Isotopes as Indicators of Ecological Processes

Louis Santiago and Todd Dawson University of California

The isotopic composition of biological materials records sources of plant nutrients

Time since clearing (yr)

15N

(‰

)

-2

0

2

4

6

8

10

10 20 40

N from soil 15N of reference plant

N from fixation

15N (‰)

-10 -8 -6 -4 -2 0 2 4 6 8 10

13C

(‰

)

-35

-30

-25

-20

-15

-10

Ecological Niches in Isotope Space

Epiphytes Cacti

Trees andHerbs

CAM/C4

C3

N deposition Soil N

Isotope systems and expected patterns

Gradient Isotope system High -values Low -values

Trophic level 13C / 15N High levels Low levels

C3-C4 Vegetation 13C C4 plants C3 plants

Marine-Terrestrial 15N / 13C / 34S Marine Terrestrial

Latitude 18O / 2H Low latitudes High latitudes

Altitude 13C High altitude Low altitude

Inshore-offshore 13C Inshore Offshore

Aridity 15N / 13C Xeric Mesic / hydric

Modified from Newsome et al. (2007)

Geographic patterns in 18O of precipitation

Used to:

• track animal migration• monitor temperature• study population connectivity

“Iso-scapes”

www.waterisotopes.org

Validation of sensors with isotopes

Networked Infomechanical Systems (NIMS)

Isotope ratio mass spectrometer (IRMS)

Validation of environmental

process by multiple

measurements

Eddy Flux

Ideas for Collaboration• Validation of sensor and flux outputs with isotopes • Linking isotopes with satellite/remote sensing data• Exploring/monitoring sources of organismal nutrients

and water• Use of isotopes to construct ecological niches

Resources:• BASIN (Biosphere-Atmosphere Stable Isotope Network)

• CSIB (Center for Stable Isotope Biogeochemistry)