Datació de Posidonia oceanica mitjançant 210Pb

La Posidonia oceanica és una fanerògama marina endèmica del Mediterrani. Es tracta d'una espècie molt important a les zones costeres, i en les últimes dècades la seva producció s'ha vist reduïda. En aquest estudi s'ha volgut demostrar la viabilitat d'utilitzar l'espècie Posidonia oceanica com a arxiu de contaminants al llarg del temps, alhora que s'han desenvolupat eines per a l'estudi de la dinàmica de les poblacions d'aquesta espècie. Les concentracions de 210Pb observades als rizomes de Posidonia oceanica demostren que la datació d'organismes vius d'aquesta espècie mitjançant tècniques de 210Pb no son viables. D'altre banda, s'ha aconseguit crear una cronologia del seu matte, la qual ens ha permès distingir entre diferents ritmes de sedimentació de la zona. Estudis paral·lels de la quantitat de carboni orgànic i inorgànic del matte han reafirmat els resultats obtinguts de la datació, permetent, al mateix temps, identificar una possible causa de la variació en el ritme de sedimentació de la zona estudiada.La Posidonia oceanica es una fanerógama marina endémica del Mediterraneo. Se trata de una especie muy importante en las zonas costeras, y en las últimas décadas su producción se ha visto reducida. En este estudio se ha querido demostrar la viabilidad de utilizar la especie Posidonia oceánica como archivo de contaminantes a lo largo del tiempo, al mismo tiempo que se han desarrollado herramientas para el estudio de la dinámica de poblaciones de esta especie. Las concentraciones de 210Pb observadas en los rizomas de Posidonia oceánica demuestran que la datación de organismos vivos de esta especie mediante técnicas de 210Pb es inviable. Por otro lado, se ha conseguido crear una cronología de su matte, la cual nos ha permitido distinguir entre diferentes ritmos de sedimentación en la zona a lo largo del tiempo. Estudios paralelos de la cantidad de carbono orgánico e inorgánico del matte han reafirmado los resultados obtenidos mediante la datación, permitiendo al mismo tiempo identificar una posible causa de la variación en el ritmo de sedimentación de la zona estudiada.Posidonia oceanica is an endemic Mediterranean seagrass. It is a very important species in coastal areas, and in recent decades its production has been reduced. This study has sought to demonstrate the feasibility of using the species Posidonia oceanica as an archive of pollutants over time, as well as tools have been developed to study the population dynamics. 210Pb concentrations observed in rhizomes of Posidonia oceanica show that dating living organisms of this species by 210Pb techniques is not viable. On the other hand, we have managed to create a timeline of its matte, which allowed us to distinguish between different rates of sedimentation in the area. Parallel determinations of organic and inorganic carbon in the matte has reaffirmed the results of the dating, allowing at the same time, to identify a possible cause of the variation in the rate of sedimentation in the studied area

Intensive grassland management disrupts below-ground multi-trophic resource transfer in response to drought

Modification of soil food webs by land management may alter the response of ecosystem processes to climate extremes, but empirical support is limited and the mechanisms involved remain unclear. Here we quantify how grassland management modifies the transfer of recent photosynthates and soil nitrogen through plants and soil food webs during a post-drought period in a controlled field experiment, using in situ 13C and 15N pulse-labelling in intensively and extensively managed fields. We show that intensive management decrease plant carbon (C) capture and its transfer through components of food webs and soil respiration compared to extensive management. We observe a legacy effect of drought on C transfer pathways mainly in intensively managed grasslands, by increasing plant C assimilation and 13C released as soil CO2 efflux but decreasing its transfer to roots, bacteria and Collembola. Our work provides insight into the interactive effects of grassland management and drought on C transfer pathways, and highlights that capture and rapid transfer of photosynthates through multi-trophic networks are key for maintaining grassland resistance to drought

Land management shapes drought responses of dominant soil microbial taxa across grasslands

Soil microbial communities are dominated by a relatively small number of taxa that may play outsized roles in ecosystem functioning, yet little is known about their capacities to resist and recover from climate extremes such as drought, or how environmental context mediates those responses. Here, we imposed an in situ experimental drought across 30 diverse UK grassland sites with contrasting management intensities and found that: (1) the majority of dominant bacterial (85%) and fungal (89%) taxa exhibit resistant or opportunistic drought strategies, possibly contributing to their ubiquity and dominance across sites; and (2) intensive grassland management decreases the proportion of drought-sensitive and non-resilient dominant bacteria-likely via alleviation of nutrient limitation and pH-related stress under fertilisation and liming-but has the opposite impact on dominant fungi. Our results suggest a potential mechanism by which intensive management promotes bacteria over fungi under drought with implications for soil functioning

Drought decreases incorporation of recent plant photosynthate into soil food webs regardless of their trophic complexity

Theory suggests that more complex food webs promote stability and can buffer the effects of perturbations, such as drought, on soil organisms and ecosystem functions. Here, we tested experimentally how soil food web trophic complexity modulates the response to drought of soil functions related to carbon cycling and the capture and transfer below‐ground of recent photosynthate by plants. We constructed experimental systems comprising soil communities with one, two or three trophic levels (microorganisms, detritivores and predators) and subjected them to drought. We investigated how food web trophic complexity in interaction with drought influenced litter decomposition, soil CO2 efflux, mycorrhizal colonization, fungal production, microbial communities and soil fauna biomass. Plants were pulse‐labelled after the drought with 13C‐CO2 to quantify the capture of recent photosynthate and its transfer below‐ground. Overall, our results show that drought and soil food web trophic complexity do not interact to affect soil functions and microbial community composition, but act independently, with an overall stronger effect of drought. After drought, the net uptake of 13C by plants was reduced and its retention in plant biomass was greater, leading to a strong decrease in carbon transfer below‐ground. Although food web trophic complexity influenced the biomass of Collembola and fungal hyphal length, 13C enrichment and the net transfer of carbon from plant shoots to microbes and soil CO2 efflux were not affected significantly by varying the number of trophic groups. Our results indicate that drought has a strong effect on above‐ground–below‐ground linkages by reducing the flow of recent photosynthate. Our results emphasize the sensitivity of the critical pathway of recent photosynthate transfer from plants to soil organisms to a drought perturbation, and show that these effects may not be mitigated by the trophic complexity of soil communities, at least at the level manipulated in this experiment.info:eu-repo/semantics/publishedVersio

Datació de Posidonia oceanica mitjançant 210Pb

La Posidonia oceanica és una fanerògama marina endèmica del Mediterrani. Es tracta d’una espècie molt important a les zones costeres, i en les últimes dècades la seva producció s’ha vist reduïda. En aquest estudi s’ha volgut demostrar la viabilitat d’utilitzar l’espècie Posidonia oceanica com a arxiu de contaminants al llarg del temps, alhora que s’han desenvolupat eines per a l’estudi de la dinàmica de les poblacions d’aquesta espècie. Les concentracions de 210Pb observades als rizomes de Posidonia oceanica demostren que la datació d’organismes vius d’aquesta espècie mitjançant tècniques de 210Pb no son viables. D’altre banda, s’ha aconseguit crear una cronologia del seu matte, la qual ens ha permès distingir entre diferents ritmes de sedimentació de la zona. Estudis paral·lels de la quantitat de carboni orgànic i inorgànic del matte han reafirmat els resultats obtinguts de la datació, permetent, al mateix temps, identificar una possible causa de la variació en el ritme de sedimentació de la zona estudiada.La Posidonia oceanica es una fanerógama marina endémica del Mediterraneo. Se trata de una especie muy importante en las zonas costeras, y en las últimas décadas su producción se ha visto reducida. En este estudio se ha querido demostrar la viabilidad de utilizar la especie Posidonia oceánica como archivo de contaminantes a lo largo del tiempo, al mismo tiempo que se han desarrollado herramientas para el estudio de la dinámica de poblaciones de esta especie. Las concentraciones de 210Pb observadas en los rizomas de Posidonia oceánica demuestran que la datación de organismos vivos de esta especie mediante técnicas de 210Pb es inviable. Por otro lado, se ha conseguido crear una cronología de su matte, la cual nos ha permitido distinguir entre diferentes ritmos de sedimentación en la zona a lo largo del tiempo. Estudios paralelos de la cantidad de carbono orgánico e inorgánico del matte han reafirmado los resultados obtenidos mediante la datación, permitiendo al mismo tiempo identificar una posible causa de la variación en el ritmo de sedimentación de la zona estudiada.Posidonia oceanica is an endemic Mediterranean seagrass. It is a very important species in coastal areas, and in recent decades its production has been reduced. This study has sought to demonstrate the feasibility of using the species Posidonia oceanica as an archive of pollutants over time, as well as tools have been developed to study the population dynamics. 210Pb concentrations observed in rhizomes of Posidonia oceanica show that dating living organisms of this species by 210Pb techniques is not viable. On the other hand, we have managed to create a timeline of its matte, which allowed us to distinguish between different rates of sedimentation in the area. Parallel determinations of organic and inorganic carbon in the matte has reaffirmed the results of the dating, allowing at the same time, to identify a possible cause of the variation in the rate of sedimentation in the studied area