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Table of Content

    25 January 2019, Volume 29 Issue 1 Previous Issue    Next Issue
    Research Articles
    Tracking climate change in Central Asia through temperature and precipitation extremes
    Man ZHANG, Yaning CHEN, Yanjun SHEN, Baofu LI
    2019, 29 (1):  3-28.  doi: 10.1007/s11442-019-1581-6
    Abstract ( 228 )   HTML ( 7 )   PDF (2700KB) ( 87 )   Save

    Under the impacts of climate change and human activities, great uncertainties still exist in the response of climate extremes, especially in Central Asia (CA). In this study, we investigated spatial-temporal variation trends and abrupt changes in 17 indices of climate extremes, based on daily climate observations from 55 meteorological stations in CA during 1957-2005. We also speculated as to which atmospheric circulation factors had the greatest impacts on climate extremes. Our results indicated that the annual mean temperature (Tav), mean maximum and minimum temperature significantly increased at a rate of 0.32oC/10a, 0.24oC/10a and 0.41oC/10a, respectively, which was far higher than the increasing rates either globally or across the Northern Hemisphere. Other temperature extremes showed widespread significant warming trends, especially for those indices derived from daily minimum temperature. All temperature extremes exhibited spatially widespread rising trends. Compared to temperature changes, precipitation extremes showed higher spatial and temporal variabilities. The annual total precipitation significantly increased at a rate of 4.76 mm/10a, and all precipitation extremes showed rising trends except for annual maximum consecutive dry days (CDD), which significantly decreased at a rate of -3.17 days/10a. On the whole, precipitation extremes experienced slight wetter trends in the Tianshan Mountains, Kazakhskiy Melkosopochnik (Hill), the Kyzylkum Desert and most of Xinjiang. The results of Cumulative Deviation showed that Tav and Txav had a significant abrupt change around 1987, and all precipitation indices experienced abrupt changes in 1986. Spearman’s correlation analysis pointed to Siberian High and Tibetan Plateau Index_B as possibly being the most important atmospheric circulation factors affecting climate extremes in CA. A full quantitative understanding of these changes is crucial for the management and mitigation of natural hazards in this region.

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    Sensitivity of arid/humid patterns in China to future climate change under a high-emissions scenario
    Danyang MA, Haoyu DENG, Yunhe YIN, Shaohong WU, Du ZHENG
    2019, 29 (1):  29-48.  doi: 10.1007/s11442-019-1582-5
    Abstract ( 167 )   HTML ( 5 )   PDF (2422KB) ( 49 )   Save

    Changes in regional moisture patterns under the impact of climate change are an important focus for science. Based on the five global climate models (GCMs) participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5), this paper projects trends in the area of arid/humid climate regions of China over the next 100 years. It also identifies the regions of arid/humid patterns change and analyzes their temperature sensitivity of responses. Results show that future change will be characterized by a significant contraction in the humid region and an expansion of arid/humid transition zones. In particular, the sub-humid region will expand by 28.69% in the long term (2070-2099) relative to the baseline period (1981-2010). Under 2°C and 4°C warming, the area of the arid/humid transition zones is projected to increase from 10.17% to 13.72% of the total of China. The humid region south of the Huaihe River Basin, which is affected mainly by a future increase in evapotranspiration, will retreat southward and change to a sub-humid region. In general, the sensitivity of responses of arid/humid patterns to climate change in China will intensify with accelerating global warming.

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    Increased soil organic carbon storage in Chinese terrestrial ecosystems from the 1980s to the 2010s
    Li XU, Guirui YU, Nianpeng HE
    2019, 29 (1):  49-66.  doi: 10.1007/s11442-019-1583-4
    Abstract ( 128 )   HTML ( 2 )   PDF (3657KB) ( 56 )   Save

    Soil stores a large amount of the terrestrial ecosystem carbon (C) and plays an important role in maintaining global C balance. However, very few studies have addressed the regional patterns of soil organic carbon (SOC) storage and the main factors influencing its changes in Chinese terrestrial ecosystems, especially using field measured data. In this study, we collected information on SOC storage in main types of ecosystems (including forest, grassland, cropland, and wetland) across 18 regions in China during the 1980s (from the Second National Soil Survey of China, SNSSC) and the 2010s (from studies published between 2004 and 2014), and evaluated its changing trends during these 30 years. The SOC storage (0-100 cm) in Chinese terrestrial ecosystems was 83.46 ± 11.89 Pg C in the 1980s and 86.50 ± 8.71 Pg C in the 2010s, and the net increase over the 30 years was 3.04 ± 1.65 Pg C, with an overall rate of 0.101 ± 0.055 Pg C yr-1. This increase was mainly observed in the topsoil (0-20 cm). Forests, grasslands, and croplands SOC storage increased 2.52 ± 0.77, 0.40 ± 0.78, and 0.07 ± 0.31 Pg C, respectively, which can be attributed to the several ecological restoration projects and agricultural practices implemented. On the other hand, SOC storage in wetlands declined 0.76 ± 0.29 Pg C, most likely because of the decrease of wetland area and SOC density. Combining these results with those of vegetation C sink (0.100 Pg C yr-1), the net C sink in Chinese terrestrial ecosystems was about 0.201 ± 0.061 Pg C yr-1, which can offset 14.85%-27.79% of the fossil fuel C emissions from the 1980s to the 2010s. These first estimates of soil C sink based on field measured data supported the premise that China’s terrestrial ecosystems have a large C sequestration potential, and further emphasized the importance of forest protection and reforestation to increase SOC storage capacity.

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    Spatio-temporal variations in extreme drought in China during 1961-2015
    Jing ZHANG, Yanjun SHEN
    2019, 29 (1):  67-83.  doi: 10.1007/s11442-019-1584-3
    Abstract ( 167 )   HTML ( 4 )   PDF (2036KB) ( 108 )   Save

    Understanding the past variations in extreme drought is especially beneficial to the improvementof drought resistance planning and drought risk management in China. Based on the monitoring data of meteorological stations from 1961 to 2015 and a meteorological drought index, the Standardized Precipitation Evapotranspiration Index (SPEI), the spatio-temporal variations in extreme drought at inter-decadal, inter-annual and seasonal scales in China were analyzed. The results revealed that 12 months cumulative precipitation with 1/2 to 5/8 of average annual precipitation will trigger extreme drought. From the period 1961-1987 to the period 1988-2015, the mean annual frequency of extreme drought (FED) increased along a strip extending from southwest China (SWC) to the western part of northeast China (NEC). The increased FED showed the highest value in spring, followed by winter, autumn and summer. There was a continuous increase in the decadal-FED from the 1990s to the 2010s on the Tibetan Plateau (TP), the southeast China (SEC) and the SW. During the period 1961-2015, the number of continuous drought stations was almost the same among 4 to 6 months and among 10 to 12 months of continuous drought, respectively. It can be inferred that drought lasting 6 or 12 months may lead to more severe drought disasters due to longer duration. The range of the longest continuous drought occurred in the 21st century had widely increased compared with that in the 1980s and the 1990s. Our findings may be helpful for water resources management and reducing the risk of drought disasters in China.

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    Glacier and snow variations and their impacts on regional water resources in mountains
    Haijun DENG, Yaning CHEN, Yang LI
    2019, 29 (1):  84-100.  doi: 10.1007/s11442-019-1585-2
    Abstract ( 107 )   HTML ( 2 )   PDF (2450KB) ( 59 )   Save

    Glaciers and snow are major constituents of solid water bodies in mountains; they can regulate the stability of local water sources. However, they are strongly affected by climate change. This study focused on the Tianshan Mountains, using glacier and snow datasets to analyse variations in glaciers, snow, water storage, and runoff. Three typical river basins (Aksu, Kaidou, and Urumqi Rivers) were selected to interpret the impacts of glacier and snow changes on regional water resources in the Tianshan Mountains. The results exhibited a nonlinear functional relationship between glacial retreat rate and area, demonstrating that small glacial retreat is more sensitive under climate change. Further, the glacial retreat rate at the low-middle elevation zone was seen to be faster than that at the high elevation zone. The regional average terrestrial water storage (TWS) decrease rate in the Tianshan Mountains was -0.7±1.53 cm/a during 2003-2015. The highest TWS deficit region was located in the central part of the Tianshan Mountains, which was closely related to sharp glacial retreats. The increases in glacier and snow meltwater led to an increase in runoff in the three typical river basins, especially that of the Aksu River (0.4×108 m3/a). The decreasing and thinning of areas, and increasing equilibrium line altitude (ELV) of glaciers have been the major causes for the decrease in runoff in the three river basins since the mid-1990s. Therefore, the results reveal the mechanisms causing the impacts of glaciers and snow reduction in mountains on regional water resources under climate change, and provide a reference for water resources management in the mountainous river basins.

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    Evaluation on glaciers ecological services value inthe Tianshan Mountains, Northwest China
    Zhengyong ZHANG, Lin LIU, Xinlin HE, Zhongqin LI, Puyu WANG
    2019, 29 (1):  101-114.  doi: 10.1007/s11442-019-1586-1
    Abstract ( 135 )   HTML ( 1 )   PDF (589KB) ( 66 )   Save

    Mountain glaciers, which perform a unique and irreplaceable ecological service, provide the material basis and characteristic cultural foundation of the ecological environment and sustainable socio-economic development in arid areas. However, few studies have estimated the service value of glaciers in regulating ecological environment and providing human welfare. According to the statistics of the First and Second Chinese Glacier Inventory (FCGI/SCGI), this study analyzed the variations in glacier area and ice volume in the Tianshan Mountains in China and modeled the ecosystem service function of mountain glaciers. The service value per unit area and equivalent factor methods were combined to determine the annual value of the ecological service provided by glaciers in the study area. The results show that: (1) In the period 1970-2010, the glacier area decreased by 1274 km2 (the ratio of area shrinkage was 13.9%) and the annual average decrease in ice volume was 4.08×109 m3. The increase in glacier area at high altitudes (> 5200 m) may be due to the fact that glacier accumulation caused by increasing precipitation is greater than glacier melting caused by rising temperatures. (2) The annual value of the ecological service provided by glaciers in the study area is 60.2 billion yuan. The values of climate regulation, hydrological regulation, and freshwater resource supply account for 66.4%, 21.6%, and 9.3% of the total value respectively. The annual value of the ecological service provided by hydroelectric power is 350 million yuan. (3) From a comparative analysis of the glaciers, forest, grassland and wetland ecosystems, the supply of freshwater resources/physical production and ecological regulation represent the main contributions of the four types of system, and the ecosystem service value of glaciers per unit area is higher than that of other types of ecosystem. This research will improve the understanding of the impact of glaciers on human welfare and maintenance of the ecological environment and will promote the ecological security of the cryosphere, environmental protection, and the sustainable use of resources.

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    Spatiotemporal characteristics of Qinghai Lakeice phenology between 2000 and 2016
    Miaomiao QI, Xiaojun YAO, Xiaofeng LI, Hongyu DUAN, Yongpeng GAO, Juan LIU
    2019, 29 (1):  115-130.  doi: 10.1007/s11442-019-1587-0
    Abstract ( 120 )   HTML ( 3 )   PDF (13019KB) ( 26 )   Save

    Lake ice phenology is considered a sensitive indicator of regional climate change. We utilized time series information of this kind extracted from a series of multi-source remote sensing (RS) datasets including the MOD09GQ surface reflectance product, Landsat TM/ETM+ images, and meteorological records to analyze spatiotemporal variations of ice phenology of Qinghai Lake between 2000 and 2016 applying both RS and GIS technology. We also identified the climatic factors that have influenced lake ice phenology over time and draw a number of conclusions. First, data show that freeze-up start (FUS), freeze-up end (FUE), break-up start (BUS), and break-up end (BUE) on Qinghai Lake usually occurred in mid-December, early January, mid-to-late March, and early April, respectively. The average freezing duration (FD, between FUE and BUE), complete freezing duration (CFD, between FUE and BUS), ice coverage duration (ICD, between FUS and BUE), and ablation duration (AD, between BUS and BUE) were 88 days, 77 days, 108 days and 10 days, respectively. Second, while the results of this analysis reveal considerable differences in ice phenology on Qinghai Lake between 2000 and 2016, there has been relatively little variation in FUS times. Data show that FUE dates had also tended to fluctuate over time, initially advancing and then being delayed, while the opposite was the case for BUS dates as these advanced between 2012 and 2016. Overall, there was a shortening trend of Qinghai Lake’s FD in two periods, 2000-2005 and 2010-2016, which was shorter than those seen on other lakes within the hinterland of the Tibetan Plateau. Third, Qinghai Lake can be characterized by similar spatial patterns in both freeze-up (FU) and break-up (BU) processes, as parts of the surface which freeze earlier also start to melt first, distinctly different from some other lakes on the Tibetan Plateau. A further feature of Qinghai Lake ice phenology is that FU duration (between 18 days and 31 days) is about 10 days longer than BU duration (between 7 days and 20 days). Fourth, data show that negative temperature accumulated during the winter half year (between October and the following April) also plays a dominant role in ice phenology variations of Qinghai Lake. Precipitation and wind speed both also exert direct influences on the formation and melting of lake ice cover and also cannot be neglected.

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    A comprehensive analysis of phenological changes in forest vegetation of the Funiu Mountains, China
    Wenbo ZHU, Xiaodong ZHANG, Jingjing ZHANG, Lianqi ZHU
    2019, 29 (1):  131-145.  doi: 10.1007/s11442-019-1588-z
    Abstract ( 113 )   HTML ( 1 )   PDF (4611KB) ( 53 )   Save

    This paper reports the phenological response of forest vegetation to climate change (changes in temperature and precipitation) based on Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) time-series images from 2000 to 2015. The phenological parameters of forest vegetation in the Funiu Mountains during this period were determined from the temperature and precipitation data using the Savitzky-Golay filter method, dynamic threshold method, Mann-Kendall trend test, the Theil-Sen estimator, ANUSPLIN interpolation and correlation analyses. The results are summarized as follows: (1) The start of the growing season (SOS) of the forest vegetation mainly concentrated in day of year (DOY) 105-120, the end of the growing season (EOS) concentrated in DOY 285-315, and the growing season length (GSL) ranged between 165 and 195 days. There is an evident correlation between forest phenology and altitude. With increasing altitude, the SOS, EOS and GSL presented a significant delayed, advanced and shortening trend, respectively. (2) Both SOS and EOS of the forest vegetation displayed the delayed trend, the delayed pixels accounted for 76.57% and 83.81% of the total, respectively. The GSL of the forest vegetation was lengthened, and the lengthened pixels accounted for 61.21% of the total. The change in GSL was mainly caused by the decrease in spring temperature in the region. (3) The SOS of the forest vegetation was significantly partially correlated with the monthly average temperature in March, with most correlations being negative; that is, the delay in SOS was mainly attributed to the temperature decrease in March. The EOS was significantly partially correlated with precipitation in September, with most correlations being positive; that is, the EOS was clearly delayed with increasing precipitation in September. The GSL of the forest vegetation was influenced by both temperature and precipitation throughout the growing season. For most regions, GSL was most closely related to the monthly average temperature and precipitation in August.

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    Threshold sediment flux for the formation of river deltas in Hainan Island, southern China
    Gaocong LI, Liang ZHOU, Yali QI, Shu GAO
    2019, 29 (1):  146-160.  doi: 10.1007/s11442-019-1589-y
    Abstract ( 141 )   HTML ( 3 )   PDF (7708KB) ( 18 )   Save

    The knowledge of geomorphological evolution from an estuary to a river delta is necessary to form the formulation of comprehensive land-ocean interaction management strategies. In this study, the dominant factor controlling the geomorphological variability and the threshold sediment flux (TSF) to form a river delta in Hainan Island, southern China, including accommodation space, sediment supply, and reworking forces, was investigated by the method of big data analytics. The results indicated the 25 estuaries in consideration can be divided into three geographical groups, i.e. the multi-factors-controlled northern mixed estuaries, wave-dominated western estuaries with river deltas, and typhoon-dominated eastern coastal lagoon estuaries. For alluvial plain (AP) estuaries, the order of magnitude of TSFs is the smallest (101 kt·yr-1), for barrier-lagoon (BL) ones is the highest (> 102 kt·yr-1), and for drowned valley (DV) ones is moderate (102kt·yr-1). The river deltas associated with DV systems should be relatively large, and those related to BLs should be small, with the AP deltas being between the above mentioned types. The present study provides a technique to evaluate the role played by TSF for the formation of river deltas in micro-tidal and wave-dominated and typhoon-influenced coastal environments.

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