Thursday, 23 January 2020

Atlas 2020, c'est tout finis

As you may have noticed, we are no longer in 2019, meaning that my favourite blog post topic, the BSBI's Atlas 2020 project, is finished. I have been meaning to write something to mark the occasion and celebrate everyone's hard work, but appallingly have been preoccupied with bryology and numerous other things this winter. However, I currently find myself becalmed in an Essex hotel, so here are some concluding thoughts on Atlas 2020 in VC23.

First, it has a been a great pleasure to receive everyone's records over the last three and a bit years. Seeing what local botanists have been up to has been very interesting and enjoyable, particularly being able to share in the excitement of unusual discoveries. I have had records from a relatively small number of regular contributors, either individuals or group recorders, some of whom have produced a considerable volume of records, as well as less frequent recorders. Many of the records that have come through me have been by email, but over the summer of last year the BSBI Distribution Database made friends with the iRecord database which gave me access to the 12,000 or so records from that source. Many of the iRecord records have been collected by a greater diversity of people than belong to the quite small circle of botanists associated with our local flora groups and the BSBI.

It is invidious of me to mention names, but special thanks must go to Tim Harrison, Jonathan Shanklin and Pete Stroh, none of whom live in the county (Jonathan and Pete live as far away as Cambridge and Peterborough, respectively) but who nevertheless spent a lot of time thoroughly surveying under-recorded areas of VC23. From the locals, we have also had regular and significant contributions from Sally Abbey, Fay Banks, Brenda Betteridge, Susan Erskine, Renée Grayer, Sue Helm, Roger Heath-Brown, Frank Hunt, Clare Malonelee, Oli Pescott, Sally Rankin, Barbara Spence and Frances Watkins. Judy Webb has been very helpful in sending me lists from her prodigious site monitoring work. Of course, as described in a previous blog, a huge contribution to the county's vascular plant data holding comes to me via my data sharing agreement with TVERC. I am very grateful to their data officer Ellen Lee for organising this, as well as to the many recorders who submit their records to TVERC, whom I am sure would be pleased to know that their records contribute to national recording projects like Atlas 2020.

Atlas records per year, excluding duplicates. Red lines are yearly number of records, on the left vertical axis, and blue lines the cumulative total, on the right. Solid and dashed lines are numbers of records with and without TVERC records.
Overall, the records gathered between 1st January 2000 and 31st December 2019 number a little over 320,800 (excluding duplicates). You can see how the records were accumulated in the graph to the left. This total is similar to most other English vice counties, being a little more than the median (~305,200) and less than the mean (~336,100). I have verified all of the Atlas records for VC23, confirming about 330,000 records (including duplicates). Questions marks remain over around 1,200, but thank you if you helped me resolve any queries.

I have shown the split between records from TVERC and other sources to highlight the importance of our data sharing agreement, which makes up more than half of the total records for Atlas 2020. This agreement with TVERC has provided a steady stream of records each year, particularly from important privately owned Local Wildlife Sites, contrasting with the more stop-start contributions direct to the BSBI. What is evident from the graph is the late start to systematic recording of the county for the Atlas project, which began I believe when Sue Helm took on the county recorder job and Atlas recording meetings were first organised. Many thanks to Sue for her hard work during her three year tenure as recorder. The spikes and troughs in the later Atlas period reflect the comings and goings of the non-VC23 based botanists thanked above.

In terms of spatial coverage and success, the county can be pleased with its Atlas dataset. This is summarised in the series of maps shown, which are stills from my interactive Atlas webmap. The project was never supposed to be a complete survey of every tetrad (2km square) in the county, but a repeat of previous hectad (10km square) national atlas surveys, based on a sample of tetrads. The re-recording rate (the coloured proportion of grid squares in the maps) is the crucial statistic for measuring progress — while there have definitely been changes to our flora, most species will still be present in most squares, so the higher the re-recording rate the more thorough and representative the sample is. The BSBI advised that a hectad re-recording rate of 70-80% should be aimed for, and this has been met for many hectads, and just about all compared to the recording period for the New Atlas (1987-1999). On the other hand, since we have no way of measuring abundance, records from too thorough a search might belie real declines, with for instance a formerly common plant reduced to a single plant both registering as present in the Atlas.

The above picture is somewhat complicated by recording effort over different periods and across taxa. The most intensive and extensive period of recording in the county was for the 1997 flora of John Killick et al, recording for which was largely complete by the late 1980s. In contrast, the New Atlas period saw less intensive recording than for the flora and the current atlas project. The difference between native and alien plants also obscures the picture, as many aliens are casual or sporadically recorded. This is well illustrated by the hectad with the city of Oxford (SP50), which has historic records of very many alien taxa from the city's old tips and waste ground. I will let the boffins at BSBI and CEH ponder how to deal with all these complications!

Drilling down to a scale more relevant to local recording, the tetrad coverage was good, indicated by the distribution, colour and size of the tetrad squares in the map shown. There were some solidly recorded areas, especially in the centre of the county, with effort thinning out to the south-east and north-west. Tim Harrison was a great help in improving several hectads in the south-east. The good results for the centre of the county doubtless reflect the very rich and varied sites around Oxford, but some recorder bias is clear, these sites also being much more accessible than in more remote areas (many are nature reserves) and this is where most of the botanists live. This includes myself, and Islip where I live (SP51H) stands out as among the most species-rich tetrads in SP51 together with the unimproved part of Otmoor (SP51R). In fact, Islip is fairly unexceptional compared with most of the nearby parishes (although there are two rivers) and many of the species I have recorded are garden escapes.

Summary of Atlas 2020 results in VC23, by hectads (top) and tetrads (bottom). The colour of grid squares is the number of species recorded (as shown in the legends), and the proportion of the coloured area is the proportion of species re-recorded from the comparison period (i.e. 1987-1999 or pre-2000). The tetrad map compares atlas records to all pre-2000 records.

After having worked so hard on Atlas, I am sure like me you are ready and rearing to start the next project. The BSBI has not yet announced the projects the society will work on over the coming years. However, it is likely that it will be something more ecology or conservation focused than Atlas 2020, for instance habitat surveys or developing site lists and registers. Myself, I'd like to direct some focus on data deficient taxa, but will be continuing the tetrad recording. The meetings I will be running this year will combine elements of these and less intense training sessions. I've already put dates in the calendar for this season — if you'd like to join me and are not already on my mailing list then do get in touch.

Monday, 6 January 2020

Bletchingdon Bryophytes

For our third recording trip of the season, after two consecutive trips to nature reserves, we decided to focus on the wider countryside, plumping for the village of Bletchingdon. A picturesque village in northern Oxfordshire built around a large green, adjacent to a grand manor house in a Palladian style. The village is adajcent to the Oolitic cornbrash limestone bedrock, and as such we expected good hunting for bryophytes on the many limestone walls of the village. Indeed, although mainly intending to focus on SP5018, we spent some time after arriving inspecting a fine wall along the road from the village green to the church. The wall had the fruiting feather (pleurocarpous) moss Homalothecium sericeum above fine and extensive sheets of Porella platyphylla, a liverwort that you may recall from our last trip to Watlington Hill. The wall also yielded Syntrichia virescens, among others; David picked this out from amongst the more abundant, larger, Syntrichia montana. A later check under the microscope proved him right! This is a probably under-recorded species, only recognised as British in 1959. The 1998 Flora of Oxfordshire hedged its bets by labelling it "?rare".

Fine sheets of Porella platyphylla in the morning sun.
Fine sheets of Porella platyphylla in the morning sun.

Homalothecium sericeum in fruit at Bletchingdon.
Homalothecium sericeum in fruit at Bletchingdon.
Hurrying on from the delights of this wall (we were in fact late to our official rendezvous point!), we then focused on the churchyard of St Giles for an hour or so. This included a range of graves of different stone, aspect, angle, and shadedness, resulting in a pretty good list. The highlight of the limestone headstones being some small patches of Tortella tortuosa. A notable near miss was an infertile Aloina species from the churchyard path; sadly these little acrocarps are unidentifable (at least without molecular techniques!) from infertile material, so this record remains at the genus level. Interestingly, Aloina ambigua was recorded from Bletchingdon stone pit in 1945. The full list from the churchyard was as follows:
Aloina sp. Orthotrichum affine
Barbula convoluta var. convoluta Orthotrichum anomalum
Barbula convoluta var. sardoa Oxyrrhynchium hians
Barbula unguiculata Phascum cuspidatum
Brachythecium rutabulum Plagiomnium undulatum
Bryum argenteum Pseudocrossidium hornschuchianum
Bryum capillare Pseudoscleropodium purum
Ceratodon purpureus Rhynchostegiella tenella
Dicranella varia Rhynchostegium confertum
Didymodon fallax Rhynchostegium murale
Didymodon insulanus Rhytidiadelphus squarrosus
Didymodon sinuosus Schistidium apocarpum s.l.
Grimmia pulvinata Thamnobryum alopecurum
Homalothecium sericeum Tortella tortuosa
Hypnum cupressiforme Tortula muralis
Hypnum cupressiforme var. resupinatum Zygodon viridissimus var. viridissimus
Kindbergia praelonga Metzgeria furcata
Porella platyphylla

The rest of the day was spent exploring SP5018, taking in a circular walk around the parkland of Bletchingdon manor, ultimately heading back into the village along the Kirtlington road. Overall we put a together a long list for the day, including Neckera complanata and more Porella together on a large ash stool, Oxyrrhynchium speciosum on the edge of a small stream in woodland, and Syntrichia papillosa on another large ash tree. On the way back to the village a stubble field was also worked over, although this yielded a fairly typical assemblage of Barbula unguiculata, Phascum cuspidatum, Oxyrrhynchium hians, and the tuberous Bryum, B. klinggraeffii. Both assemblages of fields in the calcareous parts of south-east Britain (see Preston et al., 2010 [complete the "captcha" image text to access the paper]).

Neckera complanata growing on a wall with H. sericeum at Bletchingon Park
Finally, arriving back into Bletchingdon, we spent some time grubbing around for urban ruderal species, adding Brachythecium albicans and Tortula modica from some unusually sandy soil behind kerbstones, followed by the classic wet tarmac species Didymodon nicholsonii, Ceratodon purpureus, Bryum dichotomum and Orthotrichum anomalum from a playground. A pre-Christmas pint soon followed! The full list from the wider 1km square was as follows:

Amblystegium serpens Grimmia pulvinata Rhynchostegium confertum
Barbula unguiculata Homalothecium sericeum Syntrichia laevipila
Brachythecium albicans Hypnum cupressiforme Syntrichia montana
Brachythecium rutabulum Hypnum cupressiforme var. cupressiforme Syntrichia papillosa
Bryum argenteum Hypnum cupressiforme var. resupinatum Syntrichia ruralis var. ruralis
Bryum capillare Isothecium myosuroides Thamnobryum alopecurum
Bryum dichotomum Kindbergia praelonga Tortula modica
Bryum klinggraeffii Leskea polycarpa Tortula muralis
Bryum moravicum Neckera complanata Tortula truncata
Ceratodon purpureus Orthotrichum affine Ulota bruchii
Cryphaea heteromalla Orthotrichum anomalum Zygodon conoideus
Didymodon insulanus Orthotrichum diaphanum Frullania dilatata
Didymodon nicholsonii Orthotrichum lyellii Lophocolea bidentata
Didymodon sinuosus Oxyrrhynchium hians Metzgeria furcata
Didymodon vinealis Oxyrrhynchium speciosum Porella platyphylla
Fissidens incurvus Phascum cuspidatum Radula complanata
Fissidens taxifolius Platyhypnidium riparioides

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Sunday, 15 December 2019

Bryophytes of Watlington Hill

Watlington Hill is a well-known site for chalk grassland bryophytes, although, despite this, relatively few recent records are available for the area (no post-2000 records for the main monad, SU7093, are in the BBS database or on the NBN Atlas for example). However, historically the site has been well searched. Ron Porley, when at English Nature, completed a thorough survey of the Hill in the early 90s, as a part of his work on the chalk grassland of the Chilterns. Porley found the Watlington & Pyrton Hill area to be the richest of the 13 sites he surveyed in terms of chalk grassland specialist bryophytes, recording 46 of his 69 such designated species at the site (although the site was also one of the largest in terms of the area of chalk grassland, estimated at 50.9 ha at that point).

Therefore it was with high expectations that five bryologists assembled at Watlington Hill for the second excursion of the Oxfordshire mossing season (1st Dec. 2019). A number of our group were relatively new to bryophytes, so we started in the woods surrounding the main carpark, demonstrating some of the commoner feather-mosses (pleurocarps) and epiphytes (tree-dwelling bryophytes).

A gentle start to the day!
Our list rapidly swelled, with a number of epiphytes available to demonstrate, including the mosses Orthotrichum stramineum, O. affine, O. diaphanum, Cryphaea heteromalla, and Zygodon conoideus var. conoideus, and the liverworts, Radula complanata, Frullania dilatata, Metzgeria furcata and M. violacea. When I was learning bryophytes around Sheffield in the late 2000s, this would have been considered an impressive haul indeed (at that point, these species were still recolonising after having been previously eradicated from the area due to acidic pollution)! Soon after, David discovered a fallen ash with a superabundance of another epiphyte, Orthotrichum lyellii, a distinctive moss with many brown gemmae covering its leaves. Whilst we often find this on our outings, we normally only find small tufts on standing trees: no doubt our impression is biased by our vision and reach, as this supine ash demonstrated that this species can clearly become locally abundant further up trees!

Orthotrichum lyellii (middle distance) abundant on fallen ash
O. lyellii close-up, showing the brown gemmae

Progressing through the woodland along a track along the edge of the wood, a number of species typical of soil or tree roots were found. The most handsome probably being the liverwort Porella platyphylla, which tends to be found on old limestone walls, graves, hard chalky soils, and the roots of trees on such soils in the Oxfordshire district.

Porella platyphylla on beech root at Watlington.
After lunch, we emerged into chalk grassland, and most of the rest of the excursion was spent crawling around this habitat, as proven by Joshua's tweet below...
A trampled path through the grassland provided us with our first chalk grassland specialists, including Microbryum curvicolle (no photo, but a nice illustration can be found here). Fissidens dubius, Weissia longifolia var. angustifolia, and the tiny stone-covering Seligeria calycina were all also found along this track or in grassland nearby, as well as several other currently infertile small cushion mosses (acrocarps). The idea of returning in the early spring was floated at this point!

Moving into a larger area of grassland on an east-facing slope, David soon located Entodon concinnus, a lovely species normally indicative of rich turf.

Entodon concinnus at Watlington
Sure enough, other species such as Trichostomum crispulum, Hypnum lacunosum and Ctenidium molluscum were all nearby. Mounting the brow of the hill, we encountered the more acid clay-with-flints that often heralds local concentrations of calcifugous species (i.e. those that prefer acid soils). Dicranum scoparium, Polytrichum juniperinum, and P. piliferum were all found in this area.

On circling back to the car park, more rich calcareous turf was found on west and north-west facing slopes, including Ditrichum gracile, Campylium protensum, Plagiomnium affine, Rhytidiadelphus triquetrus, and Brachythecium glareosum. The last was confirmed microscopically back at home, as was Brachythecium salebrosum found in the wood near the carpark at the start of the day. Other species confirmed microscopically included Bryum klinggraeffii, B. ruderale, B. rubens, Fissidens viridulus and Zygodon viridissimus. There were a number of Watlington rarities that we didn't find, but these will hopefully be targeted on the 2020 spring visit previously mentioned! The full list from the day is below.

Ditrichum gracile in chalk grassland at Watlington.
Amblystegium serpens Fissidens dubius Polytrichum piliferum
Barbula convoluta var. convoluta Fissidens incurvus Pseudoscleropodium purum
Barbula unguiculata Fissidens taxifolius Rhynchostegium confertum
Brachytheciastrum velutinum Fissidens viridulus Rhytidiadelphus squarrosus
Brachythecium glareosum Homalothecium lutescens Rhytidiadelphus triquetrus
Brachythecium rutabulum Homalothecium sericeum Seligeria calycina
Brachythecium salebrosum Hypnum cupressiforme var. cupressiforme Syntrichia laevipila
Bryum capillare Hypnum cupressiforme var. lacunosum Syntrichia ruralis var. ruralis
Bryum klinggraeffii Hypnum cupressiforme var. resupinatum Thuidium tamariscinum
Bryum rubens Isothecium myosuroides Trichostomum crispulum
Bryum ruderale Kindbergia praelonga Ulota bruchii
Calliergonella cuspidata Leptobryum pyriforme Weissia brachycarpa var. obliqua
Campylium protensum Microbryum curvicollum Weissia longifolia var. angustifolia
Campylopus introflexus Mnium hornum Zygodon conoideus var. conoideus
Ceratodon purpureus Orthotrichum affine Zygodon viridissimus var. viridissimus
Cryphaea heteromalla Orthotrichum diaphanum
Ctenidium molluscum Orthotrichum lyellii Cephalozia bicuspidata
Dicranella varia Orthotrichum stramineum Frullania dilatata
Dicranum scoparium Oxyrrhynchium hians Lophocolea heterophylla
Didymodon fallax Plagiomnium affine Metzgeria furcata
Ditrichum gracile Plagiomnium undulatum Metzgeria violacea
Entodon coccinus Plagiothecium nemorale Porella platyphylla
Eurhynchium striatum Polytrichum juniperinum Radula complanata

Wednesday, 4 December 2019

Bryophyte season kicks off in the Lye Valley

In a joint effort to be more organised and transparent, this season all our meetings are on the blog calendar! We will be emailing around the details of meetings a few days in advance, if you are on David's botanical mailing list, you'll get them. If not, get in touch!

Our first meeting of the season was to the eastern suburbs of Oxford to visit the Lye Valley (SP5405), incorporating the Local Nature Reserve of the same name. This site used to be known as Bullingdon Bog, and as such is something of a locus classicus for Oxonian botany. It was, for example, the site where L'Obel made the first record of Parnassia palustris for Britain; it was recorded by Sibthorp and Boswell, and featured in early ecological work on calcareous fens by Roy Clapham (later lead author of the primary British Flora in use from 1958 up to the early 90s, when it was superceded by Stace).

A view along the Lye Valley LNR
A view along the Lye Valley LNR. (O.L Pescott, CC0).
It seems that we are lucky to still have the site in the reasonable condition that it is in. Eustace Jones in the early 1950s commented that "Bullingdon Bog which must once have been an ideal example of a calcareous valley bog, is now a disturbed fragment lying in the middle of an Oxford housing estate, and obviously cannot survive much longer." Although the site was scrubbed over in recent years, and the valley sides slumping due to scouring of the valley bottom by a storm drain outflow directed along the stream, excellent management work has taken place in recent years, and is gradually restoring the valley mire to its former glories (thanks to David Morris for this information).

Bryologists assemble! (O.L. Pescott, CC0).
But to the bryophytes! We dropped into the valley from Coverley Road, recording the woodland and along the stream before the beginning of the LNR proper. Many common species were quickly found, including Tortula subulata on friable soil, and Rhyncostegiella tenella on stone. Along the stream the thallose liverworts Lunularia cruciata and Pellia endiviifolia were growing in close association at the bottom of a concrete embankment. An odd amblystegioid growth was also scraped from concrete, which, under the microscope, seemed to match descriptions of the coastal variety of Amblystegium serpens var. salinum. This, however, would be an odd turn-up for Oxford, and must await confirmation from the BBS Recorder for Mosses! Subsequently an old Hawthorn turned up a rich crop of epiphytes, including the ever expanding (and beautiful) species Orthotrichum stramineum and Syntrichia papillosa. An uncertain Ulota was later checked at home, but turned out to be the commonest taxon (at least locally) U. bruchii.

After lunch the reserve proper was tackled, and a new list was begun to ensure that records made would be traceable directly to the LNR. Many epiphytes and common species were again quickly added, including a number that chose to grow on the synthetic wood of the reserve boardwalk (Syntrichia latifolia, S. montana, S. virescens, Orthotrichum affine, O. diaphanum, among others). Next was the fen proper, and many of our expected species began to accumulate (Plagiomnium elatum, Cratoneuron filicinum, Palustriella commutata, P. falcata, Campylium stellatum, Fissidens adianthoides etc.) All previously known from the mire, but all lovely to see thriving. The curious epiphyte Platygyrium repens was also found on a pollarded willow along the stream. Deciduous branchlets of very fine leaves give this species a fuzzy appearance in the field.

Platygyrium repens at Lye Valley. (O. Pescott, CC-BY).
Some known species we failed to refind (e.g. we did not relocate Drepanocladus revolvens or Climacium dendroides), but many other species were added to the site list. A productive day, and a good start to the season.

The list of unique species seen was as follows:
?Amblystegium serpens var. salinum Platyhypnidium riparioides Brachythecium rivulare
Amblystegium serpens Rhynchostegiella tenella Bryum pseudotriquetrum
Barbula convoluta var. convoluta Rhynchostegium confertum Calliergonella cuspidata
Barbula convoluta var. sardoa Schistidium apocarpum s.l. Campylium stellatum s.str.
Brachythecium rutabulum Syntrichia laevipila Cirriphyllum piliferum
Bryum capillare Syntrichia papillosa Ctenidium molluscum
Bryum moravicum Tortula muralis Dicranoweisia cirrata
Cratoneuron filicinum Tortula subulata Didymodon fallax
Cryphaea heteromalla Ulota bruchii Fissidens adianthoides
Didymodon sinuosus Zygodon conoideus var. conoideus Fissidens incurvus
Fissidens bryoides Cololejeunea minutissima Orthotrichum lyellii
Fissidens taxifolius Frullania dilatata Palustriella commutata s.str.
Homalothecium sericeum Lophocolea heterophylla Plagiomnium elatum
Hypnum cupressiforme var. cupressiforme Lunularia cruciata Plagiomnium undulatum
Hypnum cupressiforme var. resupinatum Metzgeria furcata Syntrichia latifolia
Kindbergia praelonga Metzgeria violacea Syntrichia montana
Orthotrichum affine Pellia endiviifolia Syntrichia virescens
Orthotrichum diaphanum Radula complanata Thamnobryum alopecurum
Orthotrichum stramineum Platygyrium repens Cephalozia bicuspidata
Oxyrrhynchium hians
Oxyrrhynchium schleicheri
Palustriella falcata Lophocolea bidentata