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2000 years of Paleoclimatology and -ecology from oak stable isotopes in the Czech Republic - the PALEO project

2000 years of Paleoclimatology and -ecology from oak stable isotopes in the Czech Republic - the PALEO project

PIs: Ulf Büntgen and Mirek Trnka

Annually resolved and absolutely dated chronologies of tree-ring width and maximum latewood density represent the backbone of high-resolution paleoclimatology and -ecology. Previous studies focused on the reconstruction of summer temperature variability over the past several hundred to thousand years. Extending our paleo-perspective over the entire Common Era (CE), and improving our understanding of ecosystem and societal most relevant hydroclimatic fluctuations, is a timely need to support and even validate model simulations, and constrain the uncertainty of future climate predictions. Joining forces toward the aggregation of composite tree-ring chronologies, exploration of additional tree-ring parameters, and application of novel reconstruction methods, are of upmost international importance.

Here, we propose PALEO. In this project, we will select and analyse ~160-170 core and disc samples of living, historical, archaeological and subfossil oaks from temperate settings across the Czech Republic. This unprecedented dataset will continuously cover the last 2000 years with constant sample replication of six trees containing ~100 rings and individual sample overlaps of ~20 years. Stable carbon and oxygen isotopes (δ13C and δ18O) will be measured for each of the ~16'500 precisely cross-dated oak rings. This enormous endeavour is only possible, because PALEO will benefit from the powerful alliance between a nation-wide dendrochronological dataset and state-of-the-art laboratory facilities. Both are now accessible to the Global Change Research Institute (Czech Globe). Moreover, the application group that is clustered in Brno, for the first time, integrates an exceptional amount of diverse expertise related to tree-ring compilation and sample preparation, cellulose extraction, mass spectrometry, plant eco-physiology, as well as the appropriate statistical treatment for capturing high- to low-frequency signals in past tree growth conditions and climate reconstructions.

By developing annually resolved, absolutely dated and highly replicated δ13C and δ18O records for the last 2000 years from temperate sites, PALEO will clearly go beyond previous attempts at national and international levels. Methodological emphasize will be placed on the preservation of inter-annual to multi-centennial changes in the resulting time-series. Careful calibration and validation trials of non-pooled, yearly δ13C and δ18O cellulose fractions will, beside their ecological importance, result in at least one new summer hydroclimatic reconstruction. Hence, PALEO will fill a critical spatiotemporal gap in the existing international network of high-resolution proxy archives, and substantially contribute to a better understanding of central Europe's hydroclimatic and ecological variability since around Roman times.

In light of the above, PALEO anticipates producing a global benchmark not only for interrelated fields of high-resolution paleoclimatology and -ecology, but also for answering timely questions related to changes in plant eco-physiological performances and metabolomics. Beside a wide range of unique biological, ecological and physiological insights, immediate implications are foreseen for multi-proxy compilations as well as for the investigation of climate forcing agents and the validation of coupled climate and eco-physiological model simulations. Additional environmental gain is expected to arise from a pending long-term perspective on carbon and water cycle dynamics, as well as at the complex though exciting interface of climate variability and human history, especially since the reconstructed hydroclimatic fluctuations are most influential for the functioning and productivity not only of natural but also of agricultural system.

Spatiotemporal distribution of the 3'934 oak samples from the Czech Republic

Spatiotemporal distribution of the 3'934 oak samples from the Czech Republic (Dobrovolný et al. 2015). The upper summary table provides information on living and relict subsets (MSL = mean segment length; AGR = average growth rate; SD = standard deviation; AC1 = first-order autocorrelation; Rbar = mean inter-series correlation; EPS = expressed population signal). The smaller table reveals statistics from the overlapping period between the living and relict samples: Gl = Gleichläufigkeit; Eckstein and Bauch 1969); TBP = T-value after Baillie and Pilcher (1973); THO = T-value after Hollstein (1980).

Header image: Collection place of oaks that have been considered in a random update sampling program of extending multi-millennial-long oak ring width chronologies until present.