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11/19/071 Deciduous Forest Ecosystems. 11/19/072 Global Distribution.

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Presentation on theme: "11/19/071 Deciduous Forest Ecosystems. 11/19/072 Global Distribution."— Presentation transcript:

1 11/19/071 Deciduous Forest Ecosystems

2 11/19/072 Global Distribution

3 11/19/073 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 11/19/074 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 11/19/075 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 11/19/076 NA deciduous forests 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

7 11/19/077 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 11/19/078 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 11/19/079 (c) 2002 Steve Baskauf Visit Bioimages web page to learn more details about deciduous forest types Chestnut oak (Q. prinus) is an important canopy tree Has largely replaced American chestnut (Castanea dentata)

10 11/19/0710 Tulip poplar flowers and fruits

11 11/19/0711 Sweetgum ranges from mid- Atlantic states to southern Mexico Black oak Sugar maple

12 11/19/0712 Whittaker’s classic study in Tennessee

13 11/19/0713 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 11/19/0714 /forest/deciduous/CEGL007710.shtml Structural and floristic diversity in cove forests Charles Wilder photos Yellow buckeye sweetshrub rhododendron Silverbell

15 11/19/0715 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 11/19/0716 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 11/19/0717 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 11/19/0718 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 11/19/0719 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

20 11/19/0720

21 11/19/0721 Old-field succession in the Southeast Topography (moisture status) influences successional pathways

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