Abstract:

Drought has become a problem faced by terrestrial ecosystems globally, with its development exhibiting distinct regional characteristics. Revealing the temporal and spatial distribution characteristics of regional drought is urgently required to address climate change and ensure the safety of agricultural production. Based on the drought dynamic threshold constructed using the Solar−induced chlorophyll fluorescence (SIF) index during the entire growth period of spring maize in Northeast China, drought frequency and affected areas of spring maize in this region from 2000 to 2020 had been calculated using pixel−by−pixel analysis method. Linear trend estimation and other methods were used to analyze the drought trends and spatial distribution characteristics of spring maize in Northeast China. The research findings were as follows: (1) from 2000 to 2020, the Solar−Induced Chlorophyll Fluorescence (SIF) values of spring maize in Northeast China exhibited a fluctuating upward trend on both the interannual scale and across different developmental stages in time series. Spatially, regions with an increasing trend in SIF values accounted for more than 50%, indicating that the study area had experienced a gradual reduction in drought impacts and a decreased risk of drought over the past 20 years. (2) From 2000 to 2020, the drought−affected areas in the spring maize cultivation regions of Northeast China showed a fluctuating decreasing trend. For different drought levels, the extent of drought−affected areas was ranked as follows: mild drought > moderate drought > severe drought. For different developmental stages of spring maize, the extent of drought−affected areas was ranked with: seedling stage > jointing to booting stage > filling to maturity stage > heading to flowering stage.(3) Most of the spring maize planting areas in northeast China experienced droughts, with a frequency exceeding 40%. The frequency of droughts was higher in the west than in the east. Among different drought severity levels, light drought occurs most frequently, while moderate and severe droughts had lower frequencies. In terms of different growth stages, most of the study area experienced drought frequencies exceeding 25% during the seedling stage. In particular, the central and western parts of Jilin province had frequencies higher than 45%, indicating that the seedling stage remained a period of high drought incidence for spring maize in northeast China.

Key words:

Spring maize of northeast China, Drought rating, Dynamic thresholds, Solar-induced chlorophyll fluorescence index (SIF), Spatio-temporal characteristics