We measured forest-floor accumulation in ponderosa pine forests of central Oregon and asked whether selected ecological functions of the organic layer were altered by thinning and repeated burning. Experimental treatments included three thinning methods applied in 1989 (stem only, whole tree, no thin—control) in factorial combination with prescribed burning (spring 1991 and repeated in 2002; no burn—control). Forest-floor depth and mass were measured every 4–6 years from 1991 to 2015. Without fire, there was little temporal change in depth or mass for thinned (270 trees ha−1) and control (560–615 trees ha−1) treatments, indicating balanced litterfall and decay rates across these stand densities. Each burn consumed 50–70 percent of the forest floor, yet unlike thinning, postfire accumulation rates were fairly rapid, with forest-floor depth matching preburn levels within 15–20 years. Few differences in forest-floor function (litter decay, carbon storage, physical barrier restricting plant emergence, erosion protection) resulted from thinning or burning after 25 years. An exception was the loss of approximately 300 kg N ha−1 because of repeated burning, or approximately 13 percent of the total site N. This study documents long-term forest-floor development and suggests that common silvicultural practices pose few risks to organic layer functions in these forests. Study Implications: Mechanical thinning and prescribed fire are among the most widespread management practices used to restore forests in the western US to healthy, firewise conditions. We evaluated their effects on the long-term development of litter and duff layers, which serve dual roles as essential components of soil health and as fuel for potential wildfire. Our study showed that thinning and burning provided effective fuel reduction and resulted in no adverse effects to soil quality in dry ponderosa pine forests of central Oregon. Repeated burning reduced the site carbon and nitrogen pools approximately 9–13 percent, which is small compared to C located in tree biomass and N in mineral soil. Litter accumulation after burning was rapid, and we recommend burning on at least a 15–20-year cycle to limit its build-up.

中文翻译：

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疏伐和燃烧对黄松幼林长期凋落物积累和功能的影响

我们测量了俄勒冈州中部黄松林的森林地面堆积，并询问有机层的选定生态功能是否因间伐和反复燃烧而改变。试验性处理包括 1989 年应用的三种间伐方法（仅茎、整棵树、不稀释——对照）与规定的燃烧（1991 年春季和 2002 年重复；无燃烧——对照）的因子组合。从 1991 年到 2015 年，每 4-6 年测量一次森林地表深度和质量。在没有火的情况下，间伐（270 棵树 ha-1）和对照（560-615 棵树 ha-1）的深度或质量几乎没有时间变化处理，表明这些林分密度的凋落物和腐烂率平衡。每次燃烧消耗了 50-70% 的森林地面，但与间伐不同，火灾后的积聚速度相当快，森林地表深度与 15-20 年内的预燃水平相匹配。25 年后的疏伐或燃烧导致森林地面功能（凋落物腐烂、碳储存、限制植物出现的物理屏障、侵蚀保护）的差异很小。一个例外是由于反复燃烧损失了大约 300 kg N ha-1，约占场地总氮的 13%。这项研究记录了长期的森林​​地面发展，并表明常见的造林做法对有机层造成的风险很小在这些森林中发挥作用。研究意义：机械间伐和规定的火灾是最普遍的管理实践，用于将美国西部的森林恢复到健康的火灾条件。我们评估了它们对垫料和绒毛层长期发育的影响，它们具有双重作用，既是土壤健康的重要组成部分，又是潜在野火的燃料。我们的研究表明，间伐和燃烧可有效减少燃料消耗，并且不会对俄勒冈州中部干燥的黄松林的土壤质量产生不利影响。重复燃烧使场地碳和氮库减少了大约 9-13%，与位于树木生物量中的 C 和矿质土壤中的 N 相比，这是很小的。燃烧后的垃圾堆积很快，我们建议至少以 15-20 年为周期进行燃烧以限制其堆积。重复燃烧使场地碳和氮库减少了大约 9-13%，与位于树木生物量中的 C 和矿质土壤中的 N 相比，这是很小的。燃烧后的垃圾堆积很快，我们建议至少以 15-20 年为周期进行燃烧以限制其堆积。重复燃烧使场地碳和氮库减少了大约 9-13%，与位于树木生物量中的 C 和矿质土壤中的 N 相比，这是很小的。燃烧后的垃圾堆积很快，我们建议至少以 15-20 年为周期进行燃烧以限制其堆积。