Scotch broom [Cytisus scoparius (L.) Link] is a large nonnative, leguminous shrub that threatens native plant communities by rapidly invading recently disturbed sites, competing vigorously for soil water and nutrients, and imparting soil legacy effects that inhibit native plants. In the Pacific Northwest, logging debris retention after forest harvesting prevents or slows C. scoparius invasions. A series of studies were conducted to determine potential mechanisms by which logging debris modifies the light environment to limit germination and growth of C. scoparius. In laboratory studies, seed germination did not vary significantly (P > 0.05): (1) between presence and absence of light for several temperature regimes, (2) when exposed to red (660-nm wavelength) versus far-red (730-nm wavelength) light, and (3) across a range of red/far-red light (R/FR) ratios. These results indicate that modification of the light environment by logging debris or plant canopies has little or no influence on C. scoparius germination. In a study to simulate effects of variable mass of logging debris, “heavy” debris (2 kg m−2) caused biologically relevant reductions in photosynthetic photon flux density (PPFD) and R/FR relative to conditions under “light” debris (1 kg m−2). Cytisus scoparius germination did not differ significantly between simulated heavy and light debris; however, values of seedling root and shoot biomass under heavy debris were 16% and 71% of those observed under light debris, respectively. These results indicate that heavy debris limits biomass of C. scoparius seedlings, particularly roots, by reducing both PPFD and R/FR, which increases seedling vulnerability to summer drought or other stressors. Retention of heavy logging debris after forest harvesting has potential application on sites likely to be invaded by C. scoparius, as well as those sites with seedbanks containing C. scoparius.

中文翻译：

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苏格兰扫帚 (Cytisus scoparius) 的发芽和生长对光的反应：森林采伐后对伐木碎片保留的影响

苏格兰扫帚 [大鲵(L.) Link] 是一种大型非本地豆科灌木，通过迅速入侵最近受到干扰的地点、激烈竞争土壤水和养分以及传递抑制本地植物的土壤遗留效应来威胁本地植物群落。在太平洋西北部，森林采伐后的伐木碎片保留会阻止或减缓C. scoparius入侵。进行了一系列研究以确定伐木碎片改变光环境以限制植物发芽和生长的潜在机制。C. scoparius. 在实验室研究中，种子萌发没有显着差异（P > 0.05）：（1）在几个温度范围内有无光，（2）暴露于红色（660-nm 波长）与远红色（730- nm 波长）光，以及 (3) 在一系列红光/远红光 (R/FR) 比率范围内。这些结果表明，通过记录碎片或植物冠层来改变光环境对光环境的影响很小或没有影响。C. scoparius发芽。在一项模拟不同质量测井碎片影响的研究中，“重”碎片（2 kg m-2) 导致光合光子通量密度 (PPFD) 和 R/FR 相对于“轻”碎片 (1 kg m-2）。大鲵模拟的重碎片和轻碎片之间的发芽率没有显着差异；然而，重碎片下的幼苗根和茎生物量值分别是轻碎片下观察到的值的 16% 和 71%。这些结果表明，重的碎片限制了生物量C. scoparius通过降低 PPFD 和 R/FR 来保护幼苗，尤其是根系，这会增加幼苗对夏季干旱或其他压力源的脆弱性。在森林采伐后保留大量伐木碎片可用于可能被入侵的地点C. scoparius，以及那些种子库包含的站点C. scoparius.