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991.
The objective of this paper is to identify land-cover types where fire incidence is higher (preferred) or lower (avoided)
than expected from a random null model. Fire selectivity may be characterized by the number of fires expected in a given land-cover
class and by the mean surface area each fire will burn. These two components of fire pattern are usually independent of each
other. For instance, fire number is usually connected with socioeconomic causes whereas fire size is largely controlled by
fuel continuity. Therefore, on the basis of available fire history data for Sardinia (Italy) for the period 2000–2004 we analyzed
fire selectivity of given land-cover classes keeping both variables separate from each other. The results obtained from analysis
of 13,377 fires show that for most land-cover classes fire behaves selectively, with marked preference (or avoidance) in terms
of both fire number and fire size. Fire number is higher than expected by chance alone in urban and agricultural areas. In
contrast, in forests, grasslands, and shrublands, fire number is lower than expected. In grasslands and shrublands mean fire
size is significantly larger than expected from a random null model whereas in urban areas, permanent crops, and heterogeneous
agricultural areas there is significant resistance to fire spread. Finally, as concerns mean fire size, in our study area
forests and arable land burn in proportion to their availability without any significant tendency toward fire preference or
avoidance. The results obtained in this study contribute to fire risk assessment on the landscape scale, indicating that risk
of wildfire is closely related to land cover. 相似文献
992.
The urban region: natural systems in our place,our nourishment,our home range,our future 总被引:1,自引:1,他引:0
Richard T. T. Forman 《Landscape Ecology》2008,23(3):251-253
993.
A significant challenge facing forestry today is managing private forests sustainably in the face of continued ownership fragmentation
(i.e., parcelization). Cross-boundary coordination––where forest practices are coordinated across multiple properties––has
been proposed as a mechanism by which landscape-level ecological and economic benefits may be accrued in privately-owned landscapes,
but few tests of the concept exist. Using a case study approach, we quantify the extent to which ownership-centric forest
management is constrained by economies of scale and misses opportunities to achieve ecological objectives in three landscapes
in Wisconsin, USA. Methods are based on existing forest management plans and include spatial analysis of patch distributions
and shapes, simulation of forest practices, and calculation of net present value over a 20-year horizon. Our results indicate
substantial opportunity for cross-boundary coordination: between 62% and 88% of the managed properties within our study landscapes
were adjacent to other properties with forest management plans. At a patch scale, coordination can result in ecological benefits
that can be accrued into the future (e.g., maintenance of large patches and natural ecosystem boundaries). Because these landscapes
are already highly parcelized, however, coordination offers little opportunity to impact the overall landscape-scale structure.
Greater economies of scale can also be gained by coordinating forest practices, including increases in the size (16–99%) and
volume of timber sales (16–94%), and a modest economic advantage (3–6%). As first steps, investment in data infrastructure
and professional training are required to support cross-boundary multi-ownership forest management. More broadly is the need
to shift from policies and practices that are largely ownership-centric to those that include and better incorporate landscape-centric
perspectives. 相似文献
994.
Relationships of dead wood patterns with biophysical characteristics and ownership according to scale in Coastal Oregon,USA 总被引:1,自引:0,他引:1
Dead wood patterns and dynamics vary with biophysical factors, disturbance history, ownership, and management practices; the
relative importance of these factors is poorly understood, especially at landscape to regional scales. This study examined
current dead wood amounts in the Coastal Province of Oregon, USA, at multiple spatial scales. Objectives were to: (1) describe
current regional amounts of several characteristics of dead wood; (2) compare dead wood amounts across ownerships; (3) determine
the relative importance, according to spatial scale, of biophysical and ownership characteristics, to regional dead wood abundance.
Dead wood plot data were evaluated with respect to explanatory variables at four spatial scales of resolution: plots, subwatersheds,
watersheds and subbasins. The relationships of dead wood characteristics with biophysical attributes and ownership were diverse
and scale-specific. Region-wide dead wood abundance and types varied among ownerships, with public lands typically having
higher amounts of dead wood and more large dead wood than private lands. Regression analysis of total dead wood volume indicated
that ownership was important at the subbasin scale. Growing season moisture stress was important at plot, subwatershed, and
watershed scales. Topography was important at the two coarser scales. Multivariate analysis of dead wood gradients showed
that ownership was important at all scales, topography at the subbasin scale, historical vegetation at watershed and subbasin
scales, and current vegetation at plot and subwatershed scales. Management for dead wood and related biodiversity at watershed
to landscape scales should consider the distinct dynamics of snags and logs, the importance of historical effects, and the
relevance of ownership patterns. 相似文献
995.
Responses of species to landscape modifications are generally documented through their distribution at a given time along
an intensity gradient of land transformation. By focusing on patterns, we are limited to infer ecological processes occurring
within a system and its response to environmental disturbances which can further change over time. Using diachronic datasets
at the scale of France, we analyzed the spatial responses of the black-billed magpie, which has recently colonized cities,
to landscape urbanization. This study applied recently developed statistical approaches incorporating detection uncertainty
of the magpie, based on the capture-recapture statistical framework. We tested whether, and how, extinction and colonization
mechanisms influenced variations of magpie occupancy from 2001 to 2005. In addition, we assessed the importance of the recent
urbanization of the French countryside in determining population dynamics. Overall, our analysis proved that the proportion
of urban areas and recent urbanization in France led to an increase in the probability of magpie occupancy. Unexpectedly,
the species is concomitantly disappearing from the countryside, leading to a rapid change in the distribution of the species.
This study stressed the importance of incorporating detection uncertainty in inference process about spatial dynamics. Overall,
we show how useful it is to account for the dynamic evolution of the landscape in ecological studies. 相似文献
996.
In reply to the critique of Baird and Kerr, we emphasize that our model is a generalized vulnerability model, built from easily
acquired data from anywhere in the world, to identify areas with probable susceptibility to large tsunamis—and discuss their
other criticisms in detail. We also show that a rejection of the role of trees in helping protect vulnerable areas is not
justified in light of existing evidence. 相似文献
997.
Landscape context influences many aspects of songbird ecology during the breeding season. The importance of landscape context
at stopover sites for migrating songbirds, however, has received less attention. In particular, landscape context may affect
the availability and quality of food for refueling during stopovers, which is critical for successful migration. We evaluated
the influence of woody habitat cover in the surroundings of stopover sites at several spatial extents on the hourly changes
of body mass in two species of European-African forest-dwelling songbird migrants (Willow Warbler, Phylloscopus trochilus, and the Eurasian Redstart, Phoenicurus phoenicurus). Data were sampled by standardized methods from a network of ringing stations throughout Europe during the falls of 1994–1996.
In both species, hourly body mass gain calculated for first captures increased with woody habitat cover. We found a similar
logarithmic relationship for both species, although for Willow Warblers mass gain was more strongly related to the habitat
cover within 5 km, in contrast to 3 km for Redstarts. For Willow Warblers, where sufficient data are available for each year,
the relationship is consistent over the years. The shape of the relationship suggests existence of a threshold of landscape
suitability for refueling at stopover sites: in sites with less than 10% of woody habitat cover, birds tend to lose body mass
or to gain mass at a lower rate.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
998.
Kirtland’s warblers (Dendroica kirtlandii) persist in a naturally patchy environment of young, regenerating jack pine forests (i.e., 5–23 years old) created after
wildfires and human logging activities. We examined how changing landscape structure from 26 years of forest management and
wildfire disturbances influenced population size and spatial dispersion of male Kirtland’s warblers within their restricted
breeding range in northern Lower Michigan, USA. The male Kirtland’s warbler population was six times larger in 2004 (1,322)
compared to 1979 (205); the change was nonlinear with 1987 and 1994 identified as significant points of change. In 1987, the
population trend began increasing after a slowly declining trend prior to 1987, and the rate of increase appeared to slow
after 1994. Total amount of suitable habitat and the relative area of wildfire-regenerated habitat were the most important
factors explaining population trend. Suitable habitat increased 149% primarily due to increasing plantations from forest management.
The relative amount and location of wildfire-regenerated habitat modified the distribution of males among various habitat
types, and the spatial variation in their abundance across the primary breeding range. These findings indicate that the Kirtland’s
warbler male population shifted its use of habitat types temporally and spatially as the population increased and as the relative
availability of habitats changed through time. We demonstrate that researchers and managers need to consider not only habitat
quality, but the temporal and the spatial context of habitat availability and population levels when making habitat restoration
decisions. 相似文献
999.
1000.