I'm sure this has been discussed before.
I don't think pruning is the right term in that it is too specific. I would rather have something like tree_maintenance/tree_management which could also be applied to elements other than single trees. Note that mainly you want to map trees which are tightly pollarded on a regular cycle. Coppicing is much more likely to be tagged on an individual forest compartment or panel not on individual trees; furthermore coppicing is not pruning it's much more extensive: the two terms tend to represent two ends of a continuum.
The other problem with a pollard is that you get multiple types of pollards:
- Regularly pollarded trees, like the ones you want to map.
- Irregularly pollarded trees, such as large street Lime or Plane trees, which will receive a rather different type of pollarding treatment perhaps every 40-50 years ago, mainly to reduce the spread of the tree.
- Pollards which were pollarded once early in their life. There is a rather fine Oak about 1 km from here which was pollarded about 1500, and not since. Similarly there are lapsed pollards from more recent times.
I'm not sure about the middle category, but both the other two are worth tagging. Type 3s are really a form of the tree structure which was determined by the original practice of pollarding, but they are clearly no longer managed that way. The Birmingham data had a form column. Also styles of management may be remarkably country specific.
Some remarks about particular types of trees:
- Orchard trees will in any actively managed orchard be pruned annually: in traditional orchards the technique will often be very particular to the region. Once recognised the Central Swiss style of fruit-tree pruning can be spotted even from the train even when the orchard has long since stopped being managed. I understand that in Ticino they have a rather different style. basically pruning=yes is a default for an actively managed orchard.
- Dehesa and other wood pasture will also be subject to a regular pruning cycle. I think 15-20 years for Holm Oaks, perhaps a bit less. I'd have to ask. The pruning is actually a harvest: much of the cut wood is used for fuel. Cork Oaks are more complicated again because cork will be harvested as well. I'm not sure if the cycles coincide, as pruning & losing the bark might be rather severe. Basic pruning style is to keep the crown open with 3-4 leaders at perhaps 45 degrees from bole. I don't know what percentage of wood might be removed, but perhaps 20-30% of branches. Again pruning is the default, if managed.
Summary: I think there are (at least) two things here: the tree form (espalier, pollard, lapsed pollard, etc) and the regular tree management/maintenance (if any). The latter will also apply to other elements: natural=wood, landuse=forest, landuse=orchard, wood pasture/wood meadow, etc. So I'd like to ensure we think about both together. SK53 (talk) 21:58, 14 June 2018 (UTC)
- Thanks, this is really insightful. So I think:
- tree_management=pollard could go to mean "an actively maintained pollard, or one that has been pollarded less then a generation ago"
- tree_management=lapsed_pollared; a tree that has ever been pollarded but cannot be pollarded again, or has not been pollarded for over a generation
- tree_management="some other word": a tree which has been severely pruned (usually city trees). I was hoping there would be an English word for that, but your use of "pollard" for this type makes me pessimistic
- As for "dehesa", it seems be more of a forest_management style, having different implications for different kinds of trees and other plants. A tag which I think we should have too (e.g. in Flanders we usually say we don't have natural=wood, but our landuse=forest are often managed by nature protection agencies - without the forest necessarily being nature reserves). I think I went with pruning=* instead of something like tree_management to steer clear of exactly this kind of confusion. Of course, an oak tree in a dehesa might have a specific form, and in that sense a tree_management value might make sense.
- As for a distinction between management cycle and tree form, in't the term "lapsed pollard" already a combination of the two? I would say that the tree_management tag implies both a form and a cycle, and that whenever the cycle doesn't fit the form (say, an abandoned orchard) only then would you need an extra tag to make clear that the cycle isn't what it should be.
- Joost schouppe (talk) 07:33, 15 June 2018 (UTC)