search

SCBI-ForestGEO / McGregor_climate-sensitivity-variation

repository for linking the climate sensitity of tree growth (derived from cores) to functional traits
0 stars 0 forks source link

Retroactive canopy positions #27

Closed mcgregorian1 closed 5 years ago

mcgregorian1 commented 5 years ago

Hi @teixeirak

Further to what we discussed earlier, I tried modelling the biophysical traits only for 1999, and (of course) crown position did not come out significant. In fact, only distance to water did (odd).

This means that I probably have to separate out crown position based on DBH, and then assign positions in the past based on the past DBH we've calculated. You mentioned, however, that this basically copies the height effect.

For what it's worth, the first graph on this pdf that I've made using only the 2018 crown position makes sense with DBH anyways into the past, but of course this is looking only through one viewpoint.

What do you think?

teixeirak commented 5 years ago

What is the average change in height from the first years of data used to current? (I'd like to get a sense of how much canopy position was likely to have changed).

Also, please remind me what happens if we combine categories into just canopy and subcanopy. That at least makes it easier to interpret any bias.

I don't think that predicting canopy position based on height would work, as we're trying to look at this as an effect separate from height. If we decide we just can't use it, the only option I see would be to drop it. However, it is informative and interesting, so I'd favor just using as is and discussing potential bias from trees changing position.

I'm aware of one in-review paper that uses current canopy position to classify trees for tree-ring analysis that stretches back many years. I've asked the author about how he approached this issue.

mcgregorian1 commented 5 years ago

Interestingly, we have many trees that have height changes of <1m over the course of 1966-1999? I'm confused by that. However, if you remove the the trees that had 0m growth (only 1 height measurement), then the average growth for all trees is 1.94m.

If you only have the canopy/subcanopy groups, then position comes out in the top model for all years, and in 1999 it also comes out in the top model. Are we not seeing this same pattern, then, because we have too many groupings?

mcgregorian1 commented 5 years ago

We quickly talked about this and we decided to keep the four groupings as is. I will close this issue unless we think of something else