Based on the cost-benefit data (1980–2002) of farm products and China Agriculture Yearbooks, this paper studies the regional disparity in the changes of the agricultural land use in China during the period 1980–2002 from three aspects such as the degree of intensity, the sown area and the abandoned farmland. The results show that: (1) The degree of intensity of land use in the western region during 1980–2000 has a strong uptrend, but in the eastern and central regions the degree of intensity descends obviously and has shown a continuous downtrend since 1997. (2) The total sown area shrinks notably in the eastern region, while it enlarges constantly in the western region. (3) The sown area in the eastern, central and western regions has gone through a similar cyclic process: down (1980–1985)–up (1985–1991)–down (1991–1994)–up (1994–1999)–down (1999–2002). However, there are obvious differences in amplitude variation and tendency among them. The sown area has shrunk in the eastern region and expanded in the central and western regions especially before 1999. (4) The most cases of abandoned farmland are reported in the central region, the second in the eastern region and the least in the western region. The abandonment phenomena chiefly occurred during 1992–1995 in the eastern region, and during 1998–2002 in the central region.

Taking the typical karst agricultural region, Xiaojiang watershed in Luxi of Yunnan Province as a research unit, utilizing the groundwater quality data in 1982 and 2004, the aerial photos in 1982 and TM images in 2004, supported by the GIS, we probe into the law and the reason of its space-time change of the groundwater quality over the past 22 years in the paper. The results show: (1) There were obvious temporal and spatial changes of groundwater quality during the past 22 years. (2) Concentrations of,SO₄^2-,NO₃^-,NO₂^-,Cl^-,and the pH value, total hardness, total alkalinity increased significantly, in which NH₄⁺,NO₃^-, and NO₂^- of groundwater exceeded the drinking water standards as a result of non-point pollution caused by the expansion of cultivated land and mass use of the fertilizer and pesticide. (3) Oppositely, Ca²⁺ and HCO₃^- showed an obvious decline trend due to forest reduction and degradation and stony desertification. Meantime, there was a dynamic relation between the groundwater quality change and the land use change.

The Danxia landform of Qiyun Mountain is mainly developed on the red granule conglomerates named Xiaoyan Group (K₂x¹) of middle Cretaceous series, which is controlled mainly by three faulted zones, namely, Jingdezhen-Qimen faulted zone, Jiangwan-Jiekou compressional faulted zone and Kaihua-Chun’an folding faulted zone. During the Cretaceous period, this area firstly experienced massif subsidence to become a continental faulted basin, then having thick Cretaceous red sediments accumulated on it. In the supervened neotectonism, this area experienced an uplifting process, which made the thick Cretaceous sediments into a mountain with an altitude of 500-600 m. After undergoing the processes of vertical joint development, weathering, denudation and transportation, as well as evidently differential weathering and denudation influenced by lithology and structure between sandstone and conglomerate, the grand Danxia landscape consisting of peak forests, steep cliffs, caves, mesas, castellated peaks, natural bridges and so on formed. The three nick points located respectively at 585 m, 400 m and 150 m generally reflect the three dominated uplifting processes during the neotectonism.

The area that the railway will cross is a region with the main physiognomies of desert and Gobi, with a most fragile ecological environment. It is also a region that is highly susceptible to man-made disturbance. The construction of railway will intensify soil erosion along the railway line to a certain degree. The map of soil erosion conditions in the section from Liugou to Dunhuang City in the range of 10 km each side along the line was compiled by using the techniques of remote sensing and geographic information system (GIS). Based on analysis of the status of desertification and the influence of the railway construction projects, the changes of the types, intensities and the total amount of the soil erosion caused by the construction were predicted.

1. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; 2. College of Resources and Environment, Southwest University, Chongqing 400716, China; 3. Institute of Tibetan Plateau Research, CAS, Beijing 100085, China)

Based on multi-temporal remotely sensed materials of both 1985 and 2000, we analyzed the effects of land-use types and their conversions on desertification in Mu Us Sandy Land in the agro-pastoral transitional zone of north central China. In this study, the desertified land was classified into five degrees: potential, light, medium, severe and extreme. The results indicate that the extent of desertification expands slightly, while desertification degree is enhanced significantly. About 22.35% of the total land area in the study area is in the desertification course, and the expanded area of both severely and extremely desertified land accounts for 3.67% of the total area of Mu Us Sandy Land. About 9053 km² of area witnessed changes in land-use types between 1985 and 2000, which accounted for 10.75% of the total. More importantly, the area of conversions among cultivated land, forestland and rangeland added up to 971.6 km². This research reveals that both improper land-use types and conversions could accelerate the desertification process. Both cultivated land and forestland have more effects on the desertification development than rangeland. Some land-use type conversions, such as rangeland to cultivated land, rangeland to forestland and forestland to cultivated land, are attributed to the acceleration of the desertification development while the opposite can control the desertification development.

Rapid land landscape change has taken place in many arid and semi-arid regions such as the vulnerable ecological area over the last decade. In this paper, we quantified land landscape change of Yulin in this area between 1985 and 2000 using remote sensing and GIS. It was found that fallow landscape decreased by 125,148 hm² while grassland and woodland increased by 107,975 hm² and 17,157 hm², respectively. The major factors responsible for these changes are identified as the change in the government policy on preserving the environment, continued growth in mining, and urbanization. The efforts in restoring the deteriorated ecosystem have reaped certain benefits in reducing the spatial extent of sandy land through replacement by non-irrigated farmland, woodland and grassland. On the other hand, continued expansion of mining industry and urbanization has exerted adverse impacts on the land landscape. At present regional economic development conflicts directly with the protection of the natural environment. Such a conflict has caused the destruction to the land resources and fragmentation of the landscape accompanied by land desertification, the case is even serious in some localities.

The Huaihe River basin of Anhui is not only a transitional zone of physical geography, but also a convergent area of many cultures in China. It is one of the sensitive ecotones to global changes and the birthplace of Chinese civilization. Using the field archaeological data and the sporo-pollens and the age data of the drilling cores, we analysed Neolithic cultural development and environmental evolution in the Huaihe River basin of Anhui. According to the combination of some research results in archaeology with environmental evolution research, this paper discusses the relationship between culture and environment in the Huaihe River basin of Anhui. The Neolithic cultural development was strongly impacted by the environmental change. The primitive culture (Shishanzi) was developed in the beginning of the Holocene Megathermal Period with distinct regional feature of the culture. From 6.5 kaBP to 5.5 kaBP, the climate changed warmer and wetter. The frequent occurrence of flood and waterlog due to such a climate regime and high sea level caused the earth’s surface environment deteriorated in the Huaihe River basin of Anhui and the interruption of the Neolithic cultural development, hence a lack of archaeological sites. From 5.5 kaBP to 4.0 kaBP, the climate changed from wet to dry, the natural environment was propitious to human survival. Dawenkou Culture and Longshan Culture flourished in this period. The Neolithic cultural development, the number of the sites and their distribution characteristics of the sites in the study area differed apparently from those in Central China and Shandong Province.

Arid and semi-arid ecosystems exhibit a spatially complex biogeophysical structure. According to arid western special climate-vegetation characters, the fractional cover of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), bare soil and water are unmixed, using the remote sensing spectral mixture analysis. We try the method to unmix the canopy funation structure of arid land cover in order to avoid the differentiation of regional vegetation system and the disturbance of environmental background. We developed a modified production efficiency model NPP-PEM appropriate for the arid area at regional scale based on the concept of radiation use efficiency. This model refer to the GLO-PEM and CASA model was driven with remotely sensed observations, and calculates not just the conversion efficiency of absorbed photosynthetically active radiation but also the carbon fluxes that determine net primary productivity (NPP). We apply and validate the model in the Kaxger and Yarkant river basins in arid western China. The NPP of the study area in 1992 and 1998 was estimated based on the NPP-PEM model. The results show that the improved PEM model, considering the photosynthetical activation of heterogeneous functional vegetation, is in good agreement with field measurements and the existing literature. An accurate agreement (R² = 0.85, P<0.001) between the estimates and the ground-based measurement was obtained. The spatial distribution of mountain-oasis-desert ecosystem shows an obvious heterogeneous carbon uptake. The results are applicable to arid ecosystem studies ranging from characterizing carbon cycle, carbon flux over arid areas to monitoring change in mountain-oasis-desert productivity, stress and management.

Pollen analysis of 23 surface samples in the east of Qaidam Basin reveals the characteristics of pollen assemblages and their relationships with vegetation and climate. In pollen assemblages, Chenopodiaceae and Artemisia are preponderant types in all the samples, and Ephedra, Gramineae and Compositae are common types. The results of DCA (Detrended Correspondance Analysis) and Correlation Analysis show different pollen assemblages indicate different vegetations, coincided with respective vegetation types. A/C (Artemisia/Chenopodiaceae) in the desert can indicate the aridity. Depending on the aridity, the vegetation communities are divided into four groups: severe drought group, moderate drought group, slight drought group and tropophilous group. A/C value is less 0.2 in the severe drought group, 0.2–0.5 in the moderate drought group, 1.63 in the slight drought group and 5.72 slight-wetness group.

Using NDVI data of NOAA-AVHRR in recent 20 years and the temperature and precipitation data of West China, the vegetation activity is discussed by adopting the EOF and REOF decomposed functions. Results show that the overall increasing trend of vegetation activity in different seasons reflects an advanced and prolonged growth period of vegetation under the circumstance of climate warming, but the vegetation evolvement has much inconsistency between different regions and seasons. There are four notable regions, eight sub-areas for vegetation evolvement in spring and summer, and nine sub-areas in autumn. The vegetation activity in most sub-areas is increasing. The most notable region is represented by Lhaze station on the Tibetan Plateau. Two other marked stations are represented by Altay station in Xinjiang Uygur Autonomous Region and Pengshui station in Sichuan Province. But the time series analysis of NDVI makes clear that the trends of the other two sub-areas, Turpan station in Xinjiang and Huashan station in Shaanxi Province, are descending. It is an important reason for vegetation evolvement that temperature ascends in most of the regions and descends in the east region in some seasons. But another important reason for vegetation evolvement is that precipitation is ascending in the west and descending in the east of the region.

A study was conducted in the Taihu Lake with the aim of deriving a model for the retrieval of suspended sediment (SS) concentrations from Landsat TM images and in situ sampled data. The correlation between suspended sediment concentrations of lake and the reflectance obtained from the TM images is significant. By TM images and in situ sampled data in summer and winter, we obtained a comparative uniform model for the retrieval of suspended sediment concentrations in the Taihu Lake, that is lnSS = a*(R3/R1) + b, where lnSS is the natural logarithm of the suspended sediment concentration, R1 and R3 are the reflectance coincident with the 1st band and the 3rd band in TM images, a and b are the regression coefficients. Furthermore, we analysed the errors particularly to make sure the model is valid. The model is accurate to within 0.33(RMSE), suggesting that this model may be applicable to predict suspended sediment in the Taihu Lake from TM image throughout the year.

The spatial and temporal variability of primary productivity in the China seas from 2003 to 2005 was estimated using a size-fractionated primary productivity model. Primary productivity estimated from satellite-derived data showed spatial and temporal variability. Annual averaged primary productivity levels were 564.39, 363.08, 536.47, 413.88, 195.77, and 100.09 gCm^-2a^-1 in the Bohai Sea, northern Yellow Sea (YS), southern YS, northern East China Sea (ECS), southern ECS, and South China Sea (SCS), respectively. Peaks of primary productivity appeared in spring (April–June) and fall (October and November) in the northern YS, southern YS, and southern ECS, while a single peak (June) appeared in the Bohai Sea and northern ECS. The SCS had two peaks in primary productivity, but these peaks occurred in winter (January) and summer (August), with the winter peak far higher than the summer peak. Monthly averaged primary productivity values from 2003 to 2005 in the Bohai Sea and southern YS were higher than those in the other four seas during most months, while those in the southern ECS and SCS were the lowest. Primary productivity in spring (March–June in the southern ECS and April–July in the other five areas) contributed approximately 41% on average to the annual primary productivity in all the study seas except the SCS. The largest interannual variability also occurred in spring (average standard deviation = 6.68), according to the satellite-derived estimates. The contribution during fall (October–January in the southern ECS and August–November in the other five areas) was approximately 33% on average; the primary productivity during this period also showed interannual variability. However, in the SCS, the winter (December–March) contribution was the highest (about 42%), while the spring (April–July) contribution was the lowest (28%). The SCS did share a feature with the other five areas: the larger the contribution, the larger the interannual variability. Spatial and temporal variability of satellite-derived ocean primary productivity may be influenced by physicochemical environmental conditions, such as the chlorophyll-a concentration, sea surface temperature, photosynthetically available radiation, the seasonally reversed monsoon, river discharge, upwelling, and the Kuroshio and coastal currents.

Water is a key restricting factor of the economic development and eco-environmental protection in arid inland river basins of Northwest China. Although water supplies are short, the water utilization structure and the corresponding industrial structure are unbalanced. We constructed a System Dynamic Model for mutual optimization based on the mechanism of their interaction. This model is applied to the Heihe River Basin where the share of limited water resources among ecosystem, production and human living is optimized. Results show that, by mutual optimization, the water utilization structure and the industrial structures fit in with each other. And the relationships between the upper, middle and lower reaches of the Heihe River Basin can be harmonized. Mutual benefits of ecology, society and economy can be reached, and a sustainable ecology-production-living system can be obtained. This study gives a new insight and method for the sustainable utilization of water resources in arid inland river basins.

The analysis results of oxygen isotopes, carbon isotopes, geochemistry and the growth belt of reef coral etc. for some profiles of coral reef show that the basic pattern of climatic fluctuation during the Quaternary period can be reflected by coral reef. The trend of climate change was from cooling to warming during the Early Pleistocene with at least four cycles, and from warming to cooling with at least seven cycles during the Middle Pleistocene. The late Pleistocene is a period of the Quaternary which shows the most frequent variation of climate but generally two main cycles of warming–cooling can be seen. During the Holocene the climate went through a process of warming-rise in temperature-drop in temperature. During the historical period there were four cycles of cooling-warming at 1700 a BP. During the last 200 years climate change is characterized by two stages; a positive deviation in the former 100 years, and a negative deviation in the latter 100 years with general warming trend.

As the “Third Pole” of the world, the Tibetan Plateau has important effects on climate of its surrounding areas and even the whole world. Many results have been achieved on climate change since the last inter-glacial period in recent decades from ice core, tree-ring and lake sediment records over the Tibetan Plateau. In this paper, we review these achievements, especially those in the special periods. During the last inter-glacial period, temperature went down rapidly and went up slowly. The temperature record of the last glacial period is consistent with Greenland ice core records, also having own features over the Tibetan Plateau. Younger Dryas event agrees with the records from Europe and Greenland. Generally speaking, it is warm in the Holocene, and temperature has been rising gradually in the last 2000 years and gone up rapidly in recent decades. Climate changes on different time scales on the Tibetan Plateau occurred earlier and the change amplitude is larger than those in other parts of China.

The monitored soil samples were collected from Heihui irrigated area, Jiaokou irrigated area, Qianhe river valley and Jinghe river valley (hereafter Heihui, Jiaokou, Qianhe and Jinghe for short respectively) of Guanzhong District. According to the Environment Quality Standard for Soil (GB15618-1995II), we evaluated the pollution status of heavy metals (Cd, As, Cr and Pb) that could seriously endanger soil environment and human health by using single-factor index and synthetic pollution index methods. The results indicate that the synthetic pollution indices P of soil heavy metals are less than 0.7 in Heihui, Jiaokou, Qianhe and Jinghe of Guanzhong, the single-factor indices Pi of soil heavy metals of most soil samples are less than 0.7, so the soil environmental quality is in a good condition in Guanzhong on the whole; the enrichment degree of soil heavy metals is in the order of Heihui, Jinghe, Qianhe and Jiaokou; the contaminated degree of soil heavy metals has the feature of Cd > As > Cr > Pb; heavy metals contents in the cultivated horizon soil are generally higher than those in its underlayer soil, heavy metals contents of soil have the characteristic of enriching towards the cultivated horizon; Cd exceeds standard in the soil samples HS07a, b and HS08a, b at the Yangtao orchard in Heihui and in the soil sample QHS01a at the suburban vegetable plot in Qianhe, which was mainly caused by the long-term irrational use of chemical fertilizer and pesticide.

Henan province, located between 110°21’E—116°39’E and 31°23’N—36°22’N, stretches from warm-temperate to subtropical transitional zone. Its special position and resultant varied physical conditions, in its long geologic history, give rise to not only a rich but also complex and prominently transitional flora. Therefore, in-depth study of the floristic areal differentiation is of importance to Chinese florilization and in accurately drawing the boundary of warm-temperate and subtropic zones in China. Based on the recent floristic data, this paper conducts comparison and analysis of the floristic difference and resemblance among the Dabie, Tongbai, Funiu and Taihang Mts. in Henan province. The result shows that the Dabie and the Tongbai Mts. have the similar flora components, the northern and the southern slopes of the Funiu Mts. have identical flora, but the Taihang Mts. stand alone in their floristic character. Therefore these mountainous areas should be grouped into three floral regions in China: the Dabie and the Tongbai Mts. belong to East China Floral Region, the Taihang Mts. to North China Floral Region, and the two slopes of the Funiu Mts. to Central China region.

The agricultural climate risk in the geographical transitional zones is very sensitive to climate change. Based on previous researches, this article established the cotton climate suitability model and the risk index to analyze the cotton climate risk degree in Henan Province. The result shows that, in the last 40 years, the cotton climate risk degree has a gradual increasing trend in which the precipitation plays a very important role, and the climate suitability and its deviation have different performances in the influence on the risk change in different phases; the increase rate of risk degree has significant regional and transitional characteristics, for example, from the eastern plain to the western mountains, the risk change rate becomes slower and slower, so the contrast between the central-southern Huang-Huai plain and the Funiu mountains is the most remarkable; and in the north-south direction, the contrast between the fast increase belt from the central-southern Huang-Huai plain to the middle Yellow River and the slow increase belt near the Yellow River is particularly remarkable, which is possibly the results of topographic and climatic transitional belt; and the risk change process also has obvious regional difference. For instance, abrupt change is an important characteristic in eastern Henan where this sudden change type has notable latitudinal difference, while in the western mountainous area it is very rare. Although the temperature change over the 40 years is still increasing in this area, the trend has reduced gradually since the end of the 1980s.

A 6-m ice core was recovered in 2004 from the Naimona’Nyi Glacier, the middle Himalayas. Empirical orthogonal function (EOF) analysis on the major ion reveals that EOF1 represents the variations of majority of ions which may be originated from crustal aerosols. Comparing the calcium concentrations from the Naimona’Nyi with these from Dasuopu, East Rongbuk and Guliya ice cores, it is observed that calcium, a good indicator of the input of crustal aerosol in snow, concentrates mostly in the Guliya ice core located on the northern Tibetan Plateau, and gradually decreases from west to east in the Himalayas.

Modern physical geography in China grew from Chinese traditional geography and has been profoundly influenced by the geographical disciplines of Euro-America and Russia. Since the 1950s, integrated studies of physical geography in China have made remarkable progress in the fields of comprehensive physical geographical regionalization, land studies, landscape ecology, and land surface geographical processes. During the past few decades, under the background of global change and rapid socio-economic transformation, a series of environmental and resources problems have boomed in China. To solve these problems and promote the development of integrated studies of physical geography, the following issues were proposed as research priorities: (1) coupling of land surface patterns and processes; (2) integrated research on regional responses and adaptation to global change; (3) analysis of human dimensions of the earth system; (4) ecosystem service research from a geographical perspective; (5) integration of multi-source data and model development; (6) integrated studies on unique geographical units; and (7) important global issues and relevant international programs.

Land surface is of spatial-temporal heterogeneity. Terrestrial system (TS) comprehensively studies on land surface and physical regionalization objectively describes geographical zonation of the system. China has a vast area with apparent spatial variations in resources and environmental conditions, which highly influence on socio-economic development. In this paper, progress of the TS studies in China is overviewed and research priorities in the near future are prospected. Since the 1950s, China has paid great attention to the TS study as its socio-economic development, and conducted research on physical geographical regionalization, eco-geographical regionalization and comprehensive regionalization. Along with the deepening of global change research, dynamics of TS have been highly concerned. During the studies, methodology has been developed from qualitative research of integration of experts’ brainpower gradually to quantitative research based on field observation and experiments of the natural processes, including physical, chemical and biological processes, as well as application of information technology and mathematical simulation. In the near future, TS would combine with the ideology, objectives and key researches of Future Earth program, to focus on the mechanism and regional effects of interaction among land surface elements, the response of TS to global change, the quantitative recognition on regional unit boundary, and the application to TS in sustainable socio-economic development.

Eddy Covariance technique (EC) achieves the direct measurement on ecosystem carbon, nitrogen and water fluxes, and it provides scientific data for accurately assessing ecosystem functions in mitigating global climate change. This paper briefly reviewed the construction and development of Chinese terrestrial ecosystem flux observation and research network (ChinaFLUX), and systematically introduced the design principle and technology of the terrestrial ecosystem carbon, nitrogen and water fluxes coordinated observation system of ChinaFLUX. In addition, this paper summarized the main progress of ChinaFLUX in the ecosystem carbon, nitrogen and water exchange and environmental controlling mechanisms, the spatial pattern of carbon, nitrogen and water fluxes and biogeographical mechanisms, and the regional terrestrial ecosystem carbon budget assessment. Finally, the prospects and emphases of the terrestrial ecosystem carbon, nitrogen and water fluxes coordinated observation of ChinaFLUX are put forward to provide theoretical references for the development of flux observation and research in China.

China is distinguished by a prominent monsoonal climate in the east of the country, a continental arid climate in the northwest and a highland cold climate on the Qinghai-Tibet Plateau. Because of the long history of Chinese civilization, there are abundant and well-dated documentary records for climate variation over the whole of the country as well as many natural archives (e.g., tree-rings, ice cores, stalagmites, varved lake sediments and corals) that enable high-resolution paleoclimatic reconstruction. In this paper, we review recent advances in the reconstruction of climate and extreme events over the last 2000 years in China. In the last 10 years, many new reconstructions, based on multi-proxies with wide spatial coverage, have been published in China. These reconstructions enable us to understand the characteristics of climate change across the country as well as the uncertainties of regional reconstructions. Synthesized reconstructed temperature results show that warm intervals over the last 2000 years occurred in AD 1-200, AD 551-760, AD 951-1320, and after AD 1921, and also show that cold intervals were in AD 201-350, AD 441-530, AD 781-950, and AD 1321-1920. Extreme cold winters, seen between 1500 and 1900, were more frequent than those after 1950. The intensity of regional heat waves, in the context of recent global warming, may not in fact exceed natural climate variability seen over the last 2000 years. In the eastern monsoonal region of China, decadal, multi-decadal and centennial oscillations are seen in rainfall variability. While the ensemble mean for drought/flood spatial patterns across all cold periods shows a meridional distribution, there is a tri-pole pattern with respect to droughts south of 25°N, floods between 25° and 30°N, and droughts north of 30°N for all warm periods. Data show that extreme drought events were most frequent in the periods AD 301-400, AD 751-800, AD 1051-1150, AD 1501-1550, and AD 1601-1650, while extreme flood events were frequent in the periods AD 101-150, AD 251-300, AD 951-1000, AD 1701-1750, AD 1801-1850, and AD 1901-1950. Between AD 1551-1600, extreme droughts and flood events occurred frequently. In arid northwest China, climate was characterized by dry conditions in AD 1000-1350, wet conditions in AD 1500-1850, and has tended to be wet over recent decades. On the northeastern Qinghai-Tibet Plateau, centennial-scale oscillations in precipitation have occurred over the last 1000 years, interrupted by several multi- decadal-scale severe drought events. Of these, the most severe were in the 1480s and 1710s. In southwest China, extreme droughts as severe as those seen in Sichuan and Chongqing in 2006 are known to have occurred during historical times.

Accompanying the rapid growth of China’s population and economy, energy consumption and carbon emission increased significantly from 1978 to 2012. China is now the largest energy consumer and CO₂ emitter of the world, leading to much interest in researches on the nexus between energy consumption, carbon emissions and low-carbon economy. This article presents the domestic Chinese studies on this hotpot issue, and we obtain the following findings. First, most research fields involve geography, ecology and resource economics, and research contents contained some analysis of current situation, factors decomposition, predictive analysis and the introduction of methods and models. Second, there exists an inverted “U-shaped” curve connection between carbon emission, energy consumption and economic development. Energy consumption in China will be in a low-speed growth after 2035 and it is expected to peak between 6.19-12.13 billion TCE in 2050. China’s carbon emissions are expected to peak in 2035, or during 2020 to 2045, and the optimal range of carbon emissions is between 2.4-3.3 PgC/year (1 PgC=1 billion tons C) in 2050. Third, future research should be focused on global carbon trading, regional carbon flows, reforming the current energy structure, reducing energy consumption and innovating the low-carbon economic theory, as well as establishing a comprehensive theoretical system of energy consumption, carbon emissions and low-carbon economy.

The varied altitudinal gradient of climate and vegetation is further complicated by mass elevation effect (MEE), especially in high and extensive mountain regions. However, this effect and its implications for mountain altitudinal belts have not been well studied until recently. This paper provides an overview of the research carried out in the past 5 years. MEE is virtually the heating effect of mountain massifs and can be defined as the temperature difference on a given elevation between inside and outside of a mountain mass. It can be digitally modelled with three factors of intra-mountain base elevation (MBE), latitude and hygrometric continentality; MBE usually acts as the primary factor for the magnitude of MEE and, to a great extent, could represent MEE. MEE leads to higher treelines in the interior than in the outside of mountain masses. It makes montane forests to grow at 4800-4900 m and snowlines to develop at about 6000 m in the southern Tibetan Plateau and the central Andes, and large areas of forests to live above 3500 m in a lot of high mountains of the world. The altitudinal distribution of global treelines can be modelled with high precision when taking into account MEE and the result shows that MEE contributes the most to treeline distribution pattern. Without MEE, forests could only develop upmost to about 3500 m above sea level and the world ecological pattern would be much simpler. The quantification of MEE should be further improved with higher resolution data and its global implications are to be further revealed.

Coping with extreme climate events and its related climatic disasters caused by climate change has become a global issue and drew wide attention from scientists, policy-makers and public. This paper calculated the expected annual multiple climatic hazards intensity index based on the results of nine climatic hazards including tropical cyclone, flood, landslide, storm surge, sand-dust storm, drought, heat wave, cold wave and wildfire. Then a vulnerability model involving the coping capacity indicator with mortality rate, affected population rate and GDP loss rate, was developed to estimate the expected annual affected population, mortality and GDP loss risks. The results showed that: countries with the highest risks are also the countries with large population or GDP. To substantially reduce the global total climatic hazards risks, these countries should reduce the exposure and improving the governance of integrated climatic risk; Without considering the total exposure, countries with the high mortality rate, affected population rate or GDP loss rate, which also have higher or lower coping capacity, such as the Philippines, Bangladesh and Vietnam, are the hotspots of the planning and strategy making for the climatic disaster risk reduction and should focus on promoting the coping capacity.

Land use and land cover change (LULCC) strongly influence regional and global climate by combining both biochemical and biophysical processes. However, the biophysical process was often ignored, which may offset the biogeochemical effects, so measures to address climate change could not reach the target. Thus, the biophysical influence of LULCC is critical for understanding observed climate changes in the past and potential scenarios in the future. Therefore, it is necessary to identify the mechanisms and effects of large-scale LULCC on climate change through changing the underlying surface, and thus the energy balance. The key scientific issues on understanding the impacts of human activities on global climate that must be addressed including: (1) what are the basic scientific facts of spatial and temporal variations of LULCC in China and comparative countries? (2) How to understand the coupling driving mechanisms of human activities and climate change on the LULCC and then to forecasting the future scenarios? (3) What are the scientific mechanisms of LULCC impacts on biophysical processes of land surface, and then the climate? (4) How to estimate the contributions of LULCC to climate change by affecting biophysical processes of land surface? By international comparison, the impacts of LULCC on climate change at the local, regional and global scales were revealed and evaluated. It can provide theoretical basis for the global change, and have great significance to mitigate and adapt to global climate changes.

Hydrological monitoring and seasonal forecasting is an active research field because of its potential applications in hydrological risk assessment, preparedness and mitigation. In recent decades, developments in ground and satellite measurements have made the hydrometeorological information readily available, and advances in information technology have facilitated the data analysis in a real-time manner. New progress in climate research and modeling has enabled the prediction of seasonal climate with reasonable accuracy and increased resolution. These emerging techniques and advances have enabled more timely acquisition of accurate hydrological fluxes and status, and earlier warning of extreme hydrological events such as droughts and floods. This paper gives current state-of-the-art understanding of the uncertainties in hydrological monitoring and forecasting, reviews the efforts and progress in operational hydrological monitoring system assisted by observations from various sources and experimental seasonal hydrological forecasting, and briefly introduces the current monitoring and forecasting practices in China. The grand challenges and perspectives for the near future are also discussed, including acquiring and extracting reliable information for monitoring and forecasting, predicting realistic hydrological fluxes and states in the river basin being significantly altered by human activity, and filling the gap between numerical models and the end user. We highlight the importance of understanding the needs of the operational water management and the priority to transfer research knowledge to decision-makers.