The negative influence of timber harvesting on the forest environment is reflected through damage to the residual trees, regeneration, and forest soil. Considering that skidding, a popular extraction ...method, can cause substantial and severe damage to the remaining stand, the aim of this research was to determine damage to residual trees during skidding by an LKT 81T cable skidder, including oxen bunching. The research was conducted in eastern Bosnia and Herzegovina, in an uneven-aged mixed fir (Abies alba Mill.) and spruce (Picea abies L.) forest with pine (Pinus sylvestris L.) on limestone soils. Tree felling was conducted using a Husqvarna 372 XP chainsaw. Extraction operations caused damage to 6.31% of the residual trees in the stand. The most damage was “removed bark” (65.34%) and occurred on the lower parts of the tree, the butt end (55.11%) and root collar (32.39%). The average size of the damage was 197.08 cm2. A statistically significant correlation was found between the damage position and the diameter at the breast height (p < 0.05) and the damage position and damage size (p < 0.01) by Spearman correlation analysis. The conducted analysis by the chi-squared test showed that there is a statistically significant difference in the proportion of damage for trees with different distances to the nearest skid road (p = 0.0487), but the share of damaged trees did not decrease by increasing the distance from the skid road.
Background and Purpose: Bark thickness and its share in the volume of roundwood are the most important characteristics of the bark, particularly in the process of timber harvesting, and during ...scaling of processed logs. Therefore it is very important to have at disposal relatively accurate data regarding these characteristics of bark for particular tree species. The main goal of this paper is to investigate the thickness of the bark and its share in the volume of roundwood of Norway spruce.
Materials and Methods: The research was carried out in the area of the Canton 10 of the Federation of Bosnia and Herzegovina and it encompassed 393 trees of Norway spruce from 10 cm to 115 cm of thickness at breast height. Measuring of the mean diameter and double thickness of bark was conducted by section method. In total, 4,647 diameters and bark thicknesses were measured in different relative lengths of stems or in average 10.6 measurements per one stem.
Results: As an optimal model for the evaluation of double thickness of the bark of Norway spruce depending on mean diameter of roundwood the function with designated determination coefficient of 0.7142 was selected. The obtained results have confirmed the previously defined relations of investigate characteristics, which are as following: a) with the increase of mean diameter of roundwood (section) double bark thickness is increased from 9.26 mm (thickness class 12.5 cm) to 31.65 mm (thickness class 92.5 cm); b) with the increase of mean diameter of roundwood the share of bark in its volume decreased from 14.26% (thickness class 12.5 cm) to 6.73% (thickness class 92.5 cm).
Conclusions: By the actual method of estimating bark thickness or the share of bark in the volume of roundwood of Norway spruce in the forestry of the Federation of Bosnia and Herzegovina a significant error was created which increases with the increase of mean diameter. The obtained results point to the necessity of investigation of these bark characteristics in Bosnia and Herzegovina and represent an inevitable starting point for making adequate tables of bark thickness and its percentage share in the volume of roundwood of Norway spruce.
U radu su korišteni podaci izmjere 377 modelnih stabala smreke koja su mjerena u oborenom stanju na širem području unutar državnih raznodobnih sastojina u Kantonu 10 (Hercegbosanski Kanton). Za ...određivanje volumena krupnog drveta stabala primijenjena je metoda sekcioniranja sa sekcijama nejednakih apsolutnih dužina (najčešće od 1 – 2 m). Za izravnanje veličina volumena krupnog drveta od prsnog promjera i visine stabala primijenjena je metoda višestruke regresijske analize. Za procjenu parametara korištenih funkcija, testiranje značajnosti njihovih razlika te provođenje raznih transformacija, kao softversko rješenje korišteni su
StatGraphics Centurion
XVII. i
Statistica 8.0.
U cilju izbora „najboljeg“ modela za procjenu volumena krupnog drveta testiran je veći broj poznatih dendrometrijskih dvoparametarskih volumnih funkcija. Kvaliteta izjednačenja i prikladnost testiranih modela ocjenjivani su na bazi utvrđenih veličina osnovnih statističkih pokazatelja za karakteriziranje jačine korelacijskih veza. Najbolje ocjene parametara pokazao je model
V7=a0+a1d1,3+a2h+a3d1,3h+a4d1,32+a5 d1,32h
uz utvrđeni koeficijent determinacije:
R2 = 0,99
i veličinu standardne greške regresije
Sey=0,24 m3
. Testirajući značajnost razlika između stvarnih volumena stabala iz uzorka i volumena tih istih stabala utvrđenih primjenom odabranog regresijskog modela, utvrđen je prosječni postotak odstupanja od 0,44%. To znači da su u prosjeku za 0,44% niži volumeni u odnosu na stvarne volumene na uzorku od 377 stabala smreke, što ukazuje da je ovaj regresijski model upotrebljiv za primjenu u praktičnom radu, jer je taj prosječni postotak manji od 1%.
For assessment of growing stock in B&H forestry praxis as scientific baseline we are using volume tables and tariffs (Drinići dr. 1990). Having in mind the fact that these are constructed based on volume coefficients of the trees taken from German tree volume tables, which originate from single-age assortments, it is justified to suspect that by applying these tables one will get certain differences in quantity of large wood mass related to the actual status of those volumes. It is known that trees of the same tree species coming from single-age assortments are more full-bodied because they have larger volume coefficients compared to the trees of the same species from variable aged and selection forest assortments. That is why the objective of this research is to find “the best” regression model for levelling of volume of large wood of spruce, as dependent variable depending on diameter at breast height and tree height, as independent variables. To achieve this objective we have selected 377 model trees of spruce that were measured in felled condition on wider area of state owned variable aged assortments in Canton 10 (Livno Canton). To determine volume of large wood of trees we applied section method with sections of uneven absolute lengths (most often from 1 – 2 m). For levelling of volumes of large wood depending on diameter at breast height and tree height we applied method of multi-regression analysis. Quality of levelling and appropriateness of tested models was evaluated on the basis of determined values of basic statistical indicators for characterisation of the strength of correlation connections. The best values of the parameters showed model:
V7=a0+a1d1,3+a2h+a3d1,3h+a4d1,32+a5 d1,32h
with determined determination coefficient:
R2 = 0,99
and size of standard regression error:
Sey=0,245 m3
. By testing significance of differences between actual/real tree volumes from the sample and volume of those trees determined by application of selected regression model by using
t
-test of pairs, no statistically significant differences were recorded. Average percentage of deviation was -0.44%. That means that in average we get 0.44% lower volumes comparing to the actual volumes in the sample of 377 spruce trees which shows that this regression model is usable for application in practice, because that average percentage is less than 1%. Statistically significant differences were recorded between volumes of trees of selected regression model and volume tables and models of other authors (Stojanović i dr. 1978; Banković i dr. 2003; Špiranec, 1976.). Those deviations vary in the range from 2.53% up to 22.7%. The largest deviations were determined exactly in model that is used in B&H (Stojanović i dr. 1978) and are in amount of 22.7% while the lower deviations were determined for volumes estimated by using model created for spruce trees from Sub-Alpine belt for area of Kopaonik (Banković i dr. 2003) and those amount to 2.53%.
In the unthinned triplets of monospecific and mixed stands of Scots pine and European beech throughout Europe, we found that (a) gross stem volume growth was higher in mixed compared to monospecific ...stands. Nonetheless, net stem volume growth hardly differed, (b) stand density was higher in mixed stands, but the alien-thinning accelerated, (c) gross-overyielding increased in mixed stands with water supply, net-overyielding decreased. Thus, the stem volume dropout fraction (hatched) was higher on moist sites (for explanation of technical terms see Box 1)
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•The gross growth of mixed stands was higher, but net growth was lower compared to monocultures.•Mortality, natural thinning and volume dropout were higher in mixed stands.•In the mixture, the dropout of pine was mainly responsible for the reduction from gross to net growth, and a demixing in terms of mixing proportion and spatial segregation.•The stem volume dropout increased as water supply increased.•Thinning may utilize the gross overyielding of mixed stands and counteract the demixing.
Many studies show that mixed species stands can have higher gross growth, or so-called overyielding, compared with monocultures. However, much less is known about mortality in mixed stands. Knowledge is lacking, for example, of how much of the gross growth is retained in the standing stock and how much is lost due to mortality. Here, we addressed this knowledge gap of mixed stand dynamics by evaluating 23 middle-aged, unthinned triplets of monospecific and mixed plots of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) repeatedly surveyed over 6–8 years throughout Europe. For explanation of technical terms in this abstract see Box 1.
First, mixed stands produced more gross growth (+10%) but less net growth (−28%) compared with the weighted mean growth of monospecific stands. In monospecific stands, 73% of the gross growth was accumulated in the standing stock, whereas only 48% was accumulated in mixed stands. The gross overyielding of pine (2%) was lower than that of beech (18%). However, the net overyielding of beech was still 10%, whereas low growth and dropout of pine caused a substantial reduction from gross to net growth.
Second, the mortality rates, the self- and alien-thinning strength, and the stem volume dropout were higher in mixed stands than monospecific stands. The main reason was the lower survival of pine, whereas beech persisted more similarly in mixed compared with monospecific stands.
Third, we found a 10% higher stand density in mixed stands compared with monospecific stands at the first survey. This superiority decreased to 5% in the second survey.
Fourth, the mixing proportion of Scots pine decreased from 46% to 44% between the first and second survey. The more than doubling of the segregation index (S) calculated by Pielou index (S increased from 0.2 to 0.5), indicated a strong tendency towards demixing due to pine.
Fifth, we showed that with increasing water supply the dropout fraction of the gross growth in the mixture slightly decreased for pine, strongly increased for beech, and also increased for the stand as a whole.
We discuss how the reduction of inter-specific competition by thinning may enable a continuous benefit of diversity and overyielding of mixed compared with monospecific stands of Scots pine and European beech.
In Europe, mixed mountain forests, primarily comprised of Norway spruce (Picea abies (L.) Karst.), silver fir (Abies alba Mill.), and European beech (Fagus sylvatica L.), cover about 10 × 10
6
ha at ...elevations between ∼600 and 1600 m a.s.l. These forests provide invaluable ecosystem services. However, the growth of these forests and the competition among their main species are expected to be strongly affected by climate warming. In this study, we analyzed the growth development of spruce, fir, and beech in moist mixed mountain forests in Europe over the last 300 years. Based on tree-ring analyses on long-term observational plots, we found for all three species (i) a nondecelerating, linear diameter growth trend spanning more than 300 years; (ii) increased growth levels and trends, the latter being particularly pronounced for fir and beech; and (iii) an elevation-dependent change of fir and beech growth. Whereas in the past, the growth was highest at lower elevations, today’s growth is superior at higher elevations. This spatiotemporal pattern indicates significant changes in the growth and interspecific competition at the expense of spruce in mixed mountain forests. We discuss possible causes, consequences, and silvicultural implications of these distinct growth changes in mixed mountain forests.
•Species size distribution dynamics in mixed forests were explored using a matrix model.•Warming modifies species dynamics of mixed mountain spruce-fir-beech forests.•Warming positively effects stand ...basal area of fir but negatively effects beech.•Increasing temperature favors the size-dominance of fir over spruce and beech.•Size-dominant species identity influences stand basal area in spruce-fir-beech forests.
Forest composed of Picea abiesL., Abies alba Mill. and Fagus sylvatica L. cover a large area in the European mountain regions and have a high ecological and socio-economic importance as they supply many ecosystems services. Because of climate change, these forests are exposed to warming, and this effect increases with elevation, which may impact their delivery of goods and services. Previous studies did not find significant changes in the overall productivity of these species over the last 30 years, but they observed changes in species competitiveness at the species and tree levels.
In this study, we aimed to link previous results on tree, species and stand level growth in spruce-fir-beech mixed mountain forests by analysing species size distribution dynamics under different climate conditions and their effect on stand growth. We developed a matrix model based on data from 76 long-term experimental plots distributed throughout Europe. We used the change in stand basal area to explore whether temperature modifies species size dominances and proportions, whether the temperature effects on changes in species basal area depend on species size dominance, and whether the effect of species size dominance on changes in the stand basal area varies with temperature.
Our results showed that annual mean temperature is an important climatic driver of species dynamics in spruce-fir-beech mixed mountain forests, such that stand basal area growth was favored by higher temperatures, particularly due to positive responses of silver fir which were greater than negative effects of temperature on European beech. The high temperatures also favored the size-dominance of silver fir, while European beech tended to have smaller diameters, independent of the temperature. We also found that the identity of the size-dominant species also influenced changes in stand basal area, with the highest or the lowest changes when Norway spruce and European beech were the size-dominant species, respectively. Silver fir was less influenced by the identity of the size-dominant species than by temperature.
Therefore, although mixed mountain forests of spruce-fir-beech were found to be resilient systems in terms of stand productivity, we conclude that increasing temperatures may modify species dynamics and consequently silvicultural interventions will be needed to control species proportions and dominances.
Abstract
Mixed mountain forests of European beech (Fagus sylvatica L.), Norway spruce (Picea abies (L.) Karst), and silver fir (Abies alba Mill.) cover a total area of more than 10 million hectares ...in Europe. Due to altitudinal zoning, these forests are particularly vulnerable to climate change. However, as little is known about the long-term development of the productivity and the adaptation and mitigation potential of these forest systems in Europe, reliable information on productivity is required for sustainable forest management. Using generalized additive mixed models this study investigated 60 long-term experimental plots and provides information about the productivity of mixed mountain forests across a variety of European mountain areas in a standardized way for the first time. The average periodic annual volume increment (PAI) of these forests amounts to 9.3 m3ha−1y−1. Despite a significant increase in annual mean temperature the PAI has not changed significantly over the last 30 years. However, at the species level, we found significant changes in the growth dynamics. While beech had a PAI of 8.2 m3ha−1y−1 over the entire period (1980–2010), the PAI of spruce dropped significantly from 14.2 to 10.8 m3ha−1y−1, and the PAI of fir rose significantly from 7.2 to 11.3 m3ha−1y−1. Consequently, we observed stable stand volume increments in relation to climate change.
•Inter-specific synchrony is always lower than intra-specific synchrony.•Species asynchrony in growth occurs at short- and mid- to long-term.•Synchrony in growth response to inter-annual variation ...increases with site elevation.•There is an increasing trend in synchrony during the last century at lower elevations.•Temporal changes of synchrony are species-specific and linked to climate warming.
Spruce-fir-beech mixed forests cover a large area in European mountain regions, with high ecological and socio-economic importance. As elevation-zone systems they are highly affected by climate change, which is modifying species growth patterns and productivity shifts among species. The extent to which associated tree species can access resources and grow asynchronously may affect their resistance and persistence under climate change. Intra-specific synchrony in annual tree growth is a good indicator of species specific dependence on environmental conditions variability. However, little attention has been paid to explore the role of the inter-specific growth asynchrony in the adaptation of mixed forests to climate change. Here we used a database of 1790 tree-ring series collected from 28 experimental plots in spruce-fir-beech mixed forests across Europe to explore how spatio-temporal patterns of the intra- and inter-specific growth synchrony relate to climate variation during the past century. We further examined whether synchrony in growth response to inter-annual environmental fluctuations depended on site conditions. We found that the inter-specific growth synchrony was always lower than the intra-specific synchrony, for both high (inter-annual fluctuations) and low frequency (mid- to long-term) growth variation, suggesting between species niche complementarity at both temporal levels. Intra- and inter-specific synchronies in inter-annual growth fluctuations significantly changed along elevation, being greater at higher elevations. Moreover, the climate warming likely induced temporal changes in synchrony, but the effect varied along the elevation gradient. The synchrony strongly intensified at lower elevations likely due to climate warming and drying conditions. Our results suggest that intra- and inter-specific growth synchrony can be used as an indicator of temporal niche complementarity among species. We conclude that spruce-fir-beech mixtures should be preferred against mono-specific forests to buffer climate change impacts in mountain regions.
•The study based on 90 mature Scots pine stands along a productivity gradient across Europe.•Growth partitioning became more asymmetric and structuring with increasing site quality.•Mortality ...eliminated predominantly small trees with increasing site quality.•We found the highest size variation on poor sites and the lowest on rich sites.•As a result stand structure became more homogeneous with increasing site quality.
Heterogeneity of structure can increase mechanical stability, stress resistance and resilience, biodiversity and many other functions and services of forest stands. That is why many silvicultural measures aim at enhancing structural diversity. However, the effectiveness and potential of structuring may depend on the site conditions. Here, we revealed how the stand structure is determined by site quality and results from site-dependent partitioning of growth and mortality among the trees. We based our study on 90 mature, even-aged, fully stocked monocultures of Scots pine (Pinus sylvestris L.) sampled in 21 countries along a productivity gradient across Europe. A mini-simulation study further analyzed the site-dependency of the interplay between growth and mortality and the resulting stand structure. The overarching hypothesis was that the stand structure changes with site quality and results from the site-dependent asymmetry of competition and mortality.
First, we show that Scots pine stands structure across Europe become more homogeneous with increasing site quality. The coefficient of variation and Gini coefficient of stem diameter and tree height continuously decreased, whereas Stand Density Index and stand basal area increased with site index.
Second, we reveal a site-dependency of the growth distribution among the trees and the mortality. With increasing site index, the asymmetry of both competition and growth distribution increased and suggested, at first glance, an increase in stand heterogeneity. However, with increasing site index, mortality eliminates mainly small instead of all-sized trees, cancels the size variation and reduces the structural heterogeneity.
Third, we modelled the site-dependent interplay between growth partitioning and mortality. By scenario runs for different site conditions, we can show how the site-dependent structure at the stand level emerges from the asymmetric competition and mortality at the tree level and how the interplay changes with increasing site quality across Europe.
Our most interesting finding was that the growth partitioning became more asymmetric and structuring with increasing site quality, but that the mortality eliminated predominantly small trees, reduced their size variation and thus reversed the impact of site quality on the structure. Finally, the reverse effects of mode of growth partitioning and mortality on the stand structure resulted in the highest size variation on poor sites and decreased structural heterogeneity with increasing site quality. Since our results indicate where heterogeneous structures need silviculture interventions and where they emerge naturally, we conclude that these findings may improve system understanding and modelling and guide forest management aiming at structurally rich forests.
S obzirom na sve veći nedostatak šumskih radnika i zbog toga na otežano ostvarivanje plana sječe neizbježno je da šumarska poduzeća razmatraju, među ostalim, mogućnosti uporabe suvremenih strojeva u ...tehnološkom procesu sječe stabala i izrade drvnih sortimenata i forvardera u fazi izvoženja drva. Primjena te tehnologije rada u šumarstvu BiH nameće i potrebu istraživanja njezina utjecaja na šumski ekosustav. Stoga se u ovom radu prikazuju rezultati oštećivanja preostalih stabala u sastojini pri primjeni djelomično i potpuno mehaniziranoga sustava pridobivanja drva. Istraživanje je provedeno na području kojim gospodari Šumsko privredno društvo »Unsko-sanske šume« d.o.o. Bosanska Krupa, u Podružnici šumarija Ključ. U dva šumska odjela postavljena je mreža dimenzija 200 × 200 m i ogledne plohe u obliku kruga polumjera 25 m i površine 0,19625 ha. Analizirana su sva oštećena preostala stabla na oglednim plohama prsnoga promjera iznad 5 cm i snimljeni ovi podaci: vrsta drveća, prsni promjer, vrsta oštećenja, mjesto oštećenja i veličina oštećenja. U jednom analiziranom šumskom odjelu primijenjeni su ručno-strojna sječa i izrada motornim pilama te forvarder, skider s vitlom i samarica za privlačenje drva – djelomično mehanizirani sustav pridobivanja drva. U drugom šumskom odjelu primijenjen je harvester za sječu stabala i izradu šumskih drvnih sortimenata ili samo za izradu šumskih drvnih sortimenata od stabala posječenih motornom pilom (udaljenija stabla od puta i stabla velikih promjera), te forvarder za privlačenje (izvoženje) drva – uvjetno određeno kao potpuno mehanizirani sustav pridobivanja drva (sustav harvester i forvarder). Primjena harvestera i forvardera u tehnološkom procesu pridobivanja drva uzrokovala je oštećenja na 13,21 % preostalih stabala u analiziranom šumskom odjelu koji obuhvaća visoke šume s prirodnom obnovom i šumske kulture. Analiza prikupljenih podataka pokazala je da ne postoje statistički značajne razlike u udjelu oštećenih stabala tijekom primjene promatranih sustava pridobivanja drva u visokim šumama s prirodnom obnovom (χ2 p = 0,1005). Najčešća vrsta oštećenja u oba slučaja je »oguljena kora i oštećeno drvo«. Najveći je broj oštećenja zabilježen na žilištu i pridanku kod djelomično mehaniziranoga sustava pridobivanja drva, odnosno na deblu i pridanku kod potpuno mehaniziranoga sustava pridobivanja drva. Radi dobivanja pouzdanijih rezultata potrebno je nastaviti sa sličnim istraživanjima kojima bi se obuhvatio veći broj utjecajnih čimbenika.
Damage to residual trees during the use of semi-mechanised and fully mechanised harvesting systems is a critical factor in assessing their ecological impact on the forest ecosystem. Given the increasing trend of mechanization in forest harvesting operations in Bosnia and Herzegovina, this study conducted a comparative analysis of damage to residual trees when using semi-mechanised harvesting system (chainsaw and skidder) and fully mechanised harvesting system (harvester and forwarder). The research was carried out in the area managed by the Forest Management Company »Unsko-sanske šume« Ltd Bosanska Krupa. In two forest compartments, a systematic grid of 200 x 200 meters was established, along with circular sample plots with a radius of 25 meters (0.19625 hectares). All damaged residual trees on the sample plots with a diameter at breast height above 5 cm were analysed, and data were recorded in terms of tree species, diameter at breast height, type of damage, tree position damage and size of damage. The application of fully mechanised harvesting system resulted in damage to 13.21% of the residual trees in the analysed forest compartment, which consists of high forests with natural regeneration and forest cultures. On the other hand, the application of semi-mechanised harvesting system caused damage to 22.34% of the residual trees in high forests with natural regeneration. The analysis of the collected data revealed no statistically significant differences in the proportion of damaged trees when comparing two harvesting systems in high forests with natural regeneration (χ2 p = 0.1005). »Removed bark and damaged wood« is the most common type of damage in both cases. The majority of the damage occurred on the root collar and butt end with semi-mechanised harvesting system, and on the butt end and stem with fully mechanised harvesting systems. To obtain more reliable results, further research encompassing a broader range of influential factors is necessary.
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