Diversity of arbuscular mycorrhizal fungi in the soil of agroecosystems in semi-arid CearÃ

Os Fungos MicorrÃzicos Arbusculares - FMA sÃo microrganismos chave tanto em agroecossistemas como em ecossistemas naturais. SÃo responsÃveis por uma simbiose que ocorre com a maioria das plantas vasculares. Atuam em mutualismo com as plantas, auxiliando-as na absorÃÃo de nutrientes pouco mÃveis no solo, alÃm de aumentar a absorÃÃo de Ãgua e protegÃ-las contra patÃgenos, sendo fortemente influenciados por prÃticas agrÃcolas e variaÃÃes ambientais. Neste trabalho avaliaram-se as influÃncias de parÃmetros quÃmicos do solo, perÃodos do ano e quatro diferentes agroecossistemas com fruteiras tropicais (cajueiros - Anacardium occidentale (2 pomares), coqueiros - Cocos nucifera, e gravioleiras - Annona muricata), na diversidade de FMA em comparaÃÃo com uma Ãrea de mata nativa adjacente aos plantios, partindo da hipÃtese de que estes fatores alteram a composiÃÃo da comunidade desses fungos. Foram coletadas amostras de solo na profundidade de 0-20 cm, no perÃodo chuvoso (abril/2009) e seco (outubro/2009), e utilizados Ãndices ecolÃgicos como forma de avaliar as alteraÃÃes entre os sistemas e os perÃodos. No total foram identificados 35 diferentes morfotipos de esporos de FMA. Entre os parÃmetros quÃmicos do solo, o pH mostrou-se negativamente correlacionado com a densidade mÃdia de esporos, o Mg com a riqueza de espÃcies e o Zn com ambos. A densidade mÃdia de esporos foi influenciada negativamente pelos agroecossistemas, pois os maiores valores foram encontrados na Ãrea de mata em ambos os perÃodos, e exceto pela cultura do coqueiro, todas as outras tiveram aumento significativo no perÃodo seco. A riqueza de espÃcies de FMA mostrou-se estÃvel, sendo que apenas a gravioleira apresentou diferenÃa em relaÃÃo aos outros sistemas no perÃodo chuvoso. Jà no perÃodo seco nÃo houve diferenÃa na riqueza entre os sistemas, sendo detectado um aumento na riqueza de espÃcies, comparado ao perÃodo chuvoso. A abundÃncia relativa indicou uma maior dominÃncia nas comunidades no perÃodo chuvoso, e a freqÃÃncia relativa demonstra a prevalÃncia de espÃcies do gÃnero Glomus em todos os sistemas. A maior diversidade de FMA foi constatada no solo cultivado com coqueiro. Houve um aumento generalizado da diversidade no perÃodo chuvoso comparada com o perÃodo seco. A dominÃncia avaliada pelo Ãndice de Simpsom corrobora os resultados obtidos pela abundÃncia relativa, demonstrando que no perÃodo chuvoso a concentraÃÃo de dominÃncia foi maior em todos os sistemas A anÃlise de similaridade, utilizando o Ãndice de Bray-Curtis, demonstra que o perÃodo seco tornou os sistemas mais similares, uma vez que apresentaram maiores valores nesse perÃodo. A anÃlise de agrupamento baseada no Ãndice de similaridade demonstra que, apesar das variaÃÃes de riqueza de abundÃncia, os sistemas foram agrupados igualmente em ambos os perÃodos. A gravioleira formou um grupo isolado, enquanto a Ãrea de mata mostrou-se mais similar a cultura do cajueiro velho. O outro agrupamento foi formado pelo coqueiral e a plantaÃÃo de cajueiro novo. Os resultados deste estudo permitem concluir: as atividades agrÃcolas alteraram a composiÃÃo da comunidade de FMA em relaÃÃo à mata nativa; o agroecossistema cultivado com coqueiro apresentou a maior biodiversidade de FMA dentre os sistemas avaliados; as espÃcies do gÃnero Glomus foram mais abundantes tanto nos agroecossistemas como no ecossistema natural; houve diferenÃa na composiÃÃo e na diversidade da comunidade de fungos entre o perÃodo chuvoso e seco; e a diversidade de esporos de FMA no solo, nÃo se relacionou com a capacidade infectiva nas fruteirasArbuscular Mycorrhizal Fungi - AMF are key organisms in natural ecosystems and agroecosystems, as being responsible for a symbiosis that occurs in more than 80% of terrestrial vascular plants. Work in mutualism with plants, helping them with less mobile nutrient uptake, increase the absorption of water, protect them against diseases and are strongly influenced by agricultural practices and environmental changes. This study evaluated the influence of chemical parameters of soil, climate variation in two seasons and four different agroecosystems of tropical fruit trees (cashew- Anacardium occidentale, coconut - Cocos nucifera and soursop - Annona muricata), with the diversity of AMF compared with an area of native forest adjacent to plantations, considering the hypothesis that these factors change the community composition of these fungi. Samples were collected at depth of 0-20 cm in the rainy (April/2009) and dry season (October/2009) and used ecological indexes as a way of evaluating changes in the systems and periods. In total were identified 35 different morphotypes of spores and chemical parameters of the soil indicated that pH was negatively correlated with the average density of spores, Mg with the species richness and Zn with both. The average density of spores was negatively influenced by agroecosystems, because the highest values were found in the forested area in both periods, and except for the coconut (Cocos nucifera L.) crop, all the others had a significant increase in between the periods. Species richness was found to be stable, with only the soursop culture (Annona Muricata) different compared to other systems in the rainy season. During the dry season no differences being detected in richness. The relative abundance indicates greater dominance in the communities during the rainy season and relative frequency shows the prevalence of species of the genus Glomus on all systems. The highest diversity, as measured by the Shannon- Wiener index, indicated that the soil under coconut had the highest values in both periods. There was a general increase in diversity comparing the rainy with the dry season. The dominance assessed by the Simpson index corroborates the results obtained by relative abundance, demonstrating that in the rainy season the concentration of dominance was higher in all systems. The similarity analysis using the Bray-Curtis index shows that the dry season has made the systems more similar, since they showed higher values in this period. Cluster analysis based on similarity index shows that despite the richness of abundance variations, the systems were also grouped in both periods. The soursop formed an isolated group, the area of forest was more similar to the old cashew culture. The other cluster was formed by the coconut culture and the new cashew plantation. Results of the study allowed concluding: agricultural activities have changed the community composition of AMF in relation to the native forest; the coconut agroecosystem had the highest biodiversity of AMF among all the systems evaluated; the species of the genus Glomus were the most abundant in agroecosystems and natural ecosystem; there were differences in community composition and diversity of fungi in between the rainy and dry season; and the diversity of AMF spores in soil did not correlate with the tropical fruit treeâs infective capacity

Revealing Tropical Technosols as an Alternative for Mine Reclamation and Waste Management

This study was based on the premise that Technosols constructed under tropical conditions are a valuable tool for inexpensive mine reclamation programs. These anthropogenic soils are still poorly studied in Brazil and are not recognized by the Brazilian Soil Classification System. Given the importance of mining to the Brazilian economy (the sector accounts for 20% of all products exported and 5% of the gross domestic product), there is an urgency to properly manage the large amount of waste produced. For this purpose, we suggest the use of Technosols as a strategy to overcome both land degradation and waste production by presenting a successful case of mine rehabilitation combining limestone wastes and tropical grasses. We show that Technosols constructed from the mine spoils can develop into soils suitable for agriculture in a few years, promoting land reclamation and producing food and energy. These soils are also valuable resources that can provide important ecosystem services, such as organic carbon storage

Cu Dynamics in the Rhizosphere of Native Tropical Species: Assessing the Potential for Phytostabilization in Mining-Impacted Soils

The use of native plants for reforestation and/or remediation in areas contaminated by mining is a technique with low implantation and maintenance costs. The success of this practice depends on the plant species and geochemical processes at the soil–plant interface (e.g., rhizosphere). This study evaluated the potential of spontaneous species for mobilizing and altering mineral and metal dynamics in the rhizosphere of Cu-rich soils resulting from the abandoned Pedra Verde mine in NE Brazil. Rhizosphere and bulk soil samples were collected from five shrubby/arboreal species. The pH, organic matter content, Cu fractionation, mineralogical characterization, and Cu content in the leaves and roots of all studied species were determined. In addition, the bioaccumulation factor (BCF) and translocation factor (TF) were used to evaluate the potential of these species for Cu hyperaccumulation. The Cu concentration in leaf plant tissues varied from 18 to 34 mg kg−1, and all plants presented TF and BCF −1). Combretum aff. pisoniodes Taub was the species with the greatest potential for decreasing Cu bioavailability and phytostabilization. Our findings indicate the potential of native Brazilian plants for growth in Cu-contaminated soil. These findings may be used for reforestation programs

Constructing soils for climate-smart mining

Abstract Surface mining is inherently linked to climate change, but more precise monitoring of carbon dioxide (CO2) emissions is necessary. Here we combined the geolocation of mine sites and carbon stock datasets to show that if all legal active mining sites in Brazil are exploited over the next decades, 2.55 Gt of CO2 equivalent (CO2eq) will be emitted due to the loss of vegetation (0.87 Gt CO2eq) and soil (1.68 Gt CO2eq). To offset these emissions, we propose constructing soils (Technosols) from mine and other wastes for mine reclamation. We show that this strategy could potentially offset up to 60% (1.00 Gt CO2eq) of soil-related CO2 emissions. When constructed with suitable parent materials, Technosols can also restore important soil-related ecosystem services while improving waste management. The construction of healthy Technosols stands out as a promising nature-based solution towards carbon-neutral mining and should, therefore, be considered in future environmental policies of major mining countries