ABSTRACT Climate-smart agriculture (CSA) practices, mainly no-tillage (NT), cover cropping (CC), soil fertilization with organic amendments (OA), and crop-livestock (CL) and crop-livestock-forestry (CLF) systems, has been widely adopted in areas from Brazilian Cerrado. The CSA may partly offset former soil C losses and contribute to climate change mitigation. However, contradictory findings brought uncertainties about the effect of CSA on soil C. Here, by a systematic review of 87 papers and using 621 data pairs, we provided a pervasive biome-scale analysis of soil C stock changes associated with the adoption of CSA across Brazilian Cerrado. All CSA practices evaluated showed average positive rates of C stock change, indicating a general tendency of soil C accretion after its adoption. In areas under NT, CC and CLF, greater rates were estimated for the deeper soil profile evaluated (0.00-1.00 m) (1.24 ± 0.85, 0.54 ± 0.54 and 1.00 ± 1.47 Mg ha–1 yr–1, respectively), while OA and CL showed more soil C accretion when the assessment was limited down to 0.10 m depth (0.82 ± 0.60 and 0.59 ± 0.66 Mg ha–1 yr–1, respectively). Unfortunately, the lack of basic information precluded any attempt to statically compare our estimations. In this sense, we must be cautious in stating that soil C sequestration occurs at those rates after the adoption of CSA practices. Despite these limitations, the results clearly show that the diversification and intensification of agricultural areas in the Cerrado by the adoption of CSA is a promising pathway to increase soil C stocks, and consequently, contribute to climate change mitigation and adaptation. Finally, our findings emphasize the importance of efforts that stimulate farmers to adopt these practices on large scale, such as Brazil’s Low-Carbon Agriculture Plan, besides providing sound empirical evidence about the role of soil C sequestration in Brazil achieving its Nationally Determined Contributions commitments.

Resumo A diversidade de espécies florestais é uma característica intrínseca do bioma Amazônico, sendo a serapilheira a principal responsável pela maior parcela dos nutrientes devolvidos ao solo. Dessa forma, o objetivo deste estudo foi quantificar a produção anual de serapilheira e determinar a velocidade de decomposição ao longo de um ano, comparando os resultados nos diferentes ambientes de estudo. O estudo foi desenvolvido no município de Humaitá-AM. Para a avaliação da produção de serapilheira, foram instalados de modo aleatório dez coletores cônicos em área de Floresta Nativa, área de Reflorestamento com Teca (Tectona grandis L), área de Reflorestamento com Jenipapo (Genipa americana L.) e ambiente de Reflorestamento considerado Misto, composto pelas espécies Mogno (Swietenia macrophylla King.), Andiroba (Carapa guianensis Aubl.), Jenipapo (Genipa americana L.), Teca (Tectona grandis L.) e Sumauma (Ceiba pentandra). Cada amostra de serapilheira foi colocada, separadamente, em sacos de papel devidamente identificados e levadas para laboratório e secas em estufa de circulação de ar forçado a 65°C. A estimativa da taxa de decomposição da serapilheira foi feita pela análise de perda de massa utilizando-se litter bags. A produção de serapilheira média anual foi de 8,03 Mg ha-1 ano-1 para o ambiente de floresta nativa, e não houve diferença significativa para as demais áreas de estudo. Entre as frações da serapilheira, a que mais contribuiu foi a foliar, atingindo maior média percentual no ano de 72,1% para o ambiente de reflorestamento com teca (Tectona grandis L.). A decomposição da serapilheira ocorreu de forma mais acelerada (0,0025 g g-1dia) no ambiente de reflorestamento com jenipapo (Genipa americana L.), sendo necessários 277,26 dias para que fosse decomposta metade do material foliar.

Abstract The diversity of forest species is an intrinsic characteristic of the Amazon biome, with litter being the main responsible for the largest portion of nutrients returned to the soil. Thus, the objective of this study was to quantify the annual production of burlap and to determine the rate of decomposition over one year, comparing the results in the different study environments. The study was developed in the municipality of Humaitá-AM. For the evaluation of the litter production, ten cone collectors were randomly installed in each study area. Each litter sample was placed separately in properly identified paper bags and taken to the laboratory and dried in a forced air circulation oven at 65 ° C. The litter decomposition rate was estimated by mass loss analysis using litter bags. Litter production with the highest annual average was 8,03 Mg ha-1 year -1 for the native forest environment, with no significant difference for the other study areas. Among the fractions of the litter that contributed the most to the leaf, reaching a higher average percentage in the year of 72,1% for the environment of reforestation with teak (Tectona grandis L.). The decomposition of litter occurred more rapidly (0.0025 g g-1 day) in the reforestation environment with genipap (Genipa americana L.), requiring 277,26 days to decompose half of the leaf material.

Resumo Para explorar os atributos físicos e químicos do solo e espacializar o estoque de carbono orgânico do solo em um trecho de Floresta Atlântica (Estacional Semidecidual Submontanal, Espírito Santo, Brasil), este estudo avaliou quatro camadas de solo (0-5, 5-10, 10-20 e 20-40 cm), as inter-relações dos atributos físicos e químicos e a espacialização do estoque de carbono orgânico do solo aplicando a interpolação por “cokrigagem”. Foram coletadas 12 amostras em cada camada de solo, sendo determinados os teores de nutrientes, a densidade do solo, a textura e o teor de carbono orgânico, sendo também determinado o estoque de carbono. Os atributos do solo mais significativos na variação dos dados foram verificados pela ordenação por Análise de Componentes Principais (ACP) agrupando as parcelas semelhantes quanto às características físicas e químicas. Com base na autocorrelação espacial dos atributos do solo, os dados do modelo de elevação digital (altitude e declividade) para o local estudado foram combinados para explorar a relação de coordenadas entre os parâmetros do terreno e o estoque de carbono orgânico do solo. Foi verificado o aumento da fertilidade do solo paralelo ao aumento do teor de matéria orgânica, auxiliando no entendimento das diferenças e similaridades dos sítios identificados no campo. Observa-se diferença espacial no estoque de carbono orgânico do solo, sendo o maior verificado nas áreas de menor declividade e altitude.

Abstract This study aimed to explore the physical and chemical attributes of the soil and to spatialize the soil organic carbon stock in a stretch of Atlantic Forest by evaluating four soil layers and the interrelationships of physical and chemical attributes as well as the spatialization of soil organic carbon stock by applying cokriging interpolation. Thus, 12 soil samples were collected in a soil layer, and the nutrient content, soil density, texture, soil organic carbon content and the soil carbon stock were determined. A Principal Component Analysis (PCA) grouped the most similar plots in terms of physical and chemical characteristics. Based on the spatial autocorrelation of the soil attributes, the digital elevation model data (altitude and slope) for the studied site were combined to explore the coordinate relationship between the terrain parameters and the soil organic carbon stock. We verified an increase in the soil fertility parallel to the increase in the organic matter content in the soil, helping to understand the differences and similarities of the identified sites in the field. There is a spatial difference in the soil organic carbon stock, with the largest being observed in areas of lower slope and altitude. The physical and chemical attributes of the soil in the Atlantic Forest varied according to the sampled points, being strongly related to the relief. The spatial variability altered soil organic carbon stocks in the forest under study.

RESUMO Várias espécies lenhosas tropicais são altamente responsivas a fungos micorrízicos arbusculares (FMA) e dependem da simbiose para nutrição e sucesso no estabelecimento em campo. O objetivo deste estudo foi avaliar a resposta de Schinus terebinthifolius, uma espécie nativa da Mata Atlântica e Caatinga, à inoculação com três espécies de FMA (Dentiscutata heterogama, Gigaspora margarita e Rhizophagus clarus), individualmente ou misturadas, em diferentes níveis de adubação fosfatada (0, 71, 213 e 650 mg kg−1 de P). O experimento foi conduzido em vasos de 1 kg, seguindo um delineamento inteiramente casualizado com seis repetições por tratamento, para avaliar as características morfológicas e nutricionais, após 116 dias, incluindo diâmetro do colo, altura, biomassa e teor de P na parte aérea da planta. Nossos resultados evidenciaram que S. terebinthifolius foi altamente dependente de micorrizas e apresentou respostas diferentes dependendo da espécie de FMA. O maior acúmulo de biomassa total ocorreu quando foi utilizada uma mistura das três espécies de FMA, o que indicou sinergismo entre os fungos. De uma forma geral, a maior resposta positiva à inoculação foi observada em nível intermediário de P (213 mg kg−1), e embora a biomassa da parte aérea tenha sido reduzida nas doses intermediárias de P, foi observada uma compensação com um aumento na biomassa radicular. Esses resultados indicam complementaridade em oposição à redundância funcional das espécies de FMA e destacam a importância do uso de inóculo misto na produção de mudas de S. terebinthifolius para programas de revegetação.

ABSTRACT Several tropical woody species are highly responsive to arbuscular mycorrhizal fungi (AMF) and depend on their symbiosis for nutrition and successful establishment in the field. The objective of this study was to evaluate the response of Schinus terebinthifolius, a native species of the Brazilian Atlantic Forest and Caatinga, to inoculation with three AMF species (Dentiscutata heterogama, Gigaspora margarita, and Rhizophagus clarus), either individually or mixed, at different levels of phosphorus fertilization (0, 71, 213, and 650 mg kg−1 of P). We conducted the experiment in 1 kg pots, following a completely randomized design with six replicates per treatment, to evaluate morphological and nutritional traits after 116 days, including stem diameter, plant height, plant biomass, and shoot P content. Our results showed that S. terebinthifolius was highly dependent on mycorrhizae and presented different responses depending on the AMF species. The greatest total biomass accumulation occurred when a mixture of the three AMF species was used, which indicated synergism between the fungi. The highest overall positive response to inoculation were observed at an intermediate P level (213 mg kg−1), and although shoot biomass was reduced at the intermediate P doses, an increase in root biomass compensated for this. These results indicate complementarity as opposed to functional redundancy of the AMF species and highlight the importance of using a mixed inoculum in seedling production of S. terebinthifolius for revegetation programs.

RESUMO O objetivo deste estudo foi identificar as comunidades dos fungos micorrízicos arbusculares (FMAs) presentes em solos sob ecossistemas de silvipastagens, pastagens e mata de cerrado, além de avaliar a influência do sistema de uso do solo, textura do solo e da sazonalidade na dinâmica das comunidades destes fungos, no município de Alta Floresta D’Oeste - RO. As amostras de terra foram coletadas aleatoriamente na profundidade de 0 a 20 cm, em cada um dos ecossistemas em Julho/2010 (período seco) e Janeiro/2011 (período chuvoso). Após extraídos, os esporos foram contados e identificados. Estimou-se a densidade dos esporos e a densidade de cada espécie de FMA. Calcularam-se a frequência de ocorrência de cada espécie, o índice de diversidade de Shannon e o índice de diversidade de Simpson. Realizou-se uma análise multivariada de agrupamento baseado no número de indivíduos das espécies dos FMAs. Houve tendência de um maior número de esporos no ecossistema de mata de Cerrado independente da textura do solo ou da estação do ano, quando comparado as áreas de pastagem e silvipastagem. A espécie de Glomus macrocarpum apresentou 100% de frequência de ocorrência na estação chuvosa em ambas as texturas do solo. A influência da textura e da sazonalidade na composição e diversidade da comunidade dos FMAs foi mais expressiva no ecossistema de mata de Cerrado. O clima, a textura do solo, o manejo e o sistema de uso do solo afetam a composição e diversidade de espécies de FMAs.

ABSTRACT The objective of this study was to identify communities of arbuscular mycorrhizal fungi (AMF) in soils under pasture, silvopasture, and Cerrado forest ecosystems, and evaluate the effects of land use system, soil texture, and seasonality on the dynamics of AMF communities, in Alta Floresta D'Oeste, Rondônia, Brazil. Samples of the soil 0-20 cm layer were randomly collected in each ecosystem in July, 2010 (dry season) and January, 2011 (rainy season). Spores were extracted, counted, and identified. The spore density and density of each species of AMF were estimated. The frequency of occurrence, Shannon diversity index, and Simpson diversity index were calculated for each species. Multivariate clustering analysis was carried out, considering the number of AMF of each species. The results showed a trend of higher number of spores in the Cerrado forest ecosystem, regardless of the soil texture or season, when compared to pasture and silvopasture areas. The Glomus macrocarpum species presented 100% frequency of occurrence in the rainy season in both soil textures. The effects of texture and seasonality on the composition and diversity of AMF communities was more expressive in the Cerrado forest ecosystem. The climate, soil texture, and land use and management affected the composition and diversity of AMF species.

Understanding of the organomineral interactions in soil can elucidate the humic substances (HS) formation and the humification process. This study aimed to structurally characterize the humic acids (HA) formed in tropical soils with different pedogenesis degrees. The HA fraction was extracted from soil samples in the superficial horizons of an Inceptisol and a Mollisol in Rio de Janeiro state. The HA was characterized using spectroscopic techniques following by chemometric analyses: principal component analysis, descriptive analysis, and multivariate curve resolution. The results show that HA extracted from superficial horizon of Inceptisol and Mollisol are structurally different. The Inceptisol HA has a lower E4/E6 ratio than the Mollisol HA. The chemical groups show that most -CH groups belong to -CH2 and -CH3 and hydroxyls (-OH) for the Inceptisol HA, whereas the Mollisol HA predominantly contains aromatic C=C groups. The Inceptisol HA is mainly composed of CAlkyl-H,R and -C=O structures, whereas the Mollisol HA contains a higher quantity of CAlkyl-O,N, CAlkyl-O and CAromatic-H,R groups. The Inceptisol HA has a higher aliphatic content and hydrophobicity than the Mollisol HA. In Inceptisol, organic carbon stabilization can be facilitated by hydrophobic interactions, whereas in Mollisol, different interaction sites can stabilize proteinaceous compounds.

ABSTRACT: Reducing soil degradation and its impacts on the environment have been one of the main challenges of the 21st century, exacerbated by a direct link between increases in the human population and soil degradation that raises current and future food security concerns. Despite this, experiences worldwide reveal that degraded land restoration projects have either achieved little success or failed. Thus, understanding the underlying causes and devising appropriate restoration mechanisms is crucial. Soil amelioration using beneficial microorganisms, particularly arbuscular mycorrhizal fungi (AMF), is essential and pragmatic. Glomalin, a type of glycoprotein produced by arbuscular mycorrhizal fungi in the phylum Glomeromycota, contributes to the mitigation of soil degradation. Moreover, AMF and glomalin are highly correlated with other soil physico-chemical parameters and are sensitive to changes in the environment. As a result of this, they have been recommended for monitoring the recovery of degraded soil or stages of soil degradation. In this review, we discuss the role of AMF and glomalin in the restoration of degraded soils, including improvements to the soil structure and soil organic matter (SOM), microbial activity, reduction of fertility loss, bioremediation, and mitigation of the effects of drought and saline stress. We highlight the research gaps and discuss the prospects. This knowledge will improve our understanding of the ecological conduct of glomalin and AMF, stimulate future research, and be useful to sustainable restoration of degraded lands. Furthermore, we discussed the challenges and obstacles in the legislation and future perspectives on the production of inoculants based on AMF in Brazil.

Abstract The aim of this study was to evaluate the distribution of chemical and physical fractions of soil organic matter (SOM) in anthropic horizons of soil profiles in the west of Pará. The highest total organic carbon values were observed in the superficial horizons, especially in the antrópico LAd and antrópico CHd (45.0g kg-1). Were observed predominance of recalcitrant organic material. It appears that most of the C found in the SOM fractions is associated with C stabilization mechanisms such as the recalcitrance provided by the presence of pyrogenic coal, in addition to its ability to present carboxylic groups that increase its interaction with the mineral fraction of the soil, characterizing the mechanism of chemical protection. It is observed that the SOM fractions can function as indicators that contribute to better understanding of the soil carbon dynamics in soils with antrópico horizons.

ABSTRACT Soils in the Brazilian Pantanal classified as Espodossolos and registered in the literature diverge from the central concept of pedogenesis by podzolization, especially due to the high values of pH and basic cations, although the morphology is similar to that of spodic horizons. In this sense, this study hypothesized that the neutral to alkaline conditions along the edges of the saline basins in the Lower Nhecolândia region do not inhibit the podzolization process nor the development of spodic soils. The objectives were to analyze the attributes of soils with spodic features and evaluate whether they correspond to a podzolization process. Four profiles in a transect in Lower Nhecolândia were selected, where the morphology indicated the presence of a spodic horizon. Three profiles (P1, P2 and P4) were located in a bay and one in the transition between a bay and a “cordilheira” (small elevation between lagoons) (P3). The soils were analyzed for particle size, chemistry and X-ray fluorescence (XRF), as well as organic carbon (C org), total carbon (TC) and XRF of the nodules. The complexity of features and characteristics of soil profiles in the Lower Nhecolândia region indicate multiple pedogenetic processes in this environment. The characteristics of all profiles denote a redoximorphic process: poor profile development (except for P3), mottles formed by precipitation of Fe and Mn oxides, as well as presence of Fe and Mn nodules. The organic matter content of these nodules is mostly greater than or equal to that of the surrounding material, and aluminum is relatively not higher than in the fine earth. This reinforces a rexodimorphic process in the horizons with spodic features. The occurrence of sodic and solodic characters, as well as clay accumulation in P3 also characterize the sodification process. The neutral to alkaline pH values in water, high sum of bases and low C org and Al oxide contents of the studied soils all contradict the occurrence of a podzolization process. However, Fe, Al and C org accumulation in the nodules and some B horizons indicate a spodic character. Also, the fact that SiBCS criteria classify the studied soils as Espodossolos indicates the relevance of establishing limits for chemical attributes, which would adjust the taxonomy of soils with a spodic character according to their pedogenesis.

ABSTRACT Heavy clayey Ferralsols are known for their high capacity to form water-stable macroaggregates. However, little is known about how different size classes of macroaggregates exchange mass with increasing organic matter content. This study aimed to characterize and detail aggregation dynamics with increasing organic matter content in these soils. Profiles of three heavy clayey Ferralsols were sampled to isolate the role of organic matter on the stability of aggregates. In this sampling scenario, a conceptual model was established to calculate the aggregation rate of different size classes of water-stable aggregates. This approach allowed the establishment of a critical value for classifying microaggregates in the studied soils (≤0.50 mm) based on their behavior as “building blocks” for macroaggregates when organic matter content is increased. In surface soil layers, where organic matter is higher, most dynamics are expected to happen between macroaggregates classes because free microaggregates are scarce. Consequently, it is important to subdivide macroaggregates into different size classes when evaluating their stability. Quantifying macroaggregates as a single class (e.g., >0.25 or >0.50 mm) was insufficient in representing the macroaggregation dynamics in heavy clayey Ferralsols.

Abstract The aim of the study was to investigate Pseudobombax aff. petropolitanum (PP) contribution on annual fine litterfall, carbon content, and nutrient concentration, compared to other woody species (OS) on a neotropical inselberg in Espírito Santo state, Brazil. Annual fine litterfall was systematic monthly collected (November 2011-October 2012) by means of 15 littertraps (0.25 m2) placed in five transects, oven-dried (65 °C, 72 h), weighed, and C content and nutrients concentration (N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, Zn) were estimated. PP performed lower litterfall, C content, and nutrient concentration excepting higher K concentration, compared to OS. The results suggested that PP performed higher nutrient conservation, which indicated its potential in restoring degraded areas observed in the inselberg.

ABSTRACT Soil aggregates and their stability affect a wide range of soil properties. This study aimed to (a) verify whether biogenic aggregation provides higher macro- and microaggregate stabilization, and (b) evaluate whether biogenic aggregates are associated with higher labile organic carbon and glomalin contents. Three management systems were evaluated (permanent pasture, PP; no-tillage system, NT; and no-tillage + Brachiaria system, NT+B) as well as a reference area (Atlantic Forest biome vegetation, NF). According to their origin or formation pathway, the aggregates were separated, identified, and classified as biogenic (formed by biological processes) and physicogenic (resulting from chemical and physical actions). The PP system provided the greatest stabilization of the macroaggregates, regardless of the formation pathway, as reflected by a greater mean weight diameter (MWD). The PP system also influenced the degree of microaggregate stability by increasing the bond strength and reducing the dispersion of the clay fraction. Finally, the PP system elevated the contents of labile organic carbon (POXC), easily extractable glomalin (GRSP-EE), and total glomalin (GRSP-T) under both formation pathways. The NT+B system favored the stabilization of macroaggregates, especially in the subsurface soil layer, compared with the NT area. In the aggregates of the NT and NT+B areas, the highest values observed were for water-dispersible clay (WDC) and the lowest values observed were for non-dispersible clay (NDC), a pattern opposite to that observed in the aggregates of the PP and NF areas. In the biogenic aggregates of all areas, a high POXC content was quantified, and biogenic aggregation proportionally increased the values of MWD, GRSP-EE, and GRSP-T relative to physicogenic aggregation. The results showed that grain production systems, pasture systems, and non-anthropized environments differentially influenced aggregation and the concentrations of organic fractions associated with aggregate stability. This study highlights the need for future studies using these indicators to monitor the quality of soils, especially those with sandy texture, which are considered more fragile.

RESUMO Na região da Serra da Mantiqueira os estudos pedogenéticos podem contribuir tanto para o entendimento de eventos pretéritos como para auxiliar na conservação dos recursos naturais. Este estudo objetivou caracterizar solos de região altomontana de Minas Gerais para avaliar a influência das condições paleoambientais na pedogênese. Cinco perfis foram selecionados e caracterizados quanto aos atributos morfológicos, físicos e químicos. Análises isotópicas de 13C foram realizadas em amostras de solo coletadas nas profundidades de 10, 20, 30, 40, 50, 60, 80 e 100 cm; exceto em P2, que foi coletado até 60 cm de profundidade. A distribuição errática das frações granulométricas e de C evidenciam a natureza sedimentar dos solos, resultado da ação erosiva condicionada pelo relevo. Nos perfis P2, P4 e P5 (Cambissolos/Cambisols) a coloração brunada indica o processo de xantização, enquanto no perfil P1 (Argissolo/Lixisol) é evidenciado o processo de eluviação e iluviação, resultando no incremento de argila em profundidade e pela presença de cerosidade. Em P3 (Latossolo/Ferralsol) os pequenos valores de soma de bases, remoção de sílica e valores da razão SiO2/Al2O3 (índice ki) inferiores a 1,0 evidenciam o intemperismo avançado e o processo de alitização. Nos perfis verifica-se elevados teores de C orgânico em profundidade e acúmulo superficial, o que sugere a ocorrência do processo de melanização. A variação na assinatura isotópica do δ 13C indica uma condição pretérita mais seca, com vegetação mista, com mudança gradual de vegetação com via fotossintética predominante C3. Em P1 e P4, a diminuição dos teores de δ 13C em superfície é resultado da ação antrópica.

ABSTRACT In the Serra da Mantiqueira region the pedogenetic studies contribute to both the understanding of past events and supporting the conservation of natural resources. This study aimed to characterize the soils from the Minas Gerais high-mountains region to evaluate the influence of paleoenvironmental conditions on pedogenesis. Five profiles were selected and characterized for morphological, physical and chemical properties. Isotopic analyses of 13C were performed in soil samples collected at depths of 10, 20, 30, 40, 50, 60, 80 and 100 cm; except in P2, which was collected up to 60 cm deep. Erratic distribution of the particle-size fractions and C contents highlight the sedimentary nature of the profiles, resulting from the erosive action favored by the relief. High organic C content in subsurface and its accumulation in the surface were observed in the profiles, which suggests the occurrence of the melanization process. In the profiles P2, P4 and P5 (Cambissolos/ Cambisols) the brownish color indicates the xanthization process, while in P1 (Argissolo/ Lixisol), is highlighted the process of eluviation and illuviation resulting in the increase of clay in subsurface and presence of clay films. In P3 (Latossolo/ Ferralsol), the low values of sum of bases, silica removal and SiO2/Al2O3 ratio (ki index) values below 1.0 point to the advanced weathering and the allitization process. The variation in the isotopic signature of δ13C indicates a drier past condition, with mixed vegetation, with gradual change of vegetation with predominant C3 photosynthetic pathway. In P1 and P4, the decrease in the contents of δ13C in surface results from anthropic action.

ABSTRACT Soil evolves in landscapes in a natural process in which soil properties are gradually transformed. However, the transformation of argic to ferralic horizons in basic rock-derived soils under tropical conditions is poorly understood. Depending on the position of the soil profiles in landscape, evidence of pedogenetic transformation between different horizons might indicate the formation and destruction of aggregates with shiny faces. This study aimed to determine pedogenetic changes in basic rock-derived profiles in a toposequence, because soils derived from mafic rocks are not abundant in the study region (Pinheiral, Rio de Janeiro State, Brazil). Trenches were dug at the summit (P1), upper (P2), middle (P3), and lower (P4) thirds along the toposequence. The morphological, physical, chemical, mineralogical, and micromorphological properties of the profiles were characterized, and a weathering index was calculated from X-ray fluorescence element values. All profiles had chemical and physical properties indicating an advanced degree of weathering resulting from the parent material and tropical climate conditions. In P1 and P4 that were classified as Nitossolos, the most evident pedogenetic processes were ferralitization and nitidization, due to the advanced degree of weathering, accumulation of oxyhydroxides and kaolinite in the horizons, and formation of textural pedofeatures by mechanical-hydric stress and evidence of the illuviation process. Profiles P2 and P3 revealed a ferralitization process and were classified as Latossolos. Absence of shiny macromorphological ped faces in some Bw horizons, and their micromorphological coexistence in Bt and Bw horizons within the same profile were associated with the transformation of the blocky into a granular microstructure, suggesting argic-ferralic horizon transformation.

ABSTRACT: Reducing soil degradation and its impacts on the environment have been one of the main challenges of the 21st century, exacerbated by a direct link between increases in the human population and soil degradation that raises current and future food security concerns. Despite this, experiences worldwide reveal that degraded land restoration projects have either achieved little success or failed. Thus, understanding the underlying causes and devising appropriate restoration mechanisms is crucial. Soil amelioration using beneficial microorganisms, particularly arbuscular mycorrhizal fungi (AMF), is essential and pragmatic. Glomalin, a type of glycoprotein produced by arbuscular mycorrhizal fungi in the phylum Glomeromycota, contributes to the mitigation of soil degradation. Moreover, AMF and glomalin are highly correlated with other soil physico-chemical parameters and are sensitive to changes in the environment. As a result of this, they have been recommended for monitoring the recovery of degraded soil or stages of soil degradation. In this review, we discuss the role of AMF and glomalin in the restoration of degraded soils, including improvements to the soil structure and soil organic matter (SOM), microbial activity, reduction of fertility loss, bioremediation, and mitigation of the effects of drought and saline stress. We highlight the research gaps and discuss the prospects. This knowledge will improve our understanding of the ecological conduct of glomalin and AMF, stimulate future research, and be useful to sustainable restoration of degraded lands. Furthermore, we discussed the challenges and obstacles in the legislation and future perspectives on the production of inoculants based on AMF in Brazil.