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.
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.
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•Groundwater connection enhances soil fertility in vegetation patches.•Soil respiration responded to precipitation pulses more intensively under the patches.•Phreatophytes foster fertile islands, enhancing mineralization rates and soil quality.•Fertile islands are key for preserving the functional diversity of dryland ecosystems.
The inexorable evolution of solid-phase single chirality is demonstrated for the first time for a proteinogenic amino acid. Enantioenrichment is observed both under attrition-enhanced conditions and ...without the aid of particle grinding. Differences in the form of the conversion profiles for the process under the two sets of conditions provide suggestions concerning the mechanism of the transformation.
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.
Abstract
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 sequestration of Plasmodium falciparum infected erythrocytes in the placenta, and the resulting inflammatory response affects maternal and child health. Despite existing information, little is ...known about the direct impact of P. falciparum on the placental barrier formed by trophoblast and villous stroma. This study aimed to assess placental tissue damage caused by P. falciparum in human placental explants (HPEs).
HPEs from chorionic villi obtained of human term placentas (n = 9) from normal pregnancies were exposed to P. falciparum-infected erythrocytes (IE) for 24 h. HPEs were embedded in paraffin blocks and used to study tissue damage through histopathological and histochemical analysis and apoptosis using TUNEL staining. Culture supernatants were collected to measure cytokine and angiogenic factors and to determine LDH activity as a marker of cytotoxicity. A subset of archived human term placenta paraffin-embedded blocks from pregnant women with malaria were used to confirm ex vivo findings.
Plasmodium falciparum-IE significantly damages the trophoblast layer and the villous stroma of the chorionic villi. The increased LDH activity and pathological findings such as syncytial knots, fibrin deposits, infarction, trophoblast detachment, and collagen disorganization supported these findings. The specific damage to the trophoblast and the thickening of the subjacent basal lamina were more pronounced in the ex vivo infection. In contrast, apoptosis was higher in the in vivo infection. This disparity could be attributed to the duration of exposure to the infection, which significantly varied between individuals naturally exposed over time and the 24-h exposure in the ex vivo HPE model.
Exposure to P. falciparum-IE induces a detachment of the syncytiotrophoblast, disorganization of the stroma villi, and an increase in apoptosis, alterations that may be associated with adverse results such as intrauterine growth restriction and low birth weight.
Clonal species Agave fourcroydes and A. sisalana from ancient crops have become invasive in Mediterranean drylands, posing a severe threat to ecologically valuable native plant communities. However, ...we barely know the relative contribution of clonal mechanisms underlying their invasive behaviour. Therefore, environmental managers must face this problem without scientific evidence on the most effective methods to eradicate or control these invasions. In this study, we monitored populations of A. fourcroydes and A. sisalana and carried out field and experimental plantings (in situ and under controlled environmental conditions) to assess the efficacy of three clonal mechanisms: shoots from rhizomes, shoots from rosettes, and aerial bulbils from floral scapes). Both species showed very similar performance in their clonal expansion. Shoot production from rhizomes was the primary mechanism for densifying Agave populations, emerging to the soil 1.5 ± 2.1 shoots per individual. Moreover, we did not observe mortality of new shoots from rhizomes. These new clonal individuals seemed to ensure their survival by connecting to the mother plant (clonal integration). In addition, contractile roots, only recorded in shoots from rhizomes, could represent an advantage allowing them to react to harsh environmental conditions. Regarding shoots from rosettes, individuals produced 0.63 ± 1.01 shoots on average, with no mortality recorded, but without guaranteeing the replacement of mother plants. Finally, bulbil production and their rooting under controlled and favourable conditions were very high, although their establishment success under arid conditions proved irrelevant. These results suggest that management actions should focus on the removal of shoots from rhizomes. This approach could be an efficient, feasible, and cost-effective medium- to long-term habitat management strategy to control these Agave invasions, with widespread application worldwide in similar invasion processes.
Here we present a pluridisciplinary study of Cuesta de la Bajada site (Teruel, Spain). Our findings show that the site contains an early Middle Paleolithic assemblage similar to other European early ...Middle Paleolithic industries, allowing us to evaluate the coexistence of this industrial tradition with the Acheulean technocomplex in southwest Europe.
The process of lithic production at Cuesta de la Bajada represents a technology focused on debitage, the application of technical concepts such as ramified production sequences, and the recycling of flakes via the resharpening of tools and exhausted cores. This site was formed around a pond not far from a river and contains remains of large macrofauna other than equids and cervids. Taphonomic analysis highlights the abundance of cut marks on bones, and supports the hypothesis of selective hunting by hominids. The numerical ages derived from the combination of ESR, OSL and AAR dating methods indicate that the archaeological site was very likely formed around the MIS 8-MIS 9. The appearance of Middle Paleolithic industries in Europe could represents the autochthonous development of a technocomplex distinctly different from the Acheulean, characterised by chaînes opératoires of debitage and a progressive increase of Levallois technology and retouched tools.
These results suggest that there is a clear coexistence of assemblages with Acheulean and Middle Paleolithic industries during the last third of the Middle Pleistocene at least in the Iberian Peninsula.
•We challenge the evolutionary relationship between the Acheulean and Middle Paleolithic technocomplexes.•We propose an alternative hypothesis based on the autonomy and coexistence of both technocomplexes.•The origin of the Middle Palaeolithic likely lies in the European Lower Pleistocene core and flake industries.
The variation of plant functional traits, from the cell to the whole‐plant level, is a central question in trait‐based ecology with regard to understanding ecological strategies and adaptations that ...result from environmental drivers. Here, we analyzed whole‐plant and leaf traits of the phreatophyte Ziziphus lotus (L.) Lam., a long‐lived shrub that dominates one of the few terrestrial groundwater‐dependent ecosystems (GDEs) in Mediterranean Basin drylands. We (a) assessed architectural traits and growth patterns, (b) analyzed leaf morpho‐functional traits (specific leaf area SLA and stomata pore index SPI) and physiological traits (gas exchange rates), as well as their variations within individuals, and (c) evaluated temporal variations in modular growth (i.e., sequential iteration of structural units) between growing seasons and in leaf traits within seasons. Z. lotus' growth pattern was based on the repetition of modules composed of shoots (short and long) and branches (flowering and plagiotropic) that promoted a functional differentiation between vegetative and reproductive structures, respectively. We identified morpho‐functionally distinct leaves (i.e., heterophylly) borne on different types of branches. Leaves on flowering branches had higher SLA and water use efficiency (WUEi), but lower SPI and transpiration rates than leaves on vegetative ones. We also observed trade‐offs in the elongation of vegetative and flowering structures between growing seasons: the shorter the long shoots, the larger the flowering branches. The modular differentiation and heterophylly of Z. lotus might contribute to prioritizing the investment of resources of this phreatophyte, either for growth or reproduction, and could improve the efficiency in uptake and conservation of resources in drylands.
Through a trait‐based approach, we identified the modular growth pattern and morpho‐functionally distinct leaves (i.e., heterophylly) in the phreatophytic shrub Ziziphus lotus (Rhamnaceae), which promoted a functional differentiation between vegetative and reproductive structures. Both characteristics might contribute to prioritizing the investment of resources of this species, either for growth or reproduction, and could improve the efficiency in uptake and conservation of resources in drylands.
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