Unlike in the developed countries, Ethiopia does not have carbon inventories and databank to monitor and enhance carbon sequestration potential of different forests. Only small efforts have been made so far to assess the biomass and soil carbon sequestration at micro-level. This study was carried out to obtain sufficient information about the carbon stock potential of Gerba-Dima forest in south-western Ethiopia. A total of 90 sample plots were laid by employing stratified random sampling. Nested plots were used to collect data of the four carbon pools. For trees with a diameter range of 5 cm < diameter < 20 cm, the carbon stock was assessed from a plot size of 49 m2 (7 m * 7 m). For trees with a diameter range of 20 cm < diameter < 50 cm, the carbon stock was assessed from a plot size of 625 m2 (25 m * 25 m). For trees > 50 cm diameter, an additional larger sample of 35 * 35 m2 was used. Litter, herb and soil data were collected from 1 m2 subplot established at the center of each nested plot. To compute the above ground biomass carbon stock of trees and shrubs with DBH > 5 cm, their DBH and height were measured. The biomass carbon assessment of woody species having DBH < 5 cm, litter and herb were conducted by measuring their fresh weight in the field and dry weight in the laboratory.
Results
The mean total carbon stock density of Gerba-Dima forest was found to be 508.9 tons carbon ha−1, out of which 243.8, 45.97, 0.03 and 219.1 tons carbon ha−1 were stored in the above ground biomass, below ground biomass, litter biomass and soil organic carbon, respectively.
Conclusions
The existence of high carbon stock in the study forest shows the potential of the area for climate change mitigation. Thus, all stakeholders at the local and national level should work together to implement effective conservation measures and get benefit from the biocarbon fund.
River runoff from the four largest Siberian river basins (the Ob, Yenisei, Lena, and Kolyma) considerably contributes to freshwater flux into the Arctic Ocean from the Eurasian continent. However, the effects of variation in snow cover fraction on the ecohydrological variations in these basins are not well understood. In this study, we analysed the spatiotemporal variability of the maximum snow cover fraction (SCFmax) in the four Siberian river basins. We compared the SCFmax from 2000 to 2016 with data in terms of monthly temperature and precipitation, night-time surface temperatures, the terrestrial water storage anomaly (TWSA), the normalised difference vegetation index (NDVI), and river runoff. Our results exhibit a decreasing trend in the April SCFmax values since 2000, largely in response to warming air temperatures in April. We identified snowmelt water as the dominant control on the observed increase in the runoff contribution in May across all four Siberian river basins. In addition, we detected that the interannual river runoff was predominantly controlled by interannual variations in the TWSA. The NDVI in June was strongly controlled by the timing of the snowmelt along with the surface air temperature and TWSA in June. The rate of increase in the freshwater flux from the four Siberian rivers decreased from 2000 to 2016, exhibiting large interannual variations corresponding to interannual variations in the TWSA. However, we identified a clear increase trend in the freshwater flux of ~4 km3/year when analysing the long-term 39-year historical record (1978–2016). Our results suggest that continued global warming will accelerate the transition towards the earlier timing of snowmelt and spring freshwater flux into the Arctic Ocean. Our findings also highlight the effects of earlier snowmelt on ecohydrological changes in the Northern Hemisphere. 相似文献
We have developed a near-field vector beam measurement system covering the range of frequencies from 385 to 500 GHz. The measurement set-up is capable of measurements with dynamic range exceeding 50 dB and amplitude and phase stability respectively of 0.1 dB/h and 1 degree/5 min at room temperature. Beam patterns of the ALMA band 8 corrugated horns and receiver optics block were measured at room temperature and lately compared with physical optics calculations obtained in the far-field. Both co-polar and cross-polar beam patterns of a qualification model of the ALMA band 8 cartridge cooled in a cartridge-test-cryostat have also been measured in the near-field as a detector of a submillimeter vector network analyzer. The measurements presented in this work refer to the lowest, middle and upper frequencies of band 8. The comparisons between software model and experimental measurements at these frequencies show good agreement down to ?30 dB for the main polarization component. The cross-polarization level of the beam propagating through the receiver optics block was also characterized. We found that a cross-polarization level better than ?28 dB can be achieved at all measured frequencies. The measured beam pattern of this receiver corresponds to efficiency of greater than 92% at the sub reflector (diameter of 750 mm) of the ALMA 12 m optics. 相似文献
The orientation of the atmospheric angular momentum vector of Titan and its temporal variation predicted by a general circulation model are analysed and interpreted. The atmospheric angular momentum vector is tilted by a few degrees from the polar axis and the vector rotates (precesses) westward with a constant period of 1 Titan day. The fast westward rotation is likely to be caused by migrating diurnal thermal tides. The tilt is almost cancelled out in the troposphere by the wavenumber 2 pattern of Saturn's gravitational tide, but is more pronounced in the stratosphere, where thermal tides are significant. The predicted tilt angle and the equatorial angular momentum vary with season and maximize when the hemispheric asymmetry of the axial angular momentum or superrotation attains its peak. 相似文献
This study investigates the convective boundary layer (CBL) that develops over anon-homogeneous surface under different thermal and dynamic conditions. Analysesare based on data obtained from a Russian research aircraft equipped with turbulentsensors during the GAME-Siberia experiment over Yakutsk in Siberia, from April to June 2000.Mesoscale thermal internal boundary layers (MTIBLs) that radically modified CBLdevelopment were observed under unstable atmospheric conditions. It was found thatMTIBLs strongly influenced the vertical and horizontal structures of virtual potentialtemperature, specific humidity and, most notably, the vertical sensible and latent heatfluxes. MTIBLs in the vicinity of the Lena River lowlands were confirmed by clouddistributions in satellite pictures.MTIBLs spread through the entire CBL and radically modify its structure if the CBL isunstable, and strong thermal features on the underlying surface have horizontal scalesexceeding 10 km. MTIBL detection is facilitated through the use of special parameterslinking shear stress and convective motion.The turbulent structure of the CBL with and without MTIBLs was scaled usingthe mosaic or flux aggregate approach. A non-dimensional parameterLRau/Lhetero (where LRau is Raupach's length and Lhetero is the horizontal scale of the surface heterogeneity)estimates the application limit of similarity and local similarity scaling models forthe mosaic parts over the surface. Normalized vertical profiles of wind speed, airtemperature, turbulent sensible and latent heat fluxes for the mosaic parts withLRauLhetero < 1 could be estimated by typical scalingcurves for the homogeneous CBL. Traditional similarity scaling models for the CBLcould not be applied for the mosaic parts with LRau/Lhetero > 1.For some horizontally non-homogeneous CBLs, horizontal sensible heat fluxes werecomparable with the vertical fluxes. The largest horizontal sensible heat fluxes occurred at the top of the surface layer and below the top of the CBL.Formerly affiliated to the Frontier Observational Research System for Global ChangeFormerly affiliated to the Frontier Observational Research System for Global Change 相似文献
An ore value-tonnage diagram has been proposed for assessing mineral resources. Diagrams of W+Mo, and Pb+Zn deposits show
a good linearity between ore value and logarithms of cumulative ore tonnage. Diagrams of the massive sulfide, orthomagmatic,
placer, porphyry, replacement, and stratabound types are also linear. It is assumed, therefore, that deposits of each of these
commodities and these types belong to a single population. In contrast, the ore value-tonnage relations of all the deposits
analyzed here is approximated by the combination of two exponential functions. The same feature is seen for deposits of the
Cu+W+Mo, Cu+Pb+Zn, and Au+Ag commodities, and of the vein and unconformity-related types. This suggests that deposits belonging
to each of such categories are divided into the high and low value groups. We can expect, accordingly, to find high value
deposits of such categories. 相似文献
This paper analyzes soft X-ray spectra obtained from the Hinotori spacecraft for the investigation of plasma motions during the initial phase of the great flare, 1982 June 6. The wavelength calibration of the scanning spectrometers is determined from information on the spacecraft attitude and from the position of the Fexxv resonance line during the decay phase. Hard X-ray bursts, nonthermal line broadenings and blueshifted components in X-ray lines are temporally correlated with time differences of 0–30 s. The possible contribution of the blueshifted component to the line width decreases more rapidly than the nonthermal broadening, which suggests dominant plasma motions are taking place at higher and higher altitude in the corona, because of the increase of electron density in flaring loops. The evolution of the input kinetic energy content to the thermal plasma inferred from line broadenings in the impulsive phase resembles that of the thermal energy content in the source of the Fexxvi emission, which is different from that deduced for Fexxv source. This suggests that the origins of the nonthermal line broadening and Fexxvi source are closely coupled. 相似文献
A phase transition in pure CaSiO3 perovskite was investigated at 27 to 72 GPa and 300 to 819 K by in-situ X-ray diffraction experiments in an externally-heated diamond-anvil cell. The results show that CaSiO3 perovskite takes a tetragonal form at 300 K and undergoes phase transition to a cubic structure above 490–580 K in a pressure range studied here. The transition boundary is strongly temperature-dependent with a slightly positive dT / dP slope of 1.1 (± 1.3) K/GPa. It is known that the transition temperature depends on Al2O3 content dissolved in CaSiO3 perovskite [Kurashina et al., Phys. Earth Planet. Inter. 145 (2004) 67–74]. The phase transition in CaSiO3(+ 3 wt.% Al2O3) perovskite therefore could occur in a cold subducted mid-oceanic ridge basalt (MORB) crust at about 1200 K in the upper- to mid-lower mantle. This phase transition is possibly ferroelastic-type and may cause large seismic anomalies in a wide depth range. 相似文献