Roles of pathogens on replacement of tree seedlings in heterogeneous light environments in a temperate forest: a reciprocal seed sowing experiment
Roles of pathogens on replacement of tree seedlings in heterogeneous light environments in a temperate forest: a reciprocal seed sowing experiment
复制标题
DOI：
10.1111/1365-2745.12552
复制
发表时间：
2016-05-01
影响因子：
5.5
通讯作者：
Seiwa, Kenji
中科院分区：
文献类型：
--
作者：
Bayandala;Fukasawa, Yu;Seiwa, Kenji
1.在森林群落中，Janzen-Connell(J-C)假说认为，物种多样性是由寄主特有的天敌引起的非竞争性距离和/或密度相关的幼苗死亡所维持的。然而，在空间不同的光环境中，来自附近同种和异种的病原菌联合的影响仍然未知。硬木树种山茱萸(Cornus)和山李(Prunus)的种子被播种在6-7株山茱萸和李成虫的下方，通过砍伐成虫附近的所有木本植被而形成的林下植被(Fu)和林隙(Gap)。调查了苗木生长、死亡率、致死物质(如引起立枯病和叶部病害的病原菌)以及丛枝菌根真菌(AMF)对根的侵染。我们发现，栖息地对两种树种下土壤真菌的表达有很强的影响。土传立枯病病原菌对苗木的致死作用在FU中大于Gap，在Gap中AMF侵染对幼苗相对生长率的提高大于FU。在FU和GAP中，山茱萸和李的幼苗在同种成虫和异种成虫下的幼苗死亡率没有差异，表明该真菌几乎不具有距离依赖性或寄主选择性。在山茱萸和李的成虫下，最常见的叶部病害分别是由气传病原菌Haradamces foliicola和Phaeoisariopsis pruni-grayanae引起的带状叶枯病和角斑病。虽然这些病原菌侵染两种植物的幼苗，但同种幼苗(即家)表现出比异种幼苗更严重的叶片伤害、更早的叶片脱落和/或更少的防御行为(即细胞壁防御)，这表明这些叶片病害具有负的距离依赖性攻击(即寄主偏好)。结果表明，在FU和GAP处理下，同种幼苗的幼苗死亡率都较高。综合。在温带森林中，J-C假说很大程度上是通过气传叶部病害的强烈负面影响而不是通过土壤传播的立枯病病原菌来调节的。我们发现，空气传播的疾病表现出依赖于距离的寄主偏好，这导致了无论环境光照条件如何，同种苗木都会受到更大的伤害。
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.