The effects of fire severity and site moisture on functional properties of black spruce forests in interior

Alaska

by Emily Bernhardt

• Functional diversity– Relative abundance of functionally different

kinds of organisms Walker, B. 1992.

• Plant functional types (PFT)– Assemblage of species with certain similar

plant functional attributes (traits) Skarpe, C. 1996

• Defined by ecological properties in question Naemm and Li 1997

• Functional redundancy– Taxonomically distinct species that perform the same

functional role in the ecosystem Walker, B. 1992; Micheli and Halpurn 2003

What factors make a black spruce forest stay a black spruce forest

• If black spruce as a forest type has definable characteristics:

• Self replacing low severity fire• Cold / wet / acidic soils• Permafrost • Does an alteration of one (fire regime) affect

the communities ability to maintain the others? – By altering the community composition, thereby

altering the communities ability to maintain BS forest type characteristics, resulting in a change of forest type

Hypothesis

Post-fire change in species composition will alter functional properties of re-growth

and residual vegetation in relation to burn severity/site moisture

Burn severity

Site moistureL HH H

H L L L

• Sampled – 5 individuals per

species

• Measured– Hard / soft traits– Rooting depth

• CPCRW sites

• Conducted– Reléve

Examining changes in functional diversity

• Analyzed changes in 3 ways

– 1) Created list of plant traits for boreal species

– 2) Hypothesized trait relationships with burn severity and site moisture

– 3) Reported observed trait relationships• How plant traits are distributed across study

sites

 Trait type          

Trait Soft Hard ConstantMeasure

dLife

historyStructura

l

Growth form x x x  

Species longevity x x x  

Leaf life span x x x  

Rooting type x x x  

Dispersal type x x x  

Pollination x x x  

Seed bank x x x  

Response to fire x x x  

Nitrogen fixation x x x  

Plant height x x x

Shoot length x x x

Leaf length x x x

SLA x x x

Rooting depth x x x

Rooting substrate   x   x   x

Plant traits for each species

Ability to Establish/Flourish After Disturbance  

Ability To Withstand Disturbance  

   

Dispersal - how does it get there? Avoidance  

Dispersal type Life history Height Morphological

  Chemical defenses Life history

   

   

Establishment - how well does it germinate? Regeneration strategy  

SLAMorphological Rooting depth  

Seed bank potential Life history Growth form Life history

  Leaf life span  

  Seed bank Life history

  Root type  

   

Persistence - how well does it grow and reproduce? Tolerance  

HeightMorphological Longevity Life history

Life cycle Life history Leaf life span  

Seed persistence Life history Root type  

SLAMorphological Growth form  

Root type  

Nutrient status of plant  

   

Hypothesized trait relationships

Response to         Effect on    

 Fire

severitySite

moistureFlammabilit

ySite

moisturePermafros

t

  low high low high      

Growth form + + + + +

Resprout ability + +  

SLA + -  

Rooting depth + + + +

Rooting substrate + + + +

Root type   + + +   + +

Seed bank + - + -  

Life span + - + - +  

Seed mass + - - +  

Height +   -     + +

Leaf longevity - - + +  

Fire resistance - + - +

Seed persistence - + + -  

Shoot length - + - + +    

Leaf length +  

Life cycle +  

Dispersal              

Hypothesized trait relationships

site

trait averagewithin site

trait average of all species within a site for each trait

within BS/SM type

all sites

trait averageacross all sites

species Species trait value independent of site

Site trait value independent of species

2 tables were created from these data

Species trait value for each sampled year

Species Shoot Leaf Height Leaf Weight Leaf Area

  2005 2006 2005 2006 2005 2006 2005 2006 2005 2006

Arc lat 1.57 2.80 1.92 3.31 1.57 2.82 2.98 2.84 3.65 3.48

Arc rub 1.35 2.26 1.01 1.22 1.05 1.95 0.34 0.72 0.31 0.63

Bet gla 0.91 0.54 0.89 0.89 0.67 0.79 1.08 0.90 0.90 0.90

Bet nan 5.25 5.72 6.33 6.68 5.89 6.32 2.05 2.56 4.16 4.66

Bet neo 7.69 7.42 7.70 7.07 7.02 6.57 5.14 2.97 4.67 3.07

Cal can 15.97 18.0021.8

0 23.0516.0

9 18.2615.9

817.4

413.1

713.9

5

Cal lap 1.00 1.00 1.00 1.00 1.00 1.00 0.00 0.00 0.00 0.00

Car big 3.30 4.67 3.77 5.16 3.41 4.72 3.82 3.91 4.72 5.18

Cor can 1.30 1.84 0.77 1.29 2.42 2.89 1.95 2.36 1.73 2.31

Cor sem 1.43 2.07 1.18 2.08 1.43 2.07 1.67 1.67 1.80 1.80

Emp nig 0.83 0.08 1.00 0.10 1.00 0.10 0.00 0.00 0.00 0.00

Epi ang 25.30 24.8127.0

3 26.0025.6

1 24.86 2.55 2.5311.5

311.3

7

Epi gla 1.00 0.10 1.00 0.10 1.00 0.10 0.00 0.00 0.00 0.00

Epi pal 1.05 1.27 1.06 1.31 1.05 1.27 1.76 1.38 1.36 1.18

Equ arv 4.18 3.41 3.57 2.57 4.36 3.28 1.00 0.50 1.00 0.50

Equ sci 3.38 3.06 5.12 5.20 2.08 1.82 0.00 0.00 0.00 0.00

Equ syl 18.76 18.5018.3

4 18.3313.6

1 13.33 4.91 2.41 3.52 1.02

Eri vag 4.43 6.43 6.51 9.47 6.87 9.82 6.54 9.68 6.09 9.24

Gal bor 1.86 1.09 1.90 1.09 1.79 1.08 1.00 1.00 1.00 1.00

Hie sca 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

Led gro 10.79 10.52 3.96 3.9012.6

1 12.08 5.52 5.6410.3

510.4

9

Site trait value for each sampled year

TraitTC010

5TC010

6TC040

5TC040

6TC080

5TC080

6TC190

5TC190

6DC460

5DC460

6

Shoot 3.97 7.44 4.95 7.56 6.49 5.47 2.57 2.15 3.93 3.92

Leaf 4.70 7.79 4.15 5.31 6.46 5.81 3.53 2.91 5.29 5.42

Height 3.86 5.61 4.20 5.52 5.59 5.09 2.69 2.35 3.10 3.80

Leaf Weight 5.27 3.51 4.16 4.47 5.37 3.99 2.25 1.78 4.24 3.48

Leaf Area 4.51 3.34 5.01 5.75 5.75 4.27 2.60 2.04 4.15 4.19

H H L H L H L L H L

Determining how traits relate in ecosystem

• A ordination represents a species (or site) of interest in ordination space, where the species location along the axis represents its similarity to other species located along the axis – Using data collected from reléve

3

Preliminary results

• Certain traits appear to respond similarly to burn severity and site moisture and can potentially become a PFT group

• Site / species table:– Species with similar trait values often have different

growth forms– Low moisture sites have lowest trait values

• From ordination:– Growth form is not a good functional type grouping

variable– Burn severity and site moisture were accurately

determined– Low burn severity sites have similar trait values

Final product – species trait matrix

  Constant            

Species

Growth form

life cycle

life span shoot leaf height

leaf weight

leaf area

rootabgr ht

root abgr wt

Aln cri dec shr p        

Bet gla dec shr p        

Bet nan dec shr p        

Ros aci dec shr p        

Rub ide dec shr p        

Sal ale dec shr p        

Sal gla dec shr p        

Sal myr dec shr p        

Sal pul dec shr p        

Sal sco dec shr p        

Spi bea dec shr p        

Vac uli dec shr p                

Measured

Response to         Effect on    

 Fire

severitySite

moistureFlammabilit

ySite

moisturePermafros

t

  low high low high      

Growth form + + + + +

Resprout ability + +  

SLA + -  

Rooting depth + + + +

Rooting substrate + + + +

Root type   + + +   + +

Seed bank + - + -  

Life span + - + - +  

Seed mass + - - +  

Height +   -     + +

Leaf longevity - - + +  

Fire resistance - + - +

Seed persistence - + + -  

Shoot length - + - + +    

Leaf length +  

Life cycle +  

Dispersal              

Hypothesized trait relationships

Acknowledgments

• JFSP• UAF – Biology department• Teresa Hollingsworth• Terry Chapin• Field crew and technical advisement

– Christa Mulder, Emily Tissier, Jamie Hollingsworth, Mark Winterstien, Gretchen Garcia, Kate McGlone, Brian Charlton, Katie Villano and Dana Nossov

References• Naeem, S. and S. Li. 1997. Biodiversity enhances ecosystem reliability. Letters to nature 390:507-509.• Micheli F., and B.,S. Halpurn. 2005. Low functional redundancy in costal marine assemblages.

Ecology letter 8:391-400. • Skarpe, C. 1996. Plant functional types and climate in a southern African savanna. Journal of

vegetation science 7:397-404.• Walker, B. 1992. Biodiversity and ecological redundancy. Conservation Biology 6:18-23.

• Plant functional type example– Growth form popular– But may not be appropriate or validly explain

community response– Used a a sort of base line to compare

functional type groupings against

• Constant trait– general traits with little to no variation

(growth form)

• Variable trait– plastic morphological traits (plant height)

Rooting depth measurements in C P C R W sites (burned and unburned)

Measured rooting depth of each individual • 8 burned sites

– 2 of each site moisture/burn severity• 4 unburned sites

• Sampling design – 30m belt transect – 5 individuals of each species

Response and effect groups

• In relation to ecosystem characteristics of interest

– Flammability– Permafrost– Acidity– N-fixation– Site moisture

Examining changes in functional diversity

• Assign species into functional groups based on their growth form (evergreen vs. deciduous)

• Create a list of constant and variable traits

• Separated into– Response of plants to fire regime

(tolerance, disturbance response)– Effect of plants on fire regime

(flammability, formation of permafrost, nitrogen fixation)

Trait Value Categorization

• All measured trait values standardized

• Trait values categorized by site for each species – abundance value multiplied by trait value

• Trait values calculated between sites by species– Trait values totaled to give a species trait

value

• Trait values calculated for site – Species trait values totaled to give a site trait

value 3