Mountainous Island Research Articles

Differentiation of the Chestnut Tiger Butterfly Parantica sita (Lepidoptera: Nymphalidae: Danainae) in China

The chestnut tiger butterfly, Parantica sita (Kollar) (Lepidoptera: Nymphalidae: Danainae), occurs in Asia, along the Himalayas, and into the Malayan region. Previous studies found three types of mitogenomes with substantial genetic divergence in samples from China. To clarify the level of differentiation within P. sita, we investigated both molecular data and morphological features in 429 individuals from China. Upon examination, mitochondrial cytochrome oxidase subunit I (COI) sequences showed three substantially diverged haplotype groups. Based on microsatellite genotypes, the samples divided into three clusters that were consistent with the COI haplotype groups. With that genetic data, we named three distinguishable P. sita lineages: PS-A, PS-B, and PS-C. We also found obvious morphological differences in wing color, male sex brand, and genitalia structures among the three lineages. According to the published structure of male genitalia, that of PS-A is identical to that of P. s. sita, and that of PS-B is identical to that of P. pedonga. Based on all the results, we tentatively propose dividing P. sita into three species: PS-A (the former P. s. sita) is the typical Parantica sita [Kollar, (1844)], mainly distributed in southwestern China; PS-C (the former P. s. niphonica) is elevated to full species as Parantica niphonica (Moore, 1883), distributed in Taiwan Island and Japan; and PS-B will be Parantica pedongaFujioka, 1970, mainly distributed in Tibet and western Sichuan. Divergence time estimates showed that PS-A separated from the PS-B + PS-C clade about 8.79 million years ago (Ma), when the Hengduan Mountains underwent an appreciable elevation increase, isolating the Tibet population from the others. PS-B and PS-C diverged about 4.87 Ma, in accord with the formation of Taiwan Island mountains. The founder effect may explain why PS-C’s genetic diversity is lower than that of the other clades.

Insights into tropical cloud chemistry in Réunion (Indian Ocean): results from the BIO-MAÏDO campaign

Abstract. We present here the results obtained during an intensive field campaign conducted in the framework of the French “BIO-MAÏDO” (Bio-physico-chemistry of tropical clouds at Maïdo (Réunion Island): processes and impacts on secondary organic aerosols' formation) project. This study integrates an exhaustive chemical and microphysical characterization of cloud water obtained in March–April 2019 in Réunion (Indian Ocean). Fourteen cloud samples have been collected along the slope of this mountainous island. Comprehensive chemical characterization of these samples is performed, including inorganic ions, metals, oxidants, and organic matter (organic acids, sugars, amino acids, carbonyls, and low-solubility volatile organic compounds, VOCs). Cloud water presents high molecular complexity with elevated water-soluble organic matter content partly modulated by microphysical cloud properties. As expected, our findings show the presence of compounds of marine origin in cloud water samples (e.g. chloride, sodium) demonstrating ocean–cloud exchanges. Indeed, Na+ and Cl− dominate the inorganic composition contributing to 30 % and 27 %, respectively, to the average total ion content. The strong correlations between these species (r2 = 0.87, p value: < 0.0001) suggest similar air mass origins. However, the average molar Cl-/Na+ ratio (0.85) is lower than the sea-salt one, reflecting a chloride depletion possibly associated with strong acids such as HNO3 and H2SO4. Additionally, the non-sea-salt fraction of sulfate varies between 38 % and 91 %, indicating the presence of other sources. Also, the presence of amino acids and for the first time in cloud waters of sugars clearly indicates that biological activities contribute to the cloud water chemical composition. A significant variability between events is observed in the dissolved organic content (25.5 ± 18.4 mg C L−1), with levels reaching up to 62 mg C L−1. This variability was not similar for all the measured compounds, suggesting the presence of dissimilar emission sources or production mechanisms. For that, a statistical analysis is performed based on back-trajectory calculations using the CAT (Computing Atmospheric Trajectory Tool) model associated with the land cover registry. These investigations reveal that air mass origins and microphysical variables do not fully explain the variability observed in cloud chemical composition, highlighting the complexity of emission sources, multiphasic transfer, and chemical processing in clouds. Even though a minor contribution of VOCs (oxygenated and low-solubility VOCs) to the total dissolved organic carbon (DOC) (0.62 % and 0.06 %, respectively) has been observed, significant levels of biogenic VOC (20 to 180 nmol L−1) were detected in the aqueous phase, indicating the cloud-terrestrial vegetation exchange. Cloud scavenging of VOCs is assessed by measurements obtained in both the gas and aqueous phases and deduced experimental gas-/aqueous-phase partitioning was compared with Henry's law equilibrium to evaluate potential supersaturation or unsaturation conditions. The evaluation reveals the supersaturation of low-solubility VOCs from both natural and anthropogenic sources. Our results depict even higher supersaturation of terpenoids, evidencing a deviation from thermodynamically expected partitioning in the aqueous-phase chemistry in this highly impacted tropical area.

Impact of Flash Flood Events on the Coastal Waters Around Madeira Island: The “Land Mass Effect”

The Island Mass Effect has been primarily attributed to nutrient enhancement of waters surrounding oceanic islands due to physical processes, whereas the role of land runoff has seldom been considered. Land runoff can be particularly relevant in mountainous islands, highly susceptible to torrential rainfall that rapidly leads to flash floods. Madeira Island, located in the Northeast Atlantic Ocean, is historically known for its flash flood events, when steep streams transport high volumes of water and terrigenous material downstream. A 22-year analysis of satellite data revealed that a recent catastrophic flash flood (20 February 2010) was responsible for the most significant concentration of non-algal Suspended Particulate Matter (SPM) and Chlorophyll-a at the coast. In this context, our study aims to understand the impact of the February 2010 flash flood events on coastal waters, by assessing the impact of spatial and temporal variability of wind, precipitation, and river discharges. Two specific flash floods events are investigated in detail (2 and 20 February 2010), which coincided with northeasterly and southwesterly winds, respectively. Given the lack of in situ data documenting these events, a coupled air-sea-land numerical framework was used, including hydrological modeling. The dynamics of the modeled river plumes induced by flash floods were strongly influenced by the wind regimes subsequently affecting coastal circulation, which may help to explain the differences between observed SPM and Chlorophyll-a distributions. Model simulations showed that during northeasterly winds, coastal confinement of the buoyant river plume persisted on the island’s north coast, preventing offshore transport of SPM. This mechanism may have contributed to favorable conditions for phytoplankton growth, as captured by satellite-derived Chlorophyll-a in the northeastern coastal waters. On the island’s south coast, strong ocean currents generated in the eastern island flank promoted strong vertical shear, contributing to vertical mixing. During southwesterly winds, coastal confinement of the plume with strong vertical density gradient was observed on the south side. The switch to eastward winds spread the south river plume offshore, forming a filament of high Chlorophyll-a extending 70 km offshore. Our framework demonstrates a novel methodology to investigate ocean productivity around remote islands with sparse or absent field observations.

Erythemal and vitamin D weighted solar UV dose-rates and doses estimated from measurements in mainland France and on Réunion Island.

Solar UV radiation causes beneficial and detrimental changes in human health. International and national Health agencies recommend avoiding sun exposure when the solar rays are strongest (typically 2h before and after solar noon). In this study we detail and refine such recommendations. We estimated biologically-effective radiation (inductive of erythema and pre-vitamin D) using spectral solar UV radiation measurements on a horizontal plane at three French sites equipped with spectroradiometers: Villeneuve d'Ascq (VDA) (North of France); Observatoire de Haute-Provence (OHP) (French Southern Alps); and Saint-Denis de La Réunion (SDR) on Réunion Island, in the Indian Ocean. These sites are very different: VDA is a semi-urban site in a flat region, OHP a rural mountainous site and SDR a coastal urban site on a small mountainous island. Biologically active radiation was analyzed by studying erythema induction and measuring pre-vitamin D synthesis. Dose-rates, doses and times for sunburn induction and vitamin D production were derived. Regarding the level of vitamin D dose considered here (1000IU), we found that at mainland sites time required for vitamin D synthesis was relatively long, even around solar noon, in winter months this could be 2-3h for phototype II individuals exposing their face and hands. In the tropics vitamin D could always be synthesized in a reasonable time (e.g. 20min in winter). By contrast, in summer, the required duration times (exposing face, hands, arms and legs) are very short, approximately 2-4min on the mainland and 1min in the tropics for phototype II individuals. In all skin phototypes the duration of sun exposure required to induce erythema was generally longer than that to produce vitamin D. These quantitative results, obtained using an instrument measuring on a horizontal plane and with an unobstructed view, do not represent realistic values for human exposure. To account for realistic human body exposure, received doses and times of exposure were adjusted. Our study shows that, mostly in summer, the time periods where limited solar exposure is recommended should be extended, especially at low latitude locations.

Dynamics of southern beech (Nothofagaceae) stands in the lowland North Island of New Zealand

ABSTRACT In south-central Chile, the dynamics of southern beech (Nothofagaceae) stands vary predictably along climatic gradients. Beeches form persistent stands at high elevations, but their establishment on lowland sites depends mainly on catastrophic disturbances. In New Zealand, nearly all studies of beech forest dynamics to date have reported all-sized, persistent populations. However, previous work has focused largely on the South Island or on North Island mountains, where beeches are widespread and often dominant. Little is known about beech dynamics in the warm North Island lowlands, where beeches are less common. We aimed to clarify the circumstances that enable beeches to establish on lowland sites in the North Island. We measured population structures of beeches and associated species on 11 plots distributed across a range of climate, lithology and topography. On sites where the most shade-tolerant broadleaved trees were absent or uncommon, all-sized populations showed that beech regeneration did not depend on major disturbances. These stands were located mostly on steep faces or ridges with soil carbon:nitrogen ratios > 18, usually with ericaceous understoreys. On sites with higher N availability, where shade-tolerant broadleaved trees were abundant, beech populations were generally sparser, with restricted age ranges. One of these ± even-aged beech stands appeared to have established after windthrow, the other four after fires. Recent dieback of Weinmannia racemosa associated with insect attack had resulted in another wave of beech regeneration in one of the post-fire stands. Establishment on landslides appears to only rarely enable beeches to capture new sites in the lowland North Island. We conclude that beeches form stable self-replacing stands on lowland North Island sites with low nitrogen availability, but that exogenous disturbances occasionally enable beeches to establish as pioneers on sites with higher nitrogen availability. The early successionalrole commonly seen in lowland south-central Chile thus appears less widespread in New Zealand.

Characterization and evolution of the lowland tropical rain forest of the smallest oceanic Gondwana fragments, with implications for restoration and invasion ecology

The Seychelles granitic islands have been small, mid-oceanic, equatorial, mountainous and moist islands for at least 50 million years, with an uninterrupted vegetation cover since their separation from Gondwana. Therefore, unlike hotspot oceanic islands that drastically vary in environmental heterogeneity according to their age, the Seychelles can provide observational data where evolutionary time is de-correlated from habitat heterogeneity. In this paper, we aim to describe for the first time its most widespread, least known, and most threatened ecosystem type: the lowland rain forest. Surprisingly, this had never been done before and the reason is simply that only 6.5 % of those forests have survived untouched by the 2.5 centuries of human presence on these islands. We set six permanent vegetation plots within the largest (ca. 50 ha) and best-preserved relict of this forest, plus four permanent plots in a nearby site (1 km away) that is ecologically homologous but has been intensively modified, abandoned for the last 40 years and which is now a structurally mature late secondary forest. Each plot covered 500 m2 and all vascular plants were inventoried in a series of subplots corresponding to different strata. Within the 0.5 ha of surveyed forest, we observed 35 native species (17 canopy/under-canopy trees, 8 shrubs or small understorey trees, and 10 herbs), of which 11 are endemic (31 %). All plots within the natural forest site were floristically and structurally very similar. Their flora (within just 500 m2) represented about 87 to 92 % of the total flora of the Seychelles lowland mesic forests (defined as an ecological group). In addition, the three most dominant under-canopy trees corresponded to paleo-endemic species having the particularity to be both climax and pioneer trees, which is very unusual. Our study also shows that exotic species were hardly present in undisturbed natural forests but, in disturbed forests, on the other hand, native species were re-colonizing so-called novel ecosystems. Based on these results, we present a list of native species which are appropriate for restoration programs in the Seychelles lowland rain forests, including one that was previously considered as an exotic invasive but which could greatly improve restoration work. Finally, our study sets the basis for long term monitoring of natural ecosystem resilience to invasions on the one hand, and biotic novelty of novel ecosystems on the other.

Genetic ancestry, admixture, and population structure in rural Dominica.

The Caribbean is a genetically diverse region with heterogeneous admixture compositions influenced by local island ecologies, migrations, colonial conflicts, and demographic histories. The Commonwealth of Dominica is a mountainous island in the Lesser Antilles historically known to harbor communities with unique patterns of migration, mixture, and isolation. This community-based population genetic study adds biological evidence to inform post-colonial narrative histories in a Dominican horticultural village. High density single nucleotide polymorphism data paired with a previously compiled genealogy provide the first genome-wide insights on genetic ancestry and population structure in Dominica. We assessed family-based clustering, inferred global ancestry, and dated recent admixture by implementing the fastSTRUCTURE clustering algorithm, modeling graph-based migration with TreeMix, assessing patterns of linkage disequilibrium decay with ALDER, and visualizing data from Dominica with Human Genome Diversity Panel references. These analyses distinguish family-based genetic structure from variation in African, European, and indigenous Amerindian admixture proportions, and analyses of linkage disequilibrium decay estimate admixture dates 5–6 generations (~160 years) ago. African ancestry accounts for the largest mixture components, followed by European and then indigenous components; however, our global ancestry inferences are consistent with previous mitochondrial, Y chromosome, and ancestry marker data from Dominica that show uniquely higher proportions of indigenous ancestry and lower proportions of African ancestry relative to known admixture in other French- and English-speaking Caribbean islands. Our genetic results support local narratives about the community’s history and founding, which indicate that newly emancipated people settled in the steep, dense vegetation along Dominica’s eastern coast in the mid-19th century. Strong genetic signals of post-colonial admixture and family-based structure highlight the localized impacts of colonial forces and island ecologies in this region, and more data from other groups are needed to more broadly inform on Dominica’s complex history and present diversity.

Wildfire and topography drive woody plant diversity in a Sky Island mountain range in the Southwest USA.

AimDrastic changes in fire regimes are altering plant communities, inspiring ecologists to better understand the relationship between fire and plant species diversity. We examined the impact of a 90,000‐ha wildfire on woody plant species diversity in an arid mountain range in southern Arizona, USA. We tested recent fire‐diversity hypotheses by addressing the impacts on diversity of fire severity, fire variability, historical fire regimes, and topography.LocationChiricahua National Monument, Chiricahua Mountains, Arizona, USA, part of the Sky Islands of the US–Mexico borderlands.TaxonWoody plant species.MethodsWe sampled woody plant diversity in 138 plots before (2002–2003) and after (2017–2018) the 2011 Horseshoe Two Fire in three vegetation types and across fire severity and topographic gradients. We calculated gamma, alpha, and beta diversity and examined changes over time in burned versus unburned plots and the shapes of the relationships of diversity with fire severity and topography.ResultsAlpha species richness declined, and beta and gamma diversity increased in burned but not unburned plots. Fire‐induced enhancement of gamma diversity was confined to low fire severity plots. Alpha diversity did not exhibit a clear continuous relationship with fire severity. Beta diversity was enhanced by variation in fire severity among plots and increased with fire severity up to very high severity, where it declined slightly.Main ConclusionsThe results reject the intermediate disturbance hypothesis for alpha diversity but weakly support it for gamma diversity. Spatial variation in fire severity promoted variation among plant assemblages, supporting the pyrodiversity hypothesis. Long‐term drought probably amplified fire‐driven diversity changes. Despite the apparent benign impact of the fire on diversity, the replacement of two large conifer species with a suite of drought‐tolerant shrubs signals the potential loss of functional diversity, a pattern that may warrant restoration efforts to retain these important compositional elements.

Research on fuzzy PID droop Control method for DC microgrid in island mode

In order to solve the problem of difficult power supply in remote mountainous areas and islands, based on the traditional drooping control of DC microgrid, this paper introduces fuzzy PID to realize the self-adjustment of drooping coefficient, which solves the problem of voltage instability of DC bus caused by external environmental conditions and load mutation. MATLAB/SIMULINK simulation results show that the fuzzy PID droop control can effectively reduce the voltage drop, maintain the bus voltage stability, and realize the current sharing of all distributed power sources in the DC microgrid under the load switching condition.

Elevational plumage divergence in the Rufous‐capped Babbler (Cyanoderma ruficeps) on a mountainous island

Environment plays an important role in the evolution of plumage coloration in birds and may also lead to sexual dichromatism if males and females face different selection pressures. Mountains exhibit varying ecological conditions along their elevation gradient that may impose divergent selection on elevationally widespread species, causing intraspecific plumage divergence. For example, UV light environments often vary between montane and lowland habitats, which could potentially cause differences in plumage UV reflection between birds occurring in the two types of habitats. However, few studies have examined the effects of elevation on plumage evolution. In this study, we quantified the plumage coloration of the Rufous‐capped Babbler Cyanoderma ruficeps from montane and lowland habitats on a mountainous island, Taiwan. We aimed to examine whether their plumage showed differences associated with changing ecological environments across the elevational gradient. The results supported that the plumage of babblers occupying montane habitats had higher UV‐reflectance and brightness than that of lowland birds, corresponding to the higher UV intensity in montane than lowland background light environments. The elevational differences were mainly found across the ventral parts of babblers that had relatively higher levels of UV reflectance compared with their dorsal parts. Alternatively, the brighter plumage, with higher UV‐reflectance in montane than lowland birds, might be mediated by physiological adaptation to other ecological factors, such as parasite pressures. The elevational differences in plumage UV‐reflectance and brightness were more dramatic in males than in females. However, we found significant sexual dichromatism in different body parts between montane and lowland babblers in which females had brighter or stronger UV‐associated coloration than males, suggesting that sexual selection has little impact on babbler plumage. Our study suggests the importance of elevational divergent selection associated with UV light or other ecological environments on avian plumage evolution.

THE PHYSIOGRAPHY OF INDIA: AN OVERVIEW

Physiography is a field of geography that studies the physical patterns and processes of the Earth, such as geomorphology, hydrology, soil, rocks, biogeography, and the effects of tectonic forces on landscapes. This paper aimed to discuss the physiographic characteristics of India due to its diverse geographical features by using a systematic search and collection of publications and secondary data. The characteristics of India's physiography were discussed descriptively and visually. This study highlights the fundamental physiographic divisions, sub-divisions, and socioeconomic functions of each type of terrain in India, including the northern mountain range, northern plains, peninsular plateau, coastal plains, and islands (the eastern and western coastal plains, Andaman and Nicobar islands). This overview concluded that the physiography of India is complex, heterogeneous and could be categorized into four divisions with distinct characteristics. In detail, the Himalayan Range is a mountainous region in the northern part of the country which produced by the fold mountain processes. Meanwhile, the Indo-Gangetic Plain was well recognised for its extensive agricultural activities contributed by the Ganges River. India's diverse landforms had a profound impact on the country's cultural and economical development. On the other hand, this study also demonstrated that the plateau region in the country's southern and central regions was geographically diversified. The different landscapes of India influenced the socioeconomic characteristics of the Indian society and consequently supported national development of India.

The Dynamic of Vegetation Growth with Regular Climate and Climatic Fluctuations in a Subtropical Mountainous Island, Taiwan

Vegetation phenology is an integrative indicator of environmental change, and remotely–sensed data provide a powerful way to monitor land surface vegetation responses to climatic fluctuations across various spatiotemporal scales. In this study, we synthesize the local climate, mainly temperature and precipitation, and large-scale atmospheric anomalies, El Niño-Southern Oscillation (ENSO)-connected dynamics, on a vegetative surface in a subtropical mountainous island, the northwest Pacific of Taiwan. We used two decadal photosynthetically active vegetation cover (PV) data (2001–2020) from Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance data to portray vegetation dynamics at monthly, seasonal, and annual scales. Results show that PV is positively related to both temperature and precipitation at a monthly timescale across various land cover types, and the log-linear with one-month lagged of precipitation reveals the accumulation of seasonal rainfall having a significant effect on vegetation growth. Using TIMESAT, three annual phenological metrics, SOS (start of growing season), EOS (end of growing season), and LOS (length of growing season), have been derived from PV time series and been related to seasonal rainfall. The delayed SOS was manifestly influenced by a spring drought, <40 mm during February–March. The later SOS led to a ramification on following late EOS, shorter LOS, and reduction of annual NPP. Nevertheless, the summer rainfall (August–October) and EOS had no significant effects on vegetation growth owing to abundant rainfall. Therefore, the SOS associated with spring rainfall, instead of EOS, played an advantageous role in regulating vegetation development in this subtropical island. The PCA (principal component analysis) was applied for PV time series and explored the spatiotemporal patterns connected to local climate and climatic fluctuations for entire Taiwan, North Taiwan, and South Taiwan. The first two components, PC1 and PC2, explained most of data variance (94–95%) linked to temporal dynamics of land cover (r > 0.90) which was also regulated by local climate. While the subtle signals of PC3 and PC4 explained 0.1–0.4% of the data variance, related to regional drought (r = 0.35–0.40) especially in central and southwest Taiwan and ENSO-associated rainfall variation (r = −0.40–−0.37). Through synthesizing the relationships between vegetation dynamics and climate based on multiple timescales, there will be a comprehensive picture of vegetation growth and its cascading effects on ecosystem productivity.

Convection Initiation Associated With Ambient Winds and Local Circulations Over a Tropical Island in South China

AbstractConvection is highly active on tropical islands. Based on a 3‐year radar climatology over Hainan Island, a mountainous tropical island in South China, we identified a distinct spatial dependence of convection initiation (CI) on the speed of the large‐scale low‐level flow. Convection initiates most prominently over the lee‐side plains in high‐wind conditions while over mountains in low‐wind conditions. Quasi‐idealized numerical simulations suggest that mountain ridges stimulate the formation and growth of horizontal convective rolls (HCRs) over the lee‐side plains in high‐wind conditions. These HCRs subsequently intersect with sea‐breeze fronts, which enhances the low‐level convergence favoring CI on the lee‐side plains of the island. During low‐wind conditions, thermally driven circulations control and favor CI over the mountains during the day. The findings highlight that the response of local circulations to the lower‐troposphere ambient flow and diurnal thermal heating is an important aspect of convection initiation on the island.

Perceived Barriers to the Use of Assisted Colonization for Climate Sensitive Species in the Hawaiian Islands

Conservation actions to safeguard climate change vulnerable species may not be utilized due to a variety of perceived barriers. Assisted colonization, the intentional movement and release of an organism outside its historical range, is one tool available for species predicted to lose habitat under future climate change scenarios, particularly for single island or single mountain range endemic species. Despite the existence of policies that allow for this action, to date, assisted colonization has rarely been utilized for species of conservation concern in the Hawaiian Islands. Given the potential for climate driven biodiversity loss, the Hawaiian Islands are a prime location for the consideration of adaptation strategies. We used first-person interviews with conservation decision makers, managers, and scientists who work with endangered species in the Hawaiian Islands to identify perceived barriers to the use of assisted colonization. We found that assisted colonization was often not considered or utilized due to a lack of expertize with translocations; ecological risk and uncertainty, economic constraints, concerns regarding policies and permitting, concerns with public perception, and institutional resistance. Therefore, conservation planners may benefit from decision tools that integrate risk and uncertainty into decision models, and compare potential outcomes among conservation actions under consideration, including assisted colonization. Within a decision framework that addresses concerns, all conservation actions for climate sensitive species, including assisted colonization, may be considered in a timely manner.

A chemical weathering control on the delivery of particulate iron to the continental shelf

The delivery of potentially reactive iron minerals to the marine environment exerts a major control on ocean and marine sediment biogeochemistry, including the preservation and burial of organic carbon. One aspect of the global iron cycle that has received little attention concerns the phase partitioning of iron in highly chemically-weathered sediments from (sub)tropical mountainous regions, where the sediment is commonly deposited directly onto adjacent continental margins. Here, we report the phase partitioning of particulate iron in surface seafloor sediments deposited from oxic bottom waters along the east coast of China, including the Bohai Sea, Yellow Sea and East China Sea, in addition to the continental shelf region adjacent to the (sub)tropical mountainous island of Hainan in the northern South China Sea. We document highly reactive (FeHR) to total iron (FeT) ratios for the Bohai Sea, Yellow Sea and East China Sea that are typical of global marine sediments deposited under oxic water column conditions. By contrast, FeHR/FeT ratios in Hainan offshore sediments are significantly elevated above normal oxic marine sediments. These Hainan offshore sediments display a strong positive correlation between FeHR/FeT ratios and the chemical index of alteration (CIA) weathering proxy, suggesting that the Fe speciation systematics are controlled by the intensity of chemical weathering. This observation is supported by additional geochemical data and Nd isotope analyses, which suggest a common source lithology for all the studied regions. The Hainan sediments thus document a specific scenario, whereby highly chemically weathered sediments from the mountainous Hainan region bypass the inner shore settings that commonly disproportionately trap Fe (oxyhydr)oxide minerals, depositing high concentrations of FeHR on the adjacent continental margin. Such enrichments likely aid in the preservation of organic carbon in marine sediments, suggesting that organic carbon preservation and burial may be enhanced by elevated FeHR in such settings. We also establish a set of essential criteria for potential recognition of chemical weathering-induced enrichments in FeHR/FeT ratios in ancient marine sediments.

Topographic Amplification of Crustal Subsidence by the Rainwater Load of the 2019 Typhoon Hagibis in Japan

AbstractThe super typhoon Hagibis traveled northeastward through eastern Honshu, Japan, causing disastrous heavy rainfalls along its path on October 11 and 12, 2019. We performed a comprehensive space geodetic study of water brought by this typhoon using a dense network of Global Navigation Satellite System (GNSS) receivers in Japan. First, we studied the time evolution of altitude‐corrected precipitable water vapor field and compare the movement of water vapor centroid with the rain distribution from radar rain gauge analyzed precipitation. The total amount of water vapor derived by spatially integrating precipitable water vapor on land remained steady at ∼20 Gt. The total precipitation by this typhoon was ∼92, and ∼33 Gt of it fell onto the land area of eastern Honshu. Next, we studied crustal subsidence caused by the typhoon rainwater as surface load. The GNSS stations located under the typhoon path temporarily subsided 1–2 cm on the landfall day and the subsidence mostly recovered on the next day. Using the vertical crustal movement data, we estimated the distribution of surface water in eastern Honshu assuming the layered spherical earth. The amount of the surface load on October 12 was ∼71 Gt, which significantly exceeds the cumulative rainfall on land. We consider that the excess subsidence largely originates from the selective deployment of GNSS stations in the concave topography, for example, along valleys and within basins, in the mountainous Japanese Islands.

Stratospheric gravity waves over the mountainous island of South Georgia: testing a high-resolution dynamical model with 3-D satellite observations and radiosondes

Abstract. Atmospheric gravity waves (GWs) play an important role in atmospheric dynamics but accurately representing them in general circulation models (GCMs) is challenging. This is especially true for orographic GWs generated by wind flow over small mountainous islands in the Southern Ocean. Currently, these islands lie in the “grey zone” of global model resolution, where they are neither fully resolved nor fully parameterised. It is expected that as GCMs approach the spatial resolution of current high-resolution local-area models, small-island GW sources may be resolved without the need for parameterisations. But how realistic are the resolved GWs in these high-resolution simulations compared to observations? Here, we test a high-resolution (1.5 km horizontal grid, 118 vertical levels) local-area configuration of the Met Office Unified Model over the mountainous island of South Georgia (54∘ S, 36∘ W), running without GW parameterisations. The island's orography is well resolved in the model, and real-time boundary conditions are used for two time periods during July 2013 and June–July 2015. We compare simulated GWs in the model to coincident 3-D satellite observations from the Atmospheric Infrared Sounder (AIRS) on board Aqua. By carefully sampling the model using the AIRS resolution and measurement footprints (denoted as model sampled as AIRS hereafter), we present the first like-for-like comparison of simulated and observed 3-D GW amplitudes, wavelengths and directional GW momentum flux (GWMF) over the island using a 3-D S-transform method. We find that the timing, magnitude and direction of simulated GWMF over South Georgia are in good general agreement with observations, once the AIRS sampling and resolution are applied to the model. Area-averaged zonal GWMF during these 2 months is westward at around 5.3 and 5.6 mPa in AIRS and model sampled as AIRS datasets respectively, but values directly over the island can exceed 50 mPa. However, up to 35 % of the total GWMF in AIRS is actually found upwind of the island compared to only 17 % in the model sampled as AIRS, suggesting that non-orographic GWs observed by AIRS may be underestimated in our model configuration. Meridional GWMF results show a small northward bias (∼20 %) in the model sampled as AIRS that may correspond to a southward wind bias compared to coincident radiosonde measurements. Finally, we present one example of large-amplitude (T′≈15–20 K at 45 km altitude) GWs at short horizontal wavelengths (λH≈30–40 km) directly over the island in AIRS measurements that show excellent agreement with the model sampled as AIRS. This suggests that orographic GWs in the full-resolution model with T′≈45 K and λH≈30–40 km can occur in reality. Our study demonstrates that not only can high-resolution local-area models simulate realistic stratospheric GWs over small mountainous islands but the application of satellite sampling and resolution to these models can also be a highly effective method for their validation.

Characterizing forest ecosystem services degradation within water catchments. An application to a South West Pacific tropical and semi-arid island (New Caledonia)

New Caledonia is a tropical semi-arid archipelago in the Southwest Pacific. It is a hotspot of threatened biodiversity. Almost entirely covered in forest before human settlement, the mountainous main island, "Grande-Terre", has been subject to fire and mine related deforestation since the 19th century. The degradation of the forest has led to loss of the following ecosystem services: soil stabilization, resilience to anthropogenic pressure, and water buffering. In this study, we quantified the loss of these services through remote sensing, modeling and a statistical approach within water catchment perimeters. The main result is a synthetic geographical database of the water catchment perimeters indicating for each the loss of functions as regards the forest's ecosystem services. In the main island, we found that 54% of the water catchment perimeters were highly degraded, 38% were degraded and only 8% slightly degraded. On this basis, our findings have been presented to public bodies and decision makers in order to raise awareness and to encourage the implementation of appropriate forest management measures.

Human impact, climate and dispersal strategies determine plant invasion on islands

AbstractAimBiological invasions are likely determined by species dispersal strategies as well as environmental characteristics of a recipient region, especially climate and human impact. However, the contribution of climatic factors, human impact, and dispersal strategies in driving invasion processes is still controversial and not well embedded in the existing theoretical considerations. Here, we study how climate, species dispersal strategies, and human impact determine plant invasion processes on islands distributed in all major oceans in the context of directional ecological filtering.LocationSix mountainous, tropical, and subtropical islands in three major oceans: Island of Hawai'i and Maui (Pacific), Tenerife and La Palma (Atlantic), and La Réunion and Socotra (Indian Ocean).TaxonVascular Plants.MethodsWe recorded 360 non‐native species in 218 plots along roadside elevational transects covering the major temperature, precipitation and human impact (i.e., road density) gradients of the islands. We collected dispersal strategies for a majority of the recorded species and calculated the environmental niche per species using a hypervolume approach.ResultsNon‐native species’ generalism (i.e., mean community niche width) increased with precipitation, elevation and human impact but showed no relationship with temperature. Increasing precipitation led to environmental filtering of non‐native species resulting in more generalist species under high precipitation conditions. We found no directional filtering for temperature but an optimum range of most species between 10 and 20°C. Niche widths of non‐native species increased with the prevalence of certain dispersal strategies, particularly anemochory and anthropochory.Main conclusionsPlant invasion on tropical and subtropical islands seems to be mainly driven by precipitation and human impact, while temperature seems to be of little importance. Furthermore, anemochory and anthropochory are dispersal strategies associated with large niche widths of non‐native species. Our study allows a more detailed look at the mechanisms behind directional ecological filtering of non‐native plant species in non‐temperature‐limited ecosystems.

Erratum: Floral Color Diversity: How Are Signals Shaped by Elevational Gradient on the Tropical–Subtropical Mountainous Island of Taiwan?

[This corrects the article DOI: 10.3389/fpls.2020.582784.].