The importance of coarse woody debris for vascular plants in temperate mixed deciduous forests

Abstract

Deadwood in various stages of decomposition and diverse spatial arrangements provides habitat for numerous organisms. However, knowledge on the colonization of deadwood by vascular plants in mixed deciduous forests is insufficient. We carried out our study in an oak-lime-hornbeam forest in northeastern Poland. Downed logs were colonized by 49 vascular plant species, a number higher than reported from any other type of forest. Species richness and abundance of plants increased with log diameter and decomposition. The former was higher on broadleaf deadwood than on coniferous deadwood (46 vs. 38 species). The frequency and abundance on logs were higher for small-seeded plants (<1 mg) than for bigger, heavier seeded plants. Deadwood surface served as an ecological filter, keeping small seeds in cracks, but allowing bigger seeds to roll down. Tree seedling density increased with wood decomposition. However, for eight of nine species, it was higher on the ground than on deadwood. Only spruce seedlings were recorded almost exclusively on deadwood, constituting a crucial substrate for spruce regeneration in meso-eutrophic forests. Therefore, we stress the importance of constant deadwood supply, on the scale of decades, to ensure the diversity of this substrate and to allow the natural dynamics of deadwood-dependent species populations.Résumé : Le bois mort à divers stades de décomposition et dans divers arrangements spatiaux procure un habitat à de nombreux organismes. Cependant, nos connaissances sur la colonisation du bois mort par les plantes vasculaires dans les forêts feuillues mixtes sont insuffisantes. Nous avons réalisé notre étude dans la forêt de chêne, de tilleul et de charme du nord-est de la Pologne. Les billes au sol étaient colonisées par 49 espèces de plantes vasculaires, soit un nombre plus élevé que ce qui a été rapporté dans n'importe quel autre type de forêt. La richesse en espèces et l'abondance des plantes augmentaient avec le diamètre des billes et leur degré de décomposition. La richesse en espèces était plus grande sur le bois mort feuillu que résineux (46 vs 38 espèces). La fréquence et l'abondance des plantes avec de petites graines (<1 mg) étaient plus élevées sur les billes que celles des plantes dont les graines sont plus grosses et plus lourdes. La surface du bois mort sert probablement de filtre écologique, en conservant les petites graines dans les fissures mais en laissant les graines plus grosses rouler jusqu'au sol. La densité des semis d'arbres augmentait avec le degré de décomposition du bois. Cependant, la densité de huit des neuf espèces était plus élevée sur le sol que sur le bois mort. Seuls les semis d'épicéa ont été retrouvés presque exclusivement sur le bois mort qui constitue un substrat essentiel pour la régénération de cette espèce dans les forêts méso-eutrophes. Par conséquent nous insistons sur l'importance d'un approvisionnement constant de bois mort, sur une échelle décennale, pour assurer la diversité de ce substrat et maintenir la dynamique naturelle des populations ...

Forest Understorey Vegetation: Colonization and the Availability and Heterogeneity of Resources

“…As CWD proceeds to decompose and becomes a part of the forest floor, vascular plants will gradually replace the colonized non-vascular plants in the early stage, which allows some species from prior decay classes to persist later on [21,97,98]. Forest floors with different CWD decay classes and substrate species that are provided by mixed overstorey trees, may provide niches for species with varying resource requirements, while supporting the continuous colonization of diverse species, resulting in the higher abundance and diversity of understorey vegetation [22,90,99]. Substrate heterogeneity tends to increase gradually with advancing stand age [16], which results from increasing CWD and tip-up mounds due to self-thinning at the stem exclusion stage, and longevity induced mortality at the canopy transition stage [8].…”

Comparison of traits of non-colonized and colonized decaying logs by vascular plant species

“…As for the former, we did not study the chemical properties of the dead wood, though the bark of both species could contain different biochemical compounds, which may have an impact on the colonization and development of plants (Petrillo et al 2015). Norway spruce has a relatively smooth bark, low pH and a low nutrient content in decaying wood and it can also contain substances that inhibit plant development , Checko et al 2015. Beech has a much smoother bark than spruce.…”

“…Colonization of coarse woody debris (CWD) by vascular plants has received less attention from researchers than colonization by other groups of organisms, e.g., bryophytes, lichens, fungi and insects (Jüriado et al 2003, Odor & Van Hees 2004, Ols et al 2013, Sefidi & Etemad 2015. Nevertheless, there is some literature evidence stressing that CWD, especially decaying logs, can serve as habitats for some herbaceous and woody plants in both lowland and montane forests (Zielonka & Piatek 2004, Dittrich et al 2014, Nowinska et al 2009, Checko et al 2015. It is commonly acknowledged that the decomposition stage of decaying logs is one of the most important factors for the recruitment, survival and completion of the life cycle of wood-dwelling vascular plants.…”

Look Down to See What’s Up: A Systematic Overview of Treefall Dynamics in Forests

“…However, these dynamics are still poorly understood and results from different studies can be contradictory, or relate to very different process such as seedling establishment versus nutrient dynamics. For example, mounds and decaying wood are important substrates for the germination of the coniferous species Picea abies [13,53], but a study on meso-eutrophic forests found that only one of nine species investigated displayed higher seedling density on logs, suggesting that differences amongst species (in trait characteristics, presence or absence of mycorrhizal associations, for instance) might also play an important role [54]. Furthermore, Laiho and Prescott [55] inferred only a limited role for CWD in the nutrient cycle of north coniferous forests.…”