Chickens in the woods

Would there be long-term issues with having chicken production in the woods? I'm thinking of the soil ecology and the health of the trees with the added nitrogen via chicken defecation.

Right now there's a place near me that stocks 600 chickens on 7,000 square meters (22,300 sq feet) of chestnut woods, 600 meters (2000 feet) above sea level.
That's 11,6 sq. meters (38 sq feet) per chicken - which is in line with organic production here - but chickens don't stock themselves that thick in nature, and they don't fence themselves in either.

So, I'm sort of wondering how that plays out in the soil and for the trees.

My first impression is that it is a million times better than factory egg production.
http://bit.ly/1dFppd1
William

http://www.esa.org/tiee/vol/v4/issues/data_sets/nitrogen_additions/overview.html

After 13 years of continuous N fertilization, soil respiration in the high N plots was suppressed by 40% in both stands. Reductions in soil respiration are concomitant with reductions in microbial biomass, due primarily to a significant reduction in the fungal component of the microbial community (Frey et al., 2004).

Chickens work great in bamboo forests. They are naturally attracted to bamboo groves (they are native to SE Asia) and the fast-growing bamboo has no problem soaking up the nitrogen load from the chicken manure. Also the close spaced bamboo culms in the grove make it easy for the chickens to escape avian and large ground predators.