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.

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.

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.