Diurnal Soil Respiration Research Articles

Seasonal and diurnal soil respiration dynamics under different land management practices in the sub-tropical highland agroecology of Ethiopia.

The temporal dynamics of soil respiration change in response to different land management practices are not well documented. This study investigated the effects of soil bunds on the monthly and diurnal dynamics of soil respiration rates in the highlands of the Upper Blue Nile basin in Ethiopia. Six plots (with and without soil bunds, three replicates) were used for measurement of seasonal soil respiration, and 18 plots were used for measurement of diurnal soil respiration. We collected seasonal variation data on a monthly basis from September 2020 to August 2021. Diurnal soil respiration data were collected four times daily (5 a.m., 11 a.m., 5 p.m., and 11 p.m.) for 2weeks from 16 to 29 September 2021. A Wilcoxon signed-rank test showed that seasonal soil respiration rates differed significantly (p < 0.05) between soil bund and control plots in all seasons. In plots with soil bunds, seasonal soil respiration rates were lowest in February (1.89 ± 0.3µmol CO2 m-2s-1, mean ± SE) and highest in October (14.54 ± 0.5µmol CO2 m-2s-1). The diurnal soil respiration rate was significantly (p < 0.05) higher at 11 a.m. than at other times, and was lowest at 5 a.m. Seasonal variation in soil respiration was influenced by soil temperature negatively and moisture positively. Diurnal soil respiration was significantly affected by soil temperature but not by soil moisture. Further study is required to explore how differences in soil microorganisms between different land management practices affect soil respiration rates.

Dynamic characteristics of soil respiration in Yellow River Delta wetlands, China

The stable soil carbon (C) pool in coastal wetlands, referred to as “blue C”, which has been extensively damaged by climate change and soil degradation, is of importance to maintain global C cycle. Therefore, to investigate the dynamic characteristics of soil respiration rate and evaluate C budgets in coastal wetlands are urgently. In this study, the diurnal and seasonal variation of soil respiration rate in the reed wetland land (RL) and the bare wetland land (BL) was measured in situ with the dynamic gas-infrared CO2 method in four seasons, and the factors impacted on the dynamic characteristics of soil respiration were investigated. The results showed that the diurnal variation of soil respiration rate consistently presented a “U” curve pattern in April, July, and September, with the maximum values at 12:00 a.m. and the minimum values at 6:00 a.m. In the same season, the diurnal soil respiration rate in RL was significantly greater than those in BL (P < 0.05). In April, July, and September, the mean diurnal soil respiration rate was 0.14, 0.42, and 0.39 μmol m−2 s−1 in RL, 0.05, 0.22, 0.13, and 0.01 μmol m−2 s−1 in BL, respectively. Soil surface temperature was the primary factor that influenced soil respiration, which was confirmed by the exponential positive correlation between the soil respiration rate and soil surface temperature in BL and RL (P < 0.05). In addition, the high salinity of soils suppressed soil respiration, confirming by the significantly negative correlation between soil respiration rate and the content of soluble salt. These results will be useful for understanding the mechanisms underlying soil respiration and elevating C sequestration potential in the coastal wetlands.

Research of the diurnal soil respiration dynamic in two typical vegetation communities in Tianjin estuarine wetland

Understanding the differences and diurnal variations of soil respiration in different vegetation communities in coastal wetland is to provide basic reliable scientific evidence for the carbon "source" function of wetland ecosystems in Tianjin.Measured soil respiration rate which changed during a day between two typical vegetation communities (Phragmites australis, Suaeda salsa) in coastal wetland in October, 2015. Soil temperature and moisture were measured at the same time. Each of the diurnal curves of soil temperature in two communities had a single peak value, and the diurnal variations of soil moisture showed a "two peak-one valley" trend. The diurnal dynamic of soil respiration under the two communities had obvious volatility which showed a single peak form with its maximum between 12:00-14:00 and minimum during 18:00. The diurnal average of soil respiration rate in Phragmites australis communities was 3.37 times of that in Suaeda salsa communities. Significant relationships were found by regression analysis among soil temperature, soil moisture and soil respiration rate in Suaeda salsa communities. There could be well described by exponential models which was y = -0.245e0.105t between soil respiration rate and soil temperature, by quadratic models which was y = -0.276×2 + 15.277× - 209.566 between soil respiration rate and soil moisture. But the results of this study showed that there were no significant correlations between soil respiration and soil temperature and soil moisture in Phragmites australis communities (P > 0.05). Therefore, under the specific wetland environment conditions in Tianjin, soil temperature and moisture were not main factors influencing the diurnal variations of soil respiration rate in Phragmites australis communities.

施氮对湿地松（Pinus elliottii）林土壤呼吸和相关因子的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 施氮对湿地松(Pinus elliottii)林土壤呼吸和相关因子的影响 DOI: 10.5846/stxb201311192767 作者: 作者单位: 中南林业科技大学,国家林业局;中南林业科技大学,广西壮族自治区林业科学研究院,城市森林生态湖南省重点实验室;中南林业科技大学,城市森林生态湖南省重点实验室;中南林业科技大学,南方林业生态应用技术国家工程实验室;中南林业科技大学,城市森林生态湖南省重点实验室;中南林业科技大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家林业公益性行业科研专项(201404316);湖南省自然科学创新研究群体基金(湘基金委字[2013]7号);湖南省高校创新平台开放基金项目(12K070);国家林业局软科学研究项目(2013-R09);城市森林生态湖南省重点实验室资助 The effect of nitrogen addition on soil respiration and associated factors in Pinus elliottii forest Author: Affiliation: Central South University of Forestry and Technology,Central South University of Forestry and Technology,Central South University of Forestry and Technology,Key laboratory of Urban Forest Ecology of Hunan Province;Central South University of Forestry and Technology,Key laboratory of Urban Forest Ecology of Hunan Province;Central South University of Forestry and Technology,National Engineering Laboratory for Applied Technology of Forestry Ecology in South China,Changsha,;Central South University of Forestry and Technology,Key laboratory of Urban Forest Ecology of Hunan Province;Central South University of Forestry and Technology Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:人类活动引起陆地生态系统氮输入水平持续升高,对全球碳循环产生影响。为探究氮素对土壤呼吸的影响,2010年6月至2012年1月,采用氮添加试验对亚热带湿地松林的土壤呼吸进行了研究。试验共设置4种氮添加水平:对照CK,0 g m-2 a-1;低氮LN,5 g m-2 a-1;中氮MN,15 g m-2 a-1;高氮HN,30 g m-2 a-1;每月上、下旬采用Li-cor 8100测定土壤呼吸速率。结果表明:(1)氮添加对土壤呼吸有着显著的抑制作用,LN、MN和HN处理的土壤呼吸年累积量较CK处理分别降低了26.6%、23.7%和29.5%,而施氮处理间的土壤呼吸无显著差异;(2)林分生长期间(6-9月),施氮第1年的土壤呼吸所受抑制作用显著高于第2年同期的水平,显示施氮对土壤呼吸的影响随时间的推移而降低;(3)湿地松林土壤呼吸存在明显的季节动态,最大值出现在8月(356.32 mgCO2 m-2 h-1),最小值出现在1月(99.12 mg CO2 m-2 h-1),施氮处理并不改变土壤呼吸的季节性变化规律;(4)CK处理林分中,土壤呼吸与土壤温度间存在极显著的指数关系,而与土壤湿度无显著相关。施氮处理没有改变土壤呼吸与土壤温度之间的相互关系,但抑制了土壤呼吸的温度敏感性(Q10);(5)施氮处理显著减少了林分凋落物量、土壤微生物碳、氮量,并轻微抑制了细根生物量,这些改变导致了土壤呼吸的下降。上述结果表明施氮会显著抑制亚热带湿地松林的土壤呼吸速率,而这种抑制作用将随着时间的推移而降低。 Abstract:Human activities have raised nitrogen input to terrestrial ecosystems and influenced the global carbon cycle. To determine how soil respiration responds to nitrogen addition, a simulated nitrogen deposition experiment was conducted in Pinus elliottii forest in a subtropical zone in China from June 2010 to January 2012. Four-levels of N treatment-control check(CK,0 g m-2 a-1)、low nitrogen(LN, 5 g m-2 a-1)、medium nitrogen(MN, 15 g m-2 a-1) and high nitrogen(HN, 30 g m-2 a-1)-were applied and infrared gas analyzer techniques were used to quantify the soil respiration twice a month. The results showed that(1) soil respiration exhibited a clearly seasonal pattern, with the highest rates found in the August(356.32 mg CO2 m-2 h-1) and the lowest rates in January(99.12 mg CO2 m-2 h-1), and that nitrogen addition significantly depressed soil respiration. The soil annual accumulative soil respiration in the LN, MN, and HN treatments was 26.56%, 23.72%, and 29.54% lower, respectively, than CK treatment, but there is no significant difference between the nitrogen addition treatments. Furthermore, the inhibitory action weakened over time. Analysis of the soil respiration rate from June to September showed that(1) the inhibitory effect of nitrogen addition in the first year was weaker than that in the second year;(2) there was no strong diurnal soil respiration pattern; during daytime, nitrogen addition did not repress of soil respiration; and(3) soil respiration rates showed a significant positive exponential relationship with soil temperature at 5 cm depth. Soil temperature was the dominant driving factor and nitrogen addition reduced the Q10 values. Our results suggest that soil respiration declined in response to N addition in subtropical Pinus elliottii forest. 参考文献 相似文献 引证文献

Diurnal variation in soil respiration under different land uses on Taihang Mountain, North China

Abstract The aim of this paper is to evaluate the diurnal variation in soil respiration under different land use types on Taihang Mountain, North China, and to understand its response to environmental factors (e.g., soil temperature and moisture) and forest management. Diurnal variations in soil respiration from plantations (Robinia pseudoacacia, Punica granatum, and Ziziphus jujuba), naturally regenerated forests (Vitex negundo var. heterophylla), grasslands (Bothriochloa ischaemum), and farmlands (winter wheat/summer maize) were measured using an LI-8100 automated soil CO2 flux system from May 2012 to April 2013. The results indicated that land use type had a significant effect on the diurnal variation of soil respiration. The diurnal soil respiration from farmlands was highest, followed by Ziziphus jujube, R. pseudoacacia, P. granatum, the lower soil CO2 efflux was found from B. ischaemum and V. negundo var. heterophylla. The diurnal soil respiration across different land use types was significantly affected by soil temperature and moisture, and their interaction. Precipitation-stimulated soil respiration increased more in soil with low water content and less in soil with high water content. The lower diurnal soil respiration from naturally regenerated forests suggests that naturally regenerated vegetation is the optimal vegetation type for reducing global warming.

Field observation of diurnal dissolved oxygen fluctuations in shallow groundwater.

Dissolved oxygen (DO) concentrations influence many biogeochemical processes in groundwater systems but studies of temporal variability in DO are lacking. In this study, we used an optical DO probe to measure rapid changes in concentration due to plant-groundwater interaction at an alluvial aquifer field site in Iowa. Diurnal DO concentrations were observed during mid- to late-summer when soil conditions were dry, fluctuating approximately 0.2 to 0.3 mg/L on a daily basis. DO fluctuations in groundwater were out-of-phase with diurnal water table fluctuations, increasing during the day and decreasing at night. DO consumption at night is likely due to increased soil autotrophic and heterotrophic respiration linked with patterns of carbon supply derived from daytime photosynthetic activity, and consistent with available literature on diurnal soil respiration patterns. Although more work is needed to quantify specific processes, our results indicate the potential usefulness of the new optical DO technology to reveal insights regarding many ecohydrological processes.

浙江古田山亚热带常绿阔叶林不同干扰强度下土壤呼吸的日动态与季节变化

The aims of this study were to investigate the diurnal and seasonal variations in soil respiration in different broad-leaved forest types with different degrees of human disturbance, to identify the major abiotic and biotic factors affecting the daily and seasonal patterns of soil respiration, and to evaluate the effects of different forest management types and human disturbance on soil respiration in subtropical forests. We selected four different 1 hm2 forests with different degrees of human disturbance in Gutianshan, Zhejiang Province: An old-growth forest (OF, almost no human disturbance); two secondary forests (SF1, a secondary forest regrown after clear cutting about 50 years ago, and SF2, a secondary forest regrown after clear cutting about 50 years ago and selective cutting about 20 years ago); and a plantation forest (AF, planted about 20 years ago). We measured the diurnal and seasonal changes in soil respiration rates in each plot every month from May 2011 to July 2012. We also measured soil temperature and water content of the surface soil layer during sampling. The annual means of daily accumulated soil carbon release were 1.48, 1.48, 1.51, and 0.87 g C m-2 d-1 in OF, SF1, SF2, and AF plots, respectively. The soil respiration rate in AF was significantly lower than those in the other three forest types. On the diurnal scale, there were no significant variations in soil respiration rates among the four forest types. Our results indicated that the rate of soil respiration measured any time during the day can be used to predict daily accumulated soil carbon release. Significant positive relationships were found between soil respiration and surface soil temperature ( R 2=0.88-0.94) for all four forest types. There were no significant relationships between soil respiration and soil water content. The Q10 value of OF was significantly higher than those of the other three forest types. The results showed that the soil respiration rate and its sensitivity to temperature were significantly decreased in the plantation with the most intense human disturbance (AF). The soil respiration rates and Q10 values of both SF forests were similar to those of OF forest. Soil temperature was the most important driving factor for soil respiration. Together, our results implied that different degrees of human disturbance had different effects on soil respiration in these forests. This information is important to estimate the role of human interference in regional carbon cycles. Also, the finding that there was no significant variation in the diurnal soil respiration rates is very important for guiding further research on soil respiration in related regions.

Ecosystem photosynthesis regulates soil respiration on a diurnal scale with a short-term time lag in a coastal wetland

Although increasing evidence has provided that soil respiration is strongly related to recent canopy photosynthesis, doubts remain as to the extent to which primary productivity controls soil respiratory and the speed of the link between soil respiration and photosynthesis. Based on the automated measurements of soil respiration and eddy covariance measurements of ecosystem photosynthesis (i.e. gross primary production, GPP) in a coastal wetland, we assessed the speed of link between ecosystem photosynthesis and soil respiration on the diurnal scale, and quantified the control of the ecosystem primary production on diurnal soil respiration. On the diurnal scale, the time of daily peak soil respiration lagged GPP but preceded soil temperature on both sunny and cloudy days. Daytime soil respiration was significantly linearly correlated with GPP with a lag of 1.5 h on sunny days and 1 h on cloudy days, respectively. By taking advantage of the natural shift of sunny and cloudy days without disturbance to the plant-soil system, our results also indicated that the changes in soil temperature and GPP together explained 53% of the changes in daytime soil respiration rates between sunny days and adjacent cloudy days. Under the same soil temperature, changes in soil respiration rates were strongly correlated with changes in GPP between sunny days and adjacent cloudy days. We therefore conclude that recent canopy photosynthesis regulates soil respiration on a diurnal scale with a short-term time lag. Thus, it is necessary to take into account the influence of photosynthesis on soil respiration in order to accurately simulate the magnitude and variation of soil respiration, especially at short and medium temporal scales.

施氮对亚热带樟树林土壤呼吸的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 施氮对亚热带樟树林土壤呼吸的影响 DOI: 10.5846/stxb201203130334 作者: 作者单位: 中南林业科技大学,城市森林生态湖南省重点实验室;中南林业科技大学,中南林业科技大学,城市森林生态湖南省重点实验室;中南林业科技大学,城市森林生态湖南省重点实验室;中南林业科技大学,湖南会同杉木林生态系统国家野外科学观测研究站;中南林业科技大学 作者简介: 通讯作者: 中图分类号: 基金项目: "十二五"农村领域国家科技计划课题(2011BAD38B0204);教育部新世纪优秀人才支持计划(NCET-10-0151);湖南省科技厅项目(2010TP4011-3);湖南省教育厅项目(湘财教字[2010]70号);长沙市科技局项目(K1003009-61) Effect of nitrogen addition to soil respiration in Cinnamomum camphora forest in subtropical China Author: Affiliation: Central South University of Forestry and Technology,Key laboratory of Urban Forest Ecology of Hunan Province;Central South University of Forestry and Technology,Central South University of Forestry and Technology,Key laboratory of Urban Forest Ecology of Hunan Province;Central South University of Forestry and Technology,Key laboratory of Urban Forest Ecology of Hunan Province;Central South University of Forestry and Technology,Central South University of Forestry and Technology Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:人类活动引起全球范围内大气氮沉降量的升高,增加了陆地生态系统氮输入,从而影响土壤CO2排放。为揭示生态系统氮输入升高对土壤呼吸的影响,2010年6月至2012年1月,对亚热带樟树林(Cinnamomum camphora)进行模拟氮添加试验,每月上、下旬采用红外分析法测定4种氮输入水平(CK,0 g m-2a-1;低氮LN,5 g m-2 a-1;中氮MN,15 g m-2 a-1;高氮HN,30 g m-2 a-1)下的土壤呼吸速率。结果表明:(1)樟树林土壤呼吸存在明显的季节动态,最高值出现在6月,最小值出现在1月。氮添加处理显著抑制了樟树林的土壤呼吸,LN、MN、HN处理土壤呼吸年累积量分别较对照CK下降37.66%、30.62%、38.95%,各施氮处理间无显著差异,施氮对土壤呼吸的抑制作用随时间推移而减弱;(2)氮添加不影响土壤呼吸昼夜波动特征,但显著抑制土壤呼吸速率;(3)土壤呼吸与土壤温度间存在极显著的指数关系,与土壤湿度相关性不显著,CK、LN处理Q10相近,MN处理最小:(4)氮添加处理促进了土壤中氮的淋失,且随施氮水平的升高而增大。 Abstract:Increasing global atmospheric deposition of nitrogen caused by human activities has raised nitrogen input to terrestrial ecosystem, and thus influenced carbon dioxide emissions from soil. To explore how soil respiration response to increased nitrogen input, a simulated nitrogen deposition experiment has been conducted in Cinnamomum camphora forest in subtropical China between June 2010 and January 2012. Soil respiration rate was measured twice a month under four-levels of N treatments (CK, 0 g m-2a-1; LN, 5 g m-2a-1; MN, 15 g m-2a-1; HN, 30 g m-2a-1, experimental inputs)by infrared gas analyzer techniques, and the results showed that soil respiration exhibited a strong seasonal pattern, with the highest rates found in the June (819.31 mgCO2 m-2 h-1) and the lowest rates in January (169.70 mgCO2 m-2 h-1). Nitrogen addition inhibited soil respiration significantly. Soil respiration in CK group was higher than that in any other treatment group. Annual accumulative soil respiration in LN(2.55×104 kg/hm2), MN(2.84×104 kg/hm2) and HN(2.50×104 kg/hm2) was 37.66%、30.62%、38.95%, respectively, lower than in CK(4.09× 104 kg/hm2) group, however, there was no significant difference between nitrogen treatment groups. The inhibitory effect weakened over time. From June to September in year 2010, the mean soil respiration rate of LN, MN and HN were (386.31±44.81) mgCO2 m-2 h-1、(358.25±31.55) mgCO2 m-2 h-1and (367.35±41.72) mgCO2 m-2 h-1, respectively, which were 49.63%、53.28% and 52.10% lower than that in CK group(766.87±101.60 mgCO2 m-2 h-1). During same time in year 2011, the mean soil respiration of LN, MN and HN group increased to (512.7±73.12) mgCO2 m-2 h-1,(533.02±41.80) mgCO2 m-2 h-1,(486.20±50.12) mgCO2 m-2 h-1,respectively, which were19.70%、16.51%、23.85% lower than that in CK(638.45±74.91 mgCO2 m-2 h-1). Nitrogen addition couldn't change the diurnal soil respiration pattern, but depressed magnitude of soil respiration significantly. Soil respiration during daytime was lower than that in night, the minimums appeared in 10:00-14:00 and the maximums were in 22:00-2:00. The diurnal mean soil respiration rare in CK, LN, MN and HN treatment group was (805.86±74.95) mg CO2 m-2 h-1, (689.29±66.25) mg CO2 m-2 h-1, (778.85±73.73) mg CO2 m-2 h-1 and (609.85±65.33) mg CO2 m-2 h-1, respectively, and the mean soil respiration rate in CK group was significantly higher than that in LN and HN group(P<0.01). The differences between each nitrogen addition group were significantly. Soil respiration has the similar seasonal and diurnal pattern with soil temperature at 5cm depth. No matter in seasonal scale or diurnal scale, soil respiration rates showed a positive exponential relationship with soil temperature at 5cm depth, Exponential relationships between temperature and soil respiration were highly significant in all plots. However, almost in treatment, there was no obvious effect of soil moisture on soil respiration. LN group had the largest Q10 values (2.01), which similar to CK group (1.99) and higher than MN (1.79) and HN group (1.95). These results indicated that there is a significant decline of soil respiration to N addition in subtropical Cinnamomum camphora forest. 参考文献 相似文献 引证文献

A STELLA Model to Estimate Soil CO2 Emissions from a Short-Rotation Woody Crop

The potential for climatic factors as well as soil–plant–climate interactions to change as a result of rising levels of atmospheric CO2 concentration is an issue of increasing international environmental concern. Agricultural and forest practices and managements may be important contributors to mitigating elevated atmospheric CO2 concentrations. A computer model was developed using the Structural Thinking and Experiential Learning Laboratory with Animation (STELLA) software for soil CO2 emissions from a short-rotation woody crop as affected by soil water and temperature regimes, root and microbial respiration, and surficial processes such as rainfall, irrigation, and evapotranspiration. The resulting model was validated with good agreement between the model predictions and the experimental measurements prior to its applications. Two scenarios were then chosen to estimate both diurnal and annual soil CO2 emissions from a 1-ha mature cottonwood plantation as affected by soil temperature, soil (i.e., root and microbial) respiration, and irrigation. The simulation resulted in typical diurnal soil respiration and CO2 emission patterns, with increases from morning to early afternoon and decreases from early afternoon to midnight. This pattern was driven by diurnal soil temperature variations, indicating that soil temperature was the main influence on soil respiration and CO2 efflux into the atmosphere. Our simulations further revealed that the average seasonal soil respiration rate in summer was 1.6 times larger than in winter, whereas the average seasonal CO2 emission rate in summer was 1.77 times larger than in winter. Characteristic annual variation patterns for soil respiration and CO2 emission also were modeled, with both increasing from January 1 through June 30 followed by steady declines from September 1 through December 31. These results suggest that the STELLA model developed is a useful tool for estimating soil CO2 emission from a short-rotation woody crop plantation.

Integrated diurnal soil respiration model during growing season of a typical temperate steppe: Effects of temperature, soil water content and biomass production

Soil respiration was measured with the enclosed chamber method in an ungrazed Leymus chinensis steppe during the growing seasons of 2001 and 2002. Soil respiration rate ( R S) was significantly influenced by air temperature ( T) at the diurnal scale, and could be described by Van't Hoff's equation ( R S = R 10 exp( β( T − 10))). At the seasonal scale, the normalized soil respiration rate at 10 °C ( R 10) was mainly controlled by soil water content ( R 2 = 0.717, P < 0.001), while the sensitivity of soil respiration to temperature ( Q 10) was partially affected by absolute growth rate ( R 2 = 0.482, P = 0.004). Thus, soil respiration could be described as R S = (20.015 W − 84.085) (0.103AGR + 1.786) ( T−10)/10 during the growing seasons, integrating soil water content ( W) and absolute growth rate (AGR) into the temperature-dependent soil respiration equation. It was validated by the observed soil respiration rates in this study ( R 2 = 0.890, P < 0.001) and observations from near-field experiment ( R 2 = 0.687, P = 0.011). It implied that accurately evaluating annual soil respiration should include the effects of plant biomass production and other abiotic factors besides air temperature.

Soil respiration in a chihuahuan desert rangeland

Soil respiration of a desert soil was measured at the New Mexico State University Ranch in Southern New Mexico. Respiration rates were highest during late July and August after summer rains. Soil respiration data were used to estimate soil organic matter turnover which was 54 yr using summer data and 20 yr using both summer and winter data. The long turnover estimate for summer measurements resulted from temperatures above optimum in June and July. Diurnal soil respiration was also measured after a simulated 2.54 cm rain event. For both wetted and dry soils, temperature controlled the patterns of soil respiration with an optimum of near 41°C. Activation energy values decreased from 84.91 to 39.5 kJ mol −1 when the soil was wetted. A light-dark container method was tested as a possible means of estimating algal uptake of CO 2, however, the method was not feasible for desert soils.