Shifting patterns? Understanding peatland resilience from shifts in small scale microform patterns (SPURT)
Final Report Abstract
Most peatlands exhibit microtopography, creating a pattern of wet and dry microsites (microforms), and each microform has different greenhouse gas fluxes. Thus, a shift in microform distribution may have large consequences for the peatland carbon budget and its role in climate feedbacks. However, what remains unknown is how small-scale spatial patterns in microforms develop over long time scales. To predict future peatland functioning is it necessary to understand microform dynamics better, especially how it responds to climate change. In this project historical records of microform shifts are studied by investigating changes in the composition in plant remains (macrofossils) in subsequent peat layers. Records of twelve adjacent peat cores from a single peatland are compared to infer spatial heterogeneity in microform development. The main aims of the study are to determine microform stability during climatic changes, the interaction between microform stability and long term carbon budgets, and to quantify the strength of microform resilience to climate change. Comparison of the development in the twelve records showed high variability in the response time of different microform types. Responses to independently reconstructed climatic shifts in the region were generally delayed by a few hundred years. When Eriophurum vaginatum was dominant in the vegetation the response was faster, but among microform types dominated by Sphagnum mosses, the order of average response time was High lawns < Hummocks < Lawns. As such one can conclude that the stabilising feedback mechanisms are much stronger in microforms which are dominated by peatmosses. There was also a diverging long-term carbon accumulation between microform types, with Lawns having lowest and Eriophorum-types having highest accumulation rates. This difference was associated with varying productivity. Additional investigations aim to observe if certain chemical properties of the peat profile exhibit a shift before others, or before the vegetation, and to isolate and quantify alkanes from the peat material and subsequently to measure the n-alkane compound specific isotopic signatures (d2H) in these in order to model the past humidity from the variation in ð2H between alkanes stemming from vascular plants and Sphagnum. The delay in timing between a shift in humidity and vegetation can then be precisely analysed, to be used as quantification of microform resilience. However, due to time constraints these last steps have not been completed yet, but are planned to be published in the near future.
