PHYSIOLOGICAL MECHANISMS OF SUSTAINED GROWTH DESPITE CROWN SCORCH IN A YOUNG LONGLEAF PINE PLANTATION

Mary Anne Sword Sayer1, Stanley J. Zarnoch2, and James D. Haywood1

U.S. Forest Service, Southern Research Station,1Pineville, Louisiana2Asheville, North Carolina

2011 Ecological Society of America Annual Meeting, August 7-12 2011, Austin Texas

PRESENTATION OUTLINE

Introduction Longleaf pine (Pinus palustris Mill.) and fireLongleaf pine restorationObstacles to longleaf pine restoration

Experimental results from central LouisianaPhysiological mechanisms that sustain the growth of

forests that are frequently burned.

How does season of fire impact these physiological mechanisms?

PHYSIOLOGY OF SUSTAINED LONGLEAF PINE GROWTH IN RESPONSE TO FIRE

INTRODUCTION Range once extended from

east Texas to the Atlantic coastal plain of the U.S.

Now found on 3.8% of its historical range.

PHYSIOLOGY OF SUSTAINED LONGLEAF PINE GROWTH IN RESPONSE TO FIRE

Adapted to, and benefits from frequent low intensity fire.

Ecosystem flora and fauna are perpetuated by fire.

Repeated fire every 2 to 5 years is used to manage longleaf pine ecosystems.

Range-Wide Conservation Plan for Longleaf Pine 2009. americaslongleaf.com

Increased interest in restoring longleaf pineINTRODUCTION

Range-Wide Conservation Plan for Longleaf Pine calls for an increase in longleaf acreage from 3.4 to 8 million by 2024.

Regeneration success is likely. Highly diverse ecosystems with 29

federally listed TES. May be more tolerant of climate

change than other southern pines (e.g., hurricanes, drought).

Photos: Glenn Hughes. Mississippi State University Extension Service. ghughes@ext.msstate.edu.

Loblolly pine Longleaf pine

Successful longleaf pine restoration depends on fire as a tool. Obstacles must be overcome for fire to be welcome on private lands. Growth responses to fire are inconsistent and may be negative.

INTRODUCTION

Negative○ Boyer (1987) South J Appl For 11:154-157.○ Johansen and Wade (1987) South J Appl For 11:180-184.○ Haywood (2009) For Ecol Manage 158:195-305.○ Weise et al (1987) Res Note SE-347.

Neutral○ Brockway and Lewis (1997) For Ecol Manage 96:167-183.○ Weise et al (1987) Res Note SE-347. ○ Ford et al (2010) Can J For Res 40:1410-1420.

o Haywood (2011) New For 41:55-73.

heat damage to shallow roots

heat damage to vascular cambium

heat damage to buds

● Out of prescription● Introducing fire / heavy fuel load ● Unknown reasons

To determine if there are physiological variables that sustain growth after prescribed fire.

To determine if the seasonal variation of these physiological variables is related to forest production.

To help land managers sustain forest production by manipulating these physiological controls using silviculture.

PHYSIOLOGY OF SUSTAINED LONGLEAF PINE GROWTH IN RESPONSE TO FIRE

OBJECTIVES AND HYPOTHESIS

HypothesisSustained growth depends on maintenance of physiological factors that control whole-tree carbon fixation.

OBJECTIVES AND HYPOTHESIS

METHODS Study site

Two western Gulf coastal plain, mesic, upland sites.Palustris Experimental Forest, Calcasieu Ranger

District, Kisatchie National Forest, Rapides Parish, LA.

PHYSIOLOGY OF SUSTAINED LONGLEAF PINE GROWTH IN RESPONSE TO FIRE

Dominant understory vegetation included Schizachyrium scoparium, S. tenerum, Helianthus angustifolius, Heterotheca graminifolia.

Study Sites

longleafalliance.org

Site 1 2 blocks age 13 yrs in November 2010 Ruston and Malbis fine sandy loams, Gore silt loam

Site 2 3 blocks age 14 yrs in November 2010 Beauregard silt loam

Age 6 years Age 7 years

METHODS Study site

Sites prepared by chopping or shearing/windrowing and burning.

Treatment plots, 22 x 22 m (0.048 ha).Planted with container longleaf pine, 1.8 x 1.8 m.

METHODS

Experimental design: repeated measures RCBD with 5 blocks.

Control, C: No post-plant vegetation control.

3 vegetation management treatments

Burning, B: Prescribed fire in May 2003 and May 2005.

Herbicide, H: Post-plant herbicide application for 2 to 3 years, and hand felling of recovering woody vegetation at age 4 or 5 years.

Mid- to late May

1st flushelongated

2nd flushbud intact

Blocked by apparent soil permeability.

RESULTS- CROWN SCORCH

PHYSIOLOGY OF SUSTAINED LONGLEAF PINE GROWTH IN RESPONSE TO FIRE

Site 2 2003 Site 2 2005

2003● 40-70% scorch● 480 kJ/s/m2

● mild drought 2005

● 90% scorch● 755 kJ/s/m2

● mild to moderate drought

Haywood (2010) New Forests 41:55-73.

RESULTS- PRODUCTIONAnnual groundline basal area growth

ANOVA of annual groundline basal area growth ● H plots greater than C and B plots.● Magnitude of differences was less during drought.● Regardless of scorch, no difference between C

and B plots.

Why didn’t crown scorch reduce tree growth?

RESULTS- FOLIAGE BIOMASS

● Late summer, 4 months post-burning in 2003 and 2005.

● 3 saplings per plot (45 per year).

● 1 sapling per one-third total height percentile.

● Stem, branches, and age classes of foliage separated, dried, and weighed.

Destructive harvest in 2003, 2004, and 2005

RESULTS- FOLIAGE BIOMASS ANCOVA of foliage biomass with GLD as a covariate

● Old foliage: B plots less than C and H plots.

● New foliage: No difference among B, C, and H plots.

● Total foliage: No difference between C and B plots.

● Foliage was re-established four months after crown scorch.

Old foliage: 2003, 2004, 2005

New foliage: 2003, 2004, 2005

Total foliage: 2003, 2004, 2005 Did rapid re-establishment of leaf area sustain sapling growth?

RESULTS- FOLIAGE BIOMASS

Percentage of foliage biomass by age class

● 2003 and 2005: pct of 2nd flush foliage was greater on the B plots than the C and H plots.

ANOVA of pct foliage biomass by age class

● 2005: pct of 1st flush foliage was greater on the B plots compared to the C and H plots.

● 1st and 2nd flush foliage growth may have been accelerated on the B plots compared to the C and H plots.

singed 1st flush foliage

2nd flushbud intact

RESULTS- MECHANISMS OF FOLIAGE RE-ESTABLISHMENT Short-term increase in fascicle-level gas exchange

● Example 1 in 2003-o mild drought, mean ΨJuly pd -0.34 MPa. o morning vs. afternoon.

● Example 2 in 2005-o mild to moderate drought,

mean ΨJuly pd -0.73 MPa.o uniform response.

● By October, gas exchange rates were similar between

the C and B plots.

Amax1

before and after prescribed fire in 2003

Amax1

before and after prescribed fire in 2005

13 saplings of mean height/plot, 10 dates in 2003-2005, detached fascicles, LiCor-6400 portable photosynthesis system, ANOVA.

RESULTS- MECHANISMS OF FOLIAGE RE-ESTABLISHMENT Short-term increase in fascicle-level gas exchange

● Related to stomatal responses to water availability.

● Prescribed burning in May led to an increase in leaf water status and gas exchange for up to a 3-month period.

o gw decreased as leaf water status decreased.

o Leaf water status and gw increased after burning.

Sapling VPD and gw on the Burn plots in 2005

RESULTS- MECHANISMS OF FOLIAGE RE-ESTABLISHMENT Mobilization of stored root starch

Seasonal pattern of southern pine root starch

accumulation for storage

mobilizationfor flush growth

Root starch before and after prescribed fires1

● Small woody roots (2-10 mm diameter)

were frozen and freeze dried.

● Root starch was mobilized more rapidly on the B plots than the C and H plots.

13 saplings of mean height/plot, 12 dates in 2003-2005, enzymatic assay by Dairyland Laboratories, Inc. in Arcadia, WI, ANOVA.

SUMMARY AND CONCLUSIONS

PHYSIOLOGY OF SUSTAINED LONGLEAF PINE GROWTH IN RESPONSE TO FIRE

Two potential mechanisms that sustain pine growth in frequently burned forests.

1. Increased leaf water status and gas exchange for up to three months after burning.

2. Mobilization of stored root starch for the growth of new foliage after burning.

These mechanisms may accelerate foliage re-establishment after scorch.

These mechanisms are season-dependent.● Increased leaf water status is most beneficial during

summer and early fall. ● Root starch is least available for mobilization between

August and December.

SUMMARY AND CONCLUSIONS

Post-fire benefits to leaf area re-establishment and growth are available when the first flush is elongated but the second flush is intact and protected at the time of the burn.

A new study comparing spring and fall burning is underway to verify the physiological benefits of season of burning.

Mary Anne Sword Sayer, msword@fs.fed.usUS Forest Service, Southern Research StationRWU-SRS-4158: Restoring and Managing Longleaf Pine Ecosystems