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Landscape Ecology - This study provides a unified, holistic framework for predicting the dynamics of shrub-grass conversion throughout Mediterranean-climate shrublands. This work focuses... 相似文献
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A combination of rapid population growth and an accelerating demographic shift from rural to urbanized habitats has resulted
in urbanization becoming an increasingly global phenomenon. Two alternate hypotheses describing urban landscape trajectories
suggest urbanization is either leading to more homogeneous global patterns or urbanization has dichotomous trajectories of
increasing dispersal or coalescence. To better understand the global variation in urban land-cover patterns and trajectories
we described the variation in urban landscape structure for 120 cities distributed throughout the world assessed at circa
1990 and 2000. We coupled these data to a low-dimensional neighborhood based model of urban growth using a data-model fusion
approach. Trajectories of urban growth were assessed using both the original data and model projections to 2030. The patterns
of landscape change were related to both the rate of growth and income. The historical patterns of change showed a trend of
increasing landscape complexity and this trend was projected to continue. Urban rate of growth was closely related to the
change in several landscape metrics. Income was associated with landscape dynamics and this effect interacted with city size.
Large cities were less sensitive to the income effect than small cities. Along with changes to the magnitude of each metric,
the overall variation in metrics between years generally exhibited a decrease in variability and this variability was projected
to continue decreasing. These findings supported the hypothesis that urban landscapes are becoming more homogeneous and that
the dispersal-coalescing dichotomy represent endpoints rather than alternate states of urban growth. 相似文献
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G. Darrel Jenerette 《Landscape Ecology》2018,33(10):1655-1668
Context
Ecological research, from organismal to global scales and spanning terrestrial, hydrologic, and atmospheric domains, can contribute more to reducing health vulnerabilities. At the same, ecological research directed to health vulnerabilities provides a problem-based unifying framework for urban ecologists.Objective
Provide a framework for expanding ecological research to address human health vulnerabilities in cities.Methods
I pose an urban ecology of human health framework that considers how the ecological contributions to health risks and benefits are driven by interacting influences of the environment, active management, and historical legacies in the context of ecological self-organization. The ecology of health framework is explored for contrasting examples including heat, vector borne diseases, pollution, and accessible greenspace both individually and in a multifunctional landscape perspective.Results
Urban ecological processes affect human health vulnerability through contributions to multiple hazard and well-being pathways. The resulting multifunctional landscape of health vulnerability features prominent hotspots and regional injustices. A path forward to increase knowledge of the ecological contributions to health vulnerabilities includes increased participation in in interdisciplinary teams and applications of high resolution environmental sensing and modeling.Conclusions
Research and management from a systems and landscape perspective of ecological processes is poised to help reduce urban health vulnerability and provide a better understanding of ecological dynamics in the Anthropocene.5.
G. Darrel Jenerette Sharon L. Harlan Alexander Buyantuev William L. Stefanov Juan Declet-Barreto Benjamin L. Ruddell Soe Win Myint Shai Kaplan Xiaoxiao Li 《Landscape Ecology》2016,31(4):745-760
Context
With rapidly expanding urban regions, the effects of land cover changes on urban surface temperatures and the consequences of these changes for human health are becoming progressively larger problems.Objectives
We investigated residential parcel and neighborhood scale variations in urban land surface temperature, land cover, and residents’ perceptions of landscapes and heat illnesses in the subtropical desert city of Phoenix, AZ USA.Methods
We conducted an airborne imaging campaign that acquired high resolution urban land surface temperature data (7 m/pixel) during the day and night. We performed a geographic overlay of these data with high resolution land cover maps, parcel boundaries, neighborhood boundaries, and a household survey.Results
Land cover composition, including percentages of vegetated, building, and road areas, and values for NDVI, and albedo, was correlated with residential parcel surface temperatures and the effects differed between day and night. Vegetation was more effective at cooling hotter neighborhoods. We found consistencies between heat risk factors in neighborhood environments and residents’ perceptions of these factors. Symptoms of heat-related illness were correlated with parcel scale surface temperature patterns during the daytime but no corresponding relationship was observed with nighttime surface temperatures.Conclusions
Residents’ experiences of heat vulnerability were related to the daytime land surface thermal environment, which is influenced by micro-scale variation in land cover composition. These results provide a first look at parcel-scale causes and consequences of urban surface temperature variation and provide a critically needed perspective on heat vulnerability assessment studies conducted at much coarser scales.6.
G. Darrel Jenerette Sharon L. Harlan Anthony Brazel Nancy Jones Larissa Larsen William L. Stefanov 《Landscape Ecology》2007,22(3):353-365
Regional climate change induced by rapid urbanization is responsible for and may result from changes in coupled human-ecological
systems. Specifically, the distribution of urban vegetation may be an important intermediary between patterns of human settlement
and regional climate spatial variability. To test this hypothesis we identified the relationships between surface temperature,
one component of regional climate, vegetation, and human settlement patterns in the Phoenix, AZ, USA region. Combining satellite-derived
surface temperature and vegetation data from an early summer day with US Census and topographic data, we found substantial
surface temperature differences within the city that correlate primarily with an index of vegetation cover. Furthermore, both
of these patterns vary systematically with the social characteristics of neighborhoods through the region. Overall, every
$10,000 increase in neighborhood annual median household income was associated with a 0.28°C decrease in surface temperature
on an early summer day in Phoenix. Temperature variation within a neighborhood was negatively related to population density.
A multivariate model generated using path analysis supports our hypothesis that social impacts on surface temperature occur
primarily through modifications of vegetation cover. Higher income neighborhoods were associated with increased vegetation
cover and higher density neighborhoods were associated with decreased vegetation variability. These results suggest that settlement
patterns in the central Arizona region influence regional climate through multiple pathways that are heterogeneously distributed
throughout the city. 相似文献
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To understand how urbanization has transformed the desert landscape in the central Arizona – Phoenix region of the United States, we conducted a series of spatial analyses of the land-use pattern from 1912–1995. The results of the spatial analysis show that the extent of urban area has increased exponentially for the past 83 years, and this urban expansion is correlated with the increase in population size for the same period of time. The accelerating urbanization process has increased the degree of fragmentation and structural complexity of the desert landscape. To simulate land-use change we developed a Markov-cellular automata model. Model parameters and neighborhood rules were obtained both empirically and with a modified genetic algorithm. Land-use maps for 1975 and 1995 were used to implement the model at two distinct spatial scales with a time step of one year. Model performance was evaluated using Monte-Carlo confidence interval estimation for selected landscape pattern indices. The coarse-scale model simulated the statistical patterns of the landscape at a higher accuracy than the fine-scale model. The empirically derived parameter set poorly simulated land-use change as compared to the optimized parameter set. In summary, our results showed that landscape pattern metrics (patch density, edge density, fractal dimension, contagion) together were able to effectively capture the trend in land-use associated with urbanization for this region. The Markov-cellular automata parameterized by a modified genetic algorithm reasonably replicated the change in land-use pattern. 相似文献
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Soil respiration (R) has not been adequately studied at temperatures above 35 °C, which are common temperatures for soils in the southwestern United States and may be important for C dynamics in semi-arid regions. While frequently excluded from ecosystem models or set to 35 °C, the optimum temperature for soil R is poorly understood. Optimum temperatures are likely controlled by substrate availability, soil moisture content, and previous climate. To quantify the optimal temperature for soil R and hypothesized relationships, we collected soils from beneath and between plant canopies at three sites along a semi-arid elevation gradient. Processed soil samples were incubated at three soil moisture contents and soil R was measured at 6 temperatures, successively (25–55 °C). From these data, an activation energy for reaction kinetics and deactivation energy for enzyme functionality model was used to generate soil R curves from which two parameters were derived: Rmax, the maximum rate of soil R and Topt, the optimum temperature for soil R. Rmax was significantly greater for soils at the highest elevation and at medium soil moisture content. Topt was greater than 35 °C at all locations. In addition, Topt was significantly greater for soils with greater amounts of SOM but not significantly different along the elevation gradient or at different moisture contents. These results support inclusion of much higher optimum temperatures than currently used in many ecosystem and land-surface models and provide support for explaining variation in Topt as regulated by substrate quantity within a site and general insensitivity across climate differences. 相似文献
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Lateral flows in landscape mosaics represent a fundamentally important process in landscape ecology, but are still poorly
understood in general. For example, windblown litter nutrient transfer across a landscape has rarely been studied from an
ecosystem perspective. In this study we measured the litter nutrient transfer from an Acacia mangium plantation to a Dimocarpus longan orchard in an agroforestry landscape for 3 years from January 2002 to December 2004. About 11% of the total litterfall of
the acacia plantation were transported to the longan orchard annually, accounting for ca. 9–59% of the total litter nutrient
input of the longan orchard. The windblown litter transfer showed high spatial variation mainly caused by wind speed and directions.
Slope positions 5 m away from the source acacia plantation received significantly greater amount of allochthonous acacia litter
than those 10 m away, and the northwest-facing slope of the longan orchard received 2 to 3-fold more litter than the southeast-
and south-facing slopes because of the prevailing southeasterly wind in the region. To explore how different management practices
may influence the litterfall, leaf production, and soil nutrient status of the two ecosystems, we developed a Meta-Ecosystem
Litter Transfer (MELT) model to simulate the processes of litter-related transformation (production, deposition, and decomposition)
and transfer (wind- and management-driven movement). Our simulation results suggest that less than 30% of acacia litter should
be transferred to the longan orchard in order for the acacia plantation to sustain itself and maximize production of the longan.
Connectivity of nutrient flow between adjacent ecosystems as shown here leads to a functional meta-ecosystem with higher landscape-scale
production of ecosystem services. That is, managing this connectivity through landscape design or active litter transfers
can lead to large changes in overall landscape functioning and service production. 相似文献
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A general framework of ecosystem hotspots suggests variation in soil metabolic activity can be understood through the relative
distribution and intensity of patches of disproportionately high ecosystem process rates. To better understand the causes
of soil metabolic spatial variability and the variation in ecosystem hotspots we quantified soil respiration (R) spatial heterogeneity
across a network of seven sites spanning a 2,489 m elevation gradient in the Santa Rosa Mountains of Southern California.
At each site, soil samples were collected from 0–5 and 5–15 cm soil depths at 2 m intervals along three 100 m transects. Each
soil sample was analyzed for organic matter content (SOM) and was incubated at 40% water holding capacity for 20 days. R was
measured at days 5 and 20. Strong contrasts were observed between the relationships of soil physical variables and R at scales
of individual landscapes and the whole region. Notably, the relationship between SOM and R was positive within individual
landscapes and negative across the entire region. Plant canopy microenvironments were associated with elevated SOM and R relative
to the interspaces. This microenvironment effect on R was reduced by elevation, incubation interval, and soil depth. Geostatistical
analyses conducted individually for each site identified an increasing range of autocorrelation from 2 to 10 m and a decreasing
proportion of variation that was included in this range with elevation. These results suggest hotspots increase in size but
decrease in intensity with elevation thereby creating a maximum hotspot effect at middle elevations. 相似文献