Comparing greenhouse and field biocrust cultivation methods in the Sonoran Desert.
Abstract
Developing methods to use biocrusts in restoration is becoming more important as land use and climate change impact the health and intactness of high-stress ecosystems. Methods of cultivation to maximize the production of biocrusts for use in restoration activities are necessary because salvage opportunities are limited. Our objective for this research was to determine an optimal method for scalable biocrust cultivation. We tested two Field and one Greenhouse cultivation methods. The Field cultivation methods had a base layer of weed cloth, soil and irrigation with either (1) shade cloth immediately over the surface (Quesadilla method) or (2) with shade cloth over a 1 m tall hoophouse (Hoophouse method). The Greenhouse method had nested basins with water wicking up to the soil surface and biocrust from below, with shade cloth attached to basins. We crossed these methods with the addition of native soil or sand and with and without a base of jute using salvaged biocrusts from the Sonoran Desert. All methods led to at least doubling biocrust cover in 11 weeks. The Greenhouse method led to the highest cover of cyanobacteria and mosses, whereas the field Quesadilla method and the addition of native soil in all cultivation methods led to higher abundance of lichens. There were interactions of cultivation method and soil type, with Greenhouse cultivation and native soil promoting the highest cyanobacteria cover and chlorophyll a. We measured exopolysaccharide sheaths (EPS) in native soil and all cultivation conditions, finding no differences for tightly bound sheath fractions, but higher quantities of the loosely bound EPS in the Greenhouse. We also quantified native and non-native plants in cultivation, finding few plants in Greenhouse cultivation, but high abundance in both Field methods, and particularly with native soil and without jute for native plants. Practical implication: Together, these results demonstrate that all three cultivation methods are successful for bulking biocrust materials for restoration, and preference should be given to the method that is the easiest and most accessible for practitioners.