National Park Quiz 85: Trees

Do you know why mangroves have stilted roots that extend well above the normal water level? NOAA photo.

1. Some of the ______ trees growing in Congaree National Park are as tall as a 16-story building.
a. loblolly pine
b. bald cypress
c. sweet gum
d. water oak

2. A hiker who strays off-trail in some areas of _____ runs the risk of becoming hopelessly lost in a laurel hell.
a. Olympic National Park
b. Great Smoky Mountains National Park
c. Sleeping Bear Dunes National Lakeshore
d. Big Thicket National Preserve

3. True or false? Only one National Park System unit has the word "tree" in its name.

4. True or false? The tallest tree in the National Park System is a sequoia.

5. True or false? The dominant trees of the temperate rain forest in Olympic National Park are conifers.

6. True or false? The tamarisks (salt cedars) that have invaded many western national parks have shallow root systems that only thrive in damp soils.

7. True or false? Some aspens in our national parks are thousands of years old.

8. True or false? When conducting research in national park forests, scientists typically measure the diameter of living trees with the use of an auger-like instrument called an increment borer.

9. True or false? A large oak growing on the National Mall transpires enough water into the atmosphere each year to fill a typical bathtub more than 500 times.

10. True or false? The main reason the roots of mangrove trees in Everglades National Park are stilted, perching much of the root system above water level, is to minimize saltwater absorption.

Extra Credit Question:

11. Why is it that some sequoias in our national parks grow in a straight row?

Super Bonus Question:

12. Why did a tree named Prometheus achieve everlasting fame?


(1) a -- Congaree National Park has a number of loblolly pines over 160 feet tall, including the current national champion. Unlike other pines, a loblolly (Pinus teada) can thrive on a deeply fertile flood plain that has very damp soils and is inundated at fairly frequent intervals.

(2) b -- In the southern Appalachians, a laurel hell (aka heath bald) is an extremely dense mountainside thicket composed of thick-growing evergreen shrubs and small trees, primarily rhododendrons and mountain laurels. Making your way through a laurel hell requires you to crawl under or "swim" over the nearly impenetrable vegetation. You quickly become exhausted, and unless you are very lucky you also lose your bearings.

(3) True. California's Joshua Tree National Park is the only National Park System unit that has the word "tree" in its name.

(4) False, though not cleanly so. The tallest tree yet documented in the National Park System is "Hyperion," a 379-foot tall coast redwood growing in the southern part of California's Redwood National and State Parks. It's true that the coast redwood, scientific name Sequoia sempervirens, is a member of the Sequoia genus.

(5) True. Although there are several deciduous tree species in the park's temperate rain forest, the two dominant species, Sitka spruce and western hemlock, are both conifers.

(6) False. Tamarisks (salt cedars) have long tap roots that can reach ground water lying dozens of feet below the surface. One tamarisk that scientists studied had a tap root over 160 feet long.

(7) True. Aspens form clonal colonies consisting of numerous genetically identical stems that have grown vegetatively from a single ancestor. The cluster, which may have thousands of stems (each of which looks like an individual tree) has an interlinked root system, can be considered a single organism for most practical purposes, and is typically quite old. In fact, many people believe that aspen clonal colonies should be recognized as the world's oldest living organisms. One quaking aspen colony in Colorado is thought to be as much as 80,000 years old.

(8) False. Although boring into a tree to obtain core samples can provide useful information, such as a tree's age and the incidence of severe droughts and fires, a researcher can easily determine a tree's breast high diameter (bhd) with reasonable precision using just a tape measure and a calculator. This is done by measuring the tree's circumference and dividing by π (~3.1416).

(9) True. A five-foot bathtub like that found in most homes holds 60-67 gallons of water when unoccupied and filled to overflowing. A large oak can be expected to transpire about 40,000 gallons of water into the atmosphere each year. That's the equivalent of 600- 667 bathtubs full.

(10) False. Whether above the water or below, a mangrove's roots are nearly impermeable to sodium salts and can easily exclude harmful amounts of salt. The stilted roots of the mangrove are an adaptation to low oxygen levels. By propping themselves above the water level, mangroves can absorb more oxygen through lenticels (pores) in the bark of the roots and stem.

(11) This straight-line phenomenon is due to periodic fire. Sequoia seeds prefer mineral-rich burned ground. Fallen logs that burn long and hot leave a strip of mineral-rich soil that is an ideal place for sequoia seeds to set and grow. Years later, the result is a line of sequoias.

(12) While conducting dendrochronology studies of Little Ice Age climate dynamics on Nevada's Wheeler Peak (now in Great Basin National Park), a geography graduate student came upon an extremely old bristlecone pine. The Forest Service gave him permission to cut it down so he could count the tree rings. The tree the student killed was later determined to have been one of the oldest trees on the planet. Dubbed "Prometheus," it was at least 4,862 years old, and probably closer to 5,000.

Grading: 9 or 10 correct, rest on your laurels; 7 or 8 correct, pretty darn good; 6 correct, passable fair; 5 or fewer correct, nothing to brag about.


#8: Actually, not so much on the math; we're lazy, and after a long day in the field, we can be pretty brain-dead. Almost anybody measuring tree dbh uses either a Biltmore stick or a dbh tape. Biltmore sticks are oddly-shaped meter sticks with various scales, including one for tree diameters that adjusts for the triangle from your eye to the stick to the circular tree behind the stick (, and are quick and accurate enough for some purposes such as tallying numbers of trees in size categories. dbh tapes are scaled to already factor in the pi term, and thus directly read diameter and not circumference in mm or tenths of inches.

Your beloved Congaree NP is one of the few places in the east where "standard" 5m dbh tapes are not long enough, and 10m tapes (common in the west) are necessary. Also, because threading a dbh tape underneath all the ^%$#@! poison ivy, burchemia, and other vines on the trees is a pain, some folks use big calipers to take 2 diameters 90deg apart and average the values. And, for added joy in Congaree, many of the larger cypress have large buttresses that stick out and help prevent the tree from falling over, so dbh has to be measured above the buttresses, 8-12' above the ground. If you happen to see someone headed out the boardwalk carrying a funny aluminium ladder with a belt-like strap at one end, that's what it is. [If she's got short red hair and is walking fast enough that the technicians have trouble keeping up, that's Becky Sharitz.]

#4: if you had capitalized and italicized Sequoia, it would have been True.