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Hoover DL, Hajek OL, Smith MD, Wilkins K, Slette IJ, Knapp AK. Compound hydroclimatic extremes in a semi-arid grassland: Drought, deluge, and the carbon cycle. GLOBAL CHANGE BIOLOGY 2022; 28:2611-2621. [PMID: 35076159 DOI: 10.1111/gcb.16081] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 12/10/2021] [Accepted: 12/10/2021] [Indexed: 05/08/2023]
Abstract
Climate change is predicted to increase the frequency and intensity of extreme events including droughts and large precipitation events or "deluges." While many studies have focused on the ecological impacts of individual events (e.g., a heat wave), there is growing recognition that when extreme events co-occur as compound extremes, (e.g., a heatwave during a drought), the additive effects on ecosystems are often greater than either extreme alone. In this study, we assessed a unique type of extreme-a contrasting compound extreme-where the extremes may have offsetting, rather than additive ecological effects, by examining how a deluge during a drought impacts productivity and carbon cycling in a semi-arid grassland. The experiment consisted of four treatments: a control (average precipitation), an extreme drought (<5th percentile), an extreme drought interrupted by a single deluge (>95th percentile), or an extreme drought interrupted by the equivalent amount of precipitation added in several smaller events. We highlight three key results. First, extreme drought resulted in early senescence, reduced carbon uptake, and a decline in net primary productivity relative to the control treatment. Second, the deluge imposed during extreme drought stimulated carbon fluxes and plant growth well above the levels of both the control and the drought treatment with several additional smaller rainfall events, emphasizing the importance of precipitation amount, event size, and timing. Third, while the deluge's positive effects on carbon fluxes and plant growth persisted for 1 month, the deluge did not completely offset the negative effects of extreme drought on end-of-season productivity. Thus, in the case of these contrasting hydroclimatic extremes, a deluge during a drought can stimulate temporally dynamic ecosystem processes (e.g., net ecosystem exchange) while only partially compensating for reductions in ecosystem functions over longer time scales (e.g., aboveground net primary productivity).
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Affiliation(s)
- David L Hoover
- USDA-ARS Rangeland Resources and Systems Research Unit, Crops Research Laboratory, Fort Collins, Colorado, USA
| | - Olivia L Hajek
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - Melinda D Smith
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - Kate Wilkins
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - Ingrid J Slette
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - Alan K Knapp
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
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Wang J, Yu C, Fu G. Asymmetrical Warming Between Elevations May Result in Similar Plant Community Composition Between Elevations in Alpine Grasslands. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.757943] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Asymmetrical warming between elevations is a common phenomenon and warming magnitude increases with increasing elevations on the Tibetan Plateau, which in turn may reduce temperature differences between elevations. However, it is still unclear how such phenomenon will affect plant community composition in alpine grasslands on the Tibetan Plateau. Therefore, in this study, we performed an experiment at three elevations (i.e., 4,300 m, 4,500 m, and 4,700 m) in alpine grasslands, the Northern Tibetan Plateau since May, 2010. Open top chambers were established at the elevations 4,500 m and 4,700 m. Plant species and phylogenetic composition were investigated in August, 2011–2019. There were no significant differences in plant species and phylogenetic composition, environmental temperature and moisture conditions between the elevation 4,300 m under non-warming conditions and the elevation 4,500 m under warming conditions in 2019. There were also no significant differences in plant species composition, environmental temperature and moisture conditions between the elevation 4,500 m under non-warming conditions and the elevation 4,700 m under warming conditions in 2019. Therefore, the narrowing temperature differences between elevations may result in plant community composition between elevations tending to be similar in alpine grasslands on the Tibetan Plateau under future elevational asymmetrical warming.
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Hydraulic traits of co-existing conifers do not correlate with local hydroclimate condition: a case study in the northern Rocky Mountains, U.S.A. Oecologia 2020; 197:1049-1062. [PMID: 33025266 DOI: 10.1007/s00442-020-04772-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 09/29/2020] [Indexed: 10/23/2022]
Abstract
In this study, we examined the inter- and intra-specific variation of hydraulic traits of three conifers of the Northern Rockies: Pinus ponderosa, Picea engelmannii, and Pseudotsuga menziesii to understand the mechanisms that allow different plant species to co-exist across a watershed. We quantified differences in plant xylem water potential (ψx), xylem tissue vulnerability to cavitation (P50, or ψ causing 50% loss of hydraulic conductivity), and safety margins for co-occurring trees from low and high elevations. We then investigated xylem vulnerability to cavitation with rooting depth. We found that xylem vulnerability to cavitation did not correspond to where tree species were found in the landscape. For example, P. ponderosa grew in more xeric locations, while P. engelmannii were largely confined to more mesic locations, yet P. engelmannii had more negative P50 values. P. menziesii had the lowest P50 value, but displayed little variation in vulnerability to cavitation across the hydroclimatic gradient. These patterns were also reflected in the safety margins; P. menziesii had the widest safety margin, P. engelmannii was intermediate, and P. ponderosa displayed the narrowest safety margin. All three species were also using water sources deeper than 30 cm in depth, allowing them to persist throughout the mid-summer drought. Overall, species-specific hydraulic traits did not necessarily follow a predictable response to the environment; instead, a combination of physiological and morphological traits likely allow trees to persist across a broader hydroclimatic gradient than would be otherwise expected from hydraulic trait measurements alone.
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Winkler DE, Belnap J, Duniway MC, Hoover D, Reed SC, Yokum H, Gill R. Seasonal and individual event-responsiveness are key determinants of carbon exchange across plant functional types. Oecologia 2020; 193:811-825. [PMID: 32728948 DOI: 10.1007/s00442-020-04718-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 07/20/2020] [Indexed: 11/29/2022]
Abstract
Differentiation in physiological activity is a critical component of resource partitioning in resource-limited environments. For example, it is crucial to understand how plant physiological performance varies through time for different functional groups to forecast how terrestrial ecosystems will respond to change. Here, we tracked the seasonal progress of 13 plant species representing C3 shrub, perennial C3 and C4 grass, and annual forb functional groups of the Colorado Plateau, USA. We tested for differences in carbon assimilation strategies and how photosynthetic rates related to recent, seasonal, and annual precipitation and temperature variables. Despite seasonal shifts in species presence and activity, we found small differences in seasonally weighted annual photosynthetic rates among groups. However, differences in the timing of maximum assimilation (Anet) were strongly functional group-dependent. C3 shrubs employed a relatively consistent, low carbon capture strategy and maintained activity year-round but switched to a rapid growth strategy in response to recent climate conditions. In contrast, grasses maintained higher carbon capture during spring months when all perennials had maximum photosynthetic rates, but grasses were dormant during months when shrubs remained active. Perennial grass Anet rates were explained in part by precipitation accumulated during the preceding year and average maximum temperatures during the past 48 h, a result opposite to shrubs. These results lend insight into diverse physiological strategies and their connections to climate, and also point to the potential for shrubs to increase in abundance in response to increased climatic variability in drylands, given shrubs' ability to respond rapidly to changing conditions.
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Affiliation(s)
- Daniel E Winkler
- U.S. Geological Survey, Southwest Biological Science Center, Moab, UT, 84532, USA.
| | - Jayne Belnap
- U.S. Geological Survey, Southwest Biological Science Center, Moab, UT, 84532, USA
| | - Michael C Duniway
- U.S. Geological Survey, Southwest Biological Science Center, Moab, UT, 84532, USA
| | - David Hoover
- Rangeland Resources and Systems Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Fort Collins, 80526, USA
| | - Sasha C Reed
- U.S. Geological Survey, Southwest Biological Science Center, Moab, UT, 84532, USA
| | - Hannah Yokum
- Department of Biology, Brigham Young University, Provo, UT, 84604, USA
| | - Richard Gill
- Department of Biology, Brigham Young University, Provo, UT, 84604, USA
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Chi Y, Zhou L, Yang Q, Li S, Zheng S. Increased snowfall weakens complementarity of summer water use by different plant functional groups. Ecol Evol 2019; 9:4264-4274. [PMID: 31016003 PMCID: PMC6468069 DOI: 10.1002/ece3.5058] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 12/21/2018] [Accepted: 02/25/2019] [Indexed: 11/13/2022] Open
Abstract
Winter snowfall is an important water source for plants during summer in semiarid regions. Snow, rain, soil water, and plant water were sampled for hydrogen and oxygen stable isotopes analyses under control and increased snowfall conditions in the temperate steppe of Inner Mongolia, China. Our study showed that the snowfall contribution to plant water uptake continued throughout the growing season and was detectable even in the late growing season. Snowfall versus rainfall accounted for 30% and 70%, respectively, of the water source for plants, on the basis of hydrogen stable isotope signature (δD) analysis, and accounted for 12% and 88%, respectively, on the basis of oxygen stable isotope signature (δ18O) analysis. Water use partitioning between topsoil and subsoil was found among species with different rooting depths. Increased snowfall weakened complementarity of plant water use during summer. Our study provides insights into the relationships between precipitation regimes and species interactions in semiarid regions.
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Affiliation(s)
- Yonggang Chi
- College of Geography and Environmental SciencesZhejiang Normal UniversityJinhuaChina
- State Key Laboratory of Vegetation and Environmental Change, Institute of BotanyChinese Academy of SciencesBeijingChina
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGeorgia
| | - Lei Zhou
- College of Geography and Environmental SciencesZhejiang Normal UniversityJinhuaChina
- Key Laboratory of Ecosystem Network Observation and Modelling, Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijingChina
| | - Qingpeng Yang
- Key Laboratory of Forest Ecology and Management, Institute of Applied EcologyChinese Academy of SciencesShenyangChina
| | - Shao‐peng Li
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGeorgia
| | - Shuxia Zheng
- State Key Laboratory of Vegetation and Environmental Change, Institute of BotanyChinese Academy of SciencesBeijingChina
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Suonan J, Classen AT, Sanders NJ, He J. Plant phenological sensitivity to climate change on the Tibetan Plateau and relative to other areas of the world. Ecosphere 2019. [DOI: 10.1002/ecs2.2543] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Ji Suonan
- Department of Ecology College of Urban and Environmental Sciences Key Laboratory for Earth Surface Processes of the Ministry of Education Peking University 5 Yiheyuan Road Beijing 100871 China
- Key Laboratory of Alpine Ecology and Biodiversity Institute of Tibetan Plateau Research Chinese Academy of Sciences No. 16 Lincui Road Beijing 100101 China
- The Center for Macroecology, Evolution, and Climate Natural History Museum of Denmark University of Copenhagen Copenhagen DK‐2100 Denmark
| | - Aimée T. Classen
- The Center for Macroecology, Evolution, and Climate Natural History Museum of Denmark University of Copenhagen Copenhagen DK‐2100 Denmark
- Rubenstein School of Environment & Natural Resources University of Vermont Burlington Vermont 05405 USA
- The Gund Institute for Environment University of Vermont Burlington Vermont 05405 USA
| | - Nathan J. Sanders
- The Center for Macroecology, Evolution, and Climate Natural History Museum of Denmark University of Copenhagen Copenhagen DK‐2100 Denmark
- Rubenstein School of Environment & Natural Resources University of Vermont Burlington Vermont 05405 USA
- The Gund Institute for Environment University of Vermont Burlington Vermont 05405 USA
| | - Jin‐Sheng He
- Department of Ecology College of Urban and Environmental Sciences Key Laboratory for Earth Surface Processes of the Ministry of Education Peking University 5 Yiheyuan Road Beijing 100871 China
- State Key Laboratory of Grassland Agro‐Ecosystems College of Pastoral Agriculture Science and Technology Lanzhou University Lanzhou 730000 China
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Hopping KA, Knapp AK, Dorji T, Klein JA. Warming and land use change concurrently erode ecosystem services in Tibet. GLOBAL CHANGE BIOLOGY 2018; 24:5534-5548. [PMID: 30086187 DOI: 10.1111/gcb.14417] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 06/10/2018] [Accepted: 07/22/2018] [Indexed: 06/08/2023]
Abstract
Alpine meadows on the Tibetan Plateau comprise the largest alpine ecosystem in the world and provide critical ecosystem services, including forage production and carbon sequestration, on which people depend from local to global scales. However, the provision of these services may be threatened by climate warming combined with land use policies that are altering if and how pastoralists can continue to graze livestock, the dominant livelihood practice in this region for millennia. We synthesized findings from a climate warming and yak grazing experiment with landscape-level observations in central Tibet to gain insight into the trajectories of change that Tibet's alpine meadows will undergo in response to expected changes in climate and land use. We show that within 5 years, experimental warming drove an alpine community with intact, sedge-dominated turfs into a degraded state. With removal of livestock, consistent with policy intended to reverse degradation, a longer-term shift to a more shrub-dominated community will likely occur. Neither degraded nor shrub meadows produce forage or sequester carbon to the same degree as intact meadows, indicating that climate warming and drying will reduce the ability of Tibet's alpine meadows to provide key ecosystem services, and that livestock reduction policies intended to counteract trajectories of land degradation instead endanger contemporary livelihoods on the Tibetan Plateau.
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Affiliation(s)
- Kelly A Hopping
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado
- Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado
| | - Alan K Knapp
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado
- Department of Biology, Colorado State University, Fort Collins, Colorado
| | - Tsechoe Dorji
- Key Laboratory of Alpine Ecology and Biodiversity, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Lhasa, Tibet Autonomous Region, China
- CAS Center for Excellence in Tibetan Plateau Earth Science, Beijing, China
| | - Julia A Klein
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado
- Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado
- Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, Colorado
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Yang Y, Hopping KA, Wang G, Chen J, Peng A, Klein JA. Permafrost and drought regulate vulnerability of Tibetan Plateau grasslands to warming. Ecosphere 2018. [DOI: 10.1002/ecs2.2233] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Yan Yang
- Institute of Mountain Hazards & Environment Chinese Academy of Sciences Chengdu 610041 China
- Department of Ecosystem Science and Sustainability Colorado State University Campus Delivery 1476 Fort Collins Colorado 80523 USA
| | - Kelly A. Hopping
- Department of Earth System Science Stanford University 473 Via Ortega Stanford California 94305 USA
| | - Genxu Wang
- Institute of Mountain Hazards & Environment Chinese Academy of Sciences Chengdu 610041 China
| | - Ji Chen
- State Key Laboratory of Loess and Quaternary Geology and Key Laboratory of Aerosol Chemistry and Physics Institute of Earth Environment Chinese Academy of Sciences Xi'an 710061 China
- Center for Ecological and Environmental Sciences Northwestern Polytechnical University Xi'an 710072 China
| | - Ahui Peng
- Institute of Mountain Hazards & Environment Chinese Academy of Sciences Chengdu 610041 China
| | - Julia A. Klein
- Department of Ecosystem Science and Sustainability Colorado State University Campus Delivery 1476 Fort Collins Colorado 80523 USA
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Wei D, Wang Y, Wang Y. Considerable methane uptake by alpine grasslands despite the cold climate: in situ measurements on the central Tibetan Plateau, 2008-2013. GLOBAL CHANGE BIOLOGY 2015; 21:777-788. [PMID: 25044864 DOI: 10.1111/gcb.12690] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 06/25/2014] [Indexed: 06/03/2023]
Abstract
The uptake of CH4 by aerate soil plays a secondary role in the removal of tropospheric CH4 , but it is still highly uncertain in terms of its magnitude, spatial, and temporal variation. In an attempt to quantify the sink of the vast alpine grasslands (1,400,000 km(2)) of the Tibetan Plateau, we conducted in situ measurements in an alpine steppe (4730 m) and alpine meadow (4900 m) using the static chamber and gas chromatograph method. For the alpine steppe, measurements (2008-2013) suggested that there is large interannual variability in CH4 uptake, ranging from -48.8 to -95.8 μg CH4 m(-2) h(-1) (averaged of -71.5 ± 2.5 μg CH4 m(-2) h(-1)), due to the variability in precipitation seasonality. The seasonal pattern of CH4 uptakes in the form of stronger uptake in the early growing season and weaker uptake in the rainy season closely matched the precipitation seasonality and subsequent soil moisture variation. The relationships between alpine steppe CH4 uptake and soil moisture/temperature are best depicted by a quadratic function and an exponential function (Q10 = 1.67) respectively. Our measurements also showed that the alpine meadow soil (average of -59.2 ± 3.7 μg CH4 m(-2) h(-1)) uptake less CH4 than the alpine steppe and produces a similar seasonal pattern, which is negatively regulated by soil moisture. Our measurements quantified--at values far higher than those estimated by process-based models--that both the alpine steppe and alpine meadow are considerable CH4 sinks, despite the cold weather of this high-altitude area. The consecutive measurements gathered in this study also highlight that precipitation seasonality tends to drive the interannual variation in CH4 uptake, indicating that future study should be done to better characterize how CH4 cycling might feedback to the more extreme climate.
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Affiliation(s)
- Da Wei
- Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Key Laboratory of Alpine Ecology and Biodiversity, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
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