Updates to standardized plant and animal observation protocols of the USA National Phenology Network

The USA National Phenology Network (USA-NPN) was established to coordinate the collection of rigorous, high-quality phenology observations to support scientific discovery and management decisions and to increase awareness of phenology, its relationship to environmental conditions and its influence on ecosystems. A cornerstone of the USA-NPN's infrastructure and data collection activities is a suite of rigorous, standardized phenology observation protocols, published in 2014 (Denny et al., Int J Biometeorol 58:591-601, 2014). In the years since, users have requested modifications and additions to the existing protocols. Here, we describe changes that have been made to the original protocols since their publication in 2014. These modifications have been made to reduce confusion in the phenophase definitions, include new taxonomic groups, and expand protocols to more fully capture certain life cycle stages. We anticipate continued expansion of the protocols and future updates can be found in the University of Arizona Research Data Repository (USA National Phenology Network 2014).