Effects of stand ages on soil enzyme activities in Chinese fir plantations and natural secondary forests.

Forest type and stand age are important biological factors affecting soil enzyme activities. However, the changes in soil enzyme activities across stand ages and underlying mechanisms under the two forest restoration strate-gies of plantations and natural secondary forests remain elusive. In this study, we investigated the variations of four soil enzyme activities including cello-biohydrolase (CBH), ß-1,4-glucosidase (ßG), acid phosphatase (AP) and ß-1,4-N-acetylglucosaminidase (NAG), which were closely associated with soil carbon, nitrogen, and phosphorus cycling, across Cunninghamia lanceolata plantations and natural secondary forests (5, 8, 21, 27 and 40 years old). The results showed that soil enzyme activities showed different patterns across different forest types. The acti-vities of AP, ßG and CBH in the C. lanceolata plantations were significantly higher than those in the natural secon-dary forests, and there was no significant difference in the NAG activity. In the plantations, AP activity showed a decreasing tendency with the increasing stand ages, with the AP activity in the 5-year-old plantations significantly higher than other stand ages by more than 62.3%. The activities of NAG and CBH decreased first and then increased, and ßG enzyme activity fluctuated with the increasing stand age. In the natural secondary forests, NAG enzyme activity fluctuated with the increasing stand age, with that in the 8-year-old and 27-year-old stand ages being significantly higher than the other stand ages by more than 14.9%. ßG and CBH enzyme activities increased first and then decreased, and no significant difference was observed in the AP activity. Results of the stepwise regression analyses showed that soil predictors explained more than 34% of the variation in the best-fitting models predicting soil enzyme activities in the C. lanceolata plantations and natural secondary forests. In conclusion, there would be a risk of soil fertility degradation C. lanceolata plantations with the increasing stand age, while natural secondary forests were more conducive to maintaining soil fertility.

Delivery room resuscitation and short-term outcomes of extremely preterm and extremely low birth weight infants: a multicenter survey in North China.

BACKGROUND: Delivery room resuscitation assists preterm infants, especially extremely preterm infants (EPI) and extremely low birth weight infants (ELBWI), in breathing support, while it potentially exerts a negative impact on the lungs and outcomes of preterm infants. This study aimed to assess delivery room resuscitation and discharge outcomes of EPI and ELBWI in China. METHODS: The clinical data of EPI (gestational age [GA] <28 weeks) and ELBWI (birth weight [BW] <1000 g), admitted within 72 h of birth in 33 neonatal intensive care units from five provinces and cities in North China between 2017 and 2018, were analyzed. The primary outcomes were delivery room resuscitation and risk factors for delivery room intubation (DRI). The secondary outcomes were survival rates, incidence of bronchopulmonary dysplasia (BPD), and risk factors for BPD. RESULTS: A cohort of 952 preterm infants were enrolled. The incidence of DRI, chest compressions, and administration of epinephrine was 55.9% (532/952), 12.5% (119/952), and 7.0% (67/952), respectively. Multivariate analysis revealed that the risk factors for DRI were GA <28 weeks (odds ratio [OR], 3.147; 95% confidence interval [CI], 2.082-4.755), BW <1000 g (OR, 2.240; 95% CI, 1.606-3.125), and antepartum infection (OR, 1.429; 95% CI, 1.044-1.956). The survival rate was 65.9% (627/952) and was dependent on GA. The rate of BPD was 29.3% (181/627). Multivariate analysis showed that the risk factors for BPD were male (OR, 1.603; 95% CI, 1.061-2.424), DRI (OR, 2.094; 95% CI, 1.328-3.303), respiratory distress syndrome exposed to ≥2 doses of pulmonary surfactants (PS; OR, 2.700; 95% CI, 1.679-4.343), and mechanical ventilation ≥7 days (OR, 4.358; 95% CI, 2.777-6.837). However, a larger BW (OR, 0.998; 95% CI, 0.996-0.999), antenatal steroid (OR, 0.577; 95% CI, 0.379-0.880), and PS use in the delivery room (OR, 0.273; 95% CI, 0.160-0.467) were preventive factors for BPD (all P < 0.05). CONCLUSION: Improving delivery room resuscitation and management of respiratory complications are imperative during early management of the health of EPI and ELBWI.

[Effects of rainfall reduction on the quantity and spectroscopic characteristics of soil dissolved organic matter in a subtropical natural Castanopsis carlesii forest.] / éš”ç¦»é™é›¨å¯¹äºšçƒ­å¸¦ç±³æ§ å¤©ç„¶æž—åœŸå£¤å¯æº¶æ€§æœ‰æœºè´¨æ•°é‡åŠå ‰è°±å­¦ç‰¹å¾çš„å½±å“.

The alteration of rainfall pattern under the background of global climate change may affect the quantity and quality of soil dissolved organic matter (DOM). To better understand the responses of soil DOM to rainfall reduction in subtropical forests, we conducted a 6-year rainfall reduction experiment. There were three treatments: control (CK), 30% rainfall reduction (-30%), and 60% rainfall reduction (-60%). With ultraviolet-visible, infrared and three-dimensional fluorescence spectroscopy, we investigated the effects of rainfall reduction on the quantity and structure of DOM from different soil layers of a natural Castanopsis carlesii forest in subtropical China. Rainfall significantly reduced the content of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in the 0-10 cm soil layer. Specifically, less decreases of DOC than DON were found under the -30% treatment, while more reduction of DOC than DON for the -60% treatment. Under each treatment, the contents of DOC and DON were significantly higher in the 0-10 cm soil layer than that in the 10-20 cm soil layer. Relatively more microbial metabolite with complex structures, such as aromatic humus and alkanes, contributed to soil DOM from the -30% treatment than that from the -60% treatment. Beyond water availability, microbial activity was a key factor regulating the quantity and structure of soil DOM in response to rainfall reduction.