Innovative biotechnological strategies to improve tree drought tolerance and microbial diversity for forest restoration purposes: the application of plant associative microorganisms and nature-based materials

Climate projections indicate higher precipitation variability along this century with more frequent drought extremes, which would have strong influence on forest biodiversity due to impacts on ecosystem functioning, tree ecophysiology and microbial communities. Forest restoration with native trees has been considered an effective strategy of climate change mitigation, but its success is hindered by the high mortality of tree seedlings in the field and the difficulty in restoring native soil microbiota, which are amplified by drought events. Thus, it is of great interest to improve seedling production practices in nurseries, with the induction of mechanisms which increase drought tolerance. In this study, we aim at evaluating simultaneously the responses of trees and associated soil microbiota to drought stress in three different forest types (Brazilian Seasonal Semideciduous Atlantic Forest, French Mediterranean Oak Forest, and German Mesic Temperate Forest), allowing to search for unifying patterns among geographically distant sites, across gradients, and by the use of experimental treatments. Further, we will test the application of different nature-based solutions as innovative strategies for improving tree seedling production and soil microbiome functioning/structuring. Associative microorganisms from tree species of the three ecosystems will be isolated and characterized, to obtain beneficial microbial strains that can be used as bioinputs for seedling production. Moreover, biodegradable and biocompatible nano/micro particles and composite materials produced from natural sources will be used as carrier systems for plant growth regulators and microbial living cells, to improve their delivery to the plants. The efficiency of these nature-based solutions in inducing the tolerance of tree seedlings to drought stress and the corresponding effects on soil microbiota diversity and functioning will be evaluated using different approaches, including greenhouse cultivation, nursery seedling production, and field trials. The economical balance and social acceptance of the proposed solutions will be evaluated in order to check their cost-effectiveness, with the engagement of stakeholders (as nursery-owners, farmers, conservation unit managers, and local authorities) in the course of the project. Thus, in addition to contribute to the basic knowledge of the mechanisms of drought response of trees and soil microbiota, this proposal strongly seeks applicability for improving the success of reforestation programs, with important environmental, economic and social impacts. The success of the project is based on an international multidisciplinary consortium (plant ecophysiologists, soil and rhizosphere microbiologists, microbial ecologists, chemists, engineers, economists) that will collaborate on a range of nature-based solutions.