Scaling carbon from leaf to canopy: 
Linking  physiology, canopy imagery, and net ecosystem exchange 

A schematic showing the many scales of imagery, leaf-level physiological and functional traits, and canopy processes.

Why study phenology? 

Scaling from the leaf to the canopy 

Phenology is the annual development of life-history stages and leaf development, and the concurrent physiological processes. Many studies have observed earlier start dates of spring leaf-out in deciduous systems that is associated with warmer climate conditions. As seasons shift with environmental change, it is crucial to understand how carbon cycling in these ecosystems will also vary. 

Our research looks at leaf-level fluorescence and fluxes of respiration in the light and dark, and photosynthesis, as well as canopy-level fluxes of carbon and canopy fluorescence response across the growing season. We also aim to link these variables through multiple imaging technologies at the canopy-scale, including repeat digital camera. imagery, NDVI cameras, and LiDar, which can be more easily scaled to satellite measurements of leaf area index, gross primary productivity and NDVI. 

Related publications:
Yang H, Yang X, Heskel M, Sun S, Tang J. (2017) Seasonal variations of leaf and canopy properties
      tracked by ground based NDVI imagery in a temperate forest. Scientific Reports. 7: 1267. 

Yang H, Yang X, Zhang Y, Heskel MA, Lu X, Munger W, Sun S, Tang J. Chlorophyll fluorescence
       tracks seasonal variations of photosynthesis from leaf to canopy in a temperate forest. (2017) Global
       Change Biology. Online early.  doi: 10.1111/gcb.13590

Field work at Harvard Forest 

From May 2015 onward, we have been monitoring the canopy below the Hardwood Walkup Tower at Harvard Forest. This monitoring will allow us to better characterize how individual trees and the whole canopy cycle and store carbon through the growing season from May-October.  Sometimes you take bike to get samples, sometimes you take a canopy lift called "Bucky". Hualei Yang, a PhD student, is pictured helping in the canopy lift, and Jonathan Michelsen, an undergraduate from University of Chicago, is manning the leaf-level fluorometer.