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1.
《Biomass》1988,15(4):249-257
An experiment was conducted in the growth chamber to quantify the biomass production, N removal and N2 fixation from a synthetic medium by Chlamydomonas reinhardtii and Anabaena flos-aquae. Nitrogen was supplied at a concentration of 100 mg liter−1 of NO3−−15N and NH4+−15 (3·5 atom %), respectively. After 21 days Chlamydomonas reinhardtii removed an average of 83·8 and 78·7 mg N liter−1 as NO3− and NH4+, respectively. Averages of 0·89 and 0·71 g liter−1 (first batch), 1·63 and 0·95 g liter− (second batch) algal biomass were collected from NO3− and NH4+ media, respectively. Uptake rates of 0·11 mg 15N g−1 algae day−1 from NO3− medium and 0·10 mg 15N g−1 algae day−1 from NH4+ medium were calculated. Algal cells grown in NO3− and NH4+ medium contained 71 and 65 g N kg−1 (first batch), 39 and 58 g N kg−1 (second batch), respectively. Anabaena flos-aquae produced averages of 0·58 and 0·46 g liter−1 (first batch), 0·55 and 0·48 g liter−1 (second batch) after 14 days of growth from NO3− and NH4+ media, respectively. Blue-green algal biomass contained higher N (81–98 g kg−1) than green algae. Isotope dilution method for determining N2 fixation indicated that 55% and 77% of total N of blue-green algae grown in NO3− and NH4+ media, respectively, was derived from the atmosphere. 相似文献
2.
《Biomass》1990,21(4):273-284
A field experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) Center, Patancheru, India to study photosynthetically active radiation (PAR) interception and dry matter production relationships in pearl millet (Pennisetum americanum (L.) Leeke). Two pearl millet genotypes, BJ 104 (G1) and ICH 226 (G2) were sown at three planting geometries obtained by using combinations of row and plant spacings (S1: 37·5 cm × 26·6 cm; S2: 75·0 cm × 13·3 cm; S3: 150·0 cm × 6·6 cm) such that plant population was constant at 100 000 ha−1 in all treatments. Cumulative intercepted PAR was maximum (330 MJ m−2) in G2S2 and minimum (268 MJ m−2) in G1S3. Conversion efficiency values ranged from 1·87 g MJ−1 in G1S2 to 2·32 g MJ−1 in G2S3. Final above-ground dry matter followed the pattern of cumulative intercepted PAR and maximum dry matter (7·22 Mg ha−1) was produced by G2S2 while G1S3 produced minimum dry matter (4·97 Mg ha−1). 相似文献
3.
Maize and pigweed response to nitrogen supply and form 总被引:1,自引:0,他引:1
As nitrogen management practices change to achieve economic and environmental goals, effects on weed-crop competition must
be examined. Two greenhouse experiments investigated the influence of N amount and form on growth of maize and redroot pigweed
(Amaranthus retroflexus L.).
In Experiment 1, maize and pigweed were grown together in a replacement series (maize: pigweed ratios of 0:4, 1:3, 2:2, 3:1,
4:0) under three NH4NO3-N supplies (0, 110, and 220 mg N kg-1 soil). Maize was planted into established pigweed and plants were harvested 24 days after maize germination. Pigweed responded
more to supplemental N than maize and accumulated 2.5 times as much N in shoots at the high N supply. Competition effects
were not significant.
Maize and pigweed were grown separately in Experiment 2 and supplied 220 mg N kg-1 as either Ca(NO3)2 or (NH4)2SO4 plus a nitrification inhibitor (enhanced ammonium supply, EAS). In maize, EAS treatment did not affect shoot growth and reduced
root growth 25% relative to the NO3-N treatment. In pigweed, shoot and root growth were restricted 23 and 86% by EAS treatment, respectively. Total plant N accumulation
under EAS treatment was higher in maize, less in pigweed. Under EAS treatment, pigweed leaves were crinkled and chlorotic;
leaf disks extracted in 70% ethanol, pH 3, contained less malate and oxalate but more NH4
+ compared to the NO3-N treatment. Maize leaf disk malate levels were generally higher compared to pigweed but were less due to EAS treatment.
Ammonium level in maize leaf disks was unaffected by N form and EAS treatment increased oxalate levels. Final bulk soil pH
was generally lower in pots where pigweed were grown and tended to be lower due to EAS. Leaf disk malate levels and soil pH
were positively associated.
Results indicate that pigweed is more likely to compete with maize when high levels of NO3-N are provided. Enhancing the proportion of N supplied as NH4
+ should restrict the growth of NH4
+-sensitive pigweed. 相似文献
4.
Cover crop benefits include nitrogen accumulation and retention, weed suppression, organic matter maintenance, and reduced erosion. Organic farmers need region-specific information on winter cover crop performance to effectively integrate cover crops into their crop rotations. Our research objective was to compare cover crop seeding mixtures, planting dates, and termination dates on performance of rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) monocultures and mixtures in the maritime Pacific Northwest USA. The study included four seed mixtures (100% hairy vetch, 25% rye-75% hairy vetch, 50% rye-50% hairy vetch, and 100% rye by seed weight), two planting dates, and two termination dates, using a split-split plot design with four replications over six years. Measurements included winter ground cover; stand composition; cover crop biomass, N concentration, and N uptake; and June soil NO3
--N. Rye planted in mid-September and terminated in late April averaged 5.1 Mg ha-1 biomass, whereas mixtures averaged 4.1 Mg ha-1 and hairy vetch 2.3 Mg ha-1. Delaying planting by 2.5 weeks reduced average winter ground cover by 65%, biomass by 50%, and cover crop N accumulation by 40%. Similar reductions in biomass and N accumulation occurred for late March termination, compared with late April termination. Mixtures had less annual biomass variability than rye. Mixtures accumulated 103 kg ha-1 N and had mean C:N ratio <17:1 when planted in mid-September and terminated in late April. June soil NO3
--N (0 to 30 cm depth) averaged 62 kg ha-1 for rye, 97 kg ha-1 for the mixtures, and 119 kg ha-1 for hairy vetch. Weeds comprised less of the mixtures biomass (20% weeds by weight at termination) compared with the monocultures (29%). Cover crop mixtures provided a balance between biomass accumulation and N concentration, more consistent biomass over the six-year study, and were more effective at reducing winter weeds compared with monocultures. 相似文献
5.
Teresa Dias Adelaide Clemente Maria Amélia Martins-Lou??o Lucy Sheppard Roland Bobbink Cristina Cruz 《PloS one》2014,9(4)
Enhanced nitrogen (N) availability is one of the main drivers of biodiversity loss and degradation of ecosystem functions. However, in very nutrient-poor ecosystems, enhanced N input can, in the short-term, promote diversity. Mediterranean Basin ecosystems are nutrient-limited biodiversity hotspots, but no information is available on their medium- or long-term responses to enhanced N input. Since 2007, we have been manipulating the form and dose of available N in a Mediterranean Basin maquis in south-western Europe that has low ambient N deposition (<4 kg N ha−1 yr−1) and low soil N content (0.1%). N availability was modified by the addition of 40 kg N ha−1 yr−1 as a 1∶1 NH4Cl to (NH4)2SO4 mixture, and 40 and 80 kg N ha−1 yr−1 as NH4NO3. Over the following 5 years, the impacts on plant composition and diversity (richness and evenness) and some ecosystem characteristics (soil extractable N and organic matter, aboveground biomass and % of bare soil) were assessed. Plant species richness increased with enhanced N input and was more related to ammonium than to nitrate. Exposure to 40 kg NH4
+-N ha−1 yr−1 (alone and with nitrate) enhanced plant richness, but did not increase aboveground biomass; soil extractable N even increased under 80 kg NH4NO3-N ha−1 yr−1 and the % of bare soil increased under 40 kg NH4
+-N ha−1 yr−1. The treatment containing less ammonium, 40 kg NH4NO3-N ha−1 yr−1, did not enhance plant diversity but promoted aboveground biomass and reduced the % of bare soil. Data suggest that enhanced NHy availability affects the structure of the maquis, which may promote soil erosion and N leakage, whereas enhanced NOx availability leads to biomass accumulation which may increase the fire risk. These observations are relevant for land use management in biodiverse and fragmented ecosystems such as the maquis, especially in conservation areas. 相似文献
6.
1. While phosphorus (P) is often considered the most important growth limiting factor for plants in lakes, recent studies of shallow lakes indicate that nitrogen (N) may be of greater importance than realized hitherto and that submerged macrophytes may be lost when the N concentration exceeds a certain threshold, as long as the concentration of P is sufficiently high. 2. We studied the effects of different loadings of NH4‐N and NO3‐N on chlorophyll a and on a macrophyte tolerant of eutrophication, Vallisneria spinulosa (Hydrocharitaceae). In outdoor mesocosms we used water from a pond as control and created four levels of NH4‐N and NO3‐N (approximately 2.5, 5, 7.5 and 10 mg L−1) by dosing with NH4Cl and NaNO3, respectively. After the experiment, the plants were transferred back to a holding pond to study their recovery. In contrast to previous research, we used a low background concentration of phosphorus (TP 0.024 ± 0.003 mg L−1) so we could judge whether any effects of N were apparent when P is in short supply. 3. Chlorophyll a increased significantly with N dosing for both forms of N, but the increase was highest in the NH4‐N dosed mesocosms (maximum 58 μg L−1 versus 42 μg L−1 in the NO3‐N mesocosms), probably due to a higher total inorganic N concentration (part of the added ammonia was converted to nitrate during the experiment). 4. Although the number of ramets of V. spinulosa was not affected by the N treatment, the biomass increased up to concentrations of 7.5 mg L−1, while biomass at 10 mg L−1 remained at the control level for both N ions treatments. A similar pattern was apparent for the content of N and soluble sugar of the plant, while there were no differences in the plant P content among treatments. Five months after transplantation back to the pond no difference was found in the number of ramets or in biomass, except that the biomass of plants grown at 10 mg N L−1 during the experiment was greater than that in the control, while the N and P contents of plants were similar to those of the controls. 5. Nitrogen concentration had little influence on the growth of the eutrophication tolerant submerged macrophyte at moderately low concentrations of phosphorus. Moreover, the two N ions showed no toxic effects, suggesting that loss of macrophytes observed in other studies, run at higher phosphorus concentrations, was probably related to enhanced shading by periphyton and/or phytoplankton rather than to any toxic effects of N. 相似文献
7.
Understanding the effects of nitrogen (N) fertilization on Miscanthus × giganteus greenhouse gas emissions, nitrate leaching, and biomass production is an important consideration when using this grass as a biomass feedstock. The objective of this study was to determine the effect of three N fertilization rates (0, 60, and 120?kg?N?ha?1 using urea as the N source) on nitrous oxide (N2O) and carbon dioxide (CO2) emissions, nitrogen leaching, and the biomass yields and N content of M. × giganteus planted in July 2008, and evaluated from 2009 through early 2011 in Urbana, Illinois, USA. While there was no biomass yield response to N fertilization rates in 2009 and 2010, the amount of N in the harvested biomass in 2010 was significantly greater at the 60 and 120?kg?N?ha?1?N rates. There was no significant CO2 emission response to N rates in 2009 or 2010. Similarly, N fertilization did not increase cumulative N2O emissions in 2009, but cumulative N2O emissions did increase in 2010 with N fertilization. During 2009, nitrate (NO 3 ? ) leaching at the 50-cm soil depth was not related to fertilization rate, but there was a significant increase in NO 3 ? leaching between the 0 and 120?kg?N?ha?1 treatments in 2010 (8.9 and 28.9?kg?NO3?CN?ha?1?year?1, respectively). Overall, N fertilization of M. × giganteus led to N2O releases, increased fluxes of inorganic N (primarily NO 3 ? ) through the soil profile; and increased harvested N without a significant increase in biomass production. 相似文献
8.
Metabolic regulation and gene expression of root phosphoenolpyruvate carboxylase by different nitrogen sources 总被引:3,自引:1,他引:2
S. Pasqualini L. Ederli C. Piccioni P. Batini M. Bellucci S. Arcioni & M. Antonielli 《Plant, cell & environment》2001,24(4):439-447
Alfalfa (Medicago sativa L.) N-sufficient plants were fed 1·5 mM N in the form of NO3−, NH4+ or NO3− in conjunction with NH4+, or were N-deprived for 2 weeks. The specific activity of phosphoenolpyruvate carboxylase (PEPC) from the non-nodulated roots of N-sufficient plants was increased in comparison with that of N-deprived plants. The PEPC value was highest with NO3− nutrition, lowest with NH4+ and intermediate in plants that were fed mixed salts. The protein was more abundant in NO3−-fed plants than in either NH4+- or N mixed-fed plants. Nitrogen starvation decreased the level of PEPC mRNA, and nitrate was the N form that most stimulated PEPC gene expression. The malate content was significantly lower in NO3−-deprived than in NO3−-sufficient plants. Root malate accumulation was high in NO3−-fed plants, but decreased significantly in plants that were fed with NH4+. The effect of malate on the desalted enzyme was also investigated. Root PEPC was not very sensitive to malate and PEPC activity was inhibited only by very high concentrations of malate. Asparagine and glutamine enhanced PEPC activity markedly in NO3−-fed plants, but failed to affect plants that were either treated with other N types or N starved. Glutamate and citrate inhibited PEPC activity only at optimal pH. N-nutrition also influenced root nitrate and ammonium accumulation. Nitrate accumulated in the roots of NO3−- and (NO3− + NH4+)-fed plants, but was undetectable in those administered NH4+. Both the nitrate and the ammonium contents were significantly reduced in NO3−- and (NO3− + NH4+)-starved plants. Root accumulation of free amino acids was strongly influenced by the type of N administered. It was highest in NH4+-fed plants and the most abundant amides were asparagine and glutamine. It was concluded that root PEPC from alfalfa plants is N regulated and that nitrate exerts a strong influence on the PEPC enzyme by enhancing both PEPC gene expression and activity. 相似文献
9.
《Biomass》1989,18(1):15-29
Species screening and selection trials are being conducted to identify appropriate woody species and technology for biofuel farming in the southwest United States. During the initial phase of the program, 26 native and exotic species have been tested at sites in Texas, New Mexico and Arizona. Second season biomass estimates indicate that initial yields of 3·2–8·5 dry Mg ha−1 year−1 are possible without post-establishment irrigation. The species Atriplex canescens (Pursh) Nutt., Prosopis alba Griseb. and Leucaena leucocephala (Lam.) de Wit reached canopy closure within two seasons of growth and are identified as rapid initial biomass producers under the semi-arid conditions of the study area. 相似文献
10.
《Harmful algae》2015
The nitrogen (N) uptake kinetic parameters for Microcystis field assemblages collected from the San Francisco Bay Delta (Delta) in 2012 and non-toxic and toxic laboratory culture strains of M. aeruginosa were assessed. The 15N tracer technique was used to investigate uptake of ammonium (NH4+), nitrate (NO3−), urea and glutamic acid over short-term incubations (0.5–1 h), and to study inhibition of NO3−, NH4+ and urea uptake by NH4+, NO3− and NH4+, respectively. This study demonstrates that Delta Microcystis can utilize different forms of inorganic and organic N, with the greatest capacity for NH4+ uptake and the least for glutamic acid uptake, although N uptake did not always follow the classic Michaelis–Menten hyperbolic relationship at substrate concentrations up to 67 μmol N L−1. Current ambient N concentrations in the Delta may be at sub-saturating levels for N uptake, indicating that if N loading (especially NH4+) were to increase, Delta Microcystis assemblages have the potential for increased N uptake rates. Delta Microcystis had the highest specific affinity, α, for NH4+ and the lowest for NO3−. In culture, N uptake by non-toxic and toxic M. aeruginosa strains was much higher than from the field, but followed similar N utilization trends to those in the field. Neither strain showed severe inhibition of NO3− uptake by NH4+ or inhibition of NH4+ uptake on NO3−, but both strains showed some inhibition of urea uptake by NH4+. 相似文献
11.
Shiyu Qin Xuecheng Sun Chengxiao Hu Qiling Tan Xiaohu Zhao Juan Xin Xin Wen 《Acta Physiologiae Plantarum》2017,39(9):198
The effect of NO3 ?:NH4 + ratio (14:1, 9:6, 7.5:7.5, 1:14, total 15 mmol/L N) in the nutrient solution on biomass, root morphology, and C and N metabolism parameter in hydroponically grown oilseed rape (Brassica napus L.) was evaluated. The dry weights of leaves and roots were significantly largest at the equal NO3 ?:NH4 + ratio (7.5:7.5) compared with those of high NO3 ?:NH4 + ratio (14:1) or low NO3 ?:NH4 + ratio (1:14). Additionally, low NO3 ?:NH4 + ratio (1:14) reduced total root length and root surface area compared with the equal NO3 ?:NH4 + ratio (7.5:7.5), while high NO3 ?:NH4 + ratio (14:1) did not show any significant effect on root morphology except average diameter. The maximum of chlorophyll a, chlorophyll b and carotenoid were obtained under 7.5:7.5 treatment, whereas the maximum of the leaf net photosynthetic (P n), stomatal conductance (G s) and transpiration rate (T r) were increased with increase in NH4 + concentration in the nutrient solution. The activity of nitrate reductase (NR) showed a significant difference at different NO3 ?:NH4 + ratios and ranged 9:6 > 7.5:7.5 > 14:1 > 1:14, whereas the range of soluble sugar and soluble protein was 7.5:7.5 > 1:14 > 9:6 > 14:1. Our study reveals that oilseed rape growth is greater under 7.5:7.5 treatment than that under three other treatments. Oilseed rape growth at high or low NO3 ?:NH4 + ratios was inhibited by decreased pigments, NR activity, soluble sugar, and soluble protein, whereas subdued root growth should be apprehended considerate under high NH4 + condition. 相似文献
12.
J. Neirynck I. A. Janssens P. Roskams P. Quataert P. Verschelde R. Ceulemans 《Biogeochemistry》2008,91(2-3):201-222
Nitrogen (N) biogeochemistry of a mature Scots pine (Pinus sylvestris L.) stand subjected to an average total atmospheric N deposition of 48 kg ha?1 year?1 was studied during the period 1992–2007. The annual amount of dissolved inorganic nitrogen (DIN) in throughfall (TF) averaged 34 kg ha?1 year?1 over the 16-year monitoring period. The throughfall fluxes contained also considerable amounts of dissolved organic nitrogen (DON) (5–8.5 kg N ha?1 year?1), which should be incorporated in the estimate of N flux using throughfall collectors. Throughfall DIN fluxes declined at a rate of ?0.9 kg N ha?1 year?1, mainly due to the decreasing TF fluxes of ammonium (NH4), which accounted for 70% to TF DIN. The decrease in TF DIN was accompanied by a decrease in DIN leaching in the seepage water (?1.6 kg N ha?1 year?1), which occurred exclusively as nitrate (NO3 ?). Nitrate losses in the leachate of the forest floor (LFH) equalled the TF NO3 ? delivered to the LFH-layer. On the contrary, about half of the TF NH4 + was retained within the LFH-layer. Approximately 60% of the TF DIN fluxes were leached indicating that N inputs were far in excess of the N requirements of the forest. For DON, losses were only substantial from the LFH-layer, but no DON was leached in the seepage water. Despite the high N losses through nitrate leaching and NO x emission, the forest was still accumulating N, especially in the aggrading LFH-layer. The forest stand, on the contrary, was found to be a poor N sink. 相似文献
13.
The growth of Salvinia molesta D.S. Mitchell was studied in a greenhouse using controlled-temperature water-baths at 16, 19 and 22°C and 4 different nitrogen compounds (NO3?, NH4+, NH4NO3 and urea) at levels up to 60 mg N l?1. Little growth occurred at 16°C even if 20 mg N l?1 was supplied together with other nutrients including phosphorus (2 mg H2PO4-P l?1). The highest relative growth rate and total dry matter production occurred at 22°C when plants were supplied with 20 mg NH4-N l?1. At this temperature, the NH4+ ion was superior to the NO3? ion or urea as a nitrogen source (almost doubling the biomass), but was not significantly better than NH4NO3. Over a period of 19 days for plants receiving 0.02 mg NH4-N l?, biomass increased 4-fold at 16°C, 9-fold at 19°C and 10-fold at 22°C. In contrast, for plants receiving 20 mg NH4-N l?1, biomass increased 4-fold at 16°C, 18-fold at 19°C and 38-fold at 22°C. 相似文献
14.
It is important to understand switchgrass (Panicum virgatum L.) productivity with relation to diverse nutrient deficiency conditions in order to optimize continuous biomass production in marginal lands. This study was conducted on a wasteland sandy soil (Aridosol) to assess biomass yield, nutrient uptake and nitrogen (N) recovery of switchgrass, and soil nitrate-N (NO3?-N) accumulation responses to N (120 kg N ha?1), phosphorus (P, 100 kg P2O5 ha?1), and potassium (K, 45 kg K2O ha?1) applications during 2015 and 2016 in Inner Mongolia, China. The experiment layout was a randomized complete block design with fertilizer mixture treatments of N, P, and K (NPK), P and K (PK), N and K (NK), N and P (NP), and a control with no fertilizer input (CK). Plant height and stem diameter remained unaffected by the different fertilizer treatments. Biomass yield with the NPK treatment in 2015 was 8.9 Mg ha?1 and in 2016 it was 7.3 Mg ha?1. In 2015, compared with the NPK treatment, a significant yield reduction of 33.7% was found with PK, 22.5% with NK, 28.1% with NP, and 40.5% with CK; however, in 2016, yield declined significantly only with CK compared to the rest of the fertilizer treatments, for which yields were statistically similar. Plant N content was reduced for the treatment PK (i.e. N omission); conversely, plant P and K content remained unaffected with P and K omission treatments. Plant nutrient uptake, particularly of N and K, was severely decreased by the nutrient omission treatments when averaged across 2 years. Apparent N recovery (ANR; quantity of N uptake per unit of N applied) was reduced for the NP and NK treatments, which led to an increase in soil NO3?-N accumulation in the top 0–20 cm layer, compared with the NPK treatment. However, ANR was the highest (37.2% in 2015) with the NPK treatment, which also reduced soil NO3?-N accumulation. A balanced N, P, and K fertilizer management approach is suggested to sustain switchgrass yield and stand persistence on semiarid, marginal, sandy wasteland. 相似文献
15.
《Biological Wastes》1989,27(1):29-42
Potential biomass yield, nutrient uptake capacity and forage quality of Glyceria maxima was tested in four field lysimeters (I–IV) receiving municipal wastewater. Wastewater was applied during 3 years at different frequencies in order to achieve maximum N-reduction in the system. Accordingly lysimeters III and IV were ponded for part of the week. Harvesting (in June and August) progressively favoured competing terrestrial species in the non-ponded lysimeters (I and II). In year 3 the other species accounted for 65–70% of the harvested biomass in these lysimeters. In the ponded lysimeters (III and IV), reducing conditions in the soil probably prevented terrestrial species from establishing. The total annual yields of the single-species stands in III and IV were 870–1165 gm−2. Energy, protein, P, K and Ca content of the harvested biomass indicated a high nutritional value. NO3−N concentrations in the harvested biomass varied from 0·08 to 0·32% of dry wt, but did not generally exceed 0·2%.Maximum N and P removed with the harvested biomass was 32 and 4·8 gm−2 respectively. The relative removal of nutrients in lysimeters III and IV varied from 26 to 55% of the amount of N applied and from 12 to 28% of P applied, which illustrated the possibilities of adjusting the load for optimization of nutrient re-use rather than disposal. 相似文献
16.
Young Norway spruce trees were grown in 94 pots (2 per pot) on soil substrate derived from granite with low Mg saturation and were fertilized with different amounts of NH4NO3 (in total 25, 61, and 97 kmol N ha-1) over a period of four years, partly at an experimental station, partly at a high-elevation site in the Bavarian Forest. A fourth set of trees received 9.4 kmol Mg ha-1 in addition to 25 kmol N. Depending on the treatment, needle chlorosis developed in the course of the experiment. Improved light conditions after three years accelerated the yellowing process. The chlorotic Norway spruce trees showed a severe Mg deficiency and an imbalanced N:Mg ratio. The shoot length increment, the stem diameter, and the needle weights however were not influenced by the fertilization. Excessive applications of NH4NO3caused the substrate to become depleted of Mg. The successful experimental induction of the characteristic tip yellowing of older needles of Norway spruce growing on acidic soils at higher altitudes allowed hypotheses on the causes and processes of this type of forest decline to be tested. 相似文献
17.
High rates of deforestation in the Brazilian Amazon have the potential to alter the storage and cycling of carbon (C) and nitrogen (N) across this region. To investigate the impacts of deforestation, we quantified total aboveground biomass (TAGB), aboveground and soil pools of C and N, and soil N availability along a land-use gradient in Rondônia, Brazil, that included standing primary forest, slashed primary and secondary forest, shifting cultivation, and pasture sites. TAGB decreased substantially with increasing land use, ranging from 311 and 399 Mg ha–1 (primary forests) to 63 Mg ha–1 (pasture). Aboveground C and N pools declined in patterns and magnitudes similar to those of TAGB. Unlike aboveground pools, soil C and N concentrations and pools did not show consistent declines in response to land use. Instead, C and N concentrations were strongly related to percent clay content of soils. Concentrations of NO3-N and NH4-N generally increased in soils following slash-and-burn events along the land-use gradient and decreased with increasing land use. Increasing land use resulted in marked declines in NO3-N pools relative to NH4-N pools. Rates of net nitrification and N-mineralization were also generally higher in postfire treatments relative to prefire treatments along the land-use gradient and declined with increasing land use. Results demonstrate the linked responses of aboveground C and N pools and soil N availability to land use in the Brazilian Amazon; steady reductions in aboveground pools along the land-use gradient were accompanied by declines in inorganic soil N pools and transformation rates. 相似文献
18.
Maru K. Kering Twain J. Butler Jon T. Biermacher Jagadeesh Mosali John A. Guretzky 《Bioenergy Research》2013,6(1):329-335
Biomass demand for energy will lead to utilization of marginal, low fertility soil. Application of fertilizer to such soil may increase switchgrass (Panicum virgatum L.) biomass production. In this three-way factorial field experiment, biomass yield response to potassium (K) fertilizer (0 and 68 kg?K?ha?1) on nitrogen (N)-sufficient and N-deficient switchgrass (0 and 135 kg?N?ha?1) was evaluated under two harvest systems. Harvest system included harvesting once per year after frost (December) and twice per year in summer (July) at boot stage and subsequent regrowth after frost. Under the one-cut system, there was no response to N or K only (13.4 Mg?ha?1) compared to no fertilizer (12.4 Mg?ha?1). Switchgrass receiving both N and K (14.6 Mg?ha?1) produced 18 % greater dry matter (DM) yield compared to no fertilizer check. Under the two-cut harvest system, N only (16.0 Mg?ha?1) or K only (14.1 Mg?ha?1) fertilizer produced similar DM to no fertilizer (15.1 Mg?ha?1). Switchgrass receiving both N and K in the two-cut system (19.2 Mg?ha?1) produced the greatest (P?<?0.05) DM yield, which was 32 % greater than switchgrass receiving both N and K in the one-cut system. Nutrient removal (biomass?×?nutrient concentration) was greatest in plots receiving both N and K, and the two-cut system had greater nutrient removal than the one-cut system. Based on these results, harvesting only once during winter months reduces nutrient removal in harvested biomass and requires less inorganic fertilizer for sustained yields from year to year compared to two-cut system. 相似文献
19.
《Lichenologist (London, England)》2003,35(4):347-359
The epiphytic lichen flora of 25 European ICP-IM monitoring sites, all situated in areas remote from air pollution sources, was statistically related to measured levels of SO2in air, NH4+, NO3− and SO42− in precipitation, annual bulk precipitation, and annual average temperature. Significant regression models were calculated for eleven acidophytic species. Several species show a strong negative correlation with nitrogen compounds. At concentrations as low as 0·3 mg N l−1in precipitation, a decrease of the probability of occurrence is observed for Bryoria capillaris, B. fuscescens, Cetraria pinastri, Imshaugia aleurites and Usnea hirta. The observed pattern of correlations strongly suggests a key role of NH4+ in determining the species occurrence, but an additional role of NO3− cannot be ruled out. Some species show a distinct response to current levels of SO2as well. It may be concluded that long distance nitrogen air pollution has strong influence on the occurrence of acidophytic lichen species. 相似文献
20.
马尾松属高氮需求树种,然而在苗木培育中马尾松对氮素,尤其是不同形态氮素的需求尚不明确.该文以马尾松组培苗为试验材料,采用基质培养方法,针对硝态氮、铵态氮两种氮素形态均分别设置了2、4、8、16 mmol·L-14个处理,以不添加氮素为对照,对苗木的高径生长、根构型参数(总根长、总表面积、总体积、平均直径和根尖数)以及生... 相似文献