Amarina Wuenschel, US Forest Service Pacific Northwest Ecology Program, Baker City, OregonFollow
Jim A. Bartel, San Diego Botanic Garden, Encinitas, CaliforniaFollow
Alexis Bernal, University of California, BerkeleyFollow

Forty Years of Change in Piute Cypress (Hesperocyparis nevadensis), a Rare California Tree, After Frequent Fire and Drought

DOI

10.5642/aliso.XQGU4829

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Abstract

Piute cypress (Hesperocyparis nevadensis) is a rare cypress species endemic to the Lake Isabella region in the southern Sierra Nevada in California. Piute cypress groves have not been quantitatively studied in the last 40 years and with recent fires (some in short succession) and observed mortality, we had questions surrounding conditions in groves recovering from fire compared to other groves with no recorded fire histories. Piute cypress rarely survive fire and are obligate seeders with serotinous cones and, as such, require sufficient time after fire to grow to reproductive maturity to be able to withstand future fire. We visited five of the 12 known groves of Piute cypress to evaluate current stand conditions and make comparisons with an assessment conducted 40 years ago. We evaluated two recently burned groves nine years post-fire. One grove with a shorter interval between fires (~20 years), has only limited regeneration and is at risk of local extinction. Based on our findings, we extrapolated to unstudied groves to conclude that five recently burned groves are vulnerable to immaturity risk if these stands were to reburn soon. We recommend aggressive fire suppression tactics to protect these groves if threatened by fire. Another recently burned grove with a longer period between fires (~90 years) appears to be recovering and capable of becoming a self-sustaining population that can survive another fire based on regeneration data. While the 90-year-old trees did not have nearly the level of canopy seed bank that older trees (~200 years old) did in another part of the grove, seedling and sapling regeneration after fire occurred at higher densities than tree densities in mature stands and were already developing cones. Though theoretically long-unburned groves also may be at risk, we found no evidence of age-related decline in this long-lived species and some non-fire induced regeneration. We did discover evidence of cedar bark beetle attack (Phloeosinus), particularly in smaller trees at two unburned groves. which was correlated to high tree mortality (31.6%) at one site. While we found no evidence of encroaching non-cypress tree species threatening long-unburned groves among mature cohorts, we did document relatively high densities of regenerating non-cypress tree species in groves. We strongly recommend further monitoring in groves to assess fire, insect, and disease vulnerability in cypress populations.

Recommended Citation

Wuenschel, Amarina; Bartel, Jim A.; and Bernal, Alexis (2023) "Forty Years of Change in Piute Cypress (Hesperocyparis nevadensis), a Rare California Tree, After Frequent Fire and Drought," Aliso: A Journal of Systematic and Floristic Botany: Vol. 41: Iss. 1, Article 6.
Available at: https://scholarship.claremont.edu/aliso/vol41/iss1/6