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Pine resin is a widely used forestry by-product, and its yield can be determined using the resin flow rate (RFR). The application of phosphorus (P) fertiliser is prevalent in plantation forests; however, its effects on the RFR are currently unclear. Here, a P fertiliser addition experiment was conducted in a slash pine (Pinus elliottii Engelm) plantation in subtropical China with four treatments - P1 (25 kg P ha−1 yr−1), P2 (50 kg P ha−1 yr−1), P3 (100 kg P ha−1 yr−1), and a control. Tree growth represented by diameter at breast height (DBH), height (H) and timber volume (V) increments, the RFR over 9 months, nine needle parameters, and non-structural carbohydrates (NSC) in the organs of the slash pine were measured. The RFR was highest from June to August. The P addition, especially after the P2 and P3 treatments, enhanced the RFR overall, except during March, April, and November. Compared with other treatments, the P3 treatment improved the increments in DBH and V. Meanwhile, the P addition regulated the synthesis of soluble sugars (SS), starch (S) and other NSC, which varied among organs. P addition increased needle morphogenesis and chlorophyll content while reduced the dry matter content and the ratio of dry to fresh weight. RFR was positively correlated with tree growth and needle length, area, chlorophyll and NSC but negatively correlated with the dry matter content and the dry:fresh weight ratio of the needle. The structural equation model showed that P addition not only had a direct positive effect on the RFR but also indirectly altered it through tree growth and organ NSC. These results indicate that P fertiliser application can effectively promote resin yield by altering tree morphology and physiology in subtropical slash pine plantations. The trade-off between the P fertiliser application rate and economic and ecological benefits should be considered in the future research. [Display omitted] • Phosphorus (P) addition promoted resin yield represented by the resin flow rate (RFR). • P addition increased the needle chlorophyll while decreased dry matter content. • P addition regulated the synthesis of NSC, which varied among tree organs. • The enhanced RFR influenced by tree morphology and organs NSC after P addition. [ABSTRACT FROM AUTHOR]

An experiment including planted Tephrosia vogelii and Tithonia diversifolia fallow species and natural fallow was conducted at Maseno, Kenya, for assessing whether these fallows grown on a nutrient depleted land could produce sufficient green manure in six month period, whether their biomass retained on the same plots or transferred to continuously cropped plots with or without added P fertiliser could increase yield of consecutive maize crops and whether it is useful to regularly repeat these fallows on same plots. First fallow was established in randomized complete blocks with three replicates. At harvesting, biomass was recorded, then either incorporated in situ or transferred to continuous cropped plots split with and without added P fertiliser and monitored for the effect in improving consecutive maize crops. The second fallow was managed on this split plot design. The two-planted shrubs fallows produced more than 9 Mg total dry biomass and accumulated 154 to 234 kg N.ha-1, which were significantly higher compared to the production in the natural fallow. The shrubs were also superior to natural fallow for P accumulation (5-22 kg versus 2 kg.ha-1). The aboveground dry biomass harvested from planted T. vogelii and T. diversifolia and either incorporated in situ or transferred into continuously cropped plots increased maize yields by 2.5 folds compared to the unmanured crop, the control. Supplementing the organic materials with an additional 20 kg P inorganic fertilizer increased the 1st maize yield by about 40%. Productivity in the plots with T. vogelii or T. diversifolia aboveground biomass removal was low for the subsequent fallow and maize crops when compared to the performance in plots where biomass was incorporated. To achieve sustained yields of maize in depleted soils requires regular improved fallowing at least one season alternating with one season maize, and additional P inputs.

In China, phosphorus (P) is recognized as a "key limiting nutrient" for crop production, and its overuse results in underground leaching, ecosystem alterations and risks to humans, such as degraded surface water quality. The coupling of nitrogen (N) and P implies that soil N dynamics are largely affected by P availability. However, how the addition of P affects soil N transformations remains less understood. To determine the optimal P-input level, we performed an incubation experiment on an upland soil from Jinxian in China after long-term mineral fertilizer application and P addition. The two treatments without N addition T1 (no fertilizer) and T2 (inorganic potassium fertilizer) and the two treatments with N addition T3 (inorganic nitrogen fertilizer) and T4 (inorganic nitrogen and potassium fertilizer) were selected from the long-term experiment that involved scientific management at five P-input levels (0, 25, 50, 75, and 100 kg P 2 O 5 ha−1) with three replications. The results showed that soil organic matter (SOM) increased in the T3 and T4 treatments compared with the T1 and T2 treatments. The T4 treatment resulted in the maximum N concentration of 1.28 g kg−1, followed by that in the T3 treatment (1.25 g kg−1), T2 (0.16 g kg−1) and that in the T1 treatment (0.10 g kg−1), in the soil. Among the different treatments, soil microbial biomass carbon (SMBC) and nitrogen (SMBN) were significantly higher (492.69 mg kg−1 and 73.36 mg kg−1, respectively) in the T3 treatment than in the other treatments, while soil microbial biomass phosphorus (SMBP) was higher in the T4 treatment (17.55 mg kg−1). With the addition of P, the gross N mineralization rate was substantially enhanced when N and K were applied. After the 90-day incubation period, with higher concentrations of NO 3 --N and NH 4 +-N in the T4 treatment than in the other treatments, the concentrations were significantly increased by P addition, specifically T4P4 by 11.27% and 37.37%, T4P3 by 12.64% and 30.29%, T4P2 by 22.94% and 64.53%, and T4P1 by 3.93% and 11.09%, compared with those of T4P0, respectively; these results indicated a maximum N mineralization potential (N o) and mineralization rate constant, k (NMR). As a result of the increased gross nitrogen mineralization rates and associated NH 4 + substrate availability, the gross nitrification rate was also increased by P addition. Based on the polynomial regression analysis, the inclusion of P at the rate of 60 kg P 2 O 5 ha−1 can be used effectively to obtain maximum gross N mineralization rates in soil. Additionally, to fully understand why P addition is more effective under specific soil and environmental conditions, more research is necessary to determine the underlying mechanisms. • We determined the effects of P with different addition levels on soil N dynamics in soil with different N status. • Gross N mineralization increased with N fertilization at the optimum level of P addition. • P application at the rate of 60 kg ha−1 yr−1 appeared to be optimal for a sustained gross N mineralization rate. [ABSTRACT FROM AUTHOR]

Nutrient deposition to tropical forests is increasing, which could affect soil fluxes of nitrous oxide (N2O), a powerful greenhouse gas. We assessed the effects of 35-56 months of moderate nitrogen (N) and phosphorus (P) additions on soil N2O fluxes and net soil N-cycling rates, and quantified the relative contributions of nitrification and denitrification to N2O fluxes. In 2008, a nutrient manipulation experiment was established along an elevation gradient (1000, 2000 and 3000 m) of montane forests in southern Ecuador. Treatments included control, N, P and N+P addition (with additions of 50 kg N ha−1 yr-1 and 10 kg P ha−1 yr-1). Nitrous oxide fluxes were measured using static, vented chambers and N cycling was determined using the buried bag method. Measurements showed that denitrification was the main N2O source at all elevations, but that annual N2O emissions from control plots were low, and decreased along the elevation gradient (0.57 ± 0.26 to 0.05 ± 0.04 kg N2O-N ha-1 yr-1). We attributed the low fluxes to our sites’ conservative soil N cycling as well as gaseous N losses possibly being dominated by N2. Contrary to the first 21 months of the experiment, N addition did not affect N2O fluxes during the 35-56 month period, possibly due to low soil moisture contents during this time. With P addition, N2O fluxes and mineral N concentrations decreased during Months 35-56, presumably because plant P limitations were alleviated, increasing plant N uptake. Nitrogen plus phosphorus addition showed similar trends to N addition, but less pronounced given the counteracting effects of P addition. The combined results from this study (Months 1-21 and 35-56) showed that effects of N and P addition on soil N2O fluxes were not linear with time of exposure, highlighting the importance of long-term studies.

Mo-V-P-O y /Al 2 O 3 (denoted as 18.1Mo1.9VXP/Al: 18.1 wt% Mo, 1.9 wt% V, X wt% P) catalysts with different phosphorus content were prepared by an impregnation method, and they were applied to the acrylonitrile production by ammoxidation of propane. The effect of phosphorus content on the physicochemical properties and catalytic activities was investigated. Conversion of propane and yield for acrylonitrile showed volcano-shaped trends with respect to phosphorus content. Yield for acrylonitrile increased with decreasing binding energy of Mo 3d 5/2 . Among the catalysts, 18.1Mo1.9V0.6P/Al with the smallest binding energy of Mo 3d 5/2 showed the best catalytic performance in the ammoxidation of propane to acrylonitrile. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tropical forests with highly-weathered soils are considered to be high sensitive to nitrogen (N) deposition and subsequent soil acidification. Phosphorus (P) shortage in tropical forest ecosystems is suggested to be one important factor that makes the ecosystems more vulnerable to N-derived acidification. However, it remains poorly understood on how changes in soil P availability affect soil acidification processes in humid tropical zones with elevated atmospheric N deposition. To address this question, we conducted a long-term N and P addition experiment in an N-rich tropical forest, consisting of four treatments: control, N-addition, P-addition, and NP-addition, respectively (both N and P are 150 kg ha − 1 yr − 1 ). We hypothesized that relieving P-limitation by exogenous P addition will mitigate N-derived soil acidification. Results showed that six-year N addition significantly decreased soil pH (by 0.23, p = 0.013), soil base saturation (BS) (by 32.8%, p = 0.0017), and increased the ratio of aluminum to calcium (Al/Ca) ( p = 0.015), suggesting that soil acidification was accelerated by N input. As we expected, P addition increased soil pH in the first few years, probably because of the increased biotic uptakes of nitrate and phosphate. However, after the first few years, continuous N addition promoted acidification and made the buffering effects by P addition invisible in our soils at the Al-buffering stage. Our results suggest that P inputs cannot alleviate excess N-derived soil acidification in N-rich tropical ecosystems, and that it is urgent to reduce reactive N emission for sustainable development of the affected ecosystems in the future. [ABSTRACT FROM AUTHOR]

It is well documented that phosphorus (P) input stimulates biological nitrogen (N) fixation (BNF) in tropical forests with non-legume trees. However, in tropical legume forests with soil N enrichment and P deficiency, the effects of P availability and its combination with N on BNF remain poorly understood. In this study, we measured BNF rate in different compartments, i.e., bulk soil, forest floor, rhizosphere, and nodules, in two tropical plantations with legume trees Acacia auriculiformis ( AA) versus non-legume trees Eucalyptus urophylla, ( EU) in southern China after 4 years of P addition and combined N and P additions. The objective was to investigate how P addition and its combination with N addition regulate BNF in a tropical legume plantation, and to compare the effects with those in a non-legume plantation. Our results showed that total BNF rates were significantly higher in the P-addition plots than in the control plots by 27.4 ± 4.3 and 23.3 ± 1.7 % in the EU and AA plantations, respectively. Total BNF rates were significantly higher in the NP-addition plots than in the control plots by 27.7 ± 5.0 and 8.5 ± 1.4 % in the EU and AA plantations, respectively, which contrasted to our previous result that total BNF rates were significantly lower in N-addition plots than in the control plots in the AA plantation. These findings suggest that P input can stimulate BNF in tropical forest biome dominated by legume trees, even in consideration of elevated atmospheric N deposition. Thus, our study revealed the important role of P in regulating biological N input, which should be taken into account in the modeling of biogeochemical cycles in the future. [ABSTRACT FROM AUTHOR]

The alpine meadow on the Qinghai-Tibetan Plateau (QTP), which is sensitive to global climate change and human activities, is subjected to addition of nutrients such as nitrogen (N) and phosphorus (P) in the soil. The impacts of N or P on ecosystem structure and function depend at least partly on the response of soil fungal communities, although few studies have compared the effects of N and P addition, both separately and together. We examined the responses of composition of the soil fungal community to 3-year experimental nutrient additions (control, N, N plus P, and P) in a typical alpine meadow of the QTP. We found that P addition, regardless of N addition, significantly reduced fungal species richness and changed fungal community composition, while the effect of N was undetectable. Nitrogen plus phosphorus caused a more distinct community than either N or P addition alone. Multivariate regression tree, canonical correspondence analysis, and distance-based multivariate linear model analyses all suggested available P was a key parameter determining the diversity and composition of the fungal community. Other parameters such as dissolved organic N, aboveground net primary productivity of forbs, and dissolved organic C played important but secondary roles. The results indicated an important role of P in structuring soil fungal communities in the alpine meadow. Our results suggest that fungal diversity loss and long-term changes in ecosystem stability can result from fertilization management in the fragile alpine environment. [ABSTRACT FROM AUTHOR]

Root-associated fungi play a vital role in maintaining nutrient absorption and health of host plants. To compare the responses of root-associated fungal community structures to nitrogen (N) and/or phosphorus (P) additions across differential mycorrhizal types, we collected roots of nine plant species belonging to three mycorrhizal types (arbuscular mycorrhiza, ectomycorrhiza, and ericoid mycorrhiza) under control and N and/or P addition treatments from a subtropical forest, and detected the diversity and community composition of fungi inhabiting roots through the high-throughput sequencing technique. The results showed that root-associated fungal communities of all nine plant species were mainly composed of Basidiomycota and Ascomycota. The relative abundance of Ascomycota and Basidiomycota was significantly lower and higher under the P addition than that under control, respectively. The relative abundance of Ascomycota of ericoid mycorrhizal trees was significantly higher than those of arbuscular mycorrhizal and ectomycorrhizal trees, while the relative abundance of Basidiomycota was significantly lower than the other two mycorrhizal types. Compared with the control, P addition significantly reduced the α-diversity and changed community composition of root-associated fungi across different mycorrhizal plant types, while no effect of N addition or mycorrhizal type was observed. Compared with the control and N addition treatments, NP addition caused root-associated fungal communities of all plants becoming integrally divergent. In addition, the fungal communities of ectomycorrhizal mycorrhizal trees became apparently convergent in comparison with those of arbuscular and ericoid mycorrhizal trees under the NP addition. Collectively, our results highlighted that P was a critical factor influencing community structures of tree root-associated fungi in subtropical forest soils. This study would enhance our understanding of the responses and maintenance mechanisms of plant root-associated fungal diversity under global environmental changes in the subtropical region.

Nitrogen ( N) saturation hypothesis suggests that when an ecosystem reaches N-saturation, continued N input will cause increased N leaching, nitrous oxide ( N2 O) emission, and N mineralization and nitrification rates. It also suggests that a different element will become the main limiting factor when N saturation has been reached. Although this hypothesis has been tested in temperate forests, whether they can be directly applied to N-saturated tropical forests remain poorly addressed., To test this hypothesis, soil inorganic N, soil N mineralization and nitrification rate, soil N2 O emission rate and nitrate () leaching rate were measured in an N-saturated old-growth tropical forest in southern China, after 6 years of N and P addition. We hypothesized that N addition would stimulate further N saturation, but P addition might alleviate N saturation., As expected, our results showed that six continuous years of experimental N addition did cause further N saturation, which was indicated by significant increases in soil inorganic N concentration, N2O emission and nitrate () leaching. However, in contrast to our expectations, N addition significantly decreased in situ rates of net N mineralization and nitrification, which could be related to associated changes in enzyme activity and microbial community composition. On the other hand, P addition mitigated N saturation, as expected. Soil inorganic N concentration, N2O emission and leaching decreased significantly after P addition, but the net rates of N mineralization and nitrification were significantly increased., Our results provide a new understanding of the N saturation hypothesis, suggesting that the effects of long-term N deposition on net N mineralization and nitrification rates in N-saturated tropical forests can be negative and that P addition can alleviate N saturation in such tropical systems. [ABSTRACT FROM AUTHOR]

Aims: Plant biomass growth, storage, and decomposition connect nitrogen (N) and phosphorus (P) cycles, yet we know relatively little about the dynamics of such coupling under nutrient enriched conditions, and our understanding of the interactive relationships between plant N and P in drylands remains particularly poor. Methods: In a semiarid steppe of northern China, we examined the effects of single and combined N and P additions on soil and plant N and P pools for both mature and senesced leaves in two dominant grasses: Leymus chinensis and Stipa grandis. Results: Nitrogen additions increased N concentrations in mature and senesced leaves for each plant species, and decreased N and P resorption during leaf senescence. The effects of N additions on foliar P concentrations were species-specific, while P additions had no effect on any nutrient characteristics examined. Due to treatment effects on N resorption, N and P concentrations were tightly correlated in senesced leaves but not in mature leaves. Conclusions: Taken together, the results suggest plants in this ecosystem are much more responsive to changing N cycles than P cycles and emphasize the significance of nutrient resorption as an important plant control over the stoichiometric coupling of N and P under nutrient enriched conditions. [ABSTRACT FROM AUTHOR]

The plants in arid environment are constrained not only by water availability, but also by soil nutrient conditions. In order to clarify to what extent nutrient addition would facilitate the growth of plants in semi-arid region, we conducted a nitrogen (N) and phosphorus (P) addition experiment in Inner Mongolia temperate grassland in 2012 and 2013. In our experiment, N was added at 10 and 40 g N·m-2·a-1 alone or in combination with P addition (10 g P·m-2·a-1). N addition significantly improved plant aboveground biomass (AGB) during the two study years. AGB in the treatments of 10 and 40 g·m-2·a-1 was enhanced by 50.8% and 65.9% in 2012, and 71.6% and 93.3% in 2013, respectively. However, no significant difference in AGB enhancement was found between two N addition treatments. Compared with N addition treatments at the rates of 10 and 40 g·m-2·a-1, N plus P addition improved AGB by 98.4% and 186.8% in 2012, and 111.7% and 141.4% in 2013, respectively. N addition generally increased all the three main functional types (i.e., Gramineae, Asteraceae and others), and the three functional types contributed nearly equally to the increase of the community AGB. In comparison, Asteraceae contributed largest to the increments of AGB under the N plus P addition treatments. Our results also indicated that N and P addition remarkably increased the ground coverage, resulting in improved surface soil moisture condition, which might be one important reason that N and P addition could facilitate plant growth in arid environment. [ABSTRACT FROM AUTHOR]

Elevated nitrogen (N) deposition has dramatically altered soil phosphorus (P) and carbon (C) cycles in forests and altered extracellular enzyme activity. However, the effects of N addition and the interactive effects of combined N and P additions on soil enzyme (e.g. phosphatase and glucosidase) activity in different types of forests (young vs. old-growth) remain unclear. To better understand this, a long-term N–P fertilization experiment was initiated in January 2007 in two subtropical forests (an old-growth monsoon evergreen broadleaf forest (MEBF) and a young Masson pine forest (MPF)) in southern China. Four treatments were established, including control (no nutrient addition), N addition (150 kg N ha −1 yr −1 ), P addition (150 kg P ha −1 yr −1 ) and NP addition (150 kg N ha −1 yr −1 plus 150 kg P ha −1 yr −1 ). Soil physicochemical properties, acid phosphatase (APA-s) and β-glucosidase (BGA-s) activity per soil were measured in July 2012 and July 2013. Both APA-s and BGA-s were higher in MEBF than in MPF. N addition significantly stimulated APA-s in MEBF and BGA-s in MPF. P addition significantly suppressed APA-s in both forests and BGA-s in MEBF. Moreover, P addition decreased the stimulating effect of N addition on APA-s in MEBF and on BGA-s in MPF. Our results suggest that (1) N addition may exacerbate soil P limitation in old-growth forests and result in the deficiency of easily available C in young forests and (2) P addition may mitigate these negative effects of N addition in both forest types. Our findings suggest that P fertilization may be an effective practice to improve soil P availability in old-growth forests and soil C availability in young forests under N deposition condition. [ABSTRACT FROM AUTHOR]

Soil microbes play a crucial role in myriad ecological processes in terrestrial ecosystem. With increasing nitrogen (N) loading, phosphorus (P) may become more limiting for soil microbes and these processes. However, it remains unclear to what extent P addition impacts soil microbial communities and respiration at global scale, especially under different N loadings. Therefore, we used a global meta-analysis to examine the effects of phosphorus addition on soil microbes based on 2293 paired observations from 129 studies in the world. Overall, P addition increased significantly total as well as fungal, bacterial, and actinomycete (ACT) phospholipid fatty acids (PLFAs), together with Gram+ bacteria (G+) and Gram- bacteria (G-) abundance regardless of N input or not. The increments were more pronounced under higher P addition rate or places with higher mean annual temperature or mean annual precipitation. Moreover, the fungi: bacteria ratio significantly decreased along elevational gradients. Furthermore, higher P addition frequency tended to have significantly more ACT PLFAs, as well as higher G+:G-, but significantly lower fungi: bacteria ratio (F:B). However, the responses of P addition on bacterial PLFAs and F:B were larger in forest than grassland, and cropland and varied with P fertilizer forms. In addition, the responses of soil organic carbon (SOC) contents was positively correlated with those of microbial biomass carbon (MBC) and bacterial PLFAs, and all these three parameters, in addition to fungal PLFAs, correlated positively with the response of soil respiration (Rs). Our results suggest that phosphorus addition had globally positive effects on soil microbes with different N loadings, and the positive effects of soil microbial abundance tended to promote heterotrophic respiration (Rh) and Rs. These results deepen our understanding of soil microbial community structure and function dynamics under increasing P deposition. They also provide extensive evidences and bases for parameterization of soil carbon cycling models incorporating microbial responses under global climate change. • We found phosphorus addition had globally positive effects on soil microbes. • The soil microbial biomass positively correlated with phosphorus addition rate, mean annual temperature (MAT) and mean annual precipitation (MAP). • The responses of soil microbes varied with P addition forms and ecosystem types. • The positive effects of soil microbes tended to promote Rs and Rh. [ABSTRACT FROM AUTHOR]

[Display omitted] The effects of P addition on the soil available P, ACP activity, AM diversity and microbial N: P ratio in two tropical forests. AP, available P. ACP, acid phosphatase; AM, arbuscular mycorrhiza; +, increase; -, decline; ×, no effect. • Plants and microorganisms accessed P mainly by releasing hydrions and organic acids. • Plants and microorganisms accessed less P by root interception and mineralization. • Forest succession would not aggravate microbial P limitation. • Inorganic P addition inhibited the transformation and absorption of organic P. Increasing atmospheric nitrogen (N) and phosphorus (P) deposition affect soil nutrient availability and biogeochemical cycles, yet the impacts on the regulatory processes of soil P in P-poor tropical rainforests are not well understood. Based on a ten-year N and P addition experiment in primary and secondary rainforests in Hainan, China, we investigated the effects of N and P additions on four soil P fractions, acid phosphatase (ACP) activity, kinetic characteristics and arbuscular mycorrhizal (AM) diversity. Our results showed that P addition significantly increased soil available P (AP), but had no significant effects on microbial P and microbial N:P ratio in both rainforests. Late-successional primary rainforest had higher microbial P and lower N:P ratio compared to early-successional secondary rainforest, suggesting that forest succession would not aggravate microbial P limitation. Plants and microorganisms accessed most inorganic P by releasing hydrion and organic acids to mobilize soil P, whereas inorganic P accessed by root interception and organic P readily mineralized by ACP and phytase enzymes were relatively low. In the primary rainforest, ACP and kinetic parameters were significantly increased under low N addition, while P addition remarkedly declined ACP activity and AM diversity in both rainforests. Additionally, CaCl 2 extractable P, citrate extractable P, and HCl extractable P in the two forests were significantly positively associated with soil AP, but negatively associated with ACP activity, kinetic parameters and AM diversity. Therefore, the transformations of organic P were inhibited after the exogenous addition of inorganic P. Overall, our study evaluates the soil P acquisition strategies and regulatory processes in tropical rainforests with different successional stages, which can be used to predict the effects of long-term N and P deposition on soil P cycling in P-poor tropical rainforests. [ABSTRACT FROM AUTHOR]

Plants can alter soil microbial biomass and extracellular enzyme activities related with carbon (C), nitrogen (N), and phosphorus (P), through litter and root exudates, with consequences on soil carbon, nitrogen and phosphorus (P) cycling. However, it is not well known how the changes in soil phosphorus availability affect the relationships between plants and soil microorganisms. In this study, a factorial experiment was conducted to investigate the effects of Chinese fir ( Cunninghamia lanceolata ) planting and different levels of P addition (0, 1.95, 3.9, 7.8 and 15.6 g P·m -2 ·a -1 ) on soil microbial biomass and extracellular enzyme activities. The results showed that planting Chinese fir planting significantly altered soil microbial biomass and C- and N- and P-related extracellular enzyme activities, but the effects were dependent on P addition levels. Without P addition, Chinese fir planting significantly reduced soil nutrient availability and pH, which led to the aggravation of P limitation and lower soil microbial biomass. P addition relieved P limitation, and reduced soil acid phosphatase (ACP) activities by 30.0%, 30.5%, 35.3% and 47.1% with the increasing P addition level (1.95, 3.9, 7.8 and 15.6 g P·m -2 ·a -1 ). Under three P addition levels (1.95, 3.9 and 7.8 g P·m -2 ·a -1 ), the negative effects of Chinese fir planting on soil microbial growth were alleviated. Under the high P addition level (15.6 g P·m -2 ·a -1 ), the negative effects of Chinese fir planting on soil microbial growth occurred again due to soil N limitation. Taken together, Chinese fir planting and soil P availability generally affected soil microbial biomass and extracellular enzyme activities, and changed P limitation.

Anthropogenic activities have increased ecosystem phosphorus (P) inputs and have affected terrestrial ecosystem carbon (C) cycles. However, the fate of soil organic C (SOC) under P addition remains elusive, and the potential mechanisms underlying plant-microbial linkages mediated SOC formation and decomposition are poorly understood. Here, we conducted a field P fertilization experiment to explore the effects on SOC dynamics in a typical temperate grassland in northern China. P addition increased soil P availability and pH, thereby stimulating plant nutrient uptake and growth, leading to higher C inputs to soils via plant biomass (shoots, litter and roots). However, P addition exacerbated microbial N limitation, altered microbial community composition (with a lower fungal to bacterial ratio), shifted microbial life-history strategies, which transitioned from the K -strategy (Acidobacteria, Chloroflexi, and Verrucomicrobia dominant) to the r - strategy (Proteobacteria, Bacteroidetes, and Firmicutes dominant), and modulated their functional characteristics. All of these factors regulated microbial substrate preferences and changed the C components that undergo decomposition. These changes ultimately accelerated the utilization of active C, hampered passive C decomposition, and helped to create a longer-term stable C sink in the grassland. • P addition decreased active C and increased passive C and this resulted in a net increase of SOC. • Increased plant productivity and litter quality improved plant C inputs to the soil. • Altered microbial characteristics regulated their substrate preference, thus stimulating active C loss. • Decreased soil metallic elements may partially weaken the stability of SOC. • Accumulated passive C would be beneficial in creating a longer-term stable C sink. [ABSTRACT FROM AUTHOR]

Excessive N deposition leads to the conversion of previously N limited to N saturated forest ecosystems. The input of N can result in severe N/P imbalance and N-induced P deficiency. The present study investigates whether N addition induces P deficiency in beech saplings or if this can be counteracted by enhanced internal P (re)cycling. Furthermore, it was tested whether addition of P can mitigate N induced P deficiency. In addition, higher need of P due to enhanced growth may be realized either by enhanced P uptake or by improved internal P (re)cycling. This assumption was tested with beech saplings growing at higher light intensity. Therefore, a mesocosm approach with beech saplings and soil (O and A horizon) originating from a P-poor forest was conducted. Mesocosms were cultivated for two growing seasons in a garden. Addition of N, P, or combined addition of N and P took place during the first year and another group of saplings was exposed to higher light intensity to enhance CO 2 assimilation and growth. Soil horizons and beech saplings were harvested during the second year of growth in spring, summer, autumn, and winter. The results show that internal (re)cycling of N and P is different and mostly determined by the season. The seasonal (re)cycling of P was driven by the metabolic P demand of tissues/organs characterized by shifting P between the perennial tissues bark and wood of branches and coarse roots and deciduous leaves, fine roots and long-distance transport paths without using major storage resources. In contrast, seasonal (re)cycling of N is characterized by N storage in perennial tissues during dormancy and by N mobilization from the entire trunk, i.e. branch, stem and coarse roots, in spring. Furthermore, these seasonal dynamics were found to be independent of the treatment. [Display omitted] • P (re)cycling comprises the shift of P to the places of demand without P storage. • N storage and re-mobilization characterizes saplings seasonal (re)cycling of N. • High light induces N deficiency but sufficient P supply sustained by P (re)cycling. • N/P ratios used as indicator of nutrient imbalance show large seasonality. • Missing root establishment in the Of+Oh prevents P improvement of saplings. [ABSTRACT FROM AUTHOR]

Anthropogenic activities have drastically increased nitrogen (N) and phosphorus (P) input to the biosphere, which could potentially alter soil biogeochemical cycles. However, the responses of soil greenhouse gases (GHGs) to the interactions of N and P enrichment are not fully understood, especially for riparian forests. In this study, we measured soil carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2 O) fluxes and their potential drivers, including soil properties and soil microbes. The measurements were made across a whole season in a riparian forest, where an on-going N and P addition experiment was conducted. The experiment included low N (LN, 30 kg N ha−1 year−1), high N (HN, 150 kg N ha−1 year−1), low P (LP, 30 kg P 2 O 5 ha−1 year−1), high P (HP, 150 kg P 2 O 5 ha−1 year−1), low N and low P (LNP), high N and high P (HNP), and a control (CK) treatment. The results show that the riparian forest soil was a significant source of CO 2 and N 2 O and a sink for CH 4. The nutrient additions significantly reduced CO 2 emissions (ranging from −52.9% under HNP to −44.2% under LP treatment) across the whole season. A significant reduction in CH 4 uptake was found under both N and P addition treatments and also under the combination of N and P addition during the growing season. A significant increase in N 2 O emissions was found under HN treatment, but decrease was found under P addition treatments (LP, HP and LNP) during the growing season. The CO 2 , CH 4 , and N 2 O fluxes were significantly correlated with the seasonal patterns of fungi, Gram-negative (GN) bacteria, and net nitrification (NetN) rates, respectively. Generally, N and P addition significantly reduced the amount of fungi and GN bacteria concentration, respectively; HN addition significantly increased while LP and HP decreased the NetN rates during the growing season. Our results also indicated the interactions of N and P showed antagonistic effects on all GHGs. Our findings indicate that soil GHG fluxes in this riparian forest depend on the responses of microbes to N and P additions and highlight the need to investigate the interactions of N and P in predicting the responses of soil GHGs to global change. [ABSTRACT FROM AUTHOR]

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Abstract: The effect of phosphorus addition was studied on the hydrodesulfurization (HDS) of thiophene over Co-MoS2/P/Al2O3, which was prepared by a chemical vapor deposition (CVD) technique using Co(CO)3NO as a precursor of Co. The catalysts were characterized by means of NO adsorption, FTIR and Raman spectroscopy. The HDS activity of Co-MoS2/Al2O3 was slightly increased by the addition of 0.2wt% P, followed by a slight decrease with a further addition of phosphorus. In spite of the activity increase, the amount of NO adsorption on MoS2/P/Al2O3 steadily decreased with increasing phosphorus loading, suggesting that the dispersion of MoS2 particles is decreased by the addition of phosphorus. The TOF of the HDS over CVD-Co/MoS2/P/Al2O3 catalysts, defined by the activity per Co atom forming the Co-Mo-S phase, increased as much as 1.3 times by the addition of phosphorus, indicating that the active phase of the catalysts shifts from less active Co-Mo-S Type I to more active Co-Mo-S (pseudo) Type II. FTIR results showed that phosphoric acid reacts with the surface OH groups of Al2O3, resulting in weakened interactions between molybdenum oxides and Al2O3 surface and thus in less abundant Mo–O–Al bonds in MoS2–Al2O3 interactions. [Copyright &y& Elsevier]

The present work is aimed at studying the effect of phosphorus addition on physical and electrical properties of tantalum powder. Tantalum anodes were compacted from tantalum powder, which were doped with different concentrations of phosphorus in the form of phosphoric acid. Anodes were sintered at 1550°C for 30 min. Properties such as density, microstructure, CV (capacitance times voltage constant) and DC leakage were studied. Significant improvement in electrical properties was observed, results of which are presented here. [ABSTRACT FROM AUTHOR]

Phosphorus was added to Fe-50 wt.% Ni in the form of a coated composite powder via an electroless plating process. Addition of phosphorus to Fe-50 wt.% Ni facilitated increases in density and grain size, both of which were beneficial to magnetic performance. Because of the homogeneous distribution of phosphorus in the powder, the optimal phosphorus addition was much lower than for those using Fe3P as the phosphorus precursor. The optimal phosphorus addition was close to its maximum solubility in Fe-50 wt.% Ni (about 0.5 wt.%), above which precipitation of excessive phosphorus in the form of iron nickel phosphide, (Fe,Ni)3P, effectively degraded the magnetic properties of Fe-50 wt.% Ni. Without the addition of phosphorus, good magnetic properties could be achieved only when the sintering temperature was high enough (>1200 °C) to result in a high sintered density and large grains in the sintered structure. [ABSTRACT FROM AUTHOR]

• P addition increased N retention mainly by promoting plant N uptake. • N addition without P showed neutral effects of N retention. • N addition showed positive effects on gaseous losses of N. • N loss through NH 3 and N 2 O emissions was quite low. Nitrogen (N) and phosphorus (P) are common limiting nutrients affecting plant growth in alpine ecosystems. Anthropogenic activities significantly increase N input in ecosystems, thereby increasing P limitation when in excess. The increase of N input and P limitation may affect N retention, which is a critical ecosystem function. To understand how ecosystem N retention and N loss respond to N and P addition, this study investigated the effects of N and P addition on NH 3 volatilization, N 2 O emissions, and N pools of plants and soil in two alpine grasslands (alpine meadow and alpine steppe). The results showed that P addition (with or without N) increased N retention, mainly by promoting plant N uptake, underlining the importance of P availability in N retention in the QTP alpine grassland ecosystems while increasing N deposition. N addition without P showed neutral effects of N retention of plant, soil and microbes, and N addition (with or without P) showed positive effects on gaseous losses of N. N loss through NH 3 volatilization and N 2 O emissions was quite low (less than 1%), suggesting that N gaseous loss was not a significant pathway of N loss from the alpine grassland ecosystems. These results were meaningful for estimating the impacts of N retention and N loss under future N deposition scenarios in alpine grassland ecosystems in the QTP. [ABSTRACT FROM AUTHOR]

The productivity of terrestrial ecosystems is limited by soil fertility, such assoil phosphorus (P). The decomposition of litter is the main process that affects nutrient cycling. To understand the characteristics of litter decomposition and nutrient release under P addition, we conducted a 2-year litter bag experiment at P addition rates (0–12.5 g P m−2 yr−1). All litter decomposed faster during the second growing season due to highly concentrated precipitation, and Stipa grandis litter decomposed faster (1.02–1.63 times) than Leymus chinensis under P treatments. The decomposition of L. chinensis and mixed litter was more thoroughly at 1 g P m−2 yr−1, while S. grandis decomposed more under 5 g P m−2 yr−1. P addition promoted nitrogen (N) and P immobilization and all litter reached its maximum at 12.5 g P m−2 yr−1. Phosphorus addition increased β-glucosidase production at 5 g P m−2 yr−1, but leucine aminopeptidase production was promoted at high P. The ratio of leucine aminopeptidase to phosphatase increased over time, indicating the N deficiency and P saturation during late stages of decomposition. Our results show that Inner Mongolia's grasslands was limited by P availability and that precipitation was important in the region's decomposition processes. • P addition sped decomposition of S. grandis but not L. chinensis and mixed litter. • The decomposition of S. grandis was more sensitive to nutrient availability. • P addition promoted the immobilization of N and P in the litter. • The dominant enzyme shifted from P-acquiring enzyme to N-acquiring enzyme. • Increased precipitation changed the normal pattern of litter decomposition. [ABSTRACT FROM AUTHOR]

• Addition of phosphate to soil caused desorption of organic carbon (OC). • This effect increased from the Podzol to the Andosol to the Ferralsol. • In contrast, addition of chloride had no effect on desorption of OC. • Organic compounds larger than 600 kDa desorbed due to phosphate addition. • Phosphate addition also decreased subsequent sorption of OC in soils. The contribution of different adsorption processes to soil organic matter (SOM) stabilization and the consequences of the intensification of land use on the adsorption of SOM are not yet fully understood. Therefore, this study aimed to explore the adsorption of dissolved organic carbon (DOC) in soils as well as desorption of organic carbon (OC) caused by phosphate addition. We conducted desorption and sorption experiments with DOC, phosphate (Na 2 HPO 4), and chloride (KCl) in topsoil and subsoil samples from a Ferralsol, an Andosol, and a Podzol. Furthermore, we quantified the size of DOC by size-exclusion chromatography. We found that phosphate addition caused a strong increase in the DOC concentration in all soils. The DOC concentration was elevated by up to a factor of 4.5 compared to a control (water only) within five minutes after phosphate addition and kept increasing further with time, particularly in the Ferralsol. After 10 days, the DOC concentrations in the P addition treatment were between 5.5 and 18.0 times higher than in the control treatment. In contrast, chloride addition did not lead to increased DOC concentrations compared to the control (water only). Phosphate addition led mostly to desorption of organic matter of medium molecular size (10–100 and 100–1000 kDa) in the Ferralsol and the Andosol and of large molecular size (>1000 kDa) in the Podzol. In contrast, potassium chloride addition shifted the size distribution of DOC in the soil solution towards small compounds (<10 kDa), likely because KCl addition affected the aggregation of DOC compounds, in contrast to Na 2 HPO 4 addition. Furthermore, phosphate addition also decreased subsequent sorption of DOC in the Ferralsol and the Andosol by a factor of up to 2.9 and 2.1, respectively. Our results have far-reaching implications because they show that phosphate addition can lead to desorption, and thus to destabilization of SOM, particularly in Ferralsols, and can also prevent further sorption of organic matter in soils. Our study provides a mechanistic explanation of why phosphate addition can decrease soil organic carbon sequestration and stabilization. This mechanism should be considered in the analysis of land-use and tillage effects on SOM sequestration in the future. Furthermore, our study indicates that also medium and large molecular size organic matter is stabilized through adsorption in soils. [ABSTRACT FROM AUTHOR]

• Hydrologic changes enhanced CH 4 emission, but inhibited CO 2 and N 2 O fluxes. • N and N + P addition increased N 2 O fluxes, which is contrary to p addition. • No interactive effects of hydrologic changes and nutrient additions on GHGs fluxes. • Global warming potential was reduced by continuous flooding and enhanced by N + P. Changes in global rainfall patterns and construction of artificial dams have led to widespread alteration of hydrological processes in riparian ecosystems. At the same time, many riparian ecosystems, such as those associated with the Yangtze, are being subjected to enhanced inputs of nitrogen (N) and phosphorus (P) due to intensified agricultural activity in surrounding uplands. Together, these environmental changes may alter the magnitude and direction of greenhouse gasses (GHGs) fluxes from riparian soils. We conducted an in situ experiment combined with quantitative PCR approach (qPCR) to elucidate the effects of hydrological alterations (continuous flooding (CF), periodic flooding (PF), and no flooding (NF)) and nutrient addition (N addition (urea, 100 kg N ha−1 y−1), P addition (P 2 O 5 , 20 kg ha−1y−1), N + P addition, and control (CK)) on three major GHGs including carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2 O) fluxes as well as the underlying mechanisms. Our results showed that hydrological alterations greatly affected GHGs emissions, possibly by altering soil moisture, soil organic C, and C:N ratios. The CF, with higher soil moisture and lower C:N ratio, increased CH 4 emissions 13-fold and reduced CO 2 and N 2 O emissions by 37.3% and 72.2% averaged over the growing seasons compared with no flooding. PF enhanced CH 4 emissions 5.7-fold and decreased N 2 O emissions by 69.0% in comparison with no flooding. Nutrient additions had no significant effect on CO 2 or CH 4 flux, but P addition significantly lowered N 2 O flux. Interactions between hydrological alterations and nutrient additions were not detected for any GHGs. As a result, hydrological alterations and nutrient additions affected the global warming potential (GWP) of growing season GHG budgets on a 100-year time horizon, mainly by changing the CO 2 emissions. CF reduced GWP from 597 to 439 g CO 2 -eq m−2, and N + P addition enhanced GWP from 489 to 625 g CO 2 -eq m−2. The qPCR analysis revealed that decreased CH 4 oxidation potential may lead to the enrichment of CH 4 emissions under the hydrological alterations, and reduced nitrification and denitrification potential contributed to the reduction of N 2 O fluxes under all the treatments. Our study indicates that continuous flooding could curb the contribution of riparian GHGs fluxes to global warming but that the combination of N and P additions may increase the greenhouse effect mainly by regulating the CO 2 emissions of growing season in riparian ecosystem. [Display omitted] [ABSTRACT FROM AUTHOR]

• We compared two calculation methods for priming under nutrient addition (PE nutrient). • Calculation method affects the quantification of nutrient-effect on priming (PE). • PE nutrient differs largely when nutrient effect on microbial basal respiration is large. • Study on how nutrient addition affects PE should design full factorial experiments. • Such study should treat nutrient addition treatment as a reference to calculate PE nutrient. Priming effect (PE) plays critical roles in soil organic matter (SOM) decomposition and terrestrial carbon cycling, and is largely affected by nutrient availability. Many studies found that nutrient addition can affect PE, but the calculations for such effects differed among studies. This inconsistence partly lies in which treatment (unamended control vs. sole nutrient addition) should be treated as a reference to calculate the PE under nutrient addition (PE nutrient), as PE is not a directly measured but indirectly estimated variable. Such inconsistent calculations for PE nutrient may affect the results of how nutrient addition affects PE and associated interpretation. By conducting a global synthesis of 52 nutrient-manipulation studies worldwide, we found that the PE nutrient generated by different calculations are very different, particularly when nutrient addition alone has a large effect on SOM decomposition (or microbial basal respiration). Moreover, different calculations affected the direction, magnitude and interpretation of nutrient-addition effects on PE. We recommend that future studies investigating the effects of nutrient addition on PE should design full factorial experiments (e.g., two-factor experiment with treatments of unamended control, carbon substrate addition, nutrient addition, and carbon substrate plus nutrient addition) and treat sole nutrient addition treatment as a reference to calculate the PE nutrient. [ABSTRACT FROM AUTHOR]

Anthropogenic activities and atmospheric deposition have increased the nitrogen (N) and phosphorus (P) inputs to terrestrial ecosystems, which can significantly alter ecosystem carbon cycling. To better understand the mechanisms of soil organic carbon (SOC) responding to nutrient fertilization, we measured physical fractions (by particle-size fractionation) and chemical composition (by solid-state 13C NMR spectroscopy) of SOC, plant biomass and nutrient concentration, soil chemistry, microbial biomass and community composition after 10 years of N and P addition in an alpine meadow on the Tibetan Plateau. Our results showed that total SOC and mineral-associated organic carbon (MAOC) contents were not affected by N and P addition. However, P addition promoted particulate organic carbon (POC), which was likely attributed to hampered decomposition by lower microbial biomass (particularly fungi). In contrast, N addition did not change POC, probably because more plant biomass inputs were offset by faster decomposition of higher-quality plant litter (lower C:N ratio). Moreover, N addition rather than P addition decreased the percentage of labile functional group of O-alkyl C, whereas slightly increased alkyl-aromatic C:O-alkyl C ratio. These changes in SOC chemical composition with N inputs were likely caused by enhanced labile OM decomposition and rhizodeposit inputs. Overall, our results suggest that long-term exogenous N input could potentially accelerate SOM decomposition indicated by the chemical composition, but P input could result in inhibition of SOM decomposition and accumulation of POC stock in the alpine meadow ecosystem. • Long-term N and P addition did not change total SOC or MAOC in an alpine meadow. • N addition decreased O-alkyl C, slightly increased alkyl-aromatic C:O-alkyl C, but did not affect POC. • P addition increased POC by 9.1%, likely due to inhibited microbial biomass and decomposition. • POC is more sensitive to N or P addition than MAOC or total SOC. [ABSTRACT FROM AUTHOR]

Increased soil nitrogen (N) from atmospheric N deposition could change microbial communities and functions. However, the underlying mechanisms and whether soil phosphorus (P) status are responsible for these changes still have not been well explained. Here, we investigated the effects of N and P additions on soil bacterial and fungal communities and predicted their functional compositions in a temperate forest. We found that N addition significantly decreased soil bacterial diversity in the organic (O) horizon, but tended to increase bacterial diversity in the mineral (A) horizon soil. P addition alone did not significantly change soil bacterial diversity but mitigated the negative effect of N addition on bacterial diversity in the O horizon. Neither N addition nor P addition significantly influenced soil fungal diversity. Changes in soil microbial community composition under N and P additions were mainly due to the shifts in soil pH and NO3− contents. N addition can affect bacterial functional potentials, such as ureolysis, N fixation, respiration, decomposition of organic matter processes, and fungal guilds, such as pathogen, saprotroph, and mycorrhizal fungi, by which more C probably was lost in O horizon soil under increased N deposition. However, P addition can alleviate or switch the effects of increased N deposition on the microbial functional potentials in O horizon soil and may even be a benefit for more C sequestration in A horizon soil. Our results highlight the different responses of microorganisms to N and P additions between O and A horizons and provides an important insight for predicting the changes in forest C storage status under increasing N deposition in the future. [ABSTRACT FROM AUTHOR]

• N addition effects on tree growth and soil properties varied with tree species. • pH variation explained most of soil microbial and nutrient response to N addition. • P addition did not alter N addition effects on tree growth and microbial biomass. Increasing evidence has suggested that nitrogen (N) deposition has great effects on forest productivity and nutrient cycling, but how these effects are mediated by soil phosphorus (P) availability and tree species identity remains unclear. Here, a two-year factorial experiment was conducted to examine the short-term effects of N addition (100 kg N ha−1 year−1), P addition (50 kg P ha−1 year−1) and their interactions on tree growth and soil nutrient cycling of a Mongolian pine (Pinus sylvestris var. mongolica) plantation and a neighboring Simon poplar (Populus simonii) plantation in Northeast China. Results showed that N addition promoted tree growth (stem increment), reduced soil microbial biomass carbon (C) and N in the Mongolian pine plantation, but did not affect those in the Simon poplar plantation, and these N addition effects were not interacted by P addition. P addition significantly increased microbial biomass C and N in the Simon poplar plantation. N addition elevated soil phosphatase activities and reduced net N mineralization rate, and these N addition effects were alleviated by simultaneous P addition in both plantations. N addition decreased soil labile inorganic P concentration in both plantations and elevated labile organic P in the Mongolian pine plantation, but only the decrease in labile inorganic P with N addition in the Mongolian pine plantation was counteracted by P addition. N addition significantly reduced soil pH, with a greater extent in the Mongolian pine plantation than in the Simon poplar plantation. Moreover, soil pH response explained most of the microbial and nutrient transformation response. Above results indicated that short-term N addition impacts on tree growth and soil microbial biomass were more strongly influenced by tree species identity than by P addition, while N addition effects on soil N and P transformations were strongly influenced by P addition. Drought resistance of trees and acid buffering capacity of soils are key traits influencing the short-term N addition impacts on the growth of trees and microorganisms in this semiarid region. [ABSTRACT FROM AUTHOR]

• P addition significantly decreased AM fungal colonization rates at high soil P level. • The effects of P addition on intraradical and extraradical AM fungal communities are different. • P addition has significant effects on AM fungal community in roots but not in soil. • pH and soil organic matter structured roots and soil mycorrhizal communities, respectively. To investigate the responses of alfalfa root-/ soil-associated arbuscular mycorrhizal (AM) fungal communities to phosphorus (P) addition, we examined the intraradical and extraradical mycorrhizal communities in an alfalfa (Medicago sativa) field being fertilized with four levels of P for 9 years. We found that AM fungal colonization declined significantly at the highest P level and was negatively related to soil available phosphorus, suggesting a decreased reliance on AM fungi at this high P level. A total of 22 operational taxonomic units (OTUs) from three families were detected in roots and 25 in soil. Both AM fungal OTU richness and diversity in soil were higher than that in roots. The AM fungal diversity in roots declined significantly when P was the highest. The indicator species in roots increased in relative abundance in the P1 treatment (75 kg P 2 O 5 ha−1 a−1). Although P addition had no significant effect on OTU richness or AM fungal community composition in soil, we found that pH and soil organic matter structured roots and soil mycorrhizal communities, respectively. In conclusion, P addition affected root and soil AM fungal communities differently. Further research is needed to determine how individual AM fungal species may respond to P fertilization, and how this may impact plant productivity. [ABSTRACT FROM AUTHOR]

To understand the coupled controlling of carbon (C) and phosphorus (P) on the minera-lization of soil organic carbon and amended substrates in paddy soil, we investigated the effects of P addition on the decomposition of organic carbon and its induced priming effect by using 13 C isotope probing technique in microcosm. The results showed that P addition accelerated the release of CO 2 but inhibited the release of CH 4 , leading to 53.1% reduction of total accumulated CH 4 and 70.5% reduction of the 13 CH 4 derived from exotic glucose- 13 C. P addition altered the carbon distribution during the microbial turnover progress, with 3.6% of glucose- 13 C being transferred into the labile carbon pool, therein significantly increased potential of the mineralization rate of exogenous C. A transient negative priming effect was observed in the early stage of incubation. With time prolonging, the priming effect on CO 2 emission (PE CO 2 ) generally increased and then decreased after a peak. The priming effect on CH 4 emission (PE CH 4 ) kept increasing and finally fluctuated at a relative stable value until the end of the experiment (100 days). P addition increased PE CO 2 by 32.3% but reduced PE CH 4 by 93.4%. Results from the RDA and Pearson analysis showed that electric conductivity, oxidation-reduction potential and dissolved organic carbon significantly affected soil C mineralization. There were significantly negative correlations between available phosphorus (Olsen-P) and 13 CH 4 , and between Olsen-P and PE CH 4 . In conclusion, with the addition of exogenous organic matter, P application could reduce CH 4 emissions and inhibit its priming effect, acce-lerate the mineralization of SOC, probably improve the nutrient supply, and thus enhance the avai-lability of organic C and promote C cycling in paddy soil.

A series of nitrogen (N) and phosphorus (P) addition experiments using treatments of N 0 (0 kg N·hm -2 ·a -1 ), N 1 (50 kg N·hm -2 ·a -1 ), N 2 (100 kg N·hm -2 ·a -1 ), P (50 kg P·hm -2 ·a -1 ), N 1 P and N 2 P were conducted at Cunninghamia lanceolata plantations in subtropical China. The responses of soil organic carbon (SOC), particulate organic carbon (POC) and water-soluble organic carbon (WSOC) to the nutrient addition treatments after 3 years were determined. The results showed that N and P additions had no significant effects on SOC concentration in 0-20 cm soil layer, while P addition significantly decreased soil POC content in 0-5 cm soil layer by 26.1%. The responses of WSOC to N and P addition were mainly found in 0-5 cm soil layer, and low level N and P addition significantly increased the WSOC content in 0-5 cm soil layer. Nitrogen addition had no significant effect on POC/SOC, while the POC/SOC significantly decreased by 15.9% in response to P addition in 0-5 cm soil layer. In 5-10 cm and 10-20 cm soil layers, POC/SOC was not significantly altered in N and P addition treatments. Therefore, the forest soil C stability was mainly controlled by P content in subtropical areas. P addition was liable to cause the decomposition of surface soil active organic C and increased the soil C stability in the short term treatment.