Spruce plantations in native pine forests: effects on bird diversity. Magne Sætersdal, Norwegian Forest and Landscape Institute.

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1 Spruce plantations in native pine forests: effects on bird diversity. Magne Sætersdal, Norwegian Forest and Landscape Institute.

2 Spruce in western Norway > Mostly planted. > 13% of productive pine forests have been converted. > 25-30% of pine forests on richest soils (increment > 7m 3 /ha/year) have been converted. Photo: J. Y. Larsson

3 Questions > How does bird diversity vary in relation to the proportion of spruce plantations at a landscape scale (58ha)? > How do the abundances of two threatened woodpecker species vary in relation to the proportion of spruce plantations (1km 2 )?

4 Bird diversity - methods > 35 plots, each 58ha (1080x540m). > Representing the spectrum from pure pine to pure spruce forest. > Plots divided in groups of seven plots with mean percentage of spruce forest of 0, 24, 44, 58, and 100%. > Bird fauna surveyed (aural and visual observations).

5 Gjerde & Sætersdal (1997) Biological Conservation

6 Gjerde & Sætersdal (1997) Biological Conservation

7 Gjerde & Sætersdal (1997) Biological Conservation

8 Gjerde & Sætersdal (1997) Biological Conservation

9 Conclusions bird diversity > Species richness and density higher in pine than in spruce forest. > However, a peak in species richness is found in mosaic forests. > When mixing two habitat types (A and B) the ratio of these habitats that maximize bird diversity depends on the ratio of species confined to habitat A and B, as well as the number of sp favoured by a mixture of A and B. > Existing spruce plantations (13%) in native pine forests of western Norway have reduced the diversity of birds locally, but increased the diversity of birds on the landscape and regional scales.

10 What about two red-listed woodpecker species? White-backed Woodpecker (Dendrocopos leucotos) Grey-headed Woodpecker (Picus canus)

11 100 plots (1 km 2 ): plots <10% spruce plots 11-30% spruce plots 31-50% spruce plots 51-70% spruce plots >70% spruce

12 White-backed woodpecker (a) Probabililty of presence Proportion of spruce plantation (%) Gjerde, Sætersdal & Nilsen (2005) Biodiversity and Conservation

13 White-backed woodpecker Gjerde, Sætersdal & Nilsen (2005) Biodiversity and Conservation

14 Grey-headed woodpecker (b) Probability of presence Proportion of spruce plantation (%) Gjerde, Sætersdal & Nilsen (2005) Biodiversity and Conservation

15 Grey-headed woodpecker Gjerde, Sætersdal & Nilsen (2005) Biodiversity and Conservation

16 Conclusions white-backed woodpeckers > Negatively correlated to proportion of spruce forest. > No clear threshold, but over 60% spruce forest no white-backed woodpeckers. > Positively correlated to deciduous trees and snags.

17 Conclusions grey-headed woodpecker > Hump-shaped response to spruce forest. > Positively correlated to proximity to outer coastline. > Positively correlated to large aspen trees. > Positively correlated to snags.

18 Overall conclusions > Bird diversity and grey-headed woodpecker show a hump-shaped response to increasing proportion of spruce plantations at the landscape scale. > White-backed woodpecker and density of breeding birds show a negative response to increasing proportion of spruce plantations at the landscape scale. > Bird diversity is decreased locally (stand level), but increased at landscape and regionally scales as a result of present day proportion of spruce plantations (13%) in western Norway.

19 Thank you for your attention!