| 1. |
- Downey, Alisen E., et al.
(författare)
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Soil carbon sequestration in urban afforestation sites in New York City
- 2021
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Ingår i: Urban Forestry & Urban Greening. - : Elsevier BV. - 1618-8667 .- 1610-8167. ; 65
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Tidskriftsartikel (refereegranskat)abstract
- There is great interest in the ability of afforestation programs to sequester carbon, improve soil health, and provide other ecological benefits to urban areas. However, the capacity of urban soils to support successful afforestation and sequester carbon is poorly understood. This study quantified soil carbon in a series of experimental restoration sites established between 2009 and 2011 as part of the MillionTreesNYC Afforestation Project in New York City. Soil cores (0-100 cm) were collected at 10 sites and analyzed for total carbon content. Data were analyzed with respect to depth (0-10, 10-30, 30-70, 70-90, 90-100 cm), high (six species) versus low (two species) diversity planting palettes, and afforestation success (high or low). Results were compared with data from regional reference forest, degraded urban sites in New York City, and disturbed and undisturbed sites in other cities. High success afforestation sites had significantly larger carbon pools than low success afforestation sites and degraded NYC sites. We suggest that these differences were created by interactions between initial site conditions that facilitated plant community establishment and growth, which in turn increased soil carbon accumulation. These initial site conditions include land use history that influences soil physical and chemical factors, as well as proximity to existing forest stands. Diversity treatments had no effect on soil carbon levels, but these may need a longer time period to emerge. These results suggest that afforestation may enhance the capacity of urban soils to store carbon compared to urban degraded soils, but that urban soil properties and site characteristics constrain this capacity.
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| 2. |
- Grabowski, Zbigniew J., et al.
(författare)
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What is green infrastructure? A study of definitions in US city planning
- 2022
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Ingår i: Frontiers in Ecology and the Environment. - : Wiley. - 1540-9295 .- 1540-9309. ; 20:3, s. 152-160
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Forskningsöversikt (refereegranskat)abstract
- In response to interdependent challenges, city planners are increasingly adopting “green infrastructure” (GI). Reviewing 122 plans from 20 US cities, we identify what types of city plans address and define GI, including the concepts associated with GI, as well as the types, functions, and benefits of GI. The most common plans that feature GI, some of which focus exclusively on GI, comply with US Clean Water Act regulations for stormwater and sewer systems. Municipalities also address GI through diverse planning processes, including the creation of comprehensive citywide plans. Many of these plans (~40%) do not explicitly define GI. When they do, stormwater concepts predominate, followed by landscape concepts, along with an emergent emphasis on integrating GI with other built infrastructure systems. Large differences in GI types, functions, and benefits across concepts, plan types, and cities indicate a need for synthesis of GI definitions. To facilitate this synthesis, we provide a database of GI definitions from plans used in our analysis. We conclude with a broad synthetic definition of GI to provide clarity and stimulate discussion in rapidly evolving planning, policy, and research arenas.
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| 3. |
- Haei, Mahsa, 1981-
(författare)
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Importance of winter climate and soil frost for dissolved organic carbon (DOC) in boreal forest soils and streams : - implications for a changing climate
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dissolved organic carbon (DOC) is a defining feature of surface waters in a large part of the world and it influences a variety of physical, chemical and biological processes in aquatic ecosystems. Riparian soils exert a major control on stream water chemistry in many northern latitude regions and provide a local source of DOC to adjacent streams. As the winter climate in northern regions is predicted to be particularly affected by climate change, it is important to investigate the sensitivity of DOC in riparian soils and the potential implications for adjacent streams’ chemistry in a changing winter climate. The effects of a changing winter climate on riparian soil DOC production and export to streams has received little attention to date, and this is the focus of my thesis. In this thesis I first evaluate the hydro-climatic drivers of inter-annual variation in spring snowmelt DOC concentrations in two boreal forest streams of northern Sweden. By accounting for the effects of seasonal hydrology, I was able to statistically evaluate the importance of antecedent winter climatic conditions to inter-annual variation in stream DOC concentrations during the spring snow-melt periods. This descriptive work was complemented by a long-term field experiment where snow packs were manipulated to investigate the impacts of soil freezing on the concentration and quality of DOC in soil water. The effect of soil freezing on DOC was further addressed in a multi-factor laboratory experiment on soil samples taken from the riparian zone. The laboratory experiment was designed based on a central composite face-centered (CCF) model which applied three levels of four freezing-related factors: temperature, water content, duration and frequency of freeze-thaw cycles. The responses of soil microbial- activity and composition to the same experimental factors as well as their potential link to frost induced changes in DOC were also tested. Large inter-annual variations were observed in spring snow-melt DOC concentrations in streams. Lower export of DOC during the preceding seasons and longer, and colder, winters resulted in higher spring snow-melt DOC concentrations. Soil water DOC concentrations and lability were significantly enhanced in the upper soil horizons which experienced extensive soil frost and longer frost duration. In the laboratory experiment, similar responses of soil water DOC were observed in that the higher concentrations and greater lability were found in samples incubated at the lowest temperatures (-12°C). The fungal to bacterial growth ratio also increased in the lower temperature treatments. In addition, fungal growth rate and soil basal respiration responded positively to frost-induced increases in DOC concentration. The frequency of freeze-thaw cycle did not appear to be an influential factor in the laboratory experiment. Several significant interactions of the factors were also detected. By conducting and integrating field and laboratory experiments I highlight the importance of soil frost regime and winter climatic conditions for regulating DOC in riparian soils and their adjacent streams in areas with seasonally frozen soils. However, in a changing future winter climate, alterations in soil frost should be assessed as the result of changes in air temperature and snow-pack formation and extent, and implications for streams should be investigated with regard to changes in hydrology and export processes in soil-water interface.
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| 4. |
- McPhearson, Timon, et al.
(författare)
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A social-ecological-technological systems framework for urban ecosystem services
- 2022
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Ingår i: One Earth. - : Elsevier BV. - 2590-3330 .- 2590-3322. ; 5:5, s. 505-518
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Tidskriftsartikel (refereegranskat)abstract
- As rates of urbanization and climatic change soar, decision-makers are increasingly challenged to provide innovative solutions that simultaneously address climate change impacts and risks and inclusively ensure quality of life for urban residents. Cities have turned to nature-based solutions to help address these challenges. Nature-based solutions, through the provision of ecosystem services, can yield numerous benefits for people and address multiple challenges simultaneously. Yet, efforts to mainstream nature-based solutions are impaired by the complexity of the interacting social, ecological, and technological dimensions of urban systems. This complexity must be understood and managed to ensure ecosystem-service provisioning is effective, equitable, and resilient. Here, we provide a social-ecological-technological system (SETS) framework that builds on decades of urban ecosystem services research to better understand four core challenges associated with urban nature-based solutions: multi-functionality, systemic valuation, scale mismatch of ecosystem services, and inequity and injustice. The framework illustrates the importance of coordinating natural, technological, and socio-economic systems when designing, planning, and managing urban nature-based solutions to enable optimal social-ecological outcomes.
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| 5. |
- Mejía, Gisselle A., et al.
(författare)
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Nitrogen cycling and urban afforestation success in New York City
- 2022
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Ingår i: Ecological Applications. - : Wiley. - 1051-0761 .- 1939-5582. ; 32:3
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Tidskriftsartikel (refereegranskat)abstract
- Afforestation projects are a growing focus of urban restoration efforts to rehabilitate degraded landscapes and develop new forests. Urban forests provide myriad valuable ecosystem services essential for urban sustainability and resilience. These essential services are supported by natural soil microbial processes that transform organic matter to critical nutrients for plant community establishment and development. Nitrogen (N) is the most limiting nutrient in forest ecosystems, yet little information is known about N cycling in urban afforestation efforts. This study examined microbially mediated processes of carbon (C) and N cycling in 10 experimental afforested sites established across New York City parklands under the MillionTreesNYC initiative. Long-term research plots were established between 2009 and 2011 at each site with low and high diversity (two vs. six tree species) treatments. In 2018, 1-m soil cores were collected from plots at each site and analyzed for microbial biomass and respiration, potential net N mineralization, and nitrification, denitrification potential, soil inorganic N, and total soil N. Field observations revealed markedly different trajectories between sites that exhibited a closed canopy and leaf litter layer derived from trees that were planted and those that did not fit this description. These two metrics served to group sites into two categories (high vs. low) of afforestation success. We hypothesized that: (1) afforestation success would be correlated with rates of C and N cycling, (2) high diversity restoration techniques would affect these processes, and (3) inherent soil properties interact with plants and environmental conditions to affect the development of these processes over time. We found that high success sites had significantly higher rates of C and N cycling processes, but low and high diversity treatments showed no differences. Low success sites were more likely to have disturbed soil profiles with human-derived debris. Afforestation success appears to be driven by interactions between initial site conditions that facilitate plant community establishment and development that in turn enable N accumulation and cycling, creating positive feedbacks for success.
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