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Purpose: This study was carried out to evaluate the effects of the tillage system and consecutive application of swine slurry for seven years on arbuscular mycorrhizal fungal abundance and infective propagules in Brazilian soil with crop rotation. Method: The spore density, the external mycelium, and the most probable number of infective propagules of mycorrhizal fungal abundance were assessed in soil samples from an Oxisol in a long-term field experiment in response to soil management (no-tillage and conventional tillage) and following successive application of swine slurry (0, 30, 60, 90 and 120 m³·ha-1·year-1). Results: A greater amount of external mycelium was observed in soil under no-tillage, while mycorrhizal fungal abundance spore density was greater in soil under conventional tillage. In soil under no-tillage, mycorrhizal fungal abundance infective propagules were more abundant; however, in soil with both management systems, this variable was reduced with different levels of swine slurry application. In no-tillage, the main source of mycorrhizal fungal abundance propagules is the external mycelium, while in conventional tillage, the main inoculum component is the spores. Conclusion: In this study, we verified that the application of swine slurry, with high phosphorus contents, reduces arbuscular mycorrhizal fungi propagules. However, these effects are mitigated in no-tillage systems compared to conventional tillage. [ABSTRACT FROM AUTHOR]

Purpose: This study was carried out to evaluate the effects of the tillage system and consecutive application of swine slurry for seven years on arbuscular mycorrhizal fungal abundance and infective propagules in Brazilian soil with crop rotation. Method: The spore density, the external mycelium, and the most probable number of infective propagules of mycorrhizal fungal abundance were assessed in soil samples from an Oxisol in a long-term field experiment in response to soil management (no-tillage and conventional tillage) and following successive application of swine slurry (0, 30, 60, 90 and 120 m3·ha-1·year-1). Results: A greater amount of external mycelium was observed in soil under no-tillage, while mycorrhizal fungal abundance spore density was greater in soil under conventional tillage. In soil under no-tillage, mycorrhizal fungal abundance infective propagules were more abundant; however, in soil with both management systems, this variable was reduced with different levels of swine slurry application. In no-tillage, the main source of mycorrhizal fungal abundance propagules is the external mycelium, while in conventional tillage, the main inoculum component is the spores. Conclusion: In this study, we verified that the application of swine slurry, with high phosphorus contents, reduces arbuscular mycorrhizal fungi propagules. However, these effects are mitigated in no-tillage systems compared to conventional tillage. Highlights Swine slurry application in soil reduces infective propagules of mycorrhizal arbuscular fungal. Soil disaggregation caused by conventional tillage increases sporulation and reduces infective propagules of mycorrhizal arbuscular fungal. Reduction of infective propagules of mycorrhizal arbuscular fungal under swine slurry application is mitigated in no-tillage systems.

Arbuscular mycorrhizal fungi (AMF) contribute to resisting the stress conditions of arid ecosystems. Numerous ecological restoration works propose its inoculation, and some of them without conclusive evidence of its need. In this context, the hypotheses of the exploratory study were: a) There are potentially infective propagules in fertility islands (mounds) and areas without vegetation (inter mounds); b) The mycorrhization of specimens planted in the field does not require necessarily inoculation in the nursery, and they are not main determinants of growth. Infective propagules were evaluated in mounds (n = 25) and inter-mounds (n = 25), and their presence was evidenced in both sites, although significantly higher in mounds (p = 0.045). We analyzed the mycorrhizal colonization and height of randomly chosen individuals of A. lampa (n = 15) out of 350 specimens, with 2 years of plantation in an experimental plot. All the specimens presented mycorrhization, although there were differences in height. We conclude that: a) spontaneous mycorrhization of A. lampa occurs in different environmental conditions of a degraded soil; b) the conditions of the substrates would be decisive in the plant growth. [ABSTRACT FROM AUTHOR]

The main goal of this study was to determine the diversity and activity of arbuscular mycorrhizal fungi (AMF) in an area degraded by limestone mining within the semi-arid region of Brazil known as the caatinga (shrublands). Near a limestone quarry, we selected two areas of caatinga (preserved and degraded) for study. The number of glomerospores did not differ significantly between the two areas. There was a trend toward the most probable number of infective propagules being higher in the degraded area. Twenty AMF taxa were identified in the two sampled areas, species richness, diversity and evenness being higher in the preserved area. Two species of Racocetra represent new records for the semi-arid region of Brazil. Glomerospore production and AMF species richness were unaffected by mining activity in the study area.

Abstract: The landscape of Mexican seasonal dry forests is affected by various periodic (long and drastic drought) and random (elimination of the forest coverage for agricultural purposes) disturbance events. The community of arbuscular mycorrhizal fungi (AMF) responds to these changes, sporulating and reducing its activity during the dry season, and slowly reestablishing itself following abandonment of cultivated fields. To determine the dynamics of the AMF community in response to natural phenomena and anthropogenic disturbances, we collected soil samples during the wet and dry seasons from plots with different time periods since abandonment of agricultural activity, categorized as early (less than 5 years), middle (11–23 years), and late (over 30 years) age plots. From each plot, AMF spores were isolated and identified in order to estimate abundance, richness and diversity. In addition, the number of infective propagules and value of mycorrhizal inoculum potential were calculated for each plot. Twenty-three species were recorded, for which Glomeraceae and Acaulosporaceae were the most commonly represented families. Significant differences were found in AMF species richness among plots and seasons and the diversity index of AMF was higher than 1.0 in most cases. There were no significant differences in spore abundance. Viable propagules were observed in all soil samples, with fluctuations relating mainly to time since abandonment. Overall, seasonality has a strong influence on AMF diversity but not on AMF infectivity, while time since abandonment had a more important impact. [Copyright &y& Elsevier]

The impact of land use intensity on the abundance and diversity of arbuscular mycorrhizal fungi (AMF) was investigated at six land use types viz., natural forest, grassland, acacia plantations, cardamom plantations, coffee plantations and paddy fields in the Niligiri Biosphere of the Western Ghats in South India. There was no significant difference in AMF root colonization in different land use types during pre-monsoon but there was a significant difference in AMF root infection ratings between different land use types during post-monsoon season, where it was higher in natural forests and grasslands. The AMF spore density and infective propagules were significantly higher in grasslands and acacia plantations compared to all other land use types during both seasons. Except for paddy fields, the spore density and number of infective propagules were higher in post-monsoon season compared to premonsoon season in other land use types. The numbers of AMF species identified were 56 during pre-monsoon and 67 species during post-monsoon season suggesting seasonal variations in diversity. During both seasons Glomus fasciculatum was recorded in maximum number of sampling points across the landscape followed by G. geosporum during premonsoon and G. mosseae during post-monsoon season. The species diversity was highest in natural forests and grasslands as compared to other land use types in both seasons. The species richness index for AMF was highest in natural forests and least in paddy fields during both study periods. The sand content, bulk density, total N, organic C, alkaline and acid phosphatases positively correlated with AMF activity while clay, silt, K, total P and available P were negatively correlated. [ABSTRACT FROM AUTHOR]

Abstract: The main goal of this work was to determine the presence of arbuscular mycorrhizas in coastal dunes of Sisal, Mexico, and the seasonal and spatial changes in the arbuscular mycorrhizal fungal (AMF) community. The study was conducted at three coastal dune zones: embryonic, mobile and stabilized dunes. At each dune zone we chose five dominant plant species, collected roots and determined the percent of mycorrhizal colonization. We also took five soil samples at each dune zone to evaluate AMF spore density and number of infective propagules. The overall AMF colonization ranged from 15 to 19% depending on the dune zone and the season. The density of spores in 50g soil was higher during the rainy (11.1±2.6) compared to the dry season (1.55±0.2). AMF were present in root samples of all the plants studied, and infective propagules were present in all dune zones; this held true for both sampling seasons. The presence of viable AMF propagules across the successional vegetation gradient indicates the important role of this interaction on plant survivorship in stressful conditions such as that present in Sisal. [Copyright &y& Elsevier]

Foi avaliado o efeito da mineração gesseira sobre os fungos micorrízicos arbusculares (FMA). Amostras de solo (10/área) foram coletadas em quatro áreas de uma mineradora: caatinga nativa (CN), arredores da mina (AM), rejeito (R) e interface entre o rejeito e caatinga degradada (IN), nos períodos chuvoso (dezembro/2003) e seco (setembro/2004). Foram registradas 42 espécies de fanerógamas: 25 na CN, 14 nos AM, 10 na IN e cinco na R. A CN apresentou maior número de espécies vegetais, esporos e propágulos infectivos de FMA. Número de esporos e colonização radicular diferiram entre os períodos. Maior esporulação ocorreu no período chuvoso, o número mais provável (NMP) de propágulos e colonização foram maiores no seco. Houve correlação positiva entre NMP e esporos nos dois períodos. No período chuvoso, o NMP foi negativamente correlacionado com colonização. Esta foi maior nas áreas AM e R. A atividade mineradora diminuiu a diversidade vegetal, o NMP de propágulos e a quantidade de esporos em relação à caatinga nativa.