Sunday 22 June 2014

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.


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.

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

1 comment:

Martin Parr said...

Another great post Lucy. The orchids really are spectacular this year. The ones at the brickworks are coming up even through the brambles!