Ruderal weeds as biomonitors of urban nitrogen deposition

Abstract

The production of reactive forms of nitrogen has surpassed safe planetary boundaries, jeopardizing the proper functioning of ecosystems. Their deposition is a threat to both biodiversity and public health. Monitoring systems to quantify nitrogen deposition are often lacking, making biomonitoring a potential alternative. In biomonitoring, physiological variables responsive to nitrogen availability are identified, along with organisms tolerant to high nitrogen availability. Although epiphytic organisms are frequently used as biomonitors, many are confined to humid climates and areas with minimal anthropogenic disturbance. The aim of this review is to identify potential nitrogen deposition biomonitors for sites under anthropic disturbance. Ruderal weeds persist and thrive in urban areas, where disturbance, pollutant emissions, and nitrogen deposition rates are often high. Moreover, several weeds are identified as nitrophilic, and within a well-represented group among them, grasses, tolerance to high nitrogen deposition rates has been documented. The use of these organisms has allowed for the identification of contributions from nitrogen sources and the increase of nitrogen in environments that are restrictive for other plants.