Deciding What Your Observations and Data Mean

Deciding What Your Observations and Data Mean

Tree Height

We can see that trees exposed to higher levels of carbon dioxide grow taller more quickly. High ozone exposure, though, has the opposite effect. These trees are the shortest. These findings support our hypothesis that elevated CO2 will increase growth while elevated O3 will reduce growth.

Interestingly, we can see that the control group (the one growing without any alteration) has almost the same height as the trees exposed to both carbon dioxide and ozone. From this, we can conclude that a higher level of CO2 balances the impact of O3 on leaf physiology.

Leaf Drop Date

From the graph, we can see that trees exposed to high CO2 retained leaves the longest while trees exposed to O3 retained leaves the shortest. The control group retained leaves for less time than the CO2 trees but longer than trees exposed to CO2 plus O3.

We can conclude that higher levels of CO2 help trees to photosynthesize (make food) longer into the Fall. High O3, on the other hand, shortens time for photosynthesis (the growing season) by causing leaves to senesce sooner and fall off.

Leaf Weight

From the graph we can see that trees exposed to high CO2 produced the most leaves while trees exposed to high O3 produced the fewest leaves. The CO2 + O3 plots produced slightly more leaves than ones from the control plot and quite a bit more than the O3 trees.

We can conclude that higher levels of CO2 lead trees to produce a greater amount of leaves. This improves their light capturing ability and leads to increased photosynthesis (food production). Because leaves contain nutrients like nitrogen and phosphorous, more leaves also means more nutrients being released to the soil when the leaves fall off. High O3, on the other hand, leads to fewer leaves to capture light and photosynthesize.

Leaf Area

Our leaf area index data show us that elevated CO2 increases leaf mass while elevated O3 decreases leaf mass. The results for the plot with both gases fall in between. These findings are important because more leaves may mean more capture of sunlight. An increase in light capture would mean that trees are able to make more food.