Forest Ecology

Arlington Regional Master Naturalists

Basic Training CourseSpring 2011

Jim McGloneUrban Forest Conservationist

Virginia Department of Forestry

Outline How Trees Grow Distribution and Diversity Forest Habitats Forest Ecology Management Forest Threats DOF Citizen Action

How a Tree Grows

What is a tree?How is a tree different from a perennial herbaceous plant?

How is a tree different from a vine?

How is a tree different from a shrub?

Basic Plant CellCell Walls- made of cellulose and lignin

Central Vacuoles- stores water and gives rigidity

Plasmoderma- connects cytoplasm

Chloroplasts- conducts photosynthesis

Plant Cell WallMiddle Lamella – shared with other cells, lignin and pectin, gives compressive strength

Primary cell wall – oriented cellulose fiber, gives tensile strength

Plasma membrane – same as animal cell membrane

How does a tree grow?

Primary Meristem AKA Buds Elongates into

shoots– Produces

• Cortex• Epidermis• Lateral buds

Or becomes a leaf Or becomes a flower

Secondary Meristem

AKA Cambium Located between bark

and wood Produces vascular tissue

– Xylem persists as wood and moves water and nutrients

– Phloem becomes bark or is reabsorbed and moves sugars

Tree Cross Section

Tree Growth Review

Growth occurs only from meristem tissue (cambium, stem and root tips).

Early (spring) wood is light and softer.

Late (summer) wood is dark and denser.

1 light + 1 dark ring = 1 year’s growth

Aging and Death Must grow new sapwood every year.

Why? This becomes a bigger and bigger energy

drain. [π(2nr + n2)] Can grow less wood, but that means less

water for energy production. Eventually growth in energy demand is

greater than growth in energy production, the tree goes into energy deficit, declines and dies.

Distribution of Forests

Horizontal Distribution

Large scale– Climate– Geology

Landscape scale– Soil types– topography

Climate

Average TemperatureDate of First/Last FrostAverage & Timing of RainfallSoil weathering

Climate Zones in Virginia

Virginia Plants• Approximately 4,000 species of plants in Virginia

• Of those 609 considered rare or threatened as of 2007

• Approximately 750 plant species are introduced

• Approximately 300 tree species

Soil Types

MoistureNutrients

Soil Types

Soil Type

Soil Type

Soil Nutrients

Topography

Forest TypesDominant

tree species, but also soil type, elevation or moisture level

http://www.dcr.virginia.gov/natural_heritage/ncterrestrial.shtml

Dry-Mesic Calcareous Forests Basic Oak – Hickory Forests Acidic Oak – Hickory Forests Montane Mixed Oak and

Oak – Hickory Forests Oak / Heath Forests Eastern White Pine –

Hardwood Forests Piedmont / Coastal Plain

Oak – Beech / Heath Forests

Carolina Hemlock Forests

Pine – Oak / Heath Woodlands

Mountain / Piedmont Acidic Woodlands

Northern Virginia Geology

Forest Habitats

FaunaBirdsMammalsHerpsInsects

Habitat NeedsFoodNestingRestingWater

Forest Layers

Habitat

Coarse Woody Debris

Edge

Forest Ecology

Energy Flows

Detritus

Bio-mass

FOREST ECOLOGY PART 2Some Important Processes

Trophic Regulation

Mychorrhizae Symbiosis between

tree roots and fungi.

Trees supply energy Fungi supply

nutrients and water. Reason forest soils

are acidic. Truffles

Tree DefensesExternal Defense Chemicals

– Nicotine– Tannin– Salicylic Acid

External– Fungi and bacteria– Birds– Mammals– Herps– Insects

• Acacia and ants

Internal Defense Chemical

– Fungicides– Bactericides

Physical– Gums and resins– Growth rings– Parenchymal rays

Evolution of Natural Communities

Past ManagementSeed AvailabilityLuckMicroclimates and

Topography

Natural Communities are like Bus StationsSeed Dispersal

Competition Tolerance

Tole

ranc

e

Time

Tolerance

•Pioneer species are usually intolerant of competition for light – Virginia Pine, Eastern Red Cedar, Tulip poplar•Climax species are very tolerant of competition and can regenerate themselves in their own shade – Maple, Beech, Holly

Bio-diversityBi

o-di

vers

ity

TimeMost plants are between intolerant pioneer species and tolerant climax species.

Climaxv.

Old Growth

•Disturbance resets successional clock•Highly disturbed systems are stuck in early succession•Undisturbed systems progress to climax stage•Intermediate disturbance cycles a system between stages of succession

Disturbance

Stable Plant Matrices

FOREST MANAGEMENT

Why Manage a Forest?

Break down in regulatory processes– Loss of apex predators– Loss of disturbance regime

Introduction of stressors– Air pollution– Invasive species

Human decisions– Increase bio-diversity– Loss of habitat type

Forest Management Objectives

Harvest as Disturbance

Harvest as Disturbance

Harvest as Disturbance

A Word About Fire.In order to spread, fire needs a

continuous fuel bed. Managing fire is about managing fuel continuity.

Urban Trees

Threats to the Forest

RegulationIf the deer eat more than NPP, the population expands and increases N2P; which causes wolf population to expand and eat more deer; deer population declines, plants expand, wolves starve. It is a dynamic equilibrium.

Missing Apex Predators

Deer population is now controlled by starvation.

Deer consume all available energy on forest floor and lower shrub layer.

As death and growth remove plants from the shrub layer, it disappears without recruitment from the forest floor

EFFECT of Missing Shrub Layer

Loss of diversity in song birds

Loss of diversity in small mammals– Increased human

disease Loss of stormwater

management Loss of air quality Loss of carbon sink Loss of forest health

Deer and Invasive Plants

Deer and other native herbivores prefer native plants

Excessive browse on natives can create a vacuum into which non-natives invade

Non-native Invasive Plants

Compete with forest plants for sun and sprouting space

Vines can kill mature treesAre generally free from

predation.

Citizen ActionStart at home

– ASNV Wildlife Sanctuary– NWF Backyard Habitat– Develop a Layered

Landscape with herbs, shrubs and trees in the same space

2010

2010

Citizen ActionDeer Management

– Fairfax County Wildlife Biologist

– FCPA Deer Pellet Program– Venison Stew

Invasive Plants– ACE Program

Recommended ReadingForests in Peril, Delcourt, 2002

McNaughton & Gunn1491: New Revelations of the Americas Before Columbus, Charles C. MannCollapse, Jared DiamondPositive Impact Forestry, Thom J. McEvoy, Island Press, 2004Bringing Nature Home, Douglas Tallamy, Timber Press, 2007Teaming With Microbes, Jeff Lowenfels and Wayne Lewis, Timber Press, 2010 (Revised)