Wednesday, 26 September 2012

Sorby Botanical Outing to Derwent Reservoir

Four members met at the Fairholmes car-park on one of the few sunny days in September to enjoy a mild ramble across the Derwent Reservoir towards Dovestones Clough and Mill Brook on the eastern side of the water. As well as appreciating the botanical bounty of the many Raspberry and Blackberry plants lining our path, we also took the time to identify many plants, many of which had finishing flowering and so were tackled vegetatively. 

Several plant groups were looked at in detail, including the Vetches (Vicia species). In particular, we compared the presence of extra-floral nectaries on the stipules of Bush Vetch with their absence on Tufted Vetch. Nectaries outside of flowers are not uncommon amongst plants, in fact, they seem to have evolved on numerous occasions; for example, the common fern Bracken also has them. Their function is seemingly to attract ants that, in turn, will attack insect herbivores, providing a benefit to the plant. Interestingly, some research has found this effect to be weak, and scientists have suggested that some plant herbivores may have themselves evolved to overcome this ant-protection system! 

After this overlap between plant identification and plant-animal mutualisms, we progressed up a sunken lane with a typical acid grassland flora at head-height, for easy inspection. We were able to pick out all of the common acid grassland grasses, including Heath-grass (Danthonia decumbens), a handsome grass with large florets that make it relatively easy to spot, even though it is often at low abundance within the sward. This is also one of only three native British grasses with a ring of hairs at the junction of the leaf-sheath and blade, making confirmation relatively straightforward (for a grass!) Finally, we arrived at the junction of Mill Brook and Dovestones Clough, where a number of typical plants of upland streams and acid-neutral flushes were found and enjoyed. Lemon-scented Fern, Star Sedge, and Creeping Forget-me-not were all identified and enjoyed.

 Botanists wanting to find out more about the cloughs around the Derwent Reservoirs are strongly recommended to purchase a copy of Sorby Record No. 40 (see the Sorby website), featuring John and Valerie Middleton's thorough survey of these splendid and exciting landscapes.