Forest Restoration An Ecophysiological, or Seedlings Perspective - - PowerPoint PPT Presentation

Forest Restoration

An Ecophysiological, or Seedling’s Perspective

Steven C. Grossnickle

NurseryToForest Solutions

Foresters know how to grow trees!

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Do foresters know how trees grow?

Silvics & Ecophysiology

Silvics

Principles underlying the growth and development of single trees and of the forest as a biological unit.

Ecophysiology

Physiological and morphological processes of plants in response to the surrounding environment.

“…remedies are usually found at the whole plant level in terms of silvicultural treatments.” (Kramer 1986)

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Ecophysiological Approach

Programs across North America

Nursery Forestry Reclamation

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Information Sources

Provide practitioners and researches with a seedling’s view of regeneration silvicultural practices on field performance.

Book Available at NRC Press Publications @ https://www.researchgate.net/profile/Steve_ Grossnickle

Climate Change

“…recent studies document more rapid mortality under hotter drought due to negative tree physiological responses…” (Allen et al. 2015)

Regional Shifts

Environmental Conditions

Energy Exchange

Seedling Environment - Temperature

Kolb & Robberecht 1996

600 1200 1800 2400 Time of Day

25 50 75

Maximum Seasonal Temperature (

• C)

20 cm 1 cm S urface

Seedling Response – Temperature

Duration, Timing & Intensity

44 45 47 48 50 52 54 56 58 60 Temperature ( oC) 20 40 60 80 100 120 Minutes of Exposure

Y= (2.114 x 10

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 10 20 30 40 50 60 70 80 90 100 Stress Resistance (%)

Shoot G rowth Phase

Temperature Drought

Timing

Colombo & Timmer 1992

15 20 25 30 35 40 Air Temperature ( oC) 10 20 30 40 50 60 70 80 90 100 Percent of Maximum P n

Intensity Duration & Intensity

Hydrologic Cycle

Location of Carbon Uptake & Water Loss

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Response to Drought

Gas Exchange Response

• 2.00
• 1.50
• 1.00
• 0.50

0.00

Ψp d (MPa)

10 20 30 40 50 60 70 80 90 100 MAX Daytime gwv (% of Maximum) Y= 108.52 + 1.38x exp; r2 0.95

• 2.50
• 2.00
• 1.50
• 1.00
• 0.50

0.00

Ψpd (MPa)

• 1

1 2 3 4 5 6 Pn (µmol m-2 s-1)

Y= 6.09 + 8.00x + 3.83x

2 + 0.63x 3; r2 0.82

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Response to Drought

Growth

0 1 Julian Day 10 20 30 40 50 New Height Growth (cm) 150 175 200 225 250 275

Dry to Ψpd -0.5 MPa Dry to Ψpd -1.0 MPa

33% Decline

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Response to Drought

Lethal Level

Seedling Water Potential (MPa)

• 3
• 2
• 1

30 40 50 60 70 80 90 100 Survival (%)

Atmospheric VPD

Drying Power of Air

Typical Afternoon Summer Conditions

5 10 15 20 25 30 35 40 Air Temperature (oC) 1 2 3 4 5 6 Vapor Pressure Deficit (kPa)

2 0 % RH 5 0 % RH 8 0 % RH

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Response to VPD

Water Status

1 2 3 4 5 VPD ( kPa)

• 2.00
• 1.50
• 1.00
• 0.50

0.00 Water Potential (MPa) Y= -1.07 - 0.4(ln[x]); r

2 0.46

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Response to VPD

Gas Exchange Response

1 2 3 4 5 6 VPD (kPa) 10 20 30 40 50 60 gwv (mmol m -2 s-1)

Y= 73.39 - 34.59ln(x); r 2 0.50

0.0 1.0 2.0 3.0 4.0 5.0 6.0 VPD (kPa) 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Pn (µmol m -2 s-1)

Pn = 4.97 - 1.99 ln (x); r2 = 0.56

Summer Heat & Drought

 Seedlings can be exposed to limiting or

‘killing’ temperatures.

 Drought comes in the form of:

 Low soil water availability  High atmospheric VPD

 Drought exposes seedlings to:

 Water stress  Reduce gas exchange  Limited growth  Death

Forest Regeneration Process

“An understanding of the causes of plantation failure is necessary if there is to be an improvement in large scale reforestation work…”

Rudolf (1939)

Understanding Plantation Failure

Seedlings can grow anywhere!

Seedlings don’t always grow where we plant them!

The greatest seedling mortality occurs in the initial years after planting and is due to planting stress (Grossnickle 2005).

“The most important cause of death of

transplanted seedlings is desiccation.”

Kozlowski and Davies (1975)

Roots & Seedling Survival

Initial Root System Size Root Growth Capacity

10 20 30 40 50 60 70 80 90 100 Number of New Root s (> 1. 0 cm) 25 50 75 100 First Year Survival (%) Y= 3 6 . 8 + 14 . 4 l n ( x) ; r

2 0 . 7 1

Si mpson 1990

1 2 3 4 Root Dr y Wei ght (g) 25 50 75 100 Survival (%)

Bl ake et al . 1989

Y= 4 6 . 5 + 3 3 . 0 l n ( x) ; r

2 = 0 . 8 7

Water Movement & the SPAC

Water Flow = Difference in Ψ / resistance to water and vapor flow

Soil Factors

Water Temperature

• 1.25
• 1.00
• 0.75
• 0.50
• 0.25

0.00

Ψp d (MPa)

250 500 750 1000 Relative Plant Resistance

Y= - 1. 0 8 - 2 9 4 4 x - 10 0 7 x

2; r 2 0 . 9 4

5 10 15 20 25 Root Temperature (oC) 100 200 300 400 500 Relative Seedling Resistance (%)

Seedlings- New Roots Seedlings- No New Roots

Relative Viscosity of Water

Location of Water Uptake

Root Permeability

25 50 75 100 125 New Root Area (cm2) 0.00 0.50 1.00 1.50 2.00

Root Resistance (MPa µg-1 cm-2 s-1)

Root-Soil Contact

5.0 7.5 10.0 12.5 15.0 Root Temperat ure ( oC) 1 100 110 120 130 140 150 Relative Seedling Resistance (%)

Planted in Aerated Water Planted in Soil

Root Confinement

Limiting Water Movement into a Seedling

0.

(Root / Shoot) * 1/ Ψpd (g MPa-1)

5 10 15 20

RSPAC (MPa µg-1 cm -2 s-1)

1.00 1.50 2.00 2.50 3.00 3.50

Y= 29.1 - 16.3x + 2.75x

2; r2 = 0.65

Low High

Seedling Resistance

Newly Planted Seedlings Established Seedlings

Diurnal Seedling Response

0400 800 1030 1230 1530 1830 Time (h)

• 2.50
• 2.00
• 1.50
• 1.00
• 0.50

0.00

Ψ (MPa)

Established Seedlings Newly Planted Seedling

400 800 1030 1230 1530 1830 Time (h) 1 2 3 4 5 VPD (kPa)

Jun 15 Jun 30 Jul 16 Jul 29 Aug 15 Aug 29

• 2.50
• 2.00
• 1.50
• 1.00
• 0.50

0.00 Minimum Ψ (MPa)

F i v e -Ye a r-Ol d On e -Ye a r-Ol d

1-yr-old Seedlings Planted

Moderate Seasonal Planting Stress

1-Yr-Old 5-Yr-Old 1 2 3 4 Root Dry Wt. (g)

May 4 May 9 May 20 Jun 7 Jun 30 Jul 22 Aug 5 Aug 24

• 3.50
• 3.00
• 2.50
• 2.00
• 1.50
• 1.00
• 0.50

0.00 Ψ (MPa)

Minimum Ψ Ψt l

p

Seedling Planted

Severe Planting Stress

Day 28 Day 90 0.00 0.50 1.00 1.50 2.00 New Root Dry Weight (g)

Jun 12 Jun 30 Jul 10 Jul 29 Aug 15 Sep 5

• 3.50
• 3.00
• 2.50
• 2.00
• 1.50
• 1.00
• 0.50

0.00 Ψ (MPa)

Minimum Ψ Ψt l

p

Seedlings Planted

No Planting Stress

Day 28 Day 120 0.00 0.25 0.50 0.75 1.00 New Root Dry Weight (g)

Planting Stress- Carry Over Effect

1 2 3 4 5 Year of Growth 5 10 15 Annual Height Increment (cm) 50 100 150 200 Height at Beginning of Year (cm) 25 50 75 100 Annual Growth (cm)

Year 1 Year 2 Year 3 Year 4 Year 5

Vyse 1981 South & Zwolinski 1997

Planting Stress- Stocktype Effect

Container Bareroot

Planting Stress- Stocktype Effect

Seedling Quality

N= 27 Trials

Binder et al. 1990

0.0. Shoot to Root Ratio (g DW) 2 3 4 70 80 90 100 Survival (%)

Y= 84 + 18x - 6x

2; r2 0.98

Mexal & Dougherty 1983

Planting Stress- Stocktype Effect

Field Site Water Relations

Dixon et al. 1983

Planting Stress- Stocktype Effect

Field Performance

N= 29 Trials N= 122 Trials

Planting Stress

Overcome Planting Stress by:

 Stocktype selection in relation

to site conditions.

 Planting hardened seedlings

with high root growth capability.

 Preparing favorable planting

sites.

 Plant seedlings properly.  Proper timing of planting (i.e.,

limit exposure to stressful conditions). Root Growth = Coupling to Site

Closing Thoughts