202 research outputs found
Comparative ecology of structural groups : compositional patterns in the Swan Valley forests Montana
The lichen genus Hypogymnia in Greenland
Six species of Hypogymnia are reported from Greenland. Hypogymnia incurvoides is added to the lichen flora of the area. Morphology, chemistry, distribution, habitat and ecology are discussed, and a key to the species is presented. Distribution maps of the species are given.
Recommended from our members
Non-parametric habitat models with automatic interactions
Questions: Can a statistical model be designed to represent more directly the nature of organismal response to multiple interacting factors? Can multiplicative ernel smoothers be used for this purpose? What advantages does this approach have over more traditional habitat modelling methods?
Methods: Non-parametric multiplicative regression (NPMR)was developed from the premises that: the response variable has a minimum of zero and a physiologically-determined maximum, species respond simultaneously to multiple ecological factors, the response to any one factor is conditioned by the values of other factors, and that if any of the factors is intolerable then the response is zero. Key features of NPMR are interactive effects of predictors, no need to specify an overall model form in advance, and built-in controls on overfitting. The effectiveness of the method is demonstrated with simulated and real data sets.
Results: Empirical and theoretical relationships of species response to multiple interacting predictors can be represented effectively by multiplicative kernel smoothers. NPMR allows us to abandon simplistic assumptions about overall model form, while embracing the ecological truism that habitat factors interact.Keywords: regression, NPMR, kernel smoothing, species response surface, nonparametric multiplicative regression, habitat mode
Recommended from our members
Wind farm potential is higher in prime habitat for uncommon soil crust lichens
Introduction: Biotic soil crust communities contribute valuable ecosystem services and biodiversity in steppe ecosystems. The uncommon crust lichens Acarospora schleicheri, Fuscopannaria cyanolepra, Rhizocarpon diploschistidina, and Texosporium sancti-jacobi are associated with fine-textured soils along rivers of the Columbia Basin. A. schleicheri and R. diploschistidina indicate late-successional habitat and may serve as indicators for other rare or cryptic species associated with similar habitats. Much of the most favorable habitat for these species has been lost to urban and agricultural development. We sought to overlay favorable habitats with wind farm development potential to assess whether these species are likely to be affected by renewable energy development.
Methods: We overlaid habitat models for four lichen species on land use and wind farm potential maps. Using a sample of 5,000 points, we determined whether there were differences in probability of occurrence among wind farm potential classes within developed and natural lands using Multi-Response Permutation Procedures. Sites with modeled probability of occurrence greater than 60% were considered “favorable” habitats; for these, a χ 2 test allowed us to determine whether favorable habitats were associated with wind farm potential categories.
Results: Sites that are developed for agriculture or have higher wind farm potential coincide with more favorable habitats for uncommon soil crust lichens. Of the favorable habitats for the four focal lichens, 28–42% are already affected by development or agriculture; 5–14% of favorable habitats remain in natural vegetation and are considered sites with fair or good potential for wind farms.
Conclusions: Development of wind energy has the potential to negatively impact uncommon soil crust lichen species because favorable sites coincide with especially good habitat for these species. However, as these renewable energy resources are developed, we have the opportunity to ensure that valuable soil crust functions and diversity are maintained by surveying before construction and planning new facilities such that disturbance to existing habitat is minimized.Keywords: Acarospora schleicheri, Biotic soil crust, Agriculture, Texosporium sancti-jacobi, Land use, Columbia river, Rhizocarpon diploschistidina, Steppe, Fuscopannaria cyanolepr
Recommended from our members
Species Changes in Macrolichens of the Pacific Northwest, 2nd edition (2009)
We list additions, deletions, and other changes in species included in Macrolichens of the Pacific Northwest, 2nd edition, as compared to the 1st edition. The changes resulted from discoveries of range extensions into the Pacific Northwest, descriptions of new species, taxonomic revisions, and nomenclatural revisions
Recommended from our members
Illustration List for Macrolichens of the Pacific Northwest, 2nd edition (2009)
References are given for illustrations in the second edition of Macrolichens of the Pacific Northwest. For each illustration, we list the photographer or illustrator, the specimen photographed, where the specimen was from, collector, collection number, and herbarium
Estimating age of rock cairns in southeast Alaska by combining evidence from successional metrics, lichenometry, and carbon dating
We estimated ages of rock cairns in alpine tundra in southeast Alaska by combining information from three general classes of methods, each of them imperfect, but considered together providing better estimates than any of the three alone. We used lichenometry, radiocarbon dating, and five successional metrics: score on a nonmetric multidimensional scaling axis of vegetation composition, cover-weighted average successional class of organisms, overgrowth of contact points between rocks, sum of species cover, and species richness. Lichenometry estimated absolute ages, but with considerable error because we violated key assumptions. Successional metrics provided relative ages, probably with more precision than lichenometry, but did not provide absolute ages. Although the relative age estimates from traditional lichenometry seemed least reliable, collectively they supported the hypothesis of prehistoric origins for the cairns with a range of possible absolute ages of 258–892 years. Similarly, radiocarbon dates for the cairns suggested cairn construction before European settlement, about 450–1500 years B.P. The five successional metrics were in general agreement with each other on relative ages. Combining all methods provided more information than any of the methods alone. We conclude that the cairns were built over a range of times, probably over centuries, most likely 500–1500 years B.P
Recommended from our members
Illustration list for Macrolichens of the Pacific Northwest, 3rd edition (2023)
We give references for illustrations in the third edition of Macrolichens of the Pacific Northwest. For each illustration, we list the photographer or illustrator, the specimen photographed, where the specimen was from, collector, collection number, and herbarium
Recommended from our members
Origin of the dust bunny distribution in ecological community data
The distribution of sample units in multivariate species space typically departs strongly from the multivariate normal distribution. Instead of forming a hyperellipse in species space, the sample points tend to lie along high-dimensional edges of the space. This dust bunny distribution is seen in most ecological community data sets. The practical consequences of the distribution to the analysis of community data are well known and severe, but no one has demonstrated how population processes generate these problems. We evaluate potential causes of dust bunny distributions by simulating a large number of non-equilibrial communities under varying conditions, verifying that they resemble real data, then analyzing the relationship between the intensity of the dust bunny distribution in these data sets and the population and environmental parameters that gave rise to them. All community data sets, both simulated and real, departed strongly from multivariate normal and lognormal distributions. Four parameters influenced intensity of dust bunnies: time since community-replacing disturbance, number of environmental factors, dispersal limitation, and niche width. Samples measured soon after community-replacing disturbance had strong dust bunny distributions. Near-equilibrial communities sampled from a narrow range in environments lead to only weak dust bunnies. Community samples taken across multiple simultaneous strong environmental gradients are likely to show strong dust bunnies, regardless of the successional state, niche width of the component species, and degree of dispersal limitation. Dust bunny intensity depends not only on population processes and disturbance, but also on the properties of the sample, such as sample unit area or volume.Keywords: Simulation model, Environment, Community analysis, Disturbance, Niche widt
- …