Responses of Grassland Production to Single and Multiple Global Environmental Changes

Dukes, Jeffrey S.; Chiariello, Nona R.; Cleland, Elsa E.; Moore, Leon; Shaw, M. Rebecca; Thayer, Susan S.; Tobeck, Todd; Mooney, Harold A.; Field, Christopher B.

doi:10.1371/journal.pbio.0030319

Cited by 329 publications

(363 citation statements)

References 41 publications

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“…The JRGCE grassland is N-limited, and plant biomass responds positively to added N (ref. 26). In addition, when nutrient limitation is relieved, we see a distinct decline in arbuscular mycorrhizal fungi abundance in these soils 17 .…”

Section: Discussionmentioning

confidence: 82%

Warming and nitrogen deposition lessen microbial residue contribution to soil carbon pool

2012

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Microorganisms have a role as gatekeepers for terrestrial carbon fluxes, either causing its release to the atmosphere through their decomposition activities or preventing its release by stabilizing the carbon in a form that cannot be easily decomposed. Although research has focused on microbial sources of greenhouse gas production, somewhat limited attention has been paid to the microbial role in carbon sequestration. However, increasing numbers of reports indicate the importance of incorporating microbial-derived carbon into soil stable carbon pools. Here we investigate microbial residues in a California annual grassland after a continuous 9-year manipulation of three environmental factors (elevated CO 2 , warming and nitrogen deposition), singly and in combination. Our results indicate that warming and nitrogen deposition can both alter the fraction of carbon derived from microbes in soils, though for two very different reasons. A reduction in microbial carbon contribution to stable carbon pools may have implications for our predictions of global change impacts on soil stored carbon.

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Section: Discussionmentioning

confidence: 82%

Warming and nitrogen deposition lessen microbial residue contribution to soil carbon pool

2012

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“…At this site, grasses flower significantly earlier than forbs under ambient conditions, but elevated CO 2 and N deposition reduced the difference in flowering date between these two groups, increasing temporal overlap, decreasing phenological complementarity, and potentially increasing competition for one or more resources. In the JRGCE, elevated CO 2 suppressed the tendency of other environmental changes to stimulate primary production (40,41). Decreased phenological complementarity is one mechanism that could lead to such an effect, whereby delayed growth and resource uptake by grasses could overlap into the temporal window of forb activity, thus reducing the contribution of late-active forbs to overall production.…”

Section: Discussionmentioning

confidence: 99%

Diverse responses of phenology to global changes in a grassland ecosystem

Cleland

Chiariello²,

Loarie

et al. 2006

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

424

349

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Shifting plant phenology (i.e., timing of flowering and other developmental events) in recent decades establishes that species and ecosystems are already responding to global environmental change. Earlier flowering and an extended period of active plant growth across much of the northern hemisphere have been interpreted as responses to warming. However, several kinds of environmental change have the potential to influence the phenology of flowering and primary production. Here, we report shifts in phenology of flowering and canopy greenness (Normalized Difference Vegetation Index) in response to four experimentally simulated global changes: warming, elevated CO 2, nitrogen (N) deposition, and increased precipitation. Consistent with previous observations, warming accelerated both flowering and greening of the canopy, but phenological responses to the other global change treatments were diverse. Elevated CO 2 and N addition delayed flowering in grasses, but slightly accelerated flowering in forbs. The opposing responses of these two important functional groups decreased their phenological complementarity and potentially increased competition for limiting soil resources. At the ecosystem level, timing of canopy greenness mirrored the flowering phenology of the grasses, which dominate primary production in this system. Elevated CO 2 delayed greening, whereas N addition dampened the acceleration of greening caused by warming. Increased precipitation had no consistent impacts on phenology. This diversity of phenological changes, between plant functional groups and in response to multiple environmental changes, helps explain the diversity in large-scale observations and indicates that changing temperature is only one of several factors reshaping the seasonality of ecosystem processes.

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mentioning

confidence: 89%

“…The Cedar Creek FACE study occurs in an herbaceous community in which plant composition is dynamic, but the number of possible plant species is restricted in order to maintain experimental diversity treatments 6 . On the other hand, an annual grassland of unmanipulated composition elicited no effect of N on CO 2 response 19 .We hypothesized that differences in individual species responses to elevated CO 2 and N could feed back to regulate the whole ecosystem response to these global change factors. To test this, we manipulated atmospheric CO 2 concentration and soil N availability factorially (four treatment groups, n 5 5) in a herbaceous brackish wetland 10 where plant community composition is capable of responding rapidly to environmental change.…”

mentioning

confidence: 99%

Ecosystem response to elevated CO2 levels limited by nitrogen-induced plant species shift

Langley

Megonigal

2010

Nature

223

176

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Terrestrial ecosystems gain carbon through photosynthesis and lose it mostly in the form of carbon dioxide (CO 2 ). The extent to which the biosphere can act as a buffer against rising atmospheric CO 2 concentration in global climate change projections remains uncertain at the present stage [1][2][3][4] . Biogeochemical theory predicts that soil nitrogen (N) scarcity may limit natural ecosystem response to elevated CO 2 concentration, diminishing the CO 2 -fertilization effect on terrestrial plant productivity in unmanaged ecosystems [3][4][5][6][7] . Recent models have incorporated such carbon-nitrogen interactions and suggest that anthropogenic N sources could help sustain the future CO 2 -fertilization effect 8,9 . However, conclusive demonstration that added N enhances plant productivity in response to CO 2 -fertilization in natural ecosystems remains elusive. Here we manipulated atmospheric CO 2 concentration and soil N availability in a herbaceous brackish wetland where plant community composition is dominated by a C 3 sedge and C 4 grasses, and is capable of responding rapidly to environmental change 10 . We found that N addition enhanced the CO 2 -stimulation of plant productivity in the first year of a multi-year experiment, indicating N-limitation of the CO 2 response. But we also found that N addition strongly promotes the encroachment of C 4 plant species that respond less strongly to elevated CO 2 concentrations. Overall, we found that the observed shift in the plant community composition ultimately suppresses the CO 2 -stimulation of plant productivity by the third and fourth years. Although extensive research has shown that global change factors such as elevated CO 2 concentrations and N pollution affect plant species differently 11-13, and that they may drive plant community changes 14-17 , we demonstrate that plant community shifts can act as a feedback effect that alters the whole ecosystem response to elevated CO 2 concentrations. Moreover, we suggest that trade-offs between the abilities of plant taxa to respond positively to different perturbations may constrain natural ecosystem response to global change.The progressive nitrogen limitation (PNL) hypothesis 7 suggests that N additions should enhance CO 2 effects on plant productivity. However, only a limited number of studies have provided direct experimental evidence that N addition actually sustains or enhances the CO 2 response of productivity 3,7 . In a pine forest, N addition amplified the CO 2 effect on woody tissue increment 5 . A CO 2 3 N experiment in a grassland reported that a positive CO 2 3 N interaction emerged after three years, indicating that N addition amplified the effect of elevated CO 2 on productivity 6 . In managed ryegrass swards, N addition yielded larger CO 2 responses, an effect that strengthened over time on a relative basis, but diminished in terms of absolute magnitude 18 .As originally articulated, the PNL hypothesis does not explicitly consider the effects that elevated CO 2 and added N can have on the ecosyst...

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Responses of Grassland Production to Single and Multiple Global Environmental Changes

Cited by 329 publications

References 41 publications

Warming and nitrogen deposition lessen microbial residue contribution to soil carbon pool

Warming and nitrogen deposition lessen microbial residue contribution to soil carbon pool

Diverse responses of phenology to global changes in a grassland ecosystem

Ecosystem response to elevated CO2 levels limited by nitrogen-induced plant species shift

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