THE UNIQUE TEESDALE FLORA IN A TIME OF CLIMATE WARMING: THREATS OF AN INVASION FROM THE SOUTH?

Overview

Many of the species found in Teesdale, UK today have disjunct modern distributions, derived from a previously more geographically widespread vegetation type and the unique ‘Teesdale assemblage’ contains species of rarity within the UK. Of particular note is the diversity of the flora, which encompasses pre-Alpine, Alpine, Arctic-Alpine and sub-Arctic species and Mediterranean species at the southern or northern edge of their latitudinal ranges in the UK, respectively. The continued existence of these nationally-rare species is thought to be a result, in part, of the combination of a cool, wet, climate (a climatically-marginal location for the growth of these plants) (1). However, the climate is warming and it is vital we understand the winners and losers in components of assemblage and the reasons behind their future fortunes (2). For example, a continued history of grazing (mainly by sheep) and the low soil nutrient status, especially on outcrops of the saccharoidal (‘sugar’) limestone are potential factors in survival of species. Importantly, the latter is also closely associated with presence of veins of heavy metal-laden ores of, for example, fluorite, barium and lead (3). Over the past 20 years, grazing has reduced compared to previously and the vegetation sward is no longer as short as it was and the sward canopy is therefore more ‘closed’. At the same time some of the rare plants have declined significantly. Only in vicinities of ore veins, where plants must tolerate a potential cocktail of heavy metals, have swards remained completely open. Are these potential micro-sites for survival of threatened species in the face of climate warming?

Aims: The project aims to determine the importance of fine-scale soil-related selection pressures in maintenance of viable populations of rare plant species in the face of larger climate-driven species range shifts.

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Image Captions

Cronkley Fell-Teesdale.jpg “A view of Upper Teesdale from Cronkley Fell, N England”. Photo: Dr R Baxter
gentian.jpg “Spring Gentian (Gentiana verna) – one of the rare species in the unique Teesdale Assemblage.” Photos: R Baxter.
winter-warming.jpg “LEFT: Winter-warming chambers on limestone grassland, Cronkley Fell, Teesdale UK; RIGHT Close-up of passive warming chamber with associated temperature and soil moisture dataloggers. Photos: R Baxter.

Methodology

A spatial analysis of soil nutrient and metal concentrations will be carried out (informed by existing high-resolution vegetation and soil maps). Warming of the locality has been proven, but importantly occurs mainly in the late-autumn through winter to early-spring period (“winter warming”). Using passive warming chambers placed over vegetation sward on identical soils, other than for heavy metal status, the student will observe the impacts of warming over three winter seasons. In addition, the reciprocal transplant of vegetated cores between micro-sites of differing heavy metal status, with and without warming, will be performed. Growth and physiology of ‘northern’ and ‘southern’ species components of the sward will be determined both in the field and under controlled environment conditions (singly and competitively in mesocosm swards) to ascertain the climate and soil condition envelopes within which species currently grow and the impacts of future climatic warming upon both plants and soils (soil nutrient cycling and heavy metal availabilities).

The student will work with the Senior Reserve Manager, Natural England and his team, to ensure continued relevance of the work undertaken to Natural England priorities and policies.

Project Timeline

Year 1

Month 1: Core induction programmes for IAPETUS2 and Biosciences (Durham); field first aid training.
Months 1-3: Literature review.
Month 3: Literature review and project aims report (3000 words; thesis committee); Attend Biosciences Research Awayday.
Months 2-12: Set-up field passive warming experiment and microclimate monitoring (including adaptation of ongoing warming experiment, to provide a longer time frame than could otherwise be achieved. Initial soil analyses (Stirling). Commence in situ vegetation and soil manipulations (reciprocal transplants) and start controlled environment climate envelope investigations.
Month 9: First-year report (mini-thesis format, 5000 words; Biosciences Progress committee); official formal Progression Review.

Year 2

In addition to all IAPETUS2 core requirements:
Months 13-24: Continue field plot warming regimes; commence controlled environment soil-plant interactions single species and mesocosm studies (soil heavy metal, temperature and moisture status). Supervisory visits to Stirling regarding soil studies and associated analyses.
Month 18: Formal Poster Presentation at postgraduate research day, Biosciences; thesis committee.
Month 21: Meeting with Biosciences Progress committee for official Confirmation Review.

Year 3

Months 25-36: Continue field experimentation and controlled environment studies, based upon earlier findings. Visits to Stirling, as necessary. Write up publications and thesis for submission.
Month 28: Submission of summary of progress and thesis outline plan; Progress Committee.
Month 30: Formal oral presentation at the Postgraduate Research Day, Biosciences
Month 33: Meeting with Progress committee for the official Completion Review and submission of a thesis plan, finalized timetable for completion and submission.

Year 3.5

Months 37-42: Thesis writing, if required. Funding ceases at end of month 42.

Training
& Skills

At Durham, the IAPETUS DTP programme will provide cross-disciplinary scientific training and development. Furthermore, the student will undertake the Biosciences Departmental induction programme and core plus elective components of the formal Postgraduate Training Programme. They will be assigned a “Progress committee” within Biosciences who will interact directly with the student throughout the PhD programme. Formal training tasks will be carried out at relevant points of progression. The student will spend periods at Stirling University with Dr Subke, learning soil sampling, extraction and analysis techniques.

References & further reading

A feel for the local environment of Upper Teesdale and its vegetation can be found here: https://bsbi.org/wp-content/uploads/dlm_uploads/Visiting_Upper_Teesdale.pdf

To get a sense of the importance of the Teesdale Assemblage and the impacts of climate change please see this article: https://teesdaleflora.home.blog/

References:

(1) BELLAMY, D., BRIDGEWATER, P., MARSHALL, C. et al. Status of the Teesdale Rarities. Nature 222, 238–243 (1969). https://doi.org/10.1038/222238a0
(2) HUNTLEY, B., BAXTER, R., LEWTHWAITE, K., WILLIS, S. & ADAMSON, J. (1998). Vegetation Responses to Local Climatic Changes Induced by a Water-Storage Reservoir. Global Ecology and Biogeography Letters. 7. 241-257. 10.2307/2997599.
(3) JOHNSON, G., ROBINSON, D. & HORNUNG, M. Unique Bedrock and Soils associated with the Teesdale Flora. Nature 232, 453–456 (1971). https://doi.org/10.1038/232453a0

Further Information

For further information please contact Dr Bob Baxter, Dept. Biosciences, Durham University. E-mail: robert.baxter@durham.ac.uk

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