The temperatures for the winter (December-February) and March for Monarch Waystation #1 and for Lawrence are shown in Tables 1 and 2.

Table 1. Winter and March temperatures (2007-08) for Monarch Waystation #1, Lawrence, KS.

Table 2. Official winter and March temperatures (2007-08) for Lawrence, KS.

As I noted last month, the garden is both warmer and colder than the official weather station for Lawrence. Nevertheless, the mean temperatures are similar. How these differences will translate into growing degree days remains to be seen.

The mean temperature for Lawrence for March was 41F, quite a bit cooler than the average of 46.3F recorded from 1971-2000. In Kansas, the mean temperature for March (1895-2007) was 42.6F degrees and the temperatures this year are much lower than for 2007 in which the mean temperature was 52.2F, second only to the 54.7F recorded in 1910. As you may recall, due to the high temperatures, plant growth was advanced by as much as 12 days last spring leading to disastrous consequences when the jet stream, with temperatures in the teens, dipped into the lower Midwest and swept into the Southeast. In many areas there were 60 or more hours of freezing temperatures resulting in crop losses from Kansas to South Carolina (Figure 1). Fortunately such events are rare and less likely in years such as this one since temperatures through March have delayed plant growth to some degree.

Figure 1. Cold wave of 4-10 April 2007.

From NOAA/NESDIS/NCDC

A sample of the data from one of the data loggers in our garden is shown in Figure 2.

Figure 2. Temperatures recorded for the first 12 hours of 2 March 2008 (data logger #1).

To record the number of degree days (DD) these data have to be imported into a Degree Day Workbook. The workbook calculates the DDs for each hour and summarizes the total number of monarch degree days for each day and for each month. The DD output for the first 6 days of March 2008 for Monarch Waystation #1 is shown in Figure 2. The Degree Day Workbook now found in the Monarch Watch Forums is in the process of being modified so that you can enter data for each month of the year. You will also be able to specify if you wish to calculate the degree days for either monarchs or plants. The methods are the same but the ranges of temperatures over which growth occurs are different for plants and monarchs.

Figure 2. Temperatures and monarch degree days for the first 6 days in March 2008.

There are two things to note about Figure 2: 1) the number of DDs is zero if the temperatures for the entire day are either above or below the developmental thresholds for the monarchs or plants and 2) the most important data is the accumulated DDs (Acc. DD) in the last column.

Assuming there are no freezing temperatures during the period of measurement, the number of degree days required for each of the monarchs’ life stages is: egg 45C/113F, larva 187C/369F, and pupa 120C/248F or about 720F for each generation (egg to egg). For a further discussion of degree days please see “Degree Days and Monarch Growing Season“

The Temperature Loggers are small, relatively inexpensive, programmable recording temperature sensors. These reusable devices have a long battery life and can be used to record temperatures at defined intervals for days, weeks or even months. I recently downloaded the data from these loggers so that I might compare the temperature data from the garden with that recorded at the local airport and with the monthly mean temperatures for Kansas provided by the NOAA.

Winter is traditionally defined as the three-month period encompassing December, January, and February. The records listed in Table 1 are from 3 December 2007 until midday of the 25th of February. Our loggers were set to record the temperature every hour and to rollover and start a new record when the data limit has been reached, in this case in about 86 days. Unfortunately, rollover occurred – resulting in the loss of the earliest data from the first two days of December. Nevertheless, the data given for December and for the first 24.5 days of February should be close to the actual means for these months. Overall, the means are remarkably similar for each of these three months.

Table 1. Winter temperatures (2007-08) for Monarch Waystation #1, Lawrence, KS.

The mean temperature for December 2007 for Kansas, as found via the NOAA site, was 31.9F making December 2007 the 6th coldest over the last 30 years. The mean temperature for January was 28.9F, a bit warmer than the long time average and 11th coldest January among the last 30. These data are not yet available for February but this month has also been a bit colder than average. When all the data are assembled, this winter will measure as a tad colder than average. The mean temperatures for the garden are a bit colder than those for the state but this is not surprising since we are located in the northeast corner of a rather large state.

Of greater interest is the comparison of the garden temperature with those recorded for the official weather station for Lawrence (Table 2).

Table 2. Official winter temperatures (2007-08) for Lawrence, KS.

Interestingly, both the means highs and mean lows for the garden are consistently higher and lower for the garden than for the official weather station. The monthly means for January and February were at bit higher for the garden than those of the weather station. These differences are probably due to the location of the garden. The garden is in a slight depression and is protected to some degree from the wind, perhaps allowing heat to build up slightly during the day. However, being down-slope and in a slight depression, the area is subject to cold air drainage, perhaps accounting for the lower nighttime temperatures than at the official weather station. The differences between the two locations, though seemingly small, could have an impact on plant growth. We will compare the growing degree days through the season for both locations and will let you know if these differences are really significant.

We have big plans for this season and we need your help on several projects:

1. MONARCH WAYSTATIONS

We need to increase the number of registered Monarch Waystations by at least 1,000. There are now 1,871 registered habitats in the Monarch Waystation Registry and this number needs to grow given that we are losing 2.2 million acres of habitat per year due to development. As we’ve said before, we need you to help us market this program. Please show your Monarch Waystations to others and direct people to our web site. Your efforts will help educate the public of the need to protect habitats for monarchs and other wildlife.

2. HABITAT OBSERVATIONS

We need your to help us track the phenology (seasonal progression) of milkweeds and nectar plants. We will have a series of announcements describing how you can participate in this program in the coming weeks.

3. MONARCH OBSERVATIONS

Please report the first monarch you see this spring. We need a larger number of observations of first monarchs to determine how well the spring migration is synchronized with the growth phases of the milkweeds.

4. DEGREE DAY LOGGING

In future articles we will demonstrate how to record growing degree days for both milkweeds and monarchs in our Monarch Waystation. We hope that these demonstrations will encourage more of you to use these simple devices to learn more about the relationships between temperature and growth and development.

5. MONARCH TAGGING

Another tagging season will be here soon but it is not too soon to urge you to order your tags now. Again, we will limit the number of tags to 200,000 and once these are gone, they’re gone. So, do order early to avoid being disappointed.

Tagging Kits and other materials are available via the Monarch Watch Shop online at Shop.MonarchWatch.org

The total monarch degree days and potential number of generations for each of the last 5 years are summarized in the following table.

Table. Monarch degree day totals and potential number of generations through 23 September for 2003 – 2007.

The methods used to calculate monarch degree days can be found in the “Monarchs, Cold Summers, Jet Streams, Volcanoes, and More” article from the Monarch Watch January 2005 Update. The breeding seasons of 2006 and 2007 have been the hottest, with the greatest number of potential monarch generations, of this period. Higher temperatures can favor monarch population growth but they can also be detrimental if they co-occur with drought conditions. The summer of 2004 was the coldest during this period and the coldest since the Mount Pinatubo summer of 1992. The low temperatures during the 2004 breeding season, one that followed massive mortality at the overwintering sites in January and February 2004 and high temperatures in March in Texas, contributed to the lowest overwintering population (2.2 hectares) observed or measured at the overwintering sites. The January 2005 Update article (referenced above) contains an extensive discussion of the factors that contribute to summer temperatures.