Water sources of urban trees in the Los Angeles metropolitan area

In semi-arid cities, urban trees are often irrigated, but may also utilize natural water sources such as groundwater. Consequently, the sources of water for urban tree transpiration may be uncertain, complicating efforts to efficiently manage water resources. We used a novel approach based on stable isotopes to determine tree water sources in the Los Angeles basin, where we hypothesized that trees would rely on irrigation water in the soil rather than develop deep roots to tap into groundwater. We evaluated the oxygen (δ¹⁸O) and hydrogen (δD) isotope ratios of xylem water, irrigation water, soil water, and groundwater in a study of temporal patterns in water sources at two urban sites, and a study of spatial patterns at nine urban sites and one “natural” riparian forest. Contrary to our hypothesis, we found that despite frequent irrigation, some trees tap into groundwater, although in most species this was a small water source. Some trees appeared to be using very shallow soil water at <30 cm depth, suggesting that these mature urban trees were quite shallowly rooted. In the natural site, trees appeared to be using urban runoff in addition to shallow soil water. We were able to identify tree uptake of precipitation at only 3 sites. The results show that some irrigated trees utilize groundwater and do not rely solely on irrigation water, which may make them able to withstand drought and/or water conservation measures. However, some irrigated trees may develop very shallow root systems, which may make them more susceptible.     

Predicting tree species richness in urban forests

There has been an increasing interest in urban forests and the levels of biodiversity they contain. Currently there are no spatially explicit maps of tree species richness in urban areas. This research tests and identifies GIS and remote sensing metrics (climate, area, productivity, three-dimensional structure) hypothesized to be associated with species richness in native forests and identifies methods that can be applied to predict and map tree species richness in cities. We quantified tree species richness, floristic composition, and structure in 28 1-ha plots in the city of Los Angeles. Climate and remote sensing metrics from high-resolution aerial imagery (10 cm), QuickBird (60 cm), Landsat (30 m), MODIS (250 m), and airborne lidar (2 m) were collected for each plot. There were 1208 individual stems and 108 trees identified to species. Species richness ranged from 2 to 31 species per ha and averaged 17 species per ha. Tree canopy cover from QuickBird explained the highest portion of variance (54%) in tree species richness followed by NDVI from Landsat (42%). Tree species richness can be higher in residential urban forests than native forests in the United States. Spatially explicit species richness maps at 1 ha can be created and tested for cities in order to identify both hotspots and coldspots of tree species richness and changes in species richness over time.     

Incorporation and Gated Communities in the Greater Metro-Los Angeles Region as a Model of Privatization of Residential Communities

ABSTRACT

The privatization of urban public space has accelerated through the closing, redesign, and policing of public parks and plazas, the development of Business Improvement Districts (BIDs) that monitor and control local streets and parks, and the transfer of public air rights for the building of corporate plazas ostensibly open to the public. In the suburbs, privatization also takes the form of conservation easements that restrict access to public lands, the creation of shopping malls and new town centers relocated within these private commercial developments, and the building of gated residential communities. Accompanying this expansion of private interests are changes in strategies of governance and regional differences in how local governments and residents are encouraging private encroachment on public space. This article focuses this third set of privatization practices by discussing how gated communities manipulate municipal and town planning laws to control public space and tax dollars. To accomplish this task, I discuss the emergence of gated communities as a new form of privatization of urban/suburban space and then tease out the legal and institutional underpinnings of this spatial governance. The geography of gated communities in greater metro-Los Angeles region and their use of the strategy of incorporation to capture public taxes for private use is employed as a model for understanding the future of gating in the United States. The Los Angeles model is then compared to current gating patterns in urban and suburban gated communities in New York and Texas. These manipulations of private land use controls in the United States are not necessarily new, but with gating there is an accelerating trend away from governmental and public control of land use toward an increased reliance on privately created controls. The consequences of this shift toward privatization of land use control is an impoverishment of the public realm and access to public resources, especially public space.     

The energy and mass balance of Los Angeles County

We conducted an urban “metabolic” study of inputs and outputs of food, water, energy, and pollutants from Los Angeles County, USA. This region has been the subject of recent debate about the nature of population density and distribution as it relates to urban form and associated environmental impacts. We found that with the exception of food imports and wastewater outputs, inputs of resources and outputs of pollutants generally declined on a per capita basis from 1990 to 2000. Reductions likely reflected a combination of changes in public policy, improvements in technology and public infrastructure, and impacts of increases in population density. However, in comparison to other municipalities and urban regions, resource consumption per capita was still relatively high in some categories, particularly inputs of water and transportation energy. Per capita greenhouse gas emissions were lower in Los Angeles County than for the average of the USA as a whole but higher than previous analyses of urban areas internationally, largely due to comparatively high emissions from the transportation sector. Wastewater discharge accounted for less than 40% of water inputs excluding precipitation; however the partitioning of water outputs through other potential losses, specifically evapotranspiration, runoff, and groundwater recharge, remains highly uncertain. We suggest that more detailed information about water losses will greatly improve future mass and energy accounting for analyses of urban environmental sustainability in this semi-arid region.     

Differences in soil chemical properties with distance to roads and age of development in urban areas

The main objective of this study was to characterize variation in soil chemical properties with length of urbanization period and distance to roads. Urban boundaries from 1920’s (old), 1960’s (middle) and 2000’s (new) were identified for three cities in northeast Ohio: Massillon, Wooster and Canton. Within each identified historic boundary, soil samples were collected from two road-side and two interior lawns in one public school site in each city. Thus, there were three urban age and two distance-to-roads classes. Soil particle composition and basic chemical properties including pH, available phosphorus (P), exchangeable potassium (K), calcium (Ca), magnesium (Mg), cation exchange capacity (CEC), nitrate, total carbon (C), total nitrogen (N), and soil organic matter (SOM) were measured. Two notable spatio-temporal patterns appeared repeatedly in the data set. First, total C, total N and SOM were higher in the soils of old (>50 years) urban sites than of newly developed sites. Similar, but not always significant, trends in soil pH, and exchangeable Ca were also observed. Second, road-side soils had higher pH, Ca, total C and N than interior sites regardless of urban age. These data indicate that key soil chemical properties can vary in predictable ways with urban age and distance-to-roads classes. Such variations in key soil chemical properties may influence or reflect soil biota and biogeochemical processes in urban soils.     

Urban forest cover of the Chicago region and its relation to household density and income

Urban forests and herbaceous open space play a vital role in the environmental and aesthetic health of cities, yet they are rarely identified in land-use inventories of urban areas. To provide information on urban forests and other vegetative land cover in Illinois cities, Landsat Thematic Mapper (TM) data from June 27, 1988, were classified for the Chicago metropolitan region (9,717 km²). Ten land-cover classes were identified, including two types of forestland (occupying 5.8% of the total area), residential land with trees (14.6%) or without trees (7.8%), cropland (37.5%), two types of grassland (7.7%), urban with impervious surfaces (23.1%), water (1.6%), and miscellaneous vegetation (2.1%). Correlation analyses indicated that household income and household density are strongly related to land covers in the region, particularly those with tree cover and urbanized land. Population changes for 1980–1985 and 1985–2010 (projected) show a pattern of increasing density in the urbanized zone concurrent with continued urban sprawl, primarily into current cropland.     

The replacement principle for the provision of multiple public goods on tree networks

This article considers the provision of two public goods on tree networks where each agent has a single-peaked preference. We show that if there are at least four agents, then no social choice rule exists that satisfies efficiency and replacement-domination. In fact, these properties are incompatible, even if agents’ preferences are restricted to a smaller domain of symmetric single-peaked preferences. However, for rules on an interval, we prove that Miyagawa’s (Soc Choice Welf 18:527–541, 2001) characterization that only the left-peaks rule and the right-peaks rule satisfy both of these properties also holds on the domain of symmetric single-peaked preferences. Moreover, if agents’ peak locations are restricted to either the nodes or the endpoints of trees, rules exist on a subclass of trees. We provide a characterization of a family of such rules for this tree subclass.     

Modeling above-ground carbon storage: a remote sensing approach to derive individual tree species information in urban settings

Vegetation has gained importance in respective debates about climate change mitigation and adaptation in cities. Although recently developed remote sensing techniques provide necessary city-wide information, a sufficient and consistent city-wide information of relevant urban ecosystem services, such as carbon emissions offset, does not exist. This study uses city-wide, high-resolution, and remotely sensed data to derive individual tree species information and to estimate the above-ground carbon storage of urban forests in Berlin, Germany. The variance of tree biomass was estimated using allometric equations that contained different levels of detail regarding the tree species found in this study of 700 km², which had a tree canopy of 213 km². The average tree density was 65 trees/ha per unit of tree cover and a range from 10 to 40 trees/ha for densely urban land cover. City-wide estimates of the above-ground carbon storage ranged between 6.34 and 7.69 tC/ha per unit of land cover, depending on the level of tree species information used. Equations that did not use individually localized tree species information undervalued the total amount of urban forest carbon storage by up to 15 %. Equations using a generalized estimate of dominant tree species information provided rather precise city-wide carbon estimates. Concerning differences within a densely built area per unit of land cover approaches using individually localized tree species information prevented underestimation of mid-range carbon density areas (10–20 tC/ha), which were actually up to 8.4 % higher, and prevented overestimation of very low carbon density areas (0–5 tC/ha), which were actually up to 11.4 % lower. Park-like areas showed 10 to 30 tC/ha, whereas land cover of very high carbon density (40–80 tC/ha) mostly consisted of mixed peri-urban forest stands. Thus, this approach, which uses widely accessible and remotely sensed data, can help to improve the consistency of forest carbon estimates in cities.     

Homestead greening is widespread amongst the urban poor in three medium-sized South African towns

Trees in urban areas are important sources of ecosystem services and benefits. In most towns the bulk of urban biodiversity, and trees specifically, are found in homestead gardens. But there is only limited understanding of the tree holdings in such gardens, and how they vary within and between towns, especially for developing countries where rapid urbanisation and high poverty influence the use of and reliance on land and local resources. We report on the nature of tree holdings in private gardens of poorer suburbs in three medium-sized towns along a gradient of decreasing mean annual rainfall in northern South Africa. A total of 3 217 trees were enumerated across 450 randomly selected homesteads. Most (90 %) households had at least one tree on their homestead, with an average of 7.7?±?6.1 trees. Most householders had planted the trees themselves. The density of trees declined along the moisture gradient. Within towns, tree density was positively related to garden size, which in turn was related to relative affluence and age of the suburb. Newer and poorer suburbs had the fewest trees per household. Sixty-two tree species were recorded, which were dominated by alien species, especially fruit trees. There was no relationship between the moisture gradient and tree species richness per household, but within towns there was a difference between suburbs, being lowest in the newest suburbs. Numbers of trees and species per household was positively related to age of the household head.     

Spatial patterns of female Ailanthus altissima across an urban-to-rural land use gradient

Ailanthus altissima is an invasive, dioecious deciduous tree common at the interface between urban and rural areas in the mid-Atlantic region, U.S.A. To examine spatial patterns of abundance and associations with land use type, we mapped all mature female trees in nine 89.5 ha plots (805.5 ha total area) across a typical urban-to-rural land use gradient using aerial images obtained via remote sensing supplemented by detailed ground referencing. Rural plots were dominated by forest and had the lowest density of mature females (0.007 females ha⁻¹); urban and suburban plots did not differ significantly in mean density (0.37 females ha⁻¹ vs. 0.34 females ha⁻¹, respectively). Individuals in urban plots were more evenly distributed, but were not associated with a wider variety of land uses and were closer to roads or openings than those in suburban plots. Given less available habitat per unit area in urban than in suburban environments, these patterns suggest that Ailanthus fits the profile of an invasive species that may be proliferating outward from urban centers. With continued disturbances associated with development in the suburban areas, and timber harvesting in the rural areas, further spread of Ailanthus seems likely.     

Legal aspects of exclusive representation: Ruminations on the private-public sector analogy

From the perspective of a management labor lawyer, this article argues that any legitimate theory of employment rights must be founded on the premise that employment is a voluntary relationship governed by mutual consent. In contrast, the erosion of the doctrine of at-will employment and the substitution of its legal antithesis, the tort of wrongful discharge, depend on a conception of employment rights as something the employee possesses at the employer’s expense, that is, without the employer’s consent. The theme of this article is that an employment right does not exist apart from contract. The government cannot violate an employment right unless it prevents a willing employee and a willing employer from making a contract concerning a proper subject on terms satisfactory to both. In public sector employment, the state is one of the parties to the employment contract. In most cases, a public employer cannot be “willing” if the same sovereign or polity has enacted conditions on public employment, that is, has placed limitations on itself. This article analyzes the legal aspects of exclusive union representation and related union security arrangements within this conceptual framework. Member, State Bar of California. Associate, Latham & Watkins, Los Angeles and San Diego. I wish to thank my colleague, Mark W. Smith, for his helpful suggestions and comments during the preparation of this paper. The views expressed here are solely those of the author.     

Drivers of variability in water use of native and non-native urban trees in the greater Los Angeles area

Trees in urban ecosystems are valued for shade and cooling effects, reduction of CO₂ emissions and pollution, and aesthetics. However, in arid and semi-arid regions, urban trees must be maintained through supplemental irrigation, in competition with other water needs. Currently, a comprehensive understanding of the factors which influence water use of urban tree species is lacking. In order to study the drivers of whole tree water use of two common species in the Los Angeles Basin urban forest, four sites in Los Angeles and Orange County were instrumented with sap flow and meteorological sensors. These sites allowed comparisons of the water use of a native riparian (Platanus racemosa Nutt.; California sycamore) and non-native (Pinus canariensis C. Sm.; Canary Island pine) Mediterranean species, as well as the spatial variability in water use under different environmental and management conditions. We found higher rates of sapflux (J _O ) in native California sycamore as compared to non-native Canary Island pine. Within each species, we found considerable site-to-site variability in the magnitude and seasonality of J _O . For Canary Island pine, the majority of inter-site variability derived from differences in water availability: response to vapor pressure deficit was similar during a period without water limitations. In contrast, California sycamore did not appear to experience water limitation at any site; however, there was considerable spatial variability in water use, potentially linked to differences in nutrient availability. Whole tree transpiration (E) was similar for the two species when water was not limiting, but Canary Island pine was able to withstand unirrigated conditions with a very low E. These results add to the currently small pool of data on urban tree water use and ecophysiology, and contribute to establishing a more quantitative understanding of urban tree function.     

The Value of Hate in the Countertransference

The author looks at the experience of hate in the countertransference and develops the idea that hate can be of particular value to the treatment process. He begins with an exploration of the therapist’s needs and discusses how unmet self-regulatory needs sometimes lead to feelings of frustration and rage toward the patient. The author explores these ideas as they are connected to Winnicott’s (1949, 1971) work on aggression and Jessica Benjamin’s (1992) work on recognition and destruction. The author espouses a difference between rage and hate, where rage is seen as indicative of unmet needs, and hate is seen as a force that can emancipate the therapist from the encumbrance of unmet needs. Case examples are provided to show the utility of this perspective. Laurence Green, M.S.W., Psy.D. is on the faculty and a member of the Institute of Contemporary Psychoanalysis. He is Co-chair of the History Committee of the International Federation of Psychoanalytic Education. He is in private practice in Los Angeles, California working with children, adolescents and adults.     

Drug use,prostitution and the prevalence of AIDS: An analysis using census tracts

This paper reports on preliminary efforts to study at the census tract level the reciprocal relationships between AIDS and street crime, particularly prostitution and drug offenses and the prevalence of AIDS. The Los Angeles County Department of Public Health provided the number of reported AIDS cases by census tract. The data on reported crimes and arrests, organized by reporting districts, came primarily from the Los Angeles County Sheriff's Department and the Los Angeles City Police Department. Although this strategy needs replication and extension, the present findings suggest that sexual orientation, drug use and prostitution are useful risk variables at the census track level.     

Vegetation composition and structure of woody plant communities along urban interstate corridors in Louisville,KY, U.S.A.

Urban forests adjacent to interstate corridors are understudied ecosystems across cities. Despite their small area, these forests may be strategically located to provide large ecosystem services due to their ability to act as a barrier against air pollutants and noise as well as to provide flood control. The woody vegetation composition and structure of forests adjacent to urban interstates is an important determinant of their ability to provide these services. However, these forest communities may be particularly susceptible to the introduction of exotic invasive species via the interstate and the surrounding city that can potentially alter current and future forest composition. The purpose of this study was to investigate the distribution of native and exotic woody vegetation and tree regeneration in forests along three interstate corridors in Louisville, KY, and to determine potential factors (e.g., traffic density) that are correlated with patterns in the woody vegetation community. We found the most important determinants of vegetation composition along these interstate corridors were the distance from the city center and the presence of an exotic invasive shrub, Amur honeysuckle (Lonicera maackii). Compared with forested plots within 10 km of the city center, plots further from the city center had 81% lower stem density of Amur honeysuckle, 96% higher tree seedling regeneration, and 51% greater woody plant species richness. The primarily native species composition of adult trees in forests alongside urban interstates in Louisville and the regeneration of native tree species provide optimism that these forests can maintain native species while experiencing multiple impacts from the interstate as well as from the surrounding city, emphasizing their important potential for maintaining natural forest functions across the urban landscape.     

Conifer growth and reproduction in urban forest fragments: Predictors of future responses to global change?

Global change has a large and growing influence on forests, particularly in urban and urbanizing areas. Compared to rural forests, urban forests may experience warmer temperatures, higher CO₂ levels, and greater nitrogen deposition, with exacerbated differences at urban forest edges. Thus, comparing urban to rural forests may help predict future effects of global change on forests. We focused on the conifer western red-cedar (Thuja plicata) to test three hypotheses: at urban forest edges, relative to rural forests and urban forest centers, trees experience 1) higher temperatures and nitrogen levels, 2) lower seedling recruitment, and 3) greater growth. We additionally tested anecdotal reports that 4) tree seedling recruitment in urban and rural forests is much lower than in ??pristine?? old-growth forests. To test these hypotheses, we quantified air temperature, soil nitrate, adult T. plicata growth and seedling recruitment in five urban and three rural parks at both forest edges and centers. We also quantified T. plicata recruitment at five old-growth ??pristine?? sites. Temperatures were highest at urban forest edges, and soil nitrate was highest in urban forests. In urban relative to rural forests, we observed greater T. plicata growth, but no difference in seedling densities. However, seedling densities were lower in urban and rural forests than in old-growth forests. In all, our results suggest urban influences enhance adult T. plicata growth, but not seedling recruitment. Recruitment in urban and rural forests was reduced compared to old-growth forests, implying that fragmentation and logging reduce T. plicata seedling recruitment.     

Understanding preferences for tree attributes: the relative effects of socio-economic and local environmental factors

Urban plant biodiversity is influenced by both the physical environment and attitudes and preferences of urban residents for specific plant types. Urban residents are assumed to be disconnected from their immediate environment, and cultural and societal factors have been emphasized over environmental factors in studies of landscaping choices. However, we postulate that local climatic and environmental factors can also affect preferences for plant attributes. Therefore, spatial and temporal patterns in urban tree biodiversity may be driven not only by the direct effect of environmental variables on plant function, but also by the effect of environmental variables on attitudes toward trees and associated choices about which types of trees to plant. Here, we tested the relative effects of socio-economic and local environmental factors on preferences toward tree attributes in five counties in southern California in and surrounding Los Angeles, based on 1,029 household surveys. We found that local environmental factors have as strong an effect on preferences for tree attributes as socio-economic factors. Specifically, people located in hotter climates (average maximum temperature 25.1 °C) were more likely to value shade trees than those located in cooler regions (23.1 °C). Additionally, people located in desert areas were less likely to consider trees to be important in their city compared with people located in naturally forested areas. Overall, our research demonstrates the inherent connections between local environmental factors and perceptions of nature, even in large modern cities. Accounting for these factors can contribute to the growing interest in understanding patterns of urban biodiversity.     

Dairy Industrialization in the First Place: Urbanization,Immigration, and Political Economy in Los Angeles County, 1920–1970*

Abstract Rural sociologists are currently debating the pace and extent of industrialization in the dairy sector of the United States. We offer the perspective of historical sociology to this debate, arguing that time and place significantly determine the outcomes of processes such as industrialization. We present an historically‐grounded explanation for the rise of industrial dairying, which first occurred in Los Angeles County. Beginning with the immigration of Dutch dairy farmers to Los Angeles (L.A.) in the 1920s, a contingent and sequential process—embedded within the local/California political economy—of exploding population growth, rapid urbanization, and skyrocketing land prices led to repeated geographical relocations and expansions of large‐scale dairies during the next three decades. We conclude that agricultural industrialization is not inevitable but instead is the result of contingent factors (cultural and political‐economic) as well as the particular sequencing of events and processes. In thus historicizing the industrialization debate, we seek limited, rather than universal, generalizations.     

Works Councils and Organizational Performance

Most studies on the effects of works councils simply analyze whether their mere presence contributes to firm performance. This study seeks to offer a contribution to the literature by adding, to date, largely unexplored potential contingencies: the attitudes of Dutch top managers and works councils as to the functioning of the latter, in bad vis-à-vis good times. The overall conclusion from our probit analyses is that the way in which management and works councils interact, and hence the way in which codetermination is implemented, makes all the difference to the firm’s economic position. Our most compelling finding relates to the role of management: a positive attitude of managers toward the works council is positively associated with organizational performance, both in the private and the public sector. In the private sector, this result is even reinforced in times of reorganization.