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1.
Aim
This study aimed at better characterising background nitrous oxide (N2O) emissions (BNE) in agricultural and natural lands.Methods
We compiled and analysed field-measured data for annual background N2O emission in agricultural (BNEA) and natural (BNEN) lands from 600 and 307 independent experimental studies, respectively.Results
There were no significant differences between BNEA (median: 0.70 & mean: 1.52 kg N2O???N ha?1 yr?1) and BNEN (median:0.31 & mean:1.75 kg N2O???N ha?1 yr?1) (P?>?0.05). A simultaneous comparison across all BNEA and BNEN indicated that BNEs from riparian, vegetable crop fields and intentional fallow areas were significantly higher than from boreal forests (P?<?0.05). Correlation and regression analyses supported the underlying associations of soil organic carbon (C), nitrogen (N), pH, bulk density (BD),and/or air temperature (AT) with BNEs to a varying degree as a function of land-use or ecosystem type (Ps?<?0.05).Conclusions
Although overall BNEN tended to be lower than BNEA on median basis, results in general suggest that land-use shifts between natural and managed production systems would not result in consistent changes in BNE. 相似文献2.
Nitrous oxide emissions and nitrate leaching from a rain-fed wheat-maize rotation in the Sichuan Basin, China 总被引:3,自引:0,他引:3
Minghua Zhou Bo Zhu Klaus Butterbach-Bahl Xunhua Zheng Tao Wang Yanqiang Wang 《Plant and Soil》2013,362(1-2):149-159
Aims
A 3-year field experiment (October 2004–October 2007) was conducted to quantify N2O fluxes and determine the regulating factors from rain-fed, N fertilized wheat-maize rotation in the Sichuan Basin, China.Methods
Static chamber-GC techniques were used to measure soil N2O fluxes in three treatments (three replicates per treatment): CK (no fertilizer); N150 (300 kg N fertilizer ha?1 yr?1 or 150 kg N?ha?1 per crop); N250 (500 kg N fertilizer ha?1 yr?1 kg or 250 kg N?ha?1 per crop). Nitrate (NO 3 ? ) leaching losses were measured at nearby sites using free-drained lysimeters.Results
The annual N2O fluxes from the N fertilized treatments were in the range of 1.9 to 6.7 kg N?ha?1 yr?1 corresponding to an N2O emission factor ranging from 0.12 % to 1.06 % (mean value: 0.61 %). The relationship between monthly soil N2O fluxes and NO 3 - leaching losses can be described by a significant exponential decaying function.Conclusions
The N2O emission factor obtained in our study was somewhat lower than the current IPCC default emission factor (1 %). Nitrate leaching, through removal of topsoil NO 3 ? , is an underrated regulating factor of soil N2O fluxes from cropland, especially in the regions where high NO 3 - leaching losses occur. 相似文献3.
Sebastian Pfautsch Pablo L. Peri Craig Macfarlane Floris van Ogtrop Mark A. Adams 《Trees - Structure and Function》2014,28(1):125-136
Key message
This study is the first to quantify tree water use below 50°S. Tree morphology differs markedly among the two investigated species, reflecting adjustment to different environmental cues.Abstract
A pronounced environmental gradient dictates the dominance of Nothofagus in the foothills on the eastern side of the Andes Mountains in Patagonia, Argentina. Below 50° southern latitude, open forests of Nothofagus antarctica (ñire) dominate the landscape towards the Patagonian steppe where annual rainfall is low. With increasing rates of annual rainfall, corresponding with an increase in elevation, closed forests of N. pumilio (lenga) replace those of ñire. During a short-term study we assessed differences in stand structure and examined environmental, structural and functional traits related to tree water use of ñire and lenga. Sap velocity reached similar maximum rates (95–100 L m?2 sapwood h?1), but whole-tree water use (Q) was significantly lower in ñire (8–13 L day?1 tree?1) compared to lenga (20–90 L day?1 tree?1) resulting in lower stand transpiration (ñire: 0.51 mm day?1; lenga: 3.42 mm day?1) despite similar tree densities. Related to this, wind speed had a particularly significant impact on Q of ñire, but not lenga. The ratio of leaf area to sapwood area (A L/A S) clearly identified ñire to be more structurally proficient at conserving water. While stem diameter (DBH) and crown area (A C) were well related in both species, only lenga exhibited relationships between variables related to tree allometry and physiology (A C/Q, DBH/Q). Our results provide the first ecophysiological characterization of the two Nothofagus species that define important and widespread ecosystems in southern Patagonia (not only below 50°S), and provide useful data to scale water use of both species from tree to stand. 相似文献4.
Plant and soil responses of an alpine steppe on the Tibetan Plateau to multi-level nitrogen addition 总被引:2,自引:0,他引:2
Yongwen Liu Xu-Ri Xingliang Xu Da Wei Yinghong Wang Yuesi Wang 《Plant and Soil》2013,369(1-2):515-529
Background
Although plant growth in alpine steppes on the Tibetan Plateau has been suggested to be sensitive to nitrogen (N) addition, the N limitation conditions of alpine steppes remain uncertain.Methods
After 2 years of fertilization with NH4NO3 at six rates (0, 10, 20, 40, 80 and 160 kg N ha?1 yr?1), the responses of plant and soil parameters as well as N2O fluxes were measured.Results
At the vegetation level, N addition resulted in an increase in the aboveground N pool from 0.5?±?0.1 g m?2 in the control plots to 1.9?±?0.2 g m?2 in the plots at the highest N input rate. The aboveground C pool, biomass N concentration, foliar δ15N, soil NO3 ?-N and N2O flux were also increased by N addition. However, as the N fertilization rate increased from 10 kg N ha?1 yr?1 to 160 kg N ha?1 yr?1, the N-use efficiency decreased from 12.3?±?4.6 kg C kg N?1 to 1.6?±?0.2 kg C kg N?1, and the N-uptake efficiency decreased from 43.2?±?9.7 % to 9.1?±?1.1 %. Biomass N:P ratios increased from 14.4?±?2.6 in the control plots to 20.5?±?0.8 in the plots with the highest N input rate. Biomass N:P ratios, N-uptake efficiency and N-use efficiency flattened out at 40 kg N ha?1 yr?1. Above this level, soil NO3 ?-N began to accumulate. The seasonal average N2O flux of growing season nonlinearly increased with increased N fertilization rate and linearly increased with the weighted average foliar δ15N. At the species level, N uptake responses to relative N availability were species-specific. Biomass N concentration of seven out of the eight non-legume species increased significantly with N fertilization rates, while Kobresia macrantha and the one legume species (Oxytropics glacialis) remained stable. Both the non-legume and the legume species showed significant 15N enrichment with increasing N fertilization rate. All non-legume species showed significant increased N:P ratios with increased N fertilization rate, but not the legume species.Conclusions
Our findings suggest that the Tibetan alpine steppes might be N-saturated above a critical N load of 40 kg N ha?1 yr?1. For the entire Tibetan Plateau (ca. 2.57 million km2), a low N deposition rate (10 kg N ha?1 yr?1) could enhance plant growth, and stimulate aboveground N and C storage by at least 1.1?±?0.3 Tg N yr?1 and 31.5?±?11.8 Tg C yr?1, respectively. The non-legume species was N-limited, but the legume species was not limited by N. 相似文献5.
Annual nitrous oxide emissions from open-air and greenhouse vegetable cropping systems in China 总被引:5,自引:0,他引:5
Aims
A field experiment was conducted to quantify annual nitrous oxide (N2O) fluxes from control and fertilized plots under open-air and greenhouse vegetable cropping systems in southeast China. We compiled the reported global field annual N2O flux measurements to estimate the emission factor of N fertilizer for N2O and its background emissions from vegetable fields.Methods
Fluxes of N2O were measured using static chamber-GC techniques over the 2010–2011 annual cycle with multiple cropping seasons.Results
The mean annual N2O fluxes from the controls were 46.1?±?2.3 μg N2O-N m?2 hr?1 and 68.3?±?4.1 μg N2O-N m?2 hr?1 in the open-air and greenhouse vegetable systems, respectively. For the plots receiving 900 kg?N?ha?1, annual N2O emissions averaged 90.6?±?8.9 μg N2O-N m?2 hr?1 and 106.4?±?6.6 μg N2O-N?m?2 hr?1 in the open-air and greenhouse vegetable systems, respectively. By pooling published field N2O flux measurements taken over or close to a full year, the N2O emission factor for N fertilizer averaged 0.63?±?0.09 %, with a background emission of 2.67?±?0.80 kg N2O-N ha?1 in Chinese vegetable fields. Annual N2O emissions from Chinese vegetable systems were estimated to be 84.7 Gg N2O-N yr?1, consisting of 72.5 Gg N2O-N yr?1 and 12.2 Gg N2O-N yr?1 in the open-air and greenhouse vegetable systems, respectively.Conclusions
While N2O emissions from the greenhouse vegetable cropping system tended to be slightly higher compared to the open-air system in our experiment, the synthesis of literature data suggests that N2O emissions would be greater at low N-rates but smaller at high N-rates in greenhouse systems than in open-air vegetable cropping systems. The estimates of this study suggest that vegetable cropping systems covering 11.4 % in national total cropping area, contributed 21–25 % to the total N2O emission from Chinese croplands. 相似文献6.
Aims
Effects of different soil amendments were investigated on methane (CH4) emission, soil quality parameters and rice productivity in irrigated paddy field of Bangladesh.Methods
The experiment was laid out in a randomized complete block design with five treatments and three replications. The experimental treatments were urea (220 kg ha?1) + rice straw compost (2 t ha?1) as a control, urea (170 kg ha?1) + rice straw compost (2 t ha?1) + silicate fertilizer, urea (170 kg ha?1) + sesbania biomass (2 t ha?1 ) + silicate fertilizer, urea (170 kg ha?1) + azolla biomass (2 t ha?1) + cyanobacterial mixture 15 kg ha?1 silicate fertilizer, urea (170 kg ha?1) + cattle manure compost (2 t ha?1) + silicate fertilizer.Results
The average of two growing seasons CH4 flux 132 kg ha?1 was recorded from the conventional urea (220 kg ha?1) with rice straw compost incorporated field plot followed by 126.7 (4 % reduction), 130.7 (1.5 % reduction), 116 (12 % reduction) and 126 (5 % reduction) kg CH4 flux ha?1 respectively, with rice straw compost, sesbania biomass, azolla anabaena and cattle manure compost in combination urea and silicate fertilizer applied plots. Rice grain yield was increased by 15 % and 10 % over the control (4.95 Mg ha?1) with silicate plus composted cattle manure and silicate plus azolla anabaena, respectively. Soil quality parameters such as soil organic carbon, total nitrogen, microbial biomass carbon, soil redox status and cations exchange capacity were improved with the added organic materials and azolla biofertilizer amendments with silicate slag and optimum urea application (170 kg ha?1) in paddy field.Conclusion
Integrated application of silicate fertilizer, well composted organic manures and azolla biofertilizer could be an effective strategy to minimize the use of conventional urea fertilizer, reducing CH4 emissions, improving soil quality parameters and increasing rice productivity in subtropical countries like Bangladesh. 相似文献7.
Comparing soil carbon sequestration in coastal freshwater wetlands with various geomorphic features and plant communities in Veracruz,Mexico 总被引:1,自引:0,他引:1
José Luis Marín-Muñiz María E. Hernández Patricia Moreno-Casasola 《Plant and Soil》2014,378(1-2):189-203
Background and aims
Wetlands are important carbon sinks across the planet. However, soil carbon sequestration in tropical freshwater wetlands has been studied less than its counterpart in temperate wetlands. We compared carbon stocks and carbon sequestration in freshwater wetlands with various geomorphic features (estuarine, perilacustrine and depressional) and various plant communities (marshes and swamps) on the tropical coastal plain of the Gulf of Mexico in the state of Veracruz, Mexico. These swamps are dominated by Ficus insipida, Pachira aquatic and Annona glabra and the marshes by Typha domingensis, Thalia geniculata, Cyperus giganteus, and Pontederia sagittata.Methods
The soil carbon concentration and bulk density were measured every 2 cm along 80 cm soil profiles in five swamps and five marshes. Short-term sediment accretion rates were measured during a year using horizontal makers in three of the five swamps and marshes, the carbon sequestration was calculated using the accretion rates, and the bulk density and the percentage of organic carbon in the surficial layer was measured.Results
The average carbon concentration ranged from 50 to 150 gC kg?1 in the marshes and 50 to 225 gC kg?1 in the swamps. When the wetlands were grouped according to their geomorphic features, no significant differences in the carbon stock (P?=?0.095) were found (estuarine (25.50?±?2.26 kgC m?2), perilacustrine (28.33?±?2.74 kgC m?2) and depressional wetlands (34.93?±?4.56 kgC m?2)). However, the carbon stock was significantly higher (P?=?0.030) in the swamps (34.96?±?1.3 kgC m?2) than in the marshes (25.85?±?1.19 kgC m?2). The average sediment accretion rates were 1.55?±?0.09 cm yr?1 in the swamps and 0.84?±?0.02 cm yr?1 in the marshes with significant differences (P?=?0.040). The rate of carbon sequestration was higher (P?=?0.001) in swamp soils (0.92?±?0.12 kgC m?2 yr?1) than marsh soils (0.31?±?0.08 kgC m?2 yr?1). Differences in the rates of carbon sequestration associated with geomorphic features were found between the swamp ecosystems (P?<?0.05); i.e., higher values were found in the swamps than in the marshes in perilacustrine and estuarine wetlands (P?<?0.05). However, no significant differences (P?=?0.324) in carbon sequestration rates were found between the marsh and swamp areas of the depressional site.Conclusions
Swamp soils are more important contributors to the carbon stock and sequestration than are marsh soils, resulting in a reduction in global warming, which suggests that the plant community is an important factor that needs to be considered in global carbon budgets and projects of restoration and conservation of wetlands. 相似文献8.
Nitrogen dynamics following field application of biochar in a temperate North American maize-based production system 总被引:5,自引:0,他引:5
David Güereña Johannes Lehmann Kelly Hanley Akio Enders Charles Hyland Susan Riha 《Plant and Soil》2013,365(1-2):239-254
Background and aims
Biochar additions to tropical soils have been shown to reduce N leaching and increase N use efficiency. No studies exist verifying reduced N leaching in field experiments on temperate agricultural soils or identifying the mechanism for N retention.Methods
Biochar derived from maize stover was applied to a maize cropping system in central New York State at rates of 0, 1, 3, 12, and 30 t?ha-1 in 2007. Secondary N fertilizer was added at 100, 90, 70, and 50 % of the recommended rate (108 kg N ha-1). Nitrogen fertilizer enriched with 15?N was applied in 2009 to the 0 and 12 t?ha-1 of biochar at 100 and 50 % secondary N application.Results
Maize yield and plant N uptake did not change with biochar additions (p?>?0.05; n?=?3). Less N (by 82 %; p?<?0.05) was lost after biochar application through leaching only at 100 %?N fertilization. The reason for an observed 140 % greater retention of applied 15?N in the topsoil may have been the incorporation of added 15?N into microbial biomass which increased approximately three-fold which warrants further research. The low leaching of applied fertilizer 15?N (0.42 % of applied N; p?<?0.05) and comparatively high recovery of applied 15?N in the soil (39 %) after biochar additions after one cropping season may also indicate greater overall N retention through lower gaseous or erosion N losses with biochar.Conclusions
Addition of biochar to fertile soil in a temperate climate did not improve crop growth or N use efficiency, but increased retention of fertilizer N in the topsoil. 相似文献9.
Background and aims
Dominance of C4 grasses has been proposed as a means of increasing soil organic carbon (SOC) sequestration in restored tallgrass prairies. However, this hypothesis has not been tested on long time scales and under realistic (e.g. N-limited) environmental conditions. We sampled a restoration in southern Illinois 33 years after establishment to determine the effects of varying plant communities on SOC sequestration in the top 50 cm of soil.Methods
SOC, total nitrogen (TN), and the stable isotopic composition of SOC (δ13C) were used to calculate SOC sequestration rates, N storage, and the relative contributions of C3 vs. C4 plant communities as a function of soil depth.Results
While both a forb-dominated and a mixed forb-grass plant community showed positive sequestration rates (0.56?±?0.13 and 0.27?±?0.10 Mg C ha?1 yr?1, respectively), a C4 grass-dominated community showed SOC losses after 33 years of restoration (?0.31?±?0.08 Mg C ha?1 yr?1). Soil δ13C values were significantly more negative for forb-dominated plant communities, increasing the confidence that plant communities were stable over time and an important contributor to differences in SOC stocks among transects.Conclusion
These results suggest that functional diversity may be necessary to sustain sequestration rates on the scale of decades, and that dominance of C4 grasses, favored by frequent burning, may lead to SOC losses over time. 相似文献10.
C. Uribe R. Inclán D. M. Sánchez M. A. Clavero A. M. Fernández R. Morante A. Cardeña A. Blanco H. Van Miegroet 《Plant and Soil》2013,369(1-2):403-420
Background and Aims
Mediterranean forests are vulnerable to numerous threats including wildfires due to a combination of climatic factors and increased urbanization. In addition, increased temperatures and summer drought lead to increased risk of forest fires as a result of climate change. This may have important consequences for C dynamics and balance in these ecosystems. Soil respiration was measured over 2 successive years in Holm oak (Quercus ilex subsp. ballota; Qi); Pyrenean Oak (Quercus pyrenaica Willd; Qp); and Scots pine (Pinus sylvestris L.; Ps) forest stands located in the area surrounding Madrid (Spain), to assess the long term effects of wildfires on C efflux from the soil, soil properties, and the role of soil temperature and soil moisture in the variation of soil respiration.Methods
Soil respiration, soil temperature, soil moisture, fine root mass, microbial biomass, biological and chemical soil parameters were compared between non burned (NB) and burned sites (B).Results
The annual C losses through soil respiration from NB sites in Qi, Qp and Ps were 790, 1010, 1380 gCm?2?yr?1, respectively, with the B sites emitting 43 %, 22 % and 11 % less in Qi, Qp and Ps respectively. Soil microclimate changed with higher soil temperature and lower soil moisture in B sites after fire. Exchangeable cations and the pH also decreased. The total SOC stocks were not significantly altered, but 6–8 years after wildfires, there was still measurably lower fine root and microbial biomass, while SOC quality changed, indicated by lower the C/N ratio and the labile carbon and a relative increase in refractory SOC forms, which resulted in lower Q10 values.Conclusions
We found long term effects of wildfires on the physical, chemical and biological soil characteristics, which in turn affected soil respiration. The response of soil respiration to temperature was controlled by moisture and changed with ecosystem type, season, and between B and NB sites. Lower post-burn Q10 integrated the loss of roots and microbial biomass, change in SOC quality and a decrease in soil moisture. 相似文献11.
Aims
In this study we quantified the annual soil CO2 efflux (annual SCE) of a short rotation coppice plantation in its establishment phase. We aimed to examine the effect of former (agricultural) land use type, inter-row spacing and genotype.Methods
Annual SCE was quantified during the second growth year of the establishment rotation in a large scale poplar plantation in Flanders. Automated chambers were distributed over the two former land use types, the two different inter-row spacings and under two poplar genotypes. Additional measurements of C, N, P, K, Mg, Ca and Na concentrations of the soil, pH, bulk density, fine root biomass, microbial biomass C, soil mineralization rate, distance to trees and tree diameters were performed at the end of the second growth year.Results
Total carbon loss from soil CO2 efflux was valued at 589 g m?2 yr?1. Annual SCE was higher in former pasture as compared to cropland, higher in the narrow than in the wider inter-row spacings, but no effect of genotype was found.Conclusions
Spatial differences in site characteristics are of great importance for understanding the effect of ecosystem management and land use change on soil respiration processes and need to be taken into account in modeling efforts of the carbon balance. 相似文献12.
Assessment of nitrate leaching loss on a yield-scaled basis from maize and wheat cropping systems 总被引:9,自引:0,他引:9
Background and aims
It is so far a gap in knowledge to assess nitrate (NO3 ?) leaching loss linking with crop yield for a given cereal cropping system.Methods
We conducted a meta-analysis on 32 published studies reporting both NO3 ? leaching losses and crop yields in the maize (N?=?20) and wheat (N?=?12) systems.Results
On average, 22 % and 15 % of applied fertilizer N to wheat and maize systems worldwide are leached in the form of NO3 ?, respectively. The average area-scaled NO3 - leaching loss for maize (57.4 kg N ha?1) was approx. two times higher than for wheat (29.0 kg N ha?1). While, if scaled to crop yields, the average yield-scaled NO3 ? losses were comparable between maize (5.40 kg N Mg?1) and wheat (5.41 kg N Mg?1) systems. Across all sites, the lowest yield-scaled NO3 ? leaching losses were observed at slightly suboptimal fertilization rates, corresponding to 90 % and 96 % of maximum maize or wheat yields, respectively.Conclusions
Our findings suggest that small adjustments of agricultural N management practices can effectively reduce yield-scaled NO3 ? leaching losses. However, further targeted field experiments are still needed to identify at regional scale best agricultural management practices for reducing yield-scaled NO3 ? leaching losses in maize and wheat systems. 相似文献13.
I. Brunner M. R. Bakker R. G. Björk Y. Hirano M. Lukac X. Aranda I. Børja T. D. Eldhuset H. S. Helmisaari C. Jourdan B. Konôpka B. C. López C. Miguel Pérez H. Persson I. Ostonen 《Plant and Soil》2013,362(1-2):357-372
Background and Aims
Forest trees directly contribute to carbon cycling in forest soils through the turnover of their fine roots. In this study we aimed to calculate root turnover rates of common European forest tree species and to compare them with most frequently published values.Methods
We compiled available European data and applied various turnover rate calculation methods to the resulting database. We used Decision Matrix and Maximum-Minimum formula as suggested in the literature.Results
Mean turnover rates obtained by the combination of sequential coring and Decision Matrix were 0.86 yr?1 for Fagus sylvatica and 0.88 yr?1 for Picea abies when maximum biomass data were used for the calculation, and 1.11 yr?1 for both species when mean biomass data were used. Using mean biomass rather than maximum resulted in about 30 % higher values of root turnover. Using the Decision Matrix to calculate turnover rate doubled the rates when compared to the Maximum-Minimum formula. The Decision Matrix, however, makes use of more input information than the Maximum-Minimum formula.Conclusions
We propose that calculations using the Decision Matrix with mean biomass give the most reliable estimates of root turnover rates in European forests and should preferentially be used in models and C reporting. 相似文献14.
Aims
Decomposition of leaf litterfall plays a major role for nitrogen (N) dynamics in soils. However, little is known as to which extent beech leaf litter contributes to N turnover and nitrous oxide (N2O) emissions within one decade after litterfall.Methods
In 1997, we exchanged recently fallen leaf litter by 15N-labelled litter in a beech stand (Fagus sylvatica) at the Solling, Germany. Measurements were conducted 2–3 and 10–11 years after litter exchange.Results
Two years after litter exchange, 92 % of added 15N was recovered in the surface 10 cm of the soil. The labelled N was primarily found in the upper part of the F layer of the moder type humus. Eleven years after litter exchange, 73 % of the added 15N was lost and the remaining 27 % was mainly recovered in the lower part of the F layer indicating N sequestration. The remaining leaf litter N was subject to measurable N mineralisation (2–3 % of litter N) and N2O production (0.02 %). Between 0.3 % (eleventh year) and 0.6 % (second year) of total annual N2O emissions were attributed to beech leaf litter of a single year.Conclusions
Most of the annual N2O emissions (1.33–1.54 kg N ha?1 yr?1) were probably derived from older soil N pools. 相似文献15.
Aims
This study aimed to measure the effect of plant diversity on N uptake in grasslands and to assess the mechanisms contributing to diversity effects.Methods
Annual N uptake into above- and belowground organs and soil nitrate pools were measured in the Jena experiment on a floodplain soil with mixtures of 2–16 species and 1–4 functional groups, and monocultures. In mixtures, the deviation of measured data from data expected from monoculture performance was calculated to assess the contribution of complementarity/facilitation and selection.Results
N uptake varied from <1 to 45 g?N m?2 yr?1, and was higher in grasslands with than without legumes. On average, N uptake was higher in mixtures (21?±?1 g?N m?2 yr?1) than monocultures (13?±?1 g?N m?2 yr?1), and increased with species richness in mixtures. However, compared to N uptake expected from biomass proportions of species in mixtures, N uptake of mixtures was only slightly higher and a significant surplus N uptake was confined to mixtures containing legumes and non-legumes.Conclusions
In our study, high N uptake of species rich mixtures was mainly due to dominance of productive species and facilitation by legumes whereas complementarity among non-legumes was of minor relevance. 相似文献16.
Background and aims
The roots of tussock-forming plants contribute to the formation of microtopographic features in many ecosystems, but the dynamics of such roots are poorly understood. We examined the spatial heterogeneity of tussock fine root dynamics to investigate allocation patterns and the role of root productivity in the persistence of tussock structures.Methods
We compared the spatial variability of fine root (<1 mm, 1–2 mm) density, biomass, % live, allocation, turnover rate (using bomb 14C), and productivity of four Carex stricta Lam.-dominated tussock meadows in the upper Midwest, USA (3 reference, 1 restored site).Results
Relative to underlying microsites, tussocks were warm, dry, and high in root density, productivity, % live biomass, and turnover. Root productivity averaged 649 g?m?2 yr?1 (±208) in reference sites, comprised 57 % (±10) of total net production, and was concentrated in tussocks (70 %?±?4). Root turnover rate averaged 0.63 yr?1 (±0.08), but tussocks had ~50 % faster root turnover than the underlying soil, and <1 mm roots turned over ~40 % faster than 1–2 mm roots.Conclusions
Our detailed analysis of the spatial heterogeneity of tussock root dynamics suggests that high allocation and elevated turnover of tussock roots facilitates organic matter accumulation and tussock persistence over time. 相似文献17.
Background and aims
As low initial uptake and essentially zero later uptake limit efficacy of N fertilization for temperate conifers, we investigated factors limiting long-term tree uptake of residual 15?N-labeled fertilizer.Methods
We used a pot bioassay to assess availability of 15?N from soil sampled 10 years after fertilization of a Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand with 15?N-urea (200 kg N ha?1). Douglas-fir seedlings were grown for 2 years in organic (designated LFH) and mineral soil (0–10 cm) layers reconstructed from control and fertilized plots; residual fertilizer N amounted to 10 % of LHF and 5 % of MIN N.Results
Percentage recovery of residual 15?N in seedlings was not affected by the original season of fertilization (spring vs. fall), but differed by the source of 15?N excess. LFH was a better source of residual 15?N; 12.4 % of residual LFH 15?N was taken up by seedlings and 7.6 % transferred to soil, whereas mineral soil yielded only 8.3 % of residual 15?N to seedling uptake and 2.4 % to LFH. Extractable inorganic N was 2–3 orders of magnitude higher in fallow pots.Conclusions
Ten-year residual fertilizer 15?N was clearly cycling between LFH and mineral soil and available to seedlings, indicating that other factors such as denitrification, leaching, and asynchrony of soil N mineralization and tree uptake limit long-term residual N fertilizer uptake in the field. 相似文献18.
Fertilizer N uptake of paddy rice in two soils with different fertility under experimental warming with elevated CO2 总被引:1,自引:0,他引:1
Hong-Shik Nam Jin-Hyeob Kwak Sang-Sun Lim Woo-Jung Choi Sun-Il Lee Dong-Suk Lee Kwang-Seung Lee Han-Yong Kim Sang-Mo Lee Miwa Matsushima 《Plant and Soil》2013,369(1-2):563-575
Background and aims
Only limited information is available in the research area on the effect of elevated CO2 concentration ([CO2]) and air temperature (Tair) on the fertilizer N uptake by rice. This study was conducted to investigate changes in rice uptake of N derived from fertilizer (NDFF) and soil (NDFS) as well as fertilizer N uptake efficiency (FUE) with elevated [CO2] and Tair in two soils with different fertility.Methods
Rice (Oryza sativa L.) plants were grown with 15N-urea for two growing seasons (2007 in the less fertile and 2008 in the more fertile soil) in temperature gradient chambers under two (ambient and elevated) levels of [CO2] and Tair regimes. At harvest, dry matter (DM) and N uptake amount of rice compartments (root, shoot, and grain) were determined.Results
The DM of whole rice increased (P?<?0.01) with co-elevation of [CO2] and Tair in both years (by 28.0 % in 2007 and by 27.4 % in 2008). The DM in 2008 was greater than that in 2007 by 48.1 to 63.1 % probably due to better soil fertility as well as longer sunshine hours (456 h vs. 568 h). Co-elevation of [CO2] and Tair increased total N uptake, NDFF, and NDFS by 19.4 to 29.1 % in general compared to the ambient conditions. The FUE increased with co-elevation of [CO2] and Tair from 46.5 to 59.5 % in 2007 and from 36.7 to 43.8 % in 2008.Conclusions
The projected global warming with elevated [CO2] is expected to increase FUE via enhanced DM accumulation with less increments in the soils that have higher indigenous soil N availabilities. 相似文献19.
Zinc fertilizer placement affects zinc content in maize plant 总被引:1,自引:0,他引:1
Yue-Qiang Zhang Li-Li Pang Peng Yan Dun-Yi Liu Wei Zhang Russell Yost Fu-Suo Zhang Chun-Qin Zou 《Plant and Soil》2013,372(1-2):81-92
Background and aims
Adequate zinc (Zn) in maize (Zea mays L.) is required for obtaining Zn-enriched grain and optimum yield. This study investigated the impact of varying Zn fertilizer placements on Zn accumulation in maize plant.Methods
Two pot experiments with same design were conducted to investigate the effect of soil Zn heterogeneity by mixing ZnSO4·7H2O (10 mg Zn kg?1 soil on an average) in 10–15, 0–15, 25–30, 0–30, 30–60 and 0–60 cm soil layers on maize root growth and shoot Zn content at flowering stage in experiment-1, and assessing effects on grain Zn accumulation at mature stage in experiment-2.Results
In experiment-1, Zn placements created a large variation in soil DTPA-Zn concentration (0.3–29.0 mg kg?1), which induced a systemic and positive response of root growth within soil layers of 0–30 cm; and shoot Zn content was increased by 102 %–305 % depending on Zn placements. Supply capacity of Zn in soil, defined as sum of product of soil DTPA-Zn concentration and root surface area at different soil layers, was most related to shoot Zn content (r?=?0.82, P?<?0.001) via direct and indirect effects according to path analysis. In experiment-2, Zn placements increased grain Zn concentration by up to 51 %, but significantly reduced the grain Zn harvest index from 50 % by control to about 30 % in average.Conclusion
Matching the distribution of soil applied Zn with root by Zn placement was helpful to maximize shoot Zn content and grain Zn concentration in maize. 相似文献20.