A unique plant community aptly named the “pygmy forest” occurs in patches along the coast of Northern California. Plants of the pygmy forest are severely stunted, due to acidic, shallow soil that is extremely low in vital nutrients. In places, these trees remain only knee-height, despite being several decades old. When transplanted onto richer soils, however, these trees can grow to full height (to the dismay of gardeners who want ready-made, cute bonsai trees).
I am curious about how these plants survive and grow on these harsh soils. For my doctoral thesis, I am tackling my questions about the pygmy forest in three parts, which will be the three chapters of my thesis.
First, I examined how the leaves of pygmy plants function, and I compared them to leaves of same-species plants growing nearby, outside of the pygmy forest. I had hypothesized that the growth of the pygmy plants was so stunted because their leaves weren’t able to photosynthesize quickly. The process of photosynthesis requires enzymes and pigments that take a lot of nutrients to build, so it makes sense that plants on low-nutrient soils would have some difficulty with photosynthesis. However, I found that most pygmy forest plants have similar rates of photosynthesis as non-pygmy forest plants. Instead, pygmy plants often grow fewer leaves–instead of producing many leaves that they don’t have enough nutrients for, they grow a few leaves that they can invest more of their nutrients into. They also grow thicker/tougher leaves, so that their few, high-quality leaves are less likely to be eaten by deer, damaged by fungi, broken by passing animals, or otherwise lost. For more about my findings, check out my publications page! The article is open-access, so you don’t need a journal subscription to read it.
I am also examining how the pygmy plants deal with water. The pygmy forest plants don’t experience any real water stress throughout the year (Sholars 1982), but I hypothesize that their ability to transport water and withstand water deficit will still be affected, because nutrient limitation has the potential to affect so many different aspects of plant growth and functioning. This portion of my project is still underway, but stay tuned for what I discover!
For the third part of my project, I am looking at different patches of pygmy forest. Some patches are more stunted, remaining only knee-height, while other patches grow taller and reach over head-height. I’m hypothesizing that the shorter patches are growing on more nutrient-limited soil, and that these patches have only a few closely-related species that are especially well adapted to poor soil.
A thorough understanding of the physiology of these unique pygmy plants will help fill in our understanding of how plants can change their physiology to survive in harsh conditions.