TY - JOUR

T1 - Tree mixtures mediate negative effects of introduced tree species on bird taxonomic and functional diversity

AU - Schuldt, Andreas

AU - Huke, Pelle

AU - Glatthorn, Jonas

AU - Hagge, Jonas

AU - Wildermuth, Benjamin

AU - Matevski, Dragan

N1 - Funding Information: We thank Christian Ammer, Serena Müller and members and foresters of the RTG 2300 project for support, Mathias Eichelbrönner, Elisabeth Hans and Annika Thomas for help with tree microhabitat assessments, and Peter Kriegel for R‐code for Figure S1 . This study was supported by Deutsche Forschungsgemeinschaft (DFG), grant number 316045089/GRK 2300. Open Access funding enabled and organized by Projekt DEAL. Publisher Copyright: © 2022 The Authors. Journal of Applied Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

PY - 2022/12

Y1 - 2022/12

N2 - Recent biodiversity loss has emphasized the necessity to critically evaluate the consequences of human alterations of forest ecosystems. Stand diversification via tree species mixtures and the use of non-native trees are two such alterations currently gaining importance as climate change adaptations. However, the effects of local versus regional tree mixing on associated biodiversity and notably the modifying role of tree species growing outside their natural range remain poorly understood. We assessed how monocultures and mixtures of native and introduced tree species influence the taxonomic and functional diversity of bird communities at stand and landscape scales in north-west Germany. We focused on the dominant natural tree species (Fagus sylvatica) and economically important conifer species planted outside their natural range (the native Picea abies and non-native Pseudotsuga menziesii). We found that bird species richness and functional diversity were generally higher in pure and mixed stands of native F. sylvatica than in pure conifer stands, especially in comparison to non-native P. menziesii. These differences were particularly strong at the landscape scale. Pure conifer stands harboured only a reduced set of functionally similar bird species. Structural diversity based on tree microhabitat availability emerged as a key predictor of bird diversity. Synthesis and applications. Our study suggests that tree species mixtures do not necessarily increase bird diversity compared to pure stands of native trees, but can promote bird diversity relative to pure stands of species planted outside their natural range. Moreover, local mixtures, rather than a mosaic of pure stands, may promote bird diversity also at the landscape scale. By contrast, pure stands of tree species planted outside their natural range can increase biotic homogenization of forest birds. Promoting structural diversity of microhabitats via tree retention and ensuring that non-native trees are planted in mixtures with native trees may alleviate potential limitations of climate change-oriented management for biodiversity.

AB - Recent biodiversity loss has emphasized the necessity to critically evaluate the consequences of human alterations of forest ecosystems. Stand diversification via tree species mixtures and the use of non-native trees are two such alterations currently gaining importance as climate change adaptations. However, the effects of local versus regional tree mixing on associated biodiversity and notably the modifying role of tree species growing outside their natural range remain poorly understood. We assessed how monocultures and mixtures of native and introduced tree species influence the taxonomic and functional diversity of bird communities at stand and landscape scales in north-west Germany. We focused on the dominant natural tree species (Fagus sylvatica) and economically important conifer species planted outside their natural range (the native Picea abies and non-native Pseudotsuga menziesii). We found that bird species richness and functional diversity were generally higher in pure and mixed stands of native F. sylvatica than in pure conifer stands, especially in comparison to non-native P. menziesii. These differences were particularly strong at the landscape scale. Pure conifer stands harboured only a reduced set of functionally similar bird species. Structural diversity based on tree microhabitat availability emerged as a key predictor of bird diversity. Synthesis and applications. Our study suggests that tree species mixtures do not necessarily increase bird diversity compared to pure stands of native trees, but can promote bird diversity relative to pure stands of species planted outside their natural range. Moreover, local mixtures, rather than a mosaic of pure stands, may promote bird diversity also at the landscape scale. By contrast, pure stands of tree species planted outside their natural range can increase biotic homogenization of forest birds. Promoting structural diversity of microhabitats via tree retention and ensuring that non-native trees are planted in mixtures with native trees may alleviate potential limitations of climate change-oriented management for biodiversity.

KW - beta-diversity

KW - biotic homogenization

KW - bird functional diversity

KW - Douglas fir

KW - forest management

KW - local and regional scale

KW - non-native tree species

KW - tree species mixtures

UR - http://www.scopus.com/inward/record.url?scp=85138978713&partnerID=8YFLogxK

U2 - 10.1111/1365-2664.14300

DO - 10.1111/1365-2664.14300

M3 - Journal articles

AN - SCOPUS:85138978713

VL - 59

SP - 3049

EP - 3060

JO - Journal of Applied Ecology

JF - Journal of Applied Ecology

SN - 0021-8901

IS - 12

ER -