Assessing the response of vegetation photosynthesis to meteorological
drought across northern China
Abstract
Satellite-based solar-induced chlorophyll fluorescence (SIF) has the
potential for an early detection and accurate impact assessment of
meteorological drought on vegetation photosynthesis. However, how the
response of satellite SIF to meteorological drought varies under
different climatic conditions and biome types remains poorly understood.
In this study, we determined the drought time-scale at which the
vegetation photosynthesis response was highest based on the standardized
precipitation evapotranspiration index (SPEI) and satellite SIF, and
examined how the sensitivity of SIF signals from different ecosystems to
drought varied along an aridity gradient in northern China. The results
showed that spatial variability of the annual maximum SIF was
constrained by wetness conditions and biome types. Annual maximum SIF
was positively correlated with SPEI in 57.9% of vegetated lands (P
< 0.05). 34.8% of humid ecosystems were characterized by a
significant SIF-SPEI correlation (P < 0.05). This percentage
reached 44%, 71.4% and 86.2% for arid, sub-humid and semi-arid
ecosystems, respectively. The variation of SIF-SPEI correlations was a
Gaussian function of the aridity index (AI), with the highest SIF-SPEI
correlation appearing in the AI bin of 0.4 (0.37-0.46). The drivers for
this pattern were vegetation composition and water availability. The
variation of SIF time-scales in response to SPEI was a linear function
of the AI, but the slope varied among biomes. To summarize with
increasing aridity drought-induced declines in vegetation photosynthesis
will be quicker and more significant.