Correction to: Building houses and managing lawns could limit yard soil carbon for centuries.

An amendment to this paper has been published and can be accessed via the original article.

Residential household yard care practices along urban-exurban gradients in six climatically-diverse U.S. metropolitan areas.

Residential land is expanding in the United States, and lawn now covers more area than the country's leading irrigated crop by area. Given that lawns are widespread across diverse climatic regions and there is rising concern about the environmental impacts associated with their management, there is a clear need to understand the geographic variation, drivers, and outcomes of common yard care practices. We hypothesized that 1) income, age, and the number of neighbors known by name will be positively associated with the odds of having irrigated, fertilized, or applied pesticides in the last year, 2) irrigation, fertilization, and pesticide application will vary quadratically with population density, with the highest odds in suburban areas, and 3) the odds of irrigating will vary by climate, but fertilization and pesticide application will not. We used multi-level models to systematically address nested spatial scales within and across six U.S. metropolitan areas-Boston, Baltimore, Miami, Minneapolis-St. Paul, Phoenix, and Los Angeles. We found significant variation in yard care practices at the household (the relationship with income was positive), urban-exurban gradient (the relationship with population density was an inverted U), and regional scales (city-to-city variation). A multi-level modeling framework was useful for discerning these scale-dependent outcomes because this approach controls for autocorrelation at multiple spatial scales. Our findings may guide policies or programs seeking to mitigate the potentially deleterious outcomes associated with water use and chemical application, by identifying the subpopulations most likely to irrigate, fertilize, and/or apply pesticides.

Building houses and managing lawns could limit yard soil carbon for centuries.

BACKGROUND: Comparisons of soil carbon (C) pools across land uses can be confounded by site-specific history. To better quantify the response of soil C pools to residential development and use, we compared yard soils (n = 20) to adjacent mown fields and second-growth forests within land-use clusters (LUC; n = 12). Land uses within clusters shared site-specific legacies (land use and other soil forming history) prior to residential development (15-227 years ago). We analyzed soil cores to 60-cm depth for carbon, nitrogen, and bulk density. Within one LUC, we monitored soil dissolved organic carbon, moisture, and thermal regimes to explain soil C dynamics. RESULTS: We accounted for pre-development legacies to test how present uses affect soil properties. We found that yard soil C pools to 60-cm depth (9.07 ± 0.32 kg C m-2; mean ± SE) were smaller than fields (10.26 ± 0.44 kg C m-2) and forests (10.62 ± 0.87 kg C m-2). Fields contained more nitrogen to 60-cm depth (0.78 ± 0.043 kg N m-2) than yards (0.68 ± 0.030 kg N m-2) and forests (0.69 ± 0.057 kg N m-2). Time since development predicted decreased yard and field soil C/N, field soil N accumulation, and reduced yard bulk density. In old yards (> 150 years), where residents in recent times mowed monthly to bimonthly and left clippings on the lawn, there was evidence of soil C and N gains relative to old commercially managed yards mown weekly with clippings exported. CONCLUSIONS: Our study suggests land conversion to yard can limit soil C pools for centuries, with contemporary management key to that trajectory. Our research points to the importance of accounting for pre-development legacies to reveal the response of soil properties to land conversion and present use. This work can inform policies and land use intended to enhance the soil C sink and minimize development-related soil C losses.

Trees grow on money: urban tree canopy cover and environmental justice.

This study examines the distributional equity of urban tree canopy (UTC) cover for Baltimore, MD, Los Angeles, CA, New York, NY, Philadelphia, PA, Raleigh, NC, Sacramento, CA, and Washington, D.C. using high spatial resolution land cover data and census data. Data are analyzed at the Census Block Group levels using Spearman's correlation, ordinary least squares regression (OLS), and a spatial autoregressive model (SAR). Across all cities there is a strong positive correlation between UTC cover and median household income. Negative correlations between race and UTC cover exist in bivariate models for some cities, but they are generally not observed using multivariate regressions that include additional variables on income, education, and housing age. SAR models result in higher r-square values compared to the OLS models across all cities, suggesting that spatial autocorrelation is an important feature of our data. Similarities among cities can be found based on shared characteristics of climate, race/ethnicity, and size. Our findings suggest that a suite of variables, including income, contribute to the distribution of UTC cover. These findings can help target simultaneous strategies for UTC goals and environmental justice concerns.

Assessing the homogenization of urban land management with an application to US residential lawn care.

Changes in land use, land cover, and land management present some of the greatest potential global environmental challenges of the 21st century. Urbanization, one of the principal drivers of these transformations, is commonly thought to be generating land changes that are increasingly similar. An implication of this multiscale homogenization hypothesis is that the ecosystem structure and function and human behaviors associated with urbanization should be more similar in certain kinds of urbanized locations across biogeophysical gradients than across urbanization gradients in places with similar biogeophysical characteristics. This paper introduces an analytical framework for testing this hypothesis, and applies the framework to the case of residential lawn care. This set of land management behaviors are often assumed--not demonstrated--to exhibit homogeneity. Multivariate analyses are conducted on telephone survey responses from a geographically stratified random sample of homeowners (n = 9,480), equally distributed across six US metropolitan areas. Two behaviors are examined: lawn fertilizing and irrigating. Limited support for strong homogenization is found at two scales (i.e., multi- and single-city; 2 of 36 cases), but significant support is found for homogenization at only one scale (22 cases) or at neither scale (12 cases). These results suggest that US lawn care behaviors are more differentiated in practice than in theory. Thus, even if the biophysical outcomes of urbanization are homogenizing, managing the associated sustainability implications may require a multiscale, differentiated approach because the underlying social practices appear relatively varied. The analytical approach introduced here should also be productive for other facets of urban-ecological homogenization.