Global and regional environmental change such as land use and climate change have significant and interactive effects on forest. These integrated effects will undoubtedly alter the distribution, function and succession processes of forest ecosystems. In order to respond and adapt to these changes, it is necessary to understand their individual and integrated effects. In this study, we proposed a framework by using coupling models to gain a better understanding of the complex ecological processes. We combined an agent-based model for land use and land cover change (ABM/LUCC), an ecosystem process model (PnET-II), and a forest dynamic landscape model (LANDIS-II) to simulate the change of forest total aboveground biomass (AGB), which was driven by land use and climate change factors for the period 2010-2050 in Taihe County of southern China, where subtropical coniferous plantations dominate. We conducted a series of land use and climate change scenarios to compare the differences in forest total AGB. The results show that: (1) land use, including town expansion, deforestation and forest conversion, and climate change are likely to influence forest total AGB in the near future in Taihe County. (2) Although climate change will make a contribution to an increase in the forest total AGB, land use change can result in a rapid decrease in forest total AGB and play a vital role in the integrated simulation. The forest total AGB under the integrated scenario decreased by 33.13% (RCP2.6+land use), 32.92% (RCP4.5+land use), and 32.42% (RCP8.5+land use) by 2050, which is in comparison to the results under separate RCPs without land use disturbance. (3) The framework can offer a coupled method to better understand the complex and interactive ecological processes, which may provide some supports for adapting to land use and climate change, improving and optimizing plantation structure and function, and developing measures for sustainable forest management.
Projection of future climate change scenarios provides the scientific basis for addressing climate change and for proposing strategies of adapting climate change. This study used the simulation data of 30 climate models, which were evolved in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Through evaluating the performance of each model on simulating the historical climate change, the preferred climate models were selected. Then, using the outputs of preferred climate models as independent variables and using ground measurements as dependent variables, the partial least squares regression (PLS) models were constructed for temperature and precipitation, respectively, of each region of China. By analyzing the ensemble predictions of regional temperature and precipitation changes, we found that the PLS ensemble mean of preferred climate models is closer to the ground measurements than the PLS ensemble mean of all of the climate models and the traditionally arithmetic average-based ensemble mean. The PLS ensemble projections of preferred climate model showed that climate warming would generally continue during the 21st century, which would be stronger in the cold half-year and in the northern regions than that in the warm half-year and in the southern regions. Under the scenario of RCP 4.5, the climate warming would be stronger in the first half of the 21st century and weaker in the second half. Under the scenario of RCP 8.5, the climate warming would keep nearly constant rate and, by the end of 21st century, the temperature would rise by two folds of that under the scenario of RCP 4.5. The increasing trend of precipitation would be stronger under the scenario of RCP 8.5 than that under the scenario of RCP 4.5 and would be stronger in the dry regions than that in the rainy regions with decadal oscillations. Finally, the equal weighting ensemble projections of all of the climate models exhibit that climate warming would be stronger in summer than in winter and that precipitation would increase linearly without decadal oscillations. These findings are opposite to the primary characters of climate changes that climate warming is stronger in winter than in summer and precipitation has strong inter-decadal variability. Thereby, the PSL-based ensemble mean of preferred climate model may provide reasonable projections of future temperature and precipitation changes.
As one of the most important regions for paleoclimate study, the Altai Mountains are influenced by the prevailing westerly airflow throughout a year. In order to get a better understanding of the precipitation variations at different time scales (i.e., season, year, multi-decades, centennial and millennial scales) in the northern and southern Altai Mountains, we investigate the observed data from 11 meteorological stations and published paleoclimate documents (including tree rings, ice cores and lake cores) in the northern and southern Altai Mountains. The results show that the precipitation during the observed interval experiences a decreasing trend in the northern Altai Mountains, whereas an increasing trend in the southern Altai Mountains. The out-of-phase relationship of precipitation in the northern and southern Altai Mountains also exists in the two centennial intervals, the last millennium and the Holocene epoch. We propose that the out-of-phase relationships of precipitation variations at different time-scales (i.e., season, year, multi-decades, centennial and millennial scales) indicate that the Altai Mountains are an important climatic boundary. However, the reasons of out-of-phase relationship at different time-scales remains to be investigated in the future. The next work is not only helpful to understand the history of regional water vapor change, but also contributes to the understanding of the succession of the Silk Road culture along the Europe-Asian steppe.
The early northern China (1600 BC-300 AD) can be divided into two stages roughly: 3600-3050 cal a BP (1600 BC-1050 BC), and 3050-1800 cal a BP (1050 BC-200 AD), which were recorded in many natural sedimentary archives. The former stage, corresponding to the second dynasty - the Shang Dynasty with a time span of more than 500 years, characterized by relatively stable humid climate state, is a historical period with relatively stable political and societal environment; the latter stage, coincident to the transition from the Zhou Dynasty to the Three Kingdoms with gradually becoming dry climate, showed a sharp contrast of political and societal condition to the period during the Shang Dynasty with seven unrests and consequent occurrence of new political regimes within a 1250-year period. And, marked by the relocations of capitals, the centers of these dynasties show a trend of southeastward migration. The correlation of significant climate change (usually cold and/or dry states) and some political unrests, such as, establishment of the Zhou Dynasty, Zhouping King′s eastward relocation of capital and perishment of the Western Han Dynasty, was found. These evidences again indicate that there is a certain relationship between evolution of early stage of Chinese history and climate change of Asian monsoon. This paper suggests that the following two factors, neglected in the previous research, greatly influence the correlation between society and climate. First, northern China has fan-shaped geographic space with a sharp ecological gradient for latitudinal zonality and Asian monsoon activity, which accentuates the effects of climate change on regional human society. Second, in China the small-scale self-sufficient economy cell was very sensitive to climate change. And usually, irrational social regime accentuated the sensitivity of small-scale self-sufficient economy cell to climate change through a series of feedbacks within society and resulted in serious consequences, and eventually caused the collapses of dynasties.
Based on the glacier inventories and meteorological data, spatial-temporal variations of glaciers in Chinese Tianshan Mountains were analyzed systematically. The results show that: (1) 7934 glaciers with an area of 7179.77 km2 and volume of 756.48 km3 were identified in the study area. The number of glaciers below 1 km2 accounts for the majority part of glaciers in the Chinese Tianshan Mountains. In contrast, glaciers between 1 to 10 km2 and larger than 20 km2 have the largest proportions of the total glacier surface area. The glaciers in the study area are mainly distributed at elevations of 3800-4800 m. (2) In 10 watersheds, the Akesu River Basin contains the most of the glaciers with a surface area of 1721.75 km2, but the Yiwu River Basin has the least glaciers whose surface area is 56.03 km2. There is an obvious difference of glaciers in different regions. In the Akesu region, glacier resource is the most abundant, which accounts for 43.28% and 68.85% in total surface area and volume. In the Turpan region, glacier resource is the least, which accounts for only 0.23% and 0.07% of the total surface area and volume in this region. (3) In the past half century, the loss in glacier area and ice volume were 1619.85 km2 (-18.64%) and 104 km3 (21.63%), respectively. Glaciers smaller than 1.0 km2 constituted the main body of the decreased glacier number. Glaciers below 5 km2 experienced a significant recession. (4) The relative rates of area change for these glaciers were different for different drainage basins. The fastest change of glacier area occurred on the northern slope of the Bogda Basin and the lowest appeared in the Weigan River Basin. The main reason for glacier retreat in this region was that glacier melting caused by rising summer temperatures is greater than glacier mass supply by increased precipitation during the study period.
Debris-covered glaciers, characterized by the presence of supraglacial debris mantles in their ablation zones, are widespread in high mountain regions of western China. Supraglacial debris cover on glaciers has the unique thermal process relative to exposed snow and ice, the spatial distribution of which influences both rates and spatial patterns of melting. Due to the debris-cover effect, the responses of debris-covered glaciers to climate change are more complex compared to those of debris-free glaciers. In addition, debris-covered glaciers generally contain a large ice volume, and mass changes of these glaciers are expected to have significant impacts on the regional-scale evolution of river discharge and water resources. However, a better understanding of debris-cover effect in glacier status and hydrology at a regional scale remains a challenge. The difficulty of such a study arises mainly from limited knowledge of the large-scale spatial distribution of the thickness and properties of the debris cover in western China. This study systematically reviews the impacts of the spatial distribution of debris thickness on melting beneath surface debris, mass change and runoff process on debris-covered glaciers. In particular, a physically-based assessment model for debris-cover effect is proposed, which is based on visible and near infrared and thermal infrared bands of remotely sensed data and surface energy-balance process of the debris layer. This model does not require high-quality input parameters related to the extent, thickness and thermal properties of the debris cover, and has been applied to different glaciers of western China for systematically assessing the significance of debris cover and its influence on spatial patterns of ice melting, mass balance and runoff. This approach provides an important insight into exploring the average status of debris-covered glaciers and its impacts on regional water resources in western China. Nevertheless, this approach does not consider the effect of the complex surface composed of co-existing debris-covered ice, bare ice, ice cliffs and supraglacial ponds in the ablation zone, and needs further improvement in the future.
The numerical simulation method was used to predict the future possible changes that happened on permafrost by setting up the prediction results of the climate model from the IPCC Fifth Assessment Report as a possible climatic condition. The source area of the Yellow River with complicated permafrost conditions was chosen as the study area. The past and future permafrost distribution were predicted, and the future possible changing trends in permafrost in this area were calculated. The obtained results were, (1) during the past 30 years of 1972-2012, a small part of permafrost was degraded, which covered an area of about 833 km2. In this period, the seasonal frozen soil type was mainly distributed in the of Requ river valley, Xiaoyemaling, and Tangchama, as well as the southern part of the two lake basins. (2) Under different climatic scenarios of RCP 2.6, RCP 6.0 and RCP 8.5, little difference would happen on permafrost degradation until 2050. In details, the possible degradation area of permafrost would be 2224 km2, 2347 km2, and 2559 km2 under the scenarios of RCP 2.6, RCP 6.0, and RCP 8.5, respectively, accounting for 7.5%, 7.9%, 8.6% of the total study area. The seasonal frozen soil type would be sporadically distributed in the river valleys of Lena Qu, Duo Qu, Baima Qu, but widely distributed around Yeniugou, Yeniutan and four Madio lakes located in the Yellow River valley in the eastern part of Ngoring Lake. (3) In 2100, the predicted permafrost degradation area would be 5636 km2, 9769 km2 and 15548 km2, respectively, and they would account for 19%, 32.9% and 52.3% of the source area. The permafrost degradation mainly occurred in the areas of Xingsuhai, Gamaletan, Duogerong, of which low-temperature permafrost would be degraded into a high-temperature permafrost type. And the mean annual ground temperature of permafrost would rise differentially. (4) Under the scenario of RCP 2.6, all permafrost with current mean annual ground temperature higher than -0.15oC would be degraded into seasonal frozen soil type, and the permafrost with the mean annual ground temperature ranging from -0.15 oC to -0.44oC would be partly degraded into seasonal frozen soil type. Under the scenarios of RCP 6.0 and RCP 8.5, permafrost with the current mean annual ground temperature higher than -0.21 oC and -0.38 oC would be totally degraded, the permafrost with the mean annual ground temperature ranging from -0.21 to -0.69 oC and from -0.38 oC to -0.88 oC would be partly degraded.
Based on the research on palaeoflood hydrology in the upper reaches of Hanjiang River, the palaeoflood events recorded by slackwater deposits in upper layers of 6 loess-soil profiles were found to occur during the Eastern Han Dynasty. In this paper, the flood time of the palaeoflood events during the study period was examined textually by the historical literature analysis, and the flood simulaton was made using the HEC-RAS model. The study results showed that the palaeoflood during the Eastern Han Dynasty might be an extraordinary flood event that occurred in September (lunar month), the second year of the Jian'an period (197) in terms of the influence scope, degree, intensity, and the deposit rule of the floodmarks. Then selecting reasonable channel sections and roughness coefficient, and setting the river boundary conditions and initial conditions, we used the HEC-RAS model to conduct the flood simulation of the palaeoflood events. The errors between the simulated and the calculated flood stages were -0.18%~0.25%. Moreover, the errors of the simulated flood stages in 1983 were 0.25% less than those of the floodmark stages in 1983 found near the profiles. The flood simulation results showed that the selected channel sections and hydrological parameters were accurate and reliable, indicating that the palaeoflood events during the Eastern Han Dynasty might be an extraordinary flood event. The study results not only prolonged the flood sequences, but also provided the important hydrological data for the hydropower project construction, water resource management and the flood control and disaster mitigation in the upper reaches of the Hanjiang River.
The complicated relationship between the Yangtze River and Poyang Lake is the factor determining the exchange of water and sediment between them and has great influence on the water resources, flood control, navigation, and ecological environment of the entire region. Based on the theory of energy, this paper explains the principle of the river-lake relationship from a new perspective. By constructing a new index Fe, the authors were able to analyze the evolution of the relationship between the Yangtze River and Poyang Lake since the 1950s. The results indicate that the value of Fe shows an increasing trend, which means the river effect is weakening while the lake effect is strengthening. Operation of the Three Gorges Dam has an important impact on the river-lake relationship, which further weakens the river effect. The river effect increases slightly in the dry season but decreases significantly at the end of the flood period. In addition, the relationship between the Yangtze River and Poyang Lake may induce drought and flood disasters to some degree. Flooding is more likely to occur when flow from the five tributaries of the Poyang Lake is large and the Yangtze River blocking effect is strong. In contrast, drought is more likely to occur when flow from the five tributaries of the Poyang Lake is small, while the lake effect is strong. Meanwhile, the probability of drought in the Poyang Lake from September to October increases due to the impounding of the Three Gorges Reservoir.
The Paris Agreement recommended efforts to limit the temperature increase to 1.5℃ above pre-industrial levels. However, the current intended nationally determined contributions (INDCs) fall short of 2 ℃ scenarios, and the post-INDC period will bring severe challenges. This study details the 1.5 ℃ warming in terms of two types of restrictions. The first restriction conforms with the requirement of the Paris Agreement and requires an overall 1.5 ℃ warming restriction throughout the simulation. In the second restriction, the terminal 1.5 ℃ control relaxes the temperature restriction during the simulation and requires a 1.5 ℃ warming restriction only at the end of the simulation. Using the two restrictions, this study proposes three global cooperating abatement schemes according to different principles. Next, the study assesses the climatic effectiveness and economic feasibility of these three schemes using CIECIA, an economic-climatic integrated assessment model. The results indicate that the carbon emissions of countries should be net zero immediately following the INDC target year to meet the overall 1.5 ℃ goal in Scheme 1, and countries suffer great economic losses at the beginning of post-INDC period. In Scheme 2, the terminal 1.5 ℃ restriction allows a buffer period from INDC target years to the net zero emission period that starts in 2041. Throughout this period, approximately 52 GtC of carbon emissions are permitted. In this scheme, the economic shock around 2030 is less significant. However, by 2100 the countries suffer more cumulative utility losses than those in Scheme 1 due to warmer global temperatures during the late period. Of the three schemes, the Pareto improvement scheme permits looser carbon limits for Russia, and the high development countries (HDC) suffer more in the other schemes for industrial and geographic reasons. This scheme meets both the terminal 1.5 ℃ target and the Pareto improvement in the economies of all countries participating in global carbon abatement. Thus, it is economically feasible and climatically effective. Scheme 3 shows a link between the economies of China and the United States during carbon abatement, but it also shows that these countries are in competition with Russia and the HDC. Therefore, China could strengthen its abatement cooperation with the United States and pay attention to balance its gains with the gains of Russia and the HDC.
Datong Volcano eruption is an important geologic phenomenon of the Quaternary in North China and has been attracting scientists' attention; however, its episodic activity has remained unclear. Here, we demonstrate some new findings to reveal the episodic activity of the volcano during the Quaternary. (1) Volcano clastic layers with different ages which deposited near the paleolakeside incline with dip angles of 30°, 21°, 9° and 4°, respectively. (2) There exist four fine volcano clastic layers in the grayish-green lacustrine sediment in the paleolake inshore. (3) There are four sediment layers in the center of the paleolake which display high magnetic susceptibility value, indicating that some volcanic ash may deposit in them. Besides, the grain size of the four lacustrine layers is much coarser than that of others. (4) There exist three sediment layers in the loess section in the land some away from the paleolake, which display high magnetic susceptibilily value and low Rb/Sr one, indicating that some volcanic ash may deposit in them. (5) Magnetic boundary of B/M and Jaramillo Positive Subzone were found in the lacustrine section in the center of the paleolake. Based on these findings, we deduced that (1) Datong volcano experienced four episodic activities during the Quaternary and there occur many times volcano eruptions during each episodic activity; (2) the beginning times of four episodic activities are older than 0.90 Ma BP, ~0.47 Ma BP, ~0.31 Ma BP and 0.09 Ma BP, respectively; (3) another episodic activity with the beginning time ~0.19 Ma BP was also recorded in regional loess sediment; (4) the occurrence of each of the episodic activities of the volcano is synchronous with that of each of the paleolake regressions, implying that there is some relationship between the volcano eruptions and the paleolake regressions.
A total of 195 soil samples of farmland were collected from oasis in the Bosten Lake Basin, Xinjiang, and the concentrations of eight heavy metal elements (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn) were identified by standard methods. The spatial distribution of soil heavy metals in farmland was analyzed based on geostatistical analysis, while the pollution load index (PLI) and potential ecological risk index (RI) were employed to the assessment of the soil heavy metal pollution levels and potential ecological risk. Then the main sources of heavy metals were discussed. Results showed that: (1) The average value of the contents of Cd, Cr, Cu, Ni, Pb and Zn exceeded by 1.67, 1.13, 1.15, 1.29, 2.11 and 1.65 times of the soil background value of Xinjiang, respectively. (2) The spatial distribution of eight heavy metals showed an island-like pattern, and all the heavy metal elements showed high value areas in some parts of the study area, indicating the negative effects of human activities on soil environment of farmlands. (3) Pb presented a moderate pollution, whereas Cd, Zn, Ni, Cu and Cr a light pollution, Mn a slight pollution and As no pollution for farmland soils. The average PLI value of the heavy metals was 1.09, which showed a slight pollution. (4) The average E value for each heavy metal element was ranked as: Cd > Ni > As > Cu > Pb > Cr > Zn. The average RI value was 18.63, which showed a slight ecological risk situation. In terms of regional differences, the ecological risk index was ranked as: Hoshut County > Baghrash County > Karashahar County > Hejing County. (5) Cr, Cu, Mn, Ni and Zn contents were controlled mainly by the soil geochemical genesis and As, Cd and Pb were mainly affected by human activities. Cd and Pb were the main pollution sources of farmland soils, which should be given more attention.
Xu Xiake (1587-1641), born in an elite family in the region south of the Yangtze River, was a traveler in the Ming Dynasty. His travelogue extensively documented Southwest China's landscape and culture. Yet, Xu's reputation and writings remained less known to the general public throughout the Qing Dynasty. His geographical works were popularized in the writings of Chinese geologist Ding Wenjiang, and Department of History and Geography at Zhejiang University in the early 20th century. They employed scientism to mold their townsman Xu Xiake into a modern geographer with scientific spirits and methodology. By doing so, they implemented Western methodology to the Chinese context and ushered a paradigmatic shift in modern Chinese geography.
Based on bibliometric data from ISI-WOS during 2000 to 2015, the scientific output, influence, discipline structure, collaboration ability and highlight results of 13 international institutes in geographic science were assessed using several advanced bibliometric indices departments, including Institute of Geographic Sciences and Natural Resources Research (IGSNRR), CAS; College of Urban and Environmental Sciences, Peking University; School of Geography, Beijing Normal University; School of Geography and the Environment, University of Oxford; School of Geography, University of Cambridge; Department of Geography, University of London; Department of Geography, University of California System; Department of Geography, University of Maryland System; Department of Geography, University of Durham; Department of Geographical Sciences, University of Bristol; School of Geography and Earth and Environmental Sciences, University of Birmingham; Department of Geography at University of British Columbia; International Institute for Applied Systems Analysis. The analysis shows that the Department of Geography, University of Maryland ranked the top in many fields in light of citation indices. The IGSNRR, CAS is the first of the 13 institutes in terms of the number of papers among all the institutes. However, the lower citation rate indicates that there is a large gap in scientific influence for IGSNRR. In addition, the result also demonstrates that IGSNRR has become stronger in pioneering the discipline and realizing the innovations along with the increase of the fields and the ability in the international collaboration.
A geography paper is an important manifestation of geographical achievements as well as a significant carrier of information transmission and storage for geographical science and technology. How to publish scientific papers in a more influential scientific and technical journal so that the achievements can be recognized by the community, is a major concern of geographers. In this paper, we analyzed the types of potential journals and the choice principles of target journals and pointed out that the journal groups with unified online editing system had become the trends because they facilitated the paper submission. After that, we investigated current peer review forms and the choice rules of peer reviewers, and explored several key points of paper writing, including the innovation, research methods, abstract, introduction, discussion and conclusion, figures and tables and references. Finally, we analyzed comment types of peer reviews and identified them into two main types: revision and rejection. For a paper requiring revision, we suggested that the authors should carefully revise the paper and respond to the comments from reviewers. For a paper rejected, the authors should make clear the problems, make a comprehensive modification or improvement in the research methods, research contents and so on, and resubmit the paper.
