Development of alder carr after the abandonment of wet grasslands during the last 70 years

Abstract

Keywords:aerial photograph / Alnus glutinosa (L.) Gaertn. / dendrochronology / land abandonment / secondary succession / wetland Abstract • The secondary succession of wet grasslands to communities of alder carr dominated by Alnus glutinosa was recorded in different parts of Europe during the 20th century. However, knowledge of such development of alder carr remains insufficient.• The development of alder carr was reconstructed at five sites in the Czech Republic, using historical aerial photographs and methods of dendrochronology. The aims were to investigate the succession from wet grasslands to alder carr at sites previously intensively managed for agriculture and to find out the role of fluctuations in the groundwater table, caused by artificial drainage channels, in the observed stand dynamics and tree growth.• The spread of forest (i.e., an increase in forest cover) predominated until the 1970s at all sites. This trend was disrupted by a large-scale dieback of forest stands in four of the five sites after the 1970s, followed by an increase in patch heterogeneity, as indicated by landscape metrics. The radial growth increment in Alnus glutinosa has been affected predominately by local environmental factors, probably including the changing degree of waterlogging. Forest dieback was presumably connected with a lesser extent of drainage channels.• Our results indicate that observed successional pathways at sites of alder carr were probably caused by local changes in the groundwater table.Mots-clés : photographie aérienne / Alnus glutinosa (L.) Gaertn. / dendrochronologie / abandon des terres / succession secondaire / zones humides Résumé -Développement de taillis d'aunes après l'abandon des prairies humides au cours des 70 dernières années.• La succession secondaire des prairies humides en communautés de taillis d'aunes dominées par Alnus glutinosa a été enregistrée dans différentes parties de l'Europe au cours du 20 e siècle. Toutefois, la connaissance du développement de taillis d'aunes reste insuffisante.• Le développement de taillis d'aunes a été reconstruit dans cinq sites en République Tchèque, à l'aide de photographies aériennes historiques et des méthodologies de la dendrochronologie. Les objectifs étaient d'étudier la succession de prairies humides en taillis d'aunes sur des sites précédem-ment exploités intensivement par l'agriculture et de découvrir le rôle des fluctuations de la nappe phréatique, causées par le drainage artificiel des canaux, et d'observer la dynamique des peuplements et la croissance des arbres.• La progression de la forêt (c'est-à-dire, l'augmentation du couvert forestier) a prédominé jusque dans les années 1970 dans tous les sites. Cette tendance a été perturbée par un vaste dépérissement des peuplements forestiers dans quatre des cinq sites après les années 1970, suivie par une augmentation de l'hétérogénéité des bouquets d'arbres, comme indiqué par les paramètres du paysage. L'augmentation de la croissance radiale de Alnus glutinosa a été affectée principalement par les facteu...

Variability of alder-dominated forest vegetation along a latitudinal gradient in Slovakia

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