When the tree is first planted, its carbon-14 is at 100%. what has to happen for that number to start changing?

Carbon is the building block of all organic molecules and is present in many other forms in the environment, and for this to happen it is called "carbon dating" therefore i would say that it has to experience the cycle in which you can easily find looking up c 14 dating!

tunami b/c it is near water

a maximum–minimum thermometer. the scales are fahrenheit on the inside of the u and celsius on the outside. the current temperature is 23 degrees celsius, the maximum recorded is 25, and the minimum is 15, both read from the base of the small markers in each arm of the u tube. the bulbs are hidden by a plastic housing.

six's thermometer is a registering thermometer which can record the maximum and minimum temperatures reached over a period of time, for example 24 hours. it is used to record the extremes of temperature at a location, for instance in meteorology and horticulture. it was invented by a british scientist james six, born in canterbury, in 1780; [1] the same basic design remains in use.

it is also commonly known as a maximum–minimum, minimum–maximum, maxima–minima or minima–maxima thermometer, of which it is the earliest practical design.

the thermometer indicates the current temperature, and the highest and lowest temperatures since last reset.