Coldfall Wood
Report on a ground invertebrate survey, 30 April 2009 to 29 April 2010
Edward Milner B Sc, MIEEM
1. Introduction 2
2. The Survey 3
3. Results and interpretation 4
4. Reference 6
5. Lists of species
1. Spiders recorded during this survey 6-8
2. List of all spiders recorded from Coldfall Wood 9-11
3. List of beetles recorded during this survey 12-13
4. List of all beetles recorded from Coldfall Wood (by EM only) 14-16
5. List of other invertebrates recorded from Coldfall Wood 17
6. Pictures of trap-sites 18-20
7. Maps 21
1. Introduction
Coldfall Wood (14ha), one of the very few fragments of ancient woodland left in north London. It was originally part of the extensive area of ancient woodland north of London that existed in medieval times. This covered much of what is now the built-up areas of Finchley, Muswell Hill and parts of Barnet, and Coldfall Wood, along with Big Wood, and parts of Coppetts Wood are some of the small fragments that are left.
Until the 1940’s Coldfall was managed as a (hornbeam) coppice wood with oak standards, as were many other woods around London, managed to provide fuel for the metropolis. Colfall Wood is predominantly hornbeam with a little hazel, some wild service, holly, birch, rowan and occasional crabapple. There are wild cherry suckers but no mature cherry trees. Most of the wood was probably cut primarily for firewood but some or all of it may have been converted to charcoal on site. Coppicing was discontinued after the Second World War and the hornbeams have grown up so that by the 1990s over most of the wood the canopy had closed, allowing very little light to reach the woodland floor after early spring. As a result the ground flora, and associated invertebrates were substantially restricted.
There is a level area in the south-western part of the wood which could have been the charcoal-burners base. It was a clearing; this can be inferred from the number of birch trees which replace hornbeam in the immediate vicinity. Birches are a pioneer species which do not form a dense canopy, and the trees being very much younger than most of the other trees in the wood. Today this area has grass with bracken because the tree canopy is thinner.
In recent years coppicing of the hornbeam (and some wild service) has been reinstated on a piecemeal basis. Three areas were cut in the early 1990’s, and finally a large swathe down most of the length of the main stream was cut in the winter of 2006-7. Some pitfall-trapping was done in the early 1990’s and a preliminary species list of 104 spp. resulted. This included (from a damp area in one of the re-copppice cuts) a rare money spider (Porrhomma cambridgei) which was named as a species new to science on the basis of specimens from Coldfall Wood and five other UK sites.
As a result of the re-coppicing some plants not previously recorded from the wood have appeared as young seedlings, and the vegetation structure of these coppiced areas is very different from other parts of the wood. Studies by David Bevan (formerly the Conservation Officer for Haringey) have shown that since the most recent coppicing the number of new plant species has increased enormously, rising from 55 spp. before this cut to 230spp. by 2009. Many of these will have arrived on the wind or been brought in by birds, and some are aliens and garden escapes. However it is clear that quite a number have arisen from seeds buried in the seedbank, and of these some are rare species only known from one or two other sites in the whole of Middlesex.
Invertebrates may take longer to re-establish themselves, especially plant-feeders which need to have well-established food-plants. or appear because they are associated with some of the plants, usually as plant-feeders. Spiders are more dependant upon the complexity of the plant structure rather than the particular plant species (being carnivorous rather than plant-feeding), but the newly coppiced areas, especially the damper areas and streamside vegetation will gradually mature providing a complexity of structure that will offers a wide range of niches for different spider species.
2. The Survey
This survey concentrated on the newly coppiced area (5 trap sites) with some control sites elsewhere in the wood including the grassy Lovers Lawn. A list of the trap sites is given in Table 1 (see also Map).
Table 1: Habitat Compartments and trap-sites
Compartment / Trap-site / Habitat / Ground vegetation / No of spider spp. recordedE
/ 01 / Damp, above top pool, mainly Juncus and part shaded by Leycesteria formosa / Dense / 14E / 02 / Dry, part shaded, edge of new coppice under Carpinus / Sparse / 14
D / 03 / Dry, in ground vegetetation (Hedera helix) at edge of new coppice / Dense / 14
D / 04 / Dry, bare ground (1 m from stream) with Juncus in new coppice area / Sparse / 25
D / 05 / Damp, edge of dense Rubus and tree seedlings area in largest new coppice area / Dense / 22
H / 06 / (Control) Leaf litter under dense Carpinus canopy / Absent / 13
H / 07 / Dry, grassy area with Pteridium; old charcoal-burners clearing / Sparse / 25
H / 08 / Dry, edge of Rubus patch at base of large oak, in early (1991-2) coppice cut / Sparse / 25
H / 09 / Among dense ground vegetation (Hedera) in dense shade of hornbeam coppice from early cut (1990-91) / Dense / 12
J / 10 / Dry, grassy area (Lovers Lawn) / Dense (grass) / 27
Pitfall traps were set in standard trios with a small quantity of ethylene glycol (holding agent) and commercial detergent (wetting agent). These compounds may act as an attractant for some species and discourage others but this standard form has been used throughout London in previous surveys and presumably the same bias (if any) occurs each time. The traps were emptied and the catch sorted on a monthly basis.
The survey began when the traps were first set on April 30 2009 and will continue until April 29 2010. This interim report covers the period April 30 2009 to December 31st 2009, but updated lists of species will be provided at the conclusion of the 12-month survey period.
Spiders were identified by the author, beetles by Mr N Heal, the pseudoscorpions by Dr G Legg, and bugs (Hemiptera) by Mr T Bantock.
3. Results and interpretation
In total 56 spp. of spiders, 79 spp. of beetle, and 3 species of pseudoscorpion have been recorded during the study period. The totals for these groups for the wood as a whole are: spiders 119spp, beetles 106 spp. (including three Nationally Notable Species) and pseudoscorpions 3 spp. Complete lists of all invertebrate records for the wood are appended.
Before the present survey while few beetles had been recorded from the wood, spiders were already better known (104 spp. recorded). This was an incomplete list produced from some limited collecting and sporadic pitfall-trapping by the author. The present survey has so far produced 15 spider spp. not previously recorded for the wood.
The main conclusion to be drawn is that as a result of the new coppicing the wood provides a richer and more complex habitat for invertebrates, and this process will probably continue for many years. It is difficult to estimate what the species richness of spiders or beetles will be like in ten or fifteen years from now, but it is to be expected that both would be considerably greater than today’s figures indicate.
(a) Spiders
Most of the spiders in the wood are money spiders (Linyphiidae) which made up 64% of the catch during the survey. This was as expected. The part of the habitat sampled is the ground level, including the leaf-litter zone and under shaded or part-shaded conditions money spiders are the most abundant and diverse spiders in London woodlands, where heavy shade predominates in neglected hornbeam coppice.
The spider data given in Table 1 shows that the trap-sites divide clearly into two groups; the poorer sites with 12-14 spp. ( 01,02,03, 06 and 09) and the richer sites with 22-27 spp. (04,05,07,08,10). The mean number of species for the second group is double the mean number for the first group. In other words the second group (mostly less shaded) have a very much richer spider fauna than the first group (more heavily shaded). This may change in future as the habitats mature.
The two damper sites (02 and 05) are both somewhat shaded and have so far not produced any species characteristic of damp habitats, but such species can be expected to appear over time. The open areas of the new cut (02 and 03 especially) may also produce more non-woodland spiders taking advantage of the ‘woodland edge’ habitat.
It was hoped that the spider survey might show that new spiders had arrived in the recently cut coppice zone in a similar way to the plants. However this may take some time several years at least, and much longer than the present survey. Details about the new species recorded are given in the next section. Perhaps if trapping is to continue, one or two more trap-sites in open parts of the new cut should be considered.
The newly recorded spider species
A few of these spiders may be associated with the new coppice cut; these are the seven species marked *. Others are recorded for the first time and reflect the fact that the wood has not been much investigated for spiders apart from the pitfall-trapping.
Harpactea hombergi (Dysderidae)(six-eyed spiders)
This is not a ground-dwelling species but lives under the bark of trees and may move between trees sometimes. Recorded from site 02.
Oonops pulcher (Oonopidae)(tiny six-eyed spiders)
This tiny orange spider has a similar habit to H hombergi and is not normally found in pitfalls. Recorded from site 02.
*Walckenaeria atrotibialis (Linyphiidae)(money spiders)
This small money spider is a grassland/low vegetation species, not a woodland species. Recorded from sites 05, 07
Dismodicus bifrons (Linyphiidae)
Normally found in damp places outside woodland. Recorded from site 10.
*Oedothorax retusus (Linyphiidae)
A pioneer of damp grassland and low vegetation; not a woodland species. Recorded from sites 04 and 05.
Erigonella hiemalis (Linyphiidae)
A tiny woodland species that is often more active in the winter months. Recorded from sites 05 and 07.
*Meioneta saxatilis (Linyphiidae)
A pioneer of various habitats. Recorded from site 10.
Tapinopa longidens (Linyphiidae)
A woodland spider; not very common in London. Recorded from site 10.
Lepthyphantes mengei (Linyphiidae)
A small woodland species. Recorded from sites 02, 04, 07, and 09.
*Pardosa prativaga (Lycosidae)(wolf spiders)
A spider of open ground, not a woodland species, a pioneer. Recorded from sites 01, 04, 05.
*Pisaura mirabilis (Pisauridae)
A spider of tall vegetation and dense grass; not a woodland species. Recorded from site 08.
Clubiona comta (Clubionidae)(mouse spiders)
A woodland species that lives much of the summer in the canopy and which migrates up the trees in spring and down in winter although many remain in small silk cells under bark. Recorded from sites 03 and 04.
*Tibellus oblongus (Philiodromidae) (long-legged crab spiders)
A straw-coloured spider of long grass and open habitats; not a woodland species. Recorded from site 10.
Ozyptila praticola (Thomisidae) (crab spiders)
A spider of leaf-litter in dense woodland. Recorded from sites 02 and 08.
*Ozyptila simplex (Thomisidae)
A spider of open ground; not a woodland species. Recorded from site 08.
(b) Beetles
The most interesting beetle recorded during the survey is the very rare Lesser Glowworm, Phosphaenus hemipterus (Lampyridae). As a recent paper in the British Wildlife magazine (De Cock et al., 2009) has shown, while there is some doubt as whether it is a genuine native species, there have been very few records for the whole country. Since the first record in 1868 they detail just 19 records, all in the south east of England (and none north of the Thames). Apparently a specimen was also found in 2009 at Orpington in south London, but we have had one adult and three larvae from Coldfall Wood, at least some of these from site 05 in the middle of the newly coppiced area.
Three other beetles found are Nationally Notable B species: two carnivorous species: a ground beetle Platyderus depressus, a rove beetle Anotylus mutator; and a plant-feeding click-beetle Athous campyloides, associated with grasses as food-plants.
Most of the other beetles species found in this survey are widespread and common in London. Since most beetles are extremely mobile their occurrence in pitfall traps is less easy to interpret than spider results. However, plant-feeding species are usually found near their food-plants. So far, among the small number of plant-feeding beetles recorded, most are general feeders being found on a wide range of plant hosts. However one tiny weevil, Aracharius salicivorus a willow-gall beetle, has been trapped. This species is restricted to goat willow, one of the plants that has appeared in the wood for the first time in the newly coppiced zone.
In future seasons many further species can be expected to appear as the habitat matures and plant-feeding species follow the new plants which have arrived. This will be especially the case with those beetles which are restricted to certain plant species by their feeding preferences - many plant genera have specific weevils and flower-beetles which are restricted to them. So far, the lists for these families (Chrysomelidae, Apionidae and Curculionidae) are very poor (totalling only 13 spp.) and over the next few years the diversity of these beetles can be expected to increase to at least 50 and possibly 100.