Intensive forest management has been applied in most Fennoscandian forests for a period of almost one felling rotation. This paradigm has produced even-aged and even-structured forests of different successional stages that cover about 90% of forest land. At the same time, wildfires have been nearly eliminated in most of the Fennoscandian nature. Consequently, hundreds of species are red-listed because of forest management. To support these species, forest management requires improvements. Variable retention forestry and habitat restoration have been suggested to mitigate negative effects of forest management on biodiversity, and these have been practiced to some extent during the past few decades. Here, we review experimental results on the effects of variable retention and two restoration measures (prescribed burning and artificial addition of coarse woody debris) on different species groups in Fennoscandia. Our key findings are as follows: (i) Many species respond positively to felling within a few years, apparently due to released and often ephemeral resources, such as fresh residue and stumps. Species associated with shady conditions are negatively impacted, but any retention supports many of these, and their species composition remains almost unaffected with 50–70% retention of the initial tree volume. (ii) These effects remain detectable for at least 10–30 years or, according to some studies, nearly 100 years, e.g., in polypore fungi. (iii) Initial effects of prescribed burning on most species groups (apart from pyrophiles) are negative, but within 10–15 years post-fire sites begin to support many rare and threatened deadwood-dependent species. Epiphytic lichens, however, remain negatively affected. (iv) Artificial addition of deadwood (mostly high stumps) supports a wide spectrum of deadwood-dependent species, but the species composition differs from that of naturally died trees. (v) Moisture and micro-habitat variation are crucial for forest species at harvested sites, at least in forests dominated by Norway spruce. We conclude that felling method as such is of little importance for threatened forest species, although retention mitigates many negative effects. These species require microclimatic continuity, and maintenance and active increase of legacies, such as deadwood of different qualities (species, downed/standing, snag/log/stump, decay stage), very old trees, and tree species mixtures.

中文翻译：

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Fennoscandia中可变保留林，规定的焚烧和枯木处理对生物多样性影响的实验证据

集约化森林管理已在大多数芬诺斯堪的亚森林中应用，几乎进行了一次轮伐。这种范式已经产生了不同演替阶段的平均年龄和结构均匀的森林，覆盖了大约90％的林地。同时，在芬诺斯堪的纳维亚大自然中，野火几乎被消除了。因此，由于森林经营，数百种物种被列入红色名录。为了支持这些物种，森林管理需要改进。已提出可变保留森林和栖息地恢复以减轻森林管理对生物多样性的不利影响，并且在过去几十年中已在一定程度上实行了这些措施。这里，我们回顾了对芬诺斯坎迪亚不同物种组的可变保留率和两种恢复措施（规定的燃烧和人工添加粗木屑）的影响的实验结果。我们的主要发现如下：（i）许多物种在几年内对伐木产生了积极的反应，这显然是由于释放了并且经常是短暂的资源，例如新鲜的残留物和树桩。与阴凉条件有关的树种受到负面影响，但任何保留都支持其中许多，其树种组成几乎不会受到初始树体积的50-70％保留的影响。（ii）这些影响至少在10–30年内仍可检测到，或者根据某些研究，例如在多孔真菌中，将近100年仍可检测到。（iii）规定燃烧对大多数物种组（除嗜热菌）的最初影响是负面的，但是在火灾发生后的10-15年内，火场开始养活许多稀有和受威胁的依赖枯木的物种。然而，附生地衣仍然受到负面影响。（iv）人工添加枯木（主要是高树桩）可支持各种依赖枯木的物种，但物种组成与自然枯死的树木不同。（v）水分和微生境的变化对于收获地点的森林物种至关重要，至少在以挪威云杉为主的森林中至关重要。我们得出的结论是，尽管砍伐方法对于受威胁的森林物种而言意义不大，尽管保留可以减轻许多负面影响。这些物种需要微气候的连续性，并需要维持和积极增加遗产，例如各种品质的枯木（树种，倒下/站立，断枝/伐木/树桩，腐烂阶段），非常老的树木，