Trees should be representative of the range of basal areas present in the study area. Sampling will be made monthly, weekly or at a time interval between the two, e.g. every two or three weeks, depending mainly on climate or method used. It is recommended that samples are taken so that correct monthly values can be derived. A variety of different types of equipment exist for measuring stemflow. The majority are based on a spiral collector wrapped around the stem of the tree.
Silicone is a good but expensive material for the purpose.
Under no circumstances should the bark be damaged. Great care should be taken to ensure that the bark remains intact, otherwise sap may seep out, contaminating the stemflow. The collecting bottles must be of sufficient capacity to cope with large quantities of stemflow. For example, in beech, two 60 l containers may be necessary. Alternatively, sampling can be automated and flow measured using a tipping-bucket mechanism.