The response of soil organic matter and natural ecosystems (primarily forests) to climate change

The understanding of the response of plant communities and soils in natural and agriculturalterrestrial ecosystems to the anthropogenic elevation of CO2 levels in the atmosphere andaccompanying climate change is of key importance for sustainable development, especiallybecause the observed rate of increase of the global mean temperature (0.17 C/decade; IPCC,2001) is in excess of the critical rate of 0.1 °C/decade beyond which the ecosystems cannotadjust (Lal, 2004). The understanding of terrestrial ecosystem response is necessary because ofthe potential migration of vegetation belts, natural hazard mitigation (slides, floods), groundwaterprotection, prevention invasive plants and animals encroachment (weeds, harmful organisms),success of agricultural production, and the quality of human environment. In addition to the plantcomposition changes, increased rate of soil organic matter mineralization and consequently soiland environmental degradation may be among the possible responses of terrestrial ecosystem toelevated global temperatures. Slovenia is located in the latitudinal zone where soils are relativelyrich in humus and where the global circulation models predict higher and faster warming rates(Kattenberg et al., 1996) compared to other latitutes. At present, the Slovenian ecosystems aredominated by C3 plants, especially forests. However, future warming may increase theproportion of C4 plants, mostly grasses, which could long-term decrease the percentage of forestcover. We propose stable isotope analyses (13C, 15N) of soil organic matter in Slovenian forests,which will enable the recostruction of several-year average C3/C4 composition at the samplingsite. We hope to detect possible past changes in plant composition at the sites and establish abaseline for long-term monitoring. To estimate the representativeness of isotope analyses forecosystem composition and detect possible isotope changes during decomposition, we will alsosample and analyze average samples of fresh and partly decomposed litter. To estimate rates ofsoil organic matter turnover, we will date SOM using 14C of samples from selected sites. Isotopeanalyses will be complemented with soil and microbial ecology (structure and function of soilmicrobial communities) analyses. Rates of litter decomposition and their dependence ontemperature will be examined in in situ and column litterbag experiments. Mathematicalpredictive models will be used to foresee the future changes in plant composition and rates ofSOM turnover in Slovenian forests. We will itroduce new methods to Slovenia, especially theanalyses of soluble fractions of SOM and soil microbial ecology techniques, which we expect tobe useful also for applied plant production research. The project is interdisciplinary and involvesthe co-operation of three Slovenian institutions (Uni-Lj, BF, IJS in ZRC SAZU), which providesappropriate expertise and equipment. The advantage of the project is the on-going internationalco-operation with GSF, Germany, and University of California at Davis in Indiana University,USA, which provides both professional and financial support to the project and allows theintroduction of new cutting-edge research methodology to Slovenia.