Michal Bošeľa

Possible causes of the recent rapid increase in the radial increment of silver fir in the Western Carpathians

Silver fir is one of the most productive and ecologically valuable native European tree species, however, it has been experiencing decline which has periodically occurred over its natural range. This paper aims to investigate the recent climate-growth relationships of silver fir (Abies alba Mill.) and its temporal change along the course of its life. Long-term tree-ring databases, as well as records on climate, atmospheric SO2, NO3 and acid concentrations from four different regions in the Western Carpathians were used. The results provide clear evidence of significant increase of silver firs radial increment over the entire Western Carpathian area since 1970-1980. The results indicated that the most probable factors behind the rapid recovery of tree radial increment were reductions in emissions of NO3 and SO2, alongside a significant increase in mean June, July and April temperatures.

MODELLING EFFECTS OF WEATHER CONDITION ON SEASONAL DYNAMICS OF THE STEM CIRCUMFERENCE INCREMENT IN A MIXED STAND OF NORWAY SPRUCE AND EUROPEAN BEECH

Abstract This study was aimed at modelling seasonal variation of stem circumference increments in a mixed stand composed of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.). Moreover, we focused on the quantification of the main climatic factors governing the increments. The measurements were performed at a site established at about 970 m a.s.l. from the locality of Vrchslatina (Central Slovakia). Data was collected from 20 European beech trees and 20 Norway spruce trees, from 2009 to 2012. The increments (measured at 130 cm above ground level) were recorded circa biweekly using manual band dendrometers. Lognormal function was used for the modelling of the seasonal trend of the increments. Hourly-based records of climatic variables such as air temperature, precipitation, and derived vapour pressure deficit were used for the modelling. The effect of climatic parameters on the seasonal variations of the increments was tested by including them directly into the lognormal function. The results suggest that while the sum of precipitation was a better predicting factor for spruce, the mean temperature was the better predictor for beech. In addition, both temperature and vapour pressure deficits also had an effect on the increments of spruce, but these parameters did not contribute to the explanation of the variability of increments for beech. Overall, the variability clarified by the final model was 72% for spruce and 78% for beech. At the same time, climatic parameters as a part of the model helped to explain 10% of the variability for the spruce (precipitations) and 3% of the variability for the beech (temperature). We also found lower variability in the increments of beech compared to spruce. This suggests that for the specific site conditions spruce are more sensitive to environmental conditions than beech Resumé Štúdia bola zameraná na modelovanie sezónnej dynamiky prírastku na obvode kmeňov stromov v zmiešanom poraste smreka obyčajného a buka lesného. Okrem toho sme sa zamerali na kvantifikáciu hlavných klimatických faktorov ovplyvňujúcich prírastok. Meranie bolo vykonané na lokalite Vrchslatina (stredné Slovensko) v nadmorskej výške 970 m n. m. Prírastky boli merané na 20 stromoch buka a 20 stromoch smreka od roku 2009 do roku 2012. Prírastok (meraný na 130 cm od úrovne terénu) bol meraný v intervale približne dva týždne pomocou manuálnych denrometrov. Lognormálna funkcia bola použitá pre modelovanie sezónneho prírastku. Záznamy o klimatických premenných, ako je teplota vzduchu, zrážky a deficit nasýtenia vodných pár boli získané z meteorologickej stanice umiest nenej priamo na lokalite. Vplyv meteorologických premenných bol testovaný ich zahrnutím priamo do lognormálnej funkcie opisujúcej sezónnu dynamiku prírastku a otestovaním odhadnutých parametrov rovníc. Výsledky ukazujú, že zrážky hrajú dôležitejšiu úlohu pre smrek, avšak teplota pre buk. Taktiež, teplota a VPD majú významný vplyv na prírastok smreka, avšak pri buku rastúcom v daných podmienkach sa ukázali ako nevýznamné. Celkovo, model vysvetlil 72 % variability prírastku smreka a 78 % buka (tab. 2). Meteorologické premenné vysvetlili 10 % variability prírastku smreka, no iba 3 % pri buku.

Indices of tree competition in dense spruces stand originated from natural regeneration

Abstract This paper aims to quantify relationships between the biometric parameters of young, 15-year old spruce stands at the Experimental Site Vrchslatina. In 2011, 40 spruce trees were selected to cover four classes of bio-sociological status (dominant, co-dominant, sub-dominant, and suppressed - 10 individuals each). The trees were measured for their height increments (by recording the distances between the successive whorls) and the increments of lateral branches at all whorls. The sample trees were then cut down and discs were taken from the stem base. In the laboratory, the discs were measured for the annual ring widths using WinDendro software. We focused on detailed analyses of the relationship between the bio-sociological status of the trees on the radial and height increments. Minor differences were found in the increments in the newest lateral whorls. The ratio between height increments and lateral branch increments was found to be higher in dominant trees (height increments is two times higher than the increments on the lateral branches). Conversely, the smallest ratio was found in suppressed trees (the ratio was around 1). The ratio between tree height and diameter at the stem base, as well as the ratio between height and radial increments, was the smallest for dominant and the highest for suppressed trees. Hence, relationships between height and diameter increments (both annual and cumulative) proved to reflect competition intensity among trees.

Evaluating similarity of radial increments around tree stem circumference of European beech and Norway spruce from Central Europe

Extracting cores from a tree using an increment borer has been standard practice in dendrochronological studies for a long time. Although empirical rules exist regarding how many samples to take and which methodology to apply, comparatively few studies provide quantification of the similarity of relative tree-ring-widths (TRW) around the stem circumference. The aim of this study was therefore to precisely measure the similarity of standardised TRWs around the stem circumference and to provide objective suggestions for optimal core sampling of Norway spruce (Picea abies Karst. [L.]) and European beech (Fagus sylvatica L.) growing in Central European temperate forests.A large sample of cross-sectional discs was used from Norway spruce and European beech trees growing on various slopes, at different altitudes and biogeographic regions across the Czech Republic and Slovakia. The similarity of TRWs measured in different coring directions was analysed by testing the relativized TRW around the trunk (rTRW). Comparison of rTRWs revealed no significant differences between coring directions, indicating that the relative increment was the same around the radius. The results also showed the high similarity between the rTRWs to be independent of both slope inclination and altitude. Moreover, the reconstruction of proportional tree diameters and basal areas backward in time from one core sample and one measurement of tree diameter (basal area) at the time of sample extraction is possible with reasonable precision.

Inter- and intra-annual dynamics of height increment in young beech and spruce stands in relation to tree size and weather conditions

Abstract We investigated the seasonal dynamics of height increment, as well as total annual height increment, in 2009-2013 on young stands of beech and spruce grown at the same site. The results showed that the inter-annual dynamics of basic stand characteristics, especially tree density, were more obvious in spruce than in beech stands. Much higher tree mortality in spruce was explained by a lower light intensity under the spruce stand canopy and higher tolerance of beech to shade. Large interspecific differences were also found in the timing of height increment. Specifically, the height increment of beech trees started earlier than those of spruce. Moreover, the terminal grew for longer in spruce (nearly 70 days) compared to beech (about 45 days). The comparisons between the courses of the height increment and the ambient factors suggested that global radiation played a principal role. In the beech stand, the maximum height increment rate occurred during the same days as the maximal global radiation in 2009 and 2011, while a decline of the height increment occurred simultaneously with a depression in global radiation in 2012. As for the spruce stand, its one-peak maxima in height increment were related to the maximum of global radiation in 2009 and in 2012. On the other hand, double-peak courses of height increment in 2010 and 2011 may have been related to sudden declines in global radiation. Interspecific differences in height increment timing might play a certain role in cases of unfavourable weather conditions, e.g. drought episodes in the middle part of the growing season when the height increment would be accomplished in beech but would still be ongoing in spruce. Abstrakt Počas rokov 2009-2013 sme sledovali sezónnu dynamiku výškového prírastku, ako aj celoročný výškový prírastok v bukových a smrekových mladinách rastúcich na totožnom stanovišti. Výsledky naznačili, že medziročné zmeny základných porastových charakteristík, a to najmä hustota porastu, boli výraznejšie v smrečine než v bučine. Omnoho vyššia stromová mortalita v smrečine sa vysvetlila nižšou intenzitou svetla pod korunovou vrstvou smrekov, resp. vyššou toleranciou buka na zatienenie. Veľké medzidruhové rozdiely sa zaznamenali v „načasovaní“ výškového prírastku. Konkrétne výškový prírastok bukov začal každoročne skôr ako výškový prírastok smrekov. Ďalej, terminál smrekov rástol dlhšie (približne 70 dní) v porovnaní s bukmi (45 dní). Porovnanie priebehov výškových prírastkov vzhľadom na prostredie naznačilo, že principiálny vplyv mala globálna radiácia. V bučine bola maximálna intenzita výškového prírastku počas dní s maximálnou úrovňou globálnej radiácia, a to v rokoch 2009 a 2011, zároveň pokles intenzity sa objavil simultánne s poklesom globálnej radiácie počas roku 2012. V smrečine intenzita výškového prírastku predstavovala jednovrcholovú krivku - s najvyššou intenzitou prírastku v dňoch maximálnych hodnôt globálnej radiácie počas 2009 a 2012. Na druhej strane sa zaznamenal dvojvrcholový výskyt maxím intenzity výškového prírastku smrekov v 2010 a 2011. Tento jav súvisel s dočasným poklesom globálnej radiácie v týchto rokoch. Medzidruhové rozdiely v načasovaní výškového prírastku môžu mať relevanciu v prípade výskytu nepriaznivých poveternostných podmienok. Napríklad pri epizódach sucha v polovici vegetačného obdobia, keďže výškový prírastok je vtedy už ukončený pri bukoch avšak na smrekoch ešte prebieha

Influence of selected factors on bark beetle outbreak dynamics in the Western Carpathians

Abstract In the period from 1992 to 2013, more than 3.8 million m3 of spruce wood from an area of 55 thousand ha of forests in the Kysuce region (Western Carpathians) was affected by bark beetles. This region has had the highest volume of salvage fellings in Slovakia. While before 1991, bark-beetle outbreak usually occurred after snow and wind disturbances, since 1992 they have occurred in the years with extremely warm and dry growing seasons and the years following them. These years were also characterised by high volumes of wood affected by honey fungus (Armillaria spp.), which only rarely took part in the calamities before 1992. Extreme deterioration of the situation occurred after 2003. In fragmented and sparse stands, the volume of wood damaged by wind increased. Artificial origin of spruce stands, their high occurrence, high age and even-agedness are likely pre-disposing factors of spruce forest decline. Bark beetles have become the most important factor of spruce decline. The most important factors driving the bark beetle attack on forest stands in the period 1973–2013 were the amount of unprocessed wood in the previous year; the amount of wood affected by honey fungus, precipitation total, and average temperature in the current growing season. Another important factor that complicated the situation was also the inferior quality of forest management.

Height-diameter models for mixed-species forests consisting of spruce, fir, and beech

Abstract Height-diameter models define the general relationship between the tree height and diameter at each growth stage of the forest stand. This paper presents generalized height-diameter models for mixed-species forest stands consisting of Norway spruce (Picea abies Karst.), Silver fir (Abies alba L.), and European beech (Fagus sylvatica L.) from Slovakia. The models were derived using two growth functions from the exponential family: the two-parameter Michailoff and three-parameter Korf functions. Generalized height-diameter functions must normally be constrained to pass through the mean stand diameter and height, and then the final growth model has only one or two parameters to be estimated. These “free” parameters are then expressed over the quadratic mean diameter, height and stand age and the final mathematical form of the model is obtained. The study material included 50 long-term experimental plots located in the Western Carpathians. The plots were established 40-50 years ago and have been repeatedly measured at 5 to 10-year intervals. The dataset includes 7,950 height measurements of spruce, 21,661 of fir and 5,794 of beech. As many as 9 regression models were derived for each species. Although the “goodness of fit” of all models showed that they were generally well suited for the data, the best results were obtained for silver fir. The coefficient of determination ranged from 0.946 to 0.948, RMSE (m) was in the interval 1.94-1.97 and the bias (m) was -0.031 to 0.063. Although slightly imprecise parameter estimation was established for spruce, the estimations of the regression parameters obtained for beech were quite less precise. The coefficient of determination for beech was 0.854-0.860, RMSE (m) 2.67-2.72, and the bias (m) ranged from -0.144 to -0.056. The majority of models using Korf’s formula produced slightly better estimations than Michailoff’s, and it proved immaterial which estimated parameter was fixed and which parameters were free

Contrasting development of declining and living larch-spruce stands after a disturbance event: A case study from the High Tatra Mts.

Abstract The decline of spruce stands caused by bark beetle outbreaks is a serious economic and ecological problem of forestry in Slovakia. In the preceding period, the decline affected mainly secondary spruce forests. Over the last decade, due to large bark-beetle outbreaks this problem has been observed also in natural spruce forests, even at high elevations. We dealt with this issue in a case study of short-term development of larch-spruce stands in the High Tatras (at a site called Štart). We compared the situation in the stand infested by bark beetles several years after the wind-throw in 2004 with the stand unaffected by bark beetles. We separately analysed the development of the mature (parent) stands and the regeneration. The results indicated that forest decline caused by bark beetles significantly depended on the stand structure (mainly tree species composition), which affected the period of stand disintegration. Mortality of spruce trees slowed down biomass accumulation (and thus carbon sequestration) in the forest ecosystem. In the new stand, pioneer tree species dominated (in the conditions of the High Tatras it is primarily rowan), although their share in the parent stand was negligible. The results showed different trends in the accumulation of below-ground and above-ground biomass in the declined and living stands. In the first years after the stand decline, rowan accumulated significantly more biomass than the main tree species, i.e. spruce. The reverse situation was under the surviving stand, where spruce trees accumulated more biomass than rowan. The different share of spruce and pioneer tree species, mainly rowan, affected the ratio between fixed (in woody parts of trees) and rotating (in foliage) carbon in the undergrowth. Forest die-back is a big source of carbon emissions from dead individuals, and the compensation of these losses in the form of carbon sequestration by future stands is a matter of several decades.

Aboveground Net Primary Production of tree cover at the post-disturbance area in the Tatra National Park, Slovakia

Abstract Large-scale disturbances under the conditions of Slovakia, caused especially by storm and bark beetle, bring dramatic decline in carbon budget of the country, besides other negative consequences. The largest disturbance in modern history of the Slovak forestry was the storm damage that occurred in November 2004. The Tatra National Park (TNP) was one of the most affected regions. Thus, in this territory, two transects (T1 – the Danielov dom site and T2 – near the Horný Smokovec village) were established to survey basic dendrometric properties of trees in young stands established after the disaster. The standing stock of aboveground biomass in tree cover for the spring and autumn 2014 was calculated using the recorded variables, i.e. tree height and diameter measured at the stem base, together with the region-specific allometric relations. Then, the Aboveground Net Primary Production (ANPP) in tree cover was estimated with respect to its components (stem, branches and foliage). ANPP was 315 g m−2 per year (Transect T1), and 391 g m−2 per year (Transect T2). The differences in the structure of ANPP, i.e. contribution of tree components, were found between transects T1 and T2. They were caused by the contrasting tree species composition, specifically the ratios between Norway spruce and broadleaved species. Broadleaves allocated more biomass production to foliage than spruce. This phenomenon together with higher turnover (once a year) of foliage caused that broadleaves manifest higher share of fast-cycling carbon in comparison to the amount of carbon sequestrated in woody parts (stem and branches). High variability of ANPP was found within the transects, i.e. among the plots (microsites). As for the representative estimation of the standing stock of aboveground part of tree cover as well as ANPP at the post-disturbance area in the TNP territory, the survey should be performed on a net of research plots. Only this approach enables reliable estimates of carbon amount sequestrated in woody parts, eventually carbon yearly absorbed by young forest stands.

Effect of different management on quality and value production of pure beech stands in Slovakia

Abstract Value production is one of the most important information for comparing different management strategies in forestry. Although the value production of forest stands is affected by various factors (stem and assortment quality, stem dimension, stem injury, price of assortments), thinning can be considered as one of the most important one. This paper aims at the evaluation of qualitative and value production in homogeneous beech stands, which were managed by two different thinning types for period of 45 to 55 years: (i) – heavy thinning from below (C grade according to the German forest research institutes released in 1902) and (ii) – Štefančík´s free-crown thinning. The third variant was control (iii) – subplot with no interventions. Silvicultural quality characteristics of the lower half of the stem were assessed using a 4-class scale (A – the best quality, D – the worst quality). Assortment structure (commercial quality) was estimated for each stem by an assortment model developed in the past. Nearly 3,000 individual trees aged from 83 to 105 years from 23 subplots established across the Slovakia territory were assessed. The highest volume of the best silvicultural quality of stems (A class) has been reached in forests where Štefančík´s free-crown thinning was applied (57 – 85%) while the lowest (22 – 56%) on subplots with no management. The proportion of two best commercial quality assortments (I + II) was highest in forests managed by heavy thinning from below (21 – 29%) and the lowest when no treatment was applied (7 – 19%). The highest value production (expressed in € ha−1) was reached in the forests treated by free-crown thinning. Results suggested the overall positive impact of thinning on the increase of value production in beech forests. Particularly, the free-crown thinning focusing on selection of best quality trees should be preferred as it leads, besides its sufficient value production, to a higher vertical differentiation of the beech forests.