Biology subjects

Dragos G Zaharescu

Publications and source records attributed to Dragos G Zaharescu.

4 recordsLinked to original sources

bioRxiv2016

Ecosystem Composition Controls the Early Fate of Rare Earth Elements during Incipient Soil Genesis

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=157 SRC=\"FIGDIR/small/061846_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (86K):\norg.highwire.dtl.DTLVardef@12bcc13org.highwire.dtl.DTLVardef@631e0dorg.highwire.dtl.DTLVardef@14a18eborg.highwire.dtl.DTLVardef@1a9f217_HPS_FORMAT_FIGEXP M_FIG C_FIG We used a model rock-biota system to demonstrate that ecosystem composition (microbial and plant) regulates the fate of REE during early biota-rock interactions.\n\nGraphical abstractword cloud with article keywords, Buffalograss, and X-ray diffractogram.\n\nThe rare earth elements (REE) are of increasing importance in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. Despite their great promise, REE fractionation in early plant-microbe-rock systems has largely remained elusive. We tested the hypothesis that REE mass-partitioning during the incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, plant, and arbuscular mycorrhiza.\n\nPore-water element abundances reflected a rapid transition from abiotic to biotic weathering, the latter associated with lower aqueous loss and higher uptake. Abiotic dissolution contributed 38.6{+/-}19% to total denudation. Microbes incremented denudation, particularly in rhyolite, this effect associating with decreased bioavailable solid fractions in this rock. Total mobilization (aqueous+uptake) was ten times greater in planted treatments compared to abiotic control, REE masses in plant generally exceeding those in water. Plants of larger biomass further increased solid fractions, consistent with soil genesis. Mycorrhiza had a generally positive effect on total mobilization. The incipient REE weathering was dominated by inorganic dissolution enhanced by biotic respiration, the patterns of denudation largely dictated by mineralogy. A consistent biotic signature was observed in La:phosphate, mobilization:solid fraction in all rocks, as well as in the general pattern of denudation and uptake.

Ecology↗

bioRxiv2015

Nodes in the alpine connectome. Exploring the linkages between riparian ecosystem and geo-climatic elements across the mountain environment

Alpine regions are under increased attention worldwide do their role in storing freshwater of high quality and their high sensitivity to climate change - comparable only to the poles. Riparian ecosystems in such regions, integrating water and nutrient fluxes from aquatic and terrestrial environments, host a disproportionally rich biodiversity, despite experiencing severe climate and nutrient restrictions. With climate change rapidly encroaching in the alpine biome, it is important to fully understand how the lake and its surrounding landscape elements sustain such rich ecosystems, before their functional connectivity could be seriously severed.\n\nA total of 189 glacial origin lakes in the Central Pyrenees were surveyed to test how key elements of lake and terrestrial environments work together at different scales to shape the riparian plant composition. Secondly, we evaluated how these ecotope features drive the formation of riparian communities potentially sensitive to environmental change, and assessed their habitat distribution. At each lake plant taxonomic composition was assessed together with elemental composition of water and sediment and ecosystem-relevant geographical factors.\n\nAt macroscale vegetation composition responded to pan-climatic gradients altitude and latitude, which captured, in a narrow geographic area the transition between large European climatic zones. Hydrodynamics was the main catchment-scale factor connecting riparian vegetation with large-scale water fluxes, followed by topography and geomorphology. Lake sediment Mg and Pb, and water Mn and Fe contents reflected local connections with nutrient availability, and water saturation of the substrate.\n\nCommunity analysis identified four keystone plant communities of large niche breadths, present in a wide range of habitats, from (i) damp environments, (ii) snow bed-silicate bedrock, (iii) wet heath, and (iv) limestone bedrock. With environmental change advancing in the alpine biome, this study provides critical information on fundamental linkages between riparian ecosystem and surrounding landscape elements, which could prove invaluable in assessing future biomic impacts.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC=\"FIGDIR/small/035576_ufig1.gif\" ALT=\"Figure 6\">\nView larger version (99K):\norg.highwire.dtl.DTLVardef@2f7ed3org.highwire.dtl.DTLVardef@2f8c49org.highwire.dtl.DTLVardef@1a3493dorg.highwire.dtl.DTLVardef@11d5a2c_HPS_FORMAT_FIGEXP M_FIG Graphical abstractRiparian ecosystem of Lake Cardal (0.3ha, 2224m a.s.l) in the Pyrenees National Park (France), with a network diagram of connected landscape elements. Photo by Antonio Palanca-Soler.\n\nC_FIG

Ecology↗

bioRxiv2015

Small lakes in big landscape: External drivers of littoral ecosystem in high elevation lakes

Graphical abstract:\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC=\"FIGDIR/small/034553_ab1.gif\" ALT=\"Figure 1\">\nView larger version (51K):\norg.highwire.dtl.DTLVardef@17b9e61org.highwire.dtl.DTLVardef@db2861org.highwire.dtl.DTLVardef@38125corg.highwire.dtl.DTLVardef@13d802f_HPS_FORMAT_FIGEXP M_FIG C_FIG In low nutrient alpine lakes, the littoral zone is the most productive part of the ecosystem, and it is a biodiversity hotspot. It is not entirely clear how the scale and physical heterogeneity of surrounding catchment, its ecological composition, and larger landscape gradients work together to sustain littoral communities.\n\nA total of 114 alpine lakes in the central Pyrenees were surveyed to evaluate the functional connectivity between catchment physical and ecological elements and littoral zoobenthos, and ascertain their effect on community formation. At each lake, the zoobenthic composition was assessed together with geolocation (altitude, latitude and longitude), catchment hydrodynamics, geomorphology, topography, riparian vegetation composition, the presence of trout and frogs, water pH and conductivity.\n\nUni- and multidimensional fuzzy set ordination models integrating benthic biota and environmental variables revealed that at geographical scale longitude surpassed altitude in its effect on littoral ecosystem, reflecting a sharp transition between Atlantic and Mediterranean bioregions. Topography (through its control of catchment type, summer snow coverage, and connectivity with other lakes) was the largest catchment-scale driver, followed by hydrodynamics (waterbody size, type and inflow/outflow volumes). Locally, riparian plant composition significantly related to littoral community structure, richness and morphotype diversity. These variables, directly and indirectly create habitats for aquatic and terrestrial stages of invertebrates, and control nutrient and water cycles. Three ecologically diverse associations characterised distinct lake sets. Vertebrate predation, water conductivity and pH (broad measures of total dissolved ions/nutrients and their bioavailability) had no major influence on littoral taxa.\n\nThe work provides exhaustive information from relatively pristine sites, which unveil a strong connection between littoral ecosystem and catchment heterogeneity at scales beyond the local environment. This underpins their role as sensors of local and large-scale environmental changes, and can be used to evaluate further impacts.

Ecology↗

bioRxiv2015

A Multiscale Framework for Deconstructing the Ecosystem Physical Template of High-Altitudes Lakes

An ecosystem is generally sustained by a set of integrated physical elements forming a functional landscape unit - ecotope, which supplies nutrients, microclimate, and exchanges matter and energy with the wider environment. To better predict environmental change effects on ecosystems, particularly in critically sensitive regions such as high altitudes, it is imperative to recognise how their natural landscape heterogeneity works at different scales to shape habitats and sustain biotic communities prior to major changes.\n\nWe conducted a comprehensive survey of catchment physical, geological and ecological properties of 380 high altitude lakes and ponds in the axial Pyrenees at a variety of scales, in order to formulate and test an integrated model encompassing major flows and interactions that drive lake ecosystems.\n\nThree composite drivers encompassed most of the variability in lake catchment characteristics. In order of total percentage of variance explained they were: (i) hydrology/hydrodynamics-responsible for type and discharge of inlets/outlets, and for water body size; (ii) bedrock geomorphology, summarizing geology, slope and fractal order-all dictating vegetation cover of catchment slope and lake shore, and the presence of aquatic vegetation; and, (iii) topography, i.e. catchment formation type-driving lakes connectivity, and the presence of summer snow deposits. While driver (i) appeared to be local, (ii) and (iii) showed gradient changes along altitude and latitude. These three drivers differentiated several lake ecotopes based on their landscape similarities. The three-driver model was successfully tested on a riparian vegetation composition dataset, further illustrating the validity and fundamental nature of the concept.\n\nThe findings inform on the relative contribution of scale-dependent catchment physical elements to lake ecotope and ecosystem formation in high altitude lakes, which should be considered in any assessment of potentially major deleterious effects due to environmental/climate change.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC=\"FIGDIR/small/034405_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (85K):\norg.highwire.dtl.DTLVardef@4b92e5org.highwire.dtl.DTLVardef@198fca4org.highwire.dtl.DTLVardef@f2801dorg.highwire.dtl.DTLVardef@b8f588_HPS_FORMAT_FIGEXP M_FIG Lake Bassia at 2275m a.s.l. in the Pyrenees National Park, France, is one of the millions of remote high altitude lakes worldwide whose catchments are likely to experience severe effects due to climate change. Photo credit: Antonio Palanca-Soler.\n\nC_FIG

Ecology↗