Urban Perennials: How Diversification has Created a Sustainable Community Garden Movement in The United States     

Joshua Birky  Elizabeth Strom 《Urban geography》2013,34(8):1193-1216

Our research seeks to understand how the contemporary community garden movement in the United States differs from its predecessors and whether its new foundation increases the political and financial sustainability of today's gardens. To this end, this article reviews historical and contemporary literature, and surveys participants in three distinctive community gardens, to answer several related research questions. First, what is the current state of the US community garden movement, and how have its historical roots shaped its response to current policy concerns? Second, which populations comprise today's community gardeners, and what motivates them to participate? After considering the findings from our three study gardens, and from a review of secondary and “gray” literature, we conclude by positing that a greater diversity of gardeners and gardening motivations, accompanied by changing leading views on urban land uses, will lead to such urban gardens remaining a more lasting feature of city neighborhood landscapes.  相似文献   

Place Perception and Social Interaction on an Exurban Landscape in Central Colorado*   总被引：1，自引：0，他引：1  

Soren C. Larsen  Curt Sorenson  Dave McDermott  Joshua Long  Chris Post 《The Professional geographer》2007,59(4):421-433

An assumption commonly made in research on exurbanization is that the subdivision of land ownership necessarily creates a socially divisive landscape devoid of shared place perceptions and concerns. This article presents the results of an ethnography project undertaken in a former Colorado ranching valley that is currently exurbanizing. The study revealed not only the emergence of social networks and groups among new residents, but also the presence of distinct themes in place perception and assessment within these assemblages. In particular, the results indicated that concerns about natural hazards and environmental limitations have motivated new residents to interact with one another.  相似文献   

Reenvisioning velocity reversal as a diversity of hydraulic patch behaviours          下载免费PDF全文

Michael A. Strom  Gregory B. Pasternack  Joshua R. Wyrick 《水文研究》2016,30(13):2348-2365

Past research investigated the surpassing of mean velocity at riffle cross sections by that at pool cross sections for flows up to bankfull, termed ‘velocity reversals’, to understand one mechanism by which riffle–pool relief is maintained. This study reenvisioned the classic velocity reversal by documenting stage‐dependent changes to the locations of peak velocity without cross sections. Instead, the dynamics of peak velocity patches were considered for flows spanning 0.2 to 22 times bankfull discharge through the use of a high‐resolution DEM and two‐dimensional hydrodynamic modelling. A remarkable diversity in peak velocity patch behaviour was found across discharges, including gradual expansion and shifting as well as abrupt disappearance and emergence relative to the low‐flow patch locations. These behaviours blended together to varying degrees to produce many reversals in peak velocity across morphological units, but it took substantially higher than bankfull discharge for peak velocities to move from riffles and chutes to fast glides and pools. The discharges at which reversals occurred among morphological units were significantly higher for the valley‐confined reach than for the anastomosing reach. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Toward institutions for community-based management of inshore marine resources in the Western Indian Ocean     

Joshua E. Cinner  Andrew Wamukota  Herilala Randriamahazo  Ando Rabearisoa 《Marine Policy》2009

This paper examines the frameworks being developed to co-manage coral reefs in Kenya and Madagascar. The historical and social context, flexibility of rule-making, monitoring and enforcement, and how community-based organizations are nested within other organizations is described. A comparison of the degree to which these two frameworks contain 10 key design principles thought to be important for successful commons institutions is presented. Finally, recommendations are made for improving co-management in these countries. A principal finding is that both co-management frameworks were developed for other systems (terrestrial and lakes), which creates misfits for how marine systems can be managed.  相似文献   

Rethinking the longitudinal stream temperature paradigm: region‐wide comparison of thermal infrared imagery reveals unexpected complexity of river temperatures          下载免费PDF全文

Aimee H. Fullerton  Christian E. Torgersen  Joshua J. Lawler  Russell N. Faux  E. Ashley Steel  Timothy J. Beechie  Joseph L. Ebersole  Scott G. Leibowitz 《水文研究》2015,29(22):4719-4737

Prevailing theory suggests that stream temperature warms asymptotically in a downstream direction, beginning at the temperature of the source in the headwaters and levelling off downstream as it converges to match meteorological conditions. However, there have been few empirical examples of longitudinal patterns of temperature in large rivers due to a paucity of data. We constructed longitudinal thermal profiles (temperature vs distance) for 53 rivers in the Pacific Northwest (USA) using an extensive data set of remotely sensed summertime river temperatures and classified each profile into one of five patterns of downstream warming: asymptotic (increasing then flattening), linear (increasing steadily), uniform (not changing), parabolic (increasing then decreasing), or complex (not fitting other classes). We evaluated (1) how frequently profiles warmed asymptotically downstream as expected, and (2) whether relationships between river temperature and common hydroclimatic variables differed by profile class. We found considerable diversity in profile shape, with 47% of rivers warming asymptotically and 53% having alternative profile shapes. Water temperature did not warm substantially over the course of the river for coastal parabolic and uniform profiles, and for some linear and complex profiles. Profile classes showed no clear geographical trends. The degree of correlation between river temperature and hydroclimatic variables differed among profile classes, but there was overlap among classes. Water temperature in rivers with asymptotic or parabolic profiles was positively correlated with August air temperature, tributary temperature and velocity, and negatively correlated with elevation, August precipitation, gradient and distance upstream. Conversely, associations were less apparent in rivers with linear, uniform or complex profiles. Factors contributing to the unique shape of parabolic profiles differed for coastal and inland rivers, where downstream cooling was influenced locally by climate or cool water inputs, respectively. Potential drivers of shape for complex profiles were specific to each river. These thermal patterns indicate diverse thermal habitats that may promote resilience of aquatic biota to climate change. Without this spatial context, climate change models may incorrectly estimate loss of thermally suitable habitat. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Event-based deep drainage and percolation dynamics in Vertosols and Chromosols     

Sven Arnold  Nevenka Bulovic  Neil McIntyre  Warren K. Finch  Joshua R. Larsen  Lucy P. Reading  Thomas Baumgartl 《水文研究》2020,34(2):370-386

The quantification of percolation processes and deep drainage rates in cracking clays is challenging due to the existence of multiple flow pathways, including desiccation crack networks, and the effect of variability in antecedent soil moisture and rain event properties. While most previous research on this topic focuses on long-term average rates, this study focusses on inter-event dynamics. The study uses data from soil moisture sensors distributed vertically down 4 m profiles of Vertosol and Chromosol soils across 13 sites over an area of approximately 20 km². The objectives were to estimate the temporal and spatial variability of deep drainage rates and to investigate the effect of antecedent soil moisture conditions and rain event properties on deep drainage rates and percolation dynamics. 35 deep drainage events over a 40-month period contributed 78 % of the total deep drainage of 254 mm at 4 m depth. Average deep drainage estimates were about 15 % (ranging from 0 – 80 % between sites) of total rainfall and irrigation in the Vertosol and 8% (0 – 24 %) in the Chromosol. The event water travel times at 4 m depth were 0.25 – 38 hr and 14 – 39 hr in the Vertosol and Chromosol respectively. The event deep drainage rates averaged across sites were associated with event rainfall volumes (linear regression R² = 0.40), with the effect of antecedent conditions evident only when looking at inter-site differences. The percolation response time was strongly associated with higher rainfall intensities (R² = 0.33) with no evidence from the linear regression of an antecedent moisture effect.  相似文献   

Post-fire geomorphic response in steep,forested landscapes: Oregon Coast Range,USA     

Molly Jackson  Joshua J. Roering 《Quaternary Science Reviews》2009,28(11-12):1131-1146

The role of fire in shaping steep, forested landscapes depends on a suite of hydrologic, biologic, and geological characteristics, including the propensity for hydrophobic soil layers to promote runoff erosion during subsequent rainfall events. In the Oregon Coast Range, several studies postulate that fire primarily modulates sediment production via root reinforcement and shallow landslide susceptibility, although few studies have documented post-fire geomorphic response. Here, we describe field observations and topographic analyses for three sites in the central Oregon Coast Range that burned in 1999, 2002, and 2003. The fires generated strongly hydrophobic soil layers that did not promote runoff erosion because the continuity of the layers was interrupted by pervasive discontinuities that facilitated rapid infiltration. At each of our sites, fire generated significant colluvial transport via dry ravel, consistent with other field-based studies in the western United States. Fire-driven dry ravel accumulation in low-order valleys of our Sulphur Creek site equated to a slope-averaged landscape lowering of 2.5 mm. Given Holocene estimates of fire frequency, these results suggest that fire may contribute 10–20% of total denudation across steep, dissected portions of the Oregon Coast Range. In addition, we documented more rapid decline of root strength at our sites than has been observed after timber harvest, suggesting that root strength was compromised prior to fire or that intense heat damaged roots in the shallow subsurface. Given that fire frequencies in the Pacific Northwest are predicted to increase with continued climate change, our findings highlight the importance of fire-induced dry ravel and post-fire debris flow activity in controlling sediment delivery to channels.  相似文献   

Impact of human activities on stream flow in the Biliu River basin,China     

Chi Zhang  Christine A. Shoemaker  Joshua D. Woodbury  Mingliang Cao  Xueping Zhu 《水文研究》2013,27(17):2509-2523

The obvious decline in stream flow to the Biliu River reservoir over the period 1990–2005 has raised increasing concerns. Climate change and human activities, which mainly include land use changes, hydraulic constructions and artificial water consumption, are considered to be the most likely reasons for the decline in stream flow. This study centres on a detailed analysis of the runoff response to changes in human activities. Using a distributed hydrological model, (Soil and Water Assessment Tool), we simulated runoffs under different human activity and climate scenarios to understand how each scenario impacts stream flow. The results show that artificial water consumption correlates with the precipitation (wet, normal and dry) of the year in question and is responsible for most of the decrease in runoff during each period and for each different wetness year. A Fuzzy Inference Model is also used to find the relationship between the precipitation and artificial water consumption for different years, as well as to make inferences regarding the future average impact on runoff. Land use changes in the past have increased the runoff by only a small amount, while another middle reservoir (Yunshi) has been responsible for a decrease in runoff since operation began in 2001. We generalized the characteristics of the human activities to predict future runoff using climate change scenarios. The future annual flow will increase by approximately 10% from 2011 to 2030 under normal human activities and future climate change scenarios, as indicated by climate scenarios with a particularly wet year in the next 20 years. This study could serve as a framework to analyse and predict the potential impacts of changes both in the climate and human activities on runoff, which can be used to inform the decision making on the river basin planning and management. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Free form property rights for fisheries: The decentralized design of rights-based management through groundfish “sectors” in New England     

Daniel S. Holland  Joshua Wiersma 《Marine Policy》2010

Harvest cooperatives were implemented in several US fisheries over the last decade during a period when US law prohibited implementation of any new individual fishery quota (IFQ) systems. Harvest cooperatives provided an alternative to individual quotas as a means to end the race for fish and increase fishery profitability. The prohibition on new IFQ systems in the US was lifted, but harvest cooperatives remain a more feasible and perhaps a superior alternative to IFQs for some fisheries. The New England Fishery Management Council is on the verge of implementing a new management system for the groundfish fishery based on harvest cooperatives known as “sectors”. This paper describes the New England sector management system and discusses a number of advantages but also some drawbacks relative to IFQs. It argues that a hybrid of the two approaches could have advantages over either.  相似文献   

Evaluation of thermal equations of state for CO2 in numerical simulations     

Norbert B?ttcher  Joshua Taron  Olaf Kolditz  Chan-Hee Park  Rudolf Liedl 《Environmental Earth Sciences》2012,67(2):481-495

Three commonly used thermal equations of state for carbon dioxide, as well as the ideal gas law, have been compared against a large number of measurement data taken from the literature. Complex equations of state reach a higher accuracy than simple ones. The inaccuracy of the density function can cause large errors in fluid property correlations, such as heat capacity or viscosity. The influence of this inaccuracy on the results of numerical simulations have been evaluated by two examples: The first one assumes isothermal gas expansion from a volume, while the second one considers heat transport along a fracture. For both examples, different equations of state have been utilized. The simulations have been performed on the scientific software platform OpenGeoSys. The difference among the particular simulation results is significant. Apparently small errors in the density function can cause considerably different results of otherwise identical simulation setups.  相似文献