Divergent changes in diversity and network complexity across different trophic-level organisms drive soil multifunctionality of fire-impacted subtropical forests

Widespread forest fires pose significant challenges to the diverse communities of soil-dwelling organisms and the multiple ecosystem functions they support. However, whether the biodiversity and interactions of various taxonomic groups respond to fire consistently in terms of direction and extent, and their relative role in regulating post-fire soil functioning, remains largely unexplored. In this study, we investigated whether the diversity and co-occurrence networks of soil organisms across various trophic levels (including bacteria, fungi, protists, and invertebrates) in subtropical forests exhibit consistent responses to fire. Furthermore, we investigated their contribution to regulating soil multifunctionality, which is measured by a range of soil extracellular enzyme activities, available nutrients and reduced potential fungal plant pathogens. Our findings revealed that fire led to a decline in the richness of fungi, protists, and invertebrates, without significantly impacting bacterial richness. Fire also simplified the microbial co-occurrence networks while complexifying the invertebrate networks. Interestingly, soil multifunctionality tended to decrease with the richness of lower-trophic communities (i.e., bacteria), whereas it increased with that of high-trophic communities (i.e., protists and invertebrates). Moreover, fire indirectly influenced soil multifunctionality by altering biodiversity and network complexity, particularly pronounced in high-trophic communities. Overall, our results underscored the divergent vulnerability of biodiversity and networks to fires across taxa groups, highlighting the crucial role of biodiversity and interactions of higher trophic taxa groups in shaping the recovery and functionality of fire-affected soils

Dietary Cadmium Chloride Supplementation Impairs Renal Function and Bone Metabolism of Laying Hens

This study was conducted to evaluate the toxic effects of cadmium (Cd) on the kidney function and bone development in laying hens. A total of 480 Hy-line laying hens aged 38 weeks were randomly allocated into five treatments, each of which included six replicates of 16 birds. The concentrations of Cd in the diets of the five groups were 0.47, 7.58, 15.56, 30.55, and 60.67 mg/kg. Results showed that serum calcium (Ca) levels decreased significantly in the 60.67 mg Cd/kg diet group (p < 0.05). The activities of serum alkaline phosphatase (ALP) and bone ALP (BALP) decreased significantly in the 15.56, 30.55 and 60.67 mg Cd/kg diet groups (p < 0.05). The levels of parathyroid hormone (PTH) increased significantly in the 30.55 and 60.67 mg Cd/kg diet groups, and the estradiol (E2), 1,25-(OH)2-D3 and calcitonin (CT) decreased significantly with the increase of dietary Cd supplementation (p < 0.05). Histological results presented enlargements of renal tubules and tubular fibrosis in the kidney and decreased trabecular bone in the tibia. Tartrate-resistant acidic phosphatase (TRAP) staining results of tibia showed that osteoclast was significantly increased at the relatively high dose of dietary Cd (p < 0.05). In addition, the renal function indicators of blood urea nitrogen (BUN), urea acid (UA), and creatinine were significantly increased in Cd supplemented groups compared with the control group (p < 0.05). Low dose Cd exposure induced antioxidant defenses accompanying the increase in activities of catalase (CAT), glutathione peroxidase (GSH-Px), and the levels of glutathione (GSH) in renal tissue. At the same time, with the increased Cd levels, the activities of CAT, GSH-Px decreased significantly, and the level of malondialdehyde (MDA) increased significantly (p < 0.05). The activities of Na+/K+-ATPase and Ca2+/Mg2+-ATPase decreased significantly in the relatively high levels of dietary Cd (p < 0.05). These results suggest that Cd can damage renal function and induce disorders in bone metabolism of laying hens

An interface for online coupling capillary electrophoresis to dielectric barrier discharge ionization mass spectrometry

The online combination of capillary electrophoresis (CE) with mass spectrometry (MS) has long been desired for the capability of direct and simultaneous separation and detection with high efficiency, accuracy, and throughput. In this work, a novel CE-MS interface was developed, using dielectric barrier discharge ionization (DBDI). The interface employed a spray tip with a coaxial three-layer structure, into which the CE sample solution, the sheath liquid, and the nebulizing gas were introduced. The spray tip was put between the DBDI outlet and the MS inlet, thus the CE sample solution could be blended with the sheath liquid, then nebulized. The nebulized sample could be ionized by DBDI, and finally analyzed by MS. The key parameters of the interface were optimized. Then, proof-of-concept experiments separating and detecting the mixture of metronidazole and acetaminophen solutions were conducted. The results showed high separation efficiency, low time consumption, high reproducibility, and convenience in operation. In addition, the interface exhibited a high tolerance of non-volatile salts and surfactants, which would be widely used in CE analyses. All of these results demonstrated that the newly developed CE-DBDI-MS interface could be successfully used in CE-MS studies, and could be further utilized in multiple areas involving efficient separation and detection

Fire decreases soil respiration and its components in terrestrial ecosystems

The impact of fire on aboveground biomass has significant consequences on soil carbon (C) dynamics, which is essential in predicting the global C budget during the Anthropocene. However, there is considerable spatiotemporal variability in the directions and magnitudes of fire effects on soil respiration, and the drivers associated with these effects are not well understood. Here, we conducted a global meta-analysis of 1327 individual observations from 170 studies to determine the extent to which fire influenced soil total respiration (Rs), heterotrophic respiration (Rh), and autotrophic respiration (Ra). We found fires reduced Rs, Rh, and Ra, with an average effect of -11.0%, -17.5%, and -40.6%, compared to unburnt sites. Specifically, wildfires significantly reduced Rsand Rh (-20.4% and -25.0%, respectively), and prescribed fire significantly decreased Ra (-74.8%). The influences of fire on Rs and its components were moderated by fire severity, season, type, climate zones, and biomes. After several years from the time of the fire, the negative effects of fire on Rs diminished and then recovered to a state not significantly different from unburnt sites; Rh exhibited a similar but decayed temporal response. Similarly, the negative effects on Ra disappeared after 3 years following the latest fire. The magnitude of the effect on Rs was strongly associated with soil temperature, cation exchange capacity, total nitrogen (N) content, and N-acquiring enzyme activity. In contrast, the magnitude of the effect on Rh significantly changed with pH, bulk density, texture, soil C and nutrient contents, and C- acquiring enzyme activity. Our findings advance the understanding of the inhibition and associated mechanisms of fire on Rs and its components, highlighting the need for new research efforts to predict the spatial-temporal shifts in underground C cycling induced by fire.Funding provided by: National Natural Science Foundation of ChinaCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001809Award Number: 41930756Funding provided by: National Natural Science Foundation of ChinaCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001809Award Number: 32201528Funding provided by: Natural Science Foundation of Fujian ProvinceCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100003392Award Number: 2021J05040We extracted data directly from text, tables, figures, and appendices from the primary articles using the Getdata 2.2.5 software. In cases where site coordinates were not provided, we estimated them by referring to site descriptions and cited sources. Additionally, for unavailable climate data, we used a global database (http://www.worldclim.org/) and used spatial coordinates to fill in the missing climate data

Effects of shrub encroachment on vertical changes in soil organic carbon in Mongolian grasslands: using a multi-biomarker approach

In recent decades, ecologists have investigated the effects of shrub encroachment on regional carbon cycling in semi-arid and arid regions. Although differences in carbon sequestration and stocks have been recognized in different soil layers, the vertical changes in soil organic carbon (SOC) at the molecular level following shrub encroachment remain unexplored. In this study, we used biomarkers to assess the impacts of shrub encroachment on SOC composition. We collected soil samples along the 1-m profile within shrub patches and grassy matrix in three typical shrub-encroached grassland (SEG) sites in Inner Mongolia, and quantified the vertical distribution of the biomarkers, including free lipids, bound lipids and lignin-derived phenols. The principal component analysis (PCA) of the biomarker data showed that samples in the grassy matrix had strong positive loadings along the first two components (PCs); in contrast, samples in the upper 50 cm of the shrub patches had negative loadings along the first component (PC1) as well as a narrower range. The acid to aldehyde ratios of the vanillyl and syringyl type monomers increased simultaneously along the 1-m profile in the grassy matrix; however, this trend was not observed in the shrub patches. In addition, the vanillyls to syringyls to cinnamyls ratio was approximately 3:2:1 in the shrub patches and 3:2:1 or 2:2:1 in the grassy matrix. Shrub encroachment altered the vertical patterns in SOC composition, especially in the upper 50 cm, as well as the oxidation status of lignin-derived phenols along the entire 1-m profile. Further, shrub encroachment influenced the soil carbon composition under the shrub canopy as well as in the grassy matrix due to the sprawling canopies and the horizontal extension of the root systems of the encroaching shrubs. These results provided new insights into the vertical patterns of SOC changes after shrub encroachment at the molecular level and have important implications for understanding the mechanisms of soil carbon dynamics with changes in vegetation structure and composition

Soil extracellular enzyme activity and stoichiometry in China's forests

Ecoenzymatic stoichiometry links microbial decomposition with nutrient mineralization and improves our understanding of nutrient cycling in terrestrial ecosystems. Microbial C:N:P acquisition in the topsoil converged at a ratio of 1:1:1 in global ecosystems. However, whether the ratio of microbial acquisition is stable in forest soils, and is applicable among different soil depths remain unknown. Based on large-scale soil sampling in China's forests, we examined the patterns and environmental drivers of the eight most-widely measured enzyme activities and the relevant stoichiometry. We found that the ratio of C:N:P acquisition significantly deviated from 1:1:1. The specific enzyme activities (normalized by SOC) did not change significantly with latitude except those for xylosidase and acid phosphatase. Similarly, only the C:P acquisition ratio increased with latitude. Vertically, the specific activities of C-acquiring enzymes mainly increased, N-acquiring enzymes decreased and P-acquiring enzymes did not change with soil depth. Moreover, all ratios of microbial acquisition decreased, and the percentage of recalcitrant C increased significantly with increasing depth. Our study also showed that temperature and soil C:N ratio were the important factors in explaining the variations in specific enzyme activities and microbial nutrient acquisition, respectively. Our results indicated that no constant microbial C:N:P acquisition ratio can be widely recognized, and that SOC quality changed from labile to recalcitrant with depth. We highlight that depth-dependent enzymatic processes should be considered in future SOC dynamic models. A free Plain Language Summary can be found within the Supporting Information of this article

Shrub-encroachment induced alterations in input chemistry and soil microbial community affect topsoil organic carbon in an Inner Mongolian grassland

Shrub encroachment frequently occurs in arid and semi-arid grasslands worldwide and affects the regional carbon balance. Many previous studies have revealed the effects of shrub encroachment on bulk carbon content of grasslands, but molecular evidence is surprisingly lacking. In this study, we examined the chemical composition of plant tissues and soil organic carbon (SOC), and soil microbial communities to identify the effects of shrub (Caragana microphylla) encroachment on SOC storage in the top layer (0-10 cm) along a gradient of natural shrub cover in the grasslands of Inner Mongolia. We found that SOC in the shrub patches was derived mainly from leaves, whereas SOC in the grassy matrix was composed of a mixture of fresh root- and leaf-derived compounds. Compared with pure grassland, the SOC decreased by 29% in the shrub-encroached grasslands (SEGs), and this decrease was enhanced by increasing shrub cover. We also found that free lipids and lignin-derived phenols increased while the ratios of omega-C-18/aC(18) and suberin/cutin decreased with increasing shrub cover. In addition, the ratios of fungal to bacterial phospholipid fatty acids (PLFAs) and gram-negative to gram-positive bacterial PLFAs decreased with increasing shrub cover. These results indicate that the encroachment of nitrogen-rich legume shrubs can lead to carbon loss by altering the chemical composition of plant inputs as well as the soil microbial community in grassland ecosystems

Soil Fungal Diversity and Functionality Changes Associated with Multispecies Restoration of <i>Pinus massoniana</i> Plantation in Subtropical China

Soil fungi play a critical role in the carbon and nutrient cycling of forest ecosystems. Identifying the composition of soil fungi in response to the broadleaf restoration of Pinus massoniana plantation is essential for exploring the mechanistic linkages between tree species and ecological processes, but remains unexplored. We compared the shifts in soil fungal diversity and guilds by high–throughput sequencing between two P. massoniana plantations at different stand ages, two modes of restoration with broadleaf trees, and a secondary forest in subtropical China. We found that soil fungal taxonomic and functional compositions significantly differed among forests. The highest Chao 1, Shannon, and phylogenetic diversity indices were consistently observed in the two P. massoniana monocultures, followed by the two modes of broadleaf mixing, and the secondary forests. Fungal communities transitioned from Ascomycota-dominated at P. massoniana plantations to Basidiomycota-dominated at other forests in the topsoil. Furthermore, saprotrophs and symbiotrophs were favoured in plantations and secondary forests, respectively. Soil pH exerted the most significant effect on the relative abundance of Ascomycota and Rozellomycota, as well as the saprotrophs. Moreover, the dominant phyla of Ascomycota, Mucoromycota, and Rozellomycota were negatively related to soil microbial biomass nitrogen, ammonium nitrogen, and total nitrogen contents; however, Mortierellomycota benefited from the elevated soil ammonium nitrogen content. On the other hand, soil nitrate nitrogen and available phosphorus contents strongly and negatively influenced the ectomycorrhizal fungi, while the other fungal guilds were mainly affected by soil pH. Our findings guide an evaluation of the consequences of forest restoration and contribute to an improved understanding of the mechanisms behind soil biogeochemical cycling in subtropical forest ecosystems

Estimation of plot-level soil carbon stocks in China's forests using intensive soil sampling

Forest soil is a large carbon (C) pool and plays a pivotal role in the global C cycle. The accurate estimation of soil organic carbon (SOC) stocks in forests is the cornerstone of studying the C budget; however, current assessments of forest SOC stocks are highly uncertain. One of the key reasons for this uncertainty is that most previous studies only used a few soil profiles for their estimation, whereas SOC stocks are highly spatially heterogeneous. To accurately evaluate the plot-level SOC stocks of China's forests, we conducted intensive soil sampling (100 soil cores within a plot) in 33 plots across 11 forest sites from south to north China. The average SOC density (SOCD) of these forest sites was 137.4 +/- 12.1 Mg C ha(-1) (0-100 cm), with significant geographic variations. The highest SOCD (306.8 +/- 7.6 Mg C ha(-1)) was observed in deciduous needleleaf forest (boreal forest) in northeast China, while the lowest one (64.8 +/- 0.9 Mg C ha(-1)) was found in subtropical evergreen broadleaf forest in south China. We also showed that the error of the SOCD estimates obtained from the intensive soil sampling was significantly smaller than that of estimates obtained from the traditional sampling method (5.3 +/- 1.3% vs. 24.2 +/- 5.6%, with a confidence level of 0.95). Our results suggest that intensive sampling can significantly reduce the uncertainty in forest SOC stock estimation by guarding against the effects of spatial heterogeneity, and provide an important methodological reference for accurately evaluating forest SOC stocks and C budgets in other regions

Effects of shrub encroachment on soil organic carbon in global grasslands

This study aimed to evaluate the effect of shrub encroachment on soil organic carbon (SOC) content at broad scales and its controls. We conducted a meta-analysis using paired control data of shrubencroached grassland (SEG) vs. non-SEG collected from 142 studies worldwide. SOC contents (0-50 cm) were altered by shrub encroachment, with changes ranging from -50% to + 300%, with an effect size of 0.15 (p &lt; 0.01). The SOC contents increased in semi-arid and humid regions, and showed a greater rate of increase in grassland encroached by leguminous shrubs than by non-legumes. The SOC content decreased in silty and clay soils but increased in sand, sandy loam and sandy clay loam. The SOC content increment was significantly positively correlated with precipitation and temperature as well as with soil bulk density but significantly negatively correlated with soil total nitrogen. We conclude the main effects of shrub encroachment would be to increase topsoil organic carbon content. As structural equation model revealed, soils properties seem to be the primary factors responsible for the extent of the changes, coarse textured soils having a greater capacity than fine textured soils to increase the SOC content. This increased effect appears to be secondarily enhanced by climate and plant elements.National Basic Research Program of China on Global Change [2014CB954001]; National Natural Science Foundation of China [31330012, 31470525]; Strategic Priority Research Program of the Chinese Academy of Sciences [XDA05050300]SCI(E)[email protected]