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1. Contested Logistics: A Game-Theoretic Approach

Author

Cerny, Jakub, Ling, Chun Kai, Chakrabarti, Darshan, Zhang, Jingwen, Farina, Gabriele, Kroer, Christian, and Iyengar, Garud

Subjects
Computer Science - Computer Science and Game Theory
Abstract

We introduce Contested Logistics Games, a variant of logistics problems that account for the presence of an adversary that can disrupt the movement of goods in selected areas. We model this as a large two-player zero-sum one-shot game played on a graph representation of the physical world, with the optimal logistics plans described by the (possibly randomized) Nash equilibria of this game. Our logistics model is fairly sophisticated, and is able to handle multiple modes of transport and goods, accounting for possible storage of goods in warehouses, as well as Leontief utilities based on demand satisfied. We prove computational hardness results related to equilibrium finding and propose a practical double-oracle solver based on solving a series of best-response mixed-integer linear programs. We experiment on both synthetic and real-world maps, demonstrating that our proposed method scales to reasonably large games. We also demonstrate the importance of explicitly modeling the capabilities of the adversary via ablation studies and comparisons with a naive logistics plan based on heuristics., Comment: GameSec '24

Published
2024

2. Layered Graph Security Games

Author

Černý, Jakub, Ling, Chun Kai, Kroer, Christian, and Iyengar, Garud

Subjects
Computer Science - Computer Science and Game Theory
Abstract

Security games model strategic interactions in adversarial real-world applications. Such applications often involve extremely large but highly structured strategy sets (e.g., selecting a distribution over all patrol routes in a given graph). In this paper, we represent each player's strategy space using a layered graph whose paths represent an exponentially large strategy space. Our formulation entails not only classic pursuit-evasion games, but also other security games, such as those modeling anti-terrorism and logistical interdiction. We study two-player zero-sum games under two distinct utility models: linear and binary utilities. We show that under linear utilities, Nash equilibrium can be computed in polynomial time, while binary utilities may lead to situations where even computing a best-response is computationally intractable. To this end, we propose a practical algorithm based on incremental strategy generation and mixed integer linear programs. We show through extensive experiments that our algorithm efficiently computes $\epsilon$-equilibrium for many games of interest. We find that target values and graph structure often have a larger influence on running times as compared to the size of the graph per se., Comment: In Proceedings of the Thirty-Third International Joint Conference on Artificial Intelligence. IJCAI Press, 2024

Published
2024

3. Grasper: A Generalist Pursuer for Pursuit-Evasion Problems

Author

Li, Pengdeng, Li, Shuxin, Wang, Xinrun, Cerny, Jakub, Zhang, Youzhi, McAleer, Stephen, Chan, Hau, and An, Bo

Subjects
Computer Science - Artificial Intelligence, Computer Science - Computer Science and Game Theory, Computer Science - Multiagent Systems
Abstract

Pursuit-evasion games (PEGs) model interactions between a team of pursuers and an evader in graph-based environments such as urban street networks. Recent advancements have demonstrated the effectiveness of the pre-training and fine-tuning paradigm in PSRO to improve scalability in solving large-scale PEGs. However, these methods primarily focus on specific PEGs with fixed initial conditions that may vary substantially in real-world scenarios, which significantly hinders the applicability of the traditional methods. To address this issue, we introduce Grasper, a GeneRAlist purSuer for Pursuit-Evasion pRoblems, capable of efficiently generating pursuer policies tailored to specific PEGs. Our contributions are threefold: First, we present a novel architecture that offers high-quality solutions for diverse PEGs, comprising critical components such as (i) a graph neural network (GNN) to encode PEGs into hidden vectors, and (ii) a hypernetwork to generate pursuer policies based on these hidden vectors. As a second contribution, we develop an efficient three-stage training method involving (i) a pre-pretraining stage for learning robust PEG representations through self-supervised graph learning techniques like GraphMAE, (ii) a pre-training stage utilizing heuristic-guided multi-task pre-training (HMP) where heuristic-derived reference policies (e.g., through Dijkstra's algorithm) regularize pursuer policies, and (iii) a fine-tuning stage that employs PSRO to generate pursuer policies on designated PEGs. Finally, we perform extensive experiments on synthetic and real-world maps, showcasing Grasper's significant superiority over baselines in terms of solution quality and generalizability. We demonstrate that Grasper provides a versatile approach for solving pursuit-evasion problems across a broad range of scenarios, enabling practical deployment in real-world situations., Comment: To appear in the 23rd International Conference on Autonomous Agents and Multi-Agent Systems (AAMAS 2024)

Published
2024

4. Reducing Optimism Bias in Incomplete Cooperative Games

Author

Úradník, Filip, Sychrovský, David, Černý, Jakub, and Černý, Martin

Subjects
Computer Science - Computer Science and Game Theory, Computer Science - Machine Learning
Abstract

Cooperative game theory has diverse applications in contemporary artificial intelligence, including domains like interpretable machine learning, resource allocation, and collaborative decision-making. However, specifying a cooperative game entails assigning values to exponentially many coalitions, and obtaining even a single value can be resource-intensive in practice. Yet simply leaving certain coalition values undisclosed introduces ambiguity regarding individual contributions to the collective grand coalition. This ambiguity often leads to players holding overly optimistic expectations, stemming from either inherent biases or strategic considerations, frequently resulting in collective claims exceeding the actual grand coalition value. In this paper, we present a framework aimed at optimizing the sequence for revealing coalition values, with the overarching goal of efficiently closing the gap between players' expectations and achievable outcomes in cooperative games. Our contributions are threefold: (i) we study the individual players' optimistic completions of games with missing coalition values along with the arising gap, and investigate its analytical characteristics that facilitate more efficient optimization; (ii) we develop methods to minimize this gap over classes of games with a known prior by disclosing values of additional coalitions in both offline and online fashion; and (iii) we empirically demonstrate the algorithms' performance in practical scenarios, together with an investigation into the typical order of revealing coalition values., Comment: Proc. of the 23rd International Conference on Autonomous Agents and Multiagent Systems (AAMAS 2024)

Published
2024

5. Contested Logistics: A Game-Theoretic Approach

Author

Černý, Jakub, Ling, Chun Kai, Chakrabarti, Darshan, Zhang, Jingwen, Farina, Gabriele, Kroer, Christian, Iyengar, Garud, Goos, Gerhard, Series Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Sinha, Arunesh, editor, Fu, Jie, editor, Zhu, Quanyan, editor, and Zhang, Tao, editor

Published
2025
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6. Sessile oak (Quercus petraea [Matt.] Liebl.) and its adaptation strategies in the context of global climate change: a review

Author

Černý Jakub, Špulák Ondřej, Kománek Martin, Žižková Eliška, and Sýkora Petr

Subjects
ecological demands, mitigation, mixed stands, drought stress, resilience, sustainable management, Forestry, SD1-669.5
Abstract

This paper provides characteristic and a comprehensive overview of the adaptation strategies of sessile oak (Quercus petraea [Matt.] Liebl.) in the context of global climate change (GCC). The GCC is primarily manifested by increasing air temperatures and changing precipitation distribution. It poses a significant challenge to tree species including sessile oak, affecting its capacity for adaptation and survival. Despite the challenge, sessile oak shows significant drought tolerance due to its deep-reaching root system, which allows the tree to use available water more efficiently. Other adaptive strategies include the establishment of mixed stands that increase the resilience and biodiversity of the ecosystem. Adjustments of stand density through tending interventions play a significant role, helping to improve the stress resistance of stands. Additionally, coppice forest cultivation is applied on extremely dry sites. The sessile oak is also significant for its ecological plasticity – its ability to thrive on versatile soil and climatic conditions makes it a promising tree species for future forest management. Mixed stands with sessile oak and other tree species can enhance the ecosystem services of forests and also increase their endurance to GCC events. However, sessile oak faces several challenges, including the increasing risk of damage from pests and pathogens that require targeted measures for its protection and sustainable cultivation. The literature review suggests that a comprehensive understanding of sessile oak’s ecological requirements and interactions with the environment is crucial for its successful adaptation to GCC and the formulation of effective strategies for its protection and use in forest management.

Published
2024
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7. Price of Anarchy in a Double-Sided Critical Distribution System

Author

Sychrovský, David, Černý, Jakub, Lichau, Sylvain, and Loebl, Martin

Subjects
Computer Science - Multiagent Systems, Computer Science - Computer Science and Game Theory
Abstract

Measures of allocation optimality differ significantly when distributing standard tradable goods in peaceful times and scarce resources in crises. While realistic markets offer asymptotic efficiency, they may not necessarily guarantee fair allocation desirable when distributing the critical resources. To achieve fairness, mechanisms often rely on a central authority, which may act inefficiently in times of need when swiftness and good organization are crucial. In this work, we study a hybrid trading system called Crisdis, introduced by Jedli\v{c}kov\'{a} et al., which combines fair allocation of buying rights with a market - leveraging the best of both worlds. A frustration of a buyer in Crisdis is defined as a difference between the amount of goods they are entitled to according to the assigned buying rights and the amount of goods they are able to acquire by trading. We define a Price of Anarchy (PoA) in this system as a conceptual analogue of the original definition in the context of frustration. Our main contribution is a study of PoA in realistic complex double-sided market mechanisms for Crisdis. The performed empirical analysis suggests that in contrast to market free of governmental interventions, the PoA in our system decreases.

Published
2023

8. Offline Equilibrium Finding

Author

Li, Shuxin, Wang, Xinrun, Zhang, Youzhi, Cerny, Jakub, Li, Pengdeng, Chan, Hau, and An, Bo

Subjects
Computer Science - Artificial Intelligence, Computer Science - Computer Science and Game Theory, Computer Science - Machine Learning
Abstract

Offline reinforcement learning (offline RL) is an emerging field that has recently begun gaining attention across various application domains due to its ability to learn strategies from earlier collected datasets. Offline RL proved very successful, paving a path to solving previously intractable real-world problems, and we aim to generalize this paradigm to a multiplayer-game setting. To this end, we introduce a problem of offline equilibrium finding (OEF) and construct multiple types of datasets across a wide range of games using several established methods. To solve the OEF problem, we design a model-based framework that can directly apply any online equilibrium finding algorithm to the OEF setting while making minimal changes. The three most prominent contemporary online equilibrium finding algorithms are adapted to the context of OEF, creating three model-based variants: OEF-PSRO and OEF-CFR, which generalize the widely-used algorithms PSRO and Deep CFR to compute Nash equilibria (NEs), and OEF-JPSRO, which generalizes the JPSRO to calculate (Coarse) Correlated equilibria ((C)CEs). We also combine the behavior cloning policy with the model-based policy to further improve the performance and provide a theoretical guarantee of the solution quality. Extensive experimental results demonstrate the superiority of our approach over offline RL algorithms and the importance of using model-based methods for OEF problems. We hope our work will contribute to advancing research in large-scale equilibrium finding.

Published
2022

9. A Unified Perspective on Deep Equilibrium Finding

Author

Wang, Xinrun, Cerny, Jakub, Li, Shuxin, Yang, Chang, Yin, Zhuyun, Chan, Hau, and An, Bo

Subjects
Computer Science - Computer Science and Game Theory
Abstract

Extensive-form games provide a versatile framework for modeling interactions of multiple agents subjected to imperfect observations and stochastic events. In recent years, two paradigms, policy space response oracles (PSRO) and counterfactual regret minimization (CFR), showed that extensive-form games may indeed be solved efficiently. Both of them are capable of leveraging deep neural networks to tackle the scalability issues inherent to extensive-form games and we refer to them as deep equilibrium-finding algorithms. Even though PSRO and CFR share some similarities, they are often regarded as distinct and the answer to the question of which is superior to the other remains ambiguous. Instead of answering this question directly, in this work we propose a unified perspective on deep equilibrium finding that generalizes both PSRO and CFR. Our four main contributions include: i) a novel response oracle (RO) which computes Q values as well as reaching probability values and baseline values; ii) two transform modules -- a pre-transform and a post-transform -- represented by neural networks transforming the outputs of RO to a latent additive space (LAS), and then the LAS to action probabilities for execution; iii) two average oracles -- local average oracle (LAO) and global average oracle (GAO) -- where LAO operates on LAS and GAO is used for evaluation only; and iv) a novel method inspired by fictitious play that optimizes the transform modules and average oracles, and automatically selects the optimal combination of components of the two frameworks. Experiments on Leduc poker game demonstrate that our approach can outperform both frameworks.

Published
2022

11. Complexity and Algorithms for Exploiting Quantal Opponents in Large Two-Player Games

Author

Milec, David, Černý, Jakub, Lisý, Viliam, and An, Bo

Subjects
Computer Science - Artificial Intelligence
Abstract

Solution concepts of traditional game theory assume entirely rational players; therefore, their ability to exploit subrational opponents is limited. One type of subrationality that describes human behavior well is the quantal response. While there exist algorithms for computing solutions against quantal opponents, they either do not scale or may provide strategies that are even worse than the entirely-rational Nash strategies. This paper aims to analyze and propose scalable algorithms for computing effective and robust strategies against a quantal opponent in normal-form and extensive-form games. Our contributions are: (1) we define two different solution concepts related to exploiting quantal opponents and analyze their properties; (2) we prove that computing these solutions is computationally hard; (3) therefore, we evaluate several heuristic approximations based on scalable counterfactual regret minimization (CFR); and (4) we identify a CFR variant that exploits the bounded opponents better than the previously used variants while being less exploitable by the worst-case perfectly-rational opponent., Comment: 15 pages, 11 figures, submitted to AAAI 2021

Published
2020

12. Computing Ex Ante Coordinated Team-Maxmin Equilibria in Zero-Sum Multiplayer Extensive-Form Games

Author

Zhang, Youzhi, An, Bo, and Černý, Jakub

Subjects
Computer Science - Computer Science and Game Theory
Abstract

Computational game theory has many applications in the modern world in both adversarial situations and the optimization of social good. While there exist many algorithms for computing solutions in two-player interactions, finding optimal strategies in multiplayer interactions efficiently remains an open challenge. This paper focuses on computing the multiplayer Team-Maxmin Equilibrium with Coordination device (TMECor) in zero-sum extensive-form games. TMECor models scenarios when a team of players coordinates ex ante against an adversary. Such situations can be found in card games (e.g., in Bridge and Poker), when a team works together to beat a target player but communication is prohibited; and also in real world, e.g., in forest-protection operations, when coordinated groups have limited contact during interdicting illegal loggers. The existing algorithms struggle to find a TMECor efficiently because of their high computational costs. To compute a TMECor in larger games, we make the following key contributions: (1) we propose a hybrid-form strategy representation for the team, which preserves the set of equilibria; (2) we introduce a column-generation algorithm with a guaranteed finite-time convergence in the infinite strategy space based on a novel best-response oracle; (3) we develop an associated-representation technique for the exact representation of the multilinear terms in the best-response oracle; and (4) we experimentally show that our algorithm is several orders of magnitude faster than prior state-of-the-art algorithms in large games., Comment: AAAI 2021. This paper also is a part of the thesis: Youzhi Zhang, February 2020. Computing Team-Maxmin Equilibria in Zero-Sum Multiplayer Games. PhD Thesis, https://personal.ntu.edu.sg/boan/thesis/Zhang_Youzhi_PhD_Thesis.pdf

Published
2020

15. Unexpected fading of comet C/2003 T4 (LINEAR) and disintegration of C/2012 S1 (ISON)

Author

Cerny, Jakub

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Comet C/2003 T4 (LINEAR) exhibit a large asymmetry in brightness before and after perihelion, when it became much fainter. Large non-gravitational forces shows that mass of nucleus doesn't exceed 2.51*10^11 kg, which is nearly double than previously disintegrated comets C/2012 S1 (ISON) and C/1999 S4 (LINEAR). Amount of water mass loss of C/2003 T4 in interval between 70 days before to 60 after perihelion, was nearly 3.16(+/- 0.60)*10^10 kg or >13 % of total nucleus mass and >21 % for C/2012 S1, which is much larger than value >7 % previously stated for C/1999 S4., Comment: 5 pages, 3 figures

Published
2014

18. An Initial Study of Targeted Personality Models in the FlipIt Game

Author

Basak, Anjon, Černý, Jakub, Gutierrez, Marcus, Curtis, Shelby, Kamhoua, Charles, Jones, Daniel, Bošanský, Branislav, Kiekintveld, Christopher, Hutchison, David, Series Editor, Kanade, Takeo, Series Editor, Kittler, Josef, Series Editor, Kleinberg, Jon M., Series Editor, Mattern, Friedemann, Series Editor, Mitchell, John C., Series Editor, Naor, Moni, Series Editor, Pandu Rangan, C., Series Editor, Steffen, Bernhard, Series Editor, Terzopoulos, Demetri, Series Editor, Tygar, Doug, Series Editor, Weikum, Gerhard, Series Editor, Bushnell, Linda, editor, Poovendran, Radha, editor, and Başar, Tamer, editor

Published
2018
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19. Improvement on the decay of crossing numbers

Author

Černý, Jakub, Kynčl, Jan, and Tóth, Géza

Subjects
Mathematics - Combinatorics, Computer Science - Discrete Mathematics
Abstract

We prove that the crossing number of a graph decays in a continuous fashion in the following sense. For any epsilon>0 there is a delta>0 such that for a sufficiently large n, every graph G with n vertices and m > n^{1+epsilon} edges, has a subgraph G' of at most (1-delta)m edges and crossing number at least (1-epsilon)cr(G). This generalizes the result of J. Fox and Cs. Toth., Comment: 7 pages, 1 figure

Published
2012
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20. Effect of different stand densities on xylem and phloem formation in Norway spruce plantations.

Author

Giagli, Kyriaki, Vavrčík, Hanuš, Tsalagkas, Dimitrios, Černý, Jakub, Leugner, Jan, Hacurová, Jana, and Gryc, Vladimír

Subjects
PHLOEM, XYLEM, NORWAY spruce, SIEVE elements, TREE growth, PLANTATIONS
Abstract

Summary: Preliminary results of an investigation of the thinning effect on Norway spruce tree growth in terms of xylogenesis and phloemogenesis are presented. Three plots were selected where the stand densities were reduced by pre-commercial thinning to 1800 trees/ha (plot A; mild thinning) and 1300 trees/ha (plot C; heavy thinning) in February 2020. Plot B had no silvicultural intervention and represented a control variant (4500 trees/ha). Three dominant 14-year-old Norway spruce trees were sampled (micro-cored) for studying the xylem and phloem formation in the 2020 growing season. The total differentiation duration was determined to be around 169.7 ± 12.7–179.3 ± 4.0 days. The average number of xylem cells formed in control plot B was only 140 mature cells, plots C and A were determined to have 175 and 200 mature cells, respectively. Plot A had the fastest growth rate of all the plots studied. In all three plots (A, B, C), the beginning of the early phloem, late phloem sieve cells, and axial parenchyma cells coincided. Nonetheless, in terms of total phloem cell increase, plot C displayed the fastest growth rate among the three plots studied. The first results showed that the rate of total increment in both xylem and phloem cells, as well as the total number of produced tracheids and sieve cells, seem to be positively affected after the thinning application. [ABSTRACT FROM AUTHOR]

Published
2024
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22. VÝZNAM BUKU LESNÍHO VE STŘEDNÍ EVROPĚ V OBDOBÍ KLIMATICKÉ ZMĚNY: PŘEHLED SOUČASNÝCH POZNATKŮ.

Author

Černý, Jakub, Špulák, Ondřej, Sýkora, Petr, Novosadová, Kateřina, Kadlec, Jiří, and Kománek, Martin

Subjects
EUROPEAN beech, CLIMATE change, MIXED forests, SUSTAINABILITY, GENETIC variation, HEAT waves (Meteorology), MEDICAL climatology
Abstract

In the period of ongoing global climate change, ecosystems, including Central European forests, face significant challenges such as summer droughts and heat waves, which increase the climate risks also for the European beech (Fagus sylvatica L.), an important and dominant broadleaved tree species in this region. This article provides a comprehensive review of current knowledge on the adaptation strategies of European beech in response to changing climatic conditions, highlighting its ecological demands, development of taxonomy, ecological and economic importance and exploring its resilience, growth characteristics, and challenges such as water regime, pests, diseases, and the impact of climate change. A key finding is that despite the various stressors affecting European beech, adaptive management and the use of mixed forest stands can significantly contribute to its conservation and sustainable use. The importance of integrating the genetic diversity and adaptive capacity of European beech into forestry practices is emphasised. The review of 203 studies highlights the need for further research focused on understanding the interactions between European beech and a changing climate in order to develop more effective strategies for its conservation and sustainable management in the future. [ABSTRACT FROM AUTHOR]

Published
2024
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23. Emerging stability of forest productivity by mixing two species buffers temperature destabilizing effect

Author

Ministerio de Ciencia, Innovación y Universidades (España), del Río, Miren [0000-0001-7496-3713], Verheyen, Kris [0000-0002-2067-9108+, Bravo-Oviedo, Andrés [0000-0001-7036-7041], Pretzsch, Hans [0000-0002-4958-1868], Jactel, Hervé [0000-0002-8106-5310], Aldea, Jorge [0000-0003-2568-5192], Černý, Jakub [0000-0002-9954-1506], Pérot, Tomas [0000-0002-0806-6819], Pardos Mínguez, Marta [0000-0002-5567-5406], del Río, Miren [delrio@inia.csic.es], Río, Miren del, Ruiz-Peinado, Ricardo, Holm, Stig Olof, Jansons, Aris, Nord‐Larsen, Thomas, Verheyen, Kris, Bravo-Oviedo, Andrés, Pretzsch, Hans, Jactel, Hervé, Coll, Lluís, Löf, Magnus, Aldea, Jorge, Ammer, Christian, Avdagić, Admir, Barbeito, Ignacio, Bielak, Kamil, Bravo, Felipe, Brazaitis, Gediminas, Černý, Jakub, Collet, Catherine, Condés, Sonia, Drössler, Lars, Fabrika, Marek, Heym, Michael, Hylen, Gro, Kurylyak, Viktor, Lombardi, Fabio, Matović, Bratislav, Metslaid, Marek, Motta, Renzo, Nothdurft, Arne, Den Ouden, Jan, Pach, Maciej, Pardos, Marta, Poeydebat, Charlotte, Ponette, Quentin, Pérot, Tomas, Reventlow, Ditlev Otto Juel, Sitko, Roman, Sramek, Vit, Steckel, Mathias, Svoboda, Miroslav, Vospernik, Sonja, Wolff, Barbara, Zlatanov, Tzvetan, Ministerio de Ciencia, Innovación y Universidades (España), del Río, Miren [0000-0001-7496-3713], Verheyen, Kris [0000-0002-2067-9108+, Bravo-Oviedo, Andrés [0000-0001-7036-7041], Pretzsch, Hans [0000-0002-4958-1868], Jactel, Hervé [0000-0002-8106-5310], Aldea, Jorge [0000-0003-2568-5192], Černý, Jakub [0000-0002-9954-1506], Pérot, Tomas [0000-0002-0806-6819], Pardos Mínguez, Marta [0000-0002-5567-5406], del Río, Miren [delrio@inia.csic.es], Río, Miren del, Ruiz-Peinado, Ricardo, Holm, Stig Olof, Jansons, Aris, Nord‐Larsen, Thomas, Verheyen, Kris, Bravo-Oviedo, Andrés, Pretzsch, Hans, Jactel, Hervé, Coll, Lluís, Löf, Magnus, Aldea, Jorge, Ammer, Christian, Avdagić, Admir, Barbeito, Ignacio, Bielak, Kamil, Bravo, Felipe, Brazaitis, Gediminas, Černý, Jakub, Collet, Catherine, Condés, Sonia, Drössler, Lars, Fabrika, Marek, Heym, Michael, Hylen, Gro, Kurylyak, Viktor, Lombardi, Fabio, Matović, Bratislav, Metslaid, Marek, Motta, Renzo, Nothdurft, Arne, Den Ouden, Jan, Pach, Maciej, Pardos, Marta, Poeydebat, Charlotte, Ponette, Quentin, Pérot, Tomas, Reventlow, Ditlev Otto Juel, Sitko, Roman, Sramek, Vit, Steckel, Mathias, Svoboda, Miroslav, Vospernik, Sonja, Wolff, Barbara, and Zlatanov, Tzvetan

Abstract

The increasing disturbances in monocultures around the world are testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increase with species richness, although the ecological fundaments have mainly been investigated through diversity experiments. To adequately manage forest ecosystems, it is necessary to have a comprehensive understanding of the effect of mixing species on the temporal stability of productivity and the way in which this it is influenced by climate conditions across large geographical areas. Here, we used a unique dataset of 261 stands combining pure and two-species mixtures of four relevant tree species over a wide range of climate conditions in Europe to examine the effect of species mixing on the level and temporal stability of productivity. Structural equation modelling was employed to further explore the direct and indirect influence of climate, overyielding, species asynchrony and additive effect (i.e. temporal stability expected from the species growth in monospecific stands) on temporal stability in mixed forests. We showed that by adding only one tree species to monocultures, the level (overyielding: +6%) and stability (temporal stability: +12%) of stand growth increased significantly. We identified the key effect of temperature on destabilizing stand growth, which may be mitigated by mixing species. We further confirmed asynchrony as the main driver of temporal stability in mixed stands, through both the additive effect and species interactions, which modify between-species asynchrony in mixtures in comparison to monocultures. Synthesis and applications. This study highlights the emergent properties associated with mixing two-species, which result in resource efficient and temporally stable production systems. We reveal the negative impact of mean temperature on temporal stability of forest productivity and how the stabilizing effect of mixing two species can counterbalance thi

Published
2022

26. Tree species growth response to climate in mixtures of Quercus robur/Quercus petraea and Pinus sylvestris across Europe - a dynamic, sensitive equilibrium

Author

UCL - SST/ELI/ELIC - Earth & Climate, Vospernik, Sonja, Heym, Michael, Pretzsch, Hans, Pach, Maciej, Steckel, Mathias, Aldea, Jorge, Brazaitis, Gediminas, Bravo-Oviedo, Andrés, Del Rio, Miren, Löf, Magnus, Pardos, Marta, Bielak, Kamil, Bravo, Felipe, Coll, Lluís, Černý, Jakub, Droessler, Lars, Ehbrecht, Martin, Jansons, Aris, Korboulewsky, Nathalie, Jourdan, Marion, Nord-Larsen, Thomas, Nothdurft, Arne, Ruiz-Peinado, Ricardo, Ponette, Quentin, Sitko, Roman, Svoboda, Miroslav, Wolff, Barbara, UCL - SST/ELI/ELIC - Earth & Climate, Vospernik, Sonja, Heym, Michael, Pretzsch, Hans, Pach, Maciej, Steckel, Mathias, Aldea, Jorge, Brazaitis, Gediminas, Bravo-Oviedo, Andrés, Del Rio, Miren, Löf, Magnus, Pardos, Marta, Bielak, Kamil, Bravo, Felipe, Coll, Lluís, Černý, Jakub, Droessler, Lars, Ehbrecht, Martin, Jansons, Aris, Korboulewsky, Nathalie, Jourdan, Marion, Nord-Larsen, Thomas, Nothdurft, Arne, Ruiz-Peinado, Ricardo, Ponette, Quentin, Sitko, Roman, Svoboda, Miroslav, and Wolff, Barbara

Abstract

Quercus robur/Quercus petraea and Pinus sylvestris are widely distributed and economically important tree species in Europe co-occurring on mesotrophic, xeric and mesic sites. Increasing dry conditions may reduce their growth, but growth reductions may be modified by mixture, competition and site conditions. The annual diameter growth in monospecific and mixed stands along an ecological gradient with mean annual temperatures ranging from 5.5 °C to 11.5 °C was investigated in this study. On 36 triplets (108 plots), trees were cored and the year-ring series were cross-dated, resulting in year-ring series of 785 and 804 trees for Q. spp. and P. sylvestris, respectively. A generalized additive model with a logarithmic link was fit to the data with random effects for the intercept at the triplet, year and tree level and a random slope for the covariate age for each tree; the Tweedie-distribution was used. The final model explained 87 % of the total variation in diameter increment for both tree species. Significant covariates were age, climate variables (long-term mean, monthly), local competition variables, relative dbh, mixture, stand structure and interactions thereof. Tree growth declined with age and local density and increased with social position. It was positively influenced by mixture and structural diversity (Gini coefficient); mixture effects were significant for P. sylvestris only. The influence of potential evapotranspiration (PET) in spring and autumn on tree growth was positive and non-linear, whereas tree growth sharply decreased with increasing PET in June, which proved to be the most influential month on tree growth along the whole ecological gradient. Interactions of PET with tree social position (relative dbh) were significant in July and September for Q. spp. and in April for P. sylvestris. Interactions of climate with density or mixture were not significant. Climatic effects found agree well with previous results from intra-annual growth studies and

Published
2023

27. Effect of different stand densities on xylem and phloem formation in Norway spruce plantations

Author

Giagli, Kyriaki, Vavrčík, Hanuš, Tsalagkas, Dimitrios, Černý, Jakub, Leugner, Jan, Hacurová, Jana, Gryc, Vladimír, Giagli, Kyriaki, Vavrčík, Hanuš, Tsalagkas, Dimitrios, Černý, Jakub, Leugner, Jan, Hacurová, Jana, and Gryc, Vladimír

Abstract

Preliminary results of an investigation of the thinning effect on Norway spruce tree growth in terms of xylogenesis and phloemogenesis are presented. Three plots were selected where the stand densities were reduced by pre-commercial thinning to 1800 trees/ha (plot A; mild thinning) and 1300 trees/ha (plot C; heavy thinning) in February 2020. Plot B had no silvicultural intervention and represented a control variant (4500 trees/ha). Three dominant 14-year-old Norway spruce trees were sampled (micro-cored) for studying the xylem and phloem formation in the 2020 growing season. The total differentiation duration was determined to be around 169.7 +- 12.7-179.3 +- 4.0 days. The average number of xylem cells formed in control plot B was only 140 mature cells, plots C and A were determined to have 175 and 200 mature cells, respectively. Plot A had the fastest growth rate of all the plots studied. In all three plots (A, B, C), the beginning of the early phloem, late phloem sieve cells, and axial parenchyma cells coincided. Nonetheless, in terms of total phloem cell increase, plot C displayed the fastest growth rate among the three plots studied. The first results showed that the rate of total increment in both xylem and phloem cells, as well as the total number of produced tracheids and sieve cells, seem to be positively affected after the thinning application.

Published
2023

28. Provenance affects the growth and mortality of teak (Tectona grandis L.f.) plantations cultivated in central Nicaragua

Author

Černý, Jakub, Haninec, Peter, Novosadová, Kateřina, Patočka, Zdeněk, Haninec, Pavel, Maděra, Petr, Černý, Jakub, Haninec, Peter, Novosadová, Kateřina, Patočka, Zdeněk, Haninec, Pavel, and Maděra, Petr

Abstract

Teak has been planted extensively by smallholders in Central America within reforestation programmes and has become one of the most valuable timbers. The five-year growth and mortality of teak cultivated in a plantation in central Nicaragua, representing sites at the low limit of teak ecological valence, were evaluated. From 2006 to 2010, 72 pure teak stands were established, with 48.93 ha in total. For afforestation, planting stock from five provenances was used and planted at 1 m x 1 m spacing to stimulate the height growth and reduce broad crowns formed by self-pruning. In the pure teak stands, 144 permanent sample plots of 0.01 ha in size were established in 2011. From 2011 until 2015, the tree height and stem girth of all individuals in the studied sample plots were measured, and mortality based on the stand density was assessed. Significant differences between the provenances were observed. The highest growth was noted in the Local provenance originated from the studied area, whereas the Semilla provenance from Costa Rica, characterised by the lowest growth ability, was characterized by lower radial increment and mean tree height with high mortality., info:eu-repo/semantics/openAccess

Published
2023

29. Tree species growth response to climate in mixtures of Quercus robur/Quercus petraea and Pinus sylvestris across Europe - a dynamic, sensitive equilibrium

Author

European Commission, State Forests (Poland), Office National des Forêts (France), Ministry of Agriculture of the Czech Republic, Vospernik, Sonja, Heym, Michael, Pretzsch, Hans, Pach, Maciej, Steckel, Mathias, Aldea, Jorge, Brazaitis, Gediminas, Bravo-Oviedo, Andrés, Río, Miren del, Löf, Magnus, Pardos, Marta, Bielak, Kamil, Bravo, Felipe, Coll, Lluís, Černý, Jakub, Droessler, Lars, Ehbrecht, Martin, Jansons, Aris, Korboulewsky, Nathalie, Jourdan, Marion, Nord-Larsen, Thomas, Nothdurft, Arne, Ruiz-Peinado, Ricardo, Ponette, Quentin, Sitko, Roman, Svoboda, Miroslav, Wolff, Barbara, European Commission, State Forests (Poland), Office National des Forêts (France), Ministry of Agriculture of the Czech Republic, Vospernik, Sonja, Heym, Michael, Pretzsch, Hans, Pach, Maciej, Steckel, Mathias, Aldea, Jorge, Brazaitis, Gediminas, Bravo-Oviedo, Andrés, Río, Miren del, Löf, Magnus, Pardos, Marta, Bielak, Kamil, Bravo, Felipe, Coll, Lluís, Černý, Jakub, Droessler, Lars, Ehbrecht, Martin, Jansons, Aris, Korboulewsky, Nathalie, Jourdan, Marion, Nord-Larsen, Thomas, Nothdurft, Arne, Ruiz-Peinado, Ricardo, Ponette, Quentin, Sitko, Roman, Svoboda, Miroslav, and Wolff, Barbara

Abstract

Quercus robur/Quercus petraea and Pinus sylvestris are widely distributed and economically important tree species in Europe co-occurring on mesotrophic, xeric and mesic sites. Increasing dry conditions may reduce their growth, but growth reductions may be modified by mixture, competition and site conditions. The annual diameter growth in monospecific and mixed stands along an ecological gradient with mean annual temperatures ranging from 5.5 °C to 11.5 °C was investigated in this study. On 36 triplets (108 plots), trees were cored and the year-ring series were cross-dated, resulting in year-ring series of 785 and 804 trees for Q. spp. and P. sylvestris, respectively. A generalized additive model with a logarithmic link was fit to the data with random effects for the intercept at the triplet, year and tree level and a random slope for the covariate age for each tree; the Tweedie-distribution was used. The final model explained 87 % of the total variation in diameter increment for both tree species. Significant covariates were age, climate variables (long-term mean, monthly), local competition variables, relative dbh, mixture, stand structure and interactions thereof. Tree growth declined with age and local density and increased with social position. It was positively influenced by mixture and structural diversity (Gini coefficient); mixture effects were significant for P. sylvestris only. The influence of potential evapotranspiration (PET) in spring and autumn on tree growth was positive and non-linear, whereas tree growth sharply decreased with increasing PET in June, which proved to be the most influential month on tree growth along the whole ecological gradient. Interactions of PET with tree social position (relative dbh) were significant in July and September for Q. spp. and in April for P. sylvestris. Interactions of climate with density or mixture were not significant. Climatic effects found agree well with previous results from intra-annual growth studies and

Published
2023

30. Tree species growth response to climate in mixtures of Quercus robur/Quercus petraea and Pinus sylvestris across Europe - a dynamic, sensitive equilibrium

Author

Vospernik, Sonja, Heym, Michael, Pretzsch, Hans, Pach, Maciej, Steckel, Mathias, Aldea, Jorge, Brazaitis, Gediminas, Bravo-Oviedo, Andrés, Del Rio, Miren, Löf, Magnus, Pardos, Marta, Bielak, Kamil, Bravo, Felipe, Coll, Lluís, Černý, Jakub, Droessler, Lars, Ehbrecht, Martin, Jansons, Aris, Korboulewsky, Nathalie, Jourdan, Marion, Nord-Larsen, Thomas, Nothdurft, Arne, Ruiz-Peinado, Ricardo, Ponette, Quentin, Sitko, Roman, Svoboda, Miroslav, Wolff, Barbara, Vospernik, Sonja, Heym, Michael, Pretzsch, Hans, Pach, Maciej, Steckel, Mathias, Aldea, Jorge, Brazaitis, Gediminas, Bravo-Oviedo, Andrés, Del Rio, Miren, Löf, Magnus, Pardos, Marta, Bielak, Kamil, Bravo, Felipe, Coll, Lluís, Černý, Jakub, Droessler, Lars, Ehbrecht, Martin, Jansons, Aris, Korboulewsky, Nathalie, Jourdan, Marion, Nord-Larsen, Thomas, Nothdurft, Arne, Ruiz-Peinado, Ricardo, Ponette, Quentin, Sitko, Roman, Svoboda, Miroslav, and Wolff, Barbara

Abstract

Quercus robur/Quercus petraea and Pinus sylvestris are widely distributed and economically important tree species in Europe co-occurring on mesotrophic, xeric and mesic sites. Increasing dry conditions may reduce their growth, but growth reductions may be modified by mixture, competition and site conditions. The annual diameter growth in monospecific and mixed stands along an ecological gradient with mean annual temperatures ranging from 5.5 °C to 11.5 °C was investigated in this study. On 36 triplets (108 plots), trees were cored and the year-ring series were cross-dated, resulting in year-ring series of 785 and 804 trees for Q. spp. and P. sylvestris, respectively. A generalized additive model with a logarithmic link was fit to the data with random effects for the intercept at the triplet, year and tree level and a random slope for the covariate age for each tree; the Tweedie-distribution was used. The final model explained 87 % of the total variation in diameter increment for both tree species. Significant covariates were age, climate variables (long-term mean, monthly), local competition variables, relative dbh, mixture, stand structure and interactions thereof. Tree growth declined with age and local density and increased with social position. It was positively influenced by mixture and structural diversity (Gini coefficient); mixture effects were significant for P. sylvestris only. The influence of potential evapotranspiration (PET) in spring and autumn on tree growth was positive and non-linear, whereas tree growth sharply decreased with increasing PET in June, which proved to be the most influential month on tree growth along the whole ecological gradient. Interactions of PET with tree social position (relative dbh) were significant in July and September for Q. spp. and in April for P. sylvestris. Interactions of climate with density or mixture were not significant. Climatic effects found agree well with previous results from intra-annual growth studies a

Published
2023

31. Tree species growth response to climate in mixtures of Quercus robur/Quercus petraea and Pinus sylvestris across Europe - a dynamic, sensitive equilibrium

Author

Vospernik, Sonja, primary, Heym, Michael, additional, Pretzsch, Hans, additional, Pach, Maciej, additional, Steckel, Mathias, additional, Aldea, Jorge, additional, Brazaitis, Gediminas, additional, Bravo-Oviedo, Andrés, additional, Del Rio, Miren, additional, Löf, Magnus, additional, Pardos, Marta, additional, Bielak, Kamil, additional, Bravo, Felipe, additional, Coll, Lluís, additional, Černý, Jakub, additional, Droessler, Lars, additional, Ehbrecht, Martin, additional, Jansons, Aris, additional, Korboulewsky, Nathalie, additional, Jourdan, Marion, additional, Nord-Larsen, Thomas, additional, Nothdurft, Arne, additional, Ruiz-Peinado, Ricardo, additional, Ponette, Quentin, additional, Sitko, Roman, additional, Svoboda, Miroslav, additional, and Wolff, Barbara, additional

Published
2023
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35. Tree species growth response to climate in mixtures of Quercus robur/Quercus petraea and Pinus sylvestris across Europe - a dynamic, sensitive equilibrium

Author

Vospernik, Sonja, Heym, Michael, Pretzsch, Hans, Pach, Maciej, Steckel, Mathias, Aldea, Jorge, Brazaitis, Gediminas, Bravo-Oviedo, Andrés, Río, Miren del, Löf, Magnus, Pardos, Marta, Bielak, Kamil, Bravo, Felipe, Coll, Lluía, Černý, Jakub, Droessler, Lars, Ehbrecht, Martin, Jansons, Aris, Korboulewsky, Nathalie, Jourdan, Marion, Nord-Larsen, Thomas, Nothdurft, Arne, Ruiz-Peinado, Ricardo, Ponette, Quentin, Sitko, Roman, Svoboda, Miroslav, Wolff, Barbara, European Commission, Polish State Forests, Office National des Forêts (France), Ministry of Agriculture of the Czech Republic, and UCL - SST/ELI/ELIC - Earth & Climate

Subjects
Bioclimatologia, Monitoring, Policy and Law, Generalized additive model, Tree rings, Forestry, Management, Monitoring, Policy and Law, Ecologia, Management, ddc, Local competition, Bio-climatic zones, Mixed model, Competitive advantage, ddc:630, Nature and Landscape Conservation
Abstract

Quercus robur/Quercus petraea and Pinus sylvestris are widely distributed and economically important tree species in Europe co-occurring on mesotrophic, xeric and mesic sites. Increasing dry conditions may reduce their growth, but growth reductions may be modified by mixture, competition and site conditions. The annual diameter growth in monospecific and mixed stands along an ecological gradient with mean annual temperatures ranging from 5.5 °C to 11.5 °C was investigated in this study. On 36 triplets (108 plots), trees were cored and the year-ring series were cross-dated, resulting in year-ring series of 785 and 804 trees for Q. spp. and P. sylvestris, respectively. A generalized additive model with a logarithmic link was fit to the data with random effects for the intercept at the triplet, year and tree level and a random slope for the covariate age for each tree; the Tweedie-distribution was used. The final model explained 87 % of the total variation in diameter increment for both tree species. Significant covariates were age, climate variables (long-term mean, monthly), local competition variables, relative dbh, mixture, stand structure and interactions thereof. Tree growth declined with age and local density and increased with social position. It was positively influenced by mixture and structural diversity (Gini coefficient); mixture effects were significant for P. sylvestris only. The influence of potential evapotranspiration (PET) in spring and autumn on tree growth was positive and non-linear, whereas tree growth sharply decreased with increasing PET in June, which proved to be the most influential month on tree growth along the whole ecological gradient. Interactions of PET with tree social position (relative dbh) were significant in July and September for Q. spp. and in April for P. sylvestris. Interactions of climate with density or mixture were not significant. Climatic effects found agree well with previous results from intra-annual growth studies and indicate that the model captures the causal factors for tree growth well. Furthermore, the interaction between climate and relative dbh might indicate a longer growth duration for trees of higher social classes. Analysis of random effects across time and space showed highly dynamic patterns, with competitive advantages changing annually between species and spatial patterns showing no large-scale trends but pointing to the prevalence of local site factors. In mixed-species stands, the tree species have the same competitivity in the long-term, which is modified by climate each year. Climate warming will shift the competitive advantages, but the direction will be highly site-specific., The authors thank the European Union for funding the project “Mixed species forest management. Lowering risk, increasing resilience (REFORM)” under the framework of Sumforest ERA-NET. All contributors thank their national funding institutions to establish, measure and analyze data from the triplets. The Polish State Forests Enterprise also supported one of the Polish co-authors (Grant No: OR.271.3.15.2017). The Orléans site, OPTMix was installed thanks to ONF (National Forest Service, France), belongs to research infrastructure ANAEE-F; it is also included in the SOERE TEMPO, ZAL (LTSER Zone Atelier Loire) and the GIS oop network. This work was also supported by grant APVV-18-0347 (Slovakia). We acknowledge Institutional support MZE-RO0118 from the Ministry of Agriculture of the Czech Republic, partly funding the field measurements at Czech triplets.

Published
2022

39. Improvement on the Decay of Crossing Numbers

Author

Černý, Jakub, Kynčl, Jan, Tóth, Géza, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Hong, Seok-Hee, editor, Nishizeki, Takao, editor, and Quan, Wu, editor

Published
2008
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40. VÝCHOVNÝ ZÁSAH V MLADÝCH SMRKOVÝCH POROSTECH JAKO NÁSTROJ MITIGACE GLOBÁLNÍ KLIMATICKÉ ZMĚNY?

Author

ČERNÝ, JAKUB

Subjects
SOLAR radiation, SILVER fir, LEAF area, NORWAY spruce, KARST, SPECIES
Abstract

Although the ongoing global climate change elicits a shift in tree species composition along the vertical gradient, very extensive areas of pure Norway spruce [Picea abies (L.) Karst.] stands still occur out of their ecological optimum in the Czech Republic and Central Europe. Adaptive measures should be applied in these stands to promote productivity and stability. All measurements were performed in the 2018–2021 period on three permanent research plots located in the North-East part of Bohemia (Czech Republic). Based on the results, the most favourable way to increase solar radiation use efficiency expressed by canopy production index (CPI) and leaf area efficiency (LAE) is in-time heavy pre-commercial thinning application. Th e highest CPI and LAE values were observed in the Norway spruce stand aft er heavy pre-commercial thinning application (CPI = 2.00 and LAE = 1.59). In contrast, CPI = 1.26 and LAE = 0.99 were observed aft er the mild one, and CPI = 0.73 and LAE = 0.60 were reported in the control treatment with no silvicultural intervention. Overall, the presented results indicate a positive effect of heavy pre-commercial thinning on CPI and LAE in pure young Norway spruce stands. However, more eff ort should be devoted to studying the impact of different pre-commercial thinning intensities on solar radiation use efficacy across a broader gradient of site conditions, and future work should also be extended to other tree species. [ABSTRACT FROM AUTHOR]

Published
2023
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44. Stand growth and structure of mixed-species and monospecific stands of Scots pine (Pinus sylvestris L.) and oak (Q. robur L., Quercus petraea (Matt.) Liebl.) analysed along a productivity gradient through Europe

Author

European Commission, Bavarian State Ministry for Nutrition, Agriculture and Forestry, Research Council of Lithuania, Pretzsch, Hans [0000-0002-4958-1868], Steckel, Mathias [0000-0002-1940-5441], Heym, Michael [0000-0002-1314-2257], Biber, Peter [0000-0002-9700-8708], Ammer, Christian [0000-0002-4235-0135], Ehbrecht, Martin [0000-0002-1543-3023], Bielak, Kamil [0000-0002-1327-4911], Bravo, Felipe [0000-0001-7348-6695], Ordóñez, Cristóbal [0000-0001-5354-3760], Collet, Catherine [0000-0003-0861-7796], Drössler, Lars [0000-0002-1547-0975], Brazaitis, Gediminas [0000-0003-0234-9292], Godvod, Kšištof [0000-0002-9736-1544], Jansons, Aris [0000-0001-7981-4346], de-Dios-García, J. [0000-0003-3706-3390], Löf, Magnus [0000-0002-9173-2156], Aldea, Jorge [0000-0003-2568-5192], Korboulewsky, Nathalie [0000-0002-6017-1114], Reventlow, Ditlev Otto Juel [0000-0001-6040-5761], Nothdurft, Arne [0000-0002-7065-7601], Engel, Markus [0000-0001-6991-9021], Pach, Maciej [0000-0002-9833-867X], Skrzyszewski, Jerzy [0000-0003-4330-5827], Pardos Mínguez, Marta [0000-0002-5567-5406], Ponette, Quentin [0000-0002-2726-7392], Sitko, Roman [0000-0002-5611-2867], Fabrika, Marek [0000-0001-6993-1143], Svoboda, Miroslav [0000-0003-4050-3422], Černý, Jakub [0000-0002-9954-1506], Ruiz-Peinado, Ricardo [0000-0003-0126-1651], Río, Miren del [0000-0001-7496-3713], Pretzsch, Hans, Steckel, Mathias, Heym, Michael, Biber, Peter, Ammer, Christian, Ehbrecht, Martin, Bielak, Kamil, Bravo, Felipe, Ordóñez, Cristóbal, Collet, Catherine, Vast, Florian, Drössler, Lars, Brazaitis, Gediminas, Godvod, Kšištof, Jansons, Aris, de-Dios-García, J., Löf, Magnus, Aldea, Jorge, Korboulewsky, Nathalie, Reventlow, Ditlev Otto Juel, Nothdurft, Arne, Engel, Markus, Pach, Maciej, Skrzyszewski, Jerzy, Pardos, Marta, Ponette, Quentin, Sitko, Roman, Fabrika, Marek, Svoboda, Miroslav, Černý, Jakub, Wolff, Barbara, Ruiz-Peinado, Ricardo, Río, Miren del, European Commission, Bavarian State Ministry for Nutrition, Agriculture and Forestry, Research Council of Lithuania, Pretzsch, Hans [0000-0002-4958-1868], Steckel, Mathias [0000-0002-1940-5441], Heym, Michael [0000-0002-1314-2257], Biber, Peter [0000-0002-9700-8708], Ammer, Christian [0000-0002-4235-0135], Ehbrecht, Martin [0000-0002-1543-3023], Bielak, Kamil [0000-0002-1327-4911], Bravo, Felipe [0000-0001-7348-6695], Ordóñez, Cristóbal [0000-0001-5354-3760], Collet, Catherine [0000-0003-0861-7796], Drössler, Lars [0000-0002-1547-0975], Brazaitis, Gediminas [0000-0003-0234-9292], Godvod, Kšištof [0000-0002-9736-1544], Jansons, Aris [0000-0001-7981-4346], de-Dios-García, J. [0000-0003-3706-3390], Löf, Magnus [0000-0002-9173-2156], Aldea, Jorge [0000-0003-2568-5192], Korboulewsky, Nathalie [0000-0002-6017-1114], Reventlow, Ditlev Otto Juel [0000-0001-6040-5761], Nothdurft, Arne [0000-0002-7065-7601], Engel, Markus [0000-0001-6991-9021], Pach, Maciej [0000-0002-9833-867X], Skrzyszewski, Jerzy [0000-0003-4330-5827], Pardos Mínguez, Marta [0000-0002-5567-5406], Ponette, Quentin [0000-0002-2726-7392], Sitko, Roman [0000-0002-5611-2867], Fabrika, Marek [0000-0001-6993-1143], Svoboda, Miroslav [0000-0003-4050-3422], Černý, Jakub [0000-0002-9954-1506], Ruiz-Peinado, Ricardo [0000-0003-0126-1651], Río, Miren del [0000-0001-7496-3713], Pretzsch, Hans, Steckel, Mathias, Heym, Michael, Biber, Peter, Ammer, Christian, Ehbrecht, Martin, Bielak, Kamil, Bravo, Felipe, Ordóñez, Cristóbal, Collet, Catherine, Vast, Florian, Drössler, Lars, Brazaitis, Gediminas, Godvod, Kšištof, Jansons, Aris, de-Dios-García, J., Löf, Magnus, Aldea, Jorge, Korboulewsky, Nathalie, Reventlow, Ditlev Otto Juel, Nothdurft, Arne, Engel, Markus, Pach, Maciej, Skrzyszewski, Jerzy, Pardos, Marta, Ponette, Quentin, Sitko, Roman, Fabrika, Marek, Svoboda, Miroslav, Černý, Jakub, Wolff, Barbara, Ruiz-Peinado, Ricardo, and Río, Miren del

Abstract

Past failures of monocultures, caused by wind-throw or insect damages, and ongoing climate change currently strongly stimulate research into mixed-species stands. So far, the focus has mainly been on combinations of species with obvious complementary functional traits. However, for any generalization, a broad overview of the mixing reactions of functionally different tree species in different mixing proportions, patterns and under different site conditions is needed, including assemblages of species with rather similar demands on resources such as light. Here, we studied the growth of Scots pine and oak in mixed versus monospecific stands on 36 triplets located along a productivity gradient across Europe, reaching from Sweden to Spain and from France to Georgia. The set-up represents a wide variation in precipitation (456–1250 mm year−1), mean annual temperature (6.7–11.5 °C) and drought index by de Martonne (21–63 mm °C−1). Stand inventories and increment cores of trees stemming from 40- to 132-year-old, fully stocked stands on 0.04–0.94-ha-sized plots provided insight into how species mixing modifies stand growth and structure compared with neighbouring monospecific stands. On average, the standing stem volume was 436 and 360 m3 ha−1 in the monocultures of Scots pine and oak, respectively, and 418 m3 ha−1 in the mixed stands. The corresponding periodical annual volume increment amounted to 10.5 and 9.1 m3 ha−1 year−1 in the monocultures and 10.5 m3 ha−1 year−1 in the mixed stands. Scots pine showed a 10% larger quadratic mean diameter (p < 0.05), a 7% larger dominant diameter (p < 0.01) and a 9% higher growth of basal area and volume in mixed stands compared with neighbouring monocultures. For Scots pine, the productivity advantages of growing in mixture increased with site index (p < 0.01) and water supply (p < 0.01), while for oak they decreased with site index (p < 0.01). In total, the superior productivity of mixed stands compared to monocultures increased wit

Published
2020

45. Species mixing reduces drought susceptibility of Scots pine (Pinus sylvestris L.) and oak (Quercus robur L., Quercus petraea (Matt.) Liebl.) – Site water supply and fertility modify the mixing effect

Author

European Commission, Agencia Estatal de Investigación (España), Federal Ministry of Food and Agriculture (Germany), Steckel, Mathias [0000-0002-1940-5441], Río, Miren del [0000-0001-7496-3713], Heym, Michael [0000-0002-1314-2257], Aldea, Jorge [0000-0003-2568-5192], Bielak, Kamil [0000-0002-1327-4911], Brazaitis, Gediminas [0000-0003-0234-9292], Černý, Jakub [0000-0002-9954-1506], Coll, Lluís [0000-0002-8035-5949], Collet, Catherine [0000-0003-0861-7796], Ehbrecht, Martin [0000-0002-1543-3023], Jansons, Aris [0000-0001-7981-4346], Nothdurft, Arne [0000-0002-7065-7601], Pach, Maciej [0000-0002-9833-867X], Pardos, Marta [0000-0002-5567-5406], Ponette, Quentin [0000-0002-2726-7392], Reventlow, Ditlev Otto Juel [0000-0001-6040-5761], Sitko, Roman [0000-0002-5611-2867], Svoboda, Miroslav [0000-0003-4050-3422], Vallet, Patrick [0000-0003-2649-9447], Pretzsch, Hans [0000-0002-4958-1868], Steckel, Mathias, Río, Miren del, Heym, Michael, Aldea, Jorge, Bielak, Kamil, Brazaitis, Gediminas, Černý, Jakub, Coll, Lluís, Collet, Catherine, Ehbrecht, Martin, Jansons, Aris, Nothdurft, Arne, Pach, Maciej, Pardos, Marta, Ponette, Quentin, Reventlow, Ditlev Otto Juel, Sitko, Roman, Svoboda, Miroslav, Vallet, Patrick, Wolff, Barbara, Pretzsch, Hans, European Commission, Agencia Estatal de Investigación (España), Federal Ministry of Food and Agriculture (Germany), Steckel, Mathias [0000-0002-1940-5441], Río, Miren del [0000-0001-7496-3713], Heym, Michael [0000-0002-1314-2257], Aldea, Jorge [0000-0003-2568-5192], Bielak, Kamil [0000-0002-1327-4911], Brazaitis, Gediminas [0000-0003-0234-9292], Černý, Jakub [0000-0002-9954-1506], Coll, Lluís [0000-0002-8035-5949], Collet, Catherine [0000-0003-0861-7796], Ehbrecht, Martin [0000-0002-1543-3023], Jansons, Aris [0000-0001-7981-4346], Nothdurft, Arne [0000-0002-7065-7601], Pach, Maciej [0000-0002-9833-867X], Pardos, Marta [0000-0002-5567-5406], Ponette, Quentin [0000-0002-2726-7392], Reventlow, Ditlev Otto Juel [0000-0001-6040-5761], Sitko, Roman [0000-0002-5611-2867], Svoboda, Miroslav [0000-0003-4050-3422], Vallet, Patrick [0000-0003-2649-9447], Pretzsch, Hans [0000-0002-4958-1868], Steckel, Mathias, Río, Miren del, Heym, Michael, Aldea, Jorge, Bielak, Kamil, Brazaitis, Gediminas, Černý, Jakub, Coll, Lluís, Collet, Catherine, Ehbrecht, Martin, Jansons, Aris, Nothdurft, Arne, Pach, Maciej, Pardos, Marta, Ponette, Quentin, Reventlow, Ditlev Otto Juel, Sitko, Roman, Svoboda, Miroslav, Vallet, Patrick, Wolff, Barbara, and Pretzsch, Hans

Abstract

Tree species mixing has been widely promoted as a promising silvicultural tool for reducing drought stress. However, so far only a limited number of species combinations have been studied in detail, revealing inconsistent results. In this study, we analysed the effect of mixing Scots pine and oak (pedunculate oak and sessile oak) trees on their drought response along a comprehensive ecological gradient across Europe. The objective was to improve our knowledge of general drought response patterns of two fundamental European tree species in mixed versus monospecific stands. We focused on three null hypotheses: (HI) tree drought response does not differ between Scots pine and oak, (HII) tree drought response of Scots pine and oak is not affected by stand composition (mixture versus monoculture) and (HIII) tree drought response of Scots pine and oak in mixtures and monocultures is not modified by tree size or site conditions. To test the hypotheses, we analysed increment cores of Scots pine and oak, sampled in mixed and monospecific stands, covering a wide range of site conditions. We investigated resistance (the ability to maintain growth levels during drought), recovery (the ability to restore a level of growth after drought) and resilience (the capacity to recover to pre-drought growth levels), involving site-specific drought events that occurred between 1976 and 2015. In monocultures, oak showed a higher resistance and resilience than Scots pine, while recovery was lower. Scots pine in mixed stands exhibited a higher resistance, but also a lower recovery compared with Scots pine in monocultures. Mixing increased the resistance and resilience of oak. Ecological factors such as tree size, site water supply and site fertility were found to have significant effects on the drought response. In the case of Scots pine, resistance was increased by tree size, while recovery was lowered. Resistance of oak increased with site water supply. The observed mixing effect on the tre

Published
2020

47. Emerging stability of forest productivity by mixing two species buffers temperature destabilizing effect

Author

Ministerio de Ciencia e Innovación (España), European Commission, National Agency of Agricultural Research (Czech Republic), Ministry of Science and Higher Education (Poland), Estonian Research Council, Slovak Research and Development Agency, Río, M. del [0000-0001-7496-3713], Pardos Mínguez, Marta [0000-0002-5567-5406], Nord-Larsen, Thomas [0000-0002-5341-6435], Den Ouden, Jan [0000-0003-1518-2460], Río, Miren del, Pretzsch, Hans, Ruiz-Peinado, Ricardo, Jactel, Hervé, Coll, Lluís, Löf, Magnus, Aldea, Jorge, Ammer, Christian, Avdagić, Admir, Barbeito, Ignacio, Bielak, Kamil, Bravo, Felipe, Brazaitis, Gediminas, Černý, Jakub, Collet, Catherine, Condés, Sonia, Drössler, Lars, Fabrika, Marek, Heym, Michael, Holm, Stig Olof, Hylen, Gro, Jansons, Aris, Kurylyak, Viktor, Lombardi, Fabio, Matović, Bratislav, Metslaid, Marek, Motta, Renzo, Nord-Larsen, Thomas, Nothdurft, Arne, Den Ouden, Jan, Pach, Maciej, Pardos, Marta, Poeydebat, Charlotte, Ponette, Quentin, Pérot, Tomas, Reventlow, Ditlev Otto Juel, Sitko, Roman, Sramek, Vit, Steckel, Mathias, Svoboda, Miroslav, Verheyen, Kris, Vospernik, Sonja, Wolff, Barbara, Zlatanov, Tzvetan, Bravo-Oviedo, Andrés, Ministerio de Ciencia e Innovación (España), European Commission, National Agency of Agricultural Research (Czech Republic), Ministry of Science and Higher Education (Poland), Estonian Research Council, Slovak Research and Development Agency, Río, M. del [0000-0001-7496-3713], Pardos Mínguez, Marta [0000-0002-5567-5406], Nord-Larsen, Thomas [0000-0002-5341-6435], Den Ouden, Jan [0000-0003-1518-2460], Río, Miren del, Pretzsch, Hans, Ruiz-Peinado, Ricardo, Jactel, Hervé, Coll, Lluís, Löf, Magnus, Aldea, Jorge, Ammer, Christian, Avdagić, Admir, Barbeito, Ignacio, Bielak, Kamil, Bravo, Felipe, Brazaitis, Gediminas, Černý, Jakub, Collet, Catherine, Condés, Sonia, Drössler, Lars, Fabrika, Marek, Heym, Michael, Holm, Stig Olof, Hylen, Gro, Jansons, Aris, Kurylyak, Viktor, Lombardi, Fabio, Matović, Bratislav, Metslaid, Marek, Motta, Renzo, Nord-Larsen, Thomas, Nothdurft, Arne, Den Ouden, Jan, Pach, Maciej, Pardos, Marta, Poeydebat, Charlotte, Ponette, Quentin, Pérot, Tomas, Reventlow, Ditlev Otto Juel, Sitko, Roman, Sramek, Vit, Steckel, Mathias, Svoboda, Miroslav, Verheyen, Kris, Vospernik, Sonja, Wolff, Barbara, Zlatanov, Tzvetan, and Bravo-Oviedo, Andrés

Abstract

The increasing disturbances in monocultures around the world are testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increases with species richness, although the ecological fundamentals have mainly been investigated through diversity experiments. To adequately manage forest ecosystems, it is necessary to have a comprehensive understanding of the effect of mixing species on the temporal stability of productivity and the way in which it is influenced by climate conditions across large geographical areas. Here, we used a unique dataset of 261 stands combining pure and two-species mixtures of four relevant tree species over a wide range of climate conditions in Europe to examine the effect of species mixing on the level and temporal stability of productivity. Structural equation modelling was employed to further explore the direct and indirect influence of climate, overyielding, species asynchrony and additive effect (i.e. temporal stability expected from the species growth in monospecific stands) on temporal stability in mixed forests. We showed that by adding only one tree species to monocultures, the level (overyielding: +6%) and stability (temporal stability: +12%) of stand growth increased significantly. We identified the key effect of temperature on destabilizing stand growth, which may be mitigated by mixing species. We further confirmed asynchrony as the main driver of temporal stability in mixed stands, through both the additive effect and species interactions, which modify between-species asynchrony in mixtures in comparison to monocultures. Synthesis and applications. This study highlights the emergent properties associated with mixing two species, which result in resource efficient and temporally stable production systems. We reveal the negative impact of mean temperature on temporal stability of forest productivity and how the stabilizing effect of mixing two species can counterbalance this

Published
2022

48. With increasing site quality asymmetric competition and mortality reduces Scots pine (Pinus sylvestris L.) stand structuring across Europe

Author

European Commission, German Research Foundation, Bavarian State Ministry for Nutrition, Agriculture and Forestry, Junta de Castilla y León, Universidad de Valladolid, Estonian Research Council, National Agency of Agricultural Research (Czech Republic), Slovak Research and Development Agency, Pretzsch, Hans, Bravo-Oviedo, Andrés, Hilmers, Torben, Ruiz-Peinado, Ricardo, Coll, Lluís, Löf, Magnus, Ahmed, Shamim, Aldea, Jorge, Ammer, Christian, Avdagić, Admir, Barbeito, Ignacio, Bielak, Kamil, Bravo, Felipe, Brazaitis, Gediminas, Černý, Jakub, Collet, Catherine, Drössler, Lars, Fabrika, Marek, Heym, Michael, Holm, Stig Olof, Hylen, Gro, Jansons, Aris, Kurylyak, Viktor, Lombardi, Fabio, Matović, Bratislav, Metslaid, Marek, Motta, Renzo, Nord-Larsen, Thomas, Nothdurft, Arne, Ordóñez, Cristóbal, Reventlow, Ditlev Otto Juel, Sitko, Roman, Sramek, Vit, Steckel, Mathias, Svodoba, Miroslav, Uhl, Enno, Verheyen, Kris, Vospernik, Sonja, Wolff, Barbara, Zlatanov, Tzvetan, European Commission, German Research Foundation, Bavarian State Ministry for Nutrition, Agriculture and Forestry, Junta de Castilla y León, Universidad de Valladolid, Estonian Research Council, National Agency of Agricultural Research (Czech Republic), Slovak Research and Development Agency, Pretzsch, Hans, Bravo-Oviedo, Andrés, Hilmers, Torben, Ruiz-Peinado, Ricardo, Coll, Lluís, Löf, Magnus, Ahmed, Shamim, Aldea, Jorge, Ammer, Christian, Avdagić, Admir, Barbeito, Ignacio, Bielak, Kamil, Bravo, Felipe, Brazaitis, Gediminas, Černý, Jakub, Collet, Catherine, Drössler, Lars, Fabrika, Marek, Heym, Michael, Holm, Stig Olof, Hylen, Gro, Jansons, Aris, Kurylyak, Viktor, Lombardi, Fabio, Matović, Bratislav, Metslaid, Marek, Motta, Renzo, Nord-Larsen, Thomas, Nothdurft, Arne, Ordóñez, Cristóbal, Reventlow, Ditlev Otto Juel, Sitko, Roman, Sramek, Vit, Steckel, Mathias, Svodoba, Miroslav, Uhl, Enno, Verheyen, Kris, Vospernik, Sonja, Wolff, Barbara, and Zlatanov, Tzvetan

Abstract

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 change

Published
2022

49. „Doufali jsme, že ten byt jednou bude náš." Boj za férovou privatizaci v případu iniciativy Moje Písnice.

Author

ČERNÝ, JAKUB, MOSKVINA, YULIYA, and BÖHMOVÁ, LUDMILA

Abstract

In this article, we analyse the conditions behind the formation of the tenant initiative Moje Písnice, which existed in Prague between 2016 and 2020. In the theoretical part, we explain the concepts of urban movements and tenant movements in Central and Eastern Europe and emphasise the role of everyday life and emotions in the genesis of a collective actor. We use qualitative methodology based on an analysis of 12 in-depth semi-structured interviews with members and one supporter of the Moje Pisnice Initiative. This initiative provides an illustration of the formation of collective actors in the urban space in Central and Eastern Europe. We focus specifically on the historical and social conditions behind the initiative's development and the emergence of a shared identity and shared housing expectations and the disappointment resulting from unfulfilled hopes. Other important factors that we discuss are the intersubjectivity of emotions and the emancipatory potential of the initiative's organisational structure, which enabled the participation of people with no prior experience with activism. We also focus on the public's sense of disillusionment with civic engagement and with the political system in general since 1989. This research contributes to the study of tenant movements in postsocialist countries, which are often an overlooked actor in one of the most important processes in the post-1989 transformation - privatisation. In contrast to previous research, we focus on the role of shared emotions and the subjective experience of historical processes. [ABSTRACT FROM AUTHOR]

Published
2023
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50. Spatial Analysis of Czech Parliamentary Election: Comparison of Spatial Econometrics and Machine Learning

Author

Černý, Jakub, Šťastná, Lenka, and Gregor, Martin

Subjects
parlamentní volby, prostorová analýza, náhodné lesy, spatial analysis, strojové učení, machine learning, parliamentary election, random forest, spatial durbin error
Abstract

This thesis analyses the results of the Czech Parliamentary election in 2021 and attempts to explain the voting support of major political subjects by using aggregate data from Czech municipalities. Since the data evince spatial autocorrelation, it is necessary to specify a suitable spatial model. The thesis provides both empirical and economic evidence for the Spatial Durbin Error Model, which enables distinguishing the direct and indirect effects of particular independent variables and accounts for the spatial dependence of error terms. This method shows that variables describing the socio-economic characteristics of inhabitants, such as the share of entrepreneurs or people with university education, play the most significant role in explaining voting results and evince mostly the direct effects. On the contrary, variables describing municipalities, such as public spending or infrastructure, are more likely to impact the election result indirectly. Subsequently, the analysis is replicated using two tree-based machine learning algorithms and all models are evaluated based on their ability to predict the election results from unseen data. Even though machine learning methods estimate only relative variable importance instead of standard coefficients, this approach represents a perspective...

Published
2022

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