One possible way to test the TDH boreal forest and short-grass prairie ecosys- However, Fischer et al. He reasoned that more small birds landscape texture qualitatively, not quanti- texture in multiple landscapes within an would occur in the boreal forest because this tatively.
The characteristic length- branches than the prairie. As predicted, ent dominant habitat scales. It is unclear scale of each landscape could be obtained the categories of species with the smallest whether what we — or Holling , or using land-cover data and the techniques sizes in the boreal forest were much reduced Fischer et al.
Different in or entirely absent from the prairie. Furthermore, the sub- dominant scale , but the set of these scales vided primarily by evidence of clumped jective selection of landscapes of varying across the landscapes represents the hierar- body-mass distributions in a wide variety of texture from a human perspective may not chical habitat structure for the ecoregion.
Dashed circles A, B, and C represent landscapes where single habitat scales predominate, so the TDH predicts the predominance of a single body-size category in each. Ecological Monographs, 62, — Oikos, 59, — Landscape variance would be further evidence in de la Montana, E. Carrascal, L. Journal of Applied erogeneous landscapes via scale niche TDH, namely that landscapes dominated by diversification. Ecosystems, 9, — Ecology, 43, — However, their assessment story environment in tall, old-growth, texture in conservation biogeography: a of habitat structure is purely qualitative; we conifer forests.
Literature indicates nomadic and declining bird species populations occur at the edges of body mass aggregations more frequently than expected. Migratory bird species also may be located at the edges of body mass aggregations more frequently than expected.
The morphological spacing of species within aggregations may yield clues regarding species interactions. The distribution of species within a body mass aggregation would have low variance if species within an aggregation interact with each other strongly — morphological overdispersion has been documented in many animal communities and reflects strong competitive interactions among species. I analyzed nomadism, migration, and decline in South African birds using an information-theoretic approach.
I assembled a series of plausible models based upon suggested or theoretically predictive characteristics. Additionally, I used a series of Monte Carlo simulations to investigate the distribution of species within aggregations, in terms of body mass. Results suggest that a combination of species characteristics, including the distance to the edge of a body mass aggregation, explain the complex phenomena of nomadism, migration and decline.
It is unclear scale of each landscape could be obtained the categories of species with the smallest whether what we — or Holling , or using land-cover data and the techniques sizes in the boreal forest were much reduced Fischer et al. Quantifying the full hierarchical objects, those that can be measured at small stands thinned of their understory shrub structure of a landscape necessitates obtain- spatial and temporal scales such as shrubs layer than in unthinned stands in central ing field measurements over multiple obser- and individual trees, to coarsely textured Spain. Ecological Monographs, 62, — The morphological spacing of species within aggregations may yield clues regarding species interactions. Discontinuity approaches remain a fruitful avenue of research in the quest for quantitative measures of resilience because discontinuity analysis provides an objective means of identifying scales in complex systems and facilitates delineation of hierarchical patterns in processes, structure, and resources. Coupled nonlinear interactions can create positive feedback loops over relatively discrete spatial and temporal scales.
Ecological Monographs, 62, — Migration is thought to arise as a result of the exploitation of certain scarce or variable food resources. Habeeb, R. Nomadism, migration, and decline are complex phenomena which incorporate different species characteristics, perhaps explaining why such debate still exists over the causes of these phenomena.