30 May 2009

Sheep sorrel swards

In an area cleared of conifers a few years back, one of the most distinctive swards is created by extensive colonies of sheep sorrel (Rumex acetosella) among the tree stumps and clumps of rushes.

20090529 BHW 040

Clearly this plant, perfectly edible to our species, is not much liked by deer or rabbits.  It is, however, one of the main food plants of the small copper butterfly, so these should flourish here.

27 May 2009

Alder wood-wasp joins barbecue

There was a very jolly barbecue at the site of Brede High Farm on  Bank Holiday Monday.

20090525 BHW etc 023

Among the various creatures that joined us were one or two examples of the rare and local alder wood-wasp (Xiphydria camelus) a species which appears not to have been recorded previously from East Sussex and with only one record from West Sussex.

20090525 BHW Xiphydria camelus 008

Alder wood-wasps (about the size of ordinary wasps) belong to the Xiphydriidae a very small hymenopterous family (bees, wasps, ants, sawflies etc.) and are rather remarkable creatures.  The females have organs called 'mycangia' in which they carry fungal spores.  They lay their eggs through the bark of recently dead branches of alder or birch and the spores create an area of decay so that the larvae have either softer timber to chew on, or fungal material.

After the eggs are laid a parasitic wasp called Aulacus striatus lays her eggs in the eggs of the alder wood-wasp using the tunnels already made by the host.  The wood-wasp eggs hatch with the parasitoid, which feeds inside it on the xiphydriid larva's blood, and they grow together in a process known as  'koinobiosis'.  The Aulacus grub eventually kills its host.

This is by no means the only hazard for the wood-wasps.  When the larvae are almost fully developed within the branch the female of an ichneumon fly called Rhyssella approximator (aka Rhyssella curvipes) can sense where they are and can pierce the wood with her ovipositor to lay an egg which will hatch to feed inside the hapless host.  But this is not the end of the story:  a second species of ichneumon, Pseudorhyssa alpestris, watches the activities of R. approximator and, as she cannot drill a hole herself, forces her ovipositor down the hole left by the original parasitoid and substitutes her own egg.

There is a fourth parasitoid Xiphydriophaga meyerinckii, a small chalcid wasp that crawls down the tunnels made by the wood-wasp larvae and lays her eggs on the body of the living grub which she has paralysed by stinging it.

How did these complexities of plant and animal life evolve I wonder.

In the 1960s a pioneering nature film was made by Gerald Thompson on the activities of the alder wood-wasp and its parasites and this was an important factor in setting the BBC Natural History Unit on its present course.  There are details of Thompson's life and work here: http://www.independent.co.uk/news/obituaries/gerald-thompson-642015.html

There are also details of his film online here: http://www.worldeducationalfilms.com/films/alderwoodwasp/synopsis.htm

19 May 2009

Lousewort makes a comeback

At attractive pink-flowered plant of acid heaths and meadows has been rediscovered at two sites in Brede High Wood.

Lousewort, Pedicularis sylvatica, is a hemiparasite.  Although it has chlorophyll and can therefore photosynthesise some of its own food, it also takes nourishment from surrounding plants, mainly Agrostis grasses.  This helps it to compete, despite its lowly stature, on the low-nutrient soils it prefers. 

It is related to yellow rattle, Rhinanthus minor, another hemiparasite found usually in better, drier grasslands and lousewort also has seed pods that rattle when ripe.  By reducing the vigour of grasses, both plants help to provide opportunities for other plants and are therefore often regarded as being of particular conservation value.

20090514 BHW 030

The name 'lousewort' is said to derive from a reputation in the past that if it was grazed by sheep they suffered from lice.  Sheep and cattle grazing on the kind of poor land where it grows would have been likely to be in poor condition and therefore more susceptible to lice.

I am not entirely convinced by this explanation as 'wort' plants so often seem to have been used in medicine and lousewort was once recommended to stop bleeding.

I last saw lousewort in Brede High Woods in 1997, but then only one plant, so it is particularly surprising that it has suddenly turned up in some quantity in two separate sites, both often visited.

20090514 BHW 026

13 May 2009

Garlic mustard moths

Garlic mustard or jack-by-the-hedge (Alliaria petiolata) grows by several of the rides in Brede High Woods, often near the entrances from the roads and lanes.  Although unrelated to garlic and onions it does have the distinctive smell and taste associated with these vegetables.

I always have a look at the flowers to see if I can see eggs of the orange-tip butterfly or find the little longhorn moth Adela rufimitrella (a scientific name that translates as the 'red-turbaned unseen', referring to the area behind the head of the adult and the fact that the caterpillar makes itself almost invisible by first burrowing in a seed pod then feeding from a case covered in bits of leaf and soil low down on the stems of the food plant )

20090510 BHW Adela rufimitrella 075b

For those unfamiliar with garlic mustard there is a picture below.  The moth also feeds, like the orange-tip butterfly, on cuckoo flower or lady's smock (Cardamine pratensis)

Jack by the Hedge 20030508

10 May 2009

Homage to Equivalent VIII

20090510 BHW Pile of sleepers 2

The bridge of railway sleepers over a small stream under the transmission lines in Pond Wood became unsafe, so the Highway Authority has started to repair it. The sleepers have been carefully stacked by the path and they immediately reminded me of Carl Andre’s sculpture Equivalent VIII, usually known as the ‘pile of bricks’. This was exhibited at the Tate Gallery several times and in 1976 became the subject of an “is this art?” controversy.

Andre also did much work in wood as these sleeper-like chunks show:


And he worked for a while as a brakeman and conductor on the Pennsylvania Railroad, so a photo of railway sleepers seem even more appropriate as an homage to him.

I suspect if I had not been exposed to Equivalent VIII from time to time I would not have seen any great significance in a pile of sleepers. It seems to me that this is one of the most important aspects of art: to enable one to see things from a different perspective, or to appreciate things that would otherwise have seemed unremarkable. (What an incredibly unoriginal thought!)

It would be nice if the sleepers could remain where they are to inspire other passers-by, but I expect they will be taken for firewood or to make a raised bed in someone’s garden.

There is a link to a map showing where the sleepers are here.

8 May 2009

Beech leaves

The beech tree has, arguably, the finest leaves of any native British tree: rich brown in autumn and a wonderful fresh almost lime green in spring.

20090411 BHW 059

The above is a seedling showing above some of last year's leaves.  It looks full of potential but I doubt if it will survive the attentions of the fallow deer.

These larger examples (below) may have had the protection of a fence in their early years or, more probably, the deer were not such a problem then.

20090411 BHW 057

The beech is a shallow rooted tree and I assume that the lack of ground flora beneath them in Brede High Woods reflects the fact that their uptake of nutrients and water leaves little for other vascular plants, though mosses do well.

7 May 2009

Mystery bavin

Towards the north of Brede High Wood proper I spotted this bundle of sticks on the ground.

20090411 BHW 5g  stick bundle 035

Since it is done up with only one string it is technically a bavin rather than a fagot (which has two strings)

The bundle had clearly been lying at the ride side for some time: maybe over a year and I wondered how this circumstance came about.  Had the original collector forgotten where s/he put it?  Or maybe they had been taken ill, or spirited away by a flying saucer.  Are they firewood or peasticks?  If the latter maybe the collector suddenly realised the vast amount of labour and stress that would have to go into producing a couple of quid's worth of peas, and left the stick bundle for Brede High's saproxylics.

We shall never know unless the mystery stick-gatherer happens to read this weblog and provides an explanation.