ABSTRACT: The forest-forming giant kelp Macrocystis pyrifera and the communities it supports have been decreasing across their native ranges in many parts of the world. The sudden removal of giant kelp canopies by storms increases space and light for the colonization by understory macroalgae, such as Desmarestia herbacea, which can inhibit M. pyrifera recovery and alter local community composition. Understanding the mechanisms by which algae such as D. herbacea interact with M. pyrifera can provide insight into patterns of kelp forest recovery following these disturbances and can aid in predicting future community structure. This study experimentally tested the independent and combined effects of two likely competitive mechanisms by which D. herbacea might inhibit recovery of M. pyrifera in the Point Loma kelp forest in San Diego, California (USA). Specifically, we conducted field experiments to study the individual and combined effects of shade and scour by D. herbacea on the survival of M. pyrifera microscopic life stages, and the recruitment, survival, and growth of its young sporophytes. Our results show that scour had the strongest negative effect on the survival of M. pyrifera microscopic life stages and recruitment, but shade and scour both adversely affected survival and growth of these sporophytes as they grew larger. Canopy-removing storms are increasing in frequency and intensity, and this change could facilitate the rise of understory species, like D. herbacea, which might alter community succession and recovery of kelp forests.

中文翻译：

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藻类导致藻类抑制大型海藻萤火虫募集的机制

摘要：在世界许多地方，成林的巨型海带Macrocystis pyrifera及其所支持的社区在其原生范围内正在减少。风暴突然清除了巨大的海带冠层，增加了空间和光照，供下层大型藻类（例如Desmarestia herbacea）定殖，这可以抑制黄萎病菌的恢复并改变当地的群落组成。了解藻类（例如D. herbacea）与火棘分枝杆菌（M. pyrifera）相互作用的机制可以洞悉这些干扰后的海带森林恢复模式，并有助于预测未来的社区结构。这项研究实验性地测试了两种可能的竞争机制的独立作用和综合作用，在此作用下，禾本科D.草粉可能会抑制加利福尼亚州圣地亚哥（美国）的洛马角海带森林中斑节菜的恢复。具体来说，我们进行了现场实验，通过研究树荫和冲刷的个人和组合效应D. herbacea上的生存M. pyrifera微观的生命阶段，以及招聘，生存，和其幼孢子体的生长。我们的结果表明，冲刷对火棘分枝杆菌的存活具有最强的负面影响微观的生命阶段和募集，但是阴影和冲刷都随着这些孢子体的长大而不利地影响它们的存活和生长。去除冠层的风暴的频率和强度都在增加，这种变化可以促进草本植物如D. herbacea的生长，这可能会改变海藻森林的群落演替和恢复。