Transcript Document

Biodiversity across the forest cycle in ash
and Sitka spruce plantations: Comparison
of trends between taxonomic groups and
management recommendations
Tom Gittings1, George Smith2, Mark Wilson1, Laura French2, Anne Oxbrough1, Saoirse
O’Donoghue2, Josephine Pithon1, Vicki O’Donnell3, Anne-Marie McKee2, Sue Iremonger2,
John O’Halloran1, Daniel Kelly2, Fraser Mitchell2, Paul Giller1
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
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.
Assemblage structure
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
Mantel test analyses of similarity between
patterns of variation in species composition
All sites, excluding pre-thicket, mature ash, and outliers (n = 29-43)
Spiders Hoverflies Birds – presence Birds - densities
Vegetation – presence r = 0.225 r = 0.369 r = 0.121
Vegetation - cover
r = 0.337 r = 0.478
r = 0.245
Spiders
Hoverflies
r = 0.56
r = 0.115
r = 0.121
r = 0.373
r = 0.146
Red: p < 0.01
Brown: p < 0.1
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
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).
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).
Project Funding
State body for promoting forestry research
Environmental Protection Agency
National Development Plan
Project Website
http://bioforest.ucc.ie