What causal drivers influence carbon storage in Shanghai, China's urban and peri-urban forests?

Studies have documented many biophysical factors that are correlated with urban forest carbon storage. This urban forest function is also increasingly being promoted as a nature-based solution for cities. While urbanization affects both the structure and function of urban forest ecosystems, quantitative analyses of specific casual drivers of carbon storage in urban versus periurban forests are scarce. To address this lack of information, we used field data of random plots located along an urban to rural gradient in Shanghai, China, region-specific biomass equations, and path analysis of commonly studied urban forest socioeconomic and ecological drivers to analyze their effects on above ground tree carbon storage. An urbanization index was also developed to quantitatively differentiate urban from peri-urban sites along the transect. Results show that in both urban and peri-urban forests, percent tree and shrub cover had a significant and positive effect on tree and shrub carbon, but tree and shrub density had an even greater effect. Further, tree and shrub species diversity had no effects on carbon storage, while the effects of species composition on tree and shrub carbon in urban forests was different from those in peri-urban areas. Peri-urban forests also exhibited a significant effect of percent tree and shrub cover on tree and shrub species diversity. This approach, using a path analysis of field and plot data and site-specific dendrometric and urbanization information, can be used to quantitatively identify little explored causal dependences between drivers and ecosystem services without relying exclusively on spatial land cover data often not available in developing countries. © 2017 by the authors

The biodiversity of urban and peri-urban forests and the diverse ecosystem services they provide as socio-ecological systems

Urban and peri-urban forests provide a variety of ecosystem service benefits for urban society. Recognising and understanding the many human-tree interactions that urban forests provide may be more complex but probably just as important to our urbanised society. This paper introduces four themes that link the studies from across the globe presented in this Special Issue: (1) human-tree interactions; (2) urban tree inequity; (3) carbon sequestration in our own neighbourhoods; and (4) biodiversity of urban forests themselves and the fauna they support. Urban forests can help tackle many of the "wicked problems" that confront our towns and cities and the people that live in them. For urban forests to be accepted as an effective element of any urban adaptation strategy, we need to improve the communication of these ecosystem services and disservices and provide evidence of the benefits provided to urban society and individuals, as well as the biodiversity with which we share our town and cities. © 2016 by the authors

A socio-ecological approach to align tree stewardship programs with public health benefits in marginalized neighborhoods in Los Angeles, USA

Extreme heat in the United States is a leading cause of weather-related deaths, disproportionately affecting low-income communities of color who tend to live in substandard housing with limited indoor cooling and fewer trees. Trees in cities have been documented to improve public health in many ways and provide climate regulating ecosystem services via shading, absorbing, and transpiring heat, measurably reducing heat-related illnesses and deaths. Advancing “urban forest equity” by planting trees in marginalized neighborhoods is acknowledged as a climate health equity strategy. But information is lacking about the efficacy of tree planting programs in advancing urban forest equity and public wellbeing. There is a need for frameworks to address the mismatch between policy goals, governance, resources, and community desires on how to green marginalized neighborhoods for public health improvement—especially in water-scarce environments. Prior studies have used environmental management-based approaches to evaluate planting programs, but few have focused on equity and health outcomes. We adapted a theory-based, multi-dimensional socio-ecological systems (SES) framework regularly used in the public health field to evaluate the Tree Ambassador, orPromotor Forestal, program in Los Angeles, US. The program is modeled after the community health worker model—where frontline health workers are trusted community members. It aims to address urban forest equity and wellbeing by training, supporting, and compensating residents to organize their communities. We use focus groups, surveys, and ethnographic methods to develop our SES model of community-based tree stewardship. The model elucidates how interacting dimensions—from individual to society level—drive urban forest equity and related public health outcomes. We then present an alternative framework, adding temporal and spatial factors to these dimensions. Evaluation results and our SES model highlight drivers aiding or hindering program trainees in organizing communities, including access to properties, perceptions about irrigation responsibilities, and lack of trust in local government. We also find that as trainee experience increases, measures including self- and collective efficacy and trust in their neighbors increase. Findings can inform urban forestry policy, planning, and management actions at the government and non-profit levels that aim to increase tree cover and reduce heat exposure in marginalized communities

Efectos de la frecuencia de incendios sobre las cargas de combustible en los bosques de pino-encino de la provincia de Madrean

Loadings of downed woody fuels in pine-oak forests of the Madrean Province are heavier on sites in southeastern Arizona with low fire frequencies and lower on sites in northeastern Sonora, Mexico, with high fire frequencies. Low fire frequencies in southeastern Arizona are attributed largely to past land uses and the fire suppression policies of land management agencies in the United States. Ecologists and land managers interested in reintroducing fire into these forests to reduce fuel loadings and meet other land management objectives could use information about fuel buildups in their planning efforts. Quantifying these fuel loadings could also be useful in improving fire behavior models for the forests

From Smart Urban Forests to Edible Cities: New Approaches in Urban Planning and Design

In recent years, the pressing environmental, social, and economic problems affecting cities have resulted in the integration of the disciplines of landscape architecture and urban forestry via a transdisciplinary approach to urban planning and design. Now, new urban forestry approaches and concepts have emerged for more sustainable city planning. The discipline is using different methods and approaches to address many pressing issues such as human well-being and also food security. But, research on these topics is still limited and not available for many cities in the world. To fill this gap, we present this thematic issue “From Smart Urban Forests to Edible Cities: New Approaches in Urban Planning and Design.” The findings from this thematic issue offer new insight to policymakers and practitioners, as well as contribute to the emerging literature on edible and forest cities. Furthermore, the findings spanning different cities from different geographies can be used towards achieving the 2030 Agenda and Sustainable Development Goals of making cities and human settlements more resilient, inclusive, safe, and sustainable, as well as ending hunger, achieving food security, and improving nutrition. However, further studies are still needed, especially in developing countries and the Global South

Does greening of neotropical cities considerably mitigate carbon dioxide emissions? The case of Medellin, Colombia

Cities throughout the world are advocating highly promoted tree plantings as a climate change mitigation measure. Assessing the carbon offsets associated with urban trees relative to other climate change policies is vital for sustainable development, planning, and solving environmental and socio-economic problems, but is difficult in developing countries. We estimated and assessed carbon dioxide (CO2) storage, sequestration, and emission offsets by public trees in the Medellin Metropolitan Area, Colombia, as a viable Nature-Based Solution for the Neotropics. While previous studies have discussed nature-based solutions and explored urban tree carbon dynamics in high income countries, few have been conducted in tropical cities in low-middle income countries, particularly within South America. We used a public tree inventory for the Metropolitan Area of the Aburrá Valley and an available urban forest functional model, i-Tree Streets, calibrated for Colombia's context. We found that CO2 offsets from public trees were not as effective as cable cars or landfills. However, if available planting spaces are considered, carbon offsets become more competitive with cable cars and other air quality and socio-economic co-benefits are also provided. The use of carbon estimation models and the development of relevant carbon accounting protocols in Neotropical cities are also discussed. Our nature-based solution approach can be used to better guide management of urban forests to mitigate climate change and carbon offset accounting in tropical cities lacking available information. © 2017 by the authors

How do urban forests compare? Tree diversity in urban and periurban forests of the southeastern US

Es necesario comprender cómo las influencias antropogénicas afectan la diversidad forestal urbana y periurbana a escala regional. Este estudio tiene como objetivo comparar la composición de los árboles urbanos y periurbanos a lo largo de un gradiente geográfico, y probar hipótesis sobre la composición de especies y la homogeneidad ecológica. Combinamos datos de bosques urbanos (UF) de ocho ciudades del sureste de los EE. UU. Con datos de bosques periurbanos (PF) del programa de Análisis e Inventario Forestal del Servicio Forestal del USDA. Encontramos que la diversidad de árboles, así como los valores de riqueza de especies observados y estimados, fueron mayores en UF versus PF. El análisis de la estructura del tamaño de la comunidad también indicó una mayor proporción de árboles grandes y un mayor número de especies de árboles no nativas, invasoras y no clasificadas en la UF frente a la PF, independientemente de la ubicación. Tanto el tipo de bosque como la provincia ecológica tuvieron un efecto significativo en la composición de especies de la comunidad, ya que los bosques más cercanos en el espacio son más similares entre sí que los más distantes. Si bien el cambio y el manejo del uso de la tierra se han asociado con la homogeneización ecológica en paisajes dominados por humanos, descubrimos que la composición de las especies era más diferente a lo largo de las líneas latitudinales que entre los tipos de bosque, refutando esta hipótesis, al menos en términos de diversidad de árbolesThere is a need to understand how anthropogenic influences affect urban and periurban forest diversity at the regional scale. This study aims to compare urban and periurban tree composition along a geographic gradient, and test hypotheses about species composition and ecological homogeneity. We paired urban forest (UF) data from eight cities across the southeastern US with periurban forest (PF) data from the USDA Forest Service Forest Inventory and Analysis program. We found that tree diversity, as well as both observed and estimated species richness values were greater in UF versus PF. Community size structure analysis also indicated a greater proportion of large trees and greater numbers of non-native, invasive, and unclassified tree species in the UF versus the PF, regardless of location. Both forest type and ecological province had a significant effect on community species composition, with forests closer together in space being more similar to each other than those more distant. While land use change and management has been associated with ecological homogenization in human dominated landscapes, we found that species composition was more dissimilar along latitudinal lines than compared to between forest types, refuting this hypothesis, at least in terms of tree diversit

Spatio-temporal changes in structure for a mediterranean urban forest: Santiago, Chile 2002 to 2014

There is little information on how urban forest ecosystems in South America and Mediterranean climates change across both space and time. This study statistically and spatially analyzed the spatio-temporal dynamics of Santiago, Chile's urban forest using tree and plot-level data from permanent plots from 2002 to 2014. We found mortality, ingrowth, and tree cover remained stable over the analysis period and similar patterns were observed for basal area (BA) and biomass. However, tree cover increased, and was greater in the highest socioeconomic stratum neighborhoods while it dropped in the medium and low strata. Growth rates for the five most common tree species averaged from 0.12 to 0.36 cm· year-1. Spatially, tree biomass and BA were greater in the affluent, northeastern sections of the city and in southwest peri-urban areas. Conversely, less affluent central, northwest, and southern areas showed temporal losses in BA and biomass. Overall, we found that Santiago's urban forest follows similar patterns as in other parts of the world; affluent areas tend to have more and better managed urban forests than poorer areas, and changes are primarily influenced by social and ecological drivers. Nonetheless, care is warranted when comparing urban forest structural metrics measured with similar sampling-monitoring approaches across ecologically disparate regions and biomes. © 2016 by the authors

Measuring multi-scale urban forest carbon flux dynamics using an integrated eddy covariance technique

The multi-scale carbon-carbon dioxide (C-CO2) dynamics of subtropical urban forests and other green and grey infrastructure types were explored in an urbanized campus near Shanghai, China. We integrated eddy covariance (EC) C-CO2 flux measurements and the Agroscope Reckenholz-Tänikon footprint tool to analyze C-CO2 dynamics at the landscape-scale as well as in local-scale urban forest patches during one year. The approach measured the C-CO2 flux from different contributing areas depending on wind directions and atmospheric stability. Although the study landscape was a net carbon source (2.98 Mg C ha-1 yr-1), we found the mean CO2 flux in urban forest patches was -1.32 ?mol m-2s-1, indicating that these patches function as a carbon sink with an annual carbon balance of -5.00 Mg C ha-1. These results indicate that urban forest patches and vegetation (i.e., green infrastructure) composition can be designed to maximize the sequestration of CO2. This novel integrated modeling approach can be used to facilitate the study of the multi-scale effects of urban forests and green infrastructure on CO2 and to establish low-carbon emitting planning and planting designs in the subtropics. © 2019 by the authors

Estimating aboveground biomass and carbon stocks in periurban Andean secondary forests using very high resolution imagery

Periurban forests are key to offsetting anthropogenic carbon emissions, but they are under constant threat from urbanization. In particular, secondary Neotropical forest types in Andean periurban areas have a high potential to store carbon, but are currently poorly characterized. To address this lack of information, we developed a method to estimate periurban aboveground biomass (AGB)-a proxy for multiple ecosystem services-of secondary Andean forests near Bogotá, Colombia, based on very high resolution (VHR) GeoEye-1, Pleiades-1A imagery and field-measured plot data. Specifically, we tested a series of different pre-processing workflows to derive six vegetation indices that were regressed against in situ estimates of AGB. Overall, the coupling of linear models and the Ratio Vegetation Index produced the most satisfactory results. Atmospheric and topographic correction proved to be key in improving model fit, especially in high aerosol and rugged terrain such as the Andes. Methods and findings provide baseline AGB and carbon stock information for little studied periurban Andean secondary forests. The methodological approach can also be used for integrating limited forest monitoring plot AGB data with very high resolution imagery for cost-effective modelling of ecosystem service provision from forests, monitoring reforestation and forest cover change, and for carbon offset assessments