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.

Survival of thermotolerant coliforms in municipal biosolids after application in tropical soil cultivated with Eucalyptus.

The increasing production of biosolids in urban areas has been led to a search for alternative disposal avenues of this residue, which is rich in organic matter and nutrients. Agricultural land application of biosolids, motivated by its fertilizing power, is a widespread practice in many countries, but there are safety and regulatory concerns regarding the presence of pathogens in Class B biosolids. In addition, the scarcity of studies under tropical climate conditions raises questions that impede the agricultural use of this residue in some regions. The objective of this study was to evaluate the survival of thermotolerant coliforms over 12 months (52 weeks) after biosolids application on the surface of a Quartzipsamment neosol cultivated with Eucalyptus. Two different biosolids were studied: those generated by a biological treatment system with complete mixing aeration ponds followed by decantation ponds (Treatment A) and biosolids from a biological treatment system with conventional activated biosolids reactors (Treatment B), both delineated in randomized blocks with four replicates. After application on the forest soil, we estimated an average survival time of 54 weeks for thermotolerant coliforms present in Treatment A biosolids and 93 weeks in Treatment B biosolids. Thermotolerant coliforms persist much longer under tropical climate conditions in Brazil than in comparable studies under temperate climate conditions. This reaffirms the need to carry out studies covering the full range of moisture and temperature regimes in which biosolids are applied as fertilizer.