Morphological and Physiological Phenology of Pinus longaeva in the White Mountains of California
Natural variations and responses to climate change can be identified within climatically sensitive ecosystems by monitoring growing season events. In 1962–1964, Fritts conducted a phenologic study on Pinus longaeva in the White Mountains of California. He monitored growing season events, environmental data, and dendrometer readings. In this study morphological and physiological phenophases, dendrometer traces, and environmental data were collected throughout the summers of 2007 and 2008 in the White Mountains of California to better understand variability in Pinus longaeva phenology and identify any shifts in the growing season since the 1962–1964 study (Fritts 1969). As a result of a late-season snow storm, observable phenophases in 2008 were 12 days later than in 2007. Pollination onset was slightly earlier than in the 1962–1964, which may indicate that accumulated heat or a combination of environmental factors influence these phenophases. Duration and timing of cambial activity in the present study was similar to that recorded in the Fritts (1969) investigation despite a median summer temperature increase of at least 2°C.ABSTRACT
Historic Fritts (1969) phenology site in Cardis Valley.
Phenologic photographic diary. Pictures taken summer 2007 and 2008. Sequence begins with an overwintering bud (a), then progresses to bud swelling (b) where bud scales pull away from bud (measured diameter). Next, the bud elongates (c) with a pronounced lengthening (measured length). Initial bud opening is defined as the opening at the tip of bud where tips of needles are visible (d). This phenophase is the same as the USA-National Phenology Network emerging needles stage. After four days, tips of needles separate, and the bud for next year is visible (e). Needles continue to emerge and separate throughout the growing season (measured length) (f). Beginning to emerge from the bud is a megastrobilus and a fully emerged female cone is seen about a week later (g). Megastrobili vary from blue to purple. Microstrobili or “pollen sacs” appear at the base of the bud and vary from yellow to red (h). Reproductive parts tend to appear simultaneously on various branches of a tree. Pollination onset (i) occurs when pollen first sheds from a shaken branch whereas pollination end (j) occurs when pollen does not fall when a branch is shaken. Pinus longaeva sheds yellow pollen except for one known instance where pollen is white. Pollination onset is the same as the first pollen shedding stage in USA-NPN standards. Note in this and the Fritts studies that measurements were obtained using four designated branches per tree although USA-NPN standards use three locations on a tree for phenophase determinations.
Cambial growth in 2007 and 2008. a. Before cambial growth begins, a distinct boundary exists between prior year's lignified tracheids shown in pink to red and bark shown in white to gray. b. 2–4 weeks of growing season. Tracheids lack or show early signs of lignification as xylogenesis begins. c. 4–7 weeks of growing season. Mid to late in the growing season, several tracheids are lignified. d. Cambial growth ceased, end of growing season with all tracheids lignified.
Box plots for 1962–1964 and 2007–2008 phenophases. Appearance of reproductive parts and pollination end were only available for 2007–2008 seasons. Cambial onset and end for 1962–1964 were measured by Fritts (1969), but only available as an average. Stars represent outliers.
June–August 2007 (A) and 2008 (B) temperature, precipitation, and phenophases. Horizontal scale in Day of Year. Vertical line = mode. Wider line on needle elongation and pollination = mode.
Comparison of growth rates.
Median Point Potentiometer Dendrometer summer 2008. Precipitation in vertical bars.
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