Unimodal Pattern Research Articles

Abundance and Diurnal Activity Rhythm of Stomoxys spp. in a Wildlife-human Interface in Makokou (North East-Gabon)

The aim of the study was to determine the abundance and diurnal activity rhythm of Stomoxyinae at the Ivindo National park and its environs, 14 Vavoua traps were set-up during the rainy season (25th Sept-5th Oct and 21st Oct-9th Nov 2018), in two habitats: the forest, a part of the Ivindo National Park (INP) and village-Town. In the Village-Town habitat, 62141 Stomoxys were caught and regrouped under five species notably 36502 S. omega (58.74%), 24045 S. n. niger (38.69%), 1312 S. xanthomelas (2.11%), 265 S. n. bilineatus (0.43%) and 17 S. calcitrans (0.03%). At the INP, 4645 Stomoxys were caught and regrouped under four species notably 2364 S. n. niger (50.89%), 2153 S. omega (46.35%), 114 S. xanthomelas (2.45%) and 14 S. n. bilineatus (0.30%). Stomoxys were more abundant in the village (517.84 s/t/d) as compared to the INP (44.24 s/t/d). There was a statistically significant difference (P<0.05) in apparent density of Stomoxys in the prospected biotopes. Stomoxys spp. showed a unimodal activity pattern in Village-Town environments and forest sites of the INP. The diurnal activity trend of Stomoxys spp. was sex dependent. This base line data will be used in Stomoxys spp. management in the environs of the INP.

Community of small mammals along an elevational gradient in Biological Reserve of Serra do Japi, municipality of Jundiaí‐SP, Brazil

AbstractStudies of elevational gradients in forests are particularly interesting for the considerable differences that can be observed over short distances, such as in vegetation and temperature. Different taxonomic groups display varying types of distribution patterns along elevational gradients, with unimodal distribution being recognised as the most common pattern. The distribution of species can be affected by a range of factors that include, biotic, spatial, climatic, historic and energetic. Small mammals represent an ideal model for studies about distribution and habitat use as they can be highly abundant, tend to have different diets and use space differently. The aims of this study are to build a comprehensive understanding of the community of small mammals of the Biological Reserve of Serra do Japi and to explore its distribution pattern along elevational gradients. We investigated the influence of biomass of arthropods, fruits and seeds and percentage of ground cover, canopy cover and vertical vegetation at richness and abundance of small mammals at three different elevations. To accomplish this, we used seventy‐two pitfall traps of 63 L to capture small mammals and distributed them equally across three elevations defined as low (880–899 m), intermediate (1046–1089 m) and high (1170–1189 m). Each elevation had three lines or replicas of traps. Throughout the study, we captured one hundred and fourteen individuals belonging to eleven species of small mammals. The presence of rare and endemic species demonstrates the importance of conservation and maintenance of the Biological Reserve of Serra do Japi. In regard to the distribution of species, despite the short gradient range, we found a unimodal pattern and a positive correlation between ground cover (fallen twigs and branches up to 1 m high) and richness and abundance of small mammals. More ground cover can reduce the effects of competition and predation on small mammals’ communities.Abstract in Portuguese is available with online material.

Distribution and Succession Feature of Antibiotic Resistance Genes Along a Soil Development Chronosequence in Urumqi No.1 Glacier of China.

Primary succession of plant and microbial communities in the glacier retreating foreland has been extensively studied, but shifts of antibiotic resistance genes (ARGs) with the glacier retreating due to global warming remain elusive. Unraveling the diversity and succession features of ARGs in pristine soil during glacier retreating could contribute to a mechanistic understanding of the evolution and development of soil resistome. In this study, we quantified the abundance and diversity of ARGs along a 50-year soil development chronosequence by using a high-throughput quantitative PCR (HT-qPCR) technique. A total of 24 ARGs and two mobile genetic elements (MGEs) were detected from all the glacier samples, and the numbers of detected ARGs showed a unimodal pattern with an increasing trend at the early stage (0∼8 years) but no significant change at later stages (17∼50 years). The oprJ and mexF genes encoding multidrug resistance were the only two ARGs that were detected across all the succession ages, and the mexF gene showed an increasing trend along the succession time. Structural equation models indicated the predominant role of the intI1 gene encoding the Class 1 integron-integrase in shaping the variation of ARG profiles. These findings suggested the presence of ARGs in pristine soils devoid of anthropogenic impacts, and horizontal gene transfer mediated by MGEs may contribute to the succession patterns of ARGs during the initial soil formation stage along the chronosequence.

Insights on the effects of pH and Fe(II) regeneration during the chromate sequestration by sulfidated zero-valent iron

Recent studies showed that Fe(II) acts as the major electron donor when sulfidated zero-valent iron (S-ZVI) is used for reductive removal of pollutants. However, few studies have focused on the utilization efficiency and regeneration rate of Fe(II). In this work, the dynamic interaction between pH and S-ZVI for Cr(VI) removal and Fe(II) production was investigated at several pH levels. It was found that the maximum utilization efficiency and regeneration rate of Fe(II) was obtained at pH 5, which is consistent with the Cr(VI) removal by S-ZVI. To further study the role of Fe(II) in Cr(VI) reduction, an innovative binary correlation analysis between aqueous Cr(VI) and Fe(II) was applied with the addition of 1,10-phenanthroline as a way to control Fe(II) availability for Cr(VI) reduction. The analysis revealed that the Cr(VI) sequestration was initially controlled by Fe0/FeS and then by Fe(II), which accounts for the majority of the Cr(VI) sequestration. Additionally, the effects of several operational parameters (e.g., S/Fe ratio, S-ZVI dosage and initial concentration of Cr(VI)) on Cr(VI) removal were also evaluated and the results indicated that the removal of Cr(VI) exhibited a bimodal pattern with increasing S/Fe ratio, but followed a unimodal pattern with increase of S-ZVI dosage and chromium concentration. This study sheds additional insight into the dynamic interaction between pH and Fe(II), which is significant for further improving the efficiency of Fe(II) on contaminants.

Biological soil crusts enhance the recovery of nutrient levels of surface dune soil in arid desert regions

Abstract Revegetation, an effective method for restoring desertified lands, helps enhance the colonization and development of biological soil crusts (BSCs) and improves the nutrient conditions of desert soils. This study aims to shed light on the changes of elemental concentrations and their enrichment in fixed surface soil of sand dunes over a 50-year revegetation chronosequence linked to BSCs of different successional stages in the Tengger desert of China. We investigated the elemental levels of K, Na, Ca, Mg, Mn, Zn, Cu, and Fe in surface soil covered by cyanobacteria-lichen crusts, moss crusts and subsoil. Nutrient enrichment of BSCs and soils were analyzed to reflect the nutrient changes in the revegetated desert ecosystem. Concentrations of K, Na, Ca, Mn, Zn, and Cu in cyanobacteria-lichen crusts were significantly higher than in mobile sand dunes. Nutrient enrichment rate (except for Na) exhibited unimodal patterns, and year 31 was a key turning point after which the rate switched from increasing to decreasing over time. Our long-term study indicated that both cyanobacteria-lichen crusts and moss crusts can effectively improve nutrient accumulation and promote edaphic conditions, which is beneficial to the development and nutrient cycling of desert ecosystems.

How forest gaps shaped plant diversity along an elevational gradient in Wolong National Nature Reserve?

Understanding the underlying ecological processes that control plant diversity within (α-diversity) and among (β-diversity) forest gaps is important for managing natural forest ecosystems, and it is also a prerequisite for identifying the formation and maintenance mechanisms of forest plant communities. In this study, we focused on the interrelationships among habitat type (gap/non-gap plots), gap size, elevation and environmental factors, and we explored their effects on plant diversity (α-diversity and β-diversity). To do this, a total of 21 non-gap (i.e., closed canopy) plots (100 m2) and 63 gap plots, including 21 with large gaps (200–410 m2), 21 with medium gaps (100–200 m2) and 21 with small gaps (38.5–100 m2), were selected along an elevational gradient in a subalpine coniferous forest of southwestern China. Using structural equation models (SEMs), we analyzed how forest gaps affected plant diversity (α-diversity and β-diversity) along an elevational gradient. The results showed that (1) as elevation increased, unimodal patterns of α-diversity were found in different-sized gaps, and β-diversity showed a consistent sinusoidal function pattern in different-sized gaps. The gap size was positively related to α-diversity, but this effect disappeared above 3500 masl. Moreover, the patterns of α-diversity and β-diversity in non-gap plots were irregular along the elevational gradient. (2) SEMs demonstrated that many environmental factors, such as the annual mean air temperature (AMAT), ultraviolet-A radiation (365 nm, UV-A365), ultraviolet-B1 radiation (297 nm, UV-B297), moss thickness (MT), soil carbon/nitrogen ratio (C/N ratio), NH4-N and NO3-N, were significantly affected by elevation, which then affected α-diversity and β-diversity. The photosynthetic photon flux density (PPFD), UV-A365 and UV-B297 were significantly higher in plots with forest gaps than in the non-gap plots. Moreover, the PPFD and UV-A365 were positively and directly affected by gap size. Surprisingly, except for the NH4-N and the C/N ratios, the below-ground environmental factors showed little or no relationships with forest gaps. All of these effects contributed to plant diversity. Overall, the above-ground environmental factors were more sensitive to gap-forming disturbances than the below-ground environmental factors, which affected α-diversity and β-diversity. The predicted pathway in the SEMs of the elevational effects on α-diversity and β-diversity was relatively complicated compared with the effects of forest gaps. These results can provide valuable insights into the underlying mechanisms driving the diversity-habitat relationship in the subalpine coniferous forests of southwestern China.

Species Composition and Diurnal Activity Rhythm of Tabanids (Diptera: Tabanidae) at the Ivindo National Park and Its Environs

An entomological prospection to show the species composition and diurnal activity of tabanids was carried out using 15 Vavoua traps, during the rainy season (25th Sept-5th Oct and 21st Oct-9th Nov 2018), in the secondary forest [Ivindo National Park (INP)] and Village-Town sites in and around the biosphere reserve Ipassa-IRET Makokou in Gabon. In total, 839 tabanids were caught with 747 recorded at INP and regrouped under 11 species of the genus Tabanus [T. taeniola (57.76%), T. ricardae (26.32%), T. par (5.54%), T. ruficrus (3.74%), T. socius (3.74%), T. disjunctus (2.49%), T. marmorosus (0.28%) and T. obscurehirtus (0.14%)]. However, two species of the genus Chrysops [C. dimidiatus (70.83%) and C. silaceus (29.17%)] and one species of the genus Haematopota [H. pluvialis (100%)] were only identified at INP. While in the Village-Town sites, 92 tabanids were caught and regrouped under five species of the genus Tabanus [T. ruficrus (14.13%), T. taeniola (9.78%), T. ricardae (73.91%), T. par (1.09%), and T. marmorosus (1.09%)]. Tabanids were more abundant in the forest (7.12 tabanid/trap/day) as compared to the Village-Town (0.77 t/t/d) with a statistically significant difference (P<0.05). At INP, tabanids showed a unimodal activity pattern with peak attained between 12-14H and in the anthropized milieu (14-16H) and dominated by females.

Effects of reproduction and environmental factors on body temperature and activity patterns of wolverines

BackgroundMammals in the far north are exposed to extreme seasonal changes in environmental conditions, such as temperature and photoperiod, which have notable effects on animal physiology and behaviour. The wolverine (Gulo gulo) is a carnivore with a circumpolar distribution and well-adapted to extreme environmental conditions. Still, ecophysiological studies on free-ranging wolverines are lacking. In this study, we used abdominally implanted body temperature loggers in combination with GPS collars with acceleration sensors on 14 free-ranging wolverines in northern Sweden to study daily and seasonal variation in body temperature and activity patterns. We used generalized additive mixed modelling to investigate body temperature patterns over time and Lomb-Scargle periodogram analysis to analyse circadian rhythms.ResultsWe found that wolverines have an average core body temperature of 38.5 ± 0.2 °C with a daily variation of up to 6 °C. Body temperature patterns varied between reproductive states. Pregnant females showed a distinct decrease in body temperature during gestation. Wolverines were active both in day and night, but displayed distinct activity peaks during crepuscular hours. However, body temperature and activity patterns changed seasonally, with a gradual change from a unimodal pattern in winter with concentrated activity during the short period of day light to a bimodal pattern in autumn with activity peaks around dusk and dawn. Wolverines were less likely to display 24-h rhythms in winter, when hours of day light are limited.ConclusionsThe combination of different biologging techniques gave novel insight into the ecophysiology, activity patterns and reproductive biology of free-ranging wolverines, adding important knowledge to our understanding of animals adapted to cold environments at northern latitudes.

Fish thermoregulation and the promotion of cellular antimicrobial defenses

Despite being ectotherms, reptiles have an ability to thermoregulate which is enhanced by adopting a variety of behavioural mechanisms. Different behavioural postures, the use of retreat sites and selection of microhabitats enable reptiles to maintain their core body temperatures (Tb) above that of ambient temperatures (Ta) in winter or below Ta maximum in summer. This study describes the daily activity patterns of leopard tortoises (Stigmochelys pardalis) in relation to Tb and Ta, and the extent to which leopard tortoises can manipulate their Tb in response to seasonal changes in Ta. Ten and nine leopard tortoises were radio-tracked in 2002 and 2003, respectively and cloacal Tb and behaviours observed. Core Tbs were measured using Thermocron iButtons™ surgically implanted into the body cavities of 4 and 5 adult telemetered tortoises for summer and winter 2003, respectively. There were seasonal differences in the extent to which certain behaviours were practiced and the time of day that these occurred. Leopard tortoises generally had unimodal activity patterns in winter and bimodal ones in summer. In winter tortoises were active at lower Tbs, and at lower Ta, than in summer. Tortoises maintained their core Tb well below Ta minimum profiles in summer and well above these in winter. Core Tb closely followed the increase in Ta minimum profiles in the mornings, however tortoises exhibited an extended thermal lag when Ta minimum profiles cooled overnight. By using different behavioural mechanisms in summer and winter, leopard tortoises maintained their core Tb at different levels compared with Ta minimum and maximum profiles. Consequently although they are ectotherms, they maintained their core Tb independent of Ta.

Ontogenetic shifts in resource allocation and potential defense syndromes of a tropical medicinal treelet

Variation of plant traits across ontogeny can play an important role in shaping the vital functions of growth, reproduction and defense, depending on the priorities of resource investment. Plant functional traits in seven ontogenetic stages, following complete trajectories, of a tropical light-demanding evergreen medicinal treelet (Rauvolfia vomitoria Afzel.) were examined in a common garden experiment in the field. The highly plastic morph-physiological and potential defense traits showed complex and nonlinear variations with increasing tree height (age), revealing a mostly clear-defined transition at reproductive onset. Leaf photosynthetic rate varied in a unimodal pattern throughout ontogeny, with the highest value occurring at reproductive onset. Except for the oldest plants, priority of resource use in leaves across ontogeny shifted to enhance photosynthetic rate, photosynthetic N and P use efficiencies, and prevention of physical damage (higher leaf thickness, leaf mass per area and lignin concentration), but to decrease carbon-based chemical defense (i.e., total phenolics). Fine root phenolics were relatively stable, but lignin concentration increased throughout ontogeny. With higher levels than fine roots and aboveground parts, the concentrations of an indole alkaloid (i.e. reserpine) increased steadily in coarse roots, especially during the reproductive stages. Whereas, tree growth progressively shifted from the demand of N relative to P, based on the indirect evidence from N:P stoichiometry. Our results demonstrated that, under the conditions of no environmental interference, the pronounced trajectories in functional traits were observed throughout the life cycle of R. vomitoria plants due to strong ontogeny-induced shifts in resource allocation. The synergies or tradeoffs of the defense syndromes differed between and within the classes of defense (i.e., physical versus chemical), and also, between and within above- and below-ground tissues across the ontogenetic developmental stages, which could probably be explained by multiple defense hypotheses. The revealed variations of the growth traits and secondary metabolites of R. vomitoria plants at different developmental stages will be helpful for maximizing the reserpine yield through the suitable cultivation practices.

Depositional age and provenance in the San Luis Formation, Sierras Pampeanas, Argentina: Evidence from detrital zircon studies

The San Luis Formation is one of the lithostratigraphic units constituting the early Paleozoic crystalline basement of the Sierras de San Luis, which are part of the Sierras Pampeanas of central Argentina. The low-grade metamorphic overprint of the San Luis Formation makes it a key unit for the modelling of its sedimentary environment, which belongs to a deep-marine environment. This formation crops out in two belts named as Eastern and Western, whose stratigraphic correlation has not been clarified. Five samples from both belts of the San Luis Formation show U-Pb age distributions of detrital zircons with dominant peaks that are characteristic of orogenic systems of the West Gondwanan landmasses. However, detrital zircon age spectra and maximum depositional ages differ substantially in each belt of the San Luis Formation. While the Western belt displays polymodal age patterns with its most prominent age peaks at ∼635 Ma, a second most important population appears at 535–575 Ma with subordinate groups at 720–775 Ma and 1.7–2.2 Ga; the Eastern belt shows an almost unimodal age pattern dominated by an age peak at ∼535 Ma, with very subordinate peaks at ∼620 Ma, ∼780 Ma and ∼1,017 Ma. Regarding the maximum depositional age, two different ages have been recognized in the Western belt, ∼555 Ma at its bottom and ∼530 Ma at its top; whereas in the Eastern belt the maximum depositional age is ∼515 Ma. The age spectra of detrital zircons from the San Luis Formation record the evolution of the nearby Pampean orogen. At an early stage of exhumation, the Pampean orogenic system chiefly liberated recycled sedimentary detritus containing zircons with Neoproterozoic (∼635 Ma), Mesoproterozoic (∼1,000 Ma) and subordinate amounts of Paleoproterozoic (∼2,200 Ma) ages. Upon advanced unroofing and active erosion, the Pampean sequences sourced first-cycle detritus with latest Neoproterozoic to early Cambrian ages (555–525 Ma). A major conclusion is that the San Luis Formation accumulated in at least two stages, filling successive deep-marine basins that were marginal to the Pampean orogen during and after its latest Neoproterozoic to Cambrian development.

Transformation of soil organic phosphorus along the Hailuogou post-glacial chronosequence, southeastern edge of the Tibetan Plateau

Organic phosphorus (P) accumulates in soil during pedogenesis, yet information on the composition and transformation of organic P during the early stages of soil development remains scarce. We studied the top 5 cm of mineral soil immediately beneath the organic horizon from six sites (0, 35, 45, 57, 85 and 125 years) along the Hailuogou glacier foreland chronosequence, on the southeastern edge of the Tibetan Plateau. Phosphorus compounds in the soils were determined by NaOH–EDTA extraction and solution phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. Extractable P was dominated by phosphomonoesters (up to 51.5%) and orthophosphate (37.9–44.6%) throughout the chronosequence. The phosphomonoesters were mainly hydrolysis products of RNA and phospholipids and followed a unimodal pattern with soil age, with maximum concentration at the 57-year-old site. myo-Inositol hexakisphosphate was not detected, although scyllo-inositol hexakisphosphate accounted for 4.7–9.3% of the extracted P and d-chiro- and neo-inositol hexakisphosphates occurred small amounts in a few soils (1.1–3.3% of the extracted P). DNA accounted for 4.0–8.3% of extracted P and increased continuously along the chronosequence, associated with increased inputs of plant and microbial residues and stronger sorption to soil surfaces during the rapid decline in soil pH. Pyrophosphate, an inorganic polyphosphate, occurred in small concentrations (up to 5.0%) that fluctuated with soil age. We conclude that organic P compounds accumulate rapidly in the top mineral soil during the early stages of pedogenesis, predominantly as relatively labile compounds from plant and microbial residues.

Individual Daily and Seasonal Activity Patterns in Fox Squirrels (Sciurus niger) Quantified by Temperature-Sensitive Data Loggers

Almost all publications on the activity of tree squirrels have reported average patterns for the observed group or population and provided little information about the variability of these patterns in individual animals. As natural selection operates mainly on the level of individual animals, detailed data about the everyday life of single individuals and field data of high complexity are needed. This study provides low disturbance continuous recording of the diurnal/circadian activity cycle of individual fox squirrels (Sciurus niger) in a natural setting, which allowed us to document the intra-individual and inter-individual pattern variation over the seasons. The daily onsets and offsets of activity were inferred from recordings of skin temperature using iButtons attached to the necks of 14 individual squirrels over almost four years resulting in 25 continuous records totaling 1353 days. All squirrels were clearly diurnal but varied greatly in the number of daily activity bouts showing predominantly unimodal and bimodal patterns. Variations in activity patterns were related mostly to the seasons, followed by the inter-individual variability between squirrels. Fox squirrels spent 66-68% of the day in their nests in spring, summer and fall, and 77% in winter. In the same season, individual squirrels exited their nests at about the same time every morning. In summer, they left their nests about 3 hours earlier in the morning than in winter. The timing of first exits was significantly correlated with the number of daily nest exits and total out-of-nest time (ONT), and both variables were significantly correlated with both photoperiod and daily maximum temperature. Squirrels studied simultaneously showed substantial day-to-day variability in both number of daily exits and total ONT that either matched or exceeded the inter-individual variability. Many squirrels left their nests occasionally during the night, while about half occasionally spent entire nights outside an insulated nest. The timing of nest entries and exits, the modality of the activity pattern, the daily proportion of rest, and the occurrence of activity during the typically inactive time of the activity cycle are all aspects of an animal’s activity pattern. They should therefore receive more attention for the characterization of species-specific behavior.

Circadian rhythms in the locomotor activity of the spiders Carrhotus xanthogramma (Salticidae) and Philodromus cespitum (Philodromidae): Temporal patterns and sexual differences

Circadian rhythms play an essential role in the adaptation of organisms to the environment and may show species-specific or sex-specific differences even within a closely related taxonomic group. Although spiders (Araneae) are sexually dimorphic in several morphological and behavioural features, there are very few studies on the sex-specific differences in their biological rhythms. This study evaluated the circadian rhythm in the locomotor activity of two agrobiont hunting species of spider, Carrhotus xanthogramma (Latreille, 1819) (Salticidae) and Philodromus cespitum (Walckenaer, 1802) (Philodromidae), under natural photoperiod conditions. Particular attention was paid to possible differences between the sexes in both species. We found that C. xanthogramma is a strictly diurnal species with a mean activity peak in the morning in both sexes and the females are more active than males. The locomotor activity rhythm of males was richer in ultradian (shorter than a day but longer than an hour) components, although the relative power of these components was negligible compared to the main, 24-h period component. In accordance with these results, the diel pattern of locomotor activity of C. xanthogramma can be described by a unimodal cosine curve. In contrast to C. xanthogramma, both sexes of Ph. cespitum showed cathemeral activity (i.e., activity occur within both the light and dark portions of the daily cycle) and females and males follow quite different activity schedules: females were most active at night, shortly before nautical dawn, whereas males were most active early in the morning. Unlike C. xanthogramma, Ph. cespitum has more ultradian components, with higher relative power especially in females, where besides the 24-h circadian component there is a particularly strong 12-h ultradian period. Based on these factors, females of Ph. cespitum show a bimodal and males a unimodal pattern.

Diversity, ecology, and seasonality of hard ticks (Acari: Ixodidae) in eastern Croatia.

The diversity of hard tick fauna was studied in different forest communities in 48 localities of eastern Croatia using the dragging-flagging method and by hand from ten different vertebrate hosts. A total of 2,225 specimens comprising seven species in three genera were identified. Ixodes ricinus, the most abundant species (72.8% of all collected specimens) was recorded in 44 localities, followed by Dermacentor reticulatus in 19 localities, while the other five species (D. marginatus, H. concinna, H. inermis, I. canisuga, and I. hexagonus) were recorded in fewer localities. The highest ratio (67% of collected ticks) was in the adult stage with the predominance of females. The numbers of collected females, males, and nymphs of I. ricinus and H. concinna differed significantly. Ten new tick-host associations in Croatia were recorded. Fifty-three animals were infested with one tick species. Single species infestation with I. ricinus was found in 45.8% of animals, followed by D. reticulatus with 25.4%, D. marginatus with 10.2%, H. inermis and I. hexagonus with 3.4%, and I. canisuga with 1.7%. Coinfestation with two species of ticks were recorded in six animals. Ixodes ricinus, H. inermis, and D. reticulatus showed bimodal seasonal activity; for other species unimodal activity patterns were recorded.

The impact of sea-salt aerosols on particulate inorganic nitrogen deposition in the western Taiwan Strait region, China

Sea-salt aerosol (SSA) has significant impact on the formation of secondary nitrate and its dry deposition in the coastal region. In this study, size-segregated aerosols were collected for water-soluble ions analysis in the coastal cities and sea cruises in the western Taiwan Strait of China from 2016 to 2017 to investigate the impact of SSA on particulate inorganic N deposition. The size distributions of NH4+ were characterized by a unimodal pattern peaking at 0.44–1.0 μm while NO3− exhibited typical bimodal distributions peaking at 0.44–1.0 μm and 2.5–10 μm. Furthermore, the fine mode peaks of NO3− became insignificant or disappeared in summer and fall due to the volatilization and dissociation of NH4NO3 at higher temperatures. Elevated sea-salt contributions in the largest size bin (>16 μm) during sea cruises were attributed to vessel induced wave breaking, while there was no peak for NO3− at this range due to its short atmospheric lifetime. Although the concentrations of particulate NH4+-N showed higher levels than those of NO3−-N for both coastal and marine aerosols, the dry deposition fluxes of the particulate NO3−-N were significant higher than those of the particulate NH4+-N due to their different size distributions. The contribution of SSA to particulate inorganic N deposition was estimated on average to be 20.33% and 36.91% in the coastal and offshore region, respectively, assuming all of the chlorine depletion was caused by the reaction between nitric acid and SSA in the coarse mode. In addition, dry deposition fluxes using constant deposition velocities for fine/coarse particles and NH4+/NO3− were higher than those using size-dependent dry deposition velocities. Considering the increasing human activities at the coastal urban zone in the western Taiwan Strait, the atmospheric N deposition could have an important ecological impact on the marine environment that is already under pressure from riverine inputs and urban waste discharges.

Strongly aligned coastal boulders on Ko Larn island (Thailand): a proxy for past typhoon‐driven high‐energy wave events in the Bay of Bangkok

AbstractRecent studies of elevated carbonate boulder deposits on several rock islands near Bangkok have indicated that Thailand's capital city may not be as protected from typhoon strikes as previously thought. Here, new evidence is presented for past high‐energy wave (HEW) events in the form of statistically significant patterns of boulder alignment on exposed rocky shorelines of Ko Larn island. The long‐axis orientations of 193 coastal sandstone boulders were analysed across four study sites. Several scenarios for the unimodal, bimodal, and polymodal patterns found can be envisaged. Either the most recent HEW event was the strongest—in which case most clasts were rearranged unimodally (one observation site), or the strongest HEW event was earlier and subsequent weaker ones realigned only smaller boulders to produce bimodal or polymodal patterns (three observation sites). Inferred northeastward or eastward onshore flow directions are consistent with palaeo‐typhoons penetrating into the Bay of Bangkok on northwestward curving tracks. The calculated minimum flow velocities required to transport all sampled boulders are 5.5–7.8 m s−1, similar to other findings throughout the Asia‐Pacific region. It was observed that the absence of a fitted boulder geomorphology lends credence to the earlier proposed time frame of 150–200 years between typhoon phases in the upper Gulf of Thailand. The current work has provided additional insights into the characteristics of past HEW events that have a possibility of reoccurring again at some time in the future. Our findings continue to raise awareness for a reassessment of the risks of coastal hazards for the Chao Phraya River delta and densely populated Bangkok, for which storm surge modelling should be an urgent priority, so as to give better perceptions on how typhoon‐driven marine incursion would impact the city.

When Did the Paleotethys Ailaoshan Ocean Close: New Insights From Detrital Zircon U‐Pb age and Hf Isotopes

AbstractWe present new laser ablation (LA)‐multicollector‐inductively coupled plasma mass spectrometry detrital zircon U‐Pb age and Hf isotope data of the Triassic sedimentary rocks from the eastern and western sides of the Ailaoshan suture in SW China, which separate the Indochina and South China blocks. Detrital zircon grains of the Lower‐Middle Triassic sequences from western South China show single age population of 280–237 Ma (peak at 254–251 Ma) with mainly positive εHf(t) values (+0.15 to +9.11, ~60%). The Middle Triassic samples from eastern Indochina also contain single age population of 273–236 Ma (peak at 246–242 Ma), but with mainly negative εHf(t) values (−18.95 to −1.83, ~88%). The unimodal detrital zircon age pattern and Hf isotope features suggest that the Permian‐Triassic magmatic arcs had supplied detritus for the Lower‐Middle Triassic sequences on both sides of the Ailaoshan suture. In contrast, the Upper Triassic sequences on the either side of the suture display similar polymodal age populations at 290–230, 500–400, 850–700, 1000–900, 2000–1800, and 2600–2400 Ma. This indicates a dramatic change in detrital provenance across the Middle‐Late Triassic boundary. We interpret this change to be resulted from the closure of the Paleotethyan Ailaoshan Ocean in the early Late Triassic. The ocean closure and consequent Indochina‐South China continent‐continent collision may have connected the drainage systems of the two blocks, leading to the marked similarities in their post‐Middle Triassic sedimentary provenance.

Regulation effects of temperate broadleaved Korean pine forest on temperature and humidity in Changbai Mountain, China.

Forests can improve climate and regulate micro-environment. The study of forest micro-climate is of great significance to reveal forest ecosystem function and evaluate the benefits of forest ecological environment. With broadleaved Korean pine forest in Changbai Mountain as test material, the diurnal and seasonal variations of the mean, maximum and minimum temperature, relative humidity and surface soil temperature were analyzed based on the meteorological data of flux tower in the forest and nearby meteorological station in the open land from 2003 to 2014. The results showed that air temperature and relative humidity in the forest showed a unimodal U-shaped diurnal pattern, respectively. The diurnal range was 2.31 ℃ and 8.3% lower than that of the open land. The diurnal surface soil temperature tended to be a constant, indicating an alleviating effects of broadleaved Korean pine forest on the diurnal variation of temperature and moisture. The cooling effect was mainly observed in summer, while the warming effect was significant in winter. The air and soil temperatures in forest in summer were 1.30 and 3.91 ℃ lower than those in the open land, and were 2.06 and 5.44 ℃ higher than those in the open land in winter. Forest regulated the maximum and minimum temperatures significantly. On the season scale, the maximum air and soil temperature in forest decreased by 1.80 and 5.45 ℃ in summer, while the minimum air and soil temperature increased by 3.69 and 7.92 ℃ in winter. On the annual scale, the maximum air and soil temperature in forest were 1.60 and 4.99 ℃ lower than those in the open land, and the minimum air and soil temperature were 1.12 and 8.82 ℃ higher than those in the open land, respectively. The regulating effects of forests on soil temperature was stronger than that on air temperature. Forests mainly warmed the air and soil temperature at cold condition.

Soil respiration and its temperature sensitivity among different vegetation types in Beijing mountain area, China.

As an important component of terrestrial ecosystem carbon cycle, soil respiration is a hot topic in the studies of carbon cycle. The temperature sensitivity (Q10) of soil respiration is a critical index to estimate the effects of global warming on soil respiration. Understanding Q10 of different vegetation types is of important significance for assessing the carbon budget of forest ecosystems. We examined soil respiration and its temperature sensitivity in three typical forests (Pinus tabuliformis, Platycladus orientalis, and Quercus variabilis) in the Beijing mountainous area by measuring the soil physical and chemical properties, soil temperature, soil moisture, and soil respiration rate (Rs) during the growing season. The results showed that Rs of three typical vegetation types showed a similar trend with changes of soil temperature and humidity, which showed a unimodal pattern, with minimum value (0.45 μmol·m-2·s-1) in early April and maximum value (3.95 μmol·m-2·s-1) in early July. There were significant differences in Rs and Q10 values among the three vegetation types. Soil temperature and humidity were the important factors affecting soil respiration, together they could explain the seasonal variation of soil respiration rate from 48.1% to 56.7%. The range of Q10 value was between 2.05 and 3.19. There was a significant negative correlation between soil organic carbon content and Q10 under each vegetation type (R2>0.9). Vegetation type, elevation, and soil organic carbon content were important drivers for the variation of Q10.