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1.
  • ? We investigated the effects of flooding for three weeks on physiological responses and uptake of NH 4 + and NO 3 ? by black spruce (Picea mariana (Mill.) BSP.) and tamarack (Larix laricina (Du Roi) K. Koch) seedlings fertilized with labeled (15NH4)2SO4 or K15NO3 in a growth chamber experiment.
  • ? Flooding reduced photosynthesis (A), transpiration (E), water use efficiency (WUE), and current uptake of NH 4 + and NO 3 ? in both species.
  • ? Under flooding, there were no significant differences between the two species in uptake of either NH 4 + or NO 3 ? at the whole-plant level but black spruce had higher translocation of NH 4 + to the shoots than did tamarack.
  • ? Under non-flooded conditions, black spruce seedlings exhibited higher uptake of both NH 4 + and NO 3 ? than did tamarack and demonstrated preferential uptake of NH 4 + (19. 7 mg g?1dw) over NO 3 ? (12.3 mg g?1dw after three weeks). In contrast, non-flooded tamarack seedlings had equal uptake of NH 4 + (4.96 mg g?1dw) and NO 3 ? (4.97 mg g?1dw).
  • ? We hypothesize that the ability of tamarack to equally exploit both 15NH 4 + and 15NO 3 ? would confer an advantage over black spruce, when faced with limitations in the availability of different forms of soil nitrogen.
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    2.
    Measurements of gross NH 4 + and NO 3 ? production in forest soils were conducted using the 15N pool dilution method. Mineral topsoils (0?C10?cm depth) were collected from four forests from northern to southern Japan with a natural climate gradient to elucidate the mechanisms regulating gross nitrification rates in forest soils. Additionally, we attempted to evaluate the relative importance of heterotrophic nitrification in gross total nitrification using acetylene as a specific inhibitor of autotrophic nitrification. Distinct differences were found among sites in the gross rates of NH 4 + production (3.1?C11.4?mg?N?kg?1?day?1) and gross total nitrification (0.0?C6.1?mg?N?kg?1?day?1). The rates of gross heterotrophic nitrification were low in this study, indicating that heterotrophic nitrification is of minor importance in most forest mineral topsoils in Japan. Significant relations were found between gross autotrophic nitrification and gross NH 4 + production, soil N, and soil C concentrations, but none was found between gross autotrophic nitrification and soil pH. We determined the critical value of the gross NH 4 + production rates for gross autotrophic nitrification under which no gross autotrophic nitrification occurred, as well as the critical soil C/N ratio above which gross autotrophic nitrification ceased. Results show that tight coupling of production and consumption of NH 4 + prevents autotrophic nitrifiers from utilizing NH 4 + as long as NH 4 + availability is low.  相似文献   

    3.
  • ? The short-term effect of organic residue management on the growth and nutrition of Pinus pinaster Ait. seedlings, and on nutrient leaching and chemical properties of an acid soil was assessed through a lysimeter experiment. Treatments included absence, placement on the soil surface, and incorporation into the soil (with and without legume cover cropping) of organic residues (forest floor litter or forest floor litter plus harvest residues).
  • ? Residues placed on the soil surface enhanced seedling growth. Organic residues reduced nutrient losses (NO 3 ? , Ca and Mg) and resulted in nutrient accumulation in the soil. Harvest residues positively affected K seedling nutrition status and enhanced K soil accumulation.
  • ? Legume cover cropping reduced soil nutrient losses (N, Ca, Mg and K) during the early stage of seedling growth; it also improved seedling nutrition status (N and P), but without any effect on growth.
  • ? Harvest residues plus forest floor litter placed on the soil surface was the most appropriate management to both reduce nutrient losses through leaching and increase height of seedlings at the end of the experimental period (two years).
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    4.
    The effects of woody residues from Eucalyptus globulus Labill. plantations on N losses were assessed through a lysimetric experiment. Treatments were: (NW) forest floor litter and non-woody residues (leaves, bark, twigs) incorporated into the soil; (IP) as NW plus woody residues (branches) cut in 20-cm long pieces and incorporated into the soil; (IC) as IP, but with branches chopped into chips; (SP) non-woody and woody residues (pieces) placed on the soil surface; (SC) as SP plus branches chopped into chips; and (CT) absence of organic residues. Leaching of N-NO 3 ? and N-NH 4 + was followed during a six-year period and N mineralization was evaluated at the end of the experiment. Non-woody residues enhanced N leaching as compared with the control. Conversely, woody residues decreased N losses. Although differences between treatments were not significant at the end of the experiment, incorporation and fragmentation of woody residues resulted in the more favourable management option regarding the reduction of N leaching observed at short-term. As high amounts of residues were used, the effect observed on decrease N leaching could be higher than that existing in Portuguese eucalypt plantations.  相似文献   

    5.
    Forest fires are known to influence nutrient cycling, particularly soil nitrogen (N), as well as plant succession in northern forest ecosystems. However, few studies have addressed the dynamics of soil N and its relationship to vegetation composition after fire in these forests. To investigate soil N content and vegetation establishment after wildfire, 13 sites of varying age class were selected in the Sub-Boreal spruce zone of the central interior of British Columbia, Canada. Sites varied in time since the last forest fire and were grouped into three seral age classes: (a) early-seral (<14 years), (b) mid-seral (50–80 years) and (c) late-seral (>140 years). At each site, we estimated the percent cover occupied by trees, shrubs, herbs and mosses. In addition, the soil samples collected from the forest floor and mineral horizons were analyzed for the concentrations of total N, mineralizable N, available NO3−-N and available NH4+-N. Results indicated that soil N in both the forest floor and mineral horizons varied between the three seral age classes following wildfire. Significant differences in mineralizable N, available NO3−-N and available NH4+-N levels with respect to time indicated that available soil N content changes after forest fire. Percent tree and shrub cover was significantly correlated to the amount of available NH4+-N and mineralizable N contents in the forest floor. In the mineral horizons, percent tree cover was significantly correlated to the available NH4+-N, while herb cover was significantly correlated with available NO3−-N. Moss cover was significantly correlated with total N, available NO3−-N and mineralizable N in the forest floor and available NO3−-N in the mineral horizons. We identified several unique species of shrubs and herbs for each seral age class and suggest that plant species are most likely influencing the soil N levels by their contributions to the chemical composition and physical characteristics of the organic matter.  相似文献   

    6.

    Aims

    This study aims to evaluate the effects of wood ash application on nutrient dynamics and soil properties of an acidic forest soil (Arenosol).

    Methods

    Treatments were loose and pelleted ash application (11?Mg?ha?1), alone or together with N fertiliser, and control treatment in a lysimeter experiment. Nutrient leaching was followed during a 2-year period and soil chemical and biological properties were evaluated at the end of the experiment.

    Results

    Wood ash increased leaching of total N, NH 4 + -N, base cations and P, mainly during the first months, the effect being more pronounced for the loose formulation. At the end of the study period, a positive effect on soil nutrient availability and soil acidity reduction was seen. The application of loose and pelleted ash alone decreased N leaching and increased N microbial biomass at the end of the experiment. The C dynamics was weakly affected.

    Conclusion

    Wood ash can be used to improve nutrient availability and balance nutrient exported by tree harvesting in acid forest soils, the effects at short-term being stronger for loose than for pelleted ash. However, their application should be carried out when vegetation is established to minimise nutrient losses at short-term and reduce the potential risk for water bodies. In N-limited soils, wood ash should be applied with N fertilisers to counteract N immobilisation.  相似文献   

    7.
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    8.
    Fire induces changes in ecosystem nutrient regimes and can cause major losses of N and P. Much has been written about the effect of fire on nutrient availability in soil; most studies have been concerned with the short-term effects of shock. The primary objective of our study was to discover the effect of forest fires on long-term N and P availability, for which we used the ion exchange membrane method in a chronosequence of forest fires (1987, 1990, 1994, 1998, 2000 and 2005). The study was conducted on the island of La Palma (Canary Islands, Spain) in October 2006. We hypothesized that a rapid increase in nutrient availability would occur after the fire, followed by a reduction due to erosion and leaching, and then gradual recovery and an eventual return to initial levels. NH4-N, NO3-N and mineral-N availability peaked significantly 1 year after the fire. However, 5 years after the fire the N levels were similar to those found on unburned land. P availability decreased significantly a year after the fire, but gradually recovered over time. The N and P availability ratio increased significantly after the fire, falling during the chronosequence, with the lowest levels found on the unburned land. These results confirm that fire produces (a) a rapid and short-term increase in N availability, without a long-term decline, and (b) a long-term reduction in P availability, which tends to recover over time after the fire.  相似文献   

    9.
  • ? The effects of clearcutting and of different slash management procedures on N mineralization were assessed in a Eucalyptus globulus Labill. stand in Galicia (N W Spain). Treatments were no clearcutting (control), clearcutting combined with scattering, scattering + fertilization, windrowing, and two types of slash burning with two levels of severity: broadcast burning and windrow burning. Changes in mineral N were monitored in the soil during the 18 months following the treatments. Eleven years later, the treatment effects were again evaluated during a twelve month period to assess long-term effects.
  • ? During the first study period, slash burning led to a marked increase in the contents of N-NH 4 + , N-NO 3 ? and N-mineralization in topsoil layers (0–10 cm). In contrast, clearcutting followed by either scattering or windrowing of residues had no effect on mineral N in the top soil or in situ mineralization, relative to the control. Ammonium was the predominant form of mineral N. No residual effects of the treatments were detected eleven years later.
  • ? Fire severity, in relation to slash burn type, had significant negative effects on post-burn N mineralization and nitrification in the first period studied, but no long-term residual effects were observed. Some practical consequences for sustainable management of such stands are suggested.
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    10.
    Forest fires affect both carbon (C) and nitrogen (N) cycling in forest ecosystems, and thereby influence the soil–atmosphere exchange of major greenhouse gases (GHGs): carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). To determine changes in the soil GHG fluxes following a forest fire, we arranged a low-intensity surface fire in a white birch forest in northern Japan. We established three treatments, having four replications each: a control plot (CON), a burned plot (BURN), and a plot burned with removal of the resulting charcoal (BURN-CHA). Soil GHG fluxes and various properties of the soil were determined on four or five occasions during a period that spanned two growing seasons. We observed increased concentrations of ammonium-N (NH4-N) in BURN and BURN-CHA after the fire, while nitrate–N (NO3-N) concentration was only increased in BURN-CHA after the fire. The soil CO2 flux was significantly higher in CON than in BURN or BURN-CHA, but there was no difference in soil CH4 uptake between the three treatments. Moreover, the N2O flux from BURN-CHA soil was slightly greater than in CON or BURN. In BURN-CHA, the soil N2O flux peaked in August, but there was no peak in BURN. We found temporal correlations between soil GHG fluxes and soil variables, e.g. soil temperature or NO3-N. Our results suggest that environmental changes following fire, including the increased availability of N and the disappearance of the litter layer, have the potential to change soil GHG fluxes. Fire-produced charcoal could be significant in reducing soil N2O flux in temperate forests.  相似文献   

    11.
    Clear-cutting followed by mechanical site preparation is the major disturbance influencing nutrient and water fluxes in Fennoscandian boreal forests. The effects of soil harrowing on the fluxes of dissolved organic carbon (DOC), dissolved nitrogen compounds (organic N, NH4+ and NO3−) and water soluble phosphorus (PO43−) through a podzolic soil were studied in a clear-cut in eastern Finland for 5 years. The old, mixed coniferous stand was clear-cut and stem only harvested in 1996 followed by soil harrowing in 1998 and planting in June 1999. Zero-tension lysimeters were used to collect soil water from below different soil horizons in the three types of microsites that resulted from site preparation treatment: low ridges (25% of clear-cut area), shallow furrows (30%) and the undisturbed soil (45%). After soil harrowing, the leaching of DOC, N and P from below the B-horizon increased compared to pre-treatment levels. However, the increases were short-lasting; 1–2 years for inorganic N and P, and 5 years for DOC and organic N. The highest concentrations were associated with the ridges and lowest with the furrows, reflecting the differences in amount of organic matter present in each microsite type and, for N, to enhanced mineralization and nitrification. Leaching from below the B-horizon over the 5 years following soil harrowing for the whole clear-cut area was 36.5 kg ha−1 for DOC, 0.88 kg ha−1 for NH4-N, 0.46 kg ha−1 for NO3-N, 1.24 kg ha−1 for organic N and 0.09 kg ha−1 for PO4-P. Site preparation increased temporarily the risk for nutrient leaching into watercourses and groundwater from the clear-cut area but soil fertility was not affected since the leached amounts remained small. The main reasons for the observed low leaching values were the rapid recovery of ground vegetation and low N deposition loads.  相似文献   

    12.
    u| li]? Genotypic variation in wood total and partial shrinkage, basic density and growth traits was estimated in 51÷2 year old Acacia auriculiformis trees in a clonal test. li]? In the tangential, radial and longitudinal directions, the mean values were 2.64%, 1.64% and 0.77% for partial shrinkage, and 5.92%, 3.23%, and 0.96% for total shrinkage, respectively. Total and partial transverse shrinkage were significantly greater in sapwood than in heartwood. li]? Clonal repeatability (H C 2 ) estimates for partial shrinkage were lower than those for total shrinkage, and heartwood shrinkages had lower H C 2 than those for sapwood. Estimates of H C 2 were from 0.32 to 0.38 for total transverse shrinkage, comparable to H C 2 for both total and partial volumetric shrinkages (0.40 and 0.32, respectively). However, H C 2 for longitudinal shrinkages, total and partial coefficients of anisotropy were only from 0.09 to 0.18. li]? The genotypic coefficients of variation of all shrinkage traits varied from 5.45% to 8.02%. Total shrinkage was strongly positively correlated with partial shrinkage in each dimension. Genotypic correlations were not significant between shrinkage and growth traits or density. Strong and significant correlations between transverse shrinkage in heartwood and sapwood (0.87) indicated that juvenile shrinkage is a good genetic indicator of this trait in older trees. Utilisation du retrait du bois dans l’amélioration de l’Acacia auriculiformis A. Cunn. ex Benth à croissance rapide au Vietnam.  相似文献   

    13.
    The aim of this study was to evaluate the potential of visible and near infrared spectroscopy (Vis/NIRS) in predicting the chemical, physical and mechanical behavior of single-piece natural corks stoppers used for sealing wine bottles. Two training sets of 90 and 150 cork stoppers were used to obtain four spectra per sample in different positions: two of the stopper bases (transversal section) and two of the stopper sides (tangential section and radial section). The samples were scanned in the range of 400–2,500 nm using a Foss-NIRSystems 6500 SY II spectrophotometer equipped with a remote reflectance fiber-optic probe. On each training set, two-thirds of the samples were used to develop modified partial least square (MPLS) calibration equations, and the remaining one-third of the sample for the external validation of these MPLS equations. The best equations were obtained for the transversal section, which is the recommended one when applying Vis/NIRS technology to cork. The best results for the chemical composition were obtained for waxes and total polyphenols, showing coefficient of determination of the cross validation (r cv 2 ) values of 0.64 and 0.56 and coefficient of determination of the external validation (r EV 2 ) values of 0.53 and 0.55, respectively. The best equation for the physical and mechanical parameters was obtained for moisture content (r cv 2  = 0.86 and r EV 2  = 0.85), with somewhat lower results for density, compression force and extraction force (r cv 2  = 0.66, 0.72, 0.52 and r EV 2  = 0.52, 0.49, 0.51, respectively). The SECV (standard error of cross validation) and SEP (standard error of external validation) were similar for all the physical and mechanical parameters, thus confirming the robustness of the equations. MPLS model for moisture content fulfills the requirements for screening (RPD >2.5), but MPLS models obtained for waxes, total polyphenols, density, compression force and extraction force are not good enough for routine analysis or quality control. The results obtained from the MPLS models based on Vis/NIRS technology would permit the continuous quality control of humidity in the production line as well as obtaining information about certain chemical components (extractives contents) and some physical and mechanical parameters (density, extraction force and compression force).  相似文献   

    14.
  • ? Soil resources are heterogeneously distributed in terrestrial plant communities. This heterogeneity is important because it determines the availability of local soil resources. A forest fire may change the spatial distribution of soil nutrients, affecting nutrition and survival of colonizing plants. However, specific information on the effects of ecosystem disturbance on the spatial distribution of soil resources is scarce.
  • ? We hypothesized that, on a short-term basis, wildfire would change the spatial patterns of soil N and P availability. To test this hypothesis, we selected two Pinus canariensis forests burned in 2005 and 2000, respectively, and a third forest that was unburned since at least 1990 (unburned). We incubated ionic exchange membranes (IEMs) in replicated plots to estimate soil N and P availability and characterized the spatial pattern using SADIE (Spatial Analysis by Distance Indices).
  • ? Mineral N, NO3-N and PO4-P availability, and aggregation and cluster indices for all nutrients were higher in the 2005 wildfire plots than in the 2000 wildfire and unburned plots.
  • ? Our results suggest that surviving plants or new individuals becoming established in a burned area would find higher soil resources, but also higher small-scale heterogeneity in nutrients, which may have a major impact on the performance of individual plants and on the forest structure and dynamics.
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    15.
    Wastewater bioremediation has been practised successfully in several forests without significant adverse effect on water quality of adjacent aquatic systems. However, long-term success of wastewater irrigation systems depends on an overall positive response of the forest ecosystem to substantial amounts of added water and nutrients over time. Municipal wastewater irrigation effects on the fate of added nitrogen in a mature Appalachian hardwood forest were investigated during the first 2 years of irrigation. Wastewater was secondarily treated, chlorinated, and sprayed on the study site at five rates. Forest litter N decreased on irrigated sites due to increased litter decomposition rates. Nitrogen mineralization potential (N0) decreased greatly in soils irrigated at a rate of 140 cm year−1 for 2 years. Net nitrification and relative nitrification (the amount of NO3−-N as a proportion of the total mineral N) increased proportionally with irrigation rate. The highest irrigation rates increased denitrification activity and contributed significantly to the bioremediation process by removing nitrate that otherwise would have been subject to leaching. The increase in NO3− production in the soil and limited N sequestration by the forest system nevertheless resulted in a net loss of N via leaching. Nitrate concentrations of soil water increased owing to irrigation, with the highest rate at 11 mg 1−1 on sites receiving 70 cm year−1. During the 2-year period, the forest ecosystem experienced a net leaching loss of N that ranged from 14.8 to 105 kg N ha−1 year−1, depending on the application rate. It is likely that this mature hardwood forest will continue to lose N, and that little or no additional N will be sequestered.  相似文献   

    16.
    Fast-growing poplar plantations on agricultural land require intensive management activities, often involving fertilization. The present paper aims at investigating the effect of fertilization on growth and on groundwater quality, by examining four trials established in commercial poplar plantations in central and south Sweden. The treatments consisted of nitrogen applications (Urea N46, Tot. N: 46%) in two different dosages, 75 and 150?kg?ha?1 for two years, and a control, in three replicates (plot size: 20?×?20?m) following a randomized block design. Diameters were measured at each plot at the end of each growing season for the period 2012–2015. At the same time, groundwater pipes were installed in the center of each plot, at ca. 1.5?m depth. Samples were regularly collected and analyzed for NO3-N and PO4-P. The results show a large variation in the diameter growth response to nitrogen fertilization and the leaching of poplar plantations after canopy closure. In young plantations, the effect on growth was clear with moderate fertilization rates although it was not observed on sandy soils with already good growth, leading to high nitrogen leaching.  相似文献   

    17.
  • ? Spruce budworm outbreaks are among the major natural disturbances affecting the dynamics and functioning of Canadian boreal forests. However, the element losses potentially associated with spruce budworm outbreaks have not been quantified.
  • ? We evaluated the influence of spruce budworm outbreaks on nutrient export from boreal forest soils by comparing nutrient leaching losses during a spruce budworm outbreaks episode (1981–1984) to an unperturbed period (1999–2003) in a calibrated catchment located in a balsam fir forest.
  • ? Nutrient soil leaching losses were significantly higher during the spruce budworm outbreaks (1981–1984) for N-NO3 (30.1 fold), K (8.3 fold), N-NH4 (6.2 fold), Mg (2.7 fold) and SO4 (2.2 fold), as compared to an unperturbed period (1999–2003). When the recurrence of spruce budworm outbreaks (33 years) and a plausible average length of such events (5 years) are taken into consideration, it is estimated that in the long term, 5.6 more NO3, 1.5 more K and 1.2 more NH4 are leached from the soil profile during outbreaks.
  • ? The important leaching losses during spruce budworm outbreaks, when added to the losses due to tree harvesting and fire (and acid deposition for K), may have considerable effects on soil fertility and ecosystem sustainability.
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    18.
    Calamagrostis angustifolia is the dominant species in the typical meadow and marsh meadow communities of Sanjiang Plain. The study on its biomass, the nitrogen (N) and phosphorus (P) contents in its different organs showed that the biomass of different C. angustifolia organs in the two types of wetland communities was distinctly different, which could be described by polynomial. The biomass of aboveground part and each organ presented single peak changing, with the maximum value of the latter occurred 15 days after. The F/C values were all less than 1, which were bigger in typical meadow than those in marsh meadow. The total N and P contents in different organs of aboveground part all descended monotonically in growth season, with the order of leaf>vagina>stem. The change of total N content in roots of the two types of C. angustifolia was consistent, while that of total P was quite different. The content of total N, ammonium nitrogen (NH4 +-N) and nitrate nitrogen (NO3 −-N), especially of NH4 +-N and NO3 −-N, varied widely in different organs, with NH4 +-N/NO3 −-N>1. Root was the important storage of N and P, but the storage of N and P in stem, leaf and vagina fluctuated greatly. The N/P ratios of the two types of C. angustifolia were all less than 14, which implied that N might be the limiting nutrient of C. angustifolia, and the limitation degree was higher in typical meadow than that in marsh meadow. __________ Translated from Chinese Journal of Applied Ecology, 2006, 17(2): 221–228 [译自: 应用生态学报]  相似文献   

    19.
    Across the U.S., multiple species of riparian vegetation have proven to be effective filters of sediment and nutrients in agricultural watersheds. Research at Southern Illinois University Carbondale has focused on giant cane [Arundinaria gigantea (Walt.) Muhl.] as a potential candidate to incorporate into riparian buffer designs. In 2001, an exploratory study (i.e., Phase I) monitored nutrient and sediment concentrations from surface runoff and groundwater in the Cypress Creek watershed, while two subsequent studies (i.e., Phase II) focused on groundwater quality and added additional riparian buffer plots in the Big Creek and Cache River Watersheds. The primary objective of this research was to compare nutrient attenuation in groundwater of native giant cane and forest riparian buffers. Results from phase I showed significant nutrient reductions in groundwater over short distances in both the giant cane (~3.0 m) and forest buffers (~6.0 m), thus additional wells were installed at 1.5 and 12.0 m for the second phase. Groundwater NO3 −-N was significantly reduced by 90% in the initial 3.0 m of the giant cane buffer, where plant assimilation and microbial denitrification were likely key NO3 −-N removal mechanisms. Phase II showed significant reductions in groundwater NO3 −-N beneath the forest buffers, whereas little change occurred below the giant cane buffers. However, NO3 −-N concentrations beneath giant cane buffers were 3 times less than those observed beneath the forest buffers. Follow-up studies are being conducted on the transport of E. coli through vegetated buffers, and efforts have been expanded to the watershed-scale.  相似文献   

    20.
    Allocation of biomass and nutrient elements including Nitrogen to above and belowground compartments of beech seedlings (Fagus sylvatica L.) treated by labeled nitrogen fertilizer in the form of 15NH4 and 15NO3 were investigated at the end of two successive growing seasons. Pot cultured beech seedlings were grown at a green house on intact soil cores sampled from three adjacent stands including beech, Norway spruce and mixed beech-spruce cultures of Solling forest, Germany. Comparing biomass allocation and nutrients concentrations of the seedlings between the control and 15N-fertilized treatments revealed no significant effect of N fertilization on nutrients uptake by seedlings over the experiment. The form of N input influenced its movement into plant pools. It was demonstrated that beech seedlings take up nitrogen mainly in the form of nitrate, which is then reduced in the leaves, although the differences between the retention of NO3 ?-N and NH4 +-N in plants were not statistically significant. Percent recoveries of 15N in trees were typically greater after 15NO3 than after 15NH4 additions. It was indicated that immobilization of 15N tracer in fine roots was a slower process comparing other plant compartments such as stem and coarse roots, but a powerful sink for N during the course of study.  相似文献   

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