Tom Gittings 1, George Smith 2, Mark Wilson 1, Laura French 2, Anne Oxbrough 1, Saoirse O’Donoghue 2, Josephine Pithon 1, Vicki O’Donnell 3, Anne-Marie McKee 2, Sue Iremonger 2, John O’Halloran 1, Daniel Kelly 2, Fraser Mitchell 2, Paul Giller 1 1 BIOFOREST Project, Department of Zoology, Ecology and Plant Science, University College Cork 2 BIOFOREST Project, Department of Botany, Trinity College Dublin 3 Coastal and Marine Resources Centre, University College Cork Biodiversity across the forest cycle in ash and Sitka spruce plantations: Comparison of trends between taxonomic groups and management recommendations

BIOFOREST Project Objectives Assess the range of biodiversity in representative Irish plantation forests at key stages of the forest cycle Develop indicators of Irish plantation forest biodiversity Assess the effectiveness of the Forest Biodiversity Guidelines

Methods 3 forest types: Sitka spruce (Picea sitchensis), ash (Fraxinus excelsior) and Sitka spruce-ash mixes 5 structural groups reflecting degree of structural development Sites matched for geographical location, soil type, altitude and drainage, as far as possible Surveyed plants, spiders, hoverfly and birds and collected GIS data for surrounding landscape

Objectives of this presentation Identify similarities and differences between taxonomic groups in how their biodiversity: - Changes over the forest cycle - Varies between forest types Discuss management recommendations

Biodiversity in ash and Sitka spruce plantation forests Over the forest cycle, ash and Sitka spruce plantations can support diverse vegetation, spider, hoverfly and bird assemblages. Assemblages contain a large proportion of generalist species and we recorded few species of conservation importance. Mature stands develop a characteristic woodland flora and support forest specialist spiders and hoverflies.

Pre-thicket sites (red) clearly separated from the more structurally developed sites (all groups). Greater variation among sites in pre-thicket (red) compared to most other structural groups (spiders, hoverflies and birds). Semi-mature and mature ash sites (green circles) clearly separated from the other structural groups (vegetation, spiders and hoverflies). Vegetation Birds Assemblage structure

Mantel test analyses of similarity between patterns of variation in species composition Using an appropriately specified single structural classification as a framework for biodiversity conservation planning in ash and Sitka spruce plantation forests will represent the broad variation in assemblages of these taxonomic groups

Mantel test analyses of similarity between patterns of variation in species composition Selecting complementary sites for conservation on the basis of their vegetation assemblages will tend to capture the range of assemblage variation in spiders. But this pattern may reflect major environmental differences between sites, so may not apply when looking at sites from a narrow environmental range.

Comparison between taxonomic groups of trends in species richness across the age-cycle Total species richness: Most groups that show differences, except bryophytes, have high species richness in the pre-thicket stage and low species richness in the intermediate stages. In Sitka spruce, the mature stage generally has high species richness.

Comparison between taxonomic groups of trends in species richness across the age-cycle Forest species richness: Generally increases with increasing structural development in all the taxonomic groups. Open species richness: Generally decreases after the initial stages of structural development. May increase again at the mature stage (vascular plants in Sitka spruce, spiders in all sites).

Pairwise correlations of species richness between taxonomic groups I Total species richness: Few significant correlations. But significant correlation between spiders and hoverflies consistent across most structural groups.

Pairwise correlations of species richness between taxonomic groups II Forest species richness: All pairwise correlations significant, or nearly significant reflecting low species richness in pre- thicket sites. Most relationships (except between spiders and hoverflies) do not hold when pre-thicket sites removed.

Pairwise correlations of species richness between taxonomic groups III Plot scale (vegetation vs. spiders): Few significant correlations. Differences in responses of species assemblages to structural development complicates interpretation.

Comparison between ash and Sitka spruce Few overall differences in species richness: Total species richness of spiders and bryophytes significantly higher in Sitka spruce. Greater species richness of forest spiders in Sitka spruce. Greater species richness of vascular plants and saproxylic hoverflies in ash. Crop species (ash or Sitka spruce) does not have a major effect on stand-scale biodiversity in plantation forests

Effect of adding ash to a Sitka spruce plantation Few differences in species richness within plantations between ash and Sitka spruce components. Did not detect many differences in species richness between pure and mixed plantations (but due to problems of matching sites?). Differences within plantations in assemblage composition between ash and Sitka spruce components. Retention of mature ash component of mixed plantations into the next rotation will enhance plantation biodiversity. Adding ash to a Sitka spruce plantation increases vegetation, spider and hoverfly biodiversity at the plantation scale

Forestry Management

Recommendations: Forest planning Modifications to Forest Biodiversity Guidelines: Choose improved grassland sites over semi-natural habitats for afforestation Establish plantations in close proximity to semi-natural woodland (vegetation). Leave small unplanted areas to maintain gaps through the forest cycle (vegetation, spiders, hoverflies). Leave small areas of wet habitat unplanted and avoid drainage where possible (hoverflies). Design complex edges and leave boundaries unplanted to increase proportion and diversity of edge habitat (birds). Leave areas of scrub unplanted (birds).

Recommendations: Forest management Modifications to Forest Biodiversity Guidelines: Guidelines to help foresters to identify potentially important habitats for ground flora, spider and hoverfly biodiversity (vegetation, spiders, hoverflies). Rigorous thinning to prevent canopy closure (vegetation, spiders, hoverflies). Retain mature Sitka spruce forests, where there is no risk of damage to adjoining semi-natural habitats (vegetation, spiders). Retention of standing and fallen trees (hoverflies).

State body for promoting forestry research Environmental Protection Agency National Development Plan Project Funding

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