Browsing by Subject "ENVIRONMENTAL HETEROGENEITY"

Sort by: Order: Results:

Now showing items 1-9 of 9
  • Soininen, Janne; Heino, Jani; Wang, Jianjun (2018)
    Aim: The number of studies investigating the nestedness and turnover components of beta diversity has increased substantially, but our general understanding of the drivers of turnover and nestedness remains elusive. Here, we examined the effects of species traits, spatial extent, latitude and ecosystem type on the nestedness and turnover components of beta diversity. Location: Global. Time period: 1968-2017. Major taxa studied: From bacteria to mammals. Methods: From the 99 studies that partition total beta diversity into its turnover and nestedness components, we assembled 269 and 259 data points for the pairwise and multiple site beta-diversity metrics, respectively. Our data covered a broad variation in species dispersal type, body size and trophic position. The data were from freshwater, marine and terrestrial realms, and encompassed geographical areas from the tropics to near polar regions. We used linear modelling as a meta-regression tool to analyse the data. Results: Pairwise turnover, multiple site turnover and total beta diversity all decreased significantly with latitude. In contrast, multiple site nestedness showed a positive relationship with latitude. Beta-diversity components did not generally differ among the realms. The turnover component and total beta diversity increased with spatial extent, whereas nestedness was scale invariant for pairwise metrics. Multiple site beta-diversity components did not vary with spatial extent. Surprisingly, passively dispersed organisms had lower turnover and total beta diversity than flying organisms. Body size showed a relatively weak relationship with beta diversity but had important interactions with trophic position, thus also affecting beta diversity via interactive effects. Producers had significantly higher average pairwise turnover and total beta diversity than carnivores. Main conclusions: The present results provide evidence that species turnover, being consistently the larger component of total beta diversity, and nestedness are related to the latitude of the study area and intrinsic organismal features. We showed that two beta-diversity components had generally opposing patterns with regard to latitude. We highlight that beta-diversity partition may give additional insights into the underlying causes of spatial variability in biotic communities compared with total beta diversity alone.
  • Petsch, Danielle K.; Saito, Victor S.; Landeiro, Victor L.; Silva, Thiago S. F.; Bini, Luis M.; Heino, Jani; Soininen, Janne; Tolonen, Kimmo T.; Jyrkankallio-Mikkola, Jenny; Pajunen, Virpi; Siqueira, Tadeu; Melo, Adriano S. (2021)
    Previous studies have found mixed results regarding the relationship between beta diversity and latitude. In addition, by influencing local environmental heterogeneity, land use may modify spatial taxonomic and functional variability among communities causing biotic differentiation or homogenization. We tested 1) whether taxonomic and functional beta diversities among streams within watersheds differ between subtropical and boreal regions and 2) whether land use is related to taxonomic and functional beta diversities in both regions. We sampled aquatic insects in 100 subtropical (Brazil) and 100 boreal (Finland) streams across a wide gradient of land use, including agriculture and exotic planted, secondary, and native forests. We calculated beta diversity at the watershed scale (among 5 streams in each watershed). We found higher taxonomic beta diversity among subtropical than among boreal streams, whereas functional beta diversity was similar between the 2 regions. Total land use was positively correlated with taxonomic and functional beta diversity among subtropical streams, while local environmental heterogeneity was positively correlated with beta diversity among boreal streams. We suggest that different types and intensities of land use may increase among-stream heterogeneity, promoting distinct insect assemblage compositions among streams. Our findings also suggest that beta diversity patterns and their underlying determinants are highly context dependent.
  • Teittinen, Anette; Virta, Leena; Li, Mingjia; Wang, Jianjun (2021)
    Islands provide ideal model systems to examine the factors influencing biodiversity, yet knowledge of microbial biodiversity on islands remains scarce. We collected a dataset from 101 rock pools along a freshwater to brackish water transition on islands of the Baltic Sea and investigated the patterns and drivers of community composition and species richness of diatoms, cyanobacteria and non-cyanobacteria bacteria among islands. We also examined whether environmental heterogeneity increased beta diversity and species richness within islands. Among islands, the patterns in community composition were concordant among the microbial groups, with distinct changes along the freshwater-brackish gradient. The patterns in species richness were context-dependent for each microbial group. In general, richness patterns were most strongly associated with nutrient concentrations or the distances to potential sources of immigrants, whereas no positive relationships between ecosystem size and richness were found. Within islands, environmental heterogeneity was positively correlated with the beta diversity of each microbial group, but not species richness. Our findings provide novel insights into the factors influencing microbial biodiversity. The results suggest that island microbial biodiversity patterns are influenced by species sorting and dispersal-related mechanisms and highlight the importance of environmental heterogeneity for beta diversity.
  • Roth, Florian; Sun, Xiaole; Geibel, Marc C.; Prytherch, John; Bruchert, Volker; Bonaglia, Stefano; Broman, Elias; Nascimento, Francisco; Norkko, Alf; Humborg, Christoph (2022)
    Coastal methane (CH4) emissions dominate the global ocean CH4 budget and can offset the "blue carbon" storage capacity of vegetated coastal ecosystems. However, current estimates lack systematic, high-resolution, and long-term data from these intrinsically heterogeneous environments, making coastal budgets sensitive to statistical assumptions and uncertainties. Using continuous CH4 concentrations, delta C-13-CH4 values, and CH4 sea-air fluxes across four seasons in three globally pervasive coastal habitats, we show that the CH4 distribution is spatially patchy over meter-scales and highly variable in time. Areas with mixed vegetation, macroalgae, and their surrounding sediments exhibited a spatiotemporal variability of surface water CH4 concentrations ranging two orders of magnitude (i.e., 6-460 nM CH4) with habitat-specific seasonal and diurnal patterns. We observed (1) delta C-13-CH signatures that revealed habitat-specific CH4 production and consumption pathways, (2) daily peak concentration events that could change >100% within hours across all habitats, and (3) a high thermal sensitivity of the CH4 distribution signified by apparent activation energies of similar to 1 eV that drove seasonal changes. Bootstrapping simulations show that scaling the CH4 distribution from few samples involves large errors, and that similar to 50 concentration samples per day are needed to resolve the scale and drivers of the natural variability and improve the certainty of flux calculations by up to 70%. Finally, we identify northern temperate coastal habitats with mixed vegetation and macroalgae as understudied but seasonally relevant atmospheric CH4 sources (i.e., releasing >= 100 mu mol CH4 m(-2) day(-1) in summer). Due to the large spatial and temporal heterogeneity of coastal environments, high-resolution measurements will improve the reliability of CH4 estimates and confine the habitat-specific contribution to regional and global CH4 budgets.
  • Opedal, Øystein H.; von Numers, Mikael; Tikhonov, Gleb; Ovaskainen, Otso (2020)
    Abstract Predicting the dynamics of biotic communities is difficult because species? environmental responses are not independent, but covary due to shared or contrasting ecological strategies and the influence of species interactions. We used latent-variable joint species distribution models to analyse paired historical and contemporary inventories of 585 vascular plant species on 471 islands in the south-west Finnish archipelago. Larger, more heterogeneous islands were characterized by higher colonisation rates and lower extinction rates. Ecological and taxonomical species groups explained small but detectable proportions of variance in species? environmental responses. To assess the potential influence of species interactions on community dynamics, we estimated species associations as species-to-species residual correlations for historical occurrences, for colonisations, and for extinctions. Historical species associations could to some extent predict joint colonisation patterns, but the overall estimated influence of species associations on community dynamics was weak. These results illustrate the benefits of considering metacommunity dynamics within a joint framework, but also suggest that any influence of species interactions on community dynamics may be hard to detect from observational data.
  • Sgarbi, Luciano F.; Bini, Luis M.; Heino, Jani; Jyrkankallio-Mikkola, Jenny; Landeiro, Victor L.; Santos, Edineusa P.; Schneck, Fabiana; Siqueira, Tadeu; Soininen, Janne; Tolonen, Kimmo T.; Melo, Adriano S. (2020)
    Reliable biological assessments are essential to answer ecological and management questions but require well-designed studies and representative sample sizes. However, large sampling effort is rarely possible, because it demands large financial resources and time, restricting the number of sites sampled, the duration of the study and the sampling effort at each site. In this context, we need methods and protocols allowing cost-effective surveys that would, consequently, increase the knowledge about how biodiversity is distributed in space and time. Here, we assessed the minimal sampling effort required to correctly estimate the assemblage structure of stream insects sampled in near-pristine boreal and subtropical regions. We used five methods grouped into two different approaches. The first approach consisted of the removal of individuals 1) randomly or 2) based on a count threshold. The second approach consisted of simplification in terms of 1) sequential removal from rare to common species; 2) sequential removal from common to rare species; and 3) random species removal. The reliability of the methods was assessed using Procrustes analysis, which indicated the correlation between a reduced matrix (after removal of individuals or species) and the complete matrix. In many cases, we found a strong relationship between ordination patterns derived from presence/absence data (the extreme count threshold of a single individual) and those patterns derived from abundance data. Also, major multivariate patterns derived from the complete data matrices were retained even after the random removal of more than half of the individuals. Procrustes correlation was generally high ( > 0.8), even with the removal of 50% of the species. Removal of common species produced lower correlation than removal of rare species, indicating higher importance of the former to estimate resemblance between assemblages. Thus, we conclude that sampling designs can be optimized by reducing the sampling effort at a site. We recommend that such efforts saved should be redirected to increase the number of sites studied and the duration of the studies, which is essential to encompass larger spatial, temporal and environmental extents, and increase our knowledge of biodiversity.
  • Kärnä, Olli-Matti; Heino, Jani; Grönroos, Mira; Hjort, Jan (2018)
    Geodiversity, i.e. the variety of the abiotic environment, is considered to be positively correlated to biodiversity. In streams, the importance of physical heterogeneity for biodiversity variation is well known, but the usefulness of explicitly measured geodiversity indices to account for biodiversity has not been tested. We developed a technique to measure in-stream geodiversity, based on different types of stream flow, geomorphological processes and landforms observed from photographs taken during the field work, and substrates based on traditional field observations. We further tested the utility of these geodiversity measures in explaining variation in the biodiversity of macroinvertebrates in near-pristine streams. Our specific objective was to examine the explanatory power of geodiversity compared to traditional environmental variables, such as water chemistry, depth and current velocity. While most biodiversity indices correlated more strongly with traditional environmental variables, the influence of geodiversity on biodiversity was also evident. Unique effect of flow richness on species richness and that of total geodiversity on functional richness were higher than those of the traditional environmental variables. Our findings suggested that in-stream geodiversity offers a valuable concept for characterizing stream habitats. If further developed and tested, in-stream geodiversity can be used as a cost-efficient proxy to explain variation in biodiversity in stream environments.
  • Räsänen, Aleksi; Kuitunen, Markku; Hjort, Jan; Vaso, Asta; Kuitunen, Tuomo; Lensu, Anssi (2016)
    We explained vascular plant species richness patterns in a 286 km(2) fragmented landscape with a notable human influence. The objective of this study was two-fold: to test the relative importance of landscape, topography and geodiversity measures, and to compare three different landscape-type variables in species richness modeling. Moreover, we tested if results differ when only native species are considered. We used generalized linear modeling based variation partitioning and generalized additive models with different explanatory variable sets. Landscape and topography explained the majority of the variation but the relative importance of topography and geodiversity was higher in explaining native species richness than in explaining total species richness. Differences between the three landscape type variables were small and they provided complementary information. Finally, topography and geodiversity often direct human action and can be ultimate causes behind both landscape variability and species richness patterns.
  • Sidemo-Holm, William; Ekroos, Johan; Reina García, Santiago; Söderström, Bo; Hedblom, Marcus (2022)
    Urbanization is a major contributor to biodiversity declines. However, studies assessing effects of urban landscapes per se (i.e., disentangled from focal habitat effects) on biodiversity across spatial scales are lacking. Understanding such scale-dependent effects is fundamental to preserve habitats along an urbanization gradient in a way that maximizes overall biodiversity. We investigated the impact of landscape urbanization on communities of woodland-breeding bird species in individual (local scale) and across multiple (regional scale) cities, while controlling for the quality of sampled habitats (woodlands). We conducted bird point counts and habitat quality mapping of trees, dead wood, and shrubs in 459 woodlands along an urban to rural urbanization gradient in 32 cities in Sweden. Responses to urbanization were measured as local and regional total diversity (gamma), average site diversity (alpha), and diversity between sites (beta). We also assessed effects on individual species and to what extent dissimilarities in species composition along the urbanization gradient were driven by species nestedness or turnover. We found that landscape urbanization had a negative impact on gamma-, alpha-, and beta-diversity irrespective of spatial scale, both regarding all woodland-breeding species and red-listed species. At the regional scale, dissimilarities in species composition between urbanization levels were due to nestedness, that is, species were lost with increased landscape urbanization without being replaced. In contrast, dissimilarities at the local scale were mostly due to species turnover. Because there was no difference in habitat quality among woodlands across the urbanization gradient, we conclude that landscape urbanization as such systematically causes poorer and more homogeneous bird communities in adjacent natural habitats. However, the high local turnover and the fact that several species benefited from urbanization demonstrates that natural habitats along the entire urbanization gradient are needed to maintain maximally diverse local bird communities.