Rainfall Variability, Carbon Cycling, and Plant Species Diversity in a Mesic Grassland

Knapp, Alan K.; Fay, Philip A.; Blair, John M.; Collins, Scott L.; Smith, Melinda D.; Carlisle, Jonathan D.; Harper, C. W.; Danner, Brett T.; Lett, Michelle S.; McCarron, James K.

doi:10.1126/science.1076347

Cited by 977 publications

(953 citation statements)

References 21 publications

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“…Apart from extremes, changes in the seasonal distribution of climate factors may be decisive. This is particularly evident for water-carbon-cycle interactions, where changes in the frequency or timing of rainfall without changes in the annual total may have profound effects on ecosystem productivity 12 , as these factors determine whether the water will be used by plants and transpired, or will just run off or evaporate.…”

Section: Climate Variability and Extremesmentioning

confidence: 99%

Terrestrial ecosystem carbon dynamics and climate feedbacks

Heimann

Reichstein

2008

Nature

1,339

863

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It has only been recognized relatively recently that biological processes can control and steer the Earth system in a globally significant way. Terrestrial ecosystems constitute a major player in this respect: they can release or absorb globally relevant greenhouse gases such as carbon dioxide (CO 2 ), methane and nitrous oxide, they emit aerosols and aerosol precursors, and they control exchanges of energy, water and momentum between the atmosphere and the land surface. Ecosystems themselves are subject to local climatic conditions, implying a multitude of climate-ecosystem feedbacks that might amplify or dampen regional and global climate change. Of these feedbacks, that between the carbon cycle and climate has recently received much attention. Large quantities of carbon are stored in living vegetation and soil organic matter, and liberation of this carbon into the atmosphere as CO 2 or methane would have a serious impact on global climate. By definition, the carbon balance of an ecosystem at any point in time is the difference between its carbon gains and losses. Terrestrial ecosystems gain carbon through photosynthesis and lose it primarily as CO 2 through respiration in autotrophs (plants and photosynthetic bacteria) and heterotrophs (fungi, animals and some bacteria), although losses of carbon as volatile organic compounds, methane or dissolved carbon (that is, non-CO 2 losses) could also be significant. Quantifying and predicting these carbon-cycle-climate feedbacks is difficult, however, because of the limited understanding of the processes by which carbon and associated nutrients are transformed or recycled within ecosystems, in particular within soils, and exchanged with the overlying atmosphere.There is ample empirical evidence that the terrestrial component of the carbon cycle is responding to climate variations and trends on a global scale. This is exemplified by the strong interannual variations in the globally averaged growth rate of atmospheric CO 2 , which is tightly correlated with El Niño-Southern Oscillation climate variations (Fig. 1). Many lines of evidence show that the variations in the CO 2 growth rate are mainly caused by terrestrial effects, in particular the impacts of heat and drought on the vegetation of western Amazonia and southeastern Asia, leading to ecosystem carbon losses through decreased vegetation productivity and/or increased respiration. These interannual variations reflect short-term responses of the carbon cycle to climate perturbations, however, and cannot be expected to hold over longer timescales. Conversely, the close correlation between atmospheric concentrations of CO 2 , methane and nitrous oxide and global climate during the last glacial cycles 1 indicates that ecosystem-climate interactions are also operating on timescales of millennia and longer.Unfortunately, empirical evidence for global carbon-cycle-climate interactions on the timescale pertinent to current global climate change, that is, decades to centuries, is much scarcer. Hence the assessment on these ...

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Section: Climate Variability and Extremesmentioning

confidence: 99%

Terrestrial ecosystem carbon dynamics and climate feedbacks

Heimann

Reichstein

2008

Nature

1,339

863

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“…Studies that employ multi-scale approaches are valuable in demonstrating the importance of a holistic understanding of ecosystem responses to changing climatic variability [128] and extremity [4,14,129]. The magnitude of response to a climate extreme will likely vary with the ecological level of organization (e.g.…”

Section: Integrating Responses Across Ecological Scalesmentioning

confidence: 99%

Integrating plant ecological responses to climate extremes from individual to ecosystem levels

Felton

Smith

2017

Phil. Trans. R. Soc. B

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100

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Climate extremes will elicit responses from the individual to the ecosystem level. However, only recently have ecologists begun to synthetically assess responses to climate extremes across multiple levels of ecological organization. We review the literature to examine how plant responses vary and interact across levels of organization, focusing on how individual, population and community responses may inform ecosystem-level responses in herbaceous and forest plant communities. We report a high degree of variability at the individual level, and a consequential inconsistency in the translation of individual or population responses to directional changes in community- or ecosystem-level processes. The scaling of individual or population responses to community or ecosystem responses is often predicated upon the functional identity of the species in the community, in particular, the dominant species. Furthermore, the reported stability in plant community composition and functioning with respect to extremes is often driven by processes that operate at the community level, such as species niche partitioning and compensatory responses during or after the event. Future research efforts would benefit from assessing ecological responses across multiple levels of organization, as this will provide both a holistic and mechanistic understanding of ecosystem responses to increasing climatic variability. This article is part of the themed issue ‘Behavioural, ecological and evolutionary responses to extreme climatic events’.

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“…Aboveground net primary production (ANPP) is the main carbon fixation pathway, and even though its responses to changes in the amount of precipitation have been well studied, knowledge about the effect of precipitation variability on ANPP is rather poor, especially at the interannual to decadal time scales. A few short-term experiments focused on the effect of intra-annual precipitation variance and reported contrasting results, with null or positive effects in arid systems and negative effects in mesic systems (11)(12)(13)(14). A modeling exercise found that increased interannual precipitation variability and temperature in the Tibetan Plateau led to productivity reduction in grasslands (15).…”

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confidence: 99%

Enhanced precipitation variability decreases grass- and increases shrub-productivity

Gherardi

Sala

2015

Proc. Natl. Acad. Sci. U.S.A.

232

191

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Although projections of precipitation change indicate increases in variability, most studies of impacts of climate change on ecosystems focused on effects of changes in amount of precipitation, overlooking precipitation variability effects, especially at the interannual scale. Here, we present results from a 6-y field experiment, where we applied sequences of wet and dry years, increasing interannual precipitation coefficient of variation while maintaining a precipitation amount constant. Increased precipitation variability significantly reduced ecosystem primary production. Dominant plantfunctional types showed opposite responses: perennial-grass productivity decreased by 81%, whereas shrub productivity increased by 67%. This pattern was explained by different nonlinear responses to precipitation. Grass productivity presented a saturating response to precipitation where dry years had a larger negative effect than the positive effects of wet years. In contrast, shrubs showed an increasing response to precipitation that resulted in an increase in average productivity with increasing precipitation variability. In addition, the effects of precipitation variation increased through time. We argue that the differential responses of grasses and shrubs to precipitation variability and the amplification of this phenomenon through time result from contrasting root distributions of grasses and shrubs and competitive interactions among plant types, confirmed by structural equation analysis. Under drought conditions, grasses reduce their abundance and their ability to absorb water that then is transferred to deep soil layers that are exclusively explored by shrubs. Our work addresses an understudied dimension of climate change that might lead to widespread shrub encroachment reducing the provisioning of ecosystem services to society.C limate-change simulations project increases in precipitation variability as a result of global warming (1-3). The frequency of large precipitation events is expected to increase (3, 4), even in regions where precipitation will decrease (5). Similarly, the occurrence of wet days will decrease, resulting in a highly variable climate with enhanced probabilities of drought and heavy rainfall (5). Precipitation change will occur at intra-, interannual, and decadal scales. Mechanisms explaining such changes differ among temporal scales. At short-time scales, high precipitation variation results from the increased water-holding capacity of a warmer atmosphere that yields large rainfall events interspaced with droughts (6). At the interannual and decadal scales, climate change results in enhanced precipitation variability resulting from changes in atmospheric circulation that affect multiyear rainfall patterns (7).Although precipitation variability changes are part of the public narrative (8) and motivated a special Intergovernmental Panel on Climate Change (IPCC) report on extreme events (9), our understanding of the effect of climate variability on the carbon cycle in grasslands is still weak (10). A...

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Rainfall Variability, Carbon Cycling, and Plant Species Diversity in a Mesic Grassland

Cited by 977 publications

References 21 publications

Terrestrial ecosystem carbon dynamics and climate feedbacks

Terrestrial ecosystem carbon dynamics and climate feedbacks

Integrating plant ecological responses to climate extremes from individual to ecosystem levels

Enhanced precipitation variability decreases grass- and increases shrub-productivity

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