Desert Fertilization Experiment: investigation of Sonoran desert ecosystem response to atmospheric deposition and experimental nutrient addition, ongoing since 2006

Launched in 2006 with support from the National Science Foundation
(NSF) and leveraged by the CAP LTER, the Carbon and Nitrogen
deposition (CNdep) project sought to answer the fundamental question
of whether elemental cycles in urban ecosystems are qualitatively
different from those in non-urban ecosystems. Ecosystem scientists,
atmospheric chemists, and biogeochemists tested the hypothesis that
distinct biogeochemical pathways result from elevated inorganic
nitrogen and organic carbon deposition from the atmosphere to the
land. To test the hypothesis, scientists examined the responsiveness
of Sonoran desert ecosystems to nutrient enrichment by capitalizing on
a gradient of atmospheric deposition in and around the greater Phoenix
metropolitan area. Fifteen desert study sites were established, with
five locations each west and east of the urban core, and in the urban
core in desert preserves. In addition to the gradient of atmospheric
deposition in and around the urban core, select study plots at each of
the fifteen desert locations receive amendments of nitrogen,
phosphorus, or nitrogen + phosphorus fertilizer. Measured variables
include soil properties, perennial and annual plant growth, and
atmospheric deposition of nitrogen. At the close of the initial grant
period, the CAP LTER assumed responsibility for the project, renamed
the Desert Fertilization Experiment, which provides a remarkable
platform to study the long-term effects of nutrient enrichment on
ecosystem properties.