I thought I would spend some time comparing the 2006 and 2007 measuring of the plants at Hegg Lake. The Hegg Lake common garden is located on Minnesota DNR land and is approximately a 7.5 mile drive from the main common garden. In May 2006 3,941 seedlings were planted at Hegg Lake after they were first germinated and grown in a green house at the Chicago Botanic Garden. To learn about this large seedling growth experiment see http://echinacea.umn.edu/experiments-spring-2006.htm">http://echinacea.umn.edu/experiments-spring-2006.htm">http://echinacea.umn.edu/experiments-spring-2006.htm
In both years we counted the number of leaves and measured the longest leaf. However, this year we also recorded insects and any herbivory damage on the plants. The average tallest leaf of the living plants was 6.4 cm in 2006 and 13.7 cm in 2007.
"Can't finds��? and mortality estimates between years:
When we are measuring plants and can't find a plant we don't assume the plant is dead. Instead the measurer records that the plant is a "can't find��? and places a flag in the position he/she was searching. Later we have a different person come back and searches for the plant so that two pairs of eye look for every "can't find��? plant. In 2006 we had approximately 21% of the plants were found by the second person who went back and searched for the "can't find��? plants. Our overall estimate for mortality in the plants first year of growth was around 6% with 243 plants that were "can't finds��? after two people searched for the plant.
This year we have just started having the second person go back and search for "can't find��? plants. We have a total of 698 plants that were not found by the originally measurer. This puts the mortality estimate at 17.7% plants (cumulative) however I feel this percentage will drop significant after the second person rechecks the "can't finds��?.
One interesting note is there were 30 plants found by the originally measurer this year that were not found by EITHER person who searched for the plant in 2006. Therefore, in 2006 there were really (at most) 213 plants that died making the currently mortality estimate for 2006 at 5%.