Increase In NDVI Research Articles

Spatiotemporal changes of vegetation on the Tibetan Plateau and relationship to climatic variables during multiyear periods from 1982–2012

Understanding the dynamics of vegetation system change is often limited by relatively brief data sequences and the shortage of comparable analyses of variation over longer periods. In this study, GIMMS NDVI and MODIS NDVI datasets were integrated to establish a consistent NDVI time series from 1982 to 2012 on vegetation of the Tibetan Plateau in China. The spatiotemporal patterns of change in seasonal NDVI and their linkage with climatic variables were analyzed at regional and pixel scales over 14 periods ranging from 18 to 31 years and beginning in 1982. On a regional scale, positive trends of growing season and seasonal NDVI were observed during the 14 periods, and the increases were statistically significant for growing season NDVI during all periods, and for summer and autumn NDVI during only the last four and the last two periods, respectively. The rates of NDVI increase in growing season and spring significantly decreased over the 14 periods. NDVI rates slightly decrease in summer and significantly increase in autumn. At a pixel scale, areas with significant greening or significant browning significantly increased over the 14 periods during the growth season and during all seasons except spring, in which the proportion of vegetated area with greening rapidly decreased. Temperature was the primary climatic driver for the observed vegetation changes during multiple periods while precipitation and sunshine duration had significant impacts on vegetation growth only in limited parts of the study area or during spring. Vegetation growth response to climate change varied across seasons and regions. Trend analysis during the multiple nested time series provides a better understanding of NDVI dynamics and may help to forecast future changes. Spring NDVI is likely to continue decreasing, autumn NDVI will continue increasing, and the magnitude of the NDVI increase during growing season will decline in the future.

Warming, Sheep and Volcanoes: Land Cover Changes in Iceland Evident in Satellite NDVI Trends

In a greening Arctic, Iceland stands out as an area with very high increases in the AVHRR Normalized Difference Vegetation Index (NDVI, 1982–2010). We investigated the possible sources of this anomalous greening in Iceland’s dynamic landscape, analyzing changes due to volcanism and warming temperatures, and the effects of agricultural and industrial land use changes. The analysis showed the increases were likely due to reductions in grazing in erosion-prone rangelands, extensive reclamation and afforestation efforts, as well as a response to warming climate, including glacial retreat. Like Scandinavia and much of the rest of the Arctic, Iceland has shown a recent reduction in NDVI since 2002, but still above pre-2000 levels. Theil-Sen robust regression analysis of MODIS NDVI trends from 2002 to 2013 showed Iceland had a slightly negative NDVI trend of 0.003 NDVI units/year (p < 0.05), with significant decreases in an area three times greater (29,809 km2) than that with increases (9419 km2). Specific areas with large decreases in NDVI during the last decade were due to the formation of a large reservoir as a part of a hydroelectric power project (Kárahnjúkar, 2002–2009), and due to ashfall from two volcanic eruptions (Eyjafjallajökull, 2010; Grímsvötn, 2011). Increases in NDVI in the last decade were found in erosion control areas, around retreating glaciers, and in other areas of plant colonization following natural disturbance. Our analysis demonstrates the effectiveness of MODIS NDVI for identifying the causes of changes in land cover, and confirms the reduction in NDVI in the last decade using both the AVHRR and MODIS satellite data.

Analysis on spatio-temporal trends and drivers in vegetation growth during recent decades in Xinjiang, China

Vegetation plays an important role in regulating the terrestrial carbon balance and the climate system, and also overwhelmingly dominates the provisioning of ecosystem services. In this study, a non-stationary 1982–2012 AVHRR NDVI3g time series, the newest dataset, were used to evaluate spatio-temporal patterns of seasonal vegetation changes in Xinjiang province of China at regional, biome and pixel scales over progressively longer periods from 18 to 31 years, starting in 1982, and their linkages to climatic factors and human activities were analyzed. At regional scale, the increases were statistically significant for autumn NDVI during fourteen periods, for growing season and summer NDVI during the most periods, and for spring only during the first four periods. The rates of NDVI increase in growing season and all seasons significantly decreased over fourteen periods. At pixel scale, areas with significant browning rapidly increased over fourteen periods for growing season and all seasons, and these areas were mainly concentrated in northern desert of Xinjiang. Vegetation growth in Xinjiang was regulated by both moisture and thermal conditions: the response of NDVI in spring and autumn was more sensitive to thermal factors, such as temperature and potential evapotranspiration, and correlations between NDVI and precipitation and between NDVI and humidity index were stronger in summer and growing season. Extensive use of fertilizers and expanded farmland irrigated area increased vegetation growth for cropland. However, the rapid increase in the proportion of cotton cultivation and use of drip irrigation may reduce spring NDVI in the part of farmlands. Trend analysis during the multiple nested time series may contribute to a better and deep understanding of NDVI dynamic and foreseeing changes in the future. Accordingly, NDVI in Xinjiang will continuously increase at regional scale and the areas showing significant browning will also furthermore grow.

The relative roles of climate variations and human activities in vegetation change in North China

Using SPOT-VEGETATION Normal Difference Vegetation Index (SPOT/NDVI) data from 1998 to 2011 and climate data obtained from 223 weather stations in or near North China, vegetation variation characteristics within North China were analyzed. Vegetation variation characteristics under the influence of climate variations and human activities were distinguished through a residual analysis. Based on the results of that analysis, the relative roles of climate variations and human activities in vegetation variation were calculated. The results showed that NDVI observed by remote sensing (SPOT/NDVI) increased from 1998 to 2011. The relative roles of climate variations and human activities in vegetation increase were 30.82% and 69.18%, respectively, indicating that human activities played a major role. And observed NDVI showed an increasing trend for different land cover types overall. While NDVI increase in shrub was mainly caused by climate variations, NDVI increases in forest, grassland, farmland, deserts and urban were all primarily caused by human activities. For areas with increasing vegetation, as identified by remote sensing observations in North China, the relative roles of climate variations and human activities in vegetation change were calculated at 14.85% and 85.15% respectively, again indicating that human activities played an important role in vegetation increase. For areas of decreasing vegetation, as identified by remote sensing observations in North China, the relative roles of climate variations and human activities in vegetation change were calculated at 87.72% and 12.28% respectively, indicating that climate variations had large negative effects on vegetation condition. In addition, the relative roles of climate variations and human activities on vegetation variation have obvious spatial differences in North China. Human activities played a positive role in vegetation growth in North China. However, we cannot ignore the function of human destruction on vegetation variation in some areas.

Analysis of the Temporal and Spatial Evolution of Recovery and Degradation Processes in Vegetated Areas Using a Time Series of Landsat TM Images (1986-2011): Central Region of Chihuahua, Mexico

This paper analyzed the temporal and spatial evolution of vegetation dynamics in various land covers in the basin of the Laguna Bustillos, Region of Cuauhtémoc, Chihuahua, Mexico. We used an NDVI time series for the months of March to April (early spring). The series was constructed from Landsat TM images for the period 1986-2011. The results show an increase of NDVI for vegetated areas, especially in conifer cover, while shrub and grassland showed a positive trend but with lower statistical significance. The increase in minimum temperatures in early spring, during the study period, was the most important factor in explaining the increase of NDVI in vegetated areas. A spatially distributed analysis shows large areas without an NDVI trend, corresponding to areas with sparse vegetation cover (degraded areas). Moreover, there are also areas with a negative trend (loss of vegetation), explained by the exploitation of trees to produce firewood which is mainly carried out by the ejidos in the region. These results help to focus human and financial resources in places where the benefit will be greatest.

Warming-Induced Shrub Expansion and Lichen Decline in the Western Canadian Arctic

Strong evidence for a pan-Arctic expansion of upright shrubs comes from analysis of satellite imagery, historical photographs, vegetation plots, and growth rings. However, there are still uncertainties related to local-scale patterns of shrub growth, resulting interactions among vegetation functional groups, and the relative roles of disturbance and climate as drivers of observed change. Here, we present evidence that widespread and rapid shrub expansion and lichen declines over a 15,000 km2 area of the western Canadian Arctic have been driven by regional increases in temperature. Using 30 m resolution Landsat satellite imagery and high resolution repeat color-infrared aerial photographs, we show that 85% of the land surface has a positive 1985–2011 trend (P 0.03 NDVI/decade) occurred consistently across all landscape positions and most vegetation types. Comparison of 208, 1:2,000 scale vertical air photo pairs from 1980 and 2013 clearly shows that this greening was driven by increased canopy cover of erect dwarf and tall shrubs, with declines in terricolous lichen cover. Disturbances caused by wildfires, exploratory gas wells, and drained lakes all produced strong, yet localized increases in NDVI due to shrub growth. Our analysis also shows that a 4°C winter temperature increase over the past 30 years, leading to warmer soils and enhanced nutrient mineralization provides the best explanation for observed vegetation change. These observations thus provide early corroboration for modeling studies predicting large-scale vegetation shifts in low-Arctic ecosystems from climate change.

NDVI and vegetation phenology dynamics under the influence of sunshine duration on the Tibetan plateau

ABSTRACTClimate change has significantly influenced vegetation dynamics on the Tibetan Plateau (TP). Past research mainly focused on vegetation responses to temperature variation and water stress, but the influence of sunshine duration on NDVI and vegetation phenology on the TP is not well understood. In this study, NDVI time series from 1982–2008 were used to retrieve spatiotemporal vegetation dynamics on the TP. Empirical orthogonal function (EOF) analysis was conducted to understand the spatiotemporal variations of NDVI. The Start of Season (SOS) was estimated from NDVI time series with a local threshold method. The first EOF, accounting for 35.1% of NDVI variations on the TP, indicates that NDVI variations are larger in areas with shorter sunshine duration. The needle‐leaved forest and shrub in the southeastern TP are more sensitive to sunshine duration anomalies (p < 0.01) than broad‐leaved forest, steppe, and meadow due to spatial and altitudinal distribution of sunshine duration and vegetation types. The decrease in sunshine duration for the growing season on the TP has resulted in a decreased NDVI trend in some areas of southeastern TP (p ranging from 0.32‐0.05 with threshold ranging from 0.05 to 0.25) in spite of the overall NDVI increase. SOS dynamics in most parts of the TP were mainly related to temperature variability, with precipitation and sunshine duration playing a role in a few regions. This study enhances our understanding of vegetation responses to climatic change on the TP.

Evolución de la dinámica vegetal mediante una serie de imágenes Landsat TM(1986-2011): región central de Chihuahua, México

In this research we have analyzed the temporal and spatial evolution of vegetation dynamics on various land covers in the watershed of Laguna Bustillos, in the region ofCuauhtémoc,Chihuahua, México. It was used a time series of NDVI for the month of April (early spring). The series was constructed from Landsat TM for the period 1986-2011. The results show an increase of NDVI for vegetated areas, to a greater extent for hedging conifers, while grassland and scrub showed a positive trend but with lower statistical significance. The increase in minimum temperatures in early spring during the study period was the most important factor to explain the increase in NDVI in vegetated areas. A spatially distributed analysis shows large areas without NDVI trend, which correspond to areas with low vegetation cover (degraded areas). Moreover, also areas appear with a negative trend (loss of vegetation), that can be explained by the extraction of wood to be used like firewood, mainly carried in the communal land of the region.

Carbon sequestration and water use of a young hybrid poplar plantation in north-central Alberta

Hybrid poplar (HP) is an important fast-growing crop with the potential to provide a reliable supply of biomass for the pulp and bioenergy industries while also sequestering carbon (C) in the soil. We used the eddy-covariance technique to measure CO2, water vapor and sensible heat fluxes above a three-year-old HP plantation on high productivity land near St Albert, Alberta. Measurements showed that the annual C balance of the plantation shifted from a C source of about 1.54 Mg C ha−1 y−1 in the 2nd year (2010) to a C sink of 0.80 Mg C ha−1 y−1 in the 3rd year (2011). Water use or evapotranspiration (E) for 1 June – 31 October increased from 272 mm in 2010 to 321 mm in 2011, and exceeded the respective values of total precipitation of 251 mm and 298 mm for the same period. Annual E in 2010 of 364 mm was less than annual precipitation of 398 mm. In 2011, annual E (442 mm) exceeded annual P (411 mm) by 31 mm; it also exceeded the annual plantation water use Ewb, estimated using a water balance method assuming no drainage from the root zone, by 40 mm. However, both courses of cumulative E and Ewb closely followed cumulative P. Monthly E increased with increasing net radiation and gross primary productivity. Growing season mean albedo increased from 0.16 in 2010 to 0.21 in 2011 and was consistent with the increase in broadband NDVI. Values of albedo during winter months (November–April) exceeded 0.80. The results suggested that as the plantation grows, growing season albedo, annual C sequestration, and annual water use will increase with the possibility that the latter may exceed annual precipitation. This emphasizes the need to study the long-term sustainability of HP plantations in relation to annual P and its temporal distribution, especially when HP plantations will likely be established on large contiguous areas to supply biomass feedstock for the expanding pulp and bioenergy industries in Western Canada.

Vegetation Index Differencing for Broad-Scale Assessment of Productivity Under Prolonged Drought and Sequential High Rainfall Conditions

Spatially-explicit depictions of plant productivity over large areas are critical to monitoring landscapes in highly heterogeneous arid ecosystems. Applying radiometric change detection techniques we sought to determine whether: (1) differences between pre- and post-growing season spectral vegetation index values effectively identify areas of significant change in vegetation; and (2) areas of significant change coincide with altered ecological states. We differenced NDVI values, standardized difference values to Z-scores to identify areas of significant increase and decrease in NDVI, and examined the ecological states associated with these areas. The vegetation index differencing method and translation of growing season NDVI to Z-scores permit examination of change over large areas and can be applied by non-experts. This method identified areas with potential for vegetation/ecological state transition and serves to guide field reconnaissance efforts that may ultimately inform land management decisions for millions of acres of federal lands.

2000-2010年黄河流域植被覆盖的时空变化

Vegetation cover is one of the primary indicators of changes to ecosystems. Large scale vegetation cover observations will indicate the effect of natural factors and human activities on the ecological environment,so it is one of the hot topics in global change research. The Yellow River Basin is located in an arid,semi-arid and semi-humid area and its ecological environment is vulnerable. In recent years,the vegetation in the Yellow River Basin has had a relatively large variance in spatial and temporal patterns,affected by changes in climatic conditions and perturbations from human activities. Therefore,improving the observation of vegetation will provide us with more information about vegetation status and make us better able to understand the variations of ecological environment characteristics. With this background,this paper provides an analysis of spatio-temporal variations of MODIS / NDVI in the vegetation covered area of the Yellow River Basin. The MODIS product,which is assumed to be suitable for large scale observations of vegetation variation,was used,and MOD13Q1 data with a spatial resolution of 250 m × 250 m from 2000 to 2010 was utilized as the data source. NDVI was used as a proxy for vegetation cover and the Theil-Sen Median trend analysis with the Mann-Kendall test were both used to analyze NDVI trends as they are new methods in the long term series analysis of NDVI. Theil-Sen Median trend analysis was used to describe the trend of NDVI and the Mann-Kendall test was used to estimate the significance of trend. The combination of the result of Theil-Sen Median trend analysis and Mann-Kendall test,as well as the result of Hurst index were conducted to analyze the sustainability in NDVI trend. The results indicate that: 1) From the distribution of the annual NDVI in the Yellow River Basin,the NDVI values are high in the west and the southeast,but low in the north; 2) From the time variation of annual NDVI in the vegetation covered area in the Yellow River Basin,the values of NDVI fluctuate between 0. 3 and 0. 4,from 2000 to 2010,and NDVI from 2000—2004 shows high fluctuations,but rapid upward trend since 2005; 3) From the spatial trends of NDVI,the area where the values of NDVI increase is much larger than the area where the values of NDVI decrease and the area where the values of NDVI increase occupies 62. 9% of the vegetation covered area,while the area where the values of NDVI decrease accounts for 27. 7%. 9. 4% of the vegetation covered area remained unchanged,during the period of 2000— 2010; 4) From the spatial sustainability of NDVI trend,the overlaid result of the Theil-Sen Median trend analysis,MannKendall test and Hurst index indicates that 86. 0% of the area presents a positive sustainable development. From the overlaid result of the Theil-Sen Median trend analysis and Mann-Kendall map and Hurst index map,it can be concluded that 53. 7% of the vegetation-covered area presents a sustainable-increased state,7. 8% of the vegetation-covered area presents a sustainable-unchanged state,24. 5% of the vegetation-covered area shows a sustainable-decreased state and 14. 0% of vegetation-covered area cannot be identified in the future. These areas need to be focused upon and further researched.

Monitoring Wheat and Rapeseed by Using Synchronous Optical and Radar Satellite Data—From Temporal Signatures to Crop Parameters Estimation

This paper investigates the sensitivity of multi-temporal SAR data acquired at different frequencies (X-, C-and L-bands), polarizations (HH, VV, VH and HV) and incidence angles (from 24° to 53°) during the growing season of two winter crops (rapeseed and wheat). This study was part of a multi-sensor crop-monitoring experiment that was performed from February to November 2010 (MCM’10). During the experiment, dense series of satellite data were acquired in microwave, optical and thermal domains (more than 150 images were provided by TerraSAR-X, Radarsat-2 Alos, Formosat-2, Spot-4/5 and Landsat-5/7) were synchronous with ground measurements over an agricultural area located in southwestern France, near Toulouse. An angular normalization of radar signals is first performed for each crop type at X-and C-bands by using a dense temporal satellite series and the complementarity provided by microwave and optical data. The results show that the angular sensitivity of radar backscatter decreases with the increase of the vegetation index (from 0.4 dB.°ˉ1 over bare soils to 0.05 dB.°ˉ1 for fully vegetated fields). Lower angular sensitivity is observed at X-band (compared to C-band), and for the cross-polarized signal. Analyses of the temporal signatures of the radar backscatter show a well-marked signal dynamic at X-, C-and L-bands, depending on the crops and theirs associated phenological stages. During the stems elongation of wheat while the NDVI increases of 0.2, a dynamic of 10 dB is observed at X-band and at C-band with VV polarization. Interesting behaviors are also observed during the crop senescence with an increase of several dB (depending on the sensor configuration), while the NDVI decreases of 0.5. Over rapeseed, cross-polarized backscatters offer promising dynamic of 6 dB during the seed development, while the NDVI saturates at maximum values. The use of radar signals, in complement of optical, for crop parameters monitoring is achieved in terms of leaf area index and crop height estimations. Over rapeseed, best correlations between crop parameters and radar signals are obtained at C-band, by combining co-and cross-polarized backscatters (R2 > 0.61). Over wheat, best results are achieved by using X-band data (R2 > 0.64).

Recent climate-related terrestrial biodiversity research in Canada's Arctic national parks: review, summary, and management implications

It is now well documented that Arctic climates and ecosystems are changing at some of the fastest rates on planet Earth. These changes are significant for all Arctic biodiversity, and they are a great challenge for cooperative management boards of Canada's Arctic national parks, those legislated to maintain or improve the ecological integrity of all national parks. Owing to the inherent complexity of natural ecosystems, it is not at all clear how, nor how rapidly, these ongoing changes will affect park biodiversity and impact the traditional land-based lifestyles of Indigenous park cooperative management partners. In this context, this paper reviews and integrates recent research carried out in Canadian Arctic national parks: (1) geophysical – a reduction in glacial area and volume, active layer thickening, warming soil temperatures, and terrain instability; (2) vegetation – widespread but ecosystem-specific increases in NDVI ‘greenness’, plant biomass, shrub and herb coverage, and growing season lengths; and (3) wildlife – complex changes in small mammals and ungulate populations, very negative effects on some polar bear populations, and relatively stable mammalian predator and raptor populations at this time. This work provides a partial snapshot of ongoing and evolving ecological effects of climate change in Arctic national parks, and provides a strong foundation for prioritising future research and monitoring efforts. These evolving changes also undermine the historical paradigm of place-based conservation and necessitate a new approach for managing protected areas that involves acceptance of ongoing transformational change and adoption of a risk-based, forward looking paradigm in a changing world. It is proposed that Arctic national parks are ideal locations to focus Arctic science, especially as a component of a strategic, coordinated, and pan-Arctic approach to Arctic research that makes the most effective use of limited resources in the vast areas of Canada's north.

Remotely sensing the cooling effects of city scale efforts to reduce urban heat island

While recent years have seen many analyses of techniques to reduce urban heat island, nearly all of these studies have either been evaluations of real small scale applications or attempts to model the effects of large scale applications. This study is an attempt to analyze a real large scale application by observing recent vegetated and reflective surfaces in LANDSAT images of Chicago, a city which has deployed a variety of heat island combative methods over the last 15 years. Results show that Chicago’s new reflective surfaces since 1995 produced a noticeable impact on the citywide albedo, raising it by about 0.016, while citywide NDVI increase is around 0.007. This finding along with counts of pixels with increased albedo and NDVI suggest that the reflective strategies influenced a larger area of the city than the vegetative methods. Additionally, plots between albedo increase and corresponding LANDSAT temperature change over the test period have linear regressions with steeper slopes (−15.7) and stronger linear correlations (−0.33) than plots between NDVI increase and temperature change (−8.9 slope, −0.17 correlation). This indicates that the albedo increases produced greater LANDSAT cooling than the NDVI increases. Observation of aerial images confirmed that typical instances of efforts to increase albedo, such as reflective roofs, produced stronger LANDSAT cooling than common instances of NDVI efforts, such as green roofs, street trees and green spaces. Accordingly, the reflective strategies were likely much more effective at cooling Chicago’s LANDSAT heat island and may signify a generally more effective strategy for similar cities.

Avaliação dos efeitos atmosféricos no albedo e NDVI obtidos com imagens de satélite

O albedo é um elemento importante em estudos relacionados aos balanços de radiação e energia. Por conseguinte, alterações ocorridas em diversos biomas trazem grandes implicações ao conforto humano e animal. Neste sentido, o monitoramento do albedo através de imagens orbitais possibilita identificar a antropização de grandes áreas e seus impactos ambientais. O presente trabalho foi desenvolvido com o objetivo de avaliar o impacto da correção atmosférica na estimativa do albedo da superfície e do NDVI, utilizando-se a metodologia tradicional do SEBAL (Bastiaanssen, 2000) e a correção atmosférica no cômputo da refletância, banda a banda (Allen et al., 2007b), para quatro imagens Landsat 5 - TM da região do Cariri cearense. Os resultados mostraram diminuição no albedo da superfície e acréscimo no NDVI, corrigidos os efeitos atmosféricos para todas as áreas amostrais. De acordo com o teste de Student as diferenças entre os albedos e NDVIs, obtidas segundo os dois procedimentos considerados, são significativas a nível de significância de 0,01.

Can a 25-year trend in Soudano-Sahelian vegetation dynamics be interpreted in terms of land use change? A remote sensing approach

This study is based on the premise that, in the Sahel/Sudanian belt of Africa, the main determinants of interannual variation in vegetation dynamics are rainfall and land cover type. We analyzed the spatio-temporal sensitivity of the NOAA–AVHRR 8 km-resolution vegetation index (NDVI) to (i) annual rainfall variability (0.5° × 0.5° resolution) acquired over a 25-year period (1982–2006); and (ii) land use changes in the different eco-climatic regions of the Bani catchment in Mali (130 000 km 2). During the period 1982–2006, there was no clear trend in rainfall over the catchment, whereas there was a strong positive trend in the NDVI, both when the NDVI values were corrected using annual rainfall variability and when they were not. We divided the catchment into three eco-climatic regions based on the relationship between the annual NDVI and rainfall. In each region, we analyzed the observed greening in relation to changes in land use after correcting for the effect of annual rainfall on the NDVI. Results show that there is a mixed level of agreement between the land cover changes at the grid cell scale and the spatial pattern of the NDVI trend. Increased cropping does not explain the increase in the annual NDVI, except in the Sahelian part of the catchment. We hypothesize that the natural vegetation dynamics related to the non-linear rainfall patterns during the 25-year study period were responsible for these results.

Vegetation cover change and the driving factors over northwest China

In this paper the spatio-temporal variation of vegetation cover in northwest China during the period of 1982−2006 and its driving factors were analyzed using GIMMS/NDVI data. The annual average NDVI was increased with a rate of 0.0005/a in northwest China and there was an obvious difference be- tween regions. The trend line slopes of NDVI were higher than 0.0005 in the Tianshan Moutains and Altay Mountains of Xinjiang, the Qilian Mountains of Gansu and the eastern part of Qinghai, which indicated the vegetation cover was significantly increased in these areas. The trend line slopes of NDVI were lower than −0.0005 in the southern region of Qinghai, the border regions of Shaanxi and Ningxia, the parts of Gansu and Tarim Basin, Turpan and Tuoli in Xinjiang, which indicated the vegetation cover was declined in these areas. The NDVI of woodland, grassland and cultivated land had an ascending tendency during the study period. The study shows that the vegetation cover change was caused by both natural factors and human activities in northwest China. The natural vegetation change, such as forests was influenced by climate change, while human activities were the main reason to the change of planting vegetation. The changes of vegetation covers for different elevations, slopes and slope aspects were quite different. When the eleva- tion is exceeded to 4,000 m, the NDVI increasing trend was very low; the NDVI at the slope of less than 25° was increased by the ecological construction; the variation of NDVI on sunny slope was stronger than that on shady slope. The temperature rose significantly in recent 25 years in northwest China by an average rate of 0.67oC/10a, and precipitation increased by an average rate of 8.15 mm/10a after 1986. There was positive correlation between vegetation cover and temperature and annual precipitation changes. Rising temperature increased the evaporation and drought of soils, which is not conducive to plant growth, and the irrigation in agricultural areas reduced the correlation between agricultural vegetation NDVI and precipita- tion. The improvement of agricultural production level and the projects of ecological construction are very important causes for the NDVI increase in northwest China, and the ecological effect of large-scale eco- logical construction projects has appeared.

Climate and topography drives macroscale biodiversity through land‐use change in a human‐dominated world

Drivers of biodiversity at macroscales have long been of interest in ecology, and climate and topography are now considered to be major drivers. Because humans have transformed most of the Earth's land surface, land use may play a significant role as a driver of biodiversity at a macroscale. Here we disentangle the relationships among climate, topography, land use, available energy (measured by the normalized difference vegetation index [NDVI]), and species richness of Japanese forest birds. Species richness was better explained at 40‐ and 80‐km resolutions than at 5‐, 10‐ and 20‐km resolutions; it was explained by climate, topography, and land use, and the effects of land use were fully incorporated into those of climate and topography. As temperature increased and elevation decreased, natural forest area decreased, and this decrease intensified in warm lowland areas. With the loss of natural forest, species richness decreased below a certain threshold. As temperature increased and elevation decreased, species richness and NDVI increased slightly or were unchanged in cool highland areas and decreased in warm lowland areas. Species richness increased linearly with the increase in NDVI. Most effects of climate/topography on species richness in warm lowland areas were shared by those of land use, suggesting that the decrease in species richness in warm lowland areas has been caused by loss of natural forest. Therefore, it is suggested that climate and topography determined land use intensity, which in turn, drove species richness through the depletion of available energy. Increasing temperature and decreasing elevation leads to both benefits (increase in potential available energy) and costs (depletion of energy by human land‐use change) for forest birds. These costs seem to override benefits in warm lowland areas.

Analysis of global tendencies in land cover change using time series NOAA/AVHRR

The goal of this study is to use NDVI and LST (land surface temperature) time series NOAA/AVHRR data to estimate global tendencies in land cover changes from 1982 to 1999. As a preprocessing step, Temporal Window Operation-correction (TWO Method) was performed to reduce the effects of clouds. The mean (AVG_NDVI and AVG_LST) and standard deviation (STD_NDVI and STD_LST) values were calculated for each NDVI and LST data over the 18 period. The results showed that NDVI varied according to rate of vegetation coverage ; and LST varied by latitude, altitude and whether or not the area was vegetated. In order to identify any abnormal trends, AVG_NDVI and STD_NDVI were used to calculate the monthly deviation. These calculations revealed that Africa suffered a period of drought from July 1984 to January 1985. In addition, in order to reveal changes in land cover by season, profile matching, taking into consideration phonological shifts, was implemented, and the difference between these results and average (DIF_NDVI and DIF_LST) values were determined. The results of these comparisons allowed identification of regional changes in NDVI under the influence of abnormal weather patterns. Furthermore, the gradient was extracted for 18 years of NDVI and LST data, using the linear regression analysis from DIF_NDVI and DIF_LST. The two gradient values plotted for NDVI and LST gradient indicated several important trends, such as an increase in NDVI in many grassland areas, including farmland ; and a increase in LST in desert areas.

Effects of deglaciation on circumpolar distribution of arctic vegetation

An understanding of the factors controlling the distribution of arctic vegetation will allow better prediction of the effects of climate change. This study examines the effect of the age of landscapes on the distribution of arctic vegetation. We compared time since deglaciation with the distribution of vegetation types and Advanced Very High Resolution Radiometer (AVHRR) satellite measures of greenness (normalized difference vegetation index, NDVI). Most of the older arctic landscapes occur between the Taimyr Peninsula in Russia and the Mackenzie River in Canada. The vegetation types most commonly associated with the oldest landscapes include tussock-sedge, dwarf-shrub, moss-tundra, and sedge-shrub wetlands. Most of the Arctic, including most bioclimate subzones and most vegetation types, showed increasing NDVI with increasing landscape age. Landscapes showed rapid increases in NDVI during the first several thousand years after deglaciation. Relatively low NDVI values occurred on landscapes 5000 – 15 000 years old, as on the Canadian Shield. Higher NDVI values occurred on landscapes older than 20 000 years. Landscape age accounted for 34% of the variation in NDVI for landscapes younger than 900 000 years. The coldest parts of the Arctic (subzone A) and vegetation types that grow primarily in these areas did not show any trend with landscape age.