This is the last week for DHS, who will be knocking out week 10 before graduation day on June 9. You guys have all done an amazing job, and I hope it has been a good experience for you as well. (Quantitatively, you have spent an average of 254.0909 minutes in the field this spring!)
Without further ado, here is the data analysis for the penultimate week of the DHS spring 2017:
Interestingly, it looks like we might have had fewer live plants in week 9 than in week 8. I’m not sure why – perhaps a delayed effect of the mowing? The mowing was in week 5, and several more plants emerged after that. I expected the growing season to be longer this year because of the wet winter and spring, but I guess we’ll have to see what the data show. Compare this with 2016, when we had 233 plants alive at roughly the same time. Is this difference related to the mowing? the flooding? aging?
It looks like many of the plants continued to grow despite the mowing in week 5. While the monarch (especially larvae – ouch) counts were way down in weeks 4-6, the egg counts have bounced back a little bit now.
I wanted to take a closer look at which plants were most severely affected by the mowing, so I created a map to plot the change in the maximum stem length for each plant in the transect. Here, the point size is proportional to the total plant size in week 6, and the color is scale with the change in max stem length between week 4 and week 6 (negative values in red got shorter max stem lengths). You can see a few plants that lost some stem length throughout the transect, but also many that we still able to grow longer max stems between week 4 and week 6.
Looking at the total stem length (the estimated sum of all the stem lengths on a plant), you can see that the change in the total stem length between week 4 and week 6 is sometimes positive, often close to zero, and occasionally negative. These are the plants that lost a lot of total biomass.
Looking at these patterns another way, here is a quick plot (these are truly quick and dirty plots – excuse the unvarnished R code) of the max stem length per plant in week 4 (dmow$max.len.x) vs the max stem length for each plant in week 6 (dmow$max.len.y). The diagonal line shows the best-fit regression, and the horizonal line shows the approximate height of the mower blades. I think the plants that are below the horizontal line likely got the most severe mowing.
This plot next plot shows the max stem length in week 4 (d.mow$max.len.x) vs the change in the max length between week 4 and 6. The vertical row the points on the left probably represents plants that emerged in those 2 weeks. The diagonal row of points probably represents plants that got cut down to zero.
However, if you zoom out to look at the whole plant scale, a plot of the total stem length in week 4 vs the total stem length in week 6 shows that many plants are as large or larger in week 6 as they were in in week 4. Many plants got smaller as well, but on the whole, I think they are recovering nicely in size. It will be interesting to see how well the recover in terms of survival as well.
One more week in progress for the DHS crew, then on to the Growing Green interns! They are training now, and will be ready for the hand off next week! Happy graduation to the seniors, and happy summer to everyone.