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Regeneration in European beech forests after drought: the effects of microclimate, deadwood and browsing / Dominik Thom in European Journal of Forest Research, vol 142 n° 2 (April 2023)  

Public [article]  inEuropean Journal of Forest Research > vol 142 n° 2 (April 2023) . - pp 259 - 27 Titre : Regeneration in European beech forests after drought: the effects of microclimate, deadwood and browsing Type de document : Article/Communication Auteurs : Dominik Thom, Auteur ; Christian Ammer, Auteur ; Peter Annighöfer, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : pp 259 - 27 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] Allemagne [Termes IGN] bois mort [Termes IGN] Fagus sylvatica [Termes IGN] rayonnement lumineux [Termes IGN] régénération (sylviculture) [Termes IGN] sécheresse [Termes IGN] sous-étage [Termes IGN] température de l'air [Vedettes matières IGN] Végétation et changement climatique Résumé : (auteur) With progressing climate change, increasing weather extremes will endanger tree regeneration. Canopy openings provide light for tree establishment, but also reduce the microclimatic buffering effect of forests. Thus, disturbances can have both positive and negative impacts on tree regeneration. In 2015, three years before an extreme drought episode hit Central Europe, we established a manipulation experiment with a factorial block design in European beech (Fagus sylvatica L.)-dominated forests. At five sites located in southeastern Germany, we conducted three censuses of tree regeneration after implementing two different canopy disturbances (aggregated and distributed canopy openings), and four deadwood treatments (retaining downed, standing, downed + standing deadwood and removing all deadwood), as well as in one untreated control plot. In addition, we measured understory light levels and recorded local air temperature and humidity over five years. We (i) tested the effects of experimental disturbance and deadwood treatments on regeneration and (ii) identified the drivers of regeneration density as well as seedling species and structural diversity. Regeneration density increased over time. Aggregated canopy openings supported species and structural diversity, but reduced regeneration density. Tree regeneration was positively associated with understory light levels, while maximum vapor pressure deficit influenced tree regeneration negatively. Deadwood and browsing impacts on regeneration varied and were inconclusive. Our study indicates that despite the drought episode regeneration in beech-dominated forests persisted under moderately disturbed canopies. However, the positive effect of increased light availability on tree regeneration might have been offset by harsher microclimate after canopies have been disturbed. Numéro de notice : A2023-197 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1007/s10342-022-01520-1 Date de publication en ligne : 24/11/2022 En ligne : https://doi.org/10.1007/s10342-022-01520-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103084 [article]

Regional climate moderately influences species-mixing effect on tree growth-climate relationships and drought resistance for beech and pine across Europe / Géraud de Streel in Forest ecology and management, vol 520 (September-15 2022)  

Public [article]  inForest ecology and management > vol 520 (September-15 2022) . - n° 120317 Titre : Regional climate moderately influences species-mixing effect on tree growth-climate relationships and drought resistance for beech and pine across Europe Type de document : Article/Communication Auteurs : Géraud de Streel, Auteur ; François Lebourgeois, Auteur ; Christian Ammer, Auteur ; et al., Auteur Année de publication : 2022 Article en page(s) : n° 120317 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] analyse de groupement [Termes IGN] analyse en composantes principales [Termes IGN] Bootstrap (statistique) [Termes IGN] climat [Termes IGN] coefficient de corrélation [Termes IGN] dendrochronologie [Termes IGN] échantillonnage [Termes IGN] Europe (géographie politique) [Termes IGN] évapotranspiration [Termes IGN] Fagus sylvatica [Termes IGN] peuplement mélangé [Termes IGN] Pinus sylvestris [Termes IGN] région [Termes IGN] sécheresse [Vedettes matières IGN] Végétation et changement climatique Résumé : (auteur) Increasing species diversity is considered a promising strategy to mitigate the negative impacts of global change on forests. However, the interactions between regional climate conditions and species-mixing effects on climate-growth relationships and drought resistance remain poorly documented. In this study, we investigated the patterns of species-mixing effects over a large gradient of environmental conditions throughout Europe for European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.), two species with contrasted ecological traits. We hypothesized that across large geographical scales, the difference of climate-growth relationships and drought resistance between pure and mixed stands would be dependent on regional climate. We used tree ring chronologies derived from 1143 beech and 1164 pine trees sampled in 30 study sites, each composed of one mixed stand of beech and pine and of the two corresponding pure stands located in similar site conditions. For each site and stand, we used Bootstrapped Correlation Coefficients (BCCs) on standardized chronologies and growth reduction during drought years on raw chronologies to analyze the difference in climate-tree growth relationships and resistance to drought between pure and mixed stands. We found consistent large-scale spatial patterns of climate-growth relationships. Those patterns were similar for both species. With the exception of the driest climates where pure and mixed beech stands tended to display differences in growth correlation with the main climatic drivers, the mixing effects on the BCCs were highly variable, resulting in the lack of a coherent response to mixing. No consistent species-mixing effect on drought resistance was found within and across climate zones. On average, mixing had no significant effect on drought resistance for neither species, yet it increased pine resistance in sites with higher climatic water balance in autumn. Also, beech and pine most often differed in the timing of their drought response within similar sites, irrespective of the regional climate, which might increase the temporal stability of growth in mixed compared to pure stands. Our results showed that the impact of species mixing on tree response to climate did not strongly differ between groups of sites with distinct climate characteristics and climate-growth relationships, indicating the interacting influences of species identity, stand characteristics, drought events characteristics as well as local site conditions. Numéro de notice : A2022-557 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1016/j.foreco.2022.120317 Date de publication en ligne : 17/06/2022 En ligne : https://doi.org/10.1016/j.foreco.2022.120317 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101172 [article]