Optimizing survival and growth of inoculated biocrust-forming cyanobacteria through native plant-based habitat amelioration

Low restoration success in degraded drylands has promoted research efforts towards recovery of pioneer components of these ecosystems such as biocrusts. Biocrusts can stabilize soils and improve nutrient cycling to assist vegetation establishment, but their natural recovery following a disturbance may be very slow. Soil inoculation with biocrust-forming components such as cyanobacteria is widely spread to foster biocrust formation. However, the growth of induced biocrust can be constrained under field conditions due to the harsh environmental conditions in drylands. Thus, strategies to reduce abiotic stresses have to be explored to improve cyanobacteria survival and growth. In this study, we performed an outdoor experiment to analyze the effect of plant-based ameliorating strategies in combination with cyanobacteria inoculum on biocrust formation and improvement of degraded arid soil properties. These ameliorants consisted of a plant mesh made of Macrochloa tenacissima and a Plantago ovata-based stabilizer. Application of ameliorating treatments improved cyanobacteria growth (higher chlorophyll a content, lower albedo and higher NDVI) compared to the application of cyanobacteria inoculum alone. Inoculated soils showed higher aggregate stability than non-inoculated ones, but the highest soil stability was found in the soils treated with P. ovata and was also significantly increased in the soils covered by the M. tenacissima mesh compared to uncovered soils. Both the mesh and the P. ovata stabilizer increased soil organic carbon content by up to 10% and 172%, respectively, compared to soils without habitat amelioration. Microbial community composition was similar between control and inoculated soils and between the mesh covered and uncovered soils, indicating that neither cyanobacteria inoculation nor the vegetal mesh had negative effects on the native soil community. In contrast, the soil with the P. ovata stabilizer alone displayed a different composition, with up to 95% of the bacteria's relative abundance represented by Firmicutes. This effect needs to be considered when applying this stabilizer to prevent a potential alteration of the indigenous soil microbial community. This study indicates the viability of using plant-based ameliorating strategies to optimize the establishment and growth of cyanobacteria inoculum and maximize their effects on soil properties, thus contributing to advancing in the application of nature-based solutions for the restoration of degraded dryland ecosystems.

This work was supported by the projects TED2021-132332B-C21 and BIOPLANTFLUX (CNS2023-144749), funded by the Spanish Ministry of Science and Innovation- State Research Agency MCIN/AEI/10.13039/501100011033 and European Union funds "NextGenerationEU"/PRTR", the project CRUST R-Forze (PID2021-127631NA-I00) and REBIOARID (RTI2018-101921-B-I00) funded by FEDER/Spanish Ministry of Science and Innovation- State Research Agency, the project P_FORT_GRUPOS_2023/20 funded by Research and Transfer Plan of the University of Almeria 2023 and EU funds of 2021-2027 FEDER Operational Program of the Regional Government of Andalusia, and the EMERGIA program (EMC21_00424), funded by the Council of Economic Transformation, Industry, Knowledge and Universities of the Andalusian regional government. A.A-M. was funded by the FPI predoctoral fellowship from the Spanish Ministry of Science and Innovation (PRE2019-090869). L.M. was funded by the FPI predoctoral fellowship from the Junta de Andalucía (PREDOC_01461). M.M-R was funded from the Spanish Ministry of Science and Innovation (RYC2020-029255-I, TED2021-132332A-C22 and PID2021-123097OA-I00).

Peer reviewed