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Based on SPOT-VGT images and meteorological data, this paper applied an integrated method to investigate the vegetation dynamic and its response to climate factors during 1998-2008 in Northeast China Transect, one of 15 ecological transects listed in the International Geosphere-Biosphere Programme. The main findings are as follows: (1) The NDVI time series presented nonlinear patterns that vary with timescales. The series fluctuated greatly at the smallest timescale (20 days), showing no salient trend, whereas a trend manifested itself more and more with the increase of time scale and finally stabilized at the 320-day scale. Little difference was found between vegetation types about the NDVI periodicity, as they occurred on either a 280-day or a 290-day cycle. (2) NDVI exhibited a significant correlation with temperature, precipitation, and sunshine hours. Overall, the correlation between NDVI and temperature was the highest, followed by precipitation, sunshine hours, and relative humidity. For different vegetation types, the correlations between NDVI and climate variables diversified, increasing from desert steppe to typical steppe, meadow steppe, and forest. (3) The periodicity of temperature and precipitation occurred in either a 280-day or 290-day cycle, which was approximately coincident with that of NDVI. This further supported the significant relationship between NDVI and these two climate factors. (4) At all the time scales under examination, NDVI and temperature and precipitation are significantly, positively correlated, especially at the 160-day scale, which can be regarded as the most suitable time scale for investigating the responses of vegetation dynamics to climate factors at most stations. [ABSTRACT FROM AUTHOR]

The Three-North Shelter Forest Programme (TNSFP) covers 551 Chinese counties and an area of 4,069,000 km mostly in arid and semi-arid regions. In this paper, we discuss the temporal and spatial changes in value of the normalized-difference vegetation index (NDVI) in this region, and the relationships between NDVI and climatic factors (temperature and precipitation) based on NOAA Advanced Very High Resolution Radiometer Global Inventory Modeling and Mapping Studies NDVI data with 8-km resolution from 1982 to 2006. During the past 25 years, the vegetation cover has generally increased in eastern regions of China and the oasis in the north piedmont of Tianshan Mountains, but has decreased northwest of Xinjiang and in the Hulunbeier Plateau. The multi-year monthly average NDVI distribution map showed that NDVI increased from April to August, but in the western and northern plateau areas, the lower temperatures and high altitude created a shorter growing season (1 or 2 months). The vegetation of the study area has generally increased in the regions covered by the TNSFP. Linear regression analysis of the vegetation cover showed an increasing trend over large areas. The largest annual growth rate per pixel (the slope of the regression) was 0.009; the largest negative annual change was −0.004. The correlation between NDVI and precipitation was higher than that between NDVI and temperature, suggesting that precipitation is the most important factor that affects NDVI changes in the study area, especially for temperate desert vegetation in northwestern China. [ABSTRACT FROM AUTHOR]

Recent climatic changes have affected terrestrial net primary productivity (NPP). This paper presents an investigation of the impact of climatic changes on Chinese terrestrial vegetation NPP by analyzing 18 years' (1982 to 1999) climatic data and satellite observations of vegetation activity. Results indicate that climatic changes in China have eased some critical climatic constraint on plant growth. (1) From 1982 to 1999, modeled NPP increased by 1.42% · a-1 in water-limited regions of Northwest China, 1.46% · a-1 in temperature-limited regions of Northeast China and Tibet Plateau, and 0.99% · a-1 in radiation-limited regions of South China and East China. (2) NPP increased by 24.2%, i.e. 0.76 petagram of carbon (Pg C) over 18 years in China. Changes in climate (with constant vegetation) directly contributed nearly 11.5% (0.36 Pg C). Changes in vegetation (with constant climate) contributed 12.4% (0.40 Pg C), possibly as a result of climate-vegetation feedbacks, changes in land use, and growth stimulation from other mechanisms. (3) Globally, NPP declined during all three major El Niño events (1982 to 1983, 1987 to 1988, and 1997 to 1998) between 1982 and 2000, but Chinese vegetation productivity responded differently to them because of the monsoon dynamics. In the first three events (1982 to 1983, 1987 to 1988, and 1992), Chinese vegetation NPP declined, while in the later two events (1993, 1997 to 1998) increasing obviously. [ABSTRACT FROM AUTHOR]

Vegetation is an indicator of changes in the ecological environment and a key source of feedback on the impact of drought. In this work we selected northern China as the study area and used the standardized precipitation evapotranspiration index (SPEI) and the normalized difference vegetation index (NDVI) to assess the relationship between drought and vegetation dynamics at annual and seasonal scales for the period 1982–2015. The results indicated that annual drought showed a slight increase in northern China during this time, and it was mainly attributed to the intensified summer drought; the percentages of areas where significant drying, drying, wetting, and significant wetting occurred accounted for 3.30%, 53.36%, 40.39%, and 2.95%, respectively. Annual NDVI showed a highly significant (p < 0.01) upward trend in northern China, suggesting that vegetation there is greening. However, there was still a significant decrease in the NDVI trend in 13.65% of the study area, and forest accounted for the greatest area among the three land cover types studied. A positive correlation between annual SPEI and annual NDVI was found in most of northern China, and 18.66% of the study area (p < 0.05) were mainly distributed in the central-eastern part of Inner Mongolia, the central part of the Loess Plateau, and northwestern part of Xinjiang Province. Residual analysis found that the percentages of vegetation dynamics affected by human-induced degradation, human-induced improvement, and drought accounted for 13.91%, 47.91%, and 38.18%, respectively; however, 54.15% of the areas affected by drought were located in arid and semi-arid regions and that about 54.61% of those were grassland. The work could provide guidance for vegetation construction and water resource management in northern China. [ABSTRACT FROM AUTHOR]

Continued long-term monitoring of vegetation activity in national key ecological function zones (NKEFZs) has implications for national ecological security and sustainability in China. We used Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI3g) dataset to map and analyze the spatiotemporal patterns of change in vegetation growth and their linkage with climate change and human activities in NKEFZs during 1982–2013. Statistically significant increases of growing season, spring, and autumn NDVI were observed during all or most periods while 25 NKEFZs are taken as a whole. Non-significant decreases of NDVI were found in 7 NKEFZs during a few periods, and obvious increases were observed during fifteen periods in all other NKEFZs. Vegetation growth in NKEFZs was mainly regulated by a thermal factor, and the dominant climatic drivers varied across different regions and seasons. The influence of temperature was stronger on vegetation activity in spring and autumn for those NKEFZs located in high latitudes and high elevations, while precipitation was the main climatic control factor for NKEFZs in the arid and semi-arid regions. The effects of human activity on the NDVI of NKEFZs were not ignored; a significant decrease of NDVI in the Sanjiang Plain may be related to the rapid change in land use from wetland into farmland. [ABSTRACT FROM AUTHOR]

With the rapid development of the economy over 40 years since the initiation of Chinese economic reform, terrestrial ecosystems in China have undergone large-scale changes. In this study, we investigated vegetation dynamics in China and their relationships with climatic factors and anthropogenic drivers over 15 progressive periods of 18–32 years starting in 1982. This was accomplished by using the third-generation global satellite Advanced Very High Resolution Radiometer (AVHRR), Normalized Difference Vegetation Index (NDVI) dataset, night-time satellite data, and climate data. Across China, NDVI increased significantly during 1982–2013; especially significant increases were observed in all periods during the growing season and spring. At the pixel scale, 21–38% of the vegetated area in the 15 periods experienced a significant positive trend in vegetation growth. This increase was mostly located in central and southern China. A significant negative trend was observed in 1–8% of the vegetated area pixels, and this pattern was mainly seen in northwestern China, the Yangtze River Delta region, and the Pearl River Delta region. The contribution of spring NDVI to vegetation improvement increased, while the contribution of summer NDVI decreased. Vegetation activity in China was mainly regulated by thermal factors, especially pronounced in mountainous regions of northern China. However, the restrictive effect of moisture factors was very marked to vegetation growth in areas with less than 400 mm of precipitation. Urbanization in China has led to vegetation degradation in most urban centers and surrounding areas in central and eastern China. The increase of agricultural plantations, the Grain for Green Project, and a series ecological restoration projects in some areas have promoted vegetation coverage. [ABSTRACT FROM AUTHOR]

The relationship between climate change and vegetation dynamics in the southwestern karst region of China has been identified by recent studies. Based on previous researches and AVHRR (Advanced Very High Resolution Radiometer) GIMMS (Global Inventory Monitoring and Modeling Studies) NDVI (Normalized Difference Vegetation Index) (1982–2003) and AVHRR GloPEM (Global Production Efficiency Model) NPP (Net Primary Production) (1981–2000) datasets, vegetation dynamics impacted by climate change in the southwestern karst region of China were assessed. The results show that: (1) since the early 1980s, both vegetation cover density and net primary production have insignificant ascending tendencies. However, the inter-annual variation rates of vegetation indexes have apparent spatial differentiations; (2) the correlation coefficients between the inter-annual variations of vegetation indexes and the inter-annual variations of climate factors vary geographically; (3) as indicated by NDVI and NPP, various vegetation types have different responses to climate change, and the annual mean temperature variation has more significant impact on vegetation dynamics than the annual precipitation variation in the study area; (4) distribution laws of correlation coefficients between the inter-annual variations of vegetation indexes and the inter-annual variations of climate factors in different climate conditions are apparent. All these findings will enrich our knowledge of the natural forces which impact the stability of the karst ecosystems and provide scientific basis for the management of the karst ecosystems. [ABSTRACT FROM AUTHOR]