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 stocks were investigated in agricultural and natural areas in 17 plot-level paired sites and in a regional survey encompassing more than 100 pasture soils In the paired sites, elemental soil concentrations and stocks were determined in native vegetation (forests and savannas), pastures and crop-livestock systems (CPSs). Nutrient stocks were calculated for the soil depth intervals 0-10, 0-30, and 0-60 cm for the paired sites and 0-10, and 0-30 cm for the pasture regional survey by sum stocks obtained in each sampling intervals (0-5, 5-10, 10-20, 20-30, 30-40, 40-60 cm). 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 native vegetation soils. Additionally, soil stoichiometry has changed with changes in land use. The soil C : N ratio was lower in the native vegetation than in the pasture and CPS soils, and the carbon and nitrogen to available phosphorus ratio (P ME ) decreased from the native vegetation to the pasture to the CPS soils. In the plotlevel paired sites, the soil nitrogen stocks were lower in all depth intervals in pasture and in the CPS soils when compared with the native vegetation soils. On the other hand, the soil phosphorus stocks were higher in all depth intervals in agricultural soils when compared with the native vegetation soils. For the regional pasture survey, soil nitrogen and phosphorus stocks were lower in all soil intervals in pasture soils than in native vegetation soils. The nitrogen loss with cultivation observed here is in line with other studies and it seems to be a combination of decreasing organic matter inputs, in cases where crops replaced native forests, with an increase in soil organic matter decomposition that leads to a decrease in the long run. The main cause of the increase in soil phosphorus stocks in the CPS and pastures of the plot-level paired site seems to be linked to phosphorus fertilization by mineral and organics fertilizers. 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 and increasing nitrogen limitation but alleviating soil phosphorus deficiency.

Soil nutrients dynamics in broadleaved forest and chinese fir plantations in subtropical forests

“…We also recorded significant decline in soil nutrients with increasing soil depth in stands of all ages, supporting the results of Groppo et al (2015) and Breulmann et al (2016) who documented this phenomenon regardless of plantation species, landuse and vegetation type. This decline in soil nutrient concentration is due to deposition of large amount of plant litter and its decomposition by soil fauna, resulting in more soil nutrients accumulating in the top soil compared with lower soil layers.…”

“…This difference was due to more biomass accumulating in the soil from the understorey vegetation and broadleaved litter, which was also suggested by Chen et al (2004) and Wan et al (2013). Cultivation of selected broadleaved species reduces alleo-chemicals levels (Xia et al 2016).…”

“…Global forest plantations are estimated to cover an area of 291 million ha, corresponding to 7.2% of total forested area (FAO 2015). China has the largest area of planted forests worldwide, with 36% (69 million ha) of the country's forests covered with forest plantations (Chinese Ministry of Forestry 2014).…”

Nutrients dynamics in tropical forest fragments located in an area of Atlantic Forest of the state of Alagoas

“…We compare the soil stocks found here with the average of 16 forest sites compiled by Groppo et al (2015), which was equal to 5.1 Mg N ha -1 . This value although in the range of the values found here, is a bit higher if compared with the mean soil N stock of Coruripe mature areas that was 4.1 Mg N ha -1 .…”

“…Soil N stocks are difficult to compare with other sites because of the lack of such estimates (Groppo et al 2015). We compare the soil stocks found here with the average of 16 forest sites compiled by Groppo et al (2015), which was equal to 5.1 Mg N ha -1 .…”