共查询到20条相似文献,搜索用时 15 毫秒
1.
Net carbon flux from agriculture: Carbon emissions, carbon sequestration, crop yield, and land-use change 总被引:10,自引:0,他引:10
There is a potential to sequester carbon in soil by changing agricultural management practices. These changes in agricultural management can also result in changes in fossil-fuel use, agricultural inputs, and the carbon emissions associated with fossil fuels and other inputs. Management practices that alter crop yields and land productivity can affect the amount of land used for crop production with further significant implications for both emissions and sequestration potential. Data from a 20-year agricultural experiment were used to analyze carbon sequestration, carbon emissions, crop yield, and land-use change and to estimate the impact that carbon sequestration strategies might have on the net flux of carbon to the atmosphere. Results indicate that if changes in management result in decreased crop yields, the net carbon flux can be greater under the new system, assuming that crop demand remains the same and additional lands are brought into production. Conversely, if increasing crop yields lead to land abandonment, the overall carbon savings from changes in management will be greater than when soil carbon sequestration alone is considered. 相似文献
2.
Implications of increased carbon dioxide levels for carbon input and turnover in soils 总被引:3,自引:0,他引:3
The complexity of the plant-soil system in its interaction with the changing climate is discussed. It is shown that processes at the level of organic matter inputs into the soil and the fluxes and pools involved in the global cycle are not known in sufficient detail to allow an estimation of the future quantitative shifts. Even the direction in which the level of stored carbon in the soil organic matter pool will develop is not clear. The importance of the nitrogen cycle, which is intimately coupled to the carbon cycle through the turnover of soil organic matter is underlined. In its turn, the mineralisation of soil organic matter takes place at a rate which is highly dependent on the nature of inputs and the availability of mineral nutrients.Aspects of shifts in temperature, changes in cultivation practices (reduced tillage) and unintended spreading of inputs in chemical N-fertilizers are of great importance at a regional and global scale.The complexity of the interactions in the process of mineralisation do require further studies to clarify the point whether a substantial and durable additional storage of carbon in soil organic matter is likely, or that shifts in temperature will cause an overriding acceleration of the mineralisation, and trigger a corresponding net release of carbon. 相似文献
3.
A comparative study of dissolved organic carbon transport and stabilization in California forest and grassland soils 总被引:2,自引:0,他引:2
For soil carbon to be effectively sequestered beyond a timescale of a few decades, this carbon must become incorporated into
passive reservoirs or greater depths, yet the actual mechanisms by which this occurs is at best poorly known. In this study,
we quantified the magnitude of dissolved organic carbon (DOC) leaching and subsequent retention in soils of a coniferous forest
and a coastal prairie ecosystem. Despite small annual losses of DOC relative to respiratory losses, DOC leaching plays a significant
role in transporting C from surface horizons and stabilizing it within the mineral soil. We found that DOC movement into the
mineral soil constitutes 22% of the annual C inputs below 40 cm in a coniferous forest, whereas only 2% of the C inputs below
20 cm in a prairie soil could be accounted for by this process. In line with these C input estimates, we calculated advective
transport velocities of 1.05 and 0.45 mm year−1 for the forested and prairie sites, respectively. Radiocarbon measurements of field-collected DOC interpreted with a basic
transport-turnover model indicated that DOC which was transported and subsequently absorbed had a mean residence time of 90–150 years.
Given these residence times, the process of DOC movement and retention is responsible for 20% of the total mineral soil C
stock to 1 m in the forest soil and 9% in the prairie soil. These results provide quantitative data confirming differences
in C cycles in forests and grasslands, and suggest the need for incorporating a better mechanistic understanding of soil C
transport, storage and turnover processes into both local and regional C cycle models. 相似文献
4.
C:N:P stoichiometry in soil: is there a “Redfield ratio” for the microbial biomass? 总被引:19,自引:0,他引:19
Well-constrained carbon:nitrogen:phosphorus (C:N:P) ratios in planktonic biomass, and their importance in advancing our understanding
of biological processes and nutrient cycling in marine ecosystems, has motivated ecologists to search for similar patterns
in terrestrial ecosystems. Recent analyses indicate the existence of “Redfield-like” ratios in plants, and such data may provide
insight into the nature of nutrient limitation in terrestrial ecosystems. We searched for analogous patterns in the soil and
the soil microbial biomass by conducting a review of the literature. Although soil is characterized by high biological diversity,
structural complexity and spatial heterogeneity, we found remarkably consistent C:N:P ratios in both total soil pools and
the soil microbial biomass. Our analysis indicates that, similar to marine phytoplankton, element concentrations of individual
phylogenetic groups within the soil microbial community may vary, but on average, atomic C:N:P ratios in both the soil (186:13:1)
and the soil microbial biomass (60:7:1) are well-constrained at the global scale. We did see significant variation in soil
and microbial element ratios between vegetation types (i.e., forest versus grassland), but in most cases, the similarities
in soil and microbial element ratios among sites and across large scales were more apparent than the differences. Consistent
microbial biomass element ratios, combined with data linking specific patterns of microbial element stoichiometry with direct
evidence of microbial nutrient limitation, suggest that measuring the proportions of C, N and P in the microbial biomass may
represent another useful tool for assessing nutrient limitation of ecosystem processes in terrestrial ecosystems. 相似文献
5.
Robert K. Antibus Chris Lauber Robert L. Sinsabaugh Donald R. Zak 《Plant and Soil》2006,288(1-2):173-187
Increased use of anthropogenically fixed N and the release of N in combustion products have led to concerns about possible long-term impacts on terrestrial ecosystems. Previous studies demonstrating the potential of atmospheric N deposition to influence forest soil carbon have focused on decomposition processes with much less known about potential impacts on mycorrhiza-derived carbon. Glomalin is a unique glycoprotein produced by arbuscular mycorrhizal (AM) fungi that has been implicated in the formation of soil aggregates and potentially a significant store of soil carbon. To determine the possible impact of experimental N deposition of such stores we examined the operationally defined glomalin-related soil protein (GRSP) levels over two growing seasons in three forest types receiving background N deposition (control) or treated with 80 kg N ha−1 year−1 as NaNO3. Three sites of each of three forest types, sugar maple-basswood (SMBW), sugar maple-red oak (SMRO), and black oak-white oak (BOWO), in northern Lower Michigan were studied during the 2001 and 2002 growing seasons. GRSP were extracted from air-dried soils with citric acid and measured by the Bradford method. Analysis of variance revealed significant differences related to forest type and sample date in easily extractable Bradford reactive (EE-BRSP) and Bradford-reactive soil protein (BRSP), but failed to detect significant effects of experimental N amendment. EE-BRSP and BRSP varied in a pattern that was consistent with an AM fungal origin; a pattern that reflected the mycorrhizal types of the dominant over and understory plants of each forest ecosystem. SMBW forests dominated by AM plants had the highest levels of protein. BOWO forests with low AM plant cover had the lowest protein levels and SMRO forests were intermediate. Both Bradford-reactive fractions and their ratio varied seasonally, generally being highest in fall samples. Significant correlations observed between BRSP fractions, phosphorous, and soil organic matter were likely related to covariation of soil properties across forest types. While not statistically significant, response patterns of BRSP to N deposition were ecosystem-specific and reflected mycorrhizal types of dominant species. Abundance of these proteins reflected previously observed changes in SOC in the two forest types examined with abundant AM hosts. Specifically, nitrate addition led to BRSP decreases in SMBW and increases in SMRO forests. Changes in BRSP accounted for a small fraction of the changes in SOC; appearing to increase as a fraction of residual SOC consistent with the idea that GRSP are recalcitrant. BRSP remained unchanged at BOWO sites despite a significant increase in SOC at these sites. Our results point to the potential of proteins as contributors to differential, mycorrhizal type-specific responses to changes in soil carbon following N amendment. 相似文献
6.
J. L. M. Huntjens 《Plant and Soil》1979,53(4):529-534
Summary A differential infrared CO2 analyser combined with a 12 channel gas handling system have been used for the measurement of CO2 evolution rates of soil samples. A constant flow of air over the soil was maintained during the incubation period. Automatic sequential measurement and recording of the increase of the CO2 content of the flushed air of the 12 channels lasted 24 min with a dwell time of 2 min per channel. This technique has proven to be very useful for accurate and rapid measurement of the biological activities in untreated and treated soil. 相似文献
7.
Decomposing residues can be an important source of nutrients for plants, especially of N and P, but the relationship between
N and P release and microbial community dynamics have rarely been studied. Two pea (Pisum sativum L.) residues with contrasting chemical composition, shoots from flowering pea (Pea-Y) with 2.9 mg P and 36 mg N kg−1 and from mature pea (Pea-M) with 0.3 mg P and 13 mg N kg−1, were added at a rate of 20 g kg soil−1 to a sandy soil low in nutrients. Particulate organic matter (POM) was isolated on days (d) 0, 5, 15, 28, 42 and 61 after
residue addition and analysed for C, N, P and microbial community structure (fatty acid methyl ester analysis). The recovery
of POM from residue-amended soils decreased over time to 30–40% of added amounts for both residues. Apart from d 0, the N
concentration in POM was lower in residue-amended soil than in the control. Due to a rapid decrease in P concentration during
the first 5 days in Pea-Y and a slow increase over the whole experiment in Pea-M, P concentrations in POM on d 61 were similar
in all treatments. In Pea-Y, the dynamics of C, N and P were coupled, with amounts of C, N and P decreasing during the first
15 days and remaining stable thereafter. In Pea-M, a steady loss of C from POM was contrasted by a slight increase in P. As
a result, the C/P ratio decreased from 1,330 on d 0 to 390 on d 61. The C/N ratio of Pea-M decreased only during the second
phase of decomposition. The different nutrient dynamics in Pea-Y and Pea-M led to similar amounts of N and P in POM towards
the end of the incubation. Microbial community composition in the POM in Pea-Y and Pea-M remained distinct from the control,
even though it changed over time. POM was shown to be an important source of potentially available nutrients after addition
of plant residues. In the unamended soil, stable nutrient amounts in POM suggested very low net nutrient release from native
POM compared to POM after residue addition. 相似文献
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Christopher Swanston Peter S. Homann Bruce A. Caldwell David D. Myrold Lisa Ganio Phillip Sollins 《Biogeochemistry》2004,70(2):229-252
Nitrogen addition may alter the decomposition rate for different organic-matter pools in contrasting ways. Using a paired-plot design, we sought to determine the effects of long-term elevated N on the stability of five organic-matter pools: organic horizons (Oe+a), whole mineral soil (WS), mineral soil fractions including the light fraction (LF), heavy fraction (HF), and a physically recombined fraction (RF). These substrates were incubated for 300 days, and respiration, mineralized N, and active microbial biomass were measured. Samples with elevated N gave 15% lower cumulative respiration for all five substrates. Over the 300-day incubation, the Oe+a gave twice the cumulative respiration (gCkg–1 initial C) as the LF, which gave slightly higher respiration than the HF. Respiration was 35% higher for the WS than for the RF. Mineralized N was similar between N treatments and between the LF and HF. Net N mineralized by the LF over the course of the 300-day incubation decreased with higher C:N ratio, due presumably to N immobilization to meet metabolic demands. The pattern was opposite for HF, however, which could be explained by a release of N in excess of metabolic demands due to recalcitrance of the HF organic matter. Mineralized N increased with respiration for the HF but showed no pattern, or perhaps even decreased, for the LF. WS and RF showed decreasing active microbial biomass near the end of the incubation, which corresponded with decreasing respiration and increasing nitrate. Our results show that long-term elevated N stabilized organic matter in whole soil and soil fractions. 相似文献
12.
Assessment of the C/N ratio as an indicator of the decomposability of organic matter in forest soils
The usefulness of the C/N ratio as an indicator of the decomposability of organic matter in forest soil was assessed. The assessment was based on the relationship between the C/N ratio and the contents of soil organic carbon (SOC), soil nitrogen (total N), dissolved total organic carbon (DTOC) and dissolved inorganic nitrogen (DIN). SOC, total N, DTOC and DIN were determined in soils sampled in coniferous and coniferous–deciduous forest sites from genetic horizons of 48 soil profiles. The variability of the above soil parameters was determined and the correlation between these parameters and the C/N values were calculated. It was found that the C/N ratio in soil was shaped by the difference in the mobility of both elements, whereas the decrease in the C content in subsequent horizons was mostly higher than the decrease in the N content, which means that the C/N value decreased with the depth of a soil profile. When the loss of SOC and total N contents occurs at a similar rate, the C/N ratio is maintained at a more or less stable level despite the advancing SOM mineralization. When the rate of the carbon release from SOM differs from that of nitrogen or when there is an N input from external sources, the C/N ratio does not adequately describe the process of SOM mineralization as well. The correlation coefficients between the C/N ratio and other parameters indicate that the relationships between them are not significant or that there is no correlation at all. It was found that the percentage of DTOC in SOC seemed to be a better indicator of SOM mineralization than the C/N ratio. 相似文献
13.
Forest- and pasture-derived carbon contributions to carbon stocks and microbial respiration of tropical pasture soils 总被引:3,自引:0,他引:3
Christopher Neill Brian Fry Jerry M. Melillo Paul A. Steudler Jener F. L. Moraes Carlos C. Cerri 《Oecologia》1996,107(1):113-119
The clearing of tropical forest for pasture leads to important changes in soil organic carbon (C) stocks and cycling patterns. We used the naturally occurring distribution of13C in soil organic matter (SOM) to examine the roles of forest- and pasture-derived organic matter in the carbon balance in the soils of 3- to 81-year-old pastures created following deforestation in the western Brazilian Amazon Basin state of Rondônia. Different 13C values of C3 forest-derived C (-28) and C4 pasture-derived C (-13) allowed determination of the origin of total soil C and soil respiration. The 13C of total soil increased steadily across ecosystems from -27.8 in the forest to -15.8 in the 81-year-old pasture and indicated a replacement of forest-derived C with pasture-derived C. The 13C of respired CO2 increased more rapidly from -26.5 in the forest to -17 in the 3- to 13-year-old pastures and indicated a faster shift in the origin of more labile SOM. In 3-year-old pasture, soil C derived from pasture grasses made up 69% of respired C but only 17% of total soil C in the top 10 cm. Soils of pastures 5 years old and older had higher total C stocks to 30 cm than the original forest. This occurred because pasture-derived C in soil organic matter increased more rapidly than forest-derived C was lost. The increase of pasture-derived C in soils of young pastures suggests that C inputs derived from pasture grasses play a critical role in development of soil C stocks in addition to fueling microbial respiration. Management practices that promote high grass production will likely result in greater inputs of grass-derived C to pasture soils and will be important for maintaining tropical pasture soil C stocks. 相似文献
14.
中国陆地土壤有机碳蓄积量估算误差分析 总被引:48,自引:7,他引:48
简要介绍了土壤碳蓄积量的计算方法,包括土壤类型法、植被类型法、生命地带法、相关关系法和模型方法,以及土壤有机碳蓄积量的误差分析方法.根据中国策二次土壤普查2473个典型土种剖面数据,采用土壤类型法和两种碳密度方法计算,估算的中国陆地土壤有机碳蓄积量处于615.19×10^14-1211.37×10^14g之间,平均碳密度为10.49-10.53kg·m^-2(土壤厚度为100cm)或11.52-12.04kg·m^-3(土壤平均厚度为88cm),土壤平均碳蓄积量为913.28±298.09×10^14g,估算的不确定性在20%~50%之间.其中,土壤碳计算和采样数量的差异是导致土壤碳蓄积量估算不确定性的重要因素。 相似文献
15.
鄱阳湖流域泥沙流失及吸附态氮磷输出负荷评估 总被引:4,自引:0,他引:4
水土流失是吸附态氮磷输出负荷的主要方式,也是非点源污染评估的重要环节。鄱阳湖流域水土流失及其所带来的泥沙和吸附态氮磷等营养盐将直接影响到鄱阳湖的生态功能,进而影响着长江中下游水环境安全。科学估算鄱阳湖赣江、抚河、信江、饶河、修河等五大流域的土壤侵蚀量和吸附态氮、磷的输出负荷,将为鄱阳湖流域农业非点源污染控制及鄱阳湖生态建设和环境保护提供理论依据。以2007年全国第一次农业污染源普查数据和2007年江西省土壤质量调查数据为基础,利用RUSLE方程和GIS的空间统计功能,对江西省境内鄱阳湖流域的土壤侵蚀量和吸附态氮、吸附态磷的输出负荷进行估算。结果表明:基于RUSLE得到的2007年鄱阳湖五大流域输沙模数比较可信,鄱阳湖流域内泥沙、吸附态氮、吸附态磷的年输出负荷分别为1245183t、3383t和73t,其中赣江流域吸附态氮磷的年输出负荷最大,占鄱阳湖全流域的58.1%,抚河、饶河、信江、修河等分别占11.2%、7.2%、11.3%和12.2%。与流域内农业污染源总氮、总磷排放量相比较,尽管流域尺度内泥沙的输出负荷相对较大,但吸附态氮、磷的输出负荷较小,应该不是鄱阳湖水污染中总氮和总磷等营养盐的主要来源。 相似文献
16.
On Aneurolepidium chinease grassland, the amounts of N, P and Ktransferred from deadplants into the litters are respectively 0.7227, 0.1137 and 0.4974g·m-2·yr-1.After oneyear, the loss rates of them are respectively 59.71, 73.21 and 83.26%.Under imbalancestate, the input of these three elements is larger than their output, being at accumulationstage, while under stable state, their contents in litters are respectively 1.1859, 0.1565 and 0.5963g·m-2. 相似文献
17.
Impact of forest conversion to agriculture on carbon and nitrogen mineralization in subarctic Alaska 总被引:4,自引:0,他引:4
Land-use change is likely to be a major component of global change at high latitudes, potentially causing significant alterations in soil C and N cycling. We addressed the biogeochemical impacts of land-use change in fully replicated black spruce forests and agricultural fields of different ages (following deforestation) and under different management regimes in interior Alaska. Change from forests to cultivated fields increased summer temperatures in surface soil layers by 4–5 °C, and lengthened the season of biological activity by two to three weeks. Decomposition of a common substrate (oat stubble) was enhanced by 25% in fields compared to forests after litter bags were buried for one year. In-situ net N mineralization rates in site-specific soil were similar in forests and fields during summer, but during winter, forests were the only sites where net N immobilization occurred. Field age and management had a significant impact on C and N mineralization. Rates of annual decomposition, soil respiration and summer net N mineralization tended to be lower in young than in old fields and higher in fallow than in planted young fields. To identify the major environmental factors controlling C and N mineralization, soil temperature, moisture and N availability were studied. Decomposition and net N mineralization seemed to be mainly driven by availability of inorganic N. Soil temperature played a role only when comparing forests and fields, but not in field-to-field differences. Results from soil respiration measurements in fields confirmed low sensitivity of heterotrophic respiration, and thus decomposition to temperature. In addition, both soil respiration and net N mineralization were limited by low soil water contents. Our study showed that (1) C and N mineralization are enhanced by forest clearing in subarctic soils, and (2) N availability is more important than soil temperature in controling C and N mineralization following forest clearing. Projecting the biogeochemical impacts of land-use change at high latitudes requires an improved understanding of its interactions with other factors of global change, such as changing climate and N deposition. 相似文献
18.
增氮对青藏高原东缘典型高寒草甸土壤有机碳组成的影响 总被引:2,自引:0,他引:2
土壤有机碳动态是陆地生态系统碳平衡研究的关键环节,有关青藏高原高寒草甸土壤有机碳组成对大气氮沉降增加的响应研究至今尚未开展。基于中国科学院海北生态站的大气氮沉降模拟控制实验平台,于2010年5月、7月和9月中旬分别测定不同施氮处理下0—10cm、10—20cm、20—30cm土壤中粗颗粒态有机碳(CPOC)、细颗粒态有机碳(FPOC)和矿质结合有机碳(MOC)含量,研究不同施氮类型(NH4Cl,(NH4)2SO4和KNO3)和施氮水平(0、10、20、40 kgN.hm-.2a-1)对土壤POC和MOC含量以及POC/MOC比值的影响。结果表明:青藏高原高寒草甸土壤POC积聚在土壤表层,占总土壤有机碳(SOC)含量的64%以上,稳定性较差。施氮水平显著改变了土壤CPOC、FPOC和MOC含量,而施氮类型的影响不显著。不同月份土壤POC和MOC含量对增氮的响应不同,反映了SOC组分对增氮响应的时间异质性。在生长季中期,施氮倾向于增加表层土壤POC含量,而在生长季初期和末期恰好相反。土壤MOC对增氮的响应不敏感。另外,施氮显著降低生长季初期表层土壤POC/MOC比例,SOC稳定性增加。表明,青藏高原高寒草甸土壤有机碳活性组分较高,未来大气氮沉降增加短期内即可降低活性有机碳含量,相应地改变了其组成和稳定性。 相似文献
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Forest production is strongly nutrient limited throughout the southeastern US. If nutrient limitations constrain plant acquisition of essential resources under elevated CO2, reductions in the mass or nutrient content of forest canopies could constrain C assimilation from the atmosphere. We tested this idea by quantifying canopy biomass, foliar concentrations of N and P, and the total quantity of N and P in a loblolly pine (Pinus taeda) canopy subject to 4 years of free-air CO2 enrichment. We also used N:P ratios to detect N versus P limitation to primary production under elevated CO2. Canopy biomass was significantly higher under elevated CO2 during the first 4 years of this experiment. Elevated CO2 significantly reduced the concentration of N in loblolly pine foliage (5% relative to ambient CO2) but not P. Despite the slight reduction foliage N concentrations, there were significant increases in canopy N and P contents under elevated CO2. Foliar N:P ratios were not altered by elevated CO2 and were within a range suggesting forest production is N limited not P limited. Despite the clear limitation of NPP by N under ambient and elevated CO2 at this site, there is no evidence that the mass of N or P in the canopy is declining through the first 4 years of CO2 fumigation. As a consequence, whole-canopy C assimilation is strongly stimulated by elevated CO2 making this forest a larger net C sink under elevated CO2 than under ambient CO2. We discuss the potential for future decreases in canopy nutrient content as a result of limited changes in the size of the plant-available pools of N under elevated CO2. 相似文献