Thoughts on Priorities for the Conservation of Woodland ... · PDF fileThoughts on Priorities...

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