California’s Alpine Zone

A Shotgun Overview

Connie Millar

USDA Forest Service Pacific Southwest Research Station

Albany and Lee Vining, CA

and

Phil Rundel

Department of Ecology and Evolutionary Biology University of California, Los Angeles, CA

Alpine ecosystems cover 3% of the world’s land area

“…the exquisite beauty of these mountain carpets as they lie smoothly outspread in the savage

wilderness” -- John Muir 1894

What is “Alpine”? Ecosystems that lie above upper treeline

What, then, determines upper treeline?

-tree form: stems ≥ 3m tall -continuous patches of trees whose crowns form at least a loose canopy

Treeline: Thermally defined zone (ecotone) on the landscape where mean growing-season temperature is ~6.4 °C

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Thus, the alpine-forest ecotone is not defined by elevation, nor by as highest limit that a tree species can grow.

E.g., Krummholz matts of whitebark pine are mostly within the alpine zone, and can extend > 500 m above treeline

The treeline ecotone, alpine, and beyond… Körner 2012

Minimum temperature that permits production of

new cells and differentiation of functional tissues

Analogy: house construction

Foxtail pine Southern Sierra Nevada

Bristlecone pine White Mtns

Minimum temperature in growing season

enforces plant growth limits through control of carbon sinks not of

carbon source

Upper limit of alpine zone (bottom of nival zone): ≤ 3 °C

The Plant Side of the Alpine Zone

Sierra Nevada 385 species Mostly not alpine endemics -48% herbaceous perennials -24% graminoid perennials -12% mats & cushions -6% annuals and 6% woody

Distribution of Alpine Ecosystems in California 2700 – 3500 m (= treeline across state’s latitudes) Klamath Mtns: Trinity Alps, Marble Mtns, Scott Mtns S Cascades: Mt Shasta, Mt Lassen Sierra Nevada Great Basin Ranges: Warner, Sweetwater, Glass, White-Inyo, Panamint S California Ranges: San Gabriel, San Jacinto, San Bernardino

Alpine environments develop complex

habitats

Geomorphology and Topography

Substrates

Niches

Macro-Climates: 1000 - 20 km Global circulation, synoptic meteorology

Meso-Climates: 20 – 0.5 km Basin to range, range to range

Topo-Climates: 0.5 km - 100 m Solar radiation, lapse effects, N-S slopes,

frost pockets, wind-funneling

Micro-Climates: 100 m – 1 cm Vegetation canopies, nurse rocks, talus regimes

Alpine envrionments experience complex climates

Our Mediterranean Climate: -- Long, warm, dry summers -- Winters wet; Storms from Pacific -- Summer convectional storms

S Great Basins differ w/ bimodal precip

Mediterranean Climate of California Alpine Ecosystems

PRISM Mean Climate Values Alpine Regions in California

Mid-upper alpine, N aspects 1971-2000 means, 800 km grid

Extracted from PRISM website, 1/2014

Klamath Mtns: Trinity Alps

A Ramble Across the Alpine Regions of California

Southern Cascades; Mt Shasta

Great Basin North: Warner Mtns

N Sierra Nevada and Carson Range

Central Sierra Nevada: W Walker Watershed

Mt Conness & North Pk

Conness and North Peak Glaciers

Mt Gibbs Rock Glacier

Summer snowpatches in the Sierra tend to be consistent in location among years

Snowfield sites important in defining pocket forests, which are increasing with warming climates Brawley Pks, Bodie Hills

Millar et al. 2004

S Sierra Nevada: Palisades Basin

Southern Sierra Nevada

Great Basin, South Ranges: Sweetwater Mtns

Great Basin, South Ranges : White Mtns

Snowpacks more variable in location than in Sierra Nevada and tend to sublimate as much as melt

The few persistent snowpatches enabled prehistoric people to develop alpine villages during cool climates, White Mtns

* 300 m above current LP treeline * Dolomitic soils only * No live BCP * Areas of historic BCP forest

Limber pine in the White Mtns is leapfrogging above bristlecone pine into the alpine zone Millar & Westfall in prep

Alpine Ecosystem Responses to Changing 20th-21st Century Climates

Episodic Recruitment (What’s going on?)

Correlates with: - Annual T min, T max - Sept Precipitation - May & June Tmin - Atlantic Multidecadal Oscillation

Pulse ~ 1970-1991

Re-survey 2013

Millar et al. in prep

upright trees

Whitebark pines in the alpine zone of the Sierra Nevada are highly plastic, and respond adaptively to climate variability through changes in growth & form; No advance in treeline flags & skirts

krummholz

Forms responsive to micro-climate as well as changing regional climate

Millar et al. 2004

Region-wide growth of flags 1945-1976; reversed thereafter

Stem growth rates doubled over 20th C

Winter 2011 - 2012: Mortality of many evergreen shrubs and conifer seedlings

Widespread through Great Basin Ranges

Pinus albicaulis, Phyllodoce breweri, Linanthus pungens, Arctostaphylos spp.

Cold exposure;

Lack of snow cover

Response to Low Snowcover in the Alpine Zone

Talus-Forefield Ecosystems; Biodiversity & Climate Refugia

Millar et al. 2008, 2010, 2012a, b, 2014, in press

Talus landforms develop unique microclimates, decoupled from regional climates Cool in summer; Warm in winter

Buffered from external extremes

-Taluses maintain persistent internal ice -Support persistent springs and wetlands -Stable habitats resist climate warming

Talus/RG-Forefield Ecosystems Support High and Distinct

Species Diversity Mean # Vascular Plant Spp Rocky Surfaces (9 ha) 22 Forefields (0.6 ha) 61 Reference (large) 51 (12)

Mean # Arthropod Morpho-Spp Forefields (0.6 ha) 88 Reference (~1.0 ha) 29 (few)

Millar, Westfall, Evenden, Holmquist, Schmidt, Franklin, Nachlinger, Delany, 2014

Wetland Plants

Mono Basin pika distribution: 2191 – 3769 m; Span of 1578 m White Mountains Span: 1524 m

Talus-Wetand Ecosystems

- Provide potential climate refugia under warming temps

- Enable animals that use talus and wetlands to use a larger range of sites than expected