While deserts are increasing all over the globe, the health of existing deserts is diminishing. It’s a rough environment: desert shrubs are repeatedly damaged and cleared by humans as part of agriculture, oil and gas production, and sustainable energy development. York Professor and ecologist Christopher Lortie asked the all-important question: what can be done to help regrowth in the desert, to save these thriving habitats for animals and plants?
Lortie led a highly collaborative team of researchers that considered whether the common desert plant Ephedra californica (E. californica) could assist in the reinvigoration of the health of the California desert. His findings, published in Ecology and Evolution (2017), brought forward compelling evidence that will be applicable to other desert environments around the world.
“The ability for foundation species to recover – the key finding of our research ̶ suggests that rehabilitation of desert remnants is more likely to succeed and proceed more rapidly with an intact population of a shrub species present,” Lortie explained.
This research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Bureau of Land Management. The National Center for Ecological Analysis and Synthesis, UCSB, also supported this research.
Deserts under threat
This work is vital to the planet’s ecology. Deserts, defined as any location receiving less than 25 centimetres of precipitation per year, occupy more than one-fifth of the Earth’s surface (National Geographic). They are thriving habitats for plants and animals. However, as they expand, their health is threatened. Global desertification is a pressing issue.
This is Lortie’s area of expertise. The biologist describes himself as an integrative scientist, which means that he uses a multidisciplinary and cumulative approach to scientific study that synthesizes many disciplines and integrates them when problem solving. His research involves biogeographical comparisons of many forms of community dynamics (plants, animals and people). Research within his lab is primarily focused now on positive interactions between plants and animals in deserts.
Lortie realized that shrubs could help the health of deserts. This is because they are considered a foundational specific in ecology, which is defined by Lortie as “one with significant and often singular impacts on the structure and sometimes functioning, of an ecosystem.” In deserts, shrubs can influence other plants by seed trapping, providing shelter and refuge. This was the starting point of Lortie’s research.
Researchers tested “recovery hypothesis”
Lortie’s study sought to examine whether a common desert shrub species in California, E. californica, could recover from damage introduced during a period of extended drought.
Lortie and collaborators hypothesized or predicted three things:
- E. californica is a foundation plant species in one region of California because it will facilitate other plant species.
- This desert shrub species will significantly recover from a major physical damage event.
- Larger shrubs (estimated by canopy volume) will significantly recover more than relatively smaller shrubs.
Experiment took place in San Joaquin Desert, spanned three years
The study was conducted in the Panoche-Coalinga Area of Environmental Concern and administered by the U.S. Bureau of Land Management – within the San Joaquin Desert. This region had experienced a severe and extended “mega drought” from 2006-15.
The work was executed in collaboration with the Department of Wildlife, Humboldt State University (Arcata, Calif.), and the Bureau of Land Management, Central Coast Field Office (Marina, Calif.). Lortie underscored the collaborative aspect: “This work was done in partnership with local managers and agencies to ensure that the findings would be directly relevant.”
To study the effects of E. californica on other plant species, the researchers surveyed (measured height and diameter) a total of 225 shrubs annually, at the end of the growing seasons, for three years (2013-16).
Then came the intervention. In 2014, at the end of the winter growing season, the researchers clipped 20 E. californica plants to the ground. In December 2016, after first rains, these shrubs were measured for regrowth and then clipped to the ground again.
The research team then turned its attention to comparing the effects that the E. californica shrubs had on the surrounding plants.
The effect was positive. “The abundances of annual plants were consistently and positively associated with this shrub species E. californica in all years,” said Lortie. “This shrub clearly and consistently facilitates the abundance of other plant species,” he summarized.
The researchers refer to the positive effect of the E. californica plant on other plants as the “Groot effect,” as a nod to the sentient woody tree that re-sprouted after significant damage in the Guardians of the Galaxy movies.
Findings could have global application
This key finding could have wide-reaching application. “This is a critical precursor to understanding the role that positive interactions play in human-disturbed systems,” Lortie said, pressing for more research.
To read the article in Ecology and Evolution, visit the website. To read a related article published in Ecosphere, visit the website. To learn more about Lortie, visit his faculty profile page.
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By Megan Mueller, manager, research communications, Office of the Vice-President Research and Innovation, York University, muellerm@yorku.ca