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California’s intensive water management promotes a “live fast, live young and die” cycle in floodplain forests

A forest area of ​​a riverbank community along the lower Tuolumne River near Merced, California. The dry grassland in the background indicates a semi-dry and drought environment. Credits: JOHN STELLA, ESF

Streams and riverside forests are an important part of California’s diverse ecosystems. They are biodiversity hotspots and offer a variety of ecosystem services, including carbon sequestration and important habitats for endangered and endangered species. However, our land and water use has had a major impact on these ecosystems, sometimes in unexpected ways.


A team of researchers, including two from the University of California, Santa Barbara, found that some riparian forests were benefiting. water Humans distract for our own needs.These seem like benefits, EcosystemThe artificial water supply creates an unintended reliance on this grace and threatens the long-term survival of the natural forest community.Papers published in Minutes of the National Academy of Sciences, It highlights the need to change the way water is managed throughout the state.

Melissa Rode, the lead author of the Nature Conservancy groundwater scientist who led the study as a PhD student in the state, said: Faculty of Environmental Sciences and Forests, New York University (SUNY-ESF). “These forest ecosystems are in an unstable state as we disrupt these natural hydrological processes. Plant species It relies on supporting and maintaining important life processes. “

In California’s Mediterranean climate, plants and animals are adapted to rely on precipitation and soil recharge during the rainy winter and spring seasons, usually for reproduction and growth during dry summers. .. When the soil is depleted, Tree species Common in stream corridors such as willow, cottonwood, and oak is usually the use of deeper groundwater. However, researchers have found the story to be more complex.

By analyzing five years of vegetation greenness data from satellite imagery, the authors authorize that, in some cases, these ecosystems are provided by human regulation of emissions from rivers, canals, and wastewater treatment plants. Discovered to be affected by “water subsidies”. The modified riverside forests of the state’s driest regions remained green longer until the dry season and were less responsive to changes in groundwater levels than their natural ecosystems.

Michael Singer, a researcher at the Institute of Earth Sciences at the University of California, Santa Barbara and a professor at Cardiff University in the United Kingdom, said: .. “In waterways and canals where flow conditions have changed significantly, these trees have little opportunity to produce new offspring, which means that when these riparian forests are depleted, they cannot be replaced by forest transitions. “

Many of California’s most volatile stream ecosystems are located in California’s agricultural center, Central Valley, which produces one-third of US produce. Following the gold rush of the 1850s, large-scale human settlements led to the reclamation of 95% of the natural floodplain forest areas throughout the region. These isolated, restricted riverbanks, or riverside forests, now provide an important habitat for endangered forests. Endangered species Like California’s red-footed frogs, chinook salmon, and Swainson’s hawks.

Water is rerouted from river to canal to accommodate urbanization and multi-billion dollar agriculture, creating an artificially stable environment for riparian forest ecosystems. This encourages “live fast, live young and die” communities that prefer trees that peak and then decline within decades. Key ecosystem functions, such as the regeneration of new forest stands and the development over time, are impaired by drastic changes in river flow and waterways. They are fixed in place and do not create a new floodplain area where young trees can be established.

“We call these forests’living dead’ because there are no seedlings or young trees on the floor that can replace mature trees when they die,” Rohde said. I will. It has implications for endangered species habitats, biodiversity, carbon sequestration and climate change.

“California is one of the most biodiversity regions in the world and is home to more species than the United States and other parts of Canada combined,” Rohde said. “In the midst of the sixth mass extinction, the long-term sustainability of California’s river ecosystem and the protection of the rare and endemic species that inhabit it are now deliberate and coordinated by resources and government agencies. Relies on strict management. “

The study is part of a $ 2.5 million series of projects funded by collaborators at SUNY-ESF, the University of California, Santa Barbara, and Cardiff University throughout the southwestern United States and France. Researchers also include Dar Roberts, a professor of geography at UCSB, one of the co-authors of the study. The goal is to develop water stress indicators for dry riparian forest ecosystems threatened by climate change and increasing human water demand.

Rhode and The Nature Conservancy uses the insights gained from the study to provide California’s Natural Resources Agency with scientific guidance for the sustainable management of state-wide groundwater-dependent ecosystems. .. As the singer pointed out, the findings relate to the recent Sustainable Groundwater Act passed in California. The Sustainable Groundwater Management Act requires all groundwater stakeholders to agree on sustainability goals for groundwater use to support urban areas, agriculture, industry, and ecosystems.

The research team used Google Earth Engine, an open source tool for analyzing publicly available online data and data from satellites and other global spatial datasets. “Our methods and discoveries open up a whole new world of interdisciplinary research possibilities and ways in which water practitioners can consider the water needs of ecosystems to achieve sustainable water management. “I will.” Said Rohde.

John Stella, a professor and principal investigator of the National Science Foundation grant that funded the study, has several innovative ways to understand how climate and water management interact. To endanger these sensitive ecosystems, we have characterized this work as a “breakthrough” in the way we combine large datasets. “

“”[The] Survey results are important for the sustainable management of groundwater, not only in California as a whole, but in water-constrained areas around the world. By creatively leveraging and integrating these large environmental datasets, we are now able to answer resource management questions on a scale never before possible. .. ”


Dangerous biodiversity “hotspots” along a stream in California


For more information:
Melissa M. Rohde et al, Groundwater dependence of riparian forests and the destructive effect of artificially altered river currents, Minutes of the National Academy of Sciences (2021). DOI: 10.1073 / pnas.2026453118

Quote: California’s intensive water management, floodfield forest acquired on June 17, 2021 from https://phys.org/news/2021-06-intensive-california-fast-die (6 2021) 17th June) Promotes the “Live Fast, Die Young” Cycle-young.html

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California’s intensive water management promotes a “live fast, live young and die” cycle in floodplain forests

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