FW 404 Structure and Composition 8/28, 9/2

Scale

  • Within-stand (Alpha) diversity/richness

  • Among-stand (Beta) diversity/richness

  • Management can influence each

Stand-level Management

  • Plant composition influences wildlife

  • Plant structure influences wildlife

    • vertical structure

    • horizontal patchiness and edges

Plant Succession

  • Succession is the continual change in plant communities over time

  • Seral Stages: temporary stages of succession

  • Defined by composition

  • Herbs → shade intolerants → shade tolerants

Shade-tolerance

  • Shade-tolerant—survive under low light

    • slow growth and persist under overstory

    • released by canopy gaps

    • e.g. American beech and sugar maple

  • Shade-intolerant—do not

    • rapid growth in full light

    • e.g. loblolly pine, sycamore

Succession

  • Different animals persist in different seral stages

  • Because different structure/composition

Various stages

Early Succession (Stage 2)

  • perennial herbaceous plants

Not Early Succession (Stage 3)

  • some trees mixed in

  • defined by composition

Importance of Vegetation Composition

  • Trees, shrubs, vines, grasses, frobs

    • tall and short

    • evergreen (pine) and deciduous (hardwood)

  • High plant richness =

    • buffer foods

    • seasonality

  • Butterflies are host plant species specific—only lay their eggs on specific plants! e.g. spicebush butterflies

Buffer Foods

  • white oak acorns take 1 year to mature

  • red oaks take 2 years

Seasonality—soft mast

  • mulberry in spring

  • black cherry in summer

  • dogwood in fall

  • holly in winter

  • Mast—hard or soft fruits (hard are nuts like acorns, soft are berries and drupes)

  • redbud in spring

  • butterflyweed in summer

  • aster in fall

Vertical Structure

  • also, foliage height diversity (FHD)

  • how many forest layers?

  • birds segragate vertically

  • ground/shrub cover important (gravity)

    • deer, quail, rabbits

    • shrubland birds

    • box turtles, lizards, garter snakes

FHD and Birds

  • Max and Mac (1961) in temperate forests

  • Positive relationship because more niches

  • Exceptions to the rule

    • tropical forests

    • certain species—ovenbird (like closed canopies)

    • fire-maintained vegetation types

Burned longleaf forests have 2 layers.

Poor vertical structure

  • no cover in the understory (in an overstocked pine stand)

  • monoculture (species resistance is low, food diversity is low)

Within-stand Patchiness

  • Within a stand, there can be openings in the canopy that create gaps (treefall gaps as an example)

  • Ups and downs like stair steps are gaps in the tree cover

Other Elements Contribute

  • Snags

  • Downed logs

  • Brush piles

  • Oak groves (in a pine monoculture)

  • Ephemeral Pools

  • Blackberry thickets

Among-stand Patchiness

  • Beta Diversity/Richness

  • could miss out on species that require a large range of only one condition

More on Among-stand Patchiness (horizontal structure)

  • Edge = where two landcover types meet

    • two stand ages (seral stages) meet

    • two land uses meet

  • Ecotone = transition zone

    • conditions of 2 adjacent areas overlap

    • harbors conditions unique from adjacent

  • in the ecotone area, these conditions are mixed, allowing species from both areas to interact

  • the light is heavier in the ecotone area of the forest meeting a field

    • makes soil drier

Leopold’s “Edge-Effect”

  • Greater abundance of wildlife at edges

    • Simultaneous access to 2 vegetation types

    • increased structure

    • require the unique conditions (ecotone)

  • example: deer bedding down in old stand during the day, eating acorns in the forest at night… you’d put your deer stand on the ecotone since they are passing between the two

Is Edge Important?

  • Only as an artifact of land use and the structure provided

  • Any importance of edge is determined by the quality of adjacent vegetation types

  • Can use prescribed burning to create “edge” everywhere

Edge Types

  • Abrupt edge—narrow ecotone

  • Soft edge—broad ecotone

  • Inherent edge—long-term feature, where pond meets forest for example (permanent) (negative edge effect)

  • Induced edge—short-lived, disturbance, edge of timber harvest for example (1 year old forest vs 100 year old forest) (not associated with negative edge effects)

If Edge, Make it Soft

  • costly for land managers to reduce overstory (timber harvest) so they often just place shrubs on the edge

Small Stand = Edge *

  • Can manage by breaking land into various zones

    • perimeter is larger

    • center is smaller

Irregularly-shaped Stands*

Two ways to increase edge: irregular stands and smaller stands. Opposite for decreasing edge.

Tophat:

Which of the following is a true statement?

A

in temperate hardwood forests, bird richness increases with increased foliage height diversity

B

early seral stages are dominated by woody plants

C

early seral stages are dominated by shade-tolerant plants

D

all of the above

E

none of the above