THE ROLE OF MYCORRHIZAE, SITE PREPARATION, AND ORGANIC AMENDMENT IN THE AFFORESTATION OF A SEMIARID MEDITERRANEAN SITE WITH PINUS-HALEPENSIS

A factorial field experiment was conducted in a degraded semi-arid sit e of southeastern Spain to test the effectiveness of mycorrhization an d several soil preparation techniques on afforestation with Pinus hale pensis. The mycorrhizal treatments were nursery inoculation with Pisol ithus arhizus and forest soil addition to the planting holes. The soil preparation treatments were terracing (mechanical and manual) and the addition of an organic amendment (urban solid refuse). One year after planting, the study revealed significant differences in mycorrhizatio n levels, frequency of mycorrhizal species, fine root production and g rowth between the inoculated seedlings and the noninoculated controls. Inoculation with P. arhizus gave better pine growth and mycorrhizatio n rates than the addition of forest soil. Both mycorrhization treatmen ts were particularly effective in combination with mechanical terracin g, The organic amendment had no apparent negative influence on the myc orrhization level of the seedlings and significantly improved pine gro wth, The beneficial effects of mycorrhization treatments on P. halepen sis growth persisted 2 yr after pi anti ng, The increase in growth of the seedlings due to the treatments could be attributed to the change in soil conditions (increased fertility and soil aeration) and probabl y to a mycorrhization effect on water relations, although it has not b een clearly demonstrated.