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1.
不同森林植被下土壤活性有机碳的含量及动态变化   总被引：11，自引：0，他引：11  
Soil organic matter （SOM） in forest ecosystems is not only important to global carbon （C） storage but also to sustainable management of forestland with vegetation types, being a critical factor in controlling the quantity and dynamics of SOM. In this field experiment soil plots with three replicates were selected from three forest vegetation types： broadleaf, Masson pine （Pinus massoniana Lamb.）, and Chinese fir （Cunninghamia lanceolata Hook.）. Soil total organic C （TOC）, two easily oxidizable C levels （EOC1 and EOC2, which were oxidized by 66.7 mmol L^-1 K2Cr2O7 at 130-140℃ and 333 mmol L^-1 KMnO4 at 25 ℃, respectively）, microbial biomass C （MBC）, and water-soluble organic C （WSOC） were analyzed for soil samples. Soil under the broadleaf forest stored significantly higher TOC （P ≤ 0.05）. Because of its significantly larger total soil C storage, the soil under the broadleaf forest usually had significantly higher levels （P ≤ 0.05） of the different labile organic carbons, EOC1, EOC2, MBC, and WSOC; but when calculated as a percentage of TOC each labile C fraction of the broadleaf forest was significantly lower （P ≤ 0.05） than one of the other two forests. Under all the three vegetation types temperature as well as quality and season of litter input generally affected the dynamics of different organic C fractions in soils, with EOC1, EOC2, and MBC increasing closely following increase in temperature, whereas WSOC showed an opposite trend.  相似文献   

2.
The objective of this work was to evaluate the C and N stocks and organic‐C fractions in soil under mixed forest stands of Scots pine (Pinus sylvestris L.) and Sessile oak (Quercus petraea [Matt.] Liebl.) of different ages in NE Germany. Treatments consisted of pure pine (age 102 y), and pine (age 90–102 y) mixed with 10‐, 35‐, 106‐, and 124‐y‐old oak trees. After sampling O layers, soils in the mineral layer were taken at two different depths (0–10 and 10–20 cm). Oak admixture did not affect total organic‐C (TOC) and N stocks considering the different layers separately. However, when the sum of TOC stocks in the organic and mineral layers was considered, TOC stocks decreased with increasing in oak age (r2 = 0.58, p < 0.10). The microbial C (CMB) was not directly correlated with increase of oak age, however, it was positively related with presence of oak species. There was an increase in the percentage of the CMB‐to‐TOC ratio with increase of oak‐tree ages. On average, light‐fraction C (CLF) comprised 68% of the soil TOC in upper layer corresponding to the highest C pool in the upper layer. CLF and heavy‐fraction C (CHF) were not directly affected by the admixture of oak trees in both layers. The CHF accounted on average for 30% and 59% of the TOC at 0–10 and 10–20 cm depths, respectively. Despite low clay contents in the studied soils, the differences in the DCB‐extractable Fe and Al affected the concentrations of the CHF and TOC in the 10–20 cm layers (p < 0.05). Admixture of oak in pine stands contributed to reduce topsoil C stocks, probably due to higher soil organic matter turnover promoted by higher quality of oak litter.  相似文献   

3.
Afforestation of grasslands can increase C sequestration and provide additional economic and environmental benefits. Pine plantations, however, have often been found to deplete soil organic C and trigger detrimental effects on soils. We examined soil characteristics under a 45-year-old Pinus radiata stand and under adjacent grassland on maritime dunes in temperate Argentina. Soil under the pine plantation had greater soil organic C (+93%), total N (+55%) and available P (+100%) concentrations than under grassland. Carbon was stored under the pinestand at an estimated mean accretion rate of 0.64 Mg ha?1 y?1. At 0- to 25-cm depth, soil C amounted to 61 Mg ha?1 under pine and 27 Mg ha?1 under grassland. Soil C accumulated more on dune slopes (35 Mg ha?1 y?1) than on ridges(29 Mg ha?1 y?1) and bottoms (12 Mg ha?1 y?1). Compared with the grassland, soil acidity, cation-exchange capacity, base losses (K > Ca = Mg) and C/N ratio increased under pine. Spatial heterogeneity in soil characteristics was greater under pine than under grassland. Such variability was non-systematic and did not support the ‘single-tree influence circle’ concept. Afforestation increased C in soil, forest floor and tree biomass in dunes with ustic climate regime.  相似文献   

4.
Soil acid phosphomonoesterase activity(APA)plays a vital role in controlling phosphorus(P)cycling and reflecting the current degree of P limitation.Responses of soil APA to elevating nitrogen(N)deposition are important because of their potential applications in addressing the relationship between N and P in forest ecosystems.A study of responses of soil APA to simulated N deposition was conducted in three succession forests of subtropical China.The three forests include a Masson pine(Pinus massoniana)forest (MPF)-pioneer community,a coniferous and broad-leaved mixed forest(MF)-transition community and a monsoon evergreen broad-leaved forest(MEBF)-climax community.Four N treatments were designed for MEBF:control(without N added),low-N(50 kg N ha-1 year-1),and medium-N(100 kg N ha-1 year-1)and high-N(150 kg N ha-1 year-1),and only three N treatments(i.e.,control, low-N,medium-N)were established for MPF and MF.Results showed that soil APA was highest in MEBF,followed by MPF and MF.Soil APAs in both MPF and MF were not influenced by low-N treatments but depressed in medium-N treatments.However,soil APA in MEBF exhibited negative responses to high N additions,indicating that the environment of enhanced N depositions would reduce P supply for the mature forest ecosystem.Soil APA and its responses to N additions in subtropical forests were closely related to the succession stages in the forests.  相似文献   

5.
Elevated atmospheric inputs of NH4+ and NO3– have caused N saturation of many forest ecosystems in Central Europe, but the fate of deposited N that is not bounded by trees remains largely unknown. It is expected that an increase of NO3– leaching from forest soils may harm the quality of groundwater in many regions. The objective of this study was to analyze the input and output of NH4+ and NO3– at 57 sites with mature forest stands in Germany. These long‐term study sites are part of the European Level II program and comprise 17 beech, 14 spruce, 17 pine, and 9 oak stands. The chloride balance method was used to calculate seepage fluxes and inorganic N leaching below the rooting zone for the period from 1996 to 2001. Nitrogen input by throughfall was significantly different among most forest types, and was in the order: spruce > beech/oak > pine. These differences can be largely explained by the amount of precipitation and, thus, it mirrors the regional and climatic distribution of these forest types in Germany. Mean long‐term N output with seepage was log‐normal distributed, and ranged between 0 and 26.5 kg N ha–1 yr–1, whereby 29 % of the sites released more than 5 kg N ha–1 yr –1. Leaching of inorganic N was only significantly lower in the pine stands (P < 0.05) compared with leaching rates of the spruce stands. Median N output : input ratio ranged between 0.04 and 0.11 for the beech, oak, and pine stands, while the input : output ratio of the spruce stands was 0.24, suggesting a higher risk of NO3– leaching in spruce forests. Following log‐transformation of the data, N input explained 38 % of the variance in N output. The stratification of the data by the C : N ratio of the O horizon or the top mineral soil revealed that forests soils with a C : N ratio < 25 released significantly more NO3– (median of 4.6 kg N ha–1 yr–1) than forests with a C : N ratio > 25 (median of 0.8 kg N ha–1 yr–1). The stratification improved the correlation between N input and N output for sites with C : N ratios < 25 (r2 = 0.47) while the correlation for sites with C : N ratios > 25 was weaker (r = 0.21) compared with the complete data set. Our results suggest that NO3– leaching may increase in soils with wide C : N ratios when N deposition remains on a high level and that the potential to store inorganic N decreases with C : N ratios in the O horizons becoming more narrow.  相似文献   

6.
Humus changes after introduction of beech and oak into Scots‐pine monocultures Medium‐ and long‐term (16 to 83 years) effects of an introduction of broadleaf‐tree species (Common beech [Fagus sylvatica] and European‐Sessile Oak [Quercus robur/petraea]) into mature Scots‐pine (Pinus sylvestris) stands on humus type and chemical properties of the Oh layer (pH value, base saturation, C : N ratio) were studied on 16 sites in Bavaria/Germany. The sites investigated covered a large range with respect to elevation, climate, parent material, and soil type. At most sites, the introduction of beech resulted in a significant change of the soil humus type from biologically inactive humus types to more active ones. The strongest changes occurred on the poorest sites, where forest floors under pure pine were particularly biologically inactive. In most cases, the changes in humus type were accompanied by significant increases in the pH value and the base saturation and significant decreases in the C : N ratio of the Oh layer. However, the latter effect was not noticed at most sites with initial C : N ratios higher than 30. In contrast to beech, the introduction of oak did not result in a systematic change of the humus type, the pH value, or the base saturation of the Oh layer. In spite of the considerable change of humus type under beech to biologically more active types, the introduction of broadleaf trees did not result in a systematic change of the thickness or the mass of the forest floor. A decrease in the mass of the Of layer was compensated by an increase of the Oh‐layer mass. All studied sites considered, the introduction of broadleaf trees into Scots‐pine monocultures resulted on average in an 8% decrease of the total amount of organic carbon (Corg) in the forest floor; the Corg amount in the uppermost 10 cm mineral soil increased by 9%. At 35% of all investigated sites, broadleaf tree introduction resulted in increased (+5% to +18%) topsoil (forest floor and uppermost 10 cm mineral soil) Corg stocks. At 30% of the sites, the stock changes were less than ±5%, and on 35% of all sites, soil Corg stocks decreased by –5% to –36%. The average change in the topsoil Corg stock for all studied sites was –5%. The introduction of beech into Scots‐pine monocultures resulted in an ecologically desired translocation of soil organic matter from the forest floor into the mineral topsoil. It is an effective and sustainable silvicultural measure to restore and revitalize acidified, nutrient‐depleted topsoils with biologically inactive humus types.  相似文献   

7.
Impacts of 22-year organic and inorganic N managements on total organic carbon (TOC), water-soluble organic C (WSOC), microbial biomass C (MBC), particulate organic C (POC) and KMnO4 oxidized organic C (KMnO4-C) concentrations, C management index (CMI), and C storage in surface soil (0–20 cm) were investigated in a maize (Zea may L.) field experiment, Northeast China. The treatments included, CK: unfertilized control, M: organic manure (135 kg N ha− 1 year− 1), N: inorganic N fertilizer (135 kg N ha− 1 year− 1) and MN: combination of organic manure (67.5 kg N ha− 1 year− 1) and inorganic N fertilizer (67.5 kg N ha− 1 year− 1). TOC concentration and C storage were significantly increased under the M and MN treatments, but not under the inorganic N treatment. The organic treatments of M and MN were more effective in increasing WSOC, MBC, POC and KMnO4-C concentrations and CMI than the N treatment. The M treatment was most effective for sequestrating SOC (10.6 Mg ha− 1) and showed similar increase in degree of grain yield to the N and MN treatments, therefore it could be the best option for improving soil productivity and C storage in the maize cropping system.  相似文献   

8.
LI De-Jun  WANG Xin-Ming 《土壤圈》2009,19(6):692-699
Information about soil nitric oxide (NO) emissions from subtropical forests is quite limited, and even less is known about the pulse emission of NO when wetting soils after a long period of dryness. In this study, we measured NO fluxes following wetting of dry soil in a broadleaf forest and a pine forest in subtropical China. Large pulses of NO fluxes were observed after soil wetting in both forests. NO fluxes increased significantly within 0.5 h following wetting in both forests and reached peak 1 h and 4 h after soil wetting in the pine forest and the broadleaf forest, respectively. In the broadleaf forest, averaged peak flux of NO pulses was 157 ng N m–2 s–1, which was 8 times the flux value before wetting, and in the pine forest, the averaged peak flux was 135 ng N m–2 s–1, which was 15.5 times the flux value before wetting. The total pulses-induced NO emissions during the dry season were roughly estimated to be 29.4 mg N m–2 in the broadleaf forest and 22.2 mg N m–2 in the pine forest or made up a proportion of 4.6% of the annual NO emission in the broadleaf forest and 5.3% in the pine forest.  相似文献   

9.
Reclaimed coal mine lands have the potential to sequester atmospheric carbon (C); however, limited information exists for the western USA coalfields. This study was carried out on two chronosequences (BA‐C3 grasses and DJ‐shrubs) of reclaimed sites at two surface coal mines to determine the effects of vegetation, soil texture, and lignin content on soil total organic carbon (TOC) accumulations. In the BA chronosequence, TOC increased over 26 years at an average rate of 0·52 Mg C ha−1 yr−1 in the 0–30 cm depth and was significantly correlated with clay content. Comparison between < 1 and 16‐year‐old stockpile soils indicated TOC content did not differ significantly. In the DJ chronosequence, TOC content in the 0–30 cm depth declined from 31·3 Mg ha−1 in 5‐year‐old soils to 23·4 Mg ha−1 in 16‐year‐old soils. The C:N ratios suggested that some (up to 2·0 per cent) of the TOC was potentially derived from coal particles in these reclaimed soils. Soil total N (TN) contents followed a similar trend as TOC with TOC and TN concentrations strongly correlated. Lignin contents in TOC of all reclaimed soils and topsoil stockpiles (TSs) were higher than that of nearby undisturbed soils, indicating the recalcitrant nature of TOC in reclaimed soils and/or possibly the slow recovery of lignin degrading organism. Results indicated that TOC accumulations in DJ were largely controlled by its composition, particular lignin content. In BA sites TOC accumulation was strongly influenced by both clay and lignin contents. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

10.
在行间长期(连续6年)种植豆科植物毛苕子和禾本科植物黑麦草的苹果园,调查土壤不同深度的有机碳组分和表层土壤呼吸速率日变化。结果表明:间作2种植物后,行间土壤0—20,20—40cm土层总有机碳(TOC)、轻质有机碳(LFOC)、可溶性有机碳(DOC)、颗粒有机碳(POC)、易氧化有机碳(ROC)和微生物生物量碳(MBC)含量均显著提高;在40—60cm土层,仅DOC含量明显提高;0—20cm土层的TOC和全部有机碳组分及20—40cm土层的TOC、DOC、POC和ROC的含量在种植毛苕子后均明显高于种植黑麦草。TOC与LFOC、TOC与POC、DOC与LFOC、DOC与MBC、DOC与ROC、MBC与ROC、ROC与POC、LFOC与ROC之间均呈显著正相关,土壤呼吸速率与LFOC、DOC、MBC和ROC之间也呈显著正相关。种植2种草类均显著提高土壤呼吸速率,并使呼吸速率日变化峰型更突出,其中毛苕子的作用效果比黑麦草更显著。  相似文献   

11.
土壤有机碳活性组分沿中国长白山海拔坡度的分布情况   总被引：4，自引：0，他引：4  
Understanding the responses of soil organic carbon(SOC) fractions to altitudinal gradient variation is important for understanding changes in the carbon balance of forest ecosystems.In our study the SOC and its fractions of readily oxidizable carbon(ROC),water-soluble carbon(WSC) and microbial biomass carbon(MBC) in the soil organic and mineral horizons were investigated for four typical forest types,including mixed coniferous broad-leaved forest(MCB),dark coniferous spruce-fir forest(DCSF),dark coniferous spruce forest(DCS),and Ermans birch forest(EB),along an altitudinal gradient in the Changbai Mountain Nature Reserve in Northeast China.The results showed that there was no obvious altitudinal pattern in the SOC.Similar variation trends of SOC with altitude were observed between the organic and mineral horizons.Significant differences in the contents of SOC,WSC,MBC and ROC were found among the four forest types and between horizons.The contents of ROC in the mineral horizon,WSC in the organic horizon and MBC in both horizons in the MCB and EB forests were significantly greater than those in either DCSF or DCS forest.The proportion of soil WSC to SOC was the lowest among the three main fractions.The contents of WSC,MBC and ROC were significantly correlated(P < 0.05) with SOC content.It can be concluded that vegetation types and climate were crucial factors in regulating the distribution of soil organic carbon fractions in Changbai Mountain.  相似文献   

12.
为阐明小兴安岭两种原始红松林土壤有机碳变化特征及其影响机制,采样分析了云冷杉红松林与椴树红松林土壤总有机碳、易氧化碳、微生物生物量碳及土壤理化性质。结果表明:两种林型土壤总有机碳、易氧化碳、微生物生物量碳含量垂直分布特征一致,均自上向下逐渐减少;土壤总有机碳与易氧化碳含量表现为:云冷杉红松林 < 椴树红松林,同海拔高度变化（云冷杉红松林 < 椴树红松林）一致（仅10—20 cm土层,云冷杉红松林的两个因子高于椴树红松林,但差异不显著）,两种林型土壤微生物量碳含量的差异在不同土壤层次有所不同,但差异均不显著;两种林型间土壤活性碳占总有机碳比率的差异在不同土层无一致的规律性;两种活性碳、总有机碳与土壤全氮、C/N之间为显著（p < 0.05）或极显著（p < 0.01）正相关,与土壤容重呈极显著负相关（p < 0.01）。  相似文献   

13.
结合野外凋落物分解袋法和室内分析试验,对藏东南2种典型暗针叶林—急尖长苞冷杉(Abies georgei var.Smithii)和林芝云杉(Picea likiangensis var.linzhiensis)凋落物的分解和有机碳释放特征进行研究,分析了2种亚高山暗针叶林凋落物有机碳释放速率与土壤有机碳及其组分之间的关系。结果表明:藏东南2种原始暗针叶林凋落物分解均呈现出雨季分解快(4—9月)、旱季分解慢(10—翌年3月),前期分解快(3—9月)、后期分解慢(10—翌年2月)的特征,且冷杉(PLLF)分解速率大于云杉(AGSF),Olson指数衰减模型能够较好地模拟2种暗针叶林凋落物的分解,冷杉(PLLF)和云杉(AGSF)凋落物半分解时间为2.11,2.52年;分解95%时间为8.96,10.84年;2种暗针叶林凋落物中有机碳含量表现出先上升后下降,再平稳降低的趋势,而2种暗针叶林凋落物中有机碳释放速率表现出先短暂富集再释放的模式;2种暗针叶林土壤总有机碳(TOC)及其活性组分(MBC、POC、LOC)含量都具有明显的表聚性(p<0.01),且同一土壤层次内TOC、MBC、POC、LOC互相之间均呈极显著正相关关系(p<0.01);2种暗针叶林凋落物分解进程中有机碳的释放速率与表层土(0—10 cm)中TOC、MBC、POC、LOC含量、10—20 cm土层中的TOC、MBC含量以及20—40 cm土层中MBC含量之间呈现显著的正相关(p<0.05)。  相似文献   

14.
ABSTRACT

The forest–savanna transition zone, which contains nutrient-poor soils (Oxisols), is found throughout central Africa. To evaluate the effect of deforestation on soil phosphorus dynamics, which regulate the plant growth in this area, we quantified the relationship between phosphorus (P) and carbon (C) in different fractions and compared their relationship to forest and savanna (deforested vegetation) in eastern Cameroon. We analyzed the P, C, and nitrogen (N) contents of soil using the physical fractionation method (0.25–2.0 mm as macro-particulate organic matter [M-POM]; 0.053–0.25 mm as micro-POM; and <0.053 mm as Clay+silt) in different land management (young and old forests and annual and perennial grass savannas at 100-cm soil depth). We found larger soil P stock in forests (4.7–4.9 Mg P ha?1) than that in savannas (3.4–4.0 Mg P ha?1), though soil C and N stocks were similar between the vegetation. We also observed lower soil P stock in the active fraction (M-POM) with its higher C:P and lower C:N ratio in forest surface layer (0–10 cm), indicating that forests have lower available soil P. By using the regression analysis, we found a clear relationship between P and C in the stable fraction (Clay+silt) of the upper layer (0–40 cm) for each land management, and the coefficient of the regression was clearly different between the forest and savanna. It indicates that a more chemically complex organic P form of the stable fraction exists in forest soil than in savanna soil. These results indicate that the deforestation (savannazation) affect the active and stable P dynamics and it should cause the lower soil P stock of the upper layer in savanna than in forest.  相似文献   

15.
Increasing human demands for Earth’s resources are hastening many environmental changes and creating a need to incorporate the routine monitoring of ecosystem functions into forest management.Under global change and anthropogenic disturbances,soil carbon (C) cycling in terrestrial ecosystems is undergoing substantial changes that result in the transformation between soil C sources and sinks.Therefore,the forest C budget requires an understanding of the underlying soil C dynamic under environment...  相似文献   

16.
Land-use change significantly affects the soil organic C (SOC) dynamics and microbial activities. However, the roles of chemical composition of SOC and enzyme activity in the change in the SOC mineralization rate caused by land-use change are poorly understood. This study aimed to investigate the impact of land-use conversion from natural evergreen broadleaf forests to intensively managed moso bamboo (Phyllostachys edulis) plantations on the pool size and mineralization rate of SOC, as well as the activities of C-cycling enzymes (invertase, β-glucosidase, and cellobiohydrolase) and dehydrogenase. Four paired soil samples in two layers (0–20 and 20–40 cm) were taken from adjacent evergreen broadleaf forest-moso bamboo plantation sites in Lin’an County, Zhejiang Province, China. Soil water-soluble organic C (WSOC), hot-water-soluble organic C (HWSOC), microbial biomass C (MBC), readily oxidizable C (ROC), the activities of C-cycling enzymes and dehydrogenase, and mineralization rates of SOC were measured. The chemical composition of SOC was also determined with 13C-nuclear magnetic resonance spectroscopy. The conversion of broadleaf forests to bamboo plantations reduced SOC stock as well as WSOC, HWOC, MBC, and ROC concentrations (P?<?0.05), decreased O-alkyl, aromatic, and carbonyl C contents, but increased alkyl C content and the alkyl C to O-alkyl (A/O-A) ratio, suggesting that the land-use conversion significantly altered the chemical structure of SOC. Further, such land-use change lowered (P?<?0.05) the SOC mineralization rate and activities of the four enzymes in the 0–20-cm soil. The decreased SOC mineralization rate associated with the land-use conversion was closely linked to the decreased labile organic C concentration and soil enzyme activities. The results demonstrate that converting broadleaf forests to moso bamboo plantations markedly decreased the total and labile SOC stocks and reveal that this conversion decreased the mineralization rate of SOC via changing the chemical composition of SOC and decreasing activities of C-cycling enzymes. Management practices that enhance C input into the soil are recommended to mitigate the depletion of SOC associated with land-use conversion to moso bamboo plantations.  相似文献   

17.
During recent decades, forest ecosystems have been exposed to high levels of atmospheric pollution, and it has been argued that this affects the composition and activity of decomposer communities and, subsequently, ecosystem functioning. To investigate the effects of atmospheric pollution on protozoa and microflora, a new experimental design was used. Undisturbed soil columns, originating from six coniferous forests across Europe and representing different stages of soil acidification, were transferred to two Scots pine forests (Fontainebleau and Wekerom) with different levels of N and S deposition (NH4 +-N=4.90 and 42.50?kg ha–1 year–1; SO4 –S=10.90 and 30.40?kg ha–1 year–1, respectively). The number of protozoa, microbial biomass C and microbial activity were estimated in the organic layer (Of) of the transferred soils at the two host sites after 21 months of incubation. The experiment aimed at answering two questions: (1) Do changes in environmental conditions, studied by transferring soils from one site to another, affect protozoa and microbial communities and, if so, (2) how important are changes in both N and S deposition in explaining the effects of soil transfer on protozoa and microbial communities? The interaction between protozoa and microbial communities was addressed with regard to these changes in environmental conditions. No effect of enhanced N or S deposition on protozoan numbers and microbial biomass C, basal respiration and caloric quotient was revealed. Reciprocal transfer of various soil columns resulted in lower abundance and activity of protozoa and microbes. This reduction could not be explained by differences in N and S deposition, but by differences in microclimate and adaptation. In some cases, protozoa correlated with pH, C/N ratio, P and S content and leached mineral N.  相似文献   

18.
Nitrous oxide (N2O) is a high‐impact greenhouse gas. Due to the scarcity of unmanaged forests in Central Europe, its long‐term natural background emission level is not entirely clear. We measured soil N2O emissions in an unmanaged, old‐growth beech forest in the Hainich National Park, Germany, at 15 plots over a 1‐year period. The average annual measured N2O flux rate was (0.49 ± 0.44) kg N ha–1 y–1. The N2O emissions showed background‐emission patterns with two N2O peaks. A correlation analysis shows that the distance between plots (up to 380 m) does not control flux correlations. Comparison of measured data with annual N2O flux rates obtained from a standard model (Forest‐DNDC) without site‐specific recalibration reveals that the model overestimates the actual measured N2O flux rates mainly in spring. Temporal variability of measured N2O flux was better depicted by the model at plots with high soil organic C (SOC) content. Modeled N2O flux rates were increased during freezing only when SOC was > 0.06 kg C kg–1. The results indicate that the natural background of N2O emissions may be lower than assumed by most approaches.  相似文献   

19.
A field experiment was conducted over 9?years (1999 to 2007 growing seasons) in northeastern Saskatchewan on a S-deficient Gray Luvisol (Typic Haplocryalf) soil. The objective was to determine the relative effectiveness of N alone versus combined annual application of N (120?kg N?ha?1) and S (15?kg S?ha?1) fertilizers to a wheat–canola rotation on storage of total organic C (TOC) and N (TON) and on the light fraction organic C (LFOC) and N (LFON) in soil. Compared to N alone, annual applications of S fertilizer in spring in a combination with N resulted in an increase in soil of TOC (by 2.18?Mg C?ha?1), TON (by 0.138?Mg N?ha?1), LFOC (by 1,018?kg C?ha?1), and LFON (by 42?kg N?ha?1). The relative increases in organic C or N due to S fertilizer application were much higher for the light organic fractions (36.9% for LFOC and 27.5% for LFON) than for the total organic fractions (9.2% for TOC and 7.3% for TON). The findings demonstrate the importance of a balanced/combined application of N and S fertilizers to crops in storing more organic C and N in this S-deficient soil.  相似文献   

20.
Nitrogen mineralisation in soils of various forest sites (pine plantation, natural and thinned oak) at Uluda? University campus in Bursa, Turkey was investigated continuously over a year by the field incubation method. Net nitrogen mineralisation and nitrification rates varied depending on sampling dates. Although nitrogen mineralisation and nitrification rates increased in the spring and summer months, there was no seasonal variation in the soils of the examined forests. Annual net nitrate (NO3?–N) accumulation in the upper soil layer (0–5 cm) was higher in Oak I and Oak II (14 kg ha y?1 and 12 kg ha y?1) than in the pine plantation (8 kg ha y?1). While annual net NO3?–N accumulation (0–5 cm) varied between the oak forests (possibly due to forest management practices), annual net Nmin values were similar in these forests. No significant correlation was found between the examined soil parameters and net nitrification and mineralisation rates in the soils (P > 0.05). These results indicate that tree species and forest management practices play important roles in N cycling in forest ecosystems.  相似文献   

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