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1.
Ma del Carmen Orozco-Mosqueda Crisanto Velázquez-Becerra Lourdes I. Macías-Rodríguez Gustavo Santoyo Idolina Flores-Cortez Ruth Alfaro-Cuevas Eduardo Valencia-Cantero 《Plant and Soil》2013,362(1-2):51-66
Background and aims
Iron is an essential nutrient for plant growth. Although abundant in soil, iron is poorly available. Therefore, plants have evolved mechanisms for iron mobilization and uptake from the rhizospheric environment. In this study, we examined the physiological responses to iron deficiency in Medicago truncatula plants exposed to volatile organic compounds (VOCs) produced by Arthrobacter agilis UMCV2.Methods
The VOC profiles of the plant and bacterium were determined separately and during interaction assays using gas chromatography. M. truncatula plants exposed to A. agilis VOCs and pure dimethylhexadecylamine were transferred to conditions of iron deficiency, and parameters associated with iron nutritional status were measured.Results
The relative abundance of the bacterial VOC dimethylhexadecylamine increased 12-fold when in co-cultures of A. agilis and M. truncatula, compared to axenic cultures. Plants exposed to bacterial VOCs or dimethylhexadecylamine exhibited a higher rhizosphere acidification capacity, enhanced ferric reductase activity, higher biomass generation, and elevated chlorophyll and iron content relative to controls.Conclusions
The VOCs emitted by A. agilis UMCV2 induce iron acquisition mechanisms in vitro in the Strategy I plant M. truncatula. Dimethylhexadecylamine is the signal molecule responsible for producing the beneficial effects. 相似文献2.
Background and aims
Soil carbon storage is an important component of global carbon cycling. Andean Andisols have high carbon content and are vulnerable to erosion because of agricultural intensification and deforestation. This study examines the effects of land use on erosion and soil carbon storage in the Río Chimbo watershed of Ecuador.Methods
Soil carbon content, age, and erosion estimated from 137Cs inventories was measured along an elevational transect under annual cropping, natural forest, páramo, pasture, and tree plantations.Results
Land use, particularly annual cropping, affected 137Cs levels in the upper soil layers, but did not have an impact on total carbon storage to a depth of 1 m. Relative erosion rates estimated from 137Cs inventories at sites under annual cropping averaged 27 t ha?1?y?1 over the erosion rate of non-cultivated sites. A linear relationship was observed between soil carbon age (determined by 14C levels) and 137Cs levels, where pasture sites had lower 137Cs and older carbon compared to natural forest sites.Conclusions
The effects of land use on soil loss in the Río Chimbo watershed suggest a loss and/or removal of soil carbon, particularly under annual cropping. 相似文献3.
Yong Zhou Jiaqi Su Ivan A. Janssens Guangsheng Zhou Chunwang Xiao 《Plant and Soil》2014,374(1-2):19-32
Background and aims
Fine root and aboveground litterfall, two large fluxes of nutrients and carbon in the forest ecosystems, are key processes to be considered in efforts of measuring, modeling and predicting soil carbon sequestration.Methods
We used sequential coring and litter trap to measure seasonal dynamics of fine root and litterfall in three Korean pine dominated forests along an altitudinal gradient in the Changbai Mountain during the 2012 growing season.Results
Fine root biomass decreased significantly while necromass increased remarkably with altitude. Patterns and amounts of fine root production and mortality varied among forest types. Litterfall decreased significantly with altitude, whereas forest floor mass increased. Carbon inputs through fine root mortality and litterfall decreased significantly with altitude while carbon storage of fine root mass did not differ among forest types and carbon storage of forest floor mass was significantly larger in higher altitudinal forests due to lower turnover rates.Conclusions
This study provided an insight into the variations of fine root and litterfall dynamics among three Korean pine forests which were associated with different vegetation traits and environmental conditions, and also the quantification of carbon fluxes through fine root mortality and litterfall for estimating carbon budget of temperate forest. 相似文献4.
Minghua Zhou Bo Zhu Klaus Butterbach-Bahl Xiaoguo Wang Xunhua Zheng 《Plant and Soil》2014,383(1-2):401-414
Background and aims
High nitrous oxide (N2O) emissions may occur during the non-rice growing season of Chinese rice-upland crop rotation systems. However, our understanding of N2O emission during this season is poor due to a scarcity of available field N2O measurements.Methods
Using the static manual chamber-GC technique, seasonal N2O emissions during the non-rice growing season were simultaneously measured at two adjacent rice-wheat and rice-rapeseed fields in southwest China for three consecutive annual rotation cycles (May 2005 to May 2008).Results
Compared to the control, N fertilizer applications significantly enhanced soil N2O emissions from both wheat and rapeseed systems. Seasonal cumulative N2O fluxes from wheat systems were on average 2.6 kg N ha?1 for the recommended practice (RP [150 kg N ha?1]) and 5.0 kg N ha?1 for the conventional practice (CP [250 kg N ha?1]). Lower N2O emissions were observed from the adjacent rapeseed systems. Average cumulative seasonal N2O fluxes from rapeseed were 1.5 and 2.2 kg N ha?1 for the RP and CP treatments, respectively. The first 3 weeks after N fertilization were the “hot moment” of N2O emissions for both the wheat and rapeseed systems. The lowest yield-scaled N2O fluxes for wheat were obtained at the RP treatment (mean: 0.81 kg N Mg?1) while for rapeseed the CP treatment produced the lowest yield-scaled fluxes (mean: 0.79 kg N Mg?1). On average, the direct N2O emission factors (EFd) for the wheat system (1.76 %) were over two times higher than for the rapeseed system (0.73 %).Conclusions
Intercropping of rapeseed tends to result in lower N2O emissions than wheat for rice-upland crop rotation systems of southwest China, indicating that either the N fertilization or the cropping system need to be considered not only for improving the estimate of regional and/or national N2O fluxes but also for proposing the climate-smart agricultural management practice to reduce N2O emissions from agricultural soils. 相似文献5.
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6.
A novel method to measure the effect of temperature on diffusion of plant-available nitrogen in soil
Background and aims
Soil temperature influences nitrogen (N) diffusion in soil but until now, such effects have been difficult to quantify. This study aimed at estimating the effect of temperature on the diffusive fluxes of plant-available N forms in two contrasting soils.Methods
Using a novel technique based on micro-dialysis, we established relationships between diffusive fluxes and temperature in aqueous solutions and in soil samples.Results
Averaged for all compounds, the decreases of diffusive fluxes from the soil to the microdialysis sampler were 3.8 and 4.7% per degree Celsius in an agricultural and a boreal forest soil, respectively. The temperature-related shift of diffusive flux was, however, significantly dependent on molecular weight of the N compound. In accordance with established functions for temperature effects on diffusive fluxes, the non-linearity of this relationship resulted in a greater temperature response for small N compounds compared to larger compounds.Conclusions
Our results show that, all other factors being equal, the relative contribution of smaller N compounds to the diffusive flux of total plant-available N increases with increasing soil temperatures. 相似文献7.
Soil carbon dioxide and methane fluxes as affected by tillage and N fertilization in dryland conditions 总被引:1,自引:0,他引:1
Daniel Plaza-Bonilla Carlos Cantero-Martínez Javier Bareche José Luis Arrúe Jorge Álvaro-Fuentes 《Plant and Soil》2014,381(1-2):111-130
Background and aims
The effects of tillage and N fertilization on CO2 and CH4 emissions are a cause for concern worldwide. This paper quantifies these effects in a Mediterranean dryland area.Methods
CO2 and CH4 fluxes were measured in two field experiments. A long-term experiment compared two types of tillage (NT, no-tillage, and CT, conventional intensive tillage) and three N fertilization rates (0, 60 and 120 kg N ha?1). A short-term experiment compared NT and CT, three N fertilization doses (0, 75 and 150 kg N ha?1) and two types of fertilizer (mineral N and organic N with pig slurry). Aboveground and root biomass C inputs, soil organic carbon stocks and grain yield were also quantified.Results
The NT treatment showed a greater mean CO2 flux than the CT treatment in both experiments. In the long-term experiment CH4 oxidation was greater under NT, whereas in the short-term experiment it was greater under CT. The fertilization treatments also affected CO2 emissions in the short-term experiment, with the greatest fluxes when 75 and 150 kg organic N ha?1 was applied. Overall, the amount of CO2 emitted ranged between 0.47 and 6.0 kg CO2?equivalent kg grain?1. NT lowered yield-scaled emissions in both experiments, but these treatment effects were largely driven by an increase in grain yield.Conclusions
In dryland Mediterranean agroecosystems the combination of NT and medium rates of either mineral or organic N fertilization can be an appropriate strategy for optimizing CO2 and CH4 emissions and grain yield. 相似文献8.
Bettina H. M. Schmidt Chiao-Ping Wang Shih-Chieh Chang Egbert Matzner 《Biogeochemistry》2010,101(1-3):243-256
Fluxes of dissolved organic carbon (DOC) and nitrogen (DON) may play an important role for losses of C and N from the soils of forest ecosystems, especially under conditions of high precipitation. We studied DOC and DON fluxes and concentrations in relation to precipitation intensity in a subtropical montane Chamaecyparis obtusa var. formosana forest in Taiwan. Our objective was, to quantify DOC and DON fluxes and to understand the role of high precipitation for DOC and DON export in this ecosystem. From 2005 to 2008 we sampled bulk precipitation, throughfall, forest floor percolates and seepage (60 cm) and analyzed DOC, DON and mineral N concentrations. Average DOC fluxes in the soil were extremely high (962 and 478 kg C ha?1 year?1 in forest floor percolates and seepage, respectively) while DON fluxes were similar to other (sub)tropical ecosystems (16 and 8 kg N ha?1 year?1, respectively). Total N fluxes in the soil were dominated by DON. Dissolved organic C and N concentrations in forest floor percolates were independent of the water flux. No dilution effect was visible. Instead, the pool size of potentially soluble DOC and DON was variable as indicated by different DOC and DON concentrations in forest floor percolates at similar precipitation amounts. Therefore, we hypothesized, that these pools are not likely to be depleted in the long term. The relationship between water fluxes in bulk precipitation and DOC and DON fluxes in forest floor percolates was positive (DOC r = 0.908, DON r = 0.842, respectively, Spearman rank correlation). We concluded, that precipitation is an important driver for DOC and DON losses from this subtropical montane forest and that these DOC losses play an important role in the soil C cycle of this ecosystem. Moreover, we found that the linear relationship between bulk precipitation and DOC and DON fluxes in forest floor percolates of temperate ecosystems does not hold when incorporating additional data on these fluxes from (subtropical) ecosystems. 相似文献
9.
Aims
There is evidence that increased N inputs to boreal forests, via atmospheric deposition or intentional fertilization, may impact negatively on ectomycorrhizal (ECM) fungi leading to a reduced flux of plant-derived carbon (C) back to the atmosphere via ECM. Our aim was to investigate the impact of N fertilization of a Pinus sylvestris (L.) forest stand on the return of recently photoassimilated C via the ECM component of soil respiration.Methods
We used an in situ, large-scale, 13C-CO2 isotopic pulse labelling approach and monitored the 13C label return using soil gas efflux chambers placed over three different types of soil collar to distinguish between heterotrophic (RH), autotrophic (RA; partitioned further into contributions from ECM hyphae and total RA) and total (RS) soil respiration.Results
The impact of N fertilization was to significantly reduce RA, particularly respiration via extramatrical ECM hyphae. ECM hyphal flux in control plots showed substantial spatial variability, resulting in mean flux estimates exceeding estimates of total RA, while ECM contributions to RA in N treated plots were estimated at around 30%.Conclusion
Significant impacts on soil C cycling may be caused by reduced plant C allocation to ECM fungi in response to increased N inputs to boreal forests; ecosystem models so far lack this detail. 相似文献10.
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11.
Background and aims
Under chronically elevated N deposition, N retention mainly occur at high soil C-to-N ratio. This may be mediated through soil microbes, such as ectomycorrhizal (EM) fungi, saprotrophic fungi and bacteria, and the aim of this study was to evaluate the relationship between soil microbes and forest floor C-to-N ratios.Methods
Soil samples from 33 Norway spruce (Picea abies (L.) H. Karst) forests in Denmark and southern Sweden in a forest floor C-to-N ratio gradient (ranging from 14 to 35) were analysed regarding the content of phospholipid fatty acids (PLFAs) to estimate their soil microbial community composition and the relative biomasses of different microbial groups. The relation of EM biomass to total fungal biomass was estimated as the loss of the fungal PLFA 18:2ω6,9 during incubation of soils and the production of EM mycelia was estimated using fungal in-growth mesh bags. The soil microbial variables were correlated to forest floor C-to-N ratio, NO 3 - leaching, soil pH and stand age.Results
Fungal proportions of microbial biomass, EM to total fungi and EM mycelial production were all positively related to C-to-N ratio, while NO 3 - leaching was negatively related to C-to-N ratio.Conclusions
Both EM and saprotrophic fungi change with forest floor C-to-N ratios and appear to play a central role in N retention in forest soil. A better understanding of the mechanisms behind this process may be revealed if the role of recalcitrant fungal metabolites for N retention (and soil C sequestration) can be identified. Research along this line deserves further studies. 相似文献12.
Marcos Fernández-Martínez Sara Vicca Ivan A. Janssens Sebastiaan Luyssaert Matteo Campioli Jordi Sardans Marc Estiarte Josep Peñuelas 《Trees - Structure and Function》2014,28(2):597-611
Key message
Stand age, water availability, and the length of the warm period are the most influencing controls of forest structure, functioning, and efficiency.Abstract
We aimed to discern the distribution and controls of plant biomass, carbon fluxes, and resource-use efficiencies of forest ecosystems ranging from boreal to tropical forests. We analysed a global forest database containing estimates of stand biomass and carbon fluxes (400 and 111 sites, respectively) from which we calculated resource-use efficiencies (biomass production, carbon sequestration, light, and water-use efficiencies). We used the WorldClim climatic database and remote-sensing data derived from the Moderate Resolution Imaging Spectroradiometer to analyse climatic controls of ecosystem functioning. The influences of forest type, stand age, management, and nitrogen deposition were also explored. Tropical forests exhibited the largest gross carbon fluxes (photosynthesis and ecosystem respiration), but rather low net ecosystem production, which peaks in temperate forests. Stand age, water availability, and length of the warm period were the main factors controlling forest structure (biomass) and functionality (carbon fluxes and efficiencies). The interaction between temperature and precipitation was the main climatic driver of gross primary production and ecosystem respiration. The mean resource-use efficiency varied little among biomes. The spatial variability of biomass stocks and their distribution among ecosystem compartments were strongly correlated with the variability in carbon fluxes, and both were strongly controlled by climate (water availability, temperature) and stand characteristics (age, type of leaf). Gross primary production and ecosystem respiration were strongly correlated with mean annual temperature and precipitation only when precipitation and temperature were not limiting factors. Finally, our results suggest a global convergence in mean resource-use efficiencies. 相似文献13.
Role of maize stover incorporation on nitrogen oxide emissions in a non-irrigated Mediterranean barley field 总被引:1,自引:0,他引:1
Diego Abalos Alberto Sanz-Cobena Lourdes Garcia-Torres Jan Willem van Groenigen Antonio Vallejo 《Plant and Soil》2013,364(1-2):357-371
Aims
Agricultural soils in semiarid Mediterranean areas are characterized by low organic matter contents and low fertility levels. Application of crop residues and/or manures as amendments is a cost-effective and sustainable alternative to overcome this problem. However, these management practices may induce important changes in the nitrogen oxide emissions from these agroecosystems, with additional impacts on carbon dioxide emissions. In this context, a field experiment was carried out with a barley (Hordeum vulgare L.) crop under Mediterranean conditions to evaluate the effect of combining maize (Zea mays L.) residues and N fertilizer inputs (organic and/or mineral) on these emissions.Methods
Crop yield and N uptake, soil mineral N concentrations, dissolved organic carbon (DOC), denitrification capacity, N2O, NO and CO2 fluxes were measured during the growing season.Results
The incorporation of maize stover increased N2O emissions during the experimental period by c. 105 %. Conversely, NO emissions were significantly reduced in the plots amended with crop residues. The partial substitution of urea by pig slurry reduced net N2O emissions by 46 and 39 %, with and without the incorporation of crop residues respectively. Net emissions of NO were reduced 38 and 17 % for the same treatments. Molar DOC:NO 3 ? ratio was found to be a robust predictor of N2O and NO fluxes.Conclusions
The main effect of the interaction between crop residue and N fertilizer application occurred in the medium term (4–6 month after application), enhancing N2O emissions and decreasing NO emissions as consequence of residue incorporation. The substitution of urea by pig slurry can be considered a good management strategy since N2O and NO emissions were reduced by the use of the organic residue. 相似文献14.
Greenhouse gas emissions from forestry in East Norway 总被引:1,自引:0,他引:1
Volkmar Timmermann Janka Dibdiakova 《The International Journal of Life Cycle Assessment》2014,19(9):1593-1606
Purpose
So far no calculations have been made for greenhouse gas (GHG) emissions from forestry in East Norway. This region stands for 80 % of the Norwegian timber production. The aim of this study was to assess the annual GHG emissions of Norwegian forestry in the eastern parts of the country from seed production to final felling and transport of timber to sawmill and wood processing industry (cradle-to-gate inventory), based on specific Norwegian data.Methods
The life cycle inventory was conducted with SimaPro applying primary and secondary data from Norwegian forestry. GHG emissions of fossil-related inputs from the technosphere were calculated for the functional unit of 1 m3 timber extracted and delivered to industry gate in East Norway in 2010. The analysis includes seed and seedling production, silvicultural operations, forest road construction and upgrading, thinning, final felling, timber forwarding and timber transport on road and rail from the forest to the industry. Norwegian time studies of forestry machines and operations were used to calculate efficiency, fuel consumption and transport distances. Due to the lack of specific Norwegian data in Ecoinvent, we designed and constructed unit processes based on primary and secondary data from forestry in East Norway.Results and discussion
GHG emissions from forestry in East Norway amounted to 17.893 kg CO2-equivalents per m3 of timber delivered to industry gate in 2010. Road transport of timber accounted for almost half of the total GHG emissions, final felling and forwarding for nearly one third of the GHG emissions. Due to longer road transport distances, pulpwood had higher impact on the climate change category than saw timber. The construction of forest roads had the highest impact on the natural land transformation category. The net CO2 emissions of fossil CO2 corresponded to 2.3 % of the CO2 sequestered by 1 m3 of growing forest trees and were compared to a calculation of biogenic CO2 release from the forest floor as a direct consequence of harvesting.Conclusions
Shorter forwarding and road transport distances, increased logging truck size and higher proportion of railway transport may result in lower emissions per volume of transported timber. A life cycle assessment of forestry may also consider impacts on environmental categories other than climate change. Biogenic CO2 emissions from the soil may be up to 10 times higher than the fossil-related emissions, at least in a short-term perspective, and are highly dependent on stand rotation length. 相似文献15.
Backgrounds and aims
The functional role of volatile indole in interaction between rhizobacteria and plant remains unknown. In this study, we investigated the functional role of the volatile indole emitted by rhizobacterial strain Proteus vulgaris JBLS202 in plant growth promoting activity.Methods
P. vulgaris strain JBLS202 was used to study the role of volatile organic compounds (VOCs) on growth stimulation of Chinese cabbage (cabbage) at seedling stage. SPME-GC/MS analysis employed to identify headspace VOCs emitted from the rhizobacterium. Synthetic indole was assayed at various concentrations for the growth stimulation of cabbage and the emission of indole from the bacterized cabbage seeds was identified.Results
P. vulgaris JBLS202 promoted the growth of cabbage via volatiles in a dose-dependent manner. VOC emission assay by SPME-GC/MS revealed that indole was a major headspace volatile compound emitted from the rhizobacterium. Moreover, the growth of cabbage was promoted significantly in the presence of 0.63 μg of synthetic indole. The vigor index and fresh weight of the seedlings were increased by 39.9 % and 32.6 %, respectively when the seeds of cabbage were bacterized with P. vulgaris JBLS202 cells (1?×?107?CFU/ml). The emission of indole from the bacterized seeds was demonstrated by SPME-GC/MS.Conclusions
Results indicated that either synthetic or biological/bacterial indole could increase the growth of cabbage significantly. Though the molecular biological role of indole in plant growth promotion remains to be investigated, this is the first report on detailed interaction between bacterial indole and plants. 相似文献16.
Root carbon flow from an invasive plant to belowground foodwebs 总被引:1,自引:0,他引:1
Mark A. Bradford Michael S. Strickland Jayna L. DeVore John C. Maerz 《Plant and Soil》2012,359(1-2):233-244
Aims
Soil foodwebs are based on plant production. This production enters belowground foodwebs via numerous pathways, with root pathways likely dominating supply. Indeed, root exudation may fuel 30–50?% of belowground activity with photosynthate fixed only hours earlier. Yet we have limited knowledge of root fluxes of recent-photosynthate from invasive plants to belowground foodwebs.Methods
Using stable isotopes, we quantify the proportion of recent-photosynthate transferred belowground from the invasive grass Microstegium vimineum A. Camus, a widespread invader of forest understory. Given its minimal root biomass (~8?% of individual mass), we expected exudation to contribute little to belowground foodwebs.Results
Within 2?days of 13C-labeling, we recover ~15?% of photosynthate carbon in microbial biomass. Recovery in root and dissolved organic carbon pools is consistently low (<2?%), suggesting these pools operate as ‘pipelines’ for carbon transport to soil microbes. The recovery of the label in wolf spiders – forest floor predators that feed on soil animals – highlights that root inputs of recent photosynthate can propagate rapidly through belowground foodwebs.Conclusions
Our results suggest that root carbon-exudation, an unexplored process of invasive grass inputs to forest foodwebs, may be an important pathway through which invasive species affect the structure and function of recipient ecosystems. 相似文献17.
A. Vermue L. Philippot N. Munier-Jolain C. Hénault B. Nicolardot 《Plant and Soil》2013,373(1-2):501-514
Aims
Integrated weed management, which allows reducing the reliance of cropping systems on herbicides, is based on the use of specific combinations of innovative agricultural practices. However the impact of the introduction of these practices in cropping systems may influence soil functioning such as biogeochemical cycling. Here, we investigated N2O emissions and the abundances of N-cycling microorganisms in 11-year old cropping systems (i.e. conventional reference and integrated weed management) in order to estimate the environmental side-effects of long-term integrated weed management.Methods
N2O emissions were continuously measured using automated chambers coupled with infrared analysers. Abundances of ammonia oxidizers and denitrifiers together with total bacteria and archaea were determined monthly from 0 to 10 and 10–30 cm soil layer samples by quantitative Polymerase Chain Reaction (qPCR). The relationship between N2O emissions and microbial abundances during the study were investigated as were their relationships with soil physicochemical parameters and climatic conditions.Results
Over 7 months, the system with integrated weed management emitted significantly more N2O with cumulated measured emissions of 240 and 544 g N-N2O ha?1 for conventional and integrated systems, respectively. Abundances of microbial guilds varied slightly between systems, although ammonia-oxidizing bacteria were more abundant in the reference system (1.7 106 gene copies g?1 dry weight soil) compared to the integrated system (1.0 106 gene copies g?1 dry weight soil). These differences revealed both the long-term modification of soil biogeochemical background and the functioning of microbial processes due to 11 years of alternative field management, and the short-term impacts of the agricultural practices introduced as part of weed management during the cropping year.Conclusions
The abundances of the different microbial communities involved in N cycling and the intensity of N2O emissions were not related, punctual high N2O emissions being more dependent on favourable soil conditions for nitrifying and denitrifying activities. Future studies will be performed to check these findings for other pedoclimatic conditions and to examine the impact of such cropping systems. 相似文献18.
Methane and nitrous oxide emissions from direct-seeded and seedling-transplanted rice paddies in southeast China 总被引:2,自引:0,他引:2
Background and aims
The rice production is experiencing a shift from conventionally seedling-transplanted (TPR) to direct-seeded (DSR) cropping systems in Southeast Asia. Besides the difference in rice crop establishment, water regime is typically characterized as water-saving moist irrigation for DSR and flooding-midseason drainage-reflooding and moist irrigation for TPR fields, respectively. A field experiment was conducted to quantify methane (CH4) and nitrous oxide (N2O) emissions from the DSR and TPR rice paddies in southeast China.Methods
Seasonal measurements of CH4 and N2O fluxes from the DSR and TPR plots were simultaneously taken by static chamber-GC technique.Results
Seasonal fluxes of CH4 averaged 1.58 mg m?2 h?1 and 1.02 mg m?2 h?1 across treatments in TPR and DSR rice paddies, respectively. Compared with TPR cropping systems, seasonal N2O emissions from DSR cropping systems were increased by 49 % and 46 % for the plots with or without N application, respectively. The emission factors of N2O were estimated to be 0.45 % and 0.69 % of N application, with a background emission of 0.65 and 0.95 kg N2O-N ha?1 under the TPR and DSR cropping regimes, respectively. Rice biomass and grain yield were significantly greater in the DSR than in the TPR cropping systems. The net global warming potential (GWP) of CH4 and N2O emissions were comparable between the two cropping systems, while the greenhouse gas intensity (GHGI) was significantly lower in the DSR than in the TPR cropping systems.Conclusions
Higher grain yield, comparable GWP, and lower GHGI suggest that the DSR instead of conventional TPR rice cropping regime would weaken the radiative forcing of rice production in terms of per unit of rice grain yield in China, and DSR rice cropping regime could be a promising rice development alternative in mainland China. 相似文献19.
Behxhet Mustafa Avni Hajdari Feriz Krasniqi Esat Hoxha Hatixhe Ademi Cassandra L Quave Andrea Pieroni 《Journal of ethnobiology and ethnomedicine》2012,8(1):1-14
Background
The boreal forest of Canada is home to several hundred thousands Aboriginal people who have been using medicinal plants in traditional health care systems for thousands of years. This knowledge, transmitted by oral tradition from generation to generation, has been eroding in recent decades due to rapid cultural change. Until now, published reviews about traditional uses of medicinal plants in boreal Canada have focused either on particular Aboriginal groups or on restricted regions. Here, we present a review of traditional uses of medicinal plants by the Aboriginal people of the entire Canadian boreal forest in order to provide comprehensive documentation, identify research gaps, and suggest perspectives for future research.Methods
A review of the literature published in scientific journals, books, theses and reports.Results
A total of 546 medicinal plant taxa used by the Aboriginal people of the Canadian boreal forest were reported in the reviewed literature. These plants were used to treat 28 disease and disorder categories, with the highest number of species being used for gastro-intestinal disorders, followed by musculoskeletal disorders. Herbs were the primary source of medicinal plants, followed by shrubs. The medicinal knowledge of Aboriginal peoples of the western Canadian boreal forest has been given considerably less attention by researchers. Canada is lacking comprehensive policy on harvesting, conservation and use of medicinal plants. This could be explained by the illusion of an infinite boreal forest, or by the fact that many boreal medicinal plant species are widely distributed.Conclusion
To our knowledge, this review is the most comprehensive to date to reveal the rich traditional medicinal knowledge of Aboriginal peoples of the Canadian boreal forest. Future ethnobotanical research endeavours should focus on documenting the knowledge held by Aboriginal groups that have so far received less attention, particularly those of the western boreal forest. In addition, several critical issues need to be addressed regarding the legal, ethical and cultural aspects of the conservation of medicinal plant species and the protection of the associated traditional knowledge. 相似文献20.
Changes in stable nitrogen and carbon isotope ratios of plants and soil across a boreal forest fire chronosequence 总被引:1,自引:0,他引:1
Fujio Hyodo Soichiro Kusaka David A. Wardle Marie-Charlotte Nilsson 《Plant and Soil》2013,364(1-2):315-323