Satellite detection of cumulative and lagged effects of drought on autumn leaf senescence over the Northern Hemisphere

Abstract

Climate change has substantial influences on autumn leaf senescence, that is, the end of the growing season (EOS). Relative to the impacts of temperature and precipitation on EOS, the influence of drought is not well understood, especially considering that there are apparent cumulative and lagged effects of drought on plant growth. Here, we investigated the cumulative and lagged effects of drought (in terms of the Standardized Precipitation-Evapotranspiration Index, SPEI) on EOS derived from the normalized difference vegetation index (NDVI3g) data over the Northern Hemisphere extra-tropical ecosystems (>30°N) during 1982-2015. The cumulative effect was determined by the number of antecedent months at which SPEI showed the maximum correlation with EOS (i.e., R max-cml ) while the lag effect was determined by a month during which the maximum correlation between 1-month SPEI and EOS occurred (i.e., R max-lag ). We found cumulative effect of drought on EOS for 27.2% and lagged effect for 46.2% of the vegetated land area. For the dominant time scales where the R max-cml and R max-lag occurred, we observed 1-4 accumulated months for the cumulative effect and 2-6 lagged months for the lagged effect. At the biome level, drought had stronger impacts on EOS in grasslands, savannas, and shrubs than in forests, which may be related to the different root functional traits among vegetation types. Considering hydrological conditions, the mean values of both R max-cml and R max-lag decreased along the gradients of annual SPEI and its slope, suggesting stronger cumulative and lagged effects in drier regions as well as in areas with decreasing water availability. Furthermore, the average accumulated and lagged months tended to decline along the annual SPEI gradient but increase with increasing annual SPEI. Our results revealed that drought has strong cumulative and lagged effects on autumn phenology, and considering these effects could provide valuable information on the vegetation response to a changing climate. K E Y W O R D Sautumn phenology, cumulative effect, drought, lagged effect

Forest Phenology Dynamics to Climate Change and Topography in a Geographic and Climate Transition Zone: The Qinling Mountains in Central China

“…Some studies have indicated that LOS has been prolonged in recent years, a change that is more closely associated with temperature than with precipitation, and that the different patterns between the phenological metrics and climate factors may be associated with their growth environment [74]. Several studies have also proposed that a time-lagged and cumulative effect exists between vegetation growth and climate changes [32,[75][76][77]. Different lagged and cumulated effects between the phenological metrics and climate factors have been noticed and attributed to species, and locations, at diverse temporal and spatial scales [22].…”

Widespread decline in winds delayed autumn foliar senescence over high latitudes

“…We acquired monthly SPEI for 1982 to 2015 at a spatial resolution of 0.5°, calculated using the difference between precipitation and potential ET from the SPEI base v. 2.5 at Consejo Superior de Investigaciones Científicas (56). The SPEI data set consisted of multiscalar monthly SPEI, so we selected 3-mo SPEI, given this time duration representing the accumulated climatic water balance with the highest correlation with DFS as the final water indicator (22). X-band (10.7 GHz) VOD was obtained from the land parameter data record (LPDR version 2) developed by the Numerical Terradynamic Simulation Group at the University of Montana (57).…”

“…Global increases in autumn temperature could delay DFS (14,20), yet there are also studies showing either earlier or relatively stable DFS, with a possible explanation from opposite changes in DFS in response to daytime and nighttime warming (21). Decreases in precipitation and associated drought may have more complicated influences on DFS, depending on the severity of drought and on regional characteristics of plant functional types (22). In addition to changes in temperature and precipitation, wind speed over the last three decades shows widespread decreasing trends in the northern hemisphere (23,24) with possible impacts on plant growth, chemical composition, structure, and morphology (25)(26)(27)(28).…”

Multi-Climate Factors and the Preceding Growth Stage of Vegetation Co-Regulated the Variation of the End of Growing Season in Northeast Inner Mongolia, China

“…The Normalized Difference Vegetation Index (NDVI), which is derived from satellite remote sensing, has been widely applied in the estimation of land surface phenology in recent years [15]- [17]. Various methods have been developed to extract the EOS from the NDVI [18], which generally involve two main steps: elimination of the noise in NDVI data and identification of the EOS [19], [20]. In the first step, several methods, such as the Savitzky-Golay filter [21], Fourier decomposition [22], and logistic function [23], have been adopted to eliminate the noise in NDVI data, which is due to contamination by cloud cover, seasonal snow, and atmospheric variability.…”

“…Most studies have attempted to explain the changes in EOS through daily mean temperature and precipitation [20], [28]. However, the temperature has experienced faster warming during the nighttime than daytime over the past five decades [29], which has an asymmetric effect on phenological parameters [30].…”