New Research Opportunities in the Earth Sciences - New Research Opportunities in the Earth Sciences - page 73

BIOGEOCHEMICAL AND WATER CYCLES IN TERRESTRIAL
ENVIRONMENTS AND IMPACTS OF GLOBAL CHANGE
Human land use, climate change, and energy demand are transforming
geochemical and geobiological systems and, in particular, the cycling of water,
carbon, and nitrogen in these settings. Humans are now managing and altering 50
percent of Earth's land surface—dubbed the “critical zone” in the Basic Research
Opportunities in Earth Science report (NRC, 2001)—and, in so doing, are
transforming the physical, chemical, and biological states and feedbacks among
essential components of the Earth surface system. Over the past century, soil erosion
rates have accelerated; metals and toxins have enriched and mobilized far beyond
natural rates; agriculture has industrialized the nitrogen cycle; freshwater usage has
grown to exceed recharge in major population centers; and natural ecosystems have
been heavily overprinted by fragmentation, extinction, global-scale biogeographic
shifts, and invasive species. At the same time, atmospheric temperature and carbon
dioxide levels have increased, impacting carbon storage in the terrestrial environment,
the water cycle, and a range of intertwined biogeochemical cycles and atmospheric
properties that feed back on climate and ecosystems (terrestrial and marine). This
research opportunity differs from the earlier section on hydrogeomorphic-ecosystem
response in that its roots are more in geochemistry than geomorphology.
EAR is poised to play a leadership role in comprehensive, uniquely integrated
studies of the terrestrial environment in the face of human activity and climate
change. This work spans diverse programs within EAR and more broadly across
diverse divisions and directorates within NSF and other governmental agencies, such
as the USGS and DOE. An existing suite of observatories provide insight into Earth's
ecosystems and related dynamics. These natural laboratories include the NSF Critical
Zone Observatory (CZO) and Long Term Ecological Research (LTER) programs and
those within the National Ecological Observatory Network (NEON) and the Free-Air
Carbon Dioxide Enrichment (FACE) program of the DOE. The EarthScope facility
also shows potential for providing data needed for ecosystem and water cycle studies
through indirect measurements of soil moisture and snow cover from the EarthScope
GPS network. These programs are alike in their prioritization of integrated science,
and now, increasingly, these complementary programs are philosophically and
collaboratively bound together by common goals focused on common questions about
terrestrial ecosystems impacted under human influence and climate change.
Integrated Soil, Water, and Biogeochemical Dynamics in the Critical Zone
The dynamics of the critical zone—the dynamic interface between the solid
Earth and its fluid envelopes (NRC, 2001)—are governed by the interplay between
hydrological, geomorphic, biogeochemical, and biotic processes that transform and
rearrange materials in the Earth surface environment. Plant growth, for example,
affects surficial weathering and hill slope form through bioturbation, fracture
formation, alteration of hydrological fluxes, soil carbon dioxide generation, and
profusion of organic weathering reagents. We are not yet able to weave these and