IAP-24-077

History of tropical peatland vegetation: controls on the recent development of peatland pole forest in Peruvian Amazonia

The overall aim of this project is to understand the long-term history, and ecological, geochemical, and hydrological controls on the occurrence and development of an important but still little-studied ecosystem – the peatland pole forests of Peruvian Amazonia. These forests are concentrated in the northern part of the Pastaza-Maranon Foreland Basin, the largest peat-forming area in Amazonia. Growing in areas where the peat is thick, the peatland pole forests have the highest carbon density of all Amazon forests and the large amount of carbon stored below ground means they make a significant contribution to the tropical peatland carbon pool and thus to the global carbon cycle. These forests also contribute significantly to regional biodiversity. Although the Peruvian peatlands remain for the most part intact for now, they are under threat from oil exploration and infrastructure development, and their preservation is vitally important for both climate change mitigation (by keeping the carbon in the ground) and protecting biodiversity.

Peatland pole forests (or varillal hidromorfico) on ombrotrophic (raised, rain-fed) peatlands in the Peruvian Amazon are known, from the few palaeoecological records available, to have developed only within the last 500 years. Practical challenges in collecting an intact peat profile close to the surface, and the limited time usually available to study the most recent changes in a project that must produce records of the full peatland history (which can be up to about 8,000 years in this region) mean that the transition from the peatland palm swamp vegetation, which invariably precedes pole forest development, is not well constrained temporally nor are the ecological processes or other controls on the transition well understood.
A further challenge in identifying the ecological processes and timing of pole forest development is that the characteristic taxa of pole forest only produce small amounts of pollen and are thus under-represented in the pollen rain, meaning that high counts and large sample-sizes are required to securely establish their presence in the local forest. Thus, an opportunity exists to increase our understanding of these important ecosystems by 1) improving our ability to recognise these ecosystems in the palaeoecological record and 2) studying the transition, establishing the timing and the drivers, using palaeoecological techniques in short peat cores from present day peatland pole forests.
The aim of this project is to explore the formation of peatland pole forests. In particular, the project will address the following research questions:
RQ1. Under what ecological, geochemical and hydrological conditions do peatland pole forests form?
RQ2. How can peatland pole forests be recognised in the palaeoecological record?
RQ3. How old are peat forming pole forests compared to other peat forming ecosystem types?
RQ4. What are the vulnerabilities of peatland pole forest, and the opportunities to protect them?

RQ1. Geomorphological and ecological analysis of areas where peatland pole forest is currently mapped using remote sensing to test the hypothesis that these ecosystems only form on raised mires. Geochemical (elemental) analysis of surface peat samples to test the hypothesis that peatland pole forests form where soil nutrient status is low. Hydrological analysis (e.g. water table and rainfall monitoring and remote sensing of flooding patterns) to test the hypothesis that the only source of nutrients to these ecosystems is rainfall.

RQ2. Characterise palynological signal of peatland pole forest by comparing pollen trap and surface sample data with vegetation census data from existing forest plots. This will include improving our ability to identify pole forest taxa from their pollen (using herbarium, material collected in botanical garden collections and/or existing pollen reference material as well as the literature). There will also be the opportunity to develop a new proxy for tropical peatlands, using plant macrofossils preserved in the peat. Many peat surface samples from existing pole forest census plots have already been taken by the supervisors and colleagues in Peru, so there is material to work on even before any new field work takes place.

RQ3. Using existing peat cores (and new ones as necessary) from present day pole forest sites (50cm will span the interval of pole forest development) carry out high resolution palynological analysis to characterise the development of pole forest vegetation in detail. To test the hypothesis that these are recently developed ecosystems date the transition, and estimate rates of change, using age determination techniques suitable for the last 500 years (e.g. lead-210 dating, spheroidal carbonaceous particle analysis) across several separate peatland pole forest sites.

RQ4. Using the information gathered about controls on peatland pole forest formation, critically assess its vulnerability to likely future changes (e.g. climate, resource use, infrastructure development) and consider opportunities for conservation with reference to the literature (academic and policy-facing).

Each research question lends itself to presentation as a research publication. Project outputs will include the thesis and journal articles. The student will also be encouraged to use their results to inform policymakers and other stakeholders.

Year 1

Literature review and detailed project development. Compile existing relevant data sets from published and unpublished research. Training in methods (remote sensing product interpretation, field skills, palaeoecology). Lab analysis (geochemistry and palynology) of existing peat surface samples and cores (as pilot study and to establish specific requirements of field work). Application for outline dating support from NEIF. Introduction to the policy landscape and involvement in outreach events such as Science Week and Discovery Day.

Year 2

Fieldwork to collect water table depth, geomorphology data, install/collect pollen traps, surface samples for geochemical and pollen analysis, build reference collection for plant macro fossil identification and short peat cores. Lab analysis of new materials collected in the field. Training in data analysis using R. Presentation of first results at a conference and/or for publication. Application for more detailed dating of selected cores – support from NEIF and involvement in dating lab work.

Year 3

Completion of datasets and analysis. Writing up. Preparation of a policy-facing and/or public engagement output.

Year 3.5

Thesis completion and publication.

The supervisory team includes expertise in palaeoecology, radiocarbon, lead-210 and other relevant dating techniques, vegetation survey, geochemical analysis, peatland mapping and remote sensing, and knowledge exchange. We have published extensively on the long-term ecology of lowland Peruvian peatlands and have a long track record of working closely with partner organisations in the region.

The student will receive training from the supervisors in a focused set of techniques, including:
– Fieldwork planning and site survey and sampling methods
– Pollen analysis and related palaeoenvironmental techniques as appropriate
– Interpretation of remote sensing products and GIS
– Statistical data analysis in R.

There will be opportunities to gain hands-on experience at the NEIF Laboratory; to participate in stakeholder meetings at government level; to take part in outreach events; and to develop language skills (Spanish tuition).