Conifer encroachment of montane meadows: …...2010/03/03  · Conifer encroachment of montane meadows: effects on vegetation, seed banks and potential for restoration Ryan D. Haugo

Conifer encroachment of montane Conifer encroachment of montane meadows: effects on vegetation, meadows: effects on vegetation,

seed banks and potential for seed banks and potential for restorationrestoration

Ryan D. HaugoRyan D. HaugoNicole L. LangNicole L. Lang

Charles B. HalpernCharles B. Halpern

College of Forest ResourcesCollege of Forest ResourcesUniversity of Washington, SeattleUniversity of Washington, Seattle Photo: Jim Lutz

•• Value of unique, open meadow Value of unique, open meadow communitiescommunities–– BiodiversityBiodiversity–– Wildlife habitatWildlife habitat–– Cultural resourcesCultural resources

•• Conifer invasion of Conifer invasion of meadow habitatmeadow habitat

•• Widespread across Widespread across PNWPNW

•• Concern over the loss Concern over the loss of unique meadow of unique meadow habitathabitat

The problemThe problem……

•• Focus on the causesFocus on the causes–– Fire suppressionFire suppression–– Climate changeClimate change–– GrazingGrazing

The problemThe problem……

•• Very little Very little understanding of:understanding of:–– Vegetation dynamicsVegetation dynamics–– Restoration potentialRestoration potential–– Effectiveness of Effectiveness of

restoration treatmentsrestoration treatments

The problemThe problem……

Bunchgrass Ridge, ORBunchgrass Ridge, OR

•• Dry, montane meadowDry, montane meadow•• Willamette NF Special Habitat Area Willamette NF Special Habitat Area

BunchgrassBunchgrassMeadowMeadow

•• 1120 m to 1375 m1120 m to 1375 m•• History of conifer invasionHistory of conifer invasion

–– Grand fir (Grand fir (Abies grandisAbies grandis))–– Lodgepole pine (Lodgepole pine (Pinus contortaPinus contorta))

•• Meadow soilsMeadow soils

19971946

1.1. Vegetation Dynamics Vegetation Dynamics –– R HaugoR Haugo

2.2. Seed bank Dynamics Seed bank Dynamics –– N LangN Lang

3.3. Experimental Restoration Experimental Restoration –– In progressIn progress

Vegetation Vegetation DynamicsDynamics

•• Temporal changes in Temporal changes in vegetationvegetation–– Community Community

compositioncomposition–– Meadow and forest Meadow and forest

speciesspecies•• Abundance (cover)Abundance (cover)•• RichnessRichness

Erigeron aliceae

Vegetation Vegetation DynamicsDynamics

•• Relationship between Relationship between vegetation and vegetation and environmental environmental changeschanges–– Light levels and stand Light levels and stand

structure structure

Erigeron aliceae

Field samplingField sampling

•• 4, 1 ha blocks4, 1 ha blocks•• 356 10 x 10 m subplots356 10 x 10 m subplots

–– Basic sample unitBasic sample unit

•• Census of all overstory treesCensus of all overstory trees–– Species, size, age, Species, size, age,

locationlocation

•• Light levelsLight levels•• Vegetation samplingVegetation sampling

ChronosequenceChronosequence

•• Temporal changes Temporal changes --> space for time > space for time

substitution substitution

•• Seven encroachment Seven encroachment classesclasses–– Class 0 (open Class 0 (open

meadow) to Class 6 meadow) to Class 6 (old forest)(old forest)

Aquilegia formosa

Encroachment ClassesEncroachment Classes

Class 2n = 42

Num

ber o

f ste

ms

/ sub

plot

(100

m2 )

0

4

8

12

16

Class 1n = 17

0

4

8

0

4

8

Class 5n = 77

0

4

8

Class 6 (old forest)n = 38

Age (yr)

0

4

8

0

4

8Class 3n = 70

Class 0n = 28

0

4

8

Class 4n = 84

no trees

20 40 60 80 140 180 220100

NMS 1

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

NM

S 2

-1.0

-0.5

0.0

0.5

1.0 Forest SpeciesMeadow SpeciesRuderal Species

Ort_imbLup_lat

Phl_dif

Ely_gla

Eri_aliCar_pen

Are_mac

Osm_chi

Lac_mur

Ach_tri

Cir_alp

Smi_ste

Compositional changesCompositional changes•• Nonmetric Multidimensional Scaling (NMS) Nonmetric Multidimensional Scaling (NMS)

ordinationordination•• Strong meadow to forest gradientStrong meadow to forest gradient

Compositional changesCompositional changes•• NMS and age class centroidsNMS and age class centroids

NMS 1

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

NM

S 2

-1.0

-0.5

0.0

0.5

1.0

01

2345

6

Encroachment class centroids

TimeTime

Composition and EnvironmentComposition and Environment•• Spearman rank correlations Spearman rank correlations

NMS 1

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

-1.0

-0.5

0.0

0.5

1.0

0

1

23

45

6

NM

S 2

Pinus live densityPinus live BA

Pinus dead densityPinus dead BA

Light

Abies live density

Abies live BAAbies dead BA

Abies dead density

OpenMeadow

LodgepolePine

Grand Fir

Meadow / Meadow / Forest CoverForest Cover

•• Threshold Threshold response for response for meadow covermeadow cover

•• Gradual increase Gradual increase in forest coverin forest cover–– Low overall coverLow overall cover

0

20

40

60

80

100

120

140ShrubsHerbsGrassesSedges

Encroachment class

0 1 2 3 4 5 6

Cov

er (%

)

0

20

40

60

a. Meadow species

b. Forest species

Meadow / Meadow / Forest RichnessForest Richness•• Progressive Progressive

meadow declinemeadow decline•• Not completely Not completely

lostlost

•• More rapid forest More rapid forest increaseincrease

•• Decline from Class Decline from Class 5 to 65 to 6

0

2

4

6

8

10

12

14 ShrubsHerbsGrassesSedges / Rushes

a. Meadow species

Encroachment class

0 1 2 3 4 5 6

Spec

ies

richn

ess

(no.

spe

cies

sub

plot

-1)

0

2

4

6

8

10

12

14

b. Forest species

Class 6 Class 6 -- Old ForestOld Forest

•• Distinct Distinct composition (NMS)composition (NMS)

•• Dominated by Dominated by strongly clonal strongly clonal speciesspecies–– Limits cover / Limits cover /

richness of other richness of other speciesspecies

Smilacina stellata

•• Strong meadow to forest gradientStrong meadow to forest gradient–– Clear progression over timeClear progression over time–– Closely related to lodgepole pine to grand Closely related to lodgepole pine to grand

fir transitionfir transition

•• Rapid decline of meadow vegetationRapid decline of meadow vegetation–– Threshold response in cover meadow Threshold response in cover meadow

covercover–– Mode tree age of 40 Mode tree age of 40 –– 60 years60 years

•• Did not experience complete Did not experience complete extirpationextirpation

•• Decline of meadow vegetation Decline of meadow vegetation –– Closely related to light levels and forest Closely related to light levels and forest

structurestructure•• Colonization of forest species Colonization of forest species

–– Weaker relationship with light and Weaker relationship with light and structurestructure

–– Distinctive old forest understoriesDistinctive old forest understories

•• Management and Restoration?Management and Restoration?–– Early removal of treesEarly removal of trees–– Persistence of meadow speciesPersistence of meadow species–– Potential for regeneration from the seed Potential for regeneration from the seed

bank?bank?

Seed Bank ResponseSeed Bank Response

•• Temporal changes in Temporal changes in composition of the soil composition of the soil seed bankseed bank–– Open MeadowOpen Meadow–– Young ForestYoung Forest–– Old ForestOld Forest

Seed Bank ResponseSeed Bank Response

•• Relationship between the Relationship between the seed bank and above seed bank and above ground vegetationground vegetation

Conceptual Diagram of Seed Bank Dynamics at Bunchgrass

ruderalspecies

meadow species

ruderalspecies

forest species

ruderalspecies

meadow species

forest species

Open meadow

Young forest

Old forest

ruderalspecies

meadow species

Above-ground

vegetation

Soilseed bank

Seed Bank Methods:

•209 10 x 10m subplots sampled

•3 soil plugs per subplot

•Age classes•Open meadow•Young forest•Old forest

•Greenhouse germination

Primary Seed Bank Species

0

10

20

30

40

50

60

70

80

90

100

Agro

stis

scab

raCa

rex

pens

ylvan

icaEp

ilobi

um w

atso

nii

Lact

uca

mur

alis

Ranu

ncul

us u

ncin

atus

Frag

aria

spp

.G

aliu

m tr

ifloru

mSe

neci

o sy

lvatic

usCi

rcae

a al

pina

Achi

llea

mille

foliu

mAr

enar

ia m

acro

phyl

laCa

mpa

nula

sco

uler

iSt

ella

ria c

rispa

Freq

uenc

y (%

)

Primary Seed Bank Species and Occurrence in the Vegetation

0

10

20

30

40

50

60

70

80

90

100

Agro

stis

scab

raCa

rex p

ensy

lvanic

aEp

ilobi

um w

atso

nii

Lact

uca

mur

alis

Ranu

ncul

us u

ncin

atus

Frag

aria

spp.

Gali

um tr

ifloru

m

Sene

cio sy

lvatic

usCi

rcae

a al

pina

Achil

lea m

illefo

lium

Aren

aria

mac

roph

ylla

Cam

panu

la sc

ouler

iSt

ella

ria cr

ispa

Freq

uenc

y (%

)

vegetationseed bank

Seedbank Composition

DC

A A

xis

2

0

100

200

300

Open meadow (Class 0,1)Young forest (Class 2-5)Old forest (Class 6)

Fragaria spp.

Gnaphalium microcephalum

Danthonia intermedia

Galium triflorum

Epilobium watsonii

Circaea alpina

Lactuca muralis

Senecio sylvaticus

Carex pensylvanica

Agrostis scabra Achillea millefolium

Subplots

Seedbank species

DCA Axis 1

0 100 200 300 400 500

DC

A A

xis

2

0

100

200

300

Ruderal speciesMeadow speciesForest species

Open meadowYoung forestOld forest

DCA Ordination

Meadow, Forest, and Ruderal Species

0

10

Spec

ies

richn

ess

(no.

spe

cies

/sam

ple)

0

1

2

0

10

0

1

2

Den

sity

(no.

ger

min

ants

/sam

ple)

Richness Density

0

1

2

3

4

5

a

b

a

0

10

20

30

Oldforest

Openmeadow

Youngforest

Meadow speciesp = 0.630

Meadow speciesp = 0.664

Ruderal speciesp = 0.002 p = 0.817

Ruderal species

Forest speciesp = 0.082

Forest speciesp = 0.09

Oldforest

Openmeadow

Youngforest

Seed Bank Conclusions:

1.1. The seed bank composition is dominated by ruderal The seed bank composition is dominated by ruderal species, with limited contribution from meadow and species, with limited contribution from meadow and forest species.forest species.

2.2. The seed bank does not closely resemble the aboveThe seed bank does not closely resemble the above--ground vegetation.ground vegetation.

3.3. Few meadow species persist under meadow or forest Few meadow species persist under meadow or forest vegetation. vegetation.

Meadow Restoration?• Is restoration of invaded meadows

possible?• Impacts of forest age?• Is fire a necessary component of

meadow restoration?

Control

Cut + broadcast burn

Cut only (cut + pile/burn)

Reserve (for future treatment)

Treatments

•• HarvestHarvest–– Winter Winter ’’0505--0606–– Summer Summer ’’0606

•• BurnBurn–– Autumn Autumn ’’0606

Thanks!Thanks!•• Fred Swanson, Joe Fred Swanson, Joe

Antos, John CisselAntos, John Cissel

•• 2003, 2004, 2005 field 2003, 2004, 2005 field crewscrews

•• McKenzie District, McKenzie District, Willamette NF Willamette NF –– Cheryl Cheryl Friesen and many othersFriesen and many others

•• Joint Fire Sciences Joint Fire Sciences Program Program