Detecting spatio-temporal changes of arable land and construction land in the Beijing-Tianjin corridor during 2000–2015

Journal of Geographical Sciences - Rapid peri-urbanization has become a new challenge for sustainable urban-rural development worldwide. To clarify how unprecedented urban sprawl at the...     

Spatiotemporal characteristics of seasonal precipitation and their relationships with ENSO in Central Asia during 1901–2013

The vulnerable ecosystem of the arid and semiarid region in Central Asia is sensitive to precipitation variations. Long-term changes of the seasonal precipitation can reveal the evolution rules of the precipitation climate. Therefore, in this study, the changes of the seasonal precipitation over Central Asia have been analyzed during the last century (1901–2013) based on the latest global monthly precipitation dataset Global Precipitation Climatology Centre (GPCC) Full Data Reanalysis Version 7, as well as their relations with El Niño- Southern Oscillation (ENSO). Results show that the precipitation in Central Asia is mainly concentrated in spring and summer seasons, especially in spring. For the whole study period, increasing trends were found in spring and winter, while decreasing trends were detected in summer and fall. Inter-annual signals with 3–7 years multi-periods were derived to explain the dominant components for seasonal precipitation variability. In terms of the dominant spatial pattern, Empirical orthogonal function (EOF) results show that the spatial distribution of EOF-1 mode in summer is different from those of the other seasons during 1901–2013. Moreover, significant ENSO-associated changes in precipitation are evident during the fall, winter, spring, and absent during summer. The lagged associations between ENSO and seasonal precipitation are also obtained in Central Asia. The ENSO-based composite analyses show that these water vapor fluxes of spring, fall and winter precipitation are mainly generated in Indian and North Atlantic Oceans during El Niño. The enhanced westerlies strengthen the western water vapor path for Central Asia, thereby causing a rainy winter.     

Impacts of water conservancy and soil conservation measures on annual runoff in the Chaohe River Basin during 1961–2005

Taking the Chaohe River Basin above the Miyun Reservoir in North China as a study area, the characteristics and variation trends of annual runoff and annual precipitation during 1961–2005 were analyzed applying Mann-Kendall test method on the basis of the hydrologic data of the major hydrological station (Xiahui Station) located at the outlet of the drainage basin and the meteorological data of 17 rainfall stations. Human activities including water conservancy projects construction and water diversion as well as implementation of soil and water conservation from 1961 to 2005 were carefully studied using time series contrasting method. The referenced period (1961–1980) that influenced slightly by human activities and the compared period (1981–2005) that influenced significantly by water conservancy and soil conservation measures were identified according to the runoff variation process analysis and abrupt change points detection during 1961–2005 applying double accumulative curve method, mean shift t-test method and Mann-Kendall mutation test technique. Based on the establishment of a rainfall-runoff empirical statistical model, impacts and the runoff-reducing effects of water conservancy and soil conservation measures on runoff reduction were evaluated quantitatively. The major results could be summarized as follows: (1) The annual precipitation in the drainage basin tends to decrease while the runoff has declined markedly since the 1960s, the average annual runoff from 1991 to 2000 was only 90.9% in proportion to that from 1961 to 1970. (2) The annual runoff variations in the drainage basin are significantly related to human activities. (3) During 1981–1990, 1991–2000, 2001–2005 and 1981–2005, the average annual runoff reduction amounts were 1.15×10⁸, 0.28×10⁸, 1.10×10⁸ and 0.79×10⁸ m³ respectively and the average annual runoff-reducing effects were 31.99%, 7.13%, 40.71% and 23.79% accordingly. Runoff-reducing effects by water conservancy and soil conservation measures are more prominent in the low water period.     

Comparisons on seasonal and annual variations of δ~(18)O in precipitation

interpretationofpaleoclimaticrecordsinicecore(Dansgaardetal.,1969;Rozanskietal.,1997;Yao,1999;Thompsonetal.,2000).SincethefirstdeepicecorewasdrilledinGreenlandin1966(Dansgaardetal.,1969),hundredsoficecoreswereobtainedsuccessivelyfromicesheetsinAntarcticaandArctic,andmountainglaciersatmid-highlatitudes,fundedbynumerousresearchprogramsonglobalclimateandenvironmentalchange.Theseicecoresprovideuniqueandvaluablefirst-handinformationinrecoveringglobalpaleoenvironmentalrecordsandforecastingfuturecl…     

Variability of atmospheric freezing level height derived from radiosonde data in China during 1958–2005 and its impact to cryosphere changes

Atmospheric air temperature data from 92 stations in China’s radiosonde network were used to analyze changes in the freezing level height (FLH), glacier snow line, and ice edge from 1958–2005 (48 years) and to examine the impact of these changes on the cryosphere. In general, the FLH, glacier snow line, and ice edge exhibited latitudinal zonation, declining from south to north. Trends in the FLH, glacier snow line, and ice edge showed spatial heterogeneity during the study period, with prevailing upward trends. Temporally, the FLH, glacier snow line, and ice edge trends differed on various time scales.     

Long-term change of surface temperature in water bodies around Iran – Caspian Sea,Gulf of Oman,and Persian Gulf – using 2001–2015 MODIS data

ABSTRACT

To answer the question “what has changed the surface temperatures of water bodies around Iran under climate change conditions,” Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) data with 9.2-km spatial resolution and monthly time step were evaluated. A significant increasing trend was obtained using Pearson’s correlation coefficient and Mann-Kendall trend test on data from the Caspian Sea (June) and the Southern Gulfs (September). High correlations of 0.69 and 0.97 between remotely sensed data and ERA-Interim reanalysis data were also obtained for June and September, respectively. To assess the impact of some climatic parameters on SST variability in those two months, zonal and meridional wind at 10 m, wind speed at 10 m, air temperature at 2 m, and mean sea level pressure were evaluated. High correlations between meridional wind and the Southern Gulf SST, and meridional wind and Caspian SST were ?0.86 and 0.75, respectively. Moreover, the results showed an important role of air temperature (0.96) and sea level pressure (?0.77) in the rising temperature trends of the Southern Gulfs. Wind speed was also detected in both regions as a booster of the trend.     

Evolution of the palaeolake at Ruszkówek (central Poland) during the Eemian Interglacial based on isotope,cladoceran and diatom data

We present isotope, cladoceran and diatom results from investigations of Eemian sediments of the palaeolake at Ruszkówek, central Poland. Our analyses of the 15-m-thick sediments indicate that sandy silts occur on the bottom, followed by calcareous gyttja, interbedded with lake marl. The upper part of the sequence contains peat and peaty sands. Values of δ¹⁸O change from −9.4‰ to −3.3‰ and δ¹³C values oscillate between −3.2‰ and +7.0‰. Nine isotope zones (Is) were defined and characterized using stable isotope analysis of carbonates. Fifteen species of subfossil Cladocera were found and six faunal zones were distinguished (Cladocera zones). One hundred and twenty-three diatom taxa, representing 31 genera were identified, enabling us to discern six Diatom Assemblage Zones. The isotope, cladoceran, and diatom data correlate well with pollen data that define seven phases of evolution of the palaeolake at Ruszkówek. The palaeolake began during the final phase of the Wartanian (Late Saalian Glaciation). During the early Eemian, the palaeolake reached its maximum depth. During the Early Vistulian glaciation, the palaeolake declined. Changes in the cladoceran and diatom communities indicate initial oligotrophic conditions in the lake, then an increase to mesotrophy, and finally eutrophic conditions.     

Uncovering the spatio-temporal dynamics of land cover change and fragmentation of mangroves in the Ca Mau peninsula,Vietnam using multi-temporal SPOT satellite imagery (2004–2013)

Mangrove forests provide vital ecosystem services for millions of people living in coastal communities. The expansion of aquaculture production and urbanization have been identified as major causes of mangrove clearance in South-East Asia. The Ca Mau peninsula in Vietnam is leading the country in shrimp aquaculture and at the same time, the region is home to the largest remaining mangrove forests. This study aims to assess the spatial and temporal mangrove forest dynamics in Ngoc Hien district in Ca Mau. Land cover change and fragmentation are quantified using remote sensing imagery consisting of a series of SPOT5 scenes from 2004, 2009 and 2013. The results indicate a high turnover of land cover change, with close to half of the mangrove forests being affected by land cover changes between 2004 and 2014. Net changes in mangrove forest are found to average −0.34% annually, characterized by deforestation between 2004 and 2009 and afforestation of between 2009 and 2013. Fragmentation remains a plausible threat; approximately 35.4% of the mangrove forests in Ngoc Hien are part of interior ‘core’ forests. Forest zones with different regulation regimes play a significant role in shaping the geographic distribution of mangrove forest changes. The insights into recent mangrove forest dynamics facilitate the informed discussion on improving future protection of the mangrove forests abiding anthropogenic pressures.     

Atmospheric insight to climatic signals of δ~(18)O in a Laohugou ice core in the northeastern Tibetan Plateau during 1960–2006

δ~(18)O variations;;ice core;;outgoing longwave radiation;;meridional wind;;northeastern Tibetan Plateau     

The rate,extent and spatial predictors of forest loss (2000–2012) in the terrestrial protected areas of the Philippines

While studies on deforestation of protected areas (PAs) have been conducted in many parts of the world, no comparative study has been done over an entire country in the tropics. Thus, we conducted a country-wide assessment of forest cover loss in all terrestrial protected areas of the Philippines, covering 198 PAs with a total area of 4.68 million ha. This study utilised Hansen's Landsat-derived global maps of forest cover change from 2000 to 2012, with tree canopy cover data for 2000 as the base year. Correlation and logistic regression analyses were employed to determine the significance and magnitude of the relationships between forest cover and 11 predictor variables. The assessment of forest loss reveals that the terrestrial protected areas are generally effective in reducing forest loss. Over the 12-year period, the average rate (2.59%) of forest clearing in protected areas is marginally lower by 0.1% than the entire country (2.69%). Within the same duration, the average forest loss rate within the 2-km buffer zones of selected protected areas is 1.4 times of those inside PAs. However, there was a significant number of PAs with phenomenal forest cover loss in terms of extent (48,583 ha over 12 years) and rate (up to 21%). We found that spatial predictor variables included in this study have weak or no relationships with forest cover, and hence they are not reliable inputs for predictive modelling. Comprehensive assessments of deforestation are needed at the micro-scale (e.g. single PA level) level and relatively shorter historical timeframe (e.g. less than a decade), to generate useful information for policy formulation, planning, and management.     

Quaternary basin evolution and present tectonic regime in the area of the 1997–1998 Umbria–Marche seismic sequence (central Italy)

Geological and geomorphological surveys have been performed in the area affected by the 1997–1998 Umbria–Marche seismic sequence (M_max=6.0) aimed at defining the Quaternary tectonic history and the characteristics of the present tectonic regime. Data have been collected from: (1) the analysis of the remnant landsurfaces by means of aerial photos and field surveys; (2) geological surveys in the Cesi–San Martino basin and in the easternmost sector of the Colfiorito basin in order to identify deformative features affecting the Quaternary deposits; (3) the analysis of boreholes and geo-electrical data (derived from previous surveys performed in the 1960s) in order to reconstruct the top of the pre-Quaternary substratum in the Colfiorito basin. Two different successions of remnant landsurfaces have been identified along the faults bounding the basins to the east, in the hangingwall and the footwall, respectively. The difference accounts for a fault-controlled evolution of the landscape at least during the Upper Pliocene–Early Pleistocene. The deformation affecting the Quaternary deposits and landforms in the investigated basins indicates a decreasing tectonic activity along the master faults since the Middle Pleistocene. Surface deformation due to tectonics is faint and displayed by gentle warping of the landforms during the late Quaternary. As for the basin geometry, subsurface data show that two minor depressions formed in the Colfiorito Basin during the Quaternary, the oldest one close to the fault bounding the basin, while the youngest (and deepest) formed in the inner portion of the basin. Therefore, the present geometry is different from that of other fault-bounded Quaternary depressions of the central Apennines (typically half-graben basins), showing the maximum depth of the substratum in the area close to the master fault. Tectonic history may be summarised as follows: (1) origin of the Quaternary fault-bounded Colfiorito and Cesi–San Martino basins; (2) evolution of the basins with a half-graben style; (3) significant reduction of tectonic activity since the Middle Pleistocene. During the third phase, the evolution of the basins is no longer related to a half-graben style. In the case of the Colfiorito basin, a new depression is superimposed to on the previous half-graben whose evolution is related to the lowering of the inner portion of the basin through warping. Moreover, present activity does not result in fault-related surficial displacements but only in “continuous” deformation spread over the basins. These conclusions have fundamental implications for the seismotectonic framework of the 1997–1998 earthquake sequence. This deformation style is, indeed, in agreement with the coseismic deformation modelled by means of the SAR interferometry analyses carried out by other institutions during the seismic sequence, and with the lack of evident surface faulting related to the mentioned events in the investigated area. This evidence indicates that the evolution of the investigated area since the Middle Pleistocene resulted from the summation of deformative episodes similar to that which occurred during the recent seismic sequence. As a consequence, no earthquakes with magnitude larger than 6 are expected in the area.     

Late Quaternary (30.7–9.0 cal ka BP) vegetation history in Central Asia inferred from pollen records of Lake Balikun, northwest China

Surface and fossil pollen samples were collected to reconstruct the vegetation and environment since 30.7 cal ka BP in the Lake Balikun Basin, northwest China. This record demonstrates that the region was occupied by four vegetation communities during the interval 30.7–9.0 cal ka BP, including desert steppe (30.7–25.1 cal ka BP), Amaranthaceae-Asteraceae desert (25.1–17.7 cal ka BP), Amaranthaceae-Artemisia-Asteraceae desert (17.7–12.8 cal ka BP) and Amaranthaceae desert (12.8–9.0 cal ka BP), corresponding to relatively humid, the coldest and driest, cold and dry, and colder and drier conditions, respectively. The reconstructions of vegetation and environmental changes around Lake Balikun do not support the interpretation of an extremely humid LGM in Central Asia, challenging the cold-moist (glacial), warm-dry (interglacial) pattern of late Quaternary environmental change in Central Asia. The Last Glacial Maximum was cold and dry, and similarly harsh conditions continued into the early Holocene.     

Progress and prospects of applied research on physical geography and the living environment in China over the past 70 years (1949–2019)

Physical geography is a basic research subject of natural sciences.Its research object is the natural environment which is closely related to human living and development,and China's natural environment is complex and diverse.According to national needs and regional development,physical geographers have achieved remarkable achievements in applied basis and applied research,which also has substantially contributed to the planning of national economic growth and social development,the protection of macro ecosystems and resources,and sustainable regional development.This study summarized the practice and application of physical geography in China over the past 70 years in the following fields:regional differences in natural environments and physical regionalization;land use and land cover changes;natural hazards and risk reduction;process and prevention of desertification;upgrading of medium-and low-yield fields in the Huang-Huai-Hai region;engineering construction in permafrost areas; geochemical element anomalies and the prevention and control of endemic diseases;positioning and observation of hysical geographical elements;and identification of geospatial differentiation and geographical detectors. Furthermore, we have proposed the future direction of applied research in the field of physical geography.     

Biotic response of benthic foraminifera in Aso-kai lagoon,central Japan,to changes in terrestrial climate and ocean conditions (~AD 700–1600)

We investigated responses of shallow-water benthic foraminifera to changes in climate and ocean conditions, using sediment core ASC2 from Aso-kai lagoon, central Japan. Six AMS ¹⁴C dates reveal that the studied interval corresponds to sediments deposited from ~AD 700 to 1600. Sulfur content of the bulk sediment and multi-dimensional scaling (MDS) axis 1 of fossil benthic foraminifera indicate that the composition of the benthic foraminifera community was closely related to dissolved oxygen (DO) concentration in the hypolimnion. The sulfur content and MDS axis 1 also revealed two shifts over the 900-year interval. In the first phase (~AD 700–1250), the Shannon–Wiener Index (H′), E (S₂₀₀), evenness and rank abundance curve (RAC) kurtosis indicate a gradual deterioration in structure of the benthic foraminifera community. In that period, there are statistically significant correlations between the faunal composition (MDS axis 1) and faunal structure [Shannon–Wiener (H′), E (S₂₀₀), evenness and RAC kurtosis]. In the second phase (~AD 1250–1600), however, faunal composition and structure show no marked correspondence. Instead, abundance of benthic foraminifera fluctuated on a scale of ~200 years. Thus, a shift in the biotic response of benthic foraminifera in Aso-kai lagoon occurred in ca. AD 1250. Gradual deterioration of benthic foraminifera, with taxonomic losses, is consistent with declining DO in the first phase, possibly associated with the increasing influence of the Tsushima Warm Current. The possibility that closure of Aso-kai lagoon and development of the sand bar affected benthic foraminifera cannot, however, be ruled out. No corresponding response was observed in the second phase, during which there was no distinct taxonomic loss. Large variations in abundance, however, were a consequence of strength of the East Asian summer and winter monsoons. The shift in the biotic response of benthic foraminifera in Aso-kai lagoon during the period AD 700–1600 was apparently a result of changes in climate and ocean conditions on the East Asian continental margin.     

The Holocene–Anthropocene transition in lakes of western Spitsbergen,Svalbard (Norwegian High Arctic): climate change and nitrogen deposition

Lake sediments from four small lakes on western Spitsbergen (Svalbard Archipelago, Norwegian High Arctic) preserve biostratigraphic and isotopic evidence for a complex suite of twentieth century environmental changes. At Lake Skardtjørna and Lake Tjørnskardet on Nordenskiöldkysten, there is a marked diatom floristic change coupled to increased diatom concentrations beginning around 1920. At Lake Istjørna and Lake Istjørnelva, 25 km southwest of Longyearbyen, both diatom total valve and chrysophyte stomatocyst concentrations have increased dramatically since the beginning of the 1900s. The early twentieth century changes are probably related to climate warming after the Little Ice Age. However, the most pronounced changes in diatom assemblages seem to have occurred in the last few decades. At the same time, nitrogen stable isotopes in sediment organic matter in two of the lakes became progressively depleted by ~2‰, which is consistent with diffuse atmospheric inputs from anthropogenic sources and attendant fertilization. These data suggest that climate change and nitrogen deposition may be acting together in driving these lakes towards new ecological states that are unique in the context of the Holocene.     

Study on the distribution,abundance and growth condition of Antarctic Krill(Euphausia superba)in the Prydz Bay region,Antarctica during the Austral summer of 1999/2000

Antarctic krill (Euphausia superba) were collected from the Prydz Bay region during the austral summer of 1999/2000. The sample - collection was made at 15 sites in 3 longitudinal transects. Although krill were encountered at 14 sites, the abundance was comparatively low in general. The main component of the krill population was of post -larval stages. The mean numerical and weight density of krill integrated for all sampling stations in the survey area were 16. 17 ind. 1000 m -3and 12.02 g 1000 m -3 , respectively. In the survey area, stations with larger krill density are mainly located in the slope zone, except that the largest sample was collected in the open sea zone. No krill occurred in the only station of the shelf zone during our investigation. Krill collected from the slope zone were under better growth condition than those from the open sea zone, but when the survey area is considered as a whole, the growth condition is normal. The results of the comprehensive analysis of the environmental fa     

A new climatology of maximum and minimum temperature (1951–2010) in the Spanish mainland: a comparison between three different interpolation methods

This study presents a new climatology of monthly temperature for mainland Spain (1951–2010), performed with the highest quality and spatially dense, up-to-date monthly temperature dataset available in the study area (MOTEDAS).

Three different interpolation techniques were evaluated: the Local Weighted Linear Regression (LWLR), the Regression-Kriging (RK) and the Regression-Kriging with stepwise selection (RKS), a modification of RK. The performances of the different models were evaluated by the leave-one-out validation procedure, comparing the results from the models with the original data and calculating different error measurements.

The three techniques performed better for T_max than for T_min, and for the cold, rather than warmer months, also at lower altitude than highland areas. The best results were achieved with LWLR applied for the first time on temperatures in the Spanish mainland. This method improved the accuracy of the temperature reconstruction with respect to RK and RKS.

We present a collection of T_max and T_min monthly charts, using the same temperature legend to prevent any visual bias in the interpretation of the results. The dataset is available upon request.     

A diatom-inferred record of reduced effective precipitation during the Last Glacial Coldest Phase (28.8–18.0?cal kyr BP) and increasing Holocene seasonality at Lake Pupuke, Auckland, New Zealand

A continuous, 1,420-cm sediment record from Lake Pupuke, Auckland, New Zealand (37°S) was analysed for diatom taxonomy, concentration and flux. A New Zealand freshwater diatom transfer function was applied to infer past pH, electrical conductivity, dissolved reactive phosphorus and chlorophyll a. A precise, mixed-effect regression model of age versus depth was constructed from 11 tephra and 13 radiocarbon dates, with a basal age of 48.2?cal kyr BP. Diatom-inferred changes in paleolimnology and climate corroborate earlier inferences from geochemical analyses (Stephens et al. 2012), with respect to the timing of marked climate changes in the Last Glacial Coldest Phase (LGCP; 28.8?C18.0?cal kyr BP), the Last Glacial Interglacial Transition (LGIT; 18.0 to ca. 12?C10?cal kyr BP) and the Holocene, the onset of which is difficult to discern from LGIT amelioration, but which includes an early climatic optimum (10.2?C8.0?cal kyr BP). The LGCP is readily defined by a reduction in lake level and effective precipitation, whereas the LGIT represents a period of rising lake level, with greater biomass during the Holocene. There was limited change in diatom assemblage structure, influx or inferred water quality during a Late Glacial Reversal (LGR; 14.5?C13.8?cal kyr BP), associated with heightened erosional influx. In contrast, an LGIT peak in paleoproductivity is recorded by increased diatom influx from 13.8 to 12.8?cal kyr BP. Changes in sediment influx and biomass record complex millennial-scale events attuned to the Antarctic Cold Reversal (ACR; 14.5?C12.8?cal kyr BP). Additional millennial-scale environmental change is apparent in the Holocene, with marked changes in lake circulation beginning at 7.6?cal kyr BP, including the onset of seasonal thermal stratification and rapid species turnover at 5.7?cal kyr BP. The most rapid diatom community turnover accompanied widely varying nutrient availability and greater seasonality during the last 3.3?cal kyr. Rising seasonality appears to have been linked to strengthened Southern Westerlies at their northern margins during the middle and late Holocene.