From treeline to species line: Thermal patterns and growth relationships across the krummholz zone of whitebark pine, Sierra Nevada, California, USA

Figures & data

Table 1. Study sites, transects, and plot locations for tree-ring and temperature measurements. UTL and the tree core plots lower are upright trees; the remaining plots are krummholz

		Ground distance (m)
Site (abbreviation)	Aspect	UTL-UKL	UTL-ALP	Slope inclination (°), UTL-ALP	Tree core plots	Temperature plots	Elevation (m)
Dunderberg Peak (SPL)	North	632	934	17		ALP	3,423
					0	UKL	3,338
					100		3,300
					200	MKR	3,265
					300		3,229
					400		3,198
					500	UTL	3,166
					600		3,135
Virginia Canyon (VRG)	South	424	598	28		ALP	3,534
					0^a	UKL	3,419
					100/200		3,375
					300^a		3,344
					400	MKR	3,309
					500^a		3,276
					600		3,244
					700	UTL	3,207
					800		3,179
Tioga Peak (TIO)	North	222	378	23		ALP	3,581
					0	UKL	3,308
					100	MKR	3,273
					200	UTL	3,238
					300		3,203
Tioga Crest (GAR)	South	771	1,023	13		ALP	3,450
					0	UKL	3,415
					100		3,378
					200	MKR	3,343
					300		3,309
					400		3,277
					500	UTL	3,243
					600		3,211

Note. ^aNo useable cores retrieved.

Figure 1. Map of the study region in the eastern Sierra Nevada, California, with location of four transect sites. See Table 1 for site names

Figure 2. Transect design. Transects extended from UTL to ALP, with intermediate plots at MKR and UK (upper species line). Two pairs of transects were installed on adjacent northern and southern aspects for a total of four transects

Figure 3. Plot design. At each plot, six temperature loggers were deployed: three on a PVC pole, at 2.0 m, 1.0 m, and 0.5 m height; one buried 10 cm at the base of the pole; and two ground surface loggers, one at the base of the pole and one approximately 5 m distant

Table 2. Temperature and growing season means based on daily means. Annual temperature (T_ann); minimum (T_ann-min) and maximum (T_ann-max) annual temperature; GST; GSL; warmest month temperature (T_warm); number of DSF

				Temperature (°C)
Site	Plot	Aspect	Position	Tann	SD	Tann-min	Tann-max	GST (°C)	GST SD	GSL (days)	Twarm (°C)	DSF (days)	DSF SD
SPL	UTL	N	Pole 2.0 m	2.4	7.4	−16	24	9.2	4.7	131	12.9	234	53
VRG	UTL	S	Pole 2.0 m	4.5	8.2	−18	21	9.3	5.1	172	14.3	364	1
TIO	UTL	N	Pole 2.0 m	2.3	7.5	−17	18	9.3	4.4	142	12.7	251	44
GAR	UTL	S	Pole 2.0 m	2.9	7.3	−17	23	9.6	4.5	146	12.6	248	59
Mean				3.0	7.6	−17	22	9.4	4.7	148	13.1	274	39
SPL	UTL	N	Pole 1.0 m	2.7	6.8	−17	24					224	49
VRG	UTL	S	Pole 1.0 m	3.8	8.3	−18	19					364	1
TIO	UTL	N	Pole 1.0 m	2.7	6.7	−22	19					221	49
GAR	UTL	S	Pole 1.0 m	3.5	6.2	−16	21					186	31
Mean				3.2	7.0	−18	21					249	32
SPL	UTL	N	Pole 0.5 m	2.5	7.1	−17	26					210	45
VRG	UTL	S	Pole 0.5 m	4.0	8.3	−18	20					365	1
TIO	UTL	N	Pole 0.5 m	2.4	6.7	−17	19					200	59
GAR	UTL	S	Pole 0.5 m	3.8	5.9	−17	19					169	32
Mean				3.2	7.0	−17	21					236	34
SPL	UTL	N	Buried 10 cm	3.7	5.6	−5	18	11.2	3.7	103	13.6	128	14
VRG	UTL	S	Buried 10 cm	3.7	5.8	−11	16	8.5	3.0	156	11.1	352	15
TIO	UTL	N	Buried 10 cm	2.9	5.0	−7	26	9.0	3.3	120	10.9	165	29
GAR	UTL	S	Buried 10 cm	3.9	3.8	−1	13	8.1	2.3	133	9.9	147	26
Mean				3.6	5.1	−6	18	9.2	3.1	128	11.4	198	21
SPL	UTL	N	Ground surface at pole	3.7	6.2	−6	20					146	15
SPL	UTL	N	Ground surface at distance	3.7	5.9	−4	21					124	39
VRG	UTL	S	Ground surface at pole	4.5	7.8	−13	20					364	2
VRG	UTL	S	Ground surface at distance	7.7	7.5	−7	23					297	31
TIO	UTL	N	Ground surface at pole	3.2	5.6	−7	17					141	15
TIO	UTL	N	Ground surface at distance	3.5	6.5	−8	20					128	22
GAR	UTL	S	Ground surface at pole	3.8	5.1	−4	17					150	20
GAR	UTL	S	Ground surface at distance	5.7	7.2	−4	23					168	29
Mean				4.5	6.5	−7	20					190	22
SPL	MKR	N	Pole 2.0 m	3.1	7.7	−18	19	9.7	4.6	156	13.5	248	84
VRG	MKR	S	Pole 2.0 m	4.2	8.0	−18	19	9.0	4.9	170	13.7	365	1
TIO	MKR	N	Pole 2.0 m	2.5	7.5	−17	20	9.3	4.6	147	12.6	251	95
GAR	MKR	S	Pole 2.0 m	2.8	7.8	−20	18	8.8	4.6	154	12.7	314	102
Mean				3.2	7.8	−18	19	9.2	4.7	157	13.1	295	71
SPL	MKR	N	Pole 1.0 m	3.3	7.9	−18	22					200	30
VRG	MKR	S	Pole 1.0 m	4.2	8.3	−18	20					365	1
TIO	MKR	N	Pole 1.0 m	2.2	7.3	−17	20					236	105
GAR	MKR	S	Pole 1.0 m	3.1	8.1	−19	20					307	74
Mean				3.2	7.9	−18	21					277	53
SPL	MKR	N	Pole 0.5 m	3.0	6.6	−11	20					157	25
VRG	MKR	S	Pole 0.5 m	3.2	8.3	−18	19					363	1
TIO	MKR	N	Pole 0.5 m	2.9	6.3	−10	20					186	58
GAR	MKR	S	Pole 0.5 m	3.9	6.8	−8	20					278	88
Mean				3.3	7.0	−12	20					246	43
SPL	MKR	N	Buried 10 cm	3.6	5.0	−2	16	10.2	3.0	116	12.1	139	26
VRG	MKR	S	Buried 10 cm	3.8	5.0	−8	16	8.8	3.0	142	11.2	194	19
TIO	MKR	N	Buried 10 cm	2.3	3.9	−4	12	7.6	2.2	103	8.4	173	115
GAR	MKR	S	Buried 10 cm	3.8	4.7	−4	16	9.1	2.9	128	11.2	157	30
Mean				3.4	4.7	−5	15	8.9	2.8	122	10.7	166	48
SPL	MKR	N	Ground surface at pole	4.7	6.2	−5	20					146	17
SPL	MKR	N	Ground surface at distance	4.3	7.1	−7	23					152	21
VRG	MKR	S	Ground surface at pole	3.6	6.6	−12	20					256	39
VRG	MKR	S	Ground surface at distance	n/a	n/a	n/a	n/a					n/a	n/a
TIO	MKR	N	Ground surface at pole	3.3	6.3	−8	20					148	34
TIO	MKR	N	Ground surface at distance	4.1	7.0	−10	21					144	24
GAR	MKR	S	Ground surface at pole	4.1	7.0	−9	23					174	35
GAR	MKR	S	Ground surface at distance	5.2	6.4	−4	21					154	22
Mean				4.2	6.7	−8	21					168	27
SPL	UKL	N	Pole 2.0 m	2.4	8.4	−19	18	8.8	4.6	158	12.7	356	18
VRG	UKL	S	Pole 2.0 m	2.4	7.6	−19	18	7.8	4.5	216	12.6	364	1
TIO	UKL	N	Pole 2.0 m	2.2	8.0	−20	19	9.1	4.6	149	12.8	297	85
GAR	UKL	S	Pole 2.0 m	1.6	7.3	−21	18	8.8	4.0	147	11.6	212	36
Mean				2.2	7.8	−20	18	8.6	4.4	168	12.4	307	35
SPL	UKL	N	Pole 1.0 m	2.3	8.3	−19	23					327	57
VRG	UKL	S	Pole 1.0 m	2.7	7.9	−20	19					365	0
TIO	UKL	N	Pole 1.0 m	2.1	7.6	−17	18					247	80
GAR	UKL	S	Pole 1.0 m	3.0	6.6	−14	21					159	17
Mean				2.5	7.6	−18	20					275	39
SPL	UKL	N	Pole 0.5 m	2.5	7.2	−11	23					206	41
VRG	UKL	S	Pole 0.5 m	3.8	6.5	−13	18					316	29
TIO	UKL	N	Pole 0.5 m	2.9	7.0	−14	19					200	69
GAR	UKL	S	Pole 0.5 m	3.3	6.3	−14	20					155	17
Mean				3.1	6.8	−13	20					219	39
SPL	UKL	N	Buried 10 cm	3.0	4.9	−3	14	9.3	2.7	112	11.0	129	16
VRG	UKL	S	Buried 10 cm	4.3	5.0	−3	16	9.1	3.2	151	11.6	226	59
TIO	UKL	N	Buried 10 cm	2.6	4.1	−4	13	8.1	2.2	106	9.2	152	76
GAR	UKL	S	Buried 10 cm	4.1	4.9	−4	18	9.8	3.4	124	11.6	148	21
Mean				3.5	4.7	−4	15	9.1	2.9	123	10.9	164	43
SPL	UKL	N	Ground surface at pole	3.6	6.0	−4	18					149	33
SPL	UKL	N	Ground surface at distance	4.4	7.1	−9	23					162	63
VRG	UKL	S	Ground surface at pole	4.5	6.0	−7	18					269	68
VRG	UKL	S	Ground surface at distance	4.8	7.6	−13	20					333	14
TIO	UKL	N	Ground surface at pole	2.8	5.5	−8	16					170	49
TIO	UKL	N	Ground surface at distance	3.2	6.4	−9	22					161	47
GAR	UKL	S	Ground surface at pole	4.8	6.3	−7	21					153	21
GAR	UKL	S	Ground surface at distance	4.9	7.1	−5	24					146	17
Mean				4.1	6.5	−8	20					193	39
SPL	ALP	N	Pole 2.0 m	1.5	7.7	−17	17	8.6	4.6	144	12.3	n/a	n/a
VRG	ALP	S	Pole 2.0 m	1.8	7.6	−21	18	8.2	4.1	149	11.5	316	39
TIO	ALP	N	Pole 2.0 m	1.6	7.9	−20	17	8.6	4.3	153	12.2	322	55
GAR	ALP	S	Pole 2.0 m	1.6	7.8	−18	16	8.6	4.1	150	11.6	308	75
Mean				1.6	7.8	−19	17	8.5	4.3	149	11.9	315	56
SPL	ALP	N	Pole 1.0 m	1.5	7.8	−20	18					282	18
VRG	ALP	S	Pole 1.0 m	2.0	8.1	−20	18					356	16
TIO	ALP	N	Pole 1.0 m	1.7	7.9	−19	17					293	78
GAR	ALP	S	Pole 1.0 m	2.1	6.9	−17	16					211	22
Mean				1.8	7.7	−19	17					286	34
SPL	ALP	N	Pole 0.5 m	2.6	6.8	−19	18					214	42
VRG	ALP	S	Pole 0.5 m	2.7	8.5	−22	19					348	33
TIO	ALP	N	Pole 0.5 m	1.7	7.9	−19	19					263	73
GAR	ALP	S	Pole 0.5 m	2.8	6.1	−13	16					186	22
Mean				2.5	7.3	−18	18					253	43
SPL	ALP	N	Buried 10 cm	2.9	6.0	−8	19	10.6	3.1	108	12.2	155	36
VRG	ALP	S	Buried 10 cm	4.7	7.1	−9	20	11.3	4.3	154	15.0	276	90
TIO	ALP	N	Buried 10 cm	2.2	6.5	−11	17	10.7	3.3	106	12.8	153	36
GAR	ALP	S	Buried 10 cm	5.0	5.9	−1	19	11.4	4.1	n/a	n/a	n/a	n/a
Mean				3.7	6.4	−7	19	11.0	3.7	123	13.3	195	54
SPL	ALP	N	Ground surface at pole	2.6	7.5	−14	24					184	58
SPL	ALP	N	Ground surface at distance	2.5	7.6	−15	22					225	78
VRG	ALP	S	Ground surface at pole	4.3	7.9	−11	21					316	7
VRG	ALP	S	Ground surface at distance	3.3	8.1	−15	29					348	28
TIO	ALP	N	Ground surface at pole	2.3	7.6	−14	20					180	51
TIO	ALP	N	Ground surface at distance	2.4	7.5	−14	20					192	59
GAR	ALP	S	Ground surface at pole	4.5	6.3	−5	19					151	21
GAR	ALP	S	Ground surface at distance	4.6	6.3	−6	20					149	11
Mean				3.3	7.4	−12	22					218	39

Note. n/a = insuffient data. See Table 1 for site names.

Figure 4. Overlay plots for mean 2.0 m air temperature and mean 10 cm buried temperature, July 2015 to October 2019 for paired TIO (north) and GAR (south) transect sites, upper treeline and upper species line. (a) UTL at TIO; (b) UKL at TIO; (c) UTL at GAR; (d) UKL at GAR

Table 3. Mean number of rings (estimate of age) and number of series (cores) contributing to tree-ring demography database for krummholz and tree plots

					Number of rings
Site	Aspect	Elevation zone	Stem form	Plots included	Mean	SD	Number of series
SPL	N	Upper	Krummolz	0, 100	124.0	43.3	40
VRG	S	Upper	Krummolz	100/200	86.0	18.9	15
TIO	N	Upper	Krummolz	0	94.2	30.5	16
GAR	S	Upper	Krummolz	0, 100	94.3	30.9	42
Overall					99.6	30.9	113
SPL	N	Middle	Krummolz	200, 300, 400	196.3	82.0	70
VRG	S	Middle	Krummolz	400, 600	146.4	49.3	52
TIO	N	Middle	Krummolz	100	173.6	60.6	15
GAR	S	Middle	Krummolz	200, 300, 400	116.5	43.5	56
Overall					158.2	58.9	193
SPL	N	Lower	Tree	500, 600	225.6	58.1	44
VRG	S	Lower	Tree	700, 800	144.6	76.0	31
TIO	N	Lower	Tree	200, 300	167.3	72.7	38
GAR	S	Lower	Tree	500, 600	128.6	31.0	37
Overall					166.5	59.6	150

Figure 5. Tree ring series, demography data set. Dated series from 456 live krummholz and upright trees sampled along four transects. Series pooled and arranged by upper elevation krummholz, middle elevation krummholz, and lower elevation (upper treeline) forest strata. All stems were live at the time of sampling

Figure 6. (a)–(c) Whitebark pine radial growth and (d)–(f) composite HCN climate station means (monthly means, averaged annually, 1895–2020). Climate data averaged for Tahoe, Yosemite, Mina, and Independence HCN stations. Black dots, ring widths; red line, mean ring widths; green line, linear fit; blue curve, spline fit at lambda 10

Table 4. Model correlations and climate variables included in the best-fit stepwise regression analyses for radial ring-width models, based on the date range 1895–2020.^a

		Trees	Middle krummholz		Upper krummholz
A. Crown form (elevation) groups
R^2		0.15	0.34		0.29
Model		0.0376	<0.0001		<0.0001
Tmax*		−, 0.0469
Tmin*			+, <0.0001		+, <0.0001
WY precipitation*		+, 0.0210
	Northern			Southern
	Trees	Middle krummholz	Upper krummholz	Trees	Middle krummholz	Upper krummholz
B. Aspect and crown form (elevation) groups
R^2	0.17	0.31	0.26	0.27	0.15	0.28
Model	0.02	<0.0001	<0.0001	<0.0001	0.0026	<0.0001
Tmax*	−, 0.28	−, 0.41	−, 0.0219	—	—	—
Tmin*	−, 0.24	+, <0.0001	+, <0.0001	+, <0.0001	+, 0.0007	+, <0.0001
WY precip*	+, 0.38	+, 0.0012	+, 0.0121	+, 0.011	+, 0.09

Notes. ^a(A) All samples, grouped by crown form (elevation). (B) Samples grouped by aspect and crown form. Climate associations are derived only from tree and krummholz series that had correlations >0.4 to the master chronology.

*Sign of the correlation; probablility.