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.
We conducted a novel incubation experiment with periodically varying temperature based on the MAT of soil origin sites, and collected 140 soil samples from 22 sites along a 3,800 km long north–south transect of China forests. Changes in the Q10 values were nonlinear with latitude, and the dominant factors that regulate the regional variations in Q10 differed among the tropical, subtropical, and temperate forest ecosystems. 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.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Global atmospheric nitrogen deposition has increased steadily since the 20th century, and has complex effects on terrestrial ecosystems. This work synthesized results from 54 papers and conducted a ...meta-analysis to evaluate the general response of 15 variables related to plant root traits to simulated nitrogen deposition. Simulated nitrogen deposition resulted in significantly decreasing fine root biomass (<2 mm diameter; −12.8%), while significantly increasing coarse root (≥2 mm diameter; +56.5%) and total root (+20.2%) biomass, but had no remarkable effect on root morphology. This suggests that simulated nitrogen deposition could stimulate carbon accumulation in root biomass. The root: shoot ratio decreased (−10.7%) suggests that aboveground biomass was more sensitive to simulated nitrogen deposition than root biomass. In addition, simulated nitrogen deposition increased the fine root nitrogen content (+17.6%), but did not affect carbon content, and thus decreased the fine root C:N ratio (−13.5%). These changes delayed the decomposition of roots, combined with increasing of the fine root turnover rate (+21.4%), which suggests that simulated nitrogen deposition could increase carbon and nutrient retention in the soil. Simulated nitrogen deposition also strongly affected the functional traits of roots, which increased root respiration (+20.7%), but decreased fungal colonization (−17.0%). The effects of simulated nitrogen deposition on the plant root systems were dependent on ecosystem and climate zone types, because soil nutrient conditions and other biotic and abiotic factors vary widely. Long-term simulated experiments, in which the experimental N-addition levels were less than twofold of the average of atmospheric nitrogen deposition, would better reflect the response of ecosystems under atmospheric nitrogen deposition. These results provide a synthetic understanding of the effects of simulated nitrogen deposition on plant root systems, as well as the mechanisms underlying the effects of simulated nitrogen deposition on plants and the terrestrial ecosystem carbon cycle.
•We evaluated the responses of plant root traits to simulated nitrogen deposition.•Simulated nitrogen deposition elevated the ratio of carbon sequestered in plant.•Simulated nitrogen deposition increased carbon and nutrient retention in the soil.•The amount of N-addition of many simulated experiments was excessive.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Microorganisms are vital in soil organic carbon (SOC) mineralization. The deposition of atmospheric nitrogen (N) and phosphorus (P), as well as leaf-litter addition, may affect SOC mineralization and ...microbial community structure by changing the availability of soil nutrients and carbon (C). In this study, we added leaf-litters labeled by 13C (Pinus massoniana and Michelia macclurei) and nutrients (ammonium chloride and monopotassium phosphate) alone and in combination to soils collected from a coniferous forest in subtropical China. We aimed to investigate the effect of leaf-litter and nutrient addition on SOC mineralization and soil microbial community. CO2 production was continuously measured during 120-day laboratory incubation, and CO2 sources were partitioned using 13C isotopic techniques. The addition of P. massoniana and M. macclurei leaf-litters increased SOC mineralization by 7.4% and 22.4%, respectively. N and P addition alone decreased soil respiration by 6.6% and 7.1%, respectively. Compared with P addition, N addition exerted a higher inhibitory effect on SOC mineralization induced by leaf-litter addition. Leaf-litter addition stimulated soil microbial activity and decreased the ratio of bacteria to fungi as a result of greater promotion on fungal growth. Moreover, 16:0 and 18:1ω9c phospholipid fatty acids (PLFAs) had greater amount of 13C incorporation than other PLFAs, especially in nutrient-addition treatments. These results suggested that increased C input through leaf litter can stimulate SOC mineralization, whereas atmospheric N and P deposition can reduce this stimulatory effect and promote soil C storage in subtropical forests. Our results also illustrated that the use of 13C-labeled leaf litter coupled with 13C-PLFA profiling is a powerful tool for determining the microbial utilization of C.
•Lower-quality litter induced a greater priming effect on SOC mineralization.•N addition had higher inhibitory effect on priming effect than P addition.•Adding leaf litter and nutrients decreased in the bacteria:fungi ratio.•The 16:0 and 18:1ω9c PLFAs preferentially utilize fresh substrate-C added to soils.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•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.
We determined the effects of aboveground and belowground C inputs on soil CO2 efflux and microbial community composition by phospholipid fatty acids using aboveground litter addition or removal and root trenching in a subtropical forest in Southern China. From January 2011 to December 2011, soil respiration varied with the seasonal changes in soil temperature and water content, but its pattern was not altered by C input manipulation. The effects of C input manipulation on the temperature sensitivity of soil respiration was season-dependent, which were greater in the dormant season than in the growing season. Litter addition increased the soil respiration by 33% compared with the control, whereas litter removal decreased it by 22.6%. Root trenching decreased soil respiration by 20.4%. Aboveground litter decomposition, root and rhizosphere respiration, and mineral soil respiration contributed to 22.3%, 20.1%, and 57.6% of total soil CO2 efflux, respectively. We also found that increase in soil CO2 efflux induced by litter addition was 10.4% greater than decrease by litter removal. Litter removal increased 21.6% of the concentration of Gram-positive bacteria and decreased 32.8% of the bacteria to fungi ratio, compared with the control. Root trenching increased the concentrations of bacteria, fungi, and actinomycetes by 28.8%, 161.2% and 32.5%, respectively, but decreased the Gram-negative to Gram-positive bacteria and the bacteria to fungi ratios by 57.4% and 107.9%. C input treatment did not increase the Gram-positive bacteria but nor decreased the Gram-negative to Gram-positive bacteria ratio. The concentration of the 16:0 PLFA and the Gram-negative to Gram-positive bacteria ratio were significantly correlated with soil respiration. These results suggest that root C input has greater influence on soil microbial community composition than the aboveground litter C input.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In terrestrial ecosystems, deep soils are a major reservoir of organic carbon (C). Improving knowledge of how deep soil organic carbon (SOC) mineralization responds to fresh C supply and nitrogen (N) ...availability is essential to better understand whether this C pool will react to climate change. However, little is known about the effects of C and N inputs on SOC mineralization and microbial communities in forest deep soils. To quantify the effects of C and N inputs on SOC mineralization, we apply two species of 13C–labeled leaf litters and ammonium chloride solution while incubating soils collected from 60 cm to 70 cm depth in a coniferous forest in subtropical China. The soil phospholipid fatty acid (PLFA) profiles are also determined to establish the effects of C and N supply on microbial community structure, and the δ13C in PLFAs is used to establish pathways of leaf litter-derived C flux among microbial communities. The addition of leaf litters stimulates deep SOC mineralization, indicating that the stability of deep SOC is attributed to a lack of fresh C input, but the addition of Michelia macclurei litter with higher C:P ratio has a greater positive priming effect than adding Pinus massoniana litter. N addition reduces the magnitude of positive priming and alters the direction of priming in soils with P. massoniana litter addition, suggesting that N deposition may suppress deep SOC mineralization and favor the maintenance of SOC storage. Leaf litter addition enhances the biomass of individual PLFA and increases the fungi:bacteria ratio, suggesting that microbes are limited by energy and that soil microbial community composition is modified by C inputs. N addition decreases the fungi:bacteria ratio, but increases the Gram–positive:Gram–negative bacteria ratio. The highest 13C–enrichment and distribution of litter–derived C are found in 16:0 and 18:1ω9c PLFAs, but litter species and N addition do not affect total PLFA–C and litter-derived PLFA–C. These results support the views that a lack of fresh C supply and N deposition may prevent the mineralization of SOC pool in deep layers and that the utilization of labile substrate by 16:0 and 18:1ω9c populations promotes positive SOC priming.
•The first study to quantify effect of C supply on deep SOC decomposition in forests.•Fresh C input increased the mineralization of deep SOC and decreased its stability.•N addition decreased the priming effect induced by C addition in deep forest soils.•C and N addition altered microbial community in deep forest soils.•Utilization of labile C by 16:0 and 18:1ω9c populations promotes positive SOC–priming.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
► This is the first study on effect of forest fire on labile SOM by meta-analysis. ► The study’s aim was to identify general patterns of effects of fire on labile SOM. ► Labile SOM were significantly ...affected by fire type, soil sampling depth and time. ► Fire decreased potential rates of C sequestration and storage in forest soils.
The effects of fire on labile soil C and N in forest ecosystems are important for understanding C sequestration and N cycling not only because labile soil C and N are often variables that determine soil fertility but also because the role of soils as a source or sink for C is important on an ecosystem and on the regional level. In the current study, the literature on the effects of fire on soil organic C, total N, microbial biomass C and N, dissolved organic C, and total N, respiration, and N mineralization in mineral soil was reviewed, and the results of a meta-analysis on literature data were reported. Overall, fire significantly increased the soil total N, microbial biomass N, dissolved organic C, and total N, but decreased soil organic C, microbial biomass C, respiration and N mineralization. Among the significant effects of different fire types, wildfire had the higher effects on the soil organic C, total N, microbial biomass C and N, dissolved total N and respiration of soil than prescribed fire. In addition, responses of soil organic C, total N and N mineralization to wildfire depended on forest type and natural zone. Positive responses of soil organic C, total N were found in broadleaved forests and Mediterranean zones, and negative responses in coniferous forests and temperate zones. Wildfire significantly decreased N mineralization in coniferous forests. The effects of fire on soil microbial biomass C and N, dissolved organic C and N mineralization generally decreased with time after the fire. In general, the effects of fire on soil organic C, microbial biomass C, and dissolved total N and N mineralization decreased with increasing soil depth. These results suggest that fire increases C and N availability and increases microbial activity, which consequently decreases the potential rates of C sequestration.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Microbes are widely distributed in soils and play a very important role in nutrient cycling and ecosystem services. To understand the biogeographic distribution of forest soil bacteria, we collected ...115 soil samples in typical forest ecosystems across eastern China to investigate their bacterial community compositions using Illumina MiSeq high throughput sequencing based on 16S rRNA. We obtained 4,667,656 sequences totally and more than 70% of these sequences were classified into five dominant groups, i.e., Actinobacteria, Acidobacteria, Alphaproteobacteria, Verrucomicrobia, and Planctomycetes (relative abundance >5%). The bacterial diversity showed a parabola shape along latitude and the maximum diversity appeared at latitudes between 33.50°N and 40°N, an area characterized by warm-temperate zones and moderate temperature, neutral soil pH and high substrate availability (soil C and N) from dominant deciduous broad-leaved forests. Pairwise dissimilarity matrix in bacterial community composition showed that bacterial community structure had regional similarity and the latitude of 30°N could be used as the dividing line between southern and northern forest soils. Soil properties and climate conditions (MAT and MAP) greatly accounted for the differences in the soil bacterial structure. Among all soil parameters determined, soil pH predominantly affected the diversity and composition of the bacterial community, and soil pH = 5 probably could be used as a threshold below which soil bacterial diversity might decline and soil bacterial community structure might change significantly. Moreover, soil exchangeable cations, especially Ca(2+) (ECa(2+)) and some other soil variables were also closely related to bacterial community structure. The selected environmental variables (21.11%) explained more of the bacterial community variation than geographic distance (15.88%), indicating that the edaphic properties and environmental factors played a more important role than geographic dispersal limitation in determining the bacterial community structure in Chinese forest soils.
AIMS : Globally, extensive areas of native forest have been almost replaced by plantations to meet the demands for timber, fuel material and other forest products. This study aimed to evaluate the ...effects of forest conversion on labile soil organic C (SOC), soil respiration, and enzyme activity, and to quantify their relationship in subtropical forest ecosystems. METHODS : Surface mineral soil (0–20 cm) was collected from a Cunninghamia lanceolata Hook. plantation, Pinus massoniana Lamb. plantation, Michelia macclurei Dandy plantation, and an undisturbed native broadleaf forest. Soil microbial biomass C, dissolved organic C, permanganate-oxidizable C, basal respiration, and six enzyme activities were investigated. RESULTS : Soil microbial biomass C was higher by 45.9 % in native broadleaf forest than that in M. macclurei Dandy plantation. The ratio of soil microbial biomass C to total SOC was 27.6 % higher in the M. macclurei Dandy plantation than in the native broadleaf forest. The soil respiration increased by 25.2 % and 21.7 % after conversion from native broadleaf forest to P. massoniana Lamb. and M. macclurei Dandy plantations respectively. The effects of forest conversion on the soil enzyme activities differed among the tree species. Soil microbial biomass C had higher correlation with soil respiration than with the other SOC fractions. Moreover, soil microbial biomass C was positively correlated with urease and negatively correlated with cellulase activity. Soil respiration had higher correlation with soil microbial biomass C, dissolved organic C and permanganate-oxidizable C. CONCLUSION : Forest conversion affected the soil microbial biomass C, soil respiration, invertase, cellulase, urease, catalase, acid phosphatase, and polyphenol oxidase activities, but their response depended on tree species. Soil respiration was mainly controlled by labile SOC, not by total SOC.
▶ We investigate labile soil organic matter (SOM) in four subtropical forest ecosystems. ▶ Effects of forest vegetation on labile SOM were examined. ▶ Forest vegetation type significantly affects ...labile SOM. ▶ Hot-water-soluble method is recommended as a best measure for labile SOM in subtropical forest soils.
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 0–10
cm soil layer than in the 10–20
cm. 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 0–10
cm soil layer, which ranged from 11.7 to 29.2
g
kg
−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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The carbon sequestration of forest ecosystems plays a pivotal role in constraining global warming and mitigating climate change. The landscape pattern of forests is being altered due to the combined ...effects of climate change and human interference. Furthermore, the relationship between forest pattern changes and carbon storage distribution in a long time series remains unclear. Therefore, it is necessary to examine the relationship between forest patterns and carbon density, investigating the variations and similarities in the changes in carbon density across different modes of pattern change over time, and suggestions for forest planning were provided from a perspective focused on pattern change to enhance carbon storage. The Google Earth Engine (GEE) platform’s random forest model was used to map the spatial distribution of forests in Hunan Province for 1996 and 2020, followed by analyzing the correlation between the changes in forest patterns using the morphological spatial pattern analysis (MSPA) and carbon density simulated by the model. Results show that the net growth rate ((area in 2020-area in 1996)/area in 2020) of the forest in Hunan increased 26.76% between 1996 and 2020. The importance scores for the decade average temperature, short-wave length infrared band 1 (SWIR-1), and slope were the highest metrics in the model of carbon density, and were 0.127, 0.107 and 0.089, respectively. The vegetation carbon storage in Hunan Province increased by 31.02 Tg, from 545.91 Tg to 576.93 Tg in 25 years. This study demonstrates that vegetation carbon storage is influenced by the pattern type in both newly established and pre-existing forests (p < 0.05). The findings of this study offer empirical evidence to support forest management strategies targeted at enhancing carbon sequestration.
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