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Author: Barbara Gemmill (Herren)
Posted: 21 янв 11 - 02:55
Subject: response from Gretchen to Jonathan re monitoring protocol
Hi Jonathan,

How you sample will depend on what question you are trying to address and I'm not sure I'm clear about that.

If you are planning on running the study for 3 years and want to detect a change of 7% in the number of species or total abundance across all species of bees, you can definitely pick that amount of decline up with 75 sites (and probably fewer). You would want to sample sites in the 1st and 3rd year at a minimum. A design like this though is sensitive to the oddities of sampling. So, for example if year 1 was an extreme drought and year 3 was a normal year, you might detect an increase that was more representative of the weather than the underlying community changes. To compensate for the vagaries of weather, I suggested that a better way to sample would be to set up 3 "cohorts" of 25 sites. So, the 25 sites sampled in 2011 would get sampled again in 2013, the 25 sites sampled in 2012 would get sampled in 2014 and so on. This would expand beyond the scope of the UN funding but would lay the groundwork for an great national sampling program. You could even extend the time period so that each of these sites was sampled on a 5 year interval (e.g. the 2012 sites are sampled again in 2017....).

We used data from many different sites to estimate our CVs. I agree that for all but the most common individual bee species and especially rare species, we can't track in a 3 year time period. Their CVs are much higher than the CVs for species richness and abundance. However, you should be able to speak to species richness and abundance. As the sampling interval extends, the possibility of detecting declines in individual species becomes more and more possible. One way to think about the sampling is that if you set up say 100 sites over the next three years. You are laying the groundwork for future sampling in say 10 years that will have huge benefits.

One thing you can do to see how our assumptions about CVs fit with south africa would be to estimate the CVs from your 10 year study. You could estimate the cv of the number of species, total abundance, 5 most common species, or any other group you are interested in and see how they compare to what we found in panama, us, england and czech republic.

I haven't put my pans on sticks and still get a lot of bees. You might do a quick test and see if you get the same or different bees.

the protocol focuses on bees because of their importance as agricultural pollinators, as a scientist though, I see the by-catch as incredibly useful and interesting. I'd definitely try to do something with those groups also.

If I've missed anything, let me know. I'm happy to respond.

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