Element storage in native, agri-, and silvicultural ecosystems of the Brazilian savanna

The expanding agriculture in the Brazilian savanna, the Cerrado, changes C and nutrient storages of the savanna ecosystems thereby affecting the global C budget and the sustainability of the local land use. We examined the biomass and the C, N, P, and S storages in above- and belowground biomass, in the organic layer, and in the top 2 m of the mineral soil (Anionic Acrustoxes) of three replicate plots of each of native Cerrado, Pinus caribaea Morelet plantations, productive and degraded Bracchiaria decumbens Stapf. pastures, and of conventional and no-tillage soybean cultivation. Aboveground biomass – in the cropping systems shortly before harvest – decreased in the order, Pinus (15 kg m^–2) > Cerrado (2.3) > conventional tillage (1.9) > no tillage (1.5) > productive pasture (0.64) > degraded pasture (0.37) and belowground biomass in the order, Pinus (9.1) > Cerrado (3.0) > productive pasture (2.2) > degraded pasture (1.5) > conventional tillage (0.60) > no tillage (0.41). The aboveground biomass contained 1.1 (degraded pasture) to 19% (Pinus) of the total C storage, 0.3 (productive pasture, degraded pasture) to 3.5% of the total N storage, 0.3 (degraded pasture) to 2.1% (no tillage, conventional tillage) of the total P storage, and 0.3 (degraded pasture) to 3.7% (Pinus) of the total S storage of the ecosystems. Total C storage in the ecosystems was significantly larger in the Pinus stands (36 kg m^–2) than in all other systems; differences among Cerrado (20), degraded pasture (19), productive pasture (20), no tillage (19), and conventional tillage (19) were small and not significant. All land-use systems had larger N (Pinus, 1.5; degraded pasture, 1.3; productive pasture, 1.4; no tillage, 1.4; conventional tillage, 1.4 kg m^–2) and S storage (PI, 28; degraded pasture, 33; productive pasture, 34; no tillage, 36; conventional tillage, 38 g m^–2) than the Cerrado (N, 1.2 kg; S, 26 g m^–2). The P storages varied between 17 and 29 g m^–2 and were not significantly different among the studied ecosystems. The N and S accumulations in the 12–20-year-old land-use systems were larger than the cumulative known fertilizer inputs indicating that there were unknown inputs possibly including the exploration of the deeper subsoil by deep-reaching roots and transfer of nutrients to the topsoil. Our results indicate that afforestation with Pinus trees has the potential to sequester large amounts of C while pasture degradation, no tillage, and conventional tillage tended to result in small C losses. Land use resulted in a marked accumulation of N and S relative to the Cerrado.