Assessing soil capacity and condition for “habitat of biodiversity” in the Lower Namoi Valley

The Soil Security Assessment Framework (SSAF) has been proposed and developed as a concept to quantitatively ensure a sustainable future for soil, thereby supporting ecosystem sustainability. Evaluating the habitat of biodiversity quantitatively, particularly concerning bacterial communities, is crucial yet challenging, especially for the often-overlooked rare species. This study aims to utilise SSAF to assess the capacity and condition of soil function – the habitat of biodiversity, by examining bacterial communities to understand soil security within Lower Namoi Valley, NSW, Australia. We selected four indicators: relative abundance and alpha diversity of both soil abundant and rare bacterial communities, for capacity and condition, using the pedogenon concept. Our findings indicate significant variations in soil capacity and condition within the valley. Aggregating the indicators as utility scores revealed that the study area has a moderate capacity, with many regions in good condition relative to capacity, especially in less disturbed areas. Specifically, agricultural practices led to a significant increase in conditions for abundant bacterial communities but a decrease in rare bacterial communities. Less disturbed areas exhibited higher scores for rare sub-communities, suggesting better preservation of biodiversity. The study highlights the significant impact of human activities on soil habitat of biodiversity function in the Lower Namoi Valley. By integrating the analysis of abundant and rare microbial biodiversity into the soil security assessment framework, this study offers insights for soil management, advocating practices that support soil biodiversity to ensure long-term ecosystem sustainability.