Long-term thinning decreases the contribution of heterotrophic respiration to soil respiration in subalpine plantations

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.

Spatiotemporal Variability and Environmental Controls of Temperature Sensitivity of Ecosystem Respiration across the Tibetan Plateau

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.

Moso bamboo expansion decreased soil heterotrophic respiration but increased arbuscular mycorrhizal mycelial respiration in a subtropical broadleaved forest

Moso bamboo(Phyllostachys Pubescens)expansion into adjacent forests has been widely reported to affect plant diversity and its association with mycorrhizal fungi in subtropical China,which will likely have significant impacts on soil respiration.However,there is still limited information on how Moso bamboo expansion changes soil respiration components and their linkage with microbial community composition and activity.Based on a mesh exclusion method,soil respirations derived from roots,arbuscular mycorrhizal(AM)mycelium,and free-living microbes were investigated in a pure Moso bamboo forest(expanded),an adjacent broadleaved forest(nonexpanded),and a mixed bamboo-broadleaved forest(expanding).Our results showed that bamboo expansion decreased the cumulative CO_(2)effluxes from total soil respiration,root respiration and soil heterotrophic respiration(by 19.01%,30.34%,and 29.92%on average),whereas increased those from AM mycelium(by 78.67%in comparison with the broadleaved forests).Bamboo expansion significantly decreased soil organic carbon(C)content,bacterial and fungal abundances,and enzyme activities involved in C,N and P cycling whereas enhanced the interactive relationships among bacterial communities.In contrast,the ingrowth of AM mycelium increased the activities ofβ-glucosidase and N-acetyl-β-glucosaminidase and decreased the interactive relationships among bacterial communities.Changes in soil heterotrophic respiration and AM mycelium respiration had positive correlations with soil enzyme activities and fungal abundances.In summary,our findings suggest that bamboo expansion decreased soil heterotrophic respiration by decreasing soil microbial activity but increased the contribution of AM mycelial respiration to soil C efflux,which may potentially increase soil C loss from AM mycelial pathway.

Response of soil respiration to short-term changes in precipitation and nitrogen addition in a desert steppe

Changes in precipitation and nitrogen(N)addition may significantly affect the processes of soil carbon(C)cycle in terrestrial ecosystems,such as soil respiration.However,relatively few studies have investigated the effects of changes in precipitation and N addition on soil respiration in the upper soil layer in desert steppes.In this study,we conducted a control experiment that involved a field simulation from July 2020 to December 2021 in a desert steppe in Yanchi County,China.Specifically,we measured soil parameters including soil temperature,soil moisture,total nitrogen(TN),soil organic carbon(SOC),soil microbial biomass carbon(SMBC),soil microbial biomass nitrogen(SMBN),and contents of soil microorganisms including bacteria,fungi,actinomyces,and protozoa,and determined the components of soil respiration including soil respiration with litter(RS+L),soil respiration without litter(RS),and litter respiration(RL)under short-term changes in precipitation(control,increased precipitation by 30%,and decreased precipitation by 30%)and N addition(0.0 and 10.0 g/(m^(2)·a))treatments.Our results indicated that short-term changes in precipitation and N addition had substantial positive effects on the contents of TN,SOC,and SMBC,as well as the contents of soil actinomyces and protozoa.In addition,N addition significantly enhanced the rates of RS+L and RS by 4.8%and 8.0%(P<0.05),respectively.The increase in precipitation markedly increased the rates of RS+L and RS by 2.3%(P<0.05)and 5.7%(P<0.001),respectively.The decrease in precipitation significantly increased the rates of RS+L and RS by 12.9%(P<0.05)and 23.4%(P<0.001),respectively.In contrast,short-term changes in precipitation and N addition had no significant effects on RL rate(P>0.05).The mean RL/RS+L value observed under all treatments was 27.63%,which suggested that RL is an important component of soil respiration in the desert steppe ecosystems.The results also showed that short-term changes in precipitation and N addition had significant interactive effects on the rates of RS+L,RS,and RL(P<0.001).In addition,soil temperature was the most important abiotic factor that affected the rates of RS+L,RS,and RL.Results of the correlation analysis demonstrated that the rates of RS+L,RS,and RL were closely related to soil temperature,soil moisture,TN,SOC,and the contents of soil microorganisms,and the structural equation model revealed that SOC and SMBC are the key factors influencing the rates of RS+L,RS,and RL.This study provides further insights into the characteristics of soil C emissions in desert steppe ecosystems in the context of climate change,which can be used as a reference for future related studies.

Transcriptome Analysis Reveals New Insights into the Respiration Metabolism Mechanism of Different Feeding Rations of Sea Cucumber(Apostichopus japonicus)

Sea cucumber(Apostichopus japonicus)is an excellent model for investigating effects of bottom-dwellers on carbon mig-ration and transformation.However,the molecular mechanism of respiratory metabolism process variation caused by feeding rations is poorly understood.In this study,treatment groups set as 1%(about 0.63g),3%,and 7%of total body weight(named F1,F3 and F7 groups respectively).The potential molecular mechanisms behind the functions of respiratory tree and body wall were investigated by RNA-Seq.A total of 52411 expressed genes were identified from 89342 expressed transcripts.The results showed 759,254 and 334 genes were up-regulated,and 334,445 and 992 genes were down-regulated in respiratory tree of F1 vs.F3,F1 vs.F7 and F3 vs.F7,respectively.Meanwhile,2070,1601 and 896 genes were up-regulated,and 1303,1337 and 1144 genes were down-regulated in body wall between F1 vs.F3,F1 vs.F7 and F3 vs.F7,respectively.Differentially expressed genes were enriched in salivary secretion and ECM-receptor interaction pathways in respiratory tree,and in various types of N-glycan biosynthesis,ribosome and sphingolipid metabolism pathways in body wall.These results suggested respiratory tree and body wall were involved in activation of respiratory metabolisms in response to different feeding rations.Our research provided valuable knowledge for physiological differences in res-piratory metabolism.

Accuracy of Mean Value of Central Venous Pressure from Monitor Digital Display: Influence of Amplitude of Central Venous Pressure during Respiration

Background A simple measurement of central venous pressure(CVP)-mean by the digital monitor display has become increasingly popular.However,the agreement between CVP-mean and CVP-end(a standard method of CVP measurement by analyzing the waveform at end-expiration)is not well determined.This study was designed to identify the relationship between CVP-mean and CVP-end in critically ill patients and to introduce a new parameter of CVP amplitude(ΔCVP=CVPmax-CVPmin)during the respiratory period to identify the agreement/disagreement between CVP-mean and CVP-end.Methods In total,291 patients were included in the study.CVP-mean and CVP-end were obtained simultaneously from each patient.CVP measurement difference(|CVP-mean-CVP-end|)was defined as the difference between CVP-mean and CVP-end.TheΔCVP was calculated as the difference between the peak(CVPmax)and the nadir value(CVPmin)during the respiratory cycle,which was automatically recorded on the monitor screen.Subjects with|CVP-mean-CVP-end|≥2 mm Hg were divided into the inconsistent group,while subjects with|CVP-mean-CVP-end|2 mm Hg were divided into the consistent group.ResultsΔCVP was significantly higher in the inconsistent group[7.17(2.77)vs.5.24(2.18),P0.001]than that in the consistent group.There was a significantly positive relationship betweenΔCVP and|CVP-mean-CVP-end|(r=0.283,P 0.0001).Bland-Altman plot showed the bias was-0.61 mm Hg with a wide 95%limit of agreement(-3.34,2.10)of CVP-end and CVP-mean.The area under the receiver operating characteristic curves(AUC)ofΔCVP for predicting|CVP-mean-CVP-end|≥2 mm Hg was 0.709.With a high diagnostic specificity,usingΔCVP3 to detect|CVP-mean-CVP-end|lower than 2mm Hg(consistent measurement)resulted in a sensitivity of 22.37%and a specificity of 93.06%.UsingΔCVP8 to detect|CVP-mean-CVPend|8 mm Hg(inconsistent measurement)resulted in a sensitivity of 31.94%and a specificity of 91.32%.Conclusions CVP-end and CVP-mean have statistical discrepancies in specific clinical scenarios.ΔCVP during the respiratory period is related to the variation of the two CVP methods.A highΔCVP indicates a poor agreement between these two methods,whereas a lowΔCVP indicates a good agreement between these two methods.

Heartbeat and Respiration Rate Prediction Using Combined Photoplethysmography and Ballisto Cardiography

Owing to the recent trends in remote health monitoring,real-time appli-cations for measuring Heartbeat Rate and Respiration Rate(HARR)from video signals are growing rapidly.Photo Plethysmo Graphy(PPG)is a method that is operated by estimating the infinitesimal change in color of the human face,rigid motion of facial skin and head parts,etc.Ballisto Cardiography(BCG)is a non-surgical tool for obtaining a graphical depiction of the human body’s heartbeat by inducing repetitive movements found in the heart pulses.The resilience against motion artifacts induced by luminancefluctuation and the patient’s mobility var-iation is the major difficulty faced while processing the real-time video signals.In this research,a video-based HARR measuring framework is proposed based on combined PPG and BCG.Here,the noise from the input video signals is removed by using an Adaptive Kalmanfilter(AKF).Three different algorithms are used for estimating the HARR from the noise-free input signals.Initially,the noise-free sig-nals are subjected to Modified Adaptive Fourier Decomposition(MAFD)and then to Enhanced Hilbert vibration Decomposition(EHVD)andfinally to Improved Var-iation mode Decomposition(IVMD)for attaining three various results of HARR.The obtained values are compared with each other and found that the EHVD is showing better results when compared with all the other methods.

Supplementation of alanine improves biomass accumulation and lipid production of Chlorella pyrenoidosa by increasing the respiratory and metabolic processes

The function of exogenous alanine(Ala)in regulating biomass accumulation,lipid production,photosynthesis,and respiration in Chlorella pyrenoidosa was studied.Result shows that the supplementation of Ala increased C.pyrenoidosa biomass and lipid production in an 8-d batch culture.The concentration of 10 mmol/L of Ala was optimum and increased the microalgal cell biomass and lipid content by 39.3%and 21.4%,respectively,compared with that in the control(0-mmol/L Ala).Ala supplementation reduced photosynthetic activity while boosting respiratory activity and pyruvate levels,indicating that C.pyrenoidosa used exogenous Ala for biomass accumulation through the respiratory metabolic process.The accelerated respiratory metabolism due to Ala supplementation elevated the substrate pool and improved the lipogenic gene expression,promoting lipid production at last.This study provided a novel method for increasing biomass accumulation and lipid production and elucidated the role of Ala in regulating lipid production.

Effects of dust controls on respirable coal mine dust composition and particle sizes:case studies on auxiliary scrubbers and canopy air curtain

Control of dust in underground coal mines is critical for mitigating both safety and health hazards.For decades,the National Institute of Occupational Safety and Health(NIOSH)has led research to evaluate the effectiveness of various dust control technologies in coal mines.Recent studies have included the evaluation of auxiliary scrubbers to reduce respirable dust downstream of active mining and the use of canopy air curtains(CACs)to reduce respirable dust in key operator positions.While detailed dust characterization was not a focus of such studies,this is a growing area of interest.Using preserved filter samples from three previous NIOSH studies,the current work aims to explore the effect of two different scrubbers(one wet and one dry)and a roof bolter CAC on respirable dust composition and particle size distribution.For this,the preserved filter samples were analyzed by thermogravimetric analysis and/or scanning electron microscopy with energy dispersive X-ray.Results indicate that dust composition was not appreciably affected by either scrubber or the CAC.However,the wet scrubber and CAC appeared to decrease the overall particle size distribution.Such an effect of the dry scrubber was not consistently observed,but this is probably related to the particular sampling location downstream of the scrubber which allowed for significant mixing of the scrubber exhaust and other return air.Aside from the insights gained with respect to the three specific dust control case studies revisited here,this work demonstrates the value of preserved dust samples for follow-up investigation more broadly.

Advancing respirable coal mine dust source apportionment:a preliminary laboratory exploration of optical microscopy as a novel monitoring tool

Exposure to respirable coal mine dust(RCMD)can cause chronic and debilitating lung diseases.Real-time monitoring capabilities are sought which can enable a better understanding of dust components and sources.In many underground mines,RCMD includes three primary components which can be loosely associated with three major dust sources:coal dust from the coal seam itself,silicates from the surrounding rock strata,and carbonates from the inert‘rock dust’products that are applied to mitigate explosion hazards.A monitor which can reliably partition RCMD between these three components could thus allow source apportionment.And tracking silicates,specifically,could be valuable since the most serious health risks are typically associated with this component-particularly if abundant in crystalline silica.Envisioning a monitoring concept based on field microscopy,and following up on prior research using polarized light,the aim of the current study was to build and test a model to classify respirable-sized particles as either coal,silicates,or carbonates.For model development,composite dust samples were generated in the laboratory by successively depositing dust from high-purity materials onto a sticky transparent substrate,and imaging after each deposition event such that the identity of each particle was known a priori.Model testing followed a similar approach,except that real geologic materials were used as the source for each dust component.Results showed that the model had an overall accuracy of 86.5%,indicating that a field-microscopy based moni-tor could support RCMD source apportionment and silicates tracking in some coal mines.

Noninvasive Ventilation Interfaces in the Treatment of Acute Respiratory Insufficiency: A Critical Review

Background: Noninvasive ventilation (NIV) is an important therapeutic modality for the treatment of acute respiratory failure (ARF). In this review, we critically analyze randomized controlled trials on the most used NIV interfaces in the treatments of ARF. Methods: The searches were conducted in the Medline, Lilacs, PubMed, Cochrane, and Pedro databases from June to November 2021. The inclusion criteria were Randomized clinical trials (RCTs) published from 2016 to 2021 in Portuguese, Spanish, or English and involving adults (aged ≥ 18 years). The eligibility criteria for article selection were based on the PICO strategy: Population—Adults with ARF;Intervention—NIV Therapy;Comparison—Conventional oxygen therapy, high-flow nasal cannula (HFNC) oxygen therapy, or NIV;Outcome—improvement in ARF. The search for articles and the implementation of the inclusion criteria were independently conducted by two researchers. Results: Seven scientific articles involving 574 adults with ARF due to various causes, such as chest trauma, decompensated heart failure, coronavirus disease 2019 (COVID-19), and postoperative period, among others, were included. The interfaces cited in the studies included an oronasal mask, nasal mask, full-face mask, and helmet. In addition, some favorable outcomes related to NIV were reported in the studies, such as a reduction in the rate of orotracheal intubation and shorter length of stay in the ICU. Conclusions: The most cited interfaces in the treatment of ARF were the oronasal mask and the helmet.

Correlations Between Plant Biomass and Soil Respiration in a Leymus chinensis Community in the Xilin River Basin of Inner Mongolia

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.

The contribution of root respiration of Pinus koraiensis seedlings to total soil respiration under elevated CO_2 concentrations

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.

Seasonal changes of soil respiration in Betula platyphylla forest in Changbai Mountain, China

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.

Effects of soil temperature and soil water content on soil respiration in three forest types in Changbai Mountain

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

Stem Respiration of a Larch (Larix gmelini) Plantation in Northeast China

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.

Soil heterotrophic respiration in Casuarina equisetifolia plantation at different stand ages

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.

Effects of Enhanced UV-B Radiation on Soil Respiration of Barley Field

[Objective] The aim was to investigate the changing characteristics of soil respiration in clear day with enhanced UV-B radiation and in cloudy day without external UV-B radiation forcing.[Methods] Based on measuring soil respiration rate of barley field at jointing stage in typical clear day and cloudy day by means of Li-8100,the effects of enhanced UV-B radiation by 20% on soil respiration rate were studied. [Results] The results showed that enhanced UV-B radiation inhibited soil respiration of barley field obviously. In clear day,the average soil respiration rate of normal barley field(B) was 1.02 μmol/(m2·s) higher than that of barley field with the enhanced UV-B radiation by 20%(BU) . For cloudy day,the average soil respiration rate of B treatment was 0.71 μmol/(m2·s) lower than BU treatment without external UV-B radiation forcing. In clear day,UV-B radiation rise resulted into the decrease of Q10 value of soil respiration in barley field,but there was an increase in cloudy day without external UV-B radiation forcing,leading to various changes of soil respiration rate. [Conclusions] Supplemental UV-B radiation could inhibit soil respiration rate of barley filed significantly,thus affected the increase of crop yield.

Path Analysis on the Meteorological Factors Impacting Soil Respiration Rate of Wheat Field

[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.

Comparison of Soil Respiration in Two Grass-Dominated Communitiesin the Xil in River Basin: Correlations and Controls

A comparative study of soil respiration was conducted between in a semi-arid steppe community and in a wet meadow community in the Xilin River Basin of Nei Mongol. The seasonal pattern, the climatic controls, and the correlations of soil respiration with plant biomass components, were examined for each community. The main results are reported as follows: (1) The seasonal changes in soil respiration in the two communities had similar dynamic patterns (both being of two peaks), ranging from 312.8 to 1738.9 mg C(.)m(-2).s(-1) and from 354.6 to 2235.6 Mg C.m(-2).s(-1) in the growing season for the steppe plot and the meadow plot respectively. The soil respiration rate of the meadow plot was distinctly higher than that of the steppe plot, with the daily averages being 1349.6 mg C-m(-2).s(-1) and 785.9 mg C-m(-2).s(-1) respectively. (2) The correlation between soil respiration rate and soil moisture was much more significant than with temperature for the steppe community, and being on the contrary for the meadow community, reflecting the different effects of the two climatic factors in different habitats. Based on these regressive relations, the total CO2 efflux rate in the growing season in 2001 was estimated as 142.4 g C/m(2) in the steppe plot, and 236.1 g C/m(2) in the meadow plot. (3) There was no evident relation between the total canopy biomass and CO2 evolution rate, but a significant power function relation between the live canopy biomass and CO2 evolution rate in the meadow plot was detected. In the steppe plot, there existed only a weak relation between soil respiration and either live or total canopy biomass.