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Rhizosphere microbes in forests are key elements of the carbon sequestration of terrestrial ecosystems. To date, little is known about how the diversity and species interactions of the active rhizomicrobial community change during soil carbon sequestration and what interactions drive these changes. In this study, we used a combination of DNA and stable isotope method to explore correlations between the composition of microbial communities, N transformation, and the sequestration de novo of carbon in soils around Pinus tabuliformis and Quercus variabilis roots in North China. Rhizosphere soils from degraded lands, primary stage land (tree roots had colonized in degraded soil for 1 year), and nature forest were sampled for analyses. The results showed that microbial communities and newly sequestered soil organic carbon (SOC) contents changed with different tree species, environments, and successive stages. The fungal unweighted and weighted UniFrac distances could better show the different microbial species structures and differences in successive stages. Newly sequestered SOC was positively correlated with the bacterial order Rhizobiales (in P. tabuliformis forests), the fungal order Russulales (in Q. variabilis forests), and δ15N. Consequently, the bacterial order Rhizobiales acted as an important taxa for P. tabuliformis root-driven carbon sequestration, and the fungal order Russulales acted as an important taxa for Q. variabilis root-driven carbon sequestration. The two plant species allocated root exudates to different portion of their root systems, which in turn altered microbial community composition and function. The δ15N of soil organic matter could be an important indicator to estimate root-driven carbon sequestration. [ABSTRACT FROM AUTHOR]

To investigate the impacts of biophysical factors on light response of net ecosystem exchange (NEE), CO2 flux was measured using the eddy covariance technique in a winter wheat field in the North China Plain from 2003 to 2006. A rectangular hyperbolic function was used to describe NEE light response. Maximum photosynthetic capacity (Pmax) was 46.6±4.0 µmol CO2 m−2 s−1 and initial light use efficiency (α) 0.059±0.006 µmol µmol−1 in April−May, two or three times as high as those in March. Stepwise multiple linear regressions showed that Pmax increased with the increase in leaf area index (LAI), canopy conductance (gc) and air temperature (Ta) but declined with increasing vapor pressure deficit (VPD) (P<0.001). The factors influencing Pmax were sorted as LAI, gc, Ta and VPD. α was proportional to ln(LAI), gc, Ta and VPD (P<0.001). The effects of LAI, gc and Ta on α were larger than that of VPD. When Ta>25°C or VPD>1.1−1.3 kPa, NEE residual increased with the increase in Ta and VPD (P<0.001), indicating that temperature and water stress occurred. When gc was more than 14 mm s−1 in March and May and 26 mm s−1 in April, the NEE residuals decline disappeared, or even turned into an increase in gc (P<0.01), implying shifts from stomatal limitation to non-stomatal limitation on NEE. Although the differences between sunny and cloudy sky conditions were unremarkable for light response parameters, simulated net CO2 uptake under the same radiation intensity averaged 18% higher in cloudy days than in sunny days during the year 2003−2006. It is necessary to include these effects in relevant carbon cycle models to improve our estimation of carbon balance at regional and global scales. [ABSTRACT FROM AUTHOR]

CO2 flux was measured continuously using the eddy covariance technique in a wheatmaize rotation system in the North China Plains from October 2002 to October 2006. The annual and seasonal variation of ecosystem respiration and the bio-environmental controls on them were investigated. The results show that ecosystem respiration (Rec) in the cropland increased exponentially with soil temperature at 5 cm depth. The temperature sensitivity coefficient (Q10) for ecosystem respiration varied from 3.5 to 5.4 for wheat and from 2.4 to 4.5 for maize. In the wheat growing season, monthly average R0 (ecosystem respiration at 0°C) increased linearly with soil temperature and logarithmically with leaf area index (LAI). Monthly average Q10 decreased logarithmically with R0. Residual Rec was significantly correlated with LAI. After considering LAI, the modified Q10 model could estimate Rec better than before. The simulation results show that annual ecosystem respiration in the wheat-maize rotation system in the North China Plains was 1327, 1348, 1040 and 1171 gC m-2 yr-1 for the 4 years of the study. As a 4-year average, seasonal mean ecosystem respiration in wheat (2.60 gC m-2 day-1) was much lower than in maize (6.09 gC m-2 day-1). However, integrated ecosystem respiration for the wheat growing season (566 gC m-2) was slightly higher than that for maize (520 gC m-2). These account for 46.4 and 42.6% of the annual values, respectively. [ABSTRACT FROM AUTHOR]

Introduction: Nonalcoholic or metabolism-associated fatty liver disease (NAFLD or MAFLD) and colorectal polyps are chronic conditions strongly linked to lifestyle factors. However, the precise causal link between NAFLD or MAFLD and the development of colorectal polyps is not yet fully understood. This study aimed to evaluate the association between NAFLD or MAFLD and the risk of colorectal polyps based on a meta-analysis and two-sample Mendelian randomization (MR) analyses., Methods: PubMed, Embase, Cochrane Library databases were searched for eligible studies to be included in the meta-analysis. We conducted a thorough search of the PubMed, Embase, and Cochrane Library databases to identify eligible studies prior to 22 March 2024. Subgroup analyses were performed based on sex, age, and geographical region. Causality between NAFLD/MAFLD and colorectal polyps was explored by using two-sample Mendelian randomization (MR) analyses., Results: Based on an analysis of 17 studies encompassed within this meta-analysis, a significant correlation was identified between the presence of NAFLD/MAFLD and elevated incidence of colorectal polyps (NAFLD: OR = 1.57, 95% CI: 1.43-1.73, I 2 = 38%, p = 0.06; MAFLD: OR = 1.67, 95% CI: 1.40-2.00, I 2 = 77%, p = 0.002). However, current evidence does not support a causal relationship between NAFLD/MAFLD and the prevalence of colorectal polyps (OR = 0.9998315, 95% CI: 0.9987566-1.000907, P = 0.7587638)., Conclusion: NAFLD/MAFLD demonstrated a significant positive correlation with an elevated risk of developing colorectal polyps. However, the MR analysis suggested that no causal relationship existed between NAFLD/MAFLD and colorectal polyps. Therefore, further research is required to identify the underlying mechanism of causal link between these diseases., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhai, Xu, Liu and Tong.)

Rhizosphere microbes in forests are key elements of the carbon sequestration of terrestrial ecosystems. To date, little is known about how the diversity and species interactions of the active rhizomicrobial community change during soil carbon sequestration and what interactions drive these changes. In this study, we used a combination of DNA and stable isotope method to explore correlations between the composition of microbial communities, N transformation, and the sequestration de novo of carbon in soils around Pinus tabuliformis and Quercus variabilis roots in North China. Rhizosphere soils from degraded lands, primary stage land (tree roots had colonized in degraded soil for 1 year), and nature forest were sampled for analyses. The results showed that microbial communities and newly sequestered soil organic carbon (SOC) contents changed with different tree species, environments, and successive stages. The fungal unweighted and weighted UniFrac distances could better show the different microbial species structures and differences in successive stages. Newly sequestered SOC was positively correlated with the bacterial order Rhizobiales (in P. tabuliformis forests), the fungal order Russulales (in Q. variabilis forests), and δ 15 N. Consequently, the bacterial order Rhizobiales acted as an important taxa for P. tabuliformis root-driven carbon sequestration, and the fungal order Russulales acted as an important taxa for Q. variabilis root-driven carbon sequestration. The two plant species allocated root exudates to different portion of their root systems, which in turn altered microbial community composition and function. The δ 15 N of soil organic matter could be an important indicator to estimate root-driven carbon sequestration., (Copyright © 2020 Song, Tong, Liu and Li.)

The amount, frequency, and duration of precipitation have important impact on the occurrence and severity of forest fires. To fully understand the effects of precipitation regimes on forest fires, a drought index was developed with number of consecutive dry days (daily precipitation less than 2 mm) and total precipitation, and the relationships of drought and precipitation with fire activities were investigated over two periods (i.e., 1982-1988 and 1989-2008) in five ecoregions of Yunnan Province. The results showed that precipitation regime had a significant relationship with fire activities during the two periods. However, the influence of the drought on fire activities varied by ecoregions, with more impacts in drier ecoregions IV-V and less impacts in the more humid ecoregions I-III. The drought was more closely related to fire activities than precipitation during the two study periods, especially in the drier ecoregions, indicating that the frequency and the duration of precipitation had significant influences on forest fires in the drier areas. Drought appears to offer a better explanation than total precipitation on temporal changes in fire regimes across the five ecoregions in Yunnan. Our findings have significant implications for forecasting the local fire dangers under the future climate change.