Carbon, nitrogen and sulfur (CNS) status and dynamics in Amazon basin upland soils, Brazil

Abstract

Abstract. Given the dimensions of the Amazon basin (7.5 million km2), its internal dynamics, increasing anthropogenic strain on this large biome, and its global role as one of two continental biospheric tipping elements, it appears crucial to have data-based knowledge on carbon and nitrogen concentrations and pools as well as on possible intra-annual dynamics. We quantified carbon (Ct, Corg), nitrogen (N) and sulfur (S) concentrations in litter (ORG) and mineral soil material (TOP 0–20 cm, BOT 30–50 cm) of upland (terra firme) oxisols across Amazonas state and present a first pool calculation. Data are based on triplicate seasonal sampling at 29 sites (forest and post-forest) within the binational project EcoRespira-Amazon (ERA). Repeated sampling increased data accuracy and allows for interpreting intra-annual (seasonal) and climate-change related dynamics. Extreme conditions between the dry season in 2016 and the subsequent wet season (ENSO-related) show differences more clearly. Median CNS in the Amazon basin TOP soils (Ct 1.9, Corg 1.6, N 0.15, S 0.03 wt-% under forest canopy) as well as Corg / N ratios show concentrations similar to European soils (FOREGS, GEMAS). TOP Ct concentrations ranged from 1.02 to 3.29 wt-% (medianForest 2.17 wt-%; medianPost-Forest 1.75 wt-%), N from 0.088 to 0.233 wt-% (medianForest 0.17 wt-%; medianPost-Forest 0.09 wt-%) and S from 0.012 to 0.051 wt.-% (medianForest 0.03 wt.-%; medianPost-Forest 0.02 wt-%). Corg / N ratios ranged from 6 to 14 (median 10). A first pool calculation (hectare-based) illustrates forest versus post-forest changes. The elements are unevenly distributed in the basin with generally higher CNS values in the central part (Amazonas graben) as compared to the southern part of the basin. Deforestation and drought conditions lead to C and N losses – within 50 years after deforestation, C and N losses average 10 to 15 %. Regional climate change with increased drought will likely speed up carbon and nitrogen losses.

Physical and chemical soil quality and litter stock in agroforestry systems in the Eastern Amazon

“…Our results are aligned with previous research on the impacts of prolonged re use in forest ecosystems Considering that soil acidity negatively affects nutrient availability to plants (Malavolta, 2006; Matschullat et al 2019Matschullat et al , 2020, our results emphasize the importance of litter stock for maintaining forest ecosystems. Despite the more acidic pH, the FLO showed higher OM levels in the super cial layer compared to the other evaluated ecosystems, which may be justi ed by the high litter stock.…”

Efeito Da Seca Sobre O Balanço Hídrico Na Bacia Do Rio Xingu

“…A Bacia Amazônica, o maior sistema fluvial do planeta (FERREIRA et al, 2020), com uma área de 6,1 milhões de km², é reconhecida mundialmente pela abundante floresta tropical e disponibilidade hídrica além de prestar importantes serviços ambientais por meio de suas florestas (MATSCHULLAT et al, 2019;XU et al, 2019). Um dos seus principais afluentes é o Rio Xingu, caracterizado por suas águas claras e por sua ampla área de drenagem, 509.685 km² (ILHA et al, 2019).…”