Stable Isotopic studies of east european soils and tree rings as proxies to study past climate and vegetation changes.

Project leaders

Enrico Brugnoli, Andrey Alekseev

Agreement

RUSSIA - RAS old - Russian Academy of Sciences old

Call

CNR/RAS 2011-2013

Department

Earth and Environment

Thematic area

Earth system science and environmental technologies

Status of the project

New

Research proposal

The rapid progress of modern sciences and their diversification dictate the need for maximum integration of investigations performed in different fields of science. One promising way to improve the efficiency of investigations into the global change, evolution of soils, vegetations, environment, and human society is to perform comprehensive interdisciplinary studies of different proxies available, such as tree rings and paleosols buried under various archaeological monuments. These potentially act as natural archives of palaeoclimatic and palaeoenvironmental data and of the dominant vegetation. Especially, tree rings bring the history of prevailing growing conditions for trees during each individual year and even of part of the growing season, distinguishing early wood from late wood. Isotopic studies of tree ring allows to reconstruct past temperatures and precipitations.
Buried palaeosols, by changes in their physical and/or chemical properties, may record the soil-forming climate prior to burial (and effective fossilisation) of the soil profile. Comparative studies of different soil in different zones make it possible to trace spatial and temporal dynamics of the environment and its particular components.
The steppe belt of Eurasia, which includes the northern Caucasus, the low Volga basin, the southern Urals, will be investigated in this multidisciplinary project. Properties of palaeosols, as natural environmental recorders in the steppe belt of southern Russia, will be compared with the sequence of environmental events. Such archaeological monuments, known as khourgans, are typical attributes of the southern Russian steppe landscape. According to archaeological estimation there are near million kurgans only in the Volgograd region and Kalmykia. Some of the burial sites include hundreds of particular mounds, dating back to the Bronze Age (IV – II millennia BC), the Early Iron Age (I millennia BC – IV c. AD) and the Middle Ages (V-XIV cc. AD). Due to the well established chronological sequence of archaeological cultures it is possible to define the time of creation of the barrows quite precisely (from 200-300 to less then 50 years). Thus, burial mounds represent a unique source of geographically spaced information on the history of the environment and human society in ancient epochs.
In the same area there are many forest of different species. It is possible to collect trees and tree chronologies dating back several hundreds of years and these proxies bring climatic and physiological records of that ages It is know in fact (Farquhar et al., 1982; Brugnoli et al. 1988; Brugnoli ad Farquhar, 2000) that the C isotopic signature of plant material correlates with the ratio of intercellular and atmospheric concentration of CO2 prevailing during the growing season. On the other hand, the oxygen isotopic composition is strongly dependent on evaporation and on the evaporative isotopic enrichment occurring in leaves (Brugnoli et al., 2010). Leaf water, due to evaporation is trongly enriched in 18O compared to source water, to an extent depending on air temperature, evaporative demand and stomatal conductance (Brugnoli et al. 2010). Therefore, from such isotopic studies it is possible to reconstruct these climatic and physiological parameters and the water availability at that time.
Understanding of paleoclimate requires interdisciplinary work combining biogeochemical, mineralogical, pedological, microbiological, palynological and plant physiological data. In this project, quantitative estimates of paleoclimate changes through Holocene time will be developed from analysis of the modern soil sequences, tree rings series and archaeologically-buried soils.
Most recently, use of soil mineralogical and magnetic properties as the basis of a quantitative climofunction (of rainfall)  has been established for the area of the Russian steppe (Maher et al., 2002, 2003; Alekseev et al., 2003, Alekseeva et al ,2007, Alekseev et al., 2008, Alekseeva et al ,2010 ). There is a strong statistical correlation between modern rainfall and the pedogenic magnetic susceptibility across the Russian steppe. Critically, this climofunction can then be applied to the palaeosols of our study area to determine palaeo-rainfall and the biogeochemical processes.
Properties of palaeosols, as natural environmental recorders in the steppe belt of southern Russia, will be compared with the sequence of environmental events: (1) on a continent-wide scale,(2) with archaeological sites of Poland, Ukraine and Moldavia , (3) in archaeological sites of the Middle East, South Eurasia and West Asia, Africa  (e.g. Weiss et al., 2001)
Terrestrial higher plants assimilate atmospheric carbon dioxide into organic matter mainly by one of two photosynthetic pathways, commonly called C3 or C4 pathways. All trees, most shrubs and most grasses are C3 plants, while C4 plants (e.g., corn) are sedges, grasses and shrubs. Due to their different physiological processes, C3 and C4 plants have different growth advantages in different environments and their carbon isotopic composition is significantly different (Brugnoli and Farquahr, 2000). Therefore, the relative abundance of C3/C4 plants in local terrestrial ecosystems during historical and geological periods can be used to reconstruct paleoenvironmental change.
In this project , we will estimate the changes of C3/C4 relative abundance in East Europe steppe zone for the Holocene period. The estimated paleo C3/C4 relative abundance for each time period will then compared to corresponding data for mean annual temperature (MAT) and precipitation (MAP) obtained by tree ring analysis and by other paleoclimatic data available, to explore the relationship between paleo C3/C4 relative abundance and climatic condition in an wide region of East Europe steppe zone with variable climatic and vegetation types.

Research goals

1.       To retrieve quantitative paleoenvironment information from buried soils spanning the historical period of the Holocene, by multiproxy analyses (geochemistry, mineralogy and physico-chemical properties of soils,).
2.       To study past climatic and physiological changes by mean of tree ring dendrochronolgy and isotopic analysis.
3.       To integrate the new palaeoclimate and past climatic data across Eastern Europe, to provide unprecedented spatialand temporal resolution.
4.       To use the new climatic data to test simulations (general circulation models, GCMs), in order to improve their predictive reliability.
5.       To use new paleosols and tree rings data to evaluate the history and velocity of past climate changes and the responses of vegetation.

Last update: 05/09/2025