2013 Vol. 23, No. 5
It is critical to study how different forest management practices affect forest carbon sequestration under global climate change regime. Previous researches focused on the stand-level forest carbon sequestration with rare investigation of forest carbon stocks influenced by forest management practices and climate change at regional scale. In this study, a general integrative approach was used to simulate spatial and temporal variations of woody biomass and harvested biomass of forest in China during the 21st century under different scenarios of climate and CO2 concentration changes and management tasks by coupling Integrated Terrestrial Ecosystem Carbon budget (InTEC) model with Global Forest Model (G4M). The results showed that forest management practices have more predominant effects on forest stem stocking biomass than climate and CO2 concentration change. Meanwhile, the concurrent future changes in climate and CO2 concentration will enhance the amounts of stem stocking biomass in forests of China by 12%-23% during 2001-2100 relative to that with climate change only. The task for maximizing stem stocking biomass will dramatically enhance the stem stocking biomass from 2001-2100, while the task for maximum average increment will result in an increment of stem stocking biomass before 2050 then decline. The difference of woody biomass responding to forest management tasks was owing to the current age structure of forests in China. Meanwhile, the sensitivity of long-term woody biomass to management practices for different forest types (coniferous forest, mixed forest and deciduous forest) under changing climate and CO2 concentration was also analyzed. In addition, longer rotation length under future climate change and rising CO2 concentration scenario will dramatically increase the woody biomass of China during 2001-2100. Therefore, our estimation indicated that taking the role of forest management in the carbon cycle into the consideration at regional or national level is very important to project the forest carbon sequestration under future climate change and rising atmospheric CO2 concentration.
The Taihu Lake, a large shallow lake in the floodplain of the Changjiang (Yangtze) River in the eastern China, is faced with challenging ecological problems resulting from eutrophication, which has affected the regional freshwater supply of a large population. Although efforts have been made to assess the nutrient evolution histories in the northern bays, little is known regarding nutrient histories in different parts across the entire lake basin. In this paper, we present nutrient histories for different parts of the lake based on chironomid transfer functions applied to four short cores obtained from the northern, western and eastern regions of the lake. The chironomid-inferred total phosphorus (CI-TP) concentrations were compared with the phosphorus concentrations obtained by using instrumental and sedimentary data. The results suggest that trophic evolution histories were asynchronous throughout the lake during the past decades in response to different ecological regimes controlled by the nutrient input, wind direction and shoreline topography. The restoration of aquatic plants may be an effective option for the management of lake rehabilitation to 'natural' conditions. Given the multiple factors controlling the biotic communities in such a large and complex lake, combined analyses among the multi-proxies encountered in the sediments are necessary for comprehensive insight into paleolimnological studies. The spatial heterogeneity in the ecological trajectories within this complicated ecosystem suggests that different management practices should be undertaken for specific lake zones in the Taihu Lake.
In this paper, a methodology for Leaf Area Index (LAI) estimating was proposed by assimilating remote sensed data into crop model based on temporal and spatial knowledge. Firstly, sensitive parameters of crop model were calibrated by Shuffled Complex Evolution method developed at the University of Arizona (SCE-UA) optimization method based on phenological information, which is called temporal knowledge. The calibrated crop model will be used as the forecast operator. Then, the Taylor's mean value theorem was applied to extracting spatial information from the Moderate Resolution Imaging Spectroradiometer (MODIS) multi-scale data, which was used to calibrate the LAI inversion results by a two-layer Canopy Reflectance Model (ACRM) model. The calibrated LAI result was used as the observation operator. Finally, an Ensemble Kalman Filter (EnKF) was used to assimilate MODIS data into crop model. The results showed that the method could significantly improve the estimation accuracy of LAI and the simulated curves of LAI more conform to the crop growth situation closely comparing with MODIS LAI products. The root mean square error (RMSE) of LAI calculated by assimilation is 0.9185 which is reduced by 58.7% compared with that by simulation (0.3795), and before and after assimilation the mean error is reduced by 92.6% which is from 0.3563 to 0.0265. All these experiments indicated that the methodology proposed in this paper is reasonable and accurate for estimating crop LAI.
The northeastern China is an important commodity grain region in China, as well as a notable corn belt and major soybean producing area. It thus plays a significant role in the national food security system. However, large-scale land reclamation and non-optimum farming practices give rise to soil degradation in the region. This study analyzed the food security issues coupled with global climate change in the northeastern China during 1980-2000, which is the period of modern agriculture. The results of statistical data show that the arable land area shrank markedly in 1992, and then increased slowly, while food production generally continually increased. The stable grain yield was due to the increase of applied fertilizer and irrigated areas. Soil degradation in the northeastern China includes severe soil erosion, reduced soil nutrients, a thinner black soil layer, and deterioration of soil physical properties. The sustainable development of the northeastern China is influenced by natural-artificial binary disturbance factors which consist of meteorological conditions, climate changes, and terrain factors as well as soil physical and chemical properties. Interactions between the increasing temperature and decreasing precipitation in the region led to reduced accumulation of soil organic matter, which results in poor soil fertility. Human-induced factors, such as large-scale land reclamation and non-optimum farming practices, unsuitable cultivation systems, dredging, road building, illegal land occupation, and extensive use of fertilizers and pesticides, have led to increasingly severe soil erosion and destruction. Solutions to several problems of soil degradation in this region requiring urgent settlement are proposed. A need for clear and systematic recognition and recording of land use changes, land degradation, food production and climate change conditions is suggested, which would provide a reference for food security studies in the northeastern China.
Phosphorus fractions and adsorption-release characteristics of sediments in the Zhujiang (Pearl) River estuary wetland were investigated. Results showed that the total phosphorus (TP) content in surface sediments ranged from 648.9 mg/kg to 1064.0 mg/kg; inorganic phosphorus (IP) was the major fraction of TP and ranged from 422.5 mg/kg to 643.9 mg/kg. Among the inorganic phosphorus, the main fractions were phosphorus bound to Al and Fe (Fe/Al-P), and calcium-bound phosphorus (Ca-P), accounting for 23%-42% and 21%-67% of IP, respectively. The vertical distribution of TP contents were significantly positive correlated with organic phosphorus (Org-P) and Fe/Al-P contents. The bio-available phosphorus contents in vertical sediments varied from 128.6 mg/kg to 442.9 mg/kg, mainly existed in Fe-Al/P fraction, and increased from the bottom to top sediments. The transport of phosphorus in sediment-water interface was controlled by the soil characteristics. The active Fe and Al content was considered as the main factor that determines adsorption capacity in vegetated marsh wetland. The P buffering capacity of the sediments in vegetated marsh wetland was greater than that in mudflat wetland. The potential risk of eutrophication in the study area is high. Reducing terrestrial phosphorus discharge and preventing the sediment Fe/Al-P release to the interstitial water are the possible solutions to reduce the risk of eutrophication in estuary wetlands, and planting vegetation in estuary wetland can also reduce the release of phosphorus in surface sediment.
Sensitivity analysis of thermal equilibrium parameters in the reservoir module of MIKE 11 model was conducted for the Wuxikou Reservoir in Jiangxi Province of China in order to apply the module to the environmental impact assessment to accurately predict water temperature of reservoirs. Results showed that radiation parameter A and evaporation-first parameter were much more sensitive than other parameters. The values of the radiation parameter A ranged from 0.10 to 0.34. The values of evaporation-first parameter varied from 0 to 10. The sensitivity of solar absorption parameters was less than that of evaporation parameter, of which light attenuation values ranged from 0.5 to 0.7, and this parameter would not impact model results if it was more than 2. Constants in Beer's law ranged from 0.2 to 0.7. Radiation parameter B was not more sensitive than evaporation parameter and its reasonable range was higher than 0.48. The fitting curves showed consistent changing tendency for these parameters within the reasonable ranges. Additionally, all the thermal equilibrium parameters had much more important effects on surface water temperature than deep water temperature. Moreover, if no observed data could be obtained, the local empirical value would be used to input to the MIKE 11 model to simulate the changes in the discharged outflow-water temperature qualitatively.
The majority of multinational enterprises (MNEs) traditionally originate from developed countries. In the last ten years, however, there has been dramatic growth in foreign direct investment (FDI) from China. It is a comparatively new phenomenon that challenges the classic FDI theories. In this paper, we review the pros and cons of two important theories, known as the Ownership-Location-Internalization (OLI) model and Linkage-Leverage-Learning (LLL) model, and use the statistical data and company case studies from China to test the plausibility of these two models. We believe that neither of them suits totally: the OLI model is quite useful for understanding FDI from China to developing economies, while the LLL model is more powerful for explaining the FDI to developed economies. We argue that the companies from China attain a very advantageous position as intermediates in the global economy. They may catch up with the first movers if they integrate OLI-led and LLL-led FDI within one firm. This combination can bring together the most advanced knowledge acquired in developed economies with the knowledge about adaptation needs and the needs for cost reduction in production as expressed in developing economies. It may also accelerate the knowledge transfer globally. We thus fill a gap in research into the geographical pattern of Chinese FDI and offer a deeper understanding of the internationalization of Chinese MNEs and revolving knowledge transfer.
During the last 30 years, China has witnessed rapid economic growth and dramatic urbanization, with about 1.2×107 rural people migrating annually into urban areas. Meanwhile, especially since 1995, the rural population has been declining, which is closely linked to land circulation and the increase in farm size in many villages. Increasing scale of farming operations is often regarded as a key to avoiding the abandonment of farmland and to increasing the income of rural farmers. However, until now, there has been little research on the spatial and temporal variability of farm size at the national level in China.Using data from the national agricultural census and rural household surveys, this study examines the characteristics of land use circulation and the consequent changes in the area of farmland per household. The results show that: 1) 12.2% of rural households were involved in land circulation at the national level. The highest amounts of land circulation have occurred in those provinces where the farmland per capita is more than 0.2 ha or less than 0.1 ha; 2) over 80% of households operate less than 0.6 ha of farmland; 3) the proportion of mid-sized farms (between 0.2 ha and 0.6 ha per household) has decreased while the smallest and the largest farms have increased. This bears some similarity with the phenomenon known as the ‘disappearing middle’, referring to the changes in farm size. This study establishes a framework for interpreting the factors affecting the changes in farm size in China, which include two promoting factors (urbanization and agriculture) and four hindering factors (agricultual land system, household registration, stable clan system, and farmland loss).
Rural development inequality is an important practical issue during the course of full establishment of a ‘moderately well-off society’ in modern China, and the objective understanding and evaluation of the status and regional inequality of rural development can provide scientific basis for ‘building a new countryside’ and coordination development of rural-urban regions. Based on the county-level data of 2000, 2005 and 2009, this paper examines the rural development inequality of Jilin Province in Northeast China by establishing a rural development index. The spatio-temporal dynamic patterns and domain factors are discussed by using the method of exploratory spatial data analysis and multi-regression model. The results are shown as follows. Firstly, most of the counties were in lower development level, which accounted for 58.3%, 62.5% and 66.7% of the total counties in 2000, 2005 and 2009, respectively. The characteristics of spatial inequality were very obvious at county level. For example, rural development level of Changchun Proper and the proper of seven prefecture-level cities were much higher than that of the surrounding regions. The counties in the eastern and northern Jilin Province were the lowest regions of rural development level, while the middle counties were the rapid growth areas in rural economy. Secondly, Moran's I of rural development index (RDI) was 0.01, -0.16 and -0.06 in 2000, 2005 and 2009, respectively, which indicated that spatial agglomeration of RDI was not obvious in Jilin Province, and took on the characteristic of random distribution. The counties of both the units and its adjacent units have higher development level (HH) were transferred from the western areas to the eastern areas, while the countries of both the units and its adjacent units have lower development level (LL) were diffused from the eastern to middle and western Jilin Province. Finally, the result of multi-regression analysis showed that the improvement of agricultural production condition, development of agricultural economics and the adjustment of industrial structure were the domain factors affecting rural development inequality of Jilin Province in the later ten years.
China is experiencing a fast process of farmland conversion which is conducted mainly by local governments to fuel economic development. Social tension is aroused and policy makers take great concerns on coordinating interests among different stakeholders, especially for increasing farmers' interest. The purpose of this study is to get some insights related to land acquisition institution by exploring farmers' perception to farmland conversion. Participatory Rural Appraisal (PRA) was applied for the investigation in peri-urban area, of Xining City, Qinghai Province, China. The total of 519 householders from 15 villages completed valid questionnaire survey from July to November, 2012. The results indicate that farmland conversion has several impacts on farmers' life. Most farmers are gradually adapting to city life. Higher living expenses and more income are perceived by farmers with average score of 4.21 and 2.69, respectively. The average scores of 2.38 and 2.46 are for improvement of life security and more job opportunities. Farmers expect to get some stable ways of compensation in addition to lump-sum compensation in cash. Stable subsidies every year and obtaining same number of land received strong proposal. And these two options are cited by 49.6% and 43.9% of respondents. Farmland conversion brings about cleaner living condition and more amenities, but lower air visibility and drier air. Results reflect landless farmers' economic and life pressures and various demands. Local government should pay more attention to increase farmers' income and improve rural security system.