Rapid ex situ culture of N-fixing soil lichens and biocrusts is enhanced by complementarity

Background and aims: Rehabilitation of biological soil crusts (biocrusts) in degraded drylands may facilitate ecosystem recovery. In order to rehabilitate biocrusts, ex situ culture methods for biocrust organisms must be optimized so that biocrusts may be grown in sufficient quantities to be reintroduced into degraded areas. Our goal was to improve these culture methods. Methods: We cultured six biocrust lichens and mosses, alone or in combinations, in a full-factorial greenhouse experiment, also manipulating water quality and hydration schedule. Results: All cultures produced a multi-species biocrust. The lichen Collema grew fastest, increasing by up to 238 % over 5 months. The mosses Syntrichia caninervis, and Syntrichia ruralis also grew, whereas other lichen species failed to maintain growth. Species combinations featuring Collema and both mosses exhibited greater growth rates for all species, compared to monocultures. All species were either unaffected by water quality, or performed better when irrigated with purer water. Several species responded favorably to shorter dry periods. Conclusions: The lichen Collema is a promising restoration material because of its culturability, and its N-fixation ability. Initial species composition of a culture will likely affect its success, and complementarity among species may be exploitable in order to produce inoculum faster.