Effects of Growing-Season Drought on Phenology and Productivity in the West Region of Central Hardwood Forests, USA

Studying the effects of drought on forest ecosystems is important in developing a better understanding of forest phenology and productivity. Many previous studies were based on single drought events, whereas effects of recurrent droughts have not been yet fully investigated. This study jointly analyzed the spatial-temporal change of drought patterns with forest phenology and productivity between 2000-2015 in the western Central Hardwood Forests at Missouri, Arkansas Illinois, Oklahoma, and Kansas of the US. Characteristics of forest phenology and productivity were captured by utilizing the Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing 16-day MOD13Q1 data and Savitsky-Golay (S-G) filtering method. Spatial-temporal drought patterns were assessed by empirical orthogonal function (EOF) on self-calibrating Palmer Drought Severity Index (scPDSI) time series. Our results revealed four drought zones: sporadic severe drought zone, cyclic light drought zone, minor drought zone, and moderate drought zone. The results showed that at the regional scale, drought effects on forest phenology and productivity depended on forest type and drought intensity. The cyclic light drought did not result in a notable decline of growing season length and productivity, while both minor drought and severe drought were followed by a significant decrease of forest growing season length and productivity. This research presents an alternative method to analyze the impacts of drought on regional forest dynamics.