Based on five new reconstructions of solar irradiance, the anomalous solar activity periods during the past millennium, including 5 Solar Minimum periods, 2 Solar Maximum, and 4 high solar irradiance periods, were identified. Furthermore, the spatial patterns of drought/flood over eastern China for these 11 periods were reconstructed using an index of difference between drought and flood frequency derived from a 63-site yearly drought/flood grade dataset. It was found that there are different drought/flood patterns over eastern China within 11 solar activity anomalies. Spatial patterns showed alternative distribution of drought and flood among 5 Solar Minimum (1010-1050, 1280-1350, 1460-1550, 1645-1715, 1795-1823), with a higher probability of drought (flood) dominating the middle and lower reaches of the Yangtze River (North China). In the periods of solar maximum and high solar irradiance, drought prevailed over eastern China in Medieval Maximum (1100-1250), while flood prevailed over eastern China in 1845-1873. The remaining four periods (1351-1387, 1593-1612, 1756-1787, 1920-2000) presented a pattern of alternate drought and flood. The ensemble mean patterns of drought/flood for all the 5 Solar Minimum presented a zonal distribution with flood in South China, drought in the middle and lower Yangtze River and flood in most parts of North China, whereas the reverse distribution, drought in South China, flood in the middle and lower Yangtze River and drought in most parts of North China, were shown in the ensemble mean patterns of drought/flood for all the 6 periods with solar maximum and high solar irradiance.
Daily precipitation and temperature data at 728 stations covering a period of 1951 to 2014 across China were analyzed to investigate extreme precipitation regimes in terms of spatiotemporal patterns, precipitation magnitude, precipitation frequency, occurrence timing, non-stationarity of extreme precipitation regimes and also their responses to summer temperature changes. The methods adopted in this study are Peak over Threshold (POT) sampling technique, change point analysis, trend analysis and piecewise regression method. Results of this study indicated that magnitude of extreme precipitation events was subject to evident alterations but free of significant trends. However, occurrence rates of extreme precipitation were subject to adverse changing properties when compared to changes in magnitude of extreme precipitation. The entire China was dominated by apparent increase of occurrence rates of extreme precipitation. Besides, change points within magnitude and occurrence rates of extreme precipitation tended to modify the changing tendency therein. However, occurrence timing of extreme precipitation events seemed to be free of impacts from change points. In most regions of China, occurrence time of extreme precipitation events was delayed and no changes in occurrence time of extreme precipitation could be observed in other regions of China.
Mountain-Oasis-Desert System (MODS) is the typical landscape pattern in the inland arid area of Northwest China. We set the rainfall monitoring network in the Sangong River Basin, which is located in the middle part of northern Tianshan Mountains, southern margin of the Junggar Basin, to obtain the data of May-August rainfall for 2007-2014. Then empirical orthogonal function, fractal theory and geostatistics method were used to investigate characteristics of spatial distribution pattern and spatial variability of precipitation for the Mountain-Oasis-Desert System in arid inland areas. Results indicate that: (1) The first feature vector (contribution rates of the overall changes was 82.4%) has three load sections, namely, 70-150 km, 30-70 km and 0-30 km; accordingly, and the study area is divided into mountain area, oasis area and desert area. (2) The spatial distribution of summer precipitation presents a pattern of "overall uniformly type", which means that precipitation will increase over the whole basin, and the increase range is decreasing from mountain, oasis to desert. (3) The semi variation function curve of the mountainous region fits the Gauss model, the oasis area fits the Spherical model and the variation distance is 15.3 km. The desert area in May, June and other months fits the Gauss model, the exponential model and the spherical model respectively, and the variation distance is 58.6 km, which is longer than that of the mountain and oasis. (4) In research scale, owing to the random factors arising precipitation spatial heterogeneity take up 0.01%-9.57% of all, it was mainly caused by autocorrelation. (5) The spatial variability of precipitation in the oasis region was the largest, while that of the desert region was the smallest. The spatial heterogeneity of precipitation in June was the most significant, while the minimum value was observed in August. The variation was the greatest in both the north-south (0°) and the southeast-northwest directions (135°).
Based on the daily average temperature of 74 meteorological stations in China's oases of observation data, we calculated pentad average temperature ≤0℃ of the onset and upset pentad and pentads of cold period by using the methods of linear regression analysis, nonparametric Mann- Kendall test, wavelet analysis and correlation analysis. We also analysed the spatial and temporal variations and their causes for the onset and upset pentad and pentads of cold period in China's oases. The results show that: in recent 55 years, the onset pentad of cold period postpones and upset pentad advances, the pentads shorten gradually, the trend rates are respectively 0.3 p/10a, -0.27 p/10a and -0.58 p/10a; and the spatial difference is significant, especially for the Qaidam Basin oases, the onset pentad is the earliest, the upset is the latest, and the change trend of cold period is the most obvious. Mutation point of the onset and upset pentad and pentads of cold period is respectively observed in 1990, 1998 and 1994. The onset pentad and pentads of cold period show an aperiodic cycle, which is related to the atmospheric circulation and El Nino events, while the upset pentad of cold period shows an aperiodic cycle, which is related to the solar activity, suggesting that the onset pentad and pentads of cold period are closely related to the atmospheric circulation and El Nino events, while the upset pentad of cold period to the solar activity. The Qinghai-Tibet Plateau index, the Asia polar vortex area index, and the carbon dioxide emissions are the main factors affecting the cold period of the study area, and the South Asia summer monsoon index exerts the greatest effect on the Qaidam Basin oasis. The onset and upset pentad and pentads of cold period increase with the increase of latitude, longitude and altitude, onset pentad advances and upset pentad postpones, the pentads extends gradually, and the change of latitude is most significant. The onset and upset pentad and pentads of cold period have good response to regional warming, but the regional warming has different effects on the onset and upset pentad and pentads of cold period.
To investigate the diurnal characteristics of precipitation in the Qilian Mountains during the summer of 2008-2014, the hourly mean precipitation, frequency and intensity were calculated using an hourly merged precipitation dataset derived from the national automatic weather stations and CMORPH (Climate Precipitation Center Morphing) product at a 0.1°×0.1° resolution. In addition, the relative humidity and air temperature from ERA-Interim (European Reanalysis Interim) reanalysis database was also used to analyze the influence of meteorological variables on diurnal precipitation variation. The main results are as follows: (1) The spatial distribution and temporal variation of mean hourly precipitation and frequency are generally similar, and hourly precipitation in the eastern and central parts is larger and more frequent than that in the western part. On a monthly basis, the maximum values of precipitation and frequency usually occurred in July, while the minimum values usually occurred in August. The spatial distribution of precipitation intensity was different from that of amount and frequency, and the maximum was observed in June. (2) The increasing trends from west to east were detected for precipitation in both daytime and nighttime. The mountains usually had more precipitation in both daytime and nighttime, and the night rain was frequent for the study region. During 2008-2014, the precipitation in both daytime and nighttime increased. (3) The average relative change rate of precipitation was between 5%-38% with maximum value at 20:00 (Beijing Time). The hourly precipitation was significantly correlated with frequency, especially for the middle and eastern parts. (4) The reanalysis of data indicated that the diurnal variation of precipitation in the Qilian Mountains is related with other meteorological variables, such as relative humidity and air temperature.
Ecosystem services (ES) are the important links between natural ecosystems and human well-being, which draw the attention from many countries and organizations around the world. Traditionally conservationists have focused on conserving biodiversity, mainly through habitat protection, evaluation of endemic or endangered species distribution, and assessment of threats to survival. Recently, conservationists have focused not only on the conservation of biodiversity, but also on the sustainable provision of ES. In this study, a series of composite indicators were used to analyze the spatial-temporal patterns of four types of ES in China from 2000 to 2010. These types of ES include carbon-capture services of vegetation, water provision and purification, soil conservation and habitat protection services of ecosystems. The driving factors and conservation efficiency of the four ES types in the seven conservation and restoration regions of China were assessed based on the results of ES mapping. Finally, the priority levels of ES in China were identified in the study. The main results were as follows: (1) From 2000 to 2010, the spatial scope of four types of ES increased from the northwest to southeast of China. The significantly increased areas of the total ES are mainly distributed on the Loess Plateau while the decreased areas are mainly located in northeastern and northern China ecological regions. The main reasons for the decrease of total ES in northern China are due to the increase of artificial land and loss of cropland. The decreases of total ES in northeastern China are caused by the degradation of forest land and the conversion of forest to cropland or grassland. However, in the Loess Plateau the increases of total ES are caused by the conversion of cropland to grassland or forestland, which led to the significant increase of ES. (2) In the seven conservation and restoration regions of China, all the significant increased area of four ES types is larger than the decreased area from 2000 to 2010. The area proportions of the significantly increased regions of total ES in the Three-North Shelterbelt Project areas are greater than other regions, and the smallest region is the key ecological function area, while the most significantly decreased area is the important ecological function regions, and the smallest significant decreased regions are the Three-North Shelterbelt Project regions. (3) The final scenario of the priority levels of the ES conservational area accounted for 26.18% of China's territory, which protected 64.19% of the total ES values of China and the conservational efficiency is 2.47 times the average level of China.
In this study, we collected aboveground biomass (AGB) data by the harvesting method in the Eurasian steppe. We then discussed the spatial pattern of AGB, and correlations of AGB to its environmental controls by Meta-analysis. Our results mainly indicated that the spatial distribution of AGB had not only complex horizontal but also vertical zonality in the Eurasian steppe. Along a latitudinal gradient and an altitudinal gradient, the spatial variation in AGB was well characterized by an inverted U-shaped quadratic function, while a U-shaped quadratic function along a longitudinal gradient. In addition, the spatial variation in AGB was related to mean annual temperature (MAT), mean annual solar radiation (MAR), Gravel content and pH in topsoil (0-30 cm) of the Eurasian steppe. However, mean annual precipitation (MAP) could explain the largest proportion of AGB variation of the Eurasian steppe. Finally, the spatial variation in AGB was well correlated with MAP in a Gaussian function. The main reason was that vegetation and environment held special characteristics in the Tibetan Plateau.
By using the IBIS, a dynamic vegetation model, this study firstly simulated the NPP dynamics of China's potential vegetation in the past 50 years (1961-2010). Then according to the Fifth Assessment Report by IPCC, this study used the average climate conditions during 1986-2005 as the "standard climate", and took the NPP of the potential vegetation in this climate condition as the evaluation basis. Compared with the evaluation basis, the NPP fluctuation of each year was calculated to judge whether the potential vegetation adapts the climate change or not. Meanwhile, the degree of the inadaptability was evaluated. Finally, the NPP vulnerability of potential vegetation was evaluated by synthesizing the times and degrees of inadaptability to the climate change during the past 50 years. Results showed that: the NPP of the desert ecosystems south of the Tianshan Mountains, and the NPP of grassland ecosystems in northern China and western Tibetan Plateau were more likely to be impacted by the climate change in the study period. The NPP vulnerability of these ecosystems to climate change in the past 50 years was relatively high. The NPP of most of the forest ecosystems was not likely to be influenced by climate change. The NPP vulnerability to climate change of the evergreen broadleaved forests and coniferous forests was lower. Additionally, the NPP of the desert ecosystems north of Tianshan Mountains, and the NPP of the grassland ecosystems in the central and eastern parts of the Tibetan Plateau had lower vulnerability to climate change.
The soil effective depths are different due to regional features of various types of soils and vegetation, which impacts spatial and temporal distribution of soil moisture storage capacity and land surface water-carbon flux. In this study, the soil effective depth was calibrated using LPJ dynamic vegetation model on the target of remaining watershed water balance in three climate regions (Dongjiang River watershed in humid areas, Huaihe River watershed in humid, semi-humid areas and Jinghe River watershed in semi-humid and semi-arid areas). On this basis, we examined soil moisture storage capacity and land surface water-carbon flux (runoff R, actual evapotranspiration ET and net primary productivity NPP) resulting from variation of the soil effective depth. The results indicated that the estimated soil effective depth is 70 cm in the Dongjiang watershed, 90 cm in the Huaihe watershed and 140 cm in the Jinghe watershed. The soil effective depth and soil moisture storage capacity increase with the increase of drought degree. The correction of the soil effective depth in terms of water balance effectively reduces the simulation error, and affects the simulated results of the land surface water-carbon flux. However, the large or small effect is related to climatic conditions. The annual mean runoff and actual evapotranspiration change significantly in the humid areas, while the NPP changes significantly in the humid and semi-humid areas. The results provide a reference for improving the reliability of application of the LPJ model in different climate regions.
Using data for Chongqing Municipality, China, we conducted a coupling analysis of key indexes to accomplish the following objectives. We aimed to identify a coupling mechanism for the bearing capacity of the ecological environment (BCEE) and the quality of new urbanization based on an examination of the degree of their coupling in Chongqing during the period 2000-2012. We further aimed to evaluate the level of regional coupling and to determine the stage of urbanization at which an optimal outcome could be achieved to ensure sustainable urbanization within the region. Applying an analytic hierarchy process (AHP), we assessed the main indicators of BCEE and the quality of new urbanization in Chongqing. Accordingly, we constructed a model of ecological environment coupling coordination for analyzing the degree of regional coupling between the ecological environment and urbanization quality for evaluating the BCEE of Chongqing's cities and towns in 2000-2012. We obtained the following results for the study period. First, the overall degree of regional coupling of the quality of new urbanization and the BCEE was between 0.967 and 1.000, implying an advanced stage of coupling. Second, the coupling degree ranged between 0.884 and 1.000 in all of the districts and counties of Chongqing, implying a further advanced stage of coupling with a distinct spatial pattern of "one circle and two wings." Third, the coupling degree for all districts and counties matched that of the overall degree of regional coupling, barring obvious spatial variation, especially in relation to BCEE indicators. All of the districts and counties were classified into four types according to the degree of coupling between new urbanization quality and the BCEE. The findings indicate that rapid urbanization has led to increased ecological pressure within the Chongqing metropolitan area because of a concentration of the population within the central city. Moreover, with the fast pace of development in central city districts, their BCEE differs from that of other districts and counties. This will create a pattern of primary urbanization that can lead to an unsustainable situation in the near future. Local governments should, therefore, modify present urban development patterns accordingly. Optimization of resources utilization as well as adjustments in industrial distribution and industrial upgrading are recommended as effective measures that can disperse the population and reduce the pressure exerted by urbanization on the ecological environment.
The North China Plain (NCP) is amongst the global "hotspots" in terms of groundwater over-exploitation, and irrigation for winter wheat is the primary cause. Shrinkage of area sown to winter wheat proves to be a practical strategy to reverse groundwater over-exploitation and to promote groundwater storage. Land retirement policy was introduced by the government to encourage the extension of spring maize single cropping system in groundwater over-exploited areas. In addition, since the 1990s, large areas in the NCP in which winter wheat and summer maize are being replaced by the single cropping system of spring maize, due to the active behaviors of farmers. Not all land parcels grow winter wheat at the moment. Therefore, it is crucial to reveal the targeted land parcels for winter wheat abandonment and to assess reasonable and proper standards for ecological compensation, prior to the implementation of land retirement policy. In this paper, a case study was carried out in Cangxian county of Hebei province. Multi-level logit models were constructed using household survey data, in order to detect the determinants across plot, household and village levels on farmers' cropping system decisions, and the opportunity costs for winter wheat abandonment were calculated using cost-benefit analysis. The aim of this study was to recognize land parcels with winter wheat and to give scientific support on standards for ecological compensation. Results showed that: (1) land quality and irrigation condition at the parcel level are two essential elements influencing farmers' cropping system decisions. Nearly 70% in total area of poor land and more than 90% in total area of unirrigated land has suffered winter wheat abandonment. The targeted land parcels for land retirement policy should be the irrigated ones with land qualities being good, relative good or relative bad. (2) There were no significant differences between the net-profits of spring maize and summer maize under similar farming conditions, and the opportunity cost for land retirement should be equal to the net-profit of winter wheat. (3) When only considering the influence of winter wheat on groundwater resources, the primary purpose of the land retirement policy is to reverse the groundwater table and to induce groundwater recovery and restoration at the preliminary stage, and a high level of 350 yuan/mu was recommended as the subsidies for ecological compensation; at a later stage, the primary purpose of the policy transited to the balance of exploitation and supplement of water resources, and a lower level of 280 yuan/mu was recommended.
The study aims to investigate the spatio-temporal changes in crop patterns in China since 1980. In doing so, the analysis methods of time-series trend and spatial cluster were used to cover the major eleven crops at county scale. The results indicate that (1) There are 16 kinds of crop combinations ranking in the China's top 10 during the past 30 years. Yet since 2002, the simplified cropping structure has been gradually replaced by the multiple cropping structure, which suggests an increase in the diversity index of crop patterns. In 1980, about 82.7% of China's counties have a similar crop pattern which is composed of rice, wheat, corn and their combinations, however, this pattern largely changed after 2002 due to the increase in the planting area of fruit and vegetables. (2) In the same period, rice planting area of 47% of the counties, wheat planting area of 61% of the counties of and corn area of 29.6% of the counties experience a significant decrease, while other crops show an increasing trend. As a result, rice-dominated cereal crops in China are slightly adjusted to the coexistence of rice, wheat and maize crops. In particular, maize area proportion shows a significant change, which forms a so-called "corn decreased belt” spanning from northeast to southwest of China. Urbanization had an important impact on crop patterns as fruit and vegetable planting areas rapidly grow so as to meet the increasing demands in urbanized areas. (3) Crop patterns also show an obvious spatial cluster effect in China's 1300 counties. The proportion of high cluster accounts for 2.86%, 5.64%, 6.11%, 4.53%, 1.62%, 7.77%, 8.24%, 12%, 10%, 1.41% and 9.35% of China's counties for rice, wheat, maize, soybean, fibers, cotton, vegetables, potatoes, fruits, sugars and oils, respectively. These crops are distributed in Northeast China, Xinjiang, Northern Shaanxi Plateau, Yunnan-Guizhou Plateau and the metropolis areas. This finding of this study can support the decision making in agricultural restructuring and adaptation to climate change.
The flooding of the Yellow River has occurred many times near Kaifeng City and formed a relatively complete sedimentary sequence, which provide a rare research carrier for the exploration of the stratigraphic evidence on flood events and its pollen records in the vicinity of Kaifeng. In this research, a 25-m long core was obtained from Jinming campus of Henan University (ZKjm), which is located in the western suburbs of Kaifeng, Henan Province, China. On the basis of detailed pollen analysis, along with color identification, AMS14C dates, grain size and historical documents, sedimentary cycles in the study area were identified, and flood events and their pollen records were revealed since the middle and late Holocene. The results are as follows: According to the sand-clay ratio of grain size in the study area, ZKjm core can be divided into nine sedimentary cycles from bottom to top, and can roughly record eight large flood events. The difference between pollen assemblages is that the percentage of arboreal pollen in flood deposition period is higher than that in neighboring hiatus period, while the percentage of planted Poaceae is lower in ZKjm core. Except individual strata, the boundaries of sedimentary cycle are mainly consistent with the pollen subzones, suggesting pollen can be used as a reference indicator for dividing sedimentary cycles of strata. Notably, sedimentary cycles formed by smaller flood or plurality of intermittent short-term floods within one flood can be identified by pollen index. Therefore, the number of pollen subzones (12) is more than that of sedimentary cycles (9), indicating the accuracy of the cycle division of some intermittent pollen indexes is slightly higher than that of granularity. Due to seasonal changes, the variability of the flowing path of floods and the geographic scope, some floods of the Yellow River that lasted longer may have multiple intermittent short-term floods. However, the local pollen of Kaifeng City mainly deposited during the intermittent floods, which is different from the upper reaches of the Yellow River. Consequently, a pollen subzone may not indicate a specific flood event.
Dali Man, an archaic type of early Homo sapiens, is of great significance to the origin of Homo sapiens. However, there still exists a debate about the age of the fossil. There were a series of lacustrine or alluvial terraces in the northeast part of the Weihe Basin and in the Luohe River near the Dali Man site, and the paper adapted loess-paleosol sequence dating method to determine their ages and make clear the history of the regional paleolake regression-transgression evolution. In combination with the characteristics of the geomorphic-sedimentary body which contains the fossil Dali Man, the paper analyzed the regional paleolake regression-transgression stage during which the body formed. In the light of the particle size evidence and pollen one of the geomorphic-sedimentary body, the paper further analyzed the age of the alluvial sediment in which the fossil human skull was discovered. The result shows that there occurred several paleolake regressions and river down-cutting when S14, L9, L6, S2, L2 and L1SS developed or accumulated respectively, and that the sandy-gravel sediment with the fossil was deposited after the paleolake regression at the late stage of the deposition of L6. This lake regression made some of the paleolake bottom emerge subaerially and Luohe River flowed on it to erode the former lacustrine sediment and deposit the alluvial one. Therefore, the deposition of the alluvial sediment is probably synchronous with the formation of S5, with an average age of 0.55 Ma BP. Because of more development of the Dali Man than the Homo erectus pekinensis, the result indicates that the age of the Homo erectus pekinensis is probably more than 0.55 Ma BP.
This paper presents an analysis of the spatial distribution of 31 city sites of Han Dynasty in the Mu Us Sandy Land based on Nearest Neighbor Index (NNI) analysis, space analysis and coupling analysis. It further explores the relationships between the spatial pattern of the sites and geographical factors. Point pattern analysis of 31 city sites indicates that, the average nearest neighbor distance of city sites is 25.5 km, which belongs to causal distributional pattern with the 4 causal distribution regions: the strong influence area of the Great Wall of the Qin Dynasty - the Straight Road of the Qin Dynasty (A), the weak influence area of the Great Wall of the Qin Dynasty - the Straight Road of the Qin Dynasty (B), southwestern cluster district (C) and northwestern cluster district (D) and the strong influence area of the Great Wall of the Qin Dynasty - the Straight Road of the Qin Dynasty (A) is the most important region with a proportion of 48.39% of the total. The city sites of the Han Dynasty in the Mu Us Sandy Land Desert are sparsely distributed in the west and densely in the east, which may be characterized as "patial agglomeration". The paper includes a discussion of factors influencing the spatial pattern of city sites, notably, human factors and natural factors. Although climate condition, landforms and water resources mainly restrict the selection of the city, human-driven forces, including political, military, and transport conditions, have played a leading role in the formation of the location and the number of the city sites.
Professor Luo Laixing is a famous geomorphologist in China. He achieved a series of important research results in the loess geomorphology, river geomorphology, and tectonic geomorphology. From the 1940s to 1980s, Prof. Luo had access to numerous first-hand data of field survey in the Southeast China Hills, Yellow River Basin, Hengduan Mountains, Loess Plateau, and Tianshan Mountains. He comprehensively and systematically examined the landscape types and analyzed its causes, spatial distribution and evolution as well as published a number of papers based on original research results. He made great contribution to geomorphologic development of China in the early period of New China.
