Graduate School of Agricultural Science, Tohoku University, Naruko-onsen, Osaki, Miyagi, 989-6711, Japan.
College of Chemistry and Life Science, Chifeng University, Chifeng, 024000, Inner Mongolia, China.
Oecologia. 2020 Feb;192(2):449-462. doi: 10.1007/s00442-020-04596-x. Epub 2020 Jan 20.
In forest communities, conspecific density/distance dependence (CDD) is an important factor regulating diversity. It remains unknown how and the extent to which gap creation alters the mode and strength of CDD via changes in the relative importance of pathogens and mycorrhizae. Seeds of two hardwoods (i.e., Acer mono associated with arbuscular mycorrhizae [AM] and Quercus serrata associated with ectomycorrhizae [EM]) were sown reciprocally at four distances from the boundary between Acer- and Quercus-dominated forests towards forest interior in each of forest understories (FUs) and gaps. The causes of seed and seedling mortality, seedling growth and colonization of mycorrhizal fungi were investigated. In Acer, seed and seedling mortality were highest in Acer forests and gradually decreased towards the interior of Quercus forests in FU, mainly due to severe attack of soil pathogens, invertebrates, and leaf diseases. The reverse was true in gaps, due to reduction of damping-off damage caused by distance-dependent colonization of AM. In Quercus, most seeds and seedlings were eaten by vertebrates in FUs. The seedling mortality caused by leaf diseases was not high, even beneath conspecific forests with higher colonization of EM in gaps, suggesting a positive EM influence. In both species, seedling mass was greatest in conspecific forests and gradually decreased towards the interior of heterospecific forests in gaps, due to higher colonization of mycorrhizae near conspecifics. In conclusion, light conditions strongly altered the mode of CDD via changes in relative influence of pathogens and mycorrhizae, suggesting that gap creation may regulate species diversity via changes in the mode of CDD.
在森林群落中，种内密度/距离依赖性（CDD）是调节多样性的一个重要因素。目前尚不清楚通过改变病原体和菌根相对重要性，空隙形成如何以及在何种程度上改变 CDD 的模式和强度。两种硬木（即与丛枝菌根[AM]相关的 Acer mono 和与外生菌根[EM]相关的 Quercus serrata）的种子在每个林下（FU）和空隙中，从 Acer 和 Quercus 占主导地位的森林边界向森林内部的四个距离处被相互播种。调查了种子和幼苗死亡率、幼苗生长和菌根真菌定殖的原因。在 Acer 中，种子和幼苗死亡率在 Acer 林中最高，在 FU 中逐渐向 Quercus 林内部降低，主要是由于土壤病原体、无脊椎动物和叶病的严重侵袭。在空隙中则相反，由于距离依赖的 AM 定殖减少了猝倒病的损害。在 Quercus 中，大多数种子和幼苗在 FU 中被脊椎动物吃掉。即使在 EM 定殖率较高的同种林中，叶病引起的幼苗死亡率也不高，这表明 EM 有积极的影响。在这两个物种中，在同种林中，幼苗质量最大，在空隙中向异种种群林内部逐渐降低，这是由于靠近同种的菌根定殖率较高所致。总之，光照条件通过改变病原体和菌根的相对影响强烈改变了 CDD 的模式，这表明空隙形成可能通过改变 CDD 的模式来调节物种多样性。
