Different variations in soil CO2, CH4, and N2O fluxes and their responses to edaphic factors along a boreal secondary forest successional trajectory.

Forest succession is an important process regulating the carbon and nitrogen budgets in forest ecosystems. However, little is known about how and extent by which vegetation succession predictably affects soil CO2, CH4, and N2O fluxes, especially in boreal forest. Here, a field study was conducted along a secondary forest succession trajectory from Betula platyphylla forest (early stage), then Betula platyphylla-Larix gmelinii forest (intermediate stage), to Larix gmelinii forest (late stage) to explore the effects of forest succession on soil greenhouse gas fluxes and related soil environmental factors in Northeast China. The results showed significant differences in soil greenhouse gas fluxes during the forest succession. During the study period, the average soil CO2 flux was greatest at mid-successional stage (444.72 mg m-2 h-1), followed by the late (341.81 mg m-2 h-1) and the early-successional (347.12 mg m-2 h-1) stages. The average soil CH4 flux increased significantly during succession, ranging from -0.062 to -0.036 mg m-2 h-1. The average soil N2O flux was measured as 17.95 µg m-2 h-1 at intermediate successional stage, significantly lower than that at late (20.71 µg m-2 h-1) and early-successional (20.85 µg m-2 h-1) stages. During forest succession, soil greenhouse gas fluxes showed significant correlations with soil and environmental factors at both seasonal and successional time scales. The seasonal variations of soil GHG fluxes were mainly influenced by soil temperature and water content. Meanwhile, soil MBN and soil NO3--N content were also important factors for soil N2O fluxes. Structural equation modelling showed that forest succession affected soil CO2 fluxes by changing soil temperature and microbial biomass carbon, affected soil CH4 fluxes mainly by changing soil water content and soil pH value, and affected soil N2O fluxes mainly by changing soil temperature, microbial biomass nitrogen, and soil NO3--N content. Our study suggests that forest succession mainly alters soil nutrient and soil environment/chemical properties affecting soil CO2 and N2O fluxes and soil CH4 fluxes, respectively, in the secondary forest succession process.

Understory species composition mediates soil greenhouse gas fluxes by affecting bacterial community diversity in boreal forests.

Introduction: Plant species composition in forest ecosystems can alter soil greenhouse gas (GHG) budgets by affecting soil properties and microbial communities. However, little attention has been paid to the forest types characterized by understory vegetation, especially in boreal forests where understory species contribute significantly to carbon and nitrogen cycling. Method: In the present study, soil GHG fluxes, soil properties and bacterial community, and soil environmental conditions were investigated among three types of larch forest [Rhododendron simsii-Larix gmelinii forest (RL), Ledum palustre-Larix gmelinii forest (LL), and Sphagnum-Bryum-Ledum palustre-Larix gmelinii forest (SLL)] in the typical boreal region of northeast China to explore whether the forest types characterized by different understory species can affect soil GHG fluxes. Results: The results showed that differences in understory species significantly affected soil GHG fluxes, properties, and bacterial composition among types of larch forest. Soil CO2 and N2O fluxes were significantly higher in LL (347.12 mg m-2 h-1 and 20.71 µg m-2 h-1) and RL (335.54 mg m-2 h-1 and 20.73 µg m-2 h-1) than that in SLL (295.58 mg m-2 h-1 and 17.65 µg m-2 h-1), while lower soil CH4 uptake (-21.07 µg m-2 h-1) were found in SLL than in RL (-35.21 µg m-2 h-1) and LL (-35.85 µg m-2 h-1). No significant differences between LL and RL were found in soil CO2, CH4, and N2O fluxes. Soil bacterial composition was mainly dominated by Proteobacteria, Actinobacteria, Acidobacteria, and Chloroflexi among the three types of larch forest, while their abundances differed significantly. Soil environmental variables, soil properties, bacterial composition, and their interactions significantly affected the variations in GHG fluxes with understory species. Specifically, structural equation modeling suggested that soil bacterial composition and temperature had direct close links with variations in soil GHG fluxes among types of larch forest. Moreover, soil NO3 --N and NH4 + - N content also affected soil CO2, CH4, and N2O fluxes indirectly, via their effects on soil bacterial composition. Discussion: Our study highlights the importance of understory species in regulating soil GHG fluxes in boreal forests, which furthers our understanding of the role of boreal forests in sustainable development and climate change mitigation.

Follow-Up Study of Electrocardiographic Indices in 252 Children with Ventricular Septal Defect after Minimally Invasive Transthoracic Closure.

OBJECTIVE: The aim of this study was to explore the efficacy and safety of minimally invasive transthoracic closure (MITC) in treating ventricular septal defect (VSD). METHODS: A total of 252 children with VSD were investigated between August 2013 and March 2015. Their electrocardiographic indices were monitored at different time points (before surgery [T0], immediately after surgery [T1], and 3 days/7 days/1 month/3 months/6 months after surgery [T2-6]) and followed up every year. Related adverse events also were recorded. RESULTS: All children with VSD successfully underwent MITC. The average follow-up time was 5 years, during which no changes in the heart rate or corrected QT interval were found. The PR and QRS intervals were prolonged in the early postoperative period (T3); the SV1+RV5 amplitude decreased significantly at T6, and the left axis deviation significantly recovered at T6 (P < 0.05). A total of 32 patients developed arrhythmia within 3 days after surgery; however, no severe arrhythmia, including ventricular tachycardia, ventricular fibrillation, second-and third-degree atrioventricular block, complete left or right bundle branch block, and delayed arrhythmia, occurred during the follow-up period. Binary multivariate logistic regression revealed that the longer the surgery time and the larger the VSD diameter, the higher the risk of arrhythmia. CONCLUSIONS: The incidence of long-term arrhythmia after MITC is low, and the outcomes are good.

Analysis of the therapeutic effect of transesophageal echocardiography-guided percutaneous device closure of atrial septal defects via the right internal jugular vein in children.

BACKGROUND: Traditional X-ray-guided transcatheter closure of atrial septal defects (ASDs) via the right femoral vein carries a risk of radiation damage, which is greatly exacerbated by age and vascular conditions. Transesophageal echocardiography (TEE) guidance for the closure procedure not only broadens the indications of interventional therapy for ASDs but also avoids radiation exposure. PURPOSE: To assess the value of TEE-guided ASD device closure via the right internal jugular vein (RIJV) in children. METHODS: Nineteen pediatric patients with secondary ASD underwent TEE-guided ASD device closure via the RIJV from July 22, 2015 to July 19, 2017. After the RIJV was successfully accessed, one Fustar curve-adjustable delivery sheath was inserted. The implant depth was adjusted, and the tip of the sheath was curved to facilitate passage through the ASD for the delivery and release of the occluder. TEE was used to guide the entire procedure. RESULTS: In all 19 patients, the ASDs were successfully closed and the occluder was confirmed to have a stable position and good shape, with no residual shunt. During the follow-up period (2 months to 2 years), no pericardial effusion, thrombosis, tachyarrhythmia, atrioventricular block, or other complications were observed. CONCLUSIONS: An adjustable delivery sheath can be used to treat ASD via the RIJV. This procedure has varied indications, and its advantages include a short operation path, procedural accuracy, minimal trauma, and quick recovery, especially for young patients with large ASDs and cases in which a femoral vein approach is difficult. The procedure has great clinical significance and merits attention.

[Effect of bronchoalveolar lavage on the heart rhythm and conduction of the children with severe pneumonia].

OBJECTIVE: To observe the effect of bronchoalveolar lavage on the heart rhythm and conduction of children with severe pneumonia through monitoring the electrocardiogram change of different step of the bronchoalveolar lavage, for proving the safety of the operation of bronchoalveolar lavage from the perspective of cardiac electrophysiology. METHOD: From July 2011 to March 2012, 30 patients who were hospitalized in pneumology department of Dalian Children's Hospital and met the inclusion criteria and therapeutic indications of bronchoalveolar lavage were chosen. They were 3 to 12 years old, the average age was 5.3 years, including 17 boys and 13 girls, the ratio of boys and girls is 1.3: 1. Continuous sampling the electrocardiogram before and during the process including anesthesia, entering into glottis, lavage, aspiration, and revive, and recording the heart rate, rhythm amplitude and width of P wave, the PR interval, the form and width of QRS complex were also measured. The recorded data were analyzed and statistical analysis to reflect the change of the cardiac electrophysiology. RESULT: The incidence of heart rate increase was 100.0%, 26 (86.7%) patients began to emerge after anesthesia, the rest of the patients also developed heart rate increase after the start of bronchoscopic operation. All patients had sinus tachycardia, and were most obvious in the progress of lavage and revive. In the process of entering into glottis, lavage, aspiration, 13 (43.3%) patients had arrhythmia episodes. Types of arrhythmia included sinus bradycardia, atrioventricular block and premature beat. Incidences of intraoperative arrhythmia compared with the pre- and post-operation were all statistically significantly different (P = 0.00). The most common arrhythmia were premature beat, in 17 of the 30 cases there were premature beat including 9 cases with atrial premature beats and 8 cases ventricular premature contraction. Two patients had III° atrioventricular block accompanied by serious sinus bradycardia. All kinds of arrhythmias except sinus tachycardia disappeared after the operation was ended. Five patients (16.7%) had PR interval prolongation. Five patients (16.7%) had incomplete right bundle branch block (IRBBB) . Incidences of IRBBB compared with the pre-operation and post-operation were all not significantly different [13.3% (n = 4) vs. 0(n = 0) and 3.3% (n = 1), all P > 0.05]. Different operating progress made no significant difference in the measurement value of electrocardiogram[13.3% (n = 4) vs. 0(n = 0) and 3.3% (n = 1), all P > 0.05], but showed the most notable effect on heart rate. CONCLUSION: Bronchoalveolar lavage can influence the heart rhythm and conduction, but most of the influence with pathological significance are transient. Cardiac electrophysiological changes were the most obvious in endotracheal operation with the risk of malignant arrhythmia but the risk is low, the bronchoalveolar lavage technique is safe. The contingency plans for dealing with all kinds of adverse reactions must be ready before the operations of bronchoalveolar lavage. During the procedure, the patient's ECG changes should be closely monitored to reduce the incidence of adverse reactions.