Thursday, September 19, 2019

Leaf longevity published!

Posted by Linnea Smith

“However mean your life is, meet it and live it; do not shun it and call it hard names.”  
Henry David Thoreau. 

Our leaf longevity project for my BU Biology honors thesis and Sarah Pardo’s BU Academy senior thesis has now been published in the international journal Oecologia.  The article, titled “Leaf longevity in temperate evergreen species is related to phylogeny and leaf size” is featured as “Highlighted Student Research.”

In this project we used the living collection of the Arnold Arboretum in Boston, Massachusetts to determine the leaf longevities (LL) of 169 temperate evergreen species. To our knowledge, this is the largest dataset of its kind, collected from one site using a single unified method.

Richard Primack (left) and Linnea Smith (right), demonstrate measuring leaf longevity by counting leaves across different aged branch segments.

We found that LL has a strong phylogenetic component – different genera have different LLs (see the figure below) – and conifers with longer needles tend to have shorter leaf longevities. Of the 169 species we investigated, Labrador tea (Rhododendron tomentosum) had the shortest LL (only 1.4 years); the oldest leaves we found were of Taurus fir (Abies  cilicia), living for an average of 10.5 years.

Different genera of evergreens have very different average leaf longevities, varying from 2 to 6 years. The number of species examined is listed above each genus. From shortest to longest leaf longevity, the genera are Rhododendrons, Ilex (holly), Pinus (pine), Taxus (yew), Tsuga (hemlock), Picea (spruce), and Abies (fir). 

Because leaves play a vital role in the carbon cycle as well as other ecosystem functions, understanding their dynamics (such as LL) is important to better constrain carbon budgets and ecosystem models.

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