2000—2018年全国形变台站周边环境时空变化特征及对垂直摆观测影响分析

利用中国自主研制的全球首套30 m分辨率GlobeLand30地表覆盖产品调查全国定点形变台站周边5 km范围内的土地覆盖类型分布.应用地类面积/变化率、类型转入转出率等指标分析研究区各类型的转移规律,并辅以MODIS土地覆盖年数据集从全国和分区角度揭示2001—2018年间各土地类型时空变化格局,最后以垂直摆倾斜观测...     

Land use changes and their relations with carbon cycles over the past 300 a in China

Land use and land cover in China have changed greatly during the past 300 a, indicated by the rapid abrupt decrease of forest land area and the rapid increase of cropland area, which can affect terrestrial carbon cycle greatly. The first-hand materials are used to analyze main characteristics for land use and land cover changes in China during the study period. The following conclusions can be drawn from this study. The cropland area in China kept increasing from 60.78×106 hm2 in 1661 to 96.09×106 hm2 in 1998. Correspondingly, the forest land area decreased from 248.13×106 hm2 in 1700 to 109.01×106 hm2 in 1949. Affected by such changes, the terrestrial ecosystem carbon storage decreased in the mean time. Car-bon lost from land use and land cover changes mainly consist of the loss from vegetation biomass and soil. In the past 300 a, about 3.70 PgC was lost from vegetation biomass, and emissions from soil ranged from 0.80 to 5.84 PgC. The moderate evaluation of soil losses was 2.48 PgC. The total loss from vegetation and soil was between 4.50 and 9.54 PgC. The moderate and optimum evaluation was 6.18 PgC. Such carbon losses distribution varied spatially from region to region. Carbon lost more significantly in Northeast China and Southwest China than in other regions, because losses of forest land in these two regions were far greater than in the other regions during the past 300 a. And losses of carbon in the other regions were also definite, such as Inner Mongolia, the western part of South China, the Xinjiang Uygur Autonomous Region, and the Qinghai-Tibet Plateau. But the carbon lost very little from the traditional agricultural regions in China, such as North China and East China. Studies on the relationship between land use and land cover change and carbon cycle in China show that the land use activities, especially those related to agriculture and forest management, began to affect terrestrial carbon storage positively in recent years.     

Cropland cover change in Northeast China during the past 300 years

Land use/cover change induced by human activities has emerged as a “global” phenomenon with Earth system consequences. Northeast China is an area where the largest land cultivation activities by migrants have happened in China during the past 300 years. In this paper, methods including documentary data calibration and multi-sourced data conversion model are used to reconstruct historical cropland cover change in Northeast China during the past 300 years. It is concluded that human beings have remarkably changed the natural landscape of the region by land cultivation in the past 300 years. Cropland area has increased almost exponentially during the past 300 years, especially during the past 100 years when the ratio of cropland cover changed from 10% to 20%. Until the middle of the 19th century, the agricultural area was still mainly restricted in Liaoning Province. From the late 19th century to the early 20th century, dramatic changes took place when the northern boundary of cultivation had extended to the middle of Heilongjiang Province. During the 20th century, three agricultural regions with high ratio of cropland cover were formed after the two phases of spatial expansion of cropland area in 1900s–1930s and 1950s–1980s. Since 1930s–1940s, the expansion of new cultivated area have invaded the forest lands especially in Jilin and Heilongjiang Provinces. Supported by National Natural Science Foundation of China (Grant No. 40571165) and Innovation Foundation of Chinese Academy of Sciences (Grant No. KZCX2-YW-315)     

Decadal trend of climate in the Tibetan Plateau—regional temperature and precipitation

The Tibetan Plateau has one of the most complex climates in the world. Analysis of the climate in this region is important for understanding the climate change worldwide. In this study, climate patterns and trends in the Tibetan Plateau were analysed for the period from 1961 to 2001. Air temperature and precipitation were analysed on monthly and annual time scales using data collected from the National Meteorological Centre, China Meteorological Administration. Nonlinear slopes were estimated and analysed to investigate the spatial and temporal trends of air temperature and precipitation in the Tibetan Plateau using a Mann–Kendall method. Spatial analysis of air temperature and precipitation variability across the Tibetan Plateau was undertaken. While most trends are local in nature, there are general basinwide patterns. Temperature during the last several decades showed a long‐term warmer trend, especially the areas around Dingri and Zogong stations, which formed two increasing centres. Only one of the stations investigated exhibited decreasing trend, and this was not significant. Precipitation in the Tibetan Plateau has increased in most regions of the study area over the past several decades, especially in the eastern and central part, while the western Tibetan Region exhibited a decreased trend over the same period. Copyright © 2007 John Wiley & Sons, Ltd.     

Abrupt change of runoff and its major driving factors in Haihe River Catchment, China

Runoff in Haihe River Catchment of China is steadily declining due to climate change and human activity. Determining abrupt changes in runoff could enhance identification of the main driving factors for the sudden changes. In this study, the sequential Mann–Kendall test analysis is used to determine abrupt changes in runoff in eight sub-catchments of Haihe River Catchment, while trend analysis via the traditional Mann–Kendall test for the period 1960–1999 is used to identify the basic trend of precipitation and runoff. The results suggest an insignificant change in precipitation and a significant decline in runoff in five of the eight sub-catchments. For most of the sub-catchments, abrupt changes in runoff occurred in 1978–1985. Through correlation comparisons for precipitation and runoff for the periods prior to and after abrupt runoff changes, human activity, rather than climatic change, is identified as the main driving factor of runoff decline. It is also noted that abrupt decline in runoff was actually at the beginning of China’s 1978–1985 land reform. Given that the land reform motivated farmers to productively manage their reallocated lands, agricultural water use therefore increased. Hence percent agricultural land is analyzed in relation to land use/cover pattern for the late 1970s and early 1980s. The analysis shows that when cultivated farmland exceeds 25% of a sub-catchment area, an abrupt decline in runoff occurs. It is therefore concluded that high percent agricultural land and related agricultural water use are the most probable driving factors of runoff decline in the catchment.     

Preliminary reconstruction of the desert and sandy land distributions in China since the last interglacial period

The desert and sandy land are the products of arid climate. The spatial distribution of modern deserts and sandy land in China and their relation to climate show following characteristics: arid and hyper-arid desert zones, at isohyet of less than 200 mm, are dominated by mobile dunes; semi-arid steppe and arid desert steppe with the precipitation between 200-400mm, are dominated by semi-fixed and fixed sand dunes; the precipitation of sub-humid forest grassland and humid forest zones with scattered fixed sand land is higher than 400 mm. With this as reference, in combination with considerable amount of paleoclimatic data in desert regions and adjacent regions, the distributions of desert and sandy land in China during the last interglacial period, the last glacial maximum (LGM), and the Holocene megathermal, were preliminarily reconstructed. The results compared with that of today show that the distribution of desert and sandy land in China was greatly dwindled during last interglacial period, and the mobile dune area was about two-thirds of that of today's, but greatly expanded during LGM. However, the dwindling area of desert and sandy land in the Holocene megathermal was smaller than that in the last interglacial period. The forcing mechanism was mainly related to the changes of East Asian winter and summer monsoon, south-northward swing of the westerlies and the variations of the Qinghai-Tibet Plateau monsoon intensity caused by global climate changes during the cold and warm intervals since the last interglacial period.     

Long‐term streamflow trends in the middle reaches of the Yellow River Basin: detecting drivers of change

The catchments in the Loess Plateau, in China's middle reaches of the Yellow River Basin, experienced unprecedented land use changes in the last 50 years as a result of large‐scale soil conservation measure to control soil erosion. The climate of the region also exhibited some levels of change with decreased precipitation and increased temperature. This study combined the time‐trend analysis method with a sensitivity‐based approach and found that annual streamflow in the Loess Plateau decreased significantly since the 1950s and surface runoff trends appear to dominate the streamflow trends in most of the catchments. Annual baseflow exhibited mostly downward trends, but significant upward trends were also observed in 3 out of 38 gauging stations. Mean annual streamflow during 1979?2010 decreased by up to 65% across the catchments compared with the period of 1957?1978, indicating significant changes in the hydrological regime of the Loess Plateau. It is estimated that 70% of the streamflow reduction can be attributed to land use change, while the remaining 30% is associated with climate variability. Land use change because of the soil conservation measures and reduction in precipitation are the key drivers for the observed streamflow trends. These findings are consistent with results of previous studies for the region and appear to be reasonable given the accelerated level of the soil conservation measures implemented since the late 1970s. Changes in sea surface temperature in the Pacific Ocean, as indicated by variations in El Niño–Southern Oscillation and phase shifts of the Pacific Decadal Oscillation, appear to have also affected the annual streamflow trends. The framework described in this study shows promising results for quantifying the effects of land use change and climate variability on mean annual streamflow of catchments within the Loess Plateau. Copyright © 2015 John Wiley & Sons, Ltd.     

Regional differences and determinants of built-up area expansion in China

Based on remote sensing data on land use provided by the Chinese Academy of Sciences and socio-economic data collected by the authors,this paper analyzes the trends and regional differences in built-up area(BUA) expansion in China from the late 1980s to 2000,and empirically estimates the major determinants of BUA expansion in different regions in 1996―2000.In 1989―2000,although China's overall BUA expansion accelerated,the trends differed significantly among regions.BUA expansion in the central and western regions accelerated significantly,but it slowed down considerably in the east-ern region.The estimation results from our econometric analysis reveal that BUA expansion in the eastern region reached a period when economic growth had no further significant impact on per capita BUA,the land utilization in this region has become more intensive with further expansion of the economy.In the central and western regions,the BUA has expanded remarkably due to the relatively more flexible land development policies and the relatively cheap land prices.Therefore,as the econ-omy continues to grow rapidly,policies relating to BUA expansion and cultivated land reductions may face more serious challenges in the central and western regions.     

Quantitative analysis of agricultural land use change in China

This article reviews the potential impacts of climate change on land use change in China. Crop sown area is used as index to quantitatively analyze the temporal–spatial changes and the utilization of the agricultural land. A new concept is defined as potential multiple cropping index to reflect the potential sowing ability. The impacting mechanism, land use status and its surplus capacity are investigated as well. The main conclusions are as following;

• 1.During 1949–2010, the agricultural land was the greatest in amount in the middle of China, followed by that in the country’s eastern and western regions. The most rapid increase and decrease of agricultural land were observed in Xinjiang and North China respectively, Northwest China and South China is also changed rapid. The variation trend before 1980 differed significantly from that after 1980.
• 2.Agricultural land was affected by both natural and social factors, such as regional climate and environmental changes, population growth, economic development, and implementation of policies. In this paper, the effects of temperature and urbanization on the coverage of agriculture land are evaluated, and the results show that the urbanization can greatly affects the amount of agriculture land in South China, Northeast China, Xinjiang and Southwest China.
• 3.From 1980 to 2009, the extent of agricultural land use had increased as the surplus capacity had decreased. Still, large remaining potential space is available, but the future utilization of agricultural land should be carried out with scientific planning and management for the sustainable development.

     

Detecting water yield variability due to the small proportional land use and land cover changes in a watershed on the Loess Plateau,China

Soil conservation practices have been widely implemented on the Loess Plateau to reduce severe soil erosion in north‐central China over the past three decades. However, the hydrologic impacts of these practices are not well documented and understood. The objective of this study was to examine how water yield has changed after implementing soil conservation practices that resulted in changes in land use and land cover in a small agriculture‐dominated watershed, the LuErGou Watershed in Tianshui City, Gansu Province, China. We collected 23 years of hydro‐meteorological data along with three land use surveys of 1982, 1989, and 2000. The land use survey in 2000 suggested that the soil conservation efforts resulted in a 16·6%, 4%, and 16% increase in area of grassland, forested land, and terraces respectively over the two periods from 1982 to 1988 (baseline) and 1989 to 2003 (soil conservation measures implemented). Rainfall–runoff regression models developed for both time periods at the annual and monthly time steps were used to examine the significance of change in water yield in the second time period. The averaged annual run‐off coefficient over 1989–2003 did not change significantly (at the α = 0·05 level) as compared to that in the period 1982–1988. However, we found that soil conservation practices that included re‐vegetation and terracing reduced water yield during wet periods. This study highlights the importance of the precipitation regime in regulating hydrologic effects of soil conservation measures in a semi‐arid environment. We concluded that adequately evaluating the effects of land use change and soil conservation measures on water yield must consider the climatic variability under an arid environment. Copyright © 2009 John Wiley & Sons, Ltd.     

Modeling the impacts of drying trend scenarios on land systems in northern China using an integrated SD and CA model

Climate-induced drought has exerted obvious impacts on land systems in northern China. Although recent reports by the Intergovernmental Panel on Climate Change (IPCC) have suggested a high possibility of climate-induced drought in northern China, the potential impacts of such drying trends on land systems are still unclear. Land use models are powerful tools for assessing the impacts of future climate change. In this study, we first developed a land use scenario dynamic model (iLUSD) by integrating system dynamics and cellular automata. Then, we designed three drying trend scenarios (reversed drying trend, gradual drying trend, and acceleration of drying trend) for the next 25 years based on the IPCC emission scenarios and considering regional climatic predictions in northern China. Finally, the impacts of drying trend scenarios on the land system were simulated and compared. An accuracy assessment with historic data covering 2000 to 2005 indicated that the developed model is competent and reliable for understanding complex changes in the land use system. The results showed that water resources varied from 441.64 to 330.71 billion m³ among different drying trend scenarios, suggesting that future drying trends will have a significant influence on water resource and socioeconomic development. Under the pressures of climate change, water scarcity, and socioeconomic development, the ecotone (i.e., transition zone between cropping area and nomadic area) in northern China will become increasingly vulnerable and hotspots for land-use change. Urban land and grassland would have the most prominent response to the drying trends. Urban land will expand around major metropolitan areas and the conflict between urban and cultivated land will become more severe. The results also show that previous ecological control measures adopted by the government in these areas will play an important role in rehabilitating the environment. In order to achieve a sustainable development in northern China, issues need to be addressed such as how to arrange land use structure and patterns rationally, and how to adapt to the pressures of climate change and socioeconomic development together.     

近40年青藏高原湖泊面积变化遥感分析

以MSS、TM和ETM遥感影像作为主要信息源,综合利用RS、GIS技术,提取青藏高原1970s、1990s、2000s及2010s 4个时段的湖泊面积信息,分别从区域位置、面积规模、海拔高度3方面分析其近40年来的变化趋势及变化特征,同时结合1972-2011年间青藏高原气候变化情况,初步探讨了影响青藏高原湖泊面积变化的主要原因.研究结果表明:(1)青藏高原面积大于10 km²的湖泊有417个,这些湖泊大多是面积为10~100 km²的小型湖泊,空间上集中分布在高原西部地区,海拔上集中在4500~5000 m范围内;(2)近40年青藏高原湖泊面积的变化趋势及差异性特征在整体上表现为湖泊呈加速扩张的趋势,其中2000s-2010s时段是湖泊扩张最显著的时期;在区域位置上,北部地区的湖泊变化最为剧烈;在面积规模上,小型湖泊扩张最为显著;在海拔高度上,低海拔地区湖泊扩张剧烈;(3)近40年青藏高原气候暖湿化程度明显,气候变化对湖泊面积变化影响显著;在气象要素中,降水量的变化是青藏高原湖泊面积变化的主要驱动因子.     

Developing land use scenario dynamics model by the integration of system dynamics model and cellular automata model

Models of land use change are useful tools for un-derstanding the analysis of the cause and conse-quences of land use changes, assessing the impacts of land use system on ecological system and supporting land use planning and policy[1,2]. Modeling land use scenario changes and its potential impacts on the structure and function of the ecosystem in the typical regions are regarded as one of the good ways to un-derstand the interactive mechanism between land use system and ecological system[3―10…     

Modeling the climatic effects of the land use/cover change in eastern China

This study aims to quantify the contribution of land use/cover change (LUCC) during the last three decades to climate change conditions in eastern China. The effects of farmland expansion in Northeast China, grassland degradation in Northwest China, and deforestation in South China were simulated using the Weather Research and Forecasting (WRF) model in addition to the latest actual land cover datasets. The simulated results show that when forestland is converted to farmland, the air temperature decreased owing to an increase in surface albedo in Northeast China. The climatic effect of grassland degradation on the Loess Plateau was insignificant because of the negligible difference in albedo between grassland and cropland. In South China, deforestation generally led to a decrease in temperature. Furthermore, the temperature decrease caused by the increase in albedo counteracted the warming effects of the evapotranspiration decrease, so the summer temperature change was not significant in South China. Excluding the effects of urbanization in the North China Plain, the LUCC effects across the entire region of East China presented an overall cooling trend. However, the variation in temperature scale and magnitude was less in summer than that in winter. This result is due mainly to the cooling caused by the increase in albedo offset partly by the increase in temperature caused by the decrease in evaporation in summer. Summer precipitation showed a trend of increasing–decreasing–increasing from southeast to northwest after LUCC, which was induced mainly by the decrease in surface roughness and cyclone circulations appearing northwest of Northeast China, in the middle of the Loess Plateau, and in Yunnan province at 700 hPa after forests were converted into farmland. All results will be instructive for understanding the influence of LUCC on regional climate and future land planning in practice.     

Modelling hydrological response to different land‐use and climate change scenarios in the Zamu River basin of northwest China

Changes in climate and land use can significantly influence the hydrological cycle and hence affect water resources. Understanding the impacts of climate and land‐use changes on streamflow can facilitate development of sustainable water resources strategies. This study investigates the flow variation of the Zamu River, an inland river in the arid area of northwest China, using the Soil and Water Assessment Tool distributed hydrological model. Three different land‐use and climate‐change scenarios were considered on the basis of measured climate data and land‐use cover, and then these data were input into the hydrological model. Based on the sensitivity analysis, model calibration and verification, the hydrological response to different land‐use and climate‐change scenarios was simulated. The results indicate that the runoff varied with different land‐use type, and the runoff of the mountain reaches of the catchment increased when grassland area increased and forestland decreased. The simulated runoff increased with increased precipitation, but the mean temperature increase decreased the runoff under the same precipitation condition. Application of grey correlation analysis showed that precipitation and temperature play a critical role in the runoff of the Zamu River basin. Sensitivity analysis of runoff to precipitation and temperature by considering the 1990s land use and climate conditions was also undertaken. Copyright © 2007 John Wiley & Sons, Ltd.     

Using the SWAT model to assess impacts of land use changes on runoff generation in headwaters

The upstream regions of the Three Gorges Reservoir (TGR) have undergone significant changes in land use during recent years, and these changes have strongly influenced runoff generation downstream. In this study, the relationships between land use changes and corresponding hydrological responses in the Dong and Puli River basins in the upstream region of the TGR were quantified using the runoff coefficient. Empirical regression equations between the runoff coefficient and the percentage of land use types were developed for the study area using partial least squares regression (PLSR). The Soil and Water Assessment Tool was used to simulate the runoff generation processes in the two basins, and land use maps developed using Landsat Thematic Mapper images from 2000, 2005, and 2010 were compared to extract information on changes in land use. The results showed that the total area of forest and pasture decreased over the 10‐year study period, while paddy fields and upland increased in both basins. These land use changes dramatically affected hydrological processes. Evapotranspiration decreased by 2.13% and 2.41% between 2000 and 2010 in the Dong and Puli River basins, respectively, whereas quickflow, infiltration, and baseflow increased to varying degrees. The PLSR modeling results showed that upland had a negative effect on the runoff coefficient and was the most influential land use type in the study area. In contrast, a positive effect of forest on runoff generation was found in most of the regression models. Copyright © 2012 John Wiley & Sons, Ltd.     

Preliminary reconstruction of the desert and sandy land distributions in China since the last interglacial period

The desert and sandy land are the products of arid climate. The spatial distribution of modern deserts and sandy land in China and their relation to climate show following characteristics: arid and hyper-arid desert zones, at isohyet of less than 200 mm, are dominated by mobile dunes; semi-arid steppe and arid desert steppe with the precipitation between 200–400 mm, are dominated by semi-fixed and fixed sand dunes; the precipitation of sub-humid forest grassland and humid forest zones with scattered fixed sand land is higher than 400 mm. With this as reference, in combination with considerable amount of paleoclimatic data in desert regions and adjacent regions, the distributions of desert and sandy land in China during the last interglacial period, the last glacial maximum (LGM), and the Holocene megathermal, were preliminarily reconstructed. The results compared with that of today show that the distribution of desert and sandy land in China was greatly dwindled during last interglacial period, and the mobile dune area was about two-thirds of that of today’s, but greatly expanded during LGM. However, the dwindling area of desert and sandy land in the Holocene megathermal was smaller than that in the last interglacial period. The forcing mechanism was mainly related to the changes of East Asian winter and summer monsoon, south-northward swing of the westerlies and the variations of the Qinghai-Tibet Plateau monsoon intensity caused by global climate changes during the cold and warm intervals since the last interglacial period.     

Effects of land‐use changes on hydrological processes in the middle basin of the Heihe River,northwest China

The effects of land‐use changes on the runoff process in the midstream plain of this arid inland river basin are a key factor in the rational allocation of water resources to the middle and lower reaches. The question is whether and by how much increasingly heavy land use impacts the hydrological processes in such an arid inland river basin. The catchment of the Heihe River, one of the largest inland rivers in the arid region of northwest China, was chosen to investigate the hydrological responses to land‐use change. Flow duration curves were used to detect trends and variations in runoff between the upper and lower reaches. Relationships among precipitation, upstream runoff, and hydrological variables were identified to distinguish the effects of climatic changes and upstream runoff changes on middle and downstream runoff processes. The quantitative relation between midstream cultivated land use and various parameters of downstream runoff processes were analysed using the four periods of land‐use data since 1956. The Volterra numerical function relation of the hydrological non‐linear system response was utilized to develop a multifactor hydrological response simulation model based on the three factors of precipitation, upstream runoff, and cultivated land area. The results showed that, since 1967, the medium‐ and high‐coverage natural grassland area in the midstream region has decreased by 80·1%, and the downstream runoff has declined by 27·32% due to the continuous expansion of the cultivated land area. The contribution of cultivated land expansion to the impact on the annual total runoff is 14–31%, on the annual, spring and winter base flow it is 44–75%, and on spring and winter discharge it is 23–64%. Once the water conservation plan dominated by land‐use structural adjustments is implemented over the next 5 years, the mean annual discharge in the lower reach could increase by 8·98% and the spring discharge by 26·28%. This will significantly alleviate the imbalance between water supply and demand in both its quantity and temporal distribution in the middle and lower reaches. Copyright © 2006 John Wiley & Sons, Ltd.     

Impact of land-use induced changes on agricultural productivity in the Huang-Huai-Hai River Basin

The water resource allocation is greatly influenced by the land use, agricultural productivity and farmers’ income. Therefore analyzing the impacts of land use changes on agricultural productivity and subsequent effects on farmer’s income is an important basis of the further study on the management mechanism and optimal water resource allocation. Taking the Huang-Huai-Hai River Basin as the study area, this study examined the impacts of conversion from cultivated land to built-up land from 2000–2005 and 2005–2008. Then the agricultural productivity was estimated with the Estimation System for Agricultural Productivity model, and the changes in agricultural productivity caused by land conversion were analyzed. Thereafter, Simultaneous Equations Model was used to analyze the impacts of the conversion from cultivated land to built-up land on the agricultural productivity and subsequent effects on farmer’s income. The results showed that: (1) The agricultural productivity was stable during the whole period, reaching about 2.84 ton/ha, 3.09 ton/ha and 2.80 ton/ha on average in 2000, 2005 and 2008, respectively, but the conversion from cultivated land to built-up land had important influence on the spatial pattern of agricultural productivity. (2) The land productivity, total power of agricultural machinery and the conversion from cultivated land to built-up land had an overall positive effect on the agricultural productivity. (3) The agricultural productivity and gross domestic product had positive influence on the farmers’ income, while the cultivated land area per capita and percentage of farming employee had negative influence, indicating that the farmer’s income was mainly contributed by non-agricultural income. These results in this study showed that optimal land use management can play an important role in promoting virtuous ecosystem cycle and sustainable socioeconomic development, which can also lay an important foundation for further research on the optimal allocation of water resources in the Huang-Huai-Hai River Basin.     

北方半干旱区土地利用/覆被变化对湖泊水质的影响:以岱海流域为例(2000-2018年)

土地利用/覆被变化对明晰气候变化和人类活动对湖泊水环境的影响有重要作用.以北方典型农牧交错的岱海流域为研究对象,基于遥感解译技术、马尔可夫转移矩阵、综合污染指数法等方法,对2000-2018年岱海流域土地利用/覆被和湖泊水质的变化进行分析,并结合冗余分析法和计量分析模型探究长时间序列尺度下土地利用/覆被变化对湖泊水质的...