Biological sources of soil CO2 under Larix sibirica and Pinus sylvestris

Mycorrhizal ingrowth collars were used to study the effect of tree species on the seasonal dynamics of carbon dioxide flux from three major sources of soil respiration: (1) plant roots, (2) mycorrhizal hyphae, and (3) microorganisms. Distinct seasonality in carbon transport to mycorrhizae was revealed, with its highest values being observed during the second half of the growing season. The annual amount of C transferred through mycorrhizae did not differ between the two tree species, and the contribution of mycorrhizae to soil surface CO₂ emission was about 20%.     

Estimating ‘rhizosphere priming effect’: Comparison of the indirect <Emphasis Type="Italic">y</Emphasis>-intercept regression approach and direct bare plot Approach

Determined the contribution of root derived CO₂ efflux to total CO₂ efflux (including root and non-root derived CO₂ efflux) is import to grope the mechanism of CO₂ efflux, however, becaused of ‘rhizoshere priming effect’ (RPE), it is difficult to achieve in practice. In this study, we attempted to estimate the RPE via comparing basal soil respiration (R_b) achieved by two different methods namely, y-intercept regression and direct bare plot approach in an arid cotton field, central Asia. On the basis of the y-intercept of linear regressions between below-ground respiration (BGR) and root biomass, R_b was indirectly calculated. Comparing with the first approach, the second approach involved direct measurements of soil respiration from bare plots. R_b estimated by y-intercept method contained the component of RPE whereas direct bare plot did not. We found that RPE showed a phenological trend with highest value in flowering stage at 0.145 g CO₂ m^–2 h^–1 and lowest at budding stage (0.007 g CO₂ m^–2 s^–1), even after the data had been corrected for the influence of soil temperature. We concluded that RPE needed to be considered when R_b was estimated by y-intercept approach.     

Soil respiration in model plantations under conditions of elevated CO<Subscript>2</Subscript> in the atmosphere (Hokkaido Island,Japan)

The influence of long-term exposure of model plantations at elevated atmospheric CO₂ (550 ppm) on soil respiration under natural conditions has been studied using an automated Free-Air CO₂ Enrichment (FACE) system at the Hokkaido University, Japan. In the course of the experiment, an attempt has been made to simulate the effect of forthcoming climate change on the process of CO₂ emission from different soil types.     

A subsystem input–output decomposition analysis of CO<Subscript>2</Subscript> emissions in the service sectors: a case study of Beijing,China

The carbon emissions in service sectors have attracted increasing attention around the world. However, few studies have examined the driving forces for CO₂ emissions from service sectors in developing countries. With the process of accelerating industrialization, China’s service sectors are facing growing pressure to pursue energy savings and emission reductions, especially in several developed regions. In this paper, in order to better understand how CO₂ emissions in Beijing’s service sectors have evolved, we utilized a subsystem input–output decomposition analysis to study the pattern and driving factors of consumption-based emissions in Beijing’s service sectors. The results showed that the transportation sector and the Scientific Studies Technical Services sector caused the most CO₂ emissions in Beijing’s service sectors. The emission intensity effect potentially reduced CO₂ emissions by 10,833 Mt, primarily due to the decreased energy intensity of non-service sectors. Effects of demand and technology were mainly responsible for the increased CO₂ emissions in Beijing’s service sectors. Such influence was mainly related to the external component of service sectors, indicating a strong pull effect exerted by service sectors on non-service sectors. Thus, decarbonizing the supply chain of service sectors and improving the energy intensity are necessary to alleviate CO₂ emissions in Beijing.     

The Water Regime of Black Saxaul in Various Environmental Conditions of the Central Asian Desert

A water regime, estimated based on transpiration rate, water content of shoots, concentration of cell sap, and water consumption per unit area, was studied for black saxaul. The seasonal course of black saxaul transpiration during the growing season increased by the middle of summer (July) and decreased towards autumn. The highest transpiration rate of black saxaul was found in Karnabchul, where ground waters poorly mineralized, located at a depth of 14–20 m in nonsaline soils. The lowest transpiration rate was detected in the Nishan “steppe,” where ground waters were also located at 14–20 m, however they were highly mineralized, and the soil profile was highly salinated. The Southwestern Kyzylkum, characterized by ground waters at a very deep location (more than 100 m) and low soil salinity, occupied an intermediate position in terms of transpiration rate. The maximal water consumption for transpiration during the vegetation period was observed in Karnabchulat 642.5 mm/ha, then in the Nishan “steppe” at 352.5. The minimal value was detected in the Southwestern Kyzylkum at 171.0.

     

Economic growth and CO<Subscript>2</Subscript> emissions

This article considers a planner’s optimum control exercise with environmental pollution and derives a testable link between the growth rates of consumption and pollution. The link is then empirically estimated for the case of CO₂ emissions for a sample consisting of the union of top 25 countries in terms of CO₂ emissions, population and per capita GNP. The analysis suggests that the interrelationship between the growth rates of CO₂ emission and economic development is mostly significant for countries that have a high level of CO₂ emissions and population.     

On the Nexus of SO<Subscript>2</Subscript> and CO<Subscript>2</Subscript> emissions in China: the ancillary benefits of CO<Subscript>2</Subscript> emission reductions

This paper examines the issue of ancillary benefits by linking sulfur dioxide (SO₂) emission to CO₂ emission using a panel of 29 Chinese provinces over the period 1995–2007. In the presence of non-stationarity and cointegrating properties of these two data series, this paper applies the panel cointegration techniques to examine both the long-run and short-run elasticities of SO₂ with respect to CO₂. The major findings are that: (1) there exhibits a stable long-run equilibrium relationship between the SO₂ and CO₂ emission with the long-run elasticity being 2.15; (2) there exists a short-run relationship between these two emissions with the short-run elasticity being 0.04. In addition, following an exogenous shock that causes a deviation from the long-run equilibrium, it would take approximately 15 years for SO₂ emission to revert toward the long-run equilibrium path with an average annual convergence rate of 6.5%; (3) the derived ancillary benefits that is generated from one metric ton of CO₂ emission reduction, are 11.77 Yuan (approximately US1.7) in the short run and 196.16 Yuan (US 1.7) in the short run and 196.16 Yuan (US 30) in the long run. These findings are not only crucial from the econometric modeling perspective, but also have important policy implications.     

Analysis of the soil water balance for large-scale reforestation with <Emphasis Type="Italic">Eucommia ulmoides</Emphasis> in the hilly red soil region of southern China

Returning farmland to forests is important for the protection of ecological values. Eucommia ulmoides is considered to be a suitable species for reforestation in the hilly red soil region of southern China. The objective of this study was to investigate the relationship between the water supply and demand of an E. ulmoides plantation to provide insights into the feasibility of large-scale planting for ecological restoration and forest management activities in the hilly red soil region of southern China. With the measured precipitation, surface runoff and interflow and actual evapotranspiration (ET_c) estimated by the modified P–M model, soil water storage (SWS) was estimated based on the water balance equation. Monthly variations of SWS were then compared with in situ measured SWS. The results showed that the estimated mean monthly water losses (the sum of the surface runoff, interflow and ET_c) were 139.8 mm in a wet year and 120.0 mm in a dry year, while the measured mean monthly water input values (net precipitation) were 131.2 mm in a wet year and 70.8 mm in a dry year. Net soil water storage (ΔSWS) was negative in each month of the growing season in a dry year, but the soil water deficit was replenished during the following season. The model performance showed that the modified P–M model can be adapted to estimate the soil water storage in other forest catchments where no adequate in situ data are available. As a result of estimating the water balance and observing soil water storage in two different hydrological years, E. ulmoides is recommended as a suitable forest rehabilitation species in the study area, and a suitable plant region has been defined by the GIS technique based on the water balance model.     

Temporal signatures of advective versus diffusive radon transport at a geothermal zone in Central Nepal

Temporal variation of radon-222 concentration was studied at the Syabru-Bensi hot springs, located on the Main Central Thrust zone in Central Nepal. This site is characterized by several carbon dioxide discharges having maximum fluxes larger than 10 kg m⁻² d⁻¹. Radon concentration was monitored with autonomous Barasol™ probes between January 2008 and November 2009 in two small natural cavities with high CO₂ concentration and at six locations in the soil: four points having a high flux, and two background reference points. At the reference points, dominated by radon diffusion, radon concentration was stable from January to May, with mean values of 22 ± 6.9 and 37 ± 5.5 kBq m⁻³, but was affected by a large increase, of about a factor of 2 and 1.6, respectively, during the monsoon season from June to September. At the points dominated by CO₂ advection, by contrast, radon concentration showed higher mean values 39.0 ± 2.6 to 78 ± 1.4 kBq m⁻³, remarkably stable throughout the year with small long-term variation, including a possible modulation of period around 6 months. A significant difference between the diffusion dominated reference points and the advection-dominated points also emerged when studying the diurnal S₁ and semi-diurnal S₂ periodic components. At the advection-dominated points, radon concentration did not exhibit S₁ or S₂ components. At the reference points, however, the S₂ component, associated with barometric tide, could be identified during the dry season, but only when the probe was installed at shallow depth. The S₁ component, associated with thermal and possibly barometric diurnal forcing, was systematically observed, especially during monsoon season. The remarkable short-term and long-term temporal stability of the radon concentration at the advection-dominated points, which suggests a strong pressure source at depth, may be an important asset to detect possible temporal variations associated with the seismic cycle.     

Impacts of economic growth and urbanization on CO<Subscript>2</Subscript> emissions: regional differences in China based on panel estimation

This study analyzed the impact of urbanization and the level of economic development on CO₂ emissions using the STIRPAT model and provincial panel data for China. This study classified the 29 provinces of China into three groups (eastern, central, and western regions) and examined regional differences in the environmental impacts of urbanization and economic development levels. The results demonstrated that there was an inverted U-shaped relationship between urbanization and CO₂ emissions in the central and western regions of China. However, we did not confirm the environmental Kuznets curve relationship between urbanization and CO₂ emissions in eastern China, where CO₂ emissions increase monotonically with urbanization. This study showed that the impacts of urbanization differ considerably. There was a U-shaped relationship between economic growth and CO₂ emissions. However, the point of inflexion was very low, which indicates that economic growth will promote CO₂ emissions in China. The share of the industry output value had a marginal incremental effect on CO₂ emissions. There was a decreasing effect of population scale on CO₂ emissions. Energy efficiency is the main factor that restrains CO₂ emissions, and the effect was higher in regions with low energy efficiency.     

Regional differences and influencing factors in the CO<Subscript>2</Subscript> emissions of China’s power industry based on the panel data models considering power-consuming efficiency factor

With the economic development, China has become the largest CO₂ emissions country. China’s power industry CO₂ emissions accounted for about 50% of total CO₂ emissions. Therefore, exploring major drivers of CO₂ emissions is critical to mitigating its CO₂ emissions in power industry. Many studies considered the time series model to analyze the national influences factors of CO₂ emissions. But this paper focuses on regional differences in CO₂ emissions and adopts panel data models to explore the major impact factors of CO₂ emissions in the power industry at the regional and provincial perspectives. The results indicate economic growth level plays a dominant role in reducing CO₂ emissions. The power-consuming efficiency on the demand side has large potential to mitigate CO₂ emissions, but its influences are different in three regions. The impacts of the electric power structure on CO₂ emissions decline from the eastern region to the central and western regions. The influence of urbanization and industrialization also has significant regional differences. Therefore, the governments should consider the influencing factors and regional differences and formulate appropriate policies to decrease CO₂ emissions in the power industry.     

Profile of Methane Concentrations in Soil and Atmosphere in Alpine Steppe Ecosystem on Tibetan Plateau

The methane concentration profile from -1.5m depth in soil to 32m height in air was measured in alpine steppe located in the permafrost area. Methane concentrations showed widely variations both in air and in soil during the study period. The mean concentrations in atmosphere were all higher than those in soil, and the highest methane concentration was found in air at the height of 16m with the lowest concentration occurring at the depth of 1.5m in soil. The variations of atmospheric methane concentrations did not show any clear pattern both temporally and spatially, although they exhibited a more steadystable state than those in soil. During the seasonal variations, the methane concentrations at different depths in soil were significantly correlated （R^2〉0.6） with each other comparing to the weak correlations （R^2〈0.2） between the atmospheric concentra- tions at different heights. Mean methane concentrations in soil significantly decreased with depth. This was the compositive influence of the decreasing production rates and the increasing methane oxidation rates, which was caused by the descent soil moisture with depth. Although the methane concentrations at all depths varied widely during the growing season, they showed very distinct temporal variations in the non-growing season. It was indicated from the literatures that methane oxidation rates were positively correlated with soil temperature. The higher methane concentrations in soil during the winter were determined by the lower methane oxidation rates with decreasing soil temperatures, whereas methane production rates had no reaction to the lower temperature. Relations between methane contribution and other environmental factors were not discussed in this paper for lacking of data, which impulse us to carry out further and more detailed studies in this unique area.     

Tourism and CO<Subscript>2</Subscript> emissions nexus in Southeast Asia: new evidence from panel estimation

The past decade has seen the rapid development of the tourist industry in Southeast Asia. There is increasing concern that tourism is highly affecting CO₂ emissions, but the nature of the relationship is still unclear. The main target of this paper is to investigate the existence of a linear and/or nonlinear relationship between tourism and CO₂ emissions in the five most important countries located in Southeast Asia, using the panel cointegration and pooled mean group techniques. The results indicate that tourism and CO₂ emissions are cointegrated, implying that tourism affects CO₂ emissions in the long run. Our findings support the nonlinear relationship between tourism and emissions as well as economic activities and CO₂ emissions. Accordingly, an inverted U-shaped relationship exists between tourism and emissions confirming the existence of an Environmental Kuznets Curve in the Southeast Asian tourism industry. Furthermore, the empirical results show that economic activities and energy consumption greatly increase emissions.     

绵阳市代表性点位土壤多环芳烃剖面分布特征

通过挑选绵阳市有代表性的点位土壤柱，应用GC MS分析土壤柱垂直剖面中多环芳烃的含量水平，得出其垂直剖面分布特征。结果表明：5~20 cm深度中的PAHs含量最高，40 cm以下则含量锐减。由于表层（0～5 cm）土壤与大气之间的土气交换频繁，PAHs含量相对较低，而5~20 cm处土壤受到表层土壤的遮盖，PAHs富集较高，含量达到整个土壤柱最高值。多环芳烃总体垂直剖面分布特征表现出随深度增加含量减少的趋势。PAHs总含量以江油市点位(33024 ng/g)最高，其次是三台县点位(29989 ng/g)，最低是游仙区点位(11274 ng/g)。研究区主要污染物为Nap、Phe和Chr/y。其中不同的土质、种植物都能影响PAHs的富集和迁移速率，导致含量在不同深度上产生变化。此外，参照有关环境质量标准，发现PAHs总量上江油市点位与三台县点位属于轻微污染、游仙区点位则属于无污染。     

Persistence of radon-222 flux during monsoon at a geothermal zone in Nepal

The Syabru-Bensi hydrothermal zone, Langtang region (Nepal), is characterized by high radon-222 and CO₂ discharge. Seasonal variations of gas fluxes were studied on a reference transect in a newly discovered gas discharge zone. Radon-222 and CO₂ fluxes were measured with the accumulation chamber technique, coupled with the scintillation flask method for radon. In the reference transect, fluxes reach exceptional mean values, as high as 8700 ± 1500 g m⁻² d⁻¹ for CO₂ and 3400 ± 100 × 10⁻³ Bq m⁻² s⁻¹ for radon. Gases fluxes were measured in September 2007 during the monsoon and during the dry winter season, in December 2007 to January 2008 and in December 2008 to January 2009. Contrary to expectations, radon and its carrier gas fluxes were similar during both seasons. The integrated flux along this transect was approximately the same for radon, with a small increase of 11 ± 4% during the wet season, whereas it was reduced by 38 ± 5% during the monsoon for CO₂. In order to account for the persistence of the high gas emissions during monsoon, watering experiments have been performed at selected radon measurement points. After watering, radon flux decreased within 5 min by a factor of 2–7 depending on the point. Subsequently, it returned to its original value, firstly, by an initial partial recovery within 3–4 h, followed by a slow relaxation, lasting around 10 h and possibly superimposed by diurnal variations. Monsoon, in this part of the Himalayas, proceeds generally by brutal rainfall events separated by two- or three-day lapses. Thus, the recovery ability shown in the watering experiments accounts for the observed long-term persistence of gas discharge. This persistence is an important asset for long-term monitoring, for example to study possible temporal variations associated with stress accumulation and release.     

Depth profiles of radiocarbon and carbon isotopic compositions of organic matter and CO2 in a forest soil

Depth profiles of the specific activities of (14)C and carbon isotopic compositions (Delta(14)C, delta(13)C) in soil organic matter and soil CO(2) in a Japanese larch forest were determined. For investigating the transport of CO(2) in soil, specific activities of (14)C, Delta(14)C and delta(13)C in the organic layer, and atmospheric CO(2) in the same forest area were also determined. The specific activity of (14)C and Delta(14)C in the soil organic matter decreased with the increase in depth of 0-60cm, while that of soil CO(2) did not vary greatly at a soil depth of 13-73cm and was more prevalent than that of atmospheric CO(2). Peaks of specific activities of (14)C appeared at the depth of 0-4cm and Delta(14)C values were positive in the depth range from 0 to 15cm. These results suggest that the present soil at a depth of 0-4cm had been produced from the mid-1950s up until 1963, and the bomb C had reached the depth of 15cm in the objective soil area. The delta(13)C in the soil organic matter increased at the depth of 0-55cm, while that of soil CO(2) collected on 8 November 2004 decreased rapidly at the depth of 0-13cm and only slightly at the depth of 53-73cm. By combining the Delta(14)C and delta(13)C of the respective components and using the Keeling plot approach it was made clear that the entering of atmospheric CO(2) showed a large contribution to soil CO(2) at the depth of 0-13cm and a negligible contribution at the depth of 53-73cm for soil air collected on 8 November 2004. Respiration of live roots was presumed to be the main source of soil CO(2) at the depth of 53-73cm on 8 November 2004.     

The Rate of Carbon Dioxide Emission into the Atmosphere from a Southern Karelian Mesooligotrophic Bog

Carbon dioxide exchange in the intact and reclaimed sites of a woodless mesooligotrophic dwarf shrub–cotton grass–sphagnum bog was studied in field experiments. The average values of gross respiration in the ecosystem over the warm period (including respiration of plant cover, CO₂emission from peat, and CO₂flow from the litter) were 3.17 and 6.11 g CO₂/m²per day in the natural and drained sites, respectively.     

安徽省沿江地区棉花生长季气候变化特征及其对产量的影响

为进一步了解安徽省沿江地区棉花生长季气候变化特征及其对产量的影响，以安徽省沿江地区12个棉花主产市、县气象观测站1961～2010年逐日平均气温、降水量和日照时数气象数据为基础，采用线性趋势法和Mann Kendall非参数检验法，分析了平均气温、≥10℃积温、降水量、日照时数等气象要素的变化特征，并讨论其变化对棉花气象产量的影响。结果表明：近50 a，安徽省沿江地区棉花生长季平均气温和≥10℃积温均呈明显增加趋势(P<001)，平均每10 a分别增加016℃和3713℃·d；降水量无明显变化趋势(P>005)；日照时数显著减少(P<001)，平均每10 a减少4692 h。棉花气象产量与生长季降水量、日照时数呈极显著相关关系，与平均气温、≥10℃积温相关不明显；平均气温、≥10℃积温和日照时数的增加均有利于棉花产量的提高，而降水过多不利于棉花产量的形成     

长江河口九段沙上沙湿地芦苇与土壤之间营养元素的灰色关联分析

为探明生长季不同时期芦苇湿地生态系统植物与土壤之间营养元素的关系，利用灰色关联分析方法，对长江河口九段沙上沙芦苇湿地的芦苇营养元素吸收量与土壤营养元素含量之间的关联度进行了研究。结果表明：芦苇主要从0～15 cm土壤吸取N元素，从15～40 cm土壤获取P、K元素，而从40～60 cm土壤吸收N、P、K元素量都较少。芦苇-土壤之间营养元素关联度排序为：4月为N＞K＞P；5月为P＞K＞N，6～8月为K＞P＞N；9～11月为N＞K＞P；12月为P＞N＞K。同一营养元素不同时期芦苇-土壤之间关联度也存在差异，芦苇与土壤营养元素N、P、K元素关联最密切时期分别出现在9、12与6月，均与上层土壤营养元素关联最密切。9、12与6月分别为芦苇-土壤之间N、P、K元素迁移、转化与循环的活跃时期，上层土壤是其活动相对重要的场所。芦苇生长过程中吸收土壤营养元素均存在时空差异，不同时期芦苇对不同深度土壤的营养元素吸收强度也不尽相同。芦苇地下部分不同部位与土壤中营养元素种类的关联度排序相同，而芦苇地上部分的排序则不同。     

Subsurface nutrient modelling using finite element model under Boro rice cropping system

Boro rice, an emerging low-risk crop variety of rice, cultivated using residual or stored water after Kharif season. To enhance the quality and production of rice, potassium (K) and phosphorus (P) are the common constituents of agricultural fertilizers. However, excess application of fertilizers causes leaching of nutrients and contaminates the groundwater system. Therefore, assessment and optimization of fertilizer dose are needed for better management of fertilizers. Towards this, the present study determines the path, persistence, and mobility of K and P under the Boro rice cropping system. The experimental site consisted of four plots having Boro rice with four different fertilizer doses of nitrogen (N), P, K viz. 100%, 75%, 50%, and 25% of the recommended dose. Disturbed soil samples were analysed for K and P from pre-sown land to tillering stage at 0–5, 5–10, 10–15, 15–30, 30–45, and 45–60 cm depths. Simultaneously, K and available P were also simulated in the subsurface soil layers through the HYDRUS-1D model. The statistical comparisons were made with RMSER, E, and PBIAS between the modelled values and laboratory-measured values. Although, the results showed that all the treatments considered had agreeable simulations for both K and P, the K simulations were found to be better as compared to P simulations except for 25% where P simulations outperformed K. The simulated concentration at all doses was found most appropriate when measured for the subsurface layers (up to 45 cm), while showed an underestimation in the bottom layers (45–60 cm) of soil.