Assessing naturalness of arable weed communities. A new index applied to a case study in central Italy

The interest in the ecological role of weed communities within arable fields has increased greatly in recent years. The aim of this work was to provide an original tool for arable land naturalness estimation, based on the many features of plants that colonize crops. Taking account of taxonomic, structural, chorological and ecological features of weed taxa as exoticism, Raunkier life-form and edaphic preference, a new index (Arable Land Naturalness Index – ALNI) was developed, which allowed for an evaluation score to be obtained for a given field. To ensure easy and quick application of the tool, a program for the calculation of ALNI values was written in Java. The index was applied to segetal communities of 61 wheat (Triticum aestivum L.) fields and 44 maize (Zea mays L.) fields in Latium region (central Italy), revealing both the existence, in such cultivations, of geographic naturalness gradients and large differences between wheat and maize weed assemblages. It was detected that naturalness levels were higher in wheat weed communities than in maize weed communities and tended to increase when moving eastwards and at higher altitudes, e.g. in internal hills and low mountains. Finally, based on evidence from literature, the results were related to the most probable types of agricultural management system (extensive/traditional or intensive), showing that maize was much more often submitted to intensive agriculture, whereas traditional, extensive farming systems was clearly used in many of the wheat fields.