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121.
Confronting collinearity: comparing methods for disentangling the effects of habitat loss and fragmentation 总被引:1,自引:1,他引:0
Adam C. Smith Nicola Koper Charles M. Francis Lenore Fahrig 《Landscape Ecology》2009,24(10):1271-1285
Estimating the relative importance of habitat loss and fragmentation is necessary to estimate the potential benefits of specific
management actions and to ensure that limited conservation resources are used efficiently. However, estimating relative effects
is complicated because the two processes are highly correlated. Previous studies have used a wide variety of statistical methods
to separate their effects and we speculated that the published results may have been influenced by the methods used. We used
simulations to determine whether, under identical conditions, the following 7 methods generate different estimates of relative
importance for realistically correlated landscape predictors: residual regression, model or variable selection, averaged coefficients
from all supported models, summed Akaike weights, classical variance partitioning, hierarchical variance partitioning, and
a multiple regression model with no adjustments for collinearity. We found that different methods generated different rankings
of the predictors and that some metrics were strongly biased. Residual regression and variance partitioning were highly biased
by correlations among predictors and the bias depended on the direction of a predictor’s effect (positive vs. negative). Our
results suggest that many efforts to deal with the correlation between amount and fragmentation may have done more harm than
good. If confounding effects are controlled and adequate thought is given to the ecological mechanisms behind modeled predictors,
then standardized partial regression coefficients are unbiased estimates of the relative importance of amount and fragmentation,
even when predictors are highly correlated. 相似文献
122.
Robert A. Mccleery 《Landscape Ecology》2009,24(4):483-493
Predator stimuli created by humans in the urban environment may alter animals’ anti-predator behaviors. I hypothesized that
habituation would cause anti-predator behaviors to decrease in urban settings in response to humans. Additionally, I hypothesized
that populations habituated to humans would show reduced responses to other predator stimuli. I observed three populations
of squirrels (urban, suburban and rural) responses to human approaches, red-tailed hawk vocalizations (Buteo jamaicensis) and coyote (Canis latrans) vocalizations. Mahalanobis distances of anti-predator behaviors in response to human approaches were consistent with the
urban–rural gradient. Flight initiation distances (X
2 = 26.33, df = 2, P < 0.001) and amount of time dedicated to anti-predator behavior (X
2 = 10.94, df = 2, P = 0.004) in response to human approaches were also consistent with the urban–rural gradient. Supporting the habituation hypothesis,
naive juvenile squirrels increased flight initiation distances (X
2 = 35.89, df = 1, P < 0.001) and time dedicated to anti-predator behaviors (X
2 = 9.46, df = 1, P = 0.002) relative to adult squirrels in the same urban environment. Time dedicated to anti-predator behaviors differed among
all three sites in response to both coyote (X
2 = 9.83, df = 2, P = 0.007) and hawk (X
2 = 6.50, df = 2, P = 0.035) vocalizations. Responses to both vocalizations on rural sites (coyote = 45%, hawk = 55%) greater than twice that
found on the urban sites (coyote = 11%, hawk = 20%). This is possibly the first case of a transfer of habituation demonstrated
under field conditions. 相似文献
123.
The ecology and culture of landscape sustainability: emerging knowledge and innovation in landscape research and practice 总被引:4,自引:1,他引:3
Laura R. Musacchio 《Landscape Ecology》2009,24(8):989-992
Landscape researchers and practitioners, using the lens of sustainability science, are breaking new ground about how people’s
behaviors and actions influence the structure, function, and change of designed landscapes in an urbanizing world. The phrase—the
scientific basis of the design for landscape sustainability—is used to describe how sustainability science can contribute
to translational landscape research and practice about the systemic relationships among landscape sustainability, people’s
contact with nature, and complex place-based problems. In the first section of this article, important definitions about the
scientific basis of the design for landscape sustainability are reviewed including the six Es of landscape sustainability—environment, economic, equity, aesthetics, experience, and ethics. A conceptual framework about the six Es of landscape sustainability for designed landscapes is introduced. The interrelatedness,
opportunities, contradictions, and limitations of the conceptual framework are discussed in relation to human health/security,
ecosystem services, biodiversity, and resource management. The conceptual framework about the six Es of landscape sustainability
for designed landscapes follows the tradition in which landscape researchers and practitioners synthesize emerging trends
into conceptual frameworks for advancing basic and applied activities. 相似文献
124.
125.
The discipline of landscape ecology recognizes the importance of measuring habitat suitability variables at spatial scales
relevant to specific organisms. This paper uses a novel multi-scale hierarchical patch delineation method, PatchMorph, to
measure landscape patch characteristics at two distinct spatial scales and statistically relate them to the presence of state-listed
endangered yellow-billed cuckoos (Coccyzus americanus occidentalis) nesting in forest patches along the Sacramento River, California, USA. The landscape patch characteristics calculated were:
patch thickness, area of cottonwood forest, area of riparian scrub, area of other mixed riparian forest, and total patch area.
A third, regional spatial variable, delineating the north and south portions of study area was also analyzed for the effect
of regional processes. Using field surveys, the landscape characteristics were related to patch occupancy by yellow-billed
cuckoos. The area of cottonwood forest measured at the finest spatial scale of patches was found to be the most important
factor determining yellow-billed cuckoo presence in the forest patches, while no patch characteristics at the larger scale
of habitat patches were important. The regional spatial variable was important in two of the three analysis techniques. Model
validation using an independent data set of surveys (conducted 1987–1990) found 76–82% model accuracy for all the statistical
techniques used. Our results show that the spatial scale at which habitat characteristics are measured influences the suitability
of forest patches. This multi-scale patch and model selection approach to habitat suitability analysis can readily be generalized
for use with other organisms and systems. 相似文献
126.
Combining top-down and bottom-up dynamics in land use modeling: exploring the future of abandoned farmlands in Europe with the Dyna-CLUE model 总被引:9,自引:0,他引:9
Land use change is the result of interactions between processes operating at different scales. Simulation models at regional
to global scales are often incapable of including locally determined processes of land use change. This paper introduces a
modeling approach that integrates demand-driven changes in land area with locally determined conversion processes. The model
is illustrated with an application for European land use. Interactions between changing demands for agricultural land and
vegetation processes leading to the re-growth of (semi-) natural vegetation on abandoned farmland are explicitly addressed.
Succession of natural vegetation is simulated based on the spatial variation in biophysical and management related conditions,
while the dynamics of the agricultural area are determined by a global multi-sector model. The results allow an exploration
of the future dynamics of European land use and landscapes. The model approach is similarly suitable for other regions and
processes where large scale processes interact with local dynamics. 相似文献
127.
Russell Fairfax Rod Fensham Don Butler Kelvin Quinn Bernice Sigley James Holman 《Landscape Ecology》2009,24(10):1363-1373
There is circumstantial evidence that grasslands on the Bunya Mountains were once maintained by Aboriginal burning, and with
lack of fire under European management are being colonised by trees. To assess the efficacy of burning for maintaining grasslands,
119 fires were lit between 1996 and 2006. The total area of unburnt grasslands decreased by 27%, while grasslands burnt at
least once decreased by 1%. The density of invading trees was recorded from fixed plots on 23 grasslands burnt between one
and six times. Cassinia was virtually eliminated and the density of the Rainforest species guild slowly but continually declined. Acacia irrorata exhibited a humped response, with initial increases resulting from vegetative resprouting and gradual decline with persistent
burning. Phyllodinous Acacia and Woodland trees were the least fire sensitive guilds, having stable or increased density with repeated burning. Multi-factor
regression modelling detected no significant relationships between changes in woody plant density and the interval between
fires, fire intensity, the initial density of large trees, an index of soil moisture, or the cumulative number of fires for
any species guild. The survivorship of both Cassinia and Rainforest guilds was significantly lower with summer burning than winter burning, but a seasonal effect of burning was
not evident for other guilds. The findings suggest that regardless of fire conditions, frequent burning will reduce the number
of adult trees, maintain resprouts in an immature state, facilitate further fire and reduce the rate of grassland loss. Woodland
species are especially resilient to fire, and burning to maintain grassy ecosystems will be most successful where the main
colonisers are rainforest species and burning is conducted in summer. The findings suggest that the montane grasslands of
the Bunya Mountains were maintained by anthropogenic burning and active fire management will prolong their existence. 相似文献
128.
129.
Margarita Ramos-García Salvador Ortega-Centeno Ana N. Hernández-Lauzardo Irán Alia-Tejacal Elsa Bosquez-Molina Silvia Bautista-Baños 《Scientia Horticulturae》2009
The state of Morelos, Mexico has gradually become an important producer of gladiolus. Some preconditioning treatments of corms are empirically done causing uneven emergence and low quality of flowers. In this investigation, before planting, gladiolus corms var. ‘Blanca Borrego’ were dipped in chitosan (chitosan reagent and commercial chitosan Biorend®), in hot water at various temperatures and in treatments combined with Biorend® at 1.5% and hot water. Results indicated that the most influenced variables were corm germination, number of flowers per spike, number of cormlets and vase life. Overall, the commercial product Biorend® at 1.5% accelerated corm emergence in approximately 4 days, the number of flowers increased by 2–7 and the vase life extended for 3 days. The number of cormlets was also duplicated. Corms dipped in the commercial chitosan Biorend® at 1.5% at different intervals of time were not greatly affected except for the emergence and number of cormlets. However, for this experiment there were significant effects on the number of leaves and flowers because of the interactions between chitosan and the immersion time. The temperature of 55 °C affected plant development because emergence was delayed by 6 days; and there were less number of leaves, flowers and cormlets. On the other hand, the incidence of Fusarium oxysporum in naturally infected corms was 0% at temperatures of 55 °C and 50 °C. Immersion times (0, 10, 15 and 20 min) in hot water at 50 °C did not show significant effects on plant development and vase life. Corms dipped in Biorend® at 1.5% and hot water at 50 °C accelerated their emergence for about 1–7 days, the number of flowers increased by two, extended the storage life for 1–3 days and increased the number of cormlets. The integration of these two treatments -Biorend® and hot water- might be a good option for increasing the gladiolus plant quality and vase life. 相似文献
130.
Tradable biodiversity credit systems provide flexible means to resolve conflicts between development and conservation land-use
options for habitats occupied by threatened or endangered species. We describe an approach to incorporate the influence of
habitat fragmentation into the conservation value of tradable credits. Habitat fragmentation decreases gene flow, increases
rates of genetic drift and inbreeding, and increases probabilities of patch extinction. Importantly, tradable credit systems
will change the level of fragmentation over time for small and/or declining populations. We apply landscape equivalency analysis
(LEA), a generalizable, landscape-scale accounting system that assigns conservation value to habitat patches based on patch
contributions to abundance and genetic variance at landscape scales. By evaluating habitat trades using two models that vary
the relationship between dispersal behaviors and landscape patterns, we show that LEA provides a novel method for limiting
access to habitat at the landscape-scale, recognizing that the appropriate amount of migration needed to supplement patch
recruitment and to offset drift and inbreeding will vary as landscape pattern changes over time. We also found that decisions
based on probabilities of persistence alone would ignore changes in migration, genetic drift, and patch extinction that result
from habitat trades. The general principle of LEA is that habitat patches traded should make at least equivalent contributions
to rates of recruitment and migration estimated at a landscape scale. Traditional approaches for assessing the “take” and
“jeopardy” standards under the Endangered Species Act based on changes in abundance and probability of persistence may be
inadequate to prevent trades that increase fragmentation. 相似文献