Long- and short-term precipitation effects on soil CO2 efflux and total belowground carbon allocation

2012 ◽  
Vol 156 ◽  
pp. 54-64 ◽  
Author(s):  
Chelcy R. Ford ◽  
Jason McGee ◽  
Francesca Scandellari ◽  
Erik A. Hobbie ◽  
Robert J. Mitchell
Keyword(s):  
Carbon Allocation ◽  
Soil Co2 Efflux ◽  
Co2 Efflux ◽  
Soil Co2 ◽  
Short Term ◽  
Belowground Carbon Allocation ◽  
Belowground Carbon ◽  
Total Belowground Carbon Allocation

scholarly journals Evaluating the Community Land Model in a pine stand with <sup>13</sup>CO<sub>2</sub> labeling and shading manipulations

2015 ◽  
Vol 12 (9) ◽  
pp. 6971-7015 ◽  
Author(s):  
J. Mao ◽  
D. M. Ricciuto ◽  
P. E. Thornton ◽  
J. M. Warren ◽  
A. W. King ◽  
...  
Keyword(s):  
Land Surface ◽  
Carbon Allocation ◽  
Soil Co2 Efflux ◽  
Water Dynamics ◽  
Model Parameters ◽  
Co2 Efflux ◽  
Soil Co2 ◽  
Short Term ◽  
Response Curves ◽  
Community Land Model

Abstract. Carbon allocation and flow through ecosystems regulate land surface–atmosphere CO2 exchange and thus is a key, albeit uncertain, component of mechanistic models. The Partitioning in Trees and Soil (PiTS) experiment-model project tracked carbon allocation through a young Pinus taeda stand following pulse-labeling with 13CO2 and two levels of shading. The field component of this project provided process-oriented data that was used to evaluate and improve terrestrial biosphere model simulations of rapid shifts in carbon allocation and hydrological dynamics under varying environmental conditions. Here we tested the performance of the Community Land Model version 4 (CLM4) in capturing short-term carbon and water dynamics in relation to manipulative shading treatments, and the timing and magnitude of carbon fluxes through various compartments of the ecosystem. For CLM4 to closely simulate pretreatment conditions, we calibrated select model parameters with pretreatment observational data. Compared to CLM4 simulations with default parameters, CLM4 with calibrated model parameters was able to better simulate pretreatment vegetation carbon pools, light response curves, and other initial states and fluxes of carbon and water. Over a 3 week treatment period, the calibrated CLM4 generally reproduced the impacts of shading on average soil moisture at 15–95 cm depth, transpiration, relative change in stem carbon, and soil CO2 efflux rate, although some discrepancies in the estimation of magnitudes and temporal evolutions existed. CLM4, however, was not able to track the progression of the 13CO2 label from the atmosphere through foliage, phloem, roots or surface soil CO2 efflux, even when optimized model parameters were used. This model bias arises, in part, from the lack of a short-term non-structural carbohydrate storage pool and progressive timing of within-plant transport, thus indicating a need for future work to improve the allocation routines in CLM4. Overall, these types of detailed evaluations of CLM4, paired with intensive field manipulations, can help to identify model strengths and weaknesses, model uncertainties, and additional observations necessary for future model development.

scholarly journals Seasonal variations of belowground carbon transfer assessed by in situ <sup>13</sup>CO<sub>2</sub> pulse labelling of trees

2011 ◽  
Vol 8 (5) ◽  
pp. 1153-1168 ◽  
Author(s):  
D. Epron ◽  
J. Ngao ◽  
M. Dannoura ◽  
M. R. Bakker ◽  
B. Zeller ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Tree Species ◽  
Fine Roots ◽  
Carbon Allocation ◽  
Soil Co2 Efflux ◽  
Co2 Efflux ◽  
Time Lags ◽  
Pulse Labelling ◽  
Soil Co2 ◽  
Belowground Carbon

Abstract. Soil CO2 efflux is the main source of CO2 from forest ecosystems and it is tightly coupled to the transfer of recent photosynthetic assimilates belowground and their metabolism in roots, mycorrhiza and rhizosphere microorganisms feeding on root-derived exudates. The objective of our study was to assess patterns of belowground carbon allocation among tree species and along seasons. Pure 13CO2 pulse labelling of the entire crown of three different tree species (beech, oak and pine) was carried out at distinct phenological stages. Excess 13C in soil CO2 efflux was tracked using tuneable diode laser absorption spectrometry to determine time lags between the start of the labelling and the appearance of 13C in soil CO2 efflux and the amount of 13C allocated to soil CO2 efflux. Isotope composition (δ13C) of CO2 respired by fine roots and soil microbes was measured at several occasions after labelling, together with δ13C of bulk root tissue and microbial carbon. Time lags ranged from 0.5 to 1.3 days in beech and oak and were longer in pine (1.6–2.7 days during the active growing season, more than 4 days during the resting season), and the transfer of C to the microbial biomass was as fast as to the fine roots. The amount of 13C allocated to soil CO2 efflux was estimated from a compartment model. It varied between 1 and 21 % of the amount of 13CO2 taken up by the crown, depending on the species and the season. While rainfall exclusion that moderately decreased soil water content did not affect the pattern of carbon allocation to soil CO2 efflux in beech, seasonal patterns of carbon allocation belowground differed markedly between species, with pronounced seasonal variations in pine and beech. In beech, it may reflect competition with the strength of other sinks (aboveground growth in late spring and storage in late summer) that were not observed in oak. We report a fast transfer of recent photosynthates to the mycorhizosphere and we conclude that the patterns of carbon allocation belowground are species specific and change seasonally according to the phenology of the species.

scholarly journals Seasonal variations of belowground carbon transfer assessed by in situ <sup>13</sup>CO<sub>2</sub> pulse labelling of trees

2011 ◽  
Vol 8 (1) ◽  
pp. 885-919 ◽  
Author(s):  
D. Epron ◽  
J. Ngao ◽  
M. Dannoura ◽  
M. R. Bakker ◽  
B. Zeller ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Tree Species ◽  
Fine Roots ◽  
Carbon Allocation ◽  
Soil Co2 Efflux ◽  
Co2 Efflux ◽  
Time Lags ◽  
Pulse Labelling ◽  
Soil Co2 ◽  
Belowground Carbon

Abstract. Soil CO2 efflux is the main source of CO2 from forest ecosystems and it is tightly coupled to the transfer of recent photosynthetic assimilates belowground and their metabolism in roots, mycorrhiza and rhizosphere microorganisms feeding on root-derived exudates. The objectives of our study were to assess patterns of belowground carbon allocation among tree species and along seasons. Pure 13CO2 pulse labelling of the entire crown of three different tree species (beech, oak and pine) was carried out at distinct phenological stages. Excess 13C in soil CO2 efflux was tracked using tunable diode laser absorption spectrometry to determine time lags between the start of the labelling and the appearance of 13C in soil CO2 efflux and the amount of 13C allocated to soil CO2 efflux. Isotope composition (δ13C) of CO2 respired by fine roots and soil microbes was measured at several occasions after labelling, together with δ13C of bulk root tissue and microbial carbon. Time lags ranged from 0.5 to 1.3 days in beech and oak and were longer in pine (1.6–2.7 days during the active growing season, more than 4 days during the resting season), and the transfer of C to the microbial biomass was as fast as to the fine roots. The amount of 13C allocated to soil CO2 efflux was estimated from a compartment model. Seasonal patterns of carbon allocation to soil CO2 efflux differed markedly between species, with pronounced seasonal variations in pine and beech. In beech, it may reflect competition with other sinks (aboveground growth in late spring and storage in late summer) that were not observed in oak.

Effect of biomass cutting on soil CO2 efflux in a sandy grassland

2020 ◽  
Author(s):  
Marianna Papp ◽  
Szilvia Fóti ◽  
Krisztina Pintér ◽  
Zoltán Nagy ◽  
János Balogh
Keyword(s):  
Soil Respiration ◽  
Carbon Allocation ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Organic Carbon Content ◽  
Co2 Efflux ◽  
Belowground Carbon Allocation ◽  
Belowground Carbon ◽  
High Organic Carbon Content ◽  
Sandy Grassland

&lt;p&gt;Carbon storage in grassland ecosystems is realized mostly belowground. The changes in the management activities of grasslands also influence the below-ground carbon stocks. Soil carbon-dioxide efflux (Rs) takes a major part of the ecosystem&amp;#8217;s carbon cycle. R&lt;sub&gt;s&lt;/sub&gt; includes the respiration of different components. Rs gives 60-80% of ecosystem respiration or 40-60% of gross primary production. It is known from the literature that respiration is affected by abiotic (temperature (Ts), soil water content (SWC)) and the biotic factors.&lt;/p&gt;&lt;p&gt;In our study we investigated the biotic one, namely the belowground carbon allocation on soil respiration. The study was performed in a semi-arid sandy grassland at Bugac (Kiskuns&amp;#225;g National Park, Hungary). The vegetation of the pasture was dominated by Festuca pseudovina, Carex stenophylla and Cynodon dactylon and the soil is a chernozem type soil with high organic carbon content.&lt;/p&gt;&lt;p&gt;The soil CO&lt;sub&gt;2&lt;/sub&gt; effluxes were measured continuously by an automated soil respiration system consisted of 10 soil respiration chambers. The chambers measured 3 different experimental plots. Data was collected in every half-hour from each chamber for 6 days before the cutting event. After the cutting data was recorded from 1) non-cut, 2) half cut and 3) completely removed treatments also for 6 days. The study was repeated under laboratory conditions (constant temperature, illumination, humidity) on grass patches planted in pots. We observed that the respiration in half cut and completely removed treatments increased after they were cut off. The proportion of respiration after cutting in the completely removed treatment reduced to 85% compared to the control one. Our results highlight that the soil respiration is largely affected by belowground carbon allocation.&lt;/p&gt;

scholarly journals The impact of extreme summer drought on the short-term carbon coupling of photosynthesis to soil CO<sub>2</sub> efflux in a temperate grassland

2013 ◽  
Vol 10 (7) ◽  
pp. 11671-11704 ◽  
Author(s):  
S. Burri ◽  
P. Sturm ◽  
U. E. Prechsl ◽  
A. Knohl ◽  
N. Buchmann
Keyword(s):  
Climate Change ◽  
Tracer Uptake ◽  
Soil Co2 Efflux ◽  
Future Climate Change ◽  
Summer Drought ◽  
Co2 Efflux ◽  
Soil Co2 ◽  
Short Term ◽  
Grass Sward ◽  
The Impact

Abstract. Along with predicted climate change, increased risks for summer drought are projected for Central Europe. However, large knowledge gaps exist in terms of how drought events influence the short-term ecosystem carbon cycle. Here, we present results from 13CO2 pulse labeling experiments at an intensively managed lowland grassland in Switzerland. We investigated the effect of extreme summer drought on the short-term coupling of freshly assimilated photosynthates in shoots to roots as well as to soil CO2 efflux. Summer drought was simulated using rainout shelters during two field seasons (2010 and 2011). Soil CO2 efflux and its isotopic composition were measured with custom-built chambers coupled to a quantum cascade laser spectrometer (QCLAS-ISO, Aerodyne Research Inc., MA, USA). During the 90 min pulse labeling experiments, we added 99.9 atom % 13CO2 to the grass sward. In addition to the isotopic analysis of soil CO2 efflux, this label was traced over 31 days into bulk shoots, roots and soil. Drought reduced the incorporation of recently fixed carbon into shoots and increased carbon allocation below-ground relative to total tracer uptake. Contrary to our hypothesis, we did not find a change in allocation speed in response to drought, although drought clearly reduced soil CO2 efflux rates. 19 days after pulse labeling, only about 60% of total tracer uptake was lost via soil CO2 efflux under drought compared to about 75% under control conditions. Predisposition of grassland by spring drought lead to different responses to summer drought in 2011 compared to 2010, suggesting increased sensitivity of grassland to consecutive drought events as predicted under future climate change.

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