Closed teixeirak closed 5 years ago
Did you mean a linear model? And between which traits? If I take it as it is now, I'd be doing a linear model for TWI - PLA TWI - TLP TWI - rp
Did you want more than this?
Here's what I have currently for the hypotheses/ predictions:
2. How do species' traits--alone and in interaction with tree size--influence drought response?
2.1. Commonly measured traits including wood density (REFS), leaf mass per area [@abrams_adaptations_1990] [@guerfel_impacts_2009], and ring porosity (Elliot et al. 2015, Friedrichs et al. 2009) have been linked to drought responses and likely correlated with drought resistance in this forest. However, we hypothesize that leaf hydraulic traits such as leaf area shrinkage upon dessication and turgor loss point, which are emerging as potentially more informative traits but whose effect on drought resistance has never been tested (CONFIRM), will prove better predictors.
2.2. Traits vary with microenvironment, with more drought-resistant traits associated to taller trees (and drier topographic positions) (issue #43)
* P2.2a- traits (all 5 above) correlate with tree height
* (P2.2b- traits (all 5 above) correlate with TWI)
2.3. Size-dependent drought resistance is driven by--or alternatively, buffered by--functional traits (i.e., larger trees have more drought vulnerable traits).
I think it would be good to test all species' traits against both height and TWI.
TLP and PLA are higher priorities because they come out as the strongest predictors.
It could be interesting to expand beyond the 12 species for which we have TLP & PLA with the other traits. WD, LMA, and RP are so widely measured/ known that we could get much better coverage. Of course, that's more work-- not how long it would take you/ if worth it.
I agree, I think it would be best to get everything in, especially if we have the data for it.
Regarding TLP and PLA, though, I believe the 12 species are the only species we have data for. That's why originally we took out pist, for example, because we had no species traits data for it.
Given this, I'm also cognizant of how much time I have left before I start having no time (with schoolwork and my research assistantship). I think expanding to get more data and add more species may be too much for me to do with what I have left. In your opinion, do you think this paper would be a lot better getting that extra data in? In that case, I'd be fine doing what I can for we currently have, and then letting someone else take up the next steps.
Otherwise, I think based on the hypothesis predictions you have above, I'm assuming you want to add to this trait table? Is this what you were thinking of?
Making a table like this shouldn't take too much time, it's just a matter of inserting it into the code format I already have
I wouldn't change our existing structure for testing the traits. That is, we do still want to include height in the null model.
Testing 2.2 will just be [trait] ~ height or [trait] ~ TWI. That should be a separate table in the SI; I don't expect it will be interesting enough to make it into the main manuscript.
For hypothesis 2.3 (erroneously labeled as 3.1 before), again I wouldn't change our existing analyses. Rather, we the test of this prediction is whether the best model, including traits, still has efects of height & TWI. I've updated the text to clarify this.
Ahh I see. So that means 2.2 will be tested with just linear models. I can do that
Hi @teixeirak
Here is a chart with the p-values compared to height. According to this, it appears that everything is significant.
I noticed that in the hypotheses tables, you say community mean for the traits, relating to using all tree data for the plot. In the table, though, these results are put under the "Overall" section (though the data that's being tested is not only the overall drought trend). Did we want to update the hypothesis table?
This is for my understanding:
@teixeirak for LMA, I've found some papers confirming that higher LMA means more drought-tolerant. This is the only one of the traits that contrasts the taller trees are more drought-sensitive. Does it make sense to have this contradiction?
I don't really have any prior expectation/ reason to believe there should be a trend one way or the other. Obviously there are many traits that contribute to vulnerability or resistance, and it seems they can go opposite directions.
Keep in mind that we're only looking at canopy species, and at species-level traits. What this tells us is that drought sensitivity isn't a strong filter on which (canopy) species dominate canopy positions at this site. That's not surprising, as there's a lot of other things going on.
I do think we'd get some different results if we included the understory species.
Closing (complete).
@mcgregorian1, you've already made plots showing the relationship between mean traits and microenvironment. Can you now please test whether there are any significant trends?