Linking above and belowground carbon sequestration, soil organic matter properties, and soil health in Brazilian Atlantic Forest restoration.

Forest restoration mitigates climate change by removing CO2 and storing C in terrestrial ecosystems. However, incomplete information on C storage in restored tropical forests often fails to capture the ecosystem's holistic C dynamics. This study provides an integrated assessment of C storage in above to belowground subsystems, its consequences for greenhouse gas (GHG) fluxes, and the quantity, quality, and origin of soil organic matter (SOM) in restored Atlantic forests in Brazil. Relations between SOM properties and soil health indicators were also explored. We examined two restorations using tree planting ('active restoration'): an 8-year-old forest with green manure and native trees planted in two rounds, and a 15-year-old forest with native-planted trees in one round without green manure. Restorations were compared to reformed pasture and primary forest sites. We measured C storage in soil layers (0-10, 10-20, and 20-30 cm), litter, and plants. GHG emissions were assessed using CH4 and CO2 fluxes. SOM quantity was evaluated using C and N, quality using humification index (HLIFS), and origin using δ13C and δ15N. Nine soil health indicators were interrelated with SOM attributes. The primary forest presented the highest C stocks (107.7 Mg C ha-1), followed by 15- and 8-year-old restorations and pasture with 69.8, 55.5, and 41.8 Mg C ha-1, respectively. Soil C stocks from restorations and pasture were 20% lower than primary forest. However, 8- and 15-year-old restorations stored 12.3 and 28.3 Mg ha-1 more aboveground C than pasture. The younger forest had δ13C and δ15N values of 2.1 and 1.7‰, respectively, lower than the 15-year-old forest, indicating more C derived from C3 plants and biological N fixation. Both restorations and pasture had at least 34% higher HLIFS in deeper soil layers (10-30 cm) than primary forest, indicating a lack of labile SOM. Native and 15-year-old forests exhibited higher soil methane influx (141.1 and 61.9 µg m-2 h-1). Forests outperformed pasture in most soil health indicators, with 69% of their variance explained by SOM properties. However, SOM quantity and quality regeneration in both restorations approached the pristine forest state only in the top 10 cm layer, while deeper soil retained agricultural degradation legacies. In conclusion, active restoration of the Atlantic Forest is a superior approach compared to pasture reform for GHG mitigation. Nonetheless, the development of restoration techniques to facilitate labile C input into deeper soil layers (>10 cm) is needed to further improve soil multifunctionality and long-term C storage.

The role of land use, management, and microbial diversity depletion on glyphosate biodegradation in tropical soils.

Land use and management changes affect the composition and diversity of soil bacteria and fungi, which in turn may alter soil health and the provision of key ecological functions, such as pesticide degradation and soil detoxification. However, the extent to which these changes affect such services is still poorly understood in tropical agroecosystems. Our main goal was to evaluate how land-use (tilled versus no-tilled soil), soil management (N-fertilization), and microbial diversity depletion [tenfold (D1 = 10-1) and thousandfold (D3 = 10-3) dilutions] impacted soil enzyme activities (ß-glycosidase and acid phosphatase) involved in nutrient cycles and glyphosate mineralization. Soils were collected from a long-term experimental area (35 years) and compared to its native forest soil (NF). Glyphosate was selected due to its intensive use in agriculture worldwide and in the study area, as well as its recalcitrance in the environment by forming inner sphere complexes. Bacterial communities played a more important role than the fungi in glyphosate degradation. For this function, the role of microbial diversity was more critical than land use and soil management. Our study also revealed that conservation tillage systems, such as no-tillage, regardless of nitrogen fertilizer use, mitigates the negative effects of microbial diversity depletion, being more efficient and resilient regarding glyphosate degradation than conventional tillage systems. No-tilled soils also presented much higher ß-glycosidase and acid phosphatase activities as well as higher bacterial diversity indexes than those under conventional tillage. Consequently, conservation tillage is a key component for sustaining soil health and its functionality, providing critical ecosystem functions, such as soil detoxification in tropical agroecosystems.

Physicochemical and bacterial changes during composting of vegetable and animal-derived agro-industrial wastes.

This study investigates the impact of different agro-industrial organic wastes (i.e., sugarcane filter cake, poultry litter, and chicken manure) on the bacterial community and their relationship with physicochemical attributes during composting. Integrative analysis was performed by combining high-throughput sequencing and environmental data to decipher changes in the waste microbiome. The results revealed that animal-derived compost stabilized more carbon and mineralized a more organic nitrogen than vegetable-derived compost. Composting enhanced bacterial diversity and turned the bacterial community structure similar among all wastes, reducing Firmicutes abundance in animal-derived wastes. Potential biomarkers indicating compost maturation were Proteobacteria and Bacteroidota phyla, Chryseolinea genus and Rhizobiales order. The waste source influenced the final physicochemical attributes, whereas composting enhanced the complexity of the microbial community in the order of poultry litter > filter cake > chicken manure. Therefore, composted wastes, mainly the animal-derived ones, seem to present more sustainable attributes for agricultural use, despite their losses of C, N, and S.

Robust DNA protocols for tropical soils.

Studies in the Amazon are being intensified to evaluate the alterations in the microbial communities of soils and sediments in the face of increasing deforestation and land-use changes in the region. However, since these environments present highly heterogeneous physicochemical properties, including contaminants that hinder nucleic acids isolation and downstream techniques, the development of best molecular practices is crucial. This work aimed to optimize standard protocols for DNA extraction and gene quantification by quantitative real-time PCR (qPCR) based on natural and anthropogenic soils and sediments (primary forest, pasture, Amazonian Dark Earth, and várzea, a seasonally flooded area) of the Eastern Amazon. Our modified extraction protocol increased the fluorometric DNA concentration by 48%, reaching twice the original amount for most of the pasture and várzea samples, and the 260/280 purity ratio by 15% to values between 1.8 to 2.0, considered ideal for DNA. The addition of bovine serum albumin in the qPCR reaction improved the quantification of the 16S rRNA genes of Archaea and Bacteria and its precision among technical replicates, as well as allowed their detection in previously non-amplifiable samples. It is concluded that the changes made in the protocols improved the parameters of the DNA samples and their amplification, thus increasing the reliability of microbial communities' analysis and its ecological interpretations.