Isolation predicts compositional change after discrete disturbances in a global meta-study

Globally, anthropogenic disturbances are occurring at unprecedented rates and over extensive spatial and temporal scales. Human activities also affect natural disturbances, prompting shifts in their timing and intensities. Thus, there is an urgent need to understand and predict the response of ecosystems to disturbance. In this study, we investigated whether there are general determinants of community response to disturbance across different community types, locations, and disturbance events. We compiled 14 case studies of community response to disturbance from four continents, twelve aquatic and terrestrial ecosystem types, and eight different types of disturbance. We used community compositional differences and species richness to indicate community response. We used mixed-effects modeling to test the relationship between each of these response metrics and four potential explanatory factors: regional species pool size, isolation, number of generations passed, and relative disturbance intensity. We found that compositional similarity was higher between pre- and post-disturbance communities when the disturbed community was connected to adjacent undisturbed habitat. The number of generations that had passed since the disturbance event was a significant, but weak, predictor of community compositional change; two communities were responsible for the observed relationship. We found no significant relationships between the factors we tested and changes in species richness. To our knowledge, this is the first attempt to search for general drivers of community resilience from a diverse set of case studies. The strength of the relationship between compositional change and isolation suggests that it may be informative in resilience research and biodiversity management

Soil microbial biomass—Interpretation and consideration for soil monitoring

Since 1970, measurement of the soil microbial biomass (SMB) has been widely adopted as a relatively simple means of assessing the impact of environmental and anthropogenic change on soil microorganisms. The SMB is living and dynamic, and its activity is responsible for the regulation of organic matter transformations and associated energy and nutrient cycling in soil. At a gross level, an increase in SMB is considered beneficial, while a decline in SMB may be considered detrimental if this leads to a decline in biological function. However, absolute SMB values are more difficult to interpret. Target or reference values of SMB are needed for soil quality assessments and to allow ameliorative action to be taken at an appropriate time. However, critical values have not yet been successfully identified for SMB. This paper provides a conceptual framework which outlines how SMB values could be interpreted and measured, with examples provided within an Australian context