Search Results
. Functional trait and phylogenetic tests of community assembly across spatial scales in an Amazonian forest . Ecol. Monog. 80 : 401 – 422 . Law , R. , Illian , J. , Burslem , D
405 220 227 Gering, J.C., T.O. Crist and J.A. Veech. 2003. Additive partitioning of species diversity across multiple spatial scales: implications
: the importance of spatial scale in species assemblages. Abstr. Bot. 17: 289–302. Bartha S. Pattern, area and diversity: the importance of spatial scale in species assemblages
The recovery process of a Dutch heathland after fire is investigated. The study area, 12 m x 20 m, has been surveyed yearly between 1963 and 1993. Previous work has shown that a stationary Markov chain models the observed recovery process well. However, the Markov model fails to capture an important observation, the existence of a phase structure. The process begins deterministically, but small random (non-Markov) effects accumulate through time and at some point the process suddenly becomes noisy. Here we make use of the spatial information contained in vegetation maps to examine dynamics at a fine spatial scale. We find that the phases observed at a large spatial scale separate themselves out distinctly at finer spatial scales. This spatial information allows us to investigate hypotheses about the mechanisms governing deterministic versus noisy vegetation dynamics.
Rarefaction has long represented a powerful tool for detecting species richness and its variation across spatial scales. Some authors recently reintroduced the mathematical expression for calculating sample-based rarefaction curves. While some of them did not claim any advances, others presented this formula as a new analytical solution. We provide evidence about formulations of the sample-based rarefaction formula older than those recently proposed in ecological literature.
Tree species richness is remarkably high in many tropical forests, even at very fine spatial scales. However, the study of fine-scale richness is complicated by the rarefaction effect: that is, a trivial correlation between the number of individuals and the number of species. We developed null models to test whether fine-scale species richness differs from random expectation, and applied these models to a dataset of 1170 100 m2circular plots in the old-growth portion of La Selva Biological Station in the Atlantic Lowlands of Costa Rica. Although species richness in these plots was close to its theoretical maximum, we found that it was frequently lower than null expectation. This was a result of slightly clumped distributions within species. We found no relationships between species richness at the 100 m2scale and soil type or topography, after accounting for the effects of density
We analyzed long-term data related to temporal and spatial variation in fish assemblages from five sites along the Suquía River Basin (Córdoba, Argentina). We aimed at determining whether water quality variations generate changes in fish assemblage structure and composition along the river. Despite deterioration of water quality recorded along the basin, fish assemblages were characterized as qualitatively persistent and quantitatively stable, indicating that the specific composition were relatively constant over time. However, on a temporal scale, fish assemblages from the most polluted areas responded to the water quality degradation with a greater variation of species abundance than those from pristine sites. On a spatial scale, changes in fish assemblage structure were related with watershed disturbance gradient and indicated a strong association between fish species distribution and water quality variation. The alterations found in our study suggest a potential imbalance of fish assemblage structure in the long term.
Due to the difficulties of field-based species data collection at wide spatial scales, remotely sensed spectral diversity has been advocated as one of the most effective proxies of ecosystem and species diversity. It is widely accepted that the relationship between species and spectral diversity is scale dependent. However, few studies have evaluated the impacts of scale on species diversity estimates from remote sensing data. In this paper we tested the species versus spectral relationship over very large scales (extents) with a varying spatial grain using floristic data of North America. Spectral diversity explained a low amount of variance while spatial extent of the sampling units (floras) explained a high amount of variance based on results from our variance partitioning analyses. This leads to the conclusion that spectral diversity must be carefully related to species diversity, explicitly taking into account potential area effects.
Stand and leaf scale responses of loess grassland swards to elevated air CO 2 concentration had been investigated in a mini FACE system during 1998–2000. The study concentrated on biomass, leaf area index (LAI) and vegetation surface temperature (stand scale) and on diurnal carbohydrate pattern and gas-exchange responses (leaf scale). Leaf net CO 2 uptake under prolonged exposure to elevated CO 2 showed an upward response in the dicotyledonous and a downward one in the monocotyledonous species. Dawn and evening carbohydrate levels in leaves suggested growth stimulation of the dicot under elevated CO 2 and the opposite for the grass species and indicated sink limitation as a major factor determining photosynthetic acclimation at the species level. The smaller LAI as well as the insignificant biomass response to elevated air CO 2 was a compounded response by multi-species stands. Under mild water shortage, elevated air CO 2 concentration partly alleviated the drought effect shown by the higher relative growth rate of LAI. Canopy surface temperatures of the vegetation in the CO 2 enriched rings were higher than those in the ambient rings suggesting that decreased leaf conductance and transpiration were responsible for the temperature difference between the treatments. Increased canopy surface temperature under elevated air CO 2 concentration will probably lead to increased sensible heat flux and therefore enhanced convection at larger spatial scales.
Abstract
Terrestrial ecosystems across the world experience large-scale and widespread urbanization, causing a sharp decline, fragmentation and segregation of natural landscapes. Nevertheless, fragments of natural habitats that are found within the largest cities may still be capable of preserving high species diversity that amount to a large portion of the regional biodiversity. Knowing which variables of the urban landscape promote the conservation of species' assemblages in large cities helps us to implement measures that support biodiversity conservation. We sampled the butterfly assemblages of eight urban forest fragments in Curitiba (Southern Brazil), from September 2015 to April 2016. At each site, richness, diversity and composition of butterflies were estimated and then correlated to nine landscape variables measured at two spatial scales (buffers of 250 and 750m). A total of 298 species were recorded in these fragments, representing 53.7% of all species known to occur in the city. Despite of great difference in the size of the fragments (between 27 and 56.3 ha), there were no significant differences in species richness among the fragments. On the other hand, some significant correlations were observed between landscape variables and butterfly composition other than the fragment itself, such as the paved area and total forested area present around the fragments. These results reinforce the idea that the conservation of natural fragments in urban areas requires public policies that enhance not only the habitat quality of the fragment itself, but also enrichment of the landscape around them.
