Increasing the prevalence of broadleaf trees in conifer-dominated production forests is a recommended means of improving habitat availability for broadleaf and mixed-forest species. The implications for biodiversity are often measured by contrasting broadleaf-conifer mixtures with conifer-dominated stands. However, few studies include broadleaf-dominated stands in these assessments. Here we contrasted the bird assemblages of even-aged production forests along a mixture gradient from Norway spruce (Picea abies) dominated, to birch (Betula spp.) dominated stands in southern Sweden. We conducted point count surveys of bird individuals exhibiting breeding behaviour within 30 stands varying from <0.5% to over 98.5% broadleaf by basal area. A total of 355 birds were detected, comprising 36 bird species, seven of which are classified as near threatened by the Swedish Red-list. Our results indicate i) a distinct shift in bird community composition linked to the percentage of broadleaf trees at stand and landscape scales, ii) significantly higher bird species richness, evenness, and abundance in stands with a higher proportion of birch, iii) higher bird abundance in birch-dominated stands than in mixtures, and iv) shifts in bird species guilds as related to stand basal area, the amount of shrubs in the understory, and quantities of dead wood. All of these results have implications for the ways in which production forest management could be altered to enhance avian diversity, and we discuss these with respect to the use of broadleaf versus mixed-species stands.

在针叶树为主的生产林中增加阔叶树的流行是提高阔叶树和混交林物种栖息地可利用性的一种推荐手段。通常通过将阔叶针叶树混合物与针叶树为主的林分进行对比来衡量对生物多样性的影响。但是，很少有研究在这些评估中包括以阔叶为主的林分。在这里，我们对比了从挪威云杉（云杉（Picea abies）为主到桦木（Betula）的混合梯度，均匀老化生产林的鸟类组合。spp。）占主导地位的瑞典南部看台。我们对30个林分中表现出繁殖行为的鸟类个体进行了点计数调查，这些林地的面积从<0.5％到超过98.5％不等。总共发现了355种鸟类，其中包括36种鸟类，其中7种被归类为瑞典红名单中濒临灭绝的鸟类。我们的结果表明：i）与林分和景观尺度上的阔叶树的百分比相关的鸟类群落组成发生明显变化，ii）白桦比例更高的林分中鸟类物种的丰富度，均匀度和丰度明显提高，iii）高鸟类桦树为主的林分比混交林多，并且iv）与林分基础面积，林下灌木丛的数量和枯木量有关的鸟类协会的变化。