I am against attacking hazel with herbicides. The hazel represents a resource and the best plan to control it is to exploit it as a resource. Currently we import a lot of hazel from England for such projects as reconstruction of prehistoric settlements etc. Why not harvest our own supply? I suggest 2 other possibilities: chipped it becomes a carbon neutral fuel for CHP or other energy efficient plants, and larger stuff can be used to make charcoal for BBQs should we ever have dry summer days again. maybe there are smarter biorefinery uses for the hazel. This will create employment and add to the Burren as a living landscape [and possibly save a few carbon emissions]. Hazel scrub is presumably a seral stage on the way to forest. It would be nice to create a yew woodland, or a oak woodland.. can the hazel act as a intermediary stage in helping this along? Such woodlands will greatly extend the biodiversity in currently somewhat barren parts of the Burren. I am in favour of active intervention to help the process along by planting/seeding hazel scrub with target species.
I am posting this blog on behalf of Dr David bullock.
A majority of the limestone and chalk grasslands in north-west Europe are subject to scrub invasion. The Burren is far from unique. In France instead of hazel it might be juniper; in the Cheddar Gorge (Somerset, UK), it is ash, yew, whitebeams, Clematis, hawthorn on the deeper soils, ivy and hazel. We know for Cheddar something of what happened: sheep grazing (probably heavy and certainly in the summer) ceased around 1930 (depression time), and rabbit grazing pressure crashed around 1954 due to mxyomatosis.
Feral and free ranging goats, feral sheep and a few cows at low density since 1990 have done little to stop the establishment and spread of the non selected trees such as ash, hazel and hawthorn. Conceptually it is easy to see why: set yourself out a grid of 10 X 10 square of grassland each of which has a unique number pair (1,9; 3,2 etc). Using random number pairs black out those that are selected. These are where at random the woodmouse has cached a nut, or a blackbird has pooped out a yew seed, or the wind has blown an ash key. I appreciate that the seeds are not deposited at random so the model is hugely oversimplified, but let us say they germinate and the resultant trees/scrub covers one square, making an effective barrier to movement of the cows.
Plot on the x axis number of squares blacked out - where a scrub/tree species has established, and y the % of available grassland that can be grazed by cows that are using the largest area of grassland remaining. By 30 % scrub cover, the cows have a greatly reduced amount of grassland to graze (much less than 70 % grassland because of the smaller areas that are blocked off by scrub - these will become rank and species poor). Once you have got to 30 % scrub tree cover or thereabouts, the quality of the grassland may be very poor, it may cost a great deal to restore it to its former high species richness, and there is a good argument for it letting it go to woodland.
So the key would seem to be to target the accessible grassland patches and remove (chemically, manually, by large herbivores) aggressively any incipient scrub and certainly never let the scrub cover get to 30 % after which you might as well let it go to woodland. For the grasslands with > 30 % scrub treating them as a biofuel source as Richard suggests has merit.
Free ranging large herbivores at normal stocking densities (say up to 1 LSU per ha) would, in my view, be ineffectual at stopping the scrub invasion. If anyone doubts this, tell us of a limestone grassland site where they have been effective. The only way they can be is when fenced in at high density - this incurs high husbandry costs and the best browsing animals (goats) always escape or die if they do not want to be there. In the 6000 ha reclaimed polder of Oostvarsdesplassen (Netherlands) feral cattle, feral horses, red deer at a combined stocking rate of 2 LSU per ha and grey lag geese just about manage to keep scrub at bay in what is a hugely productive site. There are welfare issues with this high stocking rate. Many cattle die of starvation in some years.
Still not clear why hazel is dominant unless it is a combination of increasingly favourable climate, good seed dispersal (wood mouse) and goats eating all the other stuff.
I agree whole-heartedly with the potential for making more practical use of hazel. I don't think it will solve the problem, but it would help, and it would make so much sense to utilise such a prolific natural resource. It is completely under-utilised now in Ireland, and particularly in the Burren, through a loss of associated farming and harvesting traditions over the years. Burren farming families are striving to find ways to supplement their incomes, and schemes such as the Burren Beef and Lamb Producers Group are helping to give added value to products coming from the region. I have felt for a while that leadership in the area of utilising hazel has been missing howeve. Maybe we will need to import eeither the personnel(or the knowledge) in order to give guidance and advice on this front?
In relation to the other point.... I'm not so sure that hazel is necessarily always a seral stage on the way to forest. There are many limiting factors that can mean 'forest' is never attained. Also, I would be very very hesitant with 'planting-in' anything! We have enough troubles deciding what to do with the landscape, plants and animals that are already there - why complicate it, or tamper with it?
I am against attacking hazel with herbicides. The hazel represents a resource and the best plan to control it is to exploit it as a resource. Currently we import a lot of hazel from England for such projects as reconstruction of prehistoric settlements etc. Why not harvest our own supply? I suggest 2 other possibilities: chipped it becomes a carbon neutral fuel for CHP or other energy efficient plants, and larger stuff can be used to make charcoal for BBQs should we ever have dry summer days again. maybe there are smarter biorefinery uses for the hazel. This will create employment and add to the Burren as a living landscape [and possibly save a few carbon emissions].
ReplyDeleteHazel scrub is presumably a seral stage on the way to forest. It would be nice to create a yew woodland, or a oak woodland.. can the hazel act as a intermediary stage in helping this along? Such woodlands will greatly extend the biodiversity in currently somewhat barren parts of the Burren. I am in favour of active intervention to help the process along by planting/seeding hazel scrub with target species.
I am posting this blog on behalf of Dr David bullock.
ReplyDeleteA majority of the limestone and chalk grasslands in north-west Europe are subject to scrub invasion. The Burren is far from unique. In France instead of hazel it might be juniper; in the Cheddar Gorge (Somerset, UK), it is ash, yew, whitebeams, Clematis, hawthorn on the deeper soils, ivy and hazel. We know for Cheddar something of what happened: sheep grazing (probably heavy and certainly in the summer) ceased around 1930 (depression time), and rabbit grazing pressure crashed around 1954 due to mxyomatosis.
Feral and free ranging goats, feral sheep and a few cows at low density since 1990 have done little to stop the establishment and spread of the non selected trees such as ash, hazel and hawthorn. Conceptually it is easy to see why: set yourself out a grid of 10 X 10 square of grassland each of which has a unique number pair (1,9; 3,2 etc). Using random number pairs black out those that are selected. These are where at random the woodmouse has cached a nut, or a blackbird has pooped out a yew seed, or the wind has blown an ash key. I appreciate that the seeds are not deposited at random so the model is hugely oversimplified, but let us say they germinate and the resultant trees/scrub covers one square, making an effective barrier to movement of the cows.
Plot on the x axis number of squares blacked out - where a scrub/tree species has established, and y the % of available grassland that can be grazed by cows that are using the largest area of grassland remaining. By 30 % scrub cover, the cows have a greatly reduced amount of grassland to graze (much less than 70 % grassland because of the smaller areas that are blocked off by scrub - these will become rank and species poor). Once you have got to 30 % scrub tree cover or thereabouts, the quality of the grassland may be very poor, it may cost a great deal to restore it to its former high species richness, and there is a good argument for it letting it go to woodland.
So the key would seem to be to target the accessible grassland patches and remove (chemically, manually, by large herbivores) aggressively any incipient scrub and certainly never let the scrub cover get to 30 % after which you might as well let it go to woodland. For the grasslands with > 30 % scrub treating them as a biofuel source as Richard suggests has merit.
Free ranging large herbivores at normal stocking densities (say up to 1 LSU per ha) would, in my view, be ineffectual at stopping the scrub invasion. If anyone doubts this, tell us of a limestone grassland site where they have been effective. The only way they can be is when fenced in at high density - this incurs high husbandry costs and the best browsing animals (goats) always escape or die if they do not want to be there. In the 6000 ha reclaimed polder of Oostvarsdesplassen (Netherlands) feral cattle, feral horses, red deer at a combined stocking rate of 2 LSU per ha and grey lag geese just about manage to keep scrub at bay in what is a hugely productive site. There are welfare issues with this high stocking rate. Many cattle die of starvation in some years.
Still not clear why hazel is dominant unless it is a combination of increasingly favourable climate, good seed dispersal (wood mouse) and goats eating all the other stuff.
I agree whole-heartedly with the potential for making more practical use of hazel. I don't think it will solve the problem, but it would help, and it would make so much sense to utilise such a prolific natural resource. It is completely under-utilised now in Ireland, and particularly in the Burren, through a loss of associated farming and harvesting traditions over the years. Burren farming families are striving to find ways to supplement their incomes, and schemes such as the Burren Beef and Lamb Producers Group are helping to give added value to products coming from the region. I have felt for a while that leadership in the area of utilising hazel has been missing howeve. Maybe we will need to import eeither the personnel(or the knowledge) in order to give guidance and advice on this front?
ReplyDeleteIn relation to the other point.... I'm not so sure that hazel is necessarily always a seral stage on the way to forest. There are many limiting factors that can mean 'forest' is never attained. Also, I would be very very hesitant with 'planting-in' anything! We have enough troubles deciding what to do with the landscape, plants and animals that are already there - why complicate it, or tamper with it?