Elevated CO2 alters the temperature sensitivity of stem CO2 efflux in a mature eucalypt woodland

Abstract Tree autotrophic respiratory processes, especially stem respiration or stem CO2 efflux (Estem), are important components of the forest carbon budget. Despite the efforts to investigate the controlling processes of Estem in the last years a considerable lack in our knowledge remains on the abiotic and biotic drivers affecting Estem dynamics. It has been strongly advocated that long-term measurements would shed light into those processes. The expensive scientific instruments needed to measure gas exchange has prevented from applying Estem measurements on a larger temporal and spatial scale. Here, we present an automated closed dynamic chamber system based on inexpensive and industrially broadly applied CO2 sensors reducing the costs for the sensing system to a minimum. The CO2 sensor was cross-calibrated with a commonly used gas exchange system in the laboratory and in the field, and we found very good accordance of these sensors. We tested the system under harsh tropical climatic conditions, characterized by heavy tropical rainfall events, extreme humidity, and temperatures, in a moist lowland forest in Malaysia. We recorded Estem of three Dyera costulata trees with our prototype over various days. The variation of Estem was large among the three tree individuals and varied by 7.5-fold. However, clear diurnal changes in Estem were present in all three tree individuals. One tree showed high diurnal variation in Estem and the relationship between Estem and temperature was characterized by a strong hysteresis. The large variations found within one single tree species highlights the importance of continuous measurement to quantify ecosystem carbon fluxes.

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Low-cost chamber design for simultaneous CO2 and O2 flux measurements between tree stems and the atmosphere

Tree Physiology ◽

10.1093/treephys/tpab022 ◽

2021 ◽

Author(s):

Juliane Helm ◽

Henrik Hartmann ◽

Martin Göbel ◽

Boaz Hilman ◽

David Herrera ◽

...

Keyword(s):

Low Cost ◽

Co2 Flux ◽

Co2 Efflux ◽

Stem Respiration ◽

Ecosystem Carbon ◽

O2 Concentration ◽

Flux Measurements ◽

Stem Co2 Efflux ◽

Tree Stem

Abstract Tree stem CO2 efflux is an important component of ecosystem carbon fluxes and has been the focus of many studies. While CO2 efflux can easily be measured, a growing number of studies have shown that it is not identical with actual in situ respiration. Complementing measurements of CO2 flux with simultaneous measurements of O2 flux provides an additional proxy for respiration, and the combination of both fluxes can potentially help getting closer to actual measures of respiratory fluxes. To date, however, the technical challenge to measure relatively small changes in O2 concentration against its high atmospheric background has prevented routine O2 measurements in field applications. Here we present a new and low-cost field-tested device for autonomous real-time and quasi-continuous long-term measurements of stem respiration by combining CO2 (NDIR based) and O2 (quenching based) sensors in a tree stem chamber. Our device operates as a cyclic closed system and measures changes in both CO2 and O2 concentration within the chamber over time. The device is battery-powered with a > 1 week power independence and data acquisition is conveniently achieved by an internal logger. Results from both field and laboratory tests document that our sensors provide reproducible measurements of CO2 and O2 exchange fluxes under varying environmental conditions.

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Internal respiration of Amazon tree stems greatly exceeds external CO<sub>2</sub> efflux

Biogeosciences ◽

10.5194/bg-9-4979-2012 ◽

2012 ◽

Vol 9 (12) ◽

pp. 4979-4991 ◽

Cited By ~ 31

Author(s):

A. Angert ◽

J. Muhr ◽

R. Negron Juarez ◽

W. Alegria Muñoz ◽

G. Kraemer ◽

...

Keyword(s):

Tropical Trees ◽

Co2 Efflux ◽

Water Stream ◽

New Approach ◽

Stem Respiration ◽

Internal Flux ◽

Stem Co2 Efflux ◽

Internal Co2 ◽

Global Carbon ◽

Net Release

Abstract. Respiration in tree stems is an important component of forest carbon balance. The rate of CO2 efflux from the stem has often been assumed to be a measure of stem respiration. However, recent work in temperate forests has demonstrated that stem CO2 efflux can either overestimate or underestimate respiration rate because of emission or removal of CO2 by transport in xylem water. Here, we studied gas exchange from stems of tropical forest trees using a new approach to better understand respiration in an ecosystem that plays a key role in the global carbon cycle. Our main questions were (1) is internal CO2 transport important in tropical trees, and, if so, (2) does this transport result in net release of CO2 respired in the roots at the stem, or does it cause the opposite effect of net removal of stem-respired CO2? To answer these questions, we measured the ratio of stem CO2 efflux to O2 influx. This ratio, defined here as apparent respiratory quotient (ARQ), is expected to equal 1.0 if carbohydrates are the substrate for respiration, and the net transport of CO2 in the xylem water is negligible. Using a stem chamber approach to quantifying ARQ, we found values of 0.66 ± 0.18. These low ARQ values indicate that a large portion of respired CO2 (~ 35%) is not emitted locally, and is probably transported upward in the stem. ARQ values of 0.21 ± 0.10 were found for the steady-state gas concentration within the stem, sampled by in-stem equilibration probes. These lower values may result from the proximity to the xylem water stream. In contrast, we found ARQ values of 1.00 ± 0.13 for soil respiration. Our results indicate the existence of a considerable internal flux of CO2 in the stems of tropical trees. If the transported CO2 is used in the canopy as a substrate for photosynthesis, it could account for up to 10% of the C fixed by the tree, and perhaps serve as a mechanism that buffers the response of the tree to changing CO2 levels. Our results also indicate, in agreement with previous work, that the widely used CO2 efflux approach for determining stem respiration is unreliable. We demonstrate here a field applicable approach for measuring the O2 uptake rate, which we suggest to be a more appropriate method to estimate stem respiration rates.

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Significance of soil respiration from biological activity in the degradation processes of different types of organic matter

10.37281/drcsf/1.2.10 ◽

2020 ◽

Vol 1 (2) ◽

pp. 171-179

Keyword(s):

Climate Change ◽

Organic Matter ◽

Soil Moisture ◽

Soil Respiration ◽

Soil Temperature ◽

Temperature Sensitivity ◽

Soil Co2 Efflux ◽

Co2 Efflux ◽

Soil Co2 ◽

Total Soil

Soil respiration is a major component of global carbon cycle. Therefore, it is crucial to understand the environmental controls on soil respiration for evaluating potential response of ecosystems to climate change. In a temperate deciduous forest (located in Northern-Hungary) we added or removed aboveground and belowground litter to determine total soil respiration. We investigated the relationship between total soil CO2 efflux, soil moisture, and soil temperature. Soil CO2 efflux was measured at each plot using soda-lime method. Temperature sensitivity of soil respiration (Q10) was monitored via measuring soil temperature on an hourly basis, while soil moisture was determined monthly. Soil respiration increased in control plots from the second year after implementing the treatment, but results showed fluctuations from one year to another. The effect of doubled litter was less significant than the effect of removal. Removed litter and root inputs caused substantial decrease in soil respiration. We found that temperature was more influential in the control of soil respiration than soil moisture. In plots with no litter Q10 varied in the largest interval. For treatment with doubled litter layer, temperature sensitivity of CO2 efflux did not change considerably. The effect of increasing soil temperature is more conspicuous to soil respiration in litter removal treatments since lack of litter causes greater irradiation. When exclusively leaf litter was considered, the effect of temperature on soil respiration was lower in treatments with added litter than with removed litter. Our results reveal that soil life is impacted by the absence of organic matter, rather than by an excess of organic matter. Results of CO2 emission from soils with different organic matter content can contribute to sustainable land use, considering the changed climatic factors caused by global climate change.

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Soil CO2 efflux of two silver birch clones exposed to elevated CO2 and O3 levels during three growing seasons

Global Change Biology ◽

10.1111/j.1365-2486.2004.00841.x ◽

2004 ◽

Vol 10 (10) ◽

pp. 1654-1665 ◽

Cited By ~ 28

Author(s):

Anne Kasurinen ◽

Paula Kokko-Gonzales ◽

Johanna Riikonen ◽

Elina Vapaavuori ◽

Toini Holopainen

Keyword(s):

Elevated Co2 ◽

Soil Co2 Efflux ◽

Silver Birch ◽

Co2 Efflux ◽

Soil Co2 ◽

Growing Seasons ◽

Elevated Co2 And O3

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Peer review report 2 On “Stem CO2 efflux and its contribution to ecosystem CO2 efflux decrease with drought in a Mediterranean forest stand”

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2015.08.225 ◽

2015 ◽

Vol 201 ◽

pp. 637

Author(s):

Anonymous

Keyword(s):

Peer Review ◽

Forest Stand ◽

Mediterranean Forest ◽

Co2 Efflux ◽

Stem Co2 Efflux

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Variability in temperature dependence of stem CO2 efflux from Norway spruce trees

Tree Physiology ◽

10.1093/treephys/tpy006 ◽

2018 ◽

Vol 38 (9) ◽

pp. 1333-1344 ◽

Cited By ~ 4

Author(s):

Eva Darenova ◽

Manuel Acosta ◽

Radek Pokorny ◽

Marian Pavelka

Keyword(s):

Temperature Dependence ◽

Norway Spruce ◽

Co2 Efflux ◽

Stem Co2 Efflux

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Soil CO2 efflux and root respiration at three sites in a mixed pine and spruce forest: seasonal and diurnal variation

Canadian Journal of Forest Research ◽

10.1139/x01-012 ◽

2001 ◽

Vol 31 (5) ◽

pp. 786-796 ◽

Cited By ~ 86

Author(s):

Britta Widén ◽

Hooshang Majdi

Keyword(s):

Diurnal Variation ◽

Temperature Sensitivity ◽

Root Respiration ◽

Fine Root ◽

Mixed Forest ◽

Distribution Patterns ◽

Co2 Efflux ◽

Root Temperature ◽

Coarse Root ◽

N Concentration

Soil CO2 efflux and respiration of excised roots were measured with a LI-COR 6200 at three sites in a mixed forest (60°05'N, 17°3'E), from May to October 1999, both day and night. Fine-root (<5 mm in diameter) respiration was measured at ambient root temperature and soil CO2 partial pressure, and the roots were analysed for nitrogen (N) concentration. Root-density data obtained from soil cores were used to estimate fine-root biomass. Coarse-root respiration was estimated using stand data, literature data, and allometric relationships. Soil CO2 efflux, 3.07.0 µmol·m2·s1, differed between sites but showed no diurnal variation. Maximum values were obtained in July through August. Fine-root respiration, 0.34.7 nmol·g1·s1, decreased after peaking in early July and showed no diurnal variation. The seasonal mean was lowest at the South site, where also root distribution patterns were different and root N concentrations were lower. Fine-root respiration increased with root N concentration; however, the relationship was very weak, since the variation in root N concentration between sites and times of year was small. Both soil CO2 efflux and fine-root respiration increased exponentially with soil and root temperature, respectively, although fine-root respiration was twice as sensitive. The percentage of soil CO2 efflux emanating from roots was 3362% in May, thereafter decreasing to 1216% in October. This, in combination with larger temperature sensitivity for fine-root respiration, is suggested to cause the temperature sensitivity of soil CO2 efflux to diminish over the season.

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