Understorey plant species show long‐range spatial patterns in forest patches according to distance‐to‐edge

Abstract

Questions: How does the presence of understorey plant species vary with distance to edge along very large periphery-to-interior and forest patch size gradients? Can forest core and periphery species profiles be identified? What life-history traits can discriminate between forest core and forest periphery species? Location: Temperate forests in the northern half of France. Methods: Local climate, soil, stand characteristics and landscape metrics were collected on 19 989 plots in 1801 forest patches using data from the French National Forest Inventory. Very large distance-to-edge (3-1096 m) and patch size gradients (327-100 000 ha) were explored. Four logistic regression models were compared to determine the response patterns of 214 species to distance-to-edge, while controlling for patch size and local habitat quality (soil, climate and stand). The maximum distance of correlation between species occurrence and distance-to-edge was assessed using response curve characteristics. The relationships between life-history traits (habitat preference, preference for ancient forests , reproduction mode, dispersal mode, life form and autecology) and species profile according to distance-to-edge were tested. Results: Of the 214 species analysed, 40 had a core profile and 38 a periphery profile. The maximum distance of correlation was on average 748 m. Core species were more often species reproducing both by seed and vegetatively, ancient forest species, anemochores, bryophytes, pteridophytes, hemicryptophytes and acidophiles, whereas peripheral species were more often species reproducing by seed only, endozoochores, phanerophytes, thermophiles, basophiles, nitrogen-demanding and heliophiles. Conclusions: Significant periphery-to-core patterns of distribution were detected over much larger ranges than hitherto recognized for common under-storey plant species. Plant traits differentiated forest core from forest periphery species. This deep gradient cannot be solely explained by the usual edge-related biotic and abiotic factors. We hypothesized that it was due to edge displacement following general reforestation since ca. 1830. This edge shift created recent forests with new habitats on former agricultural lands where dispersal-limited core species had slowly expanded and forest edge species regressed at variable speeds. This long periphery-to-interior gradient of presence has important implications for forest plant species distribution, dynamics and conservation.

Unexpected long-range edge-to-forest interior environmental gradients

“…Here, we detected very long-range gradients, since DEI varied up to 500-700 m for MIV.pH and Ta. Using the same dataset and in total concordance with these results, significant edge-to-core patterns of distribution for common understory plant species were detected over much larger ranges than previously recognised (Pellissier et al 2013). Two reasons could explain the long-range edge gradients detected: (1) previous studies explored a small distance-to-edge gradient (Murcia 1995, Davies-Colley et al 2000Gehlhausen et al 2000;Honnay et al 2002) and (2) they were based on small sample sizes, meaning less statistical power.…”

“…Third, if we assume that recent forests are more frequently located at the periphery of the ancient forest remnants , the differences in soil properties between recent and ancient forests could be responsible for the residual decrease in MIV.pH and N from the edge. Our hypothesis was also supported by the much higher proportion of ancient forest species among the 40 species more frequently found in forest interior (Pellissier et al 2013).…”

“…Data came from the French National Forest Inventory (NFI), an organisation entrusted with inventorying and monitoring forest resources throughout France (Pellissier et al 2013). Only plots in the northern half of France were analysed so as to limit the biogeographical gradient.…”

“…A third possible explanation results from three evidences (Pellissier et al 2013): edge displacement following reforestation creating ecological patterns in space and time (Matlack 1994), the persistent effect of past land use on forest soils and plant communities , and the more frequent location of recent forests at the periphery of ancient forest remnants .…”

Écologie historique et ancienneté de l’état boisé : concepts, avancées et perspectives de la recherche

“…Unep remièrea nalyse effectuée sur une vaste région (moitié nordd el aF rance) avait mis en évidence un effet lisièreàtrès longue distance (> 800 m) sur la floref orestièree ta vait identifié des espèces de coeur et des espèces de périphérie des massifs forestiers (Pellissier et al, 2013), avec l'hypothèse que ce gradient pouvait êtree xpliqué par le déplacement des lisières au cours du temps en lien avec les changements d'occupation du sol. Cette hypothèse aé té validée en utilisant les cartes d'état-major :l ar épartition spatiale de 42 plantes forestières n'est pas seulement expliquée par l'usage passé des terres mais encorem ieux par la distance àl al isière forestières ur la carte d'état-major de 1831 (Bergès et al,2 016).…”