Distribution and nodulation of spontaneous legume species in grasslands and shrublands in Mediterranean Lebanon

In Lebanon, a country known for its biodiversity and plant richness, many threats including quarries endanger its natural habitats and ecosystems. With the objective of finding the most suitable legume-rhizobia associations for revegetation trials, we surveyed grasslands and shrublands in an altitudinal transect up to 1302 m in Mediterranean subhumid and humid regions. For comparison, two abandoned quarries on hard limestone were studied as well. Based on a number of criteria, the level of degradation of each site was estimated as: high, medium, or low. Sites submitted to a high degradation pressure presented a smaller number of species and lower ground coverage. The emphasis was put on the legume species encountered on these sites: 52 species were identified and separated according to their frequency. Of these, 18 target species were studied in the second season in terms of their habitat, frequency, and ground coverage. Ten common legume species were found regardless of the level of degradation. As the level of degradation increased, the number of annual legume species significantly decreased as well as their coverage coefficient, to the contrary of perennials. Spontaneous nodulation was encountered in individuals belonging to the genera Alhagi, Astragalus, Bituminaria, Calicotome, Cicer, Hippocrepis, Hymenocarpos, Lathyrus, Lotus, Lupinus, Medicago, Melilotus, Onobrychis, Ononis, Physanthyllis, Scorpiurus, Securigera, Spartium, Trifolium, and Vicia. The nodulation of Medicago coronata was reported for the first time. Individuals were better nodulated in medium-degraded sites as compared to high-degraded. Inoculated perennial (Calicotome, Spartium, Bituminaria) and annual legumes (Hymenocarpos, Onobrychis, Trifolium purpureum, T. campestre, T. tomentosum, Securigera, Physanthyllis, and Medicago polymorpha, M. minima) could be recommended as part of plant associations in revegetation projects