Scale Habitat Research Articles

From forest to fragment: compositional differences inside coastal forest moth assemblages and their environmental correlates

Patterns of β-diversity can provide insight into forces shaping community assembly. We analyzed species-rich insect assemblages in two reserve fragments that had once been part of one contiguous Mediterranean coastal pine forest. Local environments are still similar across both fragments, but their landscape context differs strongly, with one surrounded by intense agricultural land, while the other neighbors the urbanized area of Ravenna. Using 23,870 light-trap records of 392 moth species, and multiple local and landscape metrics, we compared the relative importance of habitat- versus landscape-scale environmental factors for shaping small-scale variation in differentiation and proportional insect β-diversity across 30 sites per reserve. Moth assemblage composition differed substantially between fragments, most likely due to ecological drift and landscape-scale variation. For proportional β-diversity, especially local forest structure was important. At well-developed forest sites, additive homogenization could be observed, whereas the lack of typical forest species at dry, dense, and younger forest sites increased species turnover (subtractive heterogenization). For differentiation β-diversity, local and landscape-scale factors were equally important in both reserves. At the landscape-scale (500 m radius around light-trapping sites) the proximity to urban areas and the fraction of human-altered land were most important. At the habitat scale, gradients in soil humidity, nutrient levels and forest structure mattered most, whereas plant diversity had very little explanatory power. Overall, landscape-scale anthropogenic alterations had major effects on moth communities inside the two conservation areas. Yet, even for these parts of one formerly contiguous forest trajectories in community change were remarkably idiosyncratic.

Spatial Niche Expansion at Multiple Habitat Scales of a Tropical Freshwater Turtle in the Absence of a Potential Competitor

Resource partitioning, the division of limited resources by species to help avoid competition, has been observed in freshwater turtle assemblages in several natural systems but has rarely been studied in tropical African ecosystems. Here, we investigate habitat preferences of two congeneric species in the family Pelomedusidae, Pelusios castaneus and P. cupulatta, in riverine/wetland habitats in the southern Ivory Coast (West Africa). Pelusios castaneus is a widespread species across West-central African savannahs and open forests, whereas P. cupulatta is endemic to the Upper Guinean forest region in West Africa. The two species have a similar diet composition (mainly carnivorous) but diverge considerably in body size, P. cupulatta being much larger. We use hand-fishing-nets and fishing funnel traps to record turtles in 18 distinct sites and analyze habitat preferences by species at two spatial scales. At a macro-habitat scale, P. castaneus is captured mainly in marshlands, whereas P. cupulatta is found in both rivers and wetlands. The two species differ significantly in their use of: (i) banks (P. castaneus being found primarily in spots with grassy banks, whereas P. cupulatta is found in spots with forested banks), and (ii) aquatic vegetation (P. cupulatta prefers spots with more abundant aquatic vegetation than P. castaneus), but both species select sites with no or moderate current. Additionally, in sites where P. cupulatta is not found, P. castaneus expands its spatial niche at multiple habitat scales, notably invading waterbodies with forested banks. Our results suggest that these two Pelomedusid turtle species potentially compete in the freshwater habitats in the southern Ivory Coast.

Estimation of trends in zone of influence of mine sites on barren-ground caribou populations in the Northwest Territories, Canada, using new methods

The zone of influence (ZOI) is the area in the vicinity of industrial development where avoidance by caribou Rangifer tarandus or other wildlife species is observed. Here we examine ZOI around two diamond mines in the Northwest Territories (NWT), Canada from 1998 to 2017. In this paper, we further develop segmented/piecewise regression methods to analyze collar location and aerial survey data with a focus on yearly trend in ZOI for the Bathurst caribou herd. A base habitat model was initially formulated to account for habitat selection around mines followed by estimation of ZOI distance and magnitude. Seasonal ranges of the herd contracted from 2009 to 2017 due to decline in herd size, which influenced the distribution of caribou relative to the mines as well as larger scale habitat selection. Models with year-specific estimates of ZOI were more supported than models assuming a constant ZOI across years. Significant ZOI's occurred for aerial survey and/or collar data in 9 of 15 years from 2003 to 2017 when both mines were in full operation, with ZOI distances ranging from 6.1 to 18.7 km. Non-significant ZOI's occurred from 1998 to 2002 before both mines were fully operational. Caribou were attracted to lakes in drought years which significantly influenced distribution relative to mines as well as the magnitude of the ZOI detected. The ZOI extent averaged 7.2 km (CI = 3.8–10.5) when standardized for mean levels of drought. Our analysis suggests that ZOI varies both annually and spatially because of the location of mines relative to habitat selection and seasonal range size. Therefore, exacting analysis methods that account for these sources of variation are required for robust ZOI estimates. Segmented regression methods have become available in the R statistical program that allow flexible ZOI estimation for implementation of the methods in this study for caribou or other wildlife species.

Do urban open spaces provide refugia for frogs in urban environments?

Urbanization is among the largest threats to wildlife populations through factors such as fragmentation, isolation, and habitat destruction. Urban open spaces, such as parks and golf courses, have the potential to provide wildlife with suitable habitat within an urbanized matrix. These refugia may be particularly important for amphibians, which represent one of the most endangered and least vagile vertebrate groups on earth. During the spring and summer of 2018, we conducted surveys to determine the presence of anurans at 51 wetland sites within the Piedmont ecoregion of South Carolina. Nearly one-third of these wetlands were located within urban open spaces, one-third in low development areas, and one-third in highly developed areas. Impervious surface and total road length surrounding the wetlands were measured at two scales, a core habitat scale (300 m) and average maximum migration scale (750 m), and we measured several within-wetland habitat variables. Urban Open Space wetlands had levels of surrounding impervious surface similar to High Urbanization wetlands at the larger scale and were intermediate between Low and High Urbanization wetlands at the smaller scale. The total length of road segments occurring within buffers (at both scales) surrounding our study wetlands was higher for Urban Open Space compared to Low and High Urbanization sites. Among the within-wetland variables measured, Low Urbanization sites had higher canopy cover and were more likely to have a terrestrial buffer zone relative to the other categories. Species richness decreased significantly as total road length increased among all wetlands. Wetland category was not a significant driver explaining species richness, but β-diversity was more variable among Urban Open Space wetlands than either Low or High Urbanization wetlands. Urban Open Space wetlands did not appear to increase suitability for anurans relative to High Urbanization wetlands. Urban Open Space wetlands had higher variability in species composition, which was perhaps attributable to the diversity among sites represented in the Urban Open Space category.

Dispersal and Good Habitat Quality Promote Neutral Genetic Diversity in Metapopulations.

Dispersal is a fundamental and crucial ecological process for a metapopulation to survive in heterogeneous or changing habitats. In this paper, we investigate the effect of the habitat quality and the dispersal on the neutral genetics diversity of a metapopulation. We model the metapopulation dynamics on heterogeneous habitats using a deterministic system of ordinary differential equations. We decompose the metapopulation into several neutral genetic fractions seeing as they could be located in different habitats. By using a mathematical model which describes their temporal dynamics inside the metapopulation, we provide the analytical results of their transient dynamics, as well as their asymptotic proportion in the different habitats. The diversity indices show how the genetic diversity at a global metapopulation scale is preserved by the correlation of two factors: the dispersal of the population, as well as the existence of adequate and sufficiently large habitats. The diversity indices show how the genetic diversity at a global metapopulation scale is preserved by the correlation of two factors: the dispersal of the population as well as the existence of adequate and sufficiently large habitats. Moreover, they ensure genetic diversity at the local habitat scale. In a source-sink metapopulation, we demonstrate that the diversity of the sink can be rescued if the condition of the sink is not too deteriorated and the migration from the source is larger than the migration from the sink. Furthermore, our study provides an analytical insight into the dynamics of the solutions of the systems of ordinary differential equations.

A multi-scale assessment of fire scar mapping in the Great Victoria Desert of Western Australia

Fire management is increasingly acknowledged as a necessary tool to maintain diversity in desert environments such as the Great Victoria Desert of Australia, but it needs to be informed by accurate fire history data. We compared and assessed the utility of Landsat-derived and Moderate Resolution Imaging Spectroradiometer (MODIS)-derived burnt area mapping (30 m and 250 m resolution, respectively) for sub-regional, landscape and habitat scale management. We did so by using Sentinel-2-derived, 10 m resolution, burnt area mapping as a reference, to determine the most appropriate product to support land management planning. At the landscape scale, Landsat had significantly lower average omission and commission errors (3.4% and 8.0%, respectively) compared with that of MODIS (42.2% and 19.9%, respectively). At the habitat scale, Landsat burnt area percentage was more accurate, in plots of 500 m × 500 m (root mean square error (RMSE) 0.6% to 8.6%), but offered lower accuracy when estimating partially burnt habitat plots of 120 m × 120 m (RMSE 14.1% to 23.9%). Only Landsat-derived fire scar mapping provided enough detail to produce reliable fire history maps to inform fire management and biodiversity conservation operations at a sub-regional scale, landscape scale and a habitat scale of 500 m by 500 m.

Integration of DNA extraction, metabarcoding and an informatics pipeline to underpin a national citizen science honey monitoring scheme

Worldwide honeybees (Apis mellifera L.) are one of the most widely kept domesticated animals, supporting domestic and commercial livelihoods through the production of honey and wax, as well as in the delivery of pollination services to crops. Quantifying which plant species are foraged upon by honeybees provides insights into their nutritional status as well as patterns of landscape scale habitat utilization. Here we outline a rapid and reproducible methodology for identifying environmental DNA (eDNA) originating principally from pollen grains suspended within honey. The process is based on a DNA extraction incorporating vacuum filtration prior to universal eukaryotic internal transcribed spacer 2 region (ITS2) amplicon generation, sequencing and identification. To provide a pre-cursor to sequence phylotyping, we outline systems for error-corrected processing amplicon sequence variant abundance tables that removes chimeras. This methodology underpins the new UK National Honey Monitoring Scheme.•We compare the efficacy and speed of centrifugation and filtration systems for removing pollen from honey samples as a precursor to plant DNA barcoding.•We introduce the ‘HONEYPI’ informatics pipeline, an open access resource implemented in python 2.7, to ensure long-term reproducibility during the process of amplicon sequence variant classification.

Bryophyte species composition at the stand scale (1 ha) – Differences between secondary stands half a century after clear-cutting and older semi-natural boreal forests

A growing proportion of the boreal biome consists of managed even-aged secondary forest stands regenerated after clear-cutting. Many disturbance-intolerant species may not be able to recolonize or reach their original abundance in these stands before the next clear-cutting, potentially causing large-scale biodiversity losses. Boreal bryophytes (mosses and liverworts) include many species intolerant to clear-cutting, and at small spatial scales species richness and occupancy has been shown to remain changed in secondary stands half a century after logging. To assess if such persistent changes occur also at the stand scale, we listed and estimated cover of all bryophyte species in 1-ha plots, comparing 14 secondary stands originating from clear-cutting 40–60 years earlier with 14 older semi-natural stands. The large plots also made it possible to assess differences in occupancy and abundance for more bryophyte species than in previous studies. Species composition differed significantly for both mosses and liverworts, but unlike earlier studies, we could not detect any significant difference between stand types in species numbers. Thirteen species were significantly associated with semi-natural stands and the total cover of liverworts was less than half in secondary stands. Secondary stands had significantly fewer species typically occurring under shady conditions and/or mostly growing on “tree substrates” (dead wood and/or bases and stems of living trees). Ordination analysis further emphasized the importance of shade and suitable deadwood substrates; the among-plot variation in bryophyte species composition was related to amount of coarse deadwood as well as to gradients from shady spruce dominated to open pine dominated stands and from polar- to equator-facing slopes. Besides lack of suitable habitat conditions in secondary stands, dispersal limitation may have caused a colonization time lag for some species. The clear importance of stand scale habitat conditions for bryophyte species composition calls for management adaptions to facilitate life boating and/or recolonization by ensuring availability of shade, coarse decomposing logs, and specific deciduous tree species (Populus, Salix, Sorbus) in secondary stands.

Intraspecific Trait Variation Dilutes Deterministic Processes in Community Assembly of Arid Shrubs across Multiple Scales

Trait-based approaches present a promising avenue for improving our understanding of species coexistence and community assembly, while intraspecific trait variation (ITV) across different spatial scales is important in trait-based community assembly mechanisms, especially in extreme environments. In this study, we focused on the functional diversity and community assembly patterns of a desert community across different spatial scales and investigated whether ITV plays a significant role in community assembly processes in arid habitats. A 50 m × 50 m plot with different small quadrats was established in a typical desert community at the transition zone between the Tengger Desert and Loess Plateau in China. A total of 14 traits were selected to assess the trait-based functional diversity and assembly processes in the community. We found that functional diversity showed different patterns when considering ITV and related to different types of traits (chemical traits or morphological traits) and some soil factors (pH and nitrate nitrogen). Plant communities in this study showed stochastic distribution patterns and similar functional diversity patterns based on functional trait approaches, regardless of spatial scales. Also, the effect of ITV on community assembly did not show more effect with increasing scales. These results indicated that ITV diluted deterministic processes in community assembly across scales in arid habitats.

High thematic resolution land use change models refine biodiversity scenarios: A case study with Belgian bumblebees

AbstractAimProjections of biodiversity scenarios often rely solely on climate change to inform species distribution shifts in the future. Land use projections are rarely used due to their unavailability and, when available, are often at coarse spatial and thematic resolutions, making them unsuitable to capture fine scale habitat suitability. This study aims to (a) show how coupled land use change (LUC) models of high thematic resolution (HTR) can be used in species distribution models (SDM), (b) compare the impacts of HTR and low thematic resolution (LTR) explanatory predictors on biodiversity scenarios and (c) assess the impact of species' present area of occupancy on the effect of thematic resolution in SDMs.LocationBelgiumTaxonBumblebees (Bombus)MethodsWe compared species distribution models with 17 land use predictors (HTR) against models with 5 land use predictors (LTR). We modelled the distribution of 17 bumblebee species in Belgium projected until 2035. We examined how model performance, variable importance and projections of distribution change differed depending on the thematic resolution of the land use predictors.ResultsOverall, HTR models performed better than LTR models. LTR models predicted greater extent per species. HTR projected a greater percentage of range gains, and both models projected similar losses of suitable habitat. However, the percentage loss and connectivity of suitable habitats varied differently for HTR and LTR models along a gradient of rare to common species. The HTR models projected greater loss of suitable areas for rare species and less loss for common species compared to LTR models.Main conclusionsThese results illustrate the importance of using ecologically relevant explanatory variables in SDMs, particularly for rare and localized species with specific habitat requirements. The results also indicate the need for large‐scale LUC projections to improve future biodiversity scenarios under climate change and to improve the ability of conservationists and policymakers to use SDM projections.

Functional rather than structural connectivity explains grassland plant diversity patterns following landscape scale habitat loss

ContextFunctional connectivity is vital for plant species dispersal, but little is known about how habitat loss and the presence of green infrastructure interact to affect both functional and structural connectivity, and the impacts of each on species groups.ObjectivesWe investigate how changes in the spatial configuration of species-rich grasslands and related green infrastructure such as road verges, hedgerows and forest borders in three European countries have influenced landscape connectivity, and the effects on grassland plant biodiversity.MethodsWe mapped past and present land use for 36 landscapes in Belgium, Germany and Sweden, to estimate connectivity based on simple habitat spatial configuration (structural connectivity) and accounting for effective dispersal and establishment (functional connectivity) around focal grasslands. We used the resulting measures of landscape change to interpret patterns in plant communities.ResultsIncreased presence of landscape connecting elements could not compensate for large scale losses of grassland area resulting in substantial declines in structural and functional connectivity. Generalist species were negatively affected by connectivity, and responded most strongly to structural connectivity, while functional connectivity determined the occurrence of grassland specialists in focal grasslands. Restored patches had more generalist species, and a lower density of grassland specialist species than ancient patches.ConclusionsProtecting both species rich grasslands and dispersal pathways within landscapes is essential for maintaining grassland biodiversity. Our results show that increases in green infrastructure have not been sufficient to offset loss of semi-natural habitat, and that landscape links must be functionally effective in order to contribute to grassland diversity.

First assessment of habitat suitability and connectivity for the golden jackal in north-eastern Italy

Compared with the rapid expansion across Europe, the golden jackal colonization of Italy is still limited and slow. No study focused on the habitat selection or landscape connectivity for this species was performed in Italy; thus, the potential distribution and dispersal patterns in the country remain unknown. Our objectives were to evaluate the suitability of the Friuli-Venezia Giulia region (north-eastern Italy) for the golden jackal, as well as to identify the ecological corridors connecting the areas currently occupied by the species. Corridors modelling allowed us both to hypothesize the dispersal dynamics occurring in the study region and to identify possible obstacles to future range expansion. We surveyed golden jackal presence in two study areas, covering an area of 500 km2, from March 2017 to February 2018. Using collected data, we modelled the species home-range scale habitat suitability based on an ensemble modelling approach. Subsequently, a habitat suitability prediction at a finer scale was used to estimate landscape resistance, starting from which, we modelled dispersal corridors among areas currently occupied by the species using a factorial least cost path and a cumulative resistant kernel approach. Our results indicated a moderate potential for large parts of the study region to support the occurrence of golden jackal family groups, whose presence seems to be mainly driven by the presence of wide areas covered by broadleaved forests and shrublands and by the absence of wide intensive agricultural areas. The predicted connectivity networks showed that three main permeable corridors are likely to connect golden jackal occurrence areas within the study region, while all the other corridors are characterized by a very low path density. Both the habitat selection and connectivity analyses showed a strong negative impact of the intensive cultivated plain on species stable presence and movement providing critical information for the conservation of the golden jackal in Italy.

A protocol for the large‐scale analysis of reefs using Structure from Motion photogrammetry

Abstract Substrate complexity is an essential metric of reef health and a strong predictor of several ecological processes connected to the reef, including disturbance, resilience, and associated community abundance and diversity. Underwater Structure from Motion (SfM) photogrammetry has been growing rapidly in use over the last 5 years due to advances in computing power, reduced costs of underwater digital cameras and a push for reproducible data. This has led to the adaptation of an originally terrestrial survey technique into the marine realm, which can now be applied at the habitat scale. This technique allows researchers to make detailed 3D reconstructions of reef surfaces for morphometric analysis of reef physical structure and perform large‐scale image‐mosaic mapping. SfM is useful for both reef‐scale and colony‐scale assessments, where visual or acoustic methods are impractical or not sufficiently detailed. Here we provide a protocol for the collection, analysis and display of 3D reef data, focussing on large‐scale habitat assessments of coral reefs using primarily open‐source software. We further suggest applications for other underwater environments and scales of assessment, and hope this standardized protocol will help researchers apply this technology and inspire new avenues of ecological research.

Ecological correlates of Golden Eagle Aquila chrysaetos breeding occurrence in Sardinia

ABSTRACT Capsule Golden Eagles Aquila chrysaetos in Sardinia are clustered across the main mountain ranges of the island, with a preference for undisturbed and homogeneous inland habitats. Aims To analyse habitat preferences of the Golden Eagle in Sardinia, Italy, at the landscape and home range spatial scales. Methods Landscape scale habitat preferences were analysed using the 10 × 10 km Universal Transverse Mercator grid and the home range scale was based on the spatial distribution of breeding territories. Generalized linear models were fitted with three different sets of environmental predictors (topographic, bioclimatic and land use variables) to analyse the spatial distribution of Golden Eagles with a case–control design. Results Eagles showed a preference for rugged and elevated areas, characterized by a certain degree of humidity and surrounded by areas of forest. The distribution of Golden Eagles on this Mediterranean island was negatively affected by the occurrence of arable farmland and coastal areas, as well as by the effects of habitat fragmentation. Conclusions The results of this study could contribute to future management strategies and conservation projects aimed to protect this species, and may be used to identify the most suitable conservation areas for this and other competing species, such as the Bonelli’s Eagle Aquila fasciata, which is currently the subject of a reintroduction project in Sardinia.

Multi-scale interaction processes modulate the population response of a benthic species to global warming

Marine organisms are currently experiencing an unprecedented rate of climatic warming, which affects their biogeography and threatens marine ecosystem integrity. To understand how benthic species will respond to ongoing seawater warming, we assessed the relative importance of processes acting at different scales using an individual-based modelling approach. Our model integrates: (1) at the individual scale, interactions between the environment, metabolism and ontogenic transitions; (2) at the habitat scale, competition for space at settlement and mortality; and (3) at the regional scale, larval dispersal and connectivity between habitats. We focused on a coastal area in the North-East Atlantic that has experienced a significant seawater warming trend over recent decades. We built and ran a population dynamics model for the blue mussel (Mytilus edulis) in this area, which is a known biogeographic boundary zone. We then compared the response for a reference scenario and a RCP8.5 temperature projection for 2100. We found that (1) increase in seawater temperature would result in a decrease in average biomass associated with a change in recruitment phenology; (2) response to seawater warming is not spatially homogeneous, showing the importance of processes at the habitat scale; (3) connectivity clearly limits the consequences of warming compared with other regulation processes; and (4) larval supply does not seem to be a limiting factor regulating population biomass. The use of such generic models would therefore be very valuable for guiding and optimizing research efforts and supporting the implementation of management and conservation measures.

Small scale habitat effects on anthropogenic litter material and sources in a coastal lagoon system

Anthropogenic litter is ubiquitous throughout marine ecosystems, but its abundance and distribution are driven by complex interactions of distinct environmental factors and thus can be extremely heterogeneous. Here we compare the extent of anthropogenic litter pollution at a sheltered lagoon habitat and nearby open coast sites. Monthly surveys over a period of five months showed that both the types and sources of litter always differed significantly between lagoon and open coast sites. Pollution within the lagoon was mainly land-derived and was largely made up of construction materials (70% to 95%). At open coast sites, construction materials represented a minor portion of pollution (4% to 12%) while plastics were the most abundant (82% to 95%). We show that stranded anthropogenic litter in adjacent marine habitats can differ significantly and stress the importance of sampling at appropriate spatial scales to gain realistic insights into the sources of pollution.

Evaluating environmental DNA as a tool for detecting an amphibian pathogen using an optimized extraction method.

Environmental DNA (eDNA) detection is a valuable conservation tool that can be used to identify and monitor imperiled or invasive species and wildlife pathogens. Batrachochytrium pathogens are of global conservation concern because they are a leading cause of amphibian decline. While eDNA techniques have been used to detect Batrachochytrium DNA in the environment, a systematic comparison of extraction methods across environmental samples is lacking. In this study, we first compared eDNA extraction methods and found that a soil extraction kit (Qiagen PowerSoil) was the most effective for detecting Batrachochytrium dendrobatidis in water samples. The PowerSoil extraction had a minimum detection level of 100 zoospores and had a two- to four-fold higher detection probability than other commonly used extraction methods (e.g., QIAamp extraction, DNeasy+Qiashredder extraction method, respectively). Next, we used this extraction method on field-collected water and sediment samples and were able to detect pathogen DNA in both. While field-collected water filters were equivalent to amphibian skin swab samples in detecting the presence of pathogen DNA, the seasonal patterns in pathogen quantity were different between skin swabs and water samples. Detection rate was lowest in sediment samples. We also found that detection probability increases with the volume of water filtered. Our results indicate that water filter eDNA samples can be accurate in detecting pathogen presence at the habitat scale but their utility for quantifying pathogen loads in the environment appears limited. We suggest that eDNA techniques be used for early warning detection to guide animal sampling efforts.

Short Communication: The presence of Bull shark Carcharhinus leucas (Elasmobranchii: Carcharhinidae) in the fresh waters of Sumatra, Indonesia

Abstract. Hasan V, Widodo MS. 2020. Short Communication: The presence of Bull shark Carcharhinus leucas (Elasmobranchii: Carcharhinidae) in the fresh waters of Sumatra, Indonesia. Biodiversitas 21: 4433-4439. A single subadult specimen of Bull shark Carcharhinus leucas was photographed and captured by local fisherman using casting net on June 2020 in the upper Indragiri River, Riau Province, Indonesia. Carcharhinus leucas are one of only a few species of elasmobranchs that live in both marine and freshwater environments. This species currently listed as a near-threatened species based on the IUCN Red List Status. Singel specimen identified as C. leucas by the coloration of fresh specimen: white belly and greyish back, first dorsal fin high, tip of second dorsal and caudal fins black. Meristic characters measurement results as follows: total length 102 cm; fork length 86.3 cm; preanal length 65.1 cm; pre pelvic length 51.9 cm; pre pectoral length 22.5 cm; pre-orbital length 8.3 cm; head length 25 cm; pre-first dorsal length 29.4 cm; pre-second dorsal length 56 cm, and pre-caudal length 78.1 cm. This photo is considered as the third record from freshwaters of Sumatra after in the Batang Hari River, Jambi Province in 1997, and in the Musi River, South Sumatra Province in 2019. The photographic records indicate that a single specimen of C. leucas was found in the upper Indragiri River recorded more than 150 km inland. These results enhanced the understanding of C. leucas distribution in Sumatra freshwaters. Monitoring is needed to assess the possibility of the importance of the upper Indragiri River as a migration route, nursery, and growth ground of C. leucas. Studying small scale habitat use of C. leucas is challenged by their preferred habitats in freshwaters environments with fast-changing environmental conditions. Water conditions in the upper Indragiri River, namely salinity 0‰, temperature 25-27°C, dissolved oxygen 3.9-11.1 mg/l, are ideal for A. leucas habitat.

Spatial and temporal evolution of detritusphere hotspots at different soil moistures

As a result of the heterogeneous spatial distribution of microorganisms and substrates in soil and their restricted accessibility, biodegradation occurs mainly in hotspots, such as in the detritusphere, induced by decomposing plant residues. Knowing the characteristics of the volume of soil involved in biodegradation of a given organic substrate will facilitate the understanding and prediction of biodegradation. Our objectives were (i) to identify the volume of soil involved in the biodegradation of plant residues and (ii) to determine to what extent this volume is affected by soil moisture under diffusive conditions by monitoring the mineralization and spatio-temporal evolution of residue C and microorganisms in soil at the microbial habitat scale. We incubated repacked soil cores with a central layer of 13C-labelled maize residues at three different matric potentials (−0.0031, −0.031 and −0.31 MPa). We monitored 13C and total C mineralization, and at different dates over 45 days of incubation, we separated soil slices with increasing distances from the residues and analysed 13C from the residues and the microbial community structure and its activity by PLFA and 13C-PLFA processing. Residue mineralization increased with increasing soil moisture. A detritusphere a few mm thick was rapidly established, with a decreasing gradient of 13C and total PLFAs and 13C-PLFAs away from the residue layer. Most 13C from the residues was located in the first 2 mm of the detritusphere and was not dependent on the matric potential. Residue mineralization seemed to take place mainly on the residues themselves, but increasing residue C was transferred to the surrounding soil with increasing soil moisture. Dry conditions slowed residue C transfer and favoured fungi, but residue mineralization was carried out by both bacteria and fungi.

Using Geomorphology to Better Define Habitat Associations of a Large-Bodied Fish, Common Snook Centropomus undecimalis, in Coastal Rivers of Florida

To adequately protect habitat for economically important fishes, the habitats used must first be identified and described. Coastal geomorphology is often overlooked as an influential parameter of fish habitat use in favor of readily available data taken at the time of sampling. We hypothesized that river dynamics (e.g., length, watershed, floodplain connectivity) and mesohabitat categories based on geomorphology (e.g., backwater, river bend) were at least as important as fine-scale microhabitat (e.g., depth, shore type) for describing the distribution and habitat affinities of Common Snook Centropomus undecimalis (hereafter referred to as snook) in coastal rivers of the Atlantic coast and Tampa Bay, Florida. Contrary to previously studied rivers where adult snook abundance increased during a seasonal prey pulse, adult snook abundance in the study rivers differed little between seasons and the rivers were used as nurseries by juveniles. Mesohabitat categories were important for describing snook distribution. For example, the smallest snook (≤ 250 mm total length, TL) strongly selected for backwater habitats while the largest (≥ 851 mm TL) selected river bends. Detailed microhabitat data collected at individual capture locations were helpful in describing the habitat associations of the smallest size group of snook (shallow depths and aquatic macrophytes with various shore types) and for characterizing river bends (high flow, deep water, and lower salinities) but were not strongly associated with other snook sizes or mesohabitat categories. Thus, broader scale habitat features were found to be equally as important as detailed microhabitat and should be considered when informing conservation efforts.