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1.
Purpose Atmospheric nitrogen (N) deposition remains globally and regionally a significant N source in forest ecosystems, with intensive
industrial activities. Stable N isotope ratio (δ 15N) is a useful indicator widely adopted to assess environmental and ecological impacts of anthropogenic N inputs. On the basis
of temporal changes in tree ring δ 15N established recently, the present study investigated the influence of N deposition on δ 15N in needles of Masson pine ( Pinus massoniana L.) and forest soil along an urban–rural gradient in the Pearl River Delta of south China. 相似文献
2.
Species‐specific uptake and allocation mechanisms for N are scarce, in particular when trees are cultivated in potted soil under more natural conditions than in hydroponic culture. The objective of this study was to compare specific N‐uptake rates for economically and ecologically important tree species in Central European forests: pine ( Pinus sylvestris), spruce ( Picea abies), oak ( Quercus petraea), beech ( Fagus sylvatica), lime ( Tilia cordata), and ash ( Fraxinus excelsior) when they grow in mineral soil from an old fallow site with a pH of 6. We used an 15N‐labeling method to measure tree seedling 15N uptake in potted soils (Humic Cambisol) when both N forms NH$ _4^+ $ and NO$ _3^- $ were simultaneously present in the soil solution for interspecies comparison and assessment of relationships between specific 15N‐uptake rates and amino acid–accumulation rates or relative growth rates (RGR). The results demonstrate that tree species varied significantly in their capacity to take up NH$ _4^+ $ or NO$ _3^- $ into roots, stems, or leaves, but indicate only marginal differences in their preference for NH$ _4^+ $ or NO$ _3^- $ when they grow in mineral soil. The ranking of specific 15N‐uptake rates for NH$ _4^+ $ and NO$ _3^- $ was oak < beech < spruce < pine < lime < ash. Fine roots of all species had the highest specific 15N‐uptake rates for both N forms, followed by total roots, leaves/needles, and stems. As regards tree seedling species, we found negative relationships between glutamine (Gln)‐accumulation rates in leaves/needles and total 15N‐uptake rates in fine roots. Noteworthy was the fact that, at high Gln‐accumulation rates, the N‐uptake system in fine roots of ash was probably lower under feedback inhibition by the amino acid. 相似文献
3.
Background and Objectives Soil nitrate nitrogen (NO 3
−-N) accumulation is related closely to NO 3
− leaching, which is an important issue in groundwater pollution, especially in intensive agricultural areas with saline soils
where volumes of water are used in irrigation to avoid salt accumulation in the root zone. However, in the saline environment
in Hai River Basin, China, the importance of detailed research into NO 3
−-N distribution in the root zone has not been adequately recognized. Considering the impacts of eco-environmental system N
and crop production, the present study aimed at contributing to an understanding of the effects of N application rate on soil
NO 3
−-N distribution, NO 3
−-N residue, N loss, and maize ( Zea mays L.) yield in this region. 相似文献
4.
Purpose We investigated the effects of weed control and fertilization at early establishment on foliar stable carbon (δ 13C) and nitrogen (N) isotope (δ 15N) compositions, foliar N concentration, tree growth and biomass, relative weed cover and other physiological traits in a 2-year old F 1 hybrid ( Pinus elliottii var. elliottii (Engelm) × Pinus caribaea var. hondurensis (Barr. ex Golf.)) plantation grown on a yellow earth in southeast Queensland of subtropical Australia. Materials and methods Treatments included routine weed control, luxury weed control, intermediate weed control, mechanical weed control, nil weed control, and routine and luxury fertilization in a randomised complete block design. Initial soil nutrition and soil fertility parameters included (hot water extractable organic carbon (C) and total nitrogen (N), total C and N, C/N ratio, labile N pools (nitrate (NO 3 ?) and ammonium (NH 4 +)), extractable potassium (K +)), soil δ 15N and δ 13C. Relative weed cover, foliar N concentrations, tree growth rate and physiological parameters including photosynthesis, stomatal conductance, photosynthetic nitrogen use efficiency, foliar δ 15N and foliar δ 13C were also measured at early establishment. Results and discussion Foliar N concentration at 1.25 years was significantly different amongst the weed control treatments and was negatively correlated to the relative weed cover at 1.1 years. Foliar N concentration was also positively correlated to foliar δ 15N and foliar δ 13C, tree height, height growth rates and tree biomass. Foliar δ 15N was negatively correlated to the relative weed cover at 0.8 and 1.1 years. The physiological measurements indicated that luxury fertilization and increasing weed competition on these soils decreased leaf xylem pressure potential (Ψ xpp) when compared to the other treatments. Conclusions These results indicate how increasing N resources and weed competition have implications for tree N and water use at establishment in F 1 hybrid plantations of southeast Queensland, Australia. These results suggest the desirability of weed control, in the inter-planting row, in the first year to maximise site N and water resources available for seedling growth. It also showed the need to avoid over-fertilisation, which interfered with the balance between available N and water on these soils. 相似文献
5.
Selection of plant species for agro-silvo-pastoral or ecological reclamation programs must be based on a deeper knowledge of the existing relationships between plant species and soil nutrient dynamics in each ecosystem. We evaluated the seasonal pattern of soil microbial carbon (C) and nitrogen (N) under two remnant tree species ( Caesalpinia eriostachys and Cordia elaeagnoides) in a tropical seasonal pasture dominated by Panicum maximum in western Mexico. Soil samples were taken from under two arboreal species and P. maximum in rainy and dry seasons. The soil C:N ratio was higher under P. maximum [17] than under both tree species [15]. The soil microbial C (Cm) was higher under C. elaeagnoides than under C. eriostachys and P. maximum. Magnitude and direction of effect of the two remnant tree species on soil biogeochemistry changed with seasonal rainfall. The interaction of plant species and seasonal rainfall did have an effect on soil microbial N (Nm). Soil samples from April and July had the lowest microbial N concentrations under the three plant species, increasing four fold in September under C. elaeagnoides and P. maximum. At the end of the wet season, C. elaeagnoides clearly had the highest Nm values (130 μg N g −1), suggesting that this tree species has a higher capacity to protect soil N within microbial biomass than C. eriostachys, because under C. elaeagnoides the soil had more organic matter due a higher input of litter and root chemical quality. Therefore, C. elaeagnoides would be the best plant species to implement in agro-silvo-pastoral programs or ecological reclamation of TDF pastures. 相似文献
6.
Background Fertilization with organic waste compost can close the nutrient cycles between urban and rural environments. However, its effect on yield and soil fertility must be investigated. Aim This study investigated the long-term effect of compost on soil nutrient and potentially toxic elements (PTEs) concentration, nutrient budgets, and nitrogen (N) mineralization and efficiency. Methods After 21 years of annual compost application (100/400 kg N ha –1 year –1 [100BC/400BC]) alone and combined with mineral fertilization, soil was analyzed for pH, organic carbon (SOC), nutrient (total N and P, N min, extractable CAL-P, CAL-K, and Mg), and PTE (Cu, Ni, Zn) concentrations. Yields were recorded and nutrient/PTE budgets and apparent net mineralization (ANM, only 2019) were calculated. Results N efficiency was the highest in maize and for mineral fertilization. Compost application led to lower N efficiencies, but increased ANM, SOC, pH, and soil N, and surpluses of N, P, and all PTEs. Higher PTE concentrations were only found in 400BC for Cu. Nutrient budgets correlated with soil nutrient concentration. A surplus of 16.1 kg P ha –1 year –1 and 19.5 kg K ha –1 year –1 resulted in 1 mg kg –1 increase in CAL-P and CAL-K over 21 years. Conclusion Compost application supplies nutrients to crops with a minor risk of soil-accumulation of PTEs. However, the nutrient stoichiometry provided by compost does not match crop offtakes causing imbalances. Synchronization of compost N mineralization and plant N demand does not match and limits the yield effect. In winter wheat only 65–70% of N mineralization occurred during the growth period. 相似文献
7.
Microbial characterization of the tree rhizosphere provides important information relating to the screening of tree species for re-vegetation of degraded land. Rhizosphere soil samples collected from a few predominant tree species growing in the coal mining ecosystem of Dhanbad, India, were analyzed for soil organic carbon (SOC), mineralizable N, microbial biomass carbon (MBC), active microbial biomass carbon (AMBC), basal soil respiration (BSR), and soil enzyme activities (dehydrogenase, urease, catalase, phenol oxidase, and peroxidase). Among the tree species studied, Aegle marmelos recorded the highest value for MBC (590 mg kg −1), urease (190.5 μg NH 4+-N g −1 h −1), catalase (513 μg H 2O 2 g −1 h −1), dehydrogenase (92.3 μg TPF g −1 h −1), phenol oxidase (0.057 μM g −1 h −1) and BSR/AMBC (0.498 mg CO 2-C mg biomass −1 day −1); Tamarindus indica for mineralizable N (69.5 mg kg −1); Morus alba for catalase (513 μg H 2O 2 g −1 h −1) and phenol oxidase (0.058 μM g −1 h −1); Tectona grandis for peroxidase (0.276 μM g −1 h −1), AMBC/MBC (99.4%), and BSR/MBC (0.108 mg CO 2-C mg biomass −1 day −1); Ficus religiosa for AMBC (128.4 mg kg −1) and BSR (12.85 mg CO 2-C kg −1 day −1); Eugenia jambolana for MBC/SOC (8.03%); Butea monosoperma for AMBC/SOC (1.32%) and Azadirachta indica for BSR/AMBC (0.1134 mg CO 2-C mg biomass −1 day −1). Principal component analysis was employed to derive a rhizosphere soil microbial index (RSMI) and accordingly, dehydrogenase, BSR/MBC, MBC/SOC, EC, phenol oxidase and AMBC were found to be the most critical properties. The observed values for the above properties were converted into a unitless score (0–1.00) and the scores were integrated into RSMI. The tree species could be arranged in decreasing order of the RSMI as: A. marmelos (0.718), A. indica (0.715), Bauhinia bauhinia (0.693), B. monosperma (0.611), E. jambolana (0.601), Moringa oleifera (0.565), Dalbergia sissoo (0.498), T. indica (0.488), Morus alba (0.415), F. religiosa (0.291), Eucalyptus sp. (0.232) and T. grandis (0.181). It was concluded that tree species in coal mining areas had diverse effects on their respective rhizosphere microbial processes, which could directly or indirectly determine the survival and performance of the planted tree species in degraded coal mining areas. Tree species with higher RSMI values could be recommended for re-vegetation of degraded coal mining area. 相似文献
8.
Nitrogen (N) fluxes through the major plant pools of an alder ( Alnus sinuta)-sweet corn ( Zea mays) alley cropping system were determined over the course of two cropping seasons. Alder trees were injected with 15NO 3–N to directly follow the flow of N between alder and corn. The contribution of the above- and below-ground tree N to corn
was determined by exchanging the labeled above-ground prunings (green manure) with those from unlabeled plots. During the
first growing season after coppicing of the injected alders, 18% of the alder 15N was taken up by the corn with 12% coming from the above-ground prunings. Of the 15N remaining in the tree/stump following coppicing, the majority was recovered by corn plants within the rows next to the labeled
trees during the first growing season. Earlier recovery of 15N by corn in the labeled root plots compared to the labeled pruning plots indicated the importance of root turnover in supplying
N to corn, especially following coppicing. By the end of the first and second growing seasons, 34% and 38% of the 15N initially present in prunings was recovered in corn plants, respectively. Approximately 80% of the total injected 15N was found in the soil during the second growing season; however, the turnover of above- and below-ground alder components
supplied only 3–4% of the N required by corn during the year of green manure application. Thus, most of the corn N demand
was met by mineralization of residual soil N within the 2 years of coppicing and green manure additions. Continued internal
cycling of tree N and movement of soil N into more labile pools would presumably allow more alder N to become available over
time. The synchronization between N mineralization from the hedgerow green manure components and nutrient uptake of the alley
crop remains a major challenge in alley cropping and other green manure systems.
Received: 9 April 1999 相似文献
9.
PurposeMany studies have shown the simulated effects of nitrogen (N) deposition on soil microbial community composition by adding N directly to the forest floor but have ignored the N retention process by the canopy. This study was conducted to compare the responses of soil microbial biomass and community composition between soil application of N (SAN) and foliage application of N (FAN). Materials and methodsA pot experiment was designed with (1) two N application methods (SAN and FAN), (2) three N application levels (5.6, 15.6 and 20.6 g N m?2 year?1), and (3) two tree species (Schima superba Gardn. et Champ. and Pinus massoniana Lamb.) following a nested factorial design. Soil microbial biomass and community composition were determined using phospholipid fatty acids (PLFAs) techniques after 1 and 1.5 years of treatments. Results and discussionNitrogen addition increased (P?<?0.05) soil NH4+-N content and soil NO3?-N content and decreased (P?<?0.05) soil pH and soil microbial (bacterial, fungal, and actinomycete) biomass for both N application methods. Compared with the SAN treatment, the FAN treatment had higher (P?<?0.05) pH and lower (P?<?0.05) contents of soil NH4+-N and soil NO3?-N. Soil microbial biomass and community composition were significantly different between the different N addition levels under the SAN treatment, but they showed no significant difference (P?<?0.05) between the different N addition levels under the FAN treatment. The soil microbial biomass in the S. superba soil was higher (P?<?0.05) than that in the P. massoniana soil for the FAN treatment, with the opposite trend observed under the SAN treatment. Moreover, redundancy analysis showed that soil microorganisms were significantly correlated with soil pH, soil water content, NH4+-N, and NO3?-N. ConclusionsThe results showed that N addition affected soil properties, microbial biomass, and the composition of microbial communities; however, the FAN treatment had less influence on soil properties and soil microorganisms than did the SAN treatment over short time scales, and the extent of this effect was different between coniferous and broadleaf trees. 相似文献
10.
Background The correct rate and timing of nitrogen (N) has the potential to improve sorghum productivity through modified grain yield components and quality. The impacts of in-season split application of N have little documentation. Aim An experiment was conducted to determine the optimum rate and timing of N to relate vegetative indices that govern nitrogen use efficiency and to maximize grain yield and quality under different soil types. Methods Pioneer 86P20 was grown in three environments on two different soil types following a completely randomized block design with nine N application treatments. Treatments included differing N rates applied at critical developmental stages of sorghum (planting, panicle initiation, and booting), accompanied with high temporal aerial phenotyping. Results Opportunities to increase grain protein content while using split N applications were observed, with panicle initiation identified as a critical developmental stage. In-season split application of N enhances grain yield under low soil mineral N. Split application of 31 kg N ha −1 each at the time of planting, panicle initiation, and booting emerged as optimum N treatment to increase protein content in sorghum. Vegetative indices, that is, normalized difference vegetation index and normalized difference red edge index are capable of predicting grain yield and protein content, respectively. Intra-panicle grain numbers and weights were altered significantly at different portions within panicles, with an opportunity to enhance yield potential at the bottom portion. The strong stay-green trait in this hybrid locked a large proportion of nitrogen in the leaves, which warrants the need for balancing stay-green and senescence in sorghum improvement programs. Conclusions Findings highlight that in grain sorghum remobilization of residual leaf N into grain is a target to increase yield and grain quality. An optimized stay-green trait balanced with senescence is recommended for enhancing sorghum yield potential. 相似文献
11.
Background, aim, and scope A large proportion of soil nitrogen (N; >80%) is present in organic form. Current research on plant N uptake in terrestrial
ecosystems has focused mainly on inorganic N such as ammonium (NH 4
+) and nitrate (NO 3
−), while soluble organic N (SON) has received little attention. In recent years, the increasing evidence showing the direct
uptake of various amino acids by plants and the predominance of the organic form in N loss by leaching in many forest ecosystems
has drawn attention to critically re-examine the nature and the ecological role of soil SON in terrestrial N cycling. However,
little is known about the sources and dynamics, chemical nature, and ecological functions of soil SON in forest ecosystems.
This paper reviews recent advances in the areas of research on current techniques for characterizing soil SON and the size,
nature, and dynamics of soil SON pools in forest ecosystems. 相似文献
12.
Information on N cycling in dryland crops and soils as influenced by long-term tillage and cropping sequence is needed to quantify soil N sequestration, mineralization, and N balance to reduce N fertilization rate and N losses through soil processes. The 21-yr effects of the combinations of tillage and cropping sequences was evaluated on dryland crop grain and biomass (stems + leaves) N, soil surface residue N, soil N fractions, and N balance at the 0–20 cm depth in Dooley sandy loam (fine-loamy, mixed, frigid, Typic Argiboroll) in eastern Montana, USA. Treatments were no-tilled continuous spring wheat ( Triticum aestivum L.) (NTCW), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat–barley ( Hordeum vulgare L.) (1984–1999) followed by spring wheat–pea ( Pisum sativum L.) (2000–2004) (FSTW-B/P), and spring-tilled spring wheat–fallow (STW-F). Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH 4-N, and NO 3-N. Annualized crop grain and biomass N varied with treatments and years and mean grain and biomass N from 1984 to 2004 were 14.3–21.2 kg N ha −1 greater in NTCW, STCW, FSTCW, and FSTW-B/P than in STW-F. Soil surface residue N was 9.1–15.2 kg N ha −1 greater in other treatments than in STW-F in 2004. The STN at 0–20 cm was 0.39–0.96 Mg N ha −1, PON 0.10–0.30 Mg N ha −1, and PNM 4.6–9.4 kg N ha −1 greater in other treatments than in STW-F. At 0–5 cm, STN, PON, and MBN were greater in STCW than in FSTW-B/P and STW-F. At 5–20 cm, STN and PON were greater in NTCW and STCW than in STW-F, PNM and MBN were greater in STCW than in NTCW and STW-F, and NO 3-N was greater in FSTW-B/P than in NTCW and FSTCW. Estimated N loss through leaching, volatilization, or denitrification at 0–20 cm depth increased with increasing tillage frequency or greater with fallow than with continuous cropping and ranged from 9 kg N ha −1 yr −1 in NTCW to 46 kg N ha −1 yr −1 in STW-F. Long-term no-till or spring till with continuous cropping increased dryland crop grain and biomass N, soil surface residue N, N storage, and potential N mineralization, and reduced N loss compared with the conventional system, such as STW-F, at the surface 20 cm layer. Greater tillage frequency, followed by pea inclusion in the last 5 out of 21 yr in FSTW-B/P, however, increased N availability at the subsurface layer in 2004. 相似文献
13.
The natural abundance of 15N and 13C, conventional soil analyses, and biomass production by maize were used to study the influence of five tropical tree species on soils and their fertility. The experiment was conducted in Morogoro, Tanzania, to compare Cassia (Senna) siamea, Eucalyptus camaldulensis, E. tereticornis (all non-N 2-fixing), Leucaena leucocephala, Prosopis chilensis (both N 2-fixing), and a grass fallow. Maize biomass production, which was correlated with N uptake ( P=0.001), was higher on soils from plots with 5-year-old Leucaena and Prosopis spp. compared to the grass fallow, while other tree species had less favourable effects on maize growth. The per cent N was higher in soil and 15N of soil total N was lower under Prosopis sp. compared to soil under other tree species, which suggests an input from N 2 fixation by Prosopis sp. A transfer of fixed N to maize or to understorey grass species was, however, not indicated by the 15N natural abundance. Prosopis sp. contributed more C to the soil than the other four tree species; the difference in 13C between soils from Prosopis sp. plots and from grass fallow plots showed that the tree contributed 11% to the total C of the soil over a period of 8 years. The leaves of the N 2-fixing species had a low ratio of lignin+phenols to N, and maize growth was negatively correlated with this parameter. The Eucalyptus spp. had leaves with a high lignin+phenols to N ratio, contributed very little C to the soil, and lowered the soil pH. 相似文献
14.
Background Labile carbon (C labile) limits soil microbial growth and is critical for soil functions like nitrogen (N) immobilization. Most experiments evaluating C labile additions use laboratory incubations. We need to field-apply C labile to fully understand its fate and effects on soils, especially at depth, but high cost and logistical difficulties hinder this approach. Aims Here, we evaluated the impact of adding an in situ pulse of an inexpensive and 13C-depleted source of C labile—crude glycerol carbon (C glyc), a by-product from biodiesel production—to agricultural soils under typical crop rotations in Iowa, USA. Methods We broadcast-applied C glyc at three rates (0, 216, and 866 kg C ha −1) in autumn after soybean harvest, tracked its fate, and measured its impact on soil C and N dynamics to four depths (0–5, 5–15, 15–30, and 30–45 cm). Nineteen days later, we measured C glyc in microbial biomass carbon (MBC), salt-extractable organic C, and potentially mineralizable C pools. We paired these measurements with nitrate N (NO 3−–N) and potential net N mineralization to examine short-term effects on N cycling. Results C glyc was found to at least 45-cm depth with the majority in MBC (18%–23% of total C glyc added). The δ13C values of the other measured C pools were too variable to accurately track the C labile fate. NO 3−–N was decreased by 13%–57% with the 216 and 866 kg C ha −1 rates, respectively, and was strongly related to greater microbial uptake of C glyc (i.e., immobilization via microbial biomass). Crude glycerol application had minor effects on soil pH—the greatest rate decreased pH 0.18 units compared to the control. Conclusions Overall, glycerol is an inexpensive and effective way to measure in situ, C labile dynamics with soil depth—analogous to how mobile, dissolved organic C might behave in soils—and can be applied to rapidly immobilize NO 3−–N. 相似文献
15.
The influence of tree leaf amendment and N fertilization on soil quality in turfgrass environments was evaluated. Our objective
was to assess changes in soil quality after additions of leaf materials and N fertilization by monitoring soil chemical and
physical parameters, microbial biomass and soil enzymes. Established perennial ryegrass ( Lolium perenne) plots were amended annually with maple ( Acer spp.) leaves at three different rates (0, 2240, and 4480 kg ha –1 year –1) and treated with three nitrogen rates (0, 63, and 126 kg N ha –1 year –1). Tree leaf mulching did not significantly affect water infiltration or bulk density. However, trends in the data suggest
increased infiltration with increasing leaf application rate. Tree leaf mulching increased total soil C and N at 0–1.3 cm
depth but not at 1.3–9.0 cm. Extracted microbial phospholipid, an indicator of microbial biomass size, ranged from 28 to 68
nmol phospholipid g –1 soil at the 1.3–9.0 cm depth. The activity of β-glucosidase estimated on samples from 0–1.3 cm and 1.3–9.0 cm depths, and
dehydrogenase activity estimated on samples from 1.3–9.0 cm were significantly increased by leaf mulching and N fertilizer
application. Changes in microbial community composition, as indicated by phospholipid fatty acid methyl ester analysis, appear
to be due to seasonal variations and did not reflect changes due to N or leaf amendment treatments. There were no negative
effects of tree leaf mulching into turfgrass and early data suggest this practice will improve soil chemical, physical, and
biological structure.
Received: 10 December 1997 相似文献
16.
Background Organic vegetable production has a demand for alternative fertilizers to replace fertilizers from sources that are not organic, that is, typically animal-based ones from conventional farming. Aims The aim of this study was to develop production strategies of plant-based fertilizers to maximize cumulative nitrogen (N) production (equal to N yield by green manure crops), while maintaining a low carbon-to-nitrogen (C:N) ratio, and to test the fertilizer value in organic vegetable production. Methods The plant-based fertilizers consisted of the perennial green manure crops—alfalfa, white clover, red clover, and a mixture of red clover and ryegrass—and the annual green-manure crops—broad bean, lupine, and pea. The crops were cut several times at different developmental stages. The harvested crops were used fresh or pelleted as fertilizers for field-grown white cabbage and leek. The fertilizer value was tested with respect to biomass, N offtake, N recovery, and soil mineral N (N min). Poultry manure and an unfertilized treatment were used as controls. Results The cumulative N production of the perennial green manure crops ranged from 300 to 640 kg N ha –1 year –1 when cut two to five times. The highest productions occurred at early and intermediate developmental stages, when cut three to four times. Annual green manure crops produced 110–320 kg N ha –1 year –1, since repeated cutting was restricted. The C:N ratio of the green manure crops was 8.5–20.5, and increased with developmental stage. The fertilizer value of green manure, as measured in white cabbage and leek, was comparable to animal-based manure on the condition that the C:N ratio was low (<18). N recovery was 20%–49% for green manure and 29%–42% for poultry manure. A positive correlation was detected between soil N min and vegetable N offtake shortly after incorporating the green manure crops, indicating synchrony between N release and crop demand. Conclusions Plant-based fertilizers represent highly productive and efficient fertilizers that can substitute conventional animal-based fertilizers in organic vegetable production. 相似文献
17.
We measured soil microbial biomass nitrogen (MBN), microbial uptake of 15N, potential net mineralization and net nitrification in the laboratory to determine the influence of tree species on nitrogen (N) transformations in soils of the Catskills Mountains, New York, USA. Organic horizon soils were taken from single species plots of beech ( Fagus grandifolia), hemlock ( Tsuga canadensis), red oak (Quercus rubra), sugar maple ( Acer saccharum) and yellow birch ( Betula alleghaniensis). 15NH 4Cl was added to the soils and N pools were sampled at 1, 3, 10 and 28 days to examine microbial uptake of 15N over time. Soil MBN was about 60% lower in red oak and sugar maple soils than in the other three species. Soil pools of NO 3− and rates of net nitrification were significantly greater in soils associated with sugar maple than hemlock, red oak and yellow birch. With the exception of sugar maple soils, microbial recovery of 15N was significantly greater after 10 and 28 days compared to 60 min and 1 day following 15N tracer addition. Microbial 15N recovery declined significantly within sugar maple stands within the first 3 days of incubation. Soil carbon to nitrogen ratio (C:N) was lowest in sugar maple soils and highest in red oak soils. However, correlations between soil C:N and MBN or rates of net mineralization and nitrification were not significant. Soil moisture could account for 22% of the variation in MBN and 36% of the variation in net mineralization. Soil microbial transformations of N vary among tree species stands and may have consequences for forest N retention and loss. 相似文献
18.
The use of biochar is expected to improve soil fertility and close nutrient cycles in degraded strongly weathered tropical soils. We, therefore, hypothesized that biochar amendment to tree plantations (a) increases nutrient fluxes with litterfall alone and with mineral fertilizer plus lime and (b) reduces N losses reflected by lower δ 15N values of litterfall and soils than in unamended controls. We grew the native leguminous Schizolobium parahyba var. amazonicum (Ducke) Barneby and the exotic Gmelina arborea Roxb at two sites. We used a replicated full factorial split–split plot design of amendment of mineral fertilizer plus lime, 3 and 6 t ha −1 biochar, and a control. We collected litterfall biweekly (2012–2013) and topsoil samples (0–0.25 m) in 2009 before tree planting, in 2011 and 2013. Fertilizer plus lime increased the mean annual concentrations of P, Ca and Zn in litterfall but decreased that of Mn. At the same time, fertilizer plus lime increased the annual fluxes of nutrients, Na and Al with litterfall. During the dry season, biochar decreased the N concentration in litterfall and the K flux with litterfall. During the rainy season, biochar increased the concentrations of Ca and Zn in litterfall and their fluxes with litterfall. Biochar did not influence the δ 15N values of soil and litterfall after 51 months of tree growth. Fertilizer plus lime decreased the δ 15N values of soil, because of the lower δ 15N value of the used urea (−0.30‰) than the soil (4.5‰–7.8‰). Moreover, fertilizer plus lime increased the δ 15N values of litterfall, possibly because of enhanced 14N leaching from the N-rich canopies. The amendment of up to 6 t ha −1 biochar did not contribute to close nutrient cycles. 相似文献
19.
Purpose Soil carbon (C) and nutrient pools under different plantation weed control and fertilizer management treatments were assessed
in a 7-year-old, F 1 hybrid ( Pinus elliottii var. elliottii × Pinus caribaea var. hondurensis) plantation in southeast Queensland, Australia. This research aimed to investigate how early establishment silvicultural
treatments would affect weed biomass, soil C, nitrogen (N) and other nutrient pools; and soil C (δ 13C) and N isotope composition (δ 15N) to help explain the key soil processes regulating the soil C and nutrient pools and dynamics. 相似文献
20.
Farmers in developing countries cannot afford inorganic fertilizers. Multipurpose tree leaves or livestock manure are major
sources of nutrients for soil fertility replenishment. Nutrient release from these organic inputs depends on their chemical
composition and on soil properties. This study determined the chemical composition of leaves of four African browse species
and manure from goats fed leaves as protein supplements, and their mineralization of C, N and P. Cumulative evolved CO 2 was significantly correlated with the initial N content of the organic inputs ( r 0.83, P<0.05) and the C : N ratio ( r 0.80, P<0.05), and was negatively correlated with the lignin : N ratio ( r–0.71, P<0.05). Cumulative P released was negatively correlated with the C : P ratio ( r 0.76, P<0.05) and positively correlated with initial P content of the organic amendments ( r 0.76, P<0.05). Cumulative N mineralized was not significantly correlated with initial N, lignin or P concentrations of the organic
inputs. Leaves from Acacia karro and Acacia nilotica had high concentrations of polyphenols, which may have caused immobilization of N in both leaves and manure. Gliricidia sepium leaves had low amounts of soluble polyphenols, a high N content and a high rate of N mineralization, but the manure from goats
fed Gliricidia leaves immobilized N. The leaves of all browse species immobilized P, but the manure released P. The results suggested that
some browse leaves cannot meet the N and P requirements of crops due to their low P content and prolonged N and P immobilization.
However, the manures had higher P contents and rates of P mineralization, which suggested that manure is a good source of
P for crops. The implications of these results for nutrient cycling in mixed farming systems is discussed.
Received: 28 October 1998 相似文献
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