IJERD – International Journal of Environmental and Rural Development (2023) 14-1

Research article
erd

Temperature Sensitivity (Q10) of Organic Carbon in
Red-yellow Soils and Its Conservation Strategies
KEIJI AROSTEGUIGraduate School of Agriculture, Tokyo University of Agriculture, Tokyo, Japan
Email: karostegui@cientifica.edu.pe

MACHITO MIHARA*
Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan
Email: m-mihara@nodai.ac.jp
Received 16 December 2022

Accepted 10 June 2023(*Corresponding Author)

Abstract Soil respiration (SR) is the second largest flux of carbon in most terrestrial
ecosystems after photosynthesis. Research indicates that a slight change in climate conditions
induces a variation of the SR that could be equal to the release of CO2 by fossil fuel emissions.
For this reason, it is important to study what conditions control the variation of SR. Soil
temperature is an important predictor of SR when there is no severe drought stress. The
estimation of SR rates by the effect of temperature has been expressed with the Q10 relationship.
This study aims to determine the Temperature Sensitivity (Q10) coefficient of the red-yellow
soil organic carbon and estimate its conservation strategy using biochar. To analyze
temperature sensitivity, each treatment was kept under 25ºC and 35ºC for 150 days, and thesoil respiration ratio (SRR) as well as soil organic carbon (SOC) content were measured by
the spectrophotometry method. Lastly, a treatment of biochar at 5% was added as a carbon
conservation mechanism. The experimental results showed a significant difference in SOC
content between different temperature conditions. After 150 days under treatment, 35ºC
treatment had a significant reduction of SOC in contrast with 25ºC treatment (3.65 and 6.02
mg C/g respectively). The addition of biochar resulted in higher values of SOC at the same
temperature, relative to non-biochar treatments. The Q10 value was higher in soil withoutbiochar (1.82), while the addition of biochar reduces the coefficient to 1.12. The SRR was
reduced gradually with higher values at 35ºC, however, the biochar reduced the emission at
25ºC lower than other treatments. The results indicated that the Q10 value of red-yellow soil
can be affected by the addition of biochar, which works as a carbon source to maintain andincrease SOC content and reduce the release of CO2 in the short term.
Keywords soil organic carbon, soil respiration rate, temperature sensitive, biochar

INTRODUCTION
The soil organic carbon is part of the organic matter in more than 50% of the content. This fulfills an
important role in plant feeding, stabilization of soil structure, soil fertility, and most important,climate change effects mitigation. The soil carbon is dynamic by the interaction of the ecosystem;
however, human activity impacts can destabilize SOC into either a net of carbon or a source ofgreenhouse gases (GHG) in the atmosphere (Trivedi et al., 2018).
The alteration of climate has a considerable effect on the SOC stocks, although it is variable
depending on the type of soil and location, Changes in temperature lead to an increase in extreme
drought events, followed by the loss of carbon in the soil. Efforts towards a better understanding of
the SOC dynamic have indeed been made, however, the mechanism of stabilization and conservationof SOC stocks are still complicated to apply and understand. Further research must focus on thevariation of soil and temperature, as well as conservation strategies (Pribyl, 2010).

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According to De Oliveira Marques et al. (2017), the Red-yellow soil (Udults soil taxonomy),
mainly located in the Amazon area, represents an important amount of global soil carbon, making
this area vulnerable to deforestation activities and land uses.
The conservation of carbon stocks in the Amazon area has had an impact on the political decisionof governments to act on reforesting rather than permitting deforestation. However, deforestation has
been accelerated and the fragmentation process of the Amazon area is resulting in significant changes
in carbon stock, as well as biomass soil (Barros and Fearnside, 2016).
Lloyd and Taylor (1994) remarked that the increase of microorganism activity in soil is
stimulated by the increase in temperature, leading to an augment of microbial CO2. This process
reduces the SOC, which contributes to the global warming problem. In a short period (one year), theincrease in temperature results in a considerable change in microbial activity and decomposition rate.
It has been demonstrated that the decomposition of SOC is higher as the temperature increases,
with the biggest proportional increase observed at low temperatures. Are important issue is toestimate in detail to what extent the rising temperature could destabilize SOC and make it available
for the decomposition process. The proportion of SOC stored in the world’s soils is still argued and
it is vulnerable to the impacts of warming of this century (Crowther et al., 2016).
In this study, we model approaches of changes in carbon availability by microbial activity thatare needed to have a better understanding of the Red-yellow soil carbon. The Amazon area has an
ecological function connected with the SOC, respiration rate, decomposition of organic matter, andestimation of conservation strategies that must be investigated.
OBJECTIVE
This study aims to determine the Temperature Sensitivity (Q10) coefficient of the Red-yellow soilorganic carbon, under different conditions of temperature (25 and 35ºC) and estimate its conservation
strategy using biochar. The present research provides a new mechanism of climate change mitigation
and a better understanding of soil and biochar.
METHODOLOGY
Soil Sample Source and Preparation
The current investigation involved sampling and analyzing three different sites of Red-yellow soil tomeasure parameters such as SOC and SRR. The sites were selected from Miyako Island, which islocated in Okinawa Prefecture, south of Japan. The soil sample was collected from a non-disturbed
forested area with four repetitions at each site (Carter and Gregorich, 2008). 1000g of soil was
sampled, after that, air-dried soil was sieved and weighed into a labeled tray followed by adding 5%(w/w) of biochar as a biochar treatment and 0% of biochar for control. Samples were kept at
approximate field capacity moisture conditions. Each treatment was divided into soil at ambientconditions (25ºC) and warm conditions (35ºC), and biochar rate (0% and 5%).
Soil Organic Carbon Determination
Each one of the treatments and repetitions was analyzed by the spectrophotometric procedure oforganic carbon contents of soil (Wallinga et al., 1992). 50 mg (±0.5 mg) of soil was weighed and it
was transferred carefully to a dry 100 mL volumetric flask. 10.0 mL of 0.333 M potassium
dichromate solution (K2Cr2O7) was added to each flask. 16.0 mL of concentrated sulfuric acid wasadded followed by putting the flasks in a boiling water bath for 45”. The samples were cooled in thesink and made up to the volume with distilled water. The samples were centrifuged for 10” at 1000
g force.
For the preparation of the standard series, 100 mL flasks containing 1000 mg sodium oxalate
with volumes of 0, 25.0, 50.0, 75.0 and 100.0 mL were used as standard into the volumetric flask.
These standard series worked as 0, 5, 10, 15, and 20 mmol Cr+3 per liter of solution of standard series.
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The absorbance of spectrophotometer Beam 4 nm was measured in a 1 cm cuvette at a wavelengthof 590 nm within 2 hours after oxidation. SOC percentages were calculated by multiplying the Cr +3
concentrations found by 0.2250/w, where “w” is the weight of the air-dry soil sampled.
Soil Respiration Rate Determination
10 g of air-dried soil was weighed from each treatment into a 450 mL glass bottle followed by adding
3 mL of distilled water. The soil and water were mixed in the bottles and then covered with perforated
films to reduce evaporation. The SRR was determined by using the infrared gas analyzer IR400 attime zero and measured again at the end of 1-h incubation (Sparda et al., 2016). The soil respiration
rate (SRR, μL CO2/h/g air-dried soil) was calculated using Eq. (1),𝑆𝑅𝑅 = (𝐶𝑂2𝑓 − 𝐶𝑂2𝑖 ) ∗ 𝑉 ∗

1000

(1)

𝑆

where CO2i and CO2f are the initial and final CO2 concentrations (ppm) of the 1-h incubation,
respectively, and V is the space volume of the bottle with the soil sample (450 mL). The number ofsoil (S) was 10.0 g. Four repetitions were measured for each one of the treatments.
Temperature Sensitivity (Q10)
The temperature response of SR was estimated through a Q10 function using Eq. (2),10

𝐶𝑖35º𝐶 −𝐶𝑓35º𝐶 𝑇𝑅−𝑇𝑊

𝑄10 = (𝐶𝑖25º𝐶 −𝐶𝑓25º𝐶)(2)

where Q10, the dependent variable, is the temperature sensitivity of SOC (carbon fluctuation
coefficient at one temperature over the flux of a temperature 10º higher), Ci and Cf are the initial andfinal carbon respectively (at 25ºC and 35ºC), and finally, TR is the temperature at the regularcondition and TW is the warmer temperature of soil (Meyer, et al., 2018).
Statistical Analysis
The comparison of the average of each one of the treatments was analyzed using the Shapiro-Wilk
Normality and Levene Homogeneity test. The one-way ANOVA tests were performed to determine
if there were differences through variance analysis. Then, the Tukey test was applied to determine
the differences between treatments. In addition, a Box-Cox transformation was performed to fit the
ANOVA test. All the tests were performed using RStudio (version 1.2.5042) for statistical analysesof the data. Analyses were performed at the significant level of p≤0.05.
RESULTS AND DISCUSSION
The fluctuation of SOC in a period of 150 days at different treatments of temperature and biochar isshown in Fig. 1. The SOC started at similar conditions, with a value of around 10 mg/g in alltreatments. However, values of SOC were decreasing gradually for different rates. Firstly, the resultof soil at 25ºC vs. 35ºC with no biochar (Fig. 1a) showed a significant effect of the temperature in
the loss of carbon. At day 150, the 35ºC was 3.65 mg/g, considerably lower than 25ºC soil with 6.02
mg/g (p<0.05). This difference was described by McTiernan et al. (2003), where the decomposition
rate of carbon components increased as temperature rose and was faster in tropical systems.
The addition of biochar kept the carbon content slightly constant. This is shown in Fig. 1b,
where the values of treatments started at just over 10 mg/g and decreased just above 7 mg/g. The
addition of biochar can increase the SOC (Singh et al., 2012) with the carbonized biomass having aslower decomposition process than fresh plant residues that are kept in the soil for longer periodsⒸ ISERD

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depending on the amendment type, type of soil, soil conditions and plants, values even in warm
conditions kept constant most of the experiment time. Figure. 1c compares treatments in ambientconditions (25ºC) for 150 days. As expected, the reduction of soil carbon was lower than treatment
at warmer conditions, moreover, the addition of biochar increased values of soil carbon by 1 mg/g.

Fig. 1 Soil organic carbon decomposition in 150 days in different conditionsa) no biochar addition at 25ºC vs 35ºC; b) biochar addition at 25ºC vs 35ºCc) 25ºC with biochar vs no biochar; and d) 35ºC with biochar vs no biochar.

The most remarkable outcome was the contrast of treatments at higher temperatures. Figure 1d
provides information about the effect of temperature in soil with biochar addition. As with theprevious experiment, values of SOC started above 10 mg/g, followed by a considerable reduction
after 150 days. The 0% biochar sample drastically reduces the SOC amount from 10.05 mg/g at day
0 to 3.65 mg/g at day 150. This reduction is explained clearly in different experiences regarding
carbon and organic matter degradation by the effect of temperature (Xu et al., 2019).
On the other hand, the addition of biochar showed a significant difference in the rate ofdegradation and soil organic carbon amount. This value started just below 11 mg/g (10.97 mg/g at
day 0) and decreased gradually to 7.39 mg/g at day 150. This value represents more than double the
0% biochar sample at day 150. The action of biochar seems to have several features that preserveand increase the organic carbon amount in the soil. According to Zimmerman et al. (2011), the highsurface area and porosity of biochar can increase the nutrient retention capacity of soil and improve
the stability of SOC, as well as increase little inputs with higher C: N that will favor the growth andprotection of SOC stocks. Nevertheless, Zimmerman reports the enhanced mineralization of existingsoil carbon in response to biochar addition as found in the soil respiration rate (Fig. 2).
The action of biochar protects the original soil's organic carbon by reducing carbon emissions.
This protection is mainly caused by the variety of aryl functional structures that are derived fromaromatic rings (Atkinson et al., 2010). These two main features make the biochar recalcitrant andstable. First, the structure and porosity that physically avoid leaching and enzymatic breakdown oforganic material and the chemical structure of biochar that relates to the type of biochar andtemperature of production (Kasozi et al., 2010). In this case, the O/C ratio is the essential feature of
the recalcitrance, which keeps the soil organic carbon at a higher level.
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The soil respiration showed different rates per month. It can be seen in Fig. 2a that the effect oftemperature was slightly higher at the beginning of the experiment, yet there were no significant
differences at day 150. Values started over 8 µL CO2/h/g and decreased just over 2 µL CO2/h/g. The
addition of biochar had a different effect on SRR, showing a higher release of CO 2 at 35ºC. In thelast three months of the analysis, there was a significant effect between the biochar application andno application (Fig. 2b).

Fig. 2 Soil respiration rate in 150 days in different conditionsa) no biochar addition at 25ºC vs 35ºC; b) biochar addition at 25ºC vs 35ºCc) 25ºC with biochar vs no biochar; and d) 35ºC with biochar vs no biochar

At ambient conditions (25ºC), the SRR did not show significant changes to the effect of biochar.
Values kept constant, starting just over 8 µL CO2/h/g and dropping just below 2 µL CO2/h/g as shownin Fig. 2c. On the other hand, Fig. 2d shows the increase of SRR with the addition of biochar in thelast period of analysis. By the addition of biochar, values started around 12 µL CO2/h/g and dropped
to 4 and 2 µL CO2/h/g at 35ºC and 25ºC respectively. The increase in temperature in soil reflects asignificant change in microbial activity in the short term. The addition of biochar in soil has affected
the SOC amount but the effect on SRR does not show a stabilization in the short-term, as this depends
on temperature and microbial activity (Xu et al., 2019). Additionally, Xu et al. (2019) describe theactivation and stabilization of carbonized material over a longer period (more than one year), which
increases the amount of soil carbon and reduction of CO2 emission.
Finally, the temperature sensitivity (Q10) described as a coefficient of the effect of temperature
in soil organic carbon showed a positive effect of the biochar action. As described in Eqs. (3) and(4), the values of initial SOC were 9.53 and 10.05 mg/g for treatment without biochar and withbiochar respectively at 25ºC and 10.97 and 10.27 mg/g for treatment without and with biochar
respectively at 35ºC. After 150 days, final values are 3.65 and 6.02 mg/g for treatment withoutbiochar, and 7.39 and 7.07 mg/g when biochar is applied.
10

𝐶𝑖35º𝐶 −𝐶𝑓35º𝐶 𝑇𝑅−𝑇𝑊

𝑄10 = (𝐶𝑖25º𝐶 −𝐶𝑓25º𝐶)

10

10.05−3.65 35−25= ( 9.53−6.02 )= 1.82Ⓒ ISERD

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10

𝐶𝑖35º𝐶 −𝐶𝑓35º𝐶 𝑇𝑅−𝑇𝑊

𝑄10 = (𝐶𝑖25º𝐶 −𝐶𝑓25º𝐶)

10

10.97−7.39 35−25= (10.27−7.07)= 1.12(4)

The outcome of Eq. (3) provides information on the coefficient value of Red-Yellow soil organiccarbon with no addition of biochar. This coefficient (1.82) represents a higher dependency of SOC
and microbial activity by the effect of temperature. In contrast, the Eq. (4), the addition of biochar
reduced this coefficient to 1.12, which represents a reduction of this dependency and an increase inresilient carbon amount. According to Yang Liu and Zhang (2017), the rate of Q10 reaction value
increases in a certain degree of temperature dependence, thus, the more temperature-dependent the
SOC, the higher the value will be Q10.
CONCLUSIONS
It is demonstrated that Red-Yellow soil is highly affected by the effect of temperature, and it can be
reduced significantly and so, degraded the soil. Although this type of soil has low organic carbon
content, this reduction can be covered by biochar. This black material fulfills a role as a carbon source
to maintain and increase SOC content. Connected to this, the addition of biochar not only affects the
carbon content but increases the amount of recalcitrant carbon in the soil over longer periods. Due tothe high content of Aryl Groups and higher O/C rate, the recalcitrant carbon reduces themineralization and the degradation of carbon, this allows a higher concentration of SOC even inwarm conditions of temperature. It seems to be that biochar works as an important conservation
strategy by reducing temperature sensitivity (Q10). Although studies over a longer period must be
considered, this outcome represents an alternative for Red-yellow soil in climate change impact andconservation of carbon in the soil.
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