In this post, Jennifer Rudgers, Professor of Biology at University of New Mexico and the current Director of the Sevilleta Long-Term Ecological Research Program in New Mexico, talks about her recent paper, Sensitivity of dryland plant allometry to climate, and the importance of long-term data.

About the paper

We used long-term data on plant allometry (relationships between body size and mass) to demonstrate that plant species commonly adjust allometry in response to natural fluctuations in climate variables, such as heat and drought. Understanding how plants allocate to biomass is fundamental to measuring ecosystem health and services, such as productivity or carbon storage. Allometry describes the relationships among an organism’s physical attributes and its size. Allometries that relate non-destructive measures of plant size, such as percentage cover, plant volume, or stem density are widely used in plant ecology to estimate plant productivity. Such size-biomass allometry is often assumed to be invariant for a given plant species, plant functional group, or ecosystem type.  However, adjustments to how plants partition biomass may be an important component of the short- or long-term responses of plants to abiotic conditions, such as climate.

Our results show that many plant species adjust patterns in the partitioning of aboveground biomass under different climatic conditions and highlight the importance of long-term data for understanding functional differences among species.

How did you come up with the idea for it?

We run a long-term ecological research site as part of the NSF-funded LTER network, the Sevilleta Long-Term Ecological Research Program (SEV-LTER). We have been tracking allometry of 85+ plant species twice yearly for 18 years. For practical applications in streamlining our field work program (do we really need to clip and weigh plants every year?), we dove into the analysis of these long-term data. We now have a much clearer understanding of how much allometry varies from year to year and in association with key aspects of our local climate.

How is your paper new or different from other work in this area?

We are aware of just one other study that has used empirical data to explore sensitivity of allometry to climate (Onodi et al. 2017, Estimating aboveground herbaceous plant biomass via proxies: The confounding effects of sampling year and precipitation). Our work differed from that study because we examined the sensitivities of individual plant species, rather than for total plant community biomass, as estimated from satellite imagery (e.g., Normalized Difference Vegetation Index -NDVI).  By tracking the allometries of individual species over a long time period, we could address new questions about how much plant species vary in the sensitivity of allometry to climate.

Does this article raise any new research questions?

We would love to explore in greater depth why do plant species differ in how strongly their allometry tracks climate and to which climate variables (temperature, rainfall) they are most sensitive. Our results suggest that sensitivities track plant evolutionary histories across the phylogeny of vascular plants. However, additional information on plant species traits and climatic niches may be key to making generalizable predictions on these “why” questions.

Who should read your paper?

Anyone who uses allometry to estimate biomass (of plants or animals) would benefit from thinking about how much allometry may vary among years or sites in their study systems.  Sensitivity of allometry is also an important aspect to consider in studies on how plants

Were you surprised by anything when working on it?

We were quite surprised that 65-70% of plant species had allometries that were sensitive to climate variables. It validated the importance of the work by generations of SEV-LTER staff to collect plant biomass twice yearly for so many (18!) years.

About the Author

How did you get involved in ecology?

I began ecological research as an undergraduate student, mentored by Dr. Julie Mulroy (Denison University) who helped me to craft a senior thesis in plant demography.  I also got hooked on ecology through the NSF-funded REU program, where I worked with Dr. Chris Smith on plant-pollinator ecology at the Konza Prairie LTER site in Kansas.

What are you currently working on?

My research program today focuses on the ecology and evolution of plant-microbe symbioses. Current projects are exploring how microbial interactions with plants influence ecological resistance and resilience to climate change. I have always been intrigued by interspecific mutualisms and have spent a lot of my career on projects that demonstrate the importance of mutualism in community dynamics and ecosystem processes.

What’s your current position?

I am a Professor of Biology at University of New Mexico and the current Director of the Sevilleta Long-Term Ecological Research Program in New Mexico.

What is the best thing about being an ecologist?

I love to facilitate new collaborations with undergraduate students, graduate students, and my colleagues. I guess you could say that my academic interest in mutualism clearly spills over into my practice as an ecologist.

What is the worst thing about being an ecologist?

There is no worst part, I love this job!

What do you do in your spare time?

I have a nine year old daughter, Elsa, and my husband is co-author Ken Whitney (also a Professor of Biology at UNM).  As a family, we enjoy hiking, gardening, reading, and traveling. We are headed to Argentina in the spring for our first ever sabbatical.

One piece of advice for someone in your field…

Long-term data can reveal new surprises that were never part of the original intent of the project. For this reason alone, continued support and infrastructure for long-term research is essential to major advancements in the complex field of ecology.

You can read Jenn Rudger’s recent paper in full in Functional Ecology. Sensitivity of dryland plant allometry to climate