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Open access

Tomáš Čihák, Tomáš Hlásny, Radka Stolariková, Monika Vejpustková and Róbert Marušák

Abstract

The Small-leaved lime (Tilia cordata Mill.) is currently not commercially important species, therefore the knowledge of biomass partitioning in a tree is rather incomplete. Moreover, lime biomass is estimated mostly using biomass functions designated for other species, without the knowledge of limits of such a use. For these reasons, we developed functions for the estimation of lime biomass in the aboveground woody parts. The functions were parameterized using 81 tree samples collected in two plots in the Czech Republic. In addition, we compared the biomass estimates produced by our functions with estimates produced by a function for beech, which have been obviously used as a surrogate for missing lime models in the Czech Republic and Slovakia.

On average, 78% of lime aboveground biomass was found to account for tree stem, 20% for branches and 2% for stump. Average biomass density was 374 kg m−3 and no significant differences between tree compartments were found. Accuracy of all models in terms of the Root Mean Square Error (RMSE) significantly differed between tree diameter classes; in case of total aboveground biomass, the RMSE was ca. 20% of the average biomass weight in a given class up to a diameter of 45 cm, and then it rose sharply. The RMSE was higher in case of compartments with variable dimensions, such as branches and stump. RMSE was slightly higher in case of estimates produced using a beech-specific function than using that developed in the current study (average RMSE 27.95 and 29.42%, respectively); at the same time, beech-specific function overestimated lime stem biomass by ca 12%. The almost equal RMSE implies the usability of both parameterisations for lime biomass estimation, though the correction of the mentioned overestimation should be applied.

Open access

Bohdan Konôpka, Jozef Pajtík, Michal Bošeľa, Tomáš Hlásny and Zuzana Sitková

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.

Open access

Jiří Trombik, Ivan Barka and Tomáš Hlásny

Abstract

Forest mortality critically affects stand structure and the quality of ecosystem services provided by forests. Spruce bark beetle (Ips typographus) generates rather complex infestation and mortality patterns, and implementation of such patterns in forest models is challenging. We present here the procedure, which allows to simulate the bark beetle-related tree mortality in the forest dynamics model Sibyla. We explored how sensitive various production and stand structure indicators are to tree mortality patterns, which can be generated by bark beetles. We compared the simulation outputs for three unmanaged forest stands with 40, 70 and 100% proportion of spruce as affected by the disturbance-related mortality that occurred in a random pattern and in a patchy pattern. The used tree species and age class-specific mortality rates were derived from the disturbance-related mortality records from Slovakia. The proposed algorithm was developed in the SQLite using the Python language, and the algorithm allowed us to define the degree of spatial clustering of dead trees ranging from a random distribution to a completely clustered distribution; a number of trees that died in either mode is set to remain equal. We found significant differences between the long-term developments of the three investigated forest stands, but we found very little effect of the tested mortality modes on stand increment, tree species composition and diversity, and tree size diversity. Hence, our hypothesis that the different pattern of dead trees emergence should affect the competitive interactions between trees and regeneration, and thus affect selected productivity and stand structure indicators was not confirmed.

Open access

Tomáš Hlásny, Dušan Kočický, Martin Maretta, Zuzana Sitková, Ivan Barka, Milan Konôpka and Helena Hlavatá

Abstract

Changes in land cover, including deforestation, can have significant effect on watershed hydrology. We used hydrological model with distributed parameters to evaluate the effect of simulated deforestation on water balance components in the watershed Ulička (97 km2, 84.3% forest cover) located in the eastern Slovakia. Under the current land cover, average interception accounted for 21.1% of the total precipitation during the calibration period 2001-2013. Most of the precipitation (77%) infiltrated into the soil profile, and less than half of this amount percolated into the ground water aquifer. The surface runoff accounted for 1.2% of the total precipitation only, while the interflow accounted for ca. 12%. The largest proportion of the precipitation contributed to the base flow (23%). Watershed`s deforestation induced significant decrease in the interception and evapotranspiration (by 76% and 12%, respectively). At the same time, total runoff, surface runoff, interflow and base flow increased by 20.4, 38.8, 9.0 and 25.5%, respectively. Daily discharge increased by 20%. The deforestation significantly increased peak discharge induced by a simulated extreme precipitation event with the recurrence interval of 100 years. In the deforested watershed, the peak discharge was higher by 58% as compared with the current land cover. Peak discharge occurred in 432 minutes with the current land cover and in 378 minutes with deforestation, after the precipitation event had started. The presented assessment emphasized the risk of adverse effect of excessive deforestation on watershed hydrology. At the same time, the developed model allows testing the effect of other land cover scenarios, and thus supports management in the investigated watershed.

Open access

Ivan Barka, Petr Lukeš, Tomáš Bucha, Tomáš Hlásny, Radim Strejček, Marek Mlčoušek and Štěpán Křístek

Abstract

Aim of this paper is to present the remote sensing-based systems of forest health assessment in the Czech Republic and Slovakia, and to analyse both their strengths and weaknesses. Nationwide assessment of forest health in the Czech Republic is based on the interpretation of Sentinel–2 satellite data using novel approaches for cloud-free image synthesis based on all available satellite observations. A predictive statistical model to yield time series of leaf area index (LAI) from satellite observations is developed above extensive in-situ data, including LAI and forest defoliation assessment. Forest health is evaluated for each pixel from yearly changes of forest LAI, while the country-wise assessment of the health status is performed at the cadastral level. Methodology developed for Slovakia is based on a two-phase regression sampling. The first phase of the procedure provides an initial fast estimate of forest damage using only satellite observations (visible and infrared channels from Landsat or Sentinel–2 systems). The second phase refines the result of the first phase using data from a ground damage assessment (site-level defoliation from ICP Forests database). Resulting forest health assessment over the whole forest area is presented in 10 defoliation classes. The Czech Republic shows 1.6% of heavily damaged forests, 12.5% of damaged forests, 79.2% of forests with stable conditions, 6.3% of regenerated forests and 0.4% of strongly regenerated forests. In Slovakia, the total share of damaged stands (i. e. with defoliation higher than 40%) increased from 6 – 8% in 2003 – 2011 to 13 – 15% in 2012 – 2017. Both methodologies conduct nationwide assessment of forest health status in a fast and automatized way with high accuracy and minimal costs. The weaknesses are, for example, a high computational demands for production cloud free mosaics, inability to identify initial phases of forest health decline, exclusion of stands older than 80 years (in the Czech Republic) and inability to differentiate between harvested and severely damaged stands (in Slovakia). Finally, the paper outlines future development of both methodologies.

Open access

Tomáš Hlásny, Csaba Mátyás, Rupert Seidl, Ladislav Kulla, Katarína Merganičová, Jiří Trombik, Laura Dobor, Zoltán Barcza and Bohdan Konôpka

Abstract

The paper presents information on the projected drought exposure of Central Europe, describes the anticipated dynamics of the regional forests, and identifies measures facilitating the adaptation of forests to climate change-induced drought risk. On the basis of an ensemble of climate change scenarios we expect substantial drying in southern Slovakia and Hungary, while such trends were found to be less pronounced for the Czech Republic and Austria. In response to these climate trajectories, a change in species composition towards a higher share of drought tolerant species as well as the use of drought resistant provenances are identified as paramount actions in forest adaptation in the region. Adaptation to aggravating climate change may need to use artificial regeneration to enrich local gene pools and increase the drought tolerance of stands. Increasing risks from pests, pathogens and other disturbances are expected as a result of more frequent and severe droughts, underlining the need to put a stronger focus on risk management principles rather than on indicators of productivity in silviculture and forest planning. A consolidation of disturbance monitoring systems and a broader use of pest dynamics and hazard rating models are paramount tools to facilitate this adaptation process in forest management. The effectiveness of all the suggested measures needs to be controlled by efficient forest monitoring systems, the consolidation of which seems to be a timely task. Systematic and long-term implementation of the presented measures should increase forest stability and resilience, and further secure the sustainable provision of ecosystem services under climate change.

Open access

Zuzana Sitková, Paulína Nalevanková, Katarína Střelcová, Peter Fleischer Jr., Marek Ježík, Roman Sitko, Pavel Pavlenda and Tomáš Hlásny

Abstract

We focus on the analysis of sap flow and stem circumference changes in European beech (Fagus sylvatica, L.) in relation to available soil water and weather conditions during the growing seasons 2012 and 2013. The objective was to examine how soil water potential affects growth and transpiration of a mature beech stand situated at the lower distributional limit of beech in Slovakia. To be able to evaluate beech response to soil water shortage, we irrigated a group of 6 trees during the period of pronounced drought, while the control group of other 6 trees remained exposed to actual weather conditions. Mean air temperatures of both seasons were considerably above the long-term average and the temporal pattern of precipitation differed between the years. During the whole growing season 2012, beech samples transpired an average volume of 6.9 m3 of water in the control and 7.7 m3 in the irrigated group. A slightly higher average volume was found in the growing season 2013 under both treatments (7.7 m3 in control and 10.5 m3 in irrigated trees). In the drought period 2012, when the irrigation experiment was commenced, the sap flow in the control group was reduced by 30% as compared with the irrigated group. In 2013, a 38.1% difference in sap flow was observed between the groups. Sap flow in the non-irrigated trees decreased with reducing soil moisture, and ceased at soil water potential -0.6 MPa. In both treatments and years, we found significant correlations between hourly sap flow and investigated weather variables. A reduction in stem circumferences of the control trees, which was observed during stem shrinkage phase, was up to 19% in 2012 and 10% in 2013. We conclude that stem circumference shrinkage during the peak of soil drought was induced by the cessation in the sap flow process.

Open access

Denisa Sedmáková, Róbert Sedmák, Michal Bosel’a, Marek Ježík, Roman Sitko, Tomáš Hlásny and Miroslav Blaženec

Abstract

The main objective of the study is to facilitate cross-dating of sensitive tree-ring series from living European beech (Fagus sylvatica L.) trees in the absence of a regional chronology. The main idea lies in the preliminary dating of marker rings or ring patterns visually identified on the wood (before the ring-width measurements), which is independently validated through a moving correlation between a tentative reference chronology and instrumental climate records (after the ring-width measurements). Following the detection of low moving correlations, potentially misdated segments or series are re-examined and a new tentative reference chronology is constructed. The process is repeated as long as a higher correlation with climate is obtainable. The applicability of this method was investigated on three difficult-to-date sets of tree-ring series of beech trees which were growing at temperature- or precipitation-sensitive locations in under-canopy or canopy positions. A good ability of the combined method for the cross-dating was practiced on datasets almost impossible to cross-date by commonly used approaches. Highlighting the actual correlation of ring widths with climate in tree-ring series makes the cross-dating process more independent from human decisions, so the com-bined cross-dating has the potential to improve the reliability of various dendrochronological studies.