The forest here is full of sierra palms – Prestoea acuminata var. montana. How large is each leaf? We need to know for our study of functional diversity. You might think that the individual sword-shaped tissues are leaves, but actually the entire palm frond comprises a single leaf with many leaflets. The leaflets are each part of a compound leaf, with a petiole attaching it to the main trunk, and a rachis joining the many leaflets.
The first step is to cut these leaves out of the canopy with pruning poles – the petioles are more than an inch thick, and the leaves drop quickly with a creaking cracking sound. To give you an idea of how big the leaves are, here is an image of part of one leaf – probably one eighth fraction of the total leaf. We cut them up into pieces in order to drag them out of the forest back to our field station.
Normally we can measure area with a digital flatbed scanner – but clearly these leaves are far too big for this. First, we remove all the leaflets, to make the leaf more manageable.
Next, we photograph the leaf pieces on a neutral background, simulating the action of a flatbed scanner. This poses a challenge at a field station – where to find somewhere with even illumination, a good background, and a large enough space to accommodate our samples? We had to improvise – here is our solution.
A balcony on an apartment for distance, old bedsheets for background, a meter tape for scale, another bedsheet for a lightbox, held up by a palm petiole. We then image all the leaf sections, and create silhouettes on the computer, and scale each image based on the conversion between pixels and meters. Our final answer – leaves of this species have surface areas that can be greater than four square meters. This is huge – more than an equivalent square with six foot sides. The diversity in leaf size across the world is immense – but for our part, as a field crew, we we prefer small leaves!