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ARTICLE IN PRESS + model YQRES-02727; No. of pages: 15; 4C: Quaternary Research xx (2006) xxx–xxx 1 www.elsevier.com/locate/yqres 2 Late holocene forest dynamics, volcanism, and climate change at whitewing 3 mountain and San Joaquin Ridge, Mono County, Sierra Nevada, CA, USA ⁎ 4 Constance I. Millar a, , John C. King b, Robert D. Westfall a, Harry A. Alden c, Diane L. Delany a 5 a USDA Forest Service, Sierra Nevada Research Center, Pacific Southwest Research Station, Berkeley, CAOF 94701, USA 6 b Lone Pine Research, Bozeman, MT 59715, USA 7 c Smithsonian Institution, Center for Materials Research and Education, Suitland, MD 20746, USA 8 Received 17 June 2005 9 Abstract 10 Deadwood tree stems scattered above treeline on tephra-covered slopes of Whitewing Mtn (3051 m) and San Joaquin Ridge (3122 m) show 11 evidence of being killed in an eruption from adjacent Glass Creek Vent, Inyo Craters. Using tree-ring methods, we dated deadwood to AD 815– 12 1350, and infer from death dates that the eruption occurred in late summer AD 1350. Based on wood anatomy, we identified deadwood species as 13 Pinus albicaulis, P. monticola, P. lambertiana, P. contorta, P. jeffreyi, and Tsuga mertensiana. Only P. albicaulis grows at these elevations 14 currently; P. lambertiana is not locally native. Using contemporary distributionsED of the species, PRO we modeled paleoclimate during the time of 15 sympatry to be significantly warmer (+3.2°C annual minimum temperature) and slightly drier (−24 mm annual precipitation) than present, 16 resembling values projected for California in the next 70–100 yr. 17 © 2006 Published by University of Washington. 18 19 Keywords: Paleoecology; Medieval climate; Late Holocene; Climate change; Long Valley volcanism; Inyo Craters; Forest history; Paleoclimatic modeling; Tree-ring 20 dating 21 22 Introduction bance remain poorly understood. Preserved vegetation in the 34 Mammoth Lakes–Long Valley Caldera region provides a 35 23 The last millennium is an important reference period for detailed record of late Holocene climatic, vegetation, and 36 24 evaluating the significance of future climate change and impacts volcanic dynamics. Scattered across the otherwise barren 37 25 ORRECT– 38 on ecosystems. The Medieval period (ca. AD 900 1350) in summits of Whitewing Mtn and San Joaquin Ridge, adjacent 26 particular has been controversial as an analog for future con- to and along the Sierra Nevada crest (Fig. 1), are abundant well- 39 27 ditions (Mann et al., 1999; Esper et al., 2002). In the eastern preserved deadwood tree stems (Fig. 2). The stems are, for the 40 28 Sierra Nevada, late Holocene climate variability (Stine, 1994; elevation, unusually large in diameter and length. The wood is 41 29 Benson et al., 2002), glacial dynamics (Clark and Gillespie, well preserved and in cross-section displays large growth rings. 42 30 1997), volcanism (Sieh and Bursik, 1986), and ecological Many stems are stumpless, while others remain rooted but 43 31 response (Woolfenden,UNC 1996) are well documented. While the buried in tephra. The summits lie directly adjacent to vents of 44 32 outline of centennial scale variability has been drawn for this the Inyo Crater volcanic chain, which has a history of late 45 33 region, interactions of forcing factors and ecological distur- Holocene eruption episodes (Miller, 1984, 1985; Sieh and 46 Bursik, 1986). The presence of dead trees above current treeline 47 suggests that past climates were different from present, while 48 the proximity of the volcanic vents and condition of the dead- 49 ⁎ Corresponding author. USDA Forest Service, Sierra Nevada Research wood suggest that an eruption killed the trees. 50 Center, Pacific Southwest Research Station, P.O. Box 245 Berkeley, CA 94701, 51 USA (street address: West Annex Bldg., 800 Buchanan St., Albany, CA 94710). We undertook this study to evaluate the climatic, ecologic, Fax: +1 510 559 6499. and disturbance history of the deadwood forest on Whitewing 52 E-mail address: [email protected] (C.I. Millar). Mtn and San Joaquin Ridge, specifically, to identify species of 53 0033-5894/$ - see front matter © 2006 Published by University of Washington. doi:10.1016/j.yqres.2006.05.001 ARTICLE IN PRESS 2 C.I. Millar et al. / Quaternary Research xx (2006) xxx–xxx F PROO ED RRECT Figure 1. A. Regional mapUNCO of Whitewing Mtn and San Joaquin Ridge, Mono Co., Eastern Sierra Nevada, CA, showing features mentioned in the text. 54 trees that grew there, determine tree ages, delimit timing of the San Joaquin Ridge (3122 m) forms the Sierra Nevada 62 55 Glass Creek eruption, model paleoclimates, and infer causes for hydrologic crest west of Whitewing Mtn, creating a low pass 63 56 the presence and death of the summit forests. at Minaret Summit, 2796 m. Thick deposits of Quaternary 64 tephras dominate all but a few surfaces (Bailey et al., 1976). 65 57 Study area These derive from eruptions of the adjacent Mono Craters and 66 Inyo Craters, a series of magmatic and phreatic eruptive centers 67 58 Location and surficial geology extending from near Mammoth Mtn to Mono Lake (Fig. 1; 68 Wood, 1977). Recent eruptive episodes of vents near White- 69 59 Whitewing Mtn (3051 m) is a distinct, flat-topped peak that wing Mtn occurred 6,000 yr ago, 1250–1400 yr ago, and 550– 70 60 projects eastward from the main crest of the central Sierra 820 yr ago (Miller, 1984, 1985; Sieh and Bursik, 1986). The 71 61 Nevada into the headwaters basin of the Owens River (Fig. 1). most recent eruption of Glass Creek Vent blasted directly onto 72 ARTICLE IN PRESS C.I. Millar et al. / Quaternary Research xx (2006) xxx–xxx 3 lodgepole pine/western white pine (Pinus monticola) forests 104 grow at 2450–2700 m, and form the lowest of the subalpine 105 types. The subalpine forests grade at lower elevations into 106 lodgepole pine/Jeffrey pine (Pinus jeffreyi) forests, which occur 107 from 2300 to 2600 m, and form extensive forests with 108 continuous canopies. Pinyon pine (P. monophylla) woodlands 109 form the lowest elevation forest, extending down to 1500 m in 110 the western Great Basin. 111 Current and paleo-climate F 112 The contemporary climate of the upper Owens River 113 watershed is montane Mediterranean with long dry summers 114 and cool wet winters. Precipitation occurs primarily in winter 115 from Pacific frontal storms that move eastward depositing snow 116 orographically over the western slope of the Sierra Nevada. 117 Gradients of precipitation and temperature are steep, and the 118 eastern slopes and western Great Basin lie in a rain-shadow. 119 Summer moisture occurs sporadically from Gulf-origin mon- 120 soon influence. SummerPROO temperatures range from warm/ 121 moderate at high elevations to hot east of the crest; atmospheric 122 Figure 2. Deadwood stems on Whitewing Mtn, showing flat summit plateau humidities are low throughout the region. 123 mantled with tephra and scattered large logs. Late Holocene climates have been described from diverse 124 records in the Sierra Nevada and Great Basin (Woolfenden, 125 73 Whitewing Mtn and San Joaquin Ridge, depositing 8 m of 1996; Stine, 1994). The last millennium began with a 450-yr 126 74 tephra on Whitewing Mtn and 1 m on San Joaquin Ridge phaseED that corresponds to the widespread Medieval Climate 127 75 (Miller, 1985). Ages for this eruption range from 530 ± 100 cal Anomaly (MCA), and extended from ca. AD 900–1350 in the 128 76 yr B.P. to 720 ± 60 cal yr B.P., with a minimum tree-ring date of Sierra Nevada. Proxy records indicate this to have been a dry 129 77 AD 1472 (Wood, 1977; Miller, 1984, 1985). Glass Creek tephra and warm period, where lake and river levels declined (Yuan 130 78 overlies deposits dated 659–737 cal yr B.P. from a nearby et al., 2004; Meko et al., 2001; Stine, 1990, 1994), treelines 131 79 phreatic crater on Mammoth Mtn (Sorey et al., 1998). increased (Graumlich, 1993; Graumlich and Lloyd, 1996), and 132 glaciers retreated (Konrad and Clark, 1998). The MCA was 133 80 Current forest types followed by a cool phase coinciding with the northern 134 hemispheric Little Ice Age (LIA), which extended in the Sierra 135 81 Plant communities represent typical eastern Sierra eleva- Nevada from AD 1400 to 1900 (Clark and Gillespie, 1997). 136 82 tional zonation, with local variations in extent. Alpine tundra Closed lake levels remained moderately low, suggesting 137 83 vegetation occurs above 2990 m on San JoaquinRRECT Ridge and decreases in effective precipitation and/or runoff relative to 138 84 Whitewing Mtn. Below this is the whitebark pine (Pinus present (Stine, 1990). Treeline elevations declined (Graumlich 139 85 albicaulis) forest type, which extends from 2700 m to local and Lloyd, 1996; Lloyd and Graumlich, 1997) and the largest 140 86 treeline at 2990 m. The upper limit of the whitebark type is glacial advances since the Pleistocene are recorded (Clark and 141 87 characterized by a zone of stunted krummholz (shrub-like) Gillespie, 1997). The LIA ended ∼ AD 1900; early 20th century 142 88 pines. This grades into a lower zone of upright pines that form proxies record rising temperatures, precipitation increases 143 89 dense clusters and occasionally continuous forest canopies. (Graumlich, 1993) and increasing lake and river levels (Stine, 144 90 Outliers occur above the general treeline in sheltered areas 1990, 1994). 145 91 around rocky outcrops. Locally, these occur near the summits of 92 Whitewing Mtn and SanUNCO Joaquin Ridge. Methods 146 93 Subalpine forest assemblages overlap the whitebark pine 94 type and extend below it. These vary with slope and aspect as a Stem mapping and stem measurements 147 95 consequence of ecological tolerances of the species.