Plant functional rarity across different land use types in the megacity of Tokyo

The rarity of species has multiple facets. Functional rarity is an integrated index that can quantify species’ sparseness and functional traits’ rarity. However, a comprehensive evaluation of various dimensions of functional rarity at different scales in urban ecosystems is under-researched. Here, we addressed two hypotheses: (1) functional rarity will not be consistent with conventional rarity at local and regional scales, and (2) land use types influence the distribution of all forms of functionally rare plants in urban ecosystems. We first selected ten functional traits to quantify the functional rarity components of 170 plant species. Second, we assessed the distribution of functional rarity and all forms of functionally rare plants across seven land use types in the megacity of Tokyo. We found that functional rarity is not consistent with conventional rarity at the local and regional scales. Several native species and two non-native species were functionally distinct and not scarce at the local scale. In addition, natural remnants and anthropogenic habitats could protect functionally rare species in urban ecosystems. We thus argue for incorporating functional rarity in the current biodiversity conservation framework and considering natural remnants and anthropogenic habitats in urban functionally rare species conservation.     

Multi-criteria site selection and hydraulic modeling of green flood retention measures in a highly urbanized basin in Costa Rica

Green flood retention measures (GFRMs) are nature-based solutions applied to. mitigate floods by slowing and storing floodwater. This study employed a hydraulic, model developed in HEC-RAS to analyze the effects of GFRMs in the Quebrada Seca-Burío basin in Costa Rica. A multi-criteria methodology was developed to select. suitable sites for implementing the measures. A baseline representing the status quo, scenarios with individually assessed measures implemented at different sites, and a scenario with all measures combined were compared concerning their flood retention. potential. Twelve suitable sites capable of providing multiple socio-ecological benefits. were identified, of which three were implemented in the model to evaluate their. hydraulic performance. The results indicate that all scenarios are effective in reducing. peak flow, volume, and inundation areas, but to varying degrees. The combination of. all measures presented the most effective results, with peak flow reductions of 5.6 –15.3% and flood volume reductions of 3.6 – 9.9%.     

Metapopulation genetic structure and migration pathways in the land snail Helix aspersa: influence of landscape heterogeneity

The spatial genetic structuring of the land snail Helix aspersa was investigated for 32 colonies within an intensive agricultural area, the polders of the Bay of Mont-Saint-Michel (France). Given the habitat patchiness and environmental instability, the setting of H. aspersa colonies meets the broader view of a metapopulation structure. The identification of extrinsic barriers to migration and their impact on the genetic distribution was addressed through the genotyping of 580 individuals using a combined set of enzyme and microsatellite loci. To evaluate the distance as well as the direction over which the spatial genetic arrangement occurs, two-dimensional spatial autocorrelation analyses, Mantel tests of association and multivariate Mantel correlograms were used. Different connectivity networks and geographical distances based on landscape features were constructed to evaluate the effect of environmental heterogeneity and to test the adequacy of an isolation by distance model on the distribution of the genetic variability. Genetic divergence was assessed using either classical IAM-based statistics, or SMM-based genetic distances specifically designed to accommodate the mutational processes thought to fit microsatellite evolution (IAM: Infinite Allele Model; SMM: Stepwise Mutation Model). Genetic distances based only on genetic drift yielded the most plausible biologically meaningful interpretation of the observed spatial structure. Applying a landscape-based geographical distance which postulates that migration arises along roadside verges, hedges or irrigation canal embankments gave a better fit to an isolation by distance model than did a simple Euclidean distance. The progressive decline of genetic similarity with physical distance appeared to be environmentally induced, leading to functional migration pathways.This revised version was published online in May 2005 with corrections to the Cover Date.     

Projecting land use transitions at forest fringes in the Philippines at two spatial scales

This paper presents two applications of a spatially explicit model of land use change at two spatial scales: a nation-wide application for the Philippines at relatively coarse resolution and an application with high spatial resolution for one island of the Philippines: Sibuyan island, Romblon province. The model is based on integrated analysis of socio-economic and biophysical factors that determine the allocation of land use change in combination with the simulation of the temporal dynamics (path-dependence and reversibility of changes), spatial policies and land requirements. Different scenarios of near-future developments in land use pattern are simulated illustrating the effects of implementing spatial policies. Results from the coarse scale model with national extent mainly serve to identify the overall pattern of land use change and hot zones of deforestation. The detailed application provides more insight in the pattern of land use change and its consequences for ecological processes. The use of the results for environmental assessments is illustrated by calculating spatial indices to assess the impact of land use change on forest fragmentation. It is concluded that spatially explicit modeling of land use change yields important information for environmental management and land use planning. The applications illustrate that the scale of analysis is an important determinant of the model configuration, the interpretation of the results and the potential use by stakeholders. There is no single, optimal, scale for land use change assessments. Each scale enables different types of analysis and assessment: applications at multiple scales therefore give complementary information needed for environmental management.This revised version was published online in May 2005 with corrections to the Cover Date.     

Distribution and dynamics of the red squirrel (Sciurus vulgaris L.) in a landscape with fragmented habitat

In a four year study data on the presence of red squirrel were collected in an agricultural landscape by counting dreys in 49 woods ranging from 0.5 to 14 ha, and differing in quality of habitat and isolation.Logit regression analysis showed that the area per woodlot covered with conifers is a good predictor of squirrel presence for each year and during the whole period, but the significance of the regression decreases with time. During the study the number of woods occupied by red squirrel increased, and smaller woods and those without conifers also became inhabited. This trend is in accordance with the positive effect of time in regression analyses on the presence of the species and on the colonization of woods, and it suggests an increase of squirrel numbers in the area. Addition of several isolation variables in the regression analyses showed significant effects in different years, and the effect of isolation was independent of time. In the first two years the area of habitat around a woodlot, the distance to the nearest woodlot larger than 30 ha, and the density of possible movement corridors have significant effects on the presence of red squirrel.In the last two years, with presumably a high number of squirrels, the (short) distance to the nearest woodlot and also the area of habitat around woods have significant effects. It is concluded that the spatial dynamics of the population can be understood as the outcome of individual spatial behaviour, rather than as the result of metapopulation processes.     

Simulating private land ownership fragmentation in the Missouri Ozarks, USA

Increasing land ownership fragmentation in the United States is causing concerns with respect to its ecological implications for forested landscapes. This is especially relevant given that human influence is one of the most significant driving forces affecting the forest landscape. A method for generating realistic land ownership maps is needed to evaluate the effects of ownership fragmentation on forest landscapes in combination with other natural processes captured in forest process models. Ownership patterns from human activities usually generate landscape boundary shapes different from those arising from natural processes. Spatial characteristics among ownership types – e.g., private, public ownership – may also differ. To address these issues, we developed the Fragmented Land Ownership Spatial Simulator (FLOSS) to generate ownership patterns that reflect the Public Land Survey System (PLSS) shapes and various patch size distributions among different types of ownership (e.g., private, public). To evaluate FLOSS performance, we compared the simulated patterns with various ownership fragmentation levels to the actual ownership patterns in the Missouri Ozarks by using selected landscape indices. FLOSS generated landscapes with spatial characteristics similar to actual landscapes, suggesting that it can simulate different levels of ownership fragmentation. This will allow FLOSS to serve as a feasible tool for evaluating forest management applications by spatially allocating various management scenarios in a realistic way. The potentials and limitations of FLOSS application are discussed.     

A multi-scaled analysis of avian response to habitat amount and fragmentation in the Canadian dry mixed-grass prairie

Previous research has suggested that ducks and songbirds may benefit from prairie landscapes that consist primarily of contiguous grasslands. However, the relative importance of landscape-level vs. local characteristics on mechanisms underlying observed patterns is unclear. We measured effects of grassland amount and fragmentation on upland and wetland songbird and duck density and nest success, and on some nest predators, across 16 landscapes in southern Alberta, Canada. We compared these landscape-level effects with local-scale responses, including distance to various edges and vegetation characteristics. We also evaluated several statistical approaches to comparing effects of habitat characteristics at multiple spatial scales. Few species were influenced by grassland amount or fragmentation. In contrast, distance to edge and local vegetation characteristics had significant effects on densities and nest success of many species. Previous studies that reported effects of landscape characteristics may have detected patterns driven by local mechanisms. As a corollary, results were very sensitive to statistical model structure; landscape level effects were much less apparent when local characteristics were included in the models.     

Spatial pattern of coniferous and deciduous forest patches in an Eastern North America agricultural landscape: the influence of land use and physical attributes

In agricultural landscapes, most studies have investigated the influence of the spatial pattern of forest patches on other ecological phenomena and processes, such as animal movement and biodiversity. However, few have focused on explaining the spatial pattern of the forest patches themselves. Understanding how these patterns relate to the processes that generate them is fundamental in developing a sound theory of landscape ecology, and in devising rational management strategies. In this paper, the pattern of the overall forest patches, as well as the pattern of deciduous and coniferous patches in an agricultural landscape of Southern Quebec, Canada, were analyzed and related to landscape physical attributes and land use, using remote sensing, geographic information systems and statistical methods. Results show that the role of landscape physical attributes on forest patch pattern has been modified by land use. In the study area, coniferous or deciduous patches are not associated with a specific surface deposit. In addition, physical attributes explain only a small proportion of the abundance of conifers on past abandoned land compared with land-use factors. Physical attributes only indirectly influence the forest pattern because they strongly influence the land-use practices. Our results reveal a conifer recovery process with the abandonment of agricultural land. On past abandoned land, conifers expand with increasing stand age, mostly by invasion from neighboring coniferous patches. Spatially, coniferous patches are usually located on the margins of the overall forest patches, and they are connected to non-forest land-use types such as crop and pasture, the latter being the most important. By showing the importance of some coniferous forest types that did not exist in the precolonial forest, a new perspective emerges when landscape, especially, land-use dynamics are taken into account.