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Knowledge on environmental variability and how it is affected by disturbances is crucial for understanding patterns of biodiversity
and determining adequate conservation strategies. The aim of this study is to assess environmental variability in patches
undergoing post-fire vegetation recovery, identifying trends of change and their relevant drivers. We particularly evaluate:
the value of three spectral indices derived from Landsat satellite data [Normalized Burn Ratio (NBR), Normalized Difference
Vegetation Index (NDVI) and Wetness Component of the Tasseled Cap Transformation (TCW)] for describing secondary succession;
the effectiveness of three metrics (diversity, evenness and richness) as indicators of patch variability; and how thematic
resolution can affect the perception of environmental variability patterns. While the system was previously characterised
as highly resilient from estimations of vegetation cover, here we noted that more time is required to fully recover pre-fire
environmental variability. Using mean diversity as indicator of patch variability, we found similar patterns of temporal change
for the three spectral indices (NBR, NDVI and TCW). Analogous conclusions could be drawn for richness and evenness. Patch
variability, measured as diversity, showed consistent patterns across thematic resolutions, although values increased with
the number of spectral classes. However, when the variance of diversity was plotted against thematic resolution, different
scale dependencies were detected for those three spectral indices, yielding a dissimilar perception of patch variability.
In general terms, NDVI was the best performing spectral index to assess patterns of vegetation recovery, while TCW was the
worst. Finally, burned patches were classified into three classes with similar trends of change in environmental variability,
which were strongly related to fire severity, elevation and vegetation type. 相似文献
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Rebecca M. Montague-Drake David B. Lindenmayer Ross B. Cunningham John A. Stein 《Landscape Ecology》2011,26(10):1383-1394
We explored the effects of a purported ‘reverse keystone species’, the Noisy Miner (Manorina melanocephala) using a long-term, large-scale dataset. Specifically, we identify whether this aggressive bird affects the landscape distribution
patterns of other avifauna, by displacing them into, or restricting their distribution to, less productive areas, and in so
doing, adheres to ‘isoleg theory’. We sought to determine the effect of abundance of the Noisy Miner on the abundance of other
birds (individual species and groups), and determine whether that effect was consistent with varying site productivity, using
a negative binomial distribution with a logarithmic link function, and an offset variable to account for variations in search
effort. Relationships between abundance of Noisy Miners and habitat variables were examined using a Poisson distribution with
a logarithmic link function scaled for extra-variation (quasi-Poisson regression). We demonstrate that when Noisy Miner abundance
is low, many small passerine species are more abundant on high productivity sites. However, as Noisy Miner abundance increases,
small passerine abundance decreases, with this decrease most apparent on productive sites. The same patterns were not evident
for birds considered ‘non-competitors’ of the Noisy Miner. We identify that both site productivity and vegetation structure influence the abundance of the Noisy Miner. We reveal that the species increasingly tolerates ‘less
desirable’ habitat attributes with increasing site productivity. The preference of the Noisy Miner for productive areas is
likely to have deleterious impacts on the long-term survival and reproductive success of other Australian woodland bird species,
many of which have already undergone severe declines. 相似文献