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Harvard Forest Symposium Abstract 2013

• Title: Seasonality of leaf spectroscopic, biochemical and biophysical properties
• Primary Author: Jim Tang (Marine Biological Laboratory)
• Additional Authors: John Mustard (Brown University); Xi Yang (Marine Biological Laboratory)
• Abstract:

  Vegetation phenology has been quantified using a variety of methods. While remote sensing technique estimates leaf chlorophyll concentration using vegetation indices, current studies of manual and digital camera observations are mainly focusing on the development of leaf size and color leaf color change and leaf ontogeny. However, the leaf color may not reflect the physiology of the plants. Equally important are the leaf biochemical and biophysical properties such as leaf nitrogen content (%N), leaf chlorophyll and carotenoids concentration (CHL and CAR, respectively) and leaf mass per area (LMA), which are directly related to the plant physiology. Each of these properties has its own footprint on different wavelengths of the reflected light from leaf surface. Leaves’ biophysical and biochemical properties change throughout the season, and so does the spectroscopic properties. Some of these changes happen within less than a month, thus a high temporal resolution (~1 week) dataset of these properties is critical. In this study, we aim to use spectroscopic properties to estimate biophysical and biochemical properties measured at high temporal frequency. Starting from May 1st, we collected leaves of three tree species (Red oak, red maple and paper birch) weekly in Harvard Forest. Both fully sun-lit leaves and shaded leaves were collected. Leaf biochemical properties (total C, N, CHL, CAR), biophysical properties (LMA), internal structure (cell arrangement) and spectroscopic properties were measured. We are still analyzing the data from year 2012 in Harvard Forest. We will present a poster based on our 2011 field campaign on the island of Martha’s Vineyard, in which we collected similar dataset (weekly) in a white oak forest. We found that there is a “decoupling” between the temporal trajectories of leaf color (visible R, G, B) and the leaf maturity.
  
  

• Research Category: Forest-Atmosphere Exchange
  Physiological Ecology, Population Dynamics, and Species Interactions