Evaluating carbon stocks in soils of fragmented Brazilian Atlantic Forests (BAF) based on soil features and different methodologies.

Brazil's Atlantic Forest (BAF) is a highly fragmented, strategic environmental and socio-economic region that represents the fourth biodiversity hotspot while also producing many commodities that are exported globally. Human disturbance plays a pivotal role as a driver of BAF's soil dynamics and behaviors. The soils under Late Primary and Secondary Semideciduous Seasonal Forests (LPSF and LSSF) were characterized by high to moderate resilience, with improved chemical properties as human disturbance decreased. The Transitional Forest to Cerrado (TFC) had the worst soil conditions. Disturbed Primary and Secondary Semideciduous Seasonal Forests (DPSF and DSSF) represent a transitional stage between LPSF/LSSF and TFC. Accordingly, SOCs stocks increased from TFC << DPSF, DSSF < LPSF, LSSF. In BAF soils, to avoid unreliable data, SOCs measurements should be (i) conducted to at least 1 m soil depth and (ii) quantified with a CHN analyzer. Human disturbance strongly affected the positive feedback between vegetation succession, SOCs, and soil nutrition. Soil development decreased as human disturbance increased, thus negatively affecting SOCs. Soils in the BAF require a long time to recover after the end of human disturbance, thus suggesting that preservation strategies should be prioritized in remnant BAF fragments.

Atlantic rainforest natural regeneration in fragmented formations affected by increasing human disturbance.

Forests provides major ecosystem services worldwide. The Brazilian Atlantic Forest (BAF) has been dramatically devastated, with fragmentation processes jeopardizing its long-term sustainability. This study investigated the structure and successional dynamics in BAF natural regeneration along an anthroposequence characterized by increasing human disturbance histories as: secondary (SF) > disturbed (DF) > late forest (LF). We aimed to understand how and the degree to which BAF fragmentation and human disturbance affected plants, soils, and the whole soil-plant relationships and feedbacks. We investigated the natural regeneration conditions of plants (using plant classification and quali-quantitative analyses) and soil chemistry (including pH-CaCl2, H + Al, C, N, Pt, cation-exchange capacity (CEC), exchangeable cations, Al, B, Cu, Fe, K, Mn, and Zn) at twelve permanent, 2000 m2 plots, distributed across LF, DF, and SF forests. Significant differences were determined by ANOVA. Correlation matrix (CM) and factor analysis (FA) were used for understanding correlations and feedbacks/variability among investigated parameters, respectively. Most of investigated plant and soil parameters showed significant differences (p < 0.05) between more developed plant formations (LF) vs less developed ones (SF), with differences mainly due to soil's development stage. All investigated forest formations are featured by a great influence of the soil-plant relationships and feedbacks, with a decreasing magnitude as LF → DF → SF. Thus, there is a direct, statistically recognizable impact of both "recent" as well as "ancient" human disturbance on investigated soil-plant formations. The anthropogenic influence clearly affected not only plant and soil as "separate" systems but the whole complex of interactions and feedbacks among ecosystem components. A decreasing quality in soil and plant parameters was observed as human disturbance increased. We demonstrated that BAF plant and soil require decades for their recovery after human disturbances, with complex mechanisms and behaviors in the relationships among ecosystem components. The results can be useful for managing future recovery in an ecosystem of worldwide strategic importance.

Comparing soil-to-plant cadmium (Cd) transfer and potential human intake among rice cultivars with different Cd tolerance levels grown in a tropical contaminated soil.

With its accumulation in upland rice, cadmium (Cd) can easily enter the human food chain, which poses a global health threat considering nearly half of the human population depends on rice as a staple food source. A study was conducted to (1) evaluate Cd accumulation by rice cultivars, grown in Cd-polluted Tropical Oxisols, with different levels of Cd tolerance; (2) quantify Cd transfer from soil to rice shoots and grain; and (3) estimate daily Cd intake by humans. Three rice cultivars, characterized by low (Cateto Seda-CS), medium (BRSMG Talento-BT), and high (BRSMG Caravera-BC) Cd uptake capacity, were investigated. Rice cultivars were exposed to increasing soil Cd concentrations (0.0, 0.7, 1.3, 3.9, 7.8, and 11.7 mg kg-1). Analysis was performed on soil, shoots, and grain. Shoot biomass and grain yield decreased with increasing Cd supply, suggesting the following Cd tolerance: CS > BT > BC. Cadmium concentrations in shoots and grain increased when exposed to Cd. Only CS did not exceed the maximum Cd limit permitted in food (0.40 mg kg-1), when rates up to 1.3 mg kg-1 of Cd were applied to soil. Considering daily rice consumption levels in Brazil, Cd intake often exceeds maximum tolerable levels. Continuous monitoring of soil Cd concentrations is a pivotal step in avoiding hazards to humans. Such monitoring is important on a global scale since outside of Asia, Brazil is the leading rice-producing and rice-consuming country.

Effects of sewage sludge application on unfertile tropical soils evaluated by multiple approaches: A field experiment in a commercial Eucalyptus plantation.

Sewage sludge (SS) reuse in forest plantation as soil fertilizer/amendment has tremendously increased in recent years. However, SS may have high concentrations of potentially toxic elements (PTE), representing a potential risk for soil and the whole ecosystem. This paper was aimed to assess the toxicity of PTE in unfertile tropical soils amended with SS in a commercial Eucalyptus plantation, with an integrated multiple approaches combining: i) the use of a battery of bioassays (Daphnia magna, Pseudokcrichirella subcapitata, Lactuca sativa, and Allium cepa); and ii) the evaluation of some PTE (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) and their availability into the pedoenvironment. Differences in total and available PTE between SS doses and time of treatments were evaluated using ANOVA; correlations between PTE and bioassays by a sparse partial robust M-regression (SPRM), while multiple correlations among parameters were performed by principal factor analysis (PFA). Results show that PTE contents in soils tended to increase with SS application doses. However this cannot be assumed as a general rule since in all the investigated treatments the PTE concentrations were consistently below both soil natural background concentrations and quality reference values. Bioassays showed a generalized low eco- and genotoxicity of SS with an increase in toxicity at increasing SS doses but with a clear decreasing trend as time went by. A. cepa was the most sensitive bioassay followed by P. subcapitata > D. magna > L. sativa. Overall, the results indicate that in realistic open field conditions SS risk may be lower than expected due to dynamic decrease in PTE toxicity with time after application. This study has an important implication that open-field trials should be strongly encouraged for evaluating environmental risk of SS application in forestry.

The impact of wildland fires on calcareous Mediterranean pedosystems (Sardinia, Italy) - An integrated multiple approach.

Sardinia (Italy), the second largest island of the Mediterranean Sea, is a fire-prone land. Most Sardinian environments over time were shaped by fire, but some of them are too intrinsically fragile to withstand the currently increasing fire frequency. Calcareous pedoenvironments represent a significant part of Mediterranean areas, and require important efforts to prevent long-lasting degradation from fire. The aim of this study was to assess through an integrated multiple approach the impact of a single and highly severe wildland fire on limestone-derived soils. For this purpose, we selected two recently burned sites, Sant'Antioco and Laconi. Soil was sampled from 80 points on a 100×100m grid - 40 in the burned area and 40 in unburned one - and analyzed for particle size fractions, pH, electrical conductivity, organic carbon, total N, total P, and water repellency (WR). Fire behavior (surface rate of spread (ROS), fireline intensity (FLI), flame length (FL)) was simulated by BehavePlus 5.0.5 software. Comparisons between burned and unburned areas were done through ANOVA as well as deterministic and stochastic interpolation techniques; multiple correlations among parameters were evaluated by principal factor analysis (PFA) and differences/similarities between areas by principal component analysis (PCA). In both sites, fires were characterized by high severity and determined significant changes to some soil properties. The PFA confirmed the key ecological role played by fire in both sites, with the variability of a four-modeled components mainly explained by fire parameters, although the induced changes on soils were mainly site-specific. The PCA revealed the presence of two main "driving factors": slope (in Sant'Antioco), which increased the magnitude of ROS and FLI; and soil properties (in Laconi), which mostly affected FL. In both sites, such factors played a direct role in differentiating fire behavior and sites, while they played an indirect role in determining some effects on soil.

Ethnopedology in the study of toponyms connected to the indigenous knowledge on soil resource.

In taking an integrated ethnopedological approach, this study aims to investigate the meaning of the distribution of the toponyms used in traditional and recent cartography of Sardinia (southern Italy). It is particularly, but not only, focused on those related to soil resources. Sardinia is particularly interesting in this respect, as its unique history, geography, and linguistic position makes it one of the Italian and Mediterranean regions with the greatest number of toponyms. This research investigated the toponyms belonging to an important sub-region of Sardinia, called Ogliastra (central-eastern Sardinia). The research was conducted through the following integrated approach: i) toponymy research and collection from different sources; ii) database creation and translation of toponyms from the Sardinian language (SL); iii) categorization of toponyms; and iv) graphical, statistical, and cartographic data processing. Distribution and diversity of toponyms were assessed using the compiled database, coupled with a geographical information system (GIS). Of around 7700 toponyms collected, 79% had already been reported in SL, while just 21% were in Italian. Of the toponyms in SL, 77% are of known meaning and 54% of these toponyms were characterized by a meaning directly and/or indirectly connected to specific environmental features. On the whole, morphology would appear to be the primary environmental factor able to explain the complex, articulated presence, distribution, and typology of the investigated toponyms. A least squares regression analysis of pedodiversity vs. topodiversity shows a very closed distribution, with an impressive high correlation index (R2 = 0.824). The principal factor analysis (PFA) shows that such a connection may be morphologically based, thereby confirming that pedodiversity and topodiversity are strongly linked each other. Overall, the research shows that an integrated ethnopedological approach, combining indigenous and scientific knowledge may be of great interest in order to mitigate the impressive phenomena of the indigenous knowledge lost.