Corrigendum to “The effect of structural diversity on the self-thinning line, yield level, and density-growth relationship in even-aged stands of...."
DOI of the correction article: https://doi.org/10.1016/j.foreco.2024.121841
http://hdl.handle.net/10261/361471, Diversity of tree species and structure have the potential to increase various forest ecosystem services such as stress resistance, biodiversity, and productivity. Recent studies indicate the relevance and potential of both diversity of tree species and diversity of stand structure. Here, we analyze the effect of stand structure on the stand-level behavior of even-aged stands of Norway spruce (Picea abies (L.) H. Karst.). Drawing from 11 long-term thinning experiments encompassing 77 plots and 425 surveys, we analyzed the effect of tree size and growth frequency distributions on (i) the self-thinning line, (ii) the Eichhorn rule and yield level, and (iii) the stand density-growth relationship. We revealed an optimum relationship between the inequality of tree size and growth within forest stands and the maximum stand density, standing volume, total yield, and stand density-growth relationship. Highest stand density, standing volume, total volume yield, and stand volume growth occurred at moderate structural diversity, in terms of the inequality of tree size and growth. All else being equal, strongly homogeneous, or very heterogeneous stand structures were found to be suboptimal in terms of growth and yield. Our findings emphasize that incorporating information about tree size frequency distributions can greatly improve upon classical models of stand dynamics, even for even-aged spruce monocultures. The profound influence of stand structure on stand growth and yield, even when the classical stand attributes are analogous, warrants further scientific attention; e.g., neglecting differences in stand structure can lead to skewed interpretations of growth reactions to density regulation or species mixing. From a forest management perspective, our results unveil the untapped potential of structural diversification, even for mono-specific and even-aged stands. We elucidate the growth trade-offs when structural diversity is either neglected or overly emphasized., The study received funding from the European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie Grant Agreement No. H2020-MSCA-ITN-2020–956355, the project 101081774, HORIZON-CL6–2022-BIODIV-01, and from the European Union’s Horizon 2020 research and innovation program under grant agreement No952314. We further thank the Bayerische Staatsforsten (BaySF) for supporting the establishment of the plots and the Bavarian State Ministry for Nutrition, Agriculture, and Forestry for the permanent support of the project "W07 Long-term experimental plots for forest growth and yield research" (# 7831–22209-2013). Open Access funding enabled and organized by Projekt DEAL. We are also grateful for the support from the Spanish Ministerio de Ciencia e Innovación (IMFLEX project# PID2021–126275OB-C21/C22). Thanks, are also due to Monika Bradatsch for the graphical artwork and two anonymous reviewers for their constructive criticism., Peer reviewed

14 Pág., 3D crown shape and tree ring development are autobiographies of the growth conditions. With advancements in terrestrial laser scanning, modeling growth from 3D crown structure offers insights into trees’ structural and functional responses in a non-destructive and repetitive way. However, how the trees in different growing conditions respond in 3D structure and manifest their responses into tree rings remains unexplored, which would help to better explain tree-level growth dynamics and forest management. To enhance this understanding, we tested a set of hypotheses: (HI) that 3D crown shape (CS) and tree ring (width) patterns (TRP) are correlated across different growing conditions or forest stands like monospecific, provenances trials, and mixed forest stands; (HII) that stand types influence the CS-TRP link; and (HⅢ) local neighborhood competition (LNC) modulates the CS-TRP link. (HⅣ) 3D crowns manifest local growth conditions; therefore, 3D crown structures can be used to predict tree ring growth. We assessed these hypotheses by employing terrestrial laser scanning-based 3D crown shape and dendrochronology-based tree ring width patterns from Norway spruce (Picea abies [L.] Karst.) trees growing in pure spruce (unthinned and thinned), provenances trial, and mixed-species trial (with European Beech, Fagus sylvatica [L.]) stands covering a large-scale competition gradient. We first show that 3D crown shape and TRP metrics differed significantly across forests (p<0.05) but were correlated (p<0.05). Neighborhood competition among the forest types influences the link between 3D crowns and tree rings. Pathway-based analyses revealed that neighborhood competition indirectly influences ring variability by modifying crown structure (p<0.05), suggesting local growth conditions are mostly manifested into crown shapes, leading to 3D crown shape-based low-error growth predictions (0.44 mm) across forest types. However, incorporating competition legacy information (competition over the last 30 years) in the model slightly improved the prediction performance (error reduced to 0.41 mm), further explaining that the crown likely loses growth information due to growing conditions (competition it faces and species with it is growing). This study reveals how trees in different growing conditions differed structurally and mechanized their responses in tree rings, providing crucial insights into tree-level growth dynamics and management., This work is funded by European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie Grant Agreement No. H2020-MSCA-ITN-2020-956355., Peer reviewed

20 Pág., Climate change is expected to intensify drought in the Mediterranean region. Previous studies indicate that tree species mixing may reduce the water stress. Our study investigates the response to past drought events of four co-occurring Mediterranean species: Pinus pinea L. (stone pine), Pinus pinaster Ait. (maritime pine), Juniperus thurifera L. (Spanish juniper) and Quercus ilex L (holm oak). The study was performed at an interannual scale, both in monospecific and mixed stands. Annual tree ring widths data measured on increment cores and stem discs obtained from 281 trees were used to quantify the responses to drought events using complementary resilience indices. Additionally, we assessed tree intra- and inter-specific competition impact over the past 25 years. We fitted and compared generalised linear mixed models to determine the influence of species identity, stand composition as intra-specific and inter-specific competition on complementary resilience indices and annual basal area increment. The co-existence with other species enhanced the resistance to drought of the stone pine as the resilience capacity of the Spanish juniper. Conversely, maritime pine’s drought resistance declined considerably in mixed stands. Notably, only the anisohydric species Spanish juniper and holm oak were able to return to pre-disturbance growth rates after the drought. The influence of competition on tree growth was found to differ according to the hydrological conditions of each year and varied based on the specific source of competition. Our study showed that mixed stands in the Spanish Northern Plateau, especially with holm oak and Spanish juniper, are more resilient to prolonged droughts due to spatio-temporal complementarity and subsequent competition reduction. That is another reason for which such composed mixed stands should be promoted in the arid conditions of the Spanish Northern Plateau., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The study is supported by ETN Skill-For.Action project that has received funding from the European Union’s HORIZON 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No. 956355., Peer reviewed

12 Pág., The use of mobile laser scanning to survey forest ecosystems is a promising, scalable technology to describe forest 3D structures at high resolution. To confirm the consistency in the retrieval of forest structural parameters using hand-held laser scanning (HLS), before operationalizing the method, confirming the data is crucial. We analyzed the performance of tree-level mapping based on HLS under different phenology conditions on a mixed forest in western Spain comprising Pinus pinaster and two deciduous species, Alnus glutinosa and Quercus pyrenaica. The area was surveyed twice during the growing season (July 2022) and once in the deciduous season (February 2022) using several scanning paths. Ground reference data (418 trees, 15 snags) was used to calibrate the HLS data and to assess the influence of phenology when converting 3D data into tree-level attributes (DBH, height and volume). The HLS-based workflow was robust at isolating tree positions and recognizing stems despite changes in phenology. Ninety-six percent of all pairs matched below 65 cm. For DBH, phenology barely altered estimates. We observed a strong agreement when comparing HLS-based tree height distributions. The values exceeded 2 m when comparing height measurements, confirming height data should be carefully used as reference in remote sensing-based inventories, especially for deciduous species. Tree volume was more precise for pines (r = 0.95, and relative RMSE = 21.3 –23.8%) compared to deciduous species (r = 0.91 –0.96, and relative RMSE = 27.3–30.5%). HLS data and the forest structural complexity tool performed remarkably, especially in tree positioning considering mixed forests and mixed phenology conditions., This publication is part of the ETN Skill For. Action project from the European Union’s Horizon 2020
research and innovation program under the Marie Skłodowska Curie, Grant Agreement 956355; this study has also been subsidized by the Junta de Castilla y León through the projects "CLU-2019-01 and CL-EI-2021-05-iuFOR Institute Unit of Excellence" of the University of Valladolid and co-fnanced by the European Regional Development Fund (ERDF "Europe drives our growth")., Peer reviewed

16 Pág., Societal Impact Statement: Forests worldwide face significant challenges due to climate change, impacting their health and productivity. In this study, we examined how European beech and Scots pine influence each other's phenology and growth in mixed forests. Our findings indicate that mixing these complementary tree species can increase resource efficiency within forest ecosystems. By leveraging informed species selection, this research highlights the potential for developing knowledge-based, resource-efficient forests. These insights are invaluable for policymakers and forest managers in designing forests that are not only productive but also sustainable and adaptable to evolving environmental conditions. Summary: We investigated the effects of interspecific neighbors on crown morphology and growth efficiency in European temperate forests, specifically focusing on European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.). Our goal was to determine whether the previously reported overyielding in this mixture is primarily due to improved space-use efficiency and packing density or enhanced resource-use efficiency. Our methodology involved a detailed analysis of 128 individual felled trees. We assessed the effect of intraspecific and interspecific neighbors on stem volume growth, the allometric relationships of tree crowns and their components, and the allocation of branch and leaf biomass along the trees' vertical structure. Our findings demonstrate that interspecific neighbors significantly influence the allometric relationships of tree crowns, especially altering the vertical biomass distribution in European beech. Additionally, we found that interspecific neighbors can significantly enhance the growth efficiency of European beech but not for Scots pine. This research provides valuable insights for enhancing forest growth models and guiding forest management practices. By understanding the critical role of crown biomass allocation and growth efficiency in mixed-species stands, policymakers and forest managers can design forests that are both productive and adaptable to changing environmental conditions. This study emphasizes the importance of species interactions in forest dynamics and bridges theoretical concepts with practical applications., The authors wish to thank the German Research Foundation-DFG (Deutsche Forschungsgemeinschaft) for funding the project “Structure and dynamics of mixed-species stands of Scots pine and European beech compared with mono-specific stands. Analysis along an ecological gradient through Europe” (# PR 292/15-1). The study received funding from the European Union's Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement no. H2020-MSCA-ITN-2020-956355, the project 101081774, HORIZON-CL6-2022-BIODIV-01, from the European Union's Horizon 2020 research and innovation program under grant agreement no. 952314 and was supported by grant number Z073 administered by the Bavarian State Ministry for Food, Agriculture, and Forests (Bayerischen Staatsministerium für Ernährung, Landwirtschaft und Forsten)., Peer reviewed

22 Pág., In forest management, merging stand structural diversity with carbon storage is essential for resilience and climate mitigation. This study assesses (1) how structural diversity in stands of spruce (Picea abies (L.) H. Karst.), pine (Pinus sylvestris L.), beech (Fagus sylvatica L.), and oak (Quercus robur L. and Quercus petraea (Matt.) Liebl.) in Central Europe varies with age, site quality, and applied thinning grade; (2) these factors' impact on carbon stock; and (3) the link between structural diversity and carbon stock. Analyzing 26 long-term thinning experiments, we used the Gini coefficient of tree heights to measure structural diversity and species-specific biomass functions for carbon stock assessments. Our results show that structural diversity, highest in beech and spruce, decreases with stand age and on richer sites. Thinning enhances structural diversity in spruce and beech but reduces it in pine and oak. Unthinned or only moderately thinned mature spruce and beech stands outperform pine and oak in carbon stock (200–300 vs. 100–150 Mg C ha−1). C- and D&E-grade thinning halves carbon stock. A decrease in vertical layering with increased carbon storage varies across species. Given the same carbon stock, thinning from above maintains structural diversity in spruce and beech, while non-thinning or thinning from below promotes structural diversity in pine and oak. Based on the current silvicultural practice reflected by the NFI data of Germany, we argue that reduced thinning in previously D&E-grade thinned stands may slightly reduce their structural diversity. However, a suspension or reduction of thinning would strongly improve carbon storage (+ 100–200 Mg C ha−1) in the next 3–5 decades. We discussed options for reconciling structural diversity and carbon storage by silvicultural management of the four considered species in Central Europe., Open Access funding enabled and organized by Projekt DEAL. Open Access funding enabled and organized by Projekt DEAL. The study received funding from the European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie Grant Agreement No. H2020-MSCA-ITN-2020-956355 and from the European Union’s Horizon 2020 research and innovation program under grant agreement No952314., Peer reviewed

Despite recent advances in understanding the structure and dynamics of mixed forests, uneven-aged forests and their inherent diversity remain underexplored. Tree size diversity, an integral component of forest structure, influences ecosystem functioning and plays a vital role in ecological modeling, monitoring, and silvicultural decision-support systems. Although a few quantitative indices exist to assess tree size diversity, it remains unclear: (i) which aspects of diversity they capture and (ii) how consistent they are with qualitative evaluations by forest experts, who base silvicultural decisions on personal perception. To explore the relationship between quantitative and qualitative approaches, we analysed 36 circular plots in Zagnańsk Forest, Central Poland, representing a gradient from even-aged, monolayered monospecific stands to uneven-aged, mixed silver fir-dominated stands. Based on state-of-the-art literature review, we selected and evaluated 54 variations of distance-independent tree size diversity indices. Six forestry experts categorized the plots into five tree size diversity classes using a structured questionnaire. Canonical correlation analysis revealed considerable variability in how the indices aligned with the perceptions of the experts, who showed a high degree of interrater reliability (Cohen's Kappa=0.64). Shannon diversity and evenness indices based on tree height classes and basal area, as well as Kurtosis and Skewness of the diameter at breast height distribution, exhibited the strongest correlations with experts' evaluations. Moreover, several other indices, including Shannon evenness, Atkinson, and Hoover indices, showed moderate to strong correlation with experts' qualitative evaluation. Our results highlight the need to bridge the gap between mathematical concepts and applied silviculture., This project was funded by the Marie Sklodowska Curie Skill−for Action programme under Grant Agreement No. 956355. Part of this work was also financially supported by the General Directorate of State Forests in Poland under Grant Agreement No. OR.271.3.16.2017., Peer reviewed

Crown trait-based ecology has significantly advanced, yet a substantial knowledge gap remains regarding its predictive power on internal tree morphology and future growth potential across different species. Our research addressed this gap by examining how crown traits of various species manifest in temporal tree growth dynamics by answering three research questions (QⅠ): Are there general relationships between crown structure and secondary growth across species? (QⅡ) How do crown structure and secondary growth links vary among species and functional groups? (QⅢ) To what extent does a tree's crown structure explain the variation in secondary growth over different periods? We conducted a comprehensive study to answer these questions, utilizing high-resolution 3D crown structure data from terrestrial laser scanning and growth ring data from tree coring. Our research explored the relationship between crown structure and growth rings in six dominant tree species in Europe (Picea abies (L.) H. Karst., Pinus sylvestris L., Pseudotsuga menziesii (Mirbel) Franco, Larix decidua Mill., Fagus sylvatica L., and Quercus robur L.) across Germany and Spain. These species, representing diverse functional identities, provide a comprehensive spectrum for analysis, ensuring the robustness of our findings. Our findings demonstrated a consistent link between crown structure (explained by projection area, crown length, ratio, slenderness, top-heaviness, etc.) and secondary growth, varying across species and functional identities. Coniferous species (e.g., P. abies, P. menziesii, L. decidua) generally exhibited stronger associations between crown structure and tree ring width than broadleaf; in contrast, P. sylvestris and Q. robur demonstrated weaker predictive relationships due to their lower crown plasticity and more episodic growth. The current crown structure was a reliable predictor of tree secondary growth over decadal scales. However, stronger relationships emerged when considering the entire tree ring series, suggesting a long-term morphological legacy effect of crown structure. These results show the importance of understanding how specific traits related to different tree species and their functional roles impact tree structure and growth. By better understanding how trees adapt (plasticity) and how their past growth affects future development (crown legacy), we can manage environmental challenges more effectively. Therefore, this knowledge is valuable for improving forest management practices and offers useful insights for professionals working in forestry., This work is funded by the European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie Grant Agreement No. H2020-MSCA-ITN-2020–956355 as part of the Skill for Action project., Peer reviewed

Accurate detection of phenological events, such as growth onset, cessation, and seasonal transitions, is essential for understanding tree growth dynamics, particularly in Mediterranean forests where bimodal growth patterns are common. While microcore analysis remains the most precise method, its labor-intensive nature has led researchers to rely on dendrometer-based approaches. However, traditional methods using dendrometer data— such as parametric growth curve fitting with phenological events detected as relative thresholds—are often biased by hydration-related fluctuations and may fail to accurately capture complex growth patterns. In this study, we compared commonly used detection methods, including the Gompertz and Richards parametric functions, a generalized additive model (GAM), and the zero-growth (ZG) concept, with a novel approach: the two-stage threshold approach (2STA). Our results showed that the 2STA consistently outperformed existing methods in identifying spring onset, summer cessation, and autumn onset, exhibiting deviations within the expected measurement uncertainty (±7 days). The method’s reliance on direct growth rate transitions, rather than smoothed curves or arbitrary percentiles, reduced errors associated with hydration-related stem fluctuations. However, year cessation was best estimated using a 95% relative growth threshold derived from the Richards function. These findings highlight the potential of the 2STA as a robust and objective method for phenological event detection using manually collected band dendrometer data, particularly for species with complex intra-annual growth patterns. Future research should focus on refining climate-based thresholds for cambial activity and validating the method across a wider range of species and environmental conditions., The author(s) declare that financial support was received for the research and/or publication of this article. The study is supported by ETN Skill-For. Action project that has received funding from: (1) the European Union’s HORIZON 2020 research and innovation programme under the Marie Skłodowska - Curie Grant Agreement No. 956355; (2) Spanish Agencia Estatal de Investigación under the agreement PID2022-136906OB-C21. BEGINPINE; (3) Ministerio para la Transición Ecológica y el Reto Demográfico, within the project MITECO2023-AF. 20234TE005. TC MITECO-CSIC. Jorge Aldea’s work was supported by the grant RYC2021-033031-I, funded by MCIN/AEI/10.13039/501100011033 and by the European Union “NextGenerationEU/PRTR.”, Peer reviewed

Scots pine (Pinus sylvestris L.) and sessile oak (Quercus petraea (Matt.) Liebl.) are species associated with drought resistance and biodiversity, respectively. Therefore, mixed stands of the two species promise stable, diverse and productive populations. However, the information about how to manage this mixture is still scarce. Here, we studied the growth of mixed and monospecific stands of Scots pine and sessile oak along an ecological gradient across Europe (France, Germany Poland and Spain), focusing on the impact of heavy tree crop thinning compared to unthinned conditions. Firstly, we analysed the effect of tree crop thinning on the gross and net stand growth in mixed compared with monospecific stands. Predominantly, the effects were negative on gross growth and neutral or positive on net growth. Secondly, we revealed that due to the similar ecological traits of both species, there was no significant overyielding in terms of gross growth and even underyielding in net growth. However, by heavy tree crop thinning underyielding was avoided. Thirdly, we found that although the productivity of pure and mixed stands was relatively similar, without thinning the mortality in mixed stands increases. Heavy tree crop thinning counteracted the decline of pine, promoted oak growth, and avoided growth losses at stand level. The results mean that future research into mixed stands and especially studies and comparisons between pure and mixed stands should pay more attention to the previous silvicultural treatment, possible anticipation of mortality, and the resulting difference between gross and net productivity of the stocks., Thanks for the support by the Spanish Ministerio de Ciencia e Innovación (MCIN/ AEI /10.13039/501100011033/) for funding the Project (PID2021–126275OB-C21/C22 - Integrated Forest Management along complexity gradients. Thanks go furthermore to the Junta de Castilla y Leon, Spain, and the European Union for funding the Project CLU-2019–01—iuFOR Institute Unit of Excellence of the University of Valladolid through the ERDF "Europe drives our growth”. We would also like to thank the Bavarian State Ministry for Nutrition, Agriculture and Forestry for permanent support of the project W007 "Long-term experimental plots for growth and yield research" (#7831–1/874). The Polish State Forests Enterprise also supported establishment of one Polish site (Grant No: OR.271.3.15.2017). Furthermore, the work was also partially supported by EU Horizon 2020 Project (Grant Agreement No. 956355) and the Polish Government (Grant Agreement No. 566953/PnH 2/2023). We thank all the people who contributed to the establishment and measurements of the study plots., Peer reviewed

[Data availability]
The data used for this study is available under the following ZENODO link: 10.5281/zenodo.15808868., In Mediterranean forests, where seasonal drought imposes severe physiological constraints, the dynamics of tree growth are shaped not only by climate but also by interspecific interactions. However, how these factors influence intra-annual growth phenology remains poorly understood. Here, we used biweekly band dendrometer data collected since May 2022 to June 2024, from 154 trees across seven pure and mixed sample plots in the Spanish Northern Plateau. Our aim was to investigate how stand composition and interspecific competition affect phenological events, seasonal growth rates, and tree water deficit (TWD) in four tree species: Pinus pinea L., Pinus pinaster Ait., Quercus ilex L. and Juniperus thurifera L. We found that the identity of surrounding species significantly altered the xylogenesis phenology as the daily growth rate, particularly in spring and early summer, but not in autumn. Species mixing tended to advance spring onset in J. thurifera (by 9 ± 3 days), but caused a delay in Q. ilex (by 9 ± 2 days) and P. pinaster (by 9 ± 3 days). Under stronger interspecific competition Juniperus thurifera, Pinus pinea and to lesser extent, Pinus pinaster showed increased daily basal area growth rates during dry springs (up to 0.024–0.067 cm2/day, depending on the species), consistent with the stress gradient hypothesis. In contrast, Q. ilex exhibited the opposite pattern, suffering increased TWD and reduced daily growth rates in mixtures. These divergent responses were likely driven by species-specific water use strategies and seasonal asynchrony in root activity. Our findings demonstrate that interspecific interactions can either buffer or amplify climatic stress, depending on species identity and season. By linking cambial phenology, growth dynamics, and water deficit under varying competition contexts, this study provides new insights into the possible effects of species mixing towards more resilience under climate change in Mediterranean forests., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The study is supported by ETN Skill-For.Action project that has received funding from the European Union’s HORIZON 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No. 956355., Peer reviewed

Mangrove forests, some of the most carbon-dense ecosystems on Earth, play an important role in climate change mitigation through storing carbon in the soil. However, increasing anthropogenic pressures and sea level rise are likely to alter mangrove forest structure and functions, including the major source of carbon in mangrove ecosystems - below-ground soil carbon stocks (BSCS). Although estimating soil carbon stocks has been a popular practice in the mangroves, but poorly understood the (I) the linkage between BSCS and key ecosystem drivers (i.e., biotic, abiotic, and functional) and in (II) determining the pathways of how BSCS and multiple forest variables interact along stress gradients. This lack of understanding limits our ability to predict ecosystem carbon dynamics under future changes in climate. Here, we aimed to understand how abiotic factors (such as salinity, canopy gap fraction, nutrients, and soil pH), biotic factors (e.g., structural parameters, canopy packing, and leaf area index, LAI), and forest functional variables (e.g., growth and aboveground biomass stocks, AGB) affect BSCS (i.e., soil organic carbon, SOC, and root carbon, RC) using spatiotemporal data collected from the Sundarbans Mangrove Forest (SMF) in Bangladesh. We observed that BSCS decreased significantly with increasing salinity (e.g., from 70.6 Mg C ha -1 in the low-saline zone to 44.6 Mg C ha -1 in the high-saline zone). In contrast, the availability of several macronutrients (such as nitrogen, phosphorous, and potassium), LAI, species diversity, AGB, and growth showed a significant positive effect on SOC and RC. Stand properties, including tree height, basal area, density, canopy packing, and structural diversity, had a non-significant but positive impact on RC, while tree height and basal area significantly influenced SOC. Pathway analysis showed that salinity affects BSCS variability directly and indirectly by regulating stand structure and restricting nutrients and forest functions, although basal area, nutrients, and LAI directly enhance RC stocks. Our results indicate that an increase in nutrient content, canopy density, species diversity, and leaf area index can enhance BSCS, as they improve forest functions and contribute to a better understanding of the underlying mechanisms.