Deciduous Forest Ecosystems

1. Deciduous Forest Ecosystems

2. Global Distribution

3. Climate (1) • Seasonal climate promotes deciduousness • Tropics: drought deciduous • Temperate: cold deciduous • Roughly 50-150 cm precipitation annually • As in coniferous forests, P/E > 1, but deciduous forests have higher AET than coniferous • More moisture is available during the growing season

4. Climate (2) • Climate is more moderate (warmer) than where coniferous forests grow • growing season is 5-6 months • trees don’t require evergreen leaves to maintain positive C balance

5. Biodiversity • Biodiversity of tree species increases at lower latitudes • More conifers are mixed in at higher latitudes and in sandy or nutrient-poor soils • Much biodiversity provided by spring “ephemerals” • Herbaceous geophytes that sprout in April and die back by July when light becomes limiting

6. These forests are very diverse! Forest land is still increasing in many areas Map by E. Lucy Braun PhD in 1914 Hiked 65,000 miles in eastern forests Advocated for conservation NA deciduous forests

7. Deciduous forest types of NA • Mixed mesophytic forest (Great Smokies figs) • Southern Appalachians • High species richness (25 tree species/ha) • Coves may harbor relict species • Maple-basswood-beech forest • Shade-tolerant trees • Moist sites with fertile soils • Dense canopy • Oak-hickory forest • Drier sites with less fertile soils than MBB • Oaks relatively shade intolerant • Canopy is more open • Fire frequency higher than other deciduous forest types

8. Deciduous forest types (2) • Floodplain forest • Disturbances are common; early seral stage species are favored • Bald Cyprus found on wet soils in riparian zone • Mixed conifer-hardwood forests • Oak-pine associations in SE (several species of each) • White pine – red pine – birch – maple in NE • Some of these forests are likely still undergoing succession following logging or farming in the last century

9. Visit Bioimages web page to learn more details about deciduous forest types http://www.cas.vanderbilt.edu/bioimages/frame.htm • Chestnut oak (Q. prinus) is an important canopy tree • Has largely replaced American chestnut (Castanea dentata) (c) 2002 Steve Baskauf

10. Tulip poplar flowers and fruits

11. Sugar maple Sweetgum ranges from mid-Atlantic states to southern Mexico Black oak

12. Whittaker’s classic study in Tennessee

13. More complex environmental gradients • Moisture status plays an important role in species distributions in coniferous and deciduous forests • Concave slopes in ravines are the moistest sites; convex, south facing slopes are the driest • Biodiversity is high and relic species are found in cove forests Spruce-fir

14. Structural and floristic diversity in cove forests Silverbell Yellow buckeye rhododendron sweetshrub Charles Wilder photos http://www.dlia.org/atbi/grsmnp_habitats/forest/deciduous/CEGL007710.shtml

15. Deciduous forest soils • Tend to have clay-rich argillic horizons • Litterfall abundant (~300-650 g m-2 y-1) and less acidic than conifer litter; maintains soil fertility • In NE, soils are young, basic cations have not been leached and so Alfisols are present • In SE, older soils have lower nutrient status and basic cations have been leached, so Ultisols are present

16. Nutrient cycling in deciduous forests • Generally nutrients are less limiting than under coniferous forests • Some areas are prone to nitrogen deposition (acid rain), which may stimulate plant growth up to a point; becomes detrimental when soils are acidified and Al is mobilized • Nutrients are resorbed from leaves before litterfall • Relatively fertile soils and long growing season made eastern deciduous forests ideal for cropping by early white settlers (well, except for those darned big trees!)

17. Succession (1) • Large scale disturbances • Wind, hurricanes, fire, insects (introduced gypsy moths) • How does topography affect disturbance? • Diseases such as Dutch elm and chestnut blight have caused large scale disturbances and loss of dominant species • Chestnuts have been replaced by oak and hickory • Some trees can resprout following logging or fire • Largest disturbance has been agriculture

18. Succession (2) • Small scale disturbances (Gap dynamics) • Much more important than in coniferous forests • About 9% of deciduous forest area is in gaps at any point in time • Old gaps fill at roughly the same rate new gaps are created; rough steady-state • Larger gaps favor greater tree diversity • “Cyclic microsuccession”

19. Old field succession: Shade-intolerant species are replaced by shade-tolerant ones • Rubus spp. (e.g., blackberries) establish soon after a cropped field is abandoned • Pin cherry seeds last up to 50 years in seed bank and play important role in early succession • Maples are very shade tolerant but have short-lived seeds, so grow from seeds that are dispersed to shady areas • Yellow birch and quaking aspen are early successional species that can persist for a century or more

21. Old-field succession in the Southeast Topography (moisture status) influences successional pathways