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1.
Methane flux from rainforest soils in northeast Queensland, Australia, was investigated using a combination of laboratory, field and simulation modelling. In aerobic laboratory incubations, CH4 uptake in the top 0.1 m of the soil (?2.5 to ?7.3 μg CH4 kg?1 SDW day?1) is approximately one order of magnitude higher than CH4 production under anaerobic conditions. The highest CH4 uptake, as well as potential CH4 production is found in the uppermost C rich soil layers. Detailed measurements from three contrasting rainforest sites identified the soils to be functioning as sinks for atmospheric CH4. Fifteen months continuous measurement at one of the lowland rainforest sites showed that the seasonality of CH4 uptake was mainly driven by changes in soil moisture rather than by temperature changes. Maximum CH4 uptake (109 μg CH4 m?2 h?1) was observed during dry season conditions, whereas during the wet season, CH4 uptake decreased significantly to near zero. Based on our laboratory experiments and on published literature we developed a semi-empirical CH4 module for the biogeochemical model ForestDNDCtropica. Tests at several sites showed the robustness of our modelling approach with mean simulated values within 12% of observed values. To estimate regional CH4 uptake by rainforest soils in the region of the ‘Wet Tropics’, Queensland, Australia, we linked CH4 uptake and production algorithms to a regional GIS database. We estimated that the lowland and montane rainforest soils in northeast Queensland, Australia, were a net sink for CH4 with a mean uptake rate of ?2.89 kg CH4 ha?1 year?1 during July 1996 to June 1997 period. 相似文献
2.
Rosa Inclán Carla Uribe Laura Sánchez Dolores M. Sánchez ángeles Clavero Ana María Fernández Ramón Morante Alfredo Blanco Robert Jandl 《Biogeochemistry》2012,107(1-3):19-41
We investigated N2O and CH4 fluxes from soils of Quercus ilex, Quercus pyrenaica and Pinus sylvestris stands located in the surrounding area of Madrid (Spain). The fluxes were measured for 18?months from both mature stands and post fire stands using the static chamber technique. Simultaneously with gas fluxes, soil temperature, soil water content, soil C and soil N were measured in the stands. Nitrous oxide fluxes ranged from ?11.43 to 8.34?μg N2O–N?m?2?h?1 in Q.ilex, ?7.74 to 13.52?μg N2O–N?m?2?h?1 in Q. pyrenaica and ?28.17 to 21.89?μg N2O–N?m?2?h?1 in P. sylvestris. Fluxes of CH4 ranged from ?8.12 to 4.11?μg CH4–C?m?2?h?1 in Q.ilex, ?7.74 to 3.0?μg CH4–C m?2?h?1 in Q. pyrenaica and ?24.46 to 6.07?μg CH4–C?m?2?h?1 in P. sylvestris. Seasonal differences were detected; N2O fluxes being higher in wet months whereas N2O fluxes declined in dry months. Net consumption of N2O was related to low N availability, high soil C contents, high soil temperatures and low moisture content. Fire decreased N2O fluxes in spring. N2O emissions were closely correlated with previous day’s rainfall and soil moisture. Our ecosystems generally were a sink for methane in the dry season and a source of CH4 during wet months. The available water in the soil influenced the observed seasonal trend. The burned sites showed higher CH4 oxidation rates in Q. ilex, and lower rates in P. sylvestris. Overall, the data suggest that fire alters both N2O and CH4 fluxes. However, the magnitude of such variation depends on the site, soil characteristics and seasonal climatic conditions. 相似文献
3.
We investigated soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) exchanges in an age‐sequence (4, 17, 32, 67 years old) of eastern white pine (Pinus strobus L.) forests in southern Ontario, Canada, for the period of mid‐April to mid‐December in 2006 and 2007. For both CH4 and N2O, we observed uptake and emission ranging from ?160 to 245 μg CH4 m?2 h?1 and ?52 to 21 μg N2O m?2 h?1, respectively (negative values indicate uptake). Mean fluxes from mid‐April to mid‐December across the 4, 17, 32, 67 years old stands were similar for CO2 fluxes (259, 246, 220, and 250 mg CO2 m?2 h?1, respectively), without pattern for N2O fluxes (?3.7, 1.5, ?2.2, and ?7.6 μg N2O m?2 h?1, respectively), whereas the uptake rates of CH4 increased with stand age (6.4, ?7.9, ?10.8, and ?23.3 μg CH4 m?2 h?1, respectively). For the same period, the combined contribution of CH4 and N2O exchanges to the global warming potential (GWP) calculated from net ecosystem exchange of CO2 and aggregated soil exchanges of CH4 and N2O was on average 4%, <1%, <1%, and 2% for the 4, 17, 32, 67 years old stand, respectively. Soil CO2 fluxes correlated positively with soil temperature but had no relationship with soil moisture. We found no control of soil temperature or soil moisture on CH4 and N2O fluxes, but CH4 emission was observed following summer rainfall events. LFH layer removal reduced CO2 emissions by 43%, increased CH4 uptake during dry and warm soil conditions by more than twofold, but did not affect N2O flux. We suggest that significant alternating sink and source potentials for both CH4 and N2O may occur in N‐ and soil water‐limited forest ecosystems, which constitute a large portion of forest cover in temperate areas. 相似文献
4.
Yangong Du Yingguang Cui Xingliang Xu Dongying Liang Ruijun Long Guangmin Cao 《Plant and Soil》2008,311(1-2):245-254
Nitrous oxide (N2O) emission was measured in a Kobresia humilis meadow and a Potentilla fruticosa meadow in the Qinghai–Tibet Plateau from June 2003 to July 2006. Five treatments were setup in the two alpine meadows. Two bare soil treatments were setup in the K. humilis meadow (BSK) and in the P. fruticosa meadow (BSP) by removing the above- and belowground plant biomass. Three plant community treatments were setup with one in the K. humilis meadow (herbaceous community in the K. humilis meadow-HCK) and two in the P. fruticosa meadow (herbaceous community in the P. fruticosa meadow-HCP, and shrub community in the P. fruticosa meadow-SCP). Nitrous oxide emission from BSP was estimated to be 38.1?±?3.6 μg m?2 h?1, significantly higher than from BSK (30.2?±?2.8 μg m?2 h?1) during the whole experiment period. Rates from the two herbaceous blocks (HCK and HCP) were close to 39.5 μg m?2 h?1 during the whole experimental period whereas shrub community (SCP) showed significant high emission rates of N2O. Annual rate of N2O emission was estimated to be 356.7?±?8.3 and 295.0?±?11.6 mg m?2 year?1 from the alpine P. fruticosa meadow and from the alpine K. humilis meadow, respectively. These results suggest that alpine meadows in the Qinghai–Tibetan Plateau are an important source of N2O, contributing an average of 0.3 Tg N2O year?1. We concluded that N2O emission will decrease, due to a predicted vegetation shift from shrubs to grasses imposed by overgrazing. 相似文献
5.
Landscape patterns of CH4 fluxes in an alpine tundra ecosystem 总被引:2,自引:0,他引:2
A.E. West P.D. Brooks M.C. Fisk L.K. Smith E.A. Holland C.H. Jaeger III S. Babcock R.S. Lai S.K. Schmidt 《Biogeochemistry》1999,45(3):243-264
We measured CH4 fluxes from three major plant communities characteristic of alpine tundra in the Colorado Front Range. Plant communities in this ecosystem are determined by soil moisture regimes induced by winter snowpack distribution. Spatial patterns of CH4 flux during the snow-free season corresponded roughly with these plant communities. InCarex-dominated meadows, which receive the most moisture from snowmelt, net CH4 production occurred. However, CH4 production in oneCarex site (seasonal mean=+8.45 mg CH4 m–2 d–1) was significantly larger than in the otherCarex sites (seasonal means=–0.06 and +0.05 mg CH4 m–2 d–1). This high CH4 flux may have resulted from shallower snowpack during the winter. InAcomastylis meadows, which have an intermediate moisture regime, CH4 oxidation dominated (seasonal mean=–0.43 mg CH4 m–2 d–1). In the windsweptKobresia meadow plant community, which receive the least amount of moisture from snowmelt, only CH4 oxidation was observed (seasonal mean=–0.77 mg CH4 m–2 d–1). Methane fluxes correlated with a different set of environmental factors within each plant community. In theCarex plant community, CH4 emission was limited by soil temperature. In theAcomastylis meadows, CH4 oxidation rates correlated positively with soil temperature and negatively with soil moisture. In theKobresia community, CH4 oxidation was stimulated by precipitation. Thus, both snow-free season CH4 fluxes and the controls on those CH4 fluxes were related to the plant communities determined by winter snowpack. 相似文献
6.
Peter E. Levy Annette Burden Mark D. A. Cooper Kerry J. Dinsmore Julia Drewer Chris Evans David Fowler Jenny Gaiawyn Alan Gray Stephanie K. Jones Timothy Jones Niall P. McNamara Robert Mills Nick Ostle Lucy J. Sheppard Ute Skiba Alwyn Sowerby Susan E. Ward Piotr Zieliński 《Global Change Biology》2012,18(5):1657-1669
Nearly 5000 chamber measurements of CH4 flux were collated from 21 sites across the United Kingdom, covering a range of soil and vegetation types, to derive a parsimonious model that explains as much of the variability as possible, with the least input requirements. Mean fluxes ranged from ?0.3 to 27.4 nmol CH4 m?2 s?1, with small emissions or low rates of net uptake in mineral soils (site means of ?0.3 to 0.7 nmol m?2 s?1) and much larger emissions from organic soils (site means of ?0.3 to 27.4 nmol m?2 s?1). Less than half of the observed variability in instantaneous fluxes could be explained by independent variables measured. The reasons for this include measurement error, stochastic processes and, probably most importantly, poor correspondence between the independent variables measured and the actual variables influencing the processes underlying methane production, transport and oxidation. When temporal variation was accounted for, and the fluxes averaged at larger spatial scales, simple models explained up to ca. 75% of the variance in CH4 fluxes. Soil carbon, peat depth, soil moisture and pH together provided the best sub‐set of explanatory variables. However, where plant species composition data were available, this provided the highest explanatory power. Linear and nonlinear models generally fitted the data equally well, with the exception that soil moisture required a power transformation. To estimate the impact of changes in peatland water table on CH4 emissions in the United Kingdom, an emission factor of +0.4 g CH4 m?2 yr?1 per cm increase in water table height was derived from the data. 相似文献
7.
青藏高原高寒草甸土壤CO2排放对模拟氮沉降的早期响应 总被引:5,自引:0,他引:5
研究大气氮沉降输入对青藏高原高寒草甸土壤-大气界面CO2交换通量的影响,对于准确评价全球变化背景下区域碳平衡至关重要。通过构建多形态、低剂量的增氮控制试验,利用静态箱-气相色谱法测定土壤CO2排放通量,同时测定相关土壤变量和地上生物量,分析高寒草甸土壤CO2排放特征及其主要驱动因子。研究结果表明:低、高剂量氮输入倾向于消耗土壤水分,而中剂量氮输入有利于土壤水分的保持;施氮初期总体上增加了土壤无机氮含量,铵态氮累积效应更为显著;施氮显著增加地上生物量和土壤CO2排放通量,铵态氮的促进效应显著高于硝态氮。另外,土壤CO2排放通量主要受土壤温度驱动,其次为地上生物量和铵态氮储量。上述结果反映了氮沉降输入短期内可能刺激了植物生长和土壤微生物活性,加剧了土壤-大气界面CO2排放。 相似文献
8.
Methane oxidation in contrasting soil types: responses to experimental warming with implication for landscape‐integrated CH4 budget
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Ludovica D'Imperio Cecilie Skov Nielsen Andreas Westergaard‐Nielsen Anders Michelsen Bo Elberling 《Global Change Biology》2017,23(2):966-976
Arctic ecosystems are characterized by a wide range of soil moisture conditions and thermal regimes and contribute differently to the net methane (CH4) budget. Yet, it is unclear how climate change will affect the capacity of those systems to act as a net source or sink of CH4. Here, we present results of in situ CH4 flux measurements made during the growing season 2014 on Disko Island (west Greenland) and quantify the contribution of contrasting soil and landscape types to the net CH4 budget and responses to summer warming. We compared gas flux measurements from a bare soil and a dry heath, at ambient conditions and increased air temperature, using open‐top chambers (OTCs). Throughout the growing season, bare soil consumed 0.22 ± 0.03 g CH4‐C m?2 (8.1 ± 1.2 g CO2‐eq m?2) at ambient conditions, while the dry heath consumed 0.10 ± 0.02 g CH4‐C m?2 (3.9 ± 0.6 g CO2‐eq m?2). These uptake rates were subsequently scaled to the entire study area of 0.15 km2, a landscape also consisting of wetlands with a seasonally integrated methane release of 0.10 ± 0.01 g CH4‐C m?2 (3.7 ± 1.2 g CO2‐eq m?2). The result was a net landscape sink of 12.71 kg CH4‐C (0.48 tonne CO2‐eq) during the growing season. A nonsignificant trend was noticed in seasonal CH4 uptake rates with experimental warming, corresponding to a 2% reduction at the bare soil, and 33% increase at the dry heath. This was due to the indirect effect of OTCs on soil moisture, which exerted the main control on CH4 fluxes. Overall, the net landscape sink of CH4 tended to increase by 20% with OTCs. Bare and dry tundra ecosystems should be considered in the net CH4 budget of the Arctic due to their potential role in counterbalancing CH4 emissions from wetlands – not the least when taking the future climatic scenarios of the Arctic into account. 相似文献
9.
Trace gas flux and the influence of short-term soil water and temperature dynamics in Australian sheep grazed pastures of differing productivity 总被引:1,自引:0,他引:1
S. J. Livesley R. Kiese J. Graham C. J. Weston K. Butterbach-Bahl S. K. Arndt 《Plant and Soil》2008,309(1-2):89-103
Temperate pastures are often managed with P fertilizers and N2-fixing legumes to maintain and increase pasture productivity which may lead to greater nitrous oxide (N2O) emissions and reduced methane (CH4) uptake. However, the diel and inter-daily variation in N2O and CH4 flux in pastures is poorly understood, especially in relation to key environmental drivers. We investigated the effect of pasture productivity, rainfall, and changing soil moisture and temperature upon short-term soil N2O and CH4 flux dynamics during spring in sheep grazed pasture systems in southeastern Australia. N2O and CH4 flux was measured continuously in a High P (23 kg P ha?1 yr?1) and No P pasture treatment and in a sheep camp area in a Low P (4 kg P ha?1 yr?1) pasture for a four week period in spring 2005 using an automated trace gas system. Although pasture productivity was three-fold greater in the High P than No P treatment, mean CH4 uptake was similar (?6.3?±?SE 0.3 to ?8.6?±?0.4 μg C m?2 hr?1) as were mean N2O emissions (6.5 to 7.9?±?0.8 μg N m?2 hr?1), although N2O flux in the No P pasture did not respond to changing soil water conditions. N2O emissions were greatest in the Low P sheep camp (12.4 μg?±?1.1 N m?2 hr?1) where there were also net CH4 emissions of 5.2?±?0.5 μg C m?2 hr?1. There were significant, but weak, relationships between soil water and N2O emissions, but not between soil water and CH4 flux. The diel temperature cycle strongly influenced CH4 and N2O emissions, but this was often masked by the confounding covariate effects of changing soil water content. There were no consistently significant differences in soil mineral N or gross N transformation rates, however, measurements of substrate induced respiration (SIR) indicated that soil microbial processes in the highly productive pasture are more N limited than P limited after >20 years of P fertilizer addition. Increased productivity, through P fertilizer and legume management, did not significantly increase N2O emissions, or reduce CH4 uptake, during this 4 week measurement period, but the lack of an N2O response to rainfall in the No P pasture suggests this may be evident over a longer measurement period. This study also suggests that small compacted and nutrient enriched areas of grazed pastures may contribute greatly to the overall N2O and CH4 trace gas balance. 相似文献
10.
Jesper Riis Christiansen David Levy-Booth Cindy E. Prescott Sue J. Grayston 《Ecosystems》2016,19(7):1255-1270
Most studies of greenhouse gas fluxes from forest soils in the coastal rainforest have considered carbon dioxide (CO2), whereas methane (CH4) has not received the same attention. Soil hydrology is a key driver of CH4 dynamics in ecosystems, but the impact on the function and distribution of the underlying microbial communities involved in CH4 cycling and the resultant net CH4 exchange is not well understood at this scale. We studied the growing season variations of in situ CH4 fluxes, microbial gene abundances of methanotrophs (CH4 oxidizers) and methanogens (CH4 producers), soil hydrology, and nutrient availability in three typical forest types across a soil moisture gradient. CH4 displayed a spatial variability changing from a net uptake in the upland soils (3.9–46 µmol CH4 m?2 h?1) to a net emission in the wetter soils (0–90 μmol CH4 m?2 h?1). Seasonal variations of CH4 fluxes were related to soil hydrology in both upland and wet soils. Thus, in the upland soils, uptake rates increased with the decreasing soil moisture, whereas CH4 emission was inversely related to the water table depth in the wet soils. Spatial variability of CH4 exchange was related to the abundance of genes involved in CH4 oxidation and production, but there was no indication of a temporal link between microbial groups and CH4 exchange. Our data show that the abundances of genes involved in CH4 oxidation and production are strongly influenced by soil moisture and each other and grouped by the upland–wetland classification but not forest type. 相似文献
11.
Craig A. Emmerton Vincent L. St. Louis Elyn R. Humphreys John A. Gamon Joel D. Barker Gilberto Z. Pastorello 《Global Change Biology》2016,22(3):1185-1200
High Arctic landscapes are expansive and changing rapidly. However, our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near‐zero sink of atmospheric CO2 (NEE: ?0.3 ± 13.5 g C m?2). A nearby meadow wetland accumulated over 300 times more carbon (NEE: ?79.3 ± 20.0 g C m?2) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southerly latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on‐site was low (mean: 0.120–0.157) and similar to satellite measurements (mean: 0.155–0.163). However, weak plant growth resulted in poor satellite NDVI–NEE relationships and created challenges for remotely detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote sensing; however, high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases enough to offset poor soil moisture retention, climate‐related changes to productivity on polar semideserts may be restricted. 相似文献
12.
Nitrogen (N) is one of the most important factors limiting plant productivity, and N fixation by legume species is an important source of N input into ecosystems. Meanwhile, N resorption from senescent plant tissues conserves nutrients taken up in the current season, which may alleviate ecosystem N limitation. N fixation was assessed by the 15N dilution technique in four types of alpine grasslands along the precipitation and soil nutrient gradients. The N resorption efficiency (NRE) was also measured in these alpine grasslands. The aboveground biomass in the alpine meadow was 4–6 times higher than in the alpine meadow steppe, alpine steppe, and alpine desert steppe. However, the proportion of legume species to community biomass in the alpine steppe and the alpine desert steppe was significantly higher than the proportion in the alpine meadow. N fixation by the legume plants in the alpine meadow was 0.236 g N/m2, which was significantly higher than N fixation in other alpine grasslands (0.041 to 0.089 g N/m2). The NRE in the alpine meadows was lower than in the other three alpine grasslands. Both the aboveground biomass and N fixation of the legume plants showed decreasing trends with the decline of precipitation and soil N gradients from east to west, while the NRE of alpine plants showed increasing trends along the gradients, which indicates that alpine plants enhance the NRE to adapt to the increasing droughts and nutrient‐poor environments. The opposite trends of N fixation and NRE along the precipitation and soil nutrient gradients indicate that alpine plants adapt to precipitation and soil nutrient limitation by promoting NRE (conservative nutrient use by alpine plants) rather than biological N fixation (open sources by legume plants) on the north Tibetan Plateau. 相似文献
13.
Indigenous broadleaf plantations are increasingly developing as a prospective silvicultural management approach for substituting in place of large pure conifer plantations in subtropical China. However, little information is known about the effects of tree species conversion on soil-atmosphere greenhouse gas (GHG) exchanges. Four adjacent monospecific plantations were selected in subtropical China to examine the effects of tree species on soil-atmosphere exchanges of N2O, CH4 and CO2. One coniferous plantation was composed of Pinus massoniana (PM), and the three broadleaf plantations were Castanopsis hystrix (CH), Michelia macclurei (MM) and Mytilaria laosensis (ML). We found that mean soil N2O and CO2 emissions in the PM plantation were 4.34 μg N m?2?h?1 and 43.25 mg C m?2?h?1, respectively, lower than those in the broadleaf plantations (>5.25 μg N m?2?h?1 and >56.38 mg C m?2?h?1). The PM plantation soil had higher mean CH4 uptake (39.03 μg C m?2?h?1) than the broadleaf plantation soils (<32.67 μg C m?2?h?1). Variations in soil N2O emissions among tree species could be primarily explained by the differences in litter C:N ratio and soil total N stock. Differences in soil CH4 uptake among tree species could be mostly attributed to the differences in mean soil CO2 flux and water filled pore space (WFPS). Litter C:N ratio could largely account for variations in soil CO2 emissions among tree species. This study confirms that there is no GHG benefit of converting PM plantation to broadleaf plantations in subtropical China. Therefore, the future strategy of tree species selection for substituting in place of large coniferous plantations in subtropical China needs to consider the potential effects of tree species on soil-atmosphere GHG exchanges. 相似文献
14.
P. Rosenkranz N. Brüggemann H. Papen Z. Xu L. Horváth K. Butterbach-Bahl 《Plant and Soil》2006,286(1-2):301-322
During two intensive field campaigns in summer and autumn 2004 nitrogen (N2O, NO/NO2) and carbon (CO2, CH4) trace gas exchange between soil and the atmosphere was measured in a sessile oak (Quercus petraea (Matt.) Liebl.) forest in Hungary. The climate can be described as continental temperate. Fluxes were measured with a fully automatic measuring system allowing for high temporal resolution. Mean N2O emission rates were 1.5 μg N m−2 h−1 in summer and 3.4 μg N m−2 h−1 in autumn, respectively. Also mean NO emission rates were higher in autumn (8.4 μg N m−2 h−1) as compared to summer (6.0 μg N m−2 h−1). However, as NO2 deposition rates continuously exceeded NO emission rates (−9.7 μg N m−2 h−1 in summer and −18.3 μg N m−2 h−1 in autumn), the forest soil always acted as a net NO
x
sink. The mean value of CO2 fluxes showed only little seasonal differences between summer (81.1 mg C m−2 h−1) and autumn (74.2 mg C m−2 h−1) measurements, likewise CH4uptake (summer: −52.6 μg C m−2 h−1; autumn: −56.5 μg C m−2 h−1). In addition, the microbial soil processes net/gross N mineralization, net/gross nitrification and heterotrophic soil respiration as well as inorganic soil nitrogen concentrations and N2O/CH4 soil air concentrations in different soil depths were determined. The respiratory quotient (ΔCO2 resp ΔO2 resp−1) for the uppermost mineral soil, which is needed for the calculation of gross nitrification via the Barometric Process Separation (BaPS) technique, was 0.8978 ± 0.008. The mean value of gross nitrification rates showed only little seasonal differences between summer (0.99 μg N kg−1 SDW d−1) and autumn measurements (0.89 μg N kg−1 SDW d−1). Gross rates of N mineralization were highest in the organic layer (20.1–137.9 μg N kg−1 SDW d−1) and significantly lower in the uppermost mineral layer (1.3–2.9 μg N kg−1 SDW d−1). Only for the organic layer seasonality in gross N mineralization rates could be demonstrated, with highest mean values in autumn, most likely caused by fresh litter decomposition. Gross mineralization rates of the organic layer were positively correlated with N2O emissions and negatively correlated with CH4 uptake, whereas soil CO2 emissions were positively correlated with heterotrophic respiration in the uppermost mineral soil layer. The most important abiotic factor influencing C and N trace gas fluxes was soil moisture, while the influence of soil temperature on trace gas exchange rates was high only in autumn. 相似文献
15.
Balathandayuthabani Panneer Selvam Sivakiruthika Natchimuthu Lakshmanan Arunachalam David Bastviken 《Global Change Biology》2014,20(11):3397-3407
Inland waters were recently recognized to be important sources of methane (CH4) and carbon dioxide (CO2) to the atmosphere, and including inland water emissions in large scale greenhouse gas (GHG) budgets may potentially offset the estimated carbon sink in many areas. However, the lack of GHG flux measurements and well‐defined inland water areas for extrapolation, make the magnitude of the potential offset unclear. This study presents coordinated flux measurements of CH4 and CO2 in multiple lakes, ponds, rivers, open wells, reservoirs, springs, and canals in India. All these inland water types, representative of common aquatic ecosystems in India, emitted substantial amounts of CH4 and a major fraction also emitted CO2. The total CH4 flux (including ebullition and diffusion) from all the 45 systems ranged from 0.01 to 52.1 mmol m?2 d?1, with a mean of 7.8 ± 12.7 (mean ± 1 SD) mmol m?2 d?1. The mean surface water CH4 concentration was 3.8 ± 14.5 μm (range 0.03–92.1 μm ). The CO2 fluxes ranged from ?28.2 to 262.4 mmol m?2 d?1 and the mean flux was 51.9 ± 71.1 mmol m?2 d?1. The mean partial pressure of CO2 was 2927 ± 3269 μatm (range: 400–11 467 μatm). Conservative extrapolation to whole India, considering the specific area of the different water types studied, yielded average emissions of 2.1 Tg CH4 yr?1 and 22.0 Tg CO2 yr?1 from India's inland waters. When expressed as CO2 equivalents, this amounts to 75 Tg CO2 equivalents yr?1 (53–98 Tg CO2 equivalents yr?1; ± 1 SD), with CH4 contributing 71%. Hence, average inland water GHG emissions, which were not previously considered, correspond to 42% (30–55%) of the estimated land carbon sink of India. Thereby this study illustrates the importance of considering inland water GHG exchange in large scale assessments. 相似文献
16.
Winter precipitation and snow accumulation drive the methane sink or source strength of Arctic tussock tundra
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Elena Blanc‐Betes Jeffrey M. Welker Neil C. Sturchio Jeffrey P. Chanton Miquel A. Gonzalez‐Meler 《Global Change Biology》2016,22(8):2818-2833
Arctic winter precipitation is projected to increase with global warming, but some areas will experience decreases in snow accumulation. Although Arctic CH4 emissions may represent a significant climate forcing feedback, long‐term impacts of changes in snow accumulation on CH4 fluxes remain uncertain. We measured ecosystem CH4 fluxes and soil CH4 and CO2 concentrations and 13C composition to investigate the metabolic pathways and transport mechanisms driving moist acidic tundra CH4 flux over the growing season (Jun–Aug) after 18 years of experimental snow depth increases and decreases. Deeper snow increased soil wetness and warming, reducing soil %O2 levels and increasing thaw depth. Soil moisture, through changes in soil %O2 saturation, determined predominance of methanotrophy or methanogenesis, with soil temperature regulating the ecosystem CH4 sink or source strength. Reduced snow (RS) increased the fraction of oxidized CH4 (Fox) by 75–120% compared to Ambient, switching the system from a small source to a net CH4 sink (21 ± 2 and ?31 ± 1 mg CH4 m?2 season?1 at Ambient and RS). Deeper snow reduced Fox by 35–40% and 90–100% in medium‐ (MS) and high‐ (HS) snow additions relative to Ambient, contributing to increasing the CH4 source strength of moist acidic tundra (464 ± 15 and 3561 ± 97 mg CH4 m?2 season?1 at MS and HS). Decreases in Fox with deeper snow were partly due to increases in plant‐mediated CH4 transport associated with the expansion of tall graminoids. Deeper snow enhanced CH4 production within newly thawed soils, responding mainly to soil warming rather than to increases in acetate fermentation expected from thaw‐induced increases in SOC availability. Our results suggest that increased winter precipitation will increase the CH4 source strength of Arctic tundra, but the resulting positive feedback on climate change will depend on the balance between areas with more or less snow accumulation than they are currently facing. 相似文献
17.
Shiping Wang Xiaoxia Yang Xingwu Lin Yigang Hu Caiyun Luo Guangping Xu Zhenhua Zhang Ailing Su Xiaofen Chang Zengguo Chao Jichuang Duan 《Biology letters》2009,5(4):535-538
Recently, plant-derived methane (CH4) emission has been questioned because limited evidence of the chemical mechanism has been identified to account for the process. We conducted an experiment with four treatments (i.e. winter-grazed, natural alpine meadow; naturally restored alpine meadow eight years after cultivation; oat pasture and bare soil without roots) during the growing seasons of 2007 and 2008 to examine the question of CH4 emission by plant communities in the alpine meadow. Each treatment consumed CH4 in closed, opaque chambers in the field, but two types of alpine meadow vegetation reduced CH4 consumption compared with bare soil, whereas oat pasture increased consumption. This result could imply that meadow vegetation produces CH4. However, measurements of soil temperature and water content showed significant differences between vegetated and bare soil and appeared to explain differences in CH4 production between treatments. Our study strongly suggests that the apparent CH4 production by vegetation, when compared with bare soil in some previous studies, might represent differences in soil temperature and water-filled pore space and not the true vegetation sources of CH4. 相似文献
18.
Different responses of ecosystem carbon exchange to warming in three types of alpine grassland on the central Qinghai–Tibetan Plateau
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Hasbagan Ganjurjav Guozheng Hu Yunfan Wan Yue Li Luobu Danjiu Qingzhu Gao 《Ecology and evolution》2018,8(3):1507-1520
Climate is a driver of terrestrial ecosystem carbon exchange, which is an important product of ecosystem function. The Qinghai–Tibetan Plateau has recently been subjected to a marked increase in temperature as a consequence of global warming. To explore the effects of warming on carbon exchange in grassland ecosystems, we conducted a whole‐year warming experiment between 2012 and 2014 using open‐top chambers placed in an alpine meadow, an alpine steppe, and a cultivated grassland on the central Qinghai–Tibetan Plateau. We measured the gross primary productivity, net ecosystem CO2 exchange (NEE), ecosystem respiration, and soil respiration using a chamber‐based method during the growing season. The results show that after 3 years of warming, there was significant stimulation of carbon assimilation and emission in the alpine meadow, but both these processes declined in the alpine steppe and the cultivated grassland. Under warming conditions, the soil water content was more important in stimulating ecosystem carbon exchange in the meadow and cultivated grassland than was soil temperature. In the steppe, the soil temperature was negatively correlated with ecosystem carbon exchange. We found that the ambient soil water content was significantly correlated with the magnitude of warming‐induced change in NEE. Under high soil moisture condition, warming has a significant positive effect on NEE, while it has a negative effect under low soil moisture condition. Our results highlight that the NEE in steppe and cultivated grassland have negative responses to warming; after reclamation, the natural meadow would subject to loose more C in warmer condition. Therefore, under future warmer condition, the overextension of cultivated grassland should be avoided and scientific planning of cultivated grassland should be achieved. 相似文献
19.
Zhisheng Yao Benjamin Wolf Weiwei Chen Klaus Butterbach-Bahl Nicolas Brüggemann Martin Wiesmeier Michael Dannenmann Benjamin Blank Xunhua Zheng 《Plant and Soil》2010,331(1-2):341-359
In order to identify the effects of land-use/cover types, soil types and soil properties on the soil-atmosphere exchange of greenhouse gases (GHG) in semiarid grasslands as well as provide a reliable estimate of the midsummer GHG budget, nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes of soil cores from 30 representative sites were determined in the upper Xilin River catchment in Inner Mongolia. The soil N2O emissions across all of the investigated sites ranged from 0.18 to 21.8 μg N m-2 h-1, with a mean of 3.4 μg N m-2 h-1 and a coefficient of variation (CV, which is given as a percentage ratio of one standard deviation to the mean) as large as 130%. CH4 fluxes ranged from -88.6 to 2,782.8 μg C m-2 h-1 (with a CV of 849%). Net CH4 emissions were only observed from cores taken from a marshland site, whereas all of the other 29 investigated sites showed net CH4 uptake (mean: -33.3 μg C m-2 h-1). CO2 emissions from all sites ranged from 3.6 to 109.3 mg C m-2 h-1, with a mean value of 37.4 mg C m-2 h-1 and a CV of 66%. Soil moisture primarily and positively regulated the spatial variability in N2O and CO2 emissions (R2?=?0.15–0.28, P?<?0.05). The spatial variation of N2O emissions was also influenced by soil inorganic N contents (P?<?0.05). By simply up-scaling the site measurements by the various land-use/cover types to the entire catchment area (3,900 km2), the fluxes of N2O, CH4 and CO2 at the time of sampling (mid-summer 2007) were estimated at 29 t CO2-C-eq d-1, -26 t CO2-C-eq d-1 and 3,223 t C d-1, respectively. This suggests that, in terms of assessing the spatial variability of total GHG fluxes from the soils at a semiarid catchment/region, intensive studies may focus on CO2 exchange, which is dominating the global warming potential of midsummer soil-atmosphere GHG fluxes. In addition, average GHG fluxes in midsummer, weighted by the areal extent of these land-use/cover types in the region, were approximately -30.0 μg C m-2 h-1 for CH4, 2.4 μg N m-2 h-1 for N2O and 34.5 mg C m-2 h-1 for CO2. 相似文献
20.
以青藏高原玛沁地区高寒草甸和沱沱河地区高寒荒漠草原为观测研究站,利用涡动协方差技术获取高寒生态系统水平上的CO2通量以及水和能量通量,通过REddyProc、随机森林(Random Forest, RF)进行了数据后处理,探究了不同下垫面典型环境因子对净生态系统CO2交换量(Net Ecosystem Exchange, NEE)的影响机制。结果表明:1)玛沁高寒草甸在6—7月以吸收为主,表现为碳汇,吸收峰值出现在11:00—12:00(北京时,下同)之间,而在3、4、5、8月以排放为主,表现为碳源,排放峰值出现在21:00—23:00之间;沱沱河高寒荒漠在3—8月以吸收为主,表现为净碳汇,吸收峰值出现在13:00—14:00之间;整个生长季前后(3—8月),玛沁和沱沱河的累计NEE分别为79.50 g C/m2和79.24 g C/m2,都表现为碳汇。2)不同尺度不同下垫面,气象因子对NEE的重要程度不同,小时尺度上,高寒草甸辐射对NEE的重要性最大,高寒荒漠草原蒸散发对NEE的重要性最大;日尺度... 相似文献