Whitebark and Foxtail Pine in Yosemite, Sequoia, and Kings Canyon National Parks: Initial Assessment of Stand Structure and Condition

Jonathan C.B Nesmith,Shawn T Mckinney,Micah Wright,Erik S Jules

doi:10.3390/f10010035

Abstract

The Inventory & Monitoring Division of the U.S. National Park Service conducts long-term monitoring to provide park managers information on the status and trends in biological and environmental attributes including white pines. White pines are foundational species in many subalpine ecosystems and are currently experiencing population declines. Here we present results on the status of whitebark and foxtail pine in the southern Sierra Nevada of California, an area understudied relative to other parts of their ranges. We selected random plot locations in Yosemite, Sequoia, and Kings Canyon national parks using an equal probability spatially-balanced approach. Tree- and plot-level data were collected on forest structure, composition, demography, cone production, crown mortality, and incidence of white pine blister rust and mountain pine beetle. We measured 7899 whitebark pine, 1112 foxtail pine, and 6085 other trees from 2012–2017. All factors for both species were spatially highly variable. Whitebark pine occurred in nearly-pure krummholz stands at or near treeline and as a minor component of mixed species forests. Ovulate cones were observed on 25% of whitebark pine and 69% of foxtail pine. Whitebark pine seedlings were recorded in 58% of plots, and foxtail pine seedlings in only 21% of plots. Crown mortality (8% in whitebark, 6% in foxtail) was low and significantly higher in 2017 compared to previous years. Less than 1% of whitebark and zero foxtail pine were infected with white pine blister rust and <1% of whitebark and foxtail pine displayed symptoms of mountain pine beetle attack. High elevation white pines in the southern Sierra Nevada are healthy compared to other portions of their range where population declines are significant and well documented. However, increasing white pine blister rust and mountain pine beetle occurrence, coupled with climate change projections, portend future declines for these species, underscoring the need for broad-scale collaborative monitoring.

Highlights

Forests across North America are experiencing rapid change driven by a combination of factors including outbreaks of native pests and pathogens, introduced exotic species, altered fire regimes, and rapid climate change [1,2,3]
This paper describes the current status of whitebark pine and foxtail pine within Yosemite National Park (YOSE) and Sequoia and Kings Canyon National Parks (SEKI) based on survey data collected from a newly established permanent plot network
Due to the increasing west to east elevation gradient in YOSE, most of the plots are located in the eastern half of the park, where the elevation is high enough for suitable whitebark pine habitat (Figure 4)

Summary

Introduction

Forests across North America are experiencing rapid change driven by a combination of factors including outbreaks of native pests and pathogens, introduced exotic species, altered fire regimes, and rapid climate change [1,2,3]. Additive or synergistic effects among stressors can lead to structure, and are species composition. Synergistic among to stressors can abrupt or rapidfunction, change and likely if multiple Additive agents actorjointly [5,6]. The changes to forest composition and function in the coming century will likely be unprecedented and have significant structure, composition and function in the coming century will likely be unprecedented and have consequences for regional and global biodiversity, carbon dynamics, and species distributions [7]. Broad-scale changes such as increased tree mortality rates over the last several decades have already distributions [7]. Broad-scale changes such as increased tree mortality rates over the last several been decades documented acrossbeen a large range ofacross latitude andrange forest types inand western

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