Effects of landscape metrics and land-use variables on macroinvertebrate communities and habitat characteristics

ABSTRACT: The growing number of studies establishing links between stream biota, environmental factors and river classification has contributed to a better understanding of fluvial ecosystem function. Environmental factors influencing river systems are distributed over hierarchically organised spatial scales. We used a nested hierarchical sampling design across four catchments to assess how benthic macroinvertebrate community composition and lower spatial scale habitat descriptors were shaped by landscape and land-use patterns. We found that benthic macroinvertebrate community structure and composition varied significantly from catchment to habitat level. We assessed and identified fractal metrics of landscape descriptors capable of explaining compositional and functional change in the benthic faunal indicators and compared them with the traditional variables describing land use and reach level habitat descriptors within a 1 km radius of each sampling site. We found that fractal landscape metrics were the best predictor variables for benthic macroinvertebrate community composition, function, instream habitat and river corridor characteristics

Mapping Spatial Variations of Land Cover in a Coastal Landscape Using Pattern Metrics

AbstractThe aim of this study is to analyze spatial variations of land cover using pattern metrics in the case of a Mediterranean coastal area. Various composition and configuration metrics were used to analyze characteristics of land cover and its spatial heterogeneity. Satellite images (i.e., SPOT) were used to classify land cover. Pattern analyses were conducted in Erdemli district of Mersin, Turkey, from coastline to about 200m ASL. Landscape patterns were quantified and mapped on the basis of number of patches (NP), edge density (ED), largest patch index (LPI), aggregation index (AI), Shannon's and Simpson's diversity and evenness indices (SHDI, SIDI, SHEI, SIEI). A relationship between observed patterns/calculated indices and current land uses were investigated. Results showed that many of the pattern features differed between the coast and upper lands due to varying composition and configuration characteristics of land cover types under investigation

Linking deep seabed structure to biodiversity: an exploration of seamounts and deeper reefs in the South and Western Indian Ocean

Environmental heterogeneity, understood as spatial or temporal variability in environmental conditions, influences biodiversity and ecosystem processes over multiple scales, including at the deep seabed. However, as a result of the inaccessibility of the ocean beyond conventional SCUBA depth (> 30 m), key knowledge gaps remain on the biotic and abiotic patterns that influence the occurrence and distribution of seabed-associated taxa, habitats and resulting ecological processes and ecosystem services. Although seabed and habitat mapping documents seabed environmental and habitat heterogeneity, very little research explicitly quantifies it to draw conclusions on its ecological consequences. To study the character and effect of environmental heterogeneity on biodiversity and marine ecological processes in the deep sea, this thesis explored the potential of combining existing seabed and habitat mapping practices with the theoretical framework and analytical techniques from land- and seascape ecology. This thesis first reviews seascape ecology and its potential to study the ecological implications of environmental heterogeneity at the deep seabed, and identifies theoretical focal areas for the application of tools and concepts from seascape ecology deeper than 30 m (Chapter 1: Introduction). The objectives of this thesis, based on these focal areas, can be divided in three main themes: 1) characterising spatial heterogeneity using spatial pattern metrics; 2) assessing the ecological relevance of spatial heterogeneity quantified using spatial pattern metrics; and 3) applying this knowledge to inform environmental management. Objectives are addressed through a set of case studies that provide the opportunity to explore the multi-scale relationship between seabed structure and ecology in habitats at seamounts (km-m scale, Chapter 2 and 3) and reefs found between 30 m-250 m on atoll slopes (m-cm scale, Chapter 4 and 5) in theWestern Indian Ocean. Case studies test specific ecological hypotheses using spatial pattern metrics quantifying seascape composition, configuration and terrain structure, which function as predictors for the occurrence and distribution of benthic assemblages and demersal fish. Chapter 2 combines habitat mapping and spatial pattern metrics from seascape ecology to quantitatively test for and compare differences in seascape composition and configuration between five seamounts on the Southwest Indian Ridge (SWIR). Results quantitatively demonstrate that seamounts are highly variable in morphology, even when part of the same geological feature. As heterogeneity in the relative proportion and spatial relationships of habitats may influence ecological functioning, habitat mappers and marine managers focusing on representational protection of seamounts could benefit from such spatially-explicit approaches to quantify seabed heterogeneity. Chapter 3 examines the influence of multi-scale seabed spatial heterogeneity on 15 commercially important fish families at three SWIR seamounts, focusing on patch affinity, patch complexity, patch size and seascape aggregation. Although strongly driven by site and depth, demersal fish respond to unique combinations of seascape composition, configuration and terrain structure depending on their family. Further, seascape composition and configuration (i.e. habitat size, shape and structural connectivity) had higher predictive power than terrain derivatives commonly used in developing proxies for deepwater fish biodiversity. These outcomes indicate the importance of incorporating spatial pattern metrics when identifying environmental predictors of fish distributions and suitable habitat in deep-sea environments. Chapter 4 tests whether multi-scale geomorphology can act as a reliable spatial proxy for deeper reef assemblage (30 m-250 m) distribution. It found that assemblage occurrence and distribution is determined by a combination of environmental parameters, explained by the functional characteristics of each assemblage. Depth and structural complexity were main predictors, and broad scale predictors (25 m) proved more informative than finer scale predictors (2 m). Findings addressed geographical gaps in our knowledge of the distribution of deeper reef habitats and generated insights into ecological relationships. Complex geomorphological structures, including terraces and paleoshorelines, supported particularly high densities of mesophotic benthic assemblages and could be considered priority habitats for management. Chapter 5 investigates the effect of fine-scale (cm-m) environmental heterogeneity on fish associated with mesophotic reefs (30 m-120 m). Spatial pattern metrics quantifying benthic composition, configuration and terrain structure were extracted from transect terrain models and orthomosaics produced with Structure-from-Motion (SfM) photogrammetry. In addition to known drivers (depth and geographic location), results show a combination of fine-scale seascape metrics of terrain structure, patch composition and patch configuration best explains mesophotic fish assemblage structure. Overall, sites with steep slopes and high terrain complexity hosted highest fish abundance and biomass. Across case studies, spatial pattern metrics allowed quantification and comparison of seascape structure and functioned as reliable predictors for the occurrence and distribution of benthic assemblages and demersal fish at deeper reefs and seamounts in the Western Indian Ocean. Overall, spatial pattern metrics facilitated a better understanding of biodiversity-environment relationships in heterogeneous environments, in some cases functioning as the main explanatory variable. This thesis therefore recommends their further application in deep sea ecology, monitoring and ecosystembased management and conservation, whilst accounting for the biological phenomenon under consideration and scale- and context dependency in survey and analysis

Potential landscape-scale pollinator networks across Great Britain: structure, stability and influence of agricultural land cover

Understanding spatial variation in the structure and stability of plant-pollinator networks, and their relationship with anthropogenic drivers, is key to maintaining pollination services and mitigating declines. Constructing sufficient networks to examine patterns over large spatial scales remains challenging. Using biological records (citizen science), we constructed potential plant-pollinator networks at 10km resolution across Great Britain, comprising all potential interactions inferred from recorded floral visitation and species co-occurrence. We calculated network metrics (species richness, connectance, pollinator and plant generality) and adapted existing methods to assess robustness to sequences of simulated plant extinctions across multiple networks. We found positive relationships between agricultural land cover and both pollinator generality and robustness to extinctions under several extinction scenarios. Increased robustness was attributable to changes in plant community composition (fewer extinction-prone species) and network structure (increased pollinator generality). Thus, traits enabling persistence in highly agricultural landscapes can confer robustness to potential future perturbations on plant-pollinator networks

Measuring temporal turnover in ecological communities

Range migrations in response to climate change, invasive species and the emergence of novel ecosystems highlight the importance of temporal turnover in community composition as a fundamental part of global change in the Anthropocene. Temporal turnover is usually quantified using a variety of metrics initially developed to capture spatial change. However, temporal turnover is the consequence of unidirectional community dynamics resulting from processes such as population growth, colonisation and local extinction. Here, we develop a framework based on community dynamics and propose a new temporal turnover measure. A simulation study and an analysis of an estuarine fish community both clearly demonstrate that our proposed turnover measure offers additional insights relative to spatial context-based metrics. Our approach reveals whether community turnover is due to shifts in community composition or in community abundance and identifies the species and/or environmental factors that are responsible for any change

Environmental drivers of benthic communities: the importance of landscape metrics

The distribution of aquatic communities is dependent on processes that act at multiplescales. This study comprised 270 samples distributed over 2 years and used a nested sampling design to estimate the variance associated with three spatial scales: basin, site and microhabitat. Habitat assessment was made using River Habitat Survey. The derived Habitat Quality Indices and the benthic composition were crossed with landscape metrics and types of soil use, obtained from GIS data, using multiple non-parametric regressions and distance-based redundancy analysis. Invertebrate variation was mainly linked with intermediate scale (site) and landscape metrics were the main drivers determining local characteristics. The aquatic community exhibited a stronger relationship with landscape metrics, especially patch size and shape complexity of the dominant uses, than with habitat quality, suggesting that instream habitat improvement is a short-term solution and that stream rehabilitation must address the influence of components at higher spatial scales

Environmental drivers of benthic communities: the importance of landscape metrics

The distribution of aquatic communities is dependent on processes that act at multiplescales. This study comprised 270 samples distributed over 2 years and used a nested sampling design to estimate the variance associated with three spatial scales: basin, site and microhabitat. Habitat assessment was made using River Habitat Survey. The derived Habitat Quality Indices and the benthic composition were crossed with landscape metrics and types of soil use, obtained from GIS data, using multiple non-parametric regressions and distance-based redundancy analysis. Invertebrate variation was mainly linked with intermediate scale (site) and landscape metrics were the main drivers determining local characteristics. The aquatic community exhibited a stronger relationship with landscape metrics, especially patch size and shape complexity of the dominant uses, than with habitat quality, suggesting that instream habitat improvement is a short-term solution and that stream rehabilitation must address the influence of components at higher spatial scales

High dissimilarity within a multiyear annual record of pollen assemblages from a North American tallgrass prairie

Citation: Commerford, J. L., McLauchlan, K. K., & Minckley, T. A. (2016). High dissimilarity within a multiyear annual record of pollen assemblages from a North American tallgrass prairie. Ecology and Evolution, 6(15), 5273-5289. doi:10.1002/ece3.2259Grassland vegetation varies in composition across North America and has been historically influenced by multiple biotic and abiotic drivers, including fire, herbivory, and topography. Yet, the amount of temporal and spatial variability exhibited among grassland pollen assemblages, and the influence of these biotic and abiotic drivers on pollen assemblage composition and diversity has been relatively understudied. Here, we examine 4 years of modern pollen assemblages collected from a series of 28 traps at the Konza Prairie Long-Term Ecological Research Area in the Flint Hills of Kansas, with the aim of evaluating the influence of these drivers, as well as quantifying the amount of spatial and temporal variability in the pollen signatures of the tallgrass prairie biome. We include all terrestrial pollen taxa in our analyses while calculating four summative metrics of pollen diversity and composition -beta-diversity, Shannon index, nonarboreal pollen percentage, and Ambrosia: Artemisia -and find different roles of fire, herbivory, and topography variables in relation to these pollen metrics. In addition, we find significant annual differences in the means of three of these metrics, particularly the year 2013 which experienced high precipitation relative to the other 3 years of data. To quantify spatial and temporal dissimilarity among the samples over the 4-year study, we calculate pairwise squared-chord distances (SCD). The SCD values indicate higher compositional dissimilarity across the traps (0.38 mean) among all years than within a single trap from year to year (0.31 mean), suggesting that grassland vegetation can have different pollen signatures across finely sampled space and time, and emphasizing the need for additional long-term annual monitoring of grassland pollen

Scales of Variability in the Size Composition and Community Structure of Fishes in Estuarine Ecosystems

Fishing, other human activities, and natural perturbations can alter the species composition and size structure of fish communities in coastal ecosystems. Normalized biomass size spectra (NBSS) and other metrics based on size and abundance of fish communities are sensitive to effects of fishing and have been proposed as useful tools for ecosystem-based management. However, these approaches based on size and abundance are unevaluated at temporal and spatial scales relevant for management within estuaries. Because individual species have important ecological and economic value, tracking temporal and spatial changes in the species composition of the fish communities using multivariate analyses, such as principal component analysis (PCA), can facilitate interpretation of patterns observed in the NBSS. A goal of my dissertation was to determine if indicators suitable for ecosystem-based management can be derived from NBSS parameters and other metrics based on size and abundance for estuarine fish and plankton communities at relatively small temporal and spatial scales. Additionally, I sought to elucidate effects of temporal and spatial variability in species composition on community size structure of estuarine fish communities by combining multivariate and NBSS analyses. Analyzing data from multiple fisheries-independent surveys and water quality monitoring programs, the objectives of my dissertation were 1) to describe and quantify the size distribution and community composition of fish and plankton in Chesapeake Bay at temporal scales ranging from months to over a decade and at spatial scales ranging from 18 km to 100 km, 2) to evaluate long-term trends in abundance, size distribution, and species composition of fish communities in Chesapeake Bay and Pamlico Sound, and 3) to analyze environmental variables and their effects on community structure and size distribution of biological communities in the Chesapeake and Pamlico Sound estuaries. Results supported the conclusion that NBSS combined with traditional community analyses permits detection of changes in ecosystem status, facilitates identification the species associated with the observed variability, and provides a framework to establish management reference points