Leveraging the Full Potential of Landsat to Investigate Inequalities in Post-Development Residential Canopy Cover (1972–2020)

Breeding bird response to habitat and landscape factors across a gradient of savanna, woodland, and forest in the Missouri Ozarks

Trees provide multiple ecosystem services in urban centers and increases in tree canopy cover is a key strategy for many municipalities. However, urban trees also experience multiple stresses and tree growth can be impacted by urban density and impervious surfaces. We investigated the impact of differences in urban form on tree growth in the City of Merri-bek, a local government area in metropolitan Melbourne, which is the temperate climate zone. Merri-bek has a gradient in population density and urban greenness from north to south, and we hypothesized that tree growth in the southern areas would be lower because trees were more likely to have less access to water with high levels of impervious surfaces. We selected three common native evergreen species, Eucalyptus leucoxylon, Melaleuca linariifolia, and Lophostemon confertus that exhibit differences in climate vulnerability and assessed the tree canopy expansion in four urban density zones in Merri-bek between 2009 and 2020 using aerial image analysis. The differences in urban form did not significantly influence tree canopy growth and all species showed similar canopy expansion rates. However, smaller trees showed a greater relative canopy increase in the ten years, whereas larger trees had a greater absolute canopy growth. Thus, older and larger trees should be protected and maintained to achieve the canopy expansion. Our study indicated that differences in urban form are unlikely to have major impacts on the growth and canopy expansion of well adapted native tree species in open, suburban centers.

This paper examines the relationship between the importance of commuting in various directions and the dis- tance from the centre of a large city. A form for this relationship is proposed, largely on the basis of deductive reasoning from an inspection of the population and employment density gradients within towns. Using statistics gathered from census publications for the period I921 to I966, the propositions are tested through a study of the Liverpool and Manchester metro- politan areas. It is concluded that there is strong evidence that employment density gradients are in the form of a cubic exponential function. The concentration of employment towards the centres of towns, and the very low density of employ- ment towards the periphery ensure that this function is statistically significant. Although there is substantial evidence that commuting towards the centre is unusually important from both the inner city and the periphery and is relatively low from other parts of the city regions, there is little statistical verification of this double-peaked or quadrinomial pattern. The evolu- tion of commuting patterns around Manchester and Liverpool is described. THIS paper discusses the relationship between distance from city centres and the directional distribution of journeys-to-work. The discussion is founded upon the characteristics of popula- tion and employment density gradients around cities. No attempt has been made to improve the existing descriptive and explanatory generalizations about population density gradients, but it is hoped that the work provides some advances in our knowledge and understanding of urban employment distributions. The paper's propositions have been derived from both deductive reasoning and a review of a small number of studies of employment distributions within towns. In later sections, it is suggested that by simply aligning these two gradients, zones around the city of job surplus and deficiency may be identified from which a number of features of urban commuting patterns may be deduced. All the suggestions are tested for their applicability to the Manchester and Liverpool conurbations since 1921; the results being presented and evaluated towards the end of the paper. It can therefore be seen that the paper's objectives are largely theoretical, as it is hoped to show that meaningful point-in-time and dynamic generalizations about the concentric structure of cities may be extended from population to kindred distributions. It is also argued that the comparison of such distributions suggests many other features of city structure which are of initial theoretical interest and, dependent on their wider verification and no doubt modification, have obvious applications in the analysis and prediction of urban areas for planning purposes. At this point it is worth making clear that this study is concerned only with aggregates of the employed population and of employment and not with the density gradients of individual social classes, age-groups or categories of jobs. It is recognized that there are pronounced divergencies from the overall pattern among these groups, but, at the same time, it is believed that it is most important to assemble clear evidence about the general pattern before the significance of such deviations can be fully understood. A similar argument is used to justify the lack of attention in this paper to sectoral variations around the city centre.

A comparison of neighborhood characteristics related to canopy cover, stem density and species richness in an urban forest

Scientists and managers often use urban forest canopy cover as an indicator of forest health. Furthermore, canopy cover is often the measure communities use to set tree planting goals. Little is known, however, about factors that contribute to variation in canopy cover. We describe canopy cover in 60 urban areas in Central Indiana. We then propose and test a model that treats canopy cover as a function of ecological and geographic factors, urban form, socioeconomic factors, and a policy index. Urban areas are more likely to have more canopy cover if they are in counties with more canopy cover, have higher proportions of their populations with college degrees, have older housing stock, have both more land and land with slopes greater than 15%, and have denser stream networks. Population density, median household income, and planning and zoning or status as a Tree City are not correlated with urban canopy cover.

The Shasta snow-wreath (Neviusia cliftonii Shevock, Ertter & D.W. Taylor; Rosaceae) is a rare shrub, endemic to areas near Shasta Lake in the eastern Klamath Range of northern California, USA. Since discovery in 1992, the number of known populations has increased from 3 to 33. Shasta snow-wreath is a thicket-forming shrub, thought to reproduce primarily vegetatively, where individual stems (ramets) arise from the root system. We provide the first descriptions of demography and site characteristics using data collected in eight populations of Shasta snow-wreath. We established permanently-marked transects and recorded the number of ramets, individual stem heights, and the number of inflorescences in 2011, 2012, and 2013. We also characterized sites by tree canopy, shrub components, fuels, vegetation, and ground cover. Using the number of ramets recorded and the total population area, we estimated the number of ramets in each population (‘ramet population size'). Ramet population size ranged from 716 to 18,641 (mean = 5467), and the average maximum stem height ranged from 50 to 159 cm (mean = 104 cm). Larger ramet population size and taller stems were both associated with less tree cover. The two largest ramet population sizes were found at the two highest elevations and most west-facing sites. The average number of inflorescences per stem over three years ranged from 0.08 to 4.91 (mean = 2.76) and showed an increase with elevation. How Shasta snow-wreath will respond to succession or disturbances is unknown, but the negative relationship of ramet population size and canopy cover indicates that fire may have been important for influencing the population size historically. Continued monitoring of the studied populations, and the addition of more populations to the monitoring program, would be useful for detecting demographic changes and for better understanding the factors that govern Shasta snow-wreath.

Zoning, land use, and urban tree canopy cover: The importance of scale

Urban green infrastructure (UGI) has a key role in improving human and environmental health in cities and contributes to several services related to climate adaptation. Accurate localization and quantification of pervious surfaces and canopy cover are envisaged to implement UGI, address sustainable spatial planning, and include adaptation and mitigation strategies in urban planning practices. This study aims to propose a simple and replicable process to map pervious surfaces and canopy cover and to investigate the reliability and the potential planning uses of UGI maps. The proposed method combines the normalized difference vegetation index (NDVI), extracted from high-resolution airborne imagery (0.20 m), with digital elevation models to map pervious surfaces and canopy cover. The approach is tested in the Municipality of Trento, Italy, and, according to a random sampling validation, has an accuracy exceeding 80%. The paper provides a detailed map of green spaces in the urban areas, describing quantity and distribution, and proposes a synthesis map expressed as a block-level degree of pervious surfaces and canopy cover to drive urban transformations. The proposed approach constitutes a useful tool to geovisualize critical areas and to compare levels of pervious surfaces and canopy cover in the municipal area. Acknowledging the role of green areas in the urban environment, the paper examines the potential applications of the maps in the policy cycle, such as land use management and monitoring, and in climate-related practices, and discusses their integration into the current planning tools to shift towards performative rather than prescriptive planning.

In many areas of North America and Europe, population densities of large herbivores are increasing and strongly affecting species composition and structure of plant communities. Although reduced resources associated with increasing density affect life history traits of large herbivores, their effects on foraging behaviour have received little attention. We experimentally controlled population density in large enclosures to assess how increasing density affected white-tailed deer (Odocoileus virginianus) space use in relation to forage biomass and cover at a fine scale. We quantified space use in 3 blocks, each with 2 enclosures, one containing deer at a density of 7.5 deer-km−2 (low density) and the other containing deer at a density of 15 deer-km−2 (high density). We interpolated forage biomass, lateral cover, and canopy cover in space by kriging and divided deer observations (radiolocations) into 3 diel-periods: dawn/dusk, day, and night. Deer space use was positively related to forage biomass and negatively related to lateral cover at both densities, but it was not affected by the diel-period. Deer increased the use of areas with dense canopy cover at low density, but not at high density. Population density thus modified deer resource use by constraining deer at high density to forage where canopy cover is lower but forage biomass higher. Our results provide evidence of density dependence in foraging decisions, as deer space use patterns appeared to be based more strongly on forage biomass than on cover, particularly when population density was high.

In this study we examined forest disturbance, largely via forest harvest, over three decades in a coastal temperate forest on Vancouver Island, British Columbia, Canada. We analysed how disturbance history relates to current canopy structural conditions by interpreting the relationship between light detection and ranging (lidar) derived canopy structure and forest disturbance trajectories derived from Landsat images to assess if a particular stand structural condition is to result based on disturbance histories. The lidar data were obtained in 2004, and are used to relate forest structural conditions at the end of the Landsat time series (1972–2004), essentially providing for a measure of resultant structure emerging from the spectral trends captured. Correlation analysis was applied between lidar-derived canopy structure (canopy cover and height) and Landsat spectral indices, such as the Tasseled Cap Angle (TCA), which showed a strong correlation coefficient (r = 0.86) with canopy cover. TCA was then used to characterize change in forest disturbance through the full temporal depth of the available Landsat image time series using a trajectory-based characterization method. Approximately 71.5% of the study area was found to correspond to “stable and undisturbed forest”. Four disturbance classes (areas characterized by disturbance, disturbance followed by revegetation, ongoing revegetation, and revegetation to stable state) accounted for approximately 10.2%, 5.3%, 2.2%, and 10.5% of the study area, respectively. We evaluated the forest structural and spectral separability between the disturbance classes. In terms of structural variability the mean airborne lidar-derived canopy cover showed clear differentiation between disturbance classes. Spectral mixture analysis (SMA) was used to extract the spectral characteristics for each disturbance class. The SMA-derived fractions were then used to analyse the class separability between the Landsat trajectory derived disturbance classes. The fraction images provided clear distinction between disturbance classes in abundances between sunlit canopy, non-photosynthetic vegetation, shade, and exposed soil. The extracted spectral indices and SMA fractions within the Landsat trajectory derived disturbance classes were used to assess if terminal forest structural conditions can be related to a complex suite of stand development trajectories and processes. The Landsat spectral indices and SMA fractions were separately modeled to estimate lidar-derived mean canopy cover and height data within each disturbance class using multiple regression. The results indicate canopy cover and height regression models developed using spectral indices provided a relatively better estimation than those using SMA endmember fractions. Compared with the relatively regular structure of fully grown undisturbed (stable) forests, the forest disturbance classes typically exhibited complex irregular structure, making it more difficult to accurately estimate their canopy cover and height. As a result, all models developed for the stable forest class performed better than those developed for other forest disturbance classes. Modeling canopy cover and height from Landsat temporal spectral indices resulted in modeled agreement to lidar measures of R2 0.82 (RMSE 0.09) and R2 0.67 (RMSE 3.21), respectively. Our results also indicate moderately accurate predictions of lidar-derived canopy height can be obtained using the Landsat-level disturbance class endmember fractions with R2 0.60 and RMSE 4.19. This study demonstrates the potential of using the over four decade record of Landsat observations (since 1972) to estimate forest canopy cover and height using prestratification of the data based on disturbance trajectories.

Tree canopy cover and carbon density are different proxy indicators for assessing the relationship between forest structure and urban socio-ecological conditions

Tree species richness around urban red maples reduces pest density but does not enhance biological control

When plotted along a gradient of population density, the mean group size in populations of several primate species has a unimodal distribution, i.e., mean group size is greater at intermediate population densities than at higher or lower population densities. In this study I present a mathematical model to clarify the cause of this relationship. Population density is assumed to affect group size by enhancing between‐ or within‐group competition and by changing the number of neighboring groups around each group. The mean group size is predicted to decline as population density increases above a critical value, owing to the increasing number of neighboring groups.

1. In many groups of species, range size and population density are positively correlated (the ‘distribution−abundance relationship’) and range size is positively correlated with latitude (‘Rapoport's Rule’). This study investigated these two relationships among Australian forest mammals, and also tested for the existence of a relationship between population density and latitude in the same fauna.2.All three relationships were significant, with the distribution–abundance relationship the strongest pattern of the three, and Rapoport's Rule the weakest. Partial correlation analysis showed that: (i) range size and population density remained positively correlated when latitude was held constant; and (ii) population density and latitude remained positively correlated when range size was held constant; but (iii) latitude and range size were not significantly correlated when population density was held constant. For (i) and (ii), partial correlation did not reveal stronger relationships than were revealed by simple correlation. These results suggest that the distribution–abundance relationship is conditioned by latitude to produce small ranges and low population densities in the tropics, and that tropical species tend to have low population densities relative to range size.3.Body mass accounted for little variation in population density, and for no variation in range size and latitudinal position. The small ranges and low population densities of tropical species were not related to a latitudinal gradient in species richness, which did not occur in this fauna.4.The latitudinal gradient in population density held within widespread species as well as among species. The effect of Bergmann's Rule (the tendency for organisms in cool environments to be larger bodied than organisms in warm environments) meant that in some species, population energy use rose more steeply with latitude than did population density.5.I argue that all three relationships might be due to a tendency for the foraging efficiency of animals to be lower in tropical than in temperate ecosystems, as a result of a lower concentration of nutrients in tropical ecosystems. For resource‐limited species, foraging efficiency should influence both range size and population density. Differences in foraging efficiency may therefore produce the distribution−abundance relationship as well as latitudinal gradients in range size and population density.

One commonly used measure of urban forest structure is canopy cover, or simply the proportion of the city that is covered by tree canopies as visualized from above. This measure is intuitive and relatively easy and inexpensive to measure. However, canopy cover only represents the urban forest in two dimensions and fails to recognize differences in species and tree condition. Many of the benefits that cities derive from their urban forest can vary directly with the total leaf area of the forest, for example, reduction in air temperature, sequestering gaseous pollutants, and carbon sequestration (Nowak, 1994a). In addition, urban forests play a role in moderating urban forest climate through shading buildings, people, and hard surfaces, and through evapotranspirational cooling and the windbreak effect (McPherson et al., 1988; Akbari and Taha, 1992; McPherson and Rowntree, 1993; Brown and Gillespie, 1995). Increasing leaf area will increase shading and evapotranspiration, and could also have a direct impact on the windbreak effect. Similarly, storm water attenuation (Xiao et al., 1998) will be affected by leaf area, as well as other factors. Consequently, an estimate of the total leaf area of the urban forest would be more informative than simply an estimate of its canopy cover. The most commonly used measure of leaf area is the leaf area index (LAI), defined as the total leaf surface area per unit land area. While LAI offers some indication of the urban forest’s ability to provide services to the community as outlined above, urban forest management and planning requires some indication of the potential that exists to expand leaf area. A low canopy cover, in itself, says little about the potential for that area to support a tree canopy. For example, a portion of a city may be found to have a canopy cover of 20%; urban forest managers may consider expanding this to say 30%. Without some indication of the carrying capacity or potential to support additional trees within the city as a whole or in specific areas, managers are unaware of the practical possibilities of reaching their goals. The potential leaf area index (PLAI) is a measure of the carrying capacity of an urban area and is a function of the amount of available growing space and its configuration (Kenney, 2000). Armed with an estimate of the LAI and PLAI, urban forest managers and planners can more effectively address the protection and enhancement of this important resource. This chapter reports on a study whose purpose was to estimate the LAI and PLAI for the City of Toronto, Ontario.