Foundations of the cover crop technique and potential use in afforestation

Introduction In many circumstances in afforestation, by tree plantation or by direct tree seeding, the quick development of very competitive herbaceous and shrubby species can compromise tree establishment (Balandier et al. 2006). At present, this vegetation is often controlled by chemical and mechanical operations, whereas they are criticized from environmental points of view; some alternatives are under study (Willoughby et al. 2009). The cover crop technique (or cover plant), i.e. sowing in place of the spontaneous competitive vegetation (mainly perennial grasses) a cover plant mixture assumed to be less competitive, is an example of potential ecological engineering (Balandier et al., 2009). In addition with the control of potential weeds and reduction of competition for resources, the cover plants are thought to offer protection against frost and scorching temperatures to the young trees, or to avoid the water run-off encountered on bare soil.