IAP2-22-446

Arctic forest change in a warming climate

Biomes and the transition zones between them are expected to shift under the influence of a changing climate because of species’ range shifts. One such very important transition zone is that of the boreal forest to arctic tundra and the potential for forest advance into tundra with climatic warming. Shifts in dominant vegetation type have profound potential impacts upon both energy balance, as well as sign and magnitude of exchanges of greenhouse gases between land and atmosphere, along what is Earth’s most extensive (by area) ecological boundary. These shifts, in turn, may feedback to promote further enhanced warming across Arctic regions and beyond. Since such shifts may be more varied than a simple, uniform, poleward displacement [1][2][4][8][9] key questions requiring urgent attention are: whether or not forest advance is underway around the circumpolar Arctic and, if so, at what rates, where and why?
This project will build upon previous, complementary, work of the supervisors in determining forest structure and potential transitions as a result of change, combining both remote sensing and plant ecology approaches [3][5][6][7], as well as drawing upon recent studies by others at localities around the circumpolar Arctic ([8], and references therein) as a solid starting point. A remote-sensing-led approach will allow us to expand significantly beyond the currently rather patchy distribution of reported sites and associated studies at localities around the Arctic. This is particularly relevant at the current time when addressing the dearth of relevant information for much of the Russian Arctic at a time of many geopolitical challenges for physical study.

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Image Captions

Figure 1. View at ground level across the forest-tundra transition zone, Abisko, northern Sweden,Figure 2. A view from above the forest-tundra transition zone, Abisko, northern Sweden

Methodology

The successful candidate will aim to answer the following questions:

Q1. To what extent has the boreal forest shifted its range over the past 50 years in the Scandinavian and Russian arctic?

Q2. What is the nature and extent of the forest-tundra transition, and can we quantify the rate(s) of change of forest advance?

Q3. What will be the likely impact of projected climate change on the transition between arctic boreal forest and tundra?

This will be achieved by undertaking the following tasks:

T1. Obtain historic HEXAGON (sub-metre spatial resolution) remotely-sensed data from 1970’s for selected regions of Scandinavia and arctic Russia to develop a baseline survey of boreal forest cover for the regions. Collaborate with Prof Rees & Dr Kukavskaya, to gain access to high resolution reference data for parts of Russia.

T2. Obtain high-resolution satellite imagery for periods from 1984 to the present day and employ state-of-the-art machine learning techniques to develop models of forest structural variables to quantify boreal forest cover from multispectral remote sensing imagery.

T3. Use field-based observations to validate forest cover and biomass models from remote sensing (T2). Emphasis will be placed upon differentiating the responses of evergreen (spruce/pine) and deciduous (birch/larch) forest. To answer Q1.

T4. Employ appropriate statistical methods to analyse the relationships between the key forest structural variables and the broader-scale climatic and topographic variables. The student will gain insights into climatic data downscaling and scaling from local to regional estimations. To answer Q2.

T5. Using the output from a range of selected GCMs and future climate scenarios estimate the change in boreal forest cover during the 21st Century. This will include estimates of the overall uncertainty in the projections based on natural variability, model uncertainty and scenario uncertainty. To answer Q3.

Project Timeline

Year 1

Month 1: Core induction programmes for IAPETUS2 and Geography (Durham) plus those at University of Stirling where relevant.
Months 1-3: Literature review
Month 3: Literature review and project aims report (3000 words; thesis committee)
Months 2-12: Work relating to tasks T1-3.
Month 9: First-year progression presentation and paper (Approx. 9000 words; thesis committee); formal Progression Review.
Months: 10-11: Fieldwork at arctic research station
Month 12: Attend IAPETUS Student Symposium

Year 2

Months 13-24: Completion of work related to tasks T3 and T4
Months 15-16: Fieldwork at arctic research station
Month 18: Formal Presentation at Geography postgraduate research day for second year progression, also poster at Biosciences RPG research day.
Month 21: Attend conference and present initial results.
Month 24: Poster presentation at the IAPETUS Student Conference

Year 3

Months 25-36: Undertake work related to tasks T4 and T5.
Month 28: Submission of summary of progress and thesis outline plan; thesis committee.
Month 30: Formal oral presentation at postgraduate research day, Geography
Month 33: Meeting with Supervisors for official Completion Review and submission of a thesis plan, timetable for completion and submission.
Month 36: Oral presentation at the IAPETUS Student Conference

Year 3.5

Months 37-39: CASE Partner placement
Months 39-42: Thesis writing and submission

Training
& Skills

The student will be based in the Geography Department at Durham University and will benefit from the expertise within the group in remote sensing and forest resources mapping as well as the extensive expertise and experience of the co-supervisor (Prof Alistair Jump, School of Biological & Environmental Sciences, University of Stirling) in climate change and forest ecology. The student will work closely with Dr Rebecca Senior and Prof Robert Baxter in Biosciences at Durham University who have extensive experience in plant-ecology and climate impacts. The student will receive training in processing, analysing remote sensing and ecological data including programming, advanced statistics and use of high-performance computing systems. We will provide the student with a supportive and inclusive working environment to gain a wide range of professional and transferable skills, including skills in project design and management, in state-of-the-art analytical methods, as well as in communication, teaching and outreach. These skills will be developed through interactions with the supervisory team, within Durham and Stirling Universities and through the IAPETUS2 specific provision, and through external courses. The student will be able to take advantage of techniques developed by the supervisors in the NERC ForeSight Grant (2019-2023). The student will develop as an independent researcher through regular participation in research group meetings, seminar series, placement work and contributing to international conferences.

References & further reading

1. Montesano, P.M., et al., 2020. The bioclimatic extent and pattern of the cold edge of the boreal forest: The circumpolar taiga-tundra ecotone. Environ. Res. Lett. 15. https://doi.org/10.1088/1748-9326/abb2c7
2. Myers-Smith, I.H., et al., 2020. Complexity revealed in the greening of the Arctic. Nat. Clim. Change 10, 106–117. https://doi.org/10.1038/s41558-019-0688-1
3. Morley, PJ, Donoghue, DNM, Chen, J-C, Jump, AS. 2020 Montane forest expansion at high elevations drives rapid reduction in non-forest area, despite no change in mean forest elevation.
J Biogeogr. 2020; 47: 2405– 2416. https://doi.org/10.1111/jbi.13951
4. Sistla, S.A., et al., 2013. Long-term warming restructures Arctic tundra without changing net soil carbon storage. Nature 497, 615–617. https://doi.org/10.1038/nature12129
5. Skre, O., Baxter, R., et al. 2002. How will the tundra-taiga interface respond to climate change?. Ambio, pp.37-46.
6. Ruiz-Benito P, Jump, A.S., et al. (2020) Available and missing data to model impact of climate change on European forests. Ecological Modelling 416, 108870
7. Morley, P.J., Donoghue, D.N., Chen, J.C. and Jump, A.S., 2019. Quantifying structural diversity to better estimate change at mountain forest margins. Remote Sensing of Environment, 223, pp.291-306. https://doi.org/10.1016/j.rse.2019.01.027
8. Rees, W.G., et al., 2020. Is subarctic forest advance able to keep pace with climate change?. Global Change Biology, 26(7), pp.3965-3977.
9. Dial, R.J. et al. Sufficient conditions for rapid range expansion of a boreal conifer. Nature 608, 546–551 (2022). https://doi.org/10.1038/s41586-022-05093-2

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