Changes in fox squirrel anti-predator behaviors across the urban–rural gradient

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.     

The ecology and culture of landscape sustainability: emerging knowledge and innovation in landscape research and practice

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.     

Multi-scale predictive habitat suitability modeling based on hierarchically delineated patches: an example for yellow-billed cuckoos nesting in riparian forests,California, USA

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.     

Combining top-down and bottom-up dynamics in land use modeling: exploring the future of abandoned farmlands in Europe with the Dyna-CLUE model

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.     

Effects of multiple fires on tree invasion in montane grasslands

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.     

Relating tradable credits for biodiversity to sustainability criteria in a dynamic landscape

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.     

Historical influences dominate the composition of regenerating plant communities in abandoned citrus groves in north-central Florida

The question of what determines plant community composition is fundamental to the study of plant community ecology. We examined the relative roles of historical land use, landscape context, and the biophysical environment as determinants of plant community composition in regenerating citrus groves in north-central Florida. Results were interpreted in light of plant functional traits. Herbaceous and woody plants responded differently to broad-scale variables; herbs correlated most strongly with surrounding land cover at a scale of 8 km, while the only significant determinant of woody species distributions was local land use history. There were significant correlations between herbaceous species and spatial context, habitat isolation, environmental variables, and historical variables. Partial Mantel tests indicated that each variable provided a unique contribution in explaining some of the variation in the herbaceous dataset. The correlation between woody plants and local historical variables remained significant even with other effects corrected for. In the herbaceous community, species composition was linked to functional traits much as expected from classical theory. While spatial influences in our study system are important for both woody and herbaceous plants, the primary determinant of plant community composition in regenerating citrus groves is historical land use. Our results suggest that the fine-scale mechanisms of local competition, tolerance and facilitation invoked by many classical studies may ultimately be less important than land use history in understanding current plant community composition in regenerating agricultural areas.     

Bahiagrass crop coefficients from eddy correlation measurements in central Florida

Bahiagrass (Paspalum notatum) is a warm-season grass used primarily in pastures and along highways and other low maintenance public areas in Florida. It is also used in landscapes to some extent because of its drought tolerance. Bahiagrass can survive under a range of moisture conditions from no irrigation to very wet conditions. Its well-watered consumptive use has not been reported previously. In this study, bahiagrass crop coefficients (K _c) for an irrigated pasture were determined for July 2003 through December 2006 in central Florida. The eddy correlation method was used to estimate crop evapotranspiration (ET_c) rates. The standardized reference evapotranspiration (ET_o) equation (ASCE-EWRI standardization of reference evapotranspiration task committee report, 2005) was applied to calculate ET_o values using on site weather data. Daily K _c values were estimated from the ratio of the measured ET_c and the calculated ET_o. The recommended K _c values for bahiagrass are 0.35 for January–February, 0.55 for March, 0.80 for April, 0.90 for May, 0.75 for June, 0.70 for July–August, 0.75 for September, 0.70 for October, 0.60 for November, and 0.45 for December in central Florida. The highest K _c value of 0.9 in May corresponded with maximum vapor pressure deficit conditions as well as cloud free conditions and the highest incoming solar radiation as compared to the rest of the year. During the summer (June to August), frequent precipitation events increased the cloud cover and reduced grass water use. The K _c annual trend was similar to estimated K _c values from another well-watered warm-season grass study in Florida.