Changes in soil carbon, nitrogen and phosphorus due to land-use changes in Brazil

Abstract

Abstract. In this paper soil carbon, nitrogen and phosphorus concentrations and related elemental ratios, as well as and nitrogen and phosphorus stocks were investigated in 17 paired sites and in a regional survey encompassing more than 100 pasture soils in the Cerrado, Atlantic Forest, and Pampa, the three important biomes of Brazil. In the paired sites, elemental soil concentrations and stocks were determined in native vegetation, pastures and crop-livestock systems (CPS). Overall, there were significant differences in soil element concentrations and ratios between different land uses, especially in the surface soil layers. Carbon and nitrogen contents were lower, while phosphorus contents were higher in the pasture and CPS soils than in forest soils. Additionally, soil stoichiometry has changed with changes in land use. The soil C : N ratio was lower in the forest than in the pasture and CPS soils; and the carbon and nitrogen to available phosphorus ratio (PME) decreased from the forest to the pasture to the CPS soils. The average native vegetation soil nitrogen stocks at 0–10, 0–30 and 0–60 cm soil depth layers were equal to approximately 2.3, 5.2, 7.3 Mg ha−1, respectively. In the paired sites, nitrogen loss in the CPS systems and pasture soils were similar and equal to 0.6, 1.3 and 1.5 Mg ha−1 at 0–10, 0–30 and 0–60 cm soil depths, respectively. In the regional pasture soil survey, nitrogen soil stocks at 0–10 and 0–30 soil layers were equal to 1.6 and 3.9 Mg ha−1, respectively, and lower than the stocks found in the native vegetation of paired sites. On the other hand, the soil phosphorus stocks were higher in the CPS and pasture of the paired sites than in the soil of the original vegetation. The original vegetation soil phosphorus stocks were equal to 11, 22, and 43 kg ha−1 in the three soil depths, respectively. The soil phosphorus stocks increased in the CPS systems to 30, 50, and 63 kg ha−1, respectively, and in the pasture pair sites to 22, 47, and 68 kg ha−1, respectively. In the regional pasture survey, the soil phosphorus stocks were lower than in the native vegetation, and equal to 9 and 15 kg ha−1 at 0–10 and 0–30 depth layer. The findings of this paper illustrate that land-use changes that are currently common in Brazil alter soil concentrations, stocks and elemental ratios of carbon, nitrogen and phosphorus. These changes could have an impact on the subsequent vegetation, decreasing soil carbon, increasing nitrogen limitation, but alleviating soil phosphorus deficiency.

Nitrogen fixer abundance has no effect on biomass recovery during tropical secondary forest succession

“…Yet, the net primary production and carbon sequestration of tropical forests may be constrained by nitrogen availability (LeBauer & Treseder, ; Wright et al., ; Yang et al., ). During early secondary forest succession, nitrogen deficiencies may be high due to the loss of biomass during deforestation and soil nutrient depletion during previous land use (Amazonas, Martinelli, Piccolo, & Rodrigues, ; Davidson et al., ; Erickson, Keller, & Davidson, ; Groppo et al., ; Powers, ), or the high demand for nitrogen driven by rapid rates of forest growth (Batterman, Hedin, et al., ; Russell & Raich, ).…”

ETNOECOLOGIA DO CAMBUCI (Campomanesia phaea (O. Berg) LANDRUM) PELA POPULAÇÃO DE PARANAPIACABA, SUDESTE DO BRASIL

“…Atualmente há grande preocupação mundial pelo uso indiscriminado de adubação nitrogenada (AUSTIN et al, 2013;GROPPO et al, 2015) ainda mais em áreas próximas a unidades de conservação, onde os danos e alteração de processos ecossistêmicos poderiam acarretar sérios riscos para a biodiversidade local (CARMO et al, 2012).…”

The necessity of management in a lake of the Atlantic Forest biodiversity hotspot: nitrogen levels connected to a persistent bloom of Cylindrospermopsis raciborskii

“…It is probable that the P input into Marola Lake could result from several human activities in watershed, including fertilization. In addition, it is also possible that the low N:P ratio in the water is a consequence of the low N availability in the Atlantic Forest soil, a condition that is even more evident in the areas submitted to human impacts (Groppo et al 2015). This fact could highlight that degradation could drive other lentic systems in the Atlantic Forest to these blooms occurrence, which could be very deleterious for the water quality.…”

“…Our hypothesis was that the climatic oscillation in the region may be controlling the seasonality of the water quality, with changes in N and P levels and consequent modification in the phytoplankton total biomass and structure. We were also expecting that nitrogen would play an important role as a limitant nutrient in the water, since it is commonly scarce in the soil of this biome (Groppo et al 2015) and no waste is released into this lake.…”