Dear all,
I want to identify tree water sources in selected trees over an entire growing season, preferably monitoring the same trees. As I will not have access to suberized branches in most cases, I'm considering to take multiple cores from a single trunk (up to 5 times). Unfortunately, this method is rather intrusive, and hence I'd like to use the smallest borer diameter possible to allow extraction (via cryogenic vacuum distillation) of an adequate amount of sap water, while keeping damage at a minimum.
I'd appreciate any comments on or experience with repeated trunk sampling (effects on sap flow, mortality) and which borer and coring depths can lead to adequate results.
Thanks in advance.
Kindest regards,
Alex
you might want to e-mail some specific individuals in labs doing isotopes, but I think it is often best to use a 10 mm diameter corer. However, I am sure a 5 mm corer will be fine
I agree with Rob, bigger would certainly be better. I assisted Jim Ehleringer's (U Utah) lab once with some similar sampling at our research sites in W Oregon. They used the Haglof 12mm corers and they worked wonderfully; cut easy and produced a nice sample. This volume of sample was sufficient for their work, which was specific to isotope levels in the individual annual wood increments. Since you are interested in water, the quantity of water would be similar to wood (by mass, green wood might be 40-60% water, depending on species and time of year). However, you expressed concerns about repeated sampling... if your trees are large, and sample numbers relatively few (perhaps monthly), then there should be no issue with repeated samples using a large corer. But if the trees are small and samples many, you may want to go small. It really depends on how much water you need for a proper sample.
Another option might be very small drilled holes with a vacuum pump and a water trap (a sample jar where the lid would have one hose in from the tree and one hose out to a vacuum pump) I have no idea if it would work... it'd be worth trying, but you could use very small holes. You might have to seal a tube around the drill hole to create enough negative pressure to fight the negative water potentials.... In temperate climates, in the months leading up to bud break, there would be positive water pressure cause by active root pumping. During this time, water will just drip out... think of tapping trees for maple syrup! You'd could easily end up with multiple litters of sap per day. Each hole will effectively seal itself in a matter of weeks, but perhaps strong negative pressure would still yield water from the sap stream.
Anyway, have fun and good luck! Sounds like you'd have a methods paper too if you can figure it out.
Thank you all for your input - much appreciated. I've decided on getting a large diameter (12 mm). I will hopefully be able to test short-term effects of repeated coring before starting the field season.
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