Upload
vuongngoc
View
214
Download
2
Embed Size (px)
Citation preview
Thoughts on Priorities for the Conservation of Woodland
Invertebrates
with aspen as an example
ASPEN
A HIGH PRIORITY TREE FOR INVERTEBRATE CONSERVATION
DISTRIBUTIONtree practically everywhere
FAUNA
Aspen only 38 species
Aspen mainly 12 species
Aspen total 139 species
8 ASPEN INSECTSapparently EXTINCT
EXTINCT MACRO-MOTHS• Dusky Clearwing 1924. Last record near Oxford• Clifden Nonpareil 1964, by felling its stand of mature aspen during woodland
coniferisation at Orlestone Forest. It may now be re-establishing on other poplars
• Lesser Belle 1972
EXTINCT MICROMOTHS• Gibberifra simplana 1938, Essex• Gypsonoma nitidulana Central Highlands, last recorded 1911 • Paraleucoptera sinuella Central Highlands, last recorded 1950
EXTINCT BEETLES• Obrium cantharinum (Cerambycidae) Formerly mainly SE England but last record
1929, South Devon. (Saproxylic)• Chrysomela tremula Chrysomelidae) Dramatic decline after Second World War.
Last records: 1957, Bookham Common, Surrey; 1958, Coventry.
8 BAP UK PRIORITY SPECIESaspen insects
MOTHS• Dark Bordered Beauty Epione vespertaria• Scarce Aspen Midget Phyllonorycta sagitella• Aspen Knot-headed Moth Scotia hostilisBEETLES• 10-spot Leaf-beetle Chrysomela populi• Aspen Leaf-roller Bytiscus populiSOLITARY WASPS• Symmorphus crassicornis• Chrysis fulgida• Scottish Hoverfly Blera falax
WHY THE PROBLEM?
• c. 50 aspen dependent species are doing 50 different things
• And those species have competition from another c. 90 species that are more generalist tree feeders ( 1 or more alternative tree species)
• Some parts of the web of life are more vulnerable to failure than others
THE TREE
• A tree, can become a big long-lived structure with lots of niches
• There is height zonation in bark texture
• But a sapling can be a very different niche and often in leaf-shape and texture
• Dead branches and rot-holes on life trees count
• And a dead tree or branches on the ground
• Not to forget both live and dead roots
SITUATION OF ASPEN
• Isolated tree
• A clump of isolated trees
• A clump with extending sucker-growth providing varied age range
• A hedge-line of trees
• Along a wood edge
• Coppice
• Sucker-growth cut in a woodland ride or edge
• Enclosed within the canopy of other trees
ECOLOGICAL PINCH POINTS
• Aspen is short-lived for a tree, rarely beyond 100 years
• It is fast growing, so the young sapling stage is brief
• It is easily shaded-out by other trees long before maturity
• Both sapling and mature/over-mature rarely have had continuity
• Dead wood is of small girth and for many past decades was removed as firewood or for tidiness
Boring in young stems
Saperda populnea
Leaf eating beetles
Chrysomela populi
Leaf-eating caterpillars
Poplar Kitten
camouflaged by day on bark
Poplar Grey
Leaf-rollers
Spinning leaves together
Poplar Lutestring
Case bearers
Sawfly larva
Palisade sawfly
Leaf-miners
Parascaptomyza tremulae
saproxylic
Xylota abiens
galls
Harmandiola tremulae
Sap sucking leaf-hoppers
Populicerus laminatus
aphids
Chaitophorus tremulae
Large mature aspen
young aspen at ride edge
Aspen coppice
OTHER WOODLAND CONSERVATION ISSUES
• Need for flowers (scrubs & herbs)• Deer browsing (sapling/coppice inhibition & herb layer reduced to
monocotyledons)• Ride & glade quality• Structure• Planting new woodland needs planting of key shrubs and herb layer• Saproxylic habitat (decaying wood etc., tree cohort age gaps)• Woody debris in streams• Importance of ground water seepages, springs and streams• Options for enhancing invertebrate faunas in plantations• Re-establishment of lost species from woods. Choices and
practicalities?• Pest control measures (especially when impinging outside
commercial forests)
wood structure
ride with muddy puddlemarshy ground with creeping buttercuptrampling by people & horses necessary
but public try to keep tp dry ground
open and shaded trackregrowth cut scrubbirch a short lived tree of
disturbed woodland
open structured wood pasturewith new pollard
Burnham Beeches
Saproxylic age gap looms on most of the classic sites for beech faunas
Windsor Forest
Beech live for 250- 350 yearsSoon there only be young beech left
Windsor Forest
The bonaza of plenty of ancient beech trees is drawing to a closeIs it possible to devise artificial larval habitat for 200 years to bridge theage gap?
The old The new
Saproxylic habitat age gap
Windsor Forest
Fauna of decaying beechsoon to become Critically Endangerd
Research on saproxylic beetles
Windsor Forest
ECOLOGICAL DESCRIPTORS
• NVC and other vegetation classifications. Pros, cons and limitations in correlating with and defining invertebrate ecologies
• HAP and its choice of Priority Habitats (the basis being EU priorities). Helpful or limitations as regards invertebrate woodland priorities
• A common language between disciplines lies behind NVC & BAP but invertebrates operate at a smaller niche scale where words may not have a ubiquitously understood definition
RUMSFELD KNOWNS AND UKNOWNS
• Need for bibliography of published and unpublished
references on key themes
• Reviews of existing work
• Funding sources will be needed
RESEARCH GAPS
• Height stratification Significance of age/height of saplings/scrubWhat is happening out of reach?
• Woodland fragmentation & isolation Population viability/metapopulationsRelevance of linear connectivityButterflies studies may not be typical for invertebrates
• Size/quantity of viable resources for priority species not just Priority in BAP designation
• BAP Priority Species. Plenty of Species Action Plans in limbo
• Better comparisons between ancient woods with different histories• Citizen science/professional balance
Harnessing amateur effort to best effect to gain the basic information