Date of Award


Semester of Degree


Document Type

Open Access Thesis

Degree Name

M.S. in Forest and Natural Resources Management


Forest and Natural Resources Management

Major Professor

Ruth Yanai

Steering Committee Member

John Drake

Steering Committee Member

Danilo Fernando


Leaf characteristics may differ within tree crowns due to light environment or the availability of nitrogen (N) and phosphorus (P) in the soil, with important considerations for ecosystem budgets. To determine the relationship of leaf characteristics as a function of depth in the crown and increased soil N and P availability, we collected sugar maple leaves and twigs vertically in a full factorial N x P fertilization experiment in three mature forest stands of the multiple element limitation in northern hardwood ecosystems project in central New Hampshire, USA. The addition of N increased the concentrations of many metabolites such as chlorophyll and amino acids, and concentration of toxins such as aluminum (Al) and manganese (Mn). Phosphorus addition dramatically increased foliar P and adjusted the relationship of leaf characteristics with depth in the crown, particularly in leaves low in the crown. Leaf characteristics showed strong relationships with both depth in the crown, and in response to nutrient availability. We did not detect a difference in twig mass or twig growth as a function of depth in the crown, or with N or P addition. Studies that ignore the vertical gradient miss the opportunity to understand the plasticity with which trees can make crown-level adjustments.