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What is Phenology

Nature has a rhythm. The occurrence of seasonal events like the unfolding of leaves in the spring, the blooming of flowers, the migration of birds and other biological events that reoccur with the passage of the seasons are influenced by an interaction of light, temperature and moisture.

The study of nature's rhythm is called phenology. Phenology is the study of how climate and the season's affect natural events.

The roots of phenology are in agriculture (excuse the pun), for instance, one important use is in pest control. Being able to predict the appearance of a pest is extremely valuable to farmers.


Hopkin's Law of Bioclimatics

Andrew Delmar Hopkins was the leading forest entomologist during the first part of the 20th century. Most of his work was done in Virginia and West Virginia. Andrew Hopkins first formulated the relationship of elevation, latitude and longitude to seasonal events like the coming of spring.

The relationship is one day for every 15 minutes of latitude, 1.25 days for each degree of longitude and one day for every 30 meters of elevation.

It seems that in North America the further west, or north, or higher, the later spring arrives. The effects of elevation, for example, are caused by a general lowering of temperature as temperature increases. Horticulturalist and gardeners around the world are quite familiar with these natural timings repeated annually.

Here are some details on Hopkins Law of Bioclimatics

1. For every ¼ degree (15 minutes of latitude) you travel North, there is a 1 day delay for the coming of spring.
2. For every degree of longitude you travel West, there is a 1 ¼ day delay for the coming of spring.
3. For every 100 feet you travel up in elevation, there is a 1 ¼ day delay for the coming of spring.
*****Note.... While some latitude and longitude notations use negative numbers to represent western longitudes and southern latitudes, you should always use POSITIVE NUMBERS.*****

Example Calcuations using Hopkins Law:
If you were to travel from Kansas City(1000 ft elevation, 39.11 degrees N latitude, -94.63 longitude) to Omaha, Nebraska(1034 feet elevation, 41.26 degrees N latitude, -95.93 longitude), the delay in the coming of spring would be…



[((1034 ft - 1000 ft)/100 ft * 1.25 days) + ((41.26 degrees - 39.11 degrees)* 4 days)
+ ((-95.93 degrees - -94.63 degrees ) * 1.25 days)] =

(34 ft /100 ft * 1.25 days) + (2.15 degrees * 4 days) + (1.3 degrees * 1.25 days) =

8.5 days + 2.6875 days + 1.625 days =

10.65 Days

According to the Hopkin's Law, flowers should bloom, trees should bud, and geese should appear around 11 days later in Omaha, Neb. Than in Kansas City, Kansas.


Phenology and Climate Change

The way the living world reaches to the seasons can serve as valuable indicators of both the health of the environment. It has been suggested (Schwartz, 1994, 1998) that changes in phenologic timing may serve as a possible measure of climatic change. One ongoing project has mapped the blooming of cloned lilac bushes, other phenology projects have been going on for over 40 years.

One important factor to include in your observations is the exact location of the plant species observed. This is because the microclimate where the plant is found is another variable to be considered. The extra warmth of a south exposure next to a building might very likely speed up the first bloom. Make as many notes as possible regarding the microclimate around each siting.

Related Link: "A Time for Every Purpose Under Heaven" by Gregory K. Scott

Next Steps
Now that you know a bit about the factors influencing the coming of spring you are encouraged to continue by recording and sharing the signs of spring in your own area. Continue on to the research methods in this project.

  1999, KanCRN Collaborative Research Network