Characteristics Of Soil Respiration Research Articles

Dynamic Characteristics of Soil Respiration in Park Green Spaces in Qingdao City

Urban green spaces play an essential role in maintaining the carbon cycle and mitigating climate change in urban ecosystems. In order to gain more carbon sinks from urban green ecosystems, it is essential to determine the carbon sequestration statuses and soil respiration rates of dominant green spaces, especially park green spaces. However, in comparison to natural ecosystems, the dynamic characteristics of soil respiration in artificial park green spaces remain unclear. This study investigated the soil respiration rates for three forest communities (dominated by Prunus serrulata var. lannesiana, Cedrus deodara, Ginkgo biloba, respectively), a shrub community (dominated by Aucuba japonica var. variegata) and a lawn community (dominated by Poa pratensis) in the Qingdao Olympic Sculpture and Culture Park. We used the CRIAS-3 portable photosynthesis system in combination with the SRC-1 soil respiration chamber to measure the soil respiration rate from July 2022 to June 2023 and analyzed the dynamic variations in the soil respiration rate for these specific plant communities. Our results showed that the diurnal variation in soil respiration presented a unimodal curve for the five plant communities, and it peaked at midday or in the early afternoon. They also exhibited a significant seasonal difference in the soil respiration rate, which was characterized by higher rates in summer and lower rates in winter. The lawn community exhibited significantly higher soil respiration rates compared to the woody plant community. The mean annual soil respiration rate (RS) was, respectively, 2.88 ± 0.49 µmol·m−2·s−1, 1.94 ± 0.31 µmol·m−2·s−1, 1.43 ± 0.21 µmol·m−2·s−1, 1.24 ± 0.14 µmol·m−2·s−1 and 1.05 ± 0.11 µmol·m−2·s−1 for the lawn community, Ginkgo biloba community, Prunus serrulata var. lannesiana community, shrub community and Cedrus deodara community. The soil temperature at a 10 cm depth (T10) accounted for 67.39–86.76% of the variation in the soil respiration rate, while the soil volumetric water content at a 5 cm depth (W5) accounted for 9.29–44.01% of the variation for the five plant communities. The explained variance for both T10 and W5 ranged from 67.8% to 87.6% for the five plant communities. The Q10 values for the five different communities ranged from 1.97 to 2.75. Based on these findings, this paper concludes that the factors influencing the soil respiration process in urban green spaces are more complicated in comparison to natural ecosystems, and it is essential to comprehensively analyze these driving factors and key controlling factors of soil respiration across urban green spaces in future studies.

Characteristics of Soil Respiration and Organic Carbon Mineralization in Dryland Potato Fields Under Different Ridge-furrow Mulching Patterns

Exploring the response mechanism of soil respiration rate to hydrothermal factors and organic carbon mineralization under different ridge-furrow mulching modes is of high importance for the development of the regional carbon cycle and assessment of its ecological benefits. An experimental study was carried out in 2020 in a dry-crop potato field in the mountainous area of southern Ningxia by setting three furrow-ridge ratios [60 cm∶30 cm （R1）, 60 cm∶45 cm （R2）, and 60 cm∶60 cm （R3）] combined with three mulching modes [ridge covered with ordinary plastic film, furrow covered with straw （DJ）, degradable water-permeable plastic film （DS）, and no mulching （DB） in furrows, respectively]. The soil hydrothermal factors, respiration rate, organic carbon content, and mineralization characteristics of potatoes during the reproductive period under different mulching modes were investigated with plain mulching without mulching （CK） as the control. The results showed that different furrow-ridge ratios combined with the mulching mode could significantly increase the soil water storage capacity in the 0-60 cm layer, and the R3DJ treatment had a better effect, with a significant increase of 24.99% compared with that in CK. The R2 treatment had the best effect of increasing temperature during the whole life cycle of the potato. The DS treatment had the effect of increasing temperature, and the DJ treatment had the effect of decreasing temperature under different mulching materials. Different furrow and ridge cover patterns could significantly increase the average soil respiration rate during the reproductive period, and the R3DS treatment was the most significant among the different furrow and ridge cover patterns, with a significant increase of 24.71% compared with that in the CK treatment. The soil organic carbon content in the 0-20 cm and 20-40 cm layers at harvest time was higher in the R2 and R1 ridges, respectively, and higher in the DB and DS treatments for different mulching materials. The soil organic carbon mineralization rate declined rapidly in the early stage of cultivation and then slowly declined and leveled off in the middle and late stages, which was highest in the R3 treatment for the three types of ridge ratios and highest in the DS treatment for different mulching materials. The fitting equations of soil respiration rate with soil hydrothermal factors during the reproductive period revealed that the synergistic effect of soil hydrothermal dual factors on soil respiration was higher than that of a soil hydrothermal single factor and that the quadratic hydrothermal dual factors could well explain 86.4% to 99.9% of the soil respiration. Correlation analysis showed that the average soil respiration rate during the whole life span of the potato was highly significantly and positively correlated with the average soil temperature in the 0-25 cm layer and the average soil organic carbon mineralization rate in the 0-40 cm layer, and the soil temperature was highly significantly and positively correlated with the organic carbon mineralization rate. The furrow-ridge ratio combined with the mulching mode was shown to improve the soil hydrothermal environment and increase the rate of organic carbon mineralization, thus affecting the soil respiration rate, with a furrow-ridge ratio of 60 cm∶45 cm or 60 cm∶60 cm under the ridge mulching mulch ditch covering biodegradable seepage mulch mode being more effective.

Soil macroporosity modulates the extent of negative microbial associations during organic substance decomposition

Microbial species interactions are expected to influence the community-level properties, such as the production of extracellular enzymes and the degradation of organic substances. This work examined how microbial diversity, composition and the overall sign of microbial associations were altered with soil texture and structure following the amendment of organic substances. Two sets of microcosms (1:100 and 1:1) of a 4 × 3 factorial design were constructed, with four artificial textural classes (a sandy loam, two loams, and a (silty) clay loam) and three organics (TSB, tryptic soy broth; CA, a mixture of cellulose and humic/fulvic acids; BS, barley straw). As the ‘microbial inoculant’, an agricultural soil was added to the 1:100 and 1:1 microcosms at 1% and 50%, respectively. A few of microbial taxa were specifically enriched after soil addition of TSB, CA, or BS, but distributions across textural classes were inconsistent between microcosms or between organic amendments. Regardless, top abundant bacterial and fungal OTUs were overall negatively associated, suggesting that microbial competition for the shared resource dominated the decomposition of both simple and complex organics. Microbial associations were also modified by soil pore size distribution (PSD), being fewer negative (or more positive) in soils of greater macroporosity than in soils of lower macroporosity. The PSD-based differences in microbial associations were coordinated with PSD-based differences in the activities of exoglucanase and β-glucosidase in TSB-amended soils or soil respiration characteristics in CA-amended soils. Our results provide new insight into how soil structure regulates microbial interactions and, accordingly, the degradation of organic matter.

Laboratory simulation of soil respiration response to environmental conditions in intertidal zones of Jiangsu Province, China

As major contributor to the blue carbon sink, intertidal zones play a crucial role in the global carbon cycle. In recent years, more attention has been given to the carbon cycle in intertidal wetlands. However, due to highly variable and uncertain environmental conditions, it is difficult to clarify the quantitative relationship between soil respiration and environmental factors through in-situ experiments. In this study, the response of soil respiration characteristics to variations in the temperature and water table was investigated using a monitoring apparatus of CO2 flux at the soil–air interface in the intertidal zone. The results showed that soil respiration flux was significantly correlated with temperature, and the correlation best fitted the DoseResp function. Meanwhile, the respiration flux was enhanced with the descent of water table, a relationship could be described by a quadratic function. The effect of the water table on soil respiration became more pronounced with the rise of temperature. These results provide significant clarification of the impact of human activities on the carbon cycle in bare intertidal zones and as well as support for numerical simulations of the carbon cycle in bare intertidal zones.

Characteristics of Soil Respiration and Its Components of a Mixed Dipterocarp Forest in China

Background: Although numerous studies have been carried out in recent decades, soil respiration remains one of the less understood elements in global carbon budget research. Tropical forests store a considerable amount of carbon, and a well-established knowledge of the patterns, components, and controls of soil respiration in these forests will be crucial in global change research. Methods: Soil respiration was separated into two components using the trenching method. Each component was measured at multiple temporal scales and in different microhabitats. A commercial soil efflux system (Li8100/8150) was used to accomplish soil respiration monitoring. Four commonly used models were compared that described the temperature dependence of soil heterotrophic respiration using nonlinear statistics. Results and Conclusions: Trenching has a limited effect on soil temperature but considerably affects soil water content due to the exclusion of water loss via tree transpiration. Soil respiration decreased gradually from 8 to 4 μmol·m−2·s−1 6 days after trenching. Soil autotrophic (Ra) and heterotrophic respiration (Rh) have contrasting diel patterns and different responses to temperature. Rh was negatively correlated with temperature but positively correlated with relative humidity. Both Ra and Rh varied dramatically among microhabitats. The Q10 value of Rh derived using the Q10 model was 2.54. The Kirschbaum–O’Connell model, which implied a strong decrease of Q10 with temperature, worked best in describing temperature dependence of Rh. Heterotrophic respiration accounted for nearly half of the total soil efflux. We found an unexpected diurnal pattern in soil heterotrophic respiration which might be related to diurnal moisture dynamics. Temperature, but not soil moisture, was the major controller of seasonal variation of soil respiration in both autotrophic and heterotrophic components. From a statistical perspective, the best model to describe the temperature sensitivity of soil respiration was the Kirschbaum–O’Connell model. Soil respiration varied strongly among the microhabitats and played a crucial role in stand-level ecosystem carbon balance assessment.

Research Progress on Spatial and Temporal Variation Characteristics of Soil Respiration

The research on soil respiration has already started as early as the 20th century, and the research in foreign countries started earlier than that in China. At present, many studies have found that soil respiration has great temporal and spatial changes. In order to understand and explore the temporal and spatial changes of soil respiration more accurately, the related articles at home and abroad were reviewed, sorted out, summed up and summarized. Temporal changes mainly included diurnal changes, seasonal changes and inter-annual changes. Spatial variability mainly included four aspects: community level, landscape level, regional scale and biotic scale. Altitude gradient also affected soil respiration.

Analysis of soil respiration and influencing factors in a semiarid dune–meadow cascade ecosystem

The characteristics of soil respiration (Rs) in semiarid regions are important with regard to the carbon cycle of complex underlying surfaces and estimation of carbon emissions from regional ecosystems. During the growing season (May–September 2016), in situ observations of Rs were obtained concurrently with measurements of soil bacteria (Bs), soil moisture (Ms), and soil temperature (Ts) at depths of 0–10 cm, in a dune–meadow cascade ecosystem. Results showed that Rs differences among the various ecosystems were significant (P < 0.01), the intensity of Rs in meadows was twice stronger than that in dunes. The average values of Rs presenting a declined trend follows MPA (11.19 μmol m−2 s−1) > MAF (7.75) > SSG (6.78) > SMAH (5.02) > SFAH (4.8) > FLC (4.28) > SBG (3.09). An extremely significant (p < 0.01) positive correlated power relationship can be found between Rs and Bs, which could explain 62.41%–86.56% of the variation in Rs in the various ecosystems. Field capacity and the saturated water content were the key demarcation points for the interactive relationship between Rs and Ms, which showing a significant (P < 0.05) positive correlated power relationship in dunes, in contrast, it presenting a significant (P < 0.05) negative correlated exponential relationship in meadows. Rs was positively exponentially correlated with Ts, significant (P < 0.05) in meadows and nonsignificant (P > 0.05) in dunes. Future research should be strengthened to consider multiple growing seasons experiencing various climatic conditions for accurate estimation of terrestrial carbon emissions in arid and semiarid ecosystems.

Soil Respiration Characteristics and Influencing Factors for Apple Orchards in Different Regions on the Loess Plateau of Shaanxi Province

To explore the characteristics of the spatial and temporal variation in soil respiration (SR) in orchard ecosystems in different regions of the Loess Plateau of Shaanxi Province and to distinguish the controlling factors, representative orchards were studied from April to October 2019. We conducted SR measurements in five locations, including Mizhi dangta (MZ), Ansai Liuzhuang (AS), Luochuan houzitou (LC), Fuping meijiaping (FP), and Yangling Wuquan (YL). The results indicated that the SR of each orchard showed clear seasonal variation. The SR increased with the distance from the trunk at the tree scale, while gradually increasing from north to south on the regional scale (p &lt; 0.05). The soil temperature and soil moisture were the main factors controlling the seasonal changes in SR in the orchards. On the tree scale, the fine root biomass was the main factor causing the tree-scale spatial variability. At the regional scale, SR was mainly influenced by the differences in the soil temperature, soil moisture, soil organic carbon, soil bulk density and pH. In agricultural management practices, the cumulative soil respiration was higher with irrigated treatment than with non-irrigated (NI) treatment (p &lt; 0.05). In addition, traditional surface drip irrigation (SDI) and root injection irrigation (RII) showed great differences in soil respiration in the early and late stages of irrigation (p &lt; 0.05), and the soil moisture was the main controlling factor. Compared with no tillage (NI), green cover (GC), deep tillage (DT), and shallow tillage (ST) increased the SR by 57%, 36% and 14%, respectively (p &lt; 0.05). Due to the great temporal and spatial variation in the SR in our study area, we determined that the soil respiration in the orchards was affected not only by environmental factors but also by agricultural measures. Therefore, greater attention should be paid to human factors when exploring SR to ensure that orchard management can promote the economic benefits of the orchards without greatly impacting the environment.

Response of Soil Respiration and Its Components to Nitrogen and Phosphorus Addition in Farming-Withdrawn Grassland in the Semiarid Loess Hilly-Gully Region

Understanding the soil respiration characteristics in response to nitrogen and phosphorus addition in farming-withdrawn grasslands within semi-arid loess hilly-gully regions is of great importance for providing a theoretical basis for evaluating the effects of artificial regulation approaches on carbon cycling. We report on a field experiment that was undertaken from May to September 2018 in a farming-withdrawn grassland ecosystem in China, which is dominated by Stipa bungeana and Lespedeza davurica. Three different levels of nitrogen and phosphorus additions were used, including three main plots of N[0, 50, and 100 kg·(hm2·a)-1] and three subplots of P (P2O5)[0,40, and 80 kg·(hm2·a)-1]. The soil respiration rate, heterotrophic respiration rate, soil temperature, and soil moisture were measured monthly in each treatment. Results showed that N and P addition had no effect on soil temperature or moisture content (P>0.05). The soil respiration rate showed an obvious monthly variation and peaked in July. In the treatment without fertilizer addition, the monthly mean soil respiration rate, heterotrophic respiration rate, and autotrophic respiration rate were 0.69, 0.39, and 0.29 g·(m2·h)-1, respectively. P addition had no significant effect on the soil respiration rate and its components without N addition (P>0.05). Under conditions of N addition, P addition significantly increased the soil respiration rate and its component (P<0.05). The monthly mean soil respiration rate, heterotrophic respiration rate, and autotrophic respiration rate were 0.93, 0.50, and 0.47 g·(m2·h)-1, respectively. The Q10 (i.e., temperature sensitivity) values for soil respiration, heterotrophic respiration, and autotrophic respiration in unfertilized soil were 1.86, 2.36, and 2.24, respectively. The addition of N and P reduced the Q10 value of soil respiration and its components. Our findings suggest that the response of soil respiration and its two components to N and P addition in studied farming-withdrawn grassland in the semiarid loess hilly-gully region were closely related to their addition amounts.

Effect of Fertilization on Soil Respiration and Its Temperature Sensitivity in a Sorghum Field

The characteristics of soil respiration under the condition of fertilization have not been fully understood,especially for a long-term fertilization condition. In this study we measured both soil respiration using an LI-COR-6400-09 soil chamber attached to LI-COR-6400 portable photosynthesis system, and the vegetation spectrum using an ASD FieldSpec HandHeld2, in five different fertilization treatment fields. The soil respiration (Rs) and vegetation spectrum were simultaneously measured with two samples per month in the growing season in 2016 and 2017. The soil temperature at 10 cm depth (T10) and moisture (Ws) for the surface of 10 cm were also measured simultaneously. The five different fertilization treatments included no fertilization (CK), inorganic fertilizer (INF), inorganic fertilizer+organic fertilizer (INF+M), inorganic fertilizer+organic fertilizer+straw turnover (INF+M+S) and organic fertilizer+straw turnover (M+S), and all treatments had been conducted since 2011. Based on those observation data, we made an analysis of Rs and its temperature sensitivity (Q10) in the five different fertilization treatments. The results showed that no significant temporal change in Rs among the five treatments was found. No significant difference was found in Rs between the CK and INF treatments. Compared with the values of Rs in CK and INF, the Rs values in INF+M, M+S, and INF+M+S treatments increased by 28.2%-39.1%, 47.9%-76.0%, and 46.2%-50.8%, respectively. This indicated that use of organic fertilization and straw application increased Rs. Both the Ts and Ws showed 14%-96% and 6%-37% in Rs seasonal variations, respectively. Among the treatments, the correlation coefficient of the fitted equations between Rsand Ts was higher in the INF+M, INF+M+S and M+S treatment than in CK and INF, but was not between Rsand Ws. For the relationship between Rs and vegetation indexes we found that the correlation coefficients between Rs and the difference vegetation index (DVI), ratio vegetation index (RVI), and enhanced vegetation index (EVI), respectively, were higher than that of Rs and the normalized differential vegetation index (NDVI); and that the correlation coefficients between Rsand the red edge slope (Dred) and red edge area (Sred) were higher than between Rs and the red edge position (λred). This indicated that the treatments in INF+M+S increased the correlation coefficient between Rs and the spectrum characteristics index. The determination coefficient of the fitted equations including the feature spectral parameters, T10, and Wsvariables was higher than that of the equations only including both T10 and Ws variables, or a single variable of T10 or Ws. Compared with CK, the Q10 value increased by 26%, 39%, 21%, and 37% for the INF, INF+M, INF+M+S, and M+S treatments, respectively. This indicated that temperature sensitivity Q10 increased under the condition of fertilization treatments. The Shannon diversity index, bulk density, and soil organic matter were the main factors causing the difference in Rs, Q10, and R10, i.e., Rs at a temperature of 10℃, in the different treatments, which could explain the 97.6%, 78.2%, and 92.8% variations in Rs, Q10, and R10, respectively.

Interactions between biochar and nitrogen impact soil carbon mineralization and the microbial community

Adding biochar (BC) to soils is proposed to enhance carbon sequestration in agricultural soils. However, there is limited knowledge regarding the effects of the interactions between BC and nitrogen (N) on soil organic carbon (SOC) mineralization at an interannual scale. We conducted a three-year field experiment to systematically reveal the impacts of BC combined with N fertilizer on a silty clay soil, including its physicochemical properties, soil respiration characteristics and microbial community. BC applied once at 0, 20 and 40 t ha−1 (B0, B1 and B2, respectively) was combined with three N fertilization levels (0, 120 and 240 kg N ha−1; N0, N1 and N2, respectively). Only winter wheat (Triticum aestivum L.) was cultivated, and it was cultivated in a winter wheat-summer fallow crop system. BC application persistently increased the SOC content by 36.3–91.6% over three years. Several soil parameters were also improved by BC combined with N after one year, such as bulk density, NO3- and available P content. Compared with its values with B0 treatments with N1 or N2, the total soil CO2 emitted decreased by 6.7–8.9% in response to BC combined with N1 but increased by 5.9–7.5% in response to BC combined with N2. B1N1 not only significantly increased microbial biomass but also decreased qCO2. In addition, B1N1 in particular increased the relative abundances of members of the microbial population associated with increased microbial C use efficiency, such as Rhizopus and Helotiaceae. However, B2N1 and B2N2 strongly disturbed the soil microbial ecosystem; moreover, the lowest alpha diversity of the bacterial community was observed in B2N2 soils. In summary, adding BC at a high rate to N-fertilized soil strongly disturbs the soil microbial ecosystem and reduces the C-sequestering potential of soil, while B1N1 treatment is recommended to enhance soil C sequestration and improve soil fertility under dryland farming.

川西平原灌区不同水旱轮作模式周年土壤呼吸特征

川西平原灌区不同水旱轮作模式周年土壤呼吸特征

Long-term characteristics of soil respiration in a Korean cool-temperate deciduous forest in a monsoon climate

ABSTRACTAnalysis of relationship between soil respiration and environmental factors has become essential for understanding changes in ecosystem carbon cycles under global warming. However, rough predictions have been made that soil respiration will increase with increasing temperature, but long-term data to support this theory were scarce. We measured soil respiration and environmental factors continuously using an automatic open-closed chamber system in a Korean cool-temperate forest from 2004 to 2016 to ascertain the reliability of this prediction and to more accurately predict changes in carbon cycle. Average air and soil temperatures were 11.0°C and 10.2°C. The increase in temperature was greater in winter (the inactive period for soil respiration) than in summer (the active period). Additionally, precipitation decreased sharply because of patter changes in 2012, and through 2016, it was approximately 69% of the previous period. Effect of precipitation on soil respiration was expected to be larger than temperature because the change in precipitation appeared in summer. Soil respiration exhibited a significant decline in 2012 because of precipitation. From 2004 to 2011, it averaged 344.4 mgCO2 m−2 h−1 and from 2012 to 2016 the average was 205.3 mgCO2 m−2 h−1. This phenomenon hasn’t been detected in short-term studies, suggesting that the prediction of previous studies is inaccurate. Additionally, to predict future ecosystem carbon cycle changes in a cool-temperate monsoon climate, changes in precipitation pattern should be regarded as equally important to temperature, and the prediction cannot be based solely on temperature. Therefore, long-term and continuous measurements are needed with consideration of the effects of both precipitation and temperature.Abbreviations: Rs: soil respiration; Ts: soil temperature; Ta: air temperature; AOCC: automatic open/closed chamber

Characteristics of soil respiration in upper and lower slope positions with different aboveground biomass: a case study in a Japanese cypress forest

Characteristics of soil respiration in upper and lower slope positions with different aboveground biomass: a case study in a Japanese cypress forest

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.

Soil Respiration Characteristics in Three Shrublands along an Elevation Gradient in a Semiarid Loess Plateau Mountain Area

ABSTRACTShrub is one of the major vegetation types distributed mostly in the mountainous area in China, and its vegetation carbon storage is approximately one-third of both forests and grasslands. It is essential to investigate how soil temperature (Ts) and soil water content (Ws) affect soil respiration (Rs) in this ecosystem. The purpose of this study was to understand the correlations of Rs with Ts, Ws, and other factors in the shrubs. In the current study, Rs was characterized in three shrublands (hereafter, shrub 1, shrub 2, and shrub 3, respectively) located in different elevations over a 4-year period at a biweekly interval in the eastern Loess Plateau (Shanxi province) of China. Our results showed that the trend of seasonal change of Rs was controlled mainly by Ts and Ws. The measured mean Rs over 4 years was 3.64 ± 2.83 (mean ± S.D.), 2.69 ± 2.05, and 4.41 ± 3.28 μmol carbon dioxide (CO2) m−2 s−1 for shrubs 1, 2, and 3, respectively, exhibiting an increase trend with elevation increment. Over the season, Rs illustrated a significant change depending on the variation of Ts and Ws, with larger values appearing in summer when both Ts and Ws were high, and smaller values in winter or in summer whenever Ws was low. An exponential model (Rs = a e bTs) fitted well the relation between Rs and Ts for shrub 3, whereas linear (Rs = a Ws + b) and power (Rs = a Ws b) models of Rs to Ws fitted well for shrub 1. This indicated that at a lower elevation, Ws had a greater effect on Rs than that at a higher elevation. The reverse trend was true between Rs and Ts, i.e., at a higher elevation Ts had a greater effect on Rs than that at a lower elevation. The calculated Q10 values of 1.61, 3.03, and 3.73 for shrubs 1, 2, and 3 increased to 2.25, 3.63, and 4.07, respectively (when the data in low Ws conditions were excluded from the analysis), showing that Q10 increased with elevation increment. Furthermore, three two-variable models, one linear (Rs = a (Ts Ws) + b), and two nonlinear (Rs = a Ts b Ws c and Rs = a ebTs Ws c), were also well developed to predict the dependency of Rs on both Ts and Ws. Our research results might have important implications for the estimation of soil carbon emissions of the shrublands in this region.

Characteristics of Soil Respiration and Soil Organic Carbon in Fava Bean Farmland Under Ridge Tillage and Straw Mulching in Southwest China

Soil respiration is an important process for carbon emission. A field study was conducted with four treatments including T (traditional tillage+straw mulching level 0 kg·hm-2), R (ridge tillage+straw mulching level 0 kg·hm-2), RS1 (ridge tillage+straw mulching level 3750 kg·hm-2), and RS2 (ridge tillage+straw mulching level 7500 kg·hm-2), so as to probe the effects of ridge tillage and straw mulching amount on soil respiration and soil organic carbon(SOC) and the relationships of soil respiration rate with soil temperature and water content (SWC) during the growth period of fava bean in the triple intercropping system of fava bean/maize/sweat pomato in dryland region of southwest China known as the purple hilly region. The changes of soil respiration rate were in accordance with crop growing, being firstly increased and then decreased during the whole growth period of fava bean, and there were significant differences in soil respiration rate among different treatments, which could be ranked as RS2[3.365 g·(m2·d)-1] > RS1[2.935 g·(m2·d)-1] > T[2.683 g·(m2·d)-1] > R[2.263 g·(m2·d)-1]. Ridge tillage reduced soil respiration in fava bean farmland, whereas straw mulching treatment increased it, whose variation trend was in accordance with that of straw mulching levels. There was a significant exponential relationship between soil respiration and soil temperature at 5 cm and 10 cm depth, and the exponential model at 10 cm produced better fitness than that at 5 cm. The temperature sensitivity (Q10) at 10 cm could be ranked as RS2 > RS1 > R > T, being 1.751,1.665,1.616, and 1.35, respectively. The combined exponential model indicated that soil temperature and water content (SWC) could jointly explain 68%(R), 79%(RS1) and 76%(RS2) of variation in soil respiration. This study results suggested that ridge tillage and straw mulching significantly increased SOC of 0-5 cm, 5-10 cm, 10-20 cm and 20-30 cm soil layers, and the increase of SOC was in accordance with that of straw mulching levels. The SOC was significantly increased in 5-10 cm and 10-20 cm soil layers, which could be ranked as RS2 > RS1 > R > T, and the increases in SOC at 5-10 cm were especially notable. The weighted average of particulate organic carbon (POC) at 0-30 cm was significantly increased, but the proportion of POC in SOC did not show significant influence.

Soil Respiration Response to Long-Term Freezing Saline Water Irrigation with Plastic Mulching in Coastal Saline Plain

The technology of freezing saline water irrigation (FSWI) with plastic mulching has been regarded as an effective way to reclaim the highly saline soil in coastal plains, which enabled the growth of crops in heavy saline soil that was not suitable for any crop growth before. However, after long-term treatment with FSWI, the microenvironment of the soil has been found to be affected by the growth of crops, which will directly influence the balance of soil carbon emissions. In this study, the characteristics of soil respiration in a typical saline field (planted with cotton) under four treatments (FSWI in Winter with plastic mulching, FSWI + Mulch; FSWI in Winter without plastic mulching, FSWI; plastic mulching in Spring without FSWI, mulch; no plastic mulching and no FSWI, CK) were investigated between June and November from 2015 to 2016. The results suggested that the soil surface temperature was an important factor that affected the soil respiration rate in each treatment during the growth period of cotton. FSWI + Mulch can reduce the soil surface salinity to 0.4% during the seedling stage, which increased the survival rate and the abundance of bacteria, fungi, and actinomycetes in the cotton field and subsequently increased soil respiration. By examining the effects of FWSI and mulching on soil respiration and its influencing factors, this study provides practical and theoretical insight into the sustainable development of agriculture in coastal saline plains.

Effect of Water Erosion on Soil Respiration Characteristics of Chernozem Topsoil

Soil respiration characteristics are an important indicator of the soil state. The aim of this study is to determine the effect of water erosion on soil respiration characteristics, in particular to determine whether erosion-damaged areas show statistically significantly worse respiratory activity compared to intact soil. Respiratory biological activity, as an indicator of soil quality, was monitored on 13 plots with chernozem soil type damaged by water erosion. There were determined basic respiration characteristics, such as basal respiration (B), respiration after adding ammonia nitrogen (N), respiration after addition of glucose (G), respiration after adding glucose and ammonia. Furthermore, from the above mentioned characteristics, following ratios were determined: N/B, G/B, G/N, NG/B and the factor of complex action (FCA). Statistical analysis showed that the position on a slope affects the respiratory characteristics. Based on results, we can say that the soil shows excessive amount of nitrogen, lack of easily degradable organic substances and poor stability of organic matter. Using statistical analysis, it was found that water erosion affects only the indicators B and G/N.

Influence of carbon inputs on soil respiration in aPlatycladus orientalisplantation in mountainous Beijing

To understand carbon source characteristics of soil respiration, a trench method was used to control carbon inputs (control treatment: CK, no litter treatment: NL, no root treatment: NR, and no litter and no root treatment: NLNR) in a Platycladus orientalis (L.) Franco plantation, so that soil respiration, temperatures and moisture content could be analyzed. Results indicate that different carbon inputs created no significant variance in soil temperatures and moisture content (P>0.05), whereas soil respiration was significantly influenced (P<0.01). During the measurement period, mean soil respiration of CK, NL, NR and NLNR were 3.69, 1.41, 3.11, and 1.99 µmol/m2/s, respectively. Soil respiration was reduced by 36.28 ±5.79%, 15.25 ±2.62% and 25.53 ±4.95% in the NL, NR and NLNR treatments, respectively. The proportions of mineral soil, litter and root respirations were 40.95%, 46.91% and 12.14%, respectively. Different carbon inputs caused no significant R2 variance in the temperature index model or in the ...