overstories in the central Oregon Cascade Range Woongsoon Jang 1 Christopher R Keyes 1 David LR Affleck 1 and Douglas A Maguire 2 1 Department ID: 528016
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Ponderosa pine seedling height growth beneath partial overstories in the central Oregon Cascade Range
Woongsoon Jang1 Christopher R. Keyes1, David L.R. Affleck1, and Douglas A. Maguire2
1Department of Forest Management, College of Forestry and Conservation, University of Montana 2Department of Forest Engineering, Resources & Management, Oregon State UniversitySlide2
Partial overstory retentionCompromise between timber production and ecological objectivesEnhance structural complexityIncrease species diversityFacilitating ponderosa pine seedling recruitment and survival
Enhance seed availabilityAmeliorate environmental stressorsFor silviculturistsEffect on growth rates of seedling?Slide3
Negative effects on seedling growthNegative relationship between seedling growth and overstory 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 temporarySlide4
ObjectivesUnderstand overstory/understory relationships of two-aged ponderosa pine stands arising from dispersed variable-retention harvestsHow the growth of seedlings and saplings is influenced by varying levels of overstory retentionHow the overstory/seedling growth relationship changes in different environmentsSlide5
Study SiteSlide6Slide7
Climate of study siteSlide8Slide9
Site descriptionBlock
StandTree ha-1BA(m2 ha
-1)QMD(cm)Ave. Ht.(m)
Ave
. LCR
(%)
Shrub
Cov
.
(%)
Warm
Springs
101
102
103
105
107
12
16
17
20
33
9.2
7.8
7.3
3.4
6.8
99.0
78.7
74.2
46.4
51.0
41.7
39.0
36.5
19.6
24.4
50
53
54
58
55
62
72
79
79
40
Pringle
Falls
203
204
205
206
207
208
128
39
103
192
33
80
22.5
10.8
17.3
24.3
13.9
18.1
47.4
59.3
46.3
40.2
72.8
53.7
26.0
31.7
25.5
23.1
34.2
29.8
66
44
58
54
57
50
48
77
39
9
73
54
Fort Rock
301
302
304
18
20
47
4.2
3.3
13.2
54.8
46.1
59.8
21.8
15.6
24.4
61
72
62
38
25
40Slide10
Collected dataVariable
GroupParameterUnitScale
Response VariableSeedling 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
ft
2
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
plotSlide11
Data analysesGeneralized linear model (GLM)Random component (probability distribution)Gamma distributionLinear predictor
Link functionLog transformation Slide12
ResultsVariable Group
ParameterEst. 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 Retention
QMD (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
<0.0001Slide13
Overstory vs. UnderstoryNegative effect on seedling height growth10 cm increase of QMD 0.92% reductione
-0.0092 = 0.9908Additional 10 tree/ha 5.35% reductione-0.0550 = 0.9465Similar results with other studies and speciesPonderosa 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)Slide14
Best measure of overstory?Basal Area (BA)Many study have usedE.g. Rose and Muir 1997; Acker et al. 1998; Page et al. 2001Not merely a measure of aboveground competition
Correlated with foliage or canopy coverage, root competition, etc.Combination of tree density and QMDAccount for more variance than BASlide15
How big should the plot size be?Key question from competition indicesSo-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 varianceBeyond 18.29 m ignorable (Hoyer 1993)Min. effective distance 12.19 m (McDonald 1976)Thus, 15 m radius is the most relevantSlide16
Shade? Or others?What causes the reduction of seedling growth?Light conditionInfluences ponderosa pine seedlings more than any other factorDecreases 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)Slide17
Prescribed burningReduces fuel load, improves seedling recruitment, simulates thinning effect, etc. However, the effect of prescribed burning has been debated for a long timeNegative effect in this study
Loss of total biomass of duff layerSubsequent nutrient deficiencyTakes long time to recover to the level of pre-burnLimitation of total nutrient supply (especially N)Delayed recovery of N-fixation shrubs (eg. Ceanothus velutinus, Purshia tridentata)Slide18
PlantingAlready selected seedlingsHave better geno- & phenotypeAlready grown enough to competePlanter could control the place to be plantedSlide19
Understory veg. & seedling growthSlide20
Management implicationsControlling seedling height growthManipulation of overstory retention levelNumber and size of overstory retention treesIntroduction of
site preparation method or artificial plantingEffects of other factors on seedling behaviorstand history, potential productivity, and understory conditionSlide21
Management implicationsSlide22
Going further…Spatial pattern of overstory retention?Palik et al. 2003; Maguire et al. 2006Climate?
How do seedlings respond to the weather during growing season?Refinement of understory veg. variablesPlot level measurement were not appropriateShrub species compositionInteraction (e.g. competition vs. facilitation?) with seedling along with site condition and seedling size, etc.Slide23
Cited literatureAcker, 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 retention. 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. Allgemeine 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. Canadian 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.Slide24
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