Standardized phenology monitoring methods to track plant and animal activity for science and resource management applications

Abstract

Phenology offers critical insights into the responses of species to climate change; shifts in species' phenologies can result in disruptions to the ecosystem processes and services upon which human livelihood depends. To better detect such shifts, scientists need long-term phenological records covering many taxa and across a broad geographic distribution. To date, phenological observation efforts across the USA have been geographically limited and have used different methods, making comparisons across sites and species difficult. To facilitate coordinated cross-site, cross-species, and geographically extensive phenological monitoring across the nation, the USA National Phenology Network has developed in situ monitoring protocols standardized across taxonomic groups and ecosystem types for terrestrial, freshwater, and marine plant and animal taxa. The protocols include elements that allow enhanced detection and description of phenological responses, including assessment of phenological "status", or the ability to track presence-absence of a particular phenophase, as well as standards for documenting the degree to which phenological activity is expressed in terms of intensity or abundance. Data collected by this method can be integrated with historical phenology data sets, enabling the development of databases for spatial and temporal assessment of changes in status and trends of disparate organisms. To build a common, spatially, and temporally extensive multi-taxa phenological data set available for a variety of research and science applications, we encourage scientists, resources managers, and others conducting ecological monitoring or research to consider utilization of these standardized protocols for tracking the seasonal activity of plants and animals.

Fig. 1

Visual comparison of data collected by monitoring phenological events, phenophase status, and phenophase status plus intensity. Event monitoring captures onset of a given phenophase, whereas status monitoring captures onset and duration. Status monitoring with intensity (or abundance) captures onset, duration, and magnitude of a phenophase. Examples are derived from 2012 data submitted in Nature’s Notebook for (a) sugar maple (Acer saccharum) leafing for one individual plant in Maine, and (b) forsythia flowering (Forsythia sp.) for one individual plant in Massachusetts. Each point represents one observation; black points indicate presence of the phenophase while white points indicate absence. (a) illustrates the date on which the first leaf appears (event), the period during which leaves are present (status), and the period and rate at which the canopy fills from 0 to 100 % capacity and then, empties back to 0 with leaf fall (status + intensity, circles and solid line) using estimates of canopy fullness. Also illustrated is the period and rate at which the canopy fills and empties of autumn colored leaves (status + intensity, triangles and dashed line). (b) illustrates the date on which the first open flower appears (event), the periods during which open flowers are present on the plant (status), and an estimate of the number of open flowers on the plant over the periods in which they are present (status + intensity). In both examples, the event point is calculated as the first date of the year where the phenophase was reported as present. Note that in (b) there are two distinct periods of flowering, the second of which would not have been captured using event monitoring alone

Fig. 2

An illustration of how an observer would make and record repeated observations for a single individual plant (in this case a black oak tree, Quercus velutina) over a period of time. Circles around the “y’s” (yes) and “n’s” (no) indicate the presence or absence of the phenophases (far left column) on the tree for each date. When a phenophase is present, an estimate of intensity is included (see Online Resource 1 for intensity measures). In this example, the phenological event of “first leaf” (Meier 2001) would have occurred between May 1st and May 11th, the dates of the last reported “no” and the first reported “yes” for the “Leaves” phenophase. Although there are approximately 10 days between each observation in this example, more frequent observation will be desired in many cases