Soil organisms in military-impacted environments: A systematic review of microbial community studies, contamination types, and methodological gaps

Military activities can significantly influence soil ecosystems through physical disturbance and the introduction of contaminants such as explosive compounds, heavy metals, and hydrocarbons. Soil microbial communities play key roles in ecosystem functioning and contaminant transformation, yet the extent to which these communities have been systematically studied in military-impacted soils remains unclear. This study presents a systematic review of research investigating soil biological communities in landscapes affected by military activity or warfare. A structured literature search was conducted across Scopus, Web of Science, Dimensions, PubMed, and Google Scholar. Following duplicate removal and multi-stage screening, 20 studies met the inclusion criteria. Data were extracted on study location, contamination types, soil physicochemical measurements, biological methods, and methodological characteristics. A Methodological Completeness Index (MCI) was calculated to evaluate the extent to which studies integrated environmental and biological measurements. Results reveal a strong reliance on 16S rRNA amplicon sequencing, used in 80% of studies, while fungal and soil fauna investigations were rare. Soil physicochemical characterization was inconsistent: soil pH was measured in 60% of studies, whereas microbial biomass and enzyme activity were reported in fewer than 20%. No studies reported soil bulk density despite the importance of soil compaction in military landscapes. Research focused mainly on explosive compounds and heavy metals, particularly TNT, RDX, and lead contamination.