Entire Island Research Articles

Sant\u2019Imbenia (Alghero): further archaeometric evidence for an Iron Age market square

Lead isotope compositions were determined for 18 metal objects from the archaeological site of Sant’Imbenia, NW Sardinia, dating to the end of the ninth century BCE onwards. The provenance of some objects is unambiguously traced to SW Sardinia; other objects could derive either from central Sardinia or the Iberian coastal ranges. The variety of the provenances attests to a wide trade network that spanned the entire island of Sardinia and extended to the Iberian sites.

Land surface temperature and vegetation cover changes and their relationships in Taiwan from 2000 to 2020

This study reported decadal trends and acceleration patterns of surface temperatures and vegetation conditions in Taiwan from 2000 to 2020. Time series data on Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI), and Land Cover (LC) types were obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Seasonal patterns, decadal trends, and acceleration rates for each LU type were evaluated using the natural cubic spline method and multivariate linear regression. Acceleration patterns were then analyzed using the correlations between derived trends and acceleration rates. Results are provided for the entire island, for sub-regions, and for the smallest area elements of 1 km2. Taiwan has had a significant mean increase in decadal trends of NDVI (95%CI: 0.013–0.025 unit/dec), but not of LST (95%CI: −0.018-0.302 °C/dec). Negative correlation between LST and NDVI was stronger in green coverage areas than in built-up areas. On sub-regional level, a larger increase in surface temperature and tremendous vegetation loss were observed at high elevations in the southern regions of the Central Mountain Range. Meanwhile, the central-western lowlands faced moderately warming temperatures and slight greening. At the pixel level, urbanization and agricultural expansion have caused rising surface temperatures, while afforestation contributes cooling. The rise in temperature in accelerating in the different LC types throughout Taiwan. Despite that, the acceleration patterns of the vegetation index have remained stable in most parts of the island. Although the rates of vegetation growth have not yet declined, practitioners and policymakers need to consider a balanced view of green cities to keep pace with the accelerating temperature conditions.

Ornithogenic vegetation: How significant has the seabird influence been on the Aleutian Island vegetation during the Holocene?

In the Aleutian Islands during the Holocene, terrestrial predators were actually absent; as a result, large seabird colonies thrived along the coasts or across entire islands. Bird guano enriches the soil with nitrogen, which can lead to the formation of highly modified ornithogenic (bird‐formed) ecosystems. For a more detailed investigation of avian influence, we reconstructed more than 10,000‐year‐old vegetation dynamics of the coast of Shemya Island (Near Islands) by pollen analysis. At the initial stages of vegetation development (10,000–4,600 cal year BP), sedge–heather tundra grew in the studied area. A seabird colony existed on Shemya from 4,600 to 2,400 cal year BP according to stable isotope analysis. During a period of at least 2,200 years, nitrogen enrichment led to the development of ornithogenic herb meadows with a high presence of Apiaceae. A long‐term increase in δ15N above 9–10‰ led to radical shifts in vegetation. Noticeable reduction of seabird colonies due to human hunting led to grass‐meadows spreading. After a prolonged decrease δ15N below 9–10‰ (2,400 cal year BP to present), there was a shift toward less productive sedge‐tundra communities. However, the significant enrichment of guano affected only the coastal vegetation and did not alter the inland Shemya Island.

Estimating monthly PM2.5 concentrations from satellite remote sensing data, meteorological variables, and land use data using ensemble statistical modeling and a random forest approach

Fine particulate matter (PM2.5) is associated with various adverse health outcomes and poses serious concerns for public health. However, ground monitoring stations for PM2.5 measurements are mostly installed in population-dense or urban areas. Thus, satellite retrieved aerosol optical depth (AOD) data, which provide spatial and temporal surrogates of exposure, have become an important tool for PM2.5 estimates in a study area. In this study, we used AOD estimates of surface PM2.5 together with meteorological and land use variables to estimate monthly PM2.5 concentrations at a spatial resolution of 3 km2 over Taiwan Island from 2015 to 2019. An ensemble two-stage estimation procedure was proposed, with a generalized additive model (GAM) for temporal-trend removal in the first stage and a random forest model used to assess residual spatiotemporal variations in the second stage. We obtained a model-fitting R2 of 0.98 with a root mean square error (RMSE) of 1.40 μg/m3. The leave-one-out cross-validation (LOOCV) R2 with seasonal stratification was 0.82, and the RMSE was 3.85 μg/m3, whereas the R2 and RMSE obtained by using the pure random forest approach produced R2 and RMSE values of 0.74 and 4.60 μg/m3, respectively. The results indicated that the ensemble modeling approach had a higher predictive ability than the pure machine learning method and could provide reliable PM2.5 estimates over the entire island, which has complex terrain in terms of land use and topography.

Tourist carrying capacity as a sustainability management tool for coral reefs in Caño Island Biological Reserve, Costa Rica

The coral reefs along Caño Island are among the best preserved in the Pacific region of Costa Rica. Owing to its biodiversity, various local communities depend on snorkeling and scuba diving tourism as a major source of income. However, tourism at Caño Island is conducted based on a management plan that lacks regulations and guidelines such as carrying capacity (CC). This investigation establishes the CC for scuba diving and snorkeling tourism in Caño Island to prevent further degradation of its coral reef ecosystems. Data were collected during April–May 2016 (transition season) and February–March 2017 (dry season). Dive sites were characterized based on the coverage of fragile species, presence of endangered and endemic species, and occurrence of key ecological processes (reproduction, feeding, or cleaning). Underwater observations were carried out to assess diver contact rates with the reef, and ultimately, CC was estimated for each location and for the entire island. The results showed that northeastern coast of Caño Island reported the highest cover of fragile benthic species (78%). The highest number of endangered species (50%) and occurrence of key ecological processes (67%) were observed in Diablo (dive site). Analyses revealed that divers made most contact with rocky bottoms (32%), mostly through fins (56%) and hands (31%). Among the fragile species, octocorals suffered the most damage (21%), followed by hard corals (16%). The CC for scuba and snorkeling activities was estimated at 162 persons per day (59,130 per year). Although the current annual visitation is below the CC, the capacity per dive site is currently exceeded. As a precaution measure it is recommended that visits per day do not exceed 162 persons and that each site's CC is respected.

Analysis of Groundwater Quality for Clean Water Supply in Pasaran Island, Bandar Lampung City, Indonesia

Pasaran is the only productive small island functioning as the anchovy and green clam production center in Bandar Lampung. Its water use has, however, increased since its designation as an economically fishery-based development area or minapolitan in 2012. This is due to the fact that groundwater resources in small island ecosystems surrounded by seawaters with a narrow diameter are easily affected by the insistence of seawater. Moreover, population pressure and land-use change are also feared to be affecting groundwater quality. Therefore, this research was conducted to analyze and evaluate groundwater resource quality in Pasaran Island using five wells on the entire island as sampling points selected based on census. The samples were tested for physical, chemical, and biological parameters in the laboratory and compared with water quality standards (Minister of Health’s Regulation No. 32/2007). The results showed relatively low water quality because the samples contained up to 3900 μS/cm salinity, 3771.9 mg/l chlorides, 31.7–141.52 mg/l nitrates, and 6.8–170 MPN/100ml total coliform which exceed the standards for drinking water. Meanwhile, wells 1, 4, and 5 were found to be safe for sanitation-hygiene purposes and well 1 was suitable for public baths even though they are not of drinking quality. This means the groundwater quality generally met Class II-water requirements for clean water supplies.

Integrating Remote Sensing and a Markov-FLUS Model to Simulate Future Land Use Changes in Hokkaido, Japan

As the second largest island in Japan, Hokkaido provides precious land resources for the Japanese people. Meanwhile, as the food base of Japan, the gradual decrease of the agricultural population and more intensive agricultural practices on Hokkaido have led its arable land use to change year by year, which has also caused changes to the whole land use pattern of the entire island of Hokkaido. To realize the sustainable use of land resources in Hokkaido, past and future changes in land use patterns must be investigated, and target-based land use planning suggestions should be given on this basis. This study uses remote sensing and GIS technology to analyze the temporal and spatial changes of land use in Hokkaido during the past two decades. The types of land use include cultivated land, forest, waterbody, construction, grassland, and others, by using the satellite images of the Landsat images in 2000, 2010, and 2019 to achieve this goal to make classification. In addition, this study used the coupled Markov-FLUS model to simulate and analyze the land use changes in three different scenarios in Hokkaido in the next 20 years. Scenario-based situational analysis shows that the cultivated land in Hokkaido will drop by about 25% in 2040 under the natural development scenario (ND), while the cultivated land area in Hokkaido will remain basically unchanged in cultivated land protection scenario (CP). In forest protection scenario (FP), the area of forest in Hokkaido will increase by 1580.8 km2. It is believed that the findings reveal that the forest land in Hokkaido has been well protected in the past and will be protected well in the next 20 years. However, in land use planning for future, Hokkaido government and enterprises should pay more attention to the protection of cultivated land.

Time since first record and population density influence range sizes of non-native plants, but also of native plants, in a chronically overgrazed island

Background and aims − Humans are increasingly introducing species to new regions. It is necessary to understand the processes that drive the expansion of non-native species into these new habitats across multiple spatiotemporal scales.Material and methods − We studied the spatial distribution of the non-native flora (39 species) of Guadalupe Island (246 km2) in the Mexican Pacific. We analyzed how residence time (time since first report in historical sources, 1875–2004) and species attributes (population density, flowering phenology, and individual height) are related with range sizes of non-native plants. To test whether the residence time – range size relationship of non-native plants can result from other factors besides time since their arrival, we compared it to the residence time – range size relationship of native plants. Range sizes were obtained using herbarium data and a systematic field sampling of 110 transects (50 × 2 m) throughout the entire island. We used beta regression to analyze the relationship of range sizes with residence time and species attributes.Key results − Range sizes of non-natives showed a positive relationship with residence time, flower phenology, and notably with plant density, but not with individual height. However, similar relationships were found for native species, casting doubts on whether our results reflect the range expansion rates of non-native species. Conclusions − Our results suggest that the production of large numbers of propagules, both as a result of long reproductive periods and large population sizes, determines to a large extent the rates of range size expansion of non-native species. However, the relationship we found between time since discovery and range size may arise from sampling biases, biological processes, or – most likely – both. This highlights the need for new approaches that allow us to discern the relative contributions of bias and process in our study of non-native species expansion.

Patterns, Trends and Drivers of Water Transparency in Sri Lanka Using Landsat 8 Observations and Google Earth Engine

Addressing inland water transparency and driver effects to ensure the sustainability and provision of good quality water in Sri Lanka has been a timely prerequisite, especially under the Sustainable Development Goals 2030 agenda. Natural and anthropogenic changes lead to significant variations in water quality in the country. Therefore, an urgent need has emerged to understand the variability, spatiotemporal patterns, changing trends and impact of drivers on transparency, which are unclear to date. This study used all available Landsat 8 images from 2013 to 2020 and a quasi-analytical approach to assess the spatiotemporal Secchi disk depth (ZSD) variability of 550 reservoirs and its relationship with natural (precipitation, wind and temperature) and anthropogenic (human activity and population density) drivers. ZSD varied from 9.68 cm to 199.47 with an average of 64.71 cm and 93% of reservoirs had transparency below 100 cm. Overall, slightly increasing trends were shown in the annual mean ZSD. Notable intra-annual variations were also indicating the highest and lowest ZSD during the north-east monsoon and south-west monsoon, respectively. The highest ZSD was found in wet zone reservoirs, while dry zone showed the least. All of the drivers were significantly affecting the water transparency in the entire island. The combined impact of natural factors on ZSD changes was more significant (77.70%) than anthropogenic variables, whereas, specifically, human activity accounted for the highest variability across all climatic zones. The findings of this study provide the first comprehensive estimation of the ZSD of entire reservoirs and driver contribution and also provides essential information for future sustainable water management and conservation strategies.

A Catalogue of Tropical Cyclone Induced Instantaneous Peak Flows Recorded in Puerto Rico and a Comparison with the World’s Maxima

Peak streamflow rates from the Insular Caribbean have received limited attention in worldwide catalogues in spite of their potential for exceptionality given many of the islands’ steep topographic relief and proneness to high rainfall rates associated with tropical cyclones. This study compiled 1922 area-normalized peak streamflow rates recorded during tropical cyclones in Puerto Rico from 1899 to 2020. The results show that the highest peak flow values recorded on the island were within the range of the world’s maxima for watersheds with drainage areas from 10 to 619 km2. Although higher tropical cyclone rainfall and streamflow rates were observed on average for the central–eastern half of Puerto Rico, the highest of all cyclone-related peaks occurred throughout the entire island and were caused by tropical depressions, tropical storms, or hurricanes. Improving our understanding of instantaneous peak flow rates in Puerto Rico and other islands of the Caribbean is locally important due to their significance in terms of flooding extent and its associated impacts, but also because these could serve as indicators of the implications of a changing climate on tropical cyclone intensity and the associated hydrologic response.

Observation and modeling of Hurricane Maria for damage assessment

The human loss due to Hurricane Maria (H-Maria) in the month of September of 2017 was quantified to be more than 4500 casualties in the entire island of Puerto Rico, making it the most devastating storm in US history. Besides, H-Maria left a lasting impact on the Island as it brought to full collapse the electrical power grid rendering the Island entirely out of power for more than ten months. The aim of this work is to fill the gap of the hydro-meteorological processes of this relevant storm due to the limited observational data available. The synoptic observational record shows that the monthly average Sea Surface Temperature of 30 °C, with an anomaly of 0.5 °C as well as low vertical wind shear of 4–8 m/s fueled H-Maria. Simulated (WRF) time series of wind speed is in close resemblance compared with the limited data available from ocean buoys with a simulated and observed peak wind speed of 30 m/s on the southern coast of the Island. The total rainfall for the event was simulated to peak at 762 mm (observed 965 mm) at the center of the Island and was validated with post-hurricane National Weather Service (NWS) rainfall with a Normalized Root Mean Square Error (RMSE) of 0.2. The orographic effects are simulated, reflecting enhancement of the rainfall at high altitudes in the central mountains of the Island. As an example of damage assessment, the risk of failure of the electrical power towers as a function of wind speed and soil saturation is simulated using statistical models for the entire Island, which results in higher risks of failure at the Northwest and center of the Island. These validated results of the storm can also be used as an input for other analysis such as hydrological models to geo-locate regions for risks due to flooding.

Intact landscape promotes gene flow and low genetic structuring in the threatened Eastern Massasauga Rattlesnake.

Genetic structuring of wild populations is dependent on environmental, ecological, and life‐history factors. The specific role environmental context plays in genetic structuring is important to conservation practitioners working with rare species across areas with varying degrees of fragmentation. We investigated fine‐scale genetic patterns of the federally threatened Eastern Massasauga Rattlesnake (Sistrurus catenatus) on a relatively undisturbed island in northern Michigan, USA. This species often persists in habitat islands throughout much of its distribution due to extensive habitat loss and distance‐limited dispersal. We found that the entire island population exhibited weak genetic structuring with spatially segregated variation in effective migration and genetic diversity. The low level of genetic structuring contrasts with previous studies in the southern part of the species’ range at comparable fine scales (~7 km), in which much higher levels of structuring were documented. The island population's genetic structuring more closely resembles that of populations from Ontario, Canada, that occupy similarly intact habitats. Intrapopulation variation in effective migration and genetic diversity likely corresponds to the presence of large inland lakes acting as barriers and more human activity in the southern portion of the island. The observed genetic structuring in this intact landscape suggests that the Eastern Massasauga is capable of sufficient interpatch movements to reduce overall genetic structuring and colonize new habitats. Landscape mosaics with multiple habitat patches and localized barriers (e.g., large water bodies or roads) will promote gene flow and natural colonization for this declining species.

High-resolution probabilistic seismic hazard analysis of West Nusa Tenggara, Indonesia

The interest to build a nuclear power plant in West Nusa Tenggara Province has caused a concern related to the seismic hazard. One of the challenges was that the existing low-resolution national seismic hazard map did not cover the entire islands of West Nusa Tenggara Province. In this paper, preliminary probabilistic seismic hazard analysis of West Nusa Tenggara was performed to complement the existing national seismic hazard map for West Nusa Tenggara. The analysis was carried out using OQ software based on the seismotectonic model and GMPE developed by PUSGEN. Similar seismotectonic model and seismic event trees were implemented using a finer grid spacing of 500–1000 m. The seismotectonic model included active shallow crustal, subduction interface, and background sources with a total number of 50 seismogenic sources and was calculated using 108 GMPE paths. Two hazard levels were considered, each representing 1% and 2% POE in a 100-year return period. A comparison to the existing national seismic hazard map on the PGA level has been presented in this study and yielded a 13–25% difference in the ground acceleration value. Spectral hazard maps representing the shorter period (0.2 s) showed a maximum ground acceleration value of more than 2 g, especially in the northern part of Sumbawa Island. Beyond the longer spectral period (1 s), ground acceleration gradually decreases to the level below the PGA level.

Impacts of Automated Mobility-on-Demand on traffic dynamics, energy and emissions: A case study of Singapore

Technological advancements have focused increasing attention on Automated Mobility-on-Demand (AMOD) as a promising solution that may improve future urban mobility. During the last decade, extensive research has been conducted on the design and evaluation of AMOD systems using simulation models. This paper adds to this growing body of literature by investigating the network impacts of AMOD through high-fidelity activity- and agent-based traffic simulation, including detailed models of AMOD fleet operations. Through scenario simulations of the entire island of Singapore, we explore network traffic dynamics by employing the concept of the Macroscopic Fundamental Diagram (MFD). Taking into account the spatial variability of density, we are able to capture the hysteresis loops, which inevitably form in a network of this size. Model estimation results at both the vehicle and passenger flow level are documented. Environmental impacts including energy and emissions are also discussed. Findings from the case study of Singapore suggest that the introduction of AMOD may bring about significant impacts on network performance in terms of increased VKT, additional travel delay and energy consumption, while reducing vehicle emissions, with respect to the baseline. Despite the increase in network congestion, production of passenger flows remains relatively unchanged.

A Large Spatial Survey of Colistin-Resistant Gene mcr-1-Carrying E. coli in Rivers across Taiwan.

Background: Colistin is one of the last-line antimicrobial agents against life-threatening infections. The distribution of the colistin resistance gene mcr-1 has been reported worldwide. However, most studies have focused on the distribution of mcr-1-positive bacteria in humans, animals, food, and sewage; few have focused on their distribution in natural environments. Method: We conducted a large spatial survey of mcr-1-positive Escherichia coli at 119 sites in 48 rivers, covering the entire island of Taiwan. We investigated the relationship between the livestock or poultry density in the surveyed riverine area and the number of mcr-1-positive E. coli in the river water. We then sequenced and characterized the isolated mcr-1-positive plasmids. Results: Seven mcr-1 positive E. coli were isolated from 5.9% of the sampling sites. The mcr-1-positive sites correlated with high chicken and pig stocking densities but not human population density or other river parameters. Four of the mcr-1-positive E. coli strains harbored epidemic IncX4 plasmids, and three of them exhibited identical sequences with a size of 33,309 bp. One of the plasmids contained identical 33,309 bp sequences but carried an additional 5711-bp transposon (Tn3 family). To our knowledge, this is the first demonstration that mcr-1-carrying IncX4 plasmids can contain an insertion of such transposons. All mcr-1-positive isolates belonged to phylogenetic group A and harbored few known virulence genes. Conclusion: This study showed a positive relationship between the number of mcr-1-positive sites and high livestock and poultry density. The sequencing analyses indicated that the epidemic plasmid in the mcr-1 isolates circulates not only in humans, animals, and food but also in the associated environments or natural habitats in Taiwan, suggesting that the surveillance of antibiotics-resistance genes for livestock or poultry farm quality control should include their associated environments.

Obsidian in prehistoric complexes of the southern Kurile islands (the Russian Far East): A review of sources, their exploitation, and population movements

Obsidian provenance studies in the southern Kuriles (Kunashir and Iturup islands), part of the insular Russian Far East, are reviewed and summarized for the first time. The sites analyzed belong to the Jomon (ca. 7300–2500 BP), Epi-Jomon (ca. 2500–1400 BP), and Okhotsk (ca. 1400–800 BP) cultural complexes, with particular attention given to the well-studied Yankito 2 site. The main sources of high-quality volcanic glass for the southern Kuriles were on the neighboring Hokkaido Island—Oketo and Shirataki (ca. 140–390 km away). The presence of obsidian at an Epi-Jomon site on southern Kunashir Island originating from remote sources on the Kamchatka Peninsula ca. 1290–1440 km away is an important contribution to understanding the prehistoric contacts and population dispersals that occurred within insular Northeast Asia. This is also supported by paleoanthropological and DNA data from Epi-Jomon human remains on Iturup, showing similarities with native Kamchatkan populations. The use of boats in the southern Kuriles is evident from the beginning of colonization, ca. 7300–7100 BP given that islands were not connected after the Early Holocene due to sea level rise. It is clear that seafaring was an important part of human activities throughout the entire island chain since the Epi-Jomon, ca. 2500 BP. Because the Kurile Islands were one of the most probable migration routes between Northeast Asia (i.e., Japan) and Northeastern Siberia and North America, study of the human colonization of the Kuriles has wider implication for the northeastern part of Eurasia as a gateway to the Americas.

Bemisia tabaci in Java, Indonesia: genetic diversity and the relationship with secondary endosymbiotic bacteria

Bemisia tabaci is a complex of cryptic species of whitefly distributed worldwide; they are serious agricultural pests and vectors of plant viruses. Whiteflies are commonly infected by endosymbiotic bacteria, but the infection profiles among genetic groups of B. tabaci are highly complex. Here we analyzed the genetic variation of B. tabaci and endosymbiont infection patterns in Java, Indonesia. Specifically, adult B. tabaci were collected from four provinces and 43 partial cytochrome oxidase subunit I gene sequences were determined to identify the genotypes. Results showed that B. tabaci was grouped into three different cryptic species, Asia I, Asia II 5, and Asia II 7, at rates of 90.70%, 6.98%, and 2.32%, respectively. The dominant group, Asia I, was distributed throughout the island, whereas Asia II 5 and Asia II 7 were detected only in West Java. In these cryptic species, the infection rates of the secondary endosymbionts Arsenophonus, Cardinium, Hamiltonella, Rickettsia, and Wolbachia were 37.21%, 72.09%, 37.21%, 88.37%, and 90.70%, respectively. Arsenophonus and Cardinium were detected two subgroups (A1 and A2; C2 and C4), but Hamiltonella, Rickettsia, and Wolbachia were detected a one subgroup (H1, R1, and W1). The A1 and A2 subgroups were distributed in a mixed manner across the entire island; however, the C2 and C4 subgroups were distributed differentially in West Java and in Central and East Java, respectively. Multiple infections were common and their patterns were highly variable in each cryptic species. In particular, Hamiltonella was detected in Asia I and Asia II 5 but never coinfected with Arsenophonus in the same individual. Overall, this study shows that Asia I is the dominant genetic B. tabaci group on Java Island and that infection by endosymbionts occurs in a highly complex and sometimes geographically related manner.

Probabilistic identification of rockfall source areas at regional scale in El Hierro (Canary Islands, Spain)

Modelling rockfall phenomena is complex and requires various inputs, including an accurate location of the source areas. Source areas are controlled by geomorphological, geological, or other geo-environmental factors and may largely influence the results of the modelling. In the Canary Islands, rockfalls are extremely common and pose a major threat to society, costing lives, disrupting infrastructure, and destroying livelihoods. In 2011, the volcanic event on the island of El Hierro triggered numerous rockfalls that affected strategic infrastructures, with a substantial impact on the local population. During the emergency, the efforts performed to map the source areas and to model the rockfalls in the considerably steep landscape characterising the island were not trivial. To better identify the rockfall source areas, we propose a probabilistic modelling framework that applies a combination of multiple statistical models using the source area locations mapped in the field as the dependent variable and a set of thematic data as independent variables. The models use as input morphometric parameters derived from the Digital Elevation Model and lithological data as an expression of the mechanical behaviour of the rocks. The analysis of different training and validation scenarios allowed us to test the model sensitivity to the input data, select the optimal model training configuration, and evaluate the model applicability outside the training areas. The final map obtained from the model for the entire island of El Hierro provides the probability of a given location being a potential source area and can be used as the input for rockfall runout simulation modelling.

Updated Segmentation Model and Cummulative Offset Measurement of the Aceh Segment of the Sumatran Fault System in West Sumatra, Indonesia

Sumatran fault in western Indonesia is one of the largest strike-slip fault in the world. The fault was formed as a result of the slip partitioning of the oblique convergence between the Indo-Australian and Eurasian plate along the Sunda trench. The right-lateral movement of the fault is accomodated by 19 fault segments that dissects the entire Sumatra island. We study the Aceh fault segment, which is located at the northernmost parts of the fault. The Aceh fault segment spans 250 km long passing through three districts: West Aceh, Pidie Jaya, and Aceh Besar and is affecting a total of ~546.143 population in the area. The current segmentation model assumes that Aceh fault segment acts as a single fault segment, which would generate closer to a M8 earthquake. This estimation is inconsistent with the ~M6-7 historical earthquake data. We conduct a detailed active fault mapping using the ~8 m resolution digital elevation model of DEMNAS and the sub-m DEM data from UAV-based photogrammetry to resolve the segmentation model of this fault. Our study indicate that the Aceh fault segment can be divided into 8 subsegments: Beutong, Kuala Tripa, Geumpang, Mane, Tangse, Jantho, Indrapuri, and Pulo Aceh. The fault kinematics identified in the field is consistent with right-lateral faulting. We measured cumulative displacement of geomorphic features (channels and ridges) ranging from 12.7 to 1931 m at some area. Findings of our study provide better estimation of the fault geometry and the maximum magnitude of potential earthquake along the Aceh fault segment as well as recommendation of prospective sliprate study sites. These informations are important for the development of seismic hazard analysis of the area.

Seed Rain, Dispersal Distance, and Germination of the Invasive Tree Spathodea campanulata on the Island of Tahiti, French Polynesia (South Pacific)

The African tulip tree Spathodea campanulata is a major invasive species on the island of Tahiti (French Polynesia), where it has established from sea level up to montane cloud forest. This invader continues to spread across the island; however, little information is available about the seed rain and germination rate of Spathodea seeds. In this study, we quantified seed rain of Spathodea, estimated potential seed dispersal distances, and determined temperatures required for seed germination. Seed traps were positioned in a Spathodea-dominated forest and monitored over 86 days during the seed-fall period. The cumulative seed rain generated a density of 289 Spathodea seeds per square meter with a mean daily frequency of 3.3 seeds/m2 in the plot. Based on seed production estimates from canopy pod counts, we inferred that many Spathodea seeds were dispersed away from the plot, rather than being deposited locally in the Spathodea invaded plot. A simple dispersal model indicated that seeds from a single tree perched on a steep precipice are capable of dispersing across the entire island of Tahiti during strong trade winds. Laboratory germination tests of freshly collected seeds showed that the maximum germination (100%) was obtained at 25 °C while 96% germination was observed at 20 °C; however, no germination was observed at 15 °C or 12 °C after 34 days. Thus, Spathodea invasion in Tahiti may currently be limited to elevations <1,500 m due to lack of germination at cooler temperatures. The large number of seeds per adult Spathodea as well as the seed dispersal ability and high rate of germination may provide an important establishment advantage to Spathodea in the tropical rainforests of Tahiti. We unexpectedly found that 61% of Spathodea seeds that fell in seed traps were depredated before falling in the traps. It is not known whether this predispersal seed predation has reduced Spathodea's rate of spread in Tahiti.