Lab 4 + PP11: Northern Trip recap

What is the “Jack Pine” ecosystem like?

Dry, excessively drained, high-elevation outwash plain dominated by jack pine and northern pin oak.

How old is the dominant jack pine forest?

About 80 years old.

What is succession in the Jack Pine ecosystem?

Succession is toward northern pin oak at all levels

Why does northern pin oak become favored over jack pine?

Light shade from intolerant jack pine favors northern pin oak but not jack pine regeneration.

How is soil-water availability in the Jack Pine ecosystem?

Very low.

How is nutrient availability in the Jack Pine ecosystem?

Low.

What are the acid-indicator species at the Jack Pine site?

Low-sweet blueberry and black huckleberry.

Why are jack pine seedlings rare or absent?

Lack of fire and too much shade.

What disturbance is important for maintaining jack pine?

Fire.

What is the “Poor Aspen” ecosystem like?

Dry, excessively drained sand on a high-elevation outwash plain dominated by bigtooth aspen.

What was the pre-settlement forest at Poor Aspen?

Hemlock-white pine-red pine forest.

What is succession at Poor Aspen?

Succession is toward white pine and red pine, possibly red maple.

What caused aspen dominance at Poor Aspen?

Logging and fires initiated aspen dominance.

What will happen to aspen at Poor Aspen without additional disturbance?

Aspen will eventually die out.

Why does white pine become favored at Poor Aspen?

Aspen shade and a white pine seed source favor white pine.

What limits white pine growth at Poor Aspen?

The dry site causes slow white pine growth.

How does red maple behave at Poor Aspen?

Red maple persists but does not increase much on the dry site.

Why is red oak recruitment slow at Poor Aspen?

Deer browsing and slow growth.

Why is hemlock absent at Poor Aspen?

The slides indicate hemlock is absent; the site does not provide a stated seed-source explanation.

What hormone is produced in the crown of aspen?

Auxin.

What does auxin do in aspen?

It inhibits sprouting.

Where is cytokinin produced in aspen?

In the roots.

What does cytokinin do?

It stimulates sprouting and suckering.

Where is gibberellin found in aspen?

In the roots.

What does gibberellin do?

It promotes growth of sprouts and suckers.

Where are carbohydrates produced in aspen?

In the crown through photosynthesis.

Where are carbohydrates moved after production?

From the crown to the roots.

What do carbohydrates provide for aspen sprouts and suckers?

They provide the energy needed for their growth.

Which hormone dominates when an aspen crown is well developed?

Auxin.

What happens when an aspen crown is removed by disturbance?

Cytokinin effects become dominant and stimulate sprouting.

Why do carbohydrates increase as an aspen crown grows?

More leaves increase photosynthesis and carbohydrate production.

What happens as an aspen crown redevelops?

Auxin builds up and suppresses new sprouting.

What is the basic hormonal pattern of aspen regeneration?

Crown removal shifts control toward cytokinin; crown redevelopment restores auxin dominance.

What is the “Good Aspen” ecosystem like?

Mesic, well-drained sand over sandy clay loam calcareous till on a moraine.

What dominates Good Aspen?

Bigtooth aspen.

What was the pre-settlement forest at Good Aspen?

Hemlock-northern hardwoods.

What is succession at Good Aspen?

Succession is toward beech, red maple, and sugar maple.

What caused aspen dominance at Good Aspen?

Logging and fires.

What was different about the disturbance at Good Aspen?

Fires did not kill all subdominant overstory and understory stems.

Why are there few or no aspens in the understory at Good Aspen?

Aspen regeneration is limited beneath the existing stand.

How is red maple affected by aspen shade at Good Aspen?

Light shade favors red maple, but heavier shade will cause it to decline.

Why are hemlock and white pine absent from regeneration at Good Aspen?

Hemlock lacks a seed source, and white pine lacks both a seed source and enough light.

What is the “Hemlock” ecosystem like?

Well-drained to moderately well-drained fine sand on an outwash plain.

What dominates the Hemlock ecosystem?

Eastern hemlock.

What is the likely succession of the Hemlock ecosystem?

It will likely remain under hemlock control.

What species established with hemlock following fire?

Paper birch.

What are the characteristics of paper birch?

Fast-growing, short-lived, and shade-intolerant.

What type of topography is present in the Hemlock ecosystem?

Pit-and-mound topography.

Why is there little or no understory in the Hemlock ecosystem?

Hemlock controls the available light and water.

What is the “Red Pine” ecosystem like?

Dry-mesic, well-drained sand on a low-elevation outwash plain.

What dominates the Red Pine ecosystem?

Red pine.

How old is the dominant red pine forest?

About 120 years old.

What is succession in the Red Pine ecosystem?

Succession is toward white pine at all levels.

Why does white pine become favored under red pine?

Light shade from red pine favors white pine.

How does red pine litter affect soil-water availability?

Heavy organic matter from red pine litter increases soil-water availability.

What is nutrient availability like at the Red Pine site?

Low, but suitable for red pine, white pine, and red maple.

What are the acid indicators at the Red Pine site?

Low-sweet blueberry and wintergreen.

Why are red pine seedlings rare or absent?

Lack of fire and heavy organic matter.

What is the “Colonial Point – Hemlock NHW” ecosystem like?

Mesic, moderately well-drained loamy sand over sandy clay loam calcareous till on a moraine.

What dominates Colonial Point – Hemlock NHW?

American beech, sugar maple, and red maple.

What was the pre-settlement forest at Colonial Point – Hemlock NHW?

Hemlock-northern hardwoods.

What is succession at Colonial Point – Hemlock NHW?

Succession is toward beech and sugar maple.

What type of topography is prevalent at Colonial Point – Hemlock NHW?

Pit-and-mound topography.

How does pit-and-mound topography affect regeneration?

It limits ground cover and tree regeneration primarily to mounds.

What is notable about hemlock regeneration at Colonial Point?

Hemlock regeneration is absent.

How does a thicker outwash layer affect the ecosystem?

It creates a drier surface and results in greater beech coverage in the overstory.

What is the “Colonial Point – Oak Plains” ecosystem like?

Mesic, moderately well-drained loamy sand over sandy clay loam calcareous till on a moraine.

What dominates Colonial Point – Oak Plains?

Northern red oak.

What was the pre-settlement forest at Colonial Point – Oak Plains?

Hemlock-northern hardwoods.

What is succession at Colonial Point – Oak Plains?

Succession is toward sugar maple.

How did the Colonial Point – Oak Plains community develop?

It developed from an abandoned cornfield.

Why did oaks become favored in Colonial Point – Oak Plains?

Higher light levels favored oak establishment.

Why is sugar maple favored over beech at Colonial Point – Oak Plains?

Sugar maple is favored on the open, mesic, nutrient-rich site.

Why are beech and red maple lacking at Colonial Point – Oak Plains?

They lack a seed source.

Why is sugar maple present despite the lack of beech and red maple?

Sugar maple has an available seed source.

Why is northern red oak absent from the understory and ground cover?

It is mid-tolerant but requires high light for recruitment.

What is the key difference between Jack Pine and Red Pine ecosystems?

Jack pine is on high-elevation, extremely dry outwash; red pine is dry-mesic on low-elevation outwash.

What do Jack Pine and Red Pine have in common?

Both have low nutrients, acidic indicator species, and poor regeneration without fire.

What is the key difference between Poor Aspen and Good Aspen?

Poor Aspen is dry and excessively drained; Good Aspen is mesic and well drained.

Why is succession different between Poor Aspen and Good Aspen?

Differences in moisture, soil conditions, seed sources, and existing vegetation affect future species.

What happens to aspen succession without disturbance?

Aspen dominance eventually declines because aspen requires disturbance for regeneration.

What is the major role of fire in aspen ecosystems?

Fire removes established crowns and stimulates aspen sprouting and suckering.

What is the major role of fire in jack pine and red pine ecosystems?

Fire helps create conditions necessary for regeneration.

What is the major ecological difference between the Hemlock and Red Pine sites?

Hemlock occurs on wetter fine sand and controls light/water; red pine is drier and favors white pine succession.

What does a thick organic layer under red pine do?

It improves soil-water availability but contributes to conditions unfavorable for red pine seedling establishment.

What is the common pattern in pit-and-mound ecosystems?

Tree establishment and ground regeneration are concentrated on raised mounds.

What causes pit-and-mound topography?

Trees are uprooted, creating pits and raised mounds.

What is the main succession pattern at Colonial Point – Hemlock NHW?

Hemlock-northern hardwoods transition toward beech and sugar maple

What is the main succession pattern at Colonial Point – Oak Plains?

Northern red oak transitions toward sugar maple.

Why can sugar maple become dominant on the Oak Plains site?

It is favored by open, mesic, nutrient-rich conditions and has a seed source.

What is the biggest factor limiting northern red oak regeneration at Oak Plains?

Insufficient light in the understory.

What general lesson does Lecture 11 show about succession?

Succession depends on site conditions, disturbance, shade tolerance, regeneration, and seed sources.

What general lesson does Lecture 11 show about disturbance?

Disturbance can reset succession and create regeneration opportunities for species that otherwise cannot establish.

What general lesson does Lecture 11 show about fire?

Fire can maintain fire-adapted species and stimulate regeneration in species such as jack pine, red pine, and aspen.

What general lesson does Lecture 11 show about seed sources?

A species cannot readily establish or increase if an adequate seed source is absent.

What general lesson does Lecture 11 show about shade?

Shade tolerance determines which species can establish and persist as forests become denser.

What general lesson does Lecture 11 show about soil moisture?

Soil-water availability strongly influences which species can survive and dominate.

What general lesson does Lecture 11 show about nutrients?

Low nutrient availability favors species adapted to poorer sites and can limit growth of less-adapted species.

What should you know about Jack Pine?

High-elevation dry outwash, extremely low water, low nutrients, pin oak succession, fire needed for regeneration.

What should you know about Poor Aspen?

Dry sand, bigtooth aspen, disturbance-created stand, succession toward white/red pine, dry conditions slow growth.