Conspecific distance-dependent seedling performance, and replacement of conspecific seedlings by heterospecifics in five
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COMMUNITY ECOLOGY – ORIGINAL RESEARCH
Conspecific distance‑dependent seedling performance, and replacement of conspecific seedlings by heterospecifics in five hardwood, temperate forest species Wataru Koga1 · Aya Suzuki1 · Kazuhiko Masaka2 · Kenji Seiwa1 Received: 26 February 2020 / Accepted: 29 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The mechanisms driving species diversity in the context of Janzen–Connell model are best understood by evaluating not only conspecific distance-dependent (CDD) seedling performance, but also replacement of conspecific seedlings by heterospecific seedlings beneath adult trees. We evaluated CDD and replacement as a log response ratio of seedling performance (height, age) directly beneath and at a distance from adult plants in a temperate forest, and examined the log response ratio of that between conspecifics and heterospecifics beneath adults for five hardwood species with different ecological traits (e.g., seed size, mycorrhizal type, relative abundance). CDD was greater in three small-seeded species with arbuscular mycorrhizae (AM) associations than it was in two large-seeded species with ectomycorrhizae (EM) associations. Replacement was also higher for small-seeded AM species compared to large-seeded EM species, resulting in a strong, positive relationship between CDD and replacement. The traits suggest that small-seeded AM seedlings are more likely to be replaced by heterologous seedlings beneath the adults than large-seeded EM seedlings, probably due to that the small-seeded AM species are more susceptible to attack by plant natural enemies (e.g., soil pathogens, leaf diseases). As a result, small-seeded AM species had lower relative abundances compared to large-seeded EM species. This study suggests that either seed size or associations with microorganisms play an important role in driving forest diversity by regulating replacement and CDD, although relative importance of the two traits (i.e., seed size, mycorrhizal type) remains unclear, because of the autocorrelation between the two traits for the five species studied. Keywords Janzen–Connell hypothesis · Mycorrhizal type · Relative abundance · Seed size · Species diversity
Introduction Biotic interactions, such as competition, mutualism, and parasitism, strongly affect the spatial distribution, abundance, and diversity of tree species in forest communities. Communicated by Casey P. terHorst. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00442-020-04725-6) contains supplementary material, which is available to authorized users. * Kenji Seiwa [email protected] 1
Graduate School of Agricultural Science, Tohoku University, Naruko‑onsen, Osaki, Miyagi 989‑6711, Japan
Faculty of Agriculture, Iwate University, Morioka, Iwate 020‑8550, Japan
2
Conspecific negative density dependency and positive distance dependency in juvenile performance (e.g., seedling survival, seedling growth) are essential in creating high local
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