Abstract. The “soils of the Anthropocene” are predominately
agricultural. To understand them, we analyzed agri- and silvicultural
intensification of Uruguayan grasslands (GLs) in a country-wide survey on
fertility proxies, pH and trace metals in topsoils originating from
different land uses across the whole country. Thus, our results reflect
interactions of both the natural diversity of Uruguayan soil formation
and the impacts of land use change. We observed a loss of nutrients, trace
metals and organic matter from GLs, croplands and timber plantations (TPs). As
an example, the cation exchange capacity was 160 % higher in native
forests (NFs) compared to GLs and lowest in TPs, reaching
only half of the cation exchange capacity (CEC) in GLs. Acidification of topsoils continues as
three-fourths of all samples are “extremely acidic” and “very strongly
acidic”. Topsoils of riverine forests accumulate more trace metals compared
to the other uses. We assume an accumulation in the topsoils of riverine
forests, where high levels of nutrients, trace metals and organic carbon (OC) are
found. The translocation of nutrients and organic matter across the
landscape to the erosion base depends on local land use trajectories.
Increasing soil acidification is driving a positive feedback loop, and land
use intensification has lead to degradation of local black soils within a
few decades. Our data raise questions about the resilience and carrying
capacity of Uruguayan soils with regard to currently implemented highly
productive management forms, including the use of TPs for
carbon sequestration, and supports more conservative forms of extensive
management on the GL biome.