Recruitment pa-erns and growth of high-­‐eleva8on pines in response to clima8c variability (1883–2013) Bob WesEall and Connie Millar PSW Research Stn, US Forest Service, Albany, CA Objec8ves •  Inves8gate responses in regenera8on of limber pine (Pinus flexilis ) and bristlecone pine (P. longaeva ) subalpine forests in Great Basin ranges of eastern California and western Nevada •  Assessed age, abundance, and density of live trees that were ≤130 years old along ecotones at high, middle, and low eleva8ons •  Analyzed mature-­‐tree radial growth •  Evaluated these for environmental and clima8c associa8ons Coauthors: Diane Delany, PSW Research Stn, USFS, Albany, CA Lorrie and Alan Flint, USGS, Sacramento, CA Millar, C.I. et al. 2015. Recruitment pa-erns and growth of high-­‐eleva8on pines in response to clima8c variability (1883–2013), in the western Great Basin, USA. CJFR 45:1299-­‐1312. Methods 18 sites represen8ng high (mean, 3373m), middle (mean, 3125 m), and low (mean, 2699 m) eleva8on zones. Surveyed belt transects, 30 m wide, perpendicular to slope. Transects subdivided into 30 m plots (900 m2). Live trees 5 > < 10 cm diameter were cored and aged by tree ring counts. Trees < 5 cm aged by internode counts. Counts of trees per age were converted to densi8es per ha. Tree ring chronologies from 4 sites represen8ng high, mid, and low eleva8ons, standardized by RCS to preserve low-­‐frequency varia8on. Clima8c variables selected by cross correla8ons, evaluated for lead and lag correla8ons. Responses of tree densi8es and tree ring growth to climate were evaluated by response surface models. Mean densi8es of limber pine and bristlecone pine trees in 2013 by site and eleva8on zone. Trees <130 yrs old. Limber
Pine
Mtn Range
Site
Bristleco
ne Pine
Density of Trees (yrs) by Elevation Zone
High
White Mtns
Low
Mid
mean
Density of Trees (yrs) by Elevation Zone
sd
sd
Bighorn Pk
144
147
44
57
Patriarch Grove
242
216
78
46
Campito Mtn
67
55
13
11
Trail Cyn
62
81
83
Crooked Cr
73
69
Relay Ridge
20
Schulman Grove
33
50
sd
15
mean
sd
mean
sd
7
10
27
25
67
Cell Ravine
22
33
2.0
4.1
Silver Cyn
9
15
0.8
3.0
53
50
1.4
3.4
Cory Pk
Glass Mtns
O'Harrell Cyn
15
20
Owens Gorge
138
108
Brawley Pks
109
133
Mt Hicks
59
31
70
92
MEAN
sd
Low
54
Wassuk Range
Bodie Mtns
mean
Mid
mean
114
mean
High
69
113
43
138
141
82
61
75
52
52
24
25
Mean densi8es of limber pine and bristlecone pine recruitment by 40-­‐yr 8me periods and en8re 130 yr period (1883-­‐2013). Densi8es are for trees ≤ 130 old. A. Limber pine. B. Bristlecone pine. A. Limber pine
Elevation
Mean Densities (stems per ha)
<1927
1927-1969
>1969
1884-2013
Low 7.1 18.9 43.6 70 Mid 11.0 26.5 44.8 82 High 3.4 14.4 95.4 113 Overall
6.8
20.6
55.8
82
B. Bristlecone pine
Elevation
Mean Densities (stems per ha)
<1927
1927-1969
>1969
1884-2013
Low 0.0 0.6 0.8 1 Mid 1.9 13.6 8.1 24 High 0.3 14.5 37.2 52 Overall
0.6
10.1
19.1
30
Model correla8ons and climate variables included in best-­‐fit stepwise regression analyses. Model Model July Water year July Sept Snow Eleva8on zone R2 (1) R2 (2) Tmin Tmax Tmax precip precip precip CWD pack A. Recruitment Full period (1883–2013 ) High 0.62 0.56 + − − + + + − + Middle 0.63 0.52 + − − + + − + Low 0.84 0.78 + − − + + + − Recruitment episode (1965–2013) High 0.89 nd + − − + + + − − Middle 0.73 nd − − − − + + − Low 0.89 nd − − − − + + − − B. Radial ring width full period (1883–2013) Corey Peak 0.75 0.70 − − + + + − Sweetwater Mtns 0.71 0.67 − − + + + − Trail Canyon 0.50 0.38 − − + + − Owens Gorge 0.85 0.78 + − − + + + − + Note: Plus or minus signs refer to the sign of the simple correla8on coefficient. Squared mul8ple correla8on coefficients are given for models with (1) and without (2) low-­‐frequency indices included. Precip, precipita8on; CWD, clima8c water deficit; nd, not done. Reanalysis Data: Correla8ons with Atmospheric Pressure Jan – Mar 700 mb Height Low-­‐Mid Plots High Plots Reanalysis Data: Correla8ons with Atmospheric Pressure Sept Lead Lag Conclusions •  Recruitment is at a limited number of sites and most abundant at upper treeline. •  At most sites, recruitment is at a single dominant pulse from 1963-­‐2000; in bristlecone pine, 1955-­‐1988. •  Where two species co-­‐occur at upper treeline, limber pine leapfroggs above bristlecone •  Similar to recruitment, radial growth reaches a peak 1963-­‐2000, decreasing aler 2000. •  Complex, addi8ve factors of water rela8ons (precipita8on, snowpack, and CWD) and temperature during cumula8ve intervals of up to 9 years explain recruitment be-er than factors related to any single year or to eleva8on .