TITLE:
Assessment of Soil C and N Stocks and Fractions across 11 European Soils under Varying Land Uses
AUTHORS:
Karolien Denef, Ilaria Del Galdo, Andrea Venturi, M. Francesca Cotrufo
KEYWORDS:
Soil Organic Carbon; Soil Nitrogen; Soil Organic Matter Fractions; Natural 15N and 13C Abundance
JOURNAL NAME:
Open Journal of Soil Science,
Vol.3 No.7,
November
18,
2013
ABSTRACT: In this study, we measured the stocks
and pool sizes of soil organic carbon (SOC) and total soil nitrogen (TN), and their natural 13C and 15N
abundance across a wide
range of temperate European ecosystems. The objectives were to examine any
distinct isotope patterns with land use or climate, and how C and N in these
different ecosystems are distributed among soil organic matter (SOM) fractions to better predict soil C and N dynamics and longer term persistence.
Soils were sampled to 30 cm depth at 11 sites of the Nitro Europe (NEU) network and included four
forests, three grasslands and four croplands. Surface soil samples were fractionated using a
combined size-density fractionation protocol separating light (LF) from heavy
particulate organic matter (hPOM) by density and silt-from-clay-associated SOM
by size. Down-profile natural abundance 15N patterns pointed towards
a closed N cycle in the forest sites, while 13C patterns suggested
differences in plant water use efficiency across the C3 grassland sites. The
forests and grassland sites stored the majority of surface SOC and TN in the LF and hPOM
pools. Sustained sequestration of C and N in these rather labile pools will rely on management
practices that minimize soil disturbance and increase C input. We also found
that the mineral fraction (silt and clay) in the cropland soils stored less C
and N per unit of fraction mass compared to the forests and grasslands, which
points towards a lower
mineral-OM stabilization efficiency of cropland soils. Finally, our study revealed total POM (LF plus hPOM)
as a strong predictor of SOC and TN differences, particularly among the non-cropped sites. This study shows that these sites,
independent of soil type and climate, store a large fraction of C and N in POM
pools that are particularly vulnerable to soil disturbance such as caused by
land use change.