Thanks for posting this. There's quite a lot of stuff in there, but I will try to work through some of the issues.
Regarding the proposed neutral grassland changes by Graham Hawker, I have seen various versions of this idea originating from different projects and I understand (as a surveyor), how frustrating the perceived lack of certain codes can appear. A year or more ago I was consulted on how the next version of IHS should deal with this situation. As far as I am aware version 3 is more or less finalised, but I cannot comment on how far SERC has got with releasing it. Perhaps Tony Price will be able to shed some light.
The changes for grassland presented in your document violate a number of the basic principles of IHS, I will try to explain how.
Firstly the existing GNZ code is what we call an inverse code. A fundamental principle of IHS is that at any given level of the hierarchy the codes should exhaustively cover all of the possibilities encompassed by the parent. The role of the inverse code (or Z-code) is to stand for all the habitats which are not covered by the other items at the same level. That is to say that GNZ represents all neutral grasslands which are neither Lowland meadows, nor Upland hay meadow (two well defined habitats representing a very small range of NVC communities). As such GNZ is a ragbag of assorted grassland types on circumneutral, mesotrophic soils which remain semi-natural enough not to be called improved. IHS does not allow for inverse categories to be subdivided in this way (e.g. GNZ1, GNZ2 etc.) for this reason and the following.
Clearly the three proposed sub-divisions (Wet, Rough and Inundation grassland) do not exhaust all the possibilities embodied by GNZ. What about dry "good semi-improved", but well managed grass? So you would need to have another category GNZZ Other other neutral grassland (which is daft) and given time I could come up with twenty other subdivisions all of which would be useful to someone.
Also the three categories (Wet, Rough and Inundation) are not mutually exclusive, how would you code wet rough grassland? Remember you can only use one habitat code.
Next the three categories also include the possibility of overlap with the priority grassland types. Some lowland meadows (especially GN11) are wet. Unmanaged for a couple of years they become rough (but remain priority habitat).
A related issue is how you deal with wet calcareous grassland (All CG types are priority grassland), or wet acid grassland?
I recognise the attempt made by the definitions supplied to justify what has been done, but they do not work.
Our solution to this problem was to add this kind of item as secondary codes rather than as primary habitat codes. I don't have access to the final structure we decided on for version 3 right now, but I have an early draft in which we added a new category section at the start of the formation codes as follows
Grassland descriptors (GD)
GD1 Wet grassland
GD2 Dry grassland
GD3 Neutral grassland with calcicoles.
Thus your GNZ2 Wet grassland becomes GNZ.GD1 but you can also have GN11.GD1 (a wet MG4 meadow). And so on.
We also discussed adding a Rough grassland code in the same series, but didn't think it was worth it. Rough grassland is to my mind just unmanaged grassland, thus GNZ.GM4 is a good description of MG1 in most circumstances. Remember this is not a community classification like NVC. You could also have GAZ.GM4 rough acid grassland etc.
Let's look at another of your suggestions GNZ12 Calcareous rough grassland as a subcategory of Neutral grassland? I laughed when I first read this, are we talking about neutral grassland or calcareous grassland here? If it is truly calcareous it belongs in GC1 and is priority. But I see from the definition that what we are talking about is MG1d a community with which Wiltshire is very well supplied. This is not a form of calcareous grassland, it is mesotrophic as demonstrated by the dominance of coarse grasses such as Arrhenatherum and Dactylis. It may include remnant calcicoles but for the most part these are deep-rooted taxa such as Pastinaca, Daucus and Tragopogon or hardier types with catholic tastes such as Lotus, or anthill specialists like Helianthemum, Thymus etc surviving on disturbed patches. Over time this community becomes more mesotrophic and eventually loses almost all calcicoles. How much more elegant is GNZ.GD3.GM4 Unmanaged neutral grassland with calcicoles?
Inundation grassland could be added as a code in this section if desired but I would think it is covered by EM22 Inundation vegetation which has been in IHS from its inception.
As for Recently reseeded meadow communities, that could cover a huge range of community types and degrees, it is certainly not a single well defined habitat. There is massive overlap between this and several of the other categories. My version of IHS has this instead, we have subdivided the grassland land-use code GL2 Non-amenity grassland as follows.
GL2 Non-amenity grassland
GL21 Permanent agricultural grassland
GL211 Arable reversion grassland
GL2111 Species-rich conservation grassland
GL211Z Other arable reversion grassland
GL21Z Other permanent agricultural grassland
GL2Z Other grassland use
So your GNZ4 could be GNZ.GL211, but you could also have GN1.GL2111 (or GC1.GL111) to describe a maturing successful reversion. I agree that this does not cover re-diversified reseeded grassland very well, but it would only require a tweak of the wording to fix that, perhaps Re-seeded or reverted grassland would suffice as an alternative.
Now the improved grassland. Firstly a technical point, everywhere else in IHS the children of (e.g.) GN0 are GN1, GN2...GNZ not GN01 GN02 etc. . So GI01 is just plain wrong. No matter... Any subdivision is incomplete without a Z-code, so you would need to add one. Ask yourself a couple of questions though.
Dou you really need to subdivide GI0? If so would NVC not be a better tool?
Are your surveyors capable of making the distinction between Typical permanent pasture and Poor semi-improved reliably? Probably not because there is a continuous spectrum of variation in improved grassland and while we may like to think we can tell the difference in the field, I question whether many can actually decide where one ends and the other begins without resorting to NVC. But give them the option and it is human nature to try. Let