Climate Change Experiment Explores Ecosystem Sensitivity
Oct. 6, 2023 - In a pioneering climate change experiment, UCI researchers have been studying a five-acre area on Loma Ridge, near the Limestone Canyon Preserve, northeast of Irvine. The project aims to gain a better understanding of Southern California’s ecosystems’ sensitivity to various environmental shifts, primarily how changes in water and nitrogen levels impact the nearby grasslands and shrublands.
A Quest for Understanding
Initiated in 2006 by Mike Goulden, a professor of earth system science at UCI, the experiment incorporates a meticulously designed study plan. It encompasses three distinct tiers of water input: ambient conditions, drought conditions (about 40% less than the actual rainfall amount), and wet conditions (about 30% more than the actual rainfall amount). Especially in recent years, Southern California has experienced erratic rainfall patterns, alternating between exceptionally dry years and those with more rainfall than usual.
One question driving this research is the impact of severe drought conditions on California’s ecosystems. To simulate drought, the team employs specialized structures that shield the experimental plots from rainfall during storms, effectively creating arid conditions. This controlled setup allows researchers to closely examine how native plants respond to reduced water availability, providing valuable insights into the resilience of the region’s vegetation.
While drought plays a role in altering vegetation, it’s not the sole factor, says Steven Allison, a professor of ecology & evolutionary biology in the UCI School of Biological Sciences. Elements such as nitrogen levels, microbial communities, and the frequency of extreme precipitation events all contribute to the complex dynamics observed in these ecosystems. This knowledge holds the key to predicting and mitigating the effects of climate change on these landscapes by offering insights into which plants may succumb to drought and which may possess the resilience to recover.
Computer Vision Meets Ecology
The project recently began a collaboration with researchers from the Computer Vision Laboratory (CVL) at CALIT2. CVL specializes in hyperspectral and multispectral image modeling and automated analysis, offering a unique perspective on the experiment.
Traditional methods of ecological observation can be labor-intensive. Researchers equipped with detectors must painstakingly measure variables like carbon movement through leaves or the rate of photosynthesis, often on a leaf-by-leaf or plant-by-plant basis.
In contrast, the CVL team employs sensors that can view a large area of the landscape in an instant which allows computer algorithms to analyze the physiological state of the plants over a region in seconds. Their objective is to detect signs of stress in the vegetation. By capturing data at the scale of the entire ecosystem and encompassing different plant species, they generate a wealth of information that can uncover variability patterns and potentially forecast future ecological shifts.
Led by Glenn Healey, CVL’s director and a professor in electrical engineering and computer science at UCI, the team leverages the power of hyperspectral imaging which utilizes cameras capable of discerning many more colors than traditional cameras or the human eye. Their approach involves using these sensors to capture a series of scans of the ridge. These scans create a rich dataset that provides unparalleled insights into the state of the ecosystem.
“We recently collected data at Loma Ridge with a team from CVL, researchers from UCI’s School of Biological Sciences, and a group from CALIT2 at UCSD,” Healey explains. “The outcome is a large set of data collected using hyperspectral, LiDAR, and photogrammetry instruments from both the ground and the air. We plan to use this data for the automated identification of different types of plants and to measure their health and to gauge air quality.”
A Story of Resilience
The experiment has encountered its share of challenges. In 2007, the Santiago fire ravaged the site, effectively resetting the entire ecosystem. Following such disturbances, ecosystems undergo a process known as ecological succession. Fast-growing weeds initially emerge, followed by slower growers that ultimately dominate the landscape.
In 2020, the Silverado fire—another uncontrolled burn—swept through the research site. The blaze revealed an unexpected outcome. The arid plots experienced less intense burning due to a lack of fuel from drought-stunted shrubs, creating an opportunity for invasive grasses to thrive. The once-sage-scrub-habitat now faced the potential of becoming a permanent grassland.
"This is a problem because grasses tend to grow back rapidly and are highly flammable," explains Allison. “The more fires we have, the more grass there is, and more grass leads to more fires.” This cycle transforms the native shrub lands into invasive grasslands. Grasslands also provide lower-quality habitat to support numerous endangered and threatened wildlife species, notes Allison.
The loss of this habitat is primarily due to development – freeways, housing and shopping centers have encroached on wildlife habitats, bringing with them greater risks from drought, wildfires and invasive plant species. Currently, the site is managed by the Irvine Ranch Conservancy, whose primary goal is to protect the ecological health of urban wildlands.
Loma Ridge is located on the ancestral lands of the Tongva and Acjachemen tribes who have long-term, ongoing cultural ties to the area. The Acjachemen use native grasses and other plants for a variety of cultural purposes. Native grasses coexist with native wildflowers, growing in tall clumps with deeper roots. “The original, native California grasslands must have been incredibly beautiful,” says Allison. “But now, all we see are wild oats, brown grass, and mustard, which are species from the Mediterranean region of Europe and were introduced by Spanish colonists.”
The research raises critical questions about the future of California’s iconic landscapes. Will the ongoing drought and climate change permanently shift these ecosystems towards a grassland-dominated state? Can native shrubs recover if rainfall patterns return to normal? These are questions with far-reaching implications for biodiversity, habitat quality, and California’s ability to adapt to a changing climate. By gaining a deeper understanding of the complex interactions of environmental drivers, solutions can be offered to safeguard California’s iconic landscapes and ensure their resilience.
– Sharon Henry
