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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
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?
•• 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