Secondary Dispersal Research Articles

Primate reintroduction promotes the recruitment of large-seeded plants via secondary dispersal

The loss of larger frugivores alters seed dispersal. Species reintroductions have been proposed as a strategy for reversing local disperser extinctions. However, their effects on ecological processes have seldom been assessed. Howler monkeys (Alouatta guariba) have been reintroduced in Tijuca National Park, a defaunated Atlantic Forest fragment. We compared the fate of seeds dispersed by howlers to dispersal by two other frugivores present in the park: capuchin monkeys (Sapajus nigritus) and guans (Penelope superciliaris). Howlers produce clumped defecations that attract dung beetles, which provide secondary dispersal by burying seeds embedded in feces. We expected that seeds dispersed by howlers would have a different fate from those dispersed by capuchins and guans, since their scattered defecations are less attractive to dung beetles. We followed the fate of seeds 3–14 mm in diameter through three processes after seed deposition: secondary dispersal, predation, and seedling emergence. We estimated the probabilities in each step according to the primary disperser and plant species. Dispersal by howlers increased the recruitment of large-seeded plants because of the higher probability of secondary dispersal of the seeds in their feces. Fewer of the seeds dispersed by capuchins or guans were buried, regardless of size, and burial depths were shallower. For 3 mm seeds, the final recruitment probability was similar across frugivores. However, more of the larger seeds reached the seedling stage when dispersed by howlers since they were buried more deeply, which increased their survival without affecting seedling emergence. Reintroductions can thus contribute to restoring ecological processes.

Stasis in forest regeneration following deer exclusion and understory gap creation: A 10-year experiment.

Chronically elevated ungulate browse pressure in temperate forests worldwide often generates ecological legacies characterized by low plant diversity and contributes to the formation of dense, nearly monodominant, and highly recalcitrant layers of understory vegetation. Once established, these recalcitrant layers combined with continued browsing may jointly constrain tree establishment and diversity so completely that understory recovery may be unattainable without mitigating browse pressure, the recalcitrant layer, or both. Here, we investigate the independent and synergistic effects of both white-tailed deer (Odocoileus virginianus) browsing and hay-scented fern (Dennstaedtia punctilobula) competition on tree regeneration in a 10-year experiment. Specifically, we examine how tree seedling establishment, growth, and composition are filtered by fern cover versus fern removal (gaps), browser presence versus absence (exclosures), and their combined effects during 10 years at three hardwood forest sites in Pennsylvania, USA. Fern gaps enhanced establishment for multiple tree species, increasing seedling density and diversity, particularly in the first 3 years post-treatment, and enhancing richness (≤1 species) over the course of the experiment. Excluding deer for a decade increased the height growth of other regeneration and altered species composition, but had no effect on diversity, richness, and density. Notably, we observed higher Prunus serotina seedling densities outside exclosures, possibly due to greater secondary dispersal. We argue that browsing legacies in second growth forests established at the turn of the last century created two conditions inimical to diverse forest regeneration: an overstory dominated by two species, P. serotina and Acer rubrum (86% of basal area), and a dense recalcitrant understory layer dominated by a native fern. The first condition limits propagule supply, the second strongly filters seedling establishment, and both create impoverished forest understories composed of few individuals and species. In undisturbed forest understories, the inertia toward impoverishment was sustained across the decade even where browsing was eliminated. Consequently, stand replacing disturbances (whether natural or anthropogenic) that disrupt the understory layer and reinitiate succession may be necessary to propel forests out of their current stasis and down a pathway leading to greater diversity.

Effective regulation of Ga active species in mesoporous ZSM-5 for catalytic upgrading of coal pyrolysis volatiles

Quality improvement of pyrolysis tar with yield increasing of high value-added components is highly desired for coal utilization. Herein, Ga-impregnated mesoporous ZSM-5 (Ga/MZ5) directed by organosilane surfactant of [3-(trimethoxysilyl) propyl] octadecyldimethylammonium chloride (TPOAC) is used as a catalyst for the catalytic upgrading of coal pyrolysis volatiles. Effective regulation by reduction and reduction/reoxidation promotes a secondary dispersion of gallium species from external surface deposition to micropore permeation. The comprehensive evaluation of catalytic upgrading performance indicates that the designedly regulated gallium species (mainly Ga+, GaH2+ and GaO+), feasible balance of Brønsted and Lewis active sites and mesopore diffusion superiority effectively contribute the yield increasing of both light-fraction (MLF/MTar) and target products of BTEXN (benzene, toluene, ethylbenzene, xylene and naphthalene). The optimal catalyst of Ga/MZ5_R/O exhibited the highest value of MLF/MTar (88 %) and highest yield of BTEXN (31.84 mg.g−1), which are 173 and 589 % higher than non-catalytic single pyrolysis and 133 and 280 % higher than those over the conventional Ga-impregnated ZSM-5 (Ga/Z5). Moreover, the possible reaction networks towards high value-added products of BTEXN based on the positive conversion of polycyclic aromatic hydrocarbons (PAHs), phenols, and other oxygen-containing compounds (abbreviated as PPO) is further proposed.

Secondary Dispersion Halos of Platinum and Palladium in the Shorzha Dunite-Peridotite Massif of the Sevan Ophiolite Belt of Armenia

Distribution of platinoids within the massifs of Sevan ophiolitic belt has been very poorly studied. As a result of the research implemented, a negative assessment of the prospects for platinum content of dunite-harzburgite massifs of Sevan ophiolitic zone was given [1,2].

The effect of alkylation on the micro-solvation of ethers revealed by highly localized water librational motion.

The specific far-infrared spectral signatures associated with highly localized large-amplitude out-of-plane librational motion of water molecules have recently been demonstrated to provide sensitive spectroscopic probes for the micro-solvation of organic molecules [Mihrin et al., Phys. Chem. Chem. Phys. 21(4), 1717 (2019)]. The present work employs this direct far-infrared spectroscopic approach to investigate the non-covalent intermolecular forces involved in the micro-solvation of a selection of seven ether molecules with systematically varied alkyl substituents: dimethyl ether, diethyl ether, diisopropyl ether, ethyl methyl ether, t-butyl methyl ether, and t-butyl ethyl ether. The ranking of the observed out-of-plane water librational band signatures for this selected series of ether-water complexes embedded in inert neon matrices at 4K reveals information about the interplay of directional intermolecular hydrogen bond motifs and non-directional and long-range dispersion interactions for the micro-solvated structures. These far-infrared observables differentiate minor subtle effects introduced by specific alkyl substituents and serve as rigorous experimental benchmarks for modern quantum chemical methodologies of various levels of scalability, which often fail to accurately predict the structural variations and corresponding vibrational signatures of the closely related systems. The accurate interaction energies of the series of ether-water complexes have been predicted by the domain based local pair natural orbital coupled cluster theory with single-, double-, and perturbative triple excitations, followed by a local energy decomposition analysis of the energy components. In some cases, the secondary dispersion forces are in direct competition with the primary intermolecular hydrogen bonds as witnessed by the specific out-of-plane librational signatures.

Geochemical methods to prospect for gold mineralization in Shamkhyia area : northern state-Sudan

Geochemical methods to prospect for gold mineralization in Shamkhyia area : northern state-Sudan
 The study area is located in the northern border of Buyda Desert at the lobe of the River Nile at coordinates: latitude 19° 27 25" N, longitude 32° 59’ 37'.
 Unconsolidates samples were collected from areas of the suspected Au bearing sector to reveal secondary dispersion patterns.
 The results which were obtained for Au and accompanying elements (Ag, Cu, Co, Cu, Pb, and Zn) Table No (7 , 8) were subjected to statistical analysis to reveal parameters such as background values (Cb) coefficient of correlation (r), coefficient of variation (c.v), geochemical factors (u), and productivities (q,Q) and coefficient of dispersion (5).
 These parameters can be used as prospecting and exploration criteria.
 The coefficient of correlation of Au with the accompanying elements in rock chip composite samples show values more reliable for prospecting than those of the soil samples.
 Geochemical factors of ratios of contents of epithermal elements to hypothermal elements indicate deeper levels of mineralization and weathering.
 Gold dispersion shows less erratic behavior and this reflects more or less the morphology of the hidden ore bodies.
 The main conclusions are:- Coefficient of corelations when they are reliable can be used to define pathfinders to prospect for the difficult gold.
 Coefficient of mobility can be used to adopt sampling intervals and grid system.
 Geochemical factors can indicate horizon of mineralization and level of weathering.
 Geochemical reserve can be used to indicate priorities for further extensive explorational studies

Gulls living in cities as overlooked seed dispersers within and outside urban environments

The yellow-legged gull is an opportunistic and generalist bird that has colonised urban areas, where it has found very favourable trophic resources but also causes disturbance to humans and damage to infrastructure. Here, we investigated the potential role that gulls play in the dispersal of plants in Barcelona, a highly populated city of north-eastern Spain. We analysed the stomach contents of 145 chicks collected in urban nests and reported the presence of seeds of 27 plant taxa. We then developed a plant dispersal model based on the movements of 20 GPS-tracked yellow-legged gulls breeding in the city of Barcelona. We estimated seed dispersal distances, seed shadows and percentage of seeds reaching habitats suitable for seeds regurgitated in pellets and those excreted in faeces. Seven of the 27 plant taxa found in the stomachs were alien taxa to Spain. Average dispersal distances of plant seeds by gulls were around 700 m, but maximum dispersal distances reached up to 35 km. Dispersal distances and seed spatial patterns did not differ between faeces and pellet models, as most strongly depended on gull movements. About 95% of the seeds were dispersed within urban environments and between 20 and 30% reached suitable habitats for seed deposition (urban woodlands, green urban parks and urban grasslands). Urban gulls frequently dispersed seeds (including alien species) within urban habitats, both via direct consumption or via secondary dispersal after consuming granivorous birds that had ingested the seeds, such as pigeons or parakeets. Urban planning for Barcelona is based on native plant species, and thus, special attention should be paid to alien plants dispersed by birds, which could pose a risk to native biodiversity in urban ecosystems.

Alien corals in a Brazilian seaport and perspectives for improving marine bioinvasion detection and management in commercial ports

Two invasive coral species, Tubastraea coccinea and T. tagusensis, were identified on underwater artificial structures during a routine inspection at the Port of São Sebastião in southwestern Brazil in 2019. Both species were previously recorded in natural and artificial substrata in the region since 2008, including marine protected areas, but never found in the Port area. Tubastraea spp. are highly invasive species that outcompete native and endemic species, trigger seascapes changes, and modify ecosystem functions. Although it is uncertain if the São Sebastião Port was the primary source of these bioinvasion, ports' activity might enhance secondary dispersion, collaborating to spread the invasive species. This finding triggered a request by the Brazilian Institute of Environment (IBAMA) to the implementation of a specific plan to control the Tubastraea invasion attached to the invasive species monitoring program, which was one of the conditions to renew the operation license of the São Sebastião Port in 2020. Here, we recommend that commercial seaports consider including biota monitoring programs focusing on detecting marine non-indigenous species. Furthermore, we provided some subjects that should be incorporated in monitoring programs and highlight the need for evaluation of underwater artificial structures additionally to adjacent rocky shores. If a potentially invasive species is detected, a specific plan to control the invaders should be developed, as well as strategies to control invasive species dispersion. The monitoring program should be planned under the guidance of environmental agencies and incorporate the scientific community and general society, stimulating partnerships and discussions focusing on better understanding biological invasions in seaports and improving their management.

Influence of intraparticle cross-linking on polymer diffusion in latex films prepared from secondary dispersions

In this work, we synthesized surfactant-free latex dispersions of nanoparticles (NPs) based upon emulsification of a preformed proprietary BASF polymer (MnGPC = 5000 g/mol, Ð = 3, denoted as Pol), in which the —COOH groups were partially neutralized by ammonia. To obtain useful coatings with polymers of such low molecular weight (MW), we approached this problem through the reaction of carboxylated polymer dispersions with neopentyl glycol diglycidyl ether (NGDE, 20 to 60 mol% based on carboxyl groups) to increase the MW and to introduce gel content. We employed AFM to monitor the influence of cross-link density on the surface roughness and found the presence of cross-links increases the resistance of particles to deformation. Fluorescence resonance energy transfer (FRET) measurements were carried out to determine the extent of polymer mixing upon film formation. Our most important finding is that the gel content substantially limited the extent of molecular mixing at long annealing times or in corresponding solvent-cast films. In parallel, we carried out a series of similar reactions on the secondary dispersion particles with a monoepoxide, consisting of a mixture of dodecyl and tetradecyl glycidyl ether. This reaction maintained the size and size distribution of the latex particles. These polymers had no gel content, but the reaction with the epoxide lowered the Tg of the polymer. FRET studies showed a pronounced influence of Tg on the rates of polymer diffusion in these films.

Secondary Seed Ingestion in Snakes: Germination Frequency and Rate, Seedling Viability, and Implications for Dispersal in Nature

The importance of vertebrate animals as seed dispersers (zoochory) has received increasing attention from researchers over the past 20 years, yet one category in particular, diploendozoochory, remains understudied. As the term implies, this is a two-phase seed dispersal system whereby a secondary seed predator (carnivorous vertebrate) consumes a primary seed predator or granivore (rodent and bird) with undamaged seeds in their digestive tract (mouth, cheek pouch, crop, stomach, or other organ), which are subsequently eliminated with feces. Surprisingly, although snakes are among the most abundant predators of granivorous vertebrates, they are the least studied group insofar as our knowledge of seed rescue and secondary dispersal in a diploendozoochorous system. Here, using live snake subjects of the Sonoran Desert (one viperid and two colubrid species) and seeds of the Foothill Palo Verde (Parkinsonia microphylla), a dominant tree of the same region, we experimentally tested germination frequency and rate, and seedling viability. Specifically, to mimic rodents with seed-laden cheek pouches, we tested whether wild-collected P. microphylla seeds placed in the abdomen of thawed laboratory mice and ingested by the snakes would retain their germination viability. Second, we examined whether seeds exposed to gut transit germinated at a greater frequency and rate than the controls. While we found strong statistical support for our first hypothesis, both aspects of the second one were not significant. Accordingly, we provide an explanation for these results based on specific life-history traits (dormant and non-dormant seeds) of P. microphylla. Our study provides support for the role of snakes as important agents of seed rescue and dispersal in nature, their potential as ecosystem engineers, and crucial evidence for the investment of field-based studies on diploendozoochorous systems in deserts and other ecosystems.

The Distinct Fruit Size and Physical Defense Promote Divergent Secondary Seed Dispersal Strategies of Three Oak Species

The Distinct Fruit Size and Physical Defense Promote Divergent Secondary Seed Dispersal Strategies of Three Oak Species

A predatory waterbird as a vector of plant seeds and aquatic invertebrates

AbstractOmnivorous waterbirds play an important role in aquatic ecosystems as dispersal vectors via direct ingestion, transportation, and egestion of plant and invertebrate propagules (i.e. endozoochory). Predatory birds also have the potential to disperse plants and invertebrates that were first carried internally or externally by their prey animals. However, the potential contribution of predatory waterbird species to propagule dispersal in aquatic ecosystems remains understudied.We chose the grey heronArdea cinerea(Ardeidae) to study the potential of predatory waterbirds to disperse propagules within and among aquatic ecosystems. We hypothesised that: (1) herons disperse a wide variety of plant and invertebrate propagules, from different habitats, with different morphologies (i.e. dispersal syndromes), and including both native and alien species; (2) propagules are ingested with prey species that are primary dispersal vectors (i.e., herons are secondary dispersers); (3) heron pellets show a similar abundance and richness of propagules across their widespread range. We collected 73 regurgitated heron pellets containing undigestible remains from 12 locations across the U.K. and The Netherlands, and examined the taxonomic diversity of plant seeds, invertebrates and prey remains.Pellets were dominated by mammal hairs (99% by volume), and bones confirmed the ingestion of small mammals (prevalence of 38%, e.g. water volesArvicola amphibius), fish (14%), and birds or amphibians (6%). A total of 266 intact plant seeds were recovered from 71% of the pellets, representing 50 taxa from 17 plant families, including the alienCotula coronopifolia. The cumulative number of plant species dispersed was lower at higher latitudes. Eight plant species recorded had not previously been recorded as dispersed via waterbirds, and only three species have anendozoochorous dispersal syndrome. Plant taxa were dominated by Caryophyllaceae, Cyperaceae, Juncaceae, and Poaceae, with 24 species from the littoral zone (Ellenberg moisture values of 7–12) and 21 terrestrial species (Ellenberg moisture values of 4–6). Intact invertebrate propagules were found in 30% of the pellets, dominated by Cladocera (Daphniidae) and Bryozoa (including the alienPlumatella casmiana).Our results demonstrate that grey herons disperse plant seeds and aquatic invertebrates widely in north‐western Europe. Herons regurgitate pellets that contain plant and invertebrate propagules from both aquatic or terrestrial habitats, for which secondary dispersal via ingestion along with prey is the likely underlying mechanism (i.e. propagules either attached to or in the digestive systems of the various prey). Our findings showcase the potential of predatory waterbirds as vectors of plants and invertebrates, and how they may facilitate connectivity between freshwater and terrestrial habitats.

Seed size and pubescence facilitate secondary dispersal by dung beetles

AbstractIn tropical forests, primary dispersal by animals is the most important form of seed dispersal. Dung beetles are secondary seed dispersers attracted to mammal feces. When they bury dung of frugivorous mammals, they move seeds to new sites, possibly protecting them from seed predation or pathogens, or moving to better micro‐climates and away from conspecifics. As a result, secondary dispersal by dung beetles potentially increases rates of seed survival and germination. Previous studies examined how dung beetles filter seeds by size. However, other seed traits have not been examined. We discovered that pubescent seeds covered with hairs on their surface hold a thin layer of dung and possibly “trick” the dung beetles into burying them like a dung ball. In a lowland tropical forest (Chocó Ecuador), we collected dung balls from dung beetles (Canthon angustatus, Oxysternon conspicillatum, Sulcophanaeus noctis, and Scybalocanthon trimaculatus), and fecal samples from brown‐headed spider monkeys (Ateles fusciceps fusciceps) and mantled howler monkey (Alouatta palliata). We characterized the traits of seed morphospecies found within samples and counted them. Our data show that larger size is coupled with a higher proportion of pubescence in seeds. The association between seed size and pubescence may extend beyond our study area supported by an analysis of the literature data for neotropical seeds at the genus level. Large pubescent seeds were more likely to be included in dung balls than smooth large seeds. Our results are consistent with the hypothesis that secondary dispersal by dung beetles exerts some selection pressure on the phenotype of endozoochorous seeds.

DISPERSAL OF ARBUSCULAR MYCORRHIZAL FUNGI BY BATS IN AN URBAN TROPICAL FOREST FRAGMENT

Associations of arbuscular mycorrhizal fungi (AMF) and plant species may occur in terrestrial and air environments and need an effective dispersal, which occurs mainly by biotic vectors. Studies on the influence of flying animals on this dispersal are scarce, thus, this study aimed to investigate the role of bats in AMF propagule dispersal and the most frequent means of transport. Analyses were performed in dorsoventral hairs and feces of bats in an urban tropical forest fragment in southern Brazil, from April to September 2018. The results were negative for the presence of spores in the hair, but spores of Glomus invermaium and Acaulospora scrobiculata were detected in feces of two bat species, evidencing that they can act as secondary spore dispersers. Efficient dispersal depends on the range extension of the dispersing species, so bats can be important dispersers of AMF, since they have the ability to fly and travel long distances.

Novel phenomena of graphene secondary dispersion and phase transformation in selective laser melting of 15-5PH/graphene composites

15-5PH, a martensitic, precipitation hardening stainless steel, can easily form a martensite structure during rapid solidification, especially in the selective laser melting (SLM) process. In our study, the 15-5PH/Gr composites with different mass ratios (0 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%) of graphene nanoplates (GNPs) were successfully prepared using SLM technology. Through the observation of optical microscopy images and Raman spectra, it is discovered that the GNPs are uniformly dispersed in the 15-5PH/Gr composites. Based on this phenomenon, a flow model is established to explain the process of the secondary dispersion of the GNPs in the molten pool at high temperatures, and then we come up with a mechanism for it. Besides, it is found that GNPs have a strong inhabiting effect on phase transformation of 15-5PH/Gr composites during the rapid solidification of the SLM process, and the inhibition will be enhanced as the GNPs content increases. The mechanical properties of metal matrix composites (MMCs) are significantly influenced by the changes in phase and additive content. According to the mechanical property tests on the 15-5PH/Gr composites, it is found that their ductility and impact toughness have maximum values of 41.1 ± 1.3% and 194.9 ± 3.1 J/cm 2 respectively, and the friction coefficient of the 15-5PH/Gr composites have a minimum value of 0.34. Compared with the SLM-ed 15-5PH, the improvement of mechanical properties of the 15-5PH/Gr composites on ductility, impact toughness and wear resistance are increased by 130.9%, 97.3% and 45.2% respectively.

High-performance flexible strain sensors based on biaxially stretched conductive polymer composites with carbon nanotubes immobilized on reduced graphene oxide

In this paper, reduced graphene oxide (rGO), decorated with immobilized carbon nanotubes (CNTs), was introduced into a thermoplastic polyurethane (TPU) matrix to obtain a conductive nanocomposite with 2 wt% nanofillers content. Hot-pressed composite sheets were then biaxially stretched into films to efficiently fabricate flexible strain sensors. The biaxial stretching process was shown to promote secondary dispersion and parallel alignment of the nanofillers, resulting in the sensors exhibited significantly higher sensitivity (GF = 150 for the rGO/TPU4×4 sensor with a stretching ratio of 4 × 4 relative to GF = 3.5 for the rGO/TPU1×1 sensor at 30% strain). Furthermore, due to the synergy of the CNTs and rGO nanoparticles, the rGO/CNT/TPU4×4 sensor had a lower resistivity (5.62 × 104 Ω·m), wider monitoring range (0.3 ∼ 400% strain), and higher stability compared with the rGO/TPU4×4 sensor. The ability of the sensor to recognize body movements and physiological activities was also shown.

Secondary dispersion haloes in the gold-bearing weathering crust of the Vasilkovskoe gold deposit, Northern Kazakhstan

The formation conditions and characteristics of secondary dispersion haloes in the gold-bearing weathering crust of a gold-sulfide-quartz deposit are considered. The fraction < 0,1mm is demonstrated to be preferable for lithochemical prospecting for the Vasilkovskoe type gold mineralization. The secondary dispersion haloes of gold, identified based on analyses of this fraction, are characterized by the maximum size and productivity.

Exploration geochemistry of surficial media over the high-grade McArthur River uranium deposit, Saskatchewan, Canada

ABSTRACT An orientation survey using surficial media was performed over the high-grade McArthur River unconformity-related U deposit (Saskatchewan, Canada) to test whether or not secondary dispersion of elements related to the ore body or alteration zone can be detected at the surface more than 500 m above the deposit. Organic-rich Ah-horizon soils, Fe-rich B-horizon soils, C-horizon soils, tree cores of Jack pine (Pinus banksiana), and glacially dispersed boulders of Manitou Falls Formation sandstone that host the U deposit were collected in four sampling grids near the mine site. Two of the grids overlaid the trace of the P2 fault that hosts the deposit and extends nearly to the surface, one grid overlaid both the P2 fault and one of the high-grade ore bodies (Zone 4), and one grid was located 2.5 km away from the ore body surface trace in the barren hanging wall of the P2 fault. The grid overlying the Zone 4 ore body had the highest proportion of samples with elevated U and low 207Pb/206Pb ratios, the latter indicative of radiogenic Pb from a high-U source, measured in two size fractions of Ah-horizon soils using Na pyrophosphate leach, pine tree cores using total digestion, and sandstone boulders using 2% HNO3 leach. A handful of pathfinder elements, such as As, Co, Ni, and Pb, are variably associated with the U and radiogenic Pb. Sandstone boulders with an assemblage of dravite + kaolinite ± illite, determined using shortwave infrared (SWIR) spectroscopy and matching the alteration mineralogy in the Manitou Falls Formation above the U deposit, were prevalent in the grid above the Zone 4 ore body and in the adjacent grid in the direction of glacial dispersion. A coarse fraction of the B-horizon soils, leached with 5% HNO3, highlighted the grid above the Zone 4 ore body to a lesser extent, whereas HNO3 leaches and aqua regia digests of C-horizon soil separates did not highlight the P2 fault or ore body trace due to influence by parent till mineralogy. Results of environmental monitoring at the mine site, which was active at the time of sampling, suggest that dust containing U, Pb, and radionuclides from waste rock piles and a ventilation shaft could influence A-horizon soil geochemistry near the mine site, and that U and radiogenic Pb anomalies in B- and C-horizon soils near the water table are close to a treated mine effluent discharge point. However, older trees that record elevated U and radiogenic Pb in annual rings that pre-date mining activity, and alteration mineralogy and geochemistry of boulders that are less susceptible to the influences of mining activity, add confidence that the geochemical anomaly in diverse surficial media above the Zone 4 ore body represents secondary dispersion from the underlying U deposit.

Roller dung beetles of dung piles suggest habitats are alike, but that of guarding pitfall traps suggest habitats are different

AbstractRoller dung beetles play a pivotal role in the nutrient distribution in soil and secondary dispersal of seeds. Dung beetles are sampled either using a dung-baited pitfall trap or an exposed dung pile on the ground. While the former method is useful for a rapid survey of dung beetles, information on the ecology and behaviour of dung beetles can be lost, which the latter method provides, but underestimates species diversity due to its inefficiency in trapping rollers. Efficiency of a new method for sampling rollers—installing guarding pitfall traps around dung piles—is assessed in three habitats—contiguous tropical rainforests, fragmented forests, and disturbed used home gardens—and two diel periods—day and night. Five guarding pitfall traps were installed at 50 cm radius around dung piles. About 98% of the total rollers were sampled in pitfall traps. The habitats were similar when the roller catches of only dung piles—conventional approach—were analyzed, but were different when the rollers of guarding pitfall traps were considered. The roller abundance was negatively affected by forest fragmentation and land-use change. About 98% of the rollers were collected at daytime. Using guarding pitfall traps around dung piles is highly recommended for dung beetle diversity studies.

Mineralogy and petrogenesis of fracture coatings in Athabasca Group sandstones from the McArthur River uranium deposit

ABSTRACT The McArthur River unconformity-related uranium deposit, located in the Athabasca Basin of Saskatchewan, Canada, is structurally hosted near the unconformity between Archean to Paleoproterozoic metasedimentary basement and the Proterozoic Athabasca Group sandstones. In this study, the mineralogy and geochemistry of fracture materials within the entire ca. 550 m thickness of the Athabasca Group sandstones and the metasedimentary (host) rocks from the McArthur River area were used to determine the paragenetic sequence and origin of minerals in and near the fractures. Our work sought to determine if the host minerals record elements associated with the uranium deposit at depth and if they could be used to guide exploration (vectoring). Fracture orientations indicate that most are moderately dipping (<50°) and provided permeable pathways for fluid movement within the basin, from below, and through the overlying sedimentary rocks. Many of the fractures and adjacent wall rocks record evidence of multiple distinct fluid events. Seven types of fracture fillings were identified from drill core intersecting the Athabasca Basin and present distinct colors, mineralogy, and chemical features. Brown (Type 1) and pink (Type 7) fractures host paragenetically late botryoidal goethite, Mn oxide minerals, and poorly crystallized kaolinite that formed from relatively recent low-temperature meteoric fluids, as indicated by poor crystallinity and low δ2H values of –198 to –115‰. These minerals variably replaced higher temperature minerals that are rarely preserved on the fractures or in wall rock near the fractures. Hydrothermal alteration associated with the mineralizing system at ca. 200 °C is recorded in assemblages of dickite, well-crystallized kaolinite, and spherulitic dravite in some white and yellow (Type 2) and white (Type 3) fractures, as reflected by the crystal habits and variable δ2H values of –85 to –44‰. Fibrous goethite in white and yellow (Type 2) and black and orange (Type 5) fractures and microfibrous Mn oxy-hydroxide minerals in black (Type 4) fractures also crystallized from hydrothermal fluids, but at temperatures less than 200 °C. White and yellow fractures (Type 2) containing fibrous goethite reflect fracture networks indicative of hydrothermal fluids associated with the mineralizing system during primary dispersion of pathfinder elements and therefore extend the deposit footprint. Brown (Type 1) and pink (Type 7) fractures have low δ2H values in botryoidal goethite and poorly crystallized kaolinite and are indicative of the movement of meteoric waters. Secondary dispersion of elements from the deposit to the surface on some fractures is evidence that fractures are pathways for element migration from the deposit to the surface, over distances exceeding ∼500 m.