## 1 Introduction  
Ancient and modern cultural heritage structures deteriorate because of variable interactions between physicochemical and biological factors. Microbial activities and their effects combined with physicochemical attack are considered central to the deterioration of cultural heritage [1]. Structural damage caused by microorganisms is defined as biodeterioration. In the past few decades, biodeterioration processes in cultural heritage structures and underlying biochemical mechanisms have been elucidated [2; 3]. Many microbial species are involved in biodeterioration processes [4]. The colonization and deterioration processes on matrices are usually induced by heterotrophic microorganisms and photoautotrophic microorganisms, including bacteria, cyanobacteria, algae, fungi, and mosses, the complexes formed by which are usually named biological soil crusts (BSCs) [5; 6]. Biomass-rich biofilms formed by photoautotrophic organisms provide good nutritional bases for subsequent heterotrophic microbial colonization [7]. Chemoorganotrophic microorganisms are deeply involved in biochemical degradation processes, and their secretions, such as organic acids and enzymes, dissolve mineral components in matrices and precipitate salts [8]. Moreover, filamentous fungi and actinomycetes can cause biophysical damage to the matrices by expanding their hyphae [9]. Biodeterioration processes caused by various microorganisms reduce the strength and weights of construction materials, affecting the structural integrity and aesthetic appeal of the cultural heritage structures [10]. However,there is little information about the biodeterioration of lime concrete materials, especially in the early architecture of China. Microbial colonization is associated with the different actions of environmental factors and the physicochemical characteristics of construction materials [11]. Environmental factors, such as light intensity, temperature, and relative humidity, contribute to physical and biophysical damages [12]. [PERSON] et al. showed that reduction in rainfall and humidity decrease the biodeterioration of Roman monuments, demonstrating that water availability is the main limiting factor for the development of microbial populations, such as cyanobacteria, algae, and lichens [13]. In addition, physicochemical properties of construction materials, including compressive strength, water content, porosity, surface roughness, and available nutrients [14], are interrelated and affect the susceptibility of a surface to microbial colonization. Building materials with rough surfaces and high porosity provide colonization sites and favorable habitats for microorganisms by retaining water and depositing organic compounds on their surfaces. Owing to metabolic variability among microorganisms (e.g., heterotrophic microorganisms rely on organic compounds to maintain growth, whereas photoautotrophic microorganisms use CO\({}_{2}\) as a carbon source and light and minerals as energy sources). The mineral and organic compound composition of building materials are related to the community composition of microorganisms [15]. Nonetheless, the effects of environmental factors on BSCs formation in lime concrete materials are not elucidated. The establishment of preventive conservation strategies for cultural heritage requires a detailed description of the impact factors and mechanisms of biodeterioration, but a lack of knowledge in regard to modern concrete cultural heritage still remains. Concrete may deteriorate due to physicochemical processes, such as freeze-thaw attack, reinforcement corrosion, and sulfate attack, which reduce the strength and weight and enhance the bioreceptivity of surfaces to severe biodeterioration [16; 17]. Lime concrete is a concrete consisting of sand, lime, and gravel and had been widely used before it was replaced by Portland cement [18; 19].