Tree Biology

1. Tree Biology Ashley Peebles Delaware Forest Service

2. Angiosperms Phylum Magnoliophyta • taxonomic class of plants in which the mature seed is surrounded by the ovule • trees are often referred to as hardwoods • Angiosperms are trees have broad leaves that usually change color and die every autumn • Examples: oaks, maples, dogwoods are examples of deciduous trees. • Some angiosperms that hold their leaves include rhododendron, live oak, and sweetbaymagnolia

4. Gymnosperms Phylum Pinophyta • taxonomic class of plants whose seeds are not enclosed in an ovule • trees are often referred to as softwoods • Gymnosperms usually have needles that stay green throughout the year • Examples: pines, cedars, spruces and firs • Some gymnosperms do drop their leaves - ginkgo, dawn redwood, and baldcypress, to name a few.

6. A TREE • is a woody perennial plant - usually more than 10 feet tall • has one main , well defined stem that is at least 3 inches in diameter • a recognizable, formed crown

7. ROOTS • absorb water and nutrients from the soil • store sugar • anchor the tree upright in the ground drip line surface roots lateral roots root hairs tap root

8. TRUNK • Comprised mostly of dead , woody tissue and supports the crown • gives the tree its support and shape • anchor the tree upright in the ground • consists of four layers of tissue

9. VASCULAR SYSTEM A peek inside • HEARTWOOD • Comprised of dead xylem cells • Gives tree its support • SAPWOOD / XYLEM • Network of thick-walled cells that transport water and nutrients from the roots to the rest of tree • CAMBIUM • Very thin layer of cells that is always dividing • Each growing season, the cambium produces new xylem/annual rings • PHLOEM / INNER BARK • A layer of living tissue found between the cambium and the outer bark • Acts as a food supply line by carrying sap produced by the leaves to the rest of the tree • BARK • Formed of old phloem cells that have died and been shed outward • Acts as a coat of armor protecting the delicate inner bark and cambium

10. heartwood (dead xylem, provides strength) Annual rings outer bark (dead phloem, provides protection) phloem/ inner bark (carries food from leaves to rest of tree) sapwood/xylem (transports water from the roots to the leaves) cambium layer (new cells)

11. CROWN • comprised of leaves born on twigs • contains the reproductive parts of the tree • helps to cool the air around it by shade • reduces the impact of rainfall on the soil below flowers and seeds branches and twigs

12. LEAVES • manufacture food through photosynthesis • aid in gas (air) exchange – cellular respiration • protect vegetative and floral buds • water transport – transpiration • store food during germination

13. Trees are producers • Photosynthesis is a process unique to green plants in which sugars (tree food) are produced • Sugars produced are a chemical way to store energy for future use (metabolism) • Energy is stored in the bonds of the sugar molecules such as glucose and fructose • These sugars are later broken apart and the released energy drives a variety of metabolic actions CO2 + H2O + ENERGY C6H12O6 + O2

14. Respiration • Trees both produce AND use oxygen • The process of breaking down sugars = respiration C6H12O6 + O2 CO2+ H2O + ENERGY

15. PHOTOSYNTHESIS: CO2 + H20 >>>>> C6H12O6 + O2

16. Energy Allocation within trees • Energy is not a limitless resource for trees • A tree will typically move energy according to the priorities below. As energy in the form of glucose becomes limited, a tree will begin to reduce resources spent beginning with the lowest priority. 1. Maintain respiration of all parts 2. Produce fine roots and leaves 3. Produce flowers and seed 4. Extend branches and roots 5. Store energy rich chemicals 6. Add wood to stem, roots, and branches, 7. Create anti-pest chemicals for defense

17. Tree Growth • The most common material made by a tree is called cellulose, a complex sugar that is the main component of woods and many other plant tissue • Cellulose is an extremely useful material for human uses (food products, paper, strengthener in plastic and concrete, clothing and other things • A tree grows in three places 1. at the twig meristem 2. at the root meristem 3. around the outside of the truck, branches, roots (cambium)

18. Buds, elongation, height growth Leaf expansion CROWN TRUNK Cambium growth Diameter increase TREE GROWTH ZONES Root hairs Root growth ROOTS

19. Tolerance of Shade • Difference species of trees have differing abilities to tolerate extended periods under a closed canopy • Trees that require high amounts of sunlight are sensitive to shade. • Species are generally divided into tolerant and intolerant (there is an intermediate category) • Shade tolerance is a key component of forest management systems

20. Intolerant Species • Intolerant species are generally the “first in” after an event such as a clear-cut or major fire that substantially opens the canopy • These trees are often called pioneer species and tend to: • be fast growing • be short lived • have light seeds Examples: Sweetgum, maples, tulip poplar, red cedar, loblolly

21. Tolerant Species • These trees normally are not the first to colonize open areas but instead grow up into an existing canopy. • These trees are usually found in a “climax community” • These trees tend to: • Live a long time • Grow slowly • Have heavier seeds Examples: American beech, some oaks, hemlocks, spruces

22. Succession • The change in species composition that occurs in a stand over time. Can be natural or man-made • An area is colonized by intolerant, fast-growing species. Eventually, tolerant trees become established in the understory and start growing into the canopy • One of two things then happens….. • The intolerants die naturally and are replaced by the tolerants that have been present in the understory for some time OR • The tolerant trees finally overtop the intolerants and shade them out, causing them to die

23. Environmental Factors • Rainfall or precipitation • As you move north and west, rainfall declines and so do number of tree species • Soil variability • This is largely related to the amount of available nutrients in the soil, the nutrient demand of a species, and the tree’s ability to extract those nutrients • Moisture • This is related to both rainfall and soils. The amount of available moisture varies during the year. • Biotic factors • These are the living parts of an ecosystem that trees interact with.

24. Range and Distribution • Each species on our planet occupies a unique geological range where members of its various populations live, feed, and reproduce • Some species have extensive geographical ranges that stretch over several continents • Geographical ranges of organisms continually shift, expand, and contract with the passage of time. • Most species appear to be limited in at least part of their geographical range by abiotic factors. • All species have specific limits of tolerance to physical factors that directly effect their survival or reproductive success.

25. Species Habitat • The place where a population of a species normally lives and its surroundings, both living and nonliving. • Habitat is generally characterized by dominant plant form (e.g. broadleaf deciduous forest) and/or physical characteristics (e.g. fast-moving stream with rocky substrate)

26. RANGE AND DISTRIBUTION Nova Scotia to Florida and westward to Lake Superior, North Dakota, southward to western Texas. Common throughout Delaware HABITAT Prefers rich deep soils but will thrive on poorer soils. Is generally tap-rooted and seems to prefer sunlight