Week 22: Of Chalk Grasslands In Hemel Hempstead

Salad Burnet (Sanguisorba minor) (I hope!), the indicator species for chalk grassland, on Further Roughdown, overlooking Hemel & the KD Tower

“Chalk grasslands have been likened to rainforest for the diversity of species they hold. But they are being lost at an alarming rate due to changes in land use causing the decline of grazing: it's estimated that we've lost 80% of our chalk grassland over the last 60 years.” BBOWT

A statement like that makes you sit up and take notice. I was fortunate to be able to attend the “Chalk grassland flowers and grasses” seminar at the Field Studies Council (FSC) in Amersham last weekend. It was led by the incredibly knowledgeable and wonderfully approachable Brenda Harold. On the up side, I could at least identify and discuss the place of Yellow Rattle within the ecology (ref Week 19). On the down side, I’d run out of energy by lunch time and it took 2+ days to recover. Well worth it though and I'd do it again, given the choice. Anyway, this week has been all about enjoying the chalk grassland at Roughdown Common and seeing it through the lens of my new knowledge.

A few notes from the course, in case they are of interest. If not, just skip it.

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Grassland

Semi-natural, Unimproved land

• Semi-natural i.e. the land has been cleared of trees by man and grazed or mowed for hay. All the plants are wild/self seeded. 
• Unimproved i.e. no mineral fertilisers or lime or other substance added.

Grasslands in general are dependent on the history of grazing, which virtually ceased after the second world war in the UK. This is where “conservation grazing” comes in (ref my “sheepish explanations of ecology” post). Sheep, rabbits, any kind of grazers, are important to prevent “thug species” like dogwood, hawthorn, bramble, thistles etc taking root, monopolising nutrients and overwhelming the smaller species and reducing species diversity.

Chalk Grassland

Calcareous, alkaline, free-draining, drought-prone soil. Low in nutrients (thus no good for agriculture) and often on slopes (so no good for building/development).

To the uninformed it is useless and even costly. Except, by the wonders of nature, it is also the most species rich in terms of the plants which thrive there and the wider ecology which follows. Incredibly, you can have up to forty different species per square metre of grassland. The key is low nutrients and high pH. Low nutrients otherwise the thug species move in and drown everything else out. High pH otherwise the acidity destroys and only the few strong or tolerant survive. It is one of the rare environments where nature is at its richest. And yet, as the BBOWT states, almost 80% of the UK’s  “unique and fragile chalk grassland has been lost....due to intensified agricultural practices, development and mismanagement.” It makes me appreciate all the more the value of places like Roughdown Common, the obligation to protect it and the need to support those who manage it.

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Ok, context set. Chalk grassland to enjoy.

Where to begin? The orchids! They really are quite spectacular at the moment. The dell, on the north side of Lower Roughdown, is cradling Common Spotted and Pyramidal orchids (both calcareous soil indicators). Something seems to have nibbled heartily at all of the Twayblades but the tell-tale leaf pairs remain. The Selfheal is also flowering now. A Robin was busy collecting food for an insistent youngster, the chiffchaff keeps on singing and a Jay bounced through the trees trying hard to remain inconspicuous.

Up on the south-west side, the bank which runs along the A41, the orchids are breathtaking. I’ve never seen anything quite like it. Swathe after swathe of deep pink/purple, white and every colour in between rising up from the earth, each a beautiful specimen, together a feast to behold.

Walking south-east along the bank, I came across a pair of Bee Orchids (Ophrys apifera), which was a lovely surprise. And, I spent a couple of contented hours completely absorbed in the nature around the grassy bank, just before you reach Further Roughdown. It was quite literally jumping with life. Meadow Grasshoppers stridulating (singing), causing grasses to ping every so often as they launched themselves on their merry way. All colours represented. This one (below) is the green variety, and could possibly be a young adult, judging by the short wings, but there were plenty of red/brown examples too. Grasshopper fact to throw into conversation next week: their ears are on their bellies (cool, eh). “On each side of the first abdominal segment, tucked under the wings, you'll find membranes that vibrate in response to sound waves. This simple eardrum, called a tympana, allows the grasshopper to hear the songs of its fellow grasshoppers.” More facts here if hoppers are your thing.

Dock bugs and Common green shieldbugs were flying between plants, butterflies too (Marbled Whites, Meadow Browns, Ringlets, a Skipper species (smaller than the Large Skipper but too quick for me to identify), Small Tortoiseshell, Speckled Wood and a few remaining Common Blues). Then there were the moths. Numerous Burnet Companions, Six-spot Burnets, a Cinnabar and three new ones for me, Knapweed Conch (Agapeta zoegana), Shaded Broad-Bar (Scotopteryx chenopodiata) and Celypha lacunana. A Great Tit family came through noisily and an adult Dunnock was trying hard to keep a squeaky juvenile well fed.

Knapweed Conch (Agapeta zoegana)

Shaded Broad-Bar (Scotopteryx chenopodiata)

Out on Further Roughdown, the Pyramidal orchids outnumber the Common Spotted, I think. They are not so numerous but the discreet clumps are fresh and vibrant. A few Swallows were hawking low over the ground, after the insects (and guaranteed to beat me to it!)

Further Roughdown Pyramidal Orchids overlooking Hemel and the KD Tower. 

Also in the mix are Birds-foot-trefoil, Fairy Flax, Yellow Rattle, White Clover and many more species besides (the names of which have yet to take root in a brain cell)! 

And, to round off this week's post, the Oak

Week 19: Beaming through the Drizzle & a Rare Moth

There’s nothing quite like stumbling across a flower that’s smiling at you, in fuchsia pink, to lift your day. It felt all the more delightful in the face of steady drizzle, leaden skies and gusty breezes.

Yesterday, I decided to embrace the rain, the wet, straggly hair and the soggy socks. I wasn’t disappointed, although I did manage to drop a lens into the sodden grass and temporarily stop my heart in horror. No harm done thankfully. Dellfield continues to be a source of joy-filled surprises. I never know what I’m going to find next. This week, it was the first spikes of the Common Spotted orchids, peering out from the expanse of wild flowers and grasses. It's a fairly common perennial, found in “grassy habitats and open woods”.

The next 3 paragraphs may look a little intimidating but are worth the effort if you fancy hearing about life-sucking, innocent-looking wild flowers; a rare Hertfordshire moth and the all too public consequences of prioritising a cup of tea over getting a decent photograph. Read on, if this appeals.

Another plant which is thriving, in its thousands, on Dellfield, is Yellow Rattle. Apparently, it is uncommon in Hertfordshire but less so on Box Moor Trust land, which is managed to encourage wild flowers and associated insect life. Above ground, it is all "sweetness and light" with its jaunty, rattling seedpods nestled behind dainty, buttercup-yellow flowers. Below ground, it's a thieving toe-rag, sending out parasitic roots into neighbouring grasses to nick their nutrients! But, it is this vampire-like behaviour which makes it such an asset to developing wild flower meadows. Potentially suffocating grasses are weakened and kept in check, allowing wild flowers to compete and establish. Yellow Rattle is also, I have learned, important in the wonderful world of moths.

It’s been nearly 4 weeks since my first mothing experience and so it was about time (not at all!) that I found a county rarity. In fact, it was another of Dellfield’s happy accidents. One of the moths I chanced upon last week, the Grass Rivulet, is, I learned, listed in the moths of Hertfordshire (2006) as “very rare”, with the only known colonies being around Long Marston. Its laval food plant is, you guessed it, Yellow Rattle and so its presence on Dellfield is neither coincidental nor insignificant. It is at this point that I must thank the Box Moor Trust mothing team for their help. In particular, Roger Prue, for providing all the information on the Grass Rivulet; for alerting me to the presence and significance of Yellow Rattle on Dellfield, and for going into the field and re-finding the moth. Hopefully, over the coming weeks, we’ll be able to get an idea of how many there are at the site and see whether the species has a stronghold. Furthermore, Ben and the team had their first ever Grass Rivulet at the Brickworks last week, so, perhaps another colony exists over there.

Although rare, following a string of emails between various knowledgable moth’ers, it transpires that the Grass Rivulet is gaining ground. In the last 3 or 4 years, there have been a number of sightings across Hertfordshire, most of which are in the west [thanks to Colin Plant, county moth recorder, for this information]. Naturally, for my most significant find to date, I pulled out all the stops and managed 2 over-exposed, off focus photographs (it's a relief I haven’t got a reputation to maintain). They may be rare but they are also right little so-and-sos to capture at rest, especially when they are the last thing you find before heading home for a much needed cup of tea! Roger did far better during his visit, but I’m consoling myself with the thought that he wasn’t gasping for a cuppa nor had he been driven to the brink of madness by disappearing Small Coppers!

Yellow Rattle (Rhinanthus minor)

[over-exposed & out of focus!] Grass Rivulet (Perizoma albulata)

The very dull, low contrast conditions gave me the opportunity to photograph the Oak with Hay Wood as its backdrop. Normally, in good light, the shadows and/or position of the sun make this composition very tricky. Silver linings and all that.

I still haven’t got used to the change from bare winter trees to lush spring vegetation. Every time I arrive at Dellfield at the moment, I have to drink in the transformation from empty, spiky, brown branches to lavish, green, soft textures of all hues and sizes. Maybe next week it'll be less of a surprise...

Left, 26 February 2014; Right, 27 May 2014