KW529
commented
2 years ago Message sent to Mendy 03-28-2022: Hi Mendy,
After reviewing all the correspondence with Juergen and between you and I, I think we may have made an error in excluding these sites. They resubmitted ANPP data for woody plants, but we still excluded woody vegetation in ANPP calculations since most values were negative in subsequent years (2015 is standing biomass, and subsequent years were subtracted from this value). Anyway, it looks like a few values (1 or 2) were still positive, which would have given their HO IDE site 2 drought plot replicates (we removed one due to an outlier ANPP value, which left them with only one drought replicate). We removed their HY IDE site because the average ANPP value was too low, but again that was because we removed woody vegetation.
What are your thoughts on how I should reply?
Best,
Kate Wilkins
tim-ohlert
"Hi Juergen,
I hope all is well! I am emailing with a question about the graminoid biomass in one of your drought plots (plot 10) from HO-IDE.
In 2015, the graminoid biomass was 207 g/m^2, followed by a precipitous decline in 2016 (8.7 g/m^2) and 2017 (3.5 g/m^2). Are these low values in 2016 and 2017 correct? If so, do you have thoughts on why this dramatic change happened?"
To which you replied:
"Hi Kate,
sorry for the late reply, and thanks a lot for spotting this! We had to dig deep into the old data and find the respective pictures which we took for every plot. Still, we cannot explain the high value for 2015. The pinpoint data has very many hits even in the field papers but the pictures clearly demonstrate little grass cover. As we cannot reconstruct meaningful values here, we suggest to replace the 207 by NA."
My follow up:
"Hi Juergen,
Thanks so much for this clarification. Apologies as I thought I sent my reply, but it was still sitting in my drafts folder! I have another follow up question to ensure the 3.5 g/m^2 biomass value is correct. Below is a snapshot of the anpp data from HO IDE. To calculate anpp, we added the anpp values for grasses and graminoids from each plot in 2017. The anpp value for the other drought plot (plot 8) is 32.7 g/m^2. Thanks so much for triple checking the 3.5 g/m^2 value for plot 10- I really appreciate your help!
To which you replied:
"Hi Kate,
great that you are doublechecking in detail! Here, we are confident that the value is correct. It fits to the pictures and the raw data. Plot 10 had relatively high standing biomass from the start with little change over time, so the value makes sense.
Best regards, Juergen"
Mendy and I consulted about this value and determined that it was an outlier that should be removed, which left your site with one drought plot (plot 8)- we require at least 2 replicates for the drought treatment. I recognize that you have other drought treatments, but these were paired with simulated grazing, thus we only selected the drought plots that did not include other treatments.
As for HY IDE, the average ANPP (8.88 g/m^2) for this site was outside the range for the biome (Heath: Europe, ANPP range: 42-263 g) according to Fahey & Knapp 2007 (T. J. Fahey, A. K. Knapp, Eds., Principles and Standards for Measuring Primary Production. Oxford University Press, 2007). In your survey, you indicated: "The main biomass in our site consists of Calluna vulgaris, a woody shrub. The ANPP would be calculated as the differences between the years." When we did this for Woody vegetation, we got negative values and thus excluded Woody vegetation from ANPP estimates.