River Islands Research Articles

Rearing of two entomopathogenic nematodes, Heterorhabditis Bacteriophora poinar and Steinernema sp. in termite (Odontotermes Obesus ramb.)

The in vivo methods for rearing of entomopathogenic nematodes requires large quantities of insect hosts like greater wax moth, Galleria mellonella (L.) which involves more time and additional costs, necessitates alternative host for multiplication of entomopathogenic nematodes. The present study was aimed to assess the infectivity and multiplication of two entomopathogenic nematodes, Heterorhabditis bacteriophora Poinar and Steinernema sp. isolated from Majuli river island of Assam in subterranean termite Odontotermes obesus (Ramb). The laboratory tests using Petri-dishes, illustrated the effectiveness of both the nematodes against O. obesus at 100 IJs termite−1 (worker/soldier) within 24–48 h, in which the nematodes could reproduce in 5–7 days. The natural mounds (250 g) containing O. obesus (80–100 workers/soldiers/nymphs) were also inoculated with H. bacteriophora and Steinernema sp. at 1000 IJs and incubated at room temperature (30±2°C) up to 20 days for multiplication. Following the Cobb decanting and sieving method, the results exhibited the optimum yields of 30, 000 and 25, 000 IJs of H. bacteriophora and Steinernema sp., respectively, at 15 days beyond which the IJs starts deterioration. Under laboratory condition entomopathogenic nematodes H. bacteriophora and Steinernema sp. can be reared and mass produced for further management practices against termite.

Housing conditions and the degree of home satisfaction of elderly riverside residents of the Amazon region

Abstract At the crossroads of environmental psychology and social gerontology, this descriptive and exploratory study investigates the housing conditions of the elderly who live close to an Amazonian river and assesses their degree of satisfaction with their housing. Using four instruments, we study 23 elderly residents of the river islands of the municipality of Cametá, Pará, Brazil. Despite high territorial isolation, low socioeconomic status, and largely inappropriate housing conditions, the results reveal the elderly’s overall satisfaction with their home environment, except in relation to accessibility and safety. The data of this study give larger visibility to people’s main needs in this context and provide relevant information for the planning of social and health policies aimed at bettering the quality of this stage of the life span.

Phytoplankton diversity of floodplain lakes of the Majuli River Island of the Brahmaputra river basin, Assam, northeast India

Phytoplankton of three floodplain lakes (beels) of the Majuli River Island of upper Assam, northeast India (NEI), sampled during September 2010–August 2012, revealed rich diversity (108 species) with Ghotonga > Holmari ≥ Bhereki beels; richness of Chlorophyta and of Cosmarium > Staurastrum > Euastrum in particular. The monthly richness and community similarities affirmed heterogeneity in phytoplankton composition. Phytoplankton comprised between 59.5±12.5, 57.1±12.3 and 48.6±13.5% of net plankton abundance of Bhereki, Holmari and Ghotonga beels, respectively. Bacillariophyta > Chlorophyta showed quantitative importance in Bhereki while Chlorophyta > Bacillariophyta recorded importance in Holmari and Ghotonga beels. Cyanophyta showed sub-dominance and Dinophyta > Euglenophyta showed low densities in the three beels. Phytoplankton richness and abundance followed oscillating monthly variations; ANOVA registered insignificant richness variations amongst beels. The results are characterized certain monthly and annual variations but mean values depicted high species diversity, low dominance and high equitability. Individual and cumulative influence ( vide CCA) yielded limited insight on the role of seventeen abiotic factors on phytoplankton in Holmari and Bhereki beels.

Variation of River Islands around a Large City along the Yangtze River from Satellite Remote Sensing Images.

River islands are sandbars formed by scouring and silting. Their evolution is affected by several factors, among which are runoff and sediment discharge. The spatial-temporal evolution of seven river islands in the Nanjing Section of the Yangtze River of China was examined using TM (Thematic Mapper) and ETM (Enhanced Thematic Mapper)+ images from 1985 to 2015 at five year intervals. The following approaches were applied in this study: the threshold value method, binarization model, image registration, image cropping, convolution and cluster analysis. Annual runoff and sediment discharge data as measured at the Datong hydrological station upstream of Nanjing section were also used to determine the roles and impacts of various factors. The results indicated that: (1) TM/ETM+ images met the criteria of information extraction of river islands; (2) generally, the total area of these islands in this section and their changing rate decreased over time; (3) sediment and river discharge were the most significant factors in island evolution. They directly affect river islands through silting or erosion. Additionally, anthropocentric influences could play increasingly important roles.

Erratum to: A GIS-based study on channel variation, erosion and deposition along the bank of Dibru Saikhowa National Park (1967–2016), Assam, India

The GIS technology presently has become an important tool for various fluvio morphological studies. The present study incorporates GIS technology to assess more precisely and accurately the rate, nature and pattern of channel variations along with erosion and deposition of the study area at the spatio-temporal scale. The Dibru Saikhowa National Park is a river island in the upper Brahmaputra valley of Assam. The island experiences frequent bank erosion by Siang and Dibang River in the north and Lohit River in the south. The total geographical area of Dibru Saikhowa National Park was about 337.96 sq in the year 1967, which reduces to 302.45 sq km in 1988, 279.38 sq km in 2001 and finally to 241.82 sq km in the year 2016. The area witnessed a net loss of 96.14 km of area (1967–2016) with total erosion of 103.84 and deposition of 7.707 sq km of area. The southward shift of Siang and Dibang River channel/bank line and northward shift of Lohit, Dibru and Dangori channel/bank line causes erosion of Dibru Saikhowa National Park. The study reveals an average shift 1425.58 m of Dibru and Dangori channel/bank line northward and 1314.97 m of Siang and Dibang channel/bank line southward during 1976–2016. The westward shift of Dibang and Siang River conjunction along with avulsion of Lohit River southward promotes erosion of the island.

A Report on Insect Community and Their Habitat Association in Daying Ering Memorial Wildlife Sanctuary, Arunachal Pradesh

Daying Ering Memorial Wildlife Sanctuary located in East Siang district, Arunachal Pradesh is a river island formed by the river Siang and Sibia. It is the only kind of sanctuary in Arunachal Pradesh which is surrounded by water bodies and most of the land covered with thatch grasses. The primary objective of the present study was to collect preliminary data on the insect diversity in this sanctuary. For this, the data were collected in four habitats viz. grassland, woodland, river bank and Jeep ghat camp area during February 04–07, 2015. The findings were analysed using Shannon index, Simpson index, Buzas and Gibson’s evenness measure, Berger–Parker index and Fisher-alpha index. During the survey undertaken, 44 species of insects belonging to 10 orders and 25 families were documented. Lepidoptera represented by 9 species showed the highest species richness as per Shannon index followed by Coleoptera, Orthoptera, Hemiptera and Hymenoptera represented by 6, 15, 5 and 4 species respectively. However, Simpson’s diversity index calculated the highest species richness of Coleoptera followed by Lepidoptera, Orthoptera, Hemiptera and Hymenoptera. The maximum number of species inhabited in the grassland (22). Among the habitats studied, the highest species richness was found in woodland followed by riverbank, grassland and the camp area. Ceratosolen solmsi marchali was estimated as the most abundant insect species in camp area, Distoleon tetragrammicus and Schizodactylus monstrosus in riverbank, Globitermes globosus and Acrida bicolour in grassland and Mycalesis heri in woodland habitat. Though, it was a preliminary survey species like yellow winged grasshopper Gastrimargus musicus, sand dune cricket S. monstrosus and globoid nest termite G. globosus can be pictured as potential flagship insects in the sanctuary. Besides, it showed the variation of diversity in entomofauna among the habitats indicating habitat specific dependence of the insect assembly in the sanctuary.

Zooplankton Diversity of Three Floodplain Lakes (Beels) of the Majuli River Island, Brahmaputra River Basin of Assam, Northeast India

Zooplankton Diversity of Three Floodplain Lakes (Beels) of the Majuli River Island, Brahmaputra River Basin of Assam, Northeast India

Phylogeography and population dynamics of Antbirds (Thamnophilidae) from Amazonian fluvial islands

AbstractAimTo investigate the evolution of the avifauna associated to Amazonian fluvial islands, focusing on the Negro River archipelagos.LocationsFluvial islands in the Amazon Basin.MethodsOne generalist floodplain species (Hypocnemoides melanopogon) and three river island specialists (Myrmotherula assimilis, Myrmoborus lugubris and Thamnophilus nigrocinereus) were studied (Thamnophilidae). We sequenced two mitochondrial genes and genotyped eight microsatellite loci. Phylogenetic relationships among intraspecific lineages and divergence times were estimated using Bayesian Inference. Haplotype networks, AMOVA (analysis of molecular variance) and Mantel tests were used to verify the spatial organization of genetic diversity. Gene flow and population structure were evaluated using a dissimilarity index, Bayesian inference and allele frequencies. Historical demography was inferred through neutrality tests and Extended Bayesian skyline plots (EBSP).ResultsRiver island specialists have evolved distinct lineages in different Amazonian tributaries, but exhibit very weak population structure within the Negro river basin. The generalist floodplain species had no population structure along the Amazon basin or within the Negro river basin. Signals of weak and recent (Pleistocene) population expansion were recovered for all species.Main conclusionsRiver islands specialists show stronger population structure within Amazonia than floodplain generalists. They show a common spatial and temporal pattern of divergence between populations from the Negro islands and western Amazonia (upper and middle Solimões), which may be related to Amazonian drainage evolution. Island specialists had low genetic diversity within the Negro basin, while the higher and unstructured diversity pattern found in the floodplain generalist species may be a consequence of higher dispersal caused by the seasonal flooding pulse. River islands populations have a recent and dynamic history of contact and isolation, with small historical fluctuations of population sizes, which is in sharp contrast with the patterns found in upland forest birds.

Dispersal capacity shapes responses of river island invertebrate assemblages to vegetation structure, island area, and flooding

Abstract Riparian invertebrate communities occupy a dynamic ecotone where hydrogeomorphological (e.g. river flows) and ecological (e.g. succession) processes may govern assemblage structure by filtering species according to their traits (e.g. dispersal capacity, niche). We surveyed terrestrial invertebrate assemblages (millipedes, carabid beetles, spiders) in 28 river islands across four river catchments over 2 years. We predicted that distinct ecological niches would produce taxon‐specific responses of abundance and species richness to: (i) disturbance from episodic floods, (ii) island area, (iii) island vegetation structure, and (iv) landscape structure. We also predicted that responses would differ according to species’ dispersal ability (aerial vs. terrestrial only), indicating migration was sustaining community structure. Invertebrate abundance and richness was affected by different combinations of vegetation structure, island area, and flood disturbance according to species’ dispersal capacity. Carabid abundance related negatively to episodic floods, particularly for flightless species, but the other taxa were insensitive to this disturbance. Larger islands supported greater abundance of carabids and all invertebrates able to disperse aerially. Vegetation structure, particularly tree canopy density and plant richness, related positively to invertebrate abundance across all taxa and aerial dispersers, whereas terrestrial disperser richness related positively to tree cover. Landscape structure did not influence richness or abundance. Multiple ecological processes govern riparian invertebrate assemblages. Overall insensitivity to flood disturbance and responses contingent on dispersal mode imply that spatial dynamics subsidise the communities through immigration. Particular habitat features (e.g. trees, speciose vegetation) may provide refuges from disturbance and concentration of niches and food resources.

Pedogenic influence on profile distribution of total and DTPA - extractable micronutrients in rice growing hydric soils of Majuli river island, Assam, India

The rice-growing river floodplain ecosystems of Majuli island, India, have been recognized as a biodiversity hotspot with a high degree of variability in geomorphological forms and geochemical conditions for trace metals in hydric soils. Ten hydric soil series in rice-growing soils of Majuli island were studied with the aim of understanding the pedogenic influence on distribution and content of total and diethylenetriamine penta acetic acid (DTPA) extractable micronutrient cations (Fe, Mn, Cu and Zn) and their enrichment levels. The correlation analysis showed that these cations were closely linked with soil texture, organic carbon, cation exchange capacity and pH levels. The multiple regressions and cluster analysis was employed to identify the effect of river fed deposits on distribution pattern and lithological enrichment of metals. The contamination status was assessed through quantitative indexes with reference material. The negative geo-accumulation index values were used to conclude that these soils had been practically unchanged by anthropogenic influences. They showed moderate Cu contamination but were otherwise unpolluted (Pollution load index < 1) with respect to total elements under study.

Archaeological Exploration in Srirangapatna and Its Environ Through Remote Sensing Analysis

This study involves exploration of archaeological structures in Srirangapatana and virtual reconstruction of Srirangapatana fort using geo-spatial techniques. Antiquity of this river island town goes back to ninth century AD which continued till British rule and hence has abundance of archaeological structures on it. Some of these structures are known and well-maintained while others are unprotected, unexcavated, hidden under thick vegetation or forgotten. To identify archaeological features such as buried/dilapidated/vegetation infested structures/features on ground, we used high resolution multispectral remote sensing data (0.5 and 5.6 m), Cartosat 1 stereo pairs (2.5 m), anaglyphs, historical documents, and analysed them on GIS platform. This study enabled us to: trace the concentric moats and fort-wall by using false colour composite image together with anaglyphs generated from Cartosat 1 stereo pair; explore hitherto unexplored and unexcavated archaeological features; identify unknown and abandoned temples/structures smothered with wild vegetation; locate exact location of currently non-existent site mentioned in historical records; identify the location of buried canal. This study also demonstrates how methodic use of various interpretation keys, image processing and analysis (such as NDVI, DEM, anaglyphs) can help in extracting archaeological features and direct archaeologists for further exploration.

Field evaluation of some insecticides against white grub, Lepidiota mansueta B. (Coleoptera: Scarabaeidae), on potato (Solanum tuberosum) in Assam (India)

Field studies were conducted to evaluate the efficacy of six insecticides against white grub, Lepidiota mansueta, in potato in 2012 and 2013 at Majuli river island in Assam (India). All the insecticide treatments significantly reduced tuber damage as against untreated control. Of the insecticides tested, fipronil 5 SC @ 150 g a.i.ha−1 showed low tuber damage on weight basis (5.24 and 4.57%) and was at par with fipronil 5 SC @ 100 g a.i.ha−1 (5.91 and 5.09%), chlorpyriphos 20 EC @ 400 g a.i. ha−1 (5.55 and 6.2%) and quinalphos 25 EC @ 400 g a.i.ha−1 (6.14 and 6.72%). On number basis, fipronil 5 SC @ 150 g a.i.ha−1 showed lowest tuber damage (4.2%), followed by chlorpyriphos 20 EC @ 400 g a.i.ha−1 (5.25%) and quinalphos 25 EC @ 400 g a.i.ha−1 (5.66%). All insecticide treatments were at par in tuber yield, except emamectin benzoate 5% SG @ 12.5 g a.i.ha−1. Highest cost benefit ratio was observed in chlorpyriphos 20 EC @ 400 g a.i.ha−1 treatment (2.50 and 2.62), followed by quinalphos 25 EC @ 400 g a.i.ha−1 (2.23 and 1.85). Chlorpyriphos 20 EC @ 400 g a.i.ha−1 and quinalphos 25 EC @ 400 g a.i.ha−1 seem better alternatives than fipronil to reduce infestation of L. mansueta in potato.

A drought & flood resilience strategy for Berat

The Berat Island study centers around on a group of temporal islands (i.e. sand bars; sediment deposits) in the Osum River which are left bare during summer, when the river’s base flow is limited. During the driest periods, only a small stream is flowing through Berat section, leaving most of the riverbed exposed. Apart from a bottleneck located on the west of the city, the river sections around Berat are relatively wide. This leaves the city with an unused wasteland, covered by temporal vegetation. Due to the flood hazard during winter, these river islands are left relatively untouched. Yet, the opportunity the islands provide for the city, might be seized given that there are either limited, or no interferences at all in the existing river sections.

INFESTED AREAS OF MAJULI, ASSAM, INDIA

Entomopathogenic nematodes (EPNs) in the genera Steinernema and Heterorhabditis and their associated bacteria such as Xenorhabdus spp. and Photorhabdus spp. are lethal parasites of soil dwelling insects. A survey was conducted to collect theentomopathogenic nematodes from Lepidiota mansueta endemic field of Majuli river island, Assam, India. During the survey, a total of 140 soil samples (1 kg each) and 80 dead grubs of L. mansueta were collected from different locations from cultivated as well as uncultivated fields of Majuli. Out of the total collection, 8 numbers of soil samples and 35 grubs were positive for entomopathogenic nematodes with 5.7 and 43.7 per cent respectively. Soil samples recorded 2.1 and 3.5 per cent Heterorhabditis and Steinernema isolates whereas the grubs registered 15 and 28.7 per cent of Heterorhabditis andSteinernema isolates respectively. Based on morphometric and cross-breeding studies, the Heterorhabditis isolates were identified as H. bacteriophora and this species was recovered from diverse habitats with different soil characteristics. Being a river island, the soil of Majuli may be the reservoir of many more species of EPNs which needs further study.

EVOLUTION OF CERRADO VEGETAL COVER ON A RIVER ISLAND BASED ON ORBITAL IMAGING DATA

This study aimed to assess vegetal cover evolution on a river island within the Ecological Station of (EEP), by remote sensing. For this purpose, Normalized Difference Vegetation Indexes were generated for Landsat 1 (1973) and Landsat 5 (1984, 1990, 2000 and 2011) images. Five landscape units were identified in the field: bare soil, Rough savanna, Typical savanna, Forested savanna and Evergreen dry woods. Only Forested savanna and Evergreen dry woods showed poor spectral splitting, being thus considered as a forestry complex. Changes throughout time have occurred in all units, with decreasing in bare soil areas (-2.56 ha year−1), Rough savanna (-0.66 ha year−1) and Typical savanna (-0.94 ha year−1) and with an increase in the Forested savanna (5.97 ha year−1). Thus, the method used in this study was effective for sorting and assessing plant cover of the landscape units studied over time.

Introduction - Submergence: A special issue on Atlantis and related mythologies

Over the last decade there has been a growing awareness of the current and likely future impacts of rising sea levels on low-lying islands and coastlines. For island nations such as Kiribati, there is a very real threat of submergence of habitable low-lying areas with a substantial proportion of the population requiring relocation to elsewhere, either collectively – allowing them to reconstitute as a single diasporic community – or else in fragmented and dispersed form. Similarly, the inhabitants of chars (temporary river islands) in Bengal may have to live with a more extreme volatility of emergence and submergence. 1 Such communities are also likely to suffer profound inter-generational shock and senses of dislocation. This of course true of all involuntary migrations but is arguably more so for such migrants in that submerged lands cannot be credibly imagined as places to return to and/or places in possession of residual cultural heritage that the displaced can identify with. As history makes apparent, displacement of populations due to changes in sea levels and/or other events has characterised human existence ever since our species’ initial movement out of Africa. 2 But while many archaeological, climatological and geographical histories have examined communities that have demonstrably accommodated this in their livelihood and habitation patterns, 3 speculation as to the likely socio-psychological impacts of these patterns have been minimal. In this regard, Jim Leary’s study The Remembered Land: Surviving Sea-level Rise after the Last Ice Age (2015) offers a valuable foray into the field. His volume describes the stages of progressive inundation of the area of land formerly lying between the east coast of England and the opposite coasts of Belgium and Holland. Referring to this region as ‘Northsealand’, 4 he initially sketches the nature of the inhabited region during the early Mesolithic period (based on his interpretation of fragmentary archaeological evidence) and then goes on to speculate as to how the human population of the low-lying region may have adapted to global warming and sea-level rise. Having characterised Northsealand as “a mostly lowlying, flat and fluvially dominated landscape... created by the processes of rivers and streams” (2015: 16) he goes on to contend that the impact of sea-level rise on ecosystems and on areas of stable dwelling land would have been gradual (rather than catastrophic), requiring groups to re-locate to areas of higher land and/or “led to groups inhabiting

Wabanaki Homeland and Mobility: Concepts of Home in Nineteenth-Century Maine

AbstractIn the nineteenth century the Penobscot and Passamaquoddy Indian nations preserved considerable mobility across their traditional homeland. This case study uses petitions and other primary sources to show that many Native families maintained connections to places that their ancestors once inhabited. While the Penobscot reservation consisted of the river islands above the head of tide, families continued to return to Penobscot Bay to harvest marine resources. Other kin groups revisited old sites on the Kennebec River. Non-Native town officials wanted to send the Indians home but were blind to the fact that the Wabanaki peoples already understood themselves to be home. For the Passamaquoddy at Pleasant Point (Sipayik), resources such as birch bark and firewood were scarce, prompting them to harvest wood on private property for survival. Tension between private property and traditional homeland remained unresolved as Wabanaki peoples persevered in their partially colonized homeland.

Floods in the Southern Alps of New Zealand: the importance of atmospheric rivers

AbstractExtremely high precipitation occurs in the Southern Alps of New Zealand, associated with both orographic enhancement and synoptic‐scale weather processes. In this study, we test the hypothesis that atmospheric rivers (ARs) are a key driver of floods in the Southern Alps of New Zealand. Vertically integrated water vapour and horizontal water vapour transport, and atmospheric circulation, are investigated concurrently with major floods on the Waitaki River (a major South Island river). Analysis of the largest eight winter maximum floods between 1979 and 2012 indicates that all are associated with ARs. Geopotential height fields reveal that these ARs are located in slow eastward moving extratropical cyclones, with high pressure to the northeast of New Zealand. The confirmation of ARs as a contributor to Waitaki flooding indicates the need for their further exploration to better understand South Island hydrometeorological extremes. Copyright © 2016 John Wiley & Sons, Ltd.

Controls on the δ13CDIC and alkalinity budget of a flashy subtropical stream (Manoa River, Hawaii)

Hawaiian streams are flashy in nature because watersheds are small and steep and receive intense and unevenly distributed rainfall. As a result, stream chemistry is characterized by considerable spatiotemporal variability. To examine how rainfall and streamflow affect the solute content of the Manoa River in Hawaii, time-series geochemical data collected during 17 sampling campaigns in spring-fall of 2010 were evaluated in a coupled δ13CDIC/major ion inversion model. Spatially, the stream is characterized by a distinct shift from a low HCO3 (43 mg/L), low pCO2 (3760 ppmv) and heavy δ13CDIC (−6.5‰) fingerprint in the upper reaches to a high HCO3 (91 mg/L), high pCO2 (8961 ppmv) and light δ13CDIC (−11.7‰) signature in the lowlands. These trends are attributed to (1) progressive weathering of exposed aluminosilicates, and (2) downstream enrichment in CO2 from organic matter decay in the soil zone. Solute (i.e., nitrate) yields from nitric acid weathering are generally low (<1% of TDS), even in the developed lowlands, where runoff of nitrate-enriched urban effluent has historically been documented. Data furthermore indicate a significant positive correlation between δ13CDIC and rainfall rates in the mid-stream section of the river which is consistent with an atmospheric CO2 dilution effect during high rainfall events. This dilution effect needs to be accounted for to reliably describe the role of volcanic island river systems in global assessments of silicate weathering and CO2 degassing.

Changing climate and its impacts on Assam, Northeast India

The paper explores climate change induced hydro hazards and its impact on tribal communities in Majuli (largest river island of Brahmaputra River Basin). The island has been experiencing recurrent floods, erosion, and siltation, which has distressed the socio-economic foundation and livelihood of the Mishing—a indigenous community on Northeast India, leading to out migration from the island. The indicators selected to capture the vulnerability of the island to climate change are dependency ratio; occurrence of natural hazards (floods) and coping methods; income of the household; and livelihood diversification. To gather the quantitative and qualitative data on these parameters the methods was designed to conduct both sample survey of households and focus group discussions. The findings reveal that in the selected villages, the dependency ratio is 4 (dependents): 1 (earning member); average income of the household is low i.e. $ 40/month and is declining as compared to last few years because of frequent floods, erosion and siltation that has decreased farm productivity which is the main source of income. The impact of changing climate and heightened flood and erosion risk to farmlands has been forced migration to cities and neighboring urban centers like Jorhar for stable livelihood. Therefore, we propose that a possible way to enhance social resilience to changing climate and vagaries of monsoon (tropical disturbances) is to promote alternative occupation like eco-tourism as (Majuli is the center of Vaisnavism and Satras in Northeast India) and invest in adaptive strategies to mitigate flood by incorporating lay and place-based knowledge of the Mishing community in flood management. Also facilitate community’s participation and awareness towards hydro hazards based on flood proof housing focusing on indigenous knowledge.