Greenup Onset Research Articles

Climate controls on vegetation phenological patterns in northern mid‐ and high latitudes inferred from MODIS data

AbstractRecent studies using both field measurements and satellite‐derived‐vegetation indices have demonstrated that global warming is influencing vegetation growth and phenology. To accurately predict the future response of vegetation to climate variation, a thorough understanding of vegetation phenological cycles and their relationship to temperature and precipitation is required. In this paper, vegetation phenological transition dates identified using data from the moderate‐resolution imaging spectroradiometer (MODIS) in 2001 are linked with MODIS land surface temperature (LST) data from the northern hemisphere between 35°N and 70°N. The results show well‐defined patterns dependent on latitude, in which vegetation greenup gradually migrates northward starting in March, and dormancy spreads southward from late September. Among natural vegetation land‐cover types, the growing‐season length for forests is strongly correlated with variation in mean annual LST. For urban areas, the onset of greenup is 4–9 days earlier on average, and the onset of dormancy is about 2–16 days later, relative to adjacent natural vegetation. This difference (especially for urban vs. forests) is apparently related to urban heat island effects that result in both the average spring temperature and the mean annual temperature in urban areas being about 1–3°C higher relative to rural areas. The results also indicate that urban heat island effects on vegetation phenology are stronger in North America than in Europe and Asia. Finally, the onset of forest greenup at continental scales can be effectively described using a thermal time‐chilling model, which can be used to infer the delay or advance of greenup onset in relation to climatic warming at global scale.

Satellite Observations of the Seasonal Vegetation Growth in Central Asia: 1982-1990

A new method called Derivation and Threshold Approach (DATA) was developed to estimate the onset of vegetation green-up (OVG) for the Mongolian Plateau from 1982 to 1990. The estimates of OVG date were highly correlated with geographic patterns and climatic variations across time and space within our study area. The date of OVG was earliest for the forest and meadow steppe, later for the typical steppe, and latest for the desert steppe. Our findings also showed that ecosystems in the Mongolian Plateau exhibited high spatiotemporal variability in the date of OVG during the study period. The date of onset was found to be most consistent for the forest ecosystem, while the desert steppe was characterized by high year-to-year variations in onset date. A comparison of the derived OVG date estimates with meteorological data showed a clear linkage between onset date and the beginning of spring precipitation in the dry region of the Mongolian Plateau.

Characterizing Ecosystem Variability Using the Onset of Green-Up Derived from Time-Series AVHRR NDVI Data

Characterizing Ecosystem Variability Using the Onset of Green-Up Derived from Time-Series AVHRR NDVI Data

Complex spatiotemporal phenological shifts as a response to rainfall changes.

• Climatic warming produces significant gradual alterations in the timing of life-cycle events, and here we study the phenological effects of rainfall-pattern changes. • We conducted ecosystem field experiments that partially excluded rain and runoff during the growing season in a Mediterranean forest and in a mediterranean shrubland. Studies of time-series of leaf-unfolding, flowering and fruiting over the last 50 yr in central Catalonia were carried out, and greenup onset in the Iberian Peninsula was monitored by satellite images. • Experimental, historical and geographical changes in rainfall produced significant, complex and strongly species-specific, as well as spatially and temporally variable, phenological effects. Among these changes, it was found that in the Iberian Peninsula, greenup onset changes from spring (triggered by rising temperatures) in the northern cool-wet regions to autumn (triggered by the arrival of autumn rainfalls) in the southern warm-dry regions. Even in the mesic Mediterranean central Catalonia (NE of the peninsula) rainfall had a stronger relative influence than temperature on fruiting phenology. • The results show that changes in rainfall and water availability, an important driver of climate change, can cause complex phenological changes with likely far-reaching consequences for ecosystem and biosphere functioning and structure. The seasonal shift in the Iberian Peninsula further highlights this importance and indicates that vegetation may respond to climate change not only with gradual, but also with abrupt temporal and spatial, changes in the timing of greenup onset.

Response of seasonal vegetation development to climatic variations in eastern central Asia

Meteorological records show that central Asia has experienced one of the strongest warming signals in the world over the last 30 years. The objective of this study was to examine the seasonal vegetation response to the recent climatic variation on the Mongolian steppes, the third largest grassland in the world. The onset date of green-up for central Asia was estimated using time-series analysis of advanced very high resolution radiometer (AVHRR) normalized difference vegetation index (NDVI) biweekly composite data collected between January 1982 and December 1991. Monthly precipitation and mean temperature data (1982–1990) were acquired from 19 meteorological stations throughout the grasslands of the eastern Mongolian steppes in China. Our results showed that while the taiga forest north of the Mongolian steppes (>50°N) experienced an earlier onset of green-up during the study period, a later onset was observed at the eastern and northern edges of the Gobi Desert (40°N–50°N). Responses of different vegetation types to climatic variability appeared to vary with vegetation characteristics and spring soil moisture availability of specific sites. Plant stress caused by drought was the most significant contributor to later vegetation green-up as observed from satellite imagery over the desert steppe. Areas with greater seasonal soil moisture greened up earlier in the growing season. Our results suggested that water budget limitations determine the pattern of vegetation responses to atmospheric warming.

Evaluating vegetation phenological patterns in Inner Mongolia using NDVI time-series analysis

Interannual changes in temperature and precipitation can profoundly influence plant phenological status such as the date of onset of green-up, the rate of biomass accumulation, and the onset and rate of vegetation senescence. The objective of this study is to examine annual climatic variation, and its influence on plant phenology of the steppes of Inner Mongolia. Variation in the date of onset of green-up was studied using a 9-year dataset of biweekly composites of the maximum Normalized Difference Vegetation Index (NDVI) values (1982-1990). We found little or no change in date of onset of green-up over the 9-year period for forest and cultivated lands. The date of onset of green-up was progressively earlier or later for the typical and desert steppes, and highly variable for the Gobi Desert. Meteorological data (monthly mean temperature and monthly precipitation) indicated a correlation between date of onset of green-up and climate measurements.