Deciduous orchards in California winters

Chandler, William Henry; Brown, D. S.

doi:10.5962/bhl.title.53410

Cited by 25 publications

(17 citation statements)

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“…The Chilling Hours Model (Chandler 1942) is the oldest method to quantify winter chill that is still widely used. It considers all hours with temperatures between 0 and 7.2°C as equally effective for winter chill accumulation.…”

Section: Methodsmentioning

confidence: 99%

A global analysis of the comparability of winter chill models for fruit and nut trees

2010

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Many fruit and nut trees must fulfill a chilling requirement to break their winter dormancy and resume normal growth in spring. Several models exist for quantifying winter chill, and growers and researchers often tacitly assume that the choice of model is not important and estimates of species chilling requirements are valid across growing regions. To test this assumption, Safe Winter Chill (the amount of winter chill that is exceeded in 90% of years) was calculated for 5,078 weather stations around the world, using the Dynamic Model [in Chill Portions (CP)], the Chilling Hours (CH) Model and the Utah Model [Utah Chill Units (UCU)]. Distributions of the ratios between different winter chill metrics were mapped on a global scale. These ratios should be constant if the models were strictly proportional. Ratios between winter chill metrics varied substantially, with the CH/CP ratio ranging between 0 and 34, the UCU/CP ratio between −155 and +20 and the UCU/CH ratio between −10 and +5. The models are thus not proportional, and chilling requirements determined in a given location may not be valid elsewhere. The Utah Model produced negative winter chill totals in many Subtropical regions, where it does not seem to be useful. Mean annual temperature and daily temperature range influenced all winter chill ratios, but explained only between 12 and 27% of the variation. Data on chilling requirements should always be amended with information on the location and experimental conditions of the study in which they were determined, ideally including site-specific conversion factors between winter chill models. This would greatly facilitate the transfer of such information across growing regions, and help prepare growers for the impact of climate change.

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Section: Methodsmentioning

confidence: 99%

A global analysis of the comparability of winter chill models for fruit and nut trees

2010

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“…Sustained periods of air temperatures below 7°C are maintained in the Central Valley of California during the winter by prolonged periods of radiative fog, also known as “tule fog” [ Chandler and Brown , ; Holets and Swanson , ; Suckling and Mitchell , ; Underwood et al ., ]. So if the occurrence of winter fog is decreasing, with global warming, it may contribute to the trend in reduced winter chill accumulation.…”

Section: Introductionmentioning

confidence: 99%

Winter fog is decreasing in the fruit growing region of the Central Valley of California

Baldocchi

Waller

2014

Geophys. Res. Lett.

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The Central Valley of California is home to a variety of fruit and nut trees. These trees account for 95% of the U.S. production, but they need a sufficient amount of winter chill to achieve rest and quiescence for the next season's buds and flowers. In prior work, we reported that the accumulation of winter chill is declining in the Central Valley. We hypothesize that a reduction in winter fog is cooccurring and is contributing to the reduction in winter chill. We examined a 33 year record of satellite remote sensing to develop a fog climatology for the Central Valley. We find that the number of winter fog events, integrated spatially, decreased 46%, on average, over 32 winters, with much year to year variability. Less fog means warmer air and an increase in the energy balance on buds, which amplifies their warming, reducing their chill accumulation more.

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“…But the possibility that iron moves from the roots to the shoots in the phloem requires further examination. Upward N transport in the phloem is believed to occur in horticultural species in which nitrate reduction occurs in the roots (8 ( 14,18,20). However, such observations can also be interpreted as revealing the normal pattern of iron distribution.…”

Section: Discussionmentioning

confidence: 92%