034