Physiological mechanisms of sustained growth despite crown - PowerPoint Presentation

Slide1

Physiological mechanisms of sustained growth despite crown scorch in a young longleaf pine plantation

Mary Anne Sword Sayer1, Stanley J. Zarnoch2, and James D. Haywood1U.S. Forest Service, Southern Research Station,1Pineville, Louisiana2Asheville, North Carolina

2011 Ecological Society of America Annual Meeting, August 7-12 2011, Austin TexasSlide2

Presentation outline

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

Experimental results from central Louisiana

Physiological 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 fireSlide3

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.comSlide4

Increased interest in restoring longleaf pine

Introduction

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 pineSlide5

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. 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 Slide6

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 hypothesisSlide7

Hypothesis

Sustained growth depends on maintenance of physiological factors that control whole-tree carbon fixation. Objectives and hypothesisSlide8

Methods

Study siteTwo 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.orgSlide9

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. Slide10

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

1

st

flush

elongated

2

nd

flush

bud intact

Blocked by apparent soil permeability.Slide11

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/m

2

mild drought

2005

90% scorch

755 kJ/s/m

2

mild to moderate drought

Haywood (2010) New Forests 41:55-73.Slide12

Results- production

Annual 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?Slide13

Results-

foliage biomassLate 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 2005Slide14

Results-

foliage biomassANCOVA of foliage biomass with GLD as a covariateOld 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?Slide15

Results-

foliage biomassPercentage of foliage biomass by age class2003 and 2005: pct of 2

nd

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 1

st

flush foliage was greater on the B plots compared to the C and H plots.

1

st

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

singed 1

st

flush foliage

2

nd

flush

bud intactSlide16

Results-

mechanisms of foliage re-establishmentShort-term increase in fascicle-level gas exchange

Example 1 in 2003-

mild drought,

mean

Ψ

July

pd

-0.34

MPa. morning vs. afternoon.

Example 2 in 2005-mild to moderate drought, mean

Ψ

July

pd

-0.73

MPa

.

uniform response.By October, gas exchange rates were similar between the C and B plots.

Amax1

before and after prescribed fire in 2003

A

max

1

before and after prescribed fire in 2005

1

3 saplings of mean height/plot, 10 dates in 2003-2005, detached fascicles, LiCor-6400 portable photosynthesis system, ANOVA.Slide17

Results-

mechanisms of foliage re-establishmentShort-term increase in fascicle-level gas exchangeRelated 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.

g

w

decreased as leaf water status decreased.

Leaf water status and

g

w

increased after burning.

Sapling VPD and

g

w

on the Burn plots in 2005Slide18

Results-

mechanisms of foliage re-establishmentMobilization of stored root starchSeasonal pattern of southern pine root starch

accumulation

for storage

mobilization

for flush growth

Root starch before and after prescribed fires

1

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.

1

3 saplings of mean height/plot, 12 dates in 2003-2005, enzymatic assay by

Dairyland

Laboratories, Inc. in Arcadia, WI, ANOVA.Slide19

Summary and Conclusions

Physiology of sustained longleaf pine growth in response to fire

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

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

.

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. Slide20

Summary and

ConclusionsPost-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.Slide21

Mary

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