Plant Fragments Research Articles

Movement of the bacterial blight pathogen Erwinia psidii in guava varieties differing in susceptibility

Erwinia psidii causes bacterial blight of guava, an important disease of this fruit crop in Brazil. Pathogen spread is associated with the movement of infected but asymptomatic propagating plant material. The objective of this study was to compare bacterial movement inside the host tissue and symptom development in two guava varieties commonly grown in Brazil. Guava plants of Pedro Sato and Kumagai varieties were inoculated with strain IBSBF435 by deposition of a bacterial suspension droplet followed by puncture at the axils of the first fully expanded pair of leaves. Disease severity was assessed in the upper third part of the plant and stem fragments were cut at intervals of 1 cm above and below the inoculation point. Samples were collected at 0.5, 1, 2, 4, 6, 8, 10 and 12 days after inoculation. Presence of viable cells of E. psidii at each sampling point was evaluated using Bio-PCR with species-specific primers after a 24 h-enrichment step. Bacterial movement was detected on both directions in both varieties, however a positive correlation between movement and disease severity was observed only for Pedro Sato. Kumagai plants remained symptomless despite the presence of E. psidii above and below the inoculation site.

Biological Inclusions in Amber from the Paleogene Chickaloon Formation of Alaska

The Chickaloon Formation in south-central Alaska contains rich coal deposits dated very close to the Paleocene-Eocene boundary, immediately beneath which occur dispersed nodules of amber along with abundant remains of Metasequoia, dicots, and monocots. The nodules are small (less than 10 mm in length), nearly 10,000 of which were screened, yielding several inclusions of fungi and plant fragments, but mostly terrestrial arthropods: 29 specimens in 10 orders and 13 families. The fungi include resinicolous hyphae and a dark, multiseptate hyphomycete. Plants include wood/bark fragments and fibers, and the microphylls of a bryophyte (probably a moss, Musci). Among the arthropods are arachnids: mites (Acari: Oribatida), Pseudoscorpionida, and the bodies and a silken cocoon of spiders (Araneae). Insecta include Blattodea, Thysanoptera, Hemiptera (Heteroptera and Aphidoidea), Coleoptera (Dermestidae: Megatominae), Trichoptera, Diptera (Chironomidae: Tanypodinae), and Hymenoptera (Formicidae: Formicinae). Nymphal aphids predominate (65% of the arthropod individuals), which were probably feeding on the source tree, likely Metasequoia. There is a bias in preservation toward small arthropods (mean body length 0.75 mm) that are surface-dwelling (nonwinged) stages and taxa. Chickaloon amber contains the most northerly fossil records of pseudoscorpions, thrips, Dermestidae, and Cenozoic ants and mites, so the deposit is contributing unique data on high-latitude paleodiversity of the Paleogene hothouse earth.

Agricultural harvesting emissions of ice-nucleating particles

Abstract. Agricultural activities can modify natural ecosystems and change the nature of the aerosols emitted from those landscapes. The harvesting of crops can loft plant fragments and soil dust into the atmosphere that can travel long distances and interact with clouds far from their sources. In this way harvesting may contribute substantially to ice-nucleating particle (INP) concentrations, especially in regions where agriculture makes up a large percentage of land use. However, a full characterization of particles emitted during harvesting has not been reported. This study characterizes immersion mode INPs emitted during harvesting of several crops in the High Plains region of the United States. The Colorado State University Continuous Flow Diffusion Chamber (CFDC) and the Ice Spectrometer (IS) were utilized to measure INP concentrations during active harvesting of four crops in Kansas and Wyoming. Large spikes of INPs were observed during harvesting, with concentrations over 200 L−1 at −30 °C measured during a wheat harvest. To differentiate between mineral and organic components, a novel heating tube method was employed in real time upstream of the CFDC to deactivate organic INPs in situ. The results indicate that harvesting produces a complex mixture of organic, soil dust, and mineral components that varies for different crops. Electron microscopy analysis showed that while mineral components made up a large proportion of INPs, organic components comprised over 40 % of measured INPs for certain crops at warm temperatures. Heating and enzyme post-treatment of aerosol samples collected for IS processing indicated that bacteria and heat-labile and heat-stable organics contributed to wheat harvest-produced INPs. These results indicate that plant material and organic particles are a significant component of harvest INPs and their impacts on ice formation in clouds and precipitation on a regional scale should be explored.

Does seasonality and pool connectivity influence fish trophic ecology in knickzone habitats?

ABSTRACTKnickzones are large rock outcrops found in upstream and middle plateau river basins. This kind of geological formation, which is considered a macrohabitat, creates a complex of mesohabitats: pools, riffles and runs, with distinct characteristics. In the present work, the aim was to evaluate the influence of connectivity and seasonality on the trophic structure of the ichthyofauna found in knickzone pools. Fish were sampled in four connected and three isolated pools, during dry and rainy seasons, and the stomach contents of 20 species were analyzed. Seasonal differences in diet occurred, with greater contribution of algae and aquatic hexapod in the dry season and of plant fragments and organic matter in the rainy season. The high diet overlap found in the isolated pools may be related to more intensive biotic interactions among individuals confined in physically restricted habitats. Seasonality in combination with connectivity to the main channel influenced the trophic structure of fish assemblage in the knickzone. Knickzones dynamics are modulated by seasonal events, such as floods, and connectivity of habitats, being extremely important for the trophic interactions between species. Alterations to these dynamics, like the construction of hydroelectric power plants, can modify significantly the trophic ecology of knickzones.

Sedimentology and chemostratigraphy of Carboniferous red beds in the western Moncton Basin, Sussex area, New Brunswick, Canada: possible evidence for a middle Mabou Group unconformity

The area around Penobsquis, east of Sussex, New Brunswick, Canada, is an important location of natural resources for the province. The McCully gas field produces from strata of the Mississippian Horton Group whereas younger strata of the Windsor Group are host to major potash and rocksalt deposits. Overlying these units are over 1 km of poorly understood red beds currently assigned to the Mississippian Mabou Group. To date, this latter unit lacks significant marker beds and has had no useful biostratigraphic recovery, despite recent extraction of close to 5 km of drill core. Research on this core broadly identifies siltstone and sandstone at the base of the Mabou Group that gradually coarsen up into conglomerate. The succession is considered the result of alluvial-fan progradation from the northeast. Within this succession, in several of the cores, is a single interval of localized, horizontally laminated to cross-stratified, bluish-grey sandstone, containing carbonaceous plant fragments and siltstone intraclasts. To assess the importance of this interval in the context of the red bed succession, a total of 131 samples of core from three boreholes have been analyzed using Inductively Coupled Plasma and spectroscopic techniques to determine chemostratigraphy. Study of various elemental ratios can delineate two packages, one that corresponds to the grey interval and overlying red beds, and the other to the underlying red beds. Changes in the elemental ratios are interpreted to mark a broader population of mineral species related to greater variation of provenance and diagenesis in the upper sediment package. The reduced horizons and rip-up clasts may have been produced by sediment reworking along a boundary that represents an unconformity (in core, a disconformity) at a stratigraphic level near to where one has been inferred by other workers.

The influence of hyperpycnal flows on the salinity of deep-marine environments, and implications for the interpretation of marine facies

Abstract Interpretation of the continental or marine character of sediments on the basis of the paleosalinity is increasingly based on the concentration of some trace elements. The paleosalinity can be affected, however, also in deep-marine environments, by discharge peaks of major sediment-laden rivers. These induce hyperpycnal flows that run down the basin slope. The huge volume of fresh water gradually mixes with the ambient saline seawater, diminishing the paleosalinity. The temporary lowered paleosalinity may be preserved in the sedimentary record in the form of ‘diverging’ concentrations of trace elements and trace-element ratios. This is exemplified for the Early Cretaceous Lingshandao Formation on Lingshan Island (western Yellow Sea). It was found during field work and geochemical analysis that hyperpycnal currents may not only lower the salinity of a deep-marine environmental setting, but may also carry along continental plant fragments and other biological remains, which may obscure the marine character of the sediments. It is deduced that detailed facies analysis in the field is consequently required to reveal the true character of a marine environment.

Blind Testing: DNA Barcoding Sheds Light Upon the Identity of Plant Fragments as a Subsidy for Cave Conservation

Plants living above and around caves represent an important, albeit poorly studied, resource within cave ecosystems. The presence of plant material (root-like structures or rhizothemes, saplings, seeds, and seedlings) correlates positively with the biodiversity of the cave dwelling animals as shown for iron-ore caves in Carajás, Pará, Brazil. Plant material collected in caves has proven to be difficult to identify by traditional botanical methods, thus this research aims to provide a qualitative insight into the taxonomy and morphology of rhizothemes and other plant fragments found in the caves. The identification process used a combination of different molecular markers (ITS2, rbcL, and trnH-psbA) followed by a comparison of the sequences obtained against publicly available databases. The rhizothemes were submitted to micromorphological analysis to ascertain their putative root or stem origin and to compare their anatomy with known patterns found in the plant families or genera recovered through molecular matches. All studied samples were Angiosperms, mostly belonging to subclass Rosideae, within four orders: Malpighiales (Euphorbiaceae, Hypericaceae), Sapindales (Anacardiaceae and Sapindaceae), Myrtales (Myrtaceae), Fabales (Fabaceae), and only two belonging to subclass Asteridae, order Gentianales (Apocynaceae). Some of the samples were matched to generic level, with ITS2 being the best marker to identify the fragments because it shows high degree of sequence variation even at specific level and result reliability. All rhizothemes turned out to be roots, and correspondence was found between the existing literature and the individual anatomical patterns for the families and genera retrieved. DNA barcode has proved to be a useful tool to identify plant fragments found in this challenging environment. However, the existence of well curated, authoritatively named collections with ample biological information has proven to be essential to achieve a reliable identification.

Colossal triple-bladed claw latches swift louse flies to feathers

Why flap yourself when you can hitch a ride on your meal ticket? In fact, parasitic swift louse flies (Crataerina pallida) are so content to piggyback on the swifts upon which they dine that they have almost done away with their wings. Yet, should the louse flies lose their footing, all is lost. Dennis Petersen from Kiel University, Germany, says, ‘Swifts can fly really fast and the louse flies are incapable of flight, so detachment is normally a death sentence’. As most flies grip onto surfaces using a combination of a grappling hook and sticky attachment pads, Petersen and his colleagues Stanislav Gorb and Lars Heepe wondered how the blood-sucking swift parasites have adapted their feet to anchor themselves so firmly to their acrobatic hosts.The parasites reside as pupae in abandoned swift nests over winter, ready to emerge as adults when the swifts return to lay their eggs, so Arndt Wellbrock and Klaudia Witte from the University of Siegen, Germany, retrieved pupae from nests under a road bridge near Siegen before the adult flies emerged in spring. However, Petersen explains that it is impossible to rear the adult insects in the lab without a supply of fresh swift blood, ‘so we put them in a wine fridge at 10°C to cool them down and prolong their life’, he says. Nils Kreuter and Sebastian Büsse, also from Kiel University, then scrutinised the insect's feet using a scanning electron microscope and were impressed to see that the flies were equipped with a colossal claw, which is huge in comparison with the size of the insect and is split into three scythe-like blades. ‘The claw looks like a three-toothed comb’, says Petersen; however, a conventional comb would just slide through the barbs of a feather, so how were the insects locking on?Petersen allowed four louse flies to clamber onto swift feathers and fasten themselves on to reveal that the feather barbs become lodged in the tapering gaps between the claws’ curving blades, effectively clamping the parasite in place. In addition, Petersen and Büsse could see that the sticky foot pads – the pulvilli, which other flies use to attach themselves to smooth surfaces – were coated in minute double-headed petal-shaped hairs that also snag on the feather. Next, Petersen and Kreuter tugged on the feet of flies that were clamped onto feathers and they were amazed that each individual leg could grip on with a force of 200 mN – 1000 times the weight of the fly; with six legs, nothing could tear the parasite free.Having tested the louse flies’ ability to latch onto feathers, the team also investigated how well they attach to smoother surfaces, as the parasites often encounter egg shell, the skin of naked nestlings and plant fragments in the nest. Encouraging the flies to scamper over smooth glass, silicone and epoxy resin, in addition to ridged versions of the silicone and epoxy resin, Kreuter and Petersen found that the insects could grip onto the smooth epoxy resin and glass with forces (∼15 mN) that were 75 times greater than their weight, but only 25 times greater (∼4 mN) on smooth silicone. However, when the insects were provided with 1.6 mm ridges to grip onto, their grasp on the epoxy resin and silicone was even tighter (∼19.5 mN and ∼19.4 mN, respectively).‘We were really surprised about the high interlocking forces observed on feathers’, says Petersen, who admits that it was impossible to detach the louse flies without damage to them or the feathers and is eager to find out whether, and how, other parasites get their claws into their hosts.

Dry season diet composition of four-horned antelope Tetracerus quadricornis in tropical dry deciduous forests, Nepal.

It is essential to assess the feeding strategies of threatened species during resource-scarce seasons to understand their dietary niche breadth and inform appropriate habitat management measures. In this study, we examined the diet composition of four-horned antelope (FHA) Tetracerus and quadricornis, one of the least studied ungulate species, in Banke National Park, Nepal. A total of 53 fresh pellet groups were collected between December 2015 and January 2016 and analyzed using micro-histological fecal analysis technique. First, we prepared 133 micro-histological photographs of different parts of 64 reference plant species. Then we compared 1,590 fragments of 53 fecal samples with photographs of reference plants to assess the percentage of occurrence of different plant species in FHA diet. A total of 30 plant species belonging to 18 different families were identified in fecal samples. Chi-square goodness of fit tests showed that FHA appeared not to feed all plant uniformly. Out of 1,520 identified fragments in fecal samples, 1,300 were browse species and 220 were grass species. Browse represented 85.5% of the identified plant fragments, suggesting that FHA might be adopting a browser strategy at least during winter when grasses are low in abundance and their nutritive quality is poor. Tree species had the highest contribution in the diet (46.55%) followed by shrubs (24.52%). The family Gramineae was consumed in the highest proportion (27.68%) followed by Euphorbiaceae (11.95%). Overall, our results suggest that FHA has the feeding plasticity to adapt to resource fluctuation. Based on the findings of this study, we recommend that dicot plant species—particularly fruit trees and shrubs, which are the major source of nutrients for FHA during resource-lean, dry season—be conserved and natural regeneration of these taxa be promoted.

Paraquanothrus n. gen. from freshwater rock pools in the USA, with new diagnoses of Aquanothrus, Aquanothrinae, and Ameronothridae (Acari, Oribatida)

Many taxa of mites inhabit long-lived freshwater environments, but the few known to live in small, ephemeral rock pools (lithotelmata) are brachypyline Oribatida. One of these is in the South African genus Aquanothrus (Ameronothridae). We describe adults and juveniles of two new rock-pool species from the USA and propose the sister-genus Paraquanothrus n. gen. to include them. The type-species, Paraquanothrus grahami n. sp., inhabits shallow weathering-depressions (‘pans’) on barren sandstone in the Colorado Plateau, especially southeastern Utah, where it seems to be an opportunistic grazer on microflora and rotifers. Paraquanothrus spooneri n. sp. inhabits rock pools on granite outcrops, is known only from the type-locality in eastern Georgia and appears to ingest mostly plant fragments. Like Aquanothrus, these mites are active only when free water exists. Paraquanothrus shares multiple apomorphic traits with Aquanothrus, for which a new diagnosis is based on corrected information on the type-species, A. montanus, and two undescribed species (one of which is represented in the paratype series). After reviewing historical concepts of Ameronothridae, we propose a new diagnosis (excluding Podacaridae) and propose a new rank and diagnosis for the subfamily Aquanothrinae, which includes Aquanothrus and Paraquanothrus. Molecular studies that have revealed links among Ameronothroidea, Cymbaeremaeoidea and Licneremaeoidea—in ways that question the monophyly of all three superfamilies—are reviewed, and a preliminary evaluation shows morphology to have a modest level of congruence with these results.

Origin and evolution processes of hybrid event beds in the Lower Cretaceous of the Lingshan Island, Eastern China

ABSTRACTOn the basis of detailed sedimentological investigation, three types of hybrid event beds (HEBs) together with debrites and turbidites were distinguished in the Lower Cretaceous sedimentary sequence on the Lingshan Island in the Yellow Sea, China. HEB 1, with a total thickness of 63–80 cm and internal bipartite structures, is characterised by a basal massive sandstone sharply overlain by a muddy sandstone interval. It is interpreted to have been formed by particle rearrangement at the base of cohesive debris flows. HEB 2, with a total thickness of 10–71 cm and an internal tripartite structure, is characterised by a normal grading sandstone base, followed by muddy siltstone middle unit and capped with siltstones; the top unit of HEB 2 may in places be partly or completely eroded. The boundary between the lowest unit and the middle unit is gradual, whereas that between the middle unit and the top unit is sharp. HEB 2 may be developed by up-dip muddy substrate erosion. HEB 3, with a total thickness up to 10 cm and an internal bipartite structure, is characterised by a basal massive sandstone sharply overlain by a muddy siltstone interval. The upper unit was probably deposited by cohesive debris flow with some plant fragments and rare mud clasts. HEB 3 may be formed by the deceleration of low-density turbidity currents. The distribution of HEBs together with debrites and turbidites implies a continuous evolution process of sediment gravity flows: debris flow → hybrid flow caused by particle rearrangement → high-density turbidity current → hybrid flow caused by muddy substrate erosion → low-density turbidity current → hybrid flow caused by deceleration.

Differential fragment regeneration in Syntrichia caninervis Mitt. from the Gurbantunggut Desert of China

Fragments of the desert moss Syntrichia caninervis Mitt. were grown on the surface of moistened sand to assess their regeneration capacity. The plant material was collected in two different years (2014 and 2015) and divided into five fragment classifications (stem apices, green leaves, yellow-green leaves, brown leaves and stems). All fragments of the stem apices, green leaves and stems regenerated within 10 days of culture while some fragments of yellow-green leaves (two 2014 fragments and one 2015 fragment) and brown leaves (three 2014 fragments and three 2015 fragments) died. Fragments of stem, stem apices and green leaves regenerated more quickly, produced longer protonemata and more shoots as compared to fragments of yellow-green and brown leaves. These differences were statistically significant but there was no difference in regeneration between the fragments from 2014 and 2015. Differential regeneration and proliferation of different plant fragments has important implications for the clonal propagation of S. caninervis in the Gurbantunggut Desert.

Palaeobotany and palynology of coprolites from the Late Triassic Chañares Formation of Argentina: implications for vegetation provinces and the diet of dicynodonts

The early Late Triassic Chañares Formation of Argentina contains one of the richest tetrapod-bearing assemblages of this age worldwide and is important for understanding the origin and early radiation of suchians, dinosauromorphs, and mammaliaforms. Here, we describe the fabric and microfossil content of herbivore coprolites produced by large kannemeyeriiform dicynodonts. Identified inclusions are dominated by fragmentary plant debris (wood, cuticles) with minor palynomorphs, the latter being of special significance as they represent the first palynological assemblage obtained for the formation. The palynological assemblage, which is dominated by bisaccate pollen grains, Alisporites and Platysaccus (Umkomasiales = Corystospermales), and minor striate pollen grains and fern spores, is characteristic of the Ipswich Phytogeographic Subprovince. Also present are Ovalipollis and Ellipsovelatisporites, which are typically absent in this phytogeographic subprovince (being characteristic elements of the Onslow Subprovince), but have been reported in the younger Ischigualasto Formation from the same basin. A statistical analysis of Triassic palynofloras across Gondwana results in a grouping containing the Ischigualasto and Chañares formations, with assemblages of East Antarctica, which together comprise a subprovince that is transitional between Ipswich and Onslow floras. The paleobotanical and palynological content of the coprolites also sheds light on the feeding behaviour of dicynodont producers, suggesting low-feeding habits and non-strict selectivity of the food source.

Tissue-specific heat-induced changes in the expression of ncRNA fragments in Brassica rapa plants

Abstract Non-coding RNA fragments (ncRFs) represent a large spectrum of short ncRNAs processed from precursor ncRNAs such as tRNA, rRNA, snoRNA and several others. Several recent papers suggest that ncRFs are processed in a specific manner in different tissues or in response to stress. Here, we analyzed alterations in the expression of ncRFs in different Brassica rapa tissues in response to heat stress. Specifically, we analyzed the abundance of tRNA fragments (tRFs), rRNA fragments (rRFs), snoRNA fragments (snoRFs) and snRNA fragments (snRFs). The most significant changes in response to heat stress were observed in tRNAGlu and tRNAAsp. Whereas the number of reads mapping to the former one dropped drastically in all tissues but the apical meristem and pollen, the number of reads mapping to the latter significantly increased. Analysis of tRFs showed that three isoacceptors, tRF5′Asp(GUC), tRFGly(UCC) and tRFPseudo(UCC) were severely underrepresented in heat-stressed tissues. Heat also induced changes in the processing of ncRFs from precursor molecules; a bias towards the processing of ncRFs from the 3′ end was even more prominent after the heat stress application. The analysis of predicted targets of ncRFs revealed an enrichment in several groups of genes involved in the response to various stresses. To conclude, our work showed that heat stress results in tissue-specific changes in the expression of ncRFs in Brassica rapa and suggested a tissue-specific regulation of various mRNAs and pathways in response to heat.

Microbial Activity in Peat Soil Treated With Ordinary Portland Cement (OPC) and Coal Ashes

Peat soil is a cumulative of decayed plant fragment which developed as a result of microbial activity. The microbes degrade the organic matter in the peat soils by the production of hydrolysis enzyme. The least decomposed peat, known as fibric peat has big particles and retain lots of water. This made peat having high moisture content, up to 1500 %. The most decomposed peat known as sapric peat having fines particles and less void ratio. The present study aimed to understand the effects of solidification process on the bacterial growth and cellulase (CMCase) enzyme activity. Two types of mixing were designed for fibric, hemic and sapric peats; (i) Ordinary Portland cement (OPC) at an equal amount of dry peat, with 25 % of fly ash (FA) and total of coarse particle, a combination of bottom ash and fibre of 22 – 34 %, (ii) fibric peat was using water-to-binder ratio (w/b) = 1, 50% OPC, 25 % bottom ash (BA) and 25 % FA. For hemic and sapric peat, w/b=3 with 50 % OPC and 50 % BA were used. All samples were prepared triplicates, and were cured for 7, 14, 28 and 56 days in a closed container at room temperature. The results revealed that the first mix design giving a continuous strength development. However, the second mix design shows a decreased in strength pattern after day 28. The influence of the environment factors such as alkaline pH, reduction of the water content and peat temperature has no significant on the reduction amount of native microbes in the peat. The microbes survived in the solidified peat but the amount of microbes were found reduced for all types of mixing Fibric Mixed 1 (FM1), Hemic Mixed 1(HM1) and Sapric Mixed 1 (SM1) were having good strength increment for about 330 – 1427 % with enzymatic activity recorded even after D56. Nevertheless, with increase in the strength development through curing days, the enzymatic activities were reduced. For the time being, it can be concluded that the microbes have the ability to adapt with new environment. The reactivity of the microbes relates with the strength of solidified peat.

Fungal sporulation in a Permian plant fragment from Antarctica

Documented evidence of fungi from the Permian of Antarctica mostly consists of dispersed remains that do not provide the whole complement of diagnostic features necessary to determine even broad systematic affinities. A dense cluster of > 250 fungal spores occurs within a degraded vascular plant (probably glossopteridalean) fragment in Permian permineralized peat from Skaar Ridge, central Transantarctic Mountains, Antarctica. Spores are spheroidal to ovoid, similar to 50 pm in diameter, and possess a massive wall composed of three wall components (wcl-3);one or two canals extend from the spore lumen to the outside. The spores are embedded in a confluent meshwork of tenuous hyphae. Structural similarities exist between the fossil spores and spores produced by certain present-day Mucoromycota, Ascomycota, and Basidiomycota;however, the precise systematic affinities of the fossils cannot be determined. The relationship between the spore producer and its also host plant remains unresolved. Nevertheless, the spatial arrangement of the spores within the plant structure suggests that the fungus required the host for sporulation, and perhaps even influenced plant development for this purpose. This discovery adds to the inventory of distinctive fungal fossils from the Permian of Antarctica and presents a new type of association/interaction between a Permian fungus and a vascular plant.

Holocene relative sea level history and Storegga tsunami run‐up in Lyngen, northern Norway

ABSTRACTWe re‐investigated three isolation basins in Lyngen in Troms, Norway, that contained a mixed facies of terrestrial and marine origin. Here we show that the mixed facies was deposited by the Storegga tsunami. We reconstruct the run‐up of the tsunami to 6–7 m above mean sea level of that time, in agreement with numerical modelling. In addition, our new cores revealed a layer of lake‐gyttja below marine deposits, and radiocarbon ages of plant fragments extracted from that gyttja date the sea level lowstand to 9400 cal a BP. These ages, and our new understanding of the mixed facies as Storegga tsunami deposits, improve the previously published sea‐level curve. The radiocarbon age of a sea urchin, assumed to have been killed in the Storegga tsunami event, shows that the reservoir age of the coastal waters in Troms was 400 years (ΔR = 45 ± 41) at that time − similar to the present‐day value.

Spatial and Temporal Variation of Plant Fragment Removal by Two Species of Atta Leaf-Cutting Ants

Leaf-cutting ants are responsible for much of living plant fragment removal in Neotropical regions, causing major damage in both in natural and agricultural systems. To understand the variation in plant fragment removal by leaf-cutting ants and the influence that temporal and spatial factors have on such variation, we evaluated plant fragments collected by two ant species, Atta laevigata and A. sexdens rubropilosa in different seasons (rainy and dry) and in different forest systems (natural area of cerrado sensu stricto and monoculture of Eucalyptus sp.) in 2014 in Goianesia, Goias, Brazil. Heavier plant fragments were removed during the dry season and in monoculture areas; A. laevigata removed heavier fragments than A. sexdens rubropilosa. Furthermore, we observed a positive association between the weight of collected fragments and the weight of worker ants and higher weights in A. laevigata. The study shows that the weight of plant fragments removed by leaf-cutting ants is conditioned temporally and spatially, and by the ant species involved. More detailed studies of each of these factors are need to better understand the dynamics of these foraging ants and how abiotic and biotic factors affect this process.

Water absorption capacity of soil-incorporated plant leaves can affect N2O emissions and soil inorganic N concentrations

Soil incorporation of aboveground plant residues contributes to enhancement of soil sustainability in agricultural systems with cover crops. However, incorporated plant fragments can affect N2O emissions by acting as micro-scale hotspots of N2O production. We hypothesize that water retention capacity of the incorporated plant material and soil pore-size distribution (PSD) are among the factors influencing the magnitude of N2O emissions from the soil subjected to aboveground plant residue additions. To test this hypothesis we compared CO2 and N2O emissions from two soil materials with contrasting PSD incubated with leaves from two legume species similar in their C and N contents, but differing in physical characteristics of their leaves, i.e., crimson and red clovers. In order to separate the effect of biochemical differences between the two species from the differences in the physical characteristics of their leaves we considered three leaf treatments: (i) intact leaves, (ii) ground leaf material aggregated to resemble the size of the intact leaves, and (iii) ground leaf material uniformly mixed with the soil. The latter two treatments minimized the physical differences between the leaves of the two species. Intact leaves of crimson clover retained more water than the red clover leaves. At the studied 50% of water filled pore space settings, both species retained more water when incubated in the soil material with prevalence of large (>30 μm) pores than in the soil material with prevalence of small (<10 μm) pores. N2O emission from the soil with large pores was greater in the incubations with intact crimson clover leaves than in the incubations with the intact red clover leaves, while no differences between the two clovers were observed in the incubations with ground leaf material. The results indicate that water retention capacity of plant residue influences N2O emissions during residue decomposition in the soils with prevalence of large (>30 μm) pores.

Qualitative and Quantitative Examination of Algal Flora in the Gut Content of &lt;i&gt;Tanypus punctipennis&lt;/i&gt; Meigen, 1818

Larval chironomids feed on algae, diatomae, detritus, decaying plant and animal fragments. The larvae in turn are food for other carnivore and omnivore animals. Thus, larval chironomids have a very important role in the aquatic food cycle. In this study, the algal flora in the stomachs of Tanypus punctipennis , which is known as a very common species in Turkish Thrace, was examined in terms of qualitative and quantitative factors. It was found that Bacillariophyta was the dominant group with 43 taxa in the stomach of T. punctipennis. It was followed by Cyanophyta with 7 taxa, Euglenophyta with 6 taxa, Chlorophyta with 4 taxa, Carophyta with 2 taxa, and Rhodophyta with 1 taxa.