Browsing by Subject "Microbial biomass"

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    Combined effects of reduced irrigation and water quality on the soil microbial community of a citrus orchard under semi-arid conditions
    (Elsevier, 2016-11) Bastida, F.; Torres, I.F.; Romero Trigueros, Cristina; Baldrian, P.; Vetrovský, T.; Bayona, J.M.; Alarcón, J.J.; Hernández, T.; García, C.; Nicolás, E.; Ingeniería Química
    Sustainable agriculture in Mediterranean areas is compromised by the structural deficit of water resources. Under this situation, the impacts of alternative water managements on the microbial community, as a critical component of the soil quality, need to be properly understood. We evaluated the longterm impacts of irrigation systems differing on the quantity and quality of water, and their interactions, on the biomass (phospholipid fatty acid analysis), diversity and composition (16S rRNA gene profiling), and enzyme activities of the soil microbial community of an orchard cultivated with grapefruit trees in South-East Spain. The impact of water quantity was evaluated by irrigation with optimal amount of water or by irrigation with a reduced volume of water in the temporal frame when the crop is less sensitive, so-called regulated deficit irrigation (RDI). The impact of water quality was evaluated attending to the source of the irrigation water: water from a river channel-transfer (TW) or reclaimed water from a wastewater treatment plant (RW). Electrical conductivity was higher in soils irrigated with RW than in soils irrigated with TW. The content of total organic C in the soil was affected by water quality but not by water quantity. Soils irrigated with TW showed higher total organic C than soils irrigated with RW. As in the case of plant productivity, RDI had a negative impact on plant productivity, soil microbial biomass and enzyme activities in summer. This finding indicates a slow-down of organic matter decomposition under restricted irrigation. Bacterial biomass was more sensitive to RDI when RW was used, whereas the fungal biomass was more sensitive to RDI when TW was used. Bacterial diversity and plant productivity were more sensitive to water quantity than to water quality. The increase of the abundance of Proteobacteria and Bacteroidetes in soils irrigated with RW in summer suggested a higher resilience of this treatment mediated by copiotrophic organisms. A recovery of the enzyme activity and microbial biomass of soils irrigated with RW and RDI was observed in January and June. The resilience of biogeochemical and the microbial biomass processes after RDI coursed through changes in the structure of the microbial community as revealed by the multivariate analyses of fatty acids. The utilisation of reclaimed water during RDI promoted a more-resilient community that translated into a recovery of microbial biomass and enzyme activities after the water restriction ended. These results imply potential ecological benefits of the irrigation with reclaimed water that should be considered under the water limitation predicted in climate change models in Mediterranean areas.
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    Complementary effects of encroachment and grazing intensity for soil quality in a mountain grassland
    (Science Direct, 2025-03) Mark, Evan; Barbosa, Jomar; Mataix, Jorje; García-Orenes, Fuensanta; Rincón, Marina; Arcenegui, Victoria; Contreras de Vera, Antonio; Sanchez-Zapata, Jose Antonio; Sanidad Animal; Sanidad Animal
    Grasslands are globally significant ecosystems held in an ecological balance by herbivory, with a natural tendency towards shrub encroachment, creating a tension between two alternative successional trajectories. The influence of grazing pressure on soil properties is not yet accurately predicted across ecosystems, nor its interaction with encroachment, with quite variable effects found. We studied the combined effect of grazing and encroachment on soil ecophysiological processes by collecting soil samples from paired locations with and without shrub presence across a managed high-altitude pastureland of 14,000 ha. By tracking 26 sheep herds with GPS collars over multiple years, we created a spatially explicit map of grazing intensity over the landscape, permitting quantification of grazing impacts on soil properties on a continuous scale. Grazing changed soil nutrient status, increasing total soil nitrogen (TN) by up to 0.77 % over the gradient, and available phosphorus (Pavail) by up to 12 times. Grazing increased soil organic carbon (SOC) content by up to 4.5 % across the gradient, and encroachment increased SOC by 1.2 %. SOC increases under these two conditions likely represent two co-occurring paths soil carbon accumulation since particulate organic carbon (POC) was increased by 44 % under shrubs, while the effect of grazing was unclear. Grazing and encroachment impacts on the soil microbial community diverged, since microbial biomass carbon (Cmic) increased by up to 86 % with grazing intensity with a simultaneous decrease in microbial basal respiration and metabolic quotient (qCO2), however neither were affected by encroachment. Overall, encroachment and grazing were seen to be complementary for soil protection and provision of ecosystem services, though their effects on certain parameters were contrasting. This knowledge may be useful for adaptive management in high nature value agroecological landscapes, and can improve large-scale projections of SOC stocks and other soil properties incorporating varying degrees of grazing intensity and the influence of encroachment