Impacts of Fine Root Turnover on Forest NPP and Soil C Sequestration Potential

Matamala, Roser; Gonzàlez-Meler, Miquel A.; Jastrow, Julie D.; Norby, Richard J.; Schlesinger, William H.

doi:10.1126/science.1089543

Cited by 450 publications

(430 citation statements)

References 20 publications

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“…C. arenaria did not seem to release appreciable amounts of this compound regardless of atmospheric CO 2 level (Figure 4). Although plant litter represents the dominant pathway by which plant C is transferred to soil, living roots also contribute significantly to this process through turnover of fine roots, sloughing of living cells and exudation (Matamala et al, 2003;Philips et al, 2006). Furthermore, root exudation probably exerts a disproportionate impact on rhizosphere communities, as it represents the most easily accessible C available to the soil microbes (Cardon, 1996).…”

Section: Antibiotic-production Genesmentioning

confidence: 99%

Specific rhizosphere bacterial and fungal groups respond differently to elevated atmospheric CO2

2009

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Soil community responses to increased atmospheric CO 2 concentrations are expected to occur mostly through interactions with changing vegetation patterns and plant physiology. To gain insight into the effects of elevated atmospheric CO 2 on the composition and functioning of microbial communities in the rhizosphere, Carex arenaria (a non-mycorrhizal plant species) and Festuca rubra (a mycorrhizal plant species) were grown under defined atmospheric conditions with either ambient (350 p.p.m.) or elevated (700 p.p.m.) CO 2 concentrations. PCR-DGGE (PCR-denaturing gradient gel electrophoresis) and quantitative-PCR were carried out to analyze, respectively, the structure and abundance of the communities of actinomycetes, Fusarium spp., Trichoderma spp., Pseudomonas spp., Burkholderia spp. and Bacillus spp. Responses of specific functional groups, such as phloroglucinol, phenazine and pyrrolnitrin producers, were also examined by quantitative-PCR, and HPLC (high performance liquid chromatography) was employed to assess changes in exuded sugars in the rhizosphere. Multivariate analysis of group-specific community profiles showed disparate responses to elevated CO 2 for the different bacterial and fungal groups examined, and these responses were dependent on plant type and soil nutrient availability. Within the bacterial community, the genera Burkholderia and Pseudomonas, typically known as successful rhizosphere colonizers, were significantly influenced by elevated CO 2 , whereas the genus Bacillus and actinomycetes, typically more dominant in bulk soil, were not. Total sugar concentrations in the rhizosphere also increased in both plants in response to elevated CO 2 . The abundances of phloroglucinol-, phenazine-and pyrrolnitrin-producing bacterial communities were also influenced by elevated CO 2 , as was the abundance of the fungal genera Fusarium and Trichoderma.

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Section: Antibiotic-production Genesmentioning

confidence: 99%

Specific rhizosphere bacterial and fungal groups respond differently to elevated atmospheric CO2

2009

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“…In parallel, more in depth analysis of the eddy covariance observations are required to more fully exploit the information content of these datasets on hourly to decadal timescales. To improve the representation of carbon flow within ecosystems, comparison with other types of measurements is necessary, including analysis of existing datasets of leaf litter decomposition (Parton et al, 2007;Zhang et al, 2008), leaf lifespan (Reich et al, 2004), decomposition of coarse woody debris, and turnover of fine roots (e.g., Matamala et al, 2003), as well as soil carbon stocks and radiocarbon estimates of soil carbon turnover times. Regional estimates of aboveground live biomass, including the spatial inventory of North America developed by Blackard et al (2008), have the potential to constrain mortality and disturbance processes, when combined with measurements of NPP and allocation.…”

Section: Existing Gapsmentioning

confidence: 99%

Systematic assessment of terrestrial biogeochemistry in coupled climate–carbon models

Randerson

Hoffman

Thornton

et al. 2009

Global Change Biology

349

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With representation of the global carbon cycle becoming increasingly complex in climate models, it is important to develop ways to quantitatively evaluate model performance against in situ and remote sensing observations. Here we present a systematic framework, the Carbon‐LAnd Model Intercomparison Project (C‐LAMP), for assessing terrestrial biogeochemistry models coupled to climate models using observations that span a wide range of temporal and spatial scales. As an example of the value of such comparisons, we used this framework to evaluate two biogeochemistry models that are integrated within the Community Climate System Model (CCSM) – Carnegie‐Ames‐Stanford Approach′ (CASA′) and carbon–nitrogen (CN). Both models underestimated the magnitude of net carbon uptake during the growing season in temperate and boreal forest ecosystems, based on comparison with atmospheric CO2 measurements and eddy covariance measurements of net ecosystem exchange. Comparison with MODerate Resolution Imaging Spectroradiometer (MODIS) measurements show that this low bias in model fluxes was caused, at least in part, by 1–3 month delays in the timing of maximum leaf area. In the tropics, the models overestimated carbon storage in woody biomass based on comparison with datasets from the Amazon. Reducing this model bias will probably weaken the sensitivity of terrestrial carbon fluxes to both atmospheric CO2 and climate. Global carbon sinks during the 1990s differed by a factor of two (2.4 Pg C yr−1 for CASA′ vs. 1.2 Pg C yr−1 for CN), with fluxes from both models compatible with the atmospheric budget given uncertainties in other terms. The models captured some of the timing of interannual global terrestrial carbon exchange during 1988–2004 based on comparison with atmospheric inversion results from TRANSCOM (r=0.66 for CASA′ and r=0.73 for CN). Adding (CASA′) or improving (CN) the representation of deforestation fires may further increase agreement with the atmospheric record. Information from C‐LAMP has enhanced model performance within CCSM and serves as a benchmark for future development. We propose that an open source, community‐wide platform for model‐data intercomparison is needed to speed model development and to strengthen ties between modeling and measurement communities. Important next steps include the design and analysis of land use change simulations (in both uncoupled and coupled modes), and the entrainment of additional ecological and earth system observations. Model results from C‐LAMP are publicly available on the Earth System Grid.

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“…Furthermore, our ability to observe directly and quantify roots in situ is limited (Majdi et al, 2005;Trumbore and Gaudinski, 2003) Estimates of C allocation to root growth and maintenance have been based on the assumption that fine roots turn over approximately annually (Jackson et al, 1997). However, measurements of isotopes in fine roots demonstrated that both the 14 C age (Gaudinski et al, 2001) and the incorporation rate of a continuous 13 C label (Matamala et al, 2003) in fine root C were inconsistent with an annual turnover. The various observations can be reconciled by assuming that fine roots are not a single homogeneous pool (Gaudinski et al, 2010;Guo et al, 2008;Strand et al, 2008;Tierney and Fahey, 2002;Trumbore, 2009).…”

Section: Introductionmentioning

confidence: 99%

Mean age of carbon in fine roots from temperate forests and grasslands with different management

et al. 2013

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Fine roots are the most dynamic portion of a plant’s root system and a major source of soil organic matter. By altering plant species diversity and composition, soil conditions and nutrient availability, and consequently belowground allocation and dynamics of root carbon (C) inputs, land-use and management changes may influence organic C storage in terrestrial ecosystems. In three German regions, we measured fine root radiocarbon (14C) content to estimate the mean time since C in root tissues was fixed from the atmosphere in 54 grassland and forest plots with different management and soil conditions. Although root biomass was on average greater in grasslands 5.1±0.8 g (mean±SE, n=27) than in forests 3.1±0.5 g (n=27) (p <0.05), the mean age of C in fine roots in forests averaged 11.3±1.8 yr and was older and more variable compared to grasslands 1.7±0.4 yr (p <0.001). We further found that management affects the mean age of fine root C in temperate grasslands mediated by changes in plant species diversity and composition. Fine root mean C age is positively correlated with plant diversity (r =0.65) and with the number of perennial species (r =0.77). Fine root mean C age in grasslands was also affected by study region with averages of 0.7±0.1 yr (n=9) on mostly organic soils in northern Germany and of 1.8±0.3 yr (n=9) and 2.6±0.3 (n=9) in central and southern Germany (p <0.05). This was probably due to differences in soil nutrient contents and soil moisture conditions between study regions, which affected plant species diversity and the presence of perennial species. Our results indicate more long-lived roots or internal redistribution of C in perennial species and suggest linkages between fine root C age and management in grasslands. These findings improve our ability to predict and model belowground C fluxes across broader spatial scales

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Impacts of Fine Root Turnover on Forest NPP and Soil C Sequestration Potential

Cited by 450 publications

References 20 publications

Specific rhizosphere bacterial and fungal groups respond differently to elevated atmospheric CO2

Specific rhizosphere bacterial and fungal groups respond differently to elevated atmospheric CO2

Systematic assessment of terrestrial biogeochemistry in coupled climate–carbon models

Mean age of carbon in fine roots from temperate forests and grasslands with different management

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