Analysis    

We have learned lots of things during our experimentation and study of budburst.

For the Silver Maple, we have learned that the leaf buds burst at different times all over the tree, over about five or six days. For the Crab Apple, the buds for both leaves and flowers burst all at the same time over about two days. The Silver Maple flowers burst earlier than the Crab Apple, but eventually they were dead and fell off a few days later. The Silver Maple’s flowers burst in mid March while the leaves did not burst until the middle of April. So we learned that different kinds of trees have different ways and different strategies for producing flowers and leaves.

We found it interesting that the Silver Maple had budburst dates 4 to 5 days later in Indiana than in Washington, DC For the Crab Apple, budburst happened a full week later in Indiana (7 days). This data seemed to support our hypothesis that Washington, DC, trees would have an earlier budburst because they are closer to the ocean.

Two students on our team at MSSD, and also at ISD, thought that being near the ocean would mean that there would be more moisture in Washington, DC. So we compared our relative humidity data shown in graphs #5 and #6 from both schools. (We wish we had absolute humidity data to compare.) There is not a lot of data from ISD, but the two graphs show that the humidity may not be that much different. In fact, the Washington, DC graph shows slightly less humidity than in Indiana. Also, we learned from watching the evening news on TV, our weather comes mainly from the west in Washington, DC, not from the direction of the ocean. So we realized that Washington, DC may not be more humid than Indiana.

We decided to look at the precipitation data. On the precipitation graph for D.C. and Indiana you can see they have similar precipitation patterns, including the very large rainfall on almost the same day in March. We concluded that, overall, at ISD, there was more rainfall than at MSSD.

We wondered if maybe the rain evaporated faster in Indiana. When we calculated Water Difference, we realized that the Crab Apple had almost the same amount of water available at both MSSD (WD is 72 mm) and ISD (WD is77 mm). But, the water differences of the Silver Maple meant slightly more water was available before the budburst at ISD (WD is 48 mm) than at MSSD (WD is 36 mm). In both cases, it was a wet year and not a drought. We suspect that the warm January in Washington, DC evaporated more than ISD because in Indiana, it was too cold to evaporate until March. But we do not think water was controlling budburst at either school because there was not really that much difference at our two schools.

Another student on our team thinks that temperature controls budburst. On the temperature graph for Indiana and Washington, DC, the graphs show similar patterns for 2007, but Indiana had colder weather patterns than Washington, DC. In DC, the temperature had 7 days when it did not get above zero degrees Celsius while in Indiana there were about 25 days that the average was not above zero degrees Celsius. We suspected the strong cold at the end of January and early February in Indiana might cause a delay in budburst for the trees this year.

We decided to compare the Growth Degree Summary for our two schools and see if that helps us understand temperature’s influence. We noticed that the Acer had a higher Growth Degrees summary (GDS) in Washington, DC (average of 740 deg) than in Indiana (average of 619 deg). The result in Crab Apple shows more GDS days in Washington, DC (average of 425 deg) than in Indiana (average of 322 deg). The comparison of GDS of the two trees shows that the Acer budburst tends to require a higher GDS (740 and 619 deg) than the Crab Apple (425 and 323 deg). So we conclude that different kinds of trees need different amounts of warming to start growth. Maybe that strategy helps some plants avoid getting damaged from snow and freezing temperatures. We are still curious about the influence of the cold period in early February and wondered if it delayed our trees.

We decided to look for more data from our locations. We found that a school named Grigsby Academy in Albany, Indiana did a budburst study in 2004 and they studied ‘Acer sacc.’. We don’t know if that means a Sugar Maple or a Silver Maple. That school is about 78 miles northeast of ISD. Their bud burst for the Acer leaves was on April 15 in 2005, which is 5-7 days earlier than our budburst in 2007.



The temperature data for Grigsby shows very cold temperatures in January 2004. Most days in the month, the average temperature was below zero deg C. The temperature became warmer and warmer in February, March, and April. January 2004 temperatures are much colder for the first 2 weeks than for 2007. They did not have cold temperatures the first week of April and all of April seems warmer in 2004, so maybe that’s why the Acer budburst was almost a week earlier.

At MSSD we had student data from our own school in 2002. When we compared the years, we learned that the Silver Maple had almost the same budburst dates in 2002 and 2007. However, the budburst for the Crab Apple in 2007 was about two weeks later (16 days) compared to the budburst in 2002. So we looked at the graph for the D.C. temperatures for the year 2002 (below).



In the 2002 temperatures graph, it was cold in January then warmer later at the end of January. In 2007, it was warm at the beginning of January then it was colder in February. It got warmer in March and April.. So on the temperature graphs from 2007 and 2002, they have opposite weather patterns in January. In 2007, the temperature had 7 days when it did not get above zero degrees C while in 2002 it always got above zero degrees C every day. We think the strong cold at the end of January and early February was the cause of the late budburst for the Crab Apple at MSSD, this year in 2007. The budburst date for the Silver Maple was not much different, so the January cold did not seem to influence the Silver Maple as much. This year (2007) February temperatures were colder than in 2002 at MSSD, and in April 2002 it was a little colder, with more days below freezing. Because the budburst for the Maple was almost the same for 2002 and 2007, we wonder if something else might be influencing the budburst of the Silver Maple.