The sensitivity of soil respiration(R_(s))to temperature(Q_(10))is a key parameter for benchmarking the carbon(C)cycle and climate feedbacks in the context of global warming.However,previous studies on the factors tha...The sensitivity of soil respiration(R_(s))to temperature(Q_(10))is a key parameter for benchmarking the carbon(C)cycle and climate feedbacks in the context of global warming.However,previous studies on the factors that drive forest soil Q_(10) have focused mostly on abiotic factors,such as climate and soil,while the role of biotic factors has been less examined.Here,we compiled a global dataset of 766 soil Q_(10) values and 17 matched biotic and abiotic factors to explore the factors that drive the variability of global forest soil Q_(10) using a random forest(RF)model.Our findings showed that soil Q_(10) increased with microbial biomass carbon(MBC),which was the most important predictor.Additionally,soil Q_(10) was positively correlated with leaf phosphorus content(LPC)but was negatively correlated with leaf N:P,indicating that plant ecological stoichiometry might be a factor that explained soil Q_(10) variability.All abiotic factors,including climate,soil properties,and elevation,had great predictive power and were significantly related to soil Q_(10).By comparing the soil Q_(10) in multispecies forests and monocultures,we found that Q_(10) in the mixed needle-leaved and broad-leaved forests(NF&BF)was lower than in monocultures.Our study revealed that,in addition to abiotic factors,biotic factors were also strong predictors of forest soil Q_(10),which can deepen our understanding of soil respiration in response to global warming and provide insights for improving carbon cycle models.展开更多
Crop straw incorporation is widely recommended to maintain crop yields and improve soil organic carbon(SOC)stocks as well as soil quality.However,the long-term effects of different straw incorporation practices on the...Crop straw incorporation is widely recommended to maintain crop yields and improve soil organic carbon(SOC)stocks as well as soil quality.However,the long-term effects of different straw incorporation practices on the SOC stock remain uncertain.In this study,a long-term experiment(2007 to 2018)with four treatments(MW_0:maize–wheat rotation with no straw incorporation,MW_(50):maize–wheat rotation with 50%chopped straw incorporation,MW_(b50):maize–wheat rotation with 50%in situ burned harvested straw,and MF_(50):maize–fallow rotation with 50%harvested maize straw incorporation)was set up to evaluate the response of the SOC stock to different straw incorporation methods.The results showed that the SOC stock significantly increased by 32.4,12.2 and 17.4%under the MW_(50),MW_(b50)and MF_(50)treatments,respectively,after continuous straw incorporation over a decade,while the SOC stock under MW0 was significantly reduced by 22.9%after the 11 year long-term experiment.Compared to MW_0,straw incorporation significantly increased organic carbon input,and improved the soil aggregate structure and the ratio of dissolved organic carbon(DOC)to particulate organic carbon(POC),but it did not significantly stimulate soil heterotrophic respiration,resulting in the increased SOC accumulation rate and SOC stocks of bulk soil.The increased ratio of DOC to microbial biomass carbon(MBC)enhanced the relative abundances of Acidobacteria and Proteobacteria but inhibited Bacteroidetes and Chloroflexi,and the bacterial relative abundances were the main reasons for the non-significant increase or even decrease in soil heterotrophic respiration with straw incorporation.The SOC stock would reach an equilibrium based on the results of Rothamsted carbon(RothC)model simulations,with a long-term equilibrium value of 18.85 Mg ha^(–1)under MW_(50).Overall,the results of the long-term field experiment(2007–2018)and RothC model simulation suggested that maize–wheat rotation with 50%chopped straw incorporation delivered the largest benefits for the SOC stock in calcareous soils of subtropical mountain landscapes over the long term.展开更多
Salmonella grows better under aerobic conditions as a facultative anaerobic foodborne pathogenic bacteria.The oxygen-scavenging activity of Lactococcus lactis in the intestinal tract is a promising strategy for preven...Salmonella grows better under aerobic conditions as a facultative anaerobic foodborne pathogenic bacteria.The oxygen-scavenging activity of Lactococcus lactis in the intestinal tract is a promising strategy for preventing Salmonella infection.In this study,the aerobic respiration requirement and preventive mechanism of L.lactis subsp.lactis KLDS 4.0325 in murine models infected by Salmonella enterica subsp.enterica serovar Typhimurium(S.Typhimurium)SL1344 were investigated.Results indicate that L.lactis KLDS 4.0325 is capable of aerobic respiratory metabolism in the host intestine when exogenous heme exists,and decrease intestinal oxygen concentration,which in turn trigger autophagy of intestinal cells to reduce S.Typhimurium load,improve gut microbiota composition,alleviate intestinal barrier injury and inflammation response.These results suggest that aerobic respiration L.lactis KLDS 4.0325 can prevent S.Typhimurium infection in a new way in which by restoring intestinal cell hypoxia,maintaining immune balance and regulating intestinal flora.展开更多
Intensive management is known to markedly alter soil carbon(C)storage and turnover in Moso bamboo forests compared with extensive management.However,the effects of intensive management on soil respiration(RS)component...Intensive management is known to markedly alter soil carbon(C)storage and turnover in Moso bamboo forests compared with extensive management.However,the effects of intensive management on soil respiration(RS)components remain unclear.This study aimed to evaluate the changes in different RScomponents(root,mycorrhizal,and free-living microorganism respiration)in Moso bamboo forests under extensive and intensive management practices.A1-year in-situ microcosm experiment was conducted to quantify the RScomponents in Moso bamboo forests under the two management practices using mesh screens of varying sizes.The results showed that the total RSand its components exhibited similar seasonal variability between the two management practices.Compared with extensive management,intensive management significantly increased cumulative respiration from mycorrhizal fungi by 36.73%,while decreased cumulative respiration from free-living soil microorganisms by 8.97%.Moreover,the abundance of arbuscular mycorrhizal fungi(AMF)increased by 43.38%,but bacterial and fungal abundances decreased by 21.65%and 33.30%,respectively,under intensive management.Both management practices significantly changed the bacterial community composition,which could be mainly explained by soil pH and available potassium.Mycorrhizal fungi and intensive management affected the interrelationships between bacterial members.Structural equation modeling indicated that intensive management changed the cumulative RSby elevating AMF abundance and lowering bacterial abundance.We concluded that intensive management reduced the microbial respiration-derived C loss,but increased mycorrhizal respiration-derived C loss.展开更多
Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicult...Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicultural practice,the long-term impacts of thinning on R_(S) and its heterotrophic and autotrophic respiration components(R_(h) and Ra,respectively)in subalpine plantations are poorly understood,espe-cially in winter.A 3-year field observation was carried out with consideration of winter CO_(2) efflux in middle-aged sub-alpine spruce plantations in northwestern China.A trench-ing method was used to explore the long-term impacts of thinning on Rs,Rn and R_(a).Seventeen years after thinning,mean annual Rs,Rn and R_(a) increased,while the contribu-tion of R_(h) to R_(s) decreased with thinning intensity.Thinning significantly decreased winter R,because of the reduction in R_(n) but had no significant effect on Ra.The temperature sensitivity(Q_(10))of R_(h) and R_(a) also increased with thinning intensity,with lower Q_(10) values for R_(h)(2.1-2.6)than for Ra(2.4-2.8).The results revealed the explanatory variables and pathways related to R_(n) and R_(a) dynamics.Thinning increased soil moisture and nitrate nitrogen(NO_(3)^(-)-N),and the enhanced nitrogen and water availability promoted R_(h) and R_(a) by improving fine root biomass and microbial activity.Our results highlight the positive roles of NO_(3)^(-)-N in stimulating R_(s) components following long-term thinning.Therefore,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO_(2) emissions.The increased Q_(10) values of R_(s) components indicate that a large increase in soil CO_(2) emissions would be expected following thinning because of more pronounced climate warming in alpineregions.展开更多
Warming-induced carbon loss via ecosystem respiration(R_(e))is probably intensifying in the alpine grassland ecosystem of the Tibetan Plateau owing to more accelerated warming and the higher temperature sensitivity of...Warming-induced carbon loss via ecosystem respiration(R_(e))is probably intensifying in the alpine grassland ecosystem of the Tibetan Plateau owing to more accelerated warming and the higher temperature sensitivity of R_(e)(Q_(10)).However,little is known about the patterns and controlling factors of Q_(10)on the plateau,impeding the comprehension of the intensity of terrestrial carbon-climate feedbacks for these sensitive and vulnerable ecosystems.Here,we synthesized and analyzed multiyear observations from 14 sites to systematically compare the spatiotemporal variations of Q_(10)values in diverse climate zones and ecosystems,and further explore the relationships between Q_(10)and environmental factors.Moreover,structural equation modeling was utilized to identify the direct and indirect factors predicting Q_(10)values during the annual,growing,and non-growing seasons.The results indicated that the estimated Q_(10)values were strongly dependent on temperature,generally,with the average Q_(10)during different time periods increasing with air temperature and soil temperature at different measurement depths(5 cm,10 cm,20 cm).The Q_(10)values differentiated among ecosystems and climatic zones,with warming-induced Q_(10)declines being stronger in colder regions than elsewhere based on spatial patterns.NDVI was the most cardinal factor in predicting annual Q_(10)values,significantly and positively correlated with Q_(10).Soil temperature(Ts)was identified as the other powerful predictor for Q_(10),and the negative Q_(10)-Ts relationship demonstrates a larger terrestrial carbon loss potentiality in colder than in warmer regions in response to global warming.Note that the interpretations of the effect of soil moisture on Q_(10)were complicated,reflected in a significant positive relationship between Q_(10)and soil moisture during the growing season and a strong quadratic correlation between the two during the annual and non-growing season.These findings are conducive to improving our understanding of alpine grassland ecosystem carbon-climate feedbacks under warming climates.展开更多
This paper reports on two years of measurement of soil respiration and canopy-root biomass in a Leymus chinensis community in the Xilin River basin of Inner Mongolia. Correlations between components of plant biomass a...This paper reports on two years of measurement of soil respiration and canopy-root biomass in a Leymus chinensis community in the Xilin River basin of Inner Mongolia. Correlations between components of plant biomass and soil respiration rates were examined. From respiration data based on CO2 uptake by NaOH and corresponding root biomass values for each run of 10 plots, a linear regression of CO2 evolution rates on root dry weights has been achieved for every ten days. By applying the approach of extrapolating the regressive line to zero root biomass, the proportion of the total soil respiration flux that is attributable to live root respiration was estimated to be about 27% on average, ranging from 14% to 39% in the growing season in 1998. There were no evident relations between the total canopy biomass or root biomass and CO2 evolution rates, but a significant exponential relation did exist between tire live-canopy biomass and CO2 evolution rates.展开更多
Soil respiration is a vital process in all terrestrial ecosystems,through which the soil releases carbon dioxide(CO_(2))into the atmosphere at an estimated annual rate of 68–101 Pg carbon,making it the second highest...Soil respiration is a vital process in all terrestrial ecosystems,through which the soil releases carbon dioxide(CO_(2))into the atmosphere at an estimated annual rate of 68–101 Pg carbon,making it the second highest terrestrial contributor to carbon fluxes.Since soil respiration consists of autotrophic and heterotrophic constituents,methods for accurately determining the contribution of each constituent to the total soil respiration are critical for understanding their differential responses to environmental factors and aiding the reduction of CO_(2)emissions.Owing to its low cost and simplicity,the root exclusion(RE)technique,combined with manual chamber measurements,is frequently used in field studies of soil respiration partitioning.Nevertheless,RE treatments alter the soil environment,leading to potential bias in respiration measurements.This review aims to elucidate the current understanding of RE,i.e.,trenching(Tr)and deep collar(DC)insertion techniques,by examining soil respiration partitioning studies performed in several ecosystems.Additionally,we discuss methodological considerations when using RE and the combinations of RE with stable isotopic and modeling approaches.Finally,future research directions for improving the Tr and DC insertion methods in RE are suggested.展开更多
The impacts of elevated atmospheric CO2 concentrations (500 靘olmol-1and 700 靘olmol-1) on total soil respiration and the contribution of root respiration of Pinus koraiensis seedlings were investigated from May to Oc...The impacts of elevated atmospheric CO2 concentrations (500 靘olmol-1and 700 靘olmol-1) on total soil respiration and the contribution of root respiration of Pinus koraiensis seedlings were investigated from May to October in 2003 at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences, Jilin Province, China. After four growing seasons in top-open chambers exposed to elevated CO2, the total soil respiration and roots respiration of Pinus koraiensis seedlings were measured by a LI-6400-09 soil CO2 flux chamber. Three PVC cylinders in each chamber were inserted about 30 cm into the soil in-stantaneously to terminate the supply of current photosynthates from the tree canopy to roots for separating the root respiration from total soil respiration. Soil respirations both inside and outside of the cylinders were measured on June 16, August 20 and October 8, respectively. The results indicated that: there was a marked diurnal change in air temperature and soil temperature at depth of 5 cm on June 16, the maximum of soil temperature at depth of 5 cm lagged behind that of air temperature, no differences in temperature between treatments were found (P>0.05). The total soil respiration and soil respiration with roots severed showed strong diurnal and seasonal patterns. There was marked difference in total soil respiration and soil respiration with roots severed between treatments (P<0.01); Mean total soil respiration and contribution of root under different treatments were 3.26, 4.78 and 1.47 靘olm 2s-1, 11.5%, 43.1% and 27.9% on June 16, August 20 and October 8, respectively.展开更多
A stdudy was conducted to determine the seasonal changes of soil respiration and the contribution of root respiration to soil respiration in Betula plaophylla forest in Changbai Mountain from May to September in 2004....A stdudy was conducted to determine the seasonal changes of soil respiration and the contribution of root respiration to soil respiration in Betula plaophylla forest in Changbai Mountain from May to September in 2004. Results indicated that the total soil respiration, root-severed soil respiration and the root respiration followed a similar seasonal trend, with a high rate in summer due to wet and high temperature and a low rate in spring and autumn due to lower temperature. The mean rates of total soil respiration, root-severed soil respiration and root respiration were 4.44, 2.30 and 2.14 μmol.m^-2.s^-1, respectively during the growing season, and they were all exponentially correlated with temperature. Soil respiration rate had a linear correlation with soil volumetric moisture. The Q10 values for total soil respiration, root-severed soil respiration and root respiration were 2,82, 2.59 and 3. 16, respectively. The contribution rate of root respiration to the total soil respiration was between 29.3% and 58.7% during the growing season, indicating that root is a major component of soil respiration. The annual mean rates of total soil respiration, root-severed soil respiration and root respiration were 1.96, 1.08, and 0.87 μmol.m^-2.s^-1, or 741.73 408.71, and 329.24 g.m^-2.a^-1, respectively. Root respiration contributed 44.4% to the annual total soil respiration. The relationship proposed for soil respiration with soil lemperature was useful for understanding and predicting potential changes in Changbai Mountain B. platyphylla forest ecosystem in response to forest management and climate change.展开更多
Mutagens are agents that cause damage to DNA and have the potential to permanently alter (mutate) its sequence, depending on the organism’s ability to repair the damage. UV radiation is a mutagen in cells. This mutag...Mutagens are agents that cause damage to DNA and have the potential to permanently alter (mutate) its sequence, depending on the organism’s ability to repair the damage. UV radiation is a mutagen in cells. This mutagen relates to both yeast cells and human skin cells, since they have similar reactions. UV radiation can cause cell mutations, but also cell death. This is examined with the absence or presence of sunscreen when in contact with cells. Since yeast cells and human cells have almost identical metabolisms, data results of yeast experiments can be associated with real life. Hypothesis for the presence of sunscreen in yeast solutions includes the exposure of yeast cells with or without sunscreen for different time periods in UV radiation. However, the role of sunscreen in yeast cell mutations, in relation to cancer prevention, may not be directly positive. Here, I show that sunscreen has a positive effect on yeast cells and prevents mutations. I found that the respiration rate differs for yeast cells without or without the presence of sunscreen when exposed to radiation. Yeast cells without sunscreen respired faster than those exposed to UV radiation. However, with sunscreen, the rate of CO2 production was higher, with a higher respiration rate. These results may be connected with skin cancer to some extent, promoting or not the use of sunscreen to protect the skin cells from mutating. This experiment may be the base for further experimentation with different yeast cells, providing clearer and more assuring data about the association of sunscreen, yeast cells, and skin cancer. Such experiments may avoid implications with weather conditions, such as slightly different temperatures, sunlight intensity, and clouds, or with the time between the end of the time period of exposure of the yeast cells to UV radiation, and the measurement of CO2 and density, which my experiment had.展开更多
An open-top chamber experiment was conducted at the University of Michigan Biological Station near Pellston, Michigan, USA, to study the effects of soil fertility and CO2 on leaf, stem and root dark respiration (Rd) o...An open-top chamber experiment was conducted at the University of Michigan Biological Station near Pellston, Michigan, USA, to study the effects of soil fertility and CO2 on leaf, stem and root dark respiration (Rd) of Populus tremuloides. Overall, area-based day-time leaf Rd (Rda) was significantly greater at elevated than at ambient CO2 in high-fertility soil, but not in low-fertility soil. Mass-based leaf Rd (Rdm) was overall greater for high- than for low-fertility soil grown trees at elected, but not at ambient CO2. Nighttime leaf Rd. and Rdm were unthected by soil fertility or CO2, nor was stem Rda, which ranged from 1.0 to 1.4 μmol m-2 s-1 in the spring and 3.5 to 4.5 μmol m-2 s-1 in the summer. Root Rda. was significantly higher in high- than in low-fertility soil, but was unaffected by CO2. Since biomass production of P. tremuloides will be significantly greater at elevated CO2 while specific Rd will either increase or remain unchanged, we predict that carbon loss to the atmosphere through respiration from this ecologically important species would increase at higher CO2. Soil fertility would also interact with elevated CO2 in affecting the carbon flow in the plant-soil-air system.展开更多
Partitioning soil respiration into three components is vital to identify CO_2 sink or source and can help us better understand soil carbon dynamics. However, knowledge about the influences of soil depth and the primin...Partitioning soil respiration into three components is vital to identify CO_2 sink or source and can help us better understand soil carbon dynamics. However, knowledge about the influences of soil depth and the priming effect on soil respiration components under field has been limited. Three components of soil respiration（root respiration, rhizomicrobial respiration and basal respiration） in a plantation in the hilly area of the North China were separated by the 13 C natural abundance method. The results showed that the average proportions of rhizomicrobial respiration, root respiration and basal respiration at the 25-65 cm depths were about 14, 23 and 63 %, respectively. Three components of soil respiration varied with soil depth, and root respiration was the main component of soil respiration in deeper soil. The priming effect was obvious for the deep soil respiration, especially at the 40-50 cm depth. Thus, depth and priming effect should be taken into account to increase the accuracy of estimations of soil carbon flux.展开更多
Based on the static opaque chamber method,the respiration rates of soil microbial respiration,soil respiration,and ecosystem respiration were measured through continuous in-situ experiments during rapid growth season ...Based on the static opaque chamber method,the respiration rates of soil microbial respiration,soil respiration,and ecosystem respiration were measured through continuous in-situ experiments during rapid growth season in semiarid Leymus chinensis steppe in the Xilin River Basin of Inner Mongolia,China. Soil temperature and moisture were the main factor affecting respiration rates. Soil temperature can explain most CO2 efflux variations （R2=0.376-0.655） excluding data of low soil water conditions. Soil moisture can also effectively explain most of the variations of soil and ecosystem respiration （R2=0.314-0.583）,but it can not explain much of the variation of microbial respiration （R2=0.063）. Low soil water content （≤5%） inhibited CO2 efflux though the soil temperature was high. Rewetting the soil after a long drought resulted in substantial increases in CO2 flux at high temperature. Bi-variable models based on soil temperature at 5 cm depth and soil moisture at 0-10 cm depth can explain about 70% of the variations of CO2 effluxes. The contribution of soil respiration to ecosystem respiration averaged 59.4%,ranging from 47.3% to 72.4%; the contribution of root respiration to soil respiration averaged 20.5%,ranging from 11.7% to 51.7%. The contribution of soil to ecosystem respiration was a little overestimated and root to soil respiration little underestimated because of the increased soil water content that occurred as a result of plant removal.展开更多
With increasingly intensifying degradation of natural grasslands and rapidly increasing demand of high quality forages, natural grasslands in China have been converted into planted grasslands at an unprecedented rate ...With increasingly intensifying degradation of natural grasslands and rapidly increasing demand of high quality forages, natural grasslands in China have been converted into planted grasslands at an unprecedented rate and the magnitude of the conversion in Inner Mongolia is among the national highest where the areal extent of planted grasslands ranks the second in China. Such land-use changes（i.e., converting natural grasslands into planted grasslands） can significantly affect carbon stocks and carbon emissions in grassland ecosystems. In this study, we analyzed the effects of converting natural grasslands into planted grasslands（including Medicago sativa, Elymus cylindricus, and M. sativa＋E. cylindricus） on ecosystem respiration（F（eco）） in Inner Mongolia of China. Diurnal F（eco） and its components（i.e., total soil respiration（F（ts））, soil heterotrophic respiration（F（sh）） and vegetation autotrophic respiration（F（va））） were measured in 2012（27 July to 5 August） and 2013（18 July to 25 July） in the natural and planted grasslands. Meteorological data, aboveground vegetation data and soil data were simultaneously collected to analyze the relationships between respiration fluxes and environmental factors in those grasslands. In 2012, the daily mean F（eco） in the M. sativa grassland was higher than that in the natural grassland, and the daily mean F（va） was higher in all planted grasslands（i.e., M. sativa, E. cylindricus, and M. sativa＋E. cylindricus） than in the natural grassland. In contrast, the daily mean F（ts） and F（sh） were lower in all planted grasslands than in the natural grassland. In 2013, the daily mean F（eco）, F（ts） and F（va） in all planted grasslands were higher than those in the natural grassland, and the daily mean F（sh） in the M. sativa＋E. cylindricus grassland was higher than that in the natural grassland. The two-year experimental results suggested that the conversion of natural grasslands into planted grasslands can generally increase the F（eco） and the increase in F（eco） is more pronounced when the plantation becomes more mature. The results also indicated that F（sh） contributed more to F（eco） in the natural grassland whereas F（va） contributed more to F（eco） in the planted grasslands. The regression analyses show that climate factors（air temperature and relative humidity） and soil properties（soil organic matter, soil temperature, and soil moisture） strongly affected respiration fluxes in all grasslands. However, our observation period was admittedly too short. To fully understand the effects of such land-use changes（i.e., converting natural grasslands into planted grasslands） on respiration fluxes, longer-term observations are badly needed.展开更多
Soil incubation experiments were conducted in lab to delineate the effect of soil temperature and soil water content on soil respirations in broad-leaved/Korean pine forest (mountain dark brown forest soil), dark coni...Soil incubation experiments were conducted in lab to delineate the effect of soil temperature and soil water content on soil respirations in broad-leaved/Korean pine forest (mountain dark brown forest soil), dark coniferous forest (mountain brown coniferous forest soil) and erman's birch forest (mountain soddy forest soil) in Changbai Mountain in September 2001. The soil water content was adjusted to five different levels (9%, 21%, 30%, and 43%) by adding certain amount of water into the soil cylinders, and the soil sample was incubated at 0, 5, 15, 25 and 35°C for 24 h. The results indicated that in broad-leaved/Korean pine forest the soil respiration rate was positively correlated to soil temperature from 0 to 35°C. Soil respiration rate increased with increase of soil water content within the limits of 21% to 37%, while it decreased with soil water content when water content was over the range. The result suggested the interactive effects of temperature and water content on soil respiration. There were significant differences in soil respiration among the various forest types. The soil respiration rate was highest in broad-leaved/Korean pine forest, middle in erman's birch forest and the lowest in dark coniferous forest. The optimal soil temperature and soil water content for soil respiration was 35°C and 37% in broad-leaved/Korean pine forest, 25°C and 21% in dark coniferous forest, and 35°C and 37% in erman's birch forest. Because the forests of broad-leaved/Korean pine, dark coniferous and erman's birch are distributed at different altitudes, the soil temperature had 4–5°C variation in different forest types during the same period. Thus, the soil respiration rates measured in brown pine mountain soil were lower than those in dark brown forest and those measured in mountain grass forest soil were higher than those in brown pine mountain soil. Key words Soil temperature - Soil water content - Soil respiration - The typical forest ecosystem in Changbai Mountain CLC number S7118.51 Document code A Foundation item: This study was supported by grant from the National Natural Science Foundation of China (No. 30271068), the grant of the Knowledge Innovation Program of Chinese Academy of Sciences (KZ-CX-SW-01-01B-12) and the grant from Advanced Programs of Institute of Applied Ecology Chinese Academy of Sciences.Biography: WANG Miao (1964-), male, associate professor in Institute of Applied Ecology, Chinese Academy of Science, Shenyang 110016, P. R. China.Responsible editor: Song Funan展开更多
Stem respiration is an important part of the activity of a tree and is an important source of CO2 evolution from a forest ecosystem. Presently, no standard methods are available for the accurate estimation of total st...Stem respiration is an important part of the activity of a tree and is an important source of CO2 evolution from a forest ecosystem. Presently, no standard methods are available for the accurate estimation of total stem CO2 efflux from a forest. In the current study, a 33-year-old (by the year 2001) larch (Larix gmelini Rupr.) plantation was measured throughout 2001-2002 to analyze its monthly and seasonal patterns of stem respiration. Stem respiration rate was also measured at different heights, at different daily intervals and any variation in the larch plantation was recorded. The relationship between stem temperature, growth status and respiration rate was analyzed. Higher respiration rates were recorded in upper reaches of the larch tree throughout the season and these were affected partially by temperature difference. Midday depression was found in the diurnal changes in stem respiration. In the morning, but not in the afternoon, stem respiration was positively correlated with stem temperature. The reason for this variation may be attributed to water deficit, which was stronger in the afternoon. In the larch plantation, a maximum 7-fold variation in stem respiration was found. The growth status (such as mean growth rate of stem and canopy projection area) instead of stem temperature difference was positively correlated with this large variation. An S-model (sigmoid curve) or Power model shows the greatest regression of the field data. In the courses of seasonal and annual changes of stem respiration, peak values were observed in July of both years, but substantial interannual differences in magnitude were observed. An exponential model can clearly show this regression of the temperature-respiration relationship. In our results, Q(10) values ranged from 2.22 in 2001 to 3.53 in 2002. Therefore, estimation of total stem CO2 efflux only by a constant Q(10) value may give biased results. More parameters of growth status and water status should be considered for more accurate estimation.展开更多
The soil respiration rates （Rh） in 6-year-old （young）, 17-year-old （middle-age）, 31-year-old （mature） Casuarina equisetifolia coastal plantations were measured using an LICOR-8100 automated soil CO2 flux syste...The soil respiration rates （Rh） in 6-year-old （young）, 17-year-old （middle-age）, 31-year-old （mature） Casuarina equisetifolia coastal plantations were measured using an LICOR-8100 automated soil CO2 flux system from May 2006 to April 2007. Results show that Rh displayed an obvious seasonal pattern across the observed years. The maximum values of Rh occurred at June and July and the minimum at December and January. Soil temperature and soil moisture as well as their interaction had significant effects on the monthly dynamics of Rh. The analysis by one-way ANOVA showed that Rh had a significantly exponential relation （p〈0.05） to soil temperature at soil depth of 5 cm, and had a linear relation （p〈0.05） to soil water content of the upper 20 cm. The result estimated by the two-factor model shows that soil temperature at soil depth of 5 cm and soil moisture at soil depth of 20 cm could explain 68.9%-91.9% of seasonal variations in Rh. The or- der of Rh rates between different stand ages was middle-age plantation〉mature plantation〉young-age plantation. With the increase of growth age of plantation, the Q10 of Rh increased. The contribution of Rh to total soil surface CO2 flux was 71.89%, 71.02% and 73.53% for the young, middle-age and mature plantation, respectively. It was estimated that the annual CO2 fluxes from Rh were 29.07, 38.964 and 30.530 t.ha^-1.a^-1 for the young, middle-age and mature plantation, respectively.展开更多
To evaluate the diurnal and seasonal variations in soil respiration （Rs） and understand the controlling factors, we measured carbon dioxide （CO2） fluxes and their environmental variables using a LI-6400 soil CO2 f...To evaluate the diurnal and seasonal variations in soil respiration （Rs） and understand the controlling factors, we measured carbon dioxide （CO2） fluxes and their environmental variables using a LI-6400 soil CO2 flux system at a temperate Leymus chinensis meadow steppe in the western Songnen Plain of China in the growing season （May-October） in 2011 and 2012. The diurnal patterns of soil respiration could be expressed as single peak curves, reaching to the maximum at 11：00-15：00 and falling to the minimum at 21：00-23：00 （or before dawn）. The time-window between 7：00 and 9：00 could be used as the optimal measuring time to represent the daily mean soil CO2 efflux. In the growing season, the daily value of soil CO2 efflux was moderate in late spring （1.06-2.51μnol/（m2.s） in May）, increased sharply and presented a peak in summer （2.95-3.94 μmol/（m2.s） in July）, and then decreased in autumn （0.74-0.97 μmol/（m2.s） in October）. Soil temperature （Ts） exerted dominant control on the diurnal and seasonal variations of soil respiration. The temperature sensitivity of soil respiration （Q10） exhibited a large seasonal variation, ranging from 1.35 to 3.32, and decreased with an increasing soil temperature. Rs gradually increased with increasing soil water content （Ws） and tended to decrease when Ws exceeded the optimum water content （27%） of Rs. The Ts and Ws had a confounding effect on Rs, and the two-variable equations could account for 72% of the variation in soil respiration （p 〈 0.01）.展开更多
[Objective]The experiment aimed to study the effects of meteorological factors under different weather conditions on soil respiration. [ Method] The path analysis was used to analyze meteorological factors which influ...[Objective]The experiment aimed to study the effects of meteorological factors under different weather conditions on soil respiration. [ Method] The path analysis was used to analyze meteorological factors which influenced soil respiration of wheat field under different weather condition and at jointing stage. [ Result] In sunny day, the correlations between ground temperature at 5 cm, solar radiation, air relative humidity, air temperature and soil respiration were all at significant level while solar radiation and ground temperature at 5 cm were the major factors which influenced soil respiration. In cloudy day, solar radiation was a major factor which influenced soil respiration.[ Conclusion] The soil respiration and surplus path coefficient in sunny day were all higher than these in cloudy day, which demonstrated that except influenced by ground temperature, air temperature, solar radiation and air relative humidity, the soil respiration was also influenced by other factors especially biological factor.展开更多
基金supported by the National Natural Science Foundation of China(No.31988102)the Key Research Program of Frontier Sciences,CAS(No.QYZDY-SSW-SMC011).
文摘The sensitivity of soil respiration(R_(s))to temperature(Q_(10))is a key parameter for benchmarking the carbon(C)cycle and climate feedbacks in the context of global warming.However,previous studies on the factors that drive forest soil Q_(10) have focused mostly on abiotic factors,such as climate and soil,while the role of biotic factors has been less examined.Here,we compiled a global dataset of 766 soil Q_(10) values and 17 matched biotic and abiotic factors to explore the factors that drive the variability of global forest soil Q_(10) using a random forest(RF)model.Our findings showed that soil Q_(10) increased with microbial biomass carbon(MBC),which was the most important predictor.Additionally,soil Q_(10) was positively correlated with leaf phosphorus content(LPC)but was negatively correlated with leaf N:P,indicating that plant ecological stoichiometry might be a factor that explained soil Q_(10) variability.All abiotic factors,including climate,soil properties,and elevation,had great predictive power and were significantly related to soil Q_(10).By comparing the soil Q_(10) in multispecies forests and monocultures,we found that Q_(10) in the mixed needle-leaved and broad-leaved forests(NF&BF)was lower than in monocultures.Our study revealed that,in addition to abiotic factors,biotic factors were also strong predictors of forest soil Q_(10),which can deepen our understanding of soil respiration in response to global warming and provide insights for improving carbon cycle models.
基金financially supported by the National Key Research and Development Program of China(2023YFD1901200)the National Natural Science Foundation of China(U22A20562)+4 种基金the Sichuan Science and Technology Program,China(2022YFS0500)the Project of Special Research Assistant of the Chinese Academy of Sciences(Jing Zheng)the China Postdoctoral Science Foundation(2022M723079)the Sichuan Provincial Postdoctoral Research Foundation,China(TB2022042)the Science and Technology Research Program of Institute of Mountain Hazards and Environment,Chinese Academy of Sciences(IMHEZYTS-08)。
文摘Crop straw incorporation is widely recommended to maintain crop yields and improve soil organic carbon(SOC)stocks as well as soil quality.However,the long-term effects of different straw incorporation practices on the SOC stock remain uncertain.In this study,a long-term experiment(2007 to 2018)with four treatments(MW_0:maize–wheat rotation with no straw incorporation,MW_(50):maize–wheat rotation with 50%chopped straw incorporation,MW_(b50):maize–wheat rotation with 50%in situ burned harvested straw,and MF_(50):maize–fallow rotation with 50%harvested maize straw incorporation)was set up to evaluate the response of the SOC stock to different straw incorporation methods.The results showed that the SOC stock significantly increased by 32.4,12.2 and 17.4%under the MW_(50),MW_(b50)and MF_(50)treatments,respectively,after continuous straw incorporation over a decade,while the SOC stock under MW0 was significantly reduced by 22.9%after the 11 year long-term experiment.Compared to MW_0,straw incorporation significantly increased organic carbon input,and improved the soil aggregate structure and the ratio of dissolved organic carbon(DOC)to particulate organic carbon(POC),but it did not significantly stimulate soil heterotrophic respiration,resulting in the increased SOC accumulation rate and SOC stocks of bulk soil.The increased ratio of DOC to microbial biomass carbon(MBC)enhanced the relative abundances of Acidobacteria and Proteobacteria but inhibited Bacteroidetes and Chloroflexi,and the bacterial relative abundances were the main reasons for the non-significant increase or even decrease in soil heterotrophic respiration with straw incorporation.The SOC stock would reach an equilibrium based on the results of Rothamsted carbon(RothC)model simulations,with a long-term equilibrium value of 18.85 Mg ha^(–1)under MW_(50).Overall,the results of the long-term field experiment(2007–2018)and RothC model simulation suggested that maize–wheat rotation with 50%chopped straw incorporation delivered the largest benefits for the SOC stock in calcareous soils of subtropical mountain landscapes over the long term.
基金supported by the National Natural Science Foundation of China(32072190 and 32101929)Academic Backbone Plan of Northeast Agricultural University(20XG12)。
文摘Salmonella grows better under aerobic conditions as a facultative anaerobic foodborne pathogenic bacteria.The oxygen-scavenging activity of Lactococcus lactis in the intestinal tract is a promising strategy for preventing Salmonella infection.In this study,the aerobic respiration requirement and preventive mechanism of L.lactis subsp.lactis KLDS 4.0325 in murine models infected by Salmonella enterica subsp.enterica serovar Typhimurium(S.Typhimurium)SL1344 were investigated.Results indicate that L.lactis KLDS 4.0325 is capable of aerobic respiratory metabolism in the host intestine when exogenous heme exists,and decrease intestinal oxygen concentration,which in turn trigger autophagy of intestinal cells to reduce S.Typhimurium load,improve gut microbiota composition,alleviate intestinal barrier injury and inflammation response.These results suggest that aerobic respiration L.lactis KLDS 4.0325 can prevent S.Typhimurium infection in a new way in which by restoring intestinal cell hypoxia,maintaining immune balance and regulating intestinal flora.
基金financially supported by the National Natural Science Foundation of China(Nos.31971631,41977083,and 41671252)。
文摘Intensive management is known to markedly alter soil carbon(C)storage and turnover in Moso bamboo forests compared with extensive management.However,the effects of intensive management on soil respiration(RS)components remain unclear.This study aimed to evaluate the changes in different RScomponents(root,mycorrhizal,and free-living microorganism respiration)in Moso bamboo forests under extensive and intensive management practices.A1-year in-situ microcosm experiment was conducted to quantify the RScomponents in Moso bamboo forests under the two management practices using mesh screens of varying sizes.The results showed that the total RSand its components exhibited similar seasonal variability between the two management practices.Compared with extensive management,intensive management significantly increased cumulative respiration from mycorrhizal fungi by 36.73%,while decreased cumulative respiration from free-living soil microorganisms by 8.97%.Moreover,the abundance of arbuscular mycorrhizal fungi(AMF)increased by 43.38%,but bacterial and fungal abundances decreased by 21.65%and 33.30%,respectively,under intensive management.Both management practices significantly changed the bacterial community composition,which could be mainly explained by soil pH and available potassium.Mycorrhizal fungi and intensive management affected the interrelationships between bacterial members.Structural equation modeling indicated that intensive management changed the cumulative RSby elevating AMF abundance and lowering bacterial abundance.We concluded that intensive management reduced the microbial respiration-derived C loss,but increased mycorrhizal respiration-derived C loss.
基金supported by the National Natural Science Foundation of China (Grant Nos.41701296 and 42277481)the Natural Science Foundation of Gansu Province (GrantNo.22JR5RA058)the Youth Science and Technology Fund Program of Gansu Province (Grant No.22JR5RA087).
文摘Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental changes.However,as a principal silvicultural practice,the long-term impacts of thinning on R_(S) and its heterotrophic and autotrophic respiration components(R_(h) and Ra,respectively)in subalpine plantations are poorly understood,espe-cially in winter.A 3-year field observation was carried out with consideration of winter CO_(2) efflux in middle-aged sub-alpine spruce plantations in northwestern China.A trench-ing method was used to explore the long-term impacts of thinning on Rs,Rn and R_(a).Seventeen years after thinning,mean annual Rs,Rn and R_(a) increased,while the contribu-tion of R_(h) to R_(s) decreased with thinning intensity.Thinning significantly decreased winter R,because of the reduction in R_(n) but had no significant effect on Ra.The temperature sensitivity(Q_(10))of R_(h) and R_(a) also increased with thinning intensity,with lower Q_(10) values for R_(h)(2.1-2.6)than for Ra(2.4-2.8).The results revealed the explanatory variables and pathways related to R_(n) and R_(a) dynamics.Thinning increased soil moisture and nitrate nitrogen(NO_(3)^(-)-N),and the enhanced nitrogen and water availability promoted R_(h) and R_(a) by improving fine root biomass and microbial activity.Our results highlight the positive roles of NO_(3)^(-)-N in stimulating R_(s) components following long-term thinning.Therefore,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO_(2) emissions.The increased Q_(10) values of R_(s) components indicate that a large increase in soil CO_(2) emissions would be expected following thinning because of more pronounced climate warming in alpineregions.
基金supported by the National Science Foundation of China(Grant No.41930759)the Gansu Provincial Science and Technology Program(Grant No.22ZD6FA005)+4 种基金the National Science Foundation of China(Grant Nos.41875018 and 41875016)the Science and Technology Research Plan of Gansu Province(Grant Nos.20JR10RA070 and 22JR5RA048)the Chinese Academy of Sciences(CAS)“Light of West China”Program(Grant No.E2290302)the Gansu Provincial Science and Technology Program(Grant No.23JRRA609)the integrated Land Ecosystem-Atmosphere Processes Study(iLEAPS).
文摘Warming-induced carbon loss via ecosystem respiration(R_(e))is probably intensifying in the alpine grassland ecosystem of the Tibetan Plateau owing to more accelerated warming and the higher temperature sensitivity of R_(e)(Q_(10)).However,little is known about the patterns and controlling factors of Q_(10)on the plateau,impeding the comprehension of the intensity of terrestrial carbon-climate feedbacks for these sensitive and vulnerable ecosystems.Here,we synthesized and analyzed multiyear observations from 14 sites to systematically compare the spatiotemporal variations of Q_(10)values in diverse climate zones and ecosystems,and further explore the relationships between Q_(10)and environmental factors.Moreover,structural equation modeling was utilized to identify the direct and indirect factors predicting Q_(10)values during the annual,growing,and non-growing seasons.The results indicated that the estimated Q_(10)values were strongly dependent on temperature,generally,with the average Q_(10)during different time periods increasing with air temperature and soil temperature at different measurement depths(5 cm,10 cm,20 cm).The Q_(10)values differentiated among ecosystems and climatic zones,with warming-induced Q_(10)declines being stronger in colder regions than elsewhere based on spatial patterns.NDVI was the most cardinal factor in predicting annual Q_(10)values,significantly and positively correlated with Q_(10).Soil temperature(Ts)was identified as the other powerful predictor for Q_(10),and the negative Q_(10)-Ts relationship demonstrates a larger terrestrial carbon loss potentiality in colder than in warmer regions in response to global warming.Note that the interpretations of the effect of soil moisture on Q_(10)were complicated,reflected in a significant positive relationship between Q_(10)and soil moisture during the growing season and a strong quadratic correlation between the two during the annual and non-growing season.These findings are conducive to improving our understanding of alpine grassland ecosystem carbon-climate feedbacks under warming climates.
文摘This paper reports on two years of measurement of soil respiration and canopy-root biomass in a Leymus chinensis community in the Xilin River basin of Inner Mongolia. Correlations between components of plant biomass and soil respiration rates were examined. From respiration data based on CO2 uptake by NaOH and corresponding root biomass values for each run of 10 plots, a linear regression of CO2 evolution rates on root dry weights has been achieved for every ten days. By applying the approach of extrapolating the regressive line to zero root biomass, the proportion of the total soil respiration flux that is attributable to live root respiration was estimated to be about 27% on average, ranging from 14% to 39% in the growing season in 1998. There were no evident relations between the total canopy biomass or root biomass and CO2 evolution rates, but a significant exponential relation did exist between tire live-canopy biomass and CO2 evolution rates.
文摘Soil respiration is a vital process in all terrestrial ecosystems,through which the soil releases carbon dioxide(CO_(2))into the atmosphere at an estimated annual rate of 68–101 Pg carbon,making it the second highest terrestrial contributor to carbon fluxes.Since soil respiration consists of autotrophic and heterotrophic constituents,methods for accurately determining the contribution of each constituent to the total soil respiration are critical for understanding their differential responses to environmental factors and aiding the reduction of CO_(2)emissions.Owing to its low cost and simplicity,the root exclusion(RE)technique,combined with manual chamber measurements,is frequently used in field studies of soil respiration partitioning.Nevertheless,RE treatments alter the soil environment,leading to potential bias in respiration measurements.This review aims to elucidate the current understanding of RE,i.e.,trenching(Tr)and deep collar(DC)insertion techniques,by examining soil respiration partitioning studies performed in several ecosystems.Additionally,we discuss methodological considerations when using RE and the combinations of RE with stable isotopic and modeling approaches.Finally,future research directions for improving the Tr and DC insertion methods in RE are suggested.
文摘The impacts of elevated atmospheric CO2 concentrations (500 靘olmol-1and 700 靘olmol-1) on total soil respiration and the contribution of root respiration of Pinus koraiensis seedlings were investigated from May to October in 2003 at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences, Jilin Province, China. After four growing seasons in top-open chambers exposed to elevated CO2, the total soil respiration and roots respiration of Pinus koraiensis seedlings were measured by a LI-6400-09 soil CO2 flux chamber. Three PVC cylinders in each chamber were inserted about 30 cm into the soil in-stantaneously to terminate the supply of current photosynthates from the tree canopy to roots for separating the root respiration from total soil respiration. Soil respirations both inside and outside of the cylinders were measured on June 16, August 20 and October 8, respectively. The results indicated that: there was a marked diurnal change in air temperature and soil temperature at depth of 5 cm on June 16, the maximum of soil temperature at depth of 5 cm lagged behind that of air temperature, no differences in temperature between treatments were found (P>0.05). The total soil respiration and soil respiration with roots severed showed strong diurnal and seasonal patterns. There was marked difference in total soil respiration and soil respiration with roots severed between treatments (P<0.01); Mean total soil respiration and contribution of root under different treatments were 3.26, 4.78 and 1.47 靘olm 2s-1, 11.5%, 43.1% and 27.9% on June 16, August 20 and October 8, respectively.
基金supported by the Knowledge Inno-vation Project of the Chinese Academy of Sciences (KZCX2-YW-416)the National Natural Science Foundation (90411020)
文摘A stdudy was conducted to determine the seasonal changes of soil respiration and the contribution of root respiration to soil respiration in Betula plaophylla forest in Changbai Mountain from May to September in 2004. Results indicated that the total soil respiration, root-severed soil respiration and the root respiration followed a similar seasonal trend, with a high rate in summer due to wet and high temperature and a low rate in spring and autumn due to lower temperature. The mean rates of total soil respiration, root-severed soil respiration and root respiration were 4.44, 2.30 and 2.14 μmol.m^-2.s^-1, respectively during the growing season, and they were all exponentially correlated with temperature. Soil respiration rate had a linear correlation with soil volumetric moisture. The Q10 values for total soil respiration, root-severed soil respiration and root respiration were 2,82, 2.59 and 3. 16, respectively. The contribution rate of root respiration to the total soil respiration was between 29.3% and 58.7% during the growing season, indicating that root is a major component of soil respiration. The annual mean rates of total soil respiration, root-severed soil respiration and root respiration were 1.96, 1.08, and 0.87 μmol.m^-2.s^-1, or 741.73 408.71, and 329.24 g.m^-2.a^-1, respectively. Root respiration contributed 44.4% to the annual total soil respiration. The relationship proposed for soil respiration with soil lemperature was useful for understanding and predicting potential changes in Changbai Mountain B. platyphylla forest ecosystem in response to forest management and climate change.
文摘Mutagens are agents that cause damage to DNA and have the potential to permanently alter (mutate) its sequence, depending on the organism’s ability to repair the damage. UV radiation is a mutagen in cells. This mutagen relates to both yeast cells and human skin cells, since they have similar reactions. UV radiation can cause cell mutations, but also cell death. This is examined with the absence or presence of sunscreen when in contact with cells. Since yeast cells and human cells have almost identical metabolisms, data results of yeast experiments can be associated with real life. Hypothesis for the presence of sunscreen in yeast solutions includes the exposure of yeast cells with or without sunscreen for different time periods in UV radiation. However, the role of sunscreen in yeast cell mutations, in relation to cancer prevention, may not be directly positive. Here, I show that sunscreen has a positive effect on yeast cells and prevents mutations. I found that the respiration rate differs for yeast cells without or without the presence of sunscreen when exposed to radiation. Yeast cells without sunscreen respired faster than those exposed to UV radiation. However, with sunscreen, the rate of CO2 production was higher, with a higher respiration rate. These results may be connected with skin cancer to some extent, promoting or not the use of sunscreen to protect the skin cells from mutating. This experiment may be the base for further experimentation with different yeast cells, providing clearer and more assuring data about the association of sunscreen, yeast cells, and skin cancer. Such experiments may avoid implications with weather conditions, such as slightly different temperatures, sunlight intensity, and clouds, or with the time between the end of the time period of exposure of the yeast cells to UV radiation, and the measurement of CO2 and density, which my experiment had.
基金the National institute for Global Environmental Change (DOENIGEC), Program for Ecosystem Research (DOE-PER Grant D E- FG O Z-9
文摘An open-top chamber experiment was conducted at the University of Michigan Biological Station near Pellston, Michigan, USA, to study the effects of soil fertility and CO2 on leaf, stem and root dark respiration (Rd) of Populus tremuloides. Overall, area-based day-time leaf Rd (Rda) was significantly greater at elevated than at ambient CO2 in high-fertility soil, but not in low-fertility soil. Mass-based leaf Rd (Rdm) was overall greater for high- than for low-fertility soil grown trees at elected, but not at ambient CO2. Nighttime leaf Rd. and Rdm were unthected by soil fertility or CO2, nor was stem Rda, which ranged from 1.0 to 1.4 μmol m-2 s-1 in the spring and 3.5 to 4.5 μmol m-2 s-1 in the summer. Root Rda. was significantly higher in high- than in low-fertility soil, but was unaffected by CO2. Since biomass production of P. tremuloides will be significantly greater at elevated CO2 while specific Rd will either increase or remain unchanged, we predict that carbon loss to the atmosphere through respiration from this ecologically important species would increase at higher CO2. Soil fertility would also interact with elevated CO2 in affecting the carbon flow in the plant-soil-air system.
基金supported by the National Natural Science Foundation of China(3157061731100322)+2 种基金Special Public Sector Research(GYHY20110400904)the Fundamental Research Funds for the Central Universities(NO.YX2011-19TD2011-07)
文摘Partitioning soil respiration into three components is vital to identify CO_2 sink or source and can help us better understand soil carbon dynamics. However, knowledge about the influences of soil depth and the priming effect on soil respiration components under field has been limited. Three components of soil respiration（root respiration, rhizomicrobial respiration and basal respiration） in a plantation in the hilly area of the North China were separated by the 13 C natural abundance method. The results showed that the average proportions of rhizomicrobial respiration, root respiration and basal respiration at the 25-65 cm depths were about 14, 23 and 63 %, respectively. Three components of soil respiration varied with soil depth, and root respiration was the main component of soil respiration in deeper soil. The priming effect was obvious for the deep soil respiration, especially at the 40-50 cm depth. Thus, depth and priming effect should be taken into account to increase the accuracy of estimations of soil carbon flux.
基金Foundation： National Natural Science Foundation of China, No.41071138 National Key Technologies R＆D Program during the 1 lth Five-year Plan of China, No.2006BAJ 10B04 Independent Innovation Project of Institute of Geographic Sciences and Natural Resources Research, CAS, No.200905009
文摘Based on the static opaque chamber method,the respiration rates of soil microbial respiration,soil respiration,and ecosystem respiration were measured through continuous in-situ experiments during rapid growth season in semiarid Leymus chinensis steppe in the Xilin River Basin of Inner Mongolia,China. Soil temperature and moisture were the main factor affecting respiration rates. Soil temperature can explain most CO2 efflux variations （R2=0.376-0.655） excluding data of low soil water conditions. Soil moisture can also effectively explain most of the variations of soil and ecosystem respiration （R2=0.314-0.583）,but it can not explain much of the variation of microbial respiration （R2=0.063）. Low soil water content （≤5%） inhibited CO2 efflux though the soil temperature was high. Rewetting the soil after a long drought resulted in substantial increases in CO2 flux at high temperature. Bi-variable models based on soil temperature at 5 cm depth and soil moisture at 0-10 cm depth can explain about 70% of the variations of CO2 effluxes. The contribution of soil respiration to ecosystem respiration averaged 59.4%,ranging from 47.3% to 72.4%; the contribution of root respiration to soil respiration averaged 20.5%,ranging from 11.7% to 51.7%. The contribution of soil to ecosystem respiration was a little overestimated and root to soil respiration little underestimated because of the increased soil water content that occurred as a result of plant removal.
基金supported by the National Basic Research Program of China (2014CB138803)the National Natural Science Foundation of China (31570451)the Program for Changjiang Scholars and Innovative Research Team in University (IRT1108)
文摘With increasingly intensifying degradation of natural grasslands and rapidly increasing demand of high quality forages, natural grasslands in China have been converted into planted grasslands at an unprecedented rate and the magnitude of the conversion in Inner Mongolia is among the national highest where the areal extent of planted grasslands ranks the second in China. Such land-use changes（i.e., converting natural grasslands into planted grasslands） can significantly affect carbon stocks and carbon emissions in grassland ecosystems. In this study, we analyzed the effects of converting natural grasslands into planted grasslands（including Medicago sativa, Elymus cylindricus, and M. sativa＋E. cylindricus） on ecosystem respiration（F（eco）） in Inner Mongolia of China. Diurnal F（eco） and its components（i.e., total soil respiration（F（ts））, soil heterotrophic respiration（F（sh）） and vegetation autotrophic respiration（F（va））） were measured in 2012（27 July to 5 August） and 2013（18 July to 25 July） in the natural and planted grasslands. Meteorological data, aboveground vegetation data and soil data were simultaneously collected to analyze the relationships between respiration fluxes and environmental factors in those grasslands. In 2012, the daily mean F（eco） in the M. sativa grassland was higher than that in the natural grassland, and the daily mean F（va） was higher in all planted grasslands（i.e., M. sativa, E. cylindricus, and M. sativa＋E. cylindricus） than in the natural grassland. In contrast, the daily mean F（ts） and F（sh） were lower in all planted grasslands than in the natural grassland. In 2013, the daily mean F（eco）, F（ts） and F（va） in all planted grasslands were higher than those in the natural grassland, and the daily mean F（sh） in the M. sativa＋E. cylindricus grassland was higher than that in the natural grassland. The two-year experimental results suggested that the conversion of natural grasslands into planted grasslands can generally increase the F（eco） and the increase in F（eco） is more pronounced when the plantation becomes more mature. The results also indicated that F（sh） contributed more to F（eco） in the natural grassland whereas F（va） contributed more to F（eco） in the planted grasslands. The regression analyses show that climate factors（air temperature and relative humidity） and soil properties（soil organic matter, soil temperature, and soil moisture） strongly affected respiration fluxes in all grasslands. However, our observation period was admittedly too short. To fully understand the effects of such land-use changes（i.e., converting natural grasslands into planted grasslands） on respiration fluxes, longer-term observations are badly needed.
基金This study was supported by grant from the National Natu-ral Science Foundation of China (No. 30271068) the grant of the Knowledge Innovation Program of Chinese Academy of Sciences (KZ
文摘Soil incubation experiments were conducted in lab to delineate the effect of soil temperature and soil water content on soil respirations in broad-leaved/Korean pine forest (mountain dark brown forest soil), dark coniferous forest (mountain brown coniferous forest soil) and erman's birch forest (mountain soddy forest soil) in Changbai Mountain in September 2001. The soil water content was adjusted to five different levels (9%, 21%, 30%, and 43%) by adding certain amount of water into the soil cylinders, and the soil sample was incubated at 0, 5, 15, 25 and 35°C for 24 h. The results indicated that in broad-leaved/Korean pine forest the soil respiration rate was positively correlated to soil temperature from 0 to 35°C. Soil respiration rate increased with increase of soil water content within the limits of 21% to 37%, while it decreased with soil water content when water content was over the range. The result suggested the interactive effects of temperature and water content on soil respiration. There were significant differences in soil respiration among the various forest types. The soil respiration rate was highest in broad-leaved/Korean pine forest, middle in erman's birch forest and the lowest in dark coniferous forest. The optimal soil temperature and soil water content for soil respiration was 35°C and 37% in broad-leaved/Korean pine forest, 25°C and 21% in dark coniferous forest, and 35°C and 37% in erman's birch forest. Because the forests of broad-leaved/Korean pine, dark coniferous and erman's birch are distributed at different altitudes, the soil temperature had 4–5°C variation in different forest types during the same period. Thus, the soil respiration rates measured in brown pine mountain soil were lower than those in dark brown forest and those measured in mountain grass forest soil were higher than those in brown pine mountain soil. Key words Soil temperature - Soil water content - Soil respiration - The typical forest ecosystem in Changbai Mountain CLC number S7118.51 Document code A Foundation item: This study was supported by grant from the National Natural Science Foundation of China (No. 30271068), the grant of the Knowledge Innovation Program of Chinese Academy of Sciences (KZ-CX-SW-01-01B-12) and the grant from Advanced Programs of Institute of Applied Ecology Chinese Academy of Sciences.Biography: WANG Miao (1964-), male, associate professor in Institute of Applied Ecology, Chinese Academy of Science, Shenyang 110016, P. R. China.Responsible editor: Song Funan
文摘Stem respiration is an important part of the activity of a tree and is an important source of CO2 evolution from a forest ecosystem. Presently, no standard methods are available for the accurate estimation of total stem CO2 efflux from a forest. In the current study, a 33-year-old (by the year 2001) larch (Larix gmelini Rupr.) plantation was measured throughout 2001-2002 to analyze its monthly and seasonal patterns of stem respiration. Stem respiration rate was also measured at different heights, at different daily intervals and any variation in the larch plantation was recorded. The relationship between stem temperature, growth status and respiration rate was analyzed. Higher respiration rates were recorded in upper reaches of the larch tree throughout the season and these were affected partially by temperature difference. Midday depression was found in the diurnal changes in stem respiration. In the morning, but not in the afternoon, stem respiration was positively correlated with stem temperature. The reason for this variation may be attributed to water deficit, which was stronger in the afternoon. In the larch plantation, a maximum 7-fold variation in stem respiration was found. The growth status (such as mean growth rate of stem and canopy projection area) instead of stem temperature difference was positively correlated with this large variation. An S-model (sigmoid curve) or Power model shows the greatest regression of the field data. In the courses of seasonal and annual changes of stem respiration, peak values were observed in July of both years, but substantial interannual differences in magnitude were observed. An exponential model can clearly show this regression of the temperature-respiration relationship. In our results, Q(10) values ranged from 2.22 in 2001 to 3.53 in 2002. Therefore, estimation of total stem CO2 efflux only by a constant Q(10) value may give biased results. More parameters of growth status and water status should be considered for more accurate estimation.
基金supported by Key Projects in the National Science & Technology Pillar Program during the EleventhFive-year Plan Period (Nos. 2006BAD03A14-01)Important Science & Technology Specific Projects of Fujian province (2006NZ0001-2)supported by the Key Laboratory of south mountain timber culti-vation, state forestry administration, P. R. China
文摘The soil respiration rates （Rh） in 6-year-old （young）, 17-year-old （middle-age）, 31-year-old （mature） Casuarina equisetifolia coastal plantations were measured using an LICOR-8100 automated soil CO2 flux system from May 2006 to April 2007. Results show that Rh displayed an obvious seasonal pattern across the observed years. The maximum values of Rh occurred at June and July and the minimum at December and January. Soil temperature and soil moisture as well as their interaction had significant effects on the monthly dynamics of Rh. The analysis by one-way ANOVA showed that Rh had a significantly exponential relation （p〈0.05） to soil temperature at soil depth of 5 cm, and had a linear relation （p〈0.05） to soil water content of the upper 20 cm. The result estimated by the two-factor model shows that soil temperature at soil depth of 5 cm and soil moisture at soil depth of 20 cm could explain 68.9%-91.9% of seasonal variations in Rh. The or- der of Rh rates between different stand ages was middle-age plantation〉mature plantation〉young-age plantation. With the increase of growth age of plantation, the Q10 of Rh increased. The contribution of Rh to total soil surface CO2 flux was 71.89%, 71.02% and 73.53% for the young, middle-age and mature plantation, respectively. It was estimated that the annual CO2 fluxes from Rh were 29.07, 38.964 and 30.530 t.ha^-1.a^-1 for the young, middle-age and mature plantation, respectively.
基金Under the auspices of Special Fund for Agro-scientific Research in Public Interest,China(No.201303095-8)National Natural Science Foundation of China(No.31100403,41101207)+1 种基金National Basic Research Program of China(No.2013CB430401)Key Laboratory of Mollisols Agroecology,Northeast Institute of Geography and Agroecology,Chinese Academy of Sciences
文摘To evaluate the diurnal and seasonal variations in soil respiration （Rs） and understand the controlling factors, we measured carbon dioxide （CO2） fluxes and their environmental variables using a LI-6400 soil CO2 flux system at a temperate Leymus chinensis meadow steppe in the western Songnen Plain of China in the growing season （May-October） in 2011 and 2012. The diurnal patterns of soil respiration could be expressed as single peak curves, reaching to the maximum at 11：00-15：00 and falling to the minimum at 21：00-23：00 （or before dawn）. The time-window between 7：00 and 9：00 could be used as the optimal measuring time to represent the daily mean soil CO2 efflux. In the growing season, the daily value of soil CO2 efflux was moderate in late spring （1.06-2.51μnol/（m2.s） in May）, increased sharply and presented a peak in summer （2.95-3.94 μmol/（m2.s） in July）, and then decreased in autumn （0.74-0.97 μmol/（m2.s） in October）. Soil temperature （Ts） exerted dominant control on the diurnal and seasonal variations of soil respiration. The temperature sensitivity of soil respiration （Q10） exhibited a large seasonal variation, ranging from 1.35 to 3.32, and decreased with an increasing soil temperature. Rs gradually increased with increasing soil water content （Ws） and tended to decrease when Ws exceeded the optimum water content （27%） of Rs. The Ts and Ws had a confounding effect on Rs, and the two-variable equations could account for 72% of the variation in soil respiration （p 〈 0.01）.
基金Supported by the Scientific Research Foundation of Nanjing Universityof Information Science and Technology(80124)~~
文摘[Objective]The experiment aimed to study the effects of meteorological factors under different weather conditions on soil respiration. [ Method] The path analysis was used to analyze meteorological factors which influenced soil respiration of wheat field under different weather condition and at jointing stage. [ Result] In sunny day, the correlations between ground temperature at 5 cm, solar radiation, air relative humidity, air temperature and soil respiration were all at significant level while solar radiation and ground temperature at 5 cm were the major factors which influenced soil respiration. In cloudy day, solar radiation was a major factor which influenced soil respiration.[ Conclusion] The soil respiration and surplus path coefficient in sunny day were all higher than these in cloudy day, which demonstrated that except influenced by ground temperature, air temperature, solar radiation and air relative humidity, the soil respiration was also influenced by other factors especially biological factor.
