Contrasting dynamics and trait controls in first-order root compared with leaf litter decomposition

Decomposition is a key component of the global carbon (C) cycle, yet current ecosystem C models do not adequately represent the contributions of plant roots and their mycorrhizae to this process. The understanding of decomposition dynamics and their control by traits is particularly limited for the most distal first-order roots. Here we followed decomposition of first-order roots and leaf litter from 35 woody plant species differing in mycorrhizal type over 6 years in a Chinese temperate forest. First-order roots decomposed more slowly (k = 0.11 +/- 0.01 years(-1)) than did leaf litter (0.35 +/- 0.02 years(-1)), losing only 35% of initial mass on average after 6 years of exposure in the field. In contrast to leaf litter, nonlignin root C chemistry (nonstructural carbohydrates, polyphenols) accounted for 82% of the large interspecific variation in first-order root decomposition. Leaf litter from ectomycorrhizal (EM) species decomposed more slowly than that from arbuscular mycorrhizal (AM) species, whereas first-order roots of EM species switched, after 2 years, from having slower to faster decomposition compared with those from AM species. The fundamentally different dynamics and control mechanisms of first-order root decomposition compared with those of leaf litter challenge current ecosystem C models, the recently suggested dichotomy between EM and AM plants, and the idea that common traits can predict decomposition across roots and leaves. Aspects of C chemistry unrelated to lignin or nitrogen, and not presently considered in decomposition models, controlled first-order root decomposition; thus, current paradigms of ecosystem C dynamics and model parameterization require revision.Peer reviewe

Biogeographic Distribution Patterns of Bacteria in Typical Chinese Forest Soils

Microbes are widely distributed in soils and play a very important role in nutrient cycling and ecosystem services. To understand the biogeographic distribution of forest soil bacteria, we collected 115 soil samples in typical forest ecosystems across eastern China to investigate their bacterial community compositions using Illumina MiSeq high throughput sequencing based on 16S rRNA. We obtained 4,667,656 sequences totally and more than 70% of these sequences were classified into five dominant groups, i.e. Actinobacteria, Acidobacteria, Alphaproteobacteria, Verrucomicrobia and Planctomycetes (relative abundance > 5%). The bacterial diversity showed a parabola shape along latitude and the maximum diversity appeared at latitudes between 33.50°N and 40°N, an area characterized by warm-temperate zones and moderate temperature, neutral soil pH and high substrate availability (soil C and N) from dominant deciduous broad-leaved forests. Pairwise dissimilarity matrix in bacterial community composition showed that bacterial community structure had regional similarity and the latitude of 30°N could be used as the dividing line between southern and northern forest soils. Soil properties and climate conditions (MAT and MAP) greatly accounted for the differences in the soil bacterial structure. Among all soil parameters determined, soil pH predominantly affected the diversity and composition of the bacterial community, and soil pH = 5 probably could be used as a threshold below which soil bacterial diversity might decline and soil bacterial community structure might change significantly. Moreover, soil exchangeable cations, especially Ca2+ (ECa2+) and some other soil variables were also closely related to bacterial community structure. The selected environmental variables (21.11%) explained more of the bacterial community variation than geographic distance (15.88%), indicating that the edaphic properties and environmental factors played a more important role than geographic dispersal limitation in determining the bacterial community structure in Chinese forest soils

Effect of Lipopolysaccharide (LPS) and Outer Membrane Protein (OMP) Vaccines on Protection of Grass Carp (Ctenopharyngodon idella) against Aeromonas hydrophila

Abstract The gram-negative bacterium, Aeromonas hydrophila, causes high mortality and economic losses to the aquaculture industry. We investigated whether lipopolysaccharide (LPS) or outer membrane proteins (OMP) from A. hydrophila can enhance specific and/or non-specific immunity in grass carp (Ctenopharyngodon idella). Fish were injected intraperitoneally with LPS, OMP, or formalin-killed cells (FKC) from A. hydrophila. The control group was injected with phosphate buffered saline (PBS). All three antigens elicited strong immune responses. Respiratory burst and phagocytic activities in head kidney leukocytes and serum lysozyme activity peaked on day 21 after vaccination. Heavy chain gene transcription of immunoglobulin M and Z in the head kidney in vaccinated fish peaked on day 28. Relative percent survival was 83.3%, 72.2%, and 55.6% in the LPS, OMP, and FKC groups, respectively, but only 10% in control fish. Results suggest that LPS and OMP isolated from A. hydrophila can enhance specific immunity, non-specific immunity, and protection against A. hydrophila in fish. Thus, LPS and OMP could be important antigens for development of vaccines to control diseases caused by A. hydrophila in grass carp and other aquatic animals

Regenerated woody plants influence soil microbial communities in a subtropical forest

10 páginas.- 4 figuras.- 3 tablas.- referencias.- upplementary data to this article can be found online at https://doi. org/10.1016/j.apsoil.2023.104890Forests are critical for supporting multiple ecosystem services such as climate change mitigation. Microbial diversity in soil provides important functions to maintain and regenerate forest ecosystems, and yet a critical knowledge gap remains in identifying the linkage between attributes of regenerated woody plant (RWP) communities and the diversity patterns of soil microbial communities in subtropical plantations. Here, we investigated the changes in soil microbial communities and plant traits in a nine hectare Chinese fir (Cunninghamia lanceolata; CF) plantation to assess how non-planted RWP communities regulate soil bacterial and fungal diversity, and further explore the potential mechanisms that structure their interaction. Our study revealed that soil bacterial richness was positively associated with RWP richness, whereas soil fungal richness was negatively associated with RWP basal area. Meanwhile, RWP richness was positively correlated with ectomycorrhizal (ECM) fungal richness but negatively correlated with the richness of both pathogenic and saprotrophic fungi, suggesting that the RWP-fungal richness relationship was trophic guild-specific. Soil microbial community beta diversity (i.e., dissimilarity in community composition) was strongly coupled with both RWP beta diversity and the heterogeneity of RWP basal area. Our study highlights the importance of community-level RWP plant attributes for the regulation of microbial biodiversity in plantation systems, which should be considered in forest management programs in the future.This work was funded by the National Key Research and Development Program of China (2021YFD2201301 and 2022YFF1303003), the National Natural Science Foundation of China (U22A20612), and the Key Project of Jiangxi Province Natural Science Foundation of China (20224ACB205003).Peer reviewe

The north–south shift of the ridge location of the western Pacific subtropical high and its influence on the July precipitation in the Jianghuai region from 1978 to 2021

The Jianghuai region is the area between the Yangtze River and the Huai River in China and is a densely populated agriculture region therefore, the economics and human activity there are significantly affected by the precipitation changes, particularly during the summer when extreme storms and droughts normally occur. It will be helpful if the summer precipitation changes can be predicted. The monthly ERA5 atmospheric reanalysis data from 1978 to 2021 are used in this study to investigate the relationship between the ridge latitudinal location of the western Pacific subtropical high (WPSH) and the precipitation in July over the Jianghuai region. The results show that the WPSH ridge location has an important impact on the amount and spatial distribution of the precipitation in this region. When the ridge was northward, an anomalous anticyclonic circulation will appear over the western Pacific, leading to the weakening of the summer monsoon and the reduction of moisture transport from the Indian Ocean, therefore decreasing precipitation in the Jianghuai region, while the situation is opposite when the ridge was southward. The Niño 3.4 index in March and the India–Burma trough intensity index in June have significant correlations with the July WPSH ridge location, and both can be used as precursors to predict the WPSH ridge location and, therefore, the precipitation in this region

Microsatellite-Based Analysis of Genetic Diversity and Relationship of Artificial Hybrid Jiyan-1 Puffer and their Parents, Takifugu flavidus and Takifugu rubripes

In this study, the genetic diversity and relationship of artificial hybrid Jiyan-1 puffer and their parents (T. flavidus ♀ and T. rubripes ♂) were evaluated using 15 microsatellite markers. The average number of alleles (Na), observed heterozygosity (Ho), and expected heterozygosity (He) of T. flavidus were higher than the average values of T. rubripes. Jiyan-1 puffer showed a relatively high level of genetic diversity, with an average allele number of 6.467 and mean observed and expected heterozygosity of 0.560 and 0.592, respectively. UPGMA cluster analysis indicated that Jiyan-1 puffer inherited more genetic information from female parents. This study indicates that the microsatellite markers will be useful for investigation of genetic background of puffer fish, as well as better conservation and sustainable utilization of puffer fish in aquaculture

Roots have greater effects on the accumulation of soil microbial residue carbon in microaggregate fractions than leaf litter in a subtropical forest

Microbial residues as the key component of the stable soil organic carbon (SOC) play a critical role in stabilizing SOC, and their accumulation is influenced by plant litter. However, how the accumulation of microbial residues in different aggregate fractions of forest soils responds to changes in the inputs of leaf and root litter remains poorly understood. Here, we test the hypothesis that root exclusion has greater effects on microbial residues than leaf-litter exclusion among soil aggregate fractions based on a litter-input manipulation experiment in a subtropical coniferous forest. The concentrations of bacterial, fungal, and total microbial residues were higher in large macroaggregates (> 2000 μm) but lower in small macroaggregates (250–2000 μm). Root exclusion decreased the concentrations of bacterial, fungal, and total microbial residues in microaggregates (< 250 μm), and leaf-litter exclusion decreased fungal residues in microaggregates. Fungal residues had higher proportions to SOC (20.7–34.9%) than bacterial residues (10.8–18.6%) in soil aggregate fractions, and their proportions were higher in large macroaggregates than other aggregate fractions. Root exclusion reduced the higher proportions of bacterial, fungal, and total microbial residues to SOC in microaggregates (14.5%, 15.7%, and 15.3%, respectively), compared to the reduction observed in large macroaggregates (10.8%, 7.1%, and 8.4%, respectively). And leaf-litter exclusion reduced the proportions of fungal and total microbial residues to SOC in microaggregates. Soil microbial residue-carbon accumulation coefficient was higher in large macroaggregates and lower in small macroaggregates. The coefficient was increased by root exclusion in macroaggregates but decreased in microaggregates, and it was also decreased by leaf-litter exclusion in large macroaggregates and microaggregates. Proportions of fungal residues to SOC were more strongly related to the live microbial biomass and nutrients than those of bacterial residues. Our results suggest that root exclusion exerts stronger effects on soil microbial residues than leaf-litter exclusion but these effects vary among soil aggregate sizes

LSNet: Learned Sampling Network for 3D Object Detection from Point Clouds

The3D object detection of LiDAR point cloud data has generated widespread discussion and implementation in recent years. In this paper, we concentrate on exploring the sampling method of point-based 3D object detection in autonomous driving scenarios, a process which attempts to reduce expenditure by reaching sufficient accuracy using fewer selected points. FPS (farthest point sampling), the most used sampling method, works poorly in small sampling size cases, and, limited by the massive points, some newly proposed sampling methods using deep learning are not suitable for autonomous driving scenarios. To address these issues, we propose the learned sampling network (LSNet), a single-stage 3D object detection network containing an LS module that can sample important points through deep learning. This advanced approach can sample points with a task-specific focus while also being differentiable. Additionally, the LS module is streamlined for computational efficiency and transferability to replace more primitive sampling methods in other point-based networks. To reduce the issue of the high repetition rates of sampled points, a sampling loss algorithm was developed. The LS module was validated with the KITTI dataset and outperformed the other sampling methods, such as FPS and F-FPS (FPS based on feature distance). Finally, LSNet achieves acceptable accuracy with only 128 sampled points and shows promising results when the number of sampled points is small, yielding up to a 60% improvement against competing methods with eight sampled points

Effect of Lipopolysaccharide (LPS) and Outer Membrane Protein (OMP) Vaccines on Protection of Grass Carp (Ctenopharyngodon idella) against Aeromonas hydrophila

The gram-negative bacterium, Aeromonas hydrophila, causes high mortality and economic losses to the aquaculture industry. We investigated whether lipopolysaccharide (LPS) or outer membrane proteins (OMP) from A. hydrophila can enhance specific and/or non-specific immunity in grass carp (Ctenopharyngodon idella). Fish were injected intraperitoneally with LPS, OMP, or formalin-killed cells (FKC) from A. hydrophila. The control group was injected with phosphate buffered saline (PBS). All three antigens elicited strong immune responses. Respiratory burst and phagocytic activities in head kidney leukocytes and serum lysozyme activity peaked on day 21 after vaccination. Heavy chain gene transcription of immunoglobulin M and Z in the head kidney in vaccinated fish peaked on day 28. Relative percent survival was 83.3%, 72.2%, and 55.6% in the LPS, OMP, and FKC groups, respectively, but only 10% in control fish. Results suggest that LPS and OMP isolated from A. hydrophila can enhance specific immunity, non-specific immunity, and protection against A. hydrophila in fish. Thus, LPS and OMP could be important antigens for development of vaccines to control diseases caused by A. hydrophila in grass carp and other aquatic animals

Effects of Litter Input on Temperature Sensitivity of Soil Organic Carbon Mineralization along a Forest Elevation Gradient

The mineralization of soil organic carbon (SOC) is generally stimulated under global warming, known as temperature sensitivity (Q10), which is critical for predicting terrestrial C-climate feedback. However, how Q10 varies in different elevations, particularly with litter input, constraining the establishment of accurate models remains poorly understood. Here, the soil samples of three elevations (750, 950, and 1150 m) were collected from the transition zone of subtropical and warm temperate forests in China for incubation. Soils were incubated with and without 13C-labeled Cunninghamia lanceolata litter at 15 °C and 17.4 °C for 97 days. Incubation process was divided into two stages (0–37 days and 38–97 days) according to the dynamics of CO2 emission. The results showed that Q10 did not change significantly with elevation in the first stage, but Q10 at 950 m was significantly higher than that at 1150 m in the second stage. The variations in Q10 with elevation were regulated by pH in the first stage, while soil C/N was the primary factors that regulated Q10 in the second stage. Q10 showed no response to litter input at 750 m, while it decreased at 950 m in both stages. Following litter input, Q10 at 1150 m increased in the first stage but kept stable in the second stage. The change in Q10 with litter input was mainly affected by the restriction of soil P availability. Overall, our findings emphasized the importance of vertical spatial heterogeneity of Q10 of SOC mineralization in order to improve the prediction accuracy of C dynamics in terrestrial ecosystems