Based on the data from 36 sampling points, we analyzed the distribution of soil active organic carbon (SAOC) of alpine grassland on the Qinghai-Tibet Plateau. The results are shown as follows. (1) In the horizontal direction, the SAOC was significantly different between grassland types and natural transects. In general, its content appeared high in southeast and low in northwest with an overall plaque-like distribution pattern. The high-SAOC areas are mainly in the hinterland of the northern plateau and the Himalayan north basin area. (2) In the vertical direction, the SAOC distribution of 0-40 cm sections of different grassland types and different natural areas could be divided into descending type, ascending type and lower-higher-lower type. There were significant differences between the SAOC contents of the 0-10 cm layers and the 30-40 cm layers. (3) Using the regression model-based standard coefficient method, we analyzed the impact of climatic factors on the SAOC content of alpine grassland, indicating that the precipitation contributed more than the temperature in the alpine grassland SAOC.
With climate warming, Glacier Lake Outburst Floods (GLOFs) are increasingly threatening people and property, which has been intensively studied worldwide. This paper takes the Himalayas region of China as the study area, where the GLOFs have frequently occurred during the past decades. The 143 potentially dangerous glacier lakes were first identified by six indexes in the study area. Then, the probabilities of three types of possible breaching modes (i.e. ice avalanche, glacier slide, ice-core melting) were quantitatively graded on the basis of the criteria of the probabilities of moraine-dammed lake breaching modes. Breach probabilities of the 143 potentially dangerous glacier lakes were further calculated by means of decision-making trees methods.
Due to water reduction, the area of oasis degraded rapidly, and many eco-environmental problems have emerged in the lower Heihe River. For the sake of improving the eco-environment, and deterring the trend of further degradation of the oasis, the water transport project in the lower reaches of the Heihe River was carried out in 2000. According to the water line, there are great changes of temporal and spatial distribution of water resources in the lower Heihe River in the past nine years. As a result, the vegetation in the lower Heihe River also changed. In order to objectively evaluate the influence of water regulation on vegetation in this region, in this paper, by means of field surveys and remote sensing, the response range and extent of the groundwater were described, and the variation of natural vegetation in the lower reaches as a result of change of the groundwater level were also described in about five years, and the rules of groundwater response to the ecological water transport were analyzed preliminarily. These results show that there are obvious effects of water regulation on the vegetation, and that the eco-environment is experiencing a good change in the lower Heihe River.
Based on the daily data of 24 meteorological stations from 1960 to 2006 and combined with the Penman-Monteith model, the changing trend of potential evaporation in the Tianshan Mountains was analyzed in this study. By the method of IDW under ArcGIS the spatial distribution of potential evaporation was drawn in order to research regional difference. And the multivariate regression method was used to discuss the dominant factor influencing potential evaporation. The results indicated that since the 1960s the annual potential evaporation has presented an undulated decreasing trend, and the decreasing trend was more evident since 1986. It began to increase since 2000. There was a decreasing trend in general because the changing rate of annual potential evaporation varied at -2.48 mm/a. The potential evaporation increased in autumn, however, decreased in other seasons especially in spring. The wind speed was a dominant factor influencing potential evaporation, while temperature was the key factor in autumn.
Paleosalinity of Tianluoshan Site is reestablished by mensurations and analyses of clay mineral, boron, strontium, barium, after sampling in a profile of Tianluoshan Site. The relative sea level changes are discussed according to the lab results. It turns out that there are at least three time periods of relative sea-level highstand not only before but also during and after Hemudu Culture in Tianluoshan Site. Based on previous researches and through studying several environmental elements comprehensively, the characteristics of environmental background and their relationships between human activities and development of Hemudu Culture are systematically discussed.
Based on the samples from the west wall of the ABYT2004 at Yuhuicun Site, the environmental substitute indexes such as the grain-size, Rb/Sr, heavy-mineral (Zircon) and magnetic susceptibility were analyzed. The age of archaeological stratigraphy was determined by the AMS14C. The results reveal that the environment evolution induced to the climate changes from 4.5kaBP to 4.0kaBP, Longshan Culture Period. Besides, the information of the ancient human activities and the cultural heritage data withdrawn from the Longshan Culture archaeological stratigraphy, shows that the Longshan culture development was an influenced mechanism. Archaeological excavation shows the following in the study area: (1) In the period before 4500aBP, from 4500aBP to the middle of the period of Longshan Culture, to the later period of Longshan Culture and to 4000aBP, most parts of the region experienced climate change such as warm and wet, cold and dry, warm and wet, cold and dry. (2) Before 4500aBP of the wet period, the Huaihe River water reached a very high level so that the Yuhuicun Site and the surrounding area were submerged and people could not live in the area around the site. From 4500aBP of the dry period, the water level in the Huaihe River and its branches started to descend. (3) Around 4100aBP, in the later period of Longshan culture, it again became cold and dry, and the river water flooded the land again. During this period, the agricultural activity was destroyed, and Longshan Culture disappeared. (4) The environmental information in sedimentary strata and the historical records from the literature confirmed each other, which reveals the close relationship between the Yuhuicun Site and the "Dayu Controlling Flood" recorded in historical documents.
The global warming conclusion is given in 4th IPCC Assessment Report. This paper analyses uncertainties of surface temperature rise in recent 100 years from data source aspect referred in IPCC report, including spatial distribution of surface temperature observation stations, temperature series length, temperature reliability, urban heat island effect etc. It is concluded that (1) the coverage of surface temperature observation station in global skin has been low in recent 100 years; (2) spatial distribution of data source in some grid boxes is uneven; (3) there are limited long time series of temperature, and there are significant differences of annual temperature record quantities in different time periods; (4) deficient successive observations in many stations lead to low reliability of mean annual temperature; (5) most temperature records are obtained from urban stations, while heat island effect is not fully excluded in climate change research.
More than 240 items of climatic information were chosen from the official historical books, local chronicles, annals and regional meteorological disaster yearbooks. By using Moisture Index and Flood-drought Index obtained from the above information, we studied the historical climate change, namely aridity-humidity conditions in the borderland of Shaanxi Province, Gansu Province and Ningxia Hui Autonomous Region. The results showed that during the period of 1208-1369, it tended to be dry in the region and the ratio of drought to flood disasters was 85-38. According to the frequency of drought-flood disasters, the period can be identified into three stages. (1) 1208-1240: drought dominated the stage with several flood disasters occasionally; (2) 1240-1320: Long-term drought disasters and the extreme drought events happened frequently; and (3) 1320-1369: The drought disasters were less severe but the flood and drought disasters happened alternately. Besides, the reconstructed aridity-humidity experenced an abrupt change as well as a periodicity in the Mongol-Yuan Period. The turning points were 1230 and 1325. There were 10-year and 23-year quasi-periods in the aridity-humidity changes, which were consistent with solar cycles, indicating that solar activity affected the aridity and humidity conditions of the study region in the Mongol-Yuan Period. The reconstructed results are consistent with two other study results rebuilt by natural evidences, and are also similar to another study result rebuilt by historical documents.
This paper analyzed the temporal and spatial responses of vegetation NDVI to the variations of temperature and precipitation in each ten-day period in the whole year, spring, summer and autumn covering 1998 to 2007 based on the SPOT VGT-NDVI data and daily temperature and precipitation data from 205 meteorological stations in eastern China. The results indicate that on the whole, the response of vegetation NDVI to the variation of temperature is greater than to that of precipitation in eastern China. Vegetation NDVI maximally responds to the variation of temperature with a lag of about 10 days, and it maximally responds to the variation of precipitation with a lag of about 30 days. The response of vegetation NDVI to temperature and precipitation is the greatest in autumn, and the lag time is longer in summer. Spatially, the maximum response of vegetation NDVI to the variation of temperature is greater in the northern and central parts than in the southern part of eastern China. The maximum response of vegetation NDVI to the variation of precipitation is greater in the northern part than in the central and southern parts of eastern China. There is more lag time of vegetation NDVI to the variation of temperature in the northern and southern parts, while less in the central part. The lag time of vegetation NDVI to the variation of precipitation gradually increases from the northern to the southern part according to the latitude. The response of vegetation NDVI to the variations of temperature and precipitation in eastern China is mainly consistent with other results obtained in eastern and southern China.
This paper analyzes the interdecadal variation of water vapor transport over East Asia and its impacts on rainfall over eastern China in summer by using EOF analysis method, NCEP/NCAR monthly reanalysis data and monthly rainfall data covering 160 stations over China from 1951 to 2004 in summer. The results show that the main distribution mode of summer rainfall over eastern China is south and north flooding/middle drought from the mid- and late of the 1970s to the beginning of the 1990s and presents a south flooding/north drought pattern since the beginning of the 1990s. The interdecadal variation of summer rainfall over eastern China is very significant and rain belt shifts southward obviously since the 1990s. The leading mode of EOF and its time series coefficients reveal that the meridional water vapor transport over east of East Asia Mainland is characterized by a turning point from strong to weak and a decadal weakening trend since 1974. The zonal water vapor transport over India Mainland and northern part of Bay of Bengal, middle and lower reaches of Yangtze River Valley, South China Sea and tropical Pacific region is characterized by a turning point from weak to strong and a decadal enforcing trend since 1973. The temporal-spatial evolution in summer water vapor transport over East Asia is one of key factors that trigger a shift from south and north flooding/middle drought to south flooding/north drought, which leads to the induction of the rain belt shifting southward.
Parameters of BCC/RCG-WG for daily precipitation simulation at 672 stations in China are calculated with historic daily precipitation data from 1951 to 1978 and from 1979 to 2007 respectively. Two sets of four parameters for the two periods are compared to review the impact of climate change on the parameters. The results show that transition probabilities from dry to wet and from wet to wet in most parts of China have a decreasing trend except parts of western China. The decreasing range of P(WW) in most parts of China are less than that of P(WD). Shape parameter ALPHA of GAMMA distribution of daily precipitation in most parts of China has a slightly increasing trend except parts of western Northwest China. Scale parameter BETA of GAMMA distribution of daily precipitation in most China, especially in parts of western Northwest China, has an obviously increasing trend. Compared with BETA, the changes of ALPHA are generally smaller (within 6%) in most China. Changes of parameters of daily precipitation simulation in each month and season are also analyzed, which shows a regional and seasonal difference.
Tree-ring width chronology was constructed by using the tree ring cores of Pinus tabulaeformis Carr. from two sites on Funiu Mountain in western Henan Province. Correlation analysis showed that the tree ring index was closely related to average maximum temperature of May-July. We reconstructed the average maximum temperature of May-July for Funiu region from 1874 to 2007. "Jackknife" and "Bootstrap" methods were used respectively to estimate reliability of regression function based on statistics between the observed and reconstructed series. The explained variance reaches 40% (39% after adjusted degree of freedom). The overall test results sufficiently supported the validity of our regression model. Reconstruction indicated that there were 4 cold and 5 warm periods for the past 134 years respectively in this area. The most significant warm period during the entire reconstruction occurred between the 1920s and 1940s, and then the temperature began to decrease and reached to the lowest point in the 1950s. After a slight rise, it decreased again during the 1970s and 1980s. The temperature has increased rapidly since the late 1980s, showing a warming trend. Both the Funiu and Nanwutai temperature curves can be well compared after 10-year moving average, and they showed the regional trends synchronously.
Mean daily maximum temperature (MDMT) is one of major indexes of heat resource. The previous models have been improved in this paper on the basis of previous studies. The influence of slope, aspect, and terrain inter-shielding on astronomical solar radiation over complex terrains (CT) is considered, and a distributed model, based on astronomical solar radiation over CT and the elevation height, the global solar radiation over CT, the sunshine percentage, for calculating monthly MDMT over CT is developed. Using this model, the elaborate distribution of monthly MDMT with a resolution of 100m×100m is generated by a DEM, meteorological observations data at 102 weather stations of the Guizhou province and surrounding area, observations data of NOAA-AVHRR and solar radiation data of 10 weather stations. The results are as follows: (1) The influence of the slope, aspect and terrain inter-shielding on spatial distribution of monthly MDMT is great. Due to the influence of local terrain factors, the spatial distribution of monthly MDMT over CT on Guizhou Plateau has obvious terrain distributing feature, and the effect of CT on monthly MDMT should be considered. (2) The effect of local terrain factors on spatial distribution of monthly MDMT over CT is different in different seasons, and it is greater in winter half year than in summer half year. The monthly MDMT decreases with the rise of above sea level. It increases with the slope accretion (decrease) on south (north)-central face of the mountain. The monthly MDMT increases from north-central face to south-central face of the mountain, and they are the highest (lowest) on south (north)-central face of the mountain from January to May and from October to December. It is opposite in July and August because of high solar altitude angle.
