Mountains: Physical, Human-Environmental, and Sociocultural Dynamics

Mark A. Fonstad

• Publisher: Taylor & Francis
• Year: 2018
• eBook ISBN: 9781351657990
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Geography
• Index: Geography

Mountains have captured the interests and passions of people for thousands of years. Today, millions of people live within mountain regions, and mountain regions are often areas of accelerated environmental change. This edited volume highlights new understanding of mountain environments and mountain peoples around the world. The understanding of mountain environments and peoples has been a focus of individual researchers for centuries; more recently the interest in mountain regions among researchers has been growing rapidly. The articles contained within are from a wide spectrum of researchers from different parts of the world who address physical, political, theoretical, social, empirical, environmental, methodological, and economic issues focused on the geography of mountains and their inhabitants. The articles in this special issue are organized into three themed sections with very loose boundaries between themes: (1) physical dynamics of mountain environments, (2) coupled human–physical dynamics, and (3) sociocultural dynamics in mountain regions. This book was first published as a special issue of the Annals of the American Association of Geographers.

Controls on Mountain Plant Diversity in Northern California: A 14,000-Year Overview

Christy E. Briles

A network of eight Holocene paleoenvironmental records from lakes in the Klamath Mountains of Northern California provides insights on how diverse coniferous forests are maintained in the face of climate change. Pollen data suggest that in most cases plants kept pace with climate change. The steep costal-to-inland precipitation gradient resulted in asynchronous responses to climate change with coastal forests responding before inland sites. This was likely due to the proximity to oceans, warm valleys, and the differential responses to changes in ocean upwelling. Plants growing on soils with heavy metals showed little response to Holocene climate variability, suggesting that they experienced stability during the Holocene, which helps explain the localized plant diversity on the harsh soils. Plant communities on soils without heavy metals adjusted their ranges along elevational gradients in response to climate change, however. Fires were a common occurrence at all sites and tracked climate; however, sites that were more coastal experienced fewer fires than inland sites. Fire severity remained similar through the Holocene at individual sites; however, it was low to moderate at southern locations and higher at more northern locations. The article highlights historical factors that help explain the diversity of plant species in the forests of Northern California and provides insights for managing these complex ecosystems.

Una cadena de ocho registros paleoambientales del Holoceno en lagos de las Montañas Klamath de la parte norte de California nos dan claves sobe la manera como se mantienen diferentes bosques de coníferas ante el cambio climático. Los datos de polen sugieren que en la mayoría de los casos las plantas siguen el paso al cambio de clima. El fuerte gradiente de precipitación de la costa hacia el interior generó respuestas asincrónicas al cambio climático, en las que se notó que los bosques litorales respondían antes de que lo hicieran los sitios del interior. Tal circunstancia probablemente se debió a la proximidad de los océanos, valles cálidos y a las diferentes respuestas a cambios en la surgencia del mar. Las plantas que crecen en suelos de metales pesados mostraron poca respuesta a la variabilidad climática del Holoceno, sugiriendo que ellos experimentaron estabilidad durante este período, lo cual ayuda a explicar la diversidad de plantas localizadas en suelos ásperos. Sin embargo, las comunidades de plantas desarrolladas en suelos carentes de metales pesados ajustaron su ámbito junto con los gradientes de altitud en respuesta al cambio climático. Los incendios forestales fueron una ocurrencia común en todos los sitios y reflejaban el clima; pero los sitios más costaneros experimentaban menos incendios que los sitios del interior. La severidad del incendio se mantuvo similar a través del Holoceno en sitios individuales; sin embargo, estaba entre baja y moderada en las localidades meridionales, y más alta en localidades situadas más al norte. El artículo destaca los factores históricos que ayudan a explicar la diversidad de especies vegetales en los bosques del norte de California y brinda buenas estrategias para el manejo de estos ecosistemas complejos.

Biodiversity is not evenly distributed across the globe and the factors involved in maintaining it are not well understood and debated (e.g., Warren et al. 2014). The Klamath Mountains of Northern California and southern Oregon harbor some of the most diverse coniferous forests in North America. They have been referred to as the “Galapagos of North America” (DellaSala 2003), yet are located thousands of kilometers north of the islands and the tropics. The factors that have been hypothesized to explain the diversity include (1) a complex geology and unusual soil makeup (Whittaker 1960), (2) a refuge during the cooling and drying of the Cenozoic (e.g., Douglas fir; Stebbins and Major 1965; Wolfe 1994; Gugger, Sugita, and Cavender-Bares 2010), (3) a steep temperature and precipitation gradient due to the spatial variability of climate (G. Taylor and Hannan 1999), and (4) a spatially heterogeneous disturbance regime (A. H. Taylor and Skinner 1998, 2003; Skinner, Taylor, and Agee 2006). How these factors play out and are intertwined in the past is critically important for understanding the maintenance of biological diversity in the region today but also into the future under a changing climate. For example, understanding how species responded through migration, or in refugia, helps devise forest management plans that acknowledge the immense spatial variability of the region. Environmental archives derived from pollen and charcoal preserved in lake sediments can help discern the relative role of different mechanisms that maintain the floristic diversity.

A large network of vegetation and fire reconstructions from lake sediments exists in the Klamath Mountains (see Figure 1; Mohr, Whitlock, and Skinner 2000; Briles, Whitlock, and Bartlein 2005; Daniels, Anderson, and Whitlock 2005; Briles et al. 2008; Colombaroli and Gavin 2010; Briles et al. 2011; Crawford et al. 2015; A. White, Briles, and Whitlock 2015). These sites provide a wide-angle snapshot into the past and a chance to understand environmental variability in a complex mountainous environment. Long-term climate records based on different proxies including ocean sediment–derived alkenones (Barron et al. 2003), speleothem oxygen isotope (Vacco et al. 2005), and tree ring and lake sediment records (Graumlich 1993; Graham and Hughes 2007; Steinman et al. 2012) exist in the region and provide records of climate variability that can be used to interpret the vegetation and fire history reconstructions. The objective of this article is to review the current records that exist since the last glacial period (~14,000 years ago) and discuss the long-term mechanisms that have maintained the diverse Klamath Mountain ecosystem. Management implications of the research are also discussed.

Figure 1. Map of the Klamath Mountains in the Pacific Northwest and the sites discussed in the text. Sites with white circles are lakes on ultramafic substrates and those with gray circles are lakes on nonultramafic substrates.

Regional Environmental Characteristics and Explanations for Diversity

The Klamath Mountains are located on the California–Oregon border west of Interstate 5 (I-5; see Figure 1). The forests harbor the tallest and largest trees in the world, Sequoia sempervirens (coast redwood), an impressive thirty-nine conifer species and subspecies, including 3,500 plant species (~220 only found there), and a host of other organisms including 115 butterfly, 235 mollusk, and 33 fish species (DellaSala et al. 1999).

Spatial variability of climate is a notable environmental characteristic of the Klamath Mountains. There is a steep ocean-to-inland climate gradient that results from close proximity to the Pacific Ocean and rain shadows created by the mountainous coastal complex. Annual precipitation averages >2,500 mm along the coast, whereas east of I-5 only 300 to 800 mm falls on average. Coastal locations are mild through the year. Valleys are cool in winter but hot during the summer months. The mountains experience freezing temperatures during the winter, with significant snowfall, and warm dry summers.

The climate of the Klamath Mountains is strongly influenced by high- and low-pressure systems that develop in the northeast Pacific Ocean. During the winter, a strong Aleutian low entrains moisture from the subtropical and tropical Pacific and delivers it to the Klamath Mountains. In summer, the Eastern Pacific Subtropical High creates subsidence and much drier conditions. Surface heating during the summer causes steep environmental lapse rates and consequently atmospheric instability and convectional storms, which are associated with lightning. In summer, fog along the coast is associated with the southward-moving California current that results in offshore flowing winds and ocean upwelling.

The diverse geology is a result of accreted terrains and the collision of the North American and Pacific continental plates (Norris and Webb 1990; Harden 1997). The mountains are composed of mudstone, limestone, sandstone, chert, schist, serpentine, peridotite, several plutonic deposits (e.g., igneous intrusions of diorite and granodiorite rocks), and volcanic rocks (e.g., basalts). A complex of mountain ranges contributes to the topographic heterogeneity of the region, giving it the nickname the Klamath Knot (Wallace 1983). Elevations range from sea level to 2,800 m (on Mount Eddy) over short distances. Several exposed sheets of ultramafic bedrock occur in the Klamaths, including the Trinity Ultramafic Sheet and Josephine and Sexton ophiolites (Irwin 1981). The soils derived from these rocks are deficient in critical minerals for plant growth, including calcium, nitrogen, phosphorus, and potassium, and they contain high concentrations of heavy metals, including nickel, magnesium, chromium, and iron, that inhibit or restrict plant growth (Kruckeburg 2002; Alexander et al. 2007). Forests on ultramafic substrates are usually open and dry compared with those growing on other soil types (Kruckeburg 1985, 2002; Alexander et al. 2007). Plants have evolved traits (e.g., hairy or waxy leaves, shallow roots) that allow them to tolerate drought conditions and methods for limiting their uptake by accumulating the minerals in their tissues (Alexander et al. 2007). The ultramafic substrates have more than forty endemic plant species, making them diversity hotspots within the region.

Fire is a common natural disturbance in the Klamath Mountains. Recently, the region has received attention as large areas of forest and protected wilderness have experienced large fires (e.g., Biscuit and Silver fires) that in some cases burned at high severity, specifically if they had burned in previous decades (Thompson, Spies, and Ganio 2007). Most of our understanding about fire in the Klamath Mountains comes from tree-ring studies extending back ~500 years. Fire regimes in the region have historically ranged from low to moderate severity with occasional high-severity fires in different forest types (A. H. Taylor and Skinner 1998, 2003; Skinner, Taylor, and Agee 2006). These studies suggest that fire activity is governed by the topographic and climatic heterogeneity of the region and also the spatial pattern of previous fires and their severity (A. H. Taylor and Skinner 1998, 2003; Skinner, Taylor, and Agee 2006; Thompson, Spies, and Ganio 2007). For example, fire severity tends to be highest on the upper third of dry south- and west-facing slopes and lowest on the lower third of slopes on north- and east-facing slopes. The size of fire is influenced by forest patch size and barriers to fire spread (e.g., ridgetops, aspect changes, riparian zones, substrate differences). Fire severity also varies with vegetation type and structure, with lower severity in forests with medium to large trees and higher severity in stands dominated by small trees (Miller et al. 2012). All of these factors combine to create a patchwork of stands of different age and composition, which helps maintain the biological diversity (Skinner, Taylor, and Agee 2006).

The Role of Historical Climate Variability on Floristic Diversity

The factors discussed earlier have contributed or helped maintain the extraordinary plant diversity in the Klamath Mountains; however, one of the least understood is the role of long-term climate change. Paleoenvironmental research during the past two decades has focused on how paleoclimate variability has influenced the mountainous plant communities in the Klamath Mountains. Mohr, Whitlock, and Skinner (2000) and Daniels, Anderson, and Whitlock (2005) laid the groundwork by reconstructing the vegetation and fire history from the southeastern Klamath Mountains using lake sediments from Bluff, Crater, and Mumbo lakes on or surrounded by ultramafic substrates. These studies established the general sequence of vegetation changes including subalpine parkland during the late glacial period (>11,000 cal yr BP) when climate was cooler and wetter than today, a xerophytic mixed-conifer woodland in the early Holocene (11,000 to ~5,000 cal yr BP) when climate was warmer and drier than today, and a diploxylon Pinus spp. (yellow pine species) forest with some Abies spp. (fir species) in the late Holocene (<5,000 cal yr BP) as modern conditions became established. Fires were prevalent over the length of the records and were more frequent during drier periods, such as the early Holocene and Medieval Climate Anomaly.

Briles, Whitlock, and Bartlein (2005) reconstructed the vegetation and fire history from Bolan Lake on diorite soils in the northern Klamath Mountains and showed that plant communities were more strongly affected by variations in climate occurring on centennial and millennial timescales than the sites in the southeastern Klamath Mountains. Bolan Lake also supported more mesophytic species, such as Picea breweriana (Brewer spruce), Tsuga mertensiana (mountain hemlock), Abies spp., and haploxylon Pinus spp. (white pine species), and less frequent fires during the late glacial period and late Holocene than the sites in the southeastern Klamath Mountains. Another important finding of the research was that individual plant species and taxon moved along elevational gradients to track changing climate. The differences in plant communities and contrasting responses through time in the northern and southern Klamath Mountains suggested that there was spa...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Contents
• Citation Information
• Notes on Contributors
• Mountains: A Special Issue
• 1. Controls on Mountain Plant Diversity in Northern California: A 14,000-Year Overview
• 2. The Scientific Discovery of Glaciers in the American West
• 3. Incorporating Autonomous Sensors and Climate Modeling to Gain Insight into Seasonal Hydrometeorological Processes within a Tropical Glacierized Valley
• 4. How Rivers Get Across Mountains: Transverse Drainages
• 5. Geomorphometric Controls on Mountain Glacier Changes since the Little Ice Age in the Eastern Tien Shan, Central Asia
• 6. Some Perspectives on Avalanche Climatology
• 7. Characteristics of Precipitating Storms in Glacierized Tropical Andean Cordilleras of Peru and Bolivia
• 8. On the Production of Climate Information in the High Mountain Forests of Guatemala
• 9. Retreating Glaciers, Incipient Soils, Emerging Forests: 100 Years of Landscape Change on Mount Baker, Washington, USA
• 10. Impacts of Glacier Recession and Declining Meltwater on Mountain Societies
• 11. Agro-environmental Transitions in African Mountains: Shifting Socio-spatial Practices Amid State-Led Commercialization in Rwanda
• 12. “Water Is Life”: Local Perceptions of Páramo Grasslands and Land Management Strategies Associated with Payment for Ecosystem Services
• 13. Natural Hazard Management from a Coevolutionary Perspective: Exposure and Policy Response in the European Alps
• 14. Bringing the Hydrosocial Cycle into Climate Change Adaptation Planning: Lessons from Two Andean Mountain Water Towers
• 15. Nanga Parbat Revisited: Evolution and Dynamics of Sociohydrological Interactions in the Northwestern Himalaya
• 16. Applied Montology Using Critical Biogeography in the Andes
• 17. Snowlines and Treelines in the Tropical Andes
• 18. Mountain Ecology, Remoteness, and the Rise of Agrobiodiversity: Tracing the Geographic Spaces of Human–Environment Knowledge
• 19. Heritage as Weapon: Contested Geographies of Conservation and Culture in the Great Himalayan National Park Conservation Area, India
• 20. Perestroika to Parkland: The Evolution of Land Protection in the Pamir Mountains of Tajikistan
• 21. Harnessing the State: Social Transformation, Infrastructural Development, and the Changing Governance of Water Systems in the Kangra District of the Indian Himalayas
• 22. Living with Earthquakes and Angry Deities at the Himalayan Borderlands
• 23. The Sacred Mountain Shiveet Khairkhan (Bayan Ölgiy aimag, Mongolia) and the Centering of Cultural Indicators in the Age of Nomadic Pastoralism
• 24. Mountain Agriculture for Global Markets: The Case of Greenhouse Floriculture in Ecuador
• 25. Mountainous Terrain and Civil Wars: Geospatial Analysis of Conflict Dynamics in the Post-Soviet Caucasus
• 26. Making Mountain Places into State Spaces: Infrastructure, Consumption, and Territorial Practice in a Himalayan Borderland
• 27. Khumbi yullha and the Beyul: Sacred Space and the Cultural Politics of Religion in Khumbu, Nepal
• Index
• Index1