1. Estimating a tree’s age- useful tool!

    October 26, 2011 by MAX

    Thank you Mr. Bowles for all this great info!

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    Field Notes

    Telling a Tree’s Age

    Favorite Forest Giants

    We always knew our favorite forest giants were old.
    Now we can know how old.

    Photo: Marlene and Joe Nowak

    Tracing a tree back to its roots has never been simpler. With a newly developed aging chart, the lifespans of the region’s giant old-growth trees are just a measurement away.

    This useful tool resulted from a 1996 study of Chicago Wilderness’ old-growth forests. Researchers Marlin Bowles of The Morton Arboretum and Michael Jones of Christopher Burke Engineering calculated the age of trees in Chicago region forests by collecting core samples from roughly 600 area specimens. The cores provided rings for the scientists to count without harming the tree (since the extractions were only 3/16″ wide, the trees’ living tissue was hardly affected).

    The researchers say that aging forest trees can help nature enthusiasts learn more about the history of their local environment. “If you can understand how old trees are in a forest or a stand of trees, then you can have a better understanding of the history of the stand,” Bowles explains.

    Bowles, a plant conservation biologist, explains that an area with mostly young trees must have experienced a major logging or fire event that took out all the older trees. “If you have a stand with very old trees in it,” Bowles continues, “you know that you can go back a long time before the stand was disturbed.” The study found that the oldest trees in the area, mostly white oaks, date back to the early- to mid-1800s, when settlers began to thin some of the wooded groves in northern Illinois. The data also confirms the conventional wisdom that human fire suppression has caused the number of sugar maples to increase, while oak and shrub populations decline.

    For someone hoping to discover this sort of rich history in a nearby preserve, the process of calculating a tree’s age takes a little botany and a little high school math.

    First, identify the tree species. (For those just starting out, a field guide may be helpful, but a tree ID field trip with a naturalist is probably better for learning). Next, measure the tree’s circumference with a tape measure or a length of string and a ruler. The tape should be wrapped around the tree at chest height to produce an accurate measurement. Then, divide the circumference measurement by pi (3.1416) to get the tree’s diameter. Finally, check the chart to determine the specimen’s age. Was the tree starting out in life as Du Sable was building the first cabin in Chicago in 1779? When Illinois was becoming a state in 1818? Or was it sprouting from an acorn when engineers reversed the Chicago River in 1900? (See more historical dates.)

    This technique will prove 90 percent accurate for forest-grown trees listed on the chart. Trees that have spent some part of their lives at a small size (perhaps due to poor growing conditions) may be older than size would suggest. Trees grown in the open, like those in a suburban backyard or a savanna, will be much younger for their size, because the added sunlight speeds their growth. As the chart shows, different species grow at different rates.

    Tree Species Ages at Different Diameters
    Bass- White Sugar Bur/Swamp Red Red Shagbark White

    Inches

    Centimeters

    wood

    Ash

    Maple

    White Oak

    Elm

    Oak

    Hickory

    Oak

    10

    25

    60 75 75 66 73 76 102 84

    12

    30

    70 87 88 79 86 89 116 100

    14

    35

    79 99 100 91 99 102 129 115

    16

    40

    89 110 112 104 112 115 142 129

    18

    45

    98 121 124 117 124 128 155 144

    20

    50

    107 131 136 129 136 141 167 159

    22

    55

    116 142 147 142 148 154 179 173

    24

    60

    125 152 159 154 160 116 190 187

    26

    65

    133 162 170 167 172 179 202 201

    28

    70

    142 172 181 179 184 191 212 215

    30

    75

    150 182 192 192 196 203 223 229

    31

    80

    159 191 203 204 207 215 234 243

    34

    86

    169 203 216 219 221 230 246 260

    35

    90

    175 210 224 229 230 239 254 271

    37

    95

    184 220 235 242 241 251 264 285

    39

    100

    192 229 245 254 253 263 274 298

    — Tegan Jones with Marlin Bowles and Michael Jones

    Related Articles:

    Read more about this research on old-growth forests on page 5 of the July 2005 CW Journal (PDF document).

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  2. What’s in bloom: mid October (fall blooming Crocus)

    October 13, 2011 by MAX

    Yes- crocus in fall! Who knew. Beautiful too!

    Crocus blooms amoungst the fallen leaves


  3. Extend the color in your landscape w/ fall foliage

    October 7, 2011 by MAX
    Hammemalis x

    Witchhazel 'Arnold's Promise' great fall color, med sized shrub, winter flower