Análisis de los patrones de distribución espacial de las poblaciones de agaves invasoras en la llanura costera eólica del parque natural de Cabo de Gata-Níjar

A finales de los años 50, dos especies de Agave, el sisal (A. sisalana) y el henequén (A. fourcroydes) fueron introducidas en el ecosistema de la llanura costera eólica del Parque Natural de Cabo de Gata-Níjar para su uso textil. El patrón uniforme inicial del cultivo ha derivado en un visible patrón agregado a través de un proceso de invasión biológica, que ha mostrado especial intensidad sobre los sustratos arenosos próximos al litoral. Creemos que este patrón puede estar regido por el crecimiento clonal de las especies y la interacción entre ellas y con respecto a Ziziphus lotus, una especie que domina un hábitat prioritario propio de este ecosistema. Mediante el análisis estadístico del patrón espacial de agaves analizamos la el proceso de densificación de las poblaciones de estas especies y su relación con las interacciones interespecíficas más relevantes del nuevo ecosistema que se ha formando

Geochemical evolution of pleistocene bears dentine amino acids

A linear correlation was established between aspartic acid racemization ratio from cave bear dentine collagen and absolute dating. The high correlation coefficient obtained allowed age calculation through amino acid racemization. Aspartic acid and glutamic acid racemization kinetics have also been explored in dentine from a North American black bear (Ursus americanus Pallas). Three sample sets were prepared for kinetic heating experiments in nitrogen atmosphere: one water soaked, one with a water-saturated nitrogen atmosphere, and one without any moisture. It was possible to show that the presence of water is a factor controlling amino acid racemization rate. The aspartic acid in a heating experiment at 105° C shows an "apparent kinetics reversal" which can be explained by a progressive hydrolysis of amino acid chains (proteins and polypeptides). Because of t h e low potential of collagen preservation over long periods of time, the apparent kinetics reversal phenomenon will not affect the dating of old material where no traces of collagen remain. An apparent kinetics reversal was not observed in glutamic acid, which racemizates more slowl

The potential of groundwater-dependent ecosystems to enhance soil biological activity and soil fertility in drylands

Water availability controls the functioning of dryland ecosystems, driving a patchy vegetation distribution, unequal nutrient availability, soil respiration in pulses, and limited productivity. Groundwater-dependent ecosystems (GDEs) are acknowledged to be decoupled from precipitation, since their vegetation relies on groundwater sources. Despite their relevance to enhance productivity in drylands, our understanding of how different components of GDEs interconnect (i.e., soil, vegetation, water) remains limited. We studied the GDE dominated by the deep-rooted phreatophyte Ziziphus lotus, a winter-deciduous shrub adapted to arid conditions along the Mediterranean basin. We aimed to disentangle whether the groundwater connection established by Z. lotus will foster soil biological activity and therefore soil fertility in drylands. We assessed (1) soil and vegetation dynamics over seasons (soil CO2 efflux and plant activity), (2) the effect of the patchy distribution on soil quality (properties and nutrient availability), and soil biological activity (microbial biomass and mineralization rates) as essential elements of biogeochemical cycles, and (3) the implications for preserving GDEs and their biogeochemical processes under climate change effects. We found that soil and vegetation dynamics respond to water availability. Whereas soil biological activity promptly responded to precipitation events, vegetation functioning relies on less superficial water and responded on different time scales. Soil quality was higher under the vegetation patches, as was soil biological activity. Our findings highlight the importance of groundwater connections and phreatophytic vegetation to increase litter inputs and organic matter into the soils, which in turn enhances soil quality and decomposition processes in drylands. However, biogeochemical processes are jeopardized in GDEs by climate change effects and land degradation due to the dependence of soil activity on: (1) precipitation for activation, and (2) phreatophytic vegetation for substrate accumulation. Therefore, desertification might modify biogeochemical cycles by disrupting key ecosystem processes such as soil microbial activity, organic matter mineralization, and plant productivity.This research was developed in the framework of the LTSER Platform “The Arid Iberian South East LTSER Platform — Spain (LTER_ EU_ES_027)” and supported by the European project LIFE Adaptamed (LIFE14349610 CCA/ES/000612). MTT and BRL were financially supported by a FPU Predoctoral Fellowship of the Spanish Government (16/02214 and 17/01886). EG was supported by the European Research Council (ERC Grant agreement 647038 [BIODESERT])

A multiple-trait analysis of ecohydrological acclimatisation in a dryland phreatophytic shrub

Water is the main limiting factor for groundwater-dependent ecosystems (GDEs) in drylands. Predicted climate change (precipitation reductions and temperature increases) and anthropogenic activities such as groundwater drawdown jeopardise the functioning of these ecosystems, presenting new challenges for their management. We developed a trait-based analysis to examine the spatiotemporal variability in the ecophysiology of Ziziphus lotus, a long-lived phreatophyte that dominates one of the few terrestrial GDEs of semiarid regions in Europe. We assessed morpho-functional traits and stem water potential along a naturally occurring gradient of depth-to-groundwater (DTGW, 2–25 m) in a coastal aquifer, and throughout the species-growing season. Increasing DTGW and salinity negatively affected photosynthetic and transpiration rates, increasing plant water stress (lower predawn and midday water potential), and positively affected Huber value (sapwood cross-sectional area per leaf area), reducing leaf area and likely, plant hydraulic demand. However, the species showed greater salt-tolerance at shallow depths. Despite groundwater characteristics, higher atmospheric evaporative demand in the study area, which occurred in summer, fostered higher transpiration rates and water stress, and promoted carbon assimilation and water loss more intensively at shallow water tables. This multiple-trait analysis allowed us to identify plant ecophysiological thresholds related to the increase in salinity, but mostly in DTGW (13 m), and in the evaporative demand during the growing season. These findings highlight the existence of tipping points in the functioning of a long-lived phreatophyte in drylands and can contribute to the sustainable management of GDEs in southern Europe, paving the way for further studies on phreatophytic species

Organic matter accumulation during the Holocene in the Guadalquivir marshlands (SW Spain)

The distribution of biomarker compounds and magnetic susceptibility observed in the sediment from a 20 m core drilled in the marshlands of the estuarine region of the Guadalquivir River (southwest coast of Spain) has allowed us to reconstruct the palaeoenvironmental evolution of this area during the Holocene. Several organic compounds (n-alkanes, ra-ketones, n-alkanols, n-alkanoic acids and organic sulphur), as well as different biomarker ratios, have been used to show changing environmental conditions through time. These geochemical proxies suggest good preservation of the organic matter, although some diagenesis has occurred to particular organic compounds, especially the n-alkanoic acids. Our data indicate a major allochthonous supply of terrestrial plants, with less influence from aquatic plants or algae through the core. There are markedly different palaeoenvironmental conditions between the uppermost 5 m (last 6ka cal. B.P.) and the rest of the core. From 5 m (ca 6ka cal. B.P.) to 19 m (ca 8ka cal. B.P.) depth the palaeoenvironmental conditions were almost constant. Based on organic sulphur content and n-alkane content logs, anoxic conditions prevailed from 8 to 6ka cal. B.P., while oxic conditions with enhanced convection of water (prevalence of fluvial input), and consequently a greater organic matter supply, predominated in the upper 5 m of the core. Similarly, little variation in the magnetic susceptibility profile below 5 m indicates stable environmental conditions, while in the upper 5 m conditions shifted to one with elevated water input and clastic sediment supply. This is linked to palaeofloral alterations in the Guadiamar/Guadalquivir drainage basins and/or anthropogenic effects. We propose that from ca 8 to 6 ka cal. B.P. a stable landscape physiognomy in the surroundings of the estuarine area of the Guadalquivir River, with a predominance of pines and grassland. However, over the last 6ka cal. B.P. a variation in the terrestrial plant biomarker compounds suggests an alternation of relatively dry and humid phases and/or the impact of human populations on altering the vegetation community have occurred

Efectos de diferentes tipos de fertilización sobre la alcachofa en reconversión a cultivo ecológico

En dos parcelas experimentales, una situada en el IVIA, en Moncada (Valencia) y otra en la fundación Caja Rural Valencia, en Paiporta (Valencia), hemos realizado sendos ensayos de fertilización. Los seis tratamientos del ensayo de Moncada han sido: testigo, dos de fertilización orgánica (a base de estiércol de ovino, y gallinaza, respectivamente), dos de fertilización organo- mineral y uno de fertilización mineral. Y en el de Paiporta hemos comparado tres tratamientos: fertilización orgánica (a base de estiércol de ovino), fertilización mineral y fertilización órgano-mineral. Las parcelas elementales con fertilización orgánica se han cultivado siguiendo técnicas de Agricultura Ecológica, mientras que en las de fertilización mineral y organo-mineral se han seguido prácticas de cultivo convencional. En la primera campaña de reconversión estudiada hemos constatado que la producción de capítulos de alcachofa resultó más baja con la fertilización orgánica que con la fertilización mineral u organo-mineral. El tipo de fertilización no afectó de forma significativa ni a la materia seca ni al contenido nutritivo de los capítulos. La variación temporal en el nivel de nitratos del suelo fue mayor que la debida al efecto tratamiento. La fertilización orgánica produjo una incidencia del barrenador de la alcachofa (Gortyna xanthenes ) más baja y un grado de parasitismo más alto que la fertilización mineral

Squandering water in drylands: the water-use strategy of the phreatophyte Ziziphus lotus in a groundwater-dependent ecosystem

PREMISE: Water is the most limiting factor in dryland ecosystems, and plants are adapted to cope with this constraint. Particularly vulnerable are phreatophytic plants from groundwater-dependent ecosystems (GDEs) in regions that have to face water regime alterations due to the impacts of climate and land-use changes. METHODS: We investigated two aspects related to the water-use strategy of a keystone species that dominates one of the few terrestrial GDEs in European drylands (Ziziphus lotus): where it obtains water and how it regulates its use. We (1) evaluated plants’ water sources and use patterns using a multiple-isotope approach (δ2H, δ18O, and Δ13C); (2) assessed the regulation of plant water potential by characterizing the species on an isohydric–anisohydric continuum; and (3) evaluated plants’ response to increasing water stress along a depth-to-groundwater (DTGW) gradient by measuring foliar gas exchange and nutrient concentrations. RESULTS: Ziziphus lotus behaves as a facultative or partial phreatophyte with extreme anisohydric stomatal regulation. However, as DTGW increased, Z. lotus (1) reduced the use of groundwater, (2) reduced total water uptake, and (3) limited transpiration water loss while increasing water-use efficiency. We also found a physiological threshold at 14 m depth to groundwater, which could indicate maximum rooting length beyond which optimal plant function could not be sustained. CONCLUSIONS: Species such as Z. lotus survive by squandering water in drylands because of a substantial groundwater uptake. However, the identification of DTGW thresholds indicates that drawdowns in groundwater level would jeopardize the functioning of the GDE

A data-driven methodological routine to identify key indicators for social-ecological system archetype mapping

The spatial mapping of social-ecological system (SES) archetypes constitutes a fundamental tool to operationalize the SES concept in empirical research. Approaches to detect, map, and characterize SES archetypes have evolved over the last decade towards more integrative and comparable perspectives guided by SES conceptual frameworks and reference lists of variables. However, hardly any studies have investigated how to empirically identify the most relevant set of indicators to map the diversity of SESs. In this study, we propose a data-driven methodological routine based on multivariate statistical analysis to identify the most relevant indicators for mapping and characterizing SES archetypes in a particular region. Taking Andalusia (Spain) as a case study, we applied this methodological routine to 86 indicators representing multiple variables and dimensions of the SES. Additionally, we assessed how the empirical relevance of these indicators contributes to previous expert and empirical knowledge on key variables for characterizing SESs. We identified 29 key indicators that allowed us to map 15 SES archetypes encompassing natural, mosaic, agricultural, and urban systems, which uncovered contrasting land sharing and land sparing patterns throughout the territory. We found synergies but also disagreements between empirical and expert knowledge on the relevance of variables: agreement on their widespread relevance (32.7% of the variables, e.g. crop and livestock production, net primary productivity, population density); relevance conditioned by the context or the scale (16.3%, e.g. land protection, educational level); lack of agreement (20.4%, e.g. economic level, land tenure); need of further assessments due to the lack of expert or empirical knowledge (30.6%). Overall, our data-driven approach can contribute to more objective selection of relevant indicators for SES mapping, which may help to produce comparable and generalizable empirical knowledge on key variables for characterizing SESs, as well as to derive more representative descriptions and causal factor configurations in SES archetype analysis

The potential of groundwater-dependent ecosystems to enhance soil biological activity and soil fertility in drylands

Water availability controls the functioning of dryland ecosystems, driving a patchy vegetation distribution, unequal nutrient availability, soil respiration in pulses, and limited productivity. Groundwater-dependent ecosystems (GDEs) are acknowledged to be decoupled from precipitation, since their vegetation relies on groundwater sources. Despite their relevance to enhance productivity in drylands, our understanding of howdifferent components of GDEs interconnect (i.e., soil, vegetation, water) remains limited. We studied the GDE dominated by the deep-rooted phreatophyte Ziziphus lotus, a winter-deciduous shrub adapted to arid conditions along the Mediterranean basin.We aimed to disentangle whether the groundwater connection established by Z. lotus will foster soil biological activity and therefore soil fertility in drylands. We assessed (1) soil and vegetation dynamics over seasons (soil CO2 efflux and plant activity), (2) the effect of the patchy distribution on soil quality (properties and nutrient availability), and soil biological activity (microbial biomass and mineralization rates) as essential elements of biogeochemical cycles, and (3) the implications for preserving GDEs and their biogeochemical processes under climate change effects. We found that soil and vegetation dynamics respond to water availability. Whereas soil biological activity promptly responded to precipitation events, vegetation functioning relies on less superficial water and responded on different time scales. Soil quality was higher under the vegetation patches, as was soil biological activity. Our findings highlight the importance of groundwater connections and phreatophytic vegetation to increase litter inputs and organic matter into the soils, which in turn enhances soil quality and decomposition processes in drylands. However, biogeochemical processes are jeopardized in GDEs by climate change effects and land degradation due to the dependence of soil activity on:(1) precipitation for activation, and (2) phreatophytic vegetation for substrate accumulation. Therefore, desertification might modify biogeochemical cycles by disrupting key ecosystem processes such as soil microbial activity, organic matter mineralization, and plant productivity

Identification of arid phases during the last 50 kyr Cal BP from the Fuentillejo maar lacustrine record (Campo de Calatrava Volcanic Field, Spain).

Geochemical (element analysis, molecular analysis of organic compounds), physical, palynological, mineralogical and sedimentary facies analysis were performed to characterise the sedimentary record in Fuentillejo maar-lake in the Central Spanish Volcanic Field of Campo de Calatrava, in order to reconstruct the palaeoenvironmental and palaeoclimatic processes which controlled vegetation patterns and deposition of different sedimentary facies. The upper 20 m of core FUENT-1 show variations in clastic input, water chemistry, vegetation and organic fraction sources in the lake throughout the Late Pleistocene and Holocene. The temporal framework provided by14C accelerator mass spectrometry dating allows assigning the sequence to the last 50 cal. ka BP. Arid phases identified in the FUENT-1 sequence are correlated to Heinrich events (HE) and to stadials of the Dansgaard/Oeschger (D/O) cycles. Siliciclastic facies with high magnetic susceptibility values, high Juniperus pollen content, a low Paq index (aquatic macrophysics proxy index), a decrease in the relative percentage of the n-C27 and an increase in the n-C31 alkanes are indicative of arid and colder climatic events related to HE 2, HE 1 and the Younger Dryas (YD). Similar short cold and arid phases during the Holocene were identified at 9.2–8.6, 7.5–7 and 5.5–5 cal. ka BP. In dolomite–mud facies, the pollen data show an increase in the herbs component, mainly – Chenopodiaceae, Artemisia andEphedra – steppe taxa; a low Paq index, a decrease in the relative percentage of the n-C27 alkane and an increase in the n-C31 alkane are also observed. This facies was probably the result of lower lake levels and more saline–alkaline conditions, which can be interpreted as linked to arid–warm periods. These warm and arid phases were more frequent during Marine Isotope Stage (MIS) 3 and the interstadials of MIS 2. HE 4, HE 2, HE 1 and the YD in core FUENT-1 were immediately followed by increases of warm steppe pollen assemblages that document rapid warming similar to the D/O cycles but do not imply increasing humidity in the area. Fuentillejo hydrology is controlled by changes in the atmospheric and oceanic systems that operated on the North Atlantic region at millennial scale during the last 50 cal. ka B