How Trees Provide Evidence about Past Climate

Dendrochronology

Tree Cookies & Tree Cores

Short explanation of Dendrochronology

What is Dendrochronology?

Trees grow in both height and width.

Trees growing in environments with distinct growing seasons produce annual growth rings.

Trees growing in environments with little seasonal variation – (such as tropical rainforests) often do not have visibly distinct growth rings.

How do Trees Hold Information about Climate?

Annual Growth Rings are formed in the Xylem layer

The xylem tissue in trees conducts water and dissolved nutrients from the soil throughout the entire tree

New xylem tissue is produced during periods of active growth

In general cells are larger and more numerous during periods with abundant moisture

How do Trees Hold Information about Climate?

In northern environments each Annual Growth Ring is composed of two ringsa Spring Ring

Thicker because there is more water present and growing conditions are ideal

Summer RingThinner and darker in colour because there is less

water and the growing xylem cells are smaller

There are no fall or winter rings because trees in northern environments are not actively growing during those seasons

How do Trees Hold Information about Climate?

The thickness of the rings is affected by weather conditions during that growing year.Rings are thicker when growing conditions are

ideal – warm and wet.Rings are thicker when growing conditions are

poor - typically hot and dry.Note: unusual weather conditions can

occasionally result in the production of additional growth rings in a single yearthese are called “false growth rings”

How do Trees Hold Information about Climate?

Build your own Climate Tree

Build a Tree Activity

Cool stuff Trees have Told us

The analysis of the oak planks making up one Viking Longship (found in Norway) showed that the wood was from trees cut down near Dublin, Ireland some time between AD 1060-1070.

Discovered in Norway in 1906, the Oseberg ship, the best preserved Viking ship ever found, reveals its Norse shipbuilders' graceful construction style. Photo credit: © Svergies TV

1. Tree Ring Detective

2. Dendrochronology and Climate Change Lab

3. Trees: Recorders of Climate Change

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