## 1 Introduction  
Biochar is a product of pyrolysis, the thermal degradation of organic materials in the absence of air. The residual solid of the pyrolysis process is distinguished from charcoal by its generally high carbon content and use in soil management as a soil amendment [1]. Among its many reported benefits to soil fertility, biochar can increase soil physical and chemical properties, which encourages soil microbial community activities [2] and soil health [3]. The improvements in soil health through biochar in agricultural systems typically translate into profits and benefits to plant growth/productivity and food quality [4, 5]. The chemical compositions and physical structures of biochar are determined by several factors, including feedstock, pyrolysis system, and pyrolysis temperature [6, 7]. These factors also play essential roles in determining how different biochar types impact soil properties and functions and microbial communities [6]. Soil microbial communities are a crucial biological factor and a potential indicator of soil health, affecting nutrient cycles and plant growth, and the cycling of soil organic matter (SOM) [8, 9, 10]. However, establishing universal methods of evaluating biochar's impacts on soil properties and microbial community functions are ongoing. Several studies have reported that the pyrolyzed soil additive may variably affect the multitude of microbial assemblages that comprise soil communities. [PERSON] et al. [11] found that biochar's addition influences microbial dynamics through changes in soil physical structure. Other studies suggest that biochar affects soil chemistry changes such as pH or cation exchange capacity (CEC) [12; 13] altering the community structure. [PERSON] et al. [14] reported that the labile C contained in biochar might serve as a substrate for the growth of specific microbial communities and stimulate their activity. Additionally, biochar's physically porous nature provides a micro-environment for less disturbed soil microbial community structural formation and protection from predation [15]. Studies using molecular methods of evaluation have shown that biochar indirectly or directly causes soil microbial group changes. Despite the growing popularity of next-generation sequencing methods, which allow for detailed analysis of soil microbial communities, the determination of soil organisms' fatty acid patterns is still one of the most commonly used methods for testing microbial biomass and community structures [16]. Ester-linked fatty acid methyl ester (EL-FAME) profiling provides a rapid, inexpensive, reproducible, and reliable approach to characterize the existing microbial community of soil. This method's major advantage is that it specifically describes the structure of the living microbiota, as phospholipids are rapidly converted into neutral lipids upon microbial death [17]. The method involves in-situ hydrolysis and the fatty acids' methylation, which free the fatty acids from soil organic matter [18]. The major microbial groups profiled are distinguished by indicator fatty acids (biomarkers). Fungal population biomarkers include sapophytic (18:1\(\omega\)9c, 18:2\(\omega\)6c, 18:3\(\omega\)6c, and 20:5\(\omega\)3) and arbuscular mycorrhizala (16:1\(\omega\) 5c, 20:1\(\omega\)9c, 20:2\(\omega\)6c, and 22:1\(\omega\)9c) indicators. Bacterial indicators include Gram-positive bacteria (i.e., 115:0, a15:0, i17:0, and a17:0), Gram-negative bacteria (i.e., cyl7:0, cyl9:0, 113:0 3 OH and i17:0 3 OH), and actinomycetes (10 Me16:0, 10 Me17:0 and 10 Me18:0) [18]. Although this method provides a historical evaluation of the microbial communities of a soil, the interpretation of EL-FAME profiles from whole soil communities can be challenging as phospholipid fatty acid (PLGA) compounds are not at all specific to organisms and are shared across microbial communities [19].