Geoscience Reference
In-Depth Information
conditions of the distant past. Examples of proxy evidence are mud from
the bottom of lakes and ponds, microscopic organisms living in the oceans,
bubbles frozen in glaciers, pencil-thin wood cores drilled from trees, and salts
precipitating in dried-up lake bottoms. Much can also be learned about early
climates through such straightforward clues as landforms: the heights and
shapes of mountains, the locations and sizes of lakes and rivers, the locations
of trees and other types of vegetation, and the sediments that accumulate at
the bottom of lakes and the mouths of rivers.
We begin our exploration of the earth's natural history with one of the
most ancient living natural archives: the bristlecone pine. h ese hardy trees,
found throughout the western United States, are the oldest living creatures
on the planet, and each season of their lives is recorded in their trunks. h ey
retain a longer “memory” of the environment in which they grew than any
other organism on Earth.
testimony of the bristlecone pine
On the harsh slopes of the White Mountains above Owens Valley in eastern
California, a trail leads up to a forest of stunted pine trees. It is 1957, and
a group of backpackers, loaded with an assortment of strange equipment,
hikes up the trail. Douglas Powell (who told this story to his close friend,
Frances Malamud-Roam, one of this topic's authors) is the youngest of the
hikers, and he i nds it challenging—with the thin air and steep climb mak-
ing breathing dii cult—but, for the older members of the group, the hike is
grueling. Powell arrives i rst at the lower reaches of a grove of scraggly trees,
out of breath but excited. He knows that here in this ragged forest, perched
at almost 11,000 feet, grows the oldest living tree on Earth. He surveys the
trees around him while he waits for his companions, wondering which of
these gnarled trees is “h e One.”
Standing at the forest's edge, Powell rel ects on the harsh environment.
Almost 8,000 feet above the Owens Valley l oor, the atmosphere is thin,
water is scarce, and the soil is rocky. h e forest is sparse, with only patches of
stunted, half-dead trees. h e younger, smaller trees look like ordinary pines,
though not as tall. h e tough living conditions, harsh climate, and dry soils
prevent the trees from growing very large. h e older trees are more contorted,
and only parts of the trunks appear to be living. Some trees appear to be all
but dead (see i gure 13).
