Ponderosa pine seedling height growth beneath partial overstories in the central Oregon Cascade...

Ponderosa pine seedling height growth be-neath partial overstories in

the central Oregon Cascade RangeWoongsoon Jang1

Christopher R. Keyes1, David L.R. Affleck1, and Douglas A. Maguire2

1Department of Forest Management, College of Forestry and Con-servation, University of Montana 2Department of Forest Engineering, Resources & Management, Oregon State University

INGY 2012 Winter Tech Meeting

AFMP University of Montana

Partial overstory retention

• Compromise between timber production and ecological objec-

tives

– Enhance structural complexity

– Increase species diversity

• Facilitating ponderosa pine seedling recruitment and survival

– Enhance seed availability

– Ameliorate environmental stressors

• For silviculturists

– Effect on growth rates of seedling?



Negative effects on seedling growth

• Negative relationship between seedling growth and over-

story density, distance, etc.

• But, number of study is few:

– Because seedling growth prior to overstory removal was not

concerned

– Overstory retention level is constrained and retained temporary



Objectives

• Understand overstory/understory relationships of two-

aged ponderosa pine stands arising from dispersed

variable-retention harvests

– How the growth of seedlings and saplings is influenced by

varying levels of overstory retention

– How the overstory/seedling growth relationship changes in

different environments



Study Site



Climate of study site

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

10

20

30

40

50

60

70

80

90

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Precipitation

Max. Temp.

Min. Temp.

Tem

per

atu

re (

F)

Pre

cip

itat

ion

(in

.)



Site description

Block Stand Tree ha-1 BA(m2 ha-1)

QMD(cm)

Ave. Ht.(m)

Ave. LCR(%)

Shrub Cov.(%)

WarmSprings

101102103105107

1216172033

9.27.87.33.46.8

99.078.774.246.451.0

41.739.036.519.624.4

5053545855

6272797940

PringleFalls

203204205206207208

12839

1031923380

22.510.817.324.313.918.1

47.459.346.340.272.853.7

26.031.725.523.134.229.8

664458545750

4877399

7354

Fort Rock301302304

182047

4.23.3

13.2

54.846.159.8

21.815.624.4

617262

382540



Collected dataVariable Group Parameter Unit Scale

Response Variable Seedling height growth (1994-99) cm individual

Potential Productivity

Seedling height at 1994 cm individual

Site index m plot

Planted treatment - plot

Site preparation - plot

Block - stand

Overstory Retention

Quadratic Mean Diameter cm plot

Tree density trees ha-1 plot

Stand Density Index - plot

Basal Area ft2 ac-1 plot

Understory Condition

Vegetation Coverage % plot

Overhead shrub presence - individual

Nearest Shrub Height cm individual

Distance to Nearest Shrub cm individual

Graminoid coverage % plot

Seedling density trees ha-1 plot



Data analyses

• Generalized linear model (GLM)

– Random component (probability distribution)

• Gamma distribution

– Linear predictor

•

– Link function

• Log transformation

•

X

)ln( X )exp( X



Results

Variable Group Parameter Est. Coeff. S.E. p-value

(Intercept) -0.2792 0.1953 0.1532

Potential Productivity

Seedling Ht (1994) 0.6464 0.0364 <0.0001

Site index 0.0490 0.004 <0.0001

Planted treatment 0.3228 0.0419 <0.0001

Site preparation -0.2825 0.0541 <0.0001

Block (PF) 1.1249 0.18270 <0.0001

Block (WS) 0.7492 0.1741 <0.0001

Ht×(PF) -0.2341 0.0426 <0.0001

Ht×(WS) -0.0333 0.0408 0.4151

Overstory RetentionQMD (15 m) -0.0009 0.0005 0.0565

Tree density (15m) -0.0055 0.0005 <0.0001

Understory condition Nearest Shrub Height 0.0018 0.0003 <0.0001



Overstory vs. Understory

• Negative effect on seedling height growth

– 10 cm increase of QMD 0.92% reduction

• e-0.0092 = 0.9908

– Additional 10 tree/ha 5.35% reduction

• e-0.0550 = 0.9465

• Similar results with other studies and species

– Ponderosa pine (Oliver and Dolph,1992; McDonald and Abbott

1994)

– Douglas-fir (Isaac 1956; Wampler 1993; Hansen et al. 1995)

– Scots pine (Elfving and Jakobsson 2006)



Best measure of overstory?

• Basal Area (BA)

– Many study have used

• E.g. Rose and Muir 1997; Acker et al. 1998; Page et al. 2001

– Not merely a measure of aboveground competition

– Correlated with foliage or canopy coverage, root com-

petition, etc.

• Combination of tree density and QMD

– Account for more variance than BA



How big should the plot size be?

• Key question from competition indices

– So-called “zone of influence” (Opie 1968)

• Optimum radius of overstory plot

– Vary with tree size (Wagner and Radosevich 1991)

– 3.5 times of the mean crown radius (Lorimer 1983)

• Bigger plot explains more variance

– Beyond 18.29 m ignorable (Hoyer 1993)

– Min. effective distance 12.19 m (McDonald 1976)

– Thus, 15 m radius is the most relevant



Shade? Or others?

• What causes the reduction of seedling growth?

– Light condition

• Influences ponderosa pine seedlings more than any other factor

• Decreases with overstory basal area increment (Oliver and Dolph

1992)

• Modifies tree attributes (Pearson 1936, Messier et al. 1999)

– Others?

• Soil moisture (McDonald and Abbot 1994)

• Competition for nutrients and low soil temperature (Lajzerowicz et al.

2004)



Prescribed burning

• Reduces fuel load, improves seedling recruitment, simulates

thinning effect, etc.

• However, the effect of prescribed burning has been debated

for a long time

• Negative effect in this study

– Loss of total biomass of duff layer

– Subsequent nutrient deficiency

• Takes long time to recover to the level of pre-burn

• Limitation of total nutrient supply (especially N)

• Delayed recovery of N-fixation shrubs

(eg. Ceanothus velutinus, Purshia tridentata)



Planting

• Already selected seedlings

– Have better geno- & phenotype

• Already grown enough to compete

• Planter could control the place to be

planted



Understory veg. & seedling growth

FR PF WS

05

01

00

15

02

00

25

03

00

Block

He

igh

t of N

ea

rest

Sh

rub

(cm

)

0 100 200 300 400

Height at 1994 (cm)

He

igh

t Gro

wth

Warm Springs

Fort Rock

Pringle Falls



Management implications

• Controlling seedling height growth

– Manipulation of overstory retention level

• Number and size of overstory retention trees

• Introduction of site preparation method or artificial planting

• Effects of other factors on seedling behavior

– stand history, potential productivity, and understory condition



Management implications

0 20 40 60 80 100 120 140

02

04

06

08

01

00

12

01

40

Number of trees per ha

QM

D (

cm)

0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13 -14 -15 -16 -17



Going further…

• Spatial pattern of overstory retention?

– Palik et al. 2003; Maguire et al. 2006

• Climate?

– How do seedlings respond to the weather during growing season?

• Refinement of understory veg. variables

– Plot level measurement were not appropriate

– Shrub species composition

– Interaction (e.g. competition vs. facilitation?) with seedling along

with site condition and seedling size, etc.



Cited literature• Acker, S.A., E. Zenner, and W. Emmingham. 1998. Structure and yield of two-aged stands on the Willamette National Forest, Oregon: implications for green tree reten-

tion. Canadian Journal of Forest Research 28(5):749-758.

• Hansen, A.J., S.L. Garman, J.F. Weigand, D.L. Urban, W.C. McComb, and M.G. Raphael. 1995. Alternative Silvicultural Regimes in the Pacific Northwest: Simulations of

Ecological and Economic Effects. Ecological Applications 5(3):535-554.

• Hoyer, G.E. 1993. The influence of Douglas-fir overstory on understory tree height growth in coastal forests of Washington. Washington Department Natural Resources

Forest Land Management Research Center. Contribution No. 348.

• Isaac, L.A. 1956. Place of partial cutting in old-growth stands of the Douglas-fir region. US Dept. of Agriculture, Forest Service, Pacific Northwest Forest and Range

Experiment Station. Research Paper 16. PNW-RP-16. p 48.

• Lajzerowicz, C.C., M.B. Walters, M. Krasowski, and H.B. Massicotte. 2004. Light and temperature differentially colimit subalpine fir and Engelmann spruce seedling

growth in partial-cut subalpine forests. Canadian Journal of Forest Research 34(1):249-260.

• Lorimer, C.G. 1983. Tests of age-independent competition indices for individual trees in natural hardwood stands. Forest Ecology and Management 6(4):343-360.

• Maguire, D., D. Mainwaring, and C. Halpern. 2006. Stand dynamics after variable-retention harvesting in mature Douglas-fir forests of western North America. Allge-

meine Forst und Jagdzeitung 177(6/7):120.

• McDonald, P.M. 1976. Inhibiting Effect of Ponderosa Pine Seed Trees on Seedling Growth. Journal of Forestry 74(4):220-224.

• McDonald, P.M., and C.S. Abbott. 1994. Seedfall, regeneration, and seedling development in group-selection openings. U.S. Department of Agriculture, Forest Service

Research Paper PSW-RP-220. 13p.

• Messier, C., R. Doucet, J.-C. Ruel, Y. Claveau, C. Kelly, and M.J. Lechowicz. 1999. Functional ecology of advance regeneration in relation to light in boreal forests. Cana-

dian Journal of Forest Research 29(6):812-823.

• Oliver, W.W., and L.K. Dolph. 1992. Mixed-conifer seedling growth varies in response to overstory release. Forest Ecology and Management 48(1-2):179-183.

• Opie, J.E. 1968. Predictability of Individual Tree Growth Using Various Definitions of Competing Basal Area. Forest Science 14(3):314-323.

• Page, L.M., A.D. Cameron, and G.C. Clarke. 2001. Influence of overstorey basal area on density and growth of advance regeneration of Sitka spruce in variably thinned

stands. Forest Ecology and Management 151(1-3):25-35.

• Palik, B., R.J. Mitchell, S. Pecot, M. Battaglia, and M. Pu. 2003. Spatial distribution of overstory retention influences resources and growth of longleaf pine seedlings.

Ecological Applications 13(3):674-686.

• Pearson, G.A. 1936. Some Observations on the Reaction of Pine Seedlings to Shade. Ecology 17(2):270-276.

• Rose, C.R., and P.S. Muir. 1997. Green-tree retention: consequences for timber production in forests of the western Cascades, Oregon. Ecological Applications

7(1):209-217.

• Wagner, R.G., and S.R. Radosevich. 1991. Neighborhood predictors of interspecific competition in young Douglas-fir plantations. Canadian Journal of Forest Research

21(6):821-828.

• Wampler, M. 1993. Growth of Douglas-fir Under Partial Overstory Retention. M.S. thesis, University of Washington, Seattle, WA.

Ponderosa pine seedling height growth beneath partial overstories in the central Oregon Cascade...

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