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1.
Leaf litter production and decomposition in a poplar short-rotation coppice exposed to free air CO2 enrichment (POPFACE) 总被引:1,自引:0,他引:1
The capacity of forest ecosystems to sequester C in the soil relies on the net balance between litter production above, as well as, below ground, and decomposition processes. Nitrogen mineralization and its availability for plant growth and microbial activity often control the speed of both processes. Litter production, decomposition and N mineralization are strongly interdependent. Thus, their responses to global environmental changes (i.e. elevated CO2, climate, N deposition, etc.) cannot be fully understood if they are studied in isolation. In the present experiment, we investigated litter fall, litter decomposition and N dynamics in decomposing litter of three Populus spp., in the second and third growing season of a short rotation coppice under FACE. Elevated CO2 did not affect annual litter production but slightly retarded litter fall in the third growing season. In all species, elevated CO2 lowered N concentration, resulting in a reduction of N input to the soil via litter fall, but did not affect lignin concentrations. Litter decomposition was studied in bags incubated in situ both in control and FACE plots. Litter lost between 15% and 18% of the original mass during the eight months of field incubation. On average, litter produced under elevated CO2 attained higher residual mass than control litter. On the other end, when litter was incubated in FACE plots it exhibited higher decay rates. These responses were strongly species‐specific. All litter increased their N content during decomposition, indicating immobilization of N from external sources. Independent of the initial quality, litter incubated on FACE soils immobilized less N, possibly as a result of lower N availability in the soil. Indeed, our results refer to a short‐term decomposition experiment. However, according to a longer‐term model extrapolation of our results, we anticipate that in Mediterranean climate, under elevated atmospheric CO2, soil organic C pool of forest ecosystems may initially display faster turnover, but soil N availability will eventually limit the process. 相似文献
2.
Beth A. Newingham Cheryl H. Vanier Therese N. Charlet Kiona Ogle Stanley D. Smith Robert S. Nowak 《Global Change Biology》2013,19(7):2168-2181
Elevated atmospheric CO2 concentrations ([CO2]) generally increase primary production of terrestrial ecosystems. Production responses to elevated [CO2] may be particularly large in deserts, but information on their long‐term response is unknown. We evaluated the cumulative effects of elevated [CO2] on primary production at the Nevada Desert FACE (free‐air carbon dioxide enrichment) Facility. Aboveground and belowground perennial plant biomass was harvested in an intact Mojave Desert ecosystem at the end of a 10‐year elevated [CO2] experiment. We measured community standing biomass, biomass allocation, canopy cover, leaf area index (LAI), carbon and nitrogen content, and isotopic composition of plant tissues for five to eight dominant species. We provide the first long‐term results of elevated [CO2] on biomass components of a desert ecosystem and offer information on understudied Mojave Desert species. In contrast to initial expectations, 10 years of elevated [CO2] had no significant effect on standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground components. However, elevated [CO2] increased short‐term responses, including leaf water‐use efficiency (WUE) as measured by carbon isotope discrimination and increased plot‐level LAI. Standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground pools significantly differed among dominant species, but responses to elevated [CO2] did not vary among species, photosynthetic pathway (C3 vs. C4), or growth form (drought‐deciduous shrub vs. evergreen shrub vs. grass). Thus, even though previous and current results occasionally show increased leaf‐level photosynthetic rates, WUE, LAI, and plant growth under elevated [CO2] during the 10‐year experiment, most responses were in wet years and did not lead to sustained increases in community biomass. We presume that the lack of sustained biomass responses to elevated [CO2] is explained by inter‐annual differences in water availability. Therefore, the high frequency of low precipitation years may constrain cumulative biomass responses to elevated [CO2] in desert environments. 相似文献
3.
Vincent Allard Paul C. D. Newton Mark Lieffering Harry Clark Cory Matthew† Jean-François Soussana‡ Yvonne S. Gray 《Global Change Biology》2003,9(12):1731-1742
In pastures grazed by large herbivores, nutrients cycle both through litter and animal excreta. We compared nitrogen (N) returns from sheep grazing a temperate pasture exposed to ambient or elevated CO2 (475 μmol mol?1) in a FACE (Free Air CO2 Enrichment) experiment established in the spring of 1997. In the spring of 2000 and 2001, we measured the chemical composition of the diet, sheep faeces and of individual plant species before grazing to characterize feed intake and to compare the intake of N to the N produced in faeces. In both years under elevated CO2, leaves of the individual species exhibited lower N concentrations and higher water‐soluble carbohydrate (WSC) concentrations. There was a significantly greater proportion of legume in the diet at elevated CO2 but, together with the changes in chemical composition of individual species, this resulted in diets that had similar N but higher WSC and digestibility for both ambient and elevated CO2. We found that a greater proportion of dietary N was partitioned to urine at elevated CO2, probably because of the higher proportion of legume N in the diet, with possible differences in protein quality. A potentially significant consequence of this change in partitioning is greater N loss through volatilization at higher CO2 levels. 相似文献
4.
Rising atmospheric CO2 concentration is a key driver of enhanced global greening, thought to account for up to 70% of increased global vegetation in recent decades. CO2 fertilization effects have further profound implications for ecosystems, food security and biosphere‐atmosphere feedbacks. However, it is also possible that current trends will not continue, due to ecosystem level constraints and as plants acclimate to future CO2 concentrations. Future predictions of plant response to rising [CO2] are often validated using single‐generation short‐term FACE (Free Air CO2 Enrichment) experiments but whether this accurately represents vegetation response over decades is unclear. The role of transgenerational plasticity and adaptation in the multigenerational response has yet to be elucidated. Here, we propose that naturally occurring high CO2 springs provide a proxy to quantify the multigenerational and long‐term impacts of rising [CO2] in herbaceous and woody species respectively, such that plasticity, transgenerational effects and genetic adaptation can be quantified together in these systems. In this first meta‐analysis of responses to elevated [CO2] at natural CO2 springs, we show that the magnitude and direction of change in eight of nine functional plant traits are consistent between spring and FACE experiments. We found increased photosynthesis (49.8% in spring experiments, comparable to 32.1% in FACE experiments) and leaf starch (58.6% spring, 84.3% FACE), decreased stomatal conductance (gs, 27.2% spring, 21.1% FACE), leaf nitrogen content (6.3% spring, 13.3% FACE) and Specific Leaf Area (SLA, 9.7% spring, 6.0% FACE). These findings not only validate the use of these sites for studying multigenerational plant response to elevated [CO2], but additionally suggest that long‐term positive photosynthetic response to rising [CO2] are likely to continue as predicted by single‐generation exposure FACE experiments. 相似文献
5.
Seth G. Pritchard Benton N. Taylor Emily R. Cooper Katilyn V. Beidler Allan E. Strand M. Luke McCormack Siyao Zhang 《Global Change Biology》2014,20(4):1313-1326
Large‐scale, long‐term FACE (Free‐Air CO2 enrichment) experiments indicate that increases in atmospheric CO2 concentrations will influence forest C cycling in unpredictable ways. It has been recently suggested that responses of mycorrhizal fungi could determine whether forest net primary productivity (NPP) is increased by elevated CO2 over long time periods and if forests soils will function as sources or sinks of C in the future. We studied the dynamic responses of ectomycorrhizae to N fertilization and atmospheric CO2 enrichment at the Duke FACE experiment using minirhizotrons over a 6 year period (2005–2010). Stimulation of mycorrhizal production by elevated CO2 was observed during only 1 (2007) of 6 years. This increased the standing crop of mycorrhizal tips during 2007 and 2008; during 2008, significantly higher mortality returned standing crop to ambient levels for the remainder of the experiment. It is therefore unlikely that increased production of mycorrhizal tips can explain the lack of progressive nitrogen limitations and associated increases in N uptake observed in CO2‐enriched plots at this site. Fertilization generally decreased tree reliance on mycorrhizae as tip production declined with the addition of nitrogen as has been shown in many other studies. Annual NPP of mycorrhizal tips was greatest during years with warm January temperatures and during years with cool spring temperatures. A 2 °C increase in average late spring temperatures (May and June) decreased annual production of mycorrhizal root tip length by 50%. This has important implications for ecosystem function in a warmer world in addition to potential for forest soils to sequester atmospheric C. 相似文献
6.
W. I. J. DIELEMAN S. LUYSSAERT A. REY P. DE ANGELIS C. V. M. BARTON M. S. J. BROADMEADOW S. B. BROADMEADOW K. S. CHIGWEREWE M. CROOKSHANKS E. DUFRÊNE P. G. JARVIS A. KASURINEN S. KELLOMÄKI V. LE DANTEC M. LIBERLOO M. MAREK B. MEDLYN R. POKORNÝ G. SCARASCIA‐MUGNOZZA V. M. TEMPERTON D. TINGEY O. URBAN R. CEULEMANS I. A. JANSSENS 《Plant, cell & environment》2010,33(12):2001-2011
Under elevated atmospheric CO2 concentrations, soil carbon (C) inputs are typically enhanced, suggesting larger soil C sequestration potential. However, soil C losses also increase and progressive nitrogen (N) limitation to plant growth may reduce the CO2 effect on soil C inputs with time. We compiled a data set from 131 manipulation experiments, and used meta‐analysis to test the hypotheses that: (1) elevated atmospheric CO2 stimulates soil C inputs more than C losses, resulting in increasing soil C stocks; and (2) that these responses are modulated by N. Our results confirm that elevated CO2 induces a C allocation shift towards below‐ground biomass compartments. However, the increased soil C inputs were offset by increased heterotrophic respiration (Rh), such that soil C content was not affected by elevated CO2. Soil N concentration strongly interacted with CO2 fumigation: the effect of elevated CO2 on fine root biomass and –production and on microbial activity increased with increasing soil N concentration, while the effect on soil C content decreased with increasing soil N concentration. These results suggest that both plant growth and microbial activity responses to elevated CO2 are modulated by N availability, and that it is essential to account for soil N concentration in C cycling analyses. 相似文献
7.
Shu K. Lam Deli Chen Rob Norton Roger Armstrong Arvin R. Mosier 《Global Change Biology》2012,18(9):2853-2859
Understanding nitrogen (N) removal and replenishment is crucial to crop sustainability under rising atmospheric carbon dioxide concentration ([CO2]). While a significant portion of N is removed in grains, the soil N taken from agroecosystems can be replenished by fertilizer application and N2 fixation by legumes. The effects of elevated [CO2] on N dynamics in grain crop and legume pasture systems were evaluated using meta‐analytic techniques (366 observations from 127 studies). The information analysed for non‐legume crops included grain N removal, residue C : N ratio, fertilizer N recovery and nitrous oxide (N2O) emission. In addition to these parameters, nodule number and mass, nitrogenase activity, the percentage and amount of N fixed from the atmosphere were also assessed in legumes. Elevated [CO2] increased grain N removal of C3 non‐legumes (11%), legumes (36%) and C4 crops (14%). The C : N ratio of residues from C3 non‐legumes and legumes increased under elevated [CO2] by 16% and 8%, respectively, but the increase for C4 crops (9%) was not statistically significant. Under elevated [CO2], there was a 38% increase in the amount of N fixed from the atmosphere by legumes, which was accompanied by greater whole plant nodule number (33%), nodule mass (39%), nitrogenase activity (37%) and %N derived from the atmosphere (10%; non‐significant). Elevated [CO2] increased the plant uptake of fertilizer N by 17%, and N2O emission by 27%. These results suggest that N demand and removal in grain cropping systems will increase under future CO2‐enriched environments, and that current N management practices (fertilizer application and legume incorporation) will need to be revised. 相似文献
8.
Juliane Kellner Tobias Houska Remy Manderscheid Hans‐Joachim Weigel Lutz Breuer Philipp Kraft 《Global Change Biology》2019,25(9):2947-2957
The rising concentration of atmospheric carbon dioxide (CO2) is known to increase the total aboveground biomass of several C3 crops, whereas C4 crops are reported to be hardly affected when water supply is sufficient. However, a free‐air carbon enrichment (FACE) experiment in Braunschweig, Germany, in 2007 and 2008 resulted in a 25% increased biomass of the C4 crop maize under restricted water conditions and elevated CO2 (550 ppm). To project future yields of maize under climate change, an accurate representation of the effects of eCO2 and drought on biomass and soil water conditions is essential. Current crop growth models reveal limitations in simulations of maize biomass under eCO2 and limited water supply. We use the coupled process‐based hydrological‐plant growth model Catchment Modeling Framework‐Plant growth Modeling Framework to overcome this limitation. We apply the coupled model to the maize‐based FACE experiment in Braunschweig that provides robust data for the investigation of combined CO2 and drought effects. We approve hypothesis I that CO2 enrichment has a small direct‐fertilizing effect with regard to the total aboveground biomass of maize and hypothesis II that CO2 enrichment decreases water stress and leads to higher yields of maize under restricted water conditions. Hypothesis III could partly be approved showing that CO2 enrichment decreases the transpiration of maize, but does not raise soil moisture, while increasing evaporation. We emphasize the importance of plant‐specific CO2 response factors derived by use of comprehensive FACE data. By now, only one FACE experiment on maize is accomplished applying different water levels. For the rigorous testing of plant growth models and their applicability in climate change studies, we call for datasets that go beyond single criteria (only yield response) and single effects (only elevated CO2). 相似文献
9.
Does nitrogen nutrition restrict the CO2 response of fertile grassland lacking legumes? 总被引:7,自引:0,他引:7
S. Zanetti U. A. Hartwig C. van Kessel A. Lüscher T. Hebeisen M. Frehner B. U. Fischer G. R. Hendrey H. Blum J. Nösberger 《Oecologia》1997,112(1):17-25
The extent of the response of plant growth to atmospheric CO2 enrichment depends on the availability of resources other than CO2. An important growth-limiting resource under field conditions is nitrogen (N). N may, therefore, influence the CO2 response of plants. The effect of elevated CO2 (60 Pa) partial pressure (pCO2) on the N nutrition of field-grown Lolium perenne swards, cultivated alone or in association with Trifolium repens, was investigated using free air carbon dioxide enrichment (FACE) technology over 3 years. The established grassland ecosystems
were treated with two N fertilization levels and were defoliated at two frequencies. Under elevated pCO2, the above-ground plant material of the L. perenne monoculture showed a consistent and significant decline in N concentration which, in general, led to a lower total annual
N yield. Despite the decline in the critical N concentration (minimum N concentration required for non-N-limited biomass production)
under elevated pCO2, the index of N nutrition (ratio of actual N concentration and critical N concentration) was lower under elevated pCO2 than under ambient pCO2 in frequently defoliated L. perenne monocultures. Thus, we suggest that reduced N yield under elevated pCO2 was evoked indirectly by a reduction of plant-available N. For L. perenne grown in association with T. repens and exposed to elevated pCO2, there was an increase in the contribution of symbiotically fixed N to the total N yield of the grass. This can be explained
by an increased apparent transfer of N from the associated N2-fixing legume species to the non-fixing grass. The total annual N yield of the mixed grass/legume swards increased under
elevated pCO2. All the additional N yielded was due to symbiotically fixed N. Through the presence of an N2-fixing plant species more symbiotically fixed N was introduced into the system and consequently helped to overcome N limitation
under elevated pCO2.
Received: 11 November 1996 / Accepted: 20 May 1997 相似文献
10.
Elevated carbon dioxide increases soil nitrogen and phosphorus availability in a phosphorus‐limited Eucalyptus woodland
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Free‐air CO2 enrichment (FACE) experiments have demonstrated increased plant productivity in response to elevated (e)CO2, with the magnitude of responses related to soil nutrient status. Whilst understanding nutrient constraints on productivity responses to eCO2 is crucial for predicting carbon uptake and storage, very little is known about how eCO2 affects nutrient cycling in phosphorus (P)‐limited ecosystems. Our study investigates eCO2 effects on soil N and P dynamics at the EucFACE experiment in Western Sydney over an 18‐month period. Three ambient and three eCO2 (+150 ppm) FACE rings were installed in a P‐limited, mature Cumberland Plain Eucalyptus woodland. Levels of plant accessible nutrients, evaluated using ion exchange resins, were increased under eCO2, compared to ambient, for nitrate (+93%), ammonium (+12%) and phosphate (+54%). There was a strong seasonality to responses, particularly for phosphate, resulting in a relatively greater stimulation in available P, compared to N, under eCO2 in spring and summer. eCO2 was also associated with faster nutrient turnover rates in the first six months of the experiment, with higher N (+175%) and P (+211%) mineralization rates compared to ambient rings, although this difference did not persist. Seasonally dependant effects of eCO2 were seen for concentrations of dissolved organic carbon in soil solution (+31%), and there was also a reduction in bulk soil pH (‐0.18 units) observed under eCO2. These results demonstrate that CO2 fertilization increases nutrient availability – particularly for phosphate – in P‐limited soils, likely via increased plant belowground investment in labile carbon and associated enhancement of microbial turnover of organic matter and mobilization of chemically bound P. Early evidence suggests that there is the potential for the observed increases in P availability to support increased ecosystem C‐accumulation under future predicted CO2 concentrations. 相似文献
11.
ELISE PENDALL YUI OSANAI AMITY L. WILLIAMS MARK J. HOVENDEN 《Global Change Biology》2011,17(1):505-514
The stability of soil organic matter (SOM) pools exposed to elevated CO2 and warming has not been evaluated adequately in long‐term experiments and represents a substantial source of uncertainty in predicting ecosystem feedbacks to climate change. We conducted a 6‐year experiment combining free‐air CO2 enrichment (FACE, 550 ppm) and warming (+2 °C) to evaluate changes in SOM accumulation in native Australian grassland. In this system, competitive interactions appear to favor C4 over C3 species under FACE and warming. We therefore investigated the role of plant functional type (FT) on biomass and SOM responses to the long‐term treatments by carefully sampling soil under patches of C3‐ and C4‐dominated vegetation. We used physical fractionation to quantify particulate organic matter (POM) and long‐term incubation to assess potential decomposition rates. Aboveground production of C4 grasses increased in response to FACE, but total root biomass declined. Across treatments, C : N ratios were higher in leaves, roots and POM of C4 vegetation. CO2 and temperature treatments interacted with FT to influence SOM, and especially POM, such that soil carbon was increased by warming under C4 vegetation, but not in combination with elevated CO2. Potential decomposition rates increased in response to FACE and decreased with warming, possibly owing to treatment effects on soil moisture and microbial community composition. Decomposition was also inversely correlated with root N concentration, suggesting increased microbial demand for older, N‐rich SOM in treatments with low root N inputs. This research suggests that C3–C4 vegetation responses to future climate conditions will strongly influence SOM storage in temperate grasslands. 相似文献
12.
Inter‐annual changes in detritus‐based food chains can enhance plant growth response to elevated atmospheric CO2
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Elevated atmospheric CO2 generally enhances plant growth, but the magnitude of the effects depend, in part, on nutrient availability and plant photosynthetic pathway. Due to their pivotal role in nutrient cycling, changes in abundance of detritivores could influence the effects of elevated atmospheric CO2 on essential ecosystem processes, such as decomposition and primary production. We conducted a field survey and a microcosm experiment to test the influence of changes in detritus‐based food chains on litter mass loss and plant growth response to elevated atmospheric CO2 using two wetland plants: a C3 sedge (Scirpus olneyi) and a C4 grass (Spartina patens). Our field study revealed that organism's sensitivity to climate increased with trophic level resulting in strong inter‐annual variation in detritus‐based food chain length. Our microcosm experiment demonstrated that increased detritivore abundance could not only enhance decomposition rates, but also enhance plant growth of S. olneyi in elevated atmospheric CO2 conditions. In contrast, we found no evidence that changes in the detritus‐based food chains influenced the growth of S. patens. Considered together, these results emphasize the importance of approaches that unite traditionally subdivided food web compartments and plant physiological processes to understand inter‐annual variation in plant production response to elevated atmospheric CO2. 相似文献
13.
V. Allard P.C.D. Newton M. Lieffering J-F. Soussana R.A. Carran C. Matthew 《Plant and Soil》2005,276(1-2):49-60
The aims of this study were to determine whether elevated atmospheric CO2 concentration modifies plant organic matter (OM) fluxes to the soil and whether any change in the fluxes can modify soil
OM accumulation. Measurements were made in a grazed temperate grassland after almost 4 years exposure to elevated atmospheric
CO2 (475 μl l-1) using a Free Air CO2 Enrichment (FACE) facility located in the North Island of New Zealand. Aboveground herbage biomass and leaf litter production
were not altered by elevated CO2 but root growth rate, as measured with the ingrowth core method, and root turnover were strongly stimulated by elevated CO2 particularly at low soil moisture contents during summer. Consequently, significantly more plant material was returned to
the soil under elevated CO2 leading to an accumulation of coarse (> 1 mm) particulate organic matter (POM) but not of finer POM fractions. The accumulating
POM exhibited a lower C/N ratio, which was attributed to the higher proportion of legumes in the pasture under elevated CO2. Only small changes were detected in the size and activity of the soil microbial biomass in response to the POM accumulation,
suggesting that higher organic substrate availability did not stimulate microbial growth and activity despite the apparent
lower C/N ratio of accumulating POM. As a result, elevated CO2 may well lead to an accumulation of OM in grazed grassland soil in the long term. 相似文献
14.
Net soil carbon input under ambient and elevated CO2 concentrations: isotopic evidence after 4 years
Chris Van Kessel William R. Horwath Ueli Hartwig David Harris Andreas LÜscher 《Global Change Biology》2000,6(4):435-444
Elevation of atmospheric CO2 concentration is predicted to increase net primary production, which could lead to additional C sequestration in terrestrial ecosystems. Soil C input was determined under ambient and Free Atmospheric Carbon dioxide Enrichment (FACE) conditions for Lolium perenne L. and Trifolium repens L. grown for four years in a sandy‐loam soil. The 13C content of the soil organic matter C had been increased by 5‰ compared to the native soil by prior cropping to corn (Zea mays) for > 20 years. Both species received low or high amounts of N fertilizer in separate plots. The total accumulated above‐ground biomass produced by L. perenne during the 4‐year period was strongly dependent on the amount of N fertilizer applied but did not respond to increased CO2. In contrast, the total accumulated above‐ground biomass of T. repens doubled under elevated CO2 but remained independent of N fertilizer rate. The C:N ratio of above‐ground biomass for both species increased under elevated CO2 whereas only the C:N ratio of L. perenne roots increased under elevated CO2. Root biomass of L. perenne doubled under elevated CO2 and again under high N fertilization. Total soil C was unaffected by CO2 treatment but dependent on species. After 4 years and for both crops, the fraction of new C (F‐value) under ambient conditions was higher (P= 0.076) than under FACE conditions: 0.43 vs. 0.38. Soil under L. perenne showed an increase in total soil organic matter whereas N fertilization or elevated CO2 had no effect on total soil organic matter content for both systems. The net amount of C sequestered in 4 years was unaffected by the CO2 concentration (overall average of 8.5 g C kg?1 soil). There was a significant species effect and more new C was sequestered under highly fertilized L. perenne. The amount of new C sequestered in the soil was primarily dependent on plant species and the response of root biomass to CO2 and N fertilization. Therefore, in this FACE study net soil C sequestration was largely depended on how the species responded to N rather than to elevated CO2. 相似文献
15.
Chris Van Kessel Jennifer Nitschelm William R. Horwath David Harris Frances Walley Andreas Lüscher Ueli Hartwig 《Global Change Biology》2000,6(1):123-135
The impact of elevated CO2 and N‐fertilization on soil C‐cycling in Lolium perenne and Trifolium repens pastures were investigated under Free Air Carbon dioxide Enrichment (FACE) conditions. For six years, swards were exposed to ambient or elevated CO2 (35 and 60 Pa pCO2) and received a low and high rate of N fertilizer. The CO2 added in the FACE plots was depleted in 13C compared to ambient (Δ? 40‰) thus the C inputs could be quantified. On average, 57% of the C associated with the sand fraction of the soil was ‘new’ C. Smaller proportions of the C associated with the silt (18%) and clay fractions (14%) were derived from FACE. Only a small fraction of the total C pool below 10 cm depth was sequestered during the FACE experiment. The annual net input of C in the FACE soil (0–10 cm) was estimated at 4.6 ± 2.2 and 6.3 ± 3.6 (95% confidence interval) Mg ha? 1 for T. repens and L. perenne, respectively. The maximum amount of labile C in the T. repens sward was estimated at 8.3 ± 1.6 Mg ha? 1 and 7.1 ± 1.0 Mg ha? 1 in the L. perenne sward. Mean residence time (MRT) for newly sequestered soil C was estimated at 1.8 years in the T. repens plots and 1.1 years for L. perenne. An average of 18% of total soil C in the 0–10 cm depth in the T. repens sward and 24% in the L. perenne sward was derived from FACE after 6 years exposure. The majority of the change in soil δ13C occurred in the first three years of the experiment. No treatment effects on total soil C were detected. The fraction of FACE‐derived C in the L. perenne sward was larger than in the T. repens sward. This suggests a priming effect in the L. perenne sward which led to increased losses of the old C. Although the rate of C cycling was affected by species and elevated CO2, the soil in this intensively managed grassland ecosystem did not become a sink for additional new C. 相似文献
16.
Jasmonate‐mediated stomatal closure under elevated CO2 revealed by time‐resolved metabolomics
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Sisi Geng Biswapriya B. Misra Evaldo de Armas David V. Huhman Hans T. Alborn Lloyd W. Sumner Sixue Chen 《The Plant journal : for cell and molecular biology》2016,88(6):947-962
Foliar stomatal movements are critical for regulating plant water loss and gas exchange. Elevated carbon dioxide (CO2) levels are known to induce stomatal closure. However, the current knowledge on CO2 signal transduction in stomatal guard cells is limited. Here we report metabolomic responses of Brassica napus guard cells to elevated CO2 using three hyphenated metabolomics platforms: gas chromatography‐mass spectrometry (MS); liquid chromatography (LC)‐multiple reaction monitoring‐MS; and ultra‐high‐performance LC‐quadrupole time‐of‐flight‐MS. A total of 358 metabolites from guard cells were quantified in a time‐course response to elevated CO2 level. Most metabolites increased under elevated CO2, showing the most significant differences at 10 min. In addition, reactive oxygen species production increased and stomatal aperture decreased with time. Major alterations in flavonoid, organic acid, sugar, fatty acid, phenylpropanoid and amino acid metabolic pathways indicated changes in both primary and specialized metabolic pathways in guard cells. Most interestingly, the jasmonic acid (JA) biosynthesis pathway was significantly altered in the course of elevated CO2 treatment. Together with results obtained from JA biosynthesis and signaling mutants as well as CO2 signaling mutants, we discovered that CO2‐induced stomatal closure is mediated by JA signaling. 相似文献
17.
Using models to guide field experiments: a priori predictions for the CO2 response of a nutrient‐ and water‐limited native Eucalypt woodland
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Belinda E. Medlyn Martin G. De Kauwe Sönke Zaehle Anthony P. Walker Remko A. Duursma Kristina Luus Mikhail Mishurov Bernard Pak Benjamin Smith Ying‐Ping Wang Xiaojuan Yang Kristine Y. Crous John E. Drake Teresa E. Gimeno Catriona A. Macdonald Richard J. Norby Sally A. Power Mark G. Tjoelker David S. Ellsworth 《Global Change Biology》2016,22(8):2834-2851
The response of terrestrial ecosystems to rising atmospheric CO2 concentration (Ca), particularly under nutrient‐limited conditions, is a major uncertainty in Earth System models. The Eucalyptus Free‐Air CO2 Enrichment (EucFACE) experiment, recently established in a nutrient‐ and water‐limited woodland presents a unique opportunity to address this uncertainty, but can best do so if key model uncertainties have been identified in advance. We applied seven vegetation models, which have previously been comprehensively assessed against earlier forest FACE experiments, to simulate a priori possible outcomes from EucFACE. Our goals were to provide quantitative projections against which to evaluate data as they are collected, and to identify key measurements that should be made in the experiment to allow discrimination among alternative model assumptions in a postexperiment model intercomparison. Simulated responses of annual net primary productivity (NPP) to elevated Ca ranged from 0.5 to 25% across models. The simulated reduction of NPP during a low‐rainfall year also varied widely, from 24 to 70%. Key processes where assumptions caused disagreement among models included nutrient limitations to growth; feedbacks to nutrient uptake; autotrophic respiration; and the impact of low soil moisture availability on plant processes. Knowledge of the causes of variation among models is now guiding data collection in the experiment, with the expectation that the experimental data can optimally inform future model improvements. 相似文献
18.
A. Christopher Oishi Sari Palmroth Kurt H. Johnsen Heather R. McCarthy Ram Oren 《Global Change Biology》2014,20(4):1146-1160
Soil CO2 efflux (Fsoil) is the largest source of carbon from forests and reflects primary productivity as well as how carbon is allocated within forest ecosystems. Through early stages of stand development, both elevated [CO2] and availability of soil nitrogen (N; sum of mineralization, deposition, and fixation) have been shown to increase gross primary productivity, but the long‐term effects of these factors on Fsoil are less clear. Expanding on previous studies at the Duke Free‐Air CO2 Enrichment (FACE) site, we quantified the effects of elevated [CO2] and N fertilization on Fsoil using daily measurements from automated chambers over 10 years. Consistent with previous results, compared to ambient unfertilized plots, annual Fsoil increased under elevated [CO2] (ca. 17%) and decreased with N (ca. 21%). N fertilization under elevated [CO2] reduced Fsoil to values similar to untreated plots. Over the study period, base respiration rates increased with leaf productivity, but declined after productivity saturated. Despite treatment‐induced differences in aboveground biomass, soil temperature and water content were similar among treatments. Interannually, low soil water content decreased annual Fsoil from potential values – estimated based on temperature alone assuming nonlimiting soil water content – by ca. 0.7% per 1.0% reduction in relative extractable water. This effect was only slightly ameliorated by elevated [CO2]. Variability in soil N availability among plots accounted for the spatial variability in Fsoil, showing a decrease of ca. 114 g C m?2 yr?1 per 1 g m?2 increase in soil N availability, with consistently higher Fsoil in elevated [CO2] plots ca. 127 g C per 100 ppm [CO2] over the +200 ppm enrichment. Altogether, reflecting increased belowground carbon partitioning in response to greater plant nutritional needs, the effects of elevated [CO2] and N fertilization on Fsoil in this stand are sustained beyond the early stages of stand development and through stabilization of annual foliage production. 相似文献
19.
Seasonal changes in the effects of elevated CO2 on rice at three levels of nitrogen supply: a free air CO2 enrichment (FACE) experiment 总被引:3,自引:1,他引:2
HAN-YONG KIM MARK LIEFFERING† KAZUHIKO KOBAYASHI‡ MASUMI OKADA§ SHU MIURA¶ 《Global Change Biology》2003,9(6):826-837
Over time, the stimulative effect of elevated CO2 on the photosynthesis of rice crops is likely to be reduced with increasing duration of CO2 exposure, but the resultant effects on crop productivity remain unclear. To investigate seasonal changes in the effect of elevated CO2 on the growth of rice (Oryza sativa L.) crops, a free air CO2 enrichment (FACE) experiment was conducted at Shizukuishi, Iwate, Japan in 1998–2000. The target CO2 concentration of the FACE plots was 200 µmol mol?1 above that of ambient. Three levels of nitrogen (N) were supplied: low (LN, 4 g N m?2), medium [MN, 8 (1998) and 9 (1999, 2000) g N m?2] and high N (HN, 12 and 15 g N m?2). For MN and HN but not for LN, elevated CO2 increased tiller number at panicle initiation (PI) but this positive response decreased with crop development. As a result, the response of green leaf area index (GLAI) to elevated CO2 greatly varied with development, showing positive responses during vegetative stages and negative responses after PI. Elevated CO2 decreased leaf N concentration over the season, except during early stage of development. For MN crops, total biomass increased with elevated CO2, but the response declined linearly with development, with average increases of 32, 28, 21, 15 and 12% at tillering, PI, anthesis, mid‐ripening and grain maturity, respectively. This decline is likely to be due to decreases in the positive effects of elevated CO2 on canopy photosynthesis because of reductions in both GLAI and leaf N. Up to PI, LN‐crops tended to have a lower response to elevated CO2 than MN‐ and HN‐crops, though by final harvest the total biomass response was similar for all N levels. For MN‐ and HN‐crops, the positive response of grain yield (ca. 15%) to elevated CO2 was slightly greater than the response of final total biomass while for LN‐crops it was less. We conclude that most of the seasonal changes in crop response to elevated CO2 are directly or indirectly associated with N uptake. 相似文献
20.
Atmospheric CO2 enrichment can affect plants directly via impacts on their performance, and indirectly, by environment‐specific traits passed down from the mother plant to the offspring. Such maternal effects can significantly alter plant species composition, especially in annual ecosystems where the entire community is recruited from seeds each year. This study assessed impacts of future, high CO2 (440 and 600 ppm) and pre‐industrial, low CO2 (280 ppm) on seed traits and offspring performance in three plant functional groups (grasses, legumes, forbs) comprising 17 annual species of a semi‐arid Mediterranean community. In grasses, seed size and seed‐reserve utilization as expressed by root elongation tended to be higher at high than at low maternal CO2, but total seed protein concentration and protein pool decreased with increasing maternal CO2. The response of seed size to high CO2 increased with increasing leaf‐mass fraction in grasses, and decreased with decreasing concentration of leaf non‐structural carbohydrates in legumes. Offspring development was studied at ambient CO2, and showed reduced emergence success of high‐CO2 progeny compared with low‐CO2 progeny in forbs. Total biomass was lower in high‐CO2 than in low‐CO2 offspring across all functional groups. The biomass response to high maternal CO2 in legume offspring correlated inversely with seed size, resulting in up to 25% lower biomass in large‐seeded species. Under the scenario of maternal effects combined with projected changes in biomass and seed production under direct exposure to high CO2, legumes might gain and forbs and grasses might lose from future CO2 enrichment. Most changes in seed traits and offspring performance were greater between pre‐industrial and near‐future CO2 than between near‐ and remote‐future CO2 concentrations. Hence, maternal effects of increasing CO2 may contribute to current changes in plant productivity and species composition, and they need to be considered when predicting impacts of global change on plant communities. 相似文献