Variability of stomatal conductance in a small and isolated population of silver fir (Abies alba Mill.)

We analyzed the response to drought of 420 individuals from eight half-sib families from a small and isolated population of silver fir (Abies alba Mill.): 105 of them were kept in well-watered conditions as control while the remaining 315 were exposed to drought for 27 days. A model describing stomatal behavior derived from Monteith and developed in beech by Leonardi et al. was fitted to experimental transpiration data obtained simply from the difference between two daily pot weighings. The estimated parameters were maximum stomatal conductance, maximum transpiration in well-watered conditions and sensitivity to soil water deficit. The model worked well: convergence for all but four individuals and concordance between experimental and fitted data were good (R(2)=0.86). Inter-individual variability for all three estimated parameters was high and two of them (maximum stomatal conductance and sensitivity to soil water deficit) were significantly different among families, suggesting genetic control. Our results validate the simplified method used to evaluate individual stomatal parameters. We also show that in the small and isolated population of our study substantial adaptive variability remains, a crucial prerequisite to endure environmental conditions determined by climatic change foreseen for the next decades.     

Relationships between local stand density and local species composition and nutrient content in the topsoil of pure and mixed stands of silver fir (Abies alba Mill.)

This study examined topsoil samples from the humic mineral horizon in four pure silver fir (Abies alba Mill.) and five mixed stands with beech (Fagus sylvatica L.), spruce (Picea abies L.; Karst.) and pine (Pinus sylvestris L.). In every stand, 60–70 sampling locations were chosen using a stratified random scheme that represented a gradient in local stand density and local species composition. One working hypothesis was that stand density and species composition affect the content of nutrients in the mineral humic soil horizon. Specifically, the analysis statistically tested for relationships between general and species-specific local stand density measures (basal area, sum of tree diameters weighted by distance, canopy openness) and the contents of total C, total N (in four stands), base cations (Ca²⁺, Mg²⁺, K⁺, Na⁺) and Mn²⁺ (in nine stands). A considerable variation in nutrient concentrations was observed; the coefficients of variation ranged from 0.21 to 0.38 for N, from 0.20 to 0.94 for the sum of base cations and from 0.56 to 0.95 for Mn. However, no clear relationship emerged between local stand density and the concentration of N and base cations; in five stands, manganese showed a negative correlation with local stand density. In the mixed fir-beech stand, significantly higher concentrations of Ca, K and Mn were found in the vicinity of beeches, and species-specific stand density explained up to 15, 29 and 34% of total variation in the content of these elements, respectively. Similar tendencies also appeared in the mixed stands with pine, although the relationships were weak. The results obtained for two fir-spruce stands were ambiguous. In sum, in the stands studied, small canopy gaps and inter-crown openings might not be considered ‘‘nutrient hot spots’’, and the admixed species, except for beech, had an insignificant effect on nutrient content in the humic mineral horizon.     

Retrospective analysis of tree architecture in silver fir (Abies alba Mill.): ontogenetic trends and responses to environmental variability

Context

Understanding the effects of exogenous factors on tree development is of major importance in the current context of global change. Assessing the structure development of trees is difficult given that they are large and complex organisms with lifespan of several decades.

Aims

We used a retrospective analysis to derive the ontogenetic trends in silver fir development and assess the effects of climate or light environment on tree architecture.

Methods

Thanks to the identification of relevant growth markers (bud cataphylls and pseudo-whorl branches), a retrospective analysis allowed to record annual shoot extension and to date them on silver firs of various sizes under different environmental conditions.

Results

The length of successive annual shoots located on different axes clearly show gradual trends related to the physiological age of meristems. Within- and between-tree variations are noted due to the plasticity of development and growth induced by light environment and climate.

Conclusion

Retrospective analysis is an efficient method for getting information on the history of trees architecture and subsequently to relate it to environmental factors.     

Epidemiology of Heterobasidion abietinum and Viscum album on silver fir (Abies alba) stands of the Pyrenees

In the last two decades, stand decline and increased mortality has affected silver fir (Abies alba) forests in the Spanish Pyrenees. Simultaneously severe occurrences of the root rot fungus Heterobasidion annosum s.l. and of the mistletoe Viscum album have been reported. We aimed to improve the understanding of the epidemiology of both pathogens in our region. All H. annosum isolates found on silver fir were typed as H. abietinum. H. abietinum was more frequently observed where cuttings had targeted fir trees rather than other species. H. abietinum fruiting bodies were observed in the most recently cut stumps. V. album was more abundant on more dominant fir trees, and in southern aspect stands. The number of V. album colonies in the stand correlated (R² = 0.40) with silver fir mortality. Stands with a high level of V. album infection tended to have a smaller percentage of basal area in species other than silver fir, and they tended to be located on more south‐facing slopes. H. abietinum was widespread in silver fir forests of the Pyrenees. Our data suggest that, in the Pyrenees, the observed H. abietinum incidence may represent a combination of both primary and secondary spread of the pathogen. Favouring mixed forests should be tested as a potential control method for V. album. The correlation between silver fir mortality and V. album infection warrants further study, as the observed tree mortality could have occurred due to other factors than V. album, such as drought damage.     

Osmotic potential and gas exchange in healthy and diseased silver firs (Abies alba Mill.)1

The present study comprises comparative investigations of transpiration, photosynthesis and osmotic potential of various twigs of a healthy and a diseased fir. Possible causes for the registered differences are discussed.     

Climatic signal in annual growth variation of silver fir (Abies alba Mill.) and spruce (Picea abies Karst.) from the French Permanent Plot Network (RENECOFOR)

This paper explores the growth/climate relationships in earlywood, latewood and total ring-width chronologies of five Norway spruce (Picea abies) and six silver fir (Abies alba) stands sampled in the French permanent plot network (RENECOFOR) (327 trees). The relationships between climate and ring widths were analyzed using extreme growth years, simple correlations and response functions analysis (bootstrapped coefficients). Monthly climatic regressors were derived by a physiological water balance model that used daily climatic data and stand parameters to estimate soil water deficits. Pointer years underline the high sensitivity to winter frosts (1956, 1986) and exceptional annual droughts (1962, 1976, 1991) for both species. For those years, growth variations were higher for Abies alba than for Picea abies. For each species, the climate information of tree ring series is not modified by local site characteristics (altitude, slope, aspect, soil water reserve). Moreover, strong specific differences appear among species. Earlywood and latewood spruce growth mainly depends on current summer soil water deficit conditions. For silver fir, winter and early summer temperatures, as well as the water supply of the previous year (August to October) play a major role for the production of earlywood, after which the current early summer water supply influences mainly latewood width.     

Effects of ozone on gas exchange,frost resistance,flushing and growth of different provenances of European silver fir (Abies alba Mill.)

Photosynthesis, respiration, and transpiration were studied in different Abies alba provenances during and alter ozone exposure at three different levels (0/control, 125, and 250 ppb O₃, respectively). The after-effects of ozone on frost resistance and growth rate were also analyzed. Pronounced reductions of photosynthesis and transpiration rates and an increased respiration were registered as a response to O₃. Five months after exposure the winter frost resistance was significantly reduced, and growth depressions were registered during the following year. Differences in ozone sensibility and regeneration ability between provenances could be demonstrated.     

Role of mycorrhiza and soil fungi in natural regeneration of fir (Abies alba Mill.) in Polish Carpathians and Sudetes

Changes occurring in mycotrophy of fir seedlings (Abies alba Mill.) and in communities of the soil fungi, fungi living in roots, and fungi from rhizosphere were studied in mountain forest stands, both with good and poor regeneration of fir. The intent of these studies was to contribute to the elucidation of the problem of whether the lack of fir regeneration could be connected with microbiological changes taking place in the soil environment.     

Spectral sensitivity in the photodegradation of fir wood (Abies alba Mill.) surfaces: colour changes in natural weathering

Activation spectra of wood under natural irradiation were investigated in detail in this work. The main purpose was to study colour changes on the wood surface over time and into the depth during natural light exposure and thus to further contribute to the optimization of surface-protecting treatments. In a natural weathering test, three 80-μm-thick strips of fir wood forming the surface layer of a wood composite were exposed to light under a series of glass cut-off filters. Samples were withdrawn at intervals and tested for colour changes. Identification of the most detrimental wavebands of light causing photodegradation was performed based on recorded colour changes. With chronological development of exposure, the colour changes shifted ever deeper into the surface and further into the visible region of the spectrum. A relatively narrow waveband from 360 to 435 nm was identified in the activation spectra to be the most active band, causing the greatest proportion of recorded colour changes. However, also visible light of wavelengths up to 515 nm significantly contributed to colour changes of the surface layers.     

An actuarial model of forest insurance against multiple natural hazards in fir (Abies Alba Mill.) stands in Slovakia

Natural hazards are the main threat for forest all over the world. Some of these disturbances may be insured such as fire and/or storm in some European countries. However, forest insurance has trouble to spread in particular because of the existence of some brakes such as the forest insurance premium, often considered as too high compared to the profitability of the forest investment. In this context, we propose an actuarial insurance model to insure multiple natural hazards (windthrow, fire, insect outbreak) in forests that determine the insurance premium in different senarios. In particular, the scenarios differ in terms of the link between the hazards, either they are mutually independent or dependent, and in terms of the parametric solutions to the actuarial problem, either a discrete time period approach or a continuous one. We propose an application of the actuarial model to a silver fir (Abies Alba Mill.) stand in the Slovak Paradise region (Slovakia). We show that gross insurance premiums range from €5.62/ha at a scale of 150,000 ha at age 150, to €6312.81/ha at a scale of 15 ha at age 50. In addition, we show that the most efficient solution in terms of the minimisation of the gross insurance premiums is provided under the assumption of random occurrence of mutually independent natural hazards and with a continuous time period approach.     

Rückgang der Tanne (Abies alba Mill.) in Polen

Decline of silver fir (Abies alba Mill.) in Poland. On the basis of his own observations and of data from the literature, the author gives a review of silver fir diseases, pests and damage by other biotic and abiotic factors in Poland and on conjectural causes of the decline of this tree species.     

Ecology of Armillaria species on silver fir (Abies alba) in the Spanish Pyrenees

? We describe the distribution and the ecology of three Armillaria species observed in silver fir (Abies alba) forests of the Pyrenees.

? We surveyed the presence and abundance of Armillaria above and belowground in 29 stands. Isolates were identified by the PCR-RFLP pattern of the IGS-1 region of their ribosomal DNA. We measured several ecological and management parameters of each stand in order to describe Armillaria infected sites.

? Armillaria cepistipes was the most abundant of three species observed. Armillaria gallica was dominant in soils with a higher pH and at lower elevations. Armillaria ostoyae seemed to be more frequent in stands where A. alba recently increased its dominance relative to other forest tree species. Thinning activities correlated with an increased abundance of Armillaria belowground. In 83% of the stands the same Armillaria species was observed above and belowground.

? It seems that in a conifer forest, A. cepistipes can be more frequent than A. ostoyae, a virulent conifer pathogen. Since logging is related to a higher abundance of Armillaria in the soil, the particular Armillaria species present in a given stand could be considered an additional site factor when making management decisions.

     

Ecophysiological reactions of different provenances of European Silver fir (Abies alba Mill.) to SO2 exposure during winter

Photosynthesis, transpiration and stomatal behavior were studied in different Abies alba provenances during and after SO₂ exposure. Differences in SO₂ sensitivity and regeneration ability between provenances could be demonstrated.     

The prospects of silver fir (Abies alba Mill.) and Norway spruce (Picea abies (L.) Karst) in mixed mountain forests under various management strategies,climate change and high browsing pressure

European Journal of Forest Research - In the Dinaric Mountains, the future of silver fir and Norway spruce appears to be uncertain, especially given the threat of climate change to both species and...     

Effects of soil moisture manipulations on fine root dynamics in a mature balsam fir (Abies balsamea L. Mill.) forest

We tested the hypothesis that moisture stress affects fine root dynamics during and after the stress. To this end, we investigated the effects of soil moisture on annual and seasonal fine root production and mortality over 4 years in a mature balsam fir (Abies balsamea L. Mill.) stand using a minirhizotron and soil coring. Droughting and irrigating treatments were imposed for 17 weeks during the third year of the study, and post-treatment recovery was measured during the fourth year. Monthly fine root production was often reduced by low soil water content (SWC) during July-September in the pre-treatment years and by imposed drought. Irrigation resulted in higher summer fine root production than in pre-treatment years. In the recovery year, increased fine root production was observed in the previously droughted plots despite low SWC in August and September. Droughting decreased year-end fine root biomass in the treatment year, but biomass returned to pre-treatment levels during the recovery year. Droughting and irrigating did not affect foliage production during the treatment and recovery years. Our results suggest that for balsam fir, establishment and maintenance of a functional balance between foliage and fine root biomass, with respect to moisture supply and demand, can depend on fine root dynamics occurring over more than one growing season. In addition, our findings provided insights into tree growth responses to interannual variation in moisture supply.     

Correlations between needle and shoot growth characteristics in Scots pine (Pinus sylvestris L.) stands

Shoot, needle and bud growth in three stands of different ages(9, 20, and 60 years) of Scots pine were studied in order toreveal relations between these variables. Within the growingseason the sizes of buds and needles developed in parallel.Significant regressions between number of short shoots and eitheraverage needle length or total needle length of the parent shootwere found. The strongest regressions were found in the twoyoungest stands as well as in the top of the canopy.     

The effect of microhabitat and trophic conditions on the colonization density of cambio-and xylophagous insects in fir stumps (Abies alba Mill.) in selected stands of the świętokrzyskie mountains (Poland)

Most of the investigated fir stumps (79%), aged 2–4 years after tree cutting, were occupied by cambio-and xylophagous insects (on average 32 individuals per 1 stump). There were identified 2 cambiophages, 1 cambio-xylophagous species and 5 xylophages. Colonization density of these insects in fir stumps was influenced by microhabitat and trophic conditions. The highest density was found in fir stumps without mosses and lichens cover, moderately decomposed and wet, situated in partly insolated places. Fir stumps are a good base for reproduction and development of secondary and technical invaders of wood, which is important for forest management. Of particular significance isPissodes piceae that apart from stumps invades also weakened and withering fir trees, causing their death.