• The influence of freeze-thaw cycles on the granulometric composition of Moscow morainic clay
• Ze Zhang, Vadim V. Pendin, WenJie Feng, ZhongQiong Zhang
• DOI: 10.3724/SP.J.1226.2015.00199
• 2015, Vol.7 (3): 199–205 Abstract ( 292) HTML PDF (426 KB) ( 403 )
• The freeze-thaw cycling process considerably changes the composition, structure, and properties of soils. Since the grain size is the most important factor in determining soil characteristics, our current research primarily aims to investigate dynamic changes of the soil fraction when exposed to freeze-thaw conditions. We observed two series of Moscow morainic clayey specimens (gQ_II^m): (I) the original series, and (II) the remolded series. We subjected each series of soil specimens to different frequencies of freeze-thaw cycles (3, 6, 20, and 40 cycles), and we used granulometric tests to analyze both series before and after exposure to freeze-thaw conditions. As a result of our experiments, the granulometric compositions tended to be distributed evenly after 40 freeze-thaw processes (i.e., content of fraction for 0.1-0.05 mm was increased after 40 freeze-thaw cycles) because the division of coarse grains and the aggregation of fine grains were synchronized during the freeze-thaw process. The soil grains in both series changed bi-directionally. In the original series, changes of the sand grains were conjugated with the clay grains, and in the remolded series, changes of the sand grains were conjugated with the silt grains, because potential energy difference caused the division and aggregation processes to relate to the counteraction process. The even distribution of soil grain size indicated the state of equilibrium or balance. The granulometric compositions were altered the most during the sixth freeze-thaw cycle, because the coefficient of the intensity variation of the grain fineness (K_var) had its maximum value at that time.

• Movement and variation of four typical glaciers in the Qilian Mountains, northwestern China
• ZheFan Jing, Kun Wang, Li Liu
• DOI: 10.3724/SP.J.1226.2015.00206
• 2015, Vol.7 (3): 206–211 Abstract ( 291) HTML PDF (262 KB) ( 351 )
• We selected four typical glaciers in the Qilian Mountains and investigated their movements and variation using advanced technologies such as remote sensing, photographic measurements, and global positioning systems. The velocity of glacier movements in the Qilian Mountains is relatively low, and there has been no significant variation during the past 50 years. Glacier motion has maintained a normal style. The movement velocity of Laohugou Glacier No. 12 presented a decreasing trend (by 48%) from 1960 to 2012. The movement velocity of the Qiyi Glacier also presented a decreasing trend (by 48.1%) from 1958 to 2012; it decreased by 29.4% from 1958 to 1977 and by 26.5% from 1977 to 2012. Therefore, the Qiyi Glacier's movement velocity varied greatly over the earlier 20 years (1958-1977), but presented a small decreasing trend during the latter 30 years (1977-2012). By comparing the movement velocity variation of these typical glaciers, we determined that the extent of variation was consistent among large glaciers (such as Laohugou Glacier No. 12) and small glaciers (such as the Qiyi Glacier and Yanglonghe Glacier No. 5), despite their different sizes.

• Experimental research on physical properties of saline soil subgrade filler in Chaerhan region
• Yu Zhang, JianHong Fang, JianKun Liu, AnHua Xu
• DOI: 10.3724/SP.J.1226.2015.00212
• 2015, Vol.7 (3): 212–215 Abstract ( 247) HTML PDF (198 KB) ( 253 )
• In order to improve the engineering stability of saline soil of high chloride content in the Chaerhan salt lake region, six typical characteristics saline soil samples were selected, and tests on their primary physical properties (total salt content, specific gravity of soil, liquid limit, plastic limit, maximum dry density, and optimal water content) were conducted. The relationships among them were analyzed, a series of variation laws between salt content and these basic physical parameters were determined, and regression equations were derived. This research can improve future engineering design and construction in saline soils and can also help prevent subgrade filler from undermining subgrade stability and producing disease.

• Comparing the seasonal variation of parameter estimation of ecosystem carbon exchange between alpine meadow and cropland in Heihe River Basin, northwestern China
• HaiBo Wang, MingGuo Ma
• DOI: 10.3724/SP.J.1226.2015.00216
• 2015, Vol.7 (3): 216–228 Abstract ( 299) HTML PDF (682 KB) ( 387 )
• Grasslands and agro-ecosystems occupy one-third of the global terrestrial area. However, great uncertainty still exists about their contributions to the global carbon cycle. This study used various combinations of a simple ecosystem respiration model and a photosynthesis model to simulate the influence of different climate factors, specifically radiation, temperature, and moisture, on the ecosystem carbon exchange at two dissimilar study sites. Using a typical alpine meadow site in a cold region and a typical cropland site in an arid region as cases, we investigated the response characteristics of productivity of grasslands and croplands to different environmental factors, and analyzed the seasonal change patterns of different model parameters. Parameter estimations and uncertainty analyses were performed based on a Bayesian approach. Our results indicated that: (1) the net ecosystem exchange (NEE) of alpine meadow and seeded maize during the growing season presented obvious diurnal and seasonal variation patterns. On the whole, the alpine meadow and seeded maize ecosystems were both apparent sinks for atmospheric CO₂; (2) in the daytime, the mean NEE of the two ecosystems had the largest values in July and the lowest values in October. However, overall carbon uptake in the cropland was greater than in the alpine meadow from June to September; (3) at the alpine meadow site, temperature was the main limiting factor influencing the ecosystem carbon exchange variations during the growing season, while the sensitivity to water limitation was relatively small since there is abundant of rainfall in this region; (4) at the cropland site, both temperature and moisture were the most important limiting factors for the variations of ecosystem carbon exchanges during the growing season; and (5) some parameters had an obvious characteristic of seasonal patterns, while others had only small seasonal variations.

• Comparative studies on leaf epidermal micromorphology and mesophyll structure of Elaeagnus angustifolia L. in two different regions of desert habitat
• MengMeng Li, YuBing Liu, MeiLing Liu, Dan Liu
• DOI: 10.3724/SP.J.1226.2015.00229
• 2015, Vol.7 (3): 229–237 Abstract ( 390) HTML PDF (1449 KB) ( 404 )
• In order to obtain qualitative and quantitative characteristics of leaf epidermal micromorphology and mesophyll structure to evaluate the responses of Elaeagnus angustifolia L. to different environmental factors, epidermal micromorphology was observed by scanning electron microscopy (SEM), and mesophyll structure was studied by light microscopy (LM) and transmission electron microscopy (TEM). Materials were selected from Linze County, Gansu Province (material A) and Qitai County, Xinjiang Uygur Autonomous Region (material B) of China. Results show that lamina thickness was higher in material A, with one layer of epidermal cells in both adaxial and abaxial surfaces, and epidermal cell radial length was significantly longer in the adaxial surface. E. angustifolia leaves are typically bifacial, with a higher ratio of palisade to spongy tissue in material A. The thickness of trichome layer of epidermis was thicker in material A. In contrast, cell wall and cuticular wax of the epidermal cells were thinner in material A than in material B. Chloroplast ultrastructure was different with the approximate spherical chloroplast containing numerous starch grains and osmiophilic granules in material A, while only the spindly chloroplast contained starch grains in material B. Multiple layers of peltate or stellate-peltate trichomes occupied both leaf surfaces in material A and the abaxial surface in material B, while the adaxial surface of material B contained few trichomes. Stomata were not observed on the leaf surfaces in materials A and B by SEM because of trichome obstruction. Our results indicate that the leaf structure of E. angustifolia is closely correlated with environmental factors, and the combination of leaf epidermal micromorphology and mesophyll structure afford resistance to environmental stress.

• Biomass and water partitioning in two age-related Caragana korshinskii plantations in desert steppe, northern China
• RenTao Liu, Fan Zhu
• DOI: 10.3724/SP.J.1226.2015.00238
• 2015, Vol.7 (3): 238–244 Abstract ( 213) HTML PDF (174 KB) ( 287 )
• Understanding of biomass and water allocation in plant populations will provide useful information on their growth pattern and resource allocation dynamics. By direct measurement, the biomass and water content partitioning were compared at the aboveground, belowground and whole-plant levels for artificial Caragana korshinskii populations between 6- and 25-year-old sites in desert steppe, northern China. The biomass was mainly allocated to third-grade branches at the aboveground level, and to first- and second-grade roots at the belowground level, and to aboveground parts at the whole-plant vegetative level. Those plant parts mentioned above became the major component of biomass pool of these shrub populations. Biomass pattern changed significantly at aboveground and/or whole-plant levels (P <0.05), but not at belowground level (P >0.05) at 25-year-old site in comparison to 6-year-old site. Also, the water relations between different plant parts changed considerably at all three levels from 6- to 25-year-old sites. These results imply that biomass pattern and relative water content of plant parts are correlated with the process of plantation development. The ratio of belowground to aboveground, though below 1, increased from 6- to 25-year-old site. These results suggest that these shrub populations can adjust biomass partition and relative water content of different compartments to alter their ecological adaptive strategies during stand development in desertified regions.

• Characterizing stand structure in a spruce forests: effects of sampling protocols
• Jun Du, WeiJun Zhao, ZhiBin He, JunJun Yang, LongFei Chen, Xi Zhu
• DOI: 10.3724/SP.J.1226.2015.00245
• 2015, Vol.7 (3): 245–256 Abstract ( 186) HTML PDF (456 KB) ( 476 )
• Spatial heterogeneity is an inherent characteristic of natural forest landscapes, therefore estimation of structural variability, including the collection and analyzing of field measurements, is a growing challenge for monitoring wildlife habitat diversity and ecosystem sustainability. In this study, we investigated the combined influence of plot shape and size on the accuracy of assessment of conventional and rare structural features in two young-growth spruce-dominated forests in northwestern China. We used a series of inventory schemes and analytical approaches. Our data showed that options for sampling protocols, especially the selection of plot size considered in structural attributes measurement, dramatically affect the minimum number of plots required to meet a certain accuracy criteria. The degree of influence of plot shape is related to survey objectives; thus, effects of plot shape differ for evaluations of the "mean" or "representative" stand structural conditions from that for the range of habitat (in extreme values). Results of Monte Carlo simulations suggested that plot sizes <0.1 ha could be the most efficient way to sample for conventional characteristics (features with relative constancy within a site, such as stem density). Also, 0.25 ha or even larger plots may have a greater likelihood of capturing rare structural attributes (features possessing high randomness and spatial heterogeneity, such as volume of coarse woody debris) in our forest type. These findings have important implications for advisable sampling protocol (plot size and shape) to adequately capture information on forest habitat structure and diversity; such efforts must be based on a clear definition of which types are structural attributes to measure.

• Elemental composition and its environmental significance for the varicolored hills in the northern foothills of the Qilian Mountains of Sunan Yugur Autonomous County, China
• CaiXia Zhang, XiaoZe Li, Zhong Sun, JinChang Li
• DOI: 10.3724/SP.J.1226.2015.00257
• 2015, Vol.7 (3): 257–264 Abstract ( 241) HTML PDF (392 KB) ( 287 )
• The varicolored hills in the northern foothills of the Qilian Mountains of northern China, in the Hexi Corridor of Gansu Province's Sunan Yugur Autonomous County, have given this region a unique geomorphology. In this paper, we describe the elemental composition, lithological characteristics, and source type of the sediments that formed the varicolored hills. We found that the major oxides that make up their sediments are SiO₂, Al₂O₃ and Na₂O. These sediments had higher Fe₂O₃, MgO, CaO, and Na₂O contents and lower SiO₂, Al₂O₃, K₂O, and TiO₂ contents than in the major Fangyan rock group of the Jianglang Mountains Danxia landform and the red paleosols that have accumulated in the Yaojia Formation of the Songliao Basin. The varicolored hills have developed their strong coloration as a result of oxidation or reduction of Fe. Our data suggest that the sediments developed from terrestrial detrital deposits.

• Aesthetic evaluation of yardang landforms landscape: the Dunhuang Yardang National Geo-park example
• RuiJie Dong, ZhiBao Dong
• DOI: 10.3724/SP.J.1226.2015.00265
• 2015, Vol.7 (3): 265–271 Abstract ( 384) HTML PDF (499 KB) ( 398 )
• Dunhuang Yardang National Geo-park, situated in the Gansu Province of northwestern China (40º25'36"N-40º33'10"N, 93º00'00"E-93º13'30"E), was chosen as a research locality of aesthetics evaluation of yardang landforms landscape. The yardang landforms landscape is a composite structural system of patch-corridor-matrix, with four landscape unit elements as dense group, sparse group, single body and remnant. The study of the landscape aesthetics spatial pattern of Dunhuang Yardang National Geo-park shows that yardang dense group, sparse group and single body provide the greatest contribution to the aesthetic value of yardang landforms landscape. Yardang bodies are scarce, unique, irreplaceable, and priceless resources in yardang landforms areas. However, they are easily destroyed under the influence of the natural and artificial factors. Therefore, when the tourism potential of yardang landforms landscape is exploited, the protection should be fully improved.

• Characterizing changes in ecosystem service values in China's eastern Loess Plateau
• JinChang Li, HaiXia Liu, ZhiZhu Su, Yong Liu, YongGang Yang
• DOI: 10.3724/SP.J.1226.2015.00272
• 2015, Vol.7 (3): 272–281 Abstract ( 247) HTML PDF (384 KB) ( 304 )
• Human activities such as the implementation of ecological protection projects and expansion of construction land can cause complex land use changes that affect ecosystem service values (ESV). In this study, we investigated changes in ESV in response to land use changes in Ningwu County, in eastern Loess Plateau of China. Our aim is to provide guidance for sustainable land use planning in this region. We used remote sensing to evaluate land use changes, and applied a fast, proxy-based method for evaluating ESV at three points in time: 1990, 2000, and 2010. More than 89% of the total ESV in Ningwu County was attributable to woodland and grassland. The ESV in western mountain areas show the greatest increase from 1990 to 2010, but ESV decreased the most in the low-elevation northeastern area of flat terrain. These tradeoffs led to a slight net decrease (1.0%) in Ningwu County's total ESV. Although the decline in ESV was relatively low compared to the rate of economic growth, total ESV was much lower than global and national average levels at the end of the study period.

• The characteristics of oasis urban expansion and drive mechanism analysis: a case study on Ganzhou District in Hexi Corridor, China
• HuaLi Tong, PeiJi Shi, GuoFeng Zhu, April Pearson, QianGuo Li, YuanFeng Liu, HaiLong Liu
• DOI: 10.3724/SP.J.1226.2015.00282
• 2015, Vol.7 (3): 282–292 Abstract ( 205) HTML PDF (471 KB) ( 314 )
• Ganzhou District is an oasis city in the Zhangye Municipality of Gansu Province, China. Based on multi-temporal TM and ETM satellite remote sensing data in 1985, 1996, 2000, and 2012, and by using corrected figures of land use status over the same periods, the spatial area of Ganzhou District since 1985 was extracted with statistical methods, and urban spatial expansion was measured by quantitative research methods. The characteristics of spatial expansion of Ganzhou District were analyzed by urban expansion rate, expansion intensity index, compactness, fractal dimension, and the city center shift method. The results showed that the built-up area of Ganzhou District increased by 3.46 times during 1985-2012. The expansion in 1985-1996 was slow, during 1996-2000 it was rapid, and during 2000-2012 it was at a high speed. This city mainly expanded to the northeast and northwest. Government decision making had a decisive influence on urban expansion. Initially the expansion was uniform, but later the local transportation, economy, resources, population, and national policies factors had an obvious influence on urban expansion.