"Vuelo" must mean "vuelo forestal" here. The term "forest cover" was proposed in previous questions and I think it's probably the best option. It means all the trees and derived products on a piece of land, as opposed to the land itself, specifically in reference to their commercial value. Here's a definition:

"El vuelo forestal; es decir, el conjunto de árboles, la madera y subproductos forestales de una plantación comercial es susceptible de entregarse como garantía para obtener recursos financieros del sistema bancario o el mercado de capitales, con independencia de la tierra en la que están plantados."
http://www.revista-mm.com/ediciones/rev68/forestal_vuelo.pdf

Here are a couple of previous questions:

http://www.proz.com/kudoz/spanish_to_english/forestry_wood_t...

http://esl.proz.com/kudoz/spanish_to_english/forestry_wood_t...

Here's a quotation from a source cited by Taña Dalglish in the latter:

"One of the challenges to the proposal is the continuation of the concept of "vuelo forestal", or forest cover, borrowed from Bolivian legislation, which considers the forest itself -- not the land -- as a good that can serve as collateral in financial or credit operations."
http://www.galdu.org/web/calahus.php?odas=1543&giella1

I wonder whether it might be appropriate to add "resources", to make it clear that this is referring the trees specifically as a commercial resource. But in context perhaps "forest cover" alone would be sufficient.