Abstract Detail

Conservation Biology

Wright, Jessica [1], Ivey, Christopher T. [2], Canning, Courtney  [3], Browne, Luke  [4], Sork, Victoria  [5].

Timing of leaf emergence in a common garden is associated with climate of origin and local climate in a California endemic oak, Quercus lobata.

Plant phenology is the result of complex interactions between the environment and genetically controlled responses. Leaf emergence in spring, bud burst, is a critical time in tree growth. Newly emerged leaves are generally highly sensitive to frost, and leafing out too early can have negative consequences. However, if leaves emerge too late, then the growing season is shortened, and less growth can take place. Clearly appropriately responding to local environmental cues is critical for tree fitness.
However, what happens when seeds or acorns are moved to a new location for reforestation projects? Do trees continue to show patterns of bud burst associated with the environment they came from, or do they leaf out at the same time as the local trees? Should impacts on phenology be included in the discussion of assisted migration?
In 2014, we established a provenance test in valley oak (Quercus lobata) to address these questions. This test includes 6000 seedlings from 694 maternal trees from across the species range in California, which were planted into two contrasting field sites. Every year since planting, we have recorded spring leaf emergence as a measure of tree phenology through weekly surveys of tree buds.
Our results show that leaf emergence occurs earlier in the warmer planting site. However, despite these environmental differences, there is variation in both sites in patterns of bud burst, and the timing of bud burst is associated with the climate of origin of the maternal lineage, with trees from warmer locations bursting bud earlier than trees from colder places. Moreover, we saw faster growth rates in trees that leafed out earlier and had a longer growing season.
The results from our valley oak provenance test will help to inform reforestation efforts. Previous analyses have shown that growth rates are higher when trees are planted into a colder environment. Understanding how climate of origin is associated with the timing of bud burst may help to identify climate transfer distances that might provide maximum growth success, while avoiding potential frost damage.

1 - USDA Forest Service, Pacific Southwest Research Station, 1731 Research Park Drive, Da, CA, 95618, USA
2 - California State University, Chico, Biological Sciences, 400 W 1st St., Chico, CA, 95929, United States
3 - USDA Forest Service, Pacific Southwest Research Station, 2480 Carson Road, Placerville, CA, 95667, USA
4 - Yale University, School of Forestry & Environmental Studies, 195 Prospect Street, New Haven, CT, 06511, USA
5 - UCLA, ECOL & EVOL BIOL, Box 957239 , Los Angeles, CA, 90095, United States

Valley Oak
Quercus lobata
provenance test.

Presentation Type: Oral Paper
Session: CB2, Conservation Biology 2
Location: Virtual/Virtual
Date: Monday, July 27th, 2020
Time: 1:30 PM
Number: CB2005
Abstract ID:483
Candidate for Awards:None

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