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Study of Growth Dynamics of Trees Based on Annual Rings

© Alexsander S. Bogolyubov, Nadejda S. Lazareva, Russia, 2001

© Michael J. Brody, USA, 2003

Study of growth dynamics of trees based on annual ringsThis manual describes an elementary procedure for the preparation of a tree trunk cross-section and subsequent counting of annual growth rings. The information will then be used to sketch a graph of the dynamics of tree growth in years and further analyze the tree growth in connection with changes in environmental factors.

This field study has instructional video featuring real students conducting the ecological field techniques in nature. Each video illustrates the primary instructional outcomes and the major steps in accomplishing the task including reporting the results.

Introduction

The given educational task is devoted to the determination of the age of a tree based on the number of annual rings and the study of peculiarities of tree growth during various years based on the width of these rings.

The annual rings seen in a cross-section cutting of a tree trunk of a tree grown in a moderate climatic zone occur as a result of the varying rates of growth during a vegetative season. The cells that are formed in the spring and summer have a lighter tone. The cells that are formed at the end of the vegetative season form wood that is composed of smaller cells whose cell walls are thicker than the ones formed in the spring and summer. The color of these smaller cells is darker than those formed in the beginning of the summer. Thus, an annual ring has light and dark components, and as a result, we can see borders of annual rings on the cut cross-section of the tree.

This occurs only in those zones of the earth where there is a noticeable change of seasons. In regions without a change of seasons, for example on the equator, annual rings are also formed, but they are practically invisible - wood has a even coloring.

By looking at the number of annual rings on the cut cross-section of a trunk it is possible quite accurately to define the age of the tree. The width of one annual ring, i.e. annual growth ring, varies from one year to the next. The width depends on tree state (condition) during the given vegetative season, which, in turn, depends on annual climatic peculiarities (features), health of the tree and many other factors.

The average width of rings of different tree species varies and is basically associated with the species, the place it is grown, and individual features of the given tree. However, there are some typical features for all tree species or for the majority of trees of the same species. For example, rings are wider on the well-illuminated side of the tree than on the side of the tree that is in the shadow, therefore the stumps that remain from lone standing (grown) trees are used for the determination of Cardinal points (where North and the South are). Within a species beginning to grow under the forest canopy (in our woods they are, for example, spruce and oak) it is possible to observe objective changes of ring width during the first years of the trees life: while the young tree is growing in the shade, rings are narrow, when it begins getting more sunlight, rings become wider.

Natural loss (fallout) and the cutting of neighboring trees during forest management (maintenance) can also influence the width of the rings. When a "window" (opening) is formed near a growing tree, it begins to actively grow, growing both in height and in thickness.

The goal of this lesson is the preparation of a tree cross-section and the construction of a graph of its growth. Interesting results can be determined if students prepare cross-sections of several trees, growing in one general area but under different environmental conditions (for example different habitats) and then comparing the graphs.

We recommend doing this laboratory-based activity as part of winter ecological field studies during cold weather, while other outdoor field studies may be difficult and uncomfortable to execute.

For this lesson it is necessary to have: two-handled saw and metal ruler. For preparation of a permanent cross-section for multiple years, it is necessary to have a metal strip and nails.

Preparation of the cut cross-section

The study of growth dynamics of a tree can be conducted at any time of year and without dependence on weather conditions. For conducting the study, a saw, a ruler, a pen, in some cases a magnifying glass and some painting substance such as bluing or potassium permanganate are required (if no prepared cross-sections are available).

A wind-fallen tree or a standing dead tree should be found in the forest, whose year of dying off can be defined. If the needles still remain on a tree, then the current year can be taken for the year that it died. If there are no needles, but the smallest branches are present – the tree died the previous year. If there are no needles and there are no small-sized branches present, but the cortex is well preserved – it died about two years ago. It is advisable not to use older trees as it is impossible to define the year of the tree’s death precisely, so all further attempts will produce no results due to absence of the "starting point" of chronological scale.

An ideal tree for the preparation of cut cross-section is a recently wind fallen tree. Its death is not caused by natural reasons, i.e. by illnesses or pests, but by the influence of...

 

This was only the first page from the manual and its full version you can see in the

Ecological Field Studies 4CD Set:

It is possible to purchase the complete set of 40 seasonal Ecological Field Study Materials (video in mpg + manuals in pdf formats) in an attractive 4 compact disk set. These compact disks are compatible with Mac and PC computers. The teacher background information and manuals can be printed out for easy reference. The videos are suitable for individual student or whole class instruction. To purchase the complete 4CD set write a request to the authors (in a free form).

Ecological Field Studies 4CD Set

Some of these manuals you can also purchase in the form of applications for Android devices on Google Play.

Ecological Field Studies Demo Disk:

We also have a free and interesting demonstration disk that explains our ecological field studies approach. The demo disk has short excerpts from all the seasonal field study videos as well as sample text from all the teacher manuals. The disk has an entertaining automatic walk through which describes the field study approach and explains how field studies meet education standards.

You can also download the Demo Disc from ecosystema.ru/eng/eftm/CD_Demo.iso. This is a virtual hybrid (for PC and Mac computers) CD-ROM image (one 563 Mb file "CD_Demo.iso"). You can write this image to the CD and use it in your computer in ordinary way. You also can use emulator software of virtual CD-ROM drive to play the disk directly from your hard disk.

Ecological Field Studies Demo Disk

 

Other Ecological Field Studies Instructive Manuals:

Autumn Season

  1. Orienteering in the Forest
  2. Procedure of the Geological Exposure Description
  3. Plotting a Profile of a River Valley Slope
  4. Simple Procedure of Soil Description
  5. Assessment of the Vital State of a Forest Based on Pine-tree Analysis
  6. Study of Species Composition and Number of Fungi
  7. Study of Species Composition and Census of Birds Using the Line Transect-counting Method
  8. Integrated Study Based on Landscape Profile
  9. Complex Environmental Assessment of Human Impact on an Area
  10. Assessment of Air Pollution by Lichen Indication Method

Winter Season

  1. Making a Campfire
  2. Simple “Eye” Survey of the Field Study Site
  3. Study of Growth Dynamics of Trees Based on Annual Rings
  4. Mapping Forest Vegetation
  5. Green Plants Under Snow
  6. Methods of Observation of a Chickadee Flock's Territorial Behavior
  7. Procedure of Winter Mammals Route Census by Footprints
  8. Study of Mammal Ecology According to Their Tracks
  9. Physical and Chemical Properties of Natural Waters
  10. Study of Snow Cover Profile

Spring Season

  1. Let's Help Birds!
  2. Study of the Ecology of Early Flowering Plants
  3. Phenology of Plant Florescence
  4. Assessment of the Vital State of Coniferous Underbrush
  5. Study of Forest Invertebrates (Part I: Forest Litter, Wood)
  6. Studies of Species Composition and Abundance of Amphibians
  7. Studying Minerals and Rocks in Your Area
  8. Studies of the Day Activity of Singing Birds
  9. Studies of Bird Populations Size by Different Methods
  10. Study of Fauna of Spring Temporary Water Bodies

Summer Season

  1. Making a Herbarium
  2. The Study of Plants in Your Local Environment
  3. Study of the Vertical Structure of a Forest
  4. Study of Forest Invertebrates (Part 2: Grass Layer, Tree Crowns and Air)
  5. Study of Birds’ Nesting Life
  6. Complex Comparative Description of Small Rivers and Streams
  7. The Study of Water Invertebrates in a Local River and Assessment of Its Environmental State
  8. Study of Plankton
  9. Assessment of Ecological Features of Meadows on the Base of Vegetation Cover
  10. Assessment of Environmental State of the Forest Based on Leaves’ Asymmetry



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