Introduction
This report is based on a study of the relationship between global warming in terms of rising temperatures and the quality of microbial respiration. The report is based on a primary study by Soong et al., who published a scientific paper in 2021 on the carbon outflow from soils due to their local warming. This paper proposes to expand the scope of the authors’ findings and determine the effect of warming on microbial respiration, that is, the process of carbon outflow from soil to the atmosphere in the form of carbon dioxide. Thus, the research question can be formulated as follows: “To what extent does increasing temperatures in the Sierra Nevada region contribute to increased rates of microbial respiration?”
Background
Microbial respiration refers to the basic process of energy generation for microorganisms, including bacteria, some fungi, and archaea. During microbial respiration, organisms consume soil macronutrients, including organic carbon, release energy, and produce metabolic byproducts, including carbon dioxide (Dacal et al. 233). In other words, microbial respiration converts soil carbon into atmospheric carbon, and the higher the intensity of microbial respiration, the more carbon dioxide accumulates in the atmosphere.
At the same time, carbon dioxide has a greenhouse effect. Its accumulation in atmospheric layers can lead to the retention of radiation reflected from the surface of the Earth, which locally and globally increases the planet’s temperature. From this, it seems that increased microbial respiration activity may be a predictor of global warming, as evidenced by the results of Soong et al.
However, the present study is interested in assessing the feedback loop, that is, to identify whether increased temperatures caused by, among other things, intense microbial respiration can lead to increased activity of this process, that is, to create cyclic relationships. The theoretical background to this question includes the documented Q10 effect, which shows that the rate of biochemical reactions, including oxygen consumption by respiration, increases about 2-3 times for every 10-degree increase in temperature (LKI). Suppose the answer to the research question turns out to be positive for the Sierra Nevada as well. In that case, it will follow that the links between warming and microbial respiration are noticeably more convoluted than might at first appear.
Environmental Issue
The choice of the region in both the source and the current report is no accident. The Sierra Nevada is a mountainous region in California, USA, which has a rather dry and warm climate and is thus vulnerable to rising temperatures (FCCA 5). Global warming can cause fires and arid conditions, lead to the extinction of local species, and disrupt ecosystem resilience. The negative effects of global warming caused by intensive microbial respiration and, in turn, potentially increasing the activity of this process, can also be characteristic of the agricultural and industrial activities of local communities. Thus, the primary concern of this study is built around the ecological phenomenon of global warming and the consequences that it may lead to.
Local and Global Connections
The problem of rising temperatures and the potentially resulting increase in microbial respiration activity has connections to environmental issues both locally and globally. From a local connection perspective, more microbial respiration due to elevated temperatures can significantly reduce the amount of carbon available in the soil. In turn, this will negatively affect soil health and affect the biodiversity and agricultural potential of local communities (Wenzel et al. 8).
At the same time, increased levels of carbon dioxide in local air can lead to pollution and negatively affect residents’ health. In terms of global linkage, this problem can lead to an intensification of the greenhouse effect, which causes global warming. It is unlikely that the potentially detectable pattern in the Sierra Nevada will cause an increase in temperatures across the planet. However, empirical data from this region could be extrapolated to other biomes, which would allow a deeper study of the effects of global warming.
Design
Variables
As the research question suggests, this report was built on two quantitative variables. Soil temperature on the Celsius scale, measured on an interval-ratio scale, was used as the independent variable. The temperature was measured with probes dipped 5, 15, 20, 30, 50, 70, 75, and 100 cm into the soil and measured every five seconds with an Omega 44005 probe, as reported by Soong et al.
Carbon dioxide production, a measure of microbial respiration of native microorganisms, was used as the dependent variable—this metric was also measured on an interval-ratio scale. To measure carbon dioxide production, 1⁄4-inch diameter tubes were used to collect samples from depths of 15, 30, 50, 70, and 90 cm (Soong et al. 5). Microbial respiration was measured in units of gC.m3.hr, which corresponded to the amount of gas produced (in grams of carbon) per unit volume (m3) per hour (hr). The experiment’s control variables were the location of the data collection, the depths to which the sensors were immersed, and the type of soil investigated.
Hypothesis
The study was built on the hypothesis that an increase in soil temperature was positively related to an increase in carbon dioxide output as a byproduct of microbial respiration. In other words, it met the condition that increased temperatures increased the intensity of microbial respiration processes. The prerequisites for this hypothesis are the existence of the Q10 effect as well as the documented results of the original study (LKI; Soong et al. 3)
Materials
- Primary data was collected by Soong et al. (DataOne).
- IBM SPSS.
Ethical Issues
Soong et al.’s primary data were published on DataOne and signed with a CC BY 4.0 license, which allows for the use of their data even for commercial purposes with attribution. In other words, the ethical norms of the academic field were not violated, and the purpose of the report is to extend the conclusions that were derived from the primary source.
Justification of Method
Spearman’s correlation coefficient and regression analysis methods were used to conduct a statistical analysis to determine the relationship and type of influence between two continuous variables. The choice of these tests was motivated by the desire to obtain a comprehensive answer to the research question and to determine. The nature of their use supports the relevance and reliability of the data, as they are primary data from other authors analyzed in this report.
Procedure
- Download freely available data from the DataOne portal.
- Primary process the .csv file, removing unused variables and leaving only relevant columns. This includes deleting all rows in the examined data that are missing information.
- Import the data into IBM SPSS and verify that it is loaded correctly.
- Run statistical tests using the Correlate and Regression functions.
- Save the results and interpret them in a report.
Data Processing
Raw Data
The raw data contains 1,260 rows for measurements of temperature and carbon dioxide produced. The initial processing removed 90 rows because they did not contain data on the measured amount of emitted gas at these temperatures; thus, the total number of records in the sample was 1169.
Data Processing
The descriptive analysis results are reflected in Table 1. The statistics contain measures of central tendency and measures of variability for each of the two distributions of continuous variables. All values of the descriptive metrics were computed using IBM SPSS and are based on the formulas shown in [1]-[4].
Table 1: Descriptive statistics results for soil temperature (°C) and amount of carbon dioxide produced by microorganisms (gC.m3.hr)
Based on the results, it is clear that the mean soil-specific temperature in the Sierra Nevada during the measurement period was 13.41°C (SD = 5.10), while the mean amount of carbon dioxide produced was 0.062 gC.m3.hr (SD = 0.122). Since the standard deviation of the dependent variable is about twice the mean, it can be inferred from this that there is a very high variance in the distribution of the data. Moreover, combined with the results of the Kolmogorov-Smirnov test, which rejected the normality of the distribution of the amount of carbon dioxide produced [D =.306, p <.001, N = 1169], this indicates that parametric tests cannot be used for analysis.
Statistical Analysis
Spearman’s correlation was performed to assess the relationship between the two variables because the condition of normality of the distribution was violated. The analysis demonstrated a statistically significant moderate positive relationship between the two variables [rs(1169) =.245, p <.001]. In other words, the result showed that when soil temperature increased, there was a significant effect on increasing the intensity of carbon dioxide excretion, which corresponds to a more intense process of microbial respiration.
Regression analysis was used to evaluate the effect that increasing temperature could have on the intensity of microbial respiration. The results showed that the regression model was significant, [F(1, 1167) = 77.850, p <.001], with each one degree Celsius increase in temperature resulting in a 0.006 gC.m3.hr increase in carbon dioxide production.
The general linear regression equation is shown in [5]. However, the results must be interpreted with caution. As shown in Fig. 1, the coefficient of determination for the model is extremely low, which corresponds to the small amount of covered variance.
- ProdCO2 = -0.019 + 0.006 * T [5]
Conclusion and Evaluation
Conclusion
The study aimed to determine the effect of increasing temperature on the intensity of microbial respiration, estimated through the production of carbon dioxide as a byproduct. Statistical tests, such as Spearman’s correlation and regression, demonstrated significant effects of temperature increase on the increase of carbon dioxide production.
The relationship between the two variables is not linear, as evidenced by the critically low value of the coefficient of determination. However, an increase in one parameter was still associated with an increase in the other. This supports the research hypothesis and shows that an increase in temperature may not only be a consequence of increased microbial activity, as pointed out by Soong et al., but also why microbes produce more gas. In other words, this study’s results confirmed that global warming, expressed through local and global temperature increases, can lead to increased microbial respiration rates in the Sierra Nevada. The results are expected to be confirmed for other regions with similar climatic conditions.
Limitations
The study has several limitations, work on which may become part of future projects. First, the high variance of the data and the lack of normality in the distribution of the dependent variable can distort the results and lead to biases. Correction is possible by increasing the sample size or using procedures to normalize the distribution (Eric).
Second, about 11% of the data in the distribution of the dependent variable are classified as outliers, which can also negatively affect the accuracy of the conclusions because they represent extreme values, affecting the trend line in the regression, the coefficient of determination, and, therefore, the correlation coefficient. Increasing the sample size can also help deal with the problem of outliers (Eric).
Third, the reliability of the constructed regression model could be better because although it is statistically significant, it only covers about 6% of the data’s variance. Adding mediating variables to the model may increase the variance coverage and reveal previously hidden causal relationships.
Further Inquiry
Future research, in addition to working on constraint corrections, suggests testing the pattern found for other regions, both with similar and dissimilar climatic conditions. One way to extend the findings could be to add moderating variables to look for mediating influences between the indicators under study. Laboratory tests to determine the effect of temperature increases on the respiratory activity of individual bacterial or fungal species may also be useful practices.
Justification of Application
The results of the secondary study confirmed the relationship between temperature growth and increases in microbial respiration. In the context of global warming, gradually increasing global temperature without proper attention will lead to an accumulation of carbon dioxide in the atmosphere, intensifying the greenhouse effect and affecting air quality and the well-being of communities and ecosystems.
It follows that preventive policy measures are needed not only to reduce the rate of temperature increase but also to contain microbial respiration processes without harming soil and microorganisms. The development of such measures, taken at local and global levels, is expected to level out the detected correlation and have a positive effect on the environment. However, the weakness of such a solution is the need for strict control over the implementation of preventive measures and the complexity of the preliminary analysis in order to avoid undesirable soil reactions. Therefore, such decisions must be made responsibly and with great care, taking into account the interests of stakeholders and professional expertise.
Works Cited
Dacal, Marina, et al. “Soil Microbial Respiration Adapts to Ambient Temperature in Global Drylands.” Nature Ecology & Evolution, vol. 3, no. 2, 2019, pp. 232-238. DataOne.
“Soil C Stock and CO2 Production Data for Soong et al. 2021: Effects of Five Years of Soil Warming at Blodgett Forest, CA.” DataOne, 2022, Web.
Eric. “Transforming Non-Normal Distribution to Normal Distribution.” Github, 2019, Web.
FCCA. “Sierra Nevada Region Report.” Energy CA, 2019, Web.
LKI. “Larvae Knowledge Incubator.” Larvae Knowledge Incubator, Web.
Soong, Jennifer L., et al. “Five Years of Whole-Soil Warming Led to Loss of Subsoil Carbon Stocks and Increased CO2 Efflux.” Science Advances, vol. 7, no. 21, 2021, pp. 1-8.
Wenzel, Walter W., et al. “Soil and Land Use Factors Control Organic Carbon Status and Accumulation in Agricultural Soils of Lower Austria.” Geoderma, vol. 409, 2022, pp. 1-12.