基于Hurst指数的1982–2013年蒙古高原植被动态变化趋势及其影响因素分析（英文）

This study analyzed the spatial and temporal variations in the Normalized Difference Vegetation Index(NDVI) on the Mongolian Plateau from 1982–2013 using Global Inventory Modeling and Mapping Studies(GIMMS) NDVI3 g data and explored the effects of climate factors and human activities on vegetation. The results indicate that NDVI has slight upward trend in the Mongolian Plateau over the last 32 years. The area in which NDVI increased was much larger than that in which it decreased. Increased NDVI was primarily distributed in the southern part of the plateau, especially in the agro-pastoral ecotone of Inner Mongolia. Improvement in the vegetative cover is predicted for a larger area compared to that in which degradation is predicted based on Hurst exponent analysis. The NDVI-indicated vegetation growth in the Mongolian Plateau is a combined result of climate variations and human activities. Specifically, the precipitation has been the dominant factor and the recent human effort in protecting the ecological environments has left readily detectable imprints in the NDVI data series.     

2000–2011年三江源区植被覆盖时空变化特征(英文)

The Three-River Headwaters Region(TRHR), which is the source area of the Yangtze River, Yellow River, and Lancang River, is of key importance to the ecological security of China. Because of climate changes and human activities, ecological degradation occurred in this region. Therefore, "The nature reserve of Three-River Source Regions" was established, and "The project of ecological protection and construction for the Three-River Headwaters Nature Reserve" was implemented by the Chinese government. This study, based on MODIS-NDVI and climate data, aims to analyze the spatiotemporal changes in vegetation coverage and its driving factors in the TRHR between 2000 and 2011, from three dimensions. Linear regression, Hurst index analysis, and partial correlation analysis were employed. The results showed the following:(1) In the past 12 years(2000–2011), the NDVI of the study area increased, with a linear tendency being 1.2%/10a, of which the Yangtze and Yellow River source regions presented an increasing trend, while the Lancang River source region showed a decreasing trend.(2) Vegetation coverage presented an obvious spatial difference in the TRHR, and the NDVI frequency was featured by a bimodal structure.(3) The area with improved vegetation coverage was larger than the degraded area, being 64.06% and 35.94%, respectively during the study period, and presented an increasing trend in the north and a decreasing trend in the south.(4) The reverse characteristics of vegetation coverage change are significant. In the future, degradation trends will be mainly found in the Yangtze River Basin and to the north of the Yellow River, while areas with improving trends are mainly distributed in the Lancang River Basin.(5) The response of vegetation coverage to precipitation and potential evapotranspiration has a time lag, while there is no such lag in the case of temperature.(6) The increased vegetation coverage is mainly attributed to the warm-wet climate change and the implementation of the ecological protection project.     

陕甘宁地区植被恢复对气候变化和人类活动的响应(英文)

The "Grain for Green Project" initiated by the governments since 1999 were the dominant contributors to the vegetation restoration in the agro-pastoral transitional zone of northern China. Climate change and human activities are responsible for the improvement and degradation to a certain degree. In order to monitor the vegetation variations and clarify the causes of rehabilitation in the Shaanxi-Gansu-Ningxia Region, this paper, based on the MODIS-NDVI and climate data during the period of 2000-2009, analyzes the main charac-teristics, spatial-temporal distribution and reasons of vegetation restoration, using methods of linear regression, the Hurst Exponent, standard deviation and other methods. Results are shown as follows. (1) From 2000 to 2009, the NDVI of the study area was improved progres-sively, with a linear tendency being 0.032/10a, faster than the growth of the Three-North Shelter Forest Program (0.007/10a) from 1982 to 2006. (2) The vegetation restoration is characterized by two fast-growing periods, with an "S-shaped" increasing curve. (3) The largest proportion of the contribution to vegetation restoration was observed in the slightly improved area, followed by the moderate and the significantly improved area; the degraded area is distributed sporadically over southern part of Ningxia Hui Autonomous Region as well as eastern Dingbian of Shaanxi province, Huanxian and Zhengyuan of Gansu province. (4) Climate change and human activities are two driving forces in vegetation restoration; more-over anthropogenic factors such as "Grain for Green Project" were the main causes leading to an increasing trend of NDVI on local scale. However, its influencing mechanism remains to be further investigated. (5) The Hurst Exponent of NDVI time series shows that the vegetation restoration was sustainable. It is expected that improvement in vegetation cover will expand to the most parts of the region.     

乡村人口迁出对生态脆弱地区植被覆被的影响——以内蒙古自治区为例（英文）

Different government departments and researchers have paid considerable attention at various levels to improving the eco-environment in ecologically fragile areas. Over the past decade, large numbers of people have emigrated from rural areas as a result of the rapid urbanization in Chinese society. The question then remains: to what extent does this migration affect the regional vegetation greenness in the areas that people have moved from Based on normalized difference vegetation index(NDVI) data with a resolution of 1 km, as well as meteorological data and socio-economic data from 2000 to 2010 in Inner Mongolia, the spatio-temporal variation of vegetation greenness in the study area was analyzed via trend analysis and significance test methods. The contributions of human activities and natural factors to the variation of vegetation conditions during this period were also quantitatively tested and verified, using a multi-regression analysis method. We found that:(1) the vegetation greenness of the study area increased by 10.1% during 2000–2010. More than 28% of the vegetation greenness increased significantly, and only about 2% decreased evidently during the study period.(2) The area with significant degradation showed a banded distribution at the northern edge of the agro-pastoral ecotone in central Inner Mongolia. This indicates that the eco-environment is still fragile in this area, which should be paid close attention. The area where vegetation greenness significantly improved showed a concentrated distribution in the southeast and west of Inner Mongolia.(3) The effect of agricultural labor on vegetation greenness exceeded those due to natural factors(i.e. precipitation and temperature). The emigration of agricultural labor improved the regional vegetation greenness significantly.     

Spatiotemporal changes in vegetation coverage and its driving factors in the Three-River Headwaters Region during 2000–2011简

The Three-River Headwaters Region （TRHR）, which is the source area of the Yangtze River, Yellow River, and Lancang River, is of key importance to the ecological secu- rity of China. Because of climate changes and human activities, ecological degradation oc- curred in this region. Therefore, ＂The nature reserve of Three-River Sou,＇ce Regions＂ was established, and ＂The project of ecological protection and construction for the Three-River Headwaters Nature Reserve＂ was implemented by the Chinese government. This study, based on MODIS-NDVI and climate data, aims to analyze the spatiotemporal changes in vegetation coverage and its driving factors in the TRHR between 2000 and 2011, from three dimensions. Linear regression, Hurst index analysis, and partial correlation analysis were employed. The results showed the following： （1） In the past 12 years （2000-2011）, the NDVI of the study area increased, with a linear tendency being 1.2%/10a, of which the Yangtze and Yellow River source regions presented an increasing trend, while the Lancang River source region showed a decreasing trend. （2） Vegetation coverage presented an obvious spatial difference in the TRHR, and the NDVI frequency was featured by a bimodal structure. （3） The area with improved vegetation coverage was larger than the degraded area, being 64.06% and 35.94%, respectively during the study period, and presented an increasing trend in the north and a decreasing trend in the south. （4） The reverse characteristics of vegetation cov- erage change are significant. In the future, degradation trends will be mainly found in the Yangtze River Basin and to the north of the Yellow River, while areas with improving trends are mainly distributed in the Lancang River Basin. （5） The response of vegetation coverage to precipitation and potential evapotranspiration has a time lag, while there is no such lag in the case of temperature. （6） The increased vegetation coverage is mainly attributed to the warm-wet climate change and the implementation of the ecological protection project.     

Land use change and its ecological effect in Qian＇an County of Jilin Province

Based on GIS and statistical methods, with the help of searching historical literatures and calculating the landscape indices, the land use changes of Qian‘an County in both spatial and temporal aspects from 1945 to 1996 has been analyzed in this paper. And the driving forces of land use changes and their ecological effects are discussed too. The main findings of this study are as follows: (1) Land use changed greatly in Qian‘an during 1945-1996, characterized by a decrease in grassland, wetland and water bodies, and an increase in cultivated land, saline-alkali land, and the land for housing and other construction purposes. Grassland decreased by 175,828.66 ha, and cultivated land increased by 102,137.23 ha over the half century. Accordingly, the main landscape type changed from a steppe landscape to a managed agricultural ecosystem. (2) Results of correlation analysis show that the land use change in the study area was mainly driven by the socioeconomic factors. (3) The ecological effects of land use change in the area are characterized by serious salinization, degression of soil fertility and the weakening, of landscaoe suitability.     

Response of revegetation to climate change with meso-and micro-scale remote sensing in an arid desert of China

The revegetation protection system(VPS)on the edge of the Tengger Desert can be referred to as a successful model of sand control technology in China and even the world,and there has been a substantial amount of research on revegetation stability.However,it is unclear how meso-and micro-scale revegetation activity has responded to climatic change over the past decades.To evaluate the relative influence of climatic variables on revegetation activities in a restored desert ecosystem,we analysed the trend of revegetation change from 2002 to 2015 using a satellite-derived normalized difference vegetation index(NDVI)dataset.The time series of the NDVI data were decomposed into trend,seasonal,and random components using a segmented regression method.The results of the segmented regression model indicate a changing trend in the NDVI in the VPS,changing from a decrease(?7×10?3/month)before 2005 to an increase(0.3×10?3/month)after 2005.We found that precipitation was the most important climatic factor influencing the growing season NDVI(P<0.05),while vegetation growth sensitivity to water and heat varied significantly in different seasons.In the case of precipitation reduction and warming in the study area,the NDVI of the VPS could still maintain an overall slow upward trend(0.04×10?3/month),indicating that the ecosystem is sustainable.Our findings suggest that the VPS has been successful in maintaining stability and sustainability under current climate change conditions and that it is possible to introduce the VPS in similar areas as a template for resistance to sand and drought hazards.     

ASSESSMENT OF 17β-ESTRADIOL IN AQUATIC ENVIRONMENTS AROUND KLANG VALLEY, MALAYSIA

This study was conducted to assess the existing concentration of 17β-estradiol(E2)in the surface water samples collected from rivers and lakes around Klang Valley,Malaysia.E2,which is a natural feminizing chemical produced in female organisms,regularly used to compare with other environmental estrogens because they behave similarly and react effectively as a hormone at a very low concentration.It was found that the average concentration of E2 in the aquatic environment of Klang Valley was(14.08 ±3.67)pg/mL,which was 14 times higher than those in the Japanese aquatic environment in this study.The river system had the average concentration of(20.02±5.26)pg/mL while the lake had an average concentration of(5.91±3.39)pg/mL.The E2 concentration was presumed high if the sources occurred nearby the area.Current levels of E2 in the aquatic environment may possess threats to existing aquatic organisms.Since high level of E2 has been discovered in the aquatic environment around Klang Valley,further studies and monitoring of E2 and other EDCs concentrations are needed to determine their levels in Malaysian aquatic environment and help to control these chemicals pollution in the aquatic environment.     

A case study on Landscape Component Niche based on Landscape Pattern Indices: Yanchi,Ningxia Province,China

Yanchi County is located in the agro-pastoral ecotone and belongs to the ecologically fragile area of Northwest China.It is important to study the evolution of landscape pattern to curb its environmental degradation.In order to intuitively show how the landscape pattern of the study area changes over time,Landsat Thematic Mappers(TM)and Landsat Operational Land Imager(OLI)data of 1991,2000,2010 and 2017 were used.This paper attempts to apply niche theories and methods into landscape ecology,and constructs a niche model of landscape components by using"n-dimentional hypervolume niche theory"and landscape pattern indices.By evaluating the spatial and temporal evolution of niche from the perspective of two-dimensional space to reflect the changes of landscape pattern in the study area over the past 26 years,new theories and methods were introduced for the characterization of landscape pattern.The results indicate that:1)The larger the attribute and dominance value of landscape components,the higher the ecological niche and the stronger the control effect on the overall landscape.2)The ecological niche of each landscape component was significantly different,just as its control effect on the overall landscape.3)The dynamic change of the ecological niche of each landscape component was different,with grassland,unused land and arable land always in a high dominant position,although the ecological niche of construction land and water area was always low.In general,the introduction of niche theory into the landscape ecology provided a new method to study the changes in regional landscape pattern.     

Sap-flow measurement and scale transferring from sample trees to entire forest stand of Populus euphratica in desert riparian forest in extreme arid region

Understanding how the transpiration of this vegetation type responds to environmental stress is important for determining the wa-ter-balance dynamics of the riparian ecosystem threatened by groundwater depletion. Transpiration and sap flow were measured using the heat-pulse technique. The results were then projected up to the stand level to investigate the stand’s water-use in relation to climate forcing in the desert riparian forest in an extreme arid region. This study took place from April through October 2003 and from May through October 2004. The experimental site was selected in the Populus euphratica Forest Reserve (101o10’ E, 41o59’ N) in Ejina county, in the lower Heihe River basin, China. The sapwood area was used as a scalar to extrapolate the stand-water consumption from the whole trees’ water consumption measured by the heat-pulse velocity recorder (HPVR). Scale transferring from a series of individual trees to a stand was done according to the existing natural variations between trees under given environmental conditions. The application of the biometric parameters available from individual tree and stand levels was proved suitable for this purpose. A significant correlation between the sapwood area and tree diameter at breast height (DBH) was found. The prediction model is well fitted by the power model. On the basis of the prediction model, the sapwood area can be cal-culated by DBH. The sap-flow density can then be used to extrapolate the stand-water use by means of a series of mathematical models.     

Luminescence dating of reticulated red clay buried in Lanshanmiao Paleolithic site in Zhejiang Province,southern China

The Lanshanmiao(LSM) Palaeolithic site,which was excavated in the summer of 2017 by the Zhejiang Provincial Institute of Cultural Relics and Archaeology,is the only excavated palaeolithic site in central Zhejiang Province to date.Luminescence dating methods,including optical stimulated luminescence(OSL) and thermal transfer OSL(TT-OSL) for quartz and post-infrared(IR) stimulated luminescence(p IRIR290) for feldspar,were used to determine the age of the LSM site.The results showed that the LSM section developed before 145.5 ± 12.5 ka and ended after 17.1 ± 1.0 ka.The TT-OSL dating of samples NJU2576 and NJU2615 showed that palaeolithic artifact-bearing layer was between 150 and 100 ka in age.The age range of the palaeolithic layer mainly corresponded to the transition between Marine Isotope Stage(MIS) 6 and MIS5.Our study showed that hominins prominently occupied the LSM site during the glacial and interglacial stages,when it exhibited a floodplain environment.     

2000-2014年秦巴山区植被覆盖时空变化特征及其归因（英文）

Using the Moderate Resolution Imaging Spectroradiometer-normalized difference vegetation index(NDVI) dataset,we investigated the patterns of spatiotemporal variation in vegetation coverage and its associated driving forces in the Qinling-Daba(Qinba) Mountains in 2000–2014.The Sen and Mann–Kendall models and partial correlation analysis were used to analyze the data,followed by calculation of the Hurst index to analyze future trends in vegetation coverage.The results of the study showed that(1) NDVI of the study area exhibited a significant increase in 2000–2014(linear tendency,2.8%/10a).During this period,a stable increase was detected before 2010(linear tendency,4.32%/10a),followed by a sharp decline after 2010(linear tendency,–6.59%/10a).(2) Spatially,vegetation cover showed a "high in the middle and a low in the surroundings" pattern.High values of vegetation coverage were mainly found in the Qinba Mountains of Shaanxi Province.(3) The area with improved vegetation coverage was larger than the degraded area,being 81.32% and 18.68%,respectively,during the study period.Piecewise analysis revealed that 71.61% of the total study area showed a decreasing trend in vegetation coverage in 2010–2014.(4) Reverse characteristics of vegetation coverage change were stronger than the same characteristics on the Qinba Mountains.About 46.89% of the entire study area is predicted to decrease in the future,while 34.44% of the total area will follow a continuously increasing trend.(5) The change of vegetation coverage was mainly attributed to the deficit in precipitation.Moreover,vegetation coverage during La Nina years was higher than that during El Nino years.(6) Human activities can induce ambiguous effects on vegetation coverage: both positive effects(through implementation of ecological restoration projects) and negative effects(through urbanization) were observed.     

Short-term Climate Characteristics at Ny-lesund over the Arctic Tundra Area

<正> Based on the Germany Koldwey Station's 1994-2003 conventional ob-servation hourly data,this paper conducts a statistical analysis on the short-termclimate characteristics for an arctic tundra region(Ny-lesund island)where ourfirst arctic expedition station(Huanghe Station)was located.Affected by theNorth Atlantic warming current,this area has a humid temperate climate,andthe air temperature at Ny-lesund rose above 0℃ even during deep winter sea-son during our research period.The wind speed in this area was low and appearedmost at southeast direction.We find that the temperature at Ny-lesund rose inthe faster rate(0.68℃/10 a)than those at the whole Arctic area.Comparedwith the floating ices where our expedition conducted in the Arctic,Ny-lesundwas warmer and more humid and had lower wind speed.Comparison of the nearsurface air temperature derived by NCEP/NCAR reanalysis to the conventionalmeasurements conducted at the Koldwey site in Ny-lesund area shows a good a-greement for winter season and a significant difference for summer season.     

清末松嫩平原耕地重建方法比较分析（英文）

To understand historical human-induced land use/cover change(LUCC) and its climatic effects,it is essential to reconstruct historical land use/cover changes with explicit spatial information. In this study,based on the historically documented cropland area at county level,we reconstructed the spatially explicit cropland distribution at a cell size of 1 km × 1 km for the Songnen Plain in the late Qing Dynasty(1908 AD). The reconstructions were carried out using two methods. One method(hereafter,referred to as method I) allocated the cropland to cells ordered from a high agricultural suitability index(ASI) to a low ASI,but they were all within the domain of potential cropland area. The potential cropland area was created by excluding natural woodland,swamp,water bodies,and mountains from the study area. The other method(hereafter,method II) allocated the cropland to cells in the order from high ASI to low ASI within the domain of cropland area in 1959. This method was based on the hypothesis that the cropland area domain in 1959 resulted from enlargement of the cropland area domain in 1908. We then compared these two reconstructions. We found that the cropland distributions reconstructed by the two methods exhibit a similar spatial distribution pattern. Both reconstructions show that the cropland was mostly found in the southern and eastern parts of the Songnen Plain. The two reconstructions matched each other for about 68% of the total cropland area. By spatially comparing the unmatched cropland cells of the two reconstructions with the settlements for each county,we found that unmatched cropland cells from method I are closer to settlements than those from method II. This finding suggests that reconstruction using method I may have less bias than reconstruction with method II.     

Settlement distribution and its relationship with environmental changes from the Neolithic to Shang-Zhou dynasties in northern Shandong, China

In this paper, the spatial and temporal distribution of the settlement sites of six periods from the Neolithic Age to the Shang and Zhou dynasties in northern Shandong was investigated using the ArcGIS program, and the relationship between settlement distribution and environmental changes was discussed, based on the proxy records of climatic and environmental change contained in the sediments from three sections at the Shuangwangcheng site and the previous work. The results show that the climate was warm and humid and the sea level was relatively high during the period of 8000-5000 a BP in the study area, and the ancient people lived in the relatively flat （slope of 〈2°） areas at high elevation （20-300 m above sea level）, such as diluvial tableland and alluvial plain. On the other hand, few archaeological sites in the low-lying plain in the west of the study area indicate that few people lived there during that period. This might be attributed to frequent flooding in the area. After 5000 years ago, the scope of human activity extended to the area close to the sea because the relatively colder and drier climate results in sea-level fall, meanwhile the low-lying plain in the west was occupied by the ancient people. The study area of this period was characterized by the rapid development of prehistoric culture, the intensified social stratification and the emergence of early city-states. However, around 4000 a BP, the abrupt change in climate and the increase in frequency and intensity of floods severely disrupted human activities, and eventually led to the decline of the Yueshi culture. During the Shang and Zhou dynasties, the climatic conditions gradually stabilized in a mild-dry state, which promoted the redevelopment and flourish of the Bronze Culture. The previous situation, which was characteristic of sparse human settlements due to freshwater shortage and unfitted conditions for sedentary agriculture, changed during the Shang and Zhou dynasties in northern coastal wetlands.Local residents effectively adapted themselves to the tough environmental conditions by producing sea-salt, which led to the rapid growth of human activities.     

鄱阳湖非平稳水位波动及其与长江的交互作用关系(英文)

Seasonal water-level fluctuations(WLF) play a dominate role in lacustrine ecosystems. River-lake interaction is a direct factor in changes of seasonal lake WLF, especially for those lakes naturally connected to upstream and downstream rivers. During the past decade, the modification of WLF in the Poyang Lake(the largest freshwater lake in China) has caused intensified flood and irrigation crises, reduced water availability, compromised water quality and extensive degradation of the lake ecosystem. There has been a conjecture as to whether the modification was caused by its interactions with Yangtze River. In this study, we investigated the variations of seasonal WLF in China’s Poyang Lake by comparing the water levels during the four distinct seasons(the dry season, the rising season, the flood season, and the retreating season) before and after 2003 when the Three Gorge Dam operated. The Water Surface Slope(WSS) was used as a representative parameter to measure the changes in river-lake interaction and its impacts on seasonal WLF. The results showed that the magnitude of seasonal WLF has changed considerably since 2003; the seasonal WLF of the Poyang Lake have been significantly altered by the fact that the water levels both rise and retreat earlier in the season and lowered water levels in general. The fluctuations of river-lake interactions, in particular the changes during the retreating season, are mainly responsible for these variations in magnitude of seasonal WLF. This study demonstrates that WSS is a representative parameter to denote river-lake interactions, and the results indicate that more emphasis should be placed on the decrease of the Poyang Lake caused by the lowered water levels of the Yangtze River, especially in the retreating season.     

Factor analysis to detect the causes of land degradation in Maduo County, northeastern Qinghai-Tibet Plateau

The area of desertified land has increased by 27.3% from 1987 to 2000 in Maduo County,northeastern Qinghai-Tibet Plateau.Driving forces of land degradation has been extensively studied in the region.Using Factor Analysis (FA),we evaluate contribution of human activity and natural environmental change to land degradation.Four common factors were extracted in this study.The result shows that climate related other than human-related factors,are the major inducing factors of land degradation in Maduo County.Climate change and consequent change of permafrost account for 70% to the land degradation.Increasing evaporation and declining precipitation in the beginning of the growing season hamper seedling establishment.Decreasing frozen days and rising active layer lower bound make surface soil loose and less soil moisture available for plant.     

The change of Ningchan River Glacier No. 3 at Lenglongling, east Qilian Mountain, China

In July, 2009, we investigated the Ningchan River Glacier No. 3. A control network was established around the glacier and the expedition used a GPS-RTK to measure glacial area, terminal and surface altitude, and used an EKKO GPR to measure glacier thickness. We used a topographic map based on 1972 aerial photo, two TM images in 1995, 2009, and GPS-RTK data in 2009, to analyze the change of the Ningchan River Glacier No. 3 since 1972. Through analysis we found this glacier has been seriously shrinking over the past 37 years. The glacier terminal retreated about 6%, the area was reduced about 13.1%, the volume was reduced about 35.3%, and glacier shrinkage is mainly in the form of thinning. Glacier average thickness reduced from 36.8 m in 1972, to 27.4 m in 2009. Meteorological data around the study area shows that this region in recent decades has undergone differential warming which is the main reason for rapid glacier shrinkage.     

Effect of shipping activity on warming trends in the Canadian Arctic

This paper presents a detailed account of the effect of shipping activity on the increasing trends of air temperatures in the Canadian Arctic region for the period of 1980–2018. Increasing trend of temperature has gained significant attention with respect to shipping activities and sea ice area in the Canadian Arctic. Temperature, sea ice area and shipping traffic datasets were investigated, and simple linear regression analyses were conducted to predict the rate of change(per decade) of the average temperature, considering winter(January) and summer(July) seasons. The results indicate that temperature generally increased over the studied region. Significant warming trend was observed during July, with an increase of up to 1℃, for the Canadian Arctic region. Such increasing trend of temperature was observed during July from the lower to higher latitudes. The increase in temperature during July is speculated to increase the melting of ice. Results also show a decline in sea ice area has a significant positive effect on the shipping traffic, and the numbers of marine vessel continue to increase in the region. The increase in temperature causes the breaking of sea ice due to shipping activities over northern Arctic Canada.     

The decreasing spring frost risks during the flowering period for woody plants in temperate area of eastern China over past 50 years

The temperate monsoon area of China is an important agricultural region but late spring frosts have frequently caused significant damage to plants there. Based on phenological data derived from the Chinese Phenological Observation Network （CPON）, corresponding meteorological data from 12 study sites and phenological modeling, changes in flowering times of multiple woody plants and the frequency of frost occurrence were analyzed. Through these analyses, frost risk during the flowering period at each site was estimated. Results of these estimates suggested that first flowering dates （FFD） in the study area advanced significantly from 1963 to 2009 at an average rate of -1.52 days/decade in North-east China （P〈0.01） and -2.22 days/decade （P〈0.01） in North China. Over the same period, the number of frost days in spring decreased and the last frost days advanced across the study area. Considering both flowering phenology and occurrence of frost, the frost risk index, which measures the percentage of species exposed to frost during the flowering period in spring, exhibited a decreasing trend of -0.37% per decade （insignificant） in Northeast China and -1.80% per decade （P〈0.01） in North China, implying that frost risk has reduced over the past half century. These conclusions provide important information to agriculture and forest managers in devising frost protection schemes in the region.