[Illustration: _An ecologist inspects cages placed around bagworm
infestations of a red cedar tree that had been injected with radioactive
cesium-134 to determine uptake of radioactivity in the larvae._]
[Illustration: _Checking pine seedlings exposed to ionizing radiation
from a radioactive source (on tripod) in a controlled ecosystem.
Seedlings on left were fully exposed, those in the middle were exposed
on their tops only, and those on the right were exposed on their stems
only._]
[Illustration: _Biologist studying the root distribution of plants by
injecting radionuclides into the soil and measuring plant uptake._]
[Illustration: _A thriving_ Messerschmidia _plant growing on Rongelap
Atoll is studied for growth-rate and root-systems data after the island
was accidentally subjected to radioactive fallout_.]
[Illustration: _Aerial view of a “Gamma Forest”, where growing trees are
exposed to chronic irradiation from a source at the center of the
picture. This environmental biology study shows varying sensitivity of
various trees. Trees in the center were killed by extremely high doses
of radiation for 20 hours a day over a 6-month period._]
[Illustration: _Apparatus containing a strong radiation source being
installed by biologists in a semitropical rain forest for terrestrial
ecology research._]
In programs of such scope and duration, the problems of interpretation
are great. Broadly, environmental studies give consideration to: