Virtual Geographic Environments (VGE) is an integrated virtual space which is used to simulate and analyze complex phenomena and process of geography. It supports activities of research on geography as collaborative work, knowledge sharing and group decision-making. It can become one of the scientific methods and advanced technologies of modern experimental geography study. In the paper, the development process and progress of VGE and experimental geography are introduced, the roll and prospect of VGE and virtual geographic experiment on modern experimental geography are focused, key issues and existing misunderstanding about current studies on VGE are discussed. Integrated research on VGE and experimental geography highlights the importance of geographic model and knowledge in geography study, stresses that VGE can promote the theory and methods of modern experimental geography study, and contribute to the development of geographic science.
The Jianglang Mountain is situated at the transitional zone of South China fold-system, Jiangshan-Shaoxing deep rip belt and Baoan-Xiakou-Zhangcun rip belt. The formation of the Xiakou basin was a result of the tensioning of the above mentioned two rips in early Cretaceous, afterward, series deposits such as Guantou formation (K1g), Chaochuan formation (K1c) and Fangyan formation (K1f) which belong to Yongkang group, lower Cretaceous phase, were gradually built, whilst the rips occurred to extrude and the basin began to rise in late Cretaceous. Meanwhile, amounts of tension fissures and joints have been produced since Cenozoic, accelerating down-cutting velocity in base rock. Consequently, landform-building activities such as weathering, eroding and collapsing etc. were prevalent as finally to develop the Danxia landform. The main sceneries to apply for world natural relics are relying on unique and unparalleled peak, split valley with vivid stones and reviving of platform. What is more, it is significant to study lithology, stratigraphy and paleo-biology. According to dating for specimen of dolerite vein through the Yongkang group of Mt. Yafeng by K-Ar method, this article revealed the uplift age of red-bed basin to be 77.89±2.6 Ma BP (K2), i.e., late Cretaceous, the first chronological datum of Danxia landform research in China.
Evidence from all over the world shows that the timing of mountain glacier maxima advances varied widely. Studies on the climatic conditions, tectonic background, glacial sequences and glacier extents show that they are different from region to region. Three glacial remains are preserved in Taiwanese mountains including the middle/early stage, last glacial maximum and late-glacial stage glaciers. The glacier extent in MIS3b is larger than MIS2. The glacier geomorphology and landforms are well perserved in Japanese high mountains, such as the MIS2, MIS3 and MIS4 stage glaciers, and the glacial extent in MIS4/3 is larger than that of MIS2. The high mountain range of the Changbai Mountains is unglaciatied at present, but numerous glacial landforms and related sediments around the Tianchi Lake, especially on the northern and western slopes of the volcanic cone, indicated that there was repeated glaciation in these areas during the last glacial cycle. The glacial landforms and deposits in the study area are assigned to the LGM (MIS2) and the Late Glacial. Seasonal and atmospheric cycle differences and different geographic locations caused different conditions of precipitation and temperature. New calculation of the modern theoretical snowline (ELA) and ELA depression during the LGM shows that the ELA is 2750-4245 m from the northernmost Japan to the southernmost Taiwan, and the ELA depression is 800-1300 m with an average value of 1000 m except in the northern part of Japan (only 400 m). The glacial development is obviously affected by the neo-tectonic actions. A 250-m mountain uplift is calculated using the minimum value of uplift rate 5 mm/yr in the Taiwanese mountains during the MIS3b glacier stage.
This study is to reveal the wetland system pattern of Huaihe River basin during the Sui-Tang (A.D.581-907) dynasties and Northern Song (A.D.960-1127) Dynasty, which were two millenarianism periods in Chinese feudal history. The data reflecting the wetland system pattern of Huaihe River basin during these two periods were mainly digitalized from "The Historical Atlas of China" and the data reflecting present wetland system pattern of Huaihe River basin were from "Basic Geographic Information Database of China". Based on ArcView GIS software, this study generated the sketch maps of wetland system pattern for the two historical periods and then discussed the pattern changes.From Sui-Tang to Northern Song, there were no significant changes for macro pattern of wetland system of Huaihe River basin. Wetland system was stable during Sui-Tang periods and relatively stable during Northern Song Dynasty. Natural wetlands in the basin, such as rivers and lake-marshes, maintained their relative stableness, which determined the stability of macro pattern of wetland system in the basin throughout the period. Stable wetland system pattern of Huaihe River basin provided good natural environmental background for the development of agricultural economy and social culture during that period. The major changes of wetland system of Huaihe River basin during these periods came from artificial wetlands.
Based on pollen, paleosol, archaeology materials and terrain features in Gansu-Qinghai Region, this paper reveals that climate was warm and humid at 4 ka BP, culture of Majiayao was distributed over forest-steppe valley region around the Yellow River and its branches. The Liupan Mountain was the eastern boundary of culture of Majiayao, which extended northward to Hexi Corridor and was mainly engaged in planting industry. Around 4 ka BP, environment went worse, and natural zones moved eastward. Meanwhile, culture of Qijia replaced that of Majiayao, and the survival environment shifted to temperate steppe. In order to respond and be adapted to the environmental changes, cultural relics moved southeastward back to low elevation regions, and the proportion of animal husbandry in industrial structure increased obviously.
Based on the temporal-spatial distribution features of ancient settlement sites from the middle and late Neolithic Age to the Han Dynasty in the Chaohu Lake Basin of Anhui Province with the methods of GIS, combining with the reconstructed paleoenvironment by the records of lake sediment since Holocene in the Chaohu Lake, the transmutation of ancient settlements with responses to environmental changes in this area has been discussed. Study shows that the main feature of the transmutation of ancient settlements from the middle and late Neolithic Age to the Han Dynasty was that the distribution of settlements in this area changed from high altitude to the low one and kept approaching to the Chaohu Lake with the passage of times. These could be the response to the climate change from warm-moist to a relatively warm-dry condition during the middle Holocene, leading to the lake level fluctuations. The large area of exposed land provided enough space for human activities. These indicate that the above changes in geomorphologic evolution and hydrology influenced by climate conditions affected the transmutation of ancient settlements greatly. The distribution pattern of settlement sites was that the number of the sites in the west was more than the east. This pattern may be related to the geomorphologic conditions such as frequent channel shifting of the Yangtze River and flood disasters during the Holocene optimum. Therefore, the climate change is the inducement of the transmutation of ancient settlements in the Chaohu Lake Basin, which exerts great influence on the distribution, expansion and development of the ancient settlements, and the transmutation of ancient settlements responded to the environmental changes evidently.
The authors developed a model to estimate annual tree growth based on tree-ring data (Abbr. TGTRing model) derived from the trunk at 0.5 m, 1.3 m and 2.5 m height. This model was applied to estimate the annual biomass and carbon accumulation of a plantation in Qianyanzhou Red-Soil Hill Comprehensive Development Experimental Station of CAS in Taihe County, Jiangxi Province (Abbr. Qianyanzhou). The results showed that the inflexion points of the biomass and carbon accumulation curves occur at 17 and 18 years of age, respectively, in Masson pine, whilst both inflexion points occurred at 15 years in slash pine and Chinese fir. The biomass and carbon accumulation in Chinese fir proved to be greater in the last 20 years than in the other species, with 171.697 t/hm2 and 92.29 tc/hm2, respectively. Masson pine, with a biomass of 133.84 t/hm2 and a carbon accumulation of 73.92 tc/hm2, was the lowest whilst slash pine was intermediate with a biomass of 147.639 t/hm2 (unturpentined) and 135.743 t/hm2 (turpentined), and a carbon accumulation of 80.18 tc/hm2 (unturpentined) and 73.72 tc/hm2 (turpentined). In 2006, the total biomass and carbon storage of the tree stratum of Masson pine in Qianyanzhou was 3324.43 t and 14156.64 tc, respectively, whilst the values for Chinese fir were 1326.97 t and 713.27 tc. For slash pine was the total biomass was 14156.64 t (unturpentined) and 13015.97 t (turpentined), and the total carbon storage was 7688.21 tc (unturpentined) and 7068.78 tc (turpentined). Following the shaving of slash pine for resin, the total biomass was reduced by 1140.67 t and the total carbon storage fell by 619.43 tc.
The Normalized Difference Vegetation Index (NDVI) data in Inner Mongolia during 1982 to 2003 were used to classify the vegetation belts in four time periods and reveal spatial shifts of the vegetation belts between two sequential periods. Then, we analyzed the spatial and temporal variations of the vegetation cover degree and its relation to thermal-moisture factors taking the tpical steppe belt as an example. During the study period, the area of the typical steppe belt showed an increscent tendency, whereas the area of the desert steppe belt indicated a decreasing tendency. Otherwise, areas of the forest belt, the forest steppe belt and the desert belt did not represent any apparent tendency. Generally speaking, an evolution succession of vegetation belts was dominant during period 1 (1982-1987) to period 2 (1988-1992), whereas a degradation succession of vegetation belts (following succession orders of forest→forest steppe→typical steppe→desert steppe→desert) was dominant during period 3 (1993-1998) to period 4 (1999-2003). In between, evolution and degradation successions of vegetation belts were counterbalanced during period 2 (1988-1992) to period 3 (1993-1998). A significantly positive correlation appeared in the western part of the Xilingol Tableland and the Ulanqab Tableland. In contrast to precipitation, the correlation between the vegetation cover degree increment and air temperature was less significant. From 1982 to 2003, areas with decreasing and increasing linear trends of the annual maximum vegetation cover degree accounted for 52.6% and 47.4% of the entire Inner Mongolia, respectively, of which significantly decreasing trends appeared at the western edge of the Hulun Buir Tableland and the both sides of the Da Hinggan Mountains.
This study aims at revealing how land use and land cover changed in the mainstream of the Tarim River since 1973. Combining the integrated technology of ecological quantity analytical method with GIS technology, based on the MSS images in 1973, TM images in 1990 and 2000, CBERS images in 2005, and the land use data of 1983, the changes of land use/cover and landscape pattern were analyzed in this paper in the mainstream of the Tarim River from 1973 to 2005. The results showed that the areas of farmland and residential land increased obviously, areas of grassland, forest and wetland decreased, and that of unused land increased first then decreased. The major patterns of land use change were the conversions of grassland, forest and wetland to farmland, farmland to residential land, and grassland to unused land. Land use change underwent a process of obvious change - slow change - obvious change - tremendous change. The analysis of landscape index showed that due to the disturbance of human activities, landscape diversity index increased while landscape dominance index decreased. Simultaneously, landscape fragmentation index increased gradually.
The pH values and Electrical Conductivity Measurement (ECM) records in three shallow ice cores from Glacier No.1 at the headwater of the Urumqi River, Kuitun Glacier No.48 and Hami Miaoergou Glacier in the eastern Tianshan Mountains, western China were measured and analyzed for the research on atmospheric environmental change. Ice core records show that the changing trends of pH and ECM at the three sites in recent about 10 years are different: Kuitun ECM increased with the change of the ice depth, but Hami site and Urumqi Glacier No.1 show a decreasing trend. The average ECM value in Hami is greater than the other two sites, just as the case of high dust concentration and ions concentration at this site. ECM records are mainly affected by Asian dust, as the correlative coefficients of ECM and mineral ions such as Ca2+, Mg2+ and Na+ are significantly high. Also, pH and ECM are significantly high correlative coefficients, which coincide with the research on the Tibetan Plateau, but different from that in the polar regions.
The cross wavelet transform method is adopted to study the time-frequency characteristics and multitime scale correlations between the runoff and precipitation, evaporation, maximum and minimum temperature in the source region of the Yellow River. The results show that the variations of runoff and regional climate in the source region of the Yellow River present periodic oscillations of different significance in frequency space and the localization characteristics in time space. There are significant periods at scales of quasi-biannual, 4a, 6-8a, 12-14a and above 20a in both of the runoff and regional climate variations. The power of periodic oscillation at different frequency scales and phase differences in time space are important causes for the unstableness and the lag correlations. The coherence of positive correlation between runoff and regional precipitation is the highest in the climatic factors, indicating that the variations of regional precipitation have a predominant effect on the runoff variations. The unconventionality of regional precipitation at pre-period has durative influence on the runoff. Negative correlation between runoff and regional evaporation is significant, but unstable with lag correlations on the interannual timescale. The coherence of negative correlation between runoff and maximum temperature is higher than the positive correlation between runoff and minimum temperature on interdecadal timescale, that is to say, the effect of decreasing the runoff supply due to maximum temperature rise induced the regional evaporation increase is greater than the effect of increasing the runoff supply due to minimum temperature rise caused ice thawing and snowmelt in the long term change. The unstableness of the interannual timescale correlations between runoff and maximum and minimum temperature is distributed in some of the time space. And the phase differences of them indicate that responding time of runoff to temperature variations is different. Analysis makes it known that the primary factor is the regional precipitation on the runoff variations, maximum temperature is important factor, and the regional evaporation and minimum temperature also have different influences on the runoff variations. Synthetic effect of regional climatic elements is the prime cause for runoff variations in the source region of the Yellow River.
