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Habitats Decreased (habitat + decreased)

Distribution by Scientific Domains

Life Sciences	50%
Earth and Environmental Science	50%

Selected Abstracts

Use of GIS to predict effects of water level on the spawning area for smelt, Retropinna retropinna, in Lake Taupo, New Zealand

FISHERIES MANAGEMENT & ECOLOGY, Issue 4 2002
D. K. ROWE
A GIS model of the littoral bathymetry and substrate composition of Lake Taupo was created using ArcInfo. Littoral substrates were mapped by aerial photography and confirmed by ground-truthing. Water depths were determined by echosounding linked to a differential GPS. These data were imported into ArcInfo where a 3D GIS model was used to calculate the total area of smelt, Retropinna retropinna Richardson, spawning habitat (i.e. clean sand between depths of 0.5,2.5 m) at each of five lake levels. There was little change in area over the first 50 cm below the natural maximum lake level, but spawning habitat decreased rapidly over the next 1.4 m such that a 30% reduction occurred at the natural minimum level. Anecdotal information on inter-annual variations in lake level and smelt abundance supported the notion that high lake levels in spring result in high recruitment of smelt. The GIS model also predicted effects of lake level change on areas of macrophyte cover and on other littoral substrates, and could be used to assess effects of lake level changes on the habitats of other biota. [source]

Post-fire recovery of ant communities in Submediterranean Pinus nigra forests

ECOGRAPHY, Issue 2 2006
Anselm Rodrigo
This study analyzes the variations in the structure and composition of ant communities in burned Pinus nigra forests in central Catalonia (NE Spain). Pinus nigra forests do not recover after fire, changing to shrublands and oak coppices. For this reason, we suggest that ant communities of burned P. nigra forests will change after fire, because the post-fire scenario, in particular with the increase of open areas, is different to the unburned one, and more favourable for some species than for others. In four locations previously occupied by P. nigra forests where different fires occurred 1, 5, 13 and 19 yr before the sampling, we sampled the structure and composition of ant communities with pitfall traps, tree traps and net sweeping in unburned plots and in plots affected by canopy and understory fire. The results obtained suggest that canopy and understory fire had little effect on the structure of ant communities. Thus, many variables concerning ant communities were not modified either by fire type (understory or canopy fire) or by time since fire. However, a number of particular species were affected, either positively or negatively, by canopy fire: three species characteristic of forest habitats decreased after fire, while eight species characteristic of open habitats increased in areas affected by canopy fire, especially in the first few years after fire. These differences in ant community composition between burned and unburned plots imply that the maximum richness is achieved when there is a mixture of unburned forests and areas burned with canopy fire. Moreover, as canopy cover in P. nigra forests burned with canopy fire is not completed in the period of time studied, the presence of the species that are characteristic of burned areas remains along the chronosequence studied, while the species that disappear after fire do not recover in the period of time considered. Overall, the results obtained indicate that there is a persistent replacement of ant species in burned P. nigra forests, as is also the case with vegetation. [source]

How does surrounding vegetation affect the course of succession: A five-year container experiment

JOURNAL OF VEGETATION SCIENCE, Issue 4 2009
ch Lanta
Abstract Question: How does location and time of insertion affect the course of succession in experimental containers? Location: Bene,ov nad Lipou, ,eskomoravská vrchovina (Czech-Moravian uplands), Czech Republic Methods: We designed a 5-year container experiment in which plant succession started from scratch. Soil conditions were constant and all containers were filled with homogeneous substrate containing no propagules. We placed the containers in two contrasting habitats (meadow and floodplain) under identical climatic conditions but differing in surrounding vegetations and hence seed input. New containers were installed (and hence succession started) in two subsequent years, twice in each year (spring and autumn). We assume that the individual dates would lead to differences in propagule input and weather conditions. Results: Although both year and season of succession initiation considerably affected the initial species composition, we observed a pronounced convergence within the set of containers located in each habitat. However, the similarity of containers initiated at the same time but located in different habitats decreased over the course of succession. Final composition of the meadow and floodplain containers was therefore mostly determined by permanent seed input from their nearby neighborhood. Conclusions: This study demonstrated that propagule availability is an important determinant of the course of succession, and that differential seed input leads to different pathways of succession, even when all other environmental conditions are equal. [source]

Growth rate constrain morphological divergence when driven by competition

OIKOS, Issue 1 2006
Jens Olsson
Resource competition has been hypothesized to be important in driving divergence by natural selection. The effect of competition on morphological divergence and plasticity has however rarely been investigated. Since low growth rates might constrain morphological modulation and individual growth rates usually are negatively related to the intensity of competition, there might be a connection between competition, growth rate and morphological divergence. We performed an aquarium experiment with young-of-the-year Eurasian perch (Perca fluviatilis L.) to investigate how individual growth rate affected morphological plasticity induced by contrasting habitat treatments. Furthermore, in a field study of 10 lakes we also related the degree of morphological differentiation between habitats to the intraspecific competitior biomass. In the aquarium experiment we found that morphological plasticity was growth rate dependent in that morphological differentiation between the habitat treatments was confined to high individual growth rates. In the field study we found that morphological differentiation between habitats decreased with increasing intraspecific competitior biomass. Since plasticity is hypothesized to be important in divergence and intraspecific biomass could serve as a proxy for the level of competition, we suggest that our results indicate that morphological divergence might be constrained during periods of intense intraspecific competition due to low growth rates. A possible scenario is that at low growth rates all energy available is used for metabolic maintenance and no surplus energy is therefore available for morphological modulation. [source]