ABSTRACT State parks are integral protection units created to protect ecosystems. However, anthropic activities may have been previously performed before their creation, forming transitional areas. Studies that evaluate the modifications of edaphic properties in these environments are scarce. The aim of this study was to evaluate the changes in soil properties and litter stock in areas of eucalyptus-forest ecotones. Litter stock (Stocklitter) and total soil organic carbon content and stock (TOCsoil), weighted mean diameter (MWD), origin of aggregates (biogenic or physicogenic) and respective content of total organic carbon (TOCBio and TOCPhy), total organic carbon (TOCAG), soil organic matter chemical fractions [fulvic acid (FAC), humic (HAC), and humin (HUMC)], and particulate, mineral-associated, free light and intra-aggregate light (POC, MAOC, FLFC, and ILFC) soil organic matter, fertility, and glomalin-related soil protein (GRSP) fractions were evaluated in aggregates (layer 0.00-0.10 m) in areas of eucalyptus-forest ecotone (Eco), preserved forest fragment (For), and eucalyptus plantation (Euc), in Nova Baden State Park, Lambari–MG. In the Euc and Eco areas, the highest Stocklitter content was found. Higher values of TOCsoil, TOCAG, GRSP, and MWD were observed in the Euc area. In the biogenic aggregates, the highest content of TOCBio, HAC, HUMC, POC, MAOC, FLFC, and ILFC was determined in detriment of the physicogenic ones. The dynamics of edaphic properties in the Eco area showed greater similarity with the For area than in the Euc area. In general, all vegetation covers contribute to the maintenance of soil quality.

ABSTRACT An important strategy for the sustainable management of Cerrado soils is no-till (NT) systems, which may improve soil properties, particularly aggregation. Soil aggregates can be categorized according to their formation pathways into physicogenic (Phy) and biogenic (Bio). This study aimed (i) to quantify the relative proportion of physicogenic and biogenic aggregates and (ii) evaluate the levels of total organic carbon and their respective humic and physical fractions in the aggregates’ formation pathways. The following managed and unmanaged sites were evaluated: a 6-year no-till site (6NT), an 18-year no-till site (18NT), a conventional tillage site (CT), and a reference Cerrado site (RS). Retained aggregates were analyzed morphologically, separated into Phy and Bio, and quantified. Subsequently, aggregates were subjected to total organic carbon (TOC) determination, fulvic acid carbon, humic acid carbon, humin carbon, particulate organic carbon (POC), mineral-associated organic carbon, and free light fraction carbon (FLFC). The proportion of Bio aggregates increased with decreasing management intensity. When TOC and humic acid carbon levels were compared between sites, it was found that Bio aggregates from 18NT and 6NT contained higher carbon content than Bio aggregates from CT. Particulate organic carbon and FLFC differed between aggregate types, with higher POC values observed in Bio aggregates from CT and 18NT and higher FLFC values in Bio aggregates from CT, 6NT, and 18NT. The practices adopted in the conservation management system favored biogenic aggregation in the Cerrado region, which can be proven through the study of the fractions of soil organic matter contained in these aggregates. The biogenic aggregation changed the SOM dynamics. Principal component analysis showed a clear distinction between conventional and conservationist management systems.

ABSTRACT Histosols provide several ecosystem services, related mainly to their reserves of carbon and nitrogen. Management practices in these soils can increase the mineralization of organic matter and contribute to the emission of greenhouse gases. This study aimed to investigate the effect of tillage with plowing and drainage on Histosol properties in three land use systems located in the municipality of Rio de Janeiro, Brazil. Three areas subjected to different land use systems over the last twenty years were chosen: Area 1, secondary forest with natural regeneration; Area 2, conventional tillage of cassava with plowing; and Area 3, intercropped coconut + cassava with an artificial drainage system. The chemical characterization, von Post scale of organic matter decomposition, percentage of rubbed fiber, organic matter, percentage of mineral material, bulk density, electrical conductivity, soluble phosphate, total organic carbon (TOC) and nitrogen (NT), organic carbon fractions, and C and N stocks were analyzed. Our results showed the critical, nearly irreversible effects of agricultural practices comprising drainage and plowing of the soil. Over twenty years, in Area 2, the TOC and NT values decreased by 33 and 20 %, respectively in the histic horizon, and by about 17 and 8 %, respectively in the gley horizon. In Area 3, the TOC and NT values decreased by 31 and 18 %, respectively, in the histic horizon, and by 27 and 21 % in the gley horizon. Our findings also showed that the loss of C is related to the labile organic carbon, which is more sensitive to environmental changes, even at deeper depths. The plowing of the soil decreases the organic matter content due to the accelerated oxidation of organic matter, increasing the bulk density. Drainage, besides the loss of organic matter by subsidence, promotes the sulfidization of the soil with a high content of SO42-, due to the oxidation of soil materials containing sulfides.