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1.
The Dinghushan flux observation site, as one of the four forest sites of ChinaFLUX, aims to acquire long-term measurements of CO2 flux over a typical southern subtropical evergreen coniferous and broad-leaved mixed forest ecosystem using the open path eddy covariance method. Based on two years of data from 2003 to 2004, the characteristics of temporal variation in CO2 flux and its response to environmental factors in the forest ecosystem are analyzed. Provided two-dimensional coordinate rotation, WPL correction and quality control, poor energy-balance and underestimation of ecosystem respiration during nighttime implied that there could be a CO2 leak during the nighttime at the site. Using daytime (PAR > 1.0 μmol?1·m?2·s?1) flux data during windy conditions (u* > 0.2 m·s?1), monthly ecosystem respiration (Reco) was derived through the Michaelis-Menten equation modeling the relationship between net ecosystem C02 exchange (NEE) and photosynthetically active radiation (PAR). Exponential function was employed to describe the relationship between Reco and soil temperature at 5 cm depth (Ts05), then Reco of both daytime and nighttime was calculated respectively by the function. The major results are: (i) Derived from the Michaelis-Menten equation, the apparent quantum yield (α) was 0.0027±0.0011 mgCO2·μmol?1 photons, and the maximum photosynthetic assimilation rate (Amax) was 1.102±0.288 mgCO2·m?2·s?1. Indistinctive seasonal variation of α or Amax was consistent with weak seasonal dynamics of leaf area index (LAf) in such a lower subtropical evergreen mixed forest, (ii) Monthly accumulated Reco was estimated as 95.3±21.1 gC·m?2mon?1, accounting for about 68% of the gross primary product (GPP). Monthly accumulated WEE was estimated as ?43.2±29.6 gC·m?2·mon?1. The forest ecosystem acted as carbon sink all year round without any seasonal carbon efflux period. Annual NEE of 2003 and 2004 was estimated as ?563.0 and ?441.2 gC·m?2·a?1 respectively, accounting for about 32% of GPP.  相似文献   

2.
Long-term measurement of carbon metabolism of old-growth forests is critical to predict their behaviors and to reduce the uncertainties of carbon accounting under changing climate. Eddy covariance technology was applied to investigate the long-term carbon exchange over a 200 year-old Chinese broad-leaved Korean pine mixed forest in the Changbai Mountains (128°28′E and 42°24′N, Jilin Province, P. R. China) since August 2002. On the data obtained with open-path eddy covariance system and CO2 profile measurement system from Jan. 2003 to Dec. 2004, this paper reports (i) annual and seasonal variation of F NEE, F GPP and R E; (ii) regulation of environmental factors on phase and amplitude of ecosystem CO2 uptake and release Corrections due to storage and friction velocity were applied to the eddy carbon flux.LAI and soil temperature determined the seasonal and annual dynamics of FGPP and RE separately. VPD and air temperature regulated ecosystem photosynthesis at finer scales in growing seasons. Water condition at the root zone exerted a significant influence on ecosystem maintenance carbon metabolism of this forest in winter.The forest was a net sink of atmospheric CO2 and sequestered ?449 g C·m?2 during the study period; ?278 and ?171 gC·m?2 for 2003 and 2004 respectively. F GPP and F RE over 2003 and 2004 were ?1332, ?1294 g C·m?2. and 1054, 1124 g C·m?2 respectively. This study shows that old-growth forest can be a strong net carbon sink of atmospheric CO2.There was significant seasonal and annual variation in carbon metabolism. In winter, there was weak photosynthesis while the ecosystem emitted CO2. Carbon exchanges were active in spring and fall but contributed little to carbon sequestration on an annual scale. The summer is the most significant season as far as ecosystem carbon balance is concerned. The 90 days of summer contributed 66.9, 68.9% of F GPP, and 60.4, 62.1% of R E of the entire year.  相似文献   

3.
We measured soil, stem and branch respiration of trees and shrubs, foliage photosynthesis and respiration in ecosystem of the needle and broad-leaved Korean pine forest in Changbai Mountain by LI-6400 CO2 analysis system. Measurement of forest microclimate was conducted simultaneously and a model was found for the relationship of soil, stem, leaf and climate factors. CO2 flux of different components in ecosystem of the broad-leaved Korean pine forest was estimated based on vegetation characteristics. The net ecosystem exchange was measured by eddy covariance technique. And we studied the effect of temperature and photosynthetic active radiation on ecosystem CO2 flux. Through analysis we found that the net ecosystem exchange was affected mainly by soil respiration and leaf photosynthesis. Annual net ecosystem exchange ranged from a minimum of about ?4.671 μmol·m?2·s?1 to a maximum of 13.80 μmol·m?2·s?1, mean net ecosystem exchange of CO2 flux was ?2.0 μmol·m?2·s?1 and 3.9 μmol·m?2·s?1 in winter and summer respectively (mean value during 24 h). Primary productivity of tree, shrub and herbage contributed about 89.7%, 3.5% and 6.8% to the gross primary productivity of the broad-leaved Korean pine forest respectively. Soil respiration contributed about 69.7% CO2 to the broad-leaved Korean pine forest ecosystem, comprising about 15.2% from tree leaves and 15.1% from branches. The net ecosystem exchange in growing season and non-growing season contributed 56.8% and 43.2% to the annual CO2 efflux respectively. The ratio of autotrophic respiration to gross primary productivity (R a:GPP) was 0.52 (NPP:GPP=0.48). Annual carbon accumulation underground accounted for 52% of the gross primary productivity, and soil respiration contributed 60% to gross primary productivity. The NPP of the needle and broad-leaved Korean pine forest was 769.3 gC·m?2·a?1. The net ecosystem exchange of this forest ecosystem (NEE) was 229.51 gC·m?2·a?1. The NEE of this forest ecosystem acquired by eddy covariance technique was lower than chamber estimates by 19.8%.  相似文献   

4.
Eddy covariance technique was used to measure carbon flux during two growing seasons in 2003 and 2004 over typical steppe in the Inner Mongolia Plateau, China. The results showed that there were two different CO2 flux diurnal patterns at the grassland ecosystem. One had a dual peak in diurnal course of CO2 fluxes with a depression of CO2 flux after noon, and the other had a single peak. In 2003, the maximum diurnal uptake and emitting value of CO2 were ?7.4 and 5.4 g·m?2·d?1 respectively and both occurred in July. While in 2004, the maximum diurnal uptake and release of CO2 were ?12.8 and 5.8 g·m?2·d?1 and occurred both in August. The grassland fixed 294.66 and 467.46 g CO2·m?2 in 2003 and 2004, and released 333.14 and 437.17 g CO2·m?2 in 2003 and 2004, respectively from May to September. Water availability and photosynthetic active radiation (PAR) are two important factors of controlling CO2 flux. Consecutive precipitation can cause reduction in the ability of ecosystem carbon exchange. Under favorable soil water conditions, daytime CO2 flux is dependent on PAR. CO2 flux, under soil water stress conditions, is obviously less than those under favorable soil water conditions, and there is a light saturation phenomena at PAR=1200 μmol·m?2·s?1. Soil respiration was temperature dependent when there was no soil water stress; otherwise, this response became accumulatively decoupled from soil temperature.  相似文献   

5.
As one component of ChinaFLUX, the measurement of CO2 flux using eddy covariance over subtropical planted coniferous ecosystem in Qianyanzhou was conducted for a long term. This paper discusses the seasonal dynamics of net ecosystem exchange (NEE), ecosystem respiration (RE) and gross ecosystem exchange (GEE) between the coniferous ecosystem and atmosphere along 2003 and 2004. The variations of NEE, RE and GEE show obvious seasonal variabilities and correlate to each other, i.e. lower in winter and drought season, but higher in summer; light, temperature and soil water content are the main factors determining NEE; air temperature and water vapor pressure deficit (VPD) influence NEE with stronger influence from VPD. Under the proper light condition, drought stress could decrease the temperature range for carbon capture in planted coniferous, air temperature and precipitation controlled RE; The NEE, RE, and GEE for planted coniferous in Qianyanzhou are ?387.2 g C·m?2 a?1, 1223.3 g C·m?2 a?1, ?1610.4 g C·m?2 a?1 in 2003 and ?423.8 g C·m?2 a?1, 1442.0 g C·m?2 a?1, ?1865.8 g C·m?2 a?1 in 2004, respectively, which suggest the intensive ability of plantation coniferous forest on carbon absorbing in Qianyanzhou.  相似文献   

6.
Based on the light-photosynthesis response measurement at leaf level, combined with over-and under-canopy eddy covariance measurements, research on photosynthetic characteristics of single trees and forest canopy was conducted. The relationship between light intensity and photosynthetic rates for leaves and canopy can be well fitted by a non-rectangular hyperbola model. Mongolian oak presented a high light compensation point, L cp (28 μmol·m?2·s?1), a light saturation point L sp (>1800 μmol·m?2·s?1), and a maximal net photosynthetic rate P max (9.96 μmol·m?2·s?1), which suggest that it is a typical heliophilous plant. Mono maple presented the highest apparent quantum efficiency α (0.066) but the lowest, L cp (16 μmol·m?2·s?1), L sp (≈800 μmol·m?2·s?1), and P max (4.51 μmol·m?2·s?1), which suggest that it is heliophilous plant. Korean pine showed the lowest α value but a higher P max, which suggest that it is a semi-heliophilous plant. At the canopy level, the values of both α and P max approached the upper limit of reported values in temperate forests, while L cp was within the lower limit. Canopy photosynthetic characteristics were well consistent with those of leaves. Both showed a high ability to photosynthesize. However, environmental stresses, especially high vapor pressure deficits, could significantly reduce the photosynthetic ability of leaves and canopy.  相似文献   

7.
Many studies on global climate have forecast major changes in the amounts and spatial patterns of precipitation that may significantly affect temperate grasslands in arid and semi-arid regions. As a part of ChinaFLUX, eddy covariance flux measurements were made at a semi-arid Leymus chinensis steppe in Inner Mongolia, China during 2003–2004 to quantify the response of carbon exchange to environmental changes. Results showed that gross ecosystem production (F GEP) and ecosystem respiration (R eco) of the steppe were significantly depressed by water stress due to lack of precipitation during the growing season. Temperature was the dominant factor affecting F GEP and R eco in 2003, whereas soil moisture imposed a significant influence on both R eco and F GEP in 2004. Under wet conditions, R eco showed an exponentially increasing trend with temperature (Q 10 = 2.0), but an apparent reduction in the value of R eco and its temperature sensitivity were observed during the periods of water stress (Q 10=1.6). Both heat and water stress can cause decrease in F GEP. The seasonality of ecosystem carbon exchange was strongly correlated with the variation of precipitation. With less precipitation in 2003, the steppe sequestrated carbon in June and July, and went into a senescence in early August due to water stress. As compared to 2003, the severe drought during the spring of 2004 delayed the growth of the steppe until late June, and the steppe became a CO2 sink from early July until mid-September, with ample precipitation in August. The semi-arid steppe released a total of 9.7 g C·m?2 from May 16 to the end of September 2003, whereas the net carbon budget during the same period in 2004 was close to zero. Long-term measurements over various grasslands are needed to quantify carbon balance in temperate grasslands.  相似文献   

8.
An open-path eddy covariance system was set up in Damxung rangeland station to measure the carbon flux from July to October, 2003. The canopy quantum yield (α) of alpine meadow was calculated by the linear function between the net ecosystem carbon dioxide exchange (NEE) and the photosynthetic active radiation (PAR) under low light, and how it was influenced by the temperature was also discussed. Results showed that the canopy α decreased almost linearly with temperature, with the decrease in every 1 °C increase of temperature similar to those measured on leaf level of C3 plant. At the beginning, the decrease of canopy α with temperature was 0.0005 μmol CO2·μmol?1 PAR; while it increased to 0.0008 μmol CO2·μmol?1 PAR in September, showing a rising trend with plant growing stages. Compared with the canopy α calculated with rectangular hyperbola function, the value in the paper was lower. However, the method advanced here has the advantages in examining the relationship between α and the key environmental factors, such as temperature.  相似文献   

9.
The study by the eddy covariance technique in the alpine shrub meadow of the Qinghai-Tibet Plateau in 2003 and 2004 showed that the net ecosystem carbon dioxide exchange (NEE) exhibited noticeable diurnal and annual variations, with more distinct daily changes during the warmer seasons. The CO2 emission of the shrub ecosystem culminated in April and September while the CO2 absorption capacity reached a maximum in July and August. The absorbed carbon dioxide during the two consecutive years was 231.4 and 274.8 g CO2·m?2 respectively, yielding an average of 253.1 gCO2·m?2 per year: that accounts for a large proportion of absorbed CO2 in the region. Obviously, the diurnal carbon flux was negatively related to temperature, radiation and other atmospheric factors. Still, minute discrepancies in kurtosis and duration of carbon emission/absorption were detected between 2003 and 2004. It was found that the CO2 flux in the daytime was similarly affected by photosynthetic photon flux density in both years. Temperature appears to be the most important determinant of CO2 flux: specifically, the high temperature during the plant growing season inhibits the carbon absorption capacity. One potential explanation is that soil respiration is enhanced under such condition. Analysis of biomass revealed that the annual net carbon fixed capacity of aboveground and belowground biomass was 544.0 in 2003 and 559.4 g C·m?2 in 2004, which coincided with the NEE absorption capacity (63.1 g C·m?2 in 2003 and 74.9 g C·m?2 in 2004) in the corresponding plant growing season.  相似文献   

10.
The light hydrocarbon composition of 209 natural gas samples and individual light hydrocarbon carbon isotopes of 53 natural gas samples from typical humic-sourced gas and sapropelic-sourced gas in the four basins of China have been determined and analyzed. Some identification parameters for humic-sourced gas and sapropelic-sourced gas are proposed or corrected. The differences of compound-specific δ 13C value of individual light hydrocarbon between humic-sourced gas and sapropelic-sourced gas have been founded. The humic-sourced gas has the distribution of δ 13Cbenzene> ?24‰, δ 13Ctoluene >?23‰, δ 13Ccyclohexane > ?24‰ and δ 13Cmethyl cyclohexane> ?24‰, while the sapropelic-sourced gas has the distribution of δ 13Cbenzene <?24‰, δ 13Ctoluene< ?24‰, δ 13Ccyclohexane< ?24‰ and δ 13Cmethyl cyclohexane< ?24‰. Among the components of C7 light hydrocarbon compound, such as normal heptane (nC7), methyl cyclohexane (MCH) and dimethyl cyclopentane (ΣDMCP), etc, relative contents of nC7 and MCH are influenced mainly by the source organic matter type of natural gas. Therefore, it is suggested that the gas with relative content of nC7 of more than 30% and relative content of MCH of less than 70% is sapropelic-sourced gas, while gas with relative content of nC7 of less than 35% and relative content of MCH of more than 50% is humic-sourced gas. Among components of C5–7 aliphatics, the gas with relative content of C5–7 normal alkane of more than 30% is sapropelic-sourced gas, while the gas with relative content of C5–7 normal alkane of less than 30% is humic-sourced gas. These paremeters have been suggested to identify humic-sourced gas and sapropelic-sourced gas.  相似文献   

11.
The distribution of the ionospheric currents during the geomagnetic storms of November 20–21, 2003, November 7–8, 2004, and November 9–10, 2004, depending on the IMF B y component, has been studied based on the data from the global network of magnetic stations. It has been indicated that, during geomagnetic disturbances, the westward electrojet intensity maximum is localized in the evening sector at IMF B y < 0 and in the morning sector at IMF B y > 0. The region of the westward electrojet intensity maximum shifts to morning hours with increasing positive B y values. Thus, the IMF azimuthal component forms not only the magnetospheric convection pattern during magnetic storms but is also responsible for the longitudinal position of ionospheric structures.  相似文献   

12.
Attenuation characteristics in the New Madrid Seismic Zone (NMSZ) are estimated from 157 local seismograph recordings out of 46 earthquakes of 2.6?≤?M?≤?4.1 with hypocentral distances up to 60 km and focal depths down to 25 km. Digital waveform seismograms were obtained from local earthquakes in the NMSZ recorded by the Center for Earthquake Research and Information (CERI) at the University of Memphis. Using the coda normalization method, we tried to determine Q values and geometrical spreading exponents at 13 center frequencies. The scatter of the data and trade-off between the geometrical spreading and the quality factor did not allow us to simultaneously derive both these parameters from inversion. Assuming 1/R 1.0 as the geometrical spreading function in the NMSZ, the Q P and Q S estimates increase with increasing frequency from 354 and 426 at 4 Hz to 729 and 1091 at 24 Hz, respectively. Fitting a power law equation to the Q estimates, we found the attenuation models for the P waves and S waves in the frequency range of 4 to 24 Hz as Q P?=?(115.80?±?1.36) f (0.495?±?0.129) and Q S?=?(161.34?±?1.73) f (0.613?±?0.067), respectively. We did not consider Q estimates from the coda normalization method for frequencies less than 4 Hz in the regression analysis since the decay of coda amplitude was not observed at most bandpass filtered seismograms for these frequencies. Q S/Q P?>?1, for 4?≤?f?≤?24 Hz as well as strong intrinsic attenuation, suggest that the crust beneath the NMSZ is partially fluid-saturated. Further, high scattering attenuation indicates the presence of a high level of small-scale heterogeneities inside the crust in this region.  相似文献   

13.
The dependence of the zonal geomagnetic indices (AE, Ap, Kp, Kn, and Dst) on the solar wind parameters (the electric field E y component, dynamic pressure P d and IMF irregularity σB) has been studied for two types of events: magnetic clouds and high-speed streams. Based on the empirical relationships, it has been established that the AE, Ap, Kp, and Kn indices are directly proportional to the E y value at E y < 12 mV m?1 and are inversely proportional to this value at E y > 12 mV m?1 for the first-type events. On the contrary, the dependence of Dst on E y is monotonous nonlinear. A linear dependence of all geomagnetic indices on E y is typical of the second-type events. It has been indicated that the specific features of geoeffectiveness of magnetic clouds and high-speed solar wind streams are caused by the dependence of the electric field potential across the polar cap on the electric field, solar wind dynamic pressure, and IMF fluctuations.  相似文献   

14.
The long-term and continuous carbon fluxes of Changbaishan temperate mixed forest (CBS), Qianyanzhou subtropical evergreen coniferous forest (QYZ), Dinghushan subtropical evergreen mixed forest (DHS) and Xishuangbana tropical rainforest (XSBN) have been measured with eddy covariance techniques. In 2003, different responses of carbon exchange to the environment appeared across the four ecosystems. At CBS, the carbon exchange was mainly determined by radiation and temperature. 0°C and 10°C were two important temperature thresholds; the former determined the length of the growing season and the latter affected the magnitude of carbon exchange. The maximum net ecosystem exchange (N EE) of CBS occurred in early summer because maximum ecosystem photosynthesis (G PP) occurred earlier than maximum ecosystem respiration (R e). During summer, QYZ experienced severe drought and N EE decreased significantly mainly as a result of the depression of G PP. At DHS and XSBN, N EE was higher in the drought season than the wet season, especially the conversion between carbon sink and source occurring during the transition season at XSBN. During the wet season, increased fog and humid weather resulted from the plentiful rainfall, the ecosystem G PP was dispressed. The Q 10 and annual respiration of XSBN were the highest among the four ecosystems, while the average daily respiration of CBS during the growing season was the highest. Annual N EE of CBS, QYZ, DHS and XSBN were 181.5, 360.9, 536.2 and ?320.0 g·C·m?2·a?1, respectively. From CBS to DHS, the temperature and precipitation increased with the decrease in latitude. The ratio of N EE/R e increased with latitude, while R e/G PP, ecosystem light use efficiency (L UE), precipitation use efficiency and average daily G PP decreased gradually. However, XSBN usually escaped such latitude trend probably because of the influence of the south-west monsoon climate which does not affect the other ecosystems. Long-term measurement and more research were necessary to understand the adaptation of forest ecosystems to climate change and to evaluate the ecosystem carbon balance due to the complexity of structure and function of forest ecosystems.  相似文献   

15.
The regularities in the southward drift of the ionospheric current centers and luminosity boundaries during strong magnetic storms of November 2003 and 2004 (with Dst ≈ ?400 and ?470 nT, respectively) are studied based on the global geomagnetic observations and TV measurements of auroras. It has been indicated that the eastward and westward electrojets in the dayside and nightside sectors simultaneously shift equatorward to minimal latitudes of Φ min ° ～53°–55°. It has been obtained that the Φ min ° latitude decreases with increasing negative values of Dst, IMF B z component, and westward electric field strength in the solar wind. The dependence of the electrojet equatorward shift velocity (V av) on the rate of IMF B z variations (ΔB z /Δt) has been determined. It is assumed that the electrojet dynamics along the meridian is caused by a change in the structure of the magnetosphere and electric fields in the solar wind and the Earth’s magnetosphere.  相似文献   

16.
To determine the relative deflections of the vertical from geodetic data and from astronomical measurements we used the method of equal altitudes, determining the time of passage by means of interrupted illumination of the field of view. The field of view of the telescope used (Zeiss Theo 010 and an astrolabe having an angle of 60°) was therefore supplied with five groups of seven horizontal fibres and during the passage of the two images the field of view was illuminated by a neon tube for a period of about 0·15 s every three seconds. The neon tube was connected either directly to an OMA 50 time signal by means of a transistor receiver or to a chronometer. The calculation was performed by means of relations (1) and (2). Apart from the corrections usually introduced, the personal-instrumental error (containing also a correction from the decimal equation) of the longitudeo λ and the correctiona η of the component η were also determined from the measurements. The correctionso λ=?0·069s ando η=?0·66″ also contain a correction from the decimal equation. Its value iso λ ′ =?0·030s for the longitude. The lago λ?o λ ′ in reading the interpolation was ?0·039 s. The valueo η=?0·66″ was introduced into the calculation of the vertical components η obtained from measurements in the High Tatras. The values of the corrections are given in Tab. 1. The method permits measurement of the passages of stars through the almucantar in the meridian. No conclusive proof was found for the impersonality (Tab. 1). The method was verified practically when determining the relative deflections of the vertical in the High Tatras for refining altitude measurements. The results are given in Tab. 2 and Fig. 2. The course of the quasigeoid profile in the Kriváňmeridian was also found (Fig. 3).  相似文献   

17.
The electric field generation at the front of the current pulse, which originates in a coronal magnetic loop owing to the development of the Rayleigh–Taylor magnetic instability at loop footpoints, has been considered. During the τA ≈ l/V A ≈ 5?25 s time (where l is the plasma plume height entering a magnetic loop as a result of the Rayleigh–Taylor instability), a disturbance related to the magnetic field tension B ?(r,t), “escapes” the instability region with the Alfvén velocity in this case. As a result, an electric current pulse Iz(z ? V A t), at the front of which an induction magnetic field E z, which is directed along the magnetic tube axis and can therefore accelerate particles, starts propagating along a magnetic loop with a characteristic scale of Δξ ≈ l. In the case of sufficiently large currents, when B ? 2/8π > p, an electric current pulse propagates nonlinearly, and a relatively large longitudinal electric field originates E z ≈ 2I z 3 V A/c 4a2Bz 2l, which can be larger than the Dreicer field, depending on the electric current value.  相似文献   

18.
To describe the cumulative distribution of the number of lithospheric plates over areas S, the dependence N(≥S) ～ S ?0.33 was proposed by Bird [2003]. Based on dimension considerations, the dependence N(≥S) ～ (?/S)1/3, where ? is the generation rate of kinetic energy of convection in the mantle estimated at 10?11 m2/s3, is proposed. The analogy of plate formation with developed hydrodynamic turbulence and other processes involving an energy input into the system and its dissipation is considered. Simple experiments on random partitioning of a surface into polygons gave their cumulative distributions over areas resembling those observed for lithospheric plates. This has led to the conclusion that the plate distribution pattern is characteristic of the random partitioning of surfaces.  相似文献   

19.
Liu  Yunfen  Yu  Guirui  Wen  Xuefa  Wang  Yinghong  Song  Xia  Li  Ju  Sun  Xiaomin  Yang  Fengting  Chen  Yongrui  Liu  Qijing 《中国科学:地球科学(英文版)》2006,49(2):99-109

As one component of ChinaFLUX, the measurement of CO2 flux using eddy covariance over subtropical planted coniferous ecosystem in Qianyanzhou was conducted for a long term. This paper discusses the seasonal dynamics of net ecosystem exchange (NEE), ecosystem respiration (RE) and gross ecosystem exchange (GEE) between the coniferous ecosystem and atmosphere along 2003 and 2004. The variations of NEE, RE and GEE show obvious seasonal variabilities and correlate to each other, i.e. lower in winter and drought season, but higher in summer; light, temperature and soil water content are the main factors determining NEE; air temperature and water vapor pressure deficit (VPD) influence NEE with stronger influence from VPD. Under the proper light condition, drought stress could decrease the temperature range for carbon capture in planted coniferous, air temperature and precipitation controlled RE; The NEE, RE, and GEE for planted coniferous in Qianyanzhou are −387.2 g C·m−2 a−1, 1223.3 g C·m−2 a−1, −1610.4 g C·m−2 a−1 in 2003 and −423.8 g C·m−2 a−1, 1442.0 g C·m−2 a−1, −1865.8 g C·m−2 a−1 in 2004, respectively, which suggest the intensive ability of plantation coniferous forest on carbon absorbing in Qianyanzhou.

  相似文献   

20.
In this study, continuous wavelet transform is applied to estimate the frequency-dependent quality factor of shear waves, Q S , in northwestern Iran. The dataset used in this study includes velocigrams of more than 50 events with magnitudes between 4.0 and 6.5, which have occurred in the study area. The CWT-based method shows a high-resolution technique for the estimation of S-wave frequency-dependent attenuation. The quality factor values are determined in the form of a power law as Q S (f)?=?(147?±?16)f 0.71?±?0.02 and (126?±?12)f 0.73?±?0.02 for vertical and horizontal components, respectively, where f is between 0.9 and 12 Hz. Furthermore, in order to verify the reliability of the suggested Q S estimator method, an additional test is performed by using accelerograms of Ahar-Varzaghan dual earthquakes on August 11, 2012, of moment magnitudes 6.4 and 6.3 and their aftershocks. Results indicate that the estimated Q S values from CWT-based method are not very sensitive to the numbers and types of waveforms used (velocity or acceleration).  相似文献   

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