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Roles of pathogens on replacement of tree seedlings in heterogeneous light environments in a temperate forest: a reciprocal seed sowing experiment

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1. In forest communities, the Janzen–Connell (J-C) hypothesis proposes that species diversity is
maintained by non-competitive distance- and/or density-dependent seedling mortality
caused by host-specific natural enemies. However, the effects of pathogen associations from
nearby conspecifics versus heterospecifics remain unknown in spatially heterogeneous light
environments.

2. Seeds of hardwood species Cornus controversa (Cornus) and Prunus grayana (Prunus) were
sown beneath 6–7 Cornus and Prunus adults in both the forest understory (FU) and in gaps (Gap)
created by felling all woody vegetation near the focal adults. Seedling growth, mortality, killing
agents (e.g. pathogens that cause damping-off and leaf diseases), and root infection by arbuscular
mycorrhizal fungi (AMF) were investigated.

3. We found strong habitat effects on the expression of soil fungi beneath both tree species.
Seedling mortality caused by soil-borne damping-off pathogens was greater in FU than in Gap, and
AMF infection, which enhanced relative seedling growth rate, was greater in Gap than in FU. Seedling
mortality caused by damping-off pathogens did not differ between Cornus and Prunus seedlings
beneath the adults of conspecific or heterospecific adults in both FU and Gap, suggesting little
distance-dependence or host preference in the fungus.

4. Beneath the adults of Cornus and Prunus, the most prevalent leaf diseases were zonate leaf blight
and angular leaf spot caused by the airborne pathogenic fungi Haradamyces foliicola and
Phaeoisariopsis pruni-grayanae, respectively. Although these pathogens attacked the seedlings of
both species, conspecific seedlings (i.e. home) showed more severe leaf damage, earlier leaf shedding
and/or less defensive behaviour (cell wall defence) relative to heterospecific seedlings (i.e.
away), suggesting negative distance-dependent attack (i.e. host preference) for these leaf diseases.
As a result, greater seedling mortality was observed for conspecific seedlings under both FU and
Gap treatments.

5. Synthesis. In the temperate forest, the J-C hypothesis is largely mediated through the strong negative
influence of airborne leaf diseases rather than through soil-borne damping-off pathogens. We
found that airborne diseases demonstrated distance-dependent host preferences, which led to greater
conspecific seedling damage regardless of environmental light conditions.

Key-words: arbuscular mycorrhizal fungi, damping-off, determinants of plant community diversity
and structure, distance-dependent mortality, host preference, Janzen–Connell hypothesis, leaf disease,
light environments, species diversity

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Informasi Detail

Judul Seri

Journal of Ecology

No. Panggil

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Penerbit

London : British Ecological Society., 2016

Deskripsi Fisik

Journal of Ecology 2016, 104, 765–772

Bahasa

English

ISBN/ISSN

doi: 10.1111/1365-27

Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

2016, 104

Subjek

EKOLOGI

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

Versi lain/terkait

Lampiran Berkas

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