Data from: Isotopic methods for non-destructive assessment of carbon dynamics in shrublands under long-term climate change manipulation

1.Long-term climate change experiments are extremely valuable for studying
ecosystem responses to environmental change. Examination of the vegetation
and the soil should be non-destructive to guarantee long-term research. In
this paper, we review field methods using isotope techniques for assessing
carbon dynamics in the plant-soil-air continuum, based on recent field
experience and examples from a European climate change manipulation
network. 2.Eight European semi-natural shrubland ecosystems were exposed
to warming and drought manipulations. One field site was additionally
exposed to elevated atmospheric CO2. We evaluate the isotope methods that
were used across the network to evaluate carbon fluxes and ecosystem
responses, including: 1) analysis of the naturally rare isotopes of carbon
(13C and 14C) and nitrogen (15N); 2) use of in-situ pulse labelling with
13CO2, soil injections of 13C- and 15N-enriched substrates, or continuous
labelling by Free Air Carbon dioxide Enrichment (FACE) and 3) manipulation
of isotopic composition of soil substrates (14C) in lab-based studies.
3.The natural 14C signature of soil respiration gave insight into a
possible long-term shift in the partitioning between the decomposition of
young and old soil carbon sources. Contrastingly, the stable isotopes 13C
and 15N were used for shorter-term processes, as the residence time in a
certain compartment of the stable isotope label signal is limited. The use
of labelled carbon-compounds to study carbon mineralization by soil
microorganisms enabled to determine the long-term effect of climate change
on microbial carbon uptake kinetics and turnover. 4.Based on the
experience with the experimental work, we provide recommendations for the
application of the reviewed methods to study carbon fluxes in the
plant-soil-air continuum in climate change experiments. 13C-labelling
techniques exert minimal physical disturbances, however, the dilution of
the applied isotopic signal can be challenging. In addition, the
contamination of the field site with excess 13C or 14C can be a problem
for subsequent natural abundance (14C and 13C) or label studies. The use
of slight changes in carbon and nitrogen natural abundance does not
present problems related to potential dilution or contamination risks, but
the usefulness depends on the fractionation rate of the studied processes.