When Phenology Meets Technology

Phenology is the biological response to the changing seasons. Day length, temperature, precipitation, and other factors drive leaf-out and leaf fall in trees. In order to avoid undergoing damage by putting their leaves out too early as winter transitions to spring, trees require a particular amount of sunlight each day before leaves can emerge. Similarly, when the hours of daylight begin to decrease with the onset of fall, trees withdrawal nutrients from their leaves, drop them and become dormant for the winter. Understanding phenology is important because climate change has already brought, and is predicted to continue bringing about seasonal anomalies. Further, changes in phenology impacts forest productivity, ecosystem functions and services, carbon cycling, logging, agriculture, and plant-pollinator interactions.

Ground observation is the oldest method for recording phenology and it involves visiting the same tree throughout the year to record dates and details of phenological activity. The oldest observations have been traced back thousands of years to China and Japan. However, the advancement of technology and the increasing interest in phenology has resulted in the development and utilization of additional observational methods. A method that is becoming increasingly popular involves using stationary digital cameras set on automatic timers to take photos of trees throughout the day. These digital images are then used to extract changes in canopy greenness using a computer algorithm. Such cameras can be found throughout Harvard Forest and in sites all around the world as part of the PhenoCam Network.

My project involves using ground observations to provide an understanding of phenological trends of deciduous trees throughout the northeastern United States. I am utilizing Harvard Forest’s phenology records (1990-2014) and the USA National Phenology Network’s (USA-NPN) Nature’s Notebook (data collected via citizen science). In addition, I am examining how urbanization and canopy position of trees influences their phenology. I hope to help improve prediction models and forecast accuracy in extrapolating measurements for other sites and for periods lacking observation. I am also contributing to a growing area of research which involves the use of data collected by citizen scientists as I incorporate USA-NPN data with Long Term Ecological Research (LTER). Citizen science data is important because it provides information that otherwise may not be attainable due to common research limitations, such as funding and time.

This summer my research team consists of myself, another summer student, and mentors David Basler and Margaret Kosmala, both Harvard postdocs. The other project we are working on involves utilizing PhenoCams at Harvard Forest to assess individual tree phenology since 2008. I am assisting with locating the trees that appear in the PhenoCams out in the field, collecting their cores, determining their age, and examining their greenness trends. My favorite part about being out in the field is going up into the tree canopy in “Bucky” (the bucket lift) to collect leaves from various species of trees.

I’ve been studying and visiting forests throughout the world for years now, but I never had the privilege of spending very much time in the canopy until this summer. Being up there has given me a whole new perspective of the forest and has made me realize that there is still much to be learned about canopy dynamics.

In addition to the great help my mentors have been throughout my project, the seminars and workshops this summer have provided me with a wealth of knowledge and skills. I look forward to utilizing everything I’ve learned at Harvard Forest as I work towards a PhD next fall and as I continue my involvement in ecological research.

Jolene Saldivar currently attends Humboldt State University and is studying Biology (ecology & biodiversity). Her research interests include forest ecology, lichens and bryophytes, plant-animal interactions, jaguar and lion conservation, and ethnobotany.