From Acid Rain to Low Precipitation: The Role Reversal of Norway Spruce, Silver Fir, and European Beech in a Selection Mountain Forest and Its Implications for Forest Management

We make use of long term observation data from a selection forest in Bavaria. Despite the changing environmental conditions, stand level productivity remains constant over time. Maintaining species and structural diversity by forest management can contribute to resilient forest ecosystems. Background and Objectives: Forests in mountains are similarly affected by environmental changes like those in northern latitudes as species are closer to the edge of their ecological niche. There are recent studies that report species-specific responses to climate change in unmanaged, mono-layered mountain mixed forests. We analyze how environmental changes modify the growth of multi-layered, managed selection forest, which are often targeted for stabilization and risk prevention. We pose the central hypothesis that different species-specific susceptibility to disturbances and structural diversity contribute to ecosystem stability. Materials and Methods: Based on the long-term experiment Freyung 129 in the montane zone of the Bavarian Forest, Germany we analyze long term chronologies of periodic single tree and stand growth of Norway Spruce, silver fir, and European beech in dependence of environmental factors and forest management. Results: First, we show that despite environmental changes in terms of air pollution and drought stress, productivity at stand level persists constantly because of structural diversity and species traits. Second, we show that the species-specific contribution to total stand growth and growth distribution among stem diameter classes may change over time; the species interactions balance total growth. Third, we reveal a role reversal of tree species growth pattern. N. spruce was superior in growth in the first half and was replaced by s. fir in the second half of the survey period. Fourth, we identify the interplay of different stress factors on species-specific growth as the main cause for species-specific asynchronous but growth stabilizing reaction pattern. Finally, we show that density regulation was limited in its impacts to mitigate prevailing stress factors. Conclusions: We discuss the reasons for the observed stability of productivity. We interpret results, where especially the diversity of species and structure typical for selection forests result in stable productivity and wider plateau of the density-productivity relationship, and the suitability of the selection forest concept for risk prevention and stress resilience. We conclude that species composition and stand structure of selection forestry in mixed mountain contribute to climate smart forestry.

STRUCTURAL AND DYNAMIC CHANGES IN MIXED FORESTS OF BEECH AND FIR ON MT. GOČ

The primary goal of this research was to analyze the structural, production and dynamic changes of theforests of beech and fir in permanent sample plots of Mt. Goč, excluded from regular management fora period of 35 years (1977–2011). The established principles of spontaneous development and selfregulatoryprocesses could have implications on the regular management in these forests located in thearea of Mt. Goč and other areas.The results of this research in the permanent sample plots indicate that the mixed forests of beech andfir have suffered a number of changes in terms of structure and production in the investigated period.Structural disruptions have been the result of a decrease in the share of small and medium-diametertrees, as well as an increase in the share of trees of large dimensions in the total number of trees. Thecurves of distribution have been moved to the right and in terms of shape they differ from the lines thatare typical of selection forests. A relatively large number of trees per hectare and the described distributionby diameter classes have resulted in the high values of basal area and stand volume. In addition,a high volume increment has also been recorded. The quality and incremental capacity of the standshave been reduced due to a significant share of old beech and fir trees. The accumulation of volumeslowed down the dynamics of stand development and hindered rejuvenation and recruitment, as thenecessary prerequisites for structural stability and functionality in selection forests.The observed trends of development in these forests in the sample plots clearly indicate that a structurallystable, socio-economically and ecologically valuable selection forest is possible to achieve only withan active and continuous implementation of a set of management procedures, which primarily refersto selection cutting. Self-regulatory processes that are allowed over time, as in the case of the analyzedsample plots, are increasingly distancing us from this goal.

Conversion of a forest managed under systems involving coupes to a selection forest on an example of the Opuky research area

This paper evaluates the development of growing stock, number of trees and diameter distribution of the standing volume in the Opuky locality where conversion to a selection forest has been the aim of management over a long period of time. With respect to species composition, the stand is divided into two plots. The initial condition and development of both plots differed. The favourable initial composition of the stand has gradually deteriorated due to delay in natural regeneration and therefore recruitment of young trees over a long period. The total number of trees on both plots has been low for target diameter of 51 cm. On the other hand, the growing stock has exceeded the model condition. The proportion of broadleaved species in the stand gradually increases, reducing the possibility of conversion to a selection forest in future.

Structure and dynamics of stands of primeval character in selected areas of the Bieszczady National Park

The investigations carried out in 1988 and 1998 on three permanent sample plots in stands of the East Carpathian beech forest (Dentario glandulosae-Fagetum) showed that in the growing up stage, the storeyed structure phase (Jawornik I stand), the stand volume increased from 547 m³/ha to 578 m³/ha while in the optimum stage, the ageing and regeneration phases (Jawornik II), it decreased from 631 m³/ha to 600 m³/ha, and in the growing up stage, the storeyed structure phase (Tworylczyk), from 611 m³/ha to 610 m³/ha. In all three stands beech dominated in the upgrowth. During the 10-year period the volume of dead trees (standing and lying ones) increased in Jawornik II and Tworylczyk stands while in Jawornik I stand it decreased. The beech stands of the Bieszczady Mountains have a largely differentiated structure, from one-storey structure in the optimum stage, the ageing phase to many-storeyed structure in the growing up stage. This creates an opportunity for forming the complex stand structure, also the selection forest structure, in managed beech forests of the Carpathians.

Evaluation of transformation from even-aged to selection forest by means of Gini index

We used the Gini index for evaluation of the 40-year transformation to selection forests in the Training Forest Enterprise Masaryk Forest Křtiny (Czech Republic). The Gini index values for particular forest stands were compared with the reference values derived from the diameter distribution model curve (type E) by Meyer. From a total of sixteen stands which were evaluated in 2013 (the last periodic inventory), only two stands reached the desired diameter structure. Four other stands reached the desired diameter structure at least once during the transformation period. We recommend the application of Gini index for determination of a success rate of even-aged stand transformation to selection forest.

Analysis of the growth characteristics of a 450-year-old silver fir tree

The growth characteristics of silver fir are of high importance for selection forest management, and for the current aims laid out in Serbia?s forest management focused on increasing the share of silver firs in Serbia?s growing stock. With the objective of increasing the understanding of the growth characteristics of silver fir, the growth of two silver fir trees felled during forest site production research on Mt. Goc, located in Central Serbia, have been analyzed. Both trees showed significant differences in their growth dynamics over long periods as results of micro-site and micro-stand effects (primarily ambient light regime). The common growth characteristic of the two trees, a 450-year-old tree as the main study object (labeled Tree A) and a 270-year-old Tree B is a long stagnation stage. For Tree A the latent phase, with small interruptions, lasted 410 years; one phase lasted 330 years in continuity, which is the longest period of silver fir stagnation recorded in Europe. Tree B showed a long-lasting stagnation stage that lasted 170 years. The long stagnation stage of Tree A, characterized by an average diameter increment of 1.4 mm/year (average growth ring width of 0.7 mm) and an average height increment of 0.08 m/year, shows the extraordinary silver fir capacity for physiological survival in complete shade. This study adds to the existing knowledge of the shade tolerance of the silver fir. Therefore, the silver fir belongs to the group of extremely shade-tolerant tree species. This characteristic makes silver fir an irreplaceable tree species in the selection forest structure. It offers a wide range of silvicultural flexibility in the management of these forests, and is applicable to silver fir selection Serbia?s forests.

Phenotypic evolution of an Atlantic Forest passerine (Xiphorhynchus fuscus): biogeographic and systematic implications

We studied the phenotypic variation of the Atlantic Forest passerine Xiphorhynchus fuscus (Aves: Dendrocolaptidae) with the broad aim of addressing whether the history and type of forest affected the evolution of endemic taxa. We also tested whether the different subspecies and genetic lineages of X. fuscus could be considered full species. We collected plumage and body size measurements and, in combination with genetic data, used multivariate tests to evaluate the working hypotheses. Our results, combined with previous biogeographic analyses, indicate that vicariant events have been important determinants in the evolution of phenotypic characters of X. fuscus, once genetic isolation was complete. Our analysis also suggests that forest heterogeneity and ecotones are important factors in the early evolution of Atlantic Forest taxa, perhaps via divergent selection. Forest instability during the Pleistocene was critical in the evolution of phenotypic traits. We confirm that the subspecies atlanticus should be considered a full species. Other lineages or populations are also phenotypically differentiated but we do not suggest considering them as full species. They share high levels of gene flow and are part of a continuous latitudinal cline of phenotypic variation. Our study suggests that not all the historic events in the Atlantic Forest that affected the evolution of genetic lineages also influenced the evolution of phenotypic characters in the same direction and intensity. Undoubtedly, natural selection played a major role in the evolution of Atlantic Forest organisms.

Crown competition in the selection forests with the different tree species composition

The presented paper is oriented on the analysis of interspecific crown competition within the middle and upper layer of the selection forest. The research was conducted in the Norway spruce and silver fir dominated selection forest (demonstration object Donovaly-Mistríky) and in the common beech dominated selection forest in the territory of School Forestry Enterprise of the Technical University in Zvolen, Slovakia. We intended to evaluate the species specific crown-stem relation through the tightness of correlation between the crown volume and the stem volume. Our research confirmed the obvious effect of crown capacity on the production of stem biomass in the selection forest. The analysis revealed significant differences between coniferous and broadleaved species. However the low correlation for both middle and upper layers did not exceed r2 = 0.46 for common beech, the high significant correlations were for spruce and fir (r2 = 0.82 and 0.78, respectively). There were also significant differences between separated canopy layers. In the middle layer, the crown-stem correlations were lower than in the upper layer, what points out the obvious spatial competitiveness in the middle canopy layer, despite the relatively autonomous position of tree crowns within the canopy.

Application and limitations of growth models for silvicultural purposes in heterogeneously structured forest in Sweden

The paper addresses the problem of estimating future stand development in heterogeneously structured forests in Sweden; specifically, multi-layered spruce stands and mature pine stands with advanced spruce undergrowth. We first introduce various supporting concepts and models with their empirical databases, model validation and constraints. Secondly, Swedish single-tree growth functions designed for more heterogeneously structured forest are tested using data from inventory plots, a thinning experiment in an uneven-aged forest stand, and yield plots in pristine forest. Future growth of a managed, multi-layered forest was simulated and is compared with other selected functions. Simulation results, expected errors and time constraints are discussed. For most models, projected stand basal area growth deviated 10–20% from the observed growth in individual stands. In single stands, the deviation ranged from 0 to 60%. Validation periods were often 5–15 years, sometimes even more than 30 years. For Swedish single-tree basal area growth functions, on average, a 5% overestimate was found for heterogeneously structured forest across Sweden. Observed growth in a boreal single-tree selection forest was underestimated by 12.5% fifteen years after thinning from above.

Beech (Fagus sylvatica L.) forests of a selection structure in the Bieszczady Mountains (southeastern Poland)

The characteristics of two beech (Fagus sylvatica L.) stands are presented in this paper. One, the Tarnicki stand, situated in the Bieszczadzki National Park, represents the growing up stage and selection phase of a forest of primeval character. The other one, the Otryt stand, is situated in managed forests of the Lutowiska Forest District. In each stand two sample plots were established. The distribution of the number of trees in each sample plot agreed with de Liocourt sequence and Meyer curve. Both stands were characterized by the structure of many generations. The Otryt stand, with respective volumes of 238 and 324 m³/hain two sample plots, was characterized by a lack of large diameter trees and a high percent of trees of the smallest diameters, while the Tarnicki stand, with volumes of 442 and 517 m³/ha, was characterized by the presence of large diameter trees (d_1.3 ≥ 72 cm). The phase of the selection forest in the Tarnicki stand is of temporary character because, due to natural processes, a two-storied structure may develop there, and with time, a one-storied structure in the optimal stage. In the Otryt stand, representing a managed forest, the maintenance of the selection structure may be expected due to selection cuttings. It has to be acknowledged that managed stands of characteristics similar to those presented in this paper makes it possible to carry out selection cutting, especially in the protection zone surrounding the Bieszczadzki National Park.