Ptyxis Ecology - Our Botany Blog

Tuesday, 27 January 2009

Blink and you'll miss it!

On one of the wettest days of a very wet summer/autumn last year, I spent an afternoon looking for mosses and liverworts in Druridge Bay - see This was part of the 'Bioblitz' event orgainsised by Northumberland BAP. When the weather is so foul it can be dispiriting doing this kind of thing and it was a real shame for the event, as it meant that (unsurprisingly) very few punters turned up.

However, our dedication (or bonkersness) paid off as we found a very rare moss! Aloina rigida is a nationally scarce species that has never been recorded in Northumberland before. The map below (from the NBN website) gives an over optimistic impression of how common it is, as most of the dots relate to records made prior to 1950. So, not only is it scarce, it has also suffered a big decline in Britain. The next nearest previous records to Northumberland are near Edinburgh and in Durham where it has been seen twice, in 2001 and sometime before 1820!

Distribution of Aloina rigida in Britain & Ireland.

As you can see very well from the picture below, it grows in bare, stony places. The picture is from Michael Luth's excellent CD called 'Bilder von Moosen' (pictures of mosses). Ok, where it grows is not actually 'bare', it is sparsely vegetated. These kind of very open habitats are undervalued but very interesting ecologically. Many specialist species of mosses, liverworts, lichens and invertebrates thrive in these areas. One of the few positive changes to nature conservation policy in recent years has been the recognition of these habitats now as UKBAP habitat, 'open mosaics on previously developed land' as they are now officially called.

If you ignore the stalk (seta) of the spore capsule, these plants grow to no more than about 2mm high, so they are not exactly 'showy'. They are also ephemeral in nature, adapted to be able to colonise new areas quickly and probably not lasting on sites for very long as they become more thickly vegetated. As the nearest recent populations are quite a distance away from Druridge Bay the spores that gave rise to the plants we found must have travelled a very long distance by wind to get there.


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Wednesday, 21 January 2009

Winter buds

One of my most memorable experiences from when I was first leaning my botany was doing a 1-day training course on winter tree identification given by Nick Bertrand. Before then I had no idea that you could use characteristics of twigs (especially the buds) to identify trees in winter. I remember getting really enthused for botany after that and I also remember enjoying showing off what I had learned to my fellow MSc students in Oxleas Wood in SE London.

Some of the characteristics that are useful are: shape of buds (rounded, pointed, conical, needle-like, etc.); number of bud scales; arrangement of buds on the twig (opposite, alternate, clustered); pattern of bud scales (opposite, herringbone, random); colour of buds (can either be very useful or very misleading!); shape of leaf scars; etc. Once you get familair with these characteristics it is fairly straightforward to identify most British species to Genus, although it is more tricky to go to species level in a couple of genera. In some ways, it is easier to identify trees in winter than at other times. Winter is a good time to do your first visit when surveying a woodland, as when the trees are naked it is much easier to assess the structural characteristic of the wood and see signs of past management. The most difficult time of year for tree identification is early spring between the time when buds start to elongate and young leaves are in the process of forming.

Here are some pictures of buds from a few species that I took yesterday down the track from our house to show some of the variety.

Ash is probably the most easily recognised tree in winter. The large terminal buds are sooty-black and conical - nothing else has buds anything like this. Note that the lateral buds are much smaller and opposite.

Willow is the only genus that has buds with only one bud scale. Lime buds looks a bit similar but have two scales. The willow buds can vary quite a bit in colour (brownish-yellow, orangey, brownish-red or purplish) on different trees of the same species, at different times of year or even on the same tree. Apart from one or two species, the others are difficult to tell apart from the buds. Most willows have alternately arranged buds.

Hawthorn have quite small buds with very small leaf scars just underneath. When I was first learning, I used to find it very difficult to tell hawthorn and blackthorn apart from their bud and twig characteristics. Now I don't have any trouble at all telling them apart as I am used to their 'jizz', but if you were to ask me to describe the key difference for identification I would stuggle to put it into words.

Oaks have clusters to tan-coloured buds at the end of the twigs with lots of bud-scales, often arranged in a herringbone pattern. Beware, that some books and keys tell you that oaks are the only genus to have terminal clusters of buds, but wild cherry often does this also. You are supposed to be able to tell the 2 British species apart by counting the number of bud-scales but I have never tested this out to be able to tell if it works or not.

Alder buds are one of the most attractive. They have a unique puple colour with a floury bloom. The lateral buds are on short stalks which is unique amongst British species.

Alder are the most decorated of British deciduous trees in winter. The old cones are unmistakable. This picture shows some tightly-closed, long males catkins with a cluster of immature female cones in the background.


Saturday, 17 January 2009

Fragrant orchids

Ok, I know I said before (see 'Orchid overdose' - July2007) that I might never blog about orchids again, but I did just say 'might'. I suppose I now have to admit that I've become an orchid fancier (almost). I've been surveying upland hay meadows in the North Pennines for the last 3 years and although orhcids are quite uncommon in hay meadows now, I have seen some of them often enough to start to get interested. I had a lot to learn about British orchids and I found Michael Foley and Sidney Clarke's book very useful. I didn't know the fragrant orchids at all when I started but have now seen all three types.

Up to a few years ago most people were happy to call them all 'fragrant orchid'. Frances Rose (who must be a leading candidate for being Britain's most outstanding field naturalist) divided them into three types a long time ago. His view has now been backed up by DNA analysis. They are likely to appear as separate species (or sub-species) in the next edition of Stace and it will be interesting to see what kind of patterns emerge in geohgraphical distribtution and habitat preferences of the three types, as more people start to record and map them. If you look at the distribution maps on the BSBI website you will see how under-recorded the sub-species are currently compared to the species.

This is Gymnadenia conopsea borealis (or just G. borealis if you prefer), which I have found in eight different meadows. It seems to be easily the most common of the three around here. In the hay meadows it is normally now confined to unmown (and unfertilised) banks, often growing in quite acidic U4c vegetation with species like betony and bitter-vetch. The lower lip of the flower (labellum) is almost not lobed at all and is longer than wide. The two lateral sepals are not exactly horizontal, but point a bit downwards.

I've found this one, Gymnadenia conopsea conopsea three times, but only a very small number of individuals in each case. (Sorry about the rubbish photo!). It is supposed to prefer more calcareous conditions. The labellum is much more lobed than borealis with the 3 lobes being about equal in size. Overall the labellum is about as long as wide. The lateral sepals are wider than borealis but still point slightly downwards.

This one is (I think) Gymnadenia conopsea densiflora, which I've only found once. It is supposed to prefer damper grasslands than the other two. It is also lobed and the middle lobe is supposed to be smaller than the two lateral lobes - although that isn't very obvious on this specimen. Overall the labellum is wider than long. The lateral sepals are wide like conposea but this time they do point out exactly horizontally. I found quite a big population of this growing on the edge of a meadow right on the riverbank of the Tees near Cronkley Bridge. The three types are supposed to have a slightly different smell, but I haven't sniffed them enough to know if that works for me yet.

Sound easy doesn't it. Well it's not! I thought it was fairly easy until I found the densiflora population. Both conopsea and borealis were there also, but the most common Gymnadenia there appeared to be intermnediate between densiflora and conopsea. Presumably these are hybrids. The three types are probably quite closely related, so its not surprising that if they grow together they would hybridise. Even if they have fairly strict habitat preferences, it is often possible to get a mixture of quite different soil conditions within a very small space, so not that unlikley to get them together at least sometimes.

They are nice plants. Its good fun trying to figure out a new botanical puzzle. But the main reason I like them is because they always grow in nice habitats.


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