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Bechtold EK, Wanek W, Nuesslein B, DaCosta M, Nüsslein K. Successional changes in bacterial phyllosphere communities are plant-host species dependent. Appl Environ Microbiol 2024; 90:e0175023. [PMID: 38349147 PMCID: PMC11206175 DOI: 10.1128/aem.01750-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 01/17/2024] [Indexed: 03/21/2024] Open
Abstract
Phyllosphere microbial communities are increasingly experiencing intense pulse disturbance events such as drought. It is currently unknown how phyllosphere communities respond to such disturbances and if they are able to recover. We explored the stability of phyllosphere communities over time, in response to drought stress, and under recovery from drought on temperate forage grasses. Compositional or functional changes were observed during the disturbance period and whether communities returned to non-stressed levels following recovery. Here, we found that phyllosphere community composition shifts as a result of simulated drought but does not fully recover after irrigation is resumed and that the degree of community response to drought is host species dependent. However, while community composition had changed, we found a high level of functional stability (resistance) over time and in the water deficit treatment. Ecological modeling enabled us to understand community assembly processes over a growing season and to determine if they were disrupted during a disturbance event. Phyllosphere community succession was characterized by a strong level of ecological drift, but drought disturbance resulted in variable selection, or, in other words, communities were diverging due to differences in selective pressures. This successional divergence of communities with drought was unique for each host species. Understanding phyllosphere responses to environmental stresses is important as climate change-induced stresses are expected to reduce crop productivity and phyllosphere functioning. IMPORTANCE Leaf surface microbiomes have the potential to influence agricultural and ecosystem productivity. We assessed their stability by determining composition, functional resistance, and resilience. Resistance is the degree to which communities remain unchanged as a result of disturbance, and resilience is the ability of a community to recover to pre-disturbance conditions. By understanding the mechanisms of community assembly and how they relate to the resistance and resilience of microbial communities under common environmental stresses such as drought, we can better understand how communities will adapt to a changing environment and how we can promote healthy agricultural microbiomes. In this study, phyllosphere compositional stability was highly related to plant host species phylogeny and, to a lesser extent, known stress tolerances. Phyllosphere community assembly and stability are a result of complex interactions of ecological processes that are differentially imposed by host species.
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Affiliation(s)
- Emily K. Bechtold
- Department of Microbiology, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Wolfgang Wanek
- Division of Terrestrial Ecosystem Research, Center of Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Benedikt Nuesslein
- Department of Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Michelle DaCosta
- Stockbridge School of Agriculture, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Klaus Nüsslein
- Department of Microbiology, University of Massachusetts Amherst, Amherst, Massachusetts, USA
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Fulé PZ, Sánchez Meador AJ, Moore MM, Covington WW, Kolb TE, Huffman DW, Normandin DP, Roccaforte JP. Forest restoration treatments increased growth and did not change survival of ponderosa pines in severe drought, Arizona. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2022; 32:e2717. [PMID: 36184740 DOI: 10.1002/eap.2717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 05/15/2022] [Accepted: 06/13/2022] [Indexed: 06/16/2023]
Abstract
We report on survival and growth of ponderosa pines (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) 2 decades after forest restoration treatments in the G. A. Pearson Natural Area, northern Arizona. Despite protection from harvest that conserved old trees, a dense forest susceptible to uncharacteristically severe disturbance had developed during more than a century of exclusion of the previous frequent surface-fire regime that ceased upon Euro-American settlement in approximately 1876. Trees were thinned in 1993 to emulate prefire-exclusion forest conditions, accumulated forest floor was removed, and surface fire was re-introduced at 4-years intervals (full restoration). There was also a partial restoration treatment consisting of thinning alone. Compared with untreated controls, mortality of old trees (mean age 243 years, maximum 462 years) differed by <1 tree ha-1 and old-tree survival was statistically indistinguishable between treatments (90.5% control, 92.3% full, 82.6% partial). Post-treatment growth as measured by basal area increment of both old (pre-1876) and young (post-1876) pines was significantly higher in both treatments than counterpart control trees for more than 2 decades following thinning. Drought meeting the definition of megadrought affected the region almost all the time since the onset of the experiment, including 3 years that were severely dry. Growth of all trees declined in the driest 3 years, but old and young treated trees had significantly less decline. Association of tree growth with temperature (negative correlation) and precipitation (positive correlation) was much weaker in treated trees, indicating that they may experience less growth decline from warmer, drier conditions predicted in future decades. Overall, tree responses after the first 2 decades following treatment suggest that forest restoration treatments have led to substantial, sustained improvement in the growth of old and young ponderosa pines without affecting old-tree survival, thereby improving resilience to a warming climate.
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Affiliation(s)
- Peter Z Fulé
- School of Forestry, Northern Arizona University, Flagstaff, Arizona, USA
| | - Andrew J Sánchez Meador
- School of Forestry, Northern Arizona University, Flagstaff, Arizona, USA
- Ecological Restoration Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Margaret M Moore
- School of Forestry, Northern Arizona University, Flagstaff, Arizona, USA
| | - W Wallace Covington
- School of Forestry, Northern Arizona University, Flagstaff, Arizona, USA
- Ecological Restoration Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Thomas E Kolb
- School of Forestry, Northern Arizona University, Flagstaff, Arizona, USA
| | - David W Huffman
- Ecological Restoration Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Donald P Normandin
- Ecological Restoration Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - John Paul Roccaforte
- Ecological Restoration Institute, Northern Arizona University, Flagstaff, Arizona, USA
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Zinke J, Browning SA, Hoell A, Goodwin ID. The West Pacific Gradient tracks ENSO and zonal Pacific sea surface temperature gradient during the last Millennium. Sci Rep 2021; 11:20395. [PMID: 34650137 PMCID: PMC8516908 DOI: 10.1038/s41598-021-99738-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 09/28/2021] [Indexed: 11/28/2022] Open
Abstract
Small changes in Pacific temperature gradients connected with the El Niño Southern Oscillation (ENSO) influence the Walker Circulation and are related to global climate anomalies. Therefore, it is of paramount importance to develop robust indices of their past behavior. Here, we reconstruct the difference in sea surface temperature between the west and central Pacific during ENSO, coined the West Pacific Gradient (WPG), based on the Last Millennium Paleo Hydrodynamics Data Assimilation. We show that the WPG tracks ENSO variability and strongly co-varies with the zonal gradient in Pacific sea surface temperature. We demonstrate that the WPG strength is related to significant atmospheric circulation and precipitation anomalies during historical El Niño and La Niña events by magnifying or weakening droughts and pluvials across the Indo-Pacific. We show that an extreme negative WPG coupled to a strong zonal Pacific temperature gradient is associated with enhanced megadroughts in North America between 1400 CE and the late sixteenth century. The twentieth century stands out in showing the most extreme swings between positive and negative WPG conditions over the past Millennium. We conclude that the WPG is a robust index together with ENSO indices to reveal past changes in Pacific zonal sea surface temperature gradient variability.
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Affiliation(s)
- J. Zinke
- grid.9918.90000 0004 1936 8411School of Geography, Geology and the Environment, University of Leicester, University Rd, Leicester, LE1 7RH UK ,grid.1032.00000 0004 0375 4078Molecular and Life Sciences, Curtin University, Kent St, Bentley, Perth, WA 6102 Australia ,grid.1046.30000 0001 0328 1619Australian Institute of Marine Science, Townville, PMB No.3, Townsville, QLD 4810 Australia ,grid.11951.3d0000 0004 1937 1135School of Geography, Archaeology and Environmental Studies, University of Witwatersrand, Braamfontein, Johannesburg, 2000 South Africa
| | | | - A. Hoell
- grid.3532.70000 0001 1266 2261Physical Sciences Laboratory, NOAA, Boulder, CO USA
| | - I. D. Goodwin
- grid.1012.20000 0004 1936 7910UWA Oceans Institute, University of Western, Crawley, WA 6009 Australia ,Climalab, Newport, NSW 2106 Australia ,grid.1005.40000 0004 4902 0432Climate Change Research Centre, University of New South Wales, Sydney, NSW 2052 Australia
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Phyllosphere Community Assembly and Response to Drought Stress on Common Tropical and Temperate Forage Grasses. Appl Environ Microbiol 2021; 87:e0089521. [PMID: 34161142 DOI: 10.1128/aem.00895-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Grasslands represent a critical ecosystem important for global food production, soil carbon storage, and water regulation. Current intensification and expansion practices add to the degradation of grasslands and dramatically increase greenhouse gas emissions and pollution. Thus, new ways to sustain and improve their productivity are needed. Research efforts focus on the plant-leaf microbiome, or phyllosphere, because its microbial members impact ecosystem function by influencing pathogen resistance, plant hormone production, and nutrient availability through processes including nitrogen fixation. However, little is known about grassland phyllospheres and their response to environmental stress. In this study, globally dominant temperate and tropical forage grass species were grown in a greenhouse under current climate conditions and drought conditions that mimic future climate predictions to understand if (i) plant host taxa influence microbial community assembly, (ii) microbial communities respond to drought stress, and (iii) phyllosphere community changes correlate to changes in plant host traits and stress-response strategies. Community analysis using high-resolution sequencing revealed Gammaproteobacteria as the dominant bacterial class, which increased under severe drought stress on both temperate and tropical grasses while overall bacterial community diversity declined. Bacterial community diversity, structure, and response to drought were significantly different between grass species. This community dependence on plant host species correlated with differences in grass species traits, which became more defined under drought stress conditions, suggesting symbiotic evolutionary relationships between plant hosts and their associated microbial community. Further understanding these strategies and the functions microbes provide to plants will help us utilize microbes to promote agricultural and ecosystem productivity in the future. IMPORTANCE Globally important grassland ecosystems are at risk of degradation due to poor management practices compounded by predicted increases in severity and duration of drought over the next century. Finding new ways to support grassland productivity is critical to maintaining their ecological and agricultural benefits. Discerning how grassland microbial communities change in response to climate stress will help us understand how plant-microbe relationships may be useful to sustainably support grasslands in the future. In this study, phyllosphere community diversity and composition were significantly altered under drought conditions. The significance of our research is demonstrating how severe climate stress reduces bacterial community diversity, which previously was directly associated with decreased plant productivity. These findings guide future questions about functional plant-microbe interactions under stress conditions, greatly enhancing our understanding of how bacteria can increase food security by promoting grassland growth and resilience.
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Global hydroclimatic response to tropical volcanic eruptions over the last millennium. Proc Natl Acad Sci U S A 2021; 118:2019145118. [PMID: 33798096 PMCID: PMC8000584 DOI: 10.1073/pnas.2019145118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Future large tropical volcanic eruptions will induce global hydroclimatic changes, superimposed on anthropogenic climate change. Understanding how volcanic eruptions affect global hydroclimate is therefore critically important. Tejedor et al. use a new paleoclimatic product, which combines information from high-resolution proxies and climate models, to estimate volcanic impacts on hydroclimate over the last millennium. They find that past eruptions caused severe drying in tropical Africa and across Central Asia and the Middle East and significantly wetter conditions over Oceania and the South American monsoon region, some of which persisted for a decade or longer. These proxy-based findings suggest that, relative to estimates from a state-of-the-art climate model, much larger and persistent hydroclimatic changes are possible across regions of important socioeconomic activity. Large tropical volcanic eruptions can affect the climate of many regions on Earth, yet it is uncertain how the largest eruptions over the past millennium may have altered Earth’s hydroclimate. Here, we analyze the global hydroclimatic response to all the tropical volcanic eruptions over the past millennium that were larger than the Mount Pinatubo eruption of 1991. Using the Paleo Hydrodynamics Data Assimilation product (PHYDA), we find that these large volcanic eruptions tended to produce dry conditions over tropical Africa, Central Asia and the Middle East and wet conditions over much of Oceania and the South American monsoon region. These anomalies are statistically significant, and they persisted for more than a decade in some regions. The persistence of the anomalies is associated with southward shifts in the Intertropical Convergence Zone and sea surface temperature changes in the Pacific and Atlantic oceans. We compare the PHYDA results with the stand-alone model response of the Community Earth System Model (CESM)-Last Millennium Ensemble. We find that the proxy-constrained PHYDA estimates are larger and more persistent than the responses simulated by CESM. Understanding which of these estimates is more realistic is critical for accurately characterizing the hydroclimate risks of future volcanic eruptions.
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Alizadeh MR, Adamowski J, Nikoo MR, AghaKouchak A, Dennison P, Sadegh M. A century of observations reveals increasing likelihood of continental-scale compound dry-hot extremes. SCIENCE ADVANCES 2020; 6:6/39/eaaz4571. [PMID: 32967839 PMCID: PMC7531886 DOI: 10.1126/sciadv.aaz4571] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 08/03/2020] [Indexed: 05/25/2023]
Abstract
Using over a century of ground-based observations over the contiguous United States, we show that the frequency of compound dry and hot extremes has increased substantially in the past decades, with an alarming increase in very rare dry-hot extremes. Our results indicate that the area affected by concurrent extremes has also increased significantly. Further, we explore homogeneity (i.e., connectedness) of dry-hot extremes across space. We show that dry-hot extremes have homogeneously enlarged over the past 122 years, pointing to spatial propagation of extreme dryness and heat and increased probability of continental-scale compound extremes. Last, we show an interesting shift between the main driver of dry-hot extremes over time. While meteorological drought was the main driver of dry-hot events in the 1930s, the observed warming trend has become the dominant driver in recent decades. Our results provide a deeper understanding of spatiotemporal variation of compound dry-hot extremes.
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Affiliation(s)
- Mohammad Reza Alizadeh
- Department of Bioresource Engineering, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada
| | - Jan Adamowski
- Department of Bioresource Engineering, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada
| | - Mohammad Reza Nikoo
- Department of Civil and Environmental Engineering, College of Engineering, Shiraz University, Shiraz 7134851156, Iran
| | - Amir AghaKouchak
- Department of Civil and Environmental Engineering, University of California, Irvine, 4130 Engineering Gateway, Irvine, CA 92697, USA
- Department of Earth System Science, University of California, Irvine, 3200 Croul Hall Irvine, CA 92697, USA
| | - Philip Dennison
- Department of Geography, University of Utah, 260 S Central Campus Dr, Rm 4625, Salt Lake City, UT 84112, USA
| | - Mojtaba Sadegh
- Department of Civil Engineering, Boise State University, 1910 University Drive, Boise, ID 83725-2060, USA.
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Erb MP, Emile-Geay J, Hakim GJ, Steiger N, Steig EJ. Atmospheric dynamics drive most interannual U.S. droughts over the last millennium. SCIENCE ADVANCES 2020; 6:eaay7268. [PMID: 32821813 PMCID: PMC7413725 DOI: 10.1126/sciadv.aay7268] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 03/16/2020] [Indexed: 06/11/2023]
Abstract
The American West exemplifies drought-sensitive regions with growing populations. Paleoclimate investigations have documented severe droughts in this region before European settling, with major implications for water management and planning. Here, we leverage paleoclimate data assimilation to reconstruct past climate states, enabling a large-scale multivariate investigation of U.S. drought dynamics over the last millennium. These results confirm that La Niña conditions significantly influence southwest U.S. drought over the past millennium but only account for, by one metric, ~13% of interannual drought variability in that region. Atlantic sea surface temperatures may also contribute a small influence, but unexplained variability suggests a substantial role for internal atmospheric variability. This conclusion is buttressed by analysis of simulations from the Community Earth System Model Last Millennium Ensemble. While greenhouse gases will increase future drought risk, as shown in other work, interannual U.S. drought variations will also be widely influenced by processes internal to the atmosphere.
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Affiliation(s)
- M. P. Erb
- Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA
- School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ, USA
| | - J. Emile-Geay
- Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA
| | - G. J. Hakim
- Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
| | - N. Steiger
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
| | - E. J. Steig
- Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
- Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA
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Williams AP, Cook ER, Smerdon JE, Cook BI, Abatzoglou JT, Bolles K, Baek SH, Badger AM, Livneh B. Large contribution from anthropogenic warming to an emerging North American megadrought. Science 2020; 368:314-318. [DOI: 10.1126/science.aaz9600] [Citation(s) in RCA: 297] [Impact Index Per Article: 74.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 03/10/2020] [Indexed: 11/02/2022]
Affiliation(s)
- A. Park Williams
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
| | - Edward R. Cook
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
| | - Jason E. Smerdon
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
| | - Benjamin I. Cook
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
- NASA Goddard Institute of Space Studies, New York, NY 10025, USA
| | - John T. Abatzoglou
- Department of Geography, University of Idaho, Moscow, ID 83844, USA
- Management of Complex Systems Department, UC Merced, Merced, CA 95343, USA
| | - Kasey Bolles
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
| | - Seung H. Baek
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
- Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027, USA
| | - Andrew M. Badger
- Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80302, USA
- Universities Space Research Association, Columbia, MD 21046, USA
- NASA Goddard Space Flight Center, Greenbelt, MD, USA 20771, USA
| | - Ben Livneh
- Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80302, USA
- Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80309, USA
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Affiliation(s)
- David W. Stahle
- Department of Geosciences, University of Arkansas, Fayetteville, AR 72701, USA
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