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• The priming effect was strengthened by low nitrogen deposition whereas inhibited by high nitrogen deposition, with a threshold of 50 kg ha−1 yr−1 in temperate forests. • No nitrogen deposition effect on the priming effect was found in subtropical forests. • The alterations in priming effect under N deposition were separately controlled by recalcitrant organic carbon content and the ratio of fungal to bacterial PLFA in temperate and subtropical forests. • A stronger role of fungi in priming soil organic carbon decomposition was revealed in subtropical forests. The priming effect (PE) of soil organic carbon (SOC) decomposition has been widely demonstrated to be affected by elevated nitrogen (N) deposition, yet the response of the PE to N deposition in diverse climatic regions remains elusive. This study aimed at exploring the effects of N deposition on the PE and their controlling factors in temperate and subtropical forest ecosystems. We conducted an incubation experiment with temperate and subtropical forest soils that had been experimentally exposed to varying levels of N deposition. A global meta -analysis of the responses of the PE to N deposition in forest ecosystems was also conducted. We found that the response of the PE to increasing N deposition depended on the climatic region. In temperate forests, the PE was strengthened by low N deposition whereas inhibited by high N deposition, with an approximate threshold of 50 kg N ha−1 yr−1. Contrastingly, no pronounced impact was observed in subtropical forests regardless of N levels. These findings generally align with our meta -analysis of global forest studies, except for low N treatment in temperate forests. In N-limited temperate forests, the alterations in PE under N deposition were primarily controlled by soil recalcitrant organic carbon content. Conversely, in P-limited subtropical forests, the lack of N impacts on PE was attributed to the persistent ratio of fungal to bacterial PLFA. Correspondingly, the microbial mechanisms underlying the process of priming also varied in diverse climatic regions, particularly emphasizing the stronger role of fungi in subtropical forests. These results highlight the noteworthy alteration of SOC dynamics in temperate forests under increasing N deposition, and suggest that previous findings might have overestimated the effect of N deposition on the PE in subtropical forests. [ABSTRACT FROM AUTHOR]

Abstract Labile organic C inputs from litter decomposition and root turnover may stimulate soil organic carbon (SOC) decomposition by a priming effect that strongly influences SOC dynamics. The direction and magnitude of this priming effect depends on the type and pattern of N and C addition. However, in which manner the type and pattern of N and C addition affect priming effect remains poorly understood. Thus, we conducted 90-day incubation to evaluate the effects of single and repeated addition of 13C-labeled glucose on SOC decomposition to soils collected from a long-term simulated N experiment with inorganic or organic N addition as the rate of 100 kg N hm−2 yr−1 as solution form. Respired CO 2 and its δ13C value were measured to calculate the added glucose and native SOC decomposition, and consequently quantify primed C, and net C balance between primed SOC and retained glucose-C. We revealed for the first time that long-term N addition significantly decreased the cumulative primed C by an average of 23.0%, but this decrease was greater under organic N (29.7%) than under inorganic N (16.3%). Therefore, the suppression effects of atmospheric N deposition on primed C may be underestimated by solely adding inorganic N. The amount of cumulative primed C induced by single glucose addition was 2.92 times as high as that induced by repeated glucose addition. This finding suggests that the single addition with a high amount of labile organic C may overestimate primed C that naturally occurs in the field. A combined effect of glucose addition patterns and N addition on primed C was also observed. After the 90-day incubation, the amount of added glucose-C that remained in soils was substantially higher than the SOC loss due to positive priming effect, resulting in a net C increase. Taken together all data, we conclude that the repeated addition of labile organic C to soils under increasing atmospheric N deposition can increase SOC sequestration and stocks despite the positive priming effects in temperate forests. Highlights • Effects of glucose addition pattern and N type on SOC turnover were assessed in a temperate forest. • Organic N addition caused greater amount of decreased cumulative primed C than inorganic N. • Glucose single-addition induced greater primed C than repeated-addition. • Adding glucose resulted in a net SOC increase despite positive PE over 90-day incubation. [ABSTRACT FROM AUTHOR]

The response of soil organic carbon (SOC) decomposition to global warming is a potentially major source of uncertainty in climate prediction. However, the magnitude and direction of SOC cycle feedbacks under climate warming remain uncertain because of the knowledge gap about the global‐scale spatial pattern and temperature sensitivity (Q10) mechanism of SOC decomposition.Here, we collected data of Q10 and corresponding soil variables from 81 peer‐reviewed papers using laboratory incubation to explore how Q10 varied among different ecosystems at the global scale and whether labile and recalcitrant SOC pools had equal Q10 values.Q10 with a global average of 2.41 substantially varied among different ecosystems, ranging from the highest in cropland soils (2.76) and the lowest in wetland soils (1.84). Hump‐shaped correlations of Q10 values with the maximum at SOC = 190 g/kg and the minimum at clay = 37% were observed. However, the main influencing factors of Q10 differed among various ecosystems. Q10 values showed a clear decrease with increasing incubation temperature but no significant decrease above 25°C. In general, labile SOC was less sensitive than recalcitrant SOC to warming. Structural equation model analyses showed that total N and SOC accounted for 53% and 46%, respectively, of the variation in Q10 of labile SOC and recalcitrant SOC. This finding suggested that Q10 values of labile and recalcitrant SOC pools had different controlling factors.Our findings highlighted the importance of Q10's variations in ecosystem types and the response of recalcitrant SOC to warming in predicting the soil C cycling and its feedback to climate change. Therefore, ecosystem type and difference in Q10 of labile and recalcitrant SOC should be considered to precisely predict the soil C dynamics under global warming. A plain language summary is available for this article. Plain Language Summary [ABSTRACT FROM AUTHOR]

Knowledge on temperature sensitivity ( Q 10 ) of soil microbial respiration is crucial to improving the accuracy in predicting soil organic carbon (C) dynamics in climate–C models. However, the responses of soil microbial respiration and its Q 10 to nitrogen (N) deposition, particularly different N types, remain unclear. Therefore, we incubated surface soils collected from a temperate forest receiving simulated N deposition under 15 °C and 25 °C for 150 days to examine the effects of different types of N deposition on soil microbial respiration and its Q 10 and reveal their underlying mechanisms. A mixture of inorganic and organic N had the highest suppression on soil microbial respiration, followed by organic N and inorganic N. This suggested that the suppression effect of atmospheric N deposition on microbial respiration was underestimated by previous studies based on single inorganic N. Q 10 values in all soils ranged from 1.96 to 2.76 with a mean of 2.41 at the end of incubation. Inorganic N significantly increased the averaged Q 10 values, suggesting that inorganic N caused soil microbial respiration to become more sensitive to climate warming than organic N. Across the incubation period, Q 10 values exhibited substantial temporal variation, which depended on the N type. Soil microbial respiration was negatively controlled by NO 3 − -N and bacteria:fungi and gram-positive:gram-negative bacteria ratios. However, Q 10 was positively controlled by soil NH 4 + -N. Our results highlighted the effects of inorganic and organic N deposition on microbial respiration and its potential mechanisms and implied the necessity of considering the N type when predicting soil C cycling and dynamics in increasing N deposition scenario. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the temperature sensitivity (Q10) of soil organic C (SOC) decomposition is critical to quantifying the climate–carbon cycle feedback and predicting the response of ecosystems to climate change. However, the driving factors of the spatial variation in Q10 at a continental scale are fully unidentified. In this study, we conducted a novel incubation experiment with periodically varying temperature based on the mean annual temperature of the soil origin sites. A total of 140 soil samples were collected from 22 sites along a 3,800 km long north–south transect of forests in China, and the Q10 of soil microbial respiration and corresponding environmental variables were measured. Results showed that changes in the Q10 values were nonlinear with latitude, particularly showing low Q10 values in subtropical forests and high Q10 values in temperate forests. The soil C:N ratio was positively related to the Q10 values, and coniferous forest soils with low SOC quality had higher Q10 values than broadleaved forest soils with high SOC quality, which supported the “C quality temperature” hypothesis. Out of the spatial variations in Q10 across all ecosystems, gram‐negative bacteria exhibited the most importance in regulating the variation in Q10 and contributed 25.1%, followed by the C:N ratio (C quality), fungi, and the fungi:bacteria ratio. However, the dominant factors that regulate the regional variations in Q10 differed among the tropical, subtropical, and temperate forest ecosystems. Overall, our findings highlight the importance of C quality and microbial controls over Q10 value in China's forest ecosystems. Meanwhile, C dynamics in temperate forests under a global warming scenario can be robustly predicted through the incorporation of substrate quality and microbial property into models. [ABSTRACT FROM AUTHOR]

Aims: Changing quantity and quality of plant C input to soils under global change influences soil C cycling in terrestrial ecosystems. However, how soil CO emission responds to changes in C input remains poorly understood. Methods: A detritus input and removal experiment was conducted in a subtropical forest ( Cunninghamia lanceolata) to investigate how aboveground and belowground litters affect soil respiration (R). In this experiment, four treatments with three replicates were included, as follows: control (CK), litter removal (NL), root trenching (NR), and no C-input (i.e. litter removal combined with root trenching, NI). R was measured for 4 years from 2011 to 2014. Results: The mean annual CO effluxes in the NL, NR, and NI plots were lower (23.4%, 24.9%, and 38.8%, respectively) than those in the CK plots, suggesting that decreasing C input significantly decreased R. Soil heterotrophic respiration (soil organic matter decomposed by microorganisms) accounted for 52.1% of R, and aboveground recent litter decomposition and belowground autotrophic respiration (live roots and associated microorganism) contributed to 23.7% and 24.2% of R, respectively. R was significantly and positively correlated with soil temperature, but negatively correlated with volumetric soil moisture. The variation in R was more explained by soil temperature than soil moisture, and the responses of R to soil temperature and moisture were altered by C input manipulation. Annual R rate was strongly and negatively related to the Gram-positive bacteria concentration and the ratio of Gram-positive to -negative bacteria. Conclusion: This study highlighted that aboveground recent leaf litter and belowground live roots and associated microbes had similar contributions to R, and soil temperature and Gram-positive bacteria were the dominant factors controlling R in a subtropical forest. [ABSTRACT FROM AUTHOR]

Increasing nitrogen (N) deposition may alter soil organic carbon (SOC) decomposition, thereby strongly affecting SOC storage in terrestrial ecosystems. Its specific influence may depend on the different types of N deposition and soil nematodes. However, little is known about how N deposition and soil nematodes affect the SOC cycle process. To address this issue, we evaluated the effects of different types of N deposition on SOC decomposition under the conditions of applying nematocide or not in a temperate forest. Soils collected from the simulated N deposition forest for 5 years were incubated in the presence and absence of soil nematocide at 15 °C for 150 days. N deposition suppressed soil C cycle processes, such as SOC decomposition and soil enzyme activities, and caused the accumulation of labile SOC, which depended on N types. A mixture of inorganic and organic N (MN) deposition had the highest suppression of SOC decomposition at 31.5%, followed by organic N (ON) deposition (24.4%) and inorganic N (IN) deposition (19.8%), thereby suggesting that inhibition effects of N deposition on SOC decomposition based on a single IN or ON source are underestimated. Nematocide application stimulated SOC decomposition, with the highest in MN (19.5%), followed by IN (13.5%), ON (11.2%), and control treatment (4.6%). The stimulation effect of SOC decomposition by soil nematode exclusion also depended on N types. N deposition and soil nematode exclusion had no interactive effect on SOC decomposition. These results imply that atmospheric N deposition favors the increase of C stocks in soil by reducing the SOC loss, and that N types should be considered during assessment of N deposition effects on soil C cycle processes. [ABSTRACT FROM AUTHOR]

Understanding the response of heterotrophic (Rh) and autotrophic (Ra) components of soil respiration (Rs) to fertilization is important to evaluate the effects of management practices on soil carbon cycling in plantation forest ecosystems. Therefore, we investigated Ra and Rh using a trenching method in a young Cunninghamia lanceolata plantation, subjected to N and P fertilization in subtropical China. Soil CO 2 efflux was measured from December 2013 to November 2015. Mean annual Rs, Ra, and Rh rates decreased on average by 18.6%, 23.6%, and 17.1% after fertilization. The contribution of Rh to Rs ranged from 70.9% to 76.7%. This contribution was greater in P-fertilized plots, suggesting that fertilization changed the contribution of Rh and Ra to Rs. The reduced rate of Rh induced by fertilization contributed on average 66.9% to the decrease in Rs rate. This contribution for Rh was higher in NP-fertilized plots than in other plots Based on a bivariate model, 51.2%–69.3% and 53.6%–66.7% of the variations in Rs and Rh among different treatments were explained by soil temperature and moisture. However, temperature sensitivity of Rs and Rh were not affected by fertilization. Ra and Rh were positively related to fine root biomass. Rh was also positively related to soil organic C, dissolved organic C, and microbial biomass C, but negatively related to soil mineral N content. Our results highlight the importance of fertilization on soil CO 2 efflux and its significance to the estimation of forest C sink potential. [ABSTRACT FROM AUTHOR]

The availabilities of carbon (C) and nitrogen (N) in soil play an important role in soil carbon dioxide (CO2) emission. However, the variation in the soil respiration (Rs) and response of microbial community to the combined changes in belowground C and N inputs in forest ecosystems are not yet fully understood. Stem girdling and N addition were performed in this study to evaluate the effects of C supply and N availability on Rs and soil microbial community in a subtropical forest. The trees were girdled on 1 July 2012. Rs was monitored from July 2012 to November 2013, and soil microbial community composition was also examined by phospholipid fatty acids (PLFAs) 1 year after girdling. Results showed that Rs decreased by 40.5% with girdling alone, but N addition only did not change Rs. Interestingly, Rs decreased by 62.7% under the girdling with N addition treatment. The reducing effect of girdling and N addition on Rs differed between dormant and growing seasons. Girdling alone reduced Rs by 33.9% in the dormant season and 54.8% in the growing season compared with the control. By contrast, girdling with N addition decreased Rs by 59.5% in the dormant season and 65.4% in the growing season. Girdling and N addition significantly decreased the total and bacterial PLFAs. Moreover, the effect of N addition was greater than girdling. Both girdling and N addition treatments separated the microbial groups on the basis of the first principal component through principal component analysis compared with control. This indicated that girdling and N addition changed the soil microbial community composition. However, the effect of girdling with N addition treatment separated the microbial groups on the basis of the second principal component compared to N addition treatment, which suggested N addition altered the effect of girdling on soil microbial community composition. These results suggest that the increase in soil N availability by N deposition alters the effect of belowground C allocation on the decomposition of soil organic matter by altering the composition of the soil microbial community. [ABSTRACT FROM AUTHOR]

Increasing rainfall and longer drought conditions lead to frequent changes in soil moisture that affect soil organic carbon (SOC) mineralization. However, how soil moisture affects response of SOC mineralization to litter addition in forest ecosystems remains unexplored. We added C-labeled litter to subtropical forest soils with three mass water contents (L, 21%; M, 33%; H, 45%). Carbon dioxide production was monitored, and the composition of soil microbial communities was determined by phospholipid fatty acid (PLFA). When no litter was added, SOC mineralization was greater in the M-treated soil. Litter addition promoted SOC mineralization, but this promotion was altered by soil moisture and litter type. Priming effects induced by P. massoniana leaf litter in the M-moistened soil were significantly ( P < 0.05) higher than those in other treatments. Litter-derived C was approximately 55% incorporated into 18:1ω9c and 16:0 PLFAs, and this proportion was not significantly affected by soil moisture. Soil moisture affected the distribution of litter-C in i15:0, i17:0, and cy19:0 individual PLFAs. The primed C evolution was significantly related to the ratio of Gram-positive to Gram-negative bacteria. These results suggest that changes in soil moisture could affect SOC mineralization in forest ecosystems. [ABSTRACT FROM AUTHOR]

Highlights: [•] Contributions of aboveground litter and roots to total soil CO2 efflux were similar. [•] Litter addition and root trenching reduced effect of soil moisture on respiration. [•] C input manipulation altered the composition of soil microbial community. [•] Root inputs exerted more impact on the soil microbial community than litter inputs. [Copyright &y& Elsevier]

Abstract: A hypothesis that when subject to biaxial stress, the strengthening effects of arbitrarily oriented stiffener can be approximated by those of regularly oriented stiffener is proved through several simulations and comparisons. It is also found that in an arbitrarily stiffened plate with multiple stiffeners, the orientation of the stiffeners does not apparently affect the plate's strength limit. Based on this find, any arbitrarily stiffened plate can be simplified as regularly stiffened plate, therefore can be analyzed through simplified semi-analytical models during buckling strength analysis. The proved hypothesis can also be explained from an existing analytical model for the arbitrarily oriented stiffener. Engineering simulation software ANSYS is used for modeling and analysis involved in this study. [Copyright &y& Elsevier]

Litter decomposition is a major fundamental ecological process that regulates nutrient cycling, thereby affecting net ecosystem carbon (C) storage as well as primary productivity in forest ecosystems. Litter decomposes in its home environment faster than in any other environment. However, evidence for this phenomenon, which is called the home-field advantage (HFA), has not been universal. We provide the first HFA quantification of litter decomposition and nutrient release through meta-analysis of published data in global forest ecosystems. Litter mass loss was 4.2 % faster on average, whereas nitrogen (N) release was 1.7 % lower at the home environment than in another environment. However, no HFA of phosphorus (P) release was observed. Broadleaf litter (4.4 %) had a higher litter mass loss HFA than coniferous litter (1.0 %). The positive HFA of N release was found in the coniferous litter. Mass loss HFA was significantly and negatively correlated with the initial lignin:N litter ratio. The litter decomposition and N release HFAs were obtained when mesh size ranged from 0.15 mm to 2.0 mm. The HFA of litter decomposition increased with decomposition duration during the early decomposition stage. The HFA of N release was well correlated with mass loss, and the greatest HFA was at mass loss less than 20 %. Our results suggest that the litter decomposition and N release HFAs are widespread in forest ecosystems. Furthermore, soil mesofauna is significantly involved in the HFA of litter decomposition. [ABSTRACT FROM AUTHOR]

Abstract: Potential changes in the quality and quantity of C inputs in soil during environmental changes may affect soil CO2 efflux in forest ecosystems. Therefore, a field debris exclusion experiment and a laboratory debris addition experiment were conducted to assess the response of soil CO2 efflux to C input manipulation. Our experiments were the first to be conducted in a subtropical Chinese fir (Cunninghamia lanceolata) plantation. The field debris exclusion experiment included the following treatments: leaf litter exclusion (NL), leaf litter and root exclusion (NLR), and control (CT). In the laboratory experiment, leaf litter and fine and coarse roots were added to soils collected from the same site and incubated for 100days at 15.0°C using the isotopic partitioning approach to determine the priming effect on soil C. The field-experimental results showed that soil CO2 efflux decreased significantly by 22.9% and 49.1% in the NL and NLR plots, respectively, compared with the CT plots. However, debris exclusion did not affect the diurnal and seasonal patterns of soil CO2 efflux. The contributions of leaf litter and roots to total soil CO2 efflux were 22.9% and 26.2%, respectively, which were positively related to soil temperature and moisture. In the laboratory experiment, the cumulative amount of soil CO2 efflux increased 1.25, 0.51, and 0.43 times in the soils with leaf litter, fine root, and coarse root additions, respectively, compared with the control soil (without debris addition) at the end of the incubation period. The amount of CO2 derived from leaf litter, fine root, and coarse root additions accounted for 44.0%, 31.1%, and 27.9% of the total amount of soil CO2 efflux, respectively. During the experimental period, the priming effect induced by fast-decomposing leaf litter (25.9%) was significantly higher than the priming effect induced by slow-decomposing fine roots (3.8%) and coarse roots (2.9%). The priming effect was negatively correlated with the initial lignin content and the lignin:N ratios of the added debris. The similar contributions of leaf litter and roots to soil CO2 efflux from the field experiment and the greater contributions of the priming of leaf litters to the fluxes from the laboratory experiment suggest that root inputs are more important than litter inputs in regulating soil C storage in Chinese fir forests. [Copyright &y& Elsevier]

Abstract: In this paper, strengthening effects of stiffeners on regular and arbitrarily stiffened plates are discussed in terms of the ultimate strength limit (USL) obtained through full nonlinear transient analysis. This study starts from the investigation of strengthening effects of regular stiffened plates which are subjected to uniaxial stress and then arbitrarily stiffened plates that are subjected to biaxial stress. The optimal height, number, and arrangement of the stiffener that provide the best strengthening effect are revealed and it is also found that the strengthening effects of an arbitrarily oriented stiffener (or oblique stiffener) can be decoupled to two perpendicular regular stiffeners which are located in appropriate positions. Nonlinear buckling analyses were performed on the arbitrarily stiffened plates with one and two arbitrarily oriented stiffeners to verify this finding. The outcome of this paper can be further extended and applied to develop simplified semi-analytical models for buckling strength analysis of constructional plates. [Copyright &y& Elsevier]

Abstract: Stumps are an important component of coarse woody debris in intensively managed forest ecosystems. However, the effect of stumps on soil biological properties is poorly understood. Therefore, the present work investigated soil microbial biomass C, soil respiration, potentially mineralizable N, and enzyme activities related to nutrient cycling (invertase, urease and acid phosphatase) in both bulk and stump soils with four different stump “ages” (stumps 5, 11, 20 and 27 years after tree cutting) in Chinese fir (Cunninghamia lanceolata Hook.) plantation ecosystems. The presence of stumps significantly enhanced invertase and acid phosphatase activities, but reduced soil microbial biomass C and urease activity. However, the effect of stump presence on soil respiration and potentially mineralizable N had an inverse pattern. Additionally, the effect of stump presence on soil biological properties depended upon stump age. Soil respiration and invertase activity were highly and positively related to stump presence, but negatively related to stump age and soil pH. On the other hand, soil microbial biomass C and urease activity showed inverse results. Acid phosphatase activity was highly and positively related to soil total P and organic C, but negatively related to Olsen-P. Potentially mineralizable N was negatively related to NO3-N content and stump age. Using variation partitioning, stumps and soil chemical variables together explained 88.3% of the total variance in soil biological properties. When either stumps or soil chemical variables was adjusted, soil chemical properties and stumps explained 30.8% and 13.7% of the total variance, respectively. These results suggest that soil chemical properties should be considered when assessing the effect of stumps on soil biological properties. [Copyright &y& Elsevier]

Abstract: Labile soil organic matter (SOM) can sensitively respond to changes in land use and management practices, and has been suggested as an early and sensitive indicator of SOM. However, knowledge of effects of forest vegetation type on labile SOM is still scarce, particularly in subtropical regions. Soil microbial biomass C and N, water-soluble soil organic C and N, and light SOM fraction in four subtropical forests were studied in subtropical China. Forest vegetation type significantly affected labile SOM. Secondary broadleaved forest (SBF) had the highest soil microbial biomass, basal respiration and water-soluble SOM, and the pure Cunninghamia lanceolata plantation (PC) the lowest. Soil microbial biomass C and N and respiration were on average 100%, 104% and 75%, respectively higher in the SBF than in the PC. The influence of vegetation on water-soluble SOM was generally larger in the 0–10cm soil layer than in the 10–20cm. Cold- and hot-water-soluble organic C and N were on average 33–70% higher in the SBF than in the PC. Cold- and hot-soluble soil organic C concentrations in the coniferous-broadleaved mixed plantations were on average 38.1 and 25.0% higher than in the pure coniferous plantation, and cold- and hot-soluble soil total N were 51.4 and 14.1% higher, respectively. Therefore, introducing native broadleaved trees into pure coniferous plantations increased water-soluble SOM. The light SOM fraction (free and occluded) in the 0–10cm soil layer, which ranged from 11.7 to 29.2gkg−1 dry weight of soil, was strongly affected by vegetation. The light fraction soil organic C, expressed as percent of total soil organic C, ranged from 18.3% in the mixed plantations of C. lanceolata and Kalopanax septemlobus to 26.3% in the SBF. In addition, there were strong correlations among soil organic C and labile fractions, suggesting that they were in close association and partly represented similar C pools in soils. Our results indicated that hot-water-soluble method could be a suitable measure for labile SOM in subtropical forest soils. [Copyright &y& Elsevier]

• Precipitation pulse promotes summer soil CO 2 emission in the rooted soil. • Precipitation pulse does not affect soil CO 2 emission in the rootless soil. • Increased soil CO 2 emission caused by water pulse is originated from root respiration. • AMF rather than fine root regulates the water pulse effect on soil CO 2 emission. Drought and extreme precipitation are projected to occur more frequently as a consequence of climate change, with uncertain implications for soil CO 2 emission. Although studies have revealed the response patterns of soil CO 2 emission to precipitation pulse, the effects of forest plant roots on this relationship after drought are still poorly understood. Here, a field experiment was performed to examine the differences in soil CO 2 emission and microbial community between rootless and rooted soils, pretreated with three drought intensities (control, moderate, and severe), and rewetted with different water additions (0, 5, 10, and 20 mm) in a temperate forest. Compared with control soils, whether the water was added or not, severe drought suppressed soil CO 2 emission for both root-excluded and -included soils. Regardless of drought intensities, significantly positive effects (19.4–44.9%) of precipitation pulse on soil CO 2 emission were only detected in the root-included soils. Both the contribution of root-derived CO 2 to the stimulated soil CO 2 emission and biomass of soil arbuscular mycorrhizal fungi (AMF) substantially increased with elevated precipitation levels. The enhanced soil CO 2 emission following precipitation pulse is primarily due to the increase in root-derived CO 2 in the rooted soils, likely resulting from the enhanced biomass of soil AMF. This study provides empirical evidence on the primacy of AMF in root-derived CO 2 and thus the response of soil CO 2 emission to precipitation pulse in forest ecosystems. [ABSTRACT FROM AUTHOR]

Immune stimulators are essential to the development of the aquaculture industry. Cinnamaldehyde (CA) and Bacillus spp. are promising immunostimulatory feed additives, as demonstrated by their beneficial effects in several fish species. This study investigated the effects of dietary CA and Bacillus subtilis either alone or in combination on the growth, digestive enzyme activity, and non-specific immunity of tongue sole, Cynoglossus semilaevis. A total of 240 C. semilaevis (188 ± 5 g) were randomly assigned to four dietary treatments. Diets containing no additives (the control group, D), 0.1 g/100 g CA (D cin), 107 CFU/g B. subtilis (D Bac), and CA combined with B. subtilis (D cin+Bac) were used to feed fish for 60 days. The results revealed significant improvements in the weight gain, specific growth rate, feed conversion ratio, and protein efficiency in the fish fed diets containing either CA or B. subtilis, and there were more significant improvements in the group with the combined supplementation (D cin+Bac) compared with the control group. Fish fed diets with CA or CA combined with B. subtilis had higher intestinal proteinase, amylase, and lipase activities than the control fish. Dietary CA and B. subtilis singularly or in combination improved the antioxidant capacity and the immune status by stimulating SOD, CAT, and T-AOC activities and GSH-Px levels, by reducing malondialdehyde (MDA) content, and by increasing lysozyme activity in the serum, liver, mid kidney, and spleen. The results of the two-way analysis of variance revealed the synergistic effects of CA and B. subtilis in improving feed conversion ratio, protease activities in the foregut and midgut, and part of the antioxidant parameters. In addition, significant shifts in the overall intestinal microbial community and diversity were analyzed using high-throughput sequencing of the V3/V4 region of the 16S rRNA gene. The results showed that both dietary supplementation of CA alone or in combination with B. subtilis increased the abundance of the probiotic bacterial genera Bacillus , Lactobacillus , and Bifidobacterium. In conclusion, dietary supplementation of cinnamaldehyde and B. subtilis both solely and in combination are beneficial for improving the growth performance, digestive ability, non-specific immunity, and intestinal microbiota community of the tongue sole, Cynoglossus semilaevis. • Dietary cinnamaldehyde and B. subtilis are beneficial for the growth and health of tongue sole. • Cinnamaldehyde + B. subtilis is more effective than their single supplementation in growth and health promotion. • Cinnamaldehyde and B. subtilis have synergistic effects in improving feed utilization and antioxidant status. [ABSTRACT FROM AUTHOR]

A novel halophilic bacterium capable of heterotrophic nitrification–aerobic denitrification was isolated from the polyethylene fiber of a recirculating aquaculture system and identified Vibrio parahaemolyticus HA2. In this study, the degradation rate of ammonia nitrogen, nitric nitrogen and nitrite nitrogen were 99.06%, 97.35% and 34.91% respectively, and the pH increases furtherly proved existing denitrification during the growth of strain HA2. Genome sequencing showed that the ammonia monooxygenase (AMO), periplasmic nitrate reductase (NAP), nitrite reductase (NIR), nitric oxide reductase (NOR), hydroxylamine oxidase (HAO) and nitrous oxide reductase (N 2 OR) of strain HA2 were associated with the progress of nitrification and denitrification. Utilization of nitrite and nitrate as well as existence of NAP gene further proved aerobic denitrification ability of strain HA2. The aim is indicating great potential of strain HA2 for future full-scale applications in aquaculture • The study on the denitrification of aerobic denitrifying bacteria in different nitrogen sources. • The functional genes of nitrification AMO and HAO were found. • The functional genes of denitrification NAP, NIR, NOR and N2OR were found. [ABSTRACT FROM AUTHOR]

• Root exclusion had higher effects on microbial residues than leaf-litter exclusion. • Fungal residues had larger responses to litter exclusion than bacterial residues. • Higher effects of litter exclusion on microbial residues were in microaggregates than large macroaggregate. • Proportions of fungal residues to SOC were more strongly related to live microbial biomass and nutrients than bacterial residues. • Changes in soil microbial residue-carbon accumulation coefficient caused by litter exclusion differently responded in aggregates. 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. [ABSTRACT FROM AUTHOR]

Home-field advantage (HFA) predicts that litter decomposes faster under its derived plant species. Growing evidence suggests that HFA depends on litter chemical traits and the microbiome's composition, but whether and how their interactions influence HFA effects has rarely been explored. Here, we conducted a reciprocal field transplantation experiment in a temperate forest to examine the effects of litter quality and microbial community composition on decomposition rates. We collected leaf litter from four dominant tree species (Pinus koraiensis, Tilla amurensis, Fraxinus mandshurica, and Acer mono) and utilized two mesh sizes (i.e., 0.5-μm and 35-μm) to manipulate the composition of decomposer communities (i.e., small-sized bacteria only or bacteria + fungi). We assessed the effects of HFA and the ability of decomposers to decay a wide range of litter, i.e., the functional breadth (FB). We found that HFA was stronger for recalcitrant litter in the fine-mesh litterbags. Low litter phosphorus (P) and nitrogen (N) content, explained the positive HFA effects when only small-sized bacteria were present during litter decomposition, but not when both bacteria and fungi were present. Soil parameters such as potassium content and dissolved organic carbon also significantly affected decomposer communities and contributed to the variability in HFA effects. Finally, the FB negatively correlated with HFA in coarse- and fine-mesh litterbags and accounted for 46 and 54% of the observed variation in HFA effects, respectively. Our results highlight that the interactive relationships between litter quality, soil properties, and the microbiome's composition, are central in understanding the functional abilities of microbes during litter decomposition, and suggest a tradeoff between the microbiome's capacity to degrade all litter efficiently and the specialization of decomposers toward their own litter. This further underscores the independent role of decomposers communities in litter decomposition rates, which should be considered when predicting biogeochemical cycling in forest ecosystems. [Display omitted] • Effects of litter and soil traits on HFA depend on the decomposer's communities. • High fertility soil decrease the FB of bacteria and fungi. • Microbial communities exhibit a trade-off between generalization and specialization. • FB negatively related with HFA and explained about half of the variation of HFA. [ABSTRACT FROM AUTHOR]

The LES and nutrient resorption are thought to jointly modulate leaf litter traits, including the litter decomposition, but it is unknown how the two factors affect the temperature sensitivity of litter decomposition (Q10). The Q10 of litter decomposition was evaluated for 15 co-occurring subtropical woody species under laboratory conditions. The LES of these species, as well as species-specific N (NRE) and P resorption efficiency (PRE) during leaf senescence, were also determined. Results showed that the Q10 values were significantly correlated to LES, with litters from resource-conservative species having higher Q10 values than those from resource-acquisitive species. Among the parameters characterizing LES, leaf N concentration, C:N ratio, and lignin:N ratio were correlated to Q10, whereas leaf P and lignin concentrations, specific leaf area, and C:P ratio showed no relationships. The LES was correlated to litter C:N and lignin:N ratios, and, in turn, litter C:N and lignin:N ratios were correlated to Q10. This result suggested that LES affects litter quality and thus the Q10 of litter decomposition. However, NRE and PRE were not correlated to Q10. In addition, the LES effects on litter quality and the Q10 of decomposition did not depend on nutrient resorption, as indicated by the lack of correlation between LES and NRE or PRE. Our results reveal an association between plant functional features and forest C dynamics in a warmer future. [ABSTRACT FROM AUTHOR]

Background and aims: Atmospheric nitrogen (N) deposition alters the priming effect (PE), which is defined as the change in native soil organic carbon (SOC) decomposition by exogenous C inputs. However, how the priming intensity varies under chemically heterogeneous N deposition, particularly with increasing labile C input, remains unclear. Methods: We collected soils from a temperate forest in northeastern China that had received simulated organic and/or inorganic N deposition for 6 years. The soils were incubated with or without three levels of 13C-labelled glucose solution for 152 days. CO2 emission and its 13C value were continuously measured to calculate the PE. Results: Enhanced SOC decomposition (i.e., a positive PE) was observed after glucose addition, regardless of the N deposition form. The PE intensity increased with the increase in the glucose addition level. However, organic N decreased the PE by 12.3-23.2%. The SOC-derived microbial biomass was 16.2-34.3% lower in organic N-treated soil, indicating that preferential utilization of exogenous labile C by microorganisms was responsible for the decrease in PE. The PE inhibition by organic N increased nonlinearly as a function of glucose level. Furthermore, the net annual change in SOC as a balance between the replenishment of added glucose-C and primed C was larger in organic N-treated soil due to a decrease in soil microbial metabolic quotient. Conclusions: In this study, we found that organic N deposition inhibited the PE, and the inhibition effect was intensified with increasing C inputs, favouring SOC sequestration. [ABSTRACT FROM AUTHOR]

Living roots and their rhizodeposits can accelerate or decelerate the decomposition of soil organic matter which refers to the rhizosphere priming effect (RPE). However, whereas plant traits are thought to be key factors controlling the RPE, little is known about how root traits representative of plant biomass allocation, morphology, architecture, or physiology influence the magnitude of the RPE. Using a natural abundance 13C tracer method allowing partitioning of native soil organic carbon (SOC) decomposition and plant rhizosphere respiration, we studied here the effects of eight C3 tree species featuring contrasting functional traits on C4 soil respiration over a 204‐day period in a microcosm experiment. All tree species enhanced the rate of SOC decomposition, by 82% on average, but the strength of the rhizosphere priming significantly differed among species. Mean diameter of first‐order roots and root exudate‐derived respiration were positively correlated with the RPE, together explaining a large part of observed variation in the RPE (R2 = 0.72), whereas root branching density was negatively associated with the RPE. Path analyses further suggested that mean diameter of first‐order roots was the main driver of the RPE owing to its positive direct effect on the RPE and its indirect effects via root exudate‐derived respiration and root branching density. Our study demonstrates that the magnitude of the RPE is regulated by complementary aspects of root morphology, architecture and physiology, implying that comprehensive approaches are needed to reveal the multiple mechanisms driving plant effects on the RPE. Overall, our results emphasize the relevance of integrating root traits in biogeochemical cycling models to improve model performance for predicting soil C dynamics. [ABSTRACT FROM AUTHOR]

Background: Plants can directly affect litter decomposition by producing litter materials of different qualities. However, whether living plants have indirect effects on litter decomposition by affecting changes in forest microenvironments is presently unclear in plantation forests. Methods: We addressed this issue by studying the decomposition of the leaf litter and fine roots of Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.], a timber species widely planted in China, in 113 non-neighboring quadrats of varying basal area of the dominant plant species (i.e., Chinese fir) and distinct basal areas and species richness of regenerated woody plants (i.e., species other than Chinese fir) in a subtropical Chinese fir forest. Results: Our results showed that fine roots decomposed significantly more rapidly than leaf litter possibly because fine roots were easier access to mineralized nutrients and microbes compared with leaf litter. Further analyses showed that leaf litter and fine root decomposition rates were significantly controlled by the plant community attributes. The decomposition of both leaf litter and fine roots was mainly controlled by woody species regenerated during stand development rather than by Chinese fir. Specifically, leaf litter and fine root decomposition rates decreased with increasing basal area of regenerated woody plants, possibly due to nutrient competition and/or reduced photodegradation. Conclusions: This study provides empirical evidence that woody species regenerated during stand development play a certain role in determining litter decomposition rates through plant-soil interactions in Chinese fir plantations. Regenerated woody plants should be considered in future studies on soil carbon and nutrient cycling in plantation forest. [ABSTRACT FROM AUTHOR]

A series of trials were designed to evaluate hydrolysates from waste streams of squid and scallop processing centers for the use in practical shrimp feeds. Towards this goal, three growth trials and a consumption trial were conducted to evaluate the use of dry hydrolysate from squid and scallop waste as specialty ingredients in commercial type feed formulations for Pacific white shrimp Litopenaeus vannamei . In the three six-week growth trials, the basal diet (35% crude protein, 8% lipid) consisted primarily of soybean meal (SBM), corn protein concentrate, corn starch, and whole wheat. In Trial 1, the basal diet was supplemented with 3%, 6%, and 9% from squid hydrolysate (Squ) or scallop hydrolysate (Sca) as well as two treatments using SBM which was impregnated with the hydrolysate prior to use. In Trial 2, the basal diet was supplemented with 3% Squ or Sca, shrimp but the shrimp were offered diets in slight excess to allow for possible increases in consumption of feeds. In Trial 3, Squ and Squid meal were compared at 6%. At the end of the three growth trials, no significant differences were found in final biomass, final mean weight, percent weight gain, feed conversion ratio, and survival. Additionally, a group of shrimp (3 g initial mean weight) were used to estimate consumption of the feeds over three 1-hour feedings over three days. Interestingly, the estimated feed intake of the basal diet was significantly higher than that of diets supplemented with 3% Squ or Sca. Results of the present study indicate that Squ and Sca as well as the SBM impregnated with Squ or Sca are good marine ingredients and can be used as feed ingredients. However, no evidence of improved feed intake or enhancement of growth were observed even though the diets were plant based. Statement of relevance In this study, a series of trials were used to assess the efficacy of dry hydrolysate from squid and scallop as well as traditional squid meal use in plant based practical diets designed for the Pacific white shrimp. These findings will be useful because the feed producers are interested in how specific produce may improve performance either as a nutrient source or attractant, particularly in diets that do not contain fishmeal. The conclusion provide valuable information that indicates feed manufacturer and researchers can use these hydrolysate products as feed ingredients in diets of shrimp, but no evidence for use of these products to improve the shrimp growth performance was observed. [ABSTRACT FROM AUTHOR]

Aim: Palaeoclimate legacies have been reported to influence microbial communities and carbon (C) stocks even after thousands of years. However, the direct and indirect influences of climate legacies on microbial C processes remain poorly understood and thus limit our capacity to predict how climate legacies regulate C cycling. Here, we conducted microbial, soil and vegetation surveys along a continental latitudinal transect of 4200 km covering a wide range of forest biomes. With these data, we evaluated the potential capacity of climate legacies to predict direct and indirect variations in microbial metabolic quotient (MMQ) across and within three main forest biomes: tropical, subtropical and temperate forests. Location: North–south transect (4200 km), China. Time period: 2019. Major taxa studied: Soil microbes. Methods: We used molecular ecology technology to determine microbial biomass and diversity, in addition to a soil incubation experiment to measure MMQ. Results: Palaeoclimate explained a unique portion of the variation in the continental distribution of MMQ, which showed a hump‐shaped pattern with latitude. Locations with increased isothermality (an index of temperature) over the last 20,000 years also showed the highest MMQ in the present day. Moreover, we found multiple indirect effects of climate legacies on MMQ caused either by changes in key soil properties, such as soil organic carbon and ammonium (NH4+), in lower latitudinal regions or by plant traits in higher latitudinal regions. Furthermore, MMQ was positively related to bacterial richness but negatively to fungal richness across forest biomes. Main conclusions: Climate legacies associated with continuous changes in temperature over the last 20,000 years influenced MMQ across forest biomes. Our findings demonstrate that including climate legacies in climate carbon models is essential for better prediction of the microbe‐driven ecosystem processes under global environmental change. [ABSTRACT FROM AUTHOR]

Aim: Soil organic carbon (SOC) stabilization has become an important topic in recent years in the context of global climate change. Microbial residues represent a significant component of stabilized SOC pools. However, spatial variations in the contributions of bacterial and fungal residues to SOC and their determinants at a continental scale remain poorly understood. We aimed to evaluate the spatial variations and controls of the contributions of microbial residues to SOC in forest topsoil. Location: North–south transect in eastern China. Time period: 2014. Major taxa studied: Forest ecosystems. Methods: A total of 195 surface (0–10 cm) soils were sampled from 28 forest sites across tropical and boreal forests in eastern China from July to August to assess how biotic and abiotic factors govern the geographic patterns of the contributions of soil microbial residues (indicated by amino sugars) to SOC. Results: Fungal residues (30.0%) had a greater average contribution to SOC than bacterial residues (15.5%). The contributions of bacterial (CBR) and total microbial residues (CMR) to SOC showed negative latitudinal patterns and were positively correlated with mean annual temperature (MAT). In contrast, the contribution of fungal residues to SOC (CFR) showed no clear geographic or climatic patterns. On average, the CBR (9.7%), CFR (21.1%) and CMR (30.8%) were lower in boreal forests than in other biome forests. SOC concentration negatively mediated CBR, CFR and CMR. The piecewise structural equation model results showed that MAT was the primary driver of the geographic pattern of CBR, whereas SOC and soil carbon : nitrogen ratio were more directly associated with the CFR. Additionally, plant factors and microbial properties (i.e., microbial biomass and composition) played relatively little roles in regulating CBR, CFR and CMR. Main conclusions These findings advance the current knowledge of the different geographic patterns of CBR and CFR regulated by different potential mechanisms in forest ecosystems. This highlights that the dynamics of microbial residues could potentially have unexpected consequences for topsoil SOC stocks under climate change. [ABSTRACT FROM AUTHOR]

Fungi and bacteria are the two dominant groups of soil microbial communities worldwide. By controlling the turnover of soil organic matter, these organisms directly regulate the cycling of carbon between the soil and the atmosphere. Fundamental differences in the physiology and life history of bacteria and fungi suggest that variation in the biogeography of relative abundance of soil fungi versus bacteria could drive striking differences in carbon decomposition and soil organic matter formation between different biomes. However, a lack of global and predictive information on the distribution of these organisms in terrestrial ecosystems has prevented the inclusion of relative abundance of soil fungi versus bacteria and the associated processes in global biogeochemical models. Here, we used a global-scale dataset of >3000 distinct observations of abundance of soil fungi versus bacteria in the surface topsoil (up to 15 cm) to generate the first quantitative and high-spatial-resolution (1 km 2) explicit map of soil fungal proportion, defined as fungi/fungi + bacteria, across terrestrial ecosystems. We reveal striking latitudinal trends where fungal dominance increases in cold and high-latitude environments with large soil carbon stocks. There was a strong nonlinear response of fungal dominance to the environmental gradient, i.e., mean annual temperature (MAT) and net primary productivity (NPP). Fungi dominated in regions with low MAT and NPP and bacteria dominated in regions with high MAT and NPP, thus representing slow vs. fast soil energy channels, respectively, a concept with a long history in soil ecology. These high-resolution models provide the first steps towards representing the major soil microbial groups and their functional differences in global biogeochemical models to improve predictions of soil organic matter turnover under current and future climate scenarios. Raw datasets and global maps generated in this study are available at 10.6084/m9.figshare.19556419 (Yu, 2022). [ABSTRACT FROM AUTHOR]

Optimal methods for incorporating soil microbial mechanisms of carbon (C) cycling into Earth system models (ESMs) are still under debate. Specifically, whether soil microbial physiology parameters and residual materials are important to soil organic C (SOC) content is still unclear. Here, we explored the effects of biotic and abiotic factors on SOC content based on a survey of soils from 16 locations along a ~4000 km forest transect in eastern China, spanning a wide range of climate, soil conditions, and microbial communities. We found that SOC was highly correlated with soil microbial biomass C (MBC) and amino sugar (AS) concentration, an index of microbial necromass. Microbial C use efficiency (CUE) was significantly related to the variations in SOC along this national‐scale transect. Furthermore, the effect of climatic and edaphic factors on SOC was mainly via their regulation on microbial physiological properties (CUE and MBC). We also found that regression models on explanation of SOC variations with microbial physiological parameters and AS performed better than the models without them. Our results provide the empirical linkages among climate, microbial characteristics, and SOC content at large scale and confirm the necessity of incorporating microbial biomass and necromass pools in ESMs under global change scenarios. [ABSTRACT FROM AUTHOR]

• Fungal-bacterial network complexity is related to soil pH. • Lower network stability and integration is found at neutral pH soil. • Microbial keystone taxa decrease towards higher pH. • pH is the strongest predictor of soil microbial network structure. Patterns in the network structure of microbial communities may give indications of their degree of interaction and interdependence, and their resilience to environmental disturbance. Geographical differences in network patterns of forest communities may reflect broad-scale differences in ecosystem structure and responses to environmental change. We analyzed a large dataset of 144 samples of soil bacterial and fungal communities characterized by 16S and ITS amplicon sequencing from forests in eastern China, along a 4,100 km latitudinal transect. This showed that fungal-bacterial network complexity was most closely related to soil pH. Results showed that pH was the strongest predictor of variation in community network structure across the forest soils of eastern China. Lower network complexity and stability were found around neutral pH, which was the strongest environmental predictor. This may be due to the optimal conditions that neutral soils provide for microorganism survival, reducing the necessity for physiological interdependence, consequently leading to fewer positive connections. Additionally, neutral soils provide more generalized niches, resulting in less specific niche exclusion, showing up as fewer negative connections. Unlike the trend for overall connectivity, the richness and relative abundances of keystone taxa were significantly and negatively correlated with pH. Overall, both connectivity and numbers of keystones were consistent in suggesting that network complexity was greatest overall at acidic pH. It appears that at the broad scale studied here, pH plays a more significant role in shaping microbial community integration than such factors as ecosystem productivity or climate. [ABSTRACT FROM AUTHOR]

Polian vesicles are considered as the site of coelomocyte formation, and play crucial roles in the inflammatory reaction in sea cucumber. After evisceration, coelomocytes and internal organs except polian vesicles are excreted. Our previous study found that the total number of coelomocytes was rapidly recovered at 6 h post-evisceration in sea cucumber Apostichopus japonicus , and this regeneration of coelomocytes might be closely related to polian vesicles. To further investigate the related-gene expression pattern of the polian vesicles at 6 h post-evisceration, the transcriptome analysis of polian vesicles was carried out. A total of 2752 differentially expressed genes (DEGs) were identified, including 1,453 up-regulated genes and 1299 down-regulated genes. Gene Ontology (GO) enrichment showed that most of the DEGs were classified under Regulation of transcription, Regulation of RNA metabolic process, Regulation of nucleic acid-templated transcription. Meanwhile, 11 significantly enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were identified. Among them, Wnt, TGF-β and Endocytosis pathways are well-related with cell proliferation and differentiation, which may be involved in the regeneration of coelomocytes in A. japonicus after evisceration. In addition, FoxO signaling pathway plays important roles in immunoregulation, in which the expression levels of the DEGs were significantly up-regulated, inferring that polian vesicles could not only participate in the coelomocyte regeneration process, but also undertake a certain immune defense function in A. japonicus after evisceration. These findings will be beneficial for understanding the mechanisms of coelomocyte regeneration and immune defense of A. japonicus after evisceration. • This is the first report on transcriptome in polian vesicles of sea cucumber Apostichopus japonicus. • A total of 2752 DEGs were identified in polian vesicles at 6 h post-evisceration. • Part of DEGs were significantly enriched in Wnt, TGF-β and endocytosis pathways. • Evisceration activated the FoxO signaling pathway in polian vesicles. [ABSTRACT FROM AUTHOR]

Thinning and understory removal are two common silvicultural practices used in plantation ecosystems, and both are expected to influence soil respiration (R S). However, little is known about how the two practices, particularly their interaction, affect the heterotrophic (R H) and autotrophic (R A) components of R S. This knowledge gap further constrains our accurate evaluation on the carbon balance in plantations upon both thinning and understory removal, because the two practices are often conducted simultaneously in plantation management. Thus, we partitioned R S into R H and R A using trenched plots in a Chinese fir (Cunninghamia lanceolata) plantation subject to thinning and understory removal. The R S and its two components were measured in 2013 and 2014 at approximately monthly intervals. The potential control factors such as soil temperature, soil moisture and soil chemical properties were also determined. We found that thinning marginally significantly (P = 0.059) increased R S in 2013 by 17.32%, while it had no influence on R S in 2014 (P > 0.1), indicating that the influence of thinning on R S weakened with time. Similarly, a significant increase in R H toward thinning also occurred in 2013 (by 32.5%) but not in 2014. However, R A showed no response to thinning in either year. No interaction effect between thinning and understory removal was found on R S , R H , and R A. The increased soil temperature in the thinned stands in 2013 played a key role in raising the post-thinning R H and R S in this year. Generally, the temperature sensitivity (Q 10) value of R S and its components increased in the order of R H < R S < R A regardless of treatment. The Q 10 value of R S showed negligible variation among different treatments, and thus was likely not affected by thinning, understory removal, or their interactions. The results highlighted that understory removal in thinned stands would not exacerbate soil carbon emission in this plantation. • The effect of thinning on the soil respiration (R S) weakened over time. • The response of R S to thinning was mainly driven by the heterotrophic respiration. • Soil temperature played a key role in regulating the effect of thinning on the R S. • No interaction between understory removal and thinning was found on the R S. [ABSTRACT FROM AUTHOR]

Soil microbes are both drivers and contributors of soil organic C (SOC) dynamics. However, information on how the multiple co-occurring environmental changes affecting microbial community and residues is unclear. Here, we measured phospholipid fatty acids and amino sugars (ASs) to explore how soil microbial community and residues changed under soil warming, throughfall reduction, root exclusion and their interactions in a natural deciduous broad-leaved oak forest. Soil warming significantly increased the Gram-positive to Gram-negative bacteria (G+/G−) ratio, and its interaction with root exclusion significantly reduced fungi-to-bacteria (F/B) ratio but stimulated the contributions of ASs to SOC (AS/SOC). Throughfall reduction also marginally increased G+/G− and AS/SOC, and suppressed F/B ratio. However, no interactive effects of soil warming and throughfall reduction on soil microbial community and residues were observed. Light fraction organic C and inorganic nitrogen were the key drivers in regulating the variation in the microbial community structure, and SOC was the controlling factor of microbial residue accumulations. Hence, soil C quality instead of water dominates the responses of microbial community structure and residues contribution to SOC to soil warming. Our results highlight the importance of soil substrate quality when predicting the terrestrial climate-C feedback. • Soil warming reshaped bacterial community towards Gram-positive bacteria. • Soil warming had greater effects on microbes in the root absence subplots. • Throughfall reduction marginally impacted microbial community and residues. [ABSTRACT FROM AUTHOR]

Background and aims: Priming effect (PE) of soil organic carbon (SOC) decomposition induced by exogenous organic C is an important ecological process in regulating the soil C cycle. The objective of this study was to evaluate how the PE varied among different ecosystems at the global scale and explore factors that drive the direction and magnitude of the PE. Methods: Using 2048 experimental comparisons compiled from 94 incubation studies with stable (13C) or radioactive (14C) carbon isotopic techniques, we performed a meta-analysis on the effect of exogenous organic C input on native SOC decomposition (i.e., PE) across multiple terrestrial ecosystems. In particular, the linear mixed-effect model was used to examine the relationship between the PE and potential influencing factors. Results: The addition of exogenous organic C significantly enhanced native SOC decomposition by 47.5% (i.e., positive PE), with the highest value in cropland soils (60.9%) and the lowest value in forest soils (26.2%). The intensity of the PE decreased with increasing SOC content, soil total nitrogen content, soil C/N, incubation duration, and incubation temperature, but increased with increasing exogenous organic C addition rate and soil pH. Soil PE was not affected by the complexity of exogenous organic C. Conclusions: Our results indicate that positive PE is a widespread phenomenon in terrestrial ecosystems, and that the magnitude is closely related to soil properties and experimental conditions. These findings may be useful for understanding soil C priming and the effect on soil C balance under climate change scenarios. [ABSTRACT FROM AUTHOR]

Forests 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. • Soil bacterial richness was positively associated with regenerated woody plant (RWP) richness. • Soil fungal richness was negatively associated with RWP basal area. • RWP-fungal richness relationship was trophic guild-specific. • Soil microbial community beta diversity was strongly coupled with RWP beta diversity. [ABSTRACT FROM AUTHOR]

To examine the interplay of C and N availability, glucose (high microbial availability) and cellulose (low microbial availability) were added to soils collected from a temperate forest that had received simulated N deposition for 6 years (organic and/or inorganic N). The priming effect was higher for glucose addition than for cellulose. N deposition decreased the priming effect of easily available glucose but increased the priming effect of cellulose. This confirmed an interactive effect of fresh organic matter (FOM) availability and N deposition on priming. Furthermore, the interactive effect was affected by the form of N deposition, with interaction mainly observed with organic N deposition. Qualitatively different patterns of priming were observed for the two FOM types and were accompanied by contrasting abundance of fungi and bacteria in the community, as determined by phospholipid fatty acid (PLFA) analysis. Organic N deposition increased bacterial biomass but decreased the intensity of priming. In contrast, a competitive advantage of fungi with respect to organic N sources may drive priming by cellulose. The results highlighted the importance of the availability of FOM in regulating the priming effect and showed that interactions between the form of N deposition and the availability of the FOM should be considered when predicting soil C cycling in scenarios of increased N deposition. Organic N deposition had a greater impact on priming effects than inorganic N deposition, and the influence of microbial availability of FOM largely depended on organic N deposition. [ABSTRACT FROM AUTHOR]

Highlights • Girdling significantly affected stem CO 2 efflux by altered substrate availability. • Effects of girdling on stem CO 2 efflux differed in degree and timing with season. • Apparent Q 10 of the stem CO 2 efflux increased above the girdle. Abstract The effect of carbohydrate supply on stem CO 2 efflux and its temperature sensitivity is crucial in predicting forest carbon cycling under climate change and forest management but has been rarely reported. In this study, we altered carbohydrate supply via stem girdling and investigated the effect of nonstructural carbohydrate concentration on stem CO 2 efflux and its temperature sensitivity in Chinese fir and sweetgum trees in spring and winter. The stem CO 2 efflux of Chinese fir increased significantly above the girdle in spring and winter, but decreased below the girdle in winter. The stem CO 2 efflux of sweetgum increased above the girdle and decreased below the girdle in spring but not in winter. Seasonal variations in the response of stem CO 2 efflux to girdling were associated with the changes in stem soluble sugar and starch concentration, especially in sweetgum tree. Girdling altered Q 10 of the stem CO 2 efflux, and this effect was dependent on location, season and species. Compared with the Q 10 of the stem CO 2 efflux in non-girdled trees, that of CO 2 efflux in Chinese fir increased by 45% above the girdle but decreased by 16% below the girdle in winter. These values also exhibited 6% and 11% responses in spring. By contrast, the Q 10 of the stem CO 2 efflux in sweetgum increased by 95% above the girdle and decreased by 45% below the girdle in spring. However, these values were nearly constant in winter. We concluded that the effect of carbohydrate supply on stem CO 2 efflux and its temperature sensitivity depends on season and species. Therefore, the vital role of carbohydrate supply that regulates stem CO 2 efflux and its temperature sensitivity should be considered for the understanding and modeling of forest carbon cycling response to forest management, especially under global climate changes. [ABSTRACT FROM AUTHOR]

Abstract: A 10‐week feeding experiment was conducted to evaluate the effects of replacing fish meal with soybean meal (SBM), with or without dietary arginine (Arg), on growth performance, immune indices and intestinal morphology of grouper, Epinephelus malabaricus. Nine experimental diets were formulated to contain 20%, 30% and 40% fish meal protein (FMP) replaced using SBM and 0, 0.5% and 1% dietary Arg supplementation. The results showed that weight gain (WG) of fish was significantly affected by the interaction of substitution level and Arg supplemental level. The maximum WG occurred at the 30% FMP substitution level and the 0.5% Arg supplemental level. The immune assay showed that the interaction between the two levels significantly influenced the production of serum nitric oxide but did not affect serum IgG concentration and alkaline phosphatase activity or the liver IGF‐1 gene expression. Significant interaction effects between the two levels were observed in muscle layer thickness (tML) and fold height (hF) in the proximal and mid‐intestine. High SBM level in diets reduced the tML and hF in the entire intestine. The results suggested that the interaction of 30% FMP substitution level and Arg supplemental level of 0.5% most benefitted growth performance, immune indices and intestinal structure of grouper. [ABSTRACT FROM AUTHOR]

Background and aims: The canopies in evergreen coniferous plantations are often composed of various-aged needles. Plantation management, such as thinning, produced abundant harvest residue, including needles with different needle ages. However, little attention was paid to the effect of needle age on decomposition, although the needle chemical properties varied substantially with leaf ages.Methods: A field experiment was conducted for 3 years to investigate the decomposition of harvest residue needles at different needle ages, and determine the main controlling factors in different stages of decomposition in a Chinese fir plantation.Results: We found that the initial decomposition rate varied 5-fold among different needle ages in a Chinese fir plantation. Litter quality controlled the overall litter decomposition rate, especially the initial decomposition rate. Needle nitrogen content was positively correlated to decomposition rate during the early stage of decomposition. However, it was negatively correlated to decomposition rate during the later stage of decomposition. The contents of needle tannins increased the asymptotic mass remaining (A, proportion of mass remaining at which decomposition approaches zero, i.e., the fraction of slowly decomposing litter). We also found that the initial litter decomposition rates in soil fauna presence were significantly higher than those in soil fauna absence across different needle ages. Moreover, the effect of soil fauna on initial litter decomposition is independent of needle quality.Conclusions: Our results suggest that needle age and plant secondary metabolites should be considered to understand the response of litter decomposition and nutrient cycling to management practices, such as thinning, in conifer plantations. [ABSTRACT FROM AUTHOR]

Summary: World‐wide conversion of natural forests to other land uses has profound effects on soil microbial communities. However, how soil microbial β‐diversity responds to land‐use change and its driving mechanisms remains poorly understood. In this study, therefore, we examined the effect of forest conversion from native broad‐leaved forest to coniferous plantation on soil microbial β‐diversity and its underlying mechanisms in both summer and winter in subtropical China. Microbial communities increasingly differed in structure as geographical distance between them increased, and the slope of the relationship among distances and community similarity differed among forest covers. In general, as with microbial β‐diversity, slopes also shifted across seasons. Finally, null deviations of bacterial and fungal communities were lower in coniferous plantation and presented opposing seasonal variations with greater influences of deterministic processes in summer for soil fungi and in winter for soil bacteria. Integrating previous frameworks with our β‐null model results, we propose a conceptual model to link microbial secondary succession to stochastic/deterministic shifts in forest ecosystems. Overall, forest conversion induced significant increases in stochastic processes in both bacterial and fungal community assemblies. Therefore, our results highlight the importance of spatiotemporal scales to assess the influence of land‐use change on microbial β‐diversity. [ABSTRACT FROM AUTHOR]

Background and Aims: Root branching leads to morphological and functional heterogeneity of fine roots. However, the structure of soil microbiota associated with root branching orders has never been investigated. Deep insights into rhizosphere microbial community could provide a better understanding of the plant-microbe relationship. Methods: Fine roots of poplar ( Populus × euramericana (Dode) Guinier.) were sampled and sorted into three groups according to their branching orders. Scanning electron microscopy (SEM) was used to observe the surface features of different orders of fine roots. Illumina MiSeq was employed to analyze the bacterial community structure of soil compartments from different root orders (i.e., R1, R2, and R3) and bulk soil compartment (NR). Results: SEM showed that the first-order root with smaller diameter had dense coverage of vigorous root hairs, whereas higher order roots with larger diameter had sloughed-off cortical tissues on the rhizoplane. The diversity of bacterial communities was higher in the R1 and R2 compartment than in R3 or NR. There were 80 genera with a relative abundance above 0.05% in soils. Ternary plot revealed that bacterial genera were significantly enriched in R1 than in R2 or R3. Redundant analysis (RDA) showed that 12 dominant bacterial genera with a relative abundance over 1% were significantly correlated with P and NH -N content of soils. Conclusions: Root orders could influence the inhabitation of bacterial communities. The core groups of bacterial communities inhabiting the rhizosphere were correlated with soil nutrients. The root order-dependent interactions of plant-microbe provided a new model about the association between roots and soils. [ABSTRACT FROM AUTHOR]

• Different patterns whereas similar controls of PE and N inhibition effect at regional and global scales was revealed. • Soil pH and N availability separately controlled the pattern of PE and N inhibition of PE. • The general N inhibition of PE supports the N mining theory at a large scale. • The PE and N inhibition effect in coniferous forests were more sensitive to latitude than those in broadleaved forests. Although the priming effect (PE) of soil organic matter mineralization and its response to nitrogen (N) amendment are widely studied in terrestrial ecosystems, great uncertainties in their geographic patterns constrain the establishment of advanced climate-carbon (C) model. By combining a laboratory experiment incubating soils from nine temperate forests in China with a meta-analysis of 32 publications across global forests, we tested the PEs and their response to N addition to explore their geographic patterns and the potential determinants. We found a weak dependence of the PE on latitude and mean annual temperature (MAT) in temperate forests in China, but a significant dependence of the PE on MAT across global forests after controlling for the exogenous C quantity. Soil pH was evidenced to control the geographic patterns of the PE. Consistent with meta-analysis, a general inhibition impact of mineral N addition on PE was detected in the laboratory experiment, ranging from −5.50 to 228.41%. In contrast with an inapparent dependence on MAT at the global scale, N inhibition effect in incubation experiment was experimentally detected to negatively correlate with MAT. Increase in soil N availability basically attenuated the response of PE to N addition. Across the globe, the PE and N inhibition effect in coniferous forests were more sensitive to latitude than those in broadleaved forests. Overall, our results uncovered distinct patterns but consistent controls of PE and N inhibition effect between the regional and global scales, and emphasized the importance of considering forest type in predicting soil C dynamics in response to global change. [ABSTRACT FROM AUTHOR]

Nitrogen addition has been shown to affect plant litter decomposition in terrestrial ecosystems. The way that nitrogen deposition impacts the relationship between plant litter decomposition and altered soil nitrogen availability is unclear, however. This study examined 18 co-occurring litter types in a subtropical forest in China in terms of their decomposition (1 yr of exposure in the field) with nitrogen addition treatment (0, 0.4, 1.6, and 4.0 mol·N·m−2·yr−1) and soil fauna exclusion (litter bags with 0.1 and 2 cm mesh size). Results showed that the plant litter decomposition rate is significantly reduced because of nitrogen addition; the strength of the nitrogen addition effect is closely related to the nitrogen addition levels. Plant litters with diverse quality responded to nitrogen addition differently. When soil fauna was present, the nitrogen addition effect on medium-quality or high-quality plant litter decomposition rate was −26% ± 5% and −29% ± 4%, respectively; these values are significantly higher than that of low-quality plant litter decomposition. The pattern is similar when soil fauna is absent. In general, the plant litter decomposition rate is decreased by soil fauna exclusion; an average inhibition of −17% ± 1.5% was exhibited across nitrogen addition treatment and litter quality groups. However, this effect is weakly related to nitrogen addition treatment and plant litter quality. We conclude that the variations in plant litter quality, nitrogen deposition, and soil fauna are important factors of decomposition and nutrient cycling in a subtropical forest ecosystem. [ABSTRACT FROM AUTHOR]

• Initial litter decomposition rates increased with litter quality. • Stable residue remaining after decay correlated negatively with litter quality. • Soil mesofauna had no effect on initial rates of litter decomposition. • Soil mesofauna decreased stable residue remaining regardless of litter quality. The regulation of factors like litter quality and soil mesofauna on litter decomposition in the early stage has been studied extensively in forest ecosystems. However, how litter decomposition was influenced by its quality and soil mesofauna in the late stage is largely unclear, especially in subtropical forest ecosystem. In the present study, litters from 16 species with contrasting chemical traits were incubated in a subtropical broadleaved forest for 2 years, and then the initial decomposition rate in early stage and stable residue remaining in late stage were calculated by using an asymptotic decomposition model. Litter bags with different mesh sizes (0.1 or 2 mm) were used to evaluate the role of soil mesofauna in regulating litter decomposition. Our results showed that litters with higher quality decomposed faster in early stage, and also had a larger fraction of stable residue remaining in the late stage. In addition, soil mesofauna exclusion had no influence on the decomposition rate at early stage, but significantly increased the stable residue remaining from 8.71% to 17.96%. We highlighted that the quality of plant litters play an important role in regulating the decomposition process in both early and late stage of decomposition, and thus the nutrient cycling and soil carbon (C) sink, in subtropical forest ecosystem. [ABSTRACT FROM AUTHOR]