Temperature stress in arbuscular mycorrhizal fungi: a test for adaptation to soil temperature in three isolates of Funneliformis mosseae from different climates

Climate change may impose stimulations or constraints on the mycorrhizal symbiosis by increasing and fluctuating temperatures. We conducted a study to compare the soil temperature response curves (6, 12, 18, and 24 oC) of three isolates of Funneliformis mosseae from different regions and climates (Finland, Denmark, Spain), to test if the isolates from cold environments were able to grow better at lower temperatures and the isolates from warmer environments grew better at higher temperatures. The results provided clear evidence suggesting no adaptation to soil temperature in these AMF isolates. All isolates showed reduced development and very little external mycelium growth at 6 and 12 oC, and similar increased development with increasing soil temperature.  These results suggest that AMF have a narrow window to develop in cold regions where temperatures below 15 oC prevail

Innovaciones ecotecnológicas para necesidades socioambientales

La ecotecnología la podemos encontrar tanto en dispositivos como en métodos y procesos que promueven el aprovechamiento sustentable de recursos naturales, al tiempo que propician beneficios sociales y económicos en contextos específicos. Con esta premisa se creó el Laboratorio Nacional de Innovación Ecotecnológica para la Sustentabilidad

Mycorrhizal Inoculation and Chemical Fertilizer Interactions in Pineapple under Field Conditions

Excessive inorganic fertilizers applied to pineapple crops in Mexico cause the progressive degradation and pollution of soils in the short- and long-term, and they also increase production costs. An alternative to reduce excessive fertilization is its partial substitution by nutrition and growth enhancing arbuscular mycorrhizal fungi (AMF). The goal of this research was to compare the effect of AMF inoculation combined with different fertilizer doses and full chemical fertilization on pineapple yield variables in a commercial plantation. We used a randomized block design with six treatments: a non-inoculated control with 100% chemical fertilization, and five treatments with AMF inoculation and fertilization doses of 0%, 25%, 50%, 75%, and 100% chemical fertilization. There were four replicates of each treatment containing 30 plants in each experimental unit (plot). We measured the dry weight of the D-leaf 9 months after planting, and the root mycorrhizal colonization percentage, yield, and fruit quality after 18 months. Mycorrhizal inoculation equated to 100% chemical fertilization already when combined with 25% fertilization and surpassed it when combined with 50% fertilization in most of the yield variables measured. The fruit mass and organoleptic variables were significantly higher in mycorrhizal plants with 50% fertilization than in the non-inoculated control and the treatments inoculated with AMF and combined with 0%, 25%, 75%, and 100% of a dose of chemical fertilizer. Inoculation with mycorrhizal fungi in the field could reduce chemical fertilizer application by 50%, with no yield loss and with improved fruit quality

Exploring Linkages between Supporting, Regulating, and Provisioning Ecosystem Services in Rangelands in a Tropical Agro-Forest Frontier

Rangeland management in former tropical rainforest areas may affect ecosystem services. We hypothesized that management practices like burning and overgrazing reduce supporting (soil quality) and consequently also provisioning (forage productivity and quality) and regulating (nutrient cycling) ecosystem services. We established 31 exclosures in two landscape categories (alluvial soils, low-hills), documented management practices, and assessed 18 soil quality indicators, litter decomposition as a proxy for nutrient cycling, and forage quantity and quality during one year in grasslands of the Lacandon region, southeast Mexico. Path analysis was used to explore direct and indirect effects of livestock management practices on soil-based ecosystem services. Landscape position had direct effects on management practices, and direct and indirect effects on soil properties. Altitude (a proxy for the soil catena, ranging from alluvial soils along the Lacantún river to Cambisols and Acrisols in the low-hills) was the variable showing most significant negative relations with soil quality and forage production. Decomposition rate was site-specific and had no relation with landscape position and management. Our study suggests that position on the landscape, which relates to nutrient and water availability, had stronger effects than management practices on forage productivity and quality and drives farmers management practices. View Full-Tex

(13)C Incorporation into Signature Fatty Acids as an Assay for Carbon Allocation in Arbuscular Mycorrhiza

The ubiquitous arbuscular mycorrhizal fungi consume significant amounts of plant assimilated C, but this C flow has been difficult to quantify. The neutral lipid fatty acid 16:1ω5 is a quantitative signature for most arbuscular mycorrhizal fungi in roots and soil. We measured carbon transfer from four plant species to the arbuscular mycorrhizal fungus Glomus intraradices by estimating (13)C enrichment of 16:1ω5 and compared it with (13)C enrichment of total root and mycelial C. Carbon allocation to mycelia was detected within 1 day in monoxenic arbuscular mycorrhizal root cultures labeled with [(13)C]glucose. The (13)C enrichment of neutral lipid fatty acid 16:1ω5 extracted from roots increased from 0.14% 1 day after labeling to 2.2% 7 days after labeling. The colonized roots usually were more enriched for (13)C in the arbuscular mycorrhizal fungal neutral lipid fatty acid 16:1ω5 than for the root specific neutral lipid fatty acid 18:2ω6,9. We labeled plant assimilates by using (13)CO(2) in whole-plant experiments. The extraradical mycelium often was more enriched for (13)C than was the intraradical mycelium, suggesting rapid translocation of carbon to and more active growth by the extraradical mycelium. Since there was a good correlation between (13)C enrichment in neutral lipid fatty acid 16:1ω5 and total (13)C in extraradical mycelia in different systems (r(2) = 0.94), we propose that the total amount of labeled C in intraradical and extraradical mycelium can be calculated from the (13)C enrichment of 16:1ω5. The method described enables evaluation of C flow from plants to arbuscular mycorrhizal fungi to be made without extraction, purification and identification of fungal mycelia

Exploring Linkages between Supporting, Regulating, and Provisioning Ecosystem Services in Rangelands in a Tropical Agro-Forest Frontier

Rangeland management in former tropical rainforest areas may affect ecosystem services. We hypothesized that management practices like burning and overgrazing reduce supporting (soil quality) and consequently also provisioning (forage productivity and quality) and regulating (nutrient cycling) ecosystem services. We established 31 exclosures in two landscape categories (alluvial soils, low-hills), documented management practices, and assessed 18 soil quality indicators, litter decomposition as a proxy for nutrient cycling, and forage quantity and quality during one year in grasslands of the Lacandon region, southeast Mexico. Path analysis was used to explore direct and indirect effects of livestock management practices on soil-based ecosystem services. Landscape position had direct effects on management practices, and direct and indirect effects on soil properties. Altitude (a proxy for the soil catena, ranging from alluvial soils along the Lacantún river to Cambisols and Acrisols in the low-hills) was the variable showing most significant negative relations with soil quality and forage production. Decomposition rate was site-specific and had no relation with landscape position and management. Our study suggests that position on the landscape, which relates to nutrient and water availability, had stronger effects than management practices on forage productivity and quality and drives farmers management practices

Explaining long-term inter-individual growth variation in plant populations : persistence of abiotic factors matters

An unanswered question in ecology is whether the environmental factors driving short-term performance also determine the often observed long-term performance differences among individuals. Here, we analyze the extent to which temporal persistence of spatial heterogeneity in environmental factors can contribute to long-term inter-individual variation in stem length growth. For a natural population of a long-lived understorey palm, we first quantified the effect of several environmental factors on stem length growth and survival. We then performed individual-based simulations of growth trajectories, in which we varied, for two environmental factors: (1) the strength of the effect on stem length growth and (2) the temporal persistence. Short-term variation in stem length growth was strongly driven by light availability. Auto-correlation in light availability and soil pH increased simulated variation in stem length growth among 20-year-old palms to levels similar to the observed variation. Analyses in which we varied both the strength of the effect on stem length growth and the temporal persistence of the environmental factors revealed that a large fraction of observed long-term growth differences can be explained, as long as one of these effects is strong. This implies that environmental factors that are relatively unimportant for short-term performance can still drive long-term performance differences when the environmental variation is sufficiently persistent over time.</p

Management practices and diversity of flower visitors and herbaceous plants in conventional and organic avocado orchards in Michoacán, Mexico

Despite alleged advantages of organic over conventional farming, management effects on biodiversity are still little known. We related the diversity of herbs and flower visitors to management indicators in avocado orchards and hypothesized that inputs, practices, and context influence diversity of herbs and flower visitors. Using basic classification units, matrix correlation, and multivariate analysis of variance, we found that low-toxicity insecticides, infrequent herb cutting, and presence of forest areas were related to high biodiversity. Intensification of agricultural management reduced biodiversity both in organic and conventional management type. Our results advocate for an improved, integrative, management classification considering intensification and ecological context, besides input-type criteria.Fil: Villamil, Laura. Universidad Nacional Autónoma de México; México. Corporación Universitaria de Santa Rosa de Cabal; ColombiaFil: Astier, Marta. Universidad Nacional Autónoma de México; MéxicoFil: Merlín, Yair. Universidad Nacional Autónoma de México; México. Unidad San Cristóbal de las Casas; MéxicoFil: Ayala Barajas, Ricardo. Universidad Nacional Autónoma de México; MéxicoFil: Ramírez García, Enrique. Universidad Nacional Autónoma de México; MéxicoFil: Martínez Cruz, Juan. Universidad Nacional Autónoma de México; MéxicoFil: Devoto, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; ArgentinaFil: Gavito, Mayra E.. Universidad Nacional Autónoma de México; Méxic