What is good for birds is not always good for lichens: Interactions between forest structure and species richness in managed boreal forests

Eva Lindberg,Julian Klein,Jörgen Sjögren,Sönke Eggers,Matthew Low,Göran Thor

doi:10.1016/j.foreco.2020.118327

Eva Lindberg, Julian Klein + Show 4 more

Open Access

https://doi.org/10.1016/j.foreco.2020.118327

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Abstract

Forestry in the boreal region increasingly replaces natural disturbances in shaping biodiversity. Large-scale removal of small diameter trees (thinning), is ubiquitous in northern European forestry, yet an understanding of how it relates to biodiversity across taxa is lacking. To address this, we examined how two forest structural elements, commonly impacted by forest thinning (i.e. vegetation density in the understory and overstory), are correlated with the species richness of forest-dwelling birds and epiphytic lichens. These taxa were chosen because they likely have opposing habitat demands: epiphytic lichens potentially benefitting from more light in open forests, and birds benefitting from structurally complex forests for foraging, nesting and cover. We used remote sensing tools, already applied in forestry planning, to see if management recommendations could be found that balance the needs of both taxonomic groups within the same forests. Our results show that richness in epiphytic lichens and forest-dwelling birds is not correlated and that a high species richness (~15 birds & ~40 epiphytic lichens) in both taxa is only predicted in the same stand under a specific vertical distribution and density of the forest’s vegetation: this occurs when the vegetation above 3 m is open (to promote epiphytic lichen richness) and below 3 m is dense (to promote bird richness). Dense vegetation up to 7 m above ground has a diverging effect on forest birds (positive) and epiphytic lichens (negative). A larger stem diameter further increases species richness in both taxa. Our study provides results that are directly implementable in forestry planning over large areas with the help of remote sensing tools (LiDAR).

Highlights

There is increasing evidence that modern forestry leads to diminished biodiversity in boreal forests (Burton et al, 2010), which has resulted in political targets that combine economic and ecological sustainability within the forestry sector (CBD, 2010)
One such management intervention is forest thinning, which in Sweden affects approximately 60% of the productive forest land (Swedish National Forest Inventory (NFI), 2019), is likely to have a significant impact on biodiversity because it strongly affects the variety and amount of forest structural elements, such as tree species composition, understory shrubs, dead wood and the ground vegetation (Holm, 2015)
In this study we focus on the tree stem diameter and the density and vertical distribution of the forest’s vegetation, which is most effectively measured with light detection and ranging (LiDAR; Lindberg et al, 2012); information that is available to forest managers nationwide

Summary

Introduction

There is increasing evidence that modern forestry leads to diminished biodiversity in boreal forests (Burton et al, 2010), which has resulted in political targets that combine economic and ecological sustainability within the forestry sector (CBD, 2010) Forest management in this region often replaces natural disturbances and succession as the drivers of structural complexity (Brumelis et al, 2011) and with that biodiversity (Stein et al, 2014). Research here is largely missing (but see Muir et al, 2006; Root et al, 2010; Widenfalk and Weslien, 2009) One such management intervention is forest thinning, which in Sweden affects approximately 60% of the productive forest land (Swedish National Forest Inventory (NFI), 2019), is likely to have a significant impact on biodiversity because it strongly affects the variety and amount of forest structural elements, such as tree species composition, understory shrubs, dead wood and the ground vegetation (Holm, 2015)

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