Rate of greening during the second growth period in 2004-2005|植被生长数据集|城市化影响数据集

By studying vegetation leafing phenology and its coupling with climate along the
urban-rural gradient in Phoenix metropolitan region, USA, we elucidated the degree
of urbanization-induced transformations of phenology and primary productivity. In
this study we used time-series of Normalized Difference Vegetation Index (NDVI) from
the Moderate Resolution Imaging Spectroradiometer (MODIS) and spatially interpolated
rainfall. Our analyses were stratified by major land covers and dominant soil
texture. We also assessed time scales at which NDVI responds most strongly to
climatic factors. No distinctive patterns in phenology were found along the
urban-rural gradient; however some important generalities were confirmed.
Agricultural and urban developments introduce growth multimodality, which is not
attributable to desert but customarily found in riparian ecosystems of the area.
Despite the existence of summer flush of growth in the desert its signal is not
detected by de-noised satellite data. Urban and agricultural vegetation is
characterized by fast growth and senescence rates. While agriculture has the
shortest growth length, most urban vegetation stays photosynthetically active for
longer periods. Growth in the desert is controlled by precipitation accumulated for
2-5 months. Spatial patterns of NDVI are predicted by precipitation grids. Positive
relationship between these two variables changes seasonally reaching the maximum
near the peak of annual growth. Spring and summer NDVI grids are in better agreement
with longer term accumulated precipitation, but the early autumn growth is
correlated more with immediate rainfall. Spatial and temporal correlations of desert
NDVI with temperature are negative confirming the role of temperature in stimulating
water loss from the soil. Our results supported the hypothesis that coarse-textured
soils limit evaporative losses of soil water and promote growth. Riparian NDVI are
moderately positively correlated with temperature but only weakly with
precipitation. NDVI dynamics in urban and agricultural land covers are completely
unsynchronized with natural vegetation communities and decoupled with precipitation.
They exhibit positive, yet low, correlation with temperature. Overall, urbanization
adds a greater diversity of phenological patterns that are not determined by
climatic variability. Instead, urban and agricultural vegetation dynamics is
expected to be explained largely by socio-economic variables.