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157 results for “carbon dynamics”
Dissolved organic carbon dynamics in an urban desert stream ecosystem in central Arizona-Phoenix
Variation in stream chemistry is a function of the strength of terrestrial-aquatic linkages, the extent to which surface and groundwater exchanges, and the rate of instream biotic processes. The importance of these variables may fluctuate as a function of climate regime, catchment geomorphology, or level of human impact. A mechanistic understanding of the influence of each of these variables on ecosystem functioning will increase understanding of the role of streams in global nutrient and carbon cycles. Of particular interest is dissolved organic carbon (DOC), an important source of carbon and energy for microbial processes. Respiration by heterotrophic bacterial communities has recently been linked to the quality (ability of microbes to utilize C source) of the DOC pool in streams. DOC not only influences stream nutrient supply, but also the transport of contaminants and the attenuation of UV radiation. This dissertation focused on DOC delivery to two arid-land stream ecosystems, one native desert (Sycamore Creek, AZ), and one urban (Phoenix, AZ). The overall objectives of this work were to (1) document patterns in DOC quantity and chemical composition in response to flooding and groundwater exchange, (2) generate and test hypotheses explaining variation in DOC quantity and quality and (3) relate this variation to microbial activity. In the native desert stream ecosystem, the climate regime influenced seasonal variation in the quantity and quality of DOC inputs, with higher complexity and higher concentrations of DOC in summer monsoonal runoff. In contrast, human alteration of geomorphology and hydrologic flowpaths in the Phoenix metropolitan area significantly influenced streamwater chemistry in comparison to low-impact streams in the Sonoran Desert. In the city, mechanisms of nutrient retention and transformation were often shifted from dominance by biotic to abiotic ones, severely dampening the influence of climate regime and substituting instead the maintenance
Soil carbon: Nitrogen Addition and Dynamics of Recovery from Cessation of N Addition
This experiment was established on top of E002 in fields A and C. In the spring of 1992, 3 randomly chosen replicates of each nutrient treatment of experiment E002 were chosen to receive no more fertilizer. For a description of these plots, see E002. For a description of fertilizer added to E097, see file fertilization details. For a list of treatments, see the treatment layouts in file trmte97.
Plant aboveground biomass carbon and nitrogen: Herbivory by Nitrogen Interactive Effects on Community and Ecosystem Processes and Dynamics
E172 is an herbivory experiment established by Dave Tilman in fall 2004 by enclosing in deer fences three randomly selected plots from the six replicates of each control and each treatment in the N addition E001 experiment in field C. These plots still receive the nutrient treatments prescribed in the Experiment 001 protocols. From 1982-2004 a fence containing all of e001 plots in Field C was designed to exclude deer and all small mammals, including mice, voles and pocket gophers. This fence was removed in Fall of 2004 and individual plots designated for e172 were enclosed in deer fences. The purpose of E001 was to measure how adding nitrogen over a long time would affect the number of species, the type of species present, the amount of annual growth, and the change from year to year in the growth of each species in a plant community which is also relieved of grazing by large and small mammals. There are 8 different levels of nitrogen addition with other nutrients added to ensure that nitrogen remains the limiting nutrient, and a control which receives no nutrients. The plots are in a 6 by 9 grid and are 4 by 4 meters in size with 1 meter aisles between plots. Nitrogen fertilizer (NH4NO3) is applied twice per year, once in early May and once in late June.
Soil carbon: Herbivory by Nitrogen Interactive Effects on Community and Ecosystem Processes and Dynamics
E172 is an herbivory experiment established by Dave Tilman in fall 2004 by enclosing in deer fences three randomly selected plots from the six replicates of each control and each treatment in the N addition E001 experiment in field C. These plots still receive the nutrient treatments prescribed in the Experiment 001 protocols. From 1982-2004 a fence containing all of e001 plots in Field C was designed to exclude deer and all small mammals, including mice, voles and pocket gophers. This fence was removed in Fall of 2004 and individual plots designated for e172 were enclosed in deer fences. The purpose of E001 was to measure how adding nitrogen over a long time would affect the number of species, the type of species present, the amount of annual growth, and the change from year to year in the growth of each species in a plant community which is also relieved of grazing by large and small mammals. There are 8 different levels of nitrogen addition with other nutrients added to ensure that nitrogen remains the limiting nutrient, and a control which receives no nutrients. The plots are in a 6 by 9 grid and are 4 by 4 meters in size with 1 meter aisles between plots. Nitrogen fertilizer (NH4NO3) is applied twice per year, once in early May and once in late June.
Data from: Plant community dynamics and carbon sequestration in Sphagnum-dominated peatlands in the era of global change
<p>Aim: Hydroclimatic shift and anthropogenic-driven nitrogen deposition are major outcomes of global change that could compromise the functioning of many peatlands as a carbon sink. For Sphagnum-dominated peatlands, an emerging hypothesis is that the change could be triggered by shifts in competitive dominance among plant functional groups, specifically from the currently predominant decay-resistant Sphagnum to the more decomposable vascular plants. However, the relationship between Sphagnum and vascular plant occurrence is notably complex and also includes facilitative interactions that are crucial to the productivity of Sphagnum and therefore carbon sequestration.</p> <p>Location: Global</p> <p>Taxa: Northern peatlands—Sphagnum moss and vascular plants</p> <p>Methods: We use a conceptual review to examine underlying mechanisms for the competitive exclusion hypothesis and the nature of facilitative interactions between Sphagnum and vascular plants under the potential global change conditions. We complement the review with an empirical study of peatlands with contrasting hydrology to provide some critical insights into the potential effects of change in plant communities on carbon sequestration. We also propose a conceptual model that presents probable combinations of global change factors and their implications for carbon sequestration.</p> <p>Results: Vegetation structure in Sphagnum-dominated peatland appears to be driven largely by hydrology, rather than competition among plant functional groups. The peat deposit also exerts some controls (e.g., nutrient immobilization) on biotic structure, thereby acting as resistance against an abrupt shift in plant communities.<br> Main conclusions: Peatland controls that constrain vegetation shifts have developed over a millennial timescale in many peatlands, and the pace of climate change may not allow enough time for the establishment of those mechanisms in younger peatlands. Thus, the persistence of a given peatland as a carbon sink also likely depends on the successional stage of the peatland.</p>
Data from: Dynamics of deep soil carbon - insights from 14C time series across a climatic gradient
Quantitative constraints on soil organic matter (SOM) dynamics are essential for comprehensive understanding of the terrestrial carbon cycle. Deep soil carbon is of particular interest, as it represents large stocks and its turnover times remain highly uncertain. In this study, SOM dynamics in both the top and deep soil across a climatic (average temperature ~1-9 °C) gradient are determined using time-series (~20 years) 14C data from bulk soil and water-extractable organic carbon (WEOC). Analytical measurements reveal enrichment of bomb-derived radiocarbon in the deep soil layers on the bulk level during the last two decades. The WEOC pool is strongly enriched in bomb-derived carbon, indicating that it is a dynamic pool. Turnover time estimates of both the bulk and WEOC pool show that the latter cycles up to a magnitude faster than the former. The presence of bomb-derived carbon in the deep soil, as well as the rapidly turning WEOC pool across the climatic gradient implies that there likely is a dynamic component of carbon in the deep soil. Precipitation and bedrock type appear to exert a stronger influence on soil C turnover time and stocks as compared to temperature.
The dynamics and stoichiometry of dissolved organic carbon release by kelp: Carbon fixation, DOC release and nutrient uptake data
<p>Canopy-forming kelps are foundational species in coastal ecosystems, fixing tremendous amounts of carbon, yet we know little about the ecological and physiological determinants of dissolved organic carbon (DOC) release by kelps. We examined DOC release by the bull kelp, <i>Nereocystis luetkeana</i>, in relation to carbon fixation, nutrient uptake, tissue nitrogen content, and light availability. DOC release was approximately 3.5 times greater during the day than at night. During the day, <i>N. luetkeana</i> blades released an average of 16.2% of fixed carbon as DOC. Carbon fixation increased with light availability but DOC release did not, leading to a lower proportion of fixed carbon released as DOC at high light levels. We found no relationship between carbon fixation and DOC release rates measured concurrently. Rather, DOC release by <i>N. luetkeana</i> blades declined with marginal significance as blade tissue nitrogen content increased and with experimental nitrate addition, supporting the role of stoichiometric relationships in DOC release. Using a stable isotope (<sup>13</sup>C) tracer method, we demonstrated that inorganic carbon is rapidly fixed and released by <i>N. luetkeana</i> blades as <sup>13</sup>DOC, within hours. However, recently fixed carbon (<sup>13</sup>DOC) comprised less than 20% of the total DOC released, indicating that isotope studies that rely on tracer production alone may underestimate total DOC release, as it is decoupled from recent kelp productivity. Comparing carbon and nitrogen assimilation dynamics of the annual kelp <i>N. luetkeana</i> with the perennial kelp <i>Macrocystis pyrifera</i> revealed that <i>N. luetkeana </i>had significantly higher carbon fixation, DOC production and nitrogen uptake rates per unit dry mass. Both kelp species were able to perform light-independent carbon fixation at night. Carbon fixation by the annual kelp <i>N. luetkeana </i>is as high as 2.35 kg C m<sup>-2</sup> yr<sup>-1</sup>, but an average of 16% of this carbon (376 g C m<sup>-2</sup> yr<sup>-1</sup>) is released as DOC. As kelp forests are increasingly viewed as vehicles for carbon sequestration, it is important to consider the fate of this substantial quantity of DOC released by canopy-forming kelps.</p>
Data from: Carbon flux and forest dynamics: increased deadwood decomposition in tropical rainforest tree-fall gaps
<p>This study was carried out within an area of lowland, old growth dipterocarp rainforest in the Maliau Basin Conservation Area, Sabah, Malaysia (4° 44' 35" to 55" N and 116° 58' 10" to 30" E; mean annual rainfall 2838 mm ± 93 mm). On the 20<sup>th</sup> of July 2017, there was a storm at the study site, which generated winds speeds of 8.4 m/s (Fig. S1). These were among the strongest winds normally experienced in inland forests of the region, which placed extreme sheer stress on trees. Consequently, a large number of trees fell within the same 24-hour period in the study location. Ten tree-fall gaps (mean length: 32 m ± 2.8, mean width: 24.5 m ± 3; see table S1 for gap characteristics) created during this event were selected for use in this investigation, along with ten adjacent closed canopy sites, located 20 m from the edge of each gap. We took 10 hemispherical photos in each gap and closed canopy sites to quantity canopy openness at each location.</p>
Data from: Carbon dynamics of mature and regrowth tropical forests derived from a pantropical database (TropForC-db)
Tropical forests play a critical role in the global carbon (C) cycle, storing ~45% of terrestrial C and constituting the largest component of the terrestrial C sink. Despite their central importance to the global C cycle, their ecosystem-level C cycles are not as well characterized as those of extra-tropical forests, and knowledge gaps hamper efforts to quantify C budgets across the tropics and to model tropical forest- climate interactions. To advance understanding of C dynamics of pantropical forests, we compiled a new database, the Tropical Forest C database (TropForC-db), which contains data on ground-based measurements of ecosystem-level C stocks and annual fluxes along with disturbance history. This database currently contains 3,568 records from 845 plots in 178 geographically distinct areas, making it the largest and most comprehensive database of its type. Using TropForC-db, we characterized C stocks and fluxes for young, intermediate-aged, and mature forests. Relative to existing C budgets of extra-tropical forests, mature tropical broadleaf evergreen forests had substantially higher gross primary productivity (GPP) and ecosystem respiration (Reco), their autotropic respiration (Ra) consumed a larger proportion (~67%) of GPP, and their woody stem growth (ANPPstem) represented a smaller proportion of net primary productivity (NPP, ~32%) or GPP (~9%). In regrowth stands, aboveground biomass increased rapidly during the first 20 years following stand-clearing disturbance, with slower accumulation following agriculture and in deciduous forests, and continued to accumulate at a slower pace in forests aged 20-100 years. Most other C stocks likewise increased with stand age, while potential to describe age trends in C fluxes was generally data-limited. We expect that TropForC-db will prove useful for model evaluation and for quantifying the contribution of forests to the global C cycle. The database version associated with this publication is archived in Dryad (DOI:10.5061/dryad.t516f) and a dynamic version is maintained at https://github.com/forc-db.
Data from: Plant economic strategies of grassland species control soil carbon dynamics through rhizodeposition
1. The plant economics spectrum is increasingly recognized as a major determinant of plant species effects on terrestrial ecosystem functioning related to carbon cycling. However, the role of plant economic strategies in the effects of living root activity on soil organic carbon (SOC) dynamics through rhizodeposition remains unexplored, despite SOC being the largest terrestrial carbon pool. 2. Using a continuous 13C-labeling method allowing partitioning of plant and soil sources to carbon fluxes and pools, we studied here the linkages between plant economic strategies and SOC cycling processes in a 'common garden' greenhouse experiment. It includes a panel of 12 grassland species selected along a gradient of economic traits and belonging to three functionnal groups (C3 grasses, forbs and legumes). 3. All species induced an acceleration of native SOC mineralization but this rhizosphere priming effect (RPE) substantially differed across species and varied eleven-fold by the end of the experiment (from +26 to +295 % relative to unplanted soil). Interspecific variation in RPE was primarily linked to plant photosynthetic activity associated to species economic strategies of light and CO2 resource acquisition and processing. Fast-growing acquisitive species, such as legumes, featured large RPE, in relation with their high canopy photosynthesis coupled to high leaf photosynthetic capacity and large net primary productivity allocated aboveground. This large RPE was further associated with high root metabolic activity, rhizodeposition and soil microbial activity. In contrast, fine-root growth and economic traits related to soil resource foraging ability were poor predictors of RPE. 4. The formation of new root-derived SOC varied nine-fold across species and was similarly positively related to the net primary productivity allocated aboveground. Fast-growing acquisitive species with a high photosynthetic activity induced a disproportionately large RPE relative to SOC formation. 5. Synthesis. Overall, our study demonstrates that rhizodeposition is a major mechanism through which plant economic strategies of grassland species control soil carbon dynamics. Acquisitive versus conservative species were associated with high versus low rates of photosynthesis and rhizodeposition, in turn leading to fast versus slow SOC turnover. This emphasizes the importance of considering rhizosphere processes for understanding plant species effects on soil biogeochemistry.
Forest disturbances and climate constrain carbon allocation dynamics in trees
<p>Forest disturbances such as drought, fire and logging affect the forest carbon dynamics and the terrestrial carbon sink. Forest mortality after disturbances creates uncertainties that need to be accounted for to understand forest dynamics and their associated C-sink. We combined data from permanent resampling plots and biomass oriented dendroecological plots to estimate time series of annual woody biomass growth (ABI) in several forests. ABI time series were used to benchmark a vegetation model to analyze dynamics in forest productivity and carbon allocation forced by environmental variability. The model implements source and sink limitations explicitly by dynamically constraining carbon allocation of assimilated photosynthates as a function of temperature and moisture. Bias in tree-ring reconstructed ABI increased back in time from data collection and with increasing disturbance intensity. ABI bias ranged from zero, in open stands without recorded mortality, to over 100% in stands with major disturbances such as thinning or snowstorms. Stand leaf area was still lower than in control plots decades after heavy thinning. Disturbances, species life-history strategy and climatic variability affected carbon partioning patterns in trees. Resprouting broadleaves reached maximum biomass growth at earlier ages than nonresprouting conifers. Environmental variability and leaf area explained much variability in woody biomass allocation. <span>Effects of </span>stand competition on C-allocation were mediated by changes in stand leaf area except after major disturbances. Divergence between tree-ring estimated and simulated ABI were caused by unaccounted changes in allocation or misrepresentation of some functional process independently of the model calibration approach. Higher disturbance intensity produced greater modifications of the C-allocation pattern, increasing error in reconstructed biomass dynamics. Legacy effects from disturbances decreased model performance and reduce the potential use of ABI as a proxy to net primary productivity. Trait-based dynamics of C-allocation in response to environmental variability need to be refined in vegetation models.</p>
Computational data for "Measurement of Coherent Vibrational Dynamics with X-ray Transient Absorption Spectroscopy Simultaneously at the Carbon K- and Chlorine L$_{2,3}$- Edges"
<p>Contains:<br><br>1. Code for and results from, time-dependent Schroedinger equation simulations for the molecular normal modes under strong electric fields inducing impulsive stimulated Raman processes.</p> <p>2. Molecular orbitals obtained from ROKS calculations for the C 1s and Cl 2p excited states (with spin-free one-electron X2C). </p>
Data from: The oldest, slowest forests in the world? Exceptional biomass and slow carbon dynamics of Fitzroya cupressoides temperate rainforests in southern Chile
Old-growth temperate rainforests are, per unit area, the largest and most long-lived stores of carbon in the terrestrial biosphere, but their carbon dynamics have rarely been described. The endangered Fitzroya cupressoides forests of southern South America include stands that are probably the oldest dense forest stands in the world, with long-lived trees and high standing biomass. We assess and compare aboveground biomass, and provide the first estimates of net primary productivity (NPP), carbon allocation and mean wood residence time in medium-age stands in the Alerce Costero National Park (AC) in the Coastal Range and in old-growth forests in the Alerce Andino National Park (AA) in the Andean Cordillera. Aboveground live biomass was 113–114 Mg C ha-1 and 448–517 Mg C ha-1 in AC and AA, respectively. Aboveground productivity was 3.35–3.36 Mg C ha-1 year-1 in AC and 2.22–2.54 Mg C ha-1 year-1 in AA, values generally lower than others reported for temperate wet forests worldwide, mainly due to the low woody growth of Fitzroya. NPP was 4.21–4.24 and 3.78–4.10 Mg C ha-1 year-1 in AC and AA, respectively. Estimated mean wood residence time was a minimum of 539–640 years for the whole forest in the Andes and 1368–1393 years for only Fitzroya in this site. Our biomass estimates for the Andes place these ecosystems among the most massive forests in the world. Differences in biomass production between sites seem mostly apparent as differences in allocation rather than productivity. Residence time estimates for Fitzroya are the highest reported for any species and carbon dynamics in these forests are the slowest reported for wet forests worldwide. Although primary productivity is low in Fitzroya forests, they probably act as ongoing biomass carbon sinks on long-term timescales due to their low mortality rates and exceptionally long residence times that allow biomass to be accumulated for millennia.
Aboveground carbon stocks and dynamics in Andean forests
<p>This dataset (Andean_AGB.xlsx) has the data employed in the paper entitled <i>Old-growth Andean forests as globally important carbon sinks and future carbon refuges</i>. The data was compiled as the results of the work of several research teams spread out across the Andean region. The information available here has data about aboveground carbon stocks and dynamics and the main explanatory variables, such as climate and symbiotic root associations.</p>
Effects of habitat types on the dynamic changes of allocation in carbon and nitrogen storage of vegetation-soil system in sandy grasslands
<p>The progressive restoration of degraded vegetation in semiarid and arid desertified areas undoubtedly formed different habitat types. The most plants regulate their growth by fixing carbon with their energy deriving from photosynthesis, carbon (C) and nitrogen (N) play the crucial role in regulating plant growth, community structure and function in the vegetation restoration progress. However, it is still unclear how habitat types affect the dynamic changes of allocation in C and N storage of vegetation-soil system in sandy grasslands. Here, we investigated plant community characteristics and soil properties across three successional stages of habitat types: semi-fixed dunes (SFD), fixed dunes (FD) and grasslands (G) in 2011, 2013 and 2015. We also examined the C and N concentrations of vegetation-soil system, and estimated their C and N storage. The C and N storage of vegetation system, soil and vegetation-soil system remarkably increased from SFD to G. The litter C and N storage in SFD, N storage of vegetation system in SFD and N storage of soil and vegetation-soil system in FD increased from 2011 to 2015, while aboveground plant C and N storage of FD were higher in 2011 than in 2013 and 2015. Most of C and N were sequestered in soil in the vegetation restoration progress. These results suggest that the dynamic changes of allocation in C and N storage in vegetation-soil systems varied with habitat types. Our study highlights that SFD has higher N sequestration rate in vegetation, while FD has the considerably N sequestration rate in the soil.</p>
Simulation data for "Impact of Dynamic Phytoplankton Stoichiometry on Global Scale Patterns of Nutrient Limitation, Nitrogen Fixation, and Carbon Export"
<p>Simulation data for our submission to GBC. Some of the files are compressed in order to minimize the size of the archive. Data files are stored as pickled python variables. The code for analysis of this data is in the github repository: https://github.com/georgehagstrom/BGCPaperFigureCode .</p>
Data from: Plant economic strategies of grassland species control soil carbon dynamics through rhizodeposition
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Data from: The oldest, slowest forests in the world? Exceptional biomass and slow carbon dynamics of Fitzroya cupressoides temperate rainforests in southern Chile
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Aboveground carbon stocks and dynamics in Andean forests
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Effects of habitat types on the dynamic changes of allocation in carbon and nitrogen storage of vegetation-soil system in sandy grasslands
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
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DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.