Agroecosystem changes across urban to rural transects in Salt Lake City, UT, and Chicago, IL

Background/Question/Methods

Urbanization is quickly making cities the fastest-growing land-use type worldwide. Urban agriculture, the establishment of agroecosystems within cities, is increasingly
common in the U.S. and abroad, and has been proposed as a means of improving the ecological
and socio-economic health of urban ecosystems. However, there is limited
scientific knowledge about this rapidly emerging ecosystem since most scientific agricultural research has been conducted in rural environments. The negative ecological consequences of urbanization have been well documented, but very little is known about the influence of urbanization on the success or failure of plant species that serve as food crops that support the growing human population. To explore the impact of urbanization on the growth and productivity of food crop plant species, we established twelve experimental sites within the urban ecosystems of greater Chicago, IL and Salt Lake City, UT, and continue to measure the responses of seven crop plant species grown in uniform soil mixtures, as well as the arthropod and soil microbial communities associated with these agroecosystems. We employ environmental towers equipped with micrometeorological and pollution sensors to collect data at each site to help explain variability in ecological responses across sites.

Results/Conclusions

Our preliminary data suggest that the influence of abiotic factors on plants in the urban agroecosystem is significant, but not consistent across cultivars, species, or plant families; this indicates that some food crops are more likely to be urban “winners” while others are urban “losers.”  In particular, urban sites were warmer than rural sites (up to 4°C in the night). Warmer temperatures coincided with increases in ambient CO₂ between 20 and 40 ppm. Ozone flux (up to 600 ppb) and vapor pressure deficit were also greatest in the most urban agroecosystems. Plant productivity appears to increase at urban sites for cool season Brassica species, while warm season Solanaceous crops were more productive at the rural sites.  Growth of two cultivars of Phaseolus vulgaris with differential susceptibility to ozone was variable among sites, but interveinal chlorosis, early senescence, and reduced productivity of the ozone susceptible cultivar was consistent across all sites. Proximity to urban forests and built structures can reduce light intensity within some urban agroecosystems, resulting in reduced plant productivity across most species and cultivars. These relationships, in addition to the potentially complex interactions with soil microbes and arthropods, represent a rich field for scientific discovery that merits further investigation, while also having broader consequences for feeding a growing urban population.