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1.
Responses of CO2 efflux from an alpine meadow soil on the Qinghai Tibetan Plateau to multi-form and low-level N addition 总被引:1,自引:0,他引:1
Huajun Fang Shulan Cheng Guirui Yu Jiaojiao Zheng Peilei Zhang Minjie Xu Yingnian Li Xueming Yang 《Plant and Soil》2012,351(1-2):177-190
Aims
To assess the effects of atmospheric N deposition on the C budget of an alpine meadow ecosystem on the Qinghai–Tibetan Plateau, it is necessary to explore the responses of soil-atmosphere carbon dioxide (CO2) exchange to N addition.Methods
Based on a multi-form, low-level N addition experiment, soil CO2 effluxes were monitored weekly using the static chamber and gas chromatograph technique. Soil variables and aboveground biomass were measured monthly to examine the key driving factors of soil CO2 efflux.Results
The results showed that low-level N input tended to decrease soil moisture, whereas medium-level N input maintained soil moisture. Three-year N additions slightly increased soil inorganic N pools, especially the soil NH 4 + -N pool. N applications significantly increased aboveground biomass and soil CO2 efflux; moreover, this effect was more significant from NH 4 + -N than from NO 3 ? -N fertilizer. In addition, the soil CO2 efflux was mainly driven by soil temperature, followed by aboveground biomass and NH 4 + -N pool.Conclusions
These results suggest that chronic atmospheric N deposition will stimulate soil CO2 efflux in the alpine meadow on the Qinghai–Tibetan Plateau by increasing available N content and promoting plant growth. 相似文献2.
Utilization of nitrogen in the form of either nitrate (NO 3 ? ) or ammonium (NH 4 + ) ions may affect the carbohydrate metabolism and energy budget of plants. Recent studies showed that greater expenses of NO 3 ? to NH 4 + reduction mostly occur in the roots and during darkness. Fertilization of corn with 15N-labeled nitrate and ammonium, combined with pulse labeling of plants in a 14CO2 atmosphere at the V6 and V8 growth stages, allowed us to evaluate the effect of N form on the CO2 efflux from soil. NH 4 + oxidation was inhibited by adding dicyandiamide. In respect to ammonium, nitrate addition increased root-derived CO2 efflux from corn by 2.6 times at stage V6 and by 1.8 times at stage V8. The time of peak 14CO2 efflux from soil also differed between two growing stages: at V6, efflux peaked only on the second day after pulse labeling, while at V8 this occurred within the first 6 h. The strong effect of NO 3 ? and NH 4 + on root respiration requires considering the N form in the soil and the nitrate reduction site location in a plant when modeling soil respiration changes and when separately estimating individual CO2 sources that contribute to the total soil CO2 efflux. 相似文献
3.
Soil moisture effects on gross nitrification differ between adjacent grassland and forested soils in central Alberta, Canada 总被引:3,自引:0,他引:3
Yi Cheng Zu-cong Cai Jin-bo Zhang Man Lang Bruno Mary Scott X. Chang 《Plant and Soil》2012,352(1-2):289-301
Background and aims
Changes in soil moisture availability seasonally and as a result of climatic variability would influence soil nitrogen (N) cycling in different land use systems. This study aimed to understand mechanisms of soil moisture availability on gross N transformation rates.Methods
A laboratory incubation experiment was conducted to evaluate the effects of soil moisture content (65 vs. 100% water holding capacity, WHC) on gross N transformation rates using the 15N tracing technique (calculated by the numerical model FLUAZ) in adjacent grassland and forest soils in central Alberta, Canada.Results
Gross N mineralization and gross NH 4 + immobilization rates were not influenced by soil moisture content for both soils. Gross nitrification rates were greater at 100 than at 65% WHC only in the forest soil. Denitrification rates during the 9 days of incubation were 2.47 and 4.91 mg N kg-1 soil d-1 in the grassland and forest soils, respectively, at 100% WHC, but were not different from zero at 65% WHC. In the forest soil, both the ratio of gross nitrification to gross NH 4 + immobilization rates (N/IA) and cumulative N2O emission were lower in the 65 than in the 100% WHC treatment, while in the grassland soil, the N/IA ratio was similar between the two soil moisture content treatments but cumulative N2O emission was lower at 65% WHC.Conclusions
The effect of soil moisture content on gross nitrification rates differ between forest and grassland soils and decreasing soil moisture content from 100 to 65% WHC reduced N2O emissions in both soils. 相似文献4.
Biofortification of rice grain with zinc through zinc fertilization in different countries 总被引:5,自引:0,他引:5
N. Phattarakul B. Rerkasem L. J. Li L. H. Wu C. Q. Zou H. Ram V. S. Sohu B. S. Kang H. Surek M. Kalayci A. Yazici F. S. Zhang I. Cakmak 《Plant and Soil》2012,358(1-2):131-141
Aims and background
The ability to suppress soil nitrification through the release of nitrification inhibitors from plant roots is termed ‘biological nitrification inhibition’ (BNI). Earlier, we reported that sorghum roots release higher BNI-activity when grown with NH 4 + , but not with NO 3 - as N source. Also for BNI release, rhizosphere pH of <5.0 is needed; beyond this, a negative effect on BNI release was observed with nearly 80% loss of BNI activity at pH >7.0. This study is aimed at understanding the inter-functional relationships associated with NH 4 + uptake, rhizosphere-pH and plasma membrane H+-ATPase (PM H+-ATPase) activity in regulating the release of BNIs (biological nitrification inhibitors) from sorghum roots.Methods
Sorghum was grown hydroponically and root exudates were collected from intact plants using a pH-stat system to separate the secondary acidification effects by NH 4 + uptake on BNIs release. A recombinant luminescent Nitrosomonas europaea bioassay was used to determine BNI-activity. Root plasma membrane was isolated using a two-phase partitioning system. Hydrolytic H+-ATPase activity was determined. Split-root system setup was deployed to understand the localized responses to NH 4 + , H+-ATPase-stimulator (fusicoccin) or H+-ATPase-inhibitor (vanadates) on BNI release by sorghum.Results
Presence of NH 4 + in the rhizosphere stimulated the expression of H+-ATPase activity and enhanced the release of BNIs from sorghum roots. Fusicoccin, which stimulates H+-ATPase activity, also stimulated BNIs release in the absence of NH 4 + ; vanadate, which suppresses H+-ATPase activity, also suppressed the release of BNIs. NH 4 + levels (in rhizosphere) positively influenced BNIs release and root H+-ATPase activity in the concentration range of 0-1.0 mM, indicating a close relationship between BNI release and root H+-ATPase activity with a possible involvement of carrier-mediated transport for the release of BNIs in sorghum.Conclusion
Our results suggest that NH 4 + uptake, PM H+-ATPase activity, and rhizosphere acidification are functionally inter-connected with BNI release in sorghum. Such knowledge is critical to gain insights into why BNI function is more effective in light-textured, mildly acidic soils compared to other soil types. 相似文献5.
The contribution of nitrogen transformation processes to total N2O emissions from soils used for intensive vegetable cultivation 总被引:3,自引:0,他引:3
The rapid expansion of intensively farmed vegetable fields has substantially contributed to the total N2O emissions from croplands in China. However, to date, the mechanisms underlying this phenomenon have not been completely understood. To quantify the contributions of autotrophic nitrification, heterotrophic nitrification, and denitrification to N2O production from the intensive vegetable fields and to identify the affecting factors, a 15N tracing experiment was conducted using five soil samples collected from adjacent fields used for rice-wheat rotation system (WF), or for consecutive vegetable cultivation (VF) for 0.5 (VF1), 6 (VF2), 8 (VF3), and 10 (VF4) years. Soil was incubated under 50% water holding capacity (WHC) at 25°C for 96 h after being labeled with 15NH4NO3 or NH 4 15 NO3. The average N2O emission rate was 24.2 ng N?kg?1 h?1 in WF soil, but it ranged from 69.6 to 507 ng N?kg?1 h?1 in VF soils. Autotrophic nitrification, heterotrophic nitrification and denitrification accounted for 0.3–31.4%, 25.4–54.4% and 22.5–57.7% of the N2O emissions, respectively. When vegetable soils were moderately acidified (pH, 6.2 to ?≥?5.7), the increased N2O emissions resulted from the increase of both the gross autotrophic and heterotrophic nitrification rates and the N2O product ratio of autotrophic nitrification. However, once severe acidification occurred (as in VF4, pH?≤?4.3) and salt stress increased, both autotrophic and heterotrophic nitrification rates were inhibited to levels similar to those of WF soil. The enhanced N2O product ratios of heterotrophic nitrification (4.84‰), autotrophic nitrification (0.93‰) and denitrification processes were the most important factors explaining high N2O emission in VF4 soil. Data from this study showed that various soil conditions (e.g., soil salinity and concentration of NO 3 - or NH 4 + ) could also significantly affect the sources and rates of N2O emission. 相似文献
6.
K. R. Reddy 《Hydrobiologia》1983,98(3):237-243
Nitrogen and P interchange between the sediments and the overlying water of a simulated retention pond used for wastewater treatment were evaluated under conditions of seasonal temperature fluctuations and varying physico-chemical conditions (exposing floodwater surface to daylight vs. dark and turbulent vs. quiscent floodwater). Natural sediment columns obtained from two types of field retention ponds were used. One type of retention pond consisted of calcareous clay loam sediment while the sediment of second retention pond contained organic soil. Nutrient interchange between sediments and the overlying water was measured once a month over a period of one year. Nitrogen removal rates from floodwater were controlled by the initial floodwater NH 4 + and NO 3 ? concentration, rate of NH 4 + diffusion from the sediments to the overlying water, ammonification in the sediments, NH3 volatilization and nitrification at the sediment-water interface, and denitrification in the sediments. Under the conditions studied, NH 4 + concentrations of the floodwater were in the range of 0.01 to 0.05 µg/ml, while NO 3 ? concentrations were in the range of 0.27 to 0.78 µg/ml. Sediments with organic soil were found to be less effective in the removal of floodwater organic N, organic C and P, compared to the sediments with calcareous clay loam. Phosphorus exchange rates were dependent on the capacity of the sediment to adsorb or desorb P. Total P exchange rates were in the range of ?1.04 to 0.34 mg P/m2 day. Seasonal temperature fluctuations, turbulent vs. quiscent water conditions or exposing the floodwater surface to daylight or dark had very little effect on N and P exchange rates. 相似文献
7.
A 15N tracing study was carried out to investigate the potential gross nitrogen (N) dynamics in thirteen forest soils in Eastern China ranging from temperate to tropical zones (five coniferous forests, six deciduous broad-leaf forests, one temperate mixed forest, one evergreen broad-leaf forests ecosystems), and to identify the major controlling factors on N cycling in these forest ecosystems. The soil pH ranged from 4.3 to 7.9 and soil organic carbon (SOC) ranged from 6.6 g?kg?1 to 83.0 g?kg?1. The potential gross N transformation rates were quantified by 15N tracing studies where either the ammonium or nitrate pools were 15N labeled in parallel treatments. Gross mineralization rates ranged from 0.915 μg N g?1 soil day?1 to 2.718 μg N g?1 soil day?1 in the studied forest soils. The average contribution of labile organic-N (M Nlab ) to total gross mineralization (M Nrec +M Nlab ) was 86% (58% to 99%), indicating that turnover of labile organic N plays a dominant role in the studied forest ecosystems. The gross mineralization rates in coniferous forest soils were significantly lower (ranging between 0.915 and 1.228 μg N g?1 soil day?1) compared to broad-leaf forest soils (ranging from 1.621 to 2.718 μg N g?1 soil day?1) (p?<?0.01). Thus, the dominant vegetation may play an important role in regulating soil N mineralization. Nitrate production (nitrification) occurred via two pathways, oxidation of NH 4 + and organic N the forest soils. Correlations with soil pH indicated that this is a key factor controlling the oxidation of NH 4 + and organic N in theses forest ecosystems. NH 4 + oxidation decreased with a decline in pH while organic N oxidation increased. The climatic conditions (e.g. moisture status) at the various sites governed the NO 3 ? -N consumption processes (dissimilatory NO 3 ? reduction to NH 4 + (DNRA) or immobilization of NO 3 ? ). Total NO 3 ? consumption and the proportion of total NO 3 ? consumption to total NO 3 ? production decreased with an increase in the drought index of ecosystems, showing that strong interactions appear to exist between climatic condition (e.g. the drought index), N mineralization and the rate of DNRA. Interactions between vegetation, climatic conditions govern internal N cycling in these forests soils. 相似文献
8.
Xiaodong Ding Li Fu Chenjia Liu Fanjun Chen Ellis Hoffland Jianbo Shen Fusuo Zhang Gu Feng 《Plant and Soil》2011,349(1-2):13-24
To test the hypothesis that rhizosphere acidification would enhance the hydrolyzation of organic phosphates by increasing phosphatase activity. A Petri dish experiment with sterile agar and a pot experiment with a low P soil were used. In the Petri dish experiment, roots of each plant were cultured in two compartments, each of which contained agar with one of three nitrogen combinations: NH 4 + /N0 (N0 = nitrogen free), NH 4 + /NO 3 - , and NO 3 - /N0. Phytin was supplied as the sole phosphorus (P) source to all compartments. In the pot experiment, the soil in each pot was treated with N0, KNO3, or (NH4)2SO4) together with 0 or 75 mg kg?1 phytin-P. Dry weight, P concentration, and P content of roots were highest in the NH 4 + compartments in the Petri dish experiment. In the pot experiment, dry weight, P concentration, and P content of both shoots and roots were higher with NH 4 + than with NO 3 - . NH 4 + treatments reduced rhizosphere pH, promoted the hydrolization of phytin, enhanced acid phosphatase activity in the rhizosphere, and increased phytin-P utilization relative to N0 and NO 3 - treatments. Phosphatase activity was negatively correlated with rhizosphere pH but was positively correlated with plant P content in both experiments. Rhizosphere acidification optimized the activity of acid phosphatase excreted by maize roots and promoted phytin mineralization. NH 4 + -induced acidification in the maize rhizosphere improved the growth of maize roots by improving P uptake from phytin; the improved growth, in turn, increased NH 4 + uptake and acidification. 相似文献
9.
Labeled nitrogen (15?N) was applied to a soil-based substrate in order to study the uptake of N by Glomus intraradices extraradical mycelium (ERM) from different mineral N (NO 3 ? vs. NH 4 + ) sources and the subsequent transfer to cowpea plants. Fungal compartments (FCs) were placed within the plant growth substrate to simulate soil patches containing root-inaccessible, but mycorrhiza-accessible, N. The fungus was able to take up both N-forms, NO 3 ? and NH 4 + . However, the amount of N transferred from the FC to the plant was higher when NO 3 ? was applied to the FC. In contrast, analysis of ERM harvested from the FC showed a higher 15?N enrichment when the FC was supplied with 15NH 4 + compared with 15NO 3 ? . The 15?N shoot/root ratio of plants supplied with 15NO 3 ? was much higher than that of plants supplied with 15NH 4 + , indicative of a faster transfer of 15NO 3 ? from the root to the shoot and a higher accumulation of 15NH 4 + in the root and/or intraradical mycelium. It is concluded that hyphae of the arbuscular mycorrhizal fungus may absorb NH 4 + preferentially over NO 3 ? but that export of N from the hyphae to the root and shoot may be greater following NO 3 ? uptake. The need for NH 4 + to be assimilated into organically bound N prior to transport into the plant is discussed. 相似文献
10.
Characterization of ammonium and nitrate uptake and assimilation in roots of tea plants 总被引:3,自引:0,他引:3
Y. Y. Yang X. H. Li R. G. Ratcliffe J. Y. Ruan 《Russian Journal of Plant Physiology》2013,60(1):91-99
It has been pointed out that tea (Camellia sinensis (L.) O. Kuntze) prefers ammonium (NH 4 + ) over nitrate (NO 3 ? ) as an inorganic nitrogen (N) source. 15N studies were conducted using hydroponically grown tea plants to clarify the characteristics of uptake and assimilation of NH 4 + and NO 3 ? by tea roots. The total 15N was detected, and kinetic parameters were calculated after feeding 15NH 4 + or 15NO 3 ? to tea plants. The process of N assimilation was studied by monitoring the dynamic 15N abundance in the free amino acids of tea plant roots by GC-MS. Tea plants supplied with 15NH 4 + absorbed significantly more 15N than those supplied with 15NO 3 ? . The kinetics of 15NH 4 + and 15NO 3 ? influx into tea plants followed a classic biphasic pattern, demonstrating the action of a high affinity transport system (HATS) and a low affinity transport system (LATS). The V max value for NH 4 + uptake was 54.5 nmol/(g dry wt min), which was higher than that observed for NO 3 ? (39.3 nmol/(g dry wt min)). KM estimates were approximately 0.06 mM for NH 4 + and 0.16 mM for NO 3 ? , indicating a higher rate of NH 4 + absorption by tea plant roots. Tea plants fed with 15NH 4 + accumulated larger amounts of assimilated N, especially glutamine (Gln), compared with those fed with 15NO 3 ? . Gln, Glu, theanine (Thea), Ser, and Asp were the main free amino acids that were labeled with 15N under both conditions. The rate of N assimilation into Thea in the roots of NO 3 ? -supplied tea plants was quicker than in NH 4 + -supplied tea plants. NO 3 ? uptake by roots, rather than reduction or transport within the plant, seems to be the main factor limiting the growth of tea plants supplied with NO 3 ? as the sole N source. The NH 4 + absorbed by tea plants directly, as well as that produced by NO 3 ? reduction, was assimilated through the glutamine synthetase-glutamine oxoglutarate aminotransferase pathway in tea plant roots. The 15N labeling experiments showed that there was no direct relationship between the Thea synthesis and the preference of tea plants for NH 4 + . 相似文献
11.
B. Matejek C. Huber M. Dannenmann M. Kohlpaintner R. Gasche H. Papen 《Plant and Soil》2010,337(1-2):93-110
Microbial N turnover processes were investigated in three different forest soil layers [organic (O) layer, 0–10 cm depth (M1), 10–40 cm depth (M2)] after the clear cutting of a nitrogen (N) saturated spruce stand at the Höglwald Forest (Bavaria, Germany). The aim of the study was to provide detailed insight into soil-layer specific microbial production and the consumption of inorganic N within the main rooting zone. Furthermore, we intended to clarify the relevance of each soil layer investigated in respect of the observed high spatial variation of seepage water nitrate (NO 3 ? ) concentration at a depth of 40 cm. The buried bag and the 15N pool dilution techniques were applied to determine the net and gross N turnover rates. In addition, soil pH, C:N ratio, pool sizes of soil ammonium (NH 4 + ) and NO 3 ? , as well as quantities of microbial biomass carbon (Cmic) and nitrogen (Nmic) were determined. The 40 cm thick upper mineral soil was found to be the main place of NO 3 ? production with a NO 3 ? supply or net nitrification three times higher than in the considerably thinner O layer. Nevertheless, O layer nitrification processes determined via in situ field experiments showed significant correlation with seepage water NO 3 ? . An improved correlation noted several months after the cut may result from a transport-induced time shift of NO 3 ? with downstream hydrological pathways. In contrast, the soil laboratory incubation experiments found no indication that mineral soil is relevant for the spatial heterogeneity of seepage water NO 3 ? . The results from our study imply that in situ experiments may be better suited to studies investigating N turnover in relation to NO 3 ? loss via seepage water in similar ecosystems in order to gain representative data. 相似文献
12.
Priming Effects of the Endophytic Fungus Phomopsis liquidambari on Soil Mineral N Transformations 总被引:1,自引:0,他引:1
Nitrogen (N) is a crucial nutrient for soil biota, and its cycling is determined by the organic carbon decomposing process. Some endophytic fungi are latent saprotrophs that trigger their saprotrophic metabolism to promote litter organic matter cycling as soon as the host tissue senesces or dies. However, the effects of endophytic fungi on litter and soil N dynamics in vitro have rarely been investigated. In this study, we investigated N dynamics (total and mineral N) in both litter and soil in incubations of a pure culture of an endophytic fungus Phomopsis liquidambari with litter and following soil burial of the litter. Soil enzymes and microbial communities participating in the N transformations were also investigated. A pure culture of P. liquidambari released litter NH 4 + –N in the initial stages (10 days) of the incubation. However, following soil burial, the presence of both P. liquidambari and soil ammonia-oxidizing bacteria (AOB) resulted in an increase in soil NO 3 ? –N. These results indicate that the endophytic fungus P. liquidambari in vitro stimulates organic mineralization and promote NH 4 + –N release. Such effects triggered soil AOB-driven nitrification process. 相似文献
13.
O. G. Polesskaya E. I. Kashirina N. D. Alekhina 《Russian Journal of Plant Physiology》2006,53(2):186-192
In plants of wheat (Triticum aestivum L.) grown in the media with nitrate (NO 3 ? plants), ammonium (NH 4 + plants), and without nitrogen (N-deficient plants), the response to oxidative stress induced by the addition of 300 mM NaCl to the nutrient solution was investigated. Three-day-long salinization induced chlorophyll degradation and accumulation of malondialdehyde (MDA) in the leaves. These signs of oxidative stress were clearly expressed in NO 3 ? and N-deficient plants and weakly manifested in NH 4 + plants. In none of the treatments, salinization induced the accumulation of MDA in the roots. Depending on the conditions of N nutrition, salt stress was accompanied by diverse changes in the activity of antioxidant enzymes in the leaves and roots. Resistance of leaves of NH 4 + plants to oxidative stress correlated with a considerable increase in the activities of ascorbate peroxidase and glutathione reductase. Thus, wheat plants grown on the NH 4 + -containing medium were more resistant to the development of oxidative stress in the leaves than those supplied with nitrate. 相似文献
14.
Growth of 2-month-old nonnodulatedHippophaë rhamnoides seedlings supplied with combined N was compared with that of nodulated seedlings grown on zero N. Plant growth was significantly better with combined N than with N2 fixation and, although not statistically significant for individual harvests, tended to be highest in the presence of NH 4 + , a mixture of NH 4 + and NO 3 ? producing the highest yields. Growth was severely reduced when solely dependent on N2 fixation and, unlike the combined-N plants, shoot to root ratios had only slightly increased after an initial decrease. An apparently insufficient nodule mass (nodule weight ratio <5 per cent) during the greater part of the experimental period is suggested as the main cause of the growth reduction in N2-fixing plants. Thein vivo nitrate reductase activity (NRA) of NO 3 ? dependent plants was almost entirely located in the roots. However, when grown with a combination of NO 3 ? and NH 4 + , root NRA was decreased by approximately 85 per cent.H. rhamnoides demonstrated in the mixed supply a strong preference for uptake of N as NH 4 + , NO 3 ? contributing only for approximately 20 per cent to the total N assimilation. Specific rates of N acquisition and ion uptake were generally highest in NO 3 ? +NH 4 + plants. The generation of organic anions per unit total plant dry weight was approximately 40 per cent less in the NH 4 + plants than in the NO 3 ? plants. Measured extrusions of H+ or OH? (HCO 3 ? ) were generally in good agreement with calculated values on the basis of plant composition, and the acidity generated with N2 fixation amounted to 0.45–0.55 meq H+. (mmol Norg)?1. Without acidity control and in the presence of NH 4 + , specific rates of ion uptake and carboxylate generation were strongly depressed and growth was reduced by 30–35 per cent. Growth of nonnodulatedH. rhamnoides plants ceased at the lower pH limit of 3.1–3.2 and deterioration set in; in the case of N2-fixing plants the nutrient solution pH stabilized at a value of 3.8–3.9 without any apparent adverse effects upon plant performance. The chemical composition of experimental and field-growing plants is being compared and some comments are made on the nitrogen supply characteristics of their natural sites. 相似文献
15.
Effects of nitrate concentration on the denitrification potential of a calcic cambisol and its fractions of N2, N2O and NO 总被引:1,自引:0,他引:1
Rui Wang Qi Feng Tingting Liao Xunhua Zheng Klaus Butterbach-Bahl Wei Zhang Chunyi Jin 《Plant and Soil》2013,363(1-2):175-189
Background and aims
The direct measurement of denitrification dynamics and its product fractions is important for parameterizing process-oriented model(s) for nitrogen cycling in various soils. The aims of this study are to a) directly measure the denitrification potential and the fractions of nitrogenous gases as products of the process in laboratory, b) investigate the effects of the nitrate (NO 3 ? ) concentration on emissions of denitrification gases, and c) test the hypothesis that denitrification can be a major pathway of nitrous oxide (N2O) and nitric oxide (NO) production in calcic cambisols under conditions of simultaneously sufficient supplies of carbon and nitrogen substrates and anaerobiosis as to be found to occur commonly in agricultural lands.Methods
Using the helium atmosphere (with or without oxygen) gas-flow-soil-core technique in laboratory, we directly measured the denitrification potential of a silt clay calcic cambisol and the production of nitrogen gas (N2), N2O and NO during denitrification under the conditions of seven levels of NO 3 ? concentrations (ranging from 10 to 250 mg N kg?1 dry soil) and an almost constant initial dissolved organic carbon concentration (300 mg C kg?1 dry soil).Results
Almost all the soil NO 3 ? was consumed during anaerobic incubation, with 80–88 % of the consumed NO 3 ? recovered by measuring nitrogenous gases. The results showed that the increases in initial NO 3 ? concentrations significantly enhanced the denitrification potential and the emissions of N2 and N2O as products of this process. Despite the wide range of initial NO 3 ? concentrations, the ratios of N2, N2O and NO products to denitrification potential showed much narrower ranges of 51–78 % for N2, 14–36 % for N2O and 5–22 % for NO.Conclusions
These results well support the above hypothesis and provide some parameters for simulating effects of variable soil NO 3 ? concentrations on denitrification process as needed for biogeochemical models. 相似文献16.
Fusuo Zhang Junfang Niu Weifeng Zhang Xinping Chen Chunjian Li Lixing Yuan Jianchang Xie 《Plant and Soil》2010,333(1-2):21-34
Biological soil crusts (BSCs) greatly influence the N cycle of semi-arid ecosystems, as some organisms forming them are able to fix atmospheric N. However, BSCs are not always taken into account when studying biotic controls on N cycling and transformations. Our main objective was to understand how BSCs modulate the availability of N in a semi-arid Mediterranean ecosystem dominated by the tussock grass Stipa tenacissima. We selected the six most frequent soil cover types in the study area: S. tenacissima tussocks (ST), Retama sphaerocarpa shrubs (RS), and open areas with very low (BS), low (LC) medium (MC) and high (HC) cover of well developed and lichen-dominated BSCs. The temporal dynamics of available N dynamics followed changes in soil moisture. Available NH 4 + -N did not differ between microsites, while available NO 3 - -N was substantially higher in the RS than in any other microsite. No significant differences in the amount of available NO 3 - -N were found between ST and BS microsites, but these microsites had more NO 3 - -N than those dominated by BSCs (LC, MC and HC). Our results suggest that BSCs may be inhibiting nitrification, and highlight the importance of this biotic community as a modulator of the availability of N in semi-arid ecosystems. 相似文献
17.
Integrated soil and plant phosphorus management for crop and environment in China. A review 总被引:25,自引:0,他引:25
H. Li G. Huang Q. Meng L. Ma L. Yuan F. Wang W. Zhang Z. Cui J. Shen X. Chen R. Jiang F. Zhang 《Plant and Soil》2011,340(1-2):157-167
In semi-arid grassland ecosystems, soil biogeochemical processes are controlled by seasonal and inter-annual rainfall variation and temperature, which may override the long-term impact of grazers on N availability and N dynamics. In a three-year (2004?C2006) case study of an Inner Mongolian grassland, we analysed time-integrated (ion-exchange resins) and instantaneous (soil mineral N extractions) inorganic N availability at three sites of varying grazing intensities and combined these data with information on soil water content (SWC), aboveground net primary productivity (ANPP) and plant N uptake. Additionally, the effects of rainfall and grazing on N-form availability (NO 3 ? -N, NH 4 + -N) were considered. Grazing had less impact on N availability compared to seasonal and annual rainfall distribution. One of the three study years (2004) showed a grazing effect with higher resin-N availability at the ungrazed site compared to the heavily grazed site. Inorganic N availability was low in the driest year (2005) and highest in a year of average rainfall amount and favourable distribution (2004). In general, we found a positive relationship between inorganic N availability and both plant productivity and plant N uptake. Rainfall also controlled the plant available NO 3 ? -N and NH 4 + -N pools; NH 4 + -N dominated the available inorganic N-form in times of low SWC, while the available NO 3 ? -N increased with SWC. We observed N availability and plant productivity in a temporal synchronized pattern. Increased rainfall variability and land-use practices affecting SWC will likely alter N availability dynamics (and the relation of N-forms) and, therefore, important processes of semi-arid natural grassland carbon and N cycling. 相似文献
18.
Background and aims
Plant physiological traits and their relation to soil N availability was investigated as regulators of the distribution of understory shrub species along a slope in a Japanese cedar (Cryptomeria japonica) plantation in central Japan.Methods
At the study site, previous studies demonstrated that both net and gross soil nitrification rates are high on the lower slope and there are dramatic declines in different sections of the slope gradient. We examined the distributions of understory plant species and their nitrate (NO 3 ? -N) use traits, and compared the results with the soil traits.Results
Our results show that boundaries between different dominant understory species correspond to boundaries between different soil types. Leucosceptrum stellipilum occurs on soil with high net and gross nitrification rates. Hydrangea hirta is dominant on soil with high net and low gross nitrification rates. Pieris japonica occurs on soil with very low net and gross nitrification rates. Dominant understory species have species-specific physiological traits in their use of NO 3 ? -N. Pieris japonica lacks the capacity to use NO 3 ? -N as a N source, but other species do use NO 3 ? -N. Lindera triloba, whose distribution is unrelated to soil NO 3 ? -N availability, changes the extent to which it uses NO 3 ? -N in response to soil NO 3 ? -N availability.Conclusions
Our results indicate that differences in the physiological capabilities and adaptabilities of plant species in using NO 3 ? -N as a N source regulate their distribution ranges. The identity of the major form of available soil N is therefore an environmental factor that influences plant distributions. 相似文献19.
20.
Alteration of nitrogen metabolism in rice variety 'Nipponbare' induced by alkali stress 总被引:1,自引:0,他引:1
Huan Wang Jianaer Ahan Zhihai Wu Decheng Shi Bao Liu Chunwu Yang 《Plant and Soil》2012,355(1-2):131-147