Report: Poor plant performance under simulated climate change is linked to mycorrhizal responses in a semiarid shrubland

An arbuscular mycorrhizal fungus (plural mycorrhizae or mycorrhizas, a.k.a. endomycorrhiza, AM fungi, or AMF) is a type of mycorrhiza in which the fungus penetrates the cortical cells of the roots of a vascular plant. Photo credit: Wikimedia Commons.

Click here to read the summary and the complete report:

Summary

1.Warmer and drier conditions associated with ongoing climate change will increase abiotic stress for plants and mycorrhizal fungi in drylands worldwide, thereby potentially reducing vegetation cover and productivity and increasing the risk of land degradation and desertification. Rhizosphere microbial interactions and feedbacks are critical processes that could either mitigate or aggravate the vulnerability of dryland vegetation to forecasted climate change.

2.We conducted a four-year manipulative study in a semiarid shrubland in the Iberian Peninsula to assess the effects of warming (~2.5°C; W), rainfall reduction (~30%; RR) and their combination (W+RR) on the performance of native shrubs (Helianthemum squamatum) and their associated mycorrhizal fungi.

3.Warming (W and W+RR) decreased the net photosynthetic rates of H. squamatum shrubs by ~31% despite concurrent increases in stomatal conductance (~33%), leading to sharp decreases (~50%) in water use efficiency. Warming also advanced growth phenology, decreased leaf nitrogen and phosphorus contents per unit area, reduced shoot biomass production by ~36% and decreased survival during a dry year in both W and W+RR plants. Plants under RR showed more moderate decreases (~10-20%) in photosynthesis, stomatal conductance and shoot growth.

4.Warming, RR and W+RR altered ectomycorrhizal fungal (EMF) community structure and drastically reduced the relative abundance of EMF sequences obtained by high-throughput sequencing, a response associated with decreases in the leaf nitrogen, phosphorus and dry matter contents of their host plants. In contrast to EMF, the community structure and relative sequence abundances of other non-mycorrhizal fungal guilds were not significantly affected by the climate manipulation treatments.

5.Synthesis: Our findings highlight the vulnerability of both native plants and their symbiotic mycorrhizal fungi to climate warming and drying in semiarid shrublands, and point to the importance of a deeper understanding of plant-soil feedbacks to predict dryland vegetation responses to forecasted aridification. The interdependent responses of plants and ectomycorrhizal fungi to warming and rainfall reduction may lead to a detrimental feedback loop on vegetation productivity and nutrient pool size, which could amplify the adverse impacts of forecasted climate change on ecosystem functioning in EMF-dominated drylands.

Study Estimates about 2.1 Million People using Wells High in Arsenic — @USGS

Here’s the release from the USGS (Joseph Ayotte/Hannah M Hamilton):

Most Arsenic Presumed to be From Naturally Occurring Sources

A new study by the U.S. Geological Survey and Centers for Disease Control and Prevention estimates about 2.1 million people in the U.S. may be getting their drinking water from private domestic wells considered to have high concentrations of arsenic, presumed to be from natural sources.

“About 44 million people in the lower 48 states use water from domestic wells,” said Joe Ayotte, a USGS hydrologist and lead author of the study. “While we’re confident our research will help well owners understand if they live in an area of higher risk for arsenic, the only way for them to be certain of what’s in their water is to have it tested.”

Using a standard of 10 micrograms of arsenic per liter — the maximum contaminant level allowed for public water supplies — the researchers developed maps of the contiguous U.S. showing locations where there are likely higher levels of arsenic in groundwater, and how many people may be using it.

Nearly all of the arsenic in the groundwater tested for this study and used to map probabilities is likely from natural sources, and is presumed to be coming primarily from rocks and minerals through which the water flows.

The findings highlight the importance of private well owners working with their local and state officials to determine the best way to test and, if necessary, treat their water supplies.

“Fortunately, in most areas of the country and with appropriate safeguards, the majority of homeowners can get good quality drinking water from private wells,” said Ayotte. “But this study is a good reminder that prudent, routine testing of the water, including its interaction with the water supply system, is an essential first step so homeowners and their families can confidently drink water from their faucets.”

Using water samples from more than 20,000 domestic wells, the researchers developed a statistical model that estimates the probability of having high arsenic in domestic wells in a specific area. They used that model in combination with information on the U.S. domestic well population to estimate the population in each county of the continental United States with potentially high concentrations of arsenic in domestic wells.

“One of our study’s basic assumptions is that the probability of high arsenic can be estimated by a statistical model. We also assume that the domestic water use population is represented by census information used in the study,” said Ayotte.

Some of the locations where it’s estimated the most people may have high-levels of arsenic in private domestic well water include:

  • Much of the West – Washington, Oregon, Nevada, California, Arizona, New Mexico
  • Parts of the Northeast and Midwest – Maine, Massachusetts, New Hampshire, New Jersey, Maryland, Michigan, Wisconsin, Illinois Ohio, Indiana
  • Some of the Atlantic southeast coastal states – Florida, Virginia, North Carolina, South Carolina
    This map shows estimates of how many private domestic well users in each county may be drinking water with high levels of arsenic. An estimated 2.1 million people throughout the U.S. may be drinking domestic well water high in arsenic

    “Although high-arsenic wells can occur in all 48 contiguous states, it is more prevalent in some states than in others,” said Ayotte. “The study did not include Alaska and Hawaii.”

    The researcher provided a cautionary note that while the study provides state and county estimates, they are not intended to take the place of more detailed or local information that may already be available in some areas.

    Long-term exposure to arsenic in domestic wells may cause health-related problems, including an increased risk of cancer. Testing and, if necessary, treating the water is an effective way of reducing or eliminating the concern. A CDC fact sheet provides more information, as does the CDC’s Agency for Toxic Substances and Disease Registry.

    “Ultimately, this study should be helpful not only in assessing the likelihood of people being exposed to arsenic in domestic well water, but the results of the study may assist other researchers evaluate situations where adverse health outcomes such as cancers or adverse birth outcomes may be related to environmental factors,” said Ayotte.

    Public water supplies are regulated by the U.S. EPA, but maintenance, testing and treatment of private water supplies are the sole responsibility of the homeowner. About 44 million people in the U.S. get their drinking water from private wells, yet surveys indicate many homeowners are unaware of some basic testing that should be done to help ensure safe drinking water in the home.

    The study, “Estimating the high-arsenic domestic-well population in the conterminous United States” by J.D. Ayotte, L. Medalie, S.L. Qi, L.C. Backer, and N. T. Nolan is available online in Environmental Science and Technology.

  • Book Review: “Water is for Fighting Over: And Other Myths about Water in the West” — @WaterLawReview

    From the University of Denver Water Law Review at the Sturm College of Law (Rebecca Spence):

    Chapter twelve, “A Beaver Returns to the Delta,” further discusses inclusivity, and shows how collaboration between formally feuding groups can help to undo much of the damage we have done to the Colorado River over the years. Fleck explained that after the Colorado River Compact creators divided the river, they found that dry spots would emerge in arid seasons, and the wildlife would migrate until the river started flowing again. Most recently when the river started flowing again in the previously dry Colorado River Delta, Mexico, the United States, and environmental groups met to devise a plan to keep the water flowing through this delta. This plan, titled Minute 319, was the first of its kind that mentioned environmental implications and wildlife preservation. This collaboration felled two myths. The first was that environmentalists and water managers could not work together to achieve common goals. The second was that the delta was dead, and that rejuvenation of wildlife and surrounding communities was impossible due to the growing water demands and the consistent population booms alongside the Colorado River.

    John Fleck photo via State of the Rockies Project — Colorado College

    The latest “e-WaterNews” is hot off the presses from @NorthernWater

    Eric Wilkinson Northern Water General Manager. Photo credit: Northern Water

    Click here to read the newsletter. Here’s an excerpt:

    Northern Water General Manager to Retire

    Northern Water General Manager Eric Wilkinson has announced he will be retiring in the early part of 2018. He made the announcement to the Northern Water Board of Directors during its September 14 meeting.

    Wilkinson has spent 30 years at Northern Water, the past 24 as general manager. He is recognized as one of Colorado’s leading water statesmen and is a past recipient of the Colorado Water Congress’ Aspinall Award given to Colorado’s water leader of the year.

    In October, the Board will be deciding its course of action to replace Wilkinson.

    Northern Water Board President Mike Applegate said, “Eric Wilkinson is one of those rare people that comes along once in a lifetime and Northern Water was blessed to have him as our manager. He built an organization with a culture based on excellence and continual improvement. The Board of Directors are confident that the next general manager will continue to lead Northern Water with that same vision of service to Northern Colorado.”

    #Minute323: Busting the “Water Wars” Myth — John Fleck #ColoradoRiver #COriver

    Roberto Salmon and Edward Drusina at the Minute 323 signing ceremony September 27, 2017. Photo credit .U.S. Bureau of Reclamation.

    From The Island Press (John Fleck):

    The Colorado River is often described as being shared among seven states, but the number is really nine—seven in the United States and two in Mexico. U.S. farms and cities use most of the river’s water, and what little is left when it arrives at the U.S.-Mexico border near the towns of Algodones and San Luis is diverted for use by Mexican farms and cities. The last hundred miles of river channel between the border and the Sea of Cortez is usually dry.

    The agreement includes provisions for the two nations to share shortages if (when?) drought and climate change shrink the river. The deal gives Mexican water users the ability to store their water in Lake Mead, the massive storage reservoir behind Hoover Dam on the Arizona-Nevada border, near the city of Las Vegas. Storage is critical to give Mexico flexibility in managing its water. U.S. water agencies will contribute under the deal to water efficiency improvements to Mexican infrastructure, with some of the saved water available for use in the United States.

    Crucially, the agreement also sets aside water for habitat restoration in the dry river channel of Mexico.

    The agreement was negotiated over a more than two-year period, but it is really rooted in more than a decade of increasingly deep collaboration between a community of water managers on both sides of the border. When the Trump administration took over in January, there was fear that the carefully crafted deal, so beneficial and important to communities on both sides of the border, would be sidelined by the heated rhetoric over free trade and immigration, over NAFTA and walls. But Wolf was right. Even as conflict raged over other issues, the trust and reciprocity built around the Colorado River proved remarkably resilient. The old saw that “water is for fighting over” was proven wrong again.

    @NASAClimate: September 2017 Was Fourth Warmest September on Record

    The GISTEMP monthly temperature anomalies superimposed on a 1980-2015 mean seasonal cycle

    From NASA (Leslie McCarthy):

    September 2017 was the fourth warmest September in 137 years of modern record-keeping, according to a monthly analysis of global temperatures by scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York.

    Last month was +0.80 degrees Celsius warmer than the mean September temperature from 1951-1980. The warmest months of September according to the analysis happened in 2016 and 2014 (+0.87 degrees Celsius) and 2015 (+0.82 degrees Celsius).

    A global map of the September 2017 LOTI (land-ocean temperature index) anomaly, relative to the 1951-1980 September average

    The monthly analysis by the GISS team is assembled from publicly available data acquired by about 6,300 meteorological stations around the world, ship- and buoy-based instruments measuring sea surface temperature, and Antarctic research stations.

    The modern global temperature record begins around 1880 because previous observations didn’t cover enough of the planet. Monthly analyses are sometimes updated when additional data becomes available, and the results are subject to change.