Coastal and interior Douglas-fir provenances differ in growth performance and response to drought episodes at adult age

Context

Since the 2003 drought and heat wave, Douglas-fir dieback has been reported in France in trees older than 30 years. Consequently, it is questioned whether selected Douglas-fir provenances are suited to the frequent and severe drought events which are forecast due to climate change.

Aims

Our objective was to contribute to the screening of variability in productivity and growth response to soil-water deficit of mature trees from provenances not currently used for plantation in France.

Methods

We sampled 22 provenances, including coastal and interior Douglas-fir, covering a wide part of its natural distribution, from Oregon to California for coastal provenances and from British Columbia to New Mexico for interior provenances. These provenances were planted at the mid 1970s in two provenance trials located in the south-west area of France. Variability of productivity, of wood density, and of radial growth in response to drought episodes among provenances was quantified and related to soil-water deficit computed by daily water balance calculations.

Results

Whatever the provenance, annual radial growth is highly dependent on local soil-water deficit (Felines R ² = 0.57, Le Treps R² = 0.49). Radial growth and wood properties exhibit large differences between provenances at 30 years old. Variability between provenances for all wood characteristics studied is mainly structured geographically. Coastal provenances perform best for productivity at 30 years old (619 cm²?±?59), and exhibit a small growth reduction in 2004, the second successive year of drought (?10.7 %?±?3.8). Surprisingly, the southern interior provenances from the driest environments in the natural range show a large growth reduction in 2004 (?30.5 %?±?5.2).

Conclusions

The provenances tested exhibited significant differences in growth performance and growth reduction induced by the soil-water deficit. The approach coupling retrospective analysis of radial growth on mature trees and water balance modelling is relevant for evaluating provenance adaptation to more frequent or severe drought episodes.     

Thinning increases cone production of stone pine (Pinus pinea L.) stands in the Northern Plateau (Spain)

Context

Edible stone pine (Pinus pinea L.) nut is a forest product which provides the highest incomes to the owners of stone pine forests.

Aim

The objective of this work is to evaluate the effect of first thinning on growth and cone production in an artificially regenerated stand in order to determine optimum intensity.

Methods

A thinning trial was installed in 2004 to compare two thinning regimes (heavy and moderate) and a control treatment. From 2004 to 2012, six inventories of forest attributes were carried out, and the cone crop was harvested annually. We evaluated the effect of thinnings on growth using repeated measures analysis of variance with a mixed model approach. With regards to cone production, we first estimated the probability of finding cones in a tree by applying a generalized mixed model and then estimated cone production by using a mixed model, including climatic variables.

Results

We found that thinning had a positive influence on tree diameter increment. Thinning increased the probability of finding cones and cone production. However, significant differences between heavy and moderate thinnings were not found.

Conclusion

We recommend early silvicultural treatments in stone pine stands to favor the development of trees and larger edible pine nut production.     

Recent expansion of Pinus nigra Arn. above the timberline in the central Apennines, Italy

? Context

The altitude of timberlines in the central Apennines has lowered over the past few thousand years due to interacting natural and anthropogenic disturbances. These timberlines are usually sharp and consist of coppiced beech forests.

? Aims

We found scattered individuals of European black pine (Pinus nigra Arn.) at two high elevation sites above the timberline on limestone slopes. We investigated the spatial and temporal pattern expansion of black pine and assessed vigour and growth dynamics of pine trees.

? Methods

Over 250 individuals were mapped in the two sites using GPS. Several site and tree parameters were measured. Tree-ring widths and the frequency of intra-annual density fluctuations were also recorded.

? Results

Black pine expansion started around 30?years ago. Pine trees are randomly distributed at higher elevations with no visible spatial pattern. Germination peaks were synchronous in the two sites, and tree growth displayed very similar chronologies, with synchronous occurrence of intra-annual density fluctuations.

? Conclusion

We hypothesise that the reduced livestock grazing over the last decades as well as climate warming are the major driving forces behind the high-altitude expansion of black pine on the central Apennines, where this species was present in pre-historic times.     

Thinning has a positive effect on growth dynamics and growth–climate relationships in Aleppo pine (Pinus halepensis) trees of different crown classes

? Context

Modification of stand density by thinning may buffer the response of tree growth and vigor to changes in climate by enhancing soil water availability.

? Aims

We tested the impact of thinning intensity on cambial growth of Aleppo pine (Pinus halepensis L.) under semi-arid, Mediterranean conditions.

? Methods

A multiple thinning experiment was established on an Aleppo pine plantation in Spain. We analysed the stem growth dynamics of two different crown classes under four different thinning intensities (15 %, 30 %, and 45 % removal of the basal area) for 2 years, based on biweekly band dendrometer recordings. Local relative extractable soil water was derived from the use of a water balance model Biljou© (available at https://appgeodb.nancy.inra.fr/biljou/) and used as an explanatory variable.

? Results

Radial growth was mainly controlled by soil water availability during the growing season, and differed by crown class. The growth rates of dominant trees were significantly higher than the growth rates of suppressed trees. Removal of 30 % and 45 % of the initial basal area produced a growth release in both dominant and suppressed trees that did not occur under less intense thinning treatments.

? Conclusions

Soil water availability was the main driver of radial growth during the growing season. Forest management confirmed its value for ameliorating the effects of water limitations on individual tree growth. These results may help managers understand how altering stand density will differentially affect diameter growth responses of Aleppo pine to short-term climatic fluctuations, promoting forests that are resilient to future climatic conditions.     

When tree rings behave like foam: moderate historical decrease in the mean ring density of common beech paralleling a strong historical growth increase

? Context

While historical increases in forest growth have been largely documented, investigations on historical wood density changes remain anecdotic. They suggest possible density decreases in softwoods and ring-porous hardwoods, but are lacking for diffuse-porous hardwoods.

? Aims

To evaluate the historical change in mean ring density of common beech, in a regional context where a ring-porous hardwood and a softwood have been studied, and assess the additional effect of past historical increases in radial growth (+50 % over 100 years), resulting from the existence of a positive ring size–density relationship in broadleaved species.

? Methods

Seventy-four trees in 28 stands were sampled in Northeastern France to accurately separate developmental stage and historical signals in ring attributes. First, the historical change in mean ring density at 1.30 m (X-ray microdensitometry) was estimated statistically, at constant developmental stage and ring width. The effect of past growth increases was then added to assess the net historical change in wood density.

? Results

A progressive centennial decrease in mean ring density of ?55 kg?m^?3 (?7.5 %) was identified (?10 % following the most recent decline). The centennial growth increase induced a maximum +25 kg?m^?3 increase in mean ring density, whose net variation thus remained negative (?30 kg?m^?3).

? Conclusions

This finding of a moderate but significant decrease in wood density that exceeds the effect of the positive growth change extends earlier reports obtained on other wood patterns in a same regional context and elsewhere. Despite their origin not being understood, such decreases hence form an issue for forest carbon accounting.     

A tree distance-dependent growth and yield model for naturally regenerated pure uneven-aged maritime pine stands in central inland of Portugal

? Context

Maritime pine (Pinus pinaster Aiton) is one of the most important Portuguese species, growing in pure stands ranging from even-aged to multi-aged structures. Current growth and yield models were developed only for even-aged, managed stands and/or for very specific regions of Portugal.

? Aims

This paper focuses on the validation of the existing size-class model PBRAVO, adapted to even-aged stands, and on the subsequent development of a single tree distance-dependent growth and yield model (PBIRROL), both in distance-independent and distance-dependent versions, for uneven-aged stands.

? Methods

The new model is composed of four modules, each with a set of sub-models for: tree variable prediction, tree volume prediction, future tree list prediction and growth projection.

? Results

The evaluation of the PBRAVO and PBIRROL models showed that the new model gives more accurate predictions. Moreover, medium-term simulations provided consistent and logical predictions.

? Conclusion

It was verified that individual tree models are more suited to simulate poorly managed uneven-aged stands than diameter distribution models. No clear superiority of distance-dependent models was found over models using just distance-independent measures of inter-tree competition.     

Carbon storage in biomass,litter, and soil of different plantations in a semiarid temperate region of northwest China

? Context

A large area of abandoned land in the semiarid temperate region of China has been converted into plantations over the past decades. However, little information is available about the ecosystem C storage in different plantations.

? Aim and methods

Our objective was to estimate the C storage in biomass, litter, and soil of four different plantations (monospecific stands of Larix gmelinii, Pinus tabuliformis, Picea crassifolia, and Populus simonii). Tree component biomass was estimated using allometric equations. The biomasses of understory vegetation and litter were determined by harvesting all the components. C fractions of plant, litter, and soil were measured.

? Results

The ecosystem C storage were as follows: Picea crassifolia (469 t C/ha)?>?Larix gmelinii (375 t C/ha), Populus simonii (330 t C/ha)?>?Pinus tabuliformis (281 t C/ha) (P?<?0.05), 59.5–91.1 % of which was in the soil. The highest tree and understory C storage were found in the plantation of Pinus tabuliformis (247 t/ha) and Larix gmelinii (1.2 t/ha) respectively. The difference in tree C fraction was significant among tree components (P?<?0.05), following the order: leaf?>?branch?>?trunk?>?root. The highest soil C (SC) was stored in Picea crassifolia plantation (411 t C/ha), while Populus simonii plantation had a higher SC sequestration rate than others.

? Conclusion

C storage and distribution varied among different plantation ecosystems. Coniferous forests had a higher live biomass and litter C storage. Broadleaf forests had considerable SC sequestration potential after 40 years establishment.     

Modeling recent bark stripping by red deer (Cervus elaphus) in South Belgium coniferous stands

? Context

Over the past few decades, the impact of large herbivorous ungulates on forest vegetation has been clearly highlighted. Among those impacts, bark stripping of coniferous trees is one of the most damaging. Bark stripping leads to rot development, inducing serious loss of timber value.

? Aims

The present study aimed firstly at evidencing the factors explaining the variations observed in fresh bark peeling rate for spruce and Douglas-fir in southern Belgium and secondly at identifying the key factors to consider when setting up a deer management plan.

? Method

Fresh bark peeling rate was recorded with a systematic sampling survey from 2004 to 2007. The covered territory was then divided into 63 distinct hunting zones of area ranging from 1,000 to 25,000 ha. About 5,000 plots were monitored annually. Each zone was characterized with a large number of explanatory variables. The explanatory variables were integrated firstly into fixed linear models using a stepwise procedure, and then into a mixed model.

? Results

The significant variables included in the model (R ²?=?44 %) are (by decreasing order of importance) red deer densities, proportion of coniferous stands and agricultural areas, snow cover, distance to urban habitats, and species diversity in the understory.

? Conclusion

The models revealed the impacts of several factors on bark peeling: deer density, deer-carrying capacity of the territory, landscape structure, and severity of winter conditions. The adjusted model allowed subtracting the impact of winter conditions in order to produce a relevant indicator for hunting management. In addition, the model was used to assess the sensitivity of a forested area to bark peeling based on its environmental characteristics.     

Influence of cambial age and climate on ring width and wood density in Pinus radiata families

? Context

The correlation between tree ring width and density and short-term climate fluctuations may be a useful tool for predicting response of wood formation process to long-term climate change.

? Aims

This study examined these correlations for different radiata pine genotypes and aimed at detecting potential genotype by climate interactions.

? Methods

Four data sets comprising ring width and density of half- and full-sib radiata pine families were used. Correlations with climate variables were examined, after the extraction of the effect of cambial age.

? Results

Cambial age explained the highest proportion of the ring to ring variation in all variables. Calendar year and year by family interaction explained a smaller but significant proportion of the variation. Rainfall had a positive correlation with ring width and, depending on test site, either a negative or positive correlation with ring density. Correlations between temperature during growing season and ring density were generally negative.

? Conclusion

Climate variables that influence ring width and wood density can be identified from ring profiles, after removing the cambial age effect. Families can be selected that consistently show desirable response to climate features expected to become prevalent as a result of climate change.     

Ectomycorrhizal communities associated with silver fir seedlings (Abies alba Mill.) differ largely in mature silver fir stands and in Scots pine forecrops

Context

The requirement for rebuilding forecrop stands besides replacement of meadow vegetation with forest plants and formation of soil humus is the presence of a compatible ectomycorrhizal (ECM) fungal community.

Aims

This study aims to assess ectomycorrhizal fungi diversity associated with silver fir (Abies alba Mill.) seedlings regenerating in silver fir stands and Scots pine forecrops.

Methods

One-year-old seedlings were sampled in six study sites: three mature fir forests and three pine forests. ECM fungi were identified by polymerase chain reaction amplification and sequencing of the internal transcribed spacer of rDNA.

Results

The mean mycorrhizal colonization exceeded 90 %. Thirty-six ectomycorrhizal taxa were identified in fir stands and 23 in pine forecrops; ten out of these species were common to both stands. The fungal communities were different between study sites (R?=?0.1721, p?=?0.0001). Tomentella stuposa was the only species present at all sites.

Conclusion

Silver fir seedlings in Scots pine forecrops supported smaller ECM fungal communities than communities identified in mature silver fir stands. Nevertheless, fungal colonization of seedling roots was similar in both cases. This suggests that pine stands afforested on formerly arable land bear enough ECM species to allow survival and growth of silver fir seedlings.     

Spatially explicit competition in a mixed planting of Araucaria cunninghamii and Flindersia brayleyana

? Context

A 20-year-old Nelder wheel planted with hoop pine (Araucaria cunninghamii Aiton ex D.Don) and Queensland maple (Flindersia brayleyana F.Muell.) in 18 spokes and 8 rings represents nominal point densities of 3,580, 2,150, 1,140, 595, 305, 158, 82, and 42 stems/ha and offers an opportunity to examine competition and spatial interaction between these two species.

? Aims

This study aimed to evaluate the intraspecific and interspecific competition between two contrasting tree species and to determine the distance over which competition can be observed.

? Methods

Competition was estimated using Hegyi’s index, implemented using the Simile visual modeling environment, and calibrated using nonlinear least squares with PEST.

? Results

Interactions were detected between pairs of stems closer than D _ij ?<?40(d _i ?+?d _j ) where D is distance (in centimeters) and d is stem diameter (in centimeters diameter at breast height). F. brayleyana trees surrounded by A. cunninghamii trees experience negligible competition, whereas A. cunninghamii surrounded by F. brayleyana trees suffer strong competition.

? Conclusion

Forty times diameter offers a useful guide to the extent of competition in even-aged stands planted with these species. Competition can be observed empirically when pairs of trees are closer than 40 times the sum of their diameters, but the intensity of the competition may vary considerably with species.     

Low soil temperatures increase carbon reserves in Picea mariana and Pinus contorta

? Context

Soil temperature can limit tree growth and function, but it is often unaddressed in understanding the successional status of trees.

? Aims

We tested how soil temperature affected carbon allocation strategies of two dominant co-occurring boreal conifer species, Pinus contorta and Picea mariana.

? Methods

We measured nonstructural carbon (NSC) concentrations, biomass, and photosynthesis of dormant and actively growing 2-year-old seedlings in response to three soil temperatures (5, 10, and 20 °C) under a common ambient air temperature.

? Results

For both species, variation in carbon reserves with soil temperature was more pronounced following seedling growth than during dormancy. For both species and all organ types (roots, needles, and stems), NSC concentrations were highest when seedlings were grown at 5 than 20 °C. Mass adjusted for NSC content was negatively correlated with NSC concentration for all organ types of both species. Soil temperature had a marginally significant effect on photosynthesis of pine; seedlings grown at 10 or 20 °C acquired more carbon than seedlings grown at 5 °C. Spruce seedlings photosynthesized more when grown at 20 °C than at 5 or 10 °C.

? Conclusion

Interspecific differences in allocation of carbon may underlie the responses of P. mariana and P. contorta to cold soils and consequently their successional status.     

Potential spread of the pine processionary moth in France: preliminary results from a simulation model and future challenges

Context

Some forest insect pests are currently extending their range as a consequence of climate warming. However, in most cases, the evidence is mainly based on correlations and the underlying mechanism is not clearly known.

Aims

One of the most severe pests of pine forests in Europe, the pine processionary moth, Thaumetopoea pityocampa, is currently expanding its distribution as a result of climate warming and does not occupy entirely its potential habitat. A model describing its spread was developed to simulate its potential range in France under various climate change scenarios.

Methods

The spread model was divided into several sub-models to describe the growth, survival and dispersal of the species. The model was validated on the observed change of species distribution, its sensitivity was tested, and spread scenarios were simulated for the future.

Results

The model shows that climate warming initiated the species range expansion in France since the early 1990s. The spread is now limited by dispersal capability, but human-mediated dispersal could accelerate the range expansion.

Conclusion

Species range expansion is an indicator of climate change. However, time lags can appear due to limited dispersal capabilities, and human-mediated dispersal could create satellite colonies and artificially accelerate the spread.     

Influence of initial plant density on sawn timber properties for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)

? Context

Mechanical wood properties are increasingly relevant for structural applications and are influenced by growing space availability. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) has an increasing market share in Europe and is mainly processed to sawn timber.

? Aim

A sample of 164 thinning trees was taken from two Douglas-fir long-term forestry research plots in Germany. The end-use quality of about 2,000 side and center boards was analyzed as a function of initial plant density (1,000, 2,000, and 4,000 trees per hectare) and log position within the stem.

? Methods

Sawn timber quality was described by knottiness, density, modulus of elasticity, and strength. Explanatory parameters were radial position, longitudinal position, and initial plant density. All boards were strength graded visually and by the grading machine GoldenEye-706 using both X-rays for detecting densities and size as well as position of knots and laser interferometry for detecting eigenfrequency (DIN 4074, DIN 2012; EN 14081-2, CEN 2010).

? Results

High plant density led to better mechanical sawn timber quality. Significant differences were especially observed between 1,000 and 2,000 trees per hectare. The yield of machine strength-graded center boards of strength class C24 increased from 50 to 89 % at low and high initial plant density, respectively.

? Conclusion

Foresters are able to improve end-product quality by controlling planting density in particular. The roundwood price that foresters get should be based on the proportion of higher strength classes within logs to give incentives for a more quality-oriented forest management.     

Models for predicting microfibril angle variation in Scots pine

Context

Microfibril angle (MFA) is one of the key determinants of solid timber performance due to its strong influence on the stiffness, strength, shrinkage properties and dimensional stability of wood.

Aims

The aim of this study was to develop a model for predicting MFA variation in plantation-grown Scots pine (Pinus sylvestris L). A specific objective was to quantify the additional influence of growth rate on the radial variation in MFA.

Methods

Twenty-three trees were sampled from four mature Scots pine stands in Scotland, UK. Pith-to-bark MFA profiles were obtained on 69 radial samples using scanning X-ray diffractometry. A nonlinear mixed-effects model based on a modified Michaelis–Menten equation was developed using cambial age and annual ring width as explanatory variables.

Results

The largest source of variation in MFA (>90 %) was within trees, while between-tree variation represented just 7 % of the total. Microfibril angle decreased rapidly near the pith before reaching stable values in later annual rings. The effect of ring width on MFA was greater at higher cambial ages.

Conclusion

A large proportion of the variation in MFA was explained by the fixed effects of cambial age and annual ring width. The final model is intended for integration into growth, yield and wood quality simulation systems.     

Within-population variability in architectural traits and suitability to forestry conditions in Nothofagus nervosa (= N. alpina; Nothofagaceae)

? Context

There is evidence that Nothofagus nervosa (= N. alpina) is suitable for timber production in temperate regions due to its wood quality and fast growth. However, high intra-specific variability in the architectural traits of this species limits its usefulness.

? Aims

This study was aimed at evaluating intra-specific variability in the architecture of N. nervosa trees at the population level, with emphasis on traits related to the suitability of trees for timber production.

? Methods

The size of 13-year-old trees installed in an experimental field population and the extent of differentiation between trunk and branches were compared among families (trees derived from different mother trees).

? Results

The large majority of trees exhibited architectural features indicative of high suitability for timber production: clear differentiation between trunk and main branches and few occurrences of permanent trunk forks, apex deaths, and sylleptic branching. Trees belonging to different families differed in height and trunk diameter. Micro-environmental conditions had a very significant effect on most architectural traits, including the trunk differentiation.

? Conclusions

N. nervosa emerges as a suitable option for timber production in temperate regions. Trunk growth seems to be under both environmental and genetic control in this species.     

Radial growth changes following hemlock woolly adelgid infestation of eastern hemlock

? Context

Hemlock woolly adelgid (Adelges tsugae) is an invasive insect that is defoliating and killing eastern hemlock (Tsuga canadensis) in the USA.

? Aims

We quantified changes in tree-ring growth rates and wood anatomy for living trees infested with hemlock woolly adelgid across six sites from Massachusetts (42°41′N) to Georgia (34°53′N) to identify growth responses of eastern hemlock that had survived infestation.

? Methods

Annual ring widths from infested eastern hemlocks were cross-dated and measured. Growth rates before and after infestation were compared. Two infested trees from Virginia were cut, and thin sections were prepared to identify changes in cell properties.

? Results

At three sites, trees experienced a significant decrease in radial growth after hemlock woolly adelgid arrival; however, the other three sites showed no change or increase in growth. Latewood produced after hemlock woolly adelgid infestation had significantly smaller cells with reduced cell wall thickness compared to latewood prior to infestation.

? Conclusion

At half the sites where hemlock woolly adelgid infested eastern hemlock trees were sampled, radial growth increased or remained unchanged. This unexpected response may be due to reduced competition due to mortality of other eastern hemlocks or physiological compensatory responses of increased photosynthetic rate and increased water use efficiency experienced by eastern hemlock infested with hemlock woolly adelgid.     

Effect of nutrient removal on radial growth of Pinus sylvestris and Quercus petraea in Southern Germany

? Context

The rising demand of energy wood for heating purposes in Germany leads to concerns regarding the overexploitation of forests. A major aspect is the impact of whole-tree harvesting on long-term productivity of forest soils.

? Aims

This study aimed to analyze the effects of nutrient removal on productivity using the historically prevalent practice of litter raking. Since there is a lack of controlled whole-tree harvesting experiments in Germany, we used litter raking as a surrogate management practice entailing the removal of nutrients from forest stands.

? Methods

We used three sites with documented litter raking to analyze the effects of nutrient removal on productivity using dendroecological methods: two recent litter removal experiments in two Scots pine stands (Siegenburg and Burglengenfeld) and one oak stand (Eichhall) with documented historic litter raking. Basal area increment (BAI) and tree-ring characteristics were compared between periods with litter raking and the preceding periods for both treatment and control plots.

? Results

For the two Scots pine sites with a relatively short litter raking period, no effects of litter raking on BAI could be ascribed to nutrient removal. On the oak site with a longer history of litter utilization, the loss in BAI due to litter raking amounts to 22 % during the period with active raking and to still 17 % in the recovery period.

? Conclusions

These results contribute to the still very limited understanding about the impact of whole-tree harvesting on forest productivity in Germany by laying down an upper limit of possible effects due to nutrient removal, as nutrient loss by litter raking tends to be higher than nutrient loss by whole-tree harvesting.     

Impact of management on nutrients,carbon, and energy in aboveground biomass components of mid-rotation loblolly pine (Pinus taeda L.) plantations

Context

To sustainably manage loblolly pine plantations for bioenergy and carbon sequestration, accurate information is required on the relationships between management regimes and energy, carbon, and nutrient export.

Aims

The effects of cultural intensity and planting density were investigated with respect to energy, carbon, and essential nutrients in aboveground biomass of mid-rotation loblolly pine plantations, and the effects of harvesting scenarios on export of nutrients were tested.

Methods

Destructive biomass sampling of a 12 years-old loblolly pine culture/density experiment, and analysis of variance were used to assess the effects of cultural intensity (operational vs. intensive) and six planting densities ranging from 741 to 4,448 trees ha^?1. Two harvesting scenarios (stem-only vs. whole-tree harvesting) were assessed in terms of energy, carbon, and nutrient export.

Results

The concentrations of energy, carbon, and nutrients varied significantly among stem wood, bark, branch, and foliage components. Cultural intensity and planting density did not significantly affect these concentrations. Differences in energy, carbon and nutrient contents among treatments were mainly mediated by changes in total biomass. Nutrient contents were affected by either cultural intensity or planting density, or both. Stem-only harvesting removed 71–79 % of aboveground energy and carbon, 29–45 % of N, 28–44 % of P, 44–57 % of K, 51–65 % of Ca, and 50–61 % of Mg.

Conclusions

Stem-only harvesting would be preferred to whole-tree harvesting, from a site nutrient conservation perspective.     

Projections of regional changes in forest net primary productivity for different tree species in Europe driven by climate change and carbon dioxide

? Context

Projecting changes in forest productivity in Europe is crucial for adapting forest management to changing environmental conditions.

? Aims

The objective of this paper is to project forest productivity changes under different climate change scenarios at a large number of sites in Europe with a stand-scale process-based model.

? Methods

We applied the process-based forest growth model 4C at 132 typical forest sites of important European tree species in ten environmental zones using climate change scenarios from three different climate models and two different assumptions about CO₂ effects on productivity.

? Results

This paper shows that future forest productivity will be affected by climate change and that these effects depend strongly on the climate scenario used and the persistence of CO₂ effects. We find that productivity increases in Northern Europe, increases or decreases in Central Europe, and decreases in Southern Europe. This geographical pattern is mirrored by the responses of the individual tree species. The productivity of Scots pine and Norway spruce, mostly located in central and northern Europe, increases while the productivity of Common beech and oak in southern regions decreases. It is important to note that we consider the physiological response to climate change excluding disturbances or management.

? Conclusions

Different climate change scenarios and assumptions about the persistence of CO₂ effects lead to uncertain projections of future forest productivity. These uncertainties need to be integrated into forest management planning and adaptation of forest management to climate change using adaptive management frameworks.