Tuesday, 26 April 2011

Forests

One interesting idea to come from Fairlie's 'Meat, A Benign Extravagence' is the that of 'climax vegetation' being nothing of the sort.

Let's cut to the chase here. When you think of 'optimal' in terms of vegetation, you think of trees....lots of them. I mean trees are great, right? Trees are 'natural' and the land without man would be covered in trees, right?  Trees are 'climax vegetation', right?

Well not according to Frans Vera in an idea he develops in 'Wilderness in Europe: What really goes on between the trees and the beasts':
  • "That the wilderness of the European lowlands once was one dense, endless forest is a myth, biologist en ecologist Frans Vera pointed out in his bestselling "Grazing Ecology and Forest History" (2000). We should rather think of scrubs, solitary trees and groves, alternating with open grassland. This half open, park-like landscape was created by the grazing and browsing of large herbivores such as tarpan, European bison and red deer. Nature managers wanting to restore some of the natural landscape, should take this original park-like character into account."
Quoting Vera, Fairlie writes:
  • "In an area of grassland, grazed by herbivores, thorny shrubs which herbivores shun will begin to appear,  Light loving pioneer species of tree, particularly oak, hazel, and wild fruit trees, whose seedlings get eaten when they appear in open grass, grow safely in the protection of this scrub.

    When the light loving tress become mature, they create a grove with a canopy which is too dark for their own seedlings, and so the seedlings of species such as beech, lime and elm are at an advantage.  Eventually the shade loving trees dominate the oaks and hazels, killing them off in the centre of the grove."
The crucial point is that when a tree dies in the grove, it is still too shady for thorny bushes to grow, but the gaps are immediately colonized by grasses.  These grasses attract herbivores who graze on the grass and trample and eat beech and lime seedlings which maintains the clearing.  The trees around the edge of the clearing are then susceptible to windblow and so a donut effect takes place where this clearing of grassland spreads outwards.  Once the central clearing is sufficiently large, it can be recolonized by thorny bushes and the cycle repeats.

The crucial point here is that of the wider role that grassland, GRAZED grassland, has in a sustainable cycle of crop rotation.

There is something pleasingly familiar about this pulsate, ever-adapting, cyclical model.  There is NO climax to steady state.  There IS dynamic, information-rich feedback.

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