Another building block is the Catalogue of Tree Microhabitats (EN), which offers an accessible typology for identifying small and valuable structures for biodiversity. The Catalogue was developed by a group of top-level experts to serve as a field guide that people can easily use in the field. The vast array of existing tree microhabitats (TreMs) is subdivided into a few concise categories of saproxylic (cavities, injuries and wounds, bark, deadwood) and epixylic (deformations, epiphytes, nests) structures that can serve as shelter or home for different flora and fauna. The TreMs form the basis of the ecological assessment of the marteloscopes sites in the I+ software, where they are linked to the ecological valuation of each tree within a given marteloscope. The field guide can however also be used on its own as a handy support for determining valuable microhabitats during forest management.