Nitrogen addition changed the relationships of fine root respiration and biomass with key physiological traits in ozone-stressed poplars.

Increasing ozone (O3) and nitrogen (N) addition may have contradictory effects on plant photosynthesis and growth. However, it remains unclear whether these effects on aboveground parts further change the root resource management strategy and the relationships of fine root respiration and biomass with other physiological traits. In this study, an open-top chamber experiment was conducted to investigate the effects of O3 alone and in combination with nitrogen (N) addition on root production and fine root respiration of poplar clone 107 (Populus × euramericana cv. '74/76'). Saplings were grown with (100 kg ha-1 year-1) or without (+0 kg ha-1 year-1) N addition under two O3 regimes (non-filtered ambient air or non-filtered ambient air + 60 ppb of O3). After about two to three months of treatment, elevated O3 significantly decreased fine root biomass and starch content but increased fine root respiration, which occurred in tandem with inhibited leaf light-saturated photosynthetic rate (Asat). Nitrogen addition did not change fine root respiration or biomass, neither did it alter the effect of elevated O3 on the fine root traits. However, N addition weakened the relationships of fine root respiration and biomass with Asat, fine root starch and N concentrations. No significant relationships of fine root biomass and respiration with soil mineralized N were observed under elevated O3 or N addition. These results imply that changed relationships of plant fine root traits under global changes should be considered into earth system process models to project more accurately future carbon cycle.

Interactive effects of ozone exposure and nitrogen addition on the rhizosphere bacterial community of poplar saplings.

It is widely documented that elevated ground-level ozone (O3) has negative effects on tree physiological characteristics, and in return, affects forest ecosystem function. However, the effect may be modified by soil nitrogen (N) availability. Numerous studies have focused on the aboveground part of trees under elevated O3 alone or in combination with soil N; however, little is known about the response of soil bacterial communities. Here, we investigated the effects of O3 (charcoal-filtered air, CF, versus ambient air +40 ppb of O3, E-O3), N addition (0 kg ha-1 yr-1, N0, versus 200 kg ha-1 yr-1, N200), and their combination on rhizosphere soil bacterial communities of hybrid poplar, using an MiSeq targeted amplicon sequencing of the bacterial 16S rRNA gene. E-O3 significantly decreased bacterial abundance, and N200 significantly decreased the α-diversity. The negative impacts of N200 on α-diversity were alleviated by E-O3. Nitrogen and E-O3-N200 combination altered bacterial community composition, with a significant increase in the relative abundance of Proteobacteria and Bacteroidetes and a decrease in the abundance of Firmicutes. From an ecological network analysis, E-O3, alone and in combination with N200, complicated the co-occurrence network of bacterial communities by inducing a microbial survival strategy, shifting the hub species from RB41 to Bacillus and Blastococcus. Conversely, N200 led to simplification and decentralization of the co-occurrence network. These findings demonstrate that the rhizosphere bacterial communities exhibit divergent responses to E-O3 and N200, suggesting the need to consider the stability of the belowground ecosystem to optimize plantation management in response to environmental changes.

Changes in nutrients and decay rate of Ginkgo biloba leaf litter exposed to elevated O3 concentration in urban area.

Ground-level ozone (O3) pollution has been widely concerned in the world, particularly in the cities of Asia, including China. Elevated O3 concentrations have potentially influenced growth and nutrient cycling of trees in urban forest. The decomposition characteristics of urban tree litters under O3 exposure are still poorly known. Ginkgo biloba is commonly planted in the cities of northern China and is one of the main tree species in the urban forest of Shenyang, where concentrations of ground-level O3 are very high in summer. Here, we hypothesized that O3 exposure at high concentrations would alter the decomposition rate of urban tree litter. In open-top chambers (OTCs), 5-year-old G. biloba saplings were planted to investigate the impact of elevated O3 concentration (120 ppb) on changes in nutrient contents and decomposition rate of leaf litters. The results showed that elevated O3 concentration significantly increased K content (6.31 ± 0.29 vs 17.93 ± 0.40, P < 0.01) in leaves of G. biloba, significantly decreased the contents of total phenols (2.82 ± 0.93 vs 1.60 ± 0.44, P < 0.05) and soluble sugars (86.51 ± 19.57 vs 53.76 ± 2.40, P < 0.05), but did not significantly alter the contents of C, N, P, lignin and condensed tannins, compared with that in ambient air. Furthermore, percent mass remaining in litterbags after 150 days under ambient air and elevated O3 concentration was 56.0% and 52.8%, respectively. No significant difference between treatments was observed in mass remaining at any sampling date during decomposition. The losses of the nutrients in leaf litters of G. biloba showed significant seasonal differences regardless of O3 treatment. However, we found that elevated O3 concentration slowed down the leaf litter decomposition only at the early decomposition stage, but slightly accelerated the litter decomposition at the late stage (after 120 days). This study provides our understanding of the ecological processes regulating biogeochemical cycles from deciduous tree species in high-O3 urban area.

[Effects of increased O3 concentration on growth, subcellular structure and reactive oxygen metabolism of turf-type Festuca arundinace]. / è‡­æ°§æµ“åº¦å‡é«˜å¯¹åªç”¨é«˜ç¾ŠèŒ ç”Ÿé•¿ã€äºšç»†èƒžç»“æž„åŠæ´»æ€§æ°§ä»£è°¢çš„å½±å“.

Taking ambient environmental O3(40 nmol·mol-1) as control, the study was conducted to assess the impact of elevated O3(80 and 160 nmol·mol-1) on the growth, subcellular structure and reactive oxygen metabolism of turf-type Festuca arundinace in open top-chambers (OTCs). The results showed that under 14-day fumigation, the height and leaf width of F. arundinace decreased significantly, and the total biomass decreased by 43.7%, and some fully expanded leaves yellowed under 80 nmol·mol-1 O3. Some visible injury symptoms, brown spots and necrosis appeared in the leaves, the total biomass decreased by 46.2%, and plasma membrane became loose from the cell wall and convoluted, chloroplast and mitochondria were damaged under 160 nmol·mol-1 O3. The rate of superoxide anion (O2-·) production, hydrogen peroxide (H2O2) content, malonaldehyde (MDA) content and the activities of antioxidant enzymes were higher under the increasing O3 concentrations (80 and 160 nmol·mol-1) compared with control. Total phenolics and the antioxidant capacity increased at first and then decreased with the rise of O3 concentration. It indicated that O3 has already affected F. arundinace growth and antioxidative metabolism before visible injury symptom appeared. F. arundinace had an adaptive response to elevated O3, but it could not protect itself from excessive O3 or long-term O3 exposure.

[Epidemiological characteristics of malaria in Leshan City, 1950-2015].

OBJECTIVE: To analyze the epidemiological characteristics of malaria in Leshan City, so as to provide the evidence for formulating the strategy and measures for consolidating the achievements of malaria elimination. METHODS: The data of epidemiological characteristics of malaria in Leshan City from 1950 to 2015 were collected and analyzed with the descriptive epidemiology method. RESULTS: There were four larger scale epidemics of malaria in Leshan City from 1950 to 2015. The order of malaria in infectious diseases dropped from the first to the twentieth. The peak season for malaria epidemics ceased. The Plasmodium species, patient age, occupation and sex distribution of malaria were different in the different periods. In November 2016, the whole city achieved the national standard for malaria elimination. CONCLUSIONS: After years of prevention and control, the epidemiological characteristics of malaria have changed significantly in Leshan City, and the effect of anti-malarial measures is significant. In the future, we should strengthen the monitoring, and prevention and control of imported malaria.

[Effects of elevated O3 on leaf litter decomposition and nutrient release of Quercus mongolica in city].

The leaf litters of 10-year-old Quercus mongolica were put in nylon bags and exposed to elevated 03 level (120 nmol . mol-1) with the control of 40 nmol . mol-1 in open top chambers (OTCs) for 150 days to test the effect of high O3 on the litter decomposition. The results showed that no significant difference was observed in residual mass between elevated O3 treatment and the control. Elevated 03 inhibited the release of C and K during the decomposition, the residual rate of K under elevated O3 treatment (23.9%) was significantly higher than that of the control (17.1%) after 150-day decomposition. Compared with the control, N mineralization and lignin degradation in elevated O3 treatment were inhibited during early period of decomposition (0-60 d), but were promoted in later period (90-150 d). The changes of lignin/N showed no significant difference between elevated O3 treatment and the control during the decomposition. Elevated O3 generally promoted the release of P in leaf litter of Q. mongolica during the decomposition. C/P ratio was higher under elevated 03 than that under control. Significant positive correlation was shown between residual dry mass of leaf litters and the residual rate of C, N, K, C/N ratio during decomposition. Elevated 03 might play an important role in the nutrient cycle of forest ecosystem in high-O3 pollution area.

[Changes and significance of inflammatory cytokines in sera of mice chronically infected with larvae of Echinococcus granulosus].

OBJECTIVE: To investigate the levels of cytokines in the sera of mice chronically infected with the larvae of Echinococcus granulosus, and explore the mechanisms of immune regulation against parasite infection. METHODS: The protoscoleces were isolated from the livers and lungs of sheep infected with E. granulosus, and then inoculated intraperitoneally to BALB/c mice (2 000 for each mouse), to establish the mouse model of E. granulosus infection. The mice in the control group were injected intraperitoneally with an equal volume of PBS. The sera of both control and infected mice were collected to test the levels of multiple cytokines by using the Cytometric Bead Array (CBA) 5 months post-infection. RESULTS: In contrast to the control group, the multiple cysts were found in the abdominal cavity, livers and lungs of the infected mice. Moreover, the levels of inflammatory cytokines such as IL-17A, IL-6, IFN-γ, MCP-1, IL-12P70 and TNF-α in the sera of the infected mice were significantly higher than those in the control group (t = 2.713-9.255, all P < 0.05) while the levels of anti-inflammatory cytokine IL-10 were elevated post-infection (t = 3.936, P < 0.001). CONCLUSIONS: Higher inflammatory cytokines in the mice chronically infected with the larvae of E. granulosus, may benefit for the limitation of parasite growth.